Aerotherm Final
Report No. 71-43
DESIGN OF A PARTICULATE
AERODYNAMIC TEST
FACILITY
by
Larry W. Anderson
William F. Lapson
John W. Schaefer
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Aerotherm Project 7034
December 7, 1971
Aerotherm Final
Report No. 71-43
DESIGN OF A PARTICULATE
AERODYNAMIC TEST
FACILITY
by
Larry W. Anderson
William F. Lapson
John W. Schaefer
Prepared for
U.S. Environmental Protection Agency
Office of Air Programs
Research Triangle Park, North Carolina
Contract No. EHSD 71-44
Technical Monitor - D. B. Harris
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FOREWORD
The efforts described here were carried out for the U.S. Environmental
Protection Agency, Office of Air Programs, Research Triangle Park, North Caro-
lina, under Contract EHSD 71-44. The project was initiated by Mr. James A.
Dorsey and Mr. John O. Burckle of EPA. Technical management at EPA was provided
by Mr. Burckle and Mr. Bruce Harris. The assistance of these individuals in
carrying out this project is gratefully acknowledged.
Dr. Larry W. Anderson was the Aerotherm program manager for the work re-
ported here. Inclusive dates for these efforts were December 7, 1970 through
October 7, 1971.
iii
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1-'-
<:
VARIABLE SPEED
DRIVE SYSTEM
COMBUSTION PRODUCTS GENERATOR
TEST SECTION SEGMENT
WINDOW
CONTRACTION SECTION
STILLING CHAMBER
PARTICLE HOPPER, FEEDER, AEROSOL GENERATOR
GAS CONDITIONER
( COOLING, HEATING,
HUMIDIFICATION)
PARTICULATE AERODYNAMIC TEST FACI LlTY
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ABSTRACT
A design for a particulate aerodynami9 test facility is presented. The
design is addressed to a particular set of performance specifications for the
test gas which include gas velocities to 90 ft/sec, temperatures to 450°F, con-
trol of the relative humidity, and occasional testing with combustion products
as the test gas. Other facility requirements become apparent as the tentative
uses for the facility are reviewed. These uses include development of particu-
late and gas sampling procedures and instrumentation, study of basic collection
mechanisms, and study of basic particle flow mechanics.
In developing the facility design presented here, basic features of other
aerodynamic test facilities are reviewed, and features which are needed in the
present design are identified. The literature on other particulate research
facilities is also briefly summarized. Engineering tradeoffs and technical con-
siderations are then presented, which ultimately result in decisions on the ba-
sic facility layout, size, shape, and techniques for heating, humidifying, cool-
ing, and filling the tunnel with exhaust products and with particulate material.
A detailed description of the final facility design is then presented.
The overall design is described first, then each major component is described
separately. Controls and instrumentation are described. The report is
concluded with some brie.f remarks on construction of the facility, and specifi-
cation sheets for each major piece of equipment.
v
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Section
1
2
3
4
5
TABLE OF CONTENTS
INTRODUCTION
TECHNICAL DISCUSSION
2.1 Facility Requirements
2.2 Basic Features of a Typical Aerodynamic Test Facility
2.3 Other Existing Particulate Wind Tunnels
2.4 Engineering Tradeoffs for this Facility
2.4.1 Open Circuit Versus Closed Circuit Tunnel
2.4.2 Horizontal Versus Vertical Test Section
2.4.3 Dust Injection Technique
2.4.4 Dust Generation and Metering
2.4.5 Test Section Diameter and Length
2.4.6 Test Gas Heating
2.4.7 Air Conditioning
2.4.8 Charging the Tunnel with Combustion ~roducts
2.4.9 Fan, Motor, and Speed Control
2.4.10 Materials of Construction
FACILITY DESIGN
3.1 General Facility Description
3.2 Detailed Description of Major Components
3.2.1 Fan, Motor, and Coupling
3.2.2 Duct
3.2.3 Gas Conditioning Section
3.2.4 Duct Heater
3.2.5 First Elbow
3.2.6 Stilling Chamber
3.2.7 Dust Feeder
3.2.8 Contraction
3.2.9 Test Section
3.2.10 Flex Co~pling Section
3.2.11 Diffuser
3.2.12 Elbow to Baghouse
3.2.13 Baghouse
3.2.14 Duct from Baghouse to Fan
3.2.15 Tunnel Inlet, Exhaust, and Open Circuit Valves
3.2.16 Combustion Products Burner and Firebox
Controls and Instrumentation
3.3.1 Control Console
3.3.2 Velocity Control
3.3.3 Test Gas Temperature
3.3.4 Test Gas Humidity
3.3.5 Test Gas Composition
3.3.6 Dust Feed Rate
3.3.7 Dust Carrier Gas Flow Rate
3.3.8 Burner Operation
3.3.9 . Baghouse cleaning Frequency
3.3.10 Inlet, Exhaust and Open Circuit.Valve Settings
Utilities
Other Design Details
3.5.1 Cleanout
3.5.2 Insulation
3.5.3 Laboratory Housing
3.5.4 Effluents
3.5.5 Air Exchange Requirements
3.3
3.4
3.5
. FACILITY CONSTRUCTION
SPECIFICATIONS
REFERENCES
APPENDIX
vii
Page
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4
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9
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A-l
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Figure
1
2
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4
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19
20
21
22
23
2.4
25
26
27
28
29
30
31
32
33
34
35
36
. LIST OF FIGURES
Floor Space Available at Durham Facility
Open and Closed Circuit Wind Tunnels
Combustion Engineering Particle Injection Technique
Approximate Plan View of Battelle Tunnel
Battelle Particle Injection System
Detai 1s of Habibi's Automotive Sampling System
Hot Gas System-Burner Source, Open Loop
Fuel Requirements for Heating an Open Circuit Flow
Cooling Water Requirements for Open Circuit Flow
Schematic Diagram of Major Components of Test Facility
Stokes Flow Particle Sink Rate
Schematic of Wind Tunnel Showing Dust Handling Equipment
Dust Flow Rate Requirements
Typical Carrier Gas Dust Loading
Turbulence Levels Downstream of Dust Injectors
Page
6
8
10
12
13
15
18
19
20
21
23
25
27
29
32
34
35
36
37
39
40
43
45
48
49
51
53
FluiaLzed Bed Aerosol Generator
Vibrating Hopper with Regulated Output
Screw Feeder
Vaned Impeller Metering Device
Belt Feeder
Rotating Disc Feeder
Boundary Layer Growth in the Test Section
Closed Circuit Test Gas Heating Methods
Psychrometric Chart
TypLcal Air Conditioning System
Rotating Drum Adsorbent Dehumidifier
Tunnel Operation During Combustion Gas Pre-Charge Period
Mole Fraction of Combustion Products in Tunnel Gas as a
Function of TLme for Various Burner Products Flow Rates
55
57
70
72
76
77
79
88
90
Combustion Products Injection Techniques
Dust Metering Valve
Nozzle Dust Feed System
Inlet, Exhaust, and Open
Circuit Valves
Valve ~rrangement. for Open Circuit and Gas Filling Operations
Firebox Exhaust Duct and Valve
Access Hatches and Drain Locations
Laboratory Housing
viiL
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'T'~,ble
1
2
3
4
5
6
7
8
9
[
[
LIST OF TABLES
Page
Effect of Nozzle Size on Carrier Gas Dust Loading
31
Feed Rates with Various Screw Sizes
38
Merits of Various Dust Feeding Methods
41
Heater Options
46
Relative Humidity Values with a Chilled Water System
Types of Wind Tunnel Fan Speed Control
52
59
Wind Tunnel Heater Requirements
66
Heater and Control Characteristics
68
Equipment Specifications
97
ix
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SECTION 1
INTRODUCTION
Aerosols emitted from stationary sources constitute one of the most com-
mon and readily observable air pollutants currently being subjected to control
measures. These aerosols, which are composed of solid and/or liquid* particles,
originate in the fuel used in a typical combustion process, or in the pre- or
post-combustion process itself. Noncombustible components of coal and oil fuels
(the ash content) pass directly through the combustion zone of a burner and are
emitted to the atmosphere generally in solid form, with characteristic dimen-
sions of one-tenth to one hundred microns and larger. Sulfur and metallic trace
species in the fuel oxidize during combustion to form other aerosol components.
Fuel-rich combustion results in many types of condensible organics, whose state
is dependent on local temperature. Dust from material handling operations can
be a problem exclusive of any combustion. Many of these particulates are nox-
ious, corrosive, or even toxic in large concentrations. Thus, the control of
aerosols is seen to be desirable not only from an aesthetic point of view, but
also from a property damage and health point of view.
Measures currently in use for the control of particulates concentrate
both on the allowable pollutant content of the fuel (i.e., the sulfur content)
and on the allowable particulate emissions at a given installation. Particulate
emissions for a given process are often controlled by mechanical means, such as
inertial separators, scrubbers, baghouses, and electrical precipitators. Fur-
ther advancement in the "particulate control" state of the art will require
basic information on the general behavior of particulates in flue gases. In
addition, more sophisticated and automated instrumentation to test the perfor-
mance of control equipment or compliance with air pollution regulations is neede~
Such basic information and instrumentation will play key roles in the specifica-
tion of particulate control legislation.
This report documents the results of a study to develop a preliminary or
conceptual design for a particulate aerodynamic test facility. The terms "pre-
liminary" and "conceptual" are used to indicate that final design drawings were
not the objective of this effort. Rather a best design solution will be
*
With the exception of water, which is not considered a pollutant.
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described in some detail, consistent with the specific uses and constraints
imposed on the desired test facility. The facility, to be installed at EPA
laboratories in North Carolina, will be used by EPA personnel to study particu-
late flow phenomenology and to evaluate control procedures and instrumentation.
More specifically, this will involve:
.
Basic particle flow research
1.
Laser holography of particle trajectories
2.
Particle condensation, precipitation, and nucleation studies
3.
Alteration of particle diffusion rates
.
Development and calibration of instrumentation
1.
Probe development and calibration
2.
Instrumentation development and calibration
3.
Sampling technique development
.
Research on particle collection mechanisms
1. Particle flow in magnetic fields
2. Particle flow with large body forces
3. Particle flow around obstacles and through sprays
4. Particle flow in ductwork and breechings
At the present time, there is no research facility available which is large
enough or versatile enough to perform the types of studies indicated above.
The need for such a research facility is apparent if significant progress is
to be made in the near future on particulate emission control technology and
legislation.
The activities performed under this contract~ in chronological order,
were as follows:
.
Identification of facility requirements
The anticipated facility uses and the desired facility specifica-
tions were reviewed and revised with EPA personnel. The literature
was reviewed for descriptions of related types of research facilities,
and visits were made to several of these. Interviews with facility
operators, designers, and particle flow researchers were particularly
useful. Preliminary engineering calculations were made for sizing
purposes, and major facility components were identified.
2
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.
Preliminary facility design
Numerous configuration tradeoff studies were carried out, with
consideration given to the allowable floor space and the type of
tests to be run. Preliminary designs for major facility components
and an overall facility layout were prepared and reviewed with EPA
personnel.
.
Detailed facility analysis and design
A detailed analysis of each major facility component, and
system as a whole, was conducted. Discussions with equipment
dors were held, and final selections of components were made.
of the
ven-
Con-
ceptual designs were finalized.
.
Drawings and specifications
Final "outline" drawings of the
component were prepared. Utilities
specified. Equipment specification
and typical vendors, were prepared.
test facility and of each major
and control circuitry were also
sheets, ,including estimated costs
The remainder of this report is organized as follows. Section 2 is a
general technical discussion of this facility, the facility requirements, the
basic features of a typical wind tunnel facility, other particulate research
facilities, and engineering tradeoffs and design calculations for this facility.
Section 3 is a technical description of the proposed facility, including the
overall layout, each of the major components, the controls and instrumentation,
utilities, and other design details. Section 4 presents some brief construc-
tion considerations, while Section 5 includes specification sheets for the tun-
nel components.
3
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SECTION 2
TECHNICAL DISCUSSION
The purpose of this section of the report is to present some of the ra-
tionale for the selected facility design. The facility requirements are r~-
viewed, as are the basic features of a modern wind tunnel. Other existing test
facilities of a related nature are described. Engineering tradeoffs and calcu-
latiqns are then presented to justify some of the decisions which were made.
2.1
FACILITY REQUIREMENTS
The requirements of this test facility were iterated somewhat during the
course of this contract as information on sizes, costs, materials, etc. became
available. The final set of requirements are as follows:
Conditioned Air Test Stream
The facility will operate with air as a test gas. The air temperature
in the test section will be 70o-l00°F with a 10-80 percent relative humidity
level. Precision control of the temperature and humidity level at any inter-
mediate setting will be provided. These test conditions will be attainable on
a 24-hours-per-day, 365-days-per-year basis using the ASHRAE 99 percent climate
criteria for Durham, North Carolina.
Exhaust Gas Test Stream
The facility will also generate and operate with typical power plant
combustion products as a test stream. The exhaust products temperature in the
test section will be 140°F to 450°F, with precision control of the gas tempera-
ture and composition provided. Exhaust products will be generated with natural
gas fuel, however the natural gas supply is interruptable and an alternate fuel
source will be provided.
Particulate Loading
The conditioned air or exhaust products test stream will be loaded with
0.1-5.0 grains/ft3 of solid particulate material. The particulate material
will range from 0.2-20 microns mean diameter, and will be uniformly mixed in
the test gas at a known axial station in the test section. Particulate matter
which may be in the laboratory air supply will be filtered out of the flow such
that the test stream has a known particle material, size distribution, and
loading.
4
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Test Section
The test stream will flow through an enclosed test section of round cross-
section, with a two-foot maximum internal diameter. The test section construc-
tion will allow interchangeable duct sections typical of fossil fuel combustion
system breechings to be installed at several locations as an integral part of
the test section. Test section length and minimum diameter will be determined
as part of the design effort. The facility design should be such that a "low"
freestream turbulence level will be encountered in the test section. Observa-
tion and lighting windows will be an intergral part of the test section construc-
tion, with window material of suitable quality for transmissometer or photo-
graphic data-taking. The flow velocity in the test section will be 5-90 ft/sec
with precision control to any intermediate velocity setting.
Hot and Cold Operation
The facility will be capable of running in either the hot flow or cold
flow mode, with a reasonably convenient method of changing from one mode to the
other. The changeover need not be performed while the facility is in operation.
Exhaust Streams
Any gaseous exhaust streams from this test facility must meet local,
state, federal, and EPA air pollution and safety regulations.
Controls
cili ty.
cal of
A single control station will be provided for the operation of this fa-
Instrumentation will include all diagnostic and safety equipment typi-
a combustion facility of this size.
Facility Cleanout
Means for accomplishing a rapid cleanout between tests of all flow sur-
faces exposed to the particulate material will be provided.
Laboratory Structure
A separate structure housing the test section, the facility controls, and
the various equipment being used or undergoing tests will be specified.
The above. items are the formal facility requirements. However, other re-
quirements have become apparent during the design activity. The first and most
apparent of these is the floor space allotment in the Durham facility. Figurel
shows the space available for this facility. Ceiling height is nominally 20
feet, with numerous air conditioning and utility ducts hanging from the ceiling.
Another requirement is the insulation of nearly all tunnel components for safety
reasons. with a test stream temperature of 450°, the possibility of burns and
5
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intense ra~iated heat requires that insulation be installed. Noise and vibra-
tion from the fan may also be a problem. The large capacity fan required to
move nearly 17,000 scfm of air or test gas will result in very high noise levels
in the vicinity of the fan, and a potential source of vibration for the support-
ing structure. Finally, ready access should be provided to the test section for
rapid modification of probe or model setups.
2.2
BASIC FEATURES OF A TYPICAL AERODYNAMIC TEST FACILITY
An aerodynamic test facility with the test section and test gas velocity
requirements described earlier is generally termed a wind tunnel. The major
difference between this facility and a typical low speed wind tunnel is the re-
quirement for a combustion products test stream and the inclusion of particulate
material. Thus, it is useful at this point to review the basic features of typ-
ical low speed wind tunnels for consideration in the present facility design.
The two types of low speed tunnels in common use are the open circuit
type and the single return closed circuit type, shown schematically in Figure 2.
The open circuit tunnel is cheaper to build, however the closed circuit design
offers better control over the test gas stream and the laboratory noise level.
In the open circuit design, the blower or fan may be located downstream of the
test section (as shown), or upstream at the air intake. Air proceeds through
the intake, which is usually filtered, into the settling chamber. The purpose
of the settling chamber is to allow turbulent eddies which may have originated
in the fan or room air to settle out. To speed up this process, the settling
chamber generally contains honeycomb and fine mesh screens. Air then proceeds
through the contraction section, which accelerates the flow to the test section
velocity through a change in cross-sectional area. There are at least two pur-
poses for the contraction: lower pressure drop through the tunnel circuit, and
lower turbulence in the test section. Since pressure drop is proportional to
the square of velocity, the lower velocity in the intake and settling chamber
results in significant power consumption economies. In addition, it can be
shownl that the ratio of turbulent fluctuation to mean velocity ~u'2/U varies
approximately as l/n2 across a contraction section of area ratio n. Thus, the
relative turbulence level is significantly reduced by a contraction of area ra-
tio on the order of 10.
