VELOCITY OF PARTICULATE IN
LAMINAR AND TURBULENT GAS FLOW
BY HOLOGRAPHIC TECHNIQUES
October 1971
J. B. Allen R. F. Tanner
D. M. Meadows L. M. Boggs
Contract EHSD 71-34
Lockheed-Georgia Company
Marietta, Georgia
-------
VELOCITY OF PARTICULATE IN
LAMINAR AND TURBULENT GAS FLOW
BY HOLOGRAPHIC TECHNIQUES
October 1971
J. B. Allen
D. M. Meadows
R. F. Tanner
L. M. Boggs
Contract EHSD 71-34
Lockheed-Georgia Company
Marietta, Georgia
-------
OFFICIAL USE ONLY
Final, interim, and monthly reports submitted under this contract
contain information and statements which are pre liminary and
represent only the state of the information developed as of the
reporting date. This information is also subject to review and
critique by NAPCA personnel before release outside of NAPCA.
To prevent inappropriate dissemination of information which could
be misinterpreted and/or misleading, you are asked to regard
these reports strictly as internal working documents and treat them
accordingly. You are requested to observe the following guidelines:
(1) Use the reports for information and coordination
purposes only.
(2) Do not discuss the reports or the information
contained in them with persons outside of NAPCA.
(3) Refer all inquiries relating to the reports to the
Project Officer.
(4) Provide comments to the Project Officer for his
use in managing the contract.
i
-------
FOREWORD
This is the final report of the contract "Velocimetry of Participate
in Laminar and Turbulent Gas Flow by Holographic Techniques, "
Contract EHSD 71-34, sponsored by the Office of Air Programs of
the Environmental Protection Agency (EPA) and carried out by the
Lockheed-Georgia Company.
The research done under this contract was carried out by members
of the Lockheed-Georgia Research Laboratory. Project Directors
for this contract were D. M. Meadows and L. M. Boggs. J. B. Allen
directed the technical effort and was responsible for the design of the
holographic systems. R. F. Tanner designed and instrumented the
duct used in the experiments. D. M. Meadows and L. M. Boggs
were responsible for the electronic instrumentation and electrical
systems used in the experiments. J. R. Williams, Consultant,
designed the particulate dispenser to seed the air flow in the duct.
C. R. Huie constructed the duct and particulate dispenser and
provided invaluable assistance in all aspects of the experimental work.
11
-------
ABSTRACT
A technique for measuring the velocity and behavior of particulate
suspended in potential and turbulent air flows by means of double-
pulsed holography is presented.
Descriptions of the air duct facility, particulate dispenser, and
holographic systems are provided as we 11 as discussions of
experimental results and theoretical considerations. Double-
pulsed holography was proved to be an exce 11ent technique for
measuring the characteristics of suspended particulate of sizes
greater than 6 microns. The measurable characteristics include
velocity, three-dimensional coordinates of the particle, size and
shape. Specific experiments were performed to determine the
feasibility of the double-pulsed holographic technique. These
experiments included studies of particulate behavior in electro-
static fields, in potential and turbulent flow, and around a
sampling probe for various sampling conditions.
Hi
-------
TABLE OF CONTENTS
Section Title Pap;e
FOREWORD ii
ABSTRACT iii
LIST OF ILLUSTRATIONS vi
I INTRODUCTION 1
II TEST FACILITY
A. General Description 3
B. Air Duct Facility
1. General Design Considerations 3
2. Turbulent Flow Test Section 6
3. Potential Flow Test Section 6
4. Fan Motor Sizing 8
C. Velocity/Density Surveys
1. Survey Stations 11
2. Probe Drive Mechanism 14
3. Profiles 18
D. Particulate Dispenser 30
E. Holographic Systems
1. Systems for Making and
Reconstructing Holograms 37
2. Systems to Obtain Data from
Holograms 49
3. Holographic Systems Selected
for Experimental Programs 59
III EXPERIMENTAL PROGRAM
A. Potential Flow Holograms 80
B. Turbulent Flow Holograms 87
iv
-------
Section Title Pav;e
C. Holograms of APCO Train Probe 87
D. Holograms of Charged Plates 101
IV CONCLUSIONS AND RECOMMENDATIONS 113
v
-------
LIST OF ILLUSTRATIONS
Figure Title Page
1 Air Duct Facility and Particulate Dispenser 4
2 Holographic Reconstruction System 5
3 Pulsed Laser System 5
4 Turbulent Test Section 7
5 Side View of Air Duct Intake 9
6 Front View of Air Duct Intake 9
7 Potential Test Section and Transition Section 10
8 Potential Flow Test Section Windows 10
9 Nozzle, Fan, and Exit Ducting 12
10 Potential Flow Test Section 13
11 Turbulent Flow Test Section 15
12 Probe Drive Mechanism Mounted at Potential
Test Section 16
13 Probe Drive Mechanism 16
14 Probe Drive Power Supply, Position Readout
(DVM), Airspeed Indicator, and Control Box 17
15 Particulate Sampling Probe (APCO Train Probe)
and Velocity Profile Probes 17
16 Velocity Profile Potential Flow Test Section
Position C-l (Upper) 20
17 Velocity Profile Potential Flow Test Section
Position C -2 21
18 Velocity Profile Potential Flow Test Section
Position C-3 22
19 Velocity Profile Potential Flow Test Section
Position C -4 (Lower) 23
vi
-------
LIST OF ILLUSTRATIONS
Figure Title Page
20 Velocity Profile Potential Flow Test Section
Position C-1 (Upper) 24
21 Velocity Profile Potential Flow Test Section
Position C-2 (Upper) 25
22 Velocity Profile Potential Flow Test Section
Position C-3 26
23 Velocity Profile Potential Flow Test Section
Position C-4 (Lower) 27
24 Velocity Profile Turbulent Flow Test Section 28
25 Velocity Profile Turbulent Flow Test Section 29
26 Blender Type Particulate Dispenser 31
27 Particulate Dispenser Assembly 32
28 Dispenser Hopper, Mixing Blades, and Mixing
Chamber 32
29 Internal Construction of Mixing Chamber 33
30 Dispenser Hopper and Auger Feed 33
31 Particulate Dispenser Drum and Preserve System 34
32 Slotted Tube (Rake) Used to Dispense Flyash
into Duct Facility 36
33 Screens and Slotted Tube 36
34 Single Beam Holographic System 38
35 Reconstruction System for Single Beam Hologram 39
36 System to Magnify and Spatially Filter the
Reconstructed Image 41
37 Schematic of Two-Beam Hologram 42
38 Reconstruction of a Two-Beam Hologram 43
39 Reconstruction of a Hologram of Small Glass Balls
Made with Forward Scattered Light 45
vii
-------
LIST OF ILLUSTRATIONS
Figure Title Page
40 Reconstruction of a Hologram of Small Glass
Balls Made with Side Scattered Light 46
41- Test Tube Dispenser for Small Glass Balls 48
42 Example of a Reconstruction from a Double Pulsed
Hologram Showing Reconstruction Pairs 51
43 Schematic of Fourier Transform Method of
Estimating Velocity 52
44 Plot of the Correlation Function of r (x, y) Showing
the Central Peak and Two Smaller Peaks at
(-xo, 0) and (xo, 0) 55
45 Schematic of the System to Make a Two-Beam
Hologram of Light from the Reconstruction
in the Focal Plane of a Lens 56
46 Schematic of Correlation Method for Measuring
the Velocity from Particle Holograms 57
47 Schematic of Potential Flow Test Section
Holographic System 60
48 Schematic of Turbulent Flow Test Section
Holographic System 60
49 Pulsed Ruby Laser Used in the Experimental Work
and the Pulse Monitoring System Consisting of
a Glass Plate Which Reflects a Small Portion of
the Beam, a Photoelectric Cell, and a Storage
Scope 61
50 Holographic System for the Potential Flow Test
Section Showing Aperture, Negative Lens,
Mirror, and Collimating Lens, and the
Test Section 63
51 The Holographic System Around the Potential Flow
Test Section Showing the Optical System, Test
Section, and Film Holder 64
52 The Holographic System for the Turbulent Flow
Test Section Showing the Laser Beam, Negative
Lens, Collimating Lens, Mirror, Test Section,
and Film Holder 65
viii
-------
LIST OF ILLUSTRATIONS
Figure
Title
53
Schematic of the System to View and Make
Measurements of the Particle Holograms
The System Used to Reconstruct the Particle Holo-
grams Showing the One-Watt, Argon Laser, Lens
Pinhole Combination, Collimating Lens, Hologram,
Microscope Objective, Spatial Filter, and Ground
Glass Viewing Screen
54
55
Close -up of the Reconstruction System Showing the
Hologram, Microscope Objective, and Spatial
Filter
Sketch of the Potential Flow Section Showing the
Cylindrical Portion of the Test Section Which
is Holographed
56
57
Micrometer Positioned Hologram Holder Used in
Particle Reconstruction Experiments
Example No.1 - Distinctively Shaped Particle Pair
58
59
Example No.2 - Distinctively Shaped Particle Pair
Two Particle Pair Reconstruction
60
61
Four Double Pulsed Particle Pairs in Potential Flow
62
Particle Reconstruction of Flow About the APCO
Train Probe (. 5 Isokinetic)
63
64
Personnel Programming Facility for Tests
Scanning Electron Microscope Photograph of
Flyash 1250 x
65
66
Potential Flow Hologram No. 110
Turbulent Flow Hologram No. 175
67
68
APCO Hologram No. 142
Particle Position Diagram for Sampling Probe
69
70
Particle Sampling System Using the APCO Train
Sampling Probe Located in Potential Flow Section
ix
Page
66
68
69
71
72
76
76
77
78
79
81
81
83
93
95
96
99
99
-------
LIST OF ILLUSTRATIONS
Figure Title Page
71 System for Calibrating APCO Train Assembly 100
72 Air Sampling System 100
73 Schematic of Calibration System and Sampling
System 102
74 Precipitator Plates Hologram No. 196 104
75 Charged Plates Device 111
76 Time Exposure Showing Corona Discharge
Patterns Between Plates and Screen 111
x
-------
LIST OF TABLES
Number Title Page
I Potential Flow Holograms 82
Ia Potential Flow Hologram No. 110 84
Ib Potential Flow Hologram No. 110 85
Ic Potential Flow Hologram No. 110 86
II Turbulent Flow Holograms 88
IIa Turbulent Flow Hologram No. 175 89
lIb Turbulent Flow Hologram No. 175 90
IIc Turbulent Flow Hologram No. 175 91
lId Turbulent Flow Hologram No. 175 92
III APCO Train 94
IlIa APCO Train Hologram No. 142 97
IV Charged Plates 103
IVa Precipitator Plate Hologram No. 196 105
IVb Precipitator Plate Hologram No. 196 106
IVc Precipitator Plate Hologram No. 196 107
IVd Precipitator Plate Hologram No. 196 108
IVe Precipitator Plate Hologram No. 196 109
IVf Precipitator Plate Hologram No. 196 110
xi
-------
1.
INTRODUCTION
The primary object of this contract was to develop a technique based on
double-pulsed holography to measure the velocity and behavior of parti-
culate in potential and turbulent duct flows. The development of this
technique provides an important method for investigating particle behavior
on a micr_oscopic level. Potential applications of this technique include the
validation of present particle sampling techniques and setting of
tolerances on probe sampling parameters. Additionally, the technique
provides an excellent method for observing and studying particle
behavior under various flow conditions such as in electrostatic precipi-
tators and in other air control systems. A better understanding of
particulate behavior in these areas should contribute to improved system
efficiencies and lower system costs.
Major sub-objectives for the contract included the following:
o Design, construct and test an air duct facility capable of
producing both potential and turbulent flow.
o Design, construct, and test a particulate dispenser for
injecting selected particulate into the air duct facility.
o Design, construct, and test a double-pulsed holo~raphic
system for recording 3-dimensional images of particulate
in both the potential and turbulent test sections.
o ~~s~~du~~t~~~~~~r~3~c~~:t t~~ ~~l~e~~~~t~~~t~~~e~~~~~
tion of particle characteristics (velocity vectors, particle
size, particle shape).
The following major experiments were conducted under the contract to
evaluate the capability of the holographic systems to meet the primary
objective.
o Holograms were made of particles suspended in potential
flows to provide base -line data and to provide a method
of validating system calibration.
o Holograms were made of particles suspended in turbulent
flow to determine the ability of the system to capture the
particles and to resolve double-pulse pairs.
o Holograms were made of a sampling probe connected to
the APCO Train to evaluate particle behavior at 1. 0
isokinetic, 1. 5 isokinetic, and. 5 isokinetic sampling
conditions.
1
-------
o Holograms were made of particles passing between charged
plates to determine the feasibility of applying double -pulsed
holography to this type of problem.
The official start date of the contract was December 9, 1970. The end
date is December 9, 1971. All technical objectives have been met, on
schedule and within budget.
2
-------
II.
TEST FACILITY
II.A. - GENERAL DESCRIPTION
The test facility was set up in two adjacent rooms, each measuring
approximately 20 x 25 feet. The air duct facility, the particulate
dispenser, and all items relating to these major items were located
in one room (See Figure 1). The holographic reconstruction system
and the pulsed laser were located in the other room (See Figures 2
and 3). A small hole was bored in the wall separating the two rooms
to allow the pulsed laser beam to pass through. A major reason for
separating the majority of the optical components from the rest of the
facility was to prevent damage to the optical systems due to particu-
late present in the air around the duct facility.
II. B. - Am DUCT FACILITY
II. B. 1 - General Desi~ Considerations
The constraints placed on the design of the air duct facility included the
following:
a.
The facility must include two test sections -- a potential
flow section and a turbulent flow section.
b.
The facility must accept various types and amounts of
particulate.
The effects of gravity and ambient air fluctuations upon
particle velocity measurements must be negligible.
c.
d.
The range of velocities was contractually set at 10 - 120
feet per second.
Wall effects upon the flow must be negligible.
e.
f.
Means must be provided to measure velocity profiles in
both the turbulent and potential flow sections.
The initial design of the system resulted in a horizontal, non-return type,
tandem test section duct (consisting of the potential and turbulent test
sections). A vertical tunnel was eliminated as a possibility due to the
potential difficulty of injecting the particulate smoothly into the air duct
against gravity in a low velocity inlet. Space was another consideration
3
-------
FIGURE 1
AIR DUCT FACILITY AND PARTICULATE DISPENSER
-------
FIGURE 2
HOLOGRAPHIC RECONSTRUCTION SYSTEM
FIGURE 3
PULSED LASER SYSTEM
5
-------
in eliminating the vertical tunnel since such an installation would have
to extend through the roof. Also, in the analysis of particulate veloci-
ties, it could have been extremely difficult to separate the effects of
gravity and fluid dynamic forces acting on the particles since the two
forces would act along the same line.
A closed circuit facility was eliminated from consideration since
varying amounts of particulate had to be injected into the tunnel. If
used, this type system would require a number of undesirable features
such as filtering systems and special particulate injection systems to
maintain proper loading conditions.
II. B. 2 - Turbulent Flow Test Section
The turbulent flow test section was located downstream of the potential
flow section and was approximately 1. 5 feet from the end of the tunnel
(See Figure 4). A circular pipe was chosen to develop the turbulent
flow since well-known fluid dynamic theory exists for precisely calcu-
lating air flow characteristics. The flow is symmetrical about the
centerline and once it becomes fully developed the boundary layer
profiles can be predicted by simply measuring the static pressure drop.
Initial plans called for a 60-foot long section to permit the flow to
become fully developed. However, due to space limitations, the length
was restricted to 10 feet which provided partially developed turbulent
flow.
The turbulent flow section was designed first since it contained the only
component constrained by commercial specifications. An aluminum
pipe was selected having a 6. 3 inch inside diameter and O. 16 inch wall.
At the test section, sections of pipe were contoured and welded normal
to the main pipe. On these sections of pipe, metal frames were mounted
for holding the viewing windows (Figure 4). Three-inch diameter holes
were cut into the pipe to allow a viewing area for the laser beam.
Provision was also made for mounting a plate above the pipe on which the
probe drive mechanism could be placed. Three static pressure ports
were installed on one side of the test section to provide for system
calibration.
II. B. 3 - Potential Flow Test Section
The primary problem in generating potential flow in an air duct facility
is to uniformly accelerate ambient air to the desired tunnel velocity
while at the same time smoothing velocity perturbations and preventing
rapid boundary layer growth on the tunnel walls. The method normally
used by smoke tunnel technologists to achieve these characteristics is
to provide a high contraction ratio of entrance area to test section area.