The size of a tunnel test section, plus the contraction ratio, determines
the size of the entire test facility. The test section size is selected to ac-
commodate any models, probes, or instruments which are to be tested with a mini-
mum of wall interference. Test section length is generally several diameters.
The walls of the test section are usually flat, and incorporate windows,
lights, and access hatches to install and observe the models.
7
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Flow proceeds out of the test section through a diffuser. The diffuser
is a gently diverging duct of approximately 5° included equivalent cone angle,
however the cross section need not be round. For open circuit tunnels, the fan
is generally mounted at a position in the diffuser section where cross-sectional
area is about twice that of the test section. The purpose of the diffuser is to
slow the flow down before exhausting it to the room, thereby minimizing both
pressure drop in the tunnel and disturbance to the room air.
The design of a closed circuit tunnel is similar to the open circuit type.
A settling chamber is provided which is generally one-half to two diameters in
length. The contraction is extremely important in a closed circuit design as it
allows low velocities in a major portion of the tunnel return circuit. The test
section in a closed circuit tunnel often contains "breather" slots at the down-
stream end. These slots provide a controlled mass flow out of the tunnel as
the recirculating air heats up, allow controlled inflow to make up for leaks else-
where in the circuit, and keep the test section static pressure near atmospheric
pressure. The return circuit is generally arranged to include four 90° turns, with
turning vanes in each corner. The test stream is usually diffused as much as
possible before the first turn in order to avoid large losses due to high velo-
.city in the turn. Axial fans are most common for both open and closed circuit
tunnels, however a centrifugal blower located at a corner in a closed circuit
. . t 2
design or at either end of an open circuit design is com1ng 1n 0 common usage.
2.3
OTHER EXISTING PARTICU~\TE WIND TUNNELS
The existing particulate wind tunnels can be classified as open circuit
collector test facilities, open circuit aerodynamic test facilities, and closed
circuit aerodynamic test facilities. The collector test facilities are designed
to provide a controlled gas stream including particles for some type of collec-
tor, such as a scrubber. While flow velocity and particle distriLution are con-
trolled, no basic research on the gas stream itself is generally performed.
Therefore high quality aerodynamic performance of this type of facility is not
required for its successful operation. JOhnson, et al.3 describe a small scrub-
ber test facility which provided a test stream 6 inches in diameter at velocities
up to 65 ft/sec. Dust loadings of up to 1.0 grains/ft3 were created with a vi-
brating hopper and a scraper-turntable combination dust generator. A Stairmand
disc in the 6-inch supply duct resulted in a uniformly distributed dust loading
at the scrubber inlet. A much larger example of this type of facility has been
constructed at the Combustion Engineering Kreisinger Deyelopment Laboratory,4
and was the object of a visit under this contract. The facility test gas is
generated by an oil-fuel fired steam boiler whose sole purpose is to supply
typical powerplant stack gas. The scrubber test facility handles 12,500
9
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cfm (at 125°F). Fly ash injection is accomplished at a corner in the rectangu-
lar cross section boiler exhaust duct just upstream of a contraction, as shown
in the figure below.
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RE~UL.TI~ PARnc.u::.
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Figure 3.
Combustion Engineering Particle Injection Technique.
Fly ash particles are metered and mixed with a carrier gas in conventional
vibrating hopper bulk material handling equipment. The gas-particle mixture is
directed through a 6-inch diameter pipe and a i-inch diameter nozzle into the
hot gas stream. Splitter vanes are included in the nozzle to direct the parti-
cles in a slightly rad~al direction. Final dust concentration in the duct var-
ies approximately from 2 to 5.grains/ft3 across the duct. More nozzles would be
required to improve this concentration variation. Injection velocity is about
twice the local duct velocity, although this particular variable has not been
optimized. Carrier gas loading in the injection system is approximately 200
grains-dust/ft3 gas.
The most common type of particulate aerodynamic test facility is the
open circuit type. There are numerous examples of these in the literature, and
only a few are discussed here, Trezak and so05 worked with a small diameter
(0.75 inches), blowdown-type test facility. Particles were fed into the bell-
mouth inlet of the 20-foot long test section which exhausted into a large volume
evacuated tank system. The effects of acceleration on the two phase, high speed
flow were studied. Byers and Calvert6 studied thermopheresis effects on wall
deposition using a cooled, 2-inch diameter copper tube test section. Their test
gas and dust were thoroughly mixed in a baffled mixing chamber, then heated to
temperatures up to 10000F before passing into the test section. Volume flow
10
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rates up to 25 scfm were used. Work is currently underway at Lockheed Georgia7
on a 6-inch diameter, 9-foot long test duct for use in a laser holograph flow
measurement system. Gas is drawn into the duct through a 37:1 contraction ra-
tio bellmouth and through five turbulence screens~ Particles in a carrier gas
are injected at the entrance to the bellmouth from a single, I-inch diameter
tube with a 1/16-inch slot along its axis. The injection tube extends across
the entire bellmouth, resulting in a "sheet" of particles being injected into
the flow. The actions of the screens and the contraction result in a reasonably
uniform mixing of particles at the test section. Flow velocities up to 60 ft/
sec are obtained using a radial blade centrifugal fan located at the downstream
end of the test sectio~.
Open circuit facilities with larger test sections have been built, but
particles are generally not uniformly distributed in the flow. Lieberman8 re-
ports experiments conducted in a 4-foot square test section, 25 feet long. Air
velocities up to 14 ft/sec were created by a downstream fan. A particle stream
from a Wright dust feeder was injected isokinetically at the center of the test
section. The apparatus was used to study the relative stabilities of charged
and uncharged aerosols composed of l-8~ dust particles.
An open loop tunnel at Battelle's Richland, Washington plant, designed
for particle deposition studies,9 is shown schematically in Figure 4. A per-
sonal visit to Battelle-Northwest was made to examine this facility in detail.
It is an open loop, constant speed tunnel, with test section velocities of ap-
proximately 44 feet per second. This velocity can be changed by changing fan-
motor pulleys. The tunnel is of the drawdown type using a centrifugal blower
at the downstream end. The tunnel cross-section is square, with a 2-foot by
2-foot test section and a 6-foot by 6-foot stilling chamber, giving a 9:1 con-
traction ratio.
Among the good features of this tunnel are its numerous windows and white-
painted internal surfaces. The large plexiglass windows provide good observation
of the test surfaces, and are removable to give ready access for tunnel cleanout.
The white painted surfaces combined with numerous windows make internal tunnel
lighting unnecessary for observation purposes. Tunnel cleanout is accomplished
by manual scrubbing with water and cleanser.
Research conducted with this tunnel involves studies of particle diffu-
sion toward and deposition rates on various kinds of surface materials installed
on one wall (the lower horizontal surface) of the tunnel test section. The
particle injection technique is therefore designed to provide only this single
wall with a "uniform" dust stream. particles in a carrier gas are injected just
upstream of the contraction through a 2-inch diameter pipe, as shown in Figure 5.
11
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The injection pipe is well below the tunnel centerline, therefore the particles
are contained in a relatively thin layer near the surface. Particles are fil-
tered out of the flow just before it is exhausted to the room. High efficiency
filters at both the inlet and exhaust ends of the tunnel (l-inch H20 pressure
drop at each filter unit at 44 ft/sec test section velocity) are used. Parti-
cle injection is controlled by a commerically-available spinning disk atomizer
which forms droplets of uranine solution, which then evaporate to form a salt
particle. Air is used as a carrier gas to inject these salt particles into the
tunnel.
Snyder and LumleylO report development of a large wind tunnel test fa-
cility designed to study particle velocity autocorrelation functions in grid-
generated turbulence. A centrifugal blower at the upstream end of the flow
system supplies filtered air to a plenum chamber. The air then passes through
a contraction to a test section whose dimensions are nominally 16" x 16" x 6'.
One wall of the test section is adjustable to allow pressure gradient control.
Also, the test section is oriented vertically to align the particle mean veloc-
ity vector with the gravity vector. Discrete particles are injected through a
single 3/16-inch diameter tube at isokinetic speeds. The particle injection
stream was found to have no effect on the tunnel turbulence level at distances
greater than 41 inches downstream of the injection point.
A final example of an open circuit particle tunnel to be discussed here
is Habibi'sll automotive particulate sampling system. The system, shown sche-
matically in Figure 6, consists of a filtered inlet, a 22-inch diameter by 40-
foot long test section, and an 1150 cfm blower at the downstream end. Automo-
tive exhaust containing particulate material is introduced at the upstream end
of the test section. In order to promote mixing between the exhaust gas and
the main air stream, the automotive exhaust is introduced at the center of a
large orifice plate. The rapid spreading of streamlines downstream of this
orifice plate was found to enhance the gas and particulate mixing ratio consi-
derably.
Closed circuit particulate aerodynamic test facilities are understand-
ably less popular since recirculation of the particulate material alters its
character through agglomeration,deposition, and re-entrainment. Nevertheless,
there are a few examples of closed loop systems that will be discussed briefly
here. Bulba and Silverman12 experimented with a stack dust simulation facility
which consisted of a 7.7-inch diameter duct flow loop. The loop was an oval
shape with outside dimensions of 4 feet by 16 feet. A small contraction was
built in at the particle injection point to enhance aerosol mixing rates.
No turning vanes, screens, or large contractions were contained in the circuit.
14
-------
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Gas velocities at the test section of 0.16 to 41.0 ft/sec were induced by a sub-
sonic, compressed air ejector. Soo and Trezak13 worked with a similar flow loop
which used a centrifugal blower as an integral part of the loop. The test sec-
tion was 5 inches in diameter and 38 feet long. Velocities of.130 ft/sec were
possible with this apparatus, which was used to investigate fully developed tur-
bulent flows with very large particulate mass loadings. The particulate mate-
rial was placed in the flow loop before each test, and was cleaned out by rout-
ing the flow through a cyclone at the conclusion of a run.
The final example of a closed loop system to be discussed here is the
McCrone Associates test facility14 in Chicago. The facility was examined in
detail during a visit to Walter C. McCrone Associates, Inc. under the contract.
The tunnel is an oval-shaped flow loop with outside dimensions of approxi-
mately 30' x 10'. The ductwork is primarily 2'0" diameter round galvanized
sheet metal duct, however a 2'0" x 2'0" square cross-section test section can
be inserted. An axial fan is built into the flow circuit, as is a 250,000
Btu/hr heater. The heater combined with fiberglass insulation on the outside
surface of the duct allows the test gas to reach temperatures of up to 400°F.
Steady state temperature of the flow with the heater shut off but at the maximum
velocity of 100 ft/sec is approximately 200°F. This high temperature is caused
by the dissipation of fan power (20 HP) in the flow circuit. Particulate mate-
rial is placed in the duct at the beginning of a run and circulates throughout
the loop. This particulate material is cleaned out by dumping approximately
20 gallons of water into the duct with the fan in operation.
The above survey of particulate test facilities and wind tunnels is admit-
tedly incomplete in that it does not include any of the meteorological research
tunnels in existence. It does provide, in part, the basis for the necessary
tradeoff considerations for the facility of interest here. These tradeoffs are
presented in the following section.
2.4
ENGINEERING TRADEOFFS FOR THIS FACILITY
There are a number of preliminary tradeoffs and engineering decisions
that must be made before specific wind tunnel component design activity can get
underway. Several of these tradeoffs and decisions are discussed below.
2.4.1
~n-Circuit Vers~s Closed Circuit Tunnel
In Section 2.2, the basic features of open and closed circuit wind tun-
nels were disc'lssed. It was pointed out that the advantages of a closed circuit
were better control over the test stream and a much lower noise level. On the
other hand, a closed ci~cuit tunnel is more expensive to build and requires much
more floor space. In choosing the best approach for the current facility design,
these facts must be weighed in light of the technical requirements of the tunnel.
16
-------
The first technical consideration is provision of a known particulate
loading in the stream. Discussions with McCrone Associates personnel, EPA per-
sonnel, and review of the Bulba and Silverman work12 have indicated that a
closed circuit particulate flow would not be satisfactory due to agglomeration,
wall deposition, and particle fracture. In addition, deposition on and erosion
of fan blades is a consideration. These undesirable processes in a recirculating
particulate flow will result iri an unknown particle size and concentration.
Therefore at least the particulate flow must be open circuit.
Another technical requirement is the need for a heated combustion pro-
ducts flow. Open circuit operation with combust~on products would involve gen-
eration of the test gas through combustion, then cooling it to the desired test
section temperature. A schematic diagram of the flow path is shown in Figure 7.
To estimate the size of the components in this system, a 2-foot diameter test
section was assumed. Also assuming that all the test gas comes from the burner,
and that a 20:1 A/F ratio is satisfactory, the fuel flow rate requirements are
shown in Figure 8. The maximum fuel flow rate of nearly 400 gallons/hour (assum-
ing fuel oil is used) is large, but not unmanageable, assuming storage space for
fuel tanks is available. A more severe limitation is the coolant required to
bring the temperature of these combustion products down to the desired test sec-
tion temperature. Assuming a combustion temperature of 3500°F and assuming that
water is the coolant with its entire heat of vaporization available (6H t ~
wa er
1000 Btu/lb), the flow rate of cooling water was calculated. The res11lts are
shown in Figure 9. The maximum coolant flow rate of 120 gallons/minute is large
enough that recirculation of the water coolant would be required for economy of
operation. However, the associated heat exchanger and control system would be
unacceptable expensive for a test facility of this size. Therefore, operation
with a hot gas in an open circuit mode does not seem feasible due to its com-
plexity and resulting high cost. Simil~r arguments can be made against opera-
tion in an open circuit mode in cold flow, due to the very large and expensive
air conditioning system. Thus, it is concluded that closed circuit operation
of the test gas, and open circuit operation of the particulate material is the
most desirable system. This can be accomplished by constructing an ordinary
closed circuit tunnel, injecting particles ahead of the test section, and col-
lecting the particles after they pass through the test section. A schematic
diagram of this type of flow circuit is shown in Figure 10.
2.4.2
Horizontal Versus Vertical Test Section
The study of aerosols may involve the consideration of body forces
particles themselves. For large particles, often the gravitational force
nat~s ,1na the particles tend to settle as they flow along. The settling
~ the
domi-
17
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direction can be made coincident with the flow direction, therefore cancelling
or masking undesirable flow stratification problems in basic research situations
by working in a vertical test section. However other factors point to the hori-
zontal test section as being more practical. In this section, the various con-
siderations are discussed and a conclusion is reached regarding horizontal ver-
sus vertical test sections.
The length of the test section in questi0n is 20 to 40 feet. Residence
time of the gas at the minimum velocity of 5 ft/sec would be 4 to 8 seconds.
The sink rate of spherical particles in air can be estimated by the Stokes
relation
2 r2
u = 9 ~ (pp - Pm)
where
r
=
particle radius
~
viscosity
density of the particle
Pp =
Pm =
density of the medium
Flyash is typical of the particles of interest for this test facility, with a
. 1 15
10 micron particle being typlca. Figure 11 shows the sink rate as a func-
tion of particle size for various specific gravity values. A typical flyash
specific gravity is 1.6 (Reference 16). The test section temperature effect
is also shown on the graph. Settling of the particles is clearly not a problem
for 1 micron particles, however it may become a problem for 20 micron particles.
This settling of particles can be easily calculated; however, the use of a verti-
cal test section appears to be an advantage for basic studies with the larger
particles of interest. It would also be of interest when the vertical stack
situation is being duplicated.
The arguments against a vertical test section are largely nontechnical.
Perhaps the most technical argument is that flow in horizontal ducts is of prac-
tical interest, therefore research into particle deposition and flow in horizon-
tal or inclined breechings may be desirable. The major argument against the
vertical test section is its lack of flexibility. This research facility will
be designed to allow rapid, easy modification of the test section and other
major components in order to accommodate various types of research programs.
Such modifications would be complicated immensely if the test sectiun were ver-
tical. Similar comments apply to installation of test models, instrumentation,
22
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23
-------
and test observation, all of which would require frequent access to numerous
stations along the test section length. The cost of research would be doubled
or tripled due to the increased facility setup, running, and shutdown time. Dust
cleanout would also be complicated by the need to wash down the lengthy vertical
duct.
Final arguments against the vertical section involve initial cost, Brac-
ing and other structural considerations will add to this cost significantly. An
extensive scaffolding and platform system must be an integral part of a vertical
duct, with means provided to install, heavy equipment at numerous axial stations.
In addition, major structural and architectural considerations are involved if
more than about 10 feet of vertical test section was required, since the ceiling
height is only 20 feet.
In conclusion, both the vertical and horizontal test sections are of in-
terest for duplication of powerplant conditions. However, cost, convenience,
and flexibility considerations indicate that a horizontal test section is a more
practical selection, and a brief technical analysis indicates that technical
objectives will not be seriously compromised for the particle size range of
interest. Thus, a horizontal test section design is recommended for this test
facility.
2.4.3
Dust Injection Technique
The wind tunnel design specification calls for a test section dust load-
ing of 0.1-5.0 grains/ft3 with an unspecified dust. Close control over the
actual dust loading and the dust size distribution at the test section is de-
sired. In order to allow the dust loading and size distribution to be an "in-
dependent" variable, an open circuit dust injection and collection system is
called for.
As shown in Figure 12, the dust handling system includes three major com-
ponents: the dust generator and metering apparatus, the dust injection apparatus,
and the dust collector. Since the dust generator design is highly dependent on
the injection technique, dust injection will be discussed first. Dust collec-
tion can most economically be accomplished for the high efficiencies required
with a baghouse collector. Since the baghouse approach does not offer any un-
usual design problems, no tradeoffs will be discussed for dust collection.
a.
Material Handling Considerations
help
Some basic engineering estimate of the flow rates, volumes, etc. will
to clarify the requirements of the dust injection apparatus. Assuming a
diameter test section, the maximum tunnel volume flow rate
2'0"
24
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10
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27
-------
In a typical operating injection system, the number of jets and the jet diameter
would be fixed, or at least it would be inconvenient to change them. When the
tunnel dust loading is to be changed, the remaining injection system variables
are carrier gas loading and jet velocity. These variables should be indepen-
dently controlled in order to provide the desired flexibility in the dust injec-
tion system. As an example of the range of carrier gas dust loadings required,
Figure 14 presents results calculated from Equation (3) assuming ten 1/4-inch
diameter jets injecting dust at 1000 ft/sec. This high injection velocity cor-
responds approximately to a sonic injection condition, and would enhance the
dust mixing rate due to the large velocity difference between the jet and the
test gas stream. The desirability of injecting at high velocity is discussed
in the next subsection.
b.
Injection Velocity Considerations
The contract calls for a tunnel design which provides a "low" free-
stream turbulence level in the test section core flow. The term "low turbulenc~'
will be taken to mean low with respect to typical powerplant stack flows. Tur-
bulence in a stack can be expected to be on the order of fully developed pipe
flow turbulence, or even larger if obstructions, wind gusts, duct transition
sections, rotating air pre-heaters, etc. are encountered by the flow. Thus,
a 5 percent turbulence level, i.e.
u' u' '
x r ~ 0.05*
- '" - '" '"
U U U
max max max
could be expected in a fully developed pipe flowl? or stack flow. Turbulence
levels are actually higher near the wall and lower near the center of a pipe,
however 5 percent is a good average value. The wind tunnel should therefore
have a turbulence level of 0.5 percent or less, if possible. This is not a
particularly low turbulence level for aerodynamic work, where tunnels operating
. 18 19
at a test sect10n turbulence level of 0.1 percent are not uncommon. '
The requirement of injecting dust into the wind tunnel and mixing this
dust with the primary tunnel flow directly conflicts with the need for low tur-
bulence. Good mixing between two flowing streams generally requires high levels
of turbulence in the mixing zone. This method could, in fact, be used
*The notation u' actually refers to VU'2 , the root mean square velocity fluc-
tuation value.
28
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LoADING,
29
-------
in this tunnel also, if dust was not the medium to be mixed. However, the re-
moval of tunnel turbulence by conventional screens and honeycombs once the dust
has been introduced is unsatisfactory in this tunnel, since the dust would col-
lect, agglomerate, break up, and generally be altered in character by the tur-
bulence damping devices.* Therefore the optimum point for injection of dust
would be downstream of any flow obstructions, and preferably with as little
generation of "new" turbulence as possible.
Generation of turbulence by the shearing action between a jet and its
surrounding medium can be minimized by matching the jet velocity to the local
medium velocity, known as isokinetic injection. It will be assumed that the
dust velocity equals the injection jet velocity. With this approach the mixing
rate is dominated by turbulence already in the mixing streams, either from ini-
tial boundary layers and wakes from the injection tubes, etc., or "freestream"
turbulence. Turbulence in the test section from the injection process can be
minimized by injecting upstream of the contraction. Isokinetic injection would
then require that Uj = Ut/CR where CR is the contraction ratio. Referring to
Equa tion (3 )
LD2N
G = 12.13 ~
(4 )
With this approach, the turn down ratio requirement on the carrier gas loading
rate is greatly reduced. Operation of the dust feeder in this mode would re-
quire setting the carrier gas feed rate such that the injection velocity matches
the settling chamber velocity, then setting the dust feed rates to get the neces-
sary carrier gas dust loading. Table I indicates the carrier gas loadings neces-
sary for ten injection nozzles and a contraction ratio of nine. It is clear that
I-inch diameter or larger nozzles will be needed for injection in the settling
chamber.
The turbulence generated by the injection of dust at the test section
velocity is expected to consist almost entirely of wake turbulence from the in-
jection tubes. The mean square turbulent intensity downstream of a cylinder
. d f h . 20
in crossflow can be estlmate rom t e expresslon
u
0.27 ~cII
(5)
u'
--
*
This opinion nas been confirmed through discussions with Lockheed/Georgia
personnel, 7 who have tried this approach. It is possible to vibrate the screens
and honeycomb, however, and minimize the particle deposition. This approach
could be used if sufficient mixing is not obtained with the proposed approach.
30
-------
TABLE 1
EFFECT OF NOZZLE SIZE ON CARRIER GAS DUST LOADING
Test Section Nozzle Carrier Gas
Dust Loading Diameter Dust Loading
(grains/ft 3 ) (inches) (lb/ft ) 3
5.0 0.25 5.84
1.0 I 1.190
0.1 0.119
5.0 1.0 0.370
1.0 I 0.0741
0.1 0.00741
5.0 2.0 0.0926
1.0 I 0.0186
0.1 0.00186
Since the wake is generated at the stilling chamber velocity, the relative tur-
bulence intensity is immediately altered by the contraction such that
U
o . 27 /CxYl
CR
(6)
u'
where
CR = contraction ratio
Figure 15 illustrates the resulting turbulence intensities for various distances
along the tunnel, assuming a contraction ratio of nine. It is apparent that,
according to this approximate analysis at least, the turbulence level will be
satisfactory within a few feet of the injection apparatus. Since the contrac-
tion region is several feet long, a large portion of the test section is ex-
pected to have a suitably low turbulence level.
The remaining question of a general nature is the definition of the axial
distance required for total mixing of the jets. Centerline concentrations must
decay from an initial maximum 3500 grains/ft3 down to 1-5 grains/ft3. This is
a decrease of three orders of magnitude in concentration, which is far beyond
the regime described in currently available jet mixing literature. The avail-
able literature does indicate that a decrease in concentration of two orders of
magnitude can be expected in the first 20-50 jet diameters. Thus, it can be
speculated that another order of magnitude decay might be expected by about 200
31
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32
-------
jet diameters. This length would not be unreasonable if numerous small jets
were used, and if sufficient test section length is available. However, experi-
mentation with the actual injector configurations (preferably on a laboratory
bench scale apparatus) will be necessary before the required mixing lengths can
be further defined.
2.4.4
Dust Generation and Metering
The various techniques for dust metering and aerosol generation include
the following:
.
Fluidized bed
.
Vibrating hopper with adjustable outlet orifice
.
Screw feeder
.
Vaned impeller
.
Slotted discs, cylinders
.
Belts or discs with scrapers
In this list, only the fluidized bed technique results directly in an
aerosol. The other techniques are a means for metering dust into an aerosol
generator, e.g., an aspirator.
A fluidized bed aerosol generator is shown in Figure 16. The dust flow
rate is regulated by the fluidizing gas flow, while the condition for isokinetic
injection is satisfied by diluting the aerosol to obtain the required nozzle
velocity. The principle advantage of this type of generator is that mostly sep-
arated particles find their way to the outlet with large agglomerates remaining
behind. More sophisticated versions of the fluidized bed using metal balls to
break up agglomerates have also been developed for special applications.
A vibrating hopper with an adjustable outlet orifice is shown in Figure
17. With this arrangement, dust is shaken into an aspirator where it is aero-
solized. The dust falls through a regulated orifice onto a balance, generating
a feedback signal to the orifice controller. By using feedback, the feed rate
can be controlled precisely.
Screws and vaned impellers (Figures 18,19) are volumetric metering de-
vices. Thus, the rotational speed determines the delivery rate. In the case
of a screw feeder, the delivery is continuous, so. that one could expect to vary
the delivery rate over a wide range. The impeller, however, provides a delivery
which is basically intermittent - a limitation on the lower delivery rates. Feed-
back regulation of rotational speed could be used to overcome variations in de-
livery rate caused, for example, by a change in dust characteristics affecting
the filling of screw or impeller cavities.
33
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36
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Another metering method involves shaking a ribbon of dust onto a belt
or disc (Figure 20,21). Belt feeders for particulate metering sometimes use
feedback (Figure 20) where the weight of material on the belt regulates belt
speed. With the disc metering device, the scraper position determines the rib-
bon cross-section and rotational speed regulates the delivery rate.
All of the previously described methods are potentially applicable to
the particulate wind tunnel. All require some developmental effort, fabrica-
tion of special components, and all make use of purchased standard components.
The various methods can be ranked by defining a figure of merit as in Table 3
As indicated by the table, the two methods most practical to pursue at the pres-
ent time are first, the vibrating hopper with orifice regulation, and second, a
screw feeder also with some form of feedback regulator.
One reason why the vibrating hopper and screw feeder rate so high is be-
cause they are commercially available with the necessary capacities. For example,
the Vibra Screw Corporation manufactures a vibrating hopper (Live Bottom Bin)
and screw feeder (Vibra Screw Live Bin Feeder).
The screw feeder has a 3 cubic foot vibrating hopper.
this small bin would be fed by the larger 50 cubic foot bin.
For our purposes,
work.
The chances are high that the large vibrating bin with regulation will
If not, the screw feeder can be added. The capacity of the basic screw
feeder can be modified by changing screw sizes, as shown in Table 2.
TABLE 2
FEED RATES WITH VARIOUS SCREW SIZES
Screw Size Pounds
(in) per Hour
1/4 0.15/1.5
3/8 0.42/4.2
1/2 0.98/9.8
5/8 2.1/21.0
3/4 4.0/40.0
1 11.4/114.0
1-1/2 35.2/352.0
2 92/920
38
-------
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HI~H
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A\e
---.
A~L
OUT
FIL:::,LJrze= 20, F3EL-r FEEDEIZ
A-~4~
39
-------
VI~eATI~
Ht:>P~~
i
II'
i!
AEU/~L
----- o.JT
'~
~
A?PIIZATo(2
I:
eXL.es~
Du?!
FiC::,U~ 21. ~OTATI NC::, D'~
F'EE-DEJZ.
A- ~., ~ )
40
-------
TABLE 3
MERITS OF VARIOUS DUST FEEDING METHODS
nl n2 n3 n4 nS N
Technique Develop- Probability Flow Flow Component Figure
ment of of Rank
Effort Success Constancy Range Cost Merit
Fluidized Bed 9 0.6 10 5 5 0.7 4
Vibrating Hopper 1 0.9 9 10 1 81.0 1
Screw Feeder 2 0.9 9 10 2 20.3 2
Vaned Impeller 5 0.5 2 3 2 0.3 6
Slotted Discs,
Cylinders 10 0.5 5 3 2 0.4 5
Belts, Discs
with Scraper 5 0.5 8 3 2 1.2 3
~
I-'
Definitions:
1
Development effort, nl' rating from 0 to 10 where the lowest numbers represent the
least effort
Probability of success, n~, rating from 0 to 1, based on predicability, knowledge of
previous successes with s1milar equipment
Flow constancy, n3' rating from 0 to 10, with smoothest delivery and constancy rated
highest.
2
3
4
Flow range, n4' rating from 0 to 10, with highest number representing greatest range
capability
Component cost, nS'
Figure of Merit, N,
5
6
rating from 0 to 10, rating increases with cost
previously described ratings combined so that
n2n3n4
N =
nlnS
The highest possible value for N is 100.
-------
It is therefore clear that the large turn-down ratio necessary in this dust
feeder can be attained through screw size change. The manufacturer claims that
"minute-to-minute deviations from any given set rate are generally less than 1
or 2 percent - from hopper full to hopper empty." The screw speed control can
be manual, electrical or pneumatic, the latter two being adaptable to a closed-
loop feed control system.
Using either a vibrating bin alone, or in conjunction with i screw feede~
the metered dust would be transformed into an aerosol by an aspirator (Figure 18)
The aerosol would then be divided up into multiple streams for the multi-jet in-
jection system described earlier. Thus, based upon the discussion presented
above and discussions with others working in the field with dust feeders, it is
recommended that the initial dust feeding system be composed of a simple live
bin hopper feeding dust to an aspirator. Initial experiments with this system
will indicate whether or not the necessary type of control is possible with a
simple slide valve in the bin. If this control is adequate, the operation of
the slide valve can be automated with a feedback system. If not, a screw-feeder
can be added, with a feedback control system if the combination is successful.
This step-by-step, modular approach to the feeder system design is deemed most
appropriate at this time, since an experimental program is mandatory before com-
mitting to a final design concept.
2.4.5
Test Section Diameter and Length
The basic considerations for selection of a test section diameter and
length are:
8 What size of models, probes, or instrumen.ts will be tested?
8 Wh.:..t types of tests will be run?
8 What length is necessary for mixing of the dust?
8 What interference might be caused by wall b..:mndary layers?
Wall boundary layer thickness can be calculated by standard methods; results
for two velocities are shown in Figure 22. The lowest velocities give the thick-
est boundary layers. Assuming that 20 feet of test section is needed for dust
mixing and that a 6-inch diameter low turbule~ce core flow is desired, the test
section must be at least 18 inches in diameter. Consideration of typical probe,
instrumentation, and model sizes indicates that a 2-foot diameter would be much
more convenient. Also, there is some interest in having the capability to test
at a minimum of 10 diameters (upstream or downstream) from any change in flow
directjon. Therefore, the optimum test section size appears to be a 2-foot diam-
eter section approximately 40 feet in length.
This length provides the additional
42
-------
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~
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L 11
-
,
~ 10
Z
\L
.\J
-:r: 8
~
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~ {p
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w
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aD
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~4
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LEN~Tt1 - FEET
~OUND~rzY LAYE{2 C9J20Wn4 IN THE-
IE-?T ?E~T'ON
FI~UJ2E 22.
. -
-------
advantage of a thick region of wall boundary layer flow near the downstream
end, allowing simultaneous testing in both low and high turbulence flow. Since
the required mixing length is unknown, a 40-foot test section is also strongly
recommended as a conservative solution to the dust mixing problem.
2.4.6
Test Gas Heating
There are several possible ways to heat the test gas to temperatures up
to 450°F. Open circuit operation using direct combustion as an energy source
has been eliminated earlier due to complex control and heat exchange problems.
With closed circuit operation, other possibilities are illustrated schematically
in Figure 23. ThEse systems include
.
Direct gas-to-gas heat exchanger
.
Indirect, condensate-to-gas heat exchanger
.
Electric resistance heater
.
Burner source with bypass and bleed system
The advantages and disadvantages of each of these systems are described in Table
4. Based on informatLon presented in this table and experience with similar sys-
tems at Aerotherm, either the indirect heat exchanger or the resistance heater
appears to be a possible solution for this test facility design. Cost and avail-
ability of these systems indicate, however, that the electric resistance heater
is the most logical choice.
A second consideration in the heater selectiQn is that a re-heater will
be needed for cold (air-conditioned) operation as well. The heater control
should allow precise operation at low power settings for use in an air-condi-
tioner capacity.
2.4.7
Air Conditioning
A brief study of the merits of running the cold flow tests open circuit
has indicated that there is little, if any, advantage in this approach. Large
savings in the complexity, size, and cost of the air conditioning system can be
realized with closed circuit air flow. Since hot flow testing requires the
closed circuit ductwork, no additional construction is required. Therefore,
the cold flow testing should be carried out in a closed circuit mode as well.
The desired conditions in the test gas during cold flow operation are
temperature:
70°-100°F
relative humidity:
10-80%
44
-------
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U1
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e~T
£..Le-.....,J IJP
~.I-
I
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II
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rl --
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-------
TABLE 4
HEP.TFR OPTIONS
~
'"
I
I
i Configurations Advantages Disadvantages
\
i
I Direct, gas-to-gas KO secondary working fl uid required. Excessive heat transfer surface material
heat exchanger economical to operate. Low maintenance. temperature or large amount of transfer
I Commercially available. surface required.
Large, expensive secondary system hardware
necessary to supply hot gas side.