6
-------
FIGURE 4
TURBULENT TEST SECTION
7
-------
Figures 5 and 6 illustrate the "bellmouth" selected for the duct facility
to assure good potential flow. A rectangular entrance section was
chosen which has the same ratio of side lengths as the potential test
section. A contraction ratio of 37. 5 to 1 was used, and the surfaces
joining the entrance area to the test section area were defined by
modified exponential curves.
The bellmouth was constructed using sheet aluminum, cut to the proper
contours and heliarc welded. A wooden frame was used to maintain the
shape during assembly. Discontinuities were removed by contouring
with putty and sanding smooth.
The potential flow test section was designed to be 7. 0 inches high and
4. 5 inches wide (See Figure 7). The cross sectional area of the
potential flow section was set to be the same as the area of the turbulent
section to minimize transition problems between the two test sections.
Figure 7 shows the transition section on the right hand side of the
photograph. The rectangular shape of the potential flow section was
selected primarily from considerations of the optical system. A rectan-
gular shape allowed the use of inexpensive, optically flat windows to be
used with a minimum of perturbations introduced into the flow by the
windows. Seven inches of height assured that the hologram viewing area
would be well above any boundary layer problems or perturbations that
might arise from the tunnel walls.
Mounting of the windows was accomplished by using aluminum plates with
4" x 5" cutouts. Figure 8 shows front and back views of the window
holders. On the back side of the holder, thin strips of metal were
attached to the holder to prevent the 1/4" thick optical windows from
moving inward. Interference of the strips with the flow was minimized by
keeping the strips small, 0.20" thick and. 375" wide and by fairing the
strips in with the holder. At the top of one of the window holders, as
shown in Figure 8, static pressure ports were implaced to provide a
reference for the air speed indicator and to provide data for calculating
air density.
The test section was constructed of 1/2" plywood to facilitate changes that
were anticipated during the test phases of the program. The internal faces
of the plywood were smoothed and coated with automotive primer paint.
II. B. 4 - Fan Motor Sizin~
High priority was given to the choice of the fan in terms of air flow
capacity and ability to withstand the abrasive effects of particulate for
long periods of time. The type fan which appeared to be most suitable
was a radial flow materials handling fan which could deliver a large
quantity of flow while working against a moderate pressure.
8
-------
FI GURE 5
SIDE VIEW OF AIR DUCT INTAKE
FIGURE 6
FRONT VIEW OF AIR DUCT INTAKE
9
-------
FIGURE 7
POTENTIAL TEST SECTION AND TRANSITION SECTION
FIGURE 8
POTENTIAL FLOW TEST SECTION WINDOWS
10
-------
Fan requirements were determined by breaking the air duct facility
into its component parts and calculating pressure losses in each of
these sections. The basic limiting system specification which
determined the assumptions made in computing the losses was the
requirement that the potential flow section have at least a 120 ft/sec.
velocity capability at standard temperature and pressure.
For each of the sections -- bellmouth, potential flow section, transi-
tion section and turbulent section -- equivalent circular cross-
sectional areas and Reynolds numbers were calculated from which
pressure losses could be determined, and the pressure losses for the
total system were approximated as a summation of the individual
losses. Since at this time plans were somewhat indeterminate as to
what form the ducting would have beyond the fan exit, the losses
associated with this ducting were assumed to be approximately equal
to the calculated losses for the tunnel. Adding these losses to those
of the tunnel provided an estimate of overall fan capacity requirements.
Several fans were found which could fulfill the requirements; however,
from the availability and cost standpoint, the final choice was a blower
made by the New York Blower Company. The model chosen was the GI
fan size 142 with LS wheel and unitary base, powered by a 3, 500 RPM,
7-1/2 HP, 3 phase, 208 volt motor. The blower had a counterclockwise
up blast configuration which was selected to facilitate installation of the
exit ducting. The blower and exit ducting are shown in Figure 9.
Since the range of air velocities required were quite large and the
particular velocities used would be dependent on holographic considera-
tions, it was decided to provide a continuous velocity adjustment on the
duct facility. This consisted of a conical diffuser section with a conical
exit nozzle immediately in front of the fan but separated from it by an
air gap. By adjusting the air gap and thereby changing the amount of
room air bled into the fan, the ve locity in the tunnel could be adjusted to
within :i:1/4 MPH of a desired velocity.
II. C.
- VELOCITY AND DENSITY SURVEYS
II. C. 1 - Survey Stations
In order to verify the nature of the flow in both the potential and turbu-
lent test sections, a number of velocity surveys were made using a
mechanically positioned pressure probe. It was anticipated that if
there were any non -symmetrical flow present it would occur in the
potential section. For this reason, it was considered important to
completely survey the potential flow whereas the turbulent flow could
be surveyed over more restricted regions. Fifteen stations were chosen
in the potential flow section and are schematically illustrated in Figure
10. These stations were selected to cover the area that would be visible
11
-------
FIGURE 9
NOZZLE, FAN AND EXIT DUCTING
12
-------
.....
t.)
7.0"
~" TYP
~
I
I
/(
,/' "
,/ "-
,/
,/
FLOW MEASUREMENT POSITIONS
CENTERLpm .
I
1
I
I
I~
I I"
1 I . "-
I' ,
~ .......
FIGURE 10 POTENTIAL FLOW TEST'SEcTION
-------
in the holograms. Three axial locations, at the front, middle, and rear
of the test section were used so that any longitudinal velocity gradients
could be measured. The five stations across the test section could
determine the exte~t of velocity variation in this direction.
Because of the symmetrical nature of the flow in the turbulent test
section, only profiles in one plane were measured (Figure 11). It was
decided that the slight distortion of the flow caused by the window holes
in the cylindrical section would not be extreme. The probe drive
mechanism had a limited travel, and it was necessary to make two
separate traverses to span the duct. Each traverse began at the upper
or lower surface and continued across the centerline of the duct. The
data was reduced and the velocity profiles matched at the appropriate
point on the centerline. In order to adequately measure the profile, a
large number of points were recorded near the tunnel surfaces. Areas
away from the wall needed less definition to adequately describe the
flow.
II. C. 2 - Probe Drive Mechanism
Figure 12 shows the probe drive mechanism mounted on top of the
potential flow test section. Figure 13 is a close up of the mechanism
with a probe attached. The mechanism consists of a steel plate free to
move linearly on guide rails, driven by an electric lead screw. Attached
to the plate is a total pressure probe and the movable end of a 0 to 10K
ohms linear potentiometer. The potentiometer is used as a position
indicator for the probe. Microswitches are used to limit the travel and
prevent damage to the mechanism. Total travel of the probe is 3.6 inches
which is slightly more than half the distance from floor to ceiling of the
tunne 1.
Figure 14 shows the digital voltmeter (DVM) used to measure displace-
ment of the probe, the airspeed indicator used for air velocity measure-
ments, the control box, and two power supplies. The regulated power
supply provides 10 volts across the linear potentiometer in the probe
drive mechanism. Therefore, the voltage output to the DVM is
proportional to probe displacement. This system was calibrated using a
depth micrometer, accurate to O. 001 inch. The overall accuracy of the
readout system was :f:0. 010 inch; i. e., the tolerance between actual probe
position versus DVM readout. The mechanical parts of the probe drive
assembly contributed little to the overall error. Over a 3.6" up and down
traverse the probe return was within 0.001" of the starting point.
The power supply used with the probe drive motor was set at 12 volts. In
Figure 14, the control box shown on top of the potentiometer power supply
was used to control direction of travel and provided incremental motion
(center button) as well as continuous motion. Velocity data was read out
on the airspeed indicator which was connected to the probe and a static
14
-------
......
c:.TI
FLOW
..
FLOW MEASUREMENT POSITION
\
/,,' \ -'....,
~ ,
- - -/r- - - ; ~ :: -\::--"'-""'-..... - - - .,~ - -
I " ~ " '
I J' \
I I I \ \
I / I \ \
I I \ \
, : \
I
T ,
\ \ ~ I I
\ J "
\ \ J / I
\ WINDOW J /
\ "J /
, , , ./ I
, ..... I ./ /
, ""'--1--- /
-- --,---- ------~---
;t'
;t'
-
--
N"\
N"\
.
-\0
,
.......
-
FIGURE 11 TURBULENT FLOW TEST SECTION
~
~
-------
FIGURE 12
PROBE DRIVE MECHANISM
MOUNTED AT POTENTIAL TEST SECTION
FIGURE 13
.. PROBE DRIVE MECHANISM
16
-------
FIGURE 14
PROBE DRIVE POWER SUPPLY, POSITION READOUT (DVM)
AIRSPEED INDICATOR, AND CONTROL BOX
FIGURE 15
PARTICULATE SAMPLING PROBE (APCO TRAIN PROBE) AND
VELOCITY PROFILE PROBES
17
-------
pressure port.
MPH.
The airspeed indicator was accurate to better than 1/4
In Figure 15, three probes are shown. The large probe at the top was
used in the air sampling experiments described later in the report. The
other two probes were used in measuring the velocity profiles. The
middle pitot probe was used to survey from the ceiling of the test section
to the centerline; the bottom probe was used to survey from the floor up
to the centerline. Both of the small probes had the same size and
orifice shape. They were made from soft stainless steel tubing flattened
at the end to form a rectangular tube with inside measurements of 0.004
inch high and approximately 0.09 inches wide, and a wall thickness of
approximately 0.0015 inches.
II. C. 3 - Profiles
Velocity profiles were recorded in both the potential flow test section
(Figures 16 - 23) and the turbulent flow test section (Figures 24 and 25)
at 25.0 feet/second and 58.7 feet/second. The stations at which the
profiles were recorded are shown in Figures 10 and 11.
Since a complete profile may require up to 200 data points, only position
C-3 was used to run the complete set of profile measurements (at 25
feet/second and 58.7 feet/second). Half profiles were made at positions
C-l, C-2, and C-4 with only spot checks made in the other half of the
profile. All fifteen positions were spot checked to assure that the flow
reflected the characteristics shown in C-l, C-2, C-3, and C-4. Position
C-4 is the mirror image of C-2. The design of the duct facility was such
that these two positions should accentuate any asymetric flow conditions
in the test section. As can be seen from the figures, agreement between
the two positions is quite good, indicating symmetrical flow.
As would be expected, the corner profile, C-l, shows a boundary layer
which is thicker than at other points in the tunnel.
As can be seen from the potential section profiles, the flow was quite
uniform throughout the test section at 25.0 feet/second and 58.7 feet/
second. Sample profiles were also made at a number of other velocities,
all of which manifested the same characteristics, the only major dif-
ference being changes in boundary layer. The boundary layers at 25. 0
feet/second and 58.7 feet/second were nominally 3/8 inch thick. In all
cases, the area viewed by the hologram was completely in the steady or
potential flow region. The recorded holographic view was two inches
above and two inches below the centerline of the duct.
While the flow in the potential test section was steady and uniform as
measured by the pitot tubes, there is some indication that the flow was
not completely irrotational. Data from the double pulsed holograms
18
-------
indicate that rotational forces were present. This was evident from
observing particles which were distinctly shaped and noting the slight
change in shape that occurred from the first light pulse re cording to
the second. It appeared that the particles in certain cases had
rotated, indicating that small rotational forces had been introduced
into the system somewhere upstream. The suspected point of rota-
tional force introduction was at the point where the flow passes through
the screens.
To assure the best potential flow, it was necessary to keep the screens
clean and sealed against the be llmouth. Leaks at this point could cause
small perturbations in the flow in the form of asymmetric flow. This
effect is noted in the small differences in boundary layer growth at the
top and bottom of the test section as shown in the profile plots.
The partially developed turbulent flow was as predicted at 58.7 feet/
second. However, at 27.9 feet/second the flow was somewhat
irregular. The difference is attributed to the short transition section
and the lower Reynolds number associated with the lower velocity.
These combined effects would cause the turbulent flow to develop slower
and be more susceptible to perturbations from upstream sources. It is
also suspected that at the lower Reynolds number, separation may have
occurred in the transition section.
Values for static pressure were obtained using the wall pressure taps
and an inclined manometer. Because of the indraft nature of the duct
facility, the pressures were slightly below the atmospheric value.
Pressures ranged from 14. 16 PSIA in the potential section at 25 feet/
second to 14. 12 PSIA in the turbulent flow section at 58.7 feet/second.
The densities corresponding to these values were O. 00228 and O. 00227
slugs/feet3. Density is constant over the cross section of the tunnel
at a particular point along the tunnel. The very small longitudinal
pressure gradients, or those along the tunnel, result in only minute
variation in density.
Since there was no density variation across the test section, no density
profiles were made. For all the eJg>erimental tests conducted, the
nominal density was O. 00228 slugs/feet3. The conversion formula is
shown below:
where p
P
R
T
g
P
P = RTg
is density in slugs/feet3
is pressure in Ibs/ft2.
is a constant (53.3 ft/degrees Rankine).
is temperature in degrees Rankine.
is gravitational acceleration (32.2 ft/sec2).
19
-------
6.0
tIJ
~
~
s::
1-4 5.0
s::
0
.....
.....
~
Q)
00
.....
tIJ 4.0
Q)
~
'+-f
0
!-4
0
0
-
~ 3.0
o
.....
-
~
S
!-4
0
Z
Q) 2.0
~
s::
~
.....
tIJ
.....
0
1.0
FIGURE 16
Velocity Profile
Potential Flow Test Section
Position C-1 (Upper)
7.0
. .
. .
. . .
..
.
.
.
.
.
.
.
.
.
- - Cente line
- - - -
.
o
30
o
15
20
25
5
10
Velocity
Ft/Sec.
20
-------
00
Q)
~
t)
I::
1-4
I::
o
.....
....
t)
Q)
00
....
00
Q)
~
....
o
~
o
o
-
~
o
....
-
ell
a
~
o
Z
Q)
t)
I::
.s
00
.....
~
1.0
FIGURE 17
Velocity Profile
Potential Flow Test Section
Position C - 2
7.0
. . .
.
"
'
. '.
.
.
.
.
.
.
.
.
Cente Irline
- - - - -
.
6.0
5.0
4.0
3.0
2.0
o
o
15
20
25
30
5
10
Velocity
Ft!Se c.
21
-------
rn
~
C)
I:: 5.0
1-4
I::
0
.....
..
C)
(1)
00 4.0
..
rn
(1)
~
'+-4
0
~
0
0 3.0
-
~
o
..
-
~
S
~
0
Z 2.0
(1)
C)
s:::
M
...,
rn
.....
CI
1.0
FIGURE 18
Velocity Profile
Potential Flow Test Section
Position C-3
7.0
o
. . . . .
. . . .
.
.
.
.
.
.
:
Center .
- ine -
- - - -
.
.
.
.
.
.
.
or . . .0
. 0 0 .
6.0
o
10
15
30
20
25
5
Velocity
Ft/Sec.
22
-------
FIGURE 19
Velocity Profile
Potential Flow Test Section
Position C-4 (Lower)
7.0
6.0
Cent r line
- - - - - - -
.
.
.
.
.
.
.
.
.
.
. .
. . . . , .
U)
,g
u
~ 5.0
1-1
~
0
....
....
u
Q)
00
.... 4.0
U)
Q)
E-i
'+-I
0
~
0
0
.... 3.0
~
o
....
....
~
8
~
0
Z 2.0
(1'
~
~
....
U)
....
Q
1.0
o
o
5
10
15
20
25
30
Velocity
Ft/Sec.
23
-------
6.0
00
~
C,)
I::
~ 5.0
I::
0
..-.
....
C,)
Q)
r:n.
.... 4.0
00
Q)
~
'H
0
~
0
0
..... 3.0
~
o
....
.....
(ij
S
~
0
Z 2.0
Q)
C,)
I::
(ij
....
00
..-.
~
1.0
FIGURE 20
Velocity Profile
Potential Flow Test Section
Position C -1 (Upper)
7.0
. .
.
"
.
.
' .
.
..~
.
.
.
Center ine .
- - - - - - -
.
o
o
30
60
40
50
10
20
Velocity
Ft/Sec.
24
-------
rn
Q)
..c:
u
~ 5.0
r:::
0
.....
...
u
Q)
U) 4.0
....
rn
Q)
~
'H
0
1-4
0
0 3.0
.....
~
o
...
.....
~
a
1-4
0
Z 2.0
Q)
u
r:::
~
...
rn
.....
Q
1.0
FIGURE 21
Velocity Profile
Potential Flow Test Section
Position C -2 (Upper)
7.0
" " "
"
, "
' .
. ,
,
,
.
,
Center ine
-- - - - - -
6.0
o
o
30
60
40
50
10
20
Velocity
Ft/Sec.
25
-------
6.0
[J]
(l)
..c:
u
s::
~ 5.0
s::
0
.....