Difficult to control
J"'.direct, condensation to I Compact exchanger design. Large trans- Two expensive secondary systems (liquid and
gas heat exchanger fer rates. Ccmnercially available. Good burner) required to supply hot side.
control characteristics over limi te.d Secondary fluid useful over limi ted tempe r a-
temperature range. ture range. Secondary fluids other than
water may be expensive.
Electrical resistance Hinimum accessory equipment required. Electrical insulation required. Expensive
heater Good control characteristics. High temp- control equipment necessary at higher
eratures possible. Comercially available. power.
Little or no maintenance.
Burner source with bypass Small amount of secondary system hard- Parallel stream mixing required to obtain
i and bleed system for \oJare required. Low pressure drop correct bulk temperature. Difficult control.
energy makeup through heater secticn. \'1ide temperature Not commercially available - development
ranGe possible. Low maintenance. necessary.
-------
1'--
Any combination of temperature and humidity in this range should be attainable.
The large range of conditions is seen more clearly on a psychrometric chart, as
shown in Figure 24. The conditioning system must provide dew points as low as
15°F and as high as 92°F. In addition, the air conditioning system must be de-
sig~ed for both startup or change in set-point operation, and steady state opera-
tion. During startup or change in set-point, heating or cooling and humidifica-
tion or dehumidification may be required depending on the initial gas condition.
During steady state operation, temperature conditioning will be primarily cool-
ing, since viscous dissipation of the test gas kinetic energy is expected to re-
sult in a steady state temperature of 150o-200°F at high speeds. A very small
amount of humidification will also be needed, as explained below.
A typical air conditioning system for this application is illustrated
schematically in Figure 25. Humidification and heating are accomplished rather
simply with steam nozzles and a small electric heater, respectively. The prob-
lems arise in the cooling coil and dehumidifying system. Cooling is most com-
monly accomplished in either of two Ways:
1. Direct expansion refrigeration - A liquid refrigerant is expanded or
throttled to a low temperature and is passed through the cooling coils. Energy
transferred from the warmer test gas evaporates the refrigerant. It is then
compressed, condensed, and is ready to circulate again through the cooling coils.
Numerous refrigerants are available, and the selection is based primarily on the
temperature desired in the refrigerated zone.
2. Indirect refrigeration - In larger systems having many cooling coils,
it is often most convenient to have a central vapor-compression or other type of
refrigeration system which cools water, ammonia, or a low temperature brine at a
central location. The chilled water or brine is then circulated to the various
cooling coils.
The second of these two options is obviously least expensive if chilled
water is already available from a central source. In the Durham Research Facil-
ity, there is a central absorption-type water chiller located in a room adjacent
to that which will, house the wind tunnel. Therefore, the suitability of utiliz-
ing this chilled water has been examined.
The first consideration in using chilled water is that its temperature
is approximately 45°F. Thus, as the test stream passes over the coils, air
immediately adjacent to the coils will attain a temperature of approximately
50°F. This, then, is the lowest dew point temperature that can be provided by
chilled water alone. If all the water (from the air stream) that collects on
the coils at 50°F is separated from the flow, and the air is heated back to 70°F
the relative humidity would be approximately 50 percent. This is far from the
47
-------
?foO I I
WE\" BUL..B AND DE.w POIN T =-\ .]
'2. 40 ,EMPE\2ATuIi2ES -1----- ('I
r-
, ~o r"
()L QL
W - '2"l.()
0 -
co ~
::J lDD
~ I
\J DEw POINT
60
- ~
11
-
\oJ ~ ~v
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~ £10
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0 bD
0 "20 40 eo 100 '1.0
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... ~ L..c;:;1W
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-r'('PICA.L.. ~\rz GONC'\iioNING ~Y~TeM.
,-
-------
,- -
desired low of 10 percent. Further dehumidification would require that water
be removed from the air by some other means. One way to accomplish this is with
a rotating drum, adsorbent dehumidifier, shown schematically in Figure 26. The
rotating drum dehumidifier complicates the conditioning system significantly
since it requires a separate scavenging air supply, heating device, and complex
controls. In addition, the unit can easily be fouled by dust in the gas flow,
and is expensive. A typical dehumidifier cost would be $10,000 for the size re-
quired in this installation, and this cost does not include any controls or in-
stallation. Other dehumidifiers are equally expensive and complex. Thus, the
use of chilled water from a central source does not seem to be an economical
choice if the entire temperature and humidity range must be attained.
The use of direct expansion refrigeration with ammonia or freon allows
lower temperatures on the coils. Assuming an average temperature of 35°F on
the coil and referring to Figure 24, it is seen that a relative humidity of 28
percent can be achieved at 70°F. Lower average coil temperatures result in ice
formation on the coils, which must be removed periodically with a defrost cycle.
This defrost cycle would result in a fluctuating test gas temperature and humid-
ity level unless the run times were held to less than 1 hour, or unless parallel
cooling systems were designed to run in an alternating mode. The 1 hour run
time is considered to be too short, while the parallel systems approach is com-
plex and expensive. Thus, a direct expansion refrigeration system offers only
a small relative humidity advantage over the chilled water approach, and also
needs a dehumidifier to attain the desired 10 percent relative humidity. Other
problems with the direct expansion system arise when it is exposed to the 450°F
flow during a hot run:
.
This temperature is higher than the critical temperature of the re-
frigerant, resulting in unacceptably high pressures in the coils.
.
This temperature may result in "baking" of oil films on ,the coolant
coil interior passages.
Thus, the direct expansion refrigeration approach is not a good choice for this
wind tunnel.
Based upon these considerations, the chilled water approach is recommended
for the initial construction phase of this facility. At a later date, if the 10
percent relative humidity value is still desired, the chilled water coils can be
used in conjunction with a dehumidifier to attain this value. With the chilled
water alone, the relative humidity values listed in Table 5 below will be
attained:
50
-------
'.
r=-
RE AC. TIV AT'ON
"Z.oNE
AD~O(ZPTI oN
cONE
--
MOIST
Al~
--
SCAVEN~IN~
AH2
~ED
COOLIN~
ZONE
ADSoJ;?8ENT
KOTATION
DI12EC.TION
F(~U~E 2~.
eOTAT/N~ DI2U~ ADSO~8ENT
DEHUM'DIF="E~
A-"!.~ '25
51
-------
TABLE 5
RELATIVE HUMIDITY VALUES WITH A CHILLED WATER SYSTEM
Air Temperature Relative Humidity
of %
1==== .".. -
70 50
80 35
90 26
100 18
2.4.8
Charging the Tunnel with Combustion Products
In many cases it will be desirable to employ as a test gas actual combus-
tion products: a realistic mix of N2' C02' and H20. Such a test gas could be
obtained either from bottled gases, appropriately mixed and injected, or from an
actual combustion source. Furthermore, .this test gas could be obtained either
in full-flow amounts, or in much smaller amounts used to pre-charge the tunnel
before test operations begin.
Brief study shows that full-flow systems are not attractive in either
supply system. For bottled gases, an inconvenient number of bottles would be
required, and for a full-flow combustion system, the furnace would be a sizeable
one, roughly equivalent to a 3000 kw generating facility. Consequently, a pre-
charge system is strongly preferred.
Figure 27 illustrates how the pre-charge system would function. At the
start the tunnel is filled with air. Tunnel circulation is established, the
air is heated to avoid condensation, and the combusiton unit exit valve is
opened. The burner is started, feeding combustion products into the tunnel. The
vent system withdraws a like amount. In 1 to 2 hours, the tunnel becomes charged
with >99 percent combustion products. The burner may then be shut down and the
burner exit valve closed. Fine tuning of the exhaust product gas composition
may be accomplished by the introduction of bottled gas, if desired. Thepre-
charged tunnel is then ready for testing.
To fill the tunnel in 1 to 2 hours will require a combustion product ad-
dition at some 10% of the tunnel volume flow rate. A simple analysis based upon
tile schematic diagram of Figure 27 and the assumption that there are only small
pressure changes around the circuit results in the expression
V 0
-L
Vt
x = 1 - e
c
52
-------
L-
.
\lp
veNT OR.
~~~u~T VA\.VE-
~.J~K
~t..Ow
t
\IF'
~16tulZE 2.7. -"'fUNNeL OPt?rz~'iI~ DulZl rJ67
~oMe?tJ~-nON ~~C; PtZ~.. ~~~E' ferZlc:Q
53
-------
where
x = mol fraction of combustion products in the tunnel
c
.
V = volumetric flow rate of combustion products into the tunnel
p
Vt = tunnel volume
8 = time from initiation of filling
Figure 28 shows the required tunnel fill time with the combustion product fill
rate as a parameter. This analysis confirms that a 400-500 scfm burner is ade-
quate. This corresponds to about 2,000,000 Btu/hr, or 15 gal/hr of fuel oil
or 3000 scfh of natural gas
b.
Combustion Products Burner
As discussed above, it is not feasible to supply combustion products
in a continuous flow equal to the test flow. Instead, a relatively small burner
will be used to "charge" the tunnel over a period of time with combustion pro-
duct test gas. A burner of approximately 2,000,000 Btu/hr capacity will result
in an acceptable charging time. A burner of this small size could physically be
located in the tunnel as a duct burner; however, such a burner would experience
unacceptably poor combustion conditions as the tunnel became charged with com-
bustion products. Therefore, the burner must be located to the side of the tun-
nel, mounted in a customary refractory combustion chamber or firebox. Great
care must be taken to optimize the burner selection and firebox design to pro-
duce combustion products as near as possible to those produced by the larger
combustion units being simulated in the tunnel experimentation programs. These
larger burners operate relatively close to stoichiometric conditions (nominally
10% to 20% excess air); most small burners of the type considered here run well
only with more than 50 percent excess air. For flexibility in test operations,
the burner should also be a dual-fuel unit capable of running either on light
distillate fuel oil or on natural gas.
c.
Injection of the Combustion Products into the Tunnel
Additional difficulties arise when one attempts to inject the hot
combustion products into the tunnel. The temperature of the combustion products
*
is expected to be approximately 2800°F as they leave the combustion chamber.
Wind tunnel internal surfaces cannot be allowed to reach these high temperatures,
therefore some action must betaken to prevent this occurrence. Possible alter-
natives are
* .'
A submerged combust1on un1t could give a lower temperature exhaust, however its
price is unacceptably high.
54
-------
40 Ceo Be>
TIME (MINUTE7)
FI~U~e::-2B. MOLE Fg~TION OF ~oMI3LJSTION
Pg,oDL.k:::TS IN TuNNEL ~A? A~ A
FUNC-TIDJ OF TIME' ~ VA~IOL.JS BtJ~NE1Z
pgoDwc.. T~ FLOW ~A. TE$
U1
U1
~
~
o
~
6
~
~
~
it
~
6
~
\lJ
...J
~
~
1.0
,e
{p
.4
Vt - ~QO F,'"
,'2.
00
'20
100
1'20
-------
1.
Transfer energy to another fluid, such as water, in a heat exchanger
before injecting the gas
2.
Protect the internal surfaces of the tunnel from the hot gases with
a refractory material until the point where sufficient mixing with
the main flow has taken place
3.
Same as above, but water-cool the tunnel surfaces
4.
Inject the combustion products such that they do not come into con-
tact with the tunnel walls until sufficient mixing has occurred.
5.
Dilute the combustion products with sufficient tunnel air such that
injection temperatures are acceptable.
These alternatives are illustrated schematically in Figure 29. Alternative 1,
the heat exchanger approach, might involve a small packaged steam boiler with
integral burner. Since hardware costs for an appropriately sized boiler may
run $6000-$8000, and since installation and maintenance would also be expensive,
other alternatives have been examined. Alternative 2, refractory duct lining,
would result in a poor aerodynamic surface, a very heavy duct, and difficult
cleaning problems. The refractory would probably generate undesirable dust par-
ticles, which may interfere with testing, depending on the injection location.
Alternative 3 requires expensive duct fabrication, and expensive auxiliary hard-
ware to pump the water. Alternative 4 is the least expensive but is risky. Forty
to eighty jet diameters are needed to bring the jet centerline temperature down
to 400°F. Thus, unless the jet were very small (-3 inches), running length for
this approach is not available. An obstruction in the flow circuit is also un-
desirable. Alternative 5 requires additional ductwork and an extended combus-
tion chamber, but these modificat~ons are relatively low in cost. Control is
easy, and the air conditioning heat exchanger can be used to keep tunnel tem-
perature down if this becomes a problem. Therefore alternative 5, employing
tunnel bypass gas as a diluent, is recommended as the most practical injection
method.
2.4.9
Fan, Motor, and Speed Control
The considerations in selecting a fan ar'.d the motor that drives it are
discussed here. Also discussed are various methods of achieving speed control
over the desired range.
a.
Fan or Blower
Most large, closed circuit tunnels used for aerodynamic studies have
a specially-designed, low speed axial fan (or fans) located downstream of the
56
-------
t
YI'ItIUIW
COUT
t) I-I~T ~J6fdZ'
2) 1Z&=FAl:r~ 1.1Nlo.I~
6,#..UilZ:
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1/1 \..VT'IiO GeM".
~'T'S -
1"YPICAL
'1"eMPW,A.1"ui'lr
f'l2c>F-1 L.sr
~
4; ~1=WL. INJEC"T"loN
IN
~) /l.~,;nV&Lv ~&D I~.L WA.l..l.
~
~ '"I\JN~
~..~
&7) DILIJTI~ ~F~1i l..JjeC:;TIe>N
FIGURE:. ~'3
COMsu~TION PRODuc..TS IN.JE.~j'ON I&c..HNIQIJ£.S
-------
test section, somewhere in the diffuser portion of the return circuit. This
approach is not appropriate for this tunnel, however, for the following reasons~
.
The fan would be exposed to heavy particulate loadings
.
Axial fans cannot generally supply the large pressure rise which will
be needed to accommodate a baghouse in the flow circuit.
The first objection can be overcome by placing the fan upstream of the test sec-
tion, and upstream of the particle injection apparatus. The second objection
can be resolved by using a centrifugal blower. The centrifugal blower located
upstream of the test section in both open and closed circuit wind tunnels has
just recently gained acceptance in the wind tunnel design community.21 The
reason for this is the commercial availability of airfoil-type blades in cen-
trifugal blowers. The conventional, radial-vane type of blower used in many
industrial applications was generally judged not suitable for wind tunnel work
due to its high noise level and pulsating flow characteristic. With the advent
of airfoil blades, the centrifugal fan offers numerous advantages compared to
the axial fan, which include
.
Higher pressure rise
.
Wider speed range with good flow quality
.
Comparable or lower noise level
.
Low swirl at the fan exit.
Thus, an airfoil-blade, centrifugal fan is incorporated into this tunnel design.
b.
Motor and Speed C~ntrol
Selection of a drive motor for the wind tunnel must involve consid-
eration of how the tunnel speed will be controlled. Since an 18:1 turn-down
ratio is required for this tunnel, use of dampers or a bypass system with a
constant speed fan will not provide the type of control needed. Additionally,
the use of gasoline engines, steam or gas turbines, and most other novel pro-
pulsion schemes can be rejected on the basis of first cost, reliability, com-
plexity of control, or any combination of these and other reasons. Thus, the
question of motor selection and speed control quickly boils down to what type
of electric motor and speed controller should be used. Table 6 summarizes some
of the more popular speed control methods which have been used in wind tunnels.
For the wide range of conditions of interest in this tunnel, the eddy current
coupling to a constant speed a.c. motor has been selected. This system offers
a wide control range, low cost, and is simple to use.
58
-------
Primary
Motor
Const. speed
a.c. motor
Const. speed
a.c. motor
U1
U)
Const. speed
a.c. motor
I Shunt wound
I
I d.c. motor
I
I
I
I
I Shunt wound
d.c. motor
Secondary
Unit
-
d.c. gen-
erator
---
---
---
---
TABLE 6
TYPES OF WIND TUNNEL FAN SPEED CONTROL
Other
Units
d.c. motor
coupled to
fan
---
Eddy current
clutch cou-
pled to fan
---
---
Speed
Control
--
Output of d.c.
generator con-
trolled by field
current. Controls
d.c. motor speed
directly
Change pulley
size
Clutch excita-
tion controls
torque trans-
mitted. Fan
speed adjusts to
torque setting
Resistance in
series with arma-
ture
Advantages
High efficiency,
excellent control
Low cost
Wide variation
in speed possi-
ble. Infinite
number of set
points. Low cost
Low cost
Shunt field rheo- Simple, reliable
stat
Disadvantages
High initial cost.
Occupies -large
amount of space
Narrow range of
speeds possible.
Cumbersome to
change tunnel
speeds
Low efficiency at
low speeds
Large power losses
at low speed.