.....
u
(l)
UJ. 4.0
.+oJ
[J]
(l)
E-t
<0-4
0
!-4
0
0 3.0
-
~
o
~
-
~
8
!-4
0
Z 2.0
(l)
u
s::
.s
[J]
.....
0
1.0
FIGURE 22
Velocity Profile
Potential Flow Test Section
Position C-3
7.0
'" ' . ,
, ,
" '"
" '
. .
,
.
,
.
Center line
- - - - - - ".
.
.
:
."
" .
. .
.
o 0
50
60
30
40
10
20
Velocity
Ft/Sec.
26
-------
6.0
rJ)
~
C,)
I::
~ 5.0
I::
0
....
....
C,)
Q)
00 4.0
....
rJ)
Q)
~
~
0
~
0
0 3.0
-
~
o
....
-
CI!
a
~
0
Z 2.0
Q)
C,)
I:
CI!
....
rJ)
....
~~
1.0
FIGURE 23
Velocity Profile
Potential Flow Te st Se ction
Position C-4 (Lower)
7.0
Cenh r 1 ine .
-- - - - - - -
.
.
.
.-
. :
.
. " .
0 10 20 30 40 50 60
o
Velocity
Ft/Sec.
27
-------
rn
Cl)
..c::
u 5.0
!::
1-4
!::
0
.....
.....
u
Cl) 4.0
00
.....
rn
Cl)
E-4
'+-I
0
s..
0 3.0
o
......
~
0
.....
......
C':!
8
s.. 2.0
o
Z
Cl)
U
!::
C':!
.....
rn
.....
~ 1.0
FIGURE 24
Velocity Profile
Turbulent Flow Test Section
6.0
.I
'.
.
.
'.
.
CentE rline
~ - - - - - -
.
.
.
o
15
20
25
30
o
10
5
Velocity
Ft/Se c.
28
-------
. ' . . . . '
. '
. .
.
'
.
.
.
.
.
'
.
.
.
.
.
Cent I> r line .
- - - - '- - - - - -
.-
.
.
.
.
.
.
.
.
.
.
. " ,
"
, ,
C/)
Q) 5.0
.c::
u
!::
1-1
!::
0
.... 4.0
...
u
Q)
U)
...
C/)
Q)
~
.....
0 3.0
J...
o
0
......
~
0
...
......
C!J
S 2.0
J...
0
Z
Q)
u
!::
C!J
...
C/) 1.0
....
~
FIGURE 25
Velocity Profile
Turbulent Flow Test Section
6.0
o
o
10
20
30
40
Velocity
Ft/Sec.
29
50
60
-------
II. D.
- PARTICULATE DISPENSER
The particulate of interest in this contract included limestone, iron oxide,
and in particular flyash. Dry powders, including those mentioned above,
generally fall into two categories: Those that can be packed into a some-
what solid cake, and those that remain free flowing regardless of all
attempts to pack them into a container. It was found that powders that
can be packed are dispersed easily by a generator similar to the Wright
dust feed generator, but such a generator was not useful for dispersing
powders such as flyash that remain free -flowing. The Wright dust feed
generator scrapes a thin layer of powder from a solid packed cake and
disperses the powder scraped off, and works well with powders such as
iron oxide that pack easily. On the other hand, powders which remain
free flowing are dispersed well by a dispenser employing high speed
mixing blades in a chamber which mix the particulate with air much like
a food blender that uniformly mixes food particles with a liquid. This
type of generator has worked well with free flowing powders such as
carbon and flyash, but does not perform satisfactorily with powders that
pack, such as tungsten or iron oxide, because of the tendency for such
powders to cake around the sides of the mixing chamber.
In the initial stages of the program, all three types of particulate were
tried in a Wright dust feed generator. A pe llet was made of each material
by compressing it in a hydraulic press to a pressure of 8,000 psi. The
pellets were placed in the Wright generator, and it was found, as antici-
pated that only the iron oxide yielded a consistent stream of particulate.
Both the flyash and limestone tended to crumble under the scraper blade
and gave inconsistent results.
Since the major portion of the contract work concentrated on flyash, the
particulate generator selected for use was one which would work well
with free flowing materials. The design selected was a modified version
of a generator which had previously been developed on a NASA sponsored
study at the Georgia Institute of Technology by Dr. Richard Williams.
The selected design is shown in Figure 26. The actual device used is
shown in Figure 27. Figure 28 shows the hopper, mixing blades and
mixing chamber as an exploded view. The internal construction of the
mixing chamber is shown in Figure 29. The hopper and auger feed
arrangement is illustrated in Figure 30. The complete assembly
(Figure 27) fits inside a pressurized, 55 gallon drum (Figure 31).
The operation of the particulate dispenser is described below: An external
air line (100 psi) was connected to a filter and regulator with the regulator
normally set at approximately 10 psi. The regulated 10 psi air supply was
connected to a tee fitting; one side of the tee fed air into the drum and the
other led to a by-pass valve. The air entering the drum was forced to
pass through a matrix of fine holes in the bottom of the mixing chamber
(Figure 29). Particulate was constantly fed into the top of the mixing
30
-------
i
2.75"
24"
"
. .
Mixing
Chamber
1-
-
FIGURE 26.
14"
-
'~N~~~ '.'.~" :.;...~~~:
;,~;..'~""'~: J:~~ ,.I'~'.:'~
I.:. .: .: II., . .. I" ..
.... "" .... ..
~J;; :"..!: \... (-...-,,,,,.)..../.
: :':7.. ..~!:l.~:~;':' i".
."..., ., "-.,. ,.,
. '. ,".."
...
-
o
31
3" O.D.
BLENDER TYPE PARTICULATE DISPEN"SER
3450 RPM
1J3HP MOTOR
19"
0-175 RPM
DC MOTOR
AND REDUCER
11.5"
13"
5"
8"
1
..
-------
'"'~
.#r
FIGURE 27
PARTICULATE DISPENSER ASSEMBLY
FIGURE 28
DISPENSER HOPPER, MIXING BLADES, AND MIXING CHAMBER
32
-------
FI GURE 29
INTERNAL CONSTRUCTION OF MIXING CHAMBER
FIGURE 30
DISPENSER HOPPER AND AUGER FEED
33
-------
FI GURE 31
PARTICULATE DISPENSER DRUM AND PRESSURE SYSTEM
34
-------
chamber from the conical hopper by a modified 3/8 inch wood auger.
The rate of feed from the hopper was controlled by a variable speed
d. c. motor connected through reduction gears to the auger. In the
mixing chamber, two sets of blades, one above the other, were used
to continuously stir the mixture of air and particulate. Two pro-
trusions were placed in the chamber to prevent the particulate from
concentrating along the walls of the chamber due to centrifugal forces
generated by the blades. The mixture of air and particulate passed
through a 3/8 inch tube connected to the mixing chamber and extended
out through the wall of the drum. The line carrying the air entrained
particulate joined the bypass air line at a tee outside the drum.
The bypass control valve allowed the concentration of particulate
emerging from the dispenser to be diluted by mixing it with controlled
amounts of bleed air. The resulting mixture was sent via a 3/4"
flexible tube to a rake positioned in front of the duct facility bellmouth.
The rake consisted of a vertical 3/4" diameter aluminum tube, slotted
on the side facing the bellmouth intake (Figure 32). Figure 33 shows
the set of screens positioned in front of the bellmouth which were used
to damp out ambient pressure fluctuations. Since particulate would
eventually build up on these screens, it was necessary to periodically
clean them with an air gun.
Pressure inside the dispenser drum was monitored by a "U" type
manometer which was normally set at 15" of water. The manometer also
served as a pressure relief valve in that if the pressure exceeded 20" of
water in the drum, the water was blown out and air was allowed to bleed
out of the drum.
The concentration of particulate emitted into the duct facility was con-
trolled by the internal pressure of the drum, the auger speed, and the
bypass control valve. For major changes in particulate loadings, the air
holes in the bottom of the mixing chamber could be opened or closed with
a sealing material; the auger could also be changed such that more or
fewer threads per unit length were available to feed particulate into the
mixing chamber, or the gear reduction ratio could be changed between the
D. C. motor and auger.
Using flyash as particulate, the grain loadings available in the duct
facility ranged from. 11 grains per standard cubic foot at 57 feet/second
to 8 grains/scf at 24 feet7second. Normal operating ranges were between
. 15 and 5.0 grains/scf at 24 feet/second.
The dispenser proved to be quite versatile, inexpensive, and capable of
operating for extended periods of time over a wide range of flow rates
and particulate loadings. For reliable operation of the dispenser, it
was necessary to use flyash with a low moisture content and to
periodically inspect and clean out any clogged holes in the mixing
chamber. The dispenser also worked well with powdered limestone, but
with a material such as iron oxide, the system did not perform as satis-
factorily due to the tendency of the material to cake in the mixing chamber.
35
-------
FIGURE 32
SLOTTED TUBE (RAKE) USED TO DISPENSE
FL YASH INTO DUCT FACILITY
FIGURE 33
SCREENS AND SLOTTED TUBE
36
-------
II.E.
- HOLOGRAPHIC SYSTE MS
The design of the holographic system consisted of two phases, namely
the system to make the holograms and the system to view and obtain
data from the holograms. One -beam and two-beam holographic systems
were considered for making the holograms. Several systems, in-
cluding automatic data reduction techniques, were considered as means
to obtain data from the holograms. The various systems which were
studied to make and to obtain holographic data are discussed below
followed by a detailed description of the systems chosen.
II. E. 1 - Systems for Making and Reconstructing Holograms
Single Beam Hologram:
The single beam hologram (sometimes referred to as the Gabor hologram)
is the simplest to implement of the various holographic systems and has
been used on other particle holography experiments. The beam leaving
the laser is expanded and collimated as illustrated in Figure 34. The
particle scene is illuminated by the collimated beam and then the light
is recorded on a photographic plate that becomes the hologram.
The operation of the single beam hologram can be best understood by
considering the beam striking the photographic plate as consisting of two
components, one, the light scattered by the particles, and two, the light
that passed by or missed the particles. Denoting the light scattered by
the particles as A (x, y) ej,0s(x, y) and the unscattered light by A , the
complex wavefron~ in the plane of the hologram is Ao + As (x, y) °eH?ls(x, y) ;
the amplitude transmission T 1 (x, y) of the resulting hologram is then
given by
T 1 (x, y) = KIAo + As (x, y) eH~s (x, y) 12
= K Ao 2 + K As(x, y)2 + K AoAs(x, y) ej0s (x, y)
+ K Ao As (x, y) e -j0s(x, y)
The unscattered light Ao is generally called the reference beam and
A s(x, y) is called the signal beam.
Figure 35 illustrates a system to reconstruct a single beam hologram.
A collimated wavefront of amplitude B strikes the hologram and the
wavefront U 1 (x, y) leaving the hologram is
37
-------
c:..:>
CP
PULSED RUBY
LASER
DUCT
COLLIMATING LENS
NEGATIVE LENS
.,/"
/"
FLOW
FIlM
FIGURE 34. SINGLE BEAM HOLOGRAPHIC SYSTEM
-------
NEGATIVE LENS
HOLOGRAM
--..-
COLLIMATllJG LENS
RECONSTRUCTION
t..:)
CD
CONTINUOUS LASER
~--
-,..- -
y
~x
FLOW
FIGURE 35.
RECONSTRUCTION SYSTEM FOR SINGLE BEAM HOLOGRAM
-------
Ul(x,y) = B KA02 + B KAS2 (x,y) + B KA~s(x,y) eH1s(x,y)
+ B K AoAs (x, y) e -H~s(x, y)
The wavefront leaving the hologram is composed of four components as
indicated by the above equation. The first two components are of low
spatial frequency and contain no useful information. The
BKA A (x, y) e -j~s(x, Y) component forms a real image of the particles
o s
and the BKAoAs(x, y) ej~s (x, y) forms a virtual image of the particles
which appears behind the hologram. Since the low frequency components
are generally bright enough to obscure or "wash out" the particle images
and the particles are often too small to see, the real image is magnified
by a lens as shown in Figure 36. The low frequency terms are brought
to focus near the focal point of the lens and can be removed by placing a
small opaque spot there. The lens, therefore, performs the dual
function of magnifying the particle reconstructions and focussing the low
frequency terms so that the spot can remove them.
Two- Beam Holograms:
The two-beam hologram (sometimes referred to as the Leith-Upatnieks
hologram) differs from the single beam hologram in that the reference
beam, rather than being the unscattered light is a separate beam intro-
duced at an angle with the beam illuminating the particles as illustrated
in Figure 37. Denoting the beam from the particle scene striking the
hologram by D(x, y) eH3(x, y) and the reference beam by Cejkex, the
amplitude transmission of the film exposed as illustrated is given by
T 2(x, y) = KID(x, y) ejO (x, Y)+cejkexI2
= KC2 + KD2(x, y) + KCD(x, y)ej [kex - {3 (x, y]
+ KCD(x, y)e -j ~ex - (3 (x, ylJ
The method of reconstructing the hologram is shown in Figure 38. The
hologram is illuminated by a collimated laser beam and the wavefronts
leaving the holograms are indicated. Note that the real and virtual
images are now separated from each other by an angle 20<. and
separated from the low frequency light components KC2 and KD2(x, y)
by an angle of (1(. The real image from the hologram has the same
amplitude as the wavefront recorded by the Gabor hologram and is
given by
40
-------
MAGNIFIED RECONSTRUCTION
HOLOGRAM
RECONSTRUCTION
/~~
~ ...."" 1
--I --r--I -+--
- I 1
\--- - I __1
-T- -I : T I
L_----1-// --+-
LENS
/ --~
" I 1
SPATIAL FILTER ~ /
.1 ---(
""""'1 I
~ .,.....,.. I 1
~
........
--
-~-
---
-~-
~
........
- - ---.
I
" f
~" I
"I
,I I
L 1 I
- _-yl
FIGURE 36. SYSTEM TO MAGNIFY AND SPATIALLY FILTER THE RECONSTRUCTED IMAGE
-------
DUCT VOLUME
...- -
~
COLLIMATING LENS
1-------
SIGNAL BEAM
~--
--~---
~,..
/..H' I
/ -,//.
- -..- - -;--/;:".#- ~
#/~/ ",..}/\I
/' /"
/ /
/' /"
FLOW .,/'" /' /
~ ~
// /" '.
/'"
/'"
/'"
~
/"
/'
/'
FIlM
~
N
/'
~
REFERENCE BEAM
FIGURE 37. SCHEMATIC OF TWO-BEAM HOLOGRAM
-------
COlLIMATED LASER BEAM
-~----~
,.
-~----'>---~
.,/
~ f\---' /
1\ /\--
I \ \
\ \
I \----)
I I I
\ I I
\ I ~
\ I "-
\ I , VIRTUAL IMAGE
\1 I
L- - --'
HOLOGRAM
#
DC(x.Y)e-jB(x.~
,///
,..
/0(
C2+ ::>2(x,y)
~
.......
~
........
DC(x,y)e+j~x,y)
.
REAL IMAGE
FIGURE 38. RECONSTRUCTtON OF A TWO-BEAM HOLOGRAM
-------
CD(x, y) ej ~ (x, Yb B + A(x, y) ej~(x, y)
The particles can be made a little easier to view by spatially filtering the
B term out by an opaque spot as was done with single beam holograms.
Comparison of One - and Two-Beam Systems
Applied to Particle Holography:
The most obvious difference between one - and two-beam systems applied
to the particle holography problem is that one -beam systems can only
make holograms of light scattered in the forward direction while two-beam
systems can make holograms of light scattered in any direction. Since the
light recorded by a hologram must coincide with the reference beam and
since the reference beam of a single beam hologram is in the forward
direction, it follows that only forward-scattered light can be recorded by a
single beam hologram. The two-beam hologram is more flexible in that
the direction of the reference beam is independent of the direction of the
beam scattered by the particle. Therefore, the two-beam system can be
used to holographically record light scattered to the side or scattered
backwards by the particles.
However, one of the goals of this effort was to precisely determine the
size and shape of the particulate and forward-scattered light is better
suited for this purpose than light scattered in other directions. First of
all, the particles considered in this experiment are 5 microns or larger
and light scattered by particles in this size range are governed by the
laws of Fraunhoffer and Mie scattering. In the Fraunhoffer and Mie
regimes, the light scattered in the forward direction is much stronger
than light scattered in the side or back directions giving the hologram a
stronger beam to record. Since such a small amount of light is scattered
by the particles, it is important that the holq?;ram records the strongest
components of the scattered light. Hence, one would expect that holograms
of forward-scattered light would record smaller particles than holograms
of light scattered in other directions. Also, forward-scattered light
contains more information about particle shape than light scattered in other
directions. The light scattered in the forward direction is related to the
particle shape by a Fresnel transform relation. The reconstruction of the
hologram performs essentially an inverse Fresnel transform yielding an
accurate replica of the shape of the particle. However, light scattered to
the side and backwards will depend on the reflectivity of the particle, and,
therefore, portions of the particle with high reflectivity will produce a
good reconstruction while portions with poor reflectivity will provide a
poor reconstruction. The net result is a poor reconstruction of the
particle. Figure 39 is a photograph of the reconstruction from a particle
hologram made with forward-scattered light while Figure 40 is a photo-
graph of a reconstruction made with side-scattered light. Note how much
more clearly the shape of the particles are shown in Figure 39 as
compared with Figure 40. The experiments carried out to obtain these
photographs are described toward the end of this section.
44
-------
FIGURE 39
RECONSTRUCTION OF A HOLOGRAM OF SMALL GLASS BALLS
MADE WITH FORWARD SCATTERED LIGHT
45
-------
FIGURE 40
RECONSTRUCTION OF A HOLOGRAM OF SMALL GLASS BALLS
MADE WITH SIDE SCATTERED LIGHT
46
-------
The light scattered in the forward direction needed to reconstruct the
particle is confined to a re lative ly small cone whereas the light required
to reconstruct the complete particle is scattered over large angles on
the side or backward directions.
The single beam hologram depends very heavily on a large portion of the
beam not being scattered at all by the particles. The unscattered
portion of the beam acts as the reference beam and is necessary in order
for a hologram to be made. If the particle concentration is so large that
virtually all of the light is scattered by the particles, effectively there is
no reference beam. A very poor hologram, if any at all, is formed. In
addition, if the particle concentration is that high, it is unlikely that
double pulsed pairs could be identified for velocity measurements.
If the particle concentration is very large, a two-beam holographic
system would likely give better results since the reference beam in the
two-beam system is independent of the beam illuminating the particles
and, therefore, is unaffected by particle concentration. The two-beam
system no doubt would reconstruct the light scattered by large concen-
trations of particles, but it might be difficult reconstructing individual
particles in the central portions of a particle cloud. Light from particles
in the center of the cloud of particles might well be scattered a second
time by other particles making reconstruction difficult. Also, light from
out of focus particles will act as noise making it difficult to see individual
particles. In any event, when the particle concentrations become very
large, it becomes very difficult to make holograms of any kind which can
resolve the individual particles. A two-beam system can make a good
hologram of the scattered light which can be used to measure the intensity
of the scattered light. However, because of secondary scattering and
light from out of focus particles, it may be difficult to see individual
particles clearly enough for velocity measurements.
Based on the above considerations, the single beam system was selected
for the experimental work in this contract. The prime advantage of two-
beam systems is for holography in dense particle clouds where the
reference beam in single beam holograms would be destroyed. However,
single beam holography worked well in all of the experiments and hence
the particle concentrations must have been low enough that a large
portion of the light was unscattered. The single beam hologram is also
much easier to set up and align which was an important factor since the
system had to be moved frequently from one test section to the other.
Since the duct and particulate dispenser were not available early in the
effort, the initial experimental work on the holographic systems was
performed with a test tube particle dispenser using small glass spheres
rather than flyash. The glass balls ranged in diameter from 35 to 200
microns which is, on the average, larger than flyash which occur in
sizes as small as one micron or less. The test tube dispenser used is
shown in Figure 41. The balls are placed in the test tube as shown and
shop air is forced into the test tube through a small glass tube. Air
47
-------
FIGURE 41
TEST TUBE DISPENSER FOR SMALL GLASS SPHERES
48
-------
going into the tube stirs up the particles and forces them out through a
second glass tube. Figure 39 is a photograph of the reconstruction of
a single beam hologram of the glass balls being ejected from the test
tube. Since the hologram is a single beam hologram, the test light
recorded is forward-scattered light. Figure 40 is a photograph of a
reconstruction from a two-beam hologram of balls ejected from the
test tube. The light recorded in this instance is side-scattered rather
than forward-scattered light. Since side-scattered light is primarily
reflected light as discussed earlier, the reconstructions of the balls
are not as clear as Figure 39.
II. E. 2 - Systems to Obtain Data from the Holograms
The approaches considered to obtain data from the holograms were
direct measurement and optical data reduction. It was necessary to
measure the size and shape of each particle, the distance between the
two reconstructions of a particle pair, and the location of the particle
pair in the test section.
The most straightforward means of obtaining the necessary data from
the hologram is by direct measurement on the reconstruction of the
particle. The reconstruction is either photographed or viewed on a
ground glass viewing screen in the plane of the magnified reconstruction
of Figure 36. The image on the screen or film can be viewed with a
comparator and the size and shape of the particles and the distance
between particle pairs can be measured. By having a reference object
recorded on the hologram and hence appearing in the reconstruction,
the location of the particle pair in the test section can be determined.
This method of measurement is time consuming, but can yield very
accurate results if done carefully.
Rather than using a ground glass viewing screen or film, a TV camera
can be used to scan a reconstruction of the hologram and the image
viewed on a television monitor. If the lenses on the camera are removed,
and if the real image from the hologram falls directly on the vidicon, the
particles will be magnified on the TV screen by the ratio of the cross-
sectional area of the real image to the area of the vidicon. With the TV
camera and monitor used in some of the experimental work in this
contract, the magnification was about 30. The magnification can be
varied by imaging and magnifying the reconstructed volume in relation
to the TV camera using a lens system.
The problem of obtaining data from particle holograms is a good candidate
for optical data processing techniques. Optical data processing techniques
are a general class of computational techniques which make use of the
mathematical properties of coherent light. Such methods have been
successfully used in reducing large quantities of data which must be
processed by linear transformations. These techniques in the past have
49
-------
been applied to the aircraft flight test data reduction problem, side-
looking radar data reduction, and particle size analysis. Optical
data processing works well when the data to be processed is large in
quantity and is available on photographic film. For the problem of
reducing the data from particle holograms, the optical data processor,
conceptually, would be a device into which the hologram is placed and
which would then give the size, shape, location, and velocity of each
particle on the hologram.
There are several optical data reduction techniques which may be
applicable to the particle holography problem. One technique makes
use of the assumption that all of the particles in a sufficiently small
region of the test section will be travelling at the same speed and in
the same direction. This situation is illustrated in Figure 42 in which
the reconstructed pairs of a group of particles are depicted. The light
amplitudes (x, y) distribution in this plane can be described by the
expression
s(x, y) = s(x - xo/2, y) + s (x+xo/2, y)
(1)
where s (x + xo/2 y) is the first reconstruction of the particles in the
double pulsed hol6gram and s (x - xo/2 y) is the second reconstruction.
It is assumed here that the velocity v of the particles is in the x
direction and that x = vT where T is the pulse separation. The two
dimensional optical <¥ourier transform of s (x, y) denoted by R (wx' wy)
is given by
R (wx' Wy) = 2s (wx' Wy) cos (wx xo/2)
where s (wx, Wy) is the Fourier transform of s (x, y). The optical
Fourier transform of s (x, y) can be performed with the system illus-
trated in Figure 43. An aperture is placed in the region of the real
image in which the velocity is to be measured. The aperture serves
primarily to allow only the light from the particles reconstructed in
the aperture to pass through the lens. In the focal plane of the lens,
the light amplitude distribution is given by Eq. (2) which is a cosine
wave with an envelope of 2s (wx, wy) . By measuring the frequency
Wo of the cosine wave, the velocity is given by
Ivl = 2;0
(2)
(3)
The aperture can be scanned in the volume occupied by the real image of
the test section in order to measure other velocities. The above discus-
sion was specialized to the entire velocity being in the x direction. If
the velocity is in other directions, the same discussion applies through
rotation of the (x, y) coordinate systems.
50
-------
s(X + X/2, y) ( s (x - x /2, y)
I 0
, .
-
, ,
." 41
I
I II
II
CJ1
I-"
A
,
.
1
I
.
\
1
FIGURE 42
EXAMPLE OF A RECONSTRUCTION
FROM A DOUBLE PULSED HOLOGRAM
SHOWING RECONSTRUCTED PAIRS
-------
COLLIMATED
BEAM
01
I:\:J
HOLOGRAM
,
~--
I
I-
I
/~-
RECONSTRUCTION
- -;1'=j
- - -("/ I
I I
Gi-:. .!. J
I ).-
/'
- - ...v
LENS
w
y
,/(
c; :I ;t . x
~.1tl" 2s(wx' Wy) CDS (WX X)
/; ,I,' PATTERN 2
FIGURE 43
SCHEMA TIC OF FOURIER TRANSFORM
METHOD OF ESTIMATING VELOCITY
-------
The problem of measuring velocity in the z direction is very difficult
and not considered in this discussion. Since the depth of focus of the
particles is in the z direction, it is difficult to tell exactly where the
particle comes to focus in that dimension. Therefore, it is difficult
to determine the z coordinate of each particle and hence the z ve locity
component. This problem is also complicated by the fact that the z
component is transverse to the free stream of the test section and for
that reason is likely to be very small. This problem of the z compo-
nent is discussed in more detail in the section describing the holo-
graphic system used in the experimental work.
Effectively, the optical data reduction technique described which can
be called the "Fourier transform method" changes the problem of
measuring distances between many individual particles to the problem
of measuring the frequency of a cosine wave. The frequency of the
cosine wave determines the magnitude of the velocity and the direction
across the cosine wave determines the direction of the velocity. This
technique would be advantageous when there are so many particles in
the incremental volume in which the velocity is being measured that it
is difficult to locate the particle pairs.
Another optical data processing technique which will be called the
"correlation method" correlates the particle reconstruction with itself.
The double pulsed reconstruction in a portion of the test section is
essentially one particle pattern in two different positions. The two
positions are separated from each other by a distance equal to the
distance the particles travelled between the two pulses from the laser
as stated in Eq. (1). The correlation function of this pattern produces
two large peaks as illustrated in Figure 44, the distance between which
can be related to the velocity by
d
V = 2T
(4)
To mathematically demonstrate this method, the correlation function
V (x, y) is by definition
V(x, y) =JJ:O(X" y') r(x' + x, y' + y) dx' dy'
-00
=J J rf(x' -Xo/2 + x, y' + y) + s (x' + xo/2 + y, y' + yll
-00
E. (x' - xo/2' y') + s (x' + Xo/2, y'B dx' dy'
=J 1;' (x' - Xo/2 + x, y' + y) s (x' - Xo/2, y') dx' dy'
-00
1 E (x' + xo/2 + x, y' + y) s (x' + Xo/2, y') dx' dy'
-co
53
-------
CD
+ r 1s (X' - xo/2 + X, y' + y) s (X' + xo/2' y') dx' dy'
J. -CD
.J J:(X' + Xo/2 + X, y' + y) s (Xl - xo/2, y') dx' dy'
-CO
(5)
The correlation v (x, y) consists of four terms as shown above. Since the
amplitude pattern s (x, y) of Eq. (1) consists of point-like particle recon-
structions, each of the four components of the correlation v (x, y) has its
maximum value I when (x, y) is such that the component reduces to
co
I =J J s2(x', y') dx' dy'
-DC)
(6)
Hence, at v (0,0), the first two integrals reduce to the form of Eq. (6).
At v (xo, 0) the third integral has its maximum value and at v (-x, 0)
the fourth integral is maximum. Hence, the plot of v (x, y) has a ~arge
central peak at (0,0) and two smaller peaks at (-xo, 0) and (xo,o) as
shown in Figure 44. By measuring the distance between the two smaller
peaks, Xo and -xo, the velocity can be determined.
The correlation method can be implemented by an optical data processing
system shown in Figures 45 and 46. The light from the real image of the
particle hologram is passed through a lens and a new two-beam hologram
is made of the light distribution in the focal plane of the lens. The wave-
front recorded on the second hologram is re lated to the Fourier transform
of the wavefront of the real image r (x, y, z) on the first hologram and is
given by
[21T" f-z 2 2~
. - (1 - ~) (w + w )
]:>-OF 1 x y:
R [wx, WY' z] e
(7)
where R( Wx w , z) is the two-dimensional Fourier transform of the
wavefront r(x,;' z). The Fourier transform is with respect to x and y for
a given value of z. For simplicity, the case in which z = 0 is now con-
sidered so that the phase factor of Eq. (7) can be ignored. For planes
other than z = 0, the phase factor must be considered. The net result of
considering the phase factor is a predictable adjustment of magnification.
The second hologram, after being developed, is placed back where it was
made as shown in Figure 46. First of all, a collimated laser beam
illuminates the particle hologram producing a real image of the particles
in front of the hologram. An aperture is placed in the region of the
reconstruction where the velocity is to be measured in this case the z = 0
plane called PI. The light from this region passes to the focal plane P2
of the lens L1 in which the hologram is located. If the wavefront in the
aperture is given by r (x, y, 0), the wavefront in the plane of the
54
-------
V(x, y)
21
c:J1
c:J1
x
-x
o
x
o
FIGURE 44
PLOT OF THE CORRELATION FUNCTION
OF r(x, y) SHOWING THE CENTRAL PEAK
AND TWO SMALLER PEAKS AT (-xo' 0)
AND (xo' 0)
-------
..... --
~
~/
.......
~
REFERENCE BEAiv[ H'OR
SECOND HOLOGRAM
PARTICLE
HOLOGRAl1
RECONSTRUCTED
VOLUME
BEAM
--~
~
y
z
CJ1
0)
FIll'I FOlt
HOLOGRAt'V[
f1
.
LEiiTS
L1
FIGURE 45
SCHEMATIC OF THE SYSTEM TO MAKE
A TWO-BEAM HOLOGRAM OF LIGHT
FROM THE RECONSTRUCTION IN THE
FOCAL PLANE OF A LENS
-------
LENS
fl --i
y
PARTICLE
HOLOGRAM
BEAM
- ----e.
r-f1
x
w
y
. --
L2
X
f2
f2
c.11
-J
RECONSTRUCTIOH
LENS
SECOND
HOLOGRAM
FIGURE 46
SCHEMA TIC OF CORRE LA TION ME THOD
FOR MEASURING THE VELOCITY
FROM PARTICLE HOLOGRAMS
-------
hologram is given by
R (wx, wx' 0)
(8)
The wavefront leaving the hologram will be the product of the amplitude
transmission of the hologram and the wavefront of Eq. (8) and is given
by
R (wx, Wy) R (wx' Wy)
Lens L2 performs an Inverse Fourier transform of the wavefront and
is given by
~ -1 [R( wx, Wy) R(wx, WyD
=J J;'(X" y') r (x + x', y + y') dx' dy'
-0)
v (x, y)
=
Hence, in plane P3, the output light amplitude distribution is the
correlation v (x, y) of the light amplitude distribution in the plane of the
aperture.
As for the optical data processing methods, both would require a consid-
erable amount of developmental work to make them efficient and workable.
The correlation method has perhaps more potential than the Fourier
transform method since the cosine fringes of the Fourier transfer method
might well be so close together, especially for wide separations of
particles in a pair, that they would be difficult to count. Also, for large
particles, the cosine fringes may become confused with the fringes
produced by the Fraunhoffer diffraction pattern of the particle.
The correlation method effectively reduces many particle pairs (so many
in fact that they might be indistinguishable as pairs) into a single pair of
bright spots whose separation is related to the velocity by Equation (4).
The separation of the spots gives the magnitude of the velocity, and the
direction of the line determined by the spots gives the direction of the
velocity. This reduction of data from many particle pairs to a single
pair of bright spots would greatly facilitate the problem of measuring
particle velocities.
During the period of the effort when the dust and particulate dispenser had
not yet been made, the above mentioned data reduction techniques were
investigated. The correlation technique was experimentally demonstrated
by using a simulated group of particle pairs on a transparency as
58
-------
the reconstruction from a hologram. The transparency resembled
Figure 42. From this transparency, a two-beam hologram was made
as shown in Figure 45. The system in Figure 46 was shown to work
quite well for particles on the transparency as small as 35 microns.
The limiting factor seemed to be the intensity of the particle recon-
struction rather than the particle size.
Since the emphasis on the contract was placed on making particle
holograms of various duct flows, the optical data processing techniques
were not pursued further. However, it is felt that if the particle
velocimetry techniques are to become standard techniques, such optical
data reduction techniques are desirable. The correlation technique has
the promise of becoming an efficient means of deriving particle
information from pulsed holograms.