Speed varies wide-
ly with load mak-
ing control diffi-
cult
Maximum turn down
ratio is 4 or 5
to 1. Controlling
large amount of
power
-------
2.4.10
Materials of Construction
All types of materials are used for wind tunnel construction. including
wood, metal, concrete, plaster, plastics, and combinations of these. The great
majority of subsonic tunnels, which are in universities or small research labor-
atories, are constructed of wood with use of some sheet metal fairings. In ad-
dition to being inexpensive and easy to work with, wood offers a good vibration
damping capability. In the present tunnel design, with operation at test sec-
tion temperatures of 450oP, wood is inappropriate as a construction material,
as are most others mentioned above. Therefore a steel tunnel appears to be in
order, and the discussion of materials of construction boils down to selecting
the type of steel - mild or stainless.
The use of stainless steel as a construction material is a straightfor-
ward but expensive solution to the problem of preventing exposed surface corro-
sion, rust formation, and undesirable particulate material in the test gas.
Raw material costs for stainless steel components are roughly five times higher
than mild steel, with fabrication costs (welding, cutting, grinding) slightly
higher as well. Alternatives are the use of high temperature protective coat-
ings, or possibly using unprotected mild steel in noncritical areas. In the
recommended tunnel design, all of these solutions are used in various sections
of the tunnel. The particular materials are discussed in Section 3 along with
the details of the tunnel design.
60
-------
L---
SECTION 3
FACILITY DESIGN
A general description of the entire facility is given, then each major
component is discussed in detail. Controls and instrumentation details are pre-
sented in Subsection 3.3 and utilities requirements are outlined in 3.4. Sup-
port equipment and other details are discussed in 3.5.
Under the present contract, a complete description of the tunnel design
along with "mechanical outline" drawings of the major tunnel components were
called for. Also, utility and control circuit layouts were required. It was
found, however, that it was not possible to arrive at satisfactory descriptions
of these major tunnel componets without fixing many of the design details.
Therefore, in addition to mechanical outline drawings, several detail drawings
have been included in this report. These drawings are included at the back of
this report in the Appendix, and ,are labeled with drawing numbers beginning
with the letter "M", (e.g., M-l). While these drawings do contain many design
details, they should not be construed as a complete set of final detail drawings.
Other drawings of a schematic nature are included in the text with ordinary
figure numbers.
GENERAL FACILITY DESCRIPTION
Layout and elevation drawings of the facility are included as drawings
M-l and M-2. These drawings indicate the placement of the tunnel in the Dur-
ham facility, give basic dimensions, and label the various pieces of equipment.
The test gas enters the airfoil-type centrifugal fan at the center and exits
horizontally through a 28" x 22" rectangular duct at velocities up to 66
feet per second. The fan forms one of the corners of the flow circuit. The
flow is immediately diffused in a simple, straight-walled diffuser to decrease.
.
its velocity. The straight-walled diffuser design was selected since flow qual-
ity at this point is not critical. The diffuser ends in a 6'0" by 6'0" duct
with a honeycomb provided at the intersection to break up any eddies or swirl
originating in the fan or diffuser. Maximum velocities in this duct are 8 feet
per second. The flow hhen passes through a shutter-type valve and along the 6 '0"
duct to the gas condi tioning section. There, it encounters aluminum-finned
cooling coils, steam distribution manifolds, and resistance heater elements. The
gas conditioning section of the duct is removable for modification, cleaning,
and maintenance. Control of the gas cooling, heating, and humidification equip-
ment is completely automatic.
61
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Gas flows out of the gas conditioning section and into the first cerner.
Turning vanes are included at this corner to prevent large separation and recir-
culation zones. A square to round transition section follows, routing the flow
into a round (cross-section) plenum or settling chamber. This plenum includes
two screens and one honeycomb who~e purpose is to reduce the turbulence level
in the tunnel. The honeycomb-screen frame is removable to allow cleaning, ac-
cess to the contraction, and modification. Dust is injected isokinetically into
the flow just downstream of the screens through seven nozzles arranged in a sym-
metric pattern. The dust-laden flow then accelerates through the 9:1 contrac-
tion section and into the test section.
The test section is a 2-foot diameter, 40-foot long duct. It is composed
of three 10-foot sections and two 5-foot sections. These sections are mounted
on rollers, are readily detachable, and can be arranged in many configurations.
The 5-foot sections contain four windows each and are intended to hold the model,
probe, or test device. The 10-foot sections contain two windows each. Instal-
latjon and access to the test fixture is accomplished by removing the Marman
clamps which hold the secUo'°>ns together, rolling one or more sections out of
the way, and reaching in through the ends. Access may also be gained through
the window openings.
Flow out of the test section proceeds into the return circuit elbow. A
large mesh screen at the entrance to this elbow catches any objects which may
have broken loose in the high speed test section flow. A vent downstream of
the screen allows the tunnel to adjust the amount of mass flowing as the tem-
perature changes and controls the test section pressure. Turning vanes are in-
cluded in both corners of the elbow and flexible duct sections allow for ther-
mal expansion and contraction of the entire test section length. Flow out of
the elbow moves into the conical diffuser section, where its velocity is re-
duced from a maximum of 90 ft/sec to a maximum of 10 ft/sec. The diffuser is
mounted above the test section to save floor space. The low speed flow out of
the diffuser then passes into a rectangular duct which leads into the baghouse.
The baghouse is fully automatic, self-cleaning model with high tempera-
ture bags. The entrance and exit to the baghouse have been modified to accom-
modate the large cross-sectional area ductwork which is appropriate for a wind
tunnel circuit. Flow out of the baghouse moves through a large rectangular duct
back to the fan inlet.
The tunnel also incorporates inlet and exhaust ducts, leading from the
top of the 6'0" by 6'0" duct just downstream of the fan, which are used to purge
the system after a test run. The exhaust duct is also opened when the tunnel is
being filled with exhaust products. The burner and firebox are located on the
floor behind the test section. Dilution of combustion products from the burner
62
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is accomplished by routing some of the test gas from the main blower into the
firebox downstream of the flame zone while the burner is in operation. Thus,
filling the tunnel with combustion products is accomplished by injecting all
the products of combustion from a burner into the tunnel, and rejecting an equal
portion of the mixed test gas to the atmosphere through the exhaust duct. Once
the tunnel is filled with combustion products, the burner is shut off.
Materials of construction were discussed in a general sense earlier in
this report. Referring to drawings M-I and M-2, materials can now be discussed
in more detail.
The factors considered in deciding which type of steel to use were
.
Environment
.
System requirements
.
Costs of material, fabrication, and maintenance
.
Durability
Going around the wind tunnel circuit,the material choices with explana-
tions are as follows:
.
Blower - handles high temperature gas of possibly corrosive nature,
difficult to refurbish protective coatings for maintenance. Loos-
ened rust or coating particles could affect tunnel test. A stain-
less steel alloy, e.g., 300 series, is recommended for this compo-
nent.
.
Blower-to-Gas Condition Section - Rusting is possible, however area
is accessible for maintenance. Stainless steel (300 series) is
preferable, however mild steel may be used for economy in construc-
tion. This section weighs about 1000 pounds so the cost in stain-
less would be about $2000 more than for mild steel. The maintenance
cost if the section were of mild steel would be about equivalent to
the cost of the stainless steel. To illustrate, assume 40 hours per
year for 5 years at $8/hour. The maintenance cost would be $1600.
Therefore stainless steel is recommended.
.
Gas Conditioning Section - Very high temperatures in this area from
heaters or condensing water from refrigerator, so corrosion poten-
tial is most severe in this location. Stainless steel should be
used. The amount of material involved is so little that it is not
a cost issue.
.
Turning Section - Readily accessible for maintenance, heavy assembly
weighing about 1200 pounds. Should be of stainless steel (300
63
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3.2
series) to eliminate chances of rust or coating particles loosening
into flow. Initial economy possible by using mild steel, but cost
of stainless steel is probably equivalent to the maintenance cost
of a mild steel assembly over a 5 year period.
.
Stilling and Converging Sections - Highly detailed components,
rication cost likely to be substantially greater than material
Should be of stainless steel.
fab-
cost.
.
Test Sections - Smooth interior surfaces required, 2-foot diameter
of test section virtually inaccessible for application or mainten-
ance of coatings. Stainless steel should be used.
.
Double Elbow - Highly detailed area so that fabrication cost domin-
ates. Use stainless steel.
.
Diffuser and Inlet Duct to Baghouse - Large bearing structures, some
corrosion tolerable since particles loosened go to baghouse. Readily
accessible for maintenance. Stainless steel desirable, but mild
steel is recommended for economy.
.
Baghouse - Difficult to maintain interior because of dust. Rusting
is almost certain to occur at the anticipated elevated temperatures
using mild steel and a protective coating. The worst consequence
of rusting is eventual penetration of the thin (14 gage) sheet metal
which the baghouse is constructed from. Rust particles could also
effect measurements in test section. One construction of the bag-
house c \lJld utilize mild steel on the inlet side and stainless steel
parts on the outlet side. This would result in some savings. The
cost of the baghouse would be about $17,000 in mild steel, $28,000
in stainless steel, and $25,000 with mild steel on the inlet side,
stainless steel on the outlet side. This latter combination is recom-
mended.
.
Duct, Baghouse to Blower - Inaccessible interior for maintenance of
protective coatings, rust detrimental to functioning of tunnel.
Stainless steel should be used.
.
Support Members - All supports for the ducting
The environment is that of the laboratory, all
Paint used for appearance and rust prevention.
can be of mild steel.
members are accessible.
DETAILED DESCRIPTION OF MAJOR COMPONENTS
in
Each of the major components of the test facility is described in detail
this subsection. Specifications of major components and vendors are listed
in Section 5.
64
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3.2.1
Fan, Motor, and Coupling
The fan selected is an airfoil-blade, centrifugal blower designed to
produce a l2-inch static pressure rise at 2350 rpm, moving 17,000 scfm of air.
The fan will operate at temperatures up to 500°F, with 17,000 acfm provided at
this higher temperature. Additional features of the fan include a large in-
spection door with quick-opening latches, flanged inlet and outlet openings,
and a drain coupling at the bottom of the housing. The fan is entirely insu-
lated to prevent thermal energy loss and personnel burns. All surfaces exposed
to the test gas are constructed of 304 stainless steel to prevent corrosion
and subsequent entrainment of rust particles in the test gas. The fan is
driven by a V-belt drive to an eddy current coupling and a 50 HP, squirrel
cage induction motor. The motor and eddy current coupling are an integral
unit, with the motor operating at a constant 1800 rpm and the output shaft
from the coupling operating at 50-1715 rpm. The eddy current coupling is con-
trolled with a solid state SCR-type controller which is wall-mounted nearby.
The fan exhausts into a diffuser and large duct section which is de-
scribed in the next subsection.
3.2.2
Duct
Flow from the fan is directed toward the gas conditioning equipment by
a 6'0" by 6'0" duct, as shown in drawing M-2. The inlet end of this duct is
a straight-walled diffuser which brings the flow to the low velocities desired
at the air conditioner and heater. The duct walls are strengthened with 2-
inch by l/4-inch bar stock, on edge, tack-welded around the circumference of
the duct every 2'0" along the duct axis. Access to the interior of the duct
for cleaning or maintenance is provided by a single hatch in the side of the
duct.
3.2.3
Gas Conditioning Section
The gas conditioning section is a removable section of the 6'0" by 6'0"
duct (drawing M-3). It includes all of the cooling, humidifying, and heating
apparatus for the tunnel operation. The cooling and humidifying apparatus will
be designed and installed by an air conditioning subcontractor. Consistent
with the conclusions of Section 2.4.7, the air cooling will be accomplished
with a chilled water coil (drawing M-4). The coil is constructed of hard-
drawn, 5/8-inch 0.0. copper tubing with aluminum fins. Tubes will be arranged
in a staggered pattern for maximum thermal efficiency. A small pump will move
up to 36 gpm of 45°F chilled water, which is provided on-site, through the
coils. The system is designed to remove approximately 150,000 Btu/hr. This
65
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heat exchanger will be specially constructed to fill the entire 6-foot by 6-
foot cross-section of duct at this section. Downstream of the cooling coils,
a dry steam humidifier will be installed, as shown in drawing M-4. Up to 76
Ib/hr of 15 psig steam, provided on site, will be injected automatically into
the air flow. Steam passes through a separator ahead of the control valve to
eliminate "spitting" or condensate from the injection manifold. The injection
manifold is steam jacketed as well, to prevent condensation. The steam injec-
tion is controlled with a pneumatically actuated control valve. A temperature
switch is also included to prevent the humidifier from coming on before it is
entirely warmed up. The air conditioning system will use the large duct heater
designed for hot flow runs when any reheat is necessary. This section of duct,
which contains the water coil, humidifiers, and heater, will be built as a sep-
arate assembly and installed as a unit. It can be removed easily for mainten-
ance or configuration changes.
The duct heater is described in the next subsection.
3.2.4
Duct Heater
The heater is designed for steady state operation of the tunnel at test
gas temperatures controllable between room temperature and 450°F in the test
section. The full temperature range can be achieved at all required flow rates,
from 950 to 17,000 cfm. The heater is designed to provide reasonable start-up
times (maximum of 2-3 hours) or any desired operating conditi{)n within the
specified range.
The limits of operating conditions are presented in Table 7.
TABLE 7
WIND TUNNEL HEATER REQUIREMENTS
Max Flow Min Flow
Variable
Steady State Operation
Test Gas Flow Rate (ft3/sec) 280 16
Heater Temperature (oF)
Outlet 80-450 80-500
Inlet (at Hottest
Condition) 450 80
Power Input (kw) 95 70
Initial Heat Up
Power Input (kw) 200 --
Time to Stabilize (hr) 2-3 --
66
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The steady state power requirements and heater inlet temperatures are
based on computed heat leaks through 2 inches of standard duct insulation on
all exterior surfaces of the duct system (including the particle collector).
Insulation exterior surface temperatures will nowhere exceed 150°F. At the
low flow condition, the test gases will enter the heater section at virtually
room temperature due to the effect of heat leaks on the relatively small mass
of gas circulating. A 50°F drop in gas temperature is expected 1n the distance
between the heater and test section at the lowest flow condition. However,
this will present no difficulties because the thermostat will be located at the
test section inlet. It should also be noted that free convection will cause
some temperature stratification in the low flow range. Mixing in the ductwork
preceding the test section will help to alleviate the stratification problem.
Tunnel start-up for elevated temperature operation is most efficiently
achieved by operating the tunnel at a high flow rate until stabilization is
attained at the desired temperature and then reducing the flow to the desired
level. The heater would become excessively large and expensive if it were
required to provide the full 200 kw in the low flow rate range.
An electric heater was selected over a gas-fired heater for the wind
tunnel design on the basis of: (1) lower operating cost, using a readily avail-
able source of energy; (2) more accurate control; (3) better temperature uni-
formity; (4) clean operation; (5) low maintenance; and (6) long lifetime. The
heater will be located as shown in drawing M-4 in the 72" x 72" duct section
between the blower and the test section. Heater control will be automatic such
that the test section temperature may be maintained accurately by setting the
desired temperature at the test section entrance. Characteristics of the heater
and its control system are summarized in Table 8.
It should be noted that the price of the heater and control system
(-$7000) could be reduced by nearly 50 percent if 440v, 3~ power was available.
This higher voltage power is not available at present, however.
3.2.5
First Elbow
Flow from the gas conditioning section is directed around a corner to
the settling chamber by an elbow, shown in detail in drawing M-S. Circular
arc turning vanes with a leading edge angle of attack of 4°-5° and a trailing
edge angle of 0° direct the flow smoothly around the corner. Turning vanes
are tack-welded in position and are constructed of light gage stainless steel,
since aerodynamic loads are small in this large cross section. Flow coming out
of the corner then passes through the "square-to-round" transition, where the
cross-section changes from a 6'0" by 6'0" square to a 6;0" diameter round
67
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TABLE 8
HEATER AND CONTROL CHARACTERISTICS
Type
Electric, 230V, 3~, 60 cycle wired
in 1 circuit
Maximum Power
200 kw
Heater Elements
54 corrosion-resistant alloy sheathed
hairpin tubular elements, each 0.5" 0.0.
by 152" long
Heater Dimensions
71-1/4" by 71-1/4" by 8" inside the
duct, flange-mounted with attached
terminal box assembly
Indicating Temperature
Controller
All solid state automatic set-point
temperature controller operating on
iron constantan thermocouple output
measured at test section entrance
Power Controller
Saturable core reactor
Proportioning Band
May be varied down to ~1/2°F
Overtemperature Control
Circuit breaker has trip shunt operated
if overtemperature occurs on heater
elements
Startup Control
Pressure-type air flow indicator up-
stream of fan prevents heater operation
without proper airflow
68
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!-
section. Access to the interior of this elbow after installation is provided
by a hatch upstream of the turning vanes, and another hatch downstream of the
turning vanes.
3.2.6
Stilling Chamber
The stilling chamber is a 6'2" diameter, 2'8" long cylinder, shown in
drawing M-6. The round cross-section in the stilling chamber allows the flow to
progress smoothly into the contraction and test section without any further
change in cross-section shape, thereby minimizing turbulence generation near
the walls. Two screens and one honeycomb (drawing M-7) are installed across
the stilling chamber which aid in damping turbulence in the tunnel flow. The
honeycomb material is commercially available stainless steel hexagon, with a
I-inch cell width and a length of 6 inches. The screens are located 2 and 9
inches downstream of the honeycomb, respectively and are 16 mesh, 28 swg stain-
less wire (drawing M-8). The screens and honeycomb are installed in such a
manner as to present a smooth, 6'0" cylindrical surface to the flow at the
walls of the stilling section. The honeycomb is installed on a 6'1-15/16"
hoop, as shown in drawing M-7, with a welded steel frame giving the honeycomb
rigidity in the flow direction. The screens are clamped on a 6'0" I.D. hoop
with a small amount of tension in the screen to smooth wrinkles and eliminate
sag. The screens and honeycomb can be removed through the hatch in the first
elbow (downstream of the turning vanes).
3.2.7
Dust Feeder
a.
Dust Generation and Metering
The proposed dust generation and metering is considered to be de-
velopmental in nature and no doubt will be modified at a later date. The sys-
tem consists of a live-bottom bin, hand-actuated slide valve, and an aspirator.
The live-bottom bin has a 50 cubic foot capacity, is 48 inches in diameter, and
has an overall height of 6'6". The outlet orifice of the bin is 1'10" from the
laboratory floor. The bottom of the bin is vibrated by a 1.5 HP motor. The
bin is constructed of 304 stainless steel. Loading is accomplished manually.
Metering of the dust flow rate is done by hand-setting a sliding plate
valve at the bottom of the bin (Figure 30). precision adjustment is possible
by rotating the knurled knob, which in turn slides the metering plate and un-
covers more (or less) of the diamond-shaped orifice. Major changes in the dust
feed rate can be accomplished by installing different sized orifices and meter-
ing plates.
69
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-'\I--
--1--
----------
SEC., \ ON A- A.
su DE PLATE
- METE: I2INq
OJ2JFIC"E
KNUI2LED ~N06
FIGU~E 30.
DUST METE2IN~ VALVt=.
70
LI VE BOTTOM
BIN
p..- '3"~b
-------
The dust aerosol is created by directing the dust through the metering
plate into a 3/4-inch air aspirator (Figure 31). The carrier gas flow rate
is controlled by a valve upstream of the aspirator. Carrier gas is also ion-
ized downstream of the aspirator to avoid dust agglomeration in the dust injec-
tor lines. The dust aerosol is then directed into a manifold which divides
the flow into seven separate streams for the seven injectors. The manifold
is designed to avoid accumulation of dust in corners or bends, and to avoid
"preferential" flow of the carrier gas into anyone tube. The particular aspi-
rator considered has been used with satisfactory results in another test facil-
ity.5 In that application, a good aerosol free of agglomerates was obtained
working with flyash dust delivered at rates up to 2 pounds per minut~ It is not
known whether this aspirator can manage 12 Ib/min. This will have to be de-
termined experimentally.
All pipe or tubing sizes are selected to keep the carrier gas velocity
above 4000 ft/min at the lowest flow rate.
b.
Dust Injection
Each dust injection tube which leads from the manifold incorporates
a short section of flexible tubing. Fine adjustments of the flow rate through
each injector can then be made by clamping the appropriate tube or tubes
slightly. The dust and carrier gas then passes through the tunnel wall and
out into the gas stream through the seven injectors, shown in drawing M-9.
All injector tubes are led to the center hub of the assembly through a pipe
with an airfoil fairing, which minimizes turbulence from the pipe. The tubes
then fan out to form a star-shaped pattern, and the aerosol is injected through
cone-shaped nozzles. The cone angle of the nozzles is shallow enough to avoid
flow separation, therefore a smooth deceleration of the carrier gas and dust
to the stilling chamber velocity is anticipated. However, the nozzles are
threaded onto the injection tubes for possible system modifications at a later
date. Also, ready access to the injection system is provided by removing the
honeycomb and screen assemblies from the upstream side.
3.2.8
contraction
The contraction (drawing M-IO) is a converging section which provides
an area ratio from inlet to outlet of 9:1, going from a 6'0" to a 2'0" diam-
eter over a length of 7'6". The contraction shape was designed by the method
of Cohen and Ritchie,22 and provides a smooth acc~leration of the flow with
minimal adverse pressure gradient at the wall near the test section end. The
upstream end is flanged for ordinary bolt attachment, while the downstream end
has a tapered flange for use with the Marman clamps to be used with the test
section duct.
71
-------
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3.2.9
Test Section
The test section is composed of five lengths of 2'0" diameter, stainless
steel duct. Three of the pieces are 10'0" long (drawing M-ll) and two are 5'0"
long (drawing M-12), giving a total length of 40'0". The segments of the test
section are connected with Marrnan-type clamps, which allow a rapid release and
removal of any or all segments for configuration changes, model installation,
or cleanout. To facilitate movement of the duct sections, each is mounted on a
cart (drawing M-l). The carts support the duct sections on specially constructed
saddles which allow vertical adjustment to align the segm~nt.
The 5'0" duct sections are intended to enclose the model, instrument, or
test fixture. The shorter length allows the model to be installed from either
open end, with additional access provided through the window openings. The 5'0"
sections each contain four 7-3/8 inch diameter window openings: two in the hori-
zontal plane and two in the vertical plane. The window opening receives the
window flange (drawing M-13) which bolts directly onto the tunnel wall. The
window flange provides a flat surface against which the 3/4-inch flat quartz
window is clamped and sealed with a-rings. The final window opening with this
assembly is 5-1/4 inch in diameter. While the windows are flat and intrude
upon the flow area slightly, the expense associated with fabricating and in-
stalling curved windows is not justified.
The 10'0" sections each have two windows, similar to those described
above, in the horizontal plane. It will be noticed that no general instrumen-
tation ports are provided. Such ports, such as for a stack sampling probe,
could easily be adapted to the window openings, or through additional holes in
the duct. Provision for instruments, models; probes, etc. can be installed at
a later date when a particular test program is designed.
3.2.10
Flex Coupling Section
The flex coupling section (drawing M-l4) forms the first component of
the flow return circuit. It consists of two 90° corners with a 2'0" diameter
connecting duct. The inlet to this duct section is screened with large mesh
(1/4"-1/2"), rigid screen to catch loose objects from the test section. The
I-inch slot near the duct entrance is manifolded and vented to ambient, pro-
viding the wind tunnel vent discussed earlier.
73
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Turning vanes are installed in each corner to minimize corner pressure
losses, which are large due to the high local velocity, and improved the veloc-
ity distribution in the diffuser. Due to floor space constraints it was not
possible to diffuse the flow from the test section before entering the first
corner. The turning vanes in this section are similar in design to those de-
scribed earlier. However they must be welded at the ends along the entire arc
to insure firm support in the aerodynamic loads which will occur in these
corners.
The two metal bellows in this duct section provide flexibility which
will be required for thermal expansion and for alignment.
3.2.11
Diffuser
The diffuser (drawing M-15) is a simple cone shape, 39'10" long, chang-
ing from a 2'0" diameter to a 6'0" diameter. This results in a 5.75° cone
angle, which is near the optimum diffuser angle for a wind tunnel of this
19
type. The diffuser saves approximately 10-15 percent on the tunnel power
requirements by recovering a large portion of the kinetic energy of the test
stream.
3.2.12
Elbow to Baghouse (Drawing M-16)
This elbow in the return circuit directs the flow into the baghouse.
Its flat-sided design allows simple fabrication techniques and maximum cross-
sectional area for the flow, thereby minimizing pressure loss. A large mesh,
expanded-metal gridwork at the outlet of this elbow prevents personnel or
tools from falling into the baghouse.
3.2.13
Baghouse (Drawing M-17)
Particle collection for this wind tunnel will be accomplished by a bag-
house permanently installed as part of the flow loop. The baghouse dust col-
lector is the only type of collector which offers the level of efficiency re-
quired in a recirculating gas flow, for a reasonable price. The baghouse is
constructed for operation at temperatures up to 425°F, using l6-ounce Nomex or
equivalent high temperature bag material. The air-to-cloth ratio of approxi-
mately 7.5 is allowable for this application, since the facility will not be
in production use. The baghouse is self-cleaning, with solenoid actuated re-
verse flow air jets.* Frequency of the reverse-flow air jets can be varied by
*
It is assumed that the cleaning action will be turned off during actual data-
taking. If data gathering activities will extend over long periods of time, a
different type of bag cleaning should probably be considered.
74
-------
the operator with an external timer setting. Dust from the collector bags
falls to a hopper which runs the length of the baghouse, and is moved out of
the hopper by a rotating vane airlock. A screw conveyor then moves the dust
along the length of the baghouse, where it can be dumped into a container.
The bagh~use is constructed of ordinary carbon steel on the dirty air side,
but uses stainless steel on the clean air side. The hopper is modified on the
intake side (drawing M-17) to receive the inlet pipe. This custom made inlet
maximizes the flow area, thereby minimizing the pressure loss as the flow ex-
pands through the opening. The baghouse will be delivered from the vendor
with 2 inches of insulation material, covered with a thin aluminum skin, on
all panels. Other features supplied by the vendor include motors and drives
for the air lock and screw conveyor, and access doors for bag maintenance.
The baghouse flow exit is also modified as shown in drawing M-17 to in-
crease the cross-sectional area and minimize pressure loss.
3.2.14
Duct from Baghouse to Fan (Drawing M-18)
Flow is directed from the baghouse to the fan inlet by a large rectan-
gular duct section. This duct section has a cross-section approximately equal
to the baghouse outlet. Each corner has turning vanes to maintain a uniform
flow leading into the fan. A rectangular-to-round section and a bellows then
leads the flow to the fan inlet.
3.2.15
Tunnel Inlet, Exhaust, and Open Circuit Valves
The wind tunnel is connected to the outside air by two parallel ducts
and associated valves on the high pressure side of the fan, as shown in Figure
32 and drawing M-2. These ducts allow the tunnel to be purged of exhaust pro-
ducts at the end of a test run by opening the valves in the inlet and exhaust
ducts and closing the "open-circuit" valv~ The open-circuit valve is a shutter
which is permanently installed in the 6'0" by 6'0" duct section downstream of
the fan. with the open circuit valve closed and the inlet and exhaust valves
open, fresh air enters the system, traverses the entire flow loop, and exits
again as shown schematically in Figure 33. Valves are actuated by small elec-
tric motors which are operated from the control console. The exhaust valve is
also opened slightly when the burner is in operation, as described in the next
subsection.
75
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(;c:::>M"'~I~1 ~DucrS
F I~U\2E"3~ VALVE A~eAN~EMENT FO~ OPEN CII2CUIT
AND. ~~S FILLlN~ OPEIC,>ATIONS.
77
-------
3.2.16
Combustion Products Burner and Firebox
a.
Burner and Blower
The burner which is used to fill the tunnel with exhaust products
is a dual fuel unit for operation on either natural gas or light distillate
fuel oil. Nominal energy release is 2,000,000 Btu/hr, corresponding to fuel
flow rates of 15 gph of oil and 2500 scfh of natural gas. Excess air should
be held to a minimum.
The air blower is an integral part of the burner. A shutter provides
air flow rate control. This will not be actively controlled, but will be set
initially to operate at an optimum air/fuel ratio. Since the burner back pres-
sure will not change, no active control of air flow is needed. A description
of the burner safety interlock systems is provided in Section 3.3.8.
b.
Firebox (Drawing M-19)
The burner firebox will be specially constructed. Since the burner
will be run at a minimum of excess air, the inner surface of the firebox should
be a super-duty firebrick useful in roughly the 2800°F to 3000°F range. Since
thermal losses from the firebox are of no practical consequence, the firebox
need not be well insulated, and a standard 4-1/2 inch thickness will be ade-
quate. This will yield an outer wall temperature of about 500°F, which will
be tolerable provided that operating personnel are kept away from the hot
surface by suitable screening provisions and also that the firebox does not
rest on a concrete floor. The location of the burner/firebox assembly is
shown in drawing M-2. Note that dilution air is brought in from the high pres-
sure side of the wind tunnel fan and injected into the firebox downstream of
the burner flame. As discussed earlier, this dilution air is necessary to
cool the exhaust products down to a useable temperature. Approximatley 2500
scfm of dilution air will be used. Indication of the dilution air flow rate
will be provided by a venturi section and associated pressure indicator in
the dilution air supply pipe, with readout at the control console. Drawing
M-19 shows a firebox of appropriate inner dimensions for the heat releases of
interest, with additional length for mixing of the dilution air. The firebox
may be constructed either of bricks or of monolithic (casting or molding) re-
fractory; the one shown is of brick. In either case the end wall in which the
burner is mounted will be at least partly of monolithic construction to allow
an exact mounting of the burner. The firebox will be jacketed in 10 or 12
gage steel to allow handling and mounting on the support structure.
c.
Exhaust to Diffuser
The diluted combustion products will be exhausted to the diffuser
through an exhaust duct (Figure 34). The duct terminates at a motor actuated
valve which closes flush with the diffuser wall, giving a clean aerodynamic
surface during tunnel operation.
78
-------
DtFF\.J5E.R
\j f>.L\lE, FLUSH CLQSfNq
o
----- Nt OTa 12
Ac... TUATO~
F\~DI2E 34-,
FlRE.!>Ox E.~H~u~T t;)0c..T A~D VALVE....
A-"!.,2.4
79
-------
3.3
CONTROLS AND INSTRUMENTATION
The controls and associated instrumentation for this wind tunnel are
much more complex than for an ordinary tunnel, where only velocity is con-
trolled. In the present system, the following quantities are automatically
controlled, usually simultaneously.
.
Test gas velocity
.
Test gas temperature
.
Test gas humidity
.
Test gas composition
.
Dust feed rate
.
Dust carrier gas flow rate
.
Burner operation
.
Burner combustion products dilution
.
Baghouse cleaning frequency
.
Inlet, exhaust and open-circuit valve settings
It is not possible to describe a complete control and instrumentation system
without carrying out the detailed mechanical and electrical designs for this
facility, which were not called for under this contract. However, it is pos-
sible to discuss the system controls in a general way, and to indicate how the
design should be carried out. This general discussion is presented below. It
begins with a discussion of the control console, then describes control of
each variable.
3.3.1
Control Console
Control over most of the system components can be carried out from a
control console, drawing M-20. This console contains on-off or open-close
buttons (green light w.hen on) for the following equipment:
.
Fan motor
.
Cooling water pump
.
Humidifiers
.
Duct heater
.
Dust feeder
.
Burner blower
.
Burner igniter
80
-------
8 Baghouse screw-conveyor
8 Baghouse rotating air-lock
8 Tunnel inlet valve
8 Tunnel exhaust valve
8 Tunnel open-circuit valve
8 Dilution air valve
8 Firebox exhaust valve
The control console contains set-point controllers for
8 Velocity in the test section
8 Temperature in the test section
8 Humidity in the test section
8 Baghouse reverse jet frequency
The control console contains indicators or meters for the following variables
8
Test section velocity
8
Temperature at seven positions in the flow circuit
8
Test section humidity
8
Air pressure at three locations
8
Facility steam pressure at the humidifier inlet
8
Water pressure at the chiller inlet
8
Dilution air flow rate
Since much of the equipment is interlocked,
installed on the console. Each fault light
ticular system interlock. Ten fault lights
dicate the following faults.
a series of fault lights is also
indicates the condition of a par-
are currently planned, which in-
1.
Fan motor - cooling air blower not operating
2.
Fan motor - fan not rotating
3.
4.
Fan motor - air temperature too high
Fan motor - open circuit valve closed, inlet and exhaust valves not
open
5.
Chilled water pump - no water flow
6.
Humidifier - no steam flow
7.
Duct heater - no air velocity through heater elements
81
-------
8.
Duct heater - element overheat
9.
Baghouse - gas temperature too high
10.
Burner - anyone of a series of interlocks on the burner is not
satisfied.
Burner faults are listed later in this section.
Two other fault lights are indicated on the panel, to be connected to dust
feeder operation at a later date.
The console also includes a writing shelf, an air pressure regulator
for the pneumatic instruments, and the duct heater controller.
3.3.2
yelocity Control
The conventional way to measure velocity in a wind tunnel, and the way
it will be measured in this facility, is to measure the static pressure de-
crease between the plenum and the test section. Then, for any measured ~P
v = ~2~P
where
6.P = Pt - P
Pt = total pressure or pressure in the stilling chamber
P
= static pressure in the test section
p
= density in the test section
Density is generally found from the perfect gas equation
p
p = ---p:--
T
1ft
where
R. = universal gas constant
'1
= molecular weight
T
= temperature
The dust loadings in this facility are not great enought to affect the local
molecular weight significantly, therefore only the gaseous components need be
considered. Temperature does vary, so it must be measured in the test section
as well as static pressure.