II. E. 3 - Holographic Systems Selected for Experimental Programs
System Used for Making Holograms:
The system used to make the holograms in the potential and turbulent
test sections was a single beam holographic system shown schematically
in Figures 47 and 48. The laser used was a Korad Model K-IQ pulsed
ruby laser with a pockels cell Q-switch and a temperature tuned
sapphire etalon. This laser operated in the TEMoo mode and had a
coherence length of about 50 cm. Due to the excellent temporal and
spatial coherence properties of this laser, holographic schemes which
have been required to compensate for the poor coherence of older ruby
lasers were not required. The pulsed ruby laser was aligned with a
Spectra-Physics Model130 helium-neon laser. The Ruby laser has the
capability of being double pulsed with pulse intervals ranging from. 2
to .9 milliseconds. Each pulse has a time duration of approximately
10 nanoseconds. Due to the excessive amount of flyash in the test
facility room where the duct was located and due to the delicate optics
of the ruby laser, the laser was placed in a separate room. The laser
beam entered the test facility room through a hole in the wall. The room
in which the laser was installed was kept clean and the air was continu-
ally filtered with electrostatic precipitators.
In order to monitor the energy of each pulse and time interval between
the pulses, a pulse monitoring system was devised as shown in the
schematic. The beam from the laser passed through a glass plate and
about 5% of the beam was reflected to a photoelectric cell followed by
an integrating circuit. The output of the integrator was displayed on a
storage oscilloscope giving the relative output pulse energies and pulse
spacing. Figure 49 is a photograph of the pulsed ruby laser and monitor
showing the laser head, the laser cooling unit, the glass plate, photo
electric cell, and storage oscilloscope.
59
-------
POCKELS
CELL AND
REAR
REFLECTOR
REMOVABLE
MIRROR
GLASS
PLATE
APERTURE
r
I
ALIGNMENT
LASER
O STORAGE
SCOPE
POTEN'l'IAL FLOW
TEST ~;ECTION
~LOGRAM
FIGURE 47 SCHEMATIC OF POTENTIAL FLOW TEST SECTION HOLOGRAPHIC SYSTEM
REMOVABLE
MIRROR
0':1
o
POCKELS CELL
AND REAR
REFLECTOR
RUBY AND FRONT
REFLECTOR
PHOTO
CELL
O STORAGE
SCOPE
ALIGNMENT
LASER
APERTURE
I
I
NEGATIVE
LENS
COLLII1ATING
LENS
FLOW
..
COLLIMATING
LENS
TURBULENT FLOW
TEST SECTION
~LOGRAM
FIGURE 48
SCHEMATIC OF TuRBULENT FLOW TEST SECTION HOLOGRAPHIC SYSTEM
-------
FIGURE 49
PULSED RUBY LASER USED IN THE EXPERIMENTAL WORK
AND THE PULSE MONITORING SYSTEM CONSISTING OF
A GLASS PLATE WHICH REFLECTS A SMALL PORTION OF
THE BEAM, A PHOTOELECTRIC CELL, AND A STORAGE
SCOPE
61
-------
The stray incoherent white light from the flashlamp of the laser can
expose the holographic film, and for this reason the white light had to
be removed. Most of the stray light did not get through the hole in
the wall to the room in which the hologram was made. The light
which did get through was removed by a 5 mm aperture placed just
before the expanding lens (negative lens) shown in the schematic. To
insure that stray light was not a factor, the laser was fired with the
system misaligned so that no laser beam was produced and only stray
white light was present. A sheet of film in the film holder where the
hologram was made was not exposed indicating that the stray white
light was negligible.
The beam was either routed to the potential flow test section or the
turbulent flow section depending on where the hologram was to be made.
Considering the system for the potential flow section first, the beam
was expanded by a negative lens (-13 mm focal length) and reflected by
a mirror as shown in the schematic in Figure 47. The beam was then
collimated by a lens which had a focal length of 24 inches and a diameter
of 3 inches. Figure 50 is a photograph of the aperture to filter out the
stray light, the negative lens, the mirror, and the collimating lens. The
beam passed through the test section to the film holder. Figur~ 51 shows
the potential flow test section and the film holder. The film was 4. 16
inches away from the test section. The test section windows were 4 by
5 inch glass plates, 1/4 inch thick, flat to 1/4 wavelength and made from
Kodak Type 649-F spectroscopic plates by removing the 649-F emulsion.
The windows are shown in Figure 8.
The holographic system for the turbulent flow test section was essentially
the same as the potential flow section. As shown in the schematic of
Figure 48, and the photograph of Figure 52, the beam was expanded by
the negative lens and collimated by the 24-inch focal length positive lens.
The beam then travelled parallel to the tunnel and was then reflected to
the turbulent flow test section by a mirror. The beam from the mirror
passed through the test section and exposed the film which, as in the
potential flow section, was placed in a holder three inches from the duct.
System Used for Reconstructing the Holograms:
The system used to reconstruct the holograms is shown schematically in
Figure 53. The laser used for reconstruction was a Spectra-Physics
Model 140 argon laser. The high power argon laser, usually operated
at 400 milliwatts, was required to make the small particle reconstruc-
tions visible. The beam was expanded and spatially filtered by a lens
pinhole combination and then collimated. The collimated beam
illuminated the hologram producing a real image of the particles in
front of the hologram.
Since the particle reconstructions were too small to be easily seen, the
reconstructions were magnified by a factor of 22 by a 2-1/2 power
microscope objective. The reconstructions were projected onto a
ground glass viewing screen allowing the observer to see magnified
62
-------
FIGURE 50
HOLOGRAPHIC SYSTEM FOR THE POTENTIAL FLOW TEST
SECTION SHOWING APERTURE, NEGATIVE LENS, MIRROR,
AND COLLIMATING LENS, AND THE TEST SECTION
63
-------
. 4
~
FIGURE 51
THE HOLOGRAPHIC SYSTEM AROUND THE POTENTIAL
FLOW TEST SECTION SHOWING THE OPTICAL SYSTEM,
TEST SECTION, AND FILM HOLDER
64
-------
FIGURE 52
THE HOLOGRAPHIC SYSTEM FOR THE TURBULENT FLOW
TEST SECTION SHOWING THE LASER BEAM, NEGATIVE
LENS, COLLIMATING LENS, MIRROR, TEST SECTION
AND FILM HOLDER
65
-------
0)
0)
ARGON
LASER
LENS/PINHOLE
COI"lliINATION
HOLOGRAM
SPATIAL FILTER
NICROSCOPE
OBJECTIVE
COLLIM.t\TING
LENS
FIGURE 53 .
SCHEMATIC OF THE SYSTEM TO VIEW
AND MAKE MEASUREMENTS OF THE
PARTICLE HOLOGRAMS
GROmm GLASS
VIEWTIifG SCREEN
-------
particle images. A small wire filament was placed at the focal point of
the microscope objective to remove the light not scattered by the
particles and thereby making the magnified particle reconstructions
easier to see. Figures 54 and 55 are photographs showing the argon
laser, lens/pinhole combination, collimating lens, hologram, micro-
scope objective, spatial filter and the ground glass viewing screen.
Resolution:
The hologram recorded a cylindrical volume of the test section 3 inches
in diameter and 4 inches long as shown in Figure 56. The resolution R
of the hologram is determined by the diameter D of the reference beam
the distance L that the hologram is from the particle, and the wavelength
)... of the laser and is given by
R = 1.22"A.L
D
=
(1,. 22) (. 6942 x 10 -6) (6. 16)
3
=
1. 74 microns.
Where D = 3 inches
~ = . 6942 microns
L = 6. 16 (distance to a particle in the middle of the test section).
In reality the resolution is somewhat less than the value of R computed
above for several reasons. The optics are not perfect and aberrations
in the optics degrade the resolution. Also, the intensity of the light
scattered to the holograms is much less for small particles than for
larger particles. Hence, only the more intense portions of the wavefront
scattered by the smaller particles is recorded and the lower intensity
portions of the light beam may we 11 be lost in the noise of the hologram
or not recorded at all. Because less light from the smaller particles is
actually recorded, the resolution of the system may be less than the
predicted value of 1. 74 microns.
The resolution of the system was measured with the aid of a USAF 1951
Resolving Power Test Target. This target consists of sets of lines
spaced progressively closer together, the sets becoming progressively
smaller. By observing the last set of lines that an optical system can
resolve, the resolution of the system can be determined. The test
chart was placed in the middle of the test section and a hologram was
made of the test chart. Upon placing the hologram into the viewing
67
-------
FIGURE 54
, THE SYSTEM USED TO RECONSTRUCT THE PARTICLE
... HOLOGRAMS SHOWING THE ONE-WATT ARGON
LASER, LENS PINHOLE COMBINATION, COLLIMATING
LENS, HOLOGRAM, MICROSCOPE OBJECTIVE, SPATIAL
FILTER, AND GROUND GLASS VIEWING SCREEN
68
-------
FIGURE 55
CLOSE-UP OF THE RECONSTRUCTION SYSTEM SHOWING
THE HOLOGRAM, MICROSCOPE OBJECTIVE, AND SPATIAL
FILTER
69
-------
section, the smallest set of lines which could be resolved was set 6.4
which corresponds to 90. 5 lines/mm or a minimum particle size of 5. 5
microns.
Obtaining Data from the Holograms:
It was required for this effort to locate the position of each particle pair
in the test section, to measure the size and shape of the particle, and to
measure the magnitude and direction of the velocity of the particle. The
coordinate systems used to record particle location differed from one
experiment to the next and were chosen primarily for convenience. The
coordinate systeJ;n for the potential flow holograms is illustrated in
Figure 56. Here, the origin is located on the bottom of the test section
as indicated and the positive x - direction is in the direction of the free
stream flow, the positive z-direction is in the direction opposite to that
of the laser beam and the positive y-direction is in the vertical
direction of the test section. For other experiments, the origin was
shifted to other points in the test section.
In order to obtain data from the holograms, the hologram was placed in
the holder shown in Figure 55 and 57. When the hologram is illuminated
a real image of the test section is formed in the front of the hologram.
Since both the beams used to make and reconstruct the hologram were
collimated, there is no magnification in the x and y directions due to the
difference in wavelengths between the laser used to make and reconstruct
the hologram. However, there is a magnification Mz in the z-direction
given by the ratio of the two wavelengths which is
Ar
Mz = ~
. 6943
- . 4880
=
1. 42
Where Ar = the wavelength of the ruber laser given by . 6943 ~
). a = the wavelength of the argon laser given by . 4880,,(L
Hence, the width of the test section in the reconstruction was not 4
inches which was the actual width, but 5.68 inches.
The microscope objective images various portions of the real image
onto a ground glass viewing screen as described earlier. S~nce the
objective aperture is only. 3 inches, only a very small portIon of the
70
-------
DIRECTION OF FLOW
-J
I-A
.
/ DIRECTION OF
/' LASER BEAM
y
x
FIGURE 56
SKETCH OF THE POTENTIAL FLOW
SECTION SHOWING THE CYLINDRICAL
PORTION OF THE TEST SECTION
WHICH IS HOLOGRAPHED
-------
I --,. ,
Ii :,~:?~,
i) I. ! <:"".."....
;L' : ',o(fL" .:~.,..
~:;: '" ' ,"~
~,--r;:' .': :,.,-~~~,,;., ",i:: ,,-.,' ,',
, -: ~-:]3'-'
J,~~,;F'.:' <,.!
.~';l,i!'"i'~ .
1"f:~;-:i..I.<~\""" r '"'. .-
:1)1.'", "' ~
FIGURE 57
MICROMETER POSITIONED HOLOGRAM HOLDER USED
IN PARTICLE RECONSTRUCTION EXPERIMENTS
72
-------
real image can be viewed at once. In order to view other portions of
the image, the objective is mounted on a drive which can be moved up
and down in the y-direction as shown in Figure 55: In order to scan
the reconstruction in the x-direction, the hologram itself is translated
in the x"1iirection by means of the two translation stages shown in
Figure 57. The real image of the test section is moved in the x-
direction by an amount equal to the distance the hologram is moved in
that direction. The test section was scanned in the z-direction by
sliding the hologram holder to different positions along the optical
bench. The edge of the bench was marked with a millimeter scale so
that the location in the z-direction of the portion of the tunnel being
viewed could be measured. The z reading had to be corrected by a
factor of 1. 42 to take into account the magnification in the z-direction.
By noting the height of the microscope objective, the readings of the
verniers in the translation stages, and the reading of the scale mounted
to the optical bench, the x, y, z coordinates of the particle pair can be
measured. Since the typical spacing between two reconstructions of a
single particle was about. 07 inches, each particle pair was assigned
one (x, y, z) location corresponding to the center of the particle pair.
It is felt that each particle pair was located by this technique to an
accuracy of about 0,05 inches.
Having located the particle in the test section, the next task was to
measure the magnitude and direction of the velocity of the particle and
the shape of the particle. The particles in the particle pairs were
generally separated by about 1 inch on the ground glass viewing screen.
The separation was measured by placing a scale which was graduated in
units of . 02 inches on the screen and measuring the separation as
accurately as the scale could be read. The scale was viewed by the
observer with a comparator so that it could be accurately read. The
particle was then viewed by the observer with the comparator (using a
. 1 mm reticle) so that the shape and size of the particle could be
determined. By correcting for the magnification of the viewing system,
the true size and particle separation were determined. By knowing the
particle pair separation, and the time interval between the pulses, the
particle velocity was computed.
The angle of the velocity vector was measured with a protractor included
on a reticle mounted in the comparator. The reference for the angle
measurement was a plumb line which was dropped in front of the test
section and recorded on the hologram. The reconstruction of the plumb
line provided a vertical reference for the measurement of the velocity
angle.
Only velocity components in the x and y directions, directions which were
transverse to the laser beam, were measured. It would have been dif-
ficult to obtain the z component of velocity for several reasons. The
primary reason was that the depth of focus of a part,icle was in the z
direction and it was difficult to determine the precIse value of z where
the parti~le was in focus. In contrast, the shape of the particle is
clearly delineated in the x and y directions allowi~g its position with
respect to these coordinates to be clearly determmed. Also, the
magnitude of the z component of velocity was likely of the same order
73
-------
as the y component, since both components were transverse to the free
stream velocity. If this was the case, the displacement of the particle
in the z direction during the interval between the two pulses was about
400 microns for the potential flow holograms. For the holographic
system used, the depth of field of a 50 micron particle would be about
200 microns which was about the same as the displacement in the z
direction. The depth of focus being on the same order as the displace-
ment further complicated the measurement of the z component. For
these reasons, only the x and y components were measured.
General Comments on the Performance
of the Holographic System:
In general, all of the holographic systems for the experiments performed
quite well. Before the holograms were made, it was necessary to make
sure that the pulsed ruby laser beam uniformly illuminated the hologram.
A slight misalignment would result in parts of the film being overexposed
and parts being underexposed. The alignment laser did not always trace
out the path of the ruby laser beam precisely enough to ensure uniform
illumination so a few test shots had to be fired with polaroid film in place
of holographic film to check for uniform illumination.
Flyash was deposited on the test section windows while the duct was
running to the extent that high quality holograms could not be made after
one minute of operation. Generally, however, one minute of operation
was enough time to make three holograms. After each run, the windows
were cleaned in an ultrasonic cleaner and then reused. The windows
usually became so "sand blasted" after ten runs, or so, that they had to
be replaced with new windows. The flyash particles on the windows had
the effect of reducing the amount of unscattered light and thereby
destroying the reference beam for the single beam holograms. Also, the
particles on the windows were out of focus in other parts of the test
section and thereby contributed noise to the particle reconstructions inside
the test section. Although the flyash deposits on the windows were a
nuisance, they did not significantly degrade the quality of the holograms
because the holograms were made as soon as possible after the duct was
turned on. However, the flow was so turbulent in the experiment with the
precipitator plates, that the windows became covered with flyash after only
10 seconds of operation. For these experiments, the windows were
removed.
The laser at times did not produce two pulses or did not produce two equal
intensity pulses. For this reason, the pulses were monitored by the
monitoring system described above each time the laser fired to make sure
that the hologram was exposed by two equal intensity pulses.
Obtaining the location, size, and velocity data from the hologram by the
techniques described above worked satisfactorily. However, it was a
tedious operation. The problem of finding matching particles in a pair
was made difficult by the fact that most flyash particles were spherical
74
-------
and hence a great many of the particles look alike. Also, the particles
in a pair were separated by a distance equal to 40 diameters on the
average. The particles in a pair could be made closer together and
consequently, more easily identified if the pulse separation of the la'ser
could be reduced. If the particles had a distinctive shape, it was
considerably easier to locate the pairs. However, distinctly shaped
particles occurred very rarely. Figures 58 and 59 are photographs of
reconstructions of distinctively shaped particles. Note that there is
little doubt that these are double pulsed pairs due to their shapes. If
the flow is reasonably parallel, double pulsed pairs can be identified
even if the shapes of all the particles in the region are about the same.
Figure 60 shows two pairs of particles. Figure 61 is a photograph of
the reconstruction from a parallel flow. Note that at least four double
pulsed pairs are visible.
If the flow were turbulent, particles in the same vicinity of the flow
would have different velocities both in magnitude and direction. Also,
distinctively shaped particles (non -spherically) might 'rotate from one
position to the second changing the particular view recorded by the
hologram. Hence, the first reconstruction of a given particle may
differ from the second because of the change in particle orientation
between the two reconstructions. The. 5 and 1. 5 isokinetic holograms
of the APCO train were so turbulent that double pulsed pairs could not
be found in the vicinity of the probe. Figure 62 is a photograph of the
reconstruction from a . 5 isokinetic double pulsed hologram of the APCO
train. Note that although plenty of particles are visible, it is difficult
with certainty to find the double pulsed pairs. Again, the difficulty in
matching reconstructions could be eliminated if the pulse interval were
smaller, making the resulting double pulsed reconstructions closer
together.
All holograms were made using Agfa-Gevaert 10E75, ~ by 5 inches,
AH backed photographic plates and were developed usmg Kodak D-19
developer.' The development time varied between 2 minutes 15 seconds
to 4 minutes depending on the exposure of the holograms and age of
the developer. Typical development time was 2 minutes 45 seconds.
75
-------
FIGURE 58
EXAMPLE # 1 - DISTINCTIVELY SHAPED PARTICLE PAIR
FIGURE 59
EXAMPLE #2 - DISTINCTIVELY SHAPED PARTICLE PAIR
76
-------
FIGURE 60
TWO PARTICLE PAIR RECONSTRUCTION
77
-------
FIGURE 61
FOUR DOUBLE PULSED PARTICLE PAIRS
IN POTENTIAL FLOW
78
-------
FIGURE 62
PARTICLE RECONSTRUCTION OF FLOW ABOUT THE
APCO TRAIN PROBE (.5 ISOKINETIC)
79
-------
ITI.
EXPERIMENTAL PROGRAM
The experimental section of the project consisted of making pulsed
holograms of four experiments, namely, potential flows, turbulent
flows, flows with the APCO train probe, and flows with charged
precipitator plates. Several pulsed holograms were made of each
flow with the single beam system described in the previous section
with the duct seeded with flyash. The size, shape, two velocity compo-
nents, and location of each particle was then measured with the
reconstruction system also described in the previous section. The
particle data from each hologram is presented in charts on the following
pages.
To conduct an experiment usually required three people: One to
manipulate instrumentation associated with the duct facility and to record
data; one to operate the particulate dispenser, change hologram plates and
fire the pulsed laser; and one to recharge the laser and monitor pulse
quality. A typical run would last approximately three minutes with three
holograms being recorded. Figure 63 illustrates a test being prepared for
a run at the potential flow test section.
The material used in the four major experiments was flyash obtained from
the Office of Air Programs and the Georgia Power Company. Figure 64
is an electron scanning microscope picture of the flyash showing the
spherical nature of the material. The larger particles in the photograph
are approximately 20 microns. The magnification ratio for the picture is
approximately 1, 250.
IIT.A.
- POTENTIAL FLOW HOLOGRAMS
Several holograms were made in the potential flow test section at mean
velocities of 25 feet/second and 33 feet/second at loadings ranging from
. 5 to 3. 5 grains/ scf. Table I lists the holograms made and gives
general comments about them. Hologram No. 110 was analyzed in
detail with many particles located, measured, and velocities computed.
The data from the hologram is presented on the following pages. The
particles in three planes parallel to the x - z plane were located and
velocities measured. The planes were located at y = 3.53", Y = 4. 53",
and y = 5.03" as indicated in the sketch of Figure 65. There were .so
many double pulsed pairs visible that they could not all be counted In
this hologram. Tables I-a, I-b, and I-c are tabulations for Hologr~m
No. 110 of particle shape, size, x-y location, x. component of velocIty,
y component of velocity, absolute value of velocIty, and angular
direction of the particle velocity in relation to the axis of the duct .
facility. The velocity profiles measured at 25 feet(secon? by the PIt?t
tube are presented in Figures 16 and 23 for comparison wIth the particle
velocities.
80
-------
FIGURE 63
PERSONNEL PROGRAMMING FACILITY FOR TESTS
FIGURE 64
SCANNING ELECTRON MICROSCOPE PHOTOGRAPH
OF FL YASH 1250 X
81
-------
TABLE I - POTENTIAL FLOW HOLOGRAMS
Mean
Hologram Velocity Loading
Number Ft/Sec (Grains/Scf) Comments
110 25 1.5 Excellent hologram, lots of double pulsed pairs
visible
112 25 .5 Few particles, double pulsed pairs visible
113 25 .5 Effectively same as 112
115 33 3. 5 Double pulse pairs visible
116 33 3. 5 Effectively same as 112
117 33 3. 5 Effectively same as 112
119 33 3. 5 Effectively same as 112
00
~ 122 33 1.5 Double pulsed pairs visible
123 33 1.5 Slightly overexposed, some double pulsed pairs
visible
124 33 . 5 Double pulsed pairs visible but few particles
125 33 . 5 Effectively same as 124
129 33 3. 5 Excellent in all respects
-------
Loading - 1.5 grains/scf
Pulse Separation - .2 milliseconds
Mean Velocity - 25 ft ./sec.
y
1-- 511~
411 /1 I
------- 5.03"
4.5311
7 1/211
/
//
//
/// /
-/-----
//-1---
------
/z
.
/
-z
FIGURE 65
POTENTIAL FLOW HOLOGRAM #110
83
LASER BEAM
a
FLOW
x
-------
v V IVI VO Size/Shape
Partie Ie No. and x y D = Diameter in
Location (x, z) (ft./sec.) Microns
1. (2.90 I 3.38) 27.60 - 1 .445 27.65 30~ Sphere D = 1 8 Loading: 1 .5 grains/sd
2. (2.90 I 3.50) 27.25 0.00 27.25 00 Sphere D = 27 Pulse Separation - .2 milliseconds
3. (1.80 I 3.50) 26.85 - 1 .405 26.90 3° t Sphere D = 1 8 Cut at y = 5.03"
4. (1 . 80 I 3. 66) 27.20 -1.905 27.25 40 ~ Sphere D = 27 . Positive y Component
5. (2070 I 2014) 27.60 -I. 94 27.65 40 ~ I rreg. £::.. 54 X Negative y Component
5~
6. (2.70 I 2.14) 27.95 -1.96 28.00 4° ~ Sphere D = 27 0 Zero y Component
7. (2070 I 2.14) 28.35 -1 .49 28.40 3° + Sphere D = 1 8
4
~ )t~+
)(..... 3 o-.z.
)(~ I
3
~..... 51~, 7
2
TABLE la
POTENTIAL FLOW HOLOGRAM #110
~
lL
l' Xi
.
2
.
3
.
4
-------
IVI t:> Size/Shape
V V V
Partie Ie No 0 and x y D = Diameter in
Location (x, z) (ft./sec.) Microns
1. (2.70, 1.30) 26.85 -1.88 26.90 40'~ Sphere D = 1 30 Loading: 1.5 grains/scf
2. (2.70, 1.35) 27.25 -0.95 27.25 2" f Sphere D = 44 Pulse Separation - .2 milliseconds
3. (2.70, 1 .44) 27.20 - 1.43 27.25 3 c) t 0 1'0=54 Cut at y = 4.53
4. (1 .80, 1.89) 27.53 -2.41 27.65 5" t Sphere D = 44 .' Positive y Component
5. (1 .80, 1.89) 27.53 -2.41 27.65 5" t Sphere D = 36 X Negative y Component
6. (1.70, 1. 89) 27.90 -2.44 28.00 5° ~ Sphere D = 54 0 Zero y Component
7. (1. 50, 1. 89) 27.55 -2.41 27.65 5° t Sphere D = 27 4 ~
8. (1.35, 1.89) 27.30 -2.39 27.40 5 0 ~ Sphere D = 44 :z
ex> 9. (1 . 1 0, 1. 95) 27 . 1 5 -2.38 27.25 5" f Sphere D = 36 t
trJ
10. (1 .05, 1.95) 27.35 -1.92 27.40 4" t .1.~~t.
11. (2.75, 2.56) 28.40 0.00 28.40 0" Sphere D = 67 3 00---'> 1'3
12. (2 . 80 , 2.65) 28.40 0.00 28.40 o. Irreg o"fp'\) ~ 0-+\2-
",.\.~~ 0-.. \ I
13. (1 .55 , 2.90) 26.90 0000 26.90 011 Sphere D = 44
2 ~JIO'
~~)Ho ~4JS,cO
8 ..,
>'-+ "3
*-> \,2.
TABLE Ib
POTENTIAL FLOW HOLOGRAM #110
-.... X
o
s .
,
z.
3
.
4-
-------
v V IVI VO 5 izejShape
Partie Ie No. and x y D = Diameter in TABLE Ie
Location (x, z) (ft ./sec .) Microns POTENTIAL FLOW HOLOGRAM #110
1. (1.85 I 2.00) 27. 1 5 -2.38 27.25 5° ~ Irreg. , ~~ Loading: 1.5 grains/scf
2. (2.65 I 1.95) 27.30 -2.39 27.40 5°~ '!.fO/' Pulse Separation - .2 milliseconds
Sphere D = 36
3. (2.80 I 1.95) 27.85 -2.93 28.00 6° i Sphere D = 27 Cut at y = 3.53
4. (2.90 I 2.05) 27.55 -2.41 27.65 5°J, Sphere D = 44 . Positive y Component
5. (3.00 I 2.08) 27.95 -1.96 28.00 4 ° J. Sphere D = 27 X Negative y Component
6. (3.00 I 2. 14) 27.65 -2.415 27.75 50 ~ Sphere D = 44 0 Zero y Component
7. (3.00, 2.14) 27.65 -2.41 27.75 5 ° J, Sphere D = 62
8. (1.75 , 2.36) 27.40 - 1 .435 27.35 30 t Sphere D = 54
3°t 4 -i ~
00 9. (1 .75 I 2.36) 27.35 - 1 .435 27.40 Sphere D = 18 ~'9
0..
10. (1 .7 5 I 2. 36) 27.35 - 1 .435 27.40 30+ Sphere D = 36
11. (1 .45 I 2.36) 26.80 -3.30 27.80 70t Sphere D = 54
12. (1 .35 , 2.31) 28.00 -2.45 28.10 50t Sphere D = 22 3 ~ ~20
2.1 }22.
13. (1 .35 I 2.31) 27.85 -2.93 28.00 60~ Sphere D = 36
14. (1 .35 I 2.31) 27.90 -2.44 28.00 50, Sphere D = 40
15. (1 .35 I 2.31) 27.25 -2.95 28.40 60t Sphere D = 40 ~~S,9/ro IG./,7,1 a
~ )f--.
16. (2.90 I 2.23) 27.65 -2.415 27.75 50.J. Sphere D = 44 2 \"%.,1'\,14,15 ~~., ~ '$ ,'-,7
~ ~~4-
4 of r 2. :J
17. (2 .90 I 2.23) 27.95 -1.96 28.00 Sphere D = 71
18. (2.90 I 2.23) 27.35 -1 .91 27.40 4GI Sphere D = 67
19. (2.40 I 3.90) 26.55 0.928 26.55 20t I rreg. c2 4&0
2.50t ,&0 1
20. (2.25 I 3.18) 26.65 1.16 26.65 Irreg. C:::Jt..2.
21. (1. 55 I 3. 16) 26.90 0.941 26.90 20 t Irreg. 110 H ~ I I I ,
~.. 1 2 3 4
22. (1 .45 I 3. 16) 26.85 1.88 26.90 4°+ D =44
-------
III. B. - TURBULENT FLOW HOLOGRAMS
Holograms of the turbulent flow section were made at mean velocities
of 24 feet/second and 33 feet/second at loadings ranging from. 5 to
3. 5 grains/sd. Table II lists the holograms with comments about
them. Hologram No. 175 was analyzed in detail, and the plots of
particle velocity are shown in Tables IIa - lId. The velocity of particles
in four parallel planes located at y = 0.446", 0.396", 0, -.891" was
measured. The location of these planes and the coordinate systems used
are shown in Figure 66. The velocity profiles measured with the pitot
tube are those flow velocities as shown in Figures 24 and 25.
From Table IIb, it would appear that a minor swirl exists in the turbu-
lent section since most particles at the top of the diagram have an "up"
component of velocity whereas all particles at the bottom of the diagram
have a "down" component. Apparently, gravitational effects were very
small in both the potential and turbulent sections since the deviation from
the horizontal was at most only a few degrees.
III. C. - HOLOGRAMS OF APCO TRAIN PROBE
Holograms were made of the APCO train probe wi th the probe operated
at . 5 isokinetic, 1. 0 isokinetic, and 1. 5 isokinetic at a mean flow
velocity of 25 feet/second. Table III lists the holograms made, and
hologram No. 142 (1. 0 isokinetic) was selected for detailed analysis.
The flow around the probe in the O. 5 and 1. 5 isokinetic cases was so
turbulent that double pulsed pairs could not easily be determined.
Figure 67 shows the coordinate system used and the plane (z=o)
selected for measuring particle characteristics. This plane is a
vertical plane located at the center of the probe. The location of the
particles in this plane are shown in Figure 68. Table IlIa is a listing
of particle characteristics.
The experimental set-up used to obtain the particulate samples is shown
in Figure 69. Figure 70 shows the sampling probe located in the
potential flow section. The probe was a 1/2" O. D. copper tube with the
inside opening beve led to form a sharp entrance such that the area of the
opening was equivalent to that determined at the outside diameter of the
probe. The bend radius of the tube was approximately 4 inches, and
the distance from the mouth of the tube to the bend was also 4 inches.
The sampling system was calibrated using the s~t-up shown i,n Figure
71. A basic assumption made was that the flow In the p~obe ,Inlet would
be potential' that is the flow would be of constant velocIty wIth no areas
of separatio'n. By ~aking this assumption, the ve locity in the inlet can
be assumed to be a function of the quantity of air removed from the
b~nnel. More specifically, V probe = Q/A ~here Q is th~ quantity ?f
aIr removed in cubic feet per second and A IS the probe Inlet area In
square feet.
87
-------
TABLE II - TURBULENT FLOW HOLOGRAMS
Mean
Hologram Velocity Loading
Number Ft/Se c (Grains/Scf) Comments
172 24 O. 5 Very few particles
174 24 O. 5 Very few particles
175 24 O. 5 Appears to be more particles than 172 or 174
177 24 O. 5 Same as 172, 174
178 24 3.5 Lots of particles, some difficulty in identifying
double pulsed pairs
179 24 3. 5 Same comments as 178
co 180 24 3.5 Same comments as 179
co 33 Double pulsed pairs visible
182 1.5
183 33 1.5 Not as many pairs as 182
184 33 3. 5 Double pulsed pairs visible
185 33 3. 5 Same comments as 184
187 33 1.5 Double pulsed pairs visible
188 33 1.5 Same comments as 187
189 33 1.5 Same comments as 189
-------
v V IVI VO Size/Shape
Partie Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
1. (-0.050 , +2.246) 23.29 0 23.29 00 Sphere D = 36 Loading: 1.5 grains/scf
2. (-0.175 , +0.970) 21.78 0 21 .78 00 OS'l. Pulse Separation - .2 milliseconds
3. (-0.500 ,+0.166) 23.48 0 23.48 0° Sphere D = 90 Cut at y = 0
4. (-0.500, -1 .608) 25.93 - .91 25.95 20 J, US ~.q, . Positive y Component
2° J. "
5. (-0.750 , -0.721) 24.98 - .87 25.00 Sphere D = 23 X Negative y Component
6. (-0.700, -0.527) 24.98 - .87 25.00 2°~ 67t. 0 Zero y Component
7. (-0.675 ,+1.026) 24.43 2.13 24.43 5°t Sphere D = 45 ;
";!
8. (-0.675 , +1.830) 22.64 1.98 22.73 5°t Sphere D = 73 +
ex:> 9. (-0.850 / +1.636) 21 .18 1.11 21 .21 30' Sphere D = 45 ~\
'D 301' 2 ~~8 'J..~ If.