82
-------
Electrical controls in the present facility design are indicated in
block diagram form in drawing M-21. The desired velocity will be set with a
dial-type potentiometer, POT 1, on the control console and the fan will be
turned on (PBl). The set-point signal will be fed into a small analog com-
puter, along with the readings from the ~P pressure transducer and the thermo-
couple which senses temperature at the desired station in the test section.
The computer then calculates an error signal, which is fed to the eddy current
coupling speed control unit. The speed in the tunnel is then automatically
held at the preset value to within 0.5 percent. Actual velocity in the test
section is indicated on the control console on the indicating velocity meter,
VMRI. While transient behavior of the tunnel can be caused with the set-point
controller, neither the tunnel nor the controller is designed for rapid transient
response.
3.3.3
Test Gas Temperature
Temperature will be measured in this facility at a number of locations
with thermocouples. At present, seven locations are planned, which include
.
One location in the test section
.
At the inlet to the baghouse
.
In the combustion chamber
.
In the duct downstream of the burner
.
At the fan outlet
.
In the duct downstream of the heater
.
In the stilling chamber
All of these temperatures will be displayed continuously on the control console
In addition, interlocks will shut off the .burner and heater if temperatures ex-
ceed the design upper limits.
Heating of the test gas in the facility will be accomplished by the elec-
trical duct heater, the saturable core reactor, and the control unit. The de-
sired set-point temperature is set (CONI) on the control console and the heater
unit is actuated (PB2). The actual temperature in the test section will be
sensed with a thermocouple. The heater control unit will compare these two
signals and control the power to the heater accordingly.
For cold runs, temperature is controlled by the chilled water cooling
system and pneumatic controller (CON2). The cooling water pump is actuated
with PBS. The dry bulb temperature reading in the plenum is sensed by a thermo-
couple and compared to the desired temperature set on the controller. The error
signal is transmitted to the pneumatically actuated three-way valve (drawing
M-22) which controls chilled water flow. More or less water is then routed to
the chiller as required.
83
-------
3.3.4
Test Gas Humidity
The humidifier is actuated along with the chilled water pump (PBS). Con-
trol of the relative humidity (CON2) requires a relatively "clean" air stream,
therefore wet bulb and dry bulb temperatures will be sensed in the plenum,
ahead of the dust injectors. Wet bulb temperature is sensed with a porous
Alundum sensor. The pressure levels which are generated by the pneumatic-
type wet and dry bulb sensors are fed to the humidity control unit, which then
compares the resulting humidity level to the set point, and actuates the steam
injectors accordingly. Both the dry bulb temperature and the relative humidity
are controlled by a single controller during cold runs. The controller also
provides a circular chart record of the dry bulb temperature and humidity level
in the tunnel.
3.3.5
Test Gas Composition
Test gas composition is controlled by the operation of the burner (Sec-
tion 3.3.8). The initial charge of air in the tunnel is recirculated at the
maximum tunnel speed, and the exhaust valve is opened slightly. The burner is
then operated with the burner exhaust emptying into the tunnel. As the burner
continues to operate, the level of C02 and H20 in the tunnel will continue to
rise until it approaches 100 percent exhaust products, as explained in Section
2.4.8. Composition of the test gas can be sensed at the test section with
existing APCO instrumentation, therefore, these instruments are not included
in this design study. It is also felt that it would be unwise to attempt to
control composition automatically at this time in the facility development,
therefore it is assumed that startup and shutdown of the burner and setting
of the various valves will be done manually.
The composition of the test gas can also be altered by injection of
bottled gas near the fan inlet, if compositions other than that supplied by
the burner are desired. No special provisions for this approach have been in-
cluded due to the simplicity of the necessary alterations.
3.3.6
Dust Feed Rate
Due to the preliminary nature of the dust feeder design, and the need
for an experimental development program to arrive at an optimum feeding sys-
tem, the dust feeder will be operated as a stand-alone system, independent of
the operation of the rest of the tunnel. At a later date, dust feeder opera-
tion can be coupled to the tunnel velocity, and all control will be carried
out at the control console.
84
-------
In the proposed design, the live-bottom bin is actuated from the con-
trol console (PB7), as is the baghouse airlock and screw conveyor (PBS and
PB9). Dust feed rate is then controlled by manually setting the position of
a slide valve at the bottom of the bin, which changes the size of an orifice
opening through which the dust falls.
3.3.7
Dust Carrier Gas Flow Rate
The dust carrier gas flow rate should be adjusted with the tunnel ve-
locity to maintain an isokinetic injection condition. This is accomplished
by manual adjustment of the valve which controls flow to the aspirator, draw-
ing M-22. Final small adjustments in each dust injector line to equalize the
flow out of each ej.ector can be made with individual clamp valves on flexible
tubing portions of the feeder lines located outside the stilling chamber.
3.3.8
Burner Operation
The burner operates in an on-off mode only, with no provi~ion for auto-
matically adjusting the air-fuel ratio, flow rates, or other burner variables.
The installation will result in a clean-burning, smokeless, "blue-flame" burner
operation, thereby avoiding problems with large amounts of soot in the tunnel
circuit.
To actuate the burner, the tunnel must be in operation and the valve
which allows combustion products to flow into the diffuser must be opened
(PBl2). The dilution air duct must also be opened (PBII). The burner-blower
start button, PB3, and the igniter button, PB4, are then depressed. Burner
control is then transferred to the burner control center, a panel near the
burner itself, which carries out the start sequence. The burner control center
includes a flame safeguard and other interlocks which do not .allow fuel flow
unless all systems are operating properly. The flame safeguard logic incorpor-
ates standard flame safety logic elements:
.
Flame-out detection and associated mandatory purge periods after
flame-out.
.
Trial-for-ignition period and associated transfer to flame-out
detector.
.
High or low ignition voltage interlock.
In addition, several other interlocks are provided to interrupt fuel flow for
the following conditions:
.
Low or no velocity in the tunnel
.
Firebox exhaust valve closed
85
-------
.
Insufficient dilution air flowing
.
Low combustion air pressure
.
High/low firebox pressure
.
Low fuel pressure
.
High firebox temperature
.
High diffuser duct temperature
3.3.9
Baghouse Cleaning Frequency
The frequency with which the reverse jet cleaning action of the bags
occurs is controlled with a timer, mounted on the control console.
3.3.10
~nlet, Exhaust and Open Circuit Valve Settings
The inlet, exhaust, and open circuit valves are opened at the conclu-
sion of an exhaust products run to purge the tunnel of combustion products.
The exhaust valve is also opened during filling the tunnel with exhaust pro-
ducts from the burner. The valves are 2ctuated electrically, and are con-
trolled individually from the control console (PB6, PBIO, and PBII, respec-
tively). The valve controls are interlocked such that the open circuit valve
cannot be closed (blocking the tunnel flow circuit) unless the fill and exhaust
valves are both open.
3.4
UTILITIES
Utility requirements for this facility are listed below.
Electric Motors
1 - 50 HP, 220V, 34J, 60Hz' electric motor
1 - 200KW, " " resistance heater
1 - 1.5 HP " " \I electric motor
I - 1.0 HP \I " " " "
8 - fractional HP, 110V, 1<1> electric motors
Compressed Air
60 scfm @ 125 psig
Tap Water
30 gpm @ 90 psig
Steam
76 Ib/hr @ 15 psig
86
-------
L
3.5
Fuel Oil
15 gpm of #2 distillate fuel oil
Natural Gas
2500 scfh @ 2 psig
Chilled Water
36 gpm @ 45°F
OTHER DESIGN DETAILS
Other features of the wind tunnel design include access hatches and
drains for tunnel maintenance and cleanout, tunnel insulation, a laboratory
housing, effluent requirements, and air exchange rates. These items are dis-
cussed below.
3.5.1
Cleanout
Tunnel cleanout is accomplished with a vacuum cleaner in heavily dust-
laden areas, followed by hosing down and scrubbing with water. Access to the
various parts of the wind tunnel for maintenance and cleanout is indicated in
Figure 35 and described below.
1.
Blower to air conditioner, 6' x 6' rectangular duct: hatchway in
side of duct on both sides of open-circuit valve.
2.
Gas conditioning section, 6' x 6' X I' section: can be lifted out
for major work or accessible from either side by means of hatches
in adjacent duct sections.
3.
Gas conditioner to turning vanes, 6' x 6' rectangular duct: hatch-
way in side of duct.
4.
Turning vanes to settling section, 6' x 6' rectangular duct: hatch-
way in side of duct.
5.
Settling section (honeycomb, screen and nozzle assembly): can be
lifted out for major cleaning, or screens and honeycomb removable
through upstream hatch. Access from other side by crawling through
converging section.
6.
Converging section: remove test section segment and crawl through
2-foot diameter opening, or remove screens and clean from upstream side.
7.
Test sections: all removable and mounted on carts.
8.
Turning section: accessible when adjacent test section is removed.
87
-------
s
o
o
00
00
l~ E-N D
s
DI2AIN Lo~IIC:>~
I 1-1"'-1"<::1-1 LCCA.'TIDN
.,--
"'-- ~,,~ ~~C.L. tt-E:tc..tf'r of ~\Jc;.T'
~!t ~Q)~!. t sc:.~ ~VM..
~\6.tLJr2E 35.
P\...~ N
AC-e-E-?7 ~AT~E-S AND DfZAJtJ L..~~-T'loNS.
-------
9.
10.
Diffuser: hatchway at large end of diffuser.
11.
Inlet to baghouse from diffuser: hatchway on side of 6' x 6' sloping
rectangular duct.
Baghouse: hopper with screw fed dust ejector; hatches in both sides
of baghouse for bag repair. Catwalks inside.
12.
Baghouse to blower duct: hatch on top end of duct and on lower hori-
zontal section before entering blower.
13.
Blower: hatchway in housing.
Water from scrub-down operations or condensation will be drained from
large drain couplings, shown in Figure 35, through large diameter hoses. Ele-
vated hatchways and important locations, e.g., end of diffuser and top of bag-
house will be accessible by means of ladders; permanently mounted if desired.
All material gages are heavy enough to support ordinary foot traffic without
damaging the tunnel surface.
3.5.2
Insulation
All surfaces of the tunnel circuit are insulated after tunnel installa-
tion (except the fan and baghouse which are insulated by the vendor). The ma-
terial used is a semi-rigid spun-glass felt with a thickness of 2.0 inches.
The insulation will be installed with metal bands, and covered with a canvas
or other suitable flame resistant material.
3.5.3
Laboratory Housing
The test section and control console will be enclosed by a modular steel
laboratory housing structure. The structure will include an ordinary door at
either end and a 10'0" wide roll-up door at the center. The overall dimensions
of this housing will 45'0" long by 15'0" wide, with an 8'0" ceiling. Space can
be provided for storing instruments used with the tunnel, shelves, workbenches,
and desks. This will be a prefabricated structure assembled after installation
of the tunnel.
The laboratory housing is not shown in drawings M-l or M-2 for clarity,
however it is illustrated schematically in Figure 36.
3.5.4
Effluents
1 t" 23
Durham County air pollution regu a ~ons applying to this facility are
as follows.
89
-------
II
FI12E:.60X
~
- ---------- -
15'
40' 'EST SecT"l~
r I :
~- . --~
10')( l' OvE..RHEAD booR
I 1-
4
'"
o
-- ---
:1
a'
4;"
. I
A'~""'"
F (G:;.URE 3(...
LABDI2ATD\2.Y
HCJUSINq
-------
!-
Section ll.b. (1) - Emissions of smoke to the atmosphere must not exceed
Ringlemann 1 for more than 4 minutes per hour, and not more than 20 minutes in
any 24 hour period. Since particulate material is removed from the stream by
the baghouse before exhausting to atmosphere, emissions are not expected to
exceed this limitation.
Section ll.b. (7) - Flyash emissions must be less than 0.6 lbs/million
Btu heat input. The baghouse will also satisfy this regulation.
Section ll.c. (1) - The lowest sulfur content fuel reasonably available
shall be burned. Natural gas operation of the burner will not present a prob-
lem, and low sulfur fuel oil should be used.
Section ll.d. - Controllable particulate matter shall not be handled
in such a manner as to cause it to become airborne. This rule should be fol-
lowed during the course of facility operation.
Other city, state, and federal regulations are expected to be satisfied
by the inclusion of the paghouse during open circuit operation, and by observa-
tion of the fuel selection and particulate handling procedures described above.
3.5.5
Air Exchange Requirements
All joints in the tunnel will be gasketed and made as leak tight as
practical. If a leak occurs, e.g., from a misaligned duct or damaged gasket,
it cannot be so substantial as to affect tunnel performance. We may assume
that a leak equal to 10 percent of the tunnel flow would be noticeable and
use this as a basis for estimating the air exchange requirements. The maximum
tunnel flow is about 17,000 cfm, so two exhaust blowers, one in the laboratory
housing around the test section and the other in the general laboratory area,
of 1700 cfm capacity would continuously remove noxious gases.
91
-------
SECTION 4
FACILITY CONSTRUCTION
The wind tunnel is divided into sections joined by
on-site assembly. Each section is small enough for truck
pass through the 10-foot wide entryways of the building.
be delivered in broken down form and assembled at the site.
bolting for ease in
shipment and can
The baghouse will
The control console will be wired as a unit with low voltage or low
pressure signals fed to the various control points, e.g., motor speed, heater
power, and valve actuators. Thus the compact, complex wiring of the console
can be confined to the fabricator's workshop while the simpler cable runs can
be prepared on site.
Due to the complexity and costs associated with construction of this
facility, it is recommended that construction take place in phases. The phased
construction and approximate costs are described below. Labor costs are typical
loaded costs, while hardware costs are costs to the prime contractor.
Phase I:
Detailed Design and Bid Package
Some revision in the design presented herein will be necessary, and
final design drawings must be prepared. Incorporating changes, checking all
drawings and component specifications, preparing bid packages, i.e., specifi-
cations and interface information, will require the following effort and asso-
ciated (approximate) costs:
Engineering
Drafting
Secretarial
$10,500
3,500
1,000
$15,000
Phase II:
Construction of Elementary Wing Tunnel
The elementary wind tunnel would consist of:
1.
All ducting for closed circuit operation & supports,
including one test section cart.
Baghouse, full capacity required, stainless steel
where required
Blower, motor & speed control (manual input)
Windows (eight) in two short, 5-foot test sections
Dust injector (borrowed hopper from EPA)
$35,000
2.
3.
4.
5.
24,000
4,500
2,000
2,500
$68,000
92
-------
i-
f
The cost of shipping, installing, and startup of the tunnel would breakdown
~s follows:
1.
2.
3.
4.
5.
Shipping
Engineering
Travel & living costs
Riggers, local contractors
Miscellaneous
5,000
23,000
3,500
2,500
8,000
$42,000
with this equipment, the aerodynamic performance of the tunnel itself
could be explored. The dust injection technique would be established. The
low costs are accomplished by deleting many of the tunnel systems which are
part of the final test facility. These deleted systems and components and
approximate costs are:
1.
Inlet & exhaust valves (space provided but
openings capped)
Valve and ducts controlling dilution air to
gas generator
Open-circuit valve in large square duct
Ducting to outside
Valve in diffuser, from burner
Gas generator & ducting, inlet & outlet
Control console & permanent installations of
thermocouples, velocity sensors, interlock
switches, valve control relays
Insulation
Chilled water coil, humidifiers, & control
1,000
600
700
1,500
900
5,900
14,000
2,500
12,000
7,000
4,500
6,000
1,500
$57,400
The total cost of the elementary tunnel would be about $114,500. If
we add the Phase I costs, the wind tunnel at the end of Phase II would cost
$125,000.
Phase III:
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Heater & control.
Laboratory housing
Vibrating hopper, screw feeder & screws
Test section carts (four)
Permanent Installation and Additional Capabilities
93
During Phase II, all instrumentation was of a temporary nature, speed
control was manual, and tunnel temperature was not controllable (limited to
150°-200°F steady state temperature). In Phase III, the following components
would be added:
-------
phase IV:
1.
Control console, permanent
engineering & fabrication)
Inlet & exhaust valves
Open-circuit valve
Exhaust duct
sensors {includes
Heater & control
Air conditioning
Insulation
14,000
1,000
700
1,500
7,000
12,000
2,500
6,000
1,500
$46,200
2.
3.
4.
5.
6.
7.
8.
9.
Dust feeder, bin, screws
Test section carts (four)
Phase III engineering, installation and checkout cost would be:
l.
2.
3.
4.
Engineering
Travel & living costs
Local contractors
Miscellaneous
20,000
3,500
2,500
~OJ}~
$31,000
The total cost for Phase III would be $77,200.
Completion of Facility
The wind tunnel facility would be completed during this phase which
involves:
l.
2.
3.
4.
5.
6.