10. (-0.800 / +1.747) 23.27 1.22 23.30 Sphere D = 54
4"t ~/O
11. (-0.900 / -1.830) 25.51 -1 .78 25.57 Sphere D = 27 <3
12. (+0.575 / +0.887) 19.44 -1 .67 19.51 50} Sphere D = 23 --'> -, ~z
~3
o
~,p
~5
-[
TABLE lIa
TURBULENT FLOW HOLOGRAM #175
~4
-l
-.x
-3
- I
o
I
-------
v V IVI VD Size/Shape
Particle No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
13. (+0.075, -1.580) 26.51 -.46 26.52 10-L- 6'3 Loading: 1.5 grains/scf
3° t """ Pulse Separation - .2 milliseconds
14. (-0.150, -2.634) 21 .75 -1 .14 21 .78 Sphere D = 81
15. (-0.150, -2.107) 23.21 -2.03 23.30 50 ~ Sphere D = 1 00 Cut at y = -0.891
16. (-0.400, -0.555) 24.43 0 24.43 00 Sphere D = 45 . Positive y Component
17. (-0.450, +1.164) 24.98 .87 25.00 20 t Sphere D = 1 8 X Negative y Component
18. (-0.450, +2.190) 21 .56 1.13 21.59 3° t Sphere D = 32 0 Zero y Component
19. (-0.450, +2.523) 20.94 1.83 21 . 02 5° l' Sphere D = 54 3 Z:
O~
20. (-0.725, +2.689) 20.64 0 20.64 OD Sphere D = 45 t ~/q,
-0 21. (-0.725, +1 .747) 21.77 .76 21.78 2° t 6.41; .~16
a
(-0.725 , -2.468) 22.26 50 -L- Sphere D = 27 2.
22. -1 .95 22.35 --+ 2.1
......".,17
o
~I~
-I
TABLE lib
TURBULENT FLOW HOLOGRAM #175 ~1'3
-2. ~/5"
*"+ Z. z
~l+ -...x
-3 -/ 0
/
-------
v V IVI VO Size/Shape
Partie Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
23. (-0.250 I +1 .192) 24. 04 - .42 24.05 1 0 ~ Sphere D = 73 Loading: 1.5 grains/scf
24. (-0.450 I -0.360) 25.89 -1 .81 25.95 4° ~ Sphere D = 23 Pulse Separation - .2 milliseconds
25. (-0.450 I -0.210) 25.74 - .90 25.76 2° ~ ~r;~ Cut at y = 0.446
1..,
26. (-0 .7 50 , - 1 . 081) 24.34 -2. 13 24.43 5 o~ Sphere D = 23 . Positive y Component
27. (-0.800, -0.444) 25.62 -2.69 25.76 6° J. Sphere D = 23 )( Negative y Component
28. (-1.00 I - 1 . 664) 24.62 -.43 24.62 1.~ c::;J '54- 0 Zero y Component
00 l...s ?1
29. ( - 1 . 00 , - 2 .412) 2~.95 0 25.95 Sphere D = 45 'i!: f).?30
30. (+0.550 I +2.911) 17.99 0 17.99 0° Sphere D = 36 +
'" 31. (+0.550 I +0.083) 25.93 0 25.95 00 Sphere D = 36
2..
32. (+0.800 I -0.776) 26.04 -2.28 26.14 50~ Sphere D = 82
~Z3
o o-a> 3 I
~2$
~ ~ 2.4
27
~~2.
-I ~ 2.(p
TABLE IIc ~l~
TURBULENT FLOW HOLOGRAM #175 -2,
0-> 2. 91
-'3 -.X
-/ () (
-------
v V IVI VO Size/Shape
Partic Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
33. (+00300 I -2.052) 24.96 1. 31 25.00 30t Sphere D = 36 Loading: 1.5 gra ins/scf
34. (-0.025, +1.081) 22.54 0 22.54 00 Sphere D = 45 Pulse Separation - .2 milliseconds
35. (-0.525 I +0.222) 23.30 .41 23.30 lOt Sphere D ~ 59 Cut at y = 0.396
- 'C!!:?
36. (-0.500, -0.832) 23.96 -2.10 24.05 50. it . Positive y Component
- 1 \ 00\
37. (-0.500, -0.222) 24.58 -1.29 24.62 3°~ Sphere D = 23 )(. Negative y Component
38. (-0.900, -0.832) 26.33 0 26.33 0° Sphere D = 36 0 Zero y Component
39. (+0.200, -1 .220) 23.02 -2.01 23.11 5°.t. Q:a."1 +2
40~ i:
40. (+0.200 I -1 .192) 23.99 -1.68 24.05 Sphere D = 45 +
'0 41. (+0.250, -0.832) 23.10 -.40 23.11 10J, Sphere D = 50
~
42. (+0.500, -1 .275) 20.83 0 20.83 00 Sphere D = 73 ~
03~ 41,4+
+1
43. (+0.450 I -1.192) 23.67 0 23.67 0° Sphere D = 50
44. (+0.400 I -1. 164) 23.86 0 23.86 00 Sphere D = 32
~,~
0
~31
0-+ x--+ 3<6 ~4t
36 3940
'k-+ ~4Z
-I
TABLE lid
TURBULENT FLOW HOLOGRAM #175
-2 ---+ 'J3
.
I .ca: . '~2- -II
. c .
-1 0 1
-------
y = 0.446
y = 0.396
y=O
y = -0.89
Loading - .5 grains/sd
Pulse Separation - .2 milliseconds
Mean Velocity - 24 ft./sec.
y
"/- = = -= = =- -:::Z LAS ER BEAM
/"/ 77
/// //
/" / // I
b// ~----- __tL-,
------ _J/ /
L__-/__- _-./ /
./
x
/
/
-_J
/'
/'
L----
-z
/-- --------,
/ I
/ /
/ /
/ /
// /
// /
L_-- -----_..J
FI GURE 66
TURBULENT FLOW HOLOGRAM #175
93
~ FLOW
-------
TABLE III - APCO TRAIN
Mean
Hologram Velocity Loading
Number Ft/Sec ( Grains/Scf).* Comments
136 25 . 5 . 5 isokinetic, lots of particles
142 25 .47 1. 0 isokinetic, lots of double pulsed pairs
143 25 .47 Same as 142
149 25 5.84 Maybe some double pulsed pairs 1. 0 isokinetic
151 25 3.4 . 5 isokinetic, some particles
152 25 3.4 Same as 152
153 25 3.4 Best of all, . 5 isokinetic
154 25 1.9 1. 5 isokinetic, high noise due to dirty windows
t!)
~ 155 25 1.9 Same as 154
156 25 1.9 Same as 154
160 25 2.93 1. 5 isokinetic some particles visible
161 25 2.93 Same as 160
162 25 2.93 Same as 160
165 25 3.06 Same as 160
166 25 .475 1. 5 isokinetic some particles
167 25 .475 . 5 isokinetic best of all, lots of particles
169 25 4.3 . 5 isokinetic lots of particles
171 25 4.3 .5 isokinetic same
* As calculated using sample obtained through probe.
-------
1 .0 Isokinetic
Loading - .47 grains/scf
Pulse Separation - .2 milliseconds
Mean Velocity - 25 h./sec.
The x and y components of velocity of particles in the z = 0 plane were measured.
The origin is at the center of probe of the APCO Train as indicated.
y
FLOW .
PRO BE
_____0,
I
I
I
I
I
I
I
I
I
L__- --
I
I
I
I
----_.-J
z
FIGURE 67
APCO TRAI N HOLOGRAM #142
95
-------
-().o
0-
-. /
I
. /
.0
. I
-.2 -.
-.~ ' . ~
.
. . ~58
. . ~55"
.. --,>wD ,l..' ~4g
tY ~S'3 ~l'"1 ~4'
~~/?I -,>5"~J51 . 1'5 ~44- --+42. ~40
~S2.
74 .-+~~S'D ~2.~
SI I --.4 ~
.2:~35"
.~3'
-.,}9 ~'3Y> -> '3'1, '33
->'34 -?JC:J
-'2..~ ~31 - .
-~
~I~+ ~2.1 +
. + -"10
.~'7.~~ 8-,> J
~ -..p .~ 8
--'3 ~2.
~23/2".J2.(p ""'-> t ~ - 2.0
~ 2..; -=-- \\-14-
~ z:z. ~1~~15
~Zl ->\1 .x
~'a l-
I ./
. I
~t- . . -0
~ I I -./
o
- .'3
-.2..
FIGURE 68
APCO HOLOGRAM #142
-------
TABLE Ilia
APCO Train Hologram #142
1.0 Isokinetic, Loadi'7 1.5 Grains/scf
Pulse Separation -. Milliseconds
Mean Velocity 25 ft ./sec.
Particle No. and V V IVI VO Size/Shape
x y
Location (x, y I z) (ft ./sec .) D = Diameter in
Microns
1. (-0.200 I -0.159 I +0.058) 22.91 - .800 22.92 2°,J, Q~SZ
2. (-0.650 I -0.205 I +0.418) 22.72 - .793 22.73 2C)~ Sphere D = 45
3. (-0.800 I -0.181 I +0.058) 22.54 - .393 22.54 lD~ ~o
~
4. (-0.875 I -0.136 I +0.058) 22.34 - .780 22.35 2" + Sphere D = 45
5. (-0.875 I -0.114 I +0.058) 22.34 - .780 22.35 2"~ a '1.~
5"4
6. (-0.950 I -0.125 I +0.058) 22053 -1 .18 22.54 3D J, Sphere D = 36
7. (-0.950 I -0.09.0 ,+0.058) 22.72 -1 .19 22.73 3° ~ Sphere D = 14
8. (- 0.7 50 I - O. 148 I +0. 085) 22.73 - .397 22.73 l"J.- Sphere D = 36
9n (-1.150 I -0.012 I +0.058) 22.53 -1.18 22.54 3"t Sphere D = 27
10. (-1.175 I -0.034 I +0.058) 22.34 -1 .17 22.35 3°"" Sphere D = 9
11. (+0.250 I -0.364 I 0.000) 23.11 0 23.11 0° Sphere D = 36
12. (+0.250 I -0.364 I 0.000) 22.34 .780 22.35 2°t Sphere D = 27
13. (+0.250 I -0.364 I 0.000) 22035 0 22.35 OD Sphere D = 23
14. (+0.250 I -0.364 I 0.000) 22.35 0 22.35 0° Sphere D = 18
15. (+0.150 I -0.409 I 0.000) 22.73 .397 22.73 lot Sphere D = 32
16. (+0.050 I -0.386 I -0.026) 22.35 0 22.35 0° Sphere D = 9
17. (-0.150 I -0.432 I -0.026) 22073 0 22.73 0° Sphere D = 9
18. (-0.250 I -0.466 I -0.186) 22.35 0 22.35 0.0 Sphere D = 54
19. (-0.400 I -0.284 I 0.000) 22073 0 22.73 0° Sphere D = 36
20. (-00400 I -0.284 I +0.030) 22.35 0 22.35 OD Sphere D = 54
21. (-0.500 I -0.432 I +0.030) 22.54 0 22.54 0° Sphere D = 27
22. (-0.500 I -0.365 I +0.030) 22073 0 22.73 041 Sphere D = 7
23. (-0.700 I -0.227 I +0.196) 22.54 0 22.54 041 Sphere D = 14
24. (-0.700 I -0.227 I +0.196) 21097 0 21.97 0° Sphere D = 1 8
25. (-0.700 I -0.284 I +0.196) 22.35 0 22.35 041 Sphere D = 36
26. (-0.700 I -0.227 I +0.196) 22035 0 22.35 041 Sphere D = 18
27. (-0.900 I 0.0 I +0. 1 96) 22.73 0 22.73 0" Sphere D = 23
28. (-0.900 I +0.307 I +0.335) 22.54 - .393 22.54 1 OJ, Sphere D = 41
97
-------
TABLE ilia (Continued)
Particle No. and V V IVI VO Size/Shape
x y
Location (x, Y I z) (ftc/sec.) D = Diameter in
Microns
29. (-0.110 I +0.295 I +0.390) 22.73 0 22.73 0° c::J '32-
5 OJ, S4
300 (-0. 1 00 I +0.034 I +0.055) 22 . 83 -2.00 22.92 Sphere D = 23
31. (-0.475 I +0.023 I -0.083) 22.68 -1.58 22.73 4°~ 6,4.5"
z.~
32. (-0.475 I +0.091 I -00083) 22.86 -1 .60 22.92 0
4 ~ Sphere D = 9
33. (-0.475 I +0.091 I -0.083) 22086 -1.60 22.92 4 ° t Sphere D = 7
34. (-0.475 I +00057 I -0.083) 22086 -1.60 22.92 4 ° ~ Sphere D = 7
350 (-00650 I +00216 I -0.055) 22.86 -1.60 22092 4 0 f Sphere D = 27
36. (-0.725 I +00216 I -00216) 22068 -1.58 22.73 4 0 ~ Sphere D = 9
37. (-0.725 I +0.182 I -0.055) 22.48 -1.57 22.54 4 () ~ ~32
380 (-0.725 I +0.091 ,-0.055) 22086 -1.60 22.92 0 S-
4 '¥ Sphere D = 27
39. (-0.825 I +00091 I -0.055) 22 . 86 -1.60 22.92 4 0 V Sphere D = 18
40. (+0. 350 I +0. 341 I 0.000) 22.54 0 Sphere D = 45
o 22.54 0
41. (+0. 1 50 I +00 386, o. 000) 22.54 0 22.54 00 c:J 3"
~9
42. (+0. 1 50 , +0. 341 I +0. 055) 22 0 1 6 - .387 22.16 0° Sphere D = 45
43. (-0.100, +0.277, o. 000) 22.72 - .793 22.73 2".j, Sphere D = 23
44. (-0.100 I +00368 I 0.000) 22053 - .787 22.54 20 t Sphere D = 27
450 (-0.225 I +0.382, o. 000) 22. 15 - .773 22 . 1 6 2°~ Sphere D = 45
460 (-0.225, +00391 I 0.000) 22. 1 0 - .772 22 . 11 2°" Sphere D = 36
47. (-0.225, +0.400, 0.000) 22.72 -1.19 22.73 3"V Sphere D = 54
48. (-0.225, +00427, 00000) 22072 - .793 22.73 2°t Sphere D = 36
49. (-0.300, +0.318, 0.000) 22.73 - 0397 22.73 1 0 it Sphere D = 32
50. (-00300 I +0.313, 00000) 22.73 - .397 22.73 lOt Sphere D = 1 8
51. (-00350 I +0.313 I 00000) 230 1 0 - .806 23.11 2 of Sphere D = 36
520 (-0.500 I +00341 I 00 000) 22.73 - .397 22.73 1 0 ~ Sphere D = 54
530 (-00500 I +0.409 I 0.000) 22.72 - .793 22073 2°.J, 045"
54. (-00575, +00341 I 0.000) 23011 .403 23011 01' <30
1 Sphere D = 45
o
550 (-00575 I +0.455 I 00000) 22.73 .397 22073 1 t Sphere D = 45
(-0.650 , +0.386 I 0
560 O. 000) 22.72 0793 22.73 2 4' Sphere D = 1 8
57. (-0.650 I +0.386, O. 000) 22.72 0793 22.73 2°t Sphere D = 27
580 (-0.900 I +0.511 I O. 000) 22 . 1 6 .387 22 0 16 1 ° + Sphere D = 90
59. (-0.900, +0.398 I 0.000) 22092 .400 22 0 92 lot Sphere D = 27
60. ( - 1 . 075 I +0. 443, 0.000) 22072 .793 22073 2 0 t Sphere D = 64
61. (-1.075 I +0.455, 00000) 22.72 .793 22.73 20 t Sphere D = 45
os:!
-------
FIGURE 69
PARTICLE SAMPLING SYSTEM
USING THE APCO TRAIN
FIGURE 70 .
SAMPLING PROBE LOCATED IN
POTENTIAL FLOW SECTION
99
-------
III
~i~
~'~;-}~~
, .
!j.;i
)
FIGURE 71
SYSTEM FOR CALIBRATING APCO TRAIN ASSEMBLY
FIGURE 72
AIR SAMPLING SYSTEM
100
-------
The sampling system was calibrated using a Brooks rotometer to
correlate the flow rate to the pressure drops in a 10" length of O. 25
I. D. tubing.
The pressure drop across the calibrated tube was read by an inclined
manometer. The flow rate was converted to probe inlet velocity and
plotted against differential pressure on log-log paper. By calibrating
a length of tubing, any additional resistance or change of resistance in
front of the 10" length of tubing such as placing the filter in the line
would have no affect on the system calibration.
Figure 72 shows a portion of the sampling system with the filter assembly
and probe replacing the rotometer. Samples were taken with the system
over a 2 minute time interval during which holograms were made of the
flow about the probe. The grain loadings shown in Table III were calcu-
1ated using data obtained from the probe samples. Both the calibration
and sampling systems are shown schematically in Figure 73.
In the isokinetic case, there were few deviations of the particles from
straight line paths as they approached the probe. The. 5 isokinetic case pro-
duced results which were predictable since it was expected that there should
be areas of separated flow due to flow stagnation ahead of the probe caused
by the inlet velocity being lower than that of the free-stream. The theoretical
expectations matched the actual situation as observed on the hologram.