Adding burner, firebox & ducting
Exit valve from firebox
Inlet air valve to firebox
5,900
900
600
4,500
7,200
8,000
Laboratory housing
Windows (12) in the 10-foot section
Miscellaneous
$27,100
Engineering, installation, and checkout costs would be about the same
as in Phase III, which is $31,000. The total costs for Phase IV would be about
$58,100. At this point, the facility is complete, checked out, and ready for
use. The costs for Phase I, II, III, IV together amount to $260,300. A sched-
ule for all four phases is shown on the next page. The entire job can be com-
pleted in two years.
94
-------
SCHEDULE
Months After Go-Ahead
Phase I
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Phase I
Phase II
Phase III
Phase IV
\0
U1
-------
SECTION
5
SPECIFICATIONS
Specifications for each major component of the wind tunnel facility,
along with three vendors (where possible), are given in Table 9.
96
-------
TABLE
9
EQUIPMENT SPECIFICATIONS
'"
.....
Item Qty. Description Vendors
1 ! 1 ! Airfoil blade, centrifugal blower, insulated housing, 304 stainless L Garden Ci ty Fan and Blower Co.,
steel construction on all airstream surfaces, flanged inle t and out- 1701 Terminal Rd.
I let, insulated inspection door, insulated drain connection. Niles, Mich. 49120
r Working conditions: 2. H.K. Porter Co.
16,700 CFH; 12" S.P.; 40 BHP - at 700F, sea level 6900 E. Elm St.
16,700 CFM; 7" S.P.; 24 BHP - at 4500F, sea level Los Angeles, Cal. 90022
3. Reese Blowpipe Co.
2929 5th Ave.
Berkeley, CaL
2 1 Constant speed, squirrel cage a.c. motor integral with eddy current L Eaton, Yale, and Towne Dynamatic
drive unit. Horizontal foot mountings, blower cooled, continuous duty. Division 3122 - 14th Ave.
Motor rating: 50 HP @ 1800 RPM, 230v, 3~ power Kenosha, Wisconsin 53140
Output speed range: 1715 - 50 RP~1 @ full rated torque 2. U. S. Electrical Motors
1660 Rollins Rd.
Burlingame, CaL
3. Allis Chalmers Mfg. Co.
Box 512
Milwaukee, wis.
3 1 Silicon - con trolled rectifier (SCR) - type solid state controller for Same as Item 2.
item 2. Wall mounted, ventilated enclosure. Equipment furnished
loose for mounting on control console includes:
1) run speed potentiometer, knob, and dial
2) run pushbutton
3) stop pushbutton
4 3 Butterfly valves L Industrial Clean Air, Inc.
Light weight valves required for installation with bulb flanges in 1/8" 2929 Fifth St.
thick steel ducting. Bubble-tight seal in closed position desirable. Berkeley, CaL 94710
Electric motor or pneumatic actuator. Maximum operating temperature 2. N. J. Hatter & Co. (Continental
approx. 450°F. Maximum pressure in closed position, 10" of water. Valve Rep.) P.O. Box 1391
Exposed to flue gas. San Mateo, CaL
2 va 1 ves @ 2' dia.; 1 valve @ l' dia. 3. Garden City Fan & Blower Co.
1701 Terminal Rd.
Niles, Michigan 49120
5 1 Shutter valve. To fit 6' x 6' duct. Installed with bulb flanges. Same Vendors as Item 4
The number of shutter sections used is not critical. Electric motor I
or pneumatic actuation. Valve must withstand 10" ~later pressure d1£-
ferential in fully closed position. Operating temperature approx.
4500F max., exposed to flue gas.
6 1 Air conditioner. Must fit within the 72" x 72" duct section and 1. Thermal Mechanical
operate in conjunction with the duct heater (item 7). Air 612 Taylor Avenue
conditioner will consist of the following equipment Sunnyvale, California 94086
Chilled water coil and pump - 36 GPM, 45°F water (plant supply) 2. Simonsen Air Conditioning
Dry steam humidifier nozzles and actuators - 76lb/hr of 15 psig, 1124 Quesada Ave.
plant steam San Francisco, CaL
Pneumatic control sys tern - use 125 psig plant air 3. Climate Engineering Inc.
855 Cherry Lane
San Carlos, Calif.
,. . -_._-------- -.--.--.-.---.-. --- ------- ..-._-_.- -- .
-------
TABLE 9 (Continued)
\D
CD
7 1 Duct heater and stainless steel frame to fit in 72" x 72" duct. . Maxi-I 1. Trent Inc.
mum heater load is 200KW @ 230V, 3<1>, 60Hz. F low through heater J.s as 201 Leverington Ave.
follows: I Philadelphia, Pa. 19172
I
Max. flow: 280 ft3/sec @ T = 70 - 450°F 2. Montgomery Brothers, Inc.
Min. flow: 16 ft3/sec @ T = 70 - 5000F I 1831 Bayshore Highway
Heater elements to be sheathed in stainless steel. Burlingame, Cal.
3. Hill and Dietrick
1927 Fairway Dr. I
San Le andro, Calif.
8 1 Saturable core reactor, 225 KVA, 230v, 3<1>, 60Hz input, 75 VDC control, 1. Burton Equipment Co.
to be use as control unit for item 7. 16708 Parks ide Ave.
P.O. Box 96
Cerri tos, Cal. 90701
9 1 Live bottom bin and cover, 50 cubic foot capacity, 304 stainless steel I 1. Vibra Screw Inc.
on all contact surfaces, 230 V, 3<1>, 60Hz vibrator motor, 1.5 HP. 755 Union Blvd.
1 Totowa, N. J. 07512
10 1 Baghouse duct collector, panel construction, 304 stainless steel on I 1. Slick Corporati,:m
clean air side, trough hopper and supports with special extended in- I rtikropul Division
'let. Capaci ti es and sizes as follows: Chatham Road
Filter Area - 2036 ft> Summit, N. J. 07901
Air Temperature - up to 425 ° F
Bag Material - Nomex, 160z. felt or equal
Insulation - 1" thick, all external surfaces
Cleaning - reverse - jet air flow, 100 psig air I
Partical Removal - 8" rotary air lock with 1/2 HP motor, 9" screw
conveyor wi th 1 HP motor
Timer for bag cleaning frequency furnished separately for mounting
on control console. I
11 - All duct work bellows, and connecting flanges 1. Krenz Engineering
Ashby Ave and 6th
Berkeley, Calif.
2. Hipp Welding Inc.
4233 Middlefield Road
Palo Alto, Cal.
3. Rees Blow Pipe Co.
2929 - 5th Ave.
Berkeley, Ca1.
12 1 Burner, natural gas or light distillate fuel oil, low excess air 1. S. T. Johnson Co.
rates possible. Capaci ty is as follows: 940 Arlington Ave.
oil - 15 GPH Oakland, Cal.
Gas - 2500 SCFH 2. Eclipse Fuel Engineering
Combustion Division
Rockford, Illinois
. 3. pyronics Inc.
Cleveland, Ohio
13 1 Burner control and safety interlock system, to be used for operation I Same as I tern 12
of item 12. Flame safeguard unit must include
1) flame-out detection and associated mandatory purge period after
flame-out I
2) trial-for-ignition period and associated transfer to flame-out
detector
-------
14
15
16
\D
\D
-
TABLE 9 (Continued)
3)
Other
1)
2)
3)
4)
5)
6)
7)
8)
high or low ignition voltage interlock
interlocks must include:
low tunnel velocity
firebox exhaust valve closed
insufficient dilution air
low combustion air pressure
high/low firebox pressure
low fuel pressure
high firebox temperature
high diffuser duct temperature
1
Firebox, drawing M-19, super-duty firebrick or monolithic refractory,
10 or 12 gage steel jacketing.
1
Velocity meter, to sense velocity in test section and control eddy
current coupling (item 2). Features must include:
1) set-point indicator, ft/sec
2) LIP sensors
3) temperature sensor
4) analog computer, to calculate actual velocity and generate error
signal
5) velocity meter, indicating in ft/sec
1
Control console (drawing M-20) for tunnel operation.
ort-off or open-close buttons for:
1) fan motor
2) cooling water pump
3) humidifiers
4) duct heater
5) dust feeder
6) burner blower
7) burner igniter
8) baghouse screw conveyor
9) baghouse rotating air-lock
10) tunnel inlet valve
11) tunnel exhaust valve
12) tunnel open circuit valve
13) dilution air valve
14) firebox exhaust valve
Set point controllers must include
1) velocity in test section
2) temperature in test section
3) humidity in test section
4) baghouse reverse jet frequency
Indicators or meters must be included for
1) test section velocity
2) temperature at seven locations
3) test section humidity
4) air pressure at three locations
5) facility steam pressure
6) facility water pressure
7) dilution air flow rate
Console contains
1. Acurex Corporation
Aerotherm Division
485 Clyde Ave.
Mt. View, Ca1. 94040
1. Acurex Corporation
Aerotherm Division
485 Clyde Ave.
Mt. View, Cal. 94040
1. Acurex Corporation
Aerotherm Division
485 Clyde Ave.
Mt. View, Cal. 94040
-------
TABLE 9 (Concluded
17
I-'
o
o
------.---.---------.--- -------~--------_.
Faul t lights indicating the condition of system interlocks must be
included as follows:
1) Fan motor - motor cooling air blower not operating
2) Fan motor - fan not rotating
3) Fan motor - air temperature too high
4) Fan motor - open circuit valve closed, inlet and exhaust valves
not open
Chilled water pump - no water flow
Humidifier - no stearn flow
Duct heater - no air velocity through heater elements
Duct heater - element overheat
Baghouse - gas temperature too high
Burner - anyone of a series of interlocks on the burner is not
satisfied. Burner faults are listed under Item 13.
The console also must include a writing shelf, the air pressure
regulator for pneumatic insturments, and the duct heater controller.
5)
6)
7)
8)
9)
10)
~- ..- ...;,.. -----'-.-..
1
Prefabricated laboratory housing surrounding test section area.
Approximate dimensions of 40' x 15' x 8', doors included at either end,
with roll-up, 10' 0" wide door at center.
1. Stran-Steel Inc.
-------
REFERENCES
1.
Pope, A. and Harper, J. J., Low Speed Wind Tunnel Testing, John Wiley and
Sons, Incorporated, New York, 1966.
~.
Bradshaw, P., "A Low-Turbulence Wind Tunnel Driven by an Aerofoil-Type
Centrifugal Blower," Journal of the Royal Aeronautical Society, Vol. 71,
February 1967, pp. 132-134.
3.
Johnson, G. A., et al., "Performance Characteristics of Centrifugal Scrub-
bers," Chemical Engineering Progress, Vol. 51, NO.4, April 1955, pp. 176-
188.
4.
Martin, J. R., Taylor, N. C., and Plumley, A. L., "The C-E Air Pollution
Control Systems," Paper presented at 1970 Industrial Coal Conference, Uni-
versity of Kentucky, April 1970.
5.
Trezak, G. J. and 500, S. L., "Gas Dynamics of Accelerating Particulate
Flow in Circular Ducts," Proceedinqs of the 1966 Heat Transfer and Fluid
Mechanics Institute," M. A. Saad and J. A. Miller, editors, Stanford Uni-
versity Press, Stanford, California, 1966.
6.
Byers, R. L. and Calvert, S., "Particle Deposition from Turbulent Streams
by Means of Thermal Force," I and EC Fundamentals, Vol. 8, No.4, November
1969.
7.
Personal communication with Mr. R. F. 'ranner, Lockheed-Georgia Research
Laboratory, Marietta, Georgia, September 1971.
8.
Lieberman, A., "Aerosol Rarefaction Studies," American Industrial Hygiene
Association Journal, September-October 1968, pp. 444-449.
9.
Sehmel, G. A. and Schwendiman, L. C., "Particle Deposition from Turbulent
Air Flow," Battelle-Northwest, Richland, Washington, Annual Report for
1969 to the USAEC Division of Biology and Medicine, BNWL-1307, Part 1,
UC-48, June 1970.
10.
Snyder, W. H. and Lumley, J. L., "Some Measurements of Particle Velocity
Autocorrelation Functions in a Turbulent Flow," unpublished report obtained
from J. L. Lumley, Department of Aerospace En~ineering, The Pennsylvania
State University, University Park, Pennsylvania, January 1971.
11.
Habibi, K., "Characterization of Particulate Lead in Vehicle Exhaust - Ex-
perimental Techniques," Environmental Science and Technology, Vol. 4, No.3,
March 1970, pp. 239-248.
12.
Bulba, E. and Silverman, L., "A Recirculating Aerosol Tunnel," APCA Paper
No. 66-82, June 1966.
13.
Soo, S. L., et. al., "Concentration and Mass Flow Distributions in a Gas-
Solid Suspension," I and EC Fundamentals, Vol. 3, No.2, May 1964, pp. 98-
106.
14.
Personal communication with Mr. Murrell Selden, Walter C. McCrone Associates,
Inc., Chicago, Illinois, March 1971.
15.
Anon., Steam, Its Generation and Use. The Babcock and Wilcox Company, New
York, 1955.
16.
Personal communication with Mr. A. Lieberman, Royco Instrument Company,
Menlo Park, California, January 1971.
101
-------
17.
Hinze, J. 0., Turbulence, McGraw-Hill Book Company, Inc., New York, 1959.
18.
Pankhurst, R. C. and Holder, D. W., Wind Tunnel Techniques, Sir Isaac Pit-
man and Sons, Ltd., London, 1952.
19.
Bradshaw, P. and Pankhurst, R. C., "The Design of Low Speed Wind Tunnels,"
in Progress in Aeronautical Sciences, Vol. 5, D. Kuchemann and L. Sterne,
editors, Oxford, pergammon Press, Ltd., New York, MacMillan Company, 1964,
pp. 1-67.
20.
Becker, H. A., Rosensweig, R. E., and Gwozdz, J. R., "Turbulent Dispersion
in a Pipe Flow,: AICHE Journal, Vol. 12, No.5, September 1966.
21.
Bradshaw, P., "Simple Wind Tunnel Design," National Physical Laboratory,
Aerodynamics Division, NPL Aero Report 1258, February 1968.
22.
Cohen, M. J. and Ritchie, N. J. B., "Low Speed Three-Dimensional Contrac-
tion Design," Journal of the Royal Aeronautical Society, Vol. 66, 1962,
p. 231.
23.
Anon., "An Ordinance Providing for the Conservation of Air Resources by
Prevention, Abatement, and Control of Air Pollution," obtained from
Mr. Copeland at Durham County Health Department, Durham, North Caroline,
January 1971.
102
-------
APPENDIX
Drawings M-l through M-22 are included in this Appendix.
A-I
-------
LTR
REVISIONS
DESCRIPTION
APPROVED
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DUe:. T
DUST BI"I
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8H MATl-BREAK EDGES .005 MAX R
ALL V SURFACES TO BE V
DIM AND TOL APPLY BEfORE FIN. TREAT.
MATERIAL
MANUFACTURER
DESCRIP110N
Dl..o..i.-..-
AEROTHERM CORPORATION
485 CLYDE AVE, MOUNTAIN VIEW, CA 94040
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CHECKED
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MANUFACTURER
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485 CL..YDE AVE, MOUNTAIN VIEW, CA 94040
PA!2iICLE WIND ,ut-JNEL
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/Vq.. L >< 1,46 It-/FT)( 7z. L4
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LIST OF MATERIALS
DESCRIP110N
AEROTHERM CORPORATION
485 CLYDE AVE, MOUNTAIN VIEW, CA 94040
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MATERIAL
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LTR
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LIST OF MATERIALS
ENGINEER
AEROTHERM CORPORATION
UNLESS OTHERWISE SPECIFIED
DIMENSIONS ARE IN INCHES
FRACTIONS DECIMALS ANGL£S
:I: V60l :I:.~:I:.;gx :1:0'30'
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'304 '5iAlNLE-SS
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485 CL.YDE AVE. MOUNTAIN VIEW, CA 94040
APPROVED
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LIST OF MATERIALS
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AEROTHERM CORPORATION
485 CLYDE AVE, MOUNTAIN VIEW, CA 94040
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AEROTHERM CORPORATION
485 CLYDE AVE, MOUNTAIN VIEW, CA 94040
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LIST OF MATERIALS
DESCRIPTION
AEROTHERM CORPORATION
485 CLYDE Ave. MOUNTAIN VIEW, CA 94040
5TI LL I N cS CHA.M @EI2
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MANUFACTURER
LIST OF MATERIALS
AEROTHERM CORPORATION
4815 CLYDE AVE, MOUNTAIN VIEW, CA 94040
UNlESS OTHERWISE SPECIFIED
DIMENSIONS ARE IN INCHES
FRACTIONS DECIMALS ANGLES
:I: V64 :I: .r.: :I:.olfX :1:0'30'
MACH COR-.OO!5 TO .015 R OR CHAM
SH MATt-BREAK EDGES .005 MAX R
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MATERIAL
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