However, the 1. 5 isokinetic case was somewhat puzzling. The flow should
have been a smoothly accelerating flow, starting at freestream conditions
and converging toward the probe. However, a great deal of turbulence was
noted in the holographic reconstructions, making the measurements of
velocity almost impossible since particle pairs were not easily matched.
No satisfying explanation was concluded.
III. D.
- HOLOGRAMS OF CHARGED PLATES
A listing of holograms made of flow between the charged plates is shown
in Table IV. There was some difficulty in making these holograms since
the mechanical structure used to support the charged plates disturbed the
flow of air in the test section and caused particulate to be deposited on
the glass windows. However, three excellent holograms were made of
the flow when the windows were removed. Hologram No. 196 was
selected for analysis.
Figure 74 shows the planes selected for taking particle data from Holo-
gram No. 196. Tables IVa through IVf are tabulations of particle
characteristics and include diagrams showing the location of each
recorded particle in the selected planes.
Figure 75 is a photograph of the device used in the charged plates
experiment. The screen was centered between the plates (2 inches from
each plate) and had a mesh of approximately 3/4 inch. The upright posts
101
-------
PROBE
CALIBRATION TUBE
. I
. I
. ..
I .
.
. ~ '
.
.'
FLOW INCLINED MANOMETER
BROOKS
ROTOMETER
APCO
TRAIN
CALIBRATION SYSTEM
PROBE INTAKE
CALIBRATION TUBE
.
FLOW
SAMPLING
FILTER
~
INCLINED MANOMETER
APCO
TRAIN
SAMPLING SYSTEM
INTAKE
FIGURE 73
SCHEMATIC OF CALIBRATION SYSTEM
AND SAMPLING SYSTEM
102
-------
TABLE IV - CHARGED PLATES
Mean Loading
Hologram Velocity (Grains/Scf) Comments
190 25 Ft/Sec 1.5 Windows so dirty that no reconstruction was visible
191 25 Ft/Sec 1.5 Same as 190
192 25 Ft/Sec 1.5 Same as 190
193 25 Ft/Sec 1.0 Windows so dirty that no reconstruction was visible
194 25 Ft/Sec 1.0 Same as 193
196 10 Ft/Sec .5 No windows in test section, double pulsed particles
visible
197 10 Ft/Sec .5 Same as 196
198 10 Ft/Sec .5 Same as 196
~
0
w
-------
Loading - .5 grains/scf
Pulse Separation - .2 milliseconds
The precipitator plates were in the y = 2" and y = -2" planes and the screen
was in the y = 0 plane. The x and y components of velocity were measured
in the planes y =-1.5", -1.0", 0, 0.495", 0.792", 0.990".
y
./ LASER BEAM
~ FLOW
x
- 1.0
/ /
/ /
0.00 L__- -===:/---/
r /
~ ~- ____1-7
~ / / /
~ / / /
r / /
7 / / /
~//- _...J/
/ /
-l.~____- --'
- z
FIGURE 74
PRECiPITATOR PLATES HOLOGRAM #196
104
-------
v V IVI VO Size/Shape
Partie Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
25- ,l, ~b 0.5 grains/sd
1. (-0.200, +0.915) 8.58 -4.00 9.47 c:::> 14- Loading:
2. (-0.350, -1.109) 9.31 6.52 11 .36 350 l' Sphere D = 36 Pulse Separation - .2 milliseconds
3. (-0.350 , -1. 1 09) 11.19 -1.97 11 .36 10o~ Sphere D = 23 Cut at y = 0.990
4. (-0.450 ,+0.776) 10.64 -1.87 10.80 10o~ Sphere D = 27 . Positive y Component
5. (-0.500 , +0,970) 7.28 -1 .28 7.39 1 OO.{, Sphere D = 23 X Negative y Component
6. (-0.600 , +1.026) 7.33 - .90 7.39 7°J, Sphere D = 45 0 Zero y Component
2.
.£
0 t
01
"
)fX7:~ J
x-> 4-
o
TABLE IVa
PRECIPITATOR PLATE HOLOGRAM #196
-I
~ 2.,5
~X
-2..
-{
o
I
z
-------
v V IVI VO Size/Shape
Partie Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
7. (-0.275 , -0.776) 11 .97 -1 .90 12.12 90 -¥ Sphere D = 64 Loading: 0.5 grains/scf
8. (-0.225 , +0.943) 8.58 -4.00 9.47 250,* Sphere D = 73 Pu Ise Separation - .2 mill iseconds
9. (-0.500 , +0.749) 8.58 -4.00 9.47 25° ~ Sphere D = 36 Cut at y = 0.792
o
10. (+0.500, -0.915) 1 4 . 63 -3.92 15.15 15 {t Sphere D = 54 . Positive y Component
X Negative y Component
o Zero y Component
2
~
1
a
0-
~8
*-"> 9
o
)(~7
TABLE IVb
PRECIPITATOR PLATE HOLOGRAM #196
-I
~IO
-.x
-2
-,
o
z
-------
v V IVI VO Size/Shape
Partic Ie No. and x y D = Diameter in
Location (x, z) (ft ./sec .) Microns
11. (+ 1 . 000 I +0.582) 12.02 5.60 13.26 25°4'- Sphere D = 73 Loading: 0.5 grains/sd
12. (+0.100 I +0.495) 10.79 2.89 11 .17 1504 ~3 Pulse Separation - .2 milliseconds
15°~ h8 Cut at y = 0.495
13. (-0.175 I +0.970) 8.41 -2.25 8.71 Sphere D = 82
14. (-0.175 I +0.970) 8.08 -3026 8.71 22°~ Sphere D = 36 . Positive y Component
15. (-0.175 I +0.638) 9.77 -4.14 10.61 230 it Sphere D = 14 X Negative y Component
16. (-0.175 I +0.305) 9.84 -3.97 10.61 22°~ Sphere D = 64 0 Zero y Component
17. (-1 .000 , +1.081) 11 .48 -8.04 1 4 . 02 35° -L.- c=J Z3
118 2-.
Z!
0 t
'J
X~17 X~ 13,,1+
~15' . :>11
~I£.
>E---->/~
0
TABLE IVc
PRECIPITATOR PLATE HOLOGRAM #196
-I
~X
-2..
-{
o
I
2-
-------
VO S izejShape
Particle No. and V V IVI D = Diameter in
x y
Location (XI Y I z) (ft ./sec.) Microns
18. (-0.600 I +0.099 I +1.164) 6.70 -6.70 9.47 45°~ Sphere D = 45
19. (-0.075 I +0.099 I +0.832) 6.37 -5.94 8.71 43° -L- Sphere D = 27
20. (+1.000 I -0.099 I -1.303) 6.96 6.96 9.85 45° + Sphere D = 36
Loading: 0.5 grains/sd
Pulse Separation - .2 milliseconds
Cut at Y = 0
. Positive y Component
X Negative y Component
o Zero y Component
Z'
o
00
~
t
I -
~18
~19
o
TABLE IVd
PRECIPITATOR PLATE HOLOGRAM #196
-I -
. ~2.0
-.X
-2.
-/
o
I
z
-------
v V IVI VO Size/Shape
Particle No. and x y D = Diameter in
Location (x, y, z) (ft./sec.) Microns
21. (-1.000, -0.891 , +0.083) 8.32 .44 8033 30t Sphere D = 32 Loading: 0.5 grains/scf
22. (+0.550, -1.188 , +0.499) 8.86 5.12 10.23 30°.f. Sphere D = 18 Pulse Separation - .2 milliseconds
23. (-0.450 , -1. 1 88 / +1, 359) 5.14 3.21 6006 32°.t Sphere D = 59 Cut at y =~1.0
24. (-0.900, -1.188/ -1.580) 1.52 1082 2.37 50°1- Sphere D = 27 . Positive y Component
250 (-1 0000 I - 10 188 , -1.188) 4.14 3.47 5.40 40° of' Sphere D = 27 X Negative y Component
o Zero y Component
z
o
-.0
~
+
~1.3
...-> 2 2.
o
~2.1
'4'-=-.59/
TABLE IVe
PRECIPITATOR PLATE HOLOGRAM #196
~ 2.. S""
-/
~ 2-4-
~x
-2-
-------
Particle No. and V V IVI
x y
Location (x, Y I z) (ft ./sec .)
26. (-0.500 I -1 .485 I +1.303) 5.19 3.64 6.34
27. (-0.150 I -1.485 I -1.359) 6.01 -6.01 8.5
28. (0.000 I - 1 .535 I +0.693) 4.88 3.42 5.96
29. ( - O. 1 00 I - 1. 535 I - 0 .41 6) 1 0 0 80 0 10.80
30. (-00650 I -1.535 I +0.998) 4.40 2.86 5.25
31. (-0.650 I -1.535 I +0.998) 4.13 4.43 6.06
32. (-0.625 I -1 .535 I +00776) 3.21 3.21 4.54
33. (-0.825 I -10535 I -1.636) .73 .87 L14
o
VO
Size/Shape
D = Diameter in
Microns
35° + Sphere D = 32
45° + Sphere D = 32
3:f1 Sphere D = 41
0° Sphere D = 27
33° t Sphere D = 23
47° .,. Sphere D = 27
45° t Sphere D = 23
50° + Sphere D = 27
2. i!!-
t
Loading: 0.5 grains/scf
Pulse Separation - .2 mi I Ii seconds
Cut at y =-1 .5
. Positive y Component
X Negative y Component
o Zero y Component
o
TABLE IVf
PRECIPITATOR PLATE HOLOGRAM #196
-{
--="" ~
.....,.. 30, S I
~32.. ~2.8
~t..,
~Z,7
~"53
x
-.
-?
-------
FIGURE 75
CHARGED PLATES DEVICE
FIGURE 76
TIME EXPOSURE SHOWING CORONA DISCHARGE
PATTERNS BETWEEN PLATES AND SCREEN
111
-------
at each corner were made of Teflon. The posts on the right were on
the up-stream side and were shaped to reduce turbulence in the air-
stream. The screen was supported from the Teflon posts by nylon
cord. The short post located at the left rear of the device was used
to support the negative electrode which was attached to the screen.
The metal plates were made of aluminum and measured 8 inches by 4
inches. The wire screen was 7-1/4 inches long by 2 inches wide.
The potential between the plates and wire screen was 26,000 volts and
was provided by a Litton Industries regulated high voltage power supply
(Model 1014). The current drawn by the charged plate device varied
from 50 microamps at 20 KV to 1 milliamp at 30 KV. At 26 KV (the
setting used for Holograms 196, 197, and 198) the current drawn was
approximately 300 microamps.
The design of the system was such that the power available would approxi-
mate the power requirements per cubic foot of processed air typical of
commercial electrostatic precipitators. The literature indicated the
range of energy requirements for precipitators to be on the order of 2 - 5
KW-hr. /1, 000, 000 ft3 or 7.2 to 18 joules/ft3. For Hologram No. 196,
mean velocity was 10 ft/sec. At this velocity, the power requirement was
calculated to be between 4 and 10 watts (corresponding to 7. 2 and 18
joules/ft3). The input power to the system was actually 7.8 watts,
mdicating a reasonable match of power input per unit volume to that
required by commercial precipitators.
Figure 76 is a time exposure (approximately 1 minute) of the corona
discharge patterns between the wire grid and plates.
Particles in the electric field were normally accelerated toward the grid.
However, under column "VOII in Table IVa - IVf, it is noted that some
particles were observed traveling in the opposite direction, indicating
that either particles of opposite polarities were in the flow or that
re -entrainment occurred of particles which had previously reached the
grid and lost their charge.
112
-------
IV - CONCLUSIONS AND RECOMMENDATIONS
IV.A.
- CONCLUSIONS
From the experimental work conducted during this program the following
conclusions have been reached: '
o Double -pulsed holography is a feasible method of determining the
velocity and behavior of particulate matter suspended in both
potential and turbulent flow.
o The Gabor hologram provides an excellent means to record the
size and shape of particulate. Experimental results showed that
a minimum particule size of 5. 5 microns could be resolved.
o The Gabor hologram is usable over a wide range of particulate
loadings. Although the best holograms were made at a low grain
loading (. 5 grains/scf or less), particles were quite visible at
grain loadings as high as 4-5 grains/scf.
o The velocities of particulate (flyash) in a given portion of a test
section appeared to be independent of particle size and shape.
o The type of duct facility designed and used in the program pro-
vides an excellent facility for investigating the behavior of
particulate material in both potential and turbulent flow.
o The "blender" type particulate dispenser proved to be a reliable
and easy-to-use method for dispensing free-flowing powders,
such as flyash, over a wide range of loadings.
o No practical utility can be made of the Stokes-Cunningham
equation based on the holographic experimental data. The Stokes-
Cunningham factor becomes significant only for particles smaller
than 1 micron (at atmospheric pressure) whereas the theoretical
resolution limit of the holographic system used was no better
than 1. 74 microns (the actual resolution was approximately 5.5
microns). Consequently, the effects to which the Stokes-
Cunningham factor relates would not be observed with the experi-
mental system;
o The accuracy of double -pulsed holography in determining
velocity of a particle is a function of the care taken in measuring
the spacing of the particles, the known accuracy of the time
interval between light pulses, the magnification ratios in the
reconstruction system, etc. The accuracy of the system used in
the program was approximately :to. 05 feet/second.
113
-------
IV. B.
- RECOMMENDATIONS
There are four areas where, in the opinion of the authors, additional
studies should be conducted: (1) determination of methods for achieving
small particle (.01 to 5 microns) sizing and velocity characteristics,
(2) development of rapid data gathering and data reduction techniques for
determining statistical characteristics of particles in air flow, (3)
determination of the maximum deviation from isokinetic conditions where
data obtained from sampling probes will produce valid information, and
(4) studies and experiments of simulated electrostatic precipitators to
determine the extent and conditions under which re -entrainment of
particles occurs.
The resolution of holographic systems is limited in a practical sense by
the distance that the holograms must be away from the particle being
recorded. Since it is probably desirable to maintain test facilities such
that the test sections are at least several inches wide and high (to
minimize wall effects and to allow conditions in smoke stacks, etc. to
be simulated), the resolution of holographic systems under these
restrictions would, most likely, continue to be inadequate for studying
particle behavior in the sub-micron region. However, the behavior of
particles in this region should be of special interest since their behavior
could vary significantly from that of larger particles due to phenomena
such as the molecular slip flow effect. Consequently, it should be
desirable to develop techniques to extend the ability to measure particle
characteristics down to the sub-micron levels.
Double pulsed holography is an exce llent means to gather data on
individual particle characteristics. However, where the interest is on
the aggregate behavior of large numbers of particles, the data reduction
problem becomes significant. As pointed out in the report, there are
several methods which could be applied directly to the hologram itself.
These techniques are suitable in areas where the particle pair patterns
are repeatable such as in potential flow regions. However, where the
flow is highly turbulent, these techniques may have serious shortcomings.
Other electro-optical techniques should be investigated to achieve the
capability of measuring particle size and velocity for large numbers of
particles in unstructured flow fields.
The double -pulsed holograms of flow about the sampling probe raised
several questions. From the tests conducted, it appeared that particle
behavior at 1. 5 isokinetic varied considerably from anticipated results.
It is not clear why the discrepancy between theory and experiment arose,
and it is felt that additional studies would be worthwhile to determine the
cause of the noted particle behavior. Additionally, the experiments were
conducted only for conditions of . 5 and 1. 5 isokinetic. At these points
considerable turbulence was noted, indicating that a valid sample of
particulate in the airstream did not occur. It would seem to be desirable
to conduct tests to determine deviations allowable from the 1. 0 isokinetic
condition for purposes of setting tolerances in sampling procedures. A
114
-------
set of double-pulsed holograms varying by increments of :t. 05 from the
1. 0 isokinetic condition would probably provide sufficient data.
The small number of particles found to be traveling in a direction
opposite to the majority of particles in the charged plate experiment
also raised a number of questions. First of all, this experiment was
not controlled aerodynamically in the same sense as the rest of the
experiments. The charged plate assembly introduced turbulence in the
test section and it was necessary to remove the windows to counter this
effect. The removal of the windows also introduced unknown effects
which would possibly account for the few particles which were found to
move counter to the majority. However, the fact that some of these
particles were very close to particles traveling in the direction of the
majority seems to indicate that other effects were present.
A suggested experiment to resolve these questions (i. e., whether the
effects were aerodynamic, re-entrainment, or initial charging of the
particles) would be to devise a larger test section and to redesign the
charged plate assembly in order to assure potential flow. Also, the
ability to measure the velocity profiles between the plates with pitot
probes would be an important feature. If desirable, the charged plate
assembly could be designed to closely approximate the characteristics
of commercial precipitators.
The existing facility could be used for the above suggestions since the
air flow capacity of the system is sufficient to allow an enlargement of
a test section and still maintain required velocities.
115
------- |