EPA-600/1-80-014
February 1980
CARBONACEOUS AEROSOL GENERATOR FOR INHALATION STUDIES
by
Thomas G. K. Lee & George U. Mulholland
National Bureau of Standards
Washington D. C. 20234
Interagency Agreement No.
EPA - 78-D-X0170
Project Officer
Judith Graham
Health Effects Research Laboratory, EPA
Research Triangle Park, N.C. 27711
HEALTH EFFECT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, N.C. 27711
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DISCLAIMER
This report was prepared by the National Bureau of Standards and
has been reviewed by the Health Effect Laboratory, U.S. Environmental
Protection Agency, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and policies
of the National Bureau of Standards or the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
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FOREWARD
The many benefits of our modern, developing, industrial society
are accompanied by certain hazards. Careful assessment of the relative
risk of existing and new man-made environmental hazards is necessary
for the establishment of sound regulatory policy. These regulations
serve to enhance the quality of our environment in order to promote the
public health and welfare and the productive capacity of our nation's
population.
The Health Effects Research Laboratory, Research Triangle Park,
conducts a coordinated environmental health research program in toxi-
cology, epidemiology, and clinical studies using human volunteer subjects.
These studies address problems in air pollution, non-ionizing radiation,
environmental carcinogenesis and the toxicology of pesticides as well as
other chemical pollutants. The Laboratory participates in the development
and revision of air quality criteria documents on pollutants for which
national ambient air quality standards exist or are proposed, provides the
data for registration of new pesticides or proposed suspension of those
already in use, conducts research on hazardous and toxic materials, and is
primarily responsible for providing the health basis for non-ionizing radia-
tion standards. Direct support to the regulatory function of the Agency is
provided in the form of expert testimony and preparation of affidavits as
well as expert advice to the Administrator to assure the adequacy of health
care and surveillance of persons having suffered imminent and substantial
endangerment of their health.
A carbonaceous aerosol generator was designed and built for inhalation
studies with animals. The aerosol generated will be carbonaceous with size
characteristics comparable to the published data on diesel exhaust
particles. Such a generator can be used to conduct a variety of studies
in animals under carefully controlled conditions.
F. G. Hueter, Ph.D.
Acting Director
Health Effects Research Laboratory
iii
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Abstract
A carbonaceous aerosol generator designed for inhalation experiments
with animals is described. The aerosol produced_from a modified
diffusion flame has a concentration of 3-10 mg/m at a flow rate of 30
L/min. The addition of a small amount of 0~ to the acetylene fuel
greatly increased the efficiency of fuel to particulate conversion, the
maximum value was 2.5%. The aerosol size characteristics were:
D =0.14 ym, based on the electrical aerosol analyzer; I) — 0.08 ym,
based on a low pressure inertial impactor; median elementary particle
— 0.023 ym and median agglomerate particle^ 0.54 ym, based on trans-
mission electron microscopy. The size characteristics of the generated
aerosol are compared with diesel exhaust based on available published data.
Key words: Aerosol generator; agglomerate; diesel exhaust; diffusion
flame; inhalation; particulates; particle size; soot
IV
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CONTENTS
Abstract iv
Figures vi
Tables vi
1. Introduction 1
2. Conclusions and Recommendations 3
3. Design of Carbonaceous Aerosol Generator 4
4. Experimental 6
Performance of Generator 8
Effect of various parameters on generation rate . 8
Comparison of diesel and generator aerosol. ... 10
5. Discussion 14
References 16
Appendices 18
A. Detailed construction and operation of
the generator 18
B. Measurement error in using electron microscopy
technique 24
v
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FIGURES
No. Page
1 Cross-sectional view of the combustion chamber ....... 25
2 Combustion chamber and connections ............. 26
3 Control panel of the generator ....... . ....... 27
4 Calibration curves for acetylene and oxygen flow meters . . 28
5 Calibration curve for nitrogen flow meter ......... 29
6 Calibration curve for air flow meter ............ 30
1 Calibration curve for dilution air gauge .......... 31
8 Cross-sectional view of the light-scattering photometer . . 32
o
9 Output stability of the soot generator at 6.5 mg/m .... 33
10 Repeatability of the generation rate with on and off
cycling of the generator ................. 34
11 Comparison of runs 2A and 2B at high concentration levels . 35
12 Photometer reading as function of mass concentration
of the aerosol ....................... 36
13 Typical number-size distribution of generated aerosol
after dilution (30:1) based on EAA measurements ...... 37
14 \/olume-size distribution on the diluted aerosol based
on data given in figure 13 ................. 38
15 Number-size distribution of aerosol based on EAA
measurement from flame burning under non-sooting
condition ......................... 39
16 Photomicrographs of carbonaceous aerosol under lower
magnification ....................... ^0
17 Photomicrographs of carbonaceous aerosol under high
magnification
TABLES
1 Properties of Carbonaceous Aerosol
2 Comparison of Diesel and Generator Aerosol
vi
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SECTION 1
INTRODUCTION
The Center for Fire Research, National Bureau of Standards,
Department of Commerce entered into an agreement with the Health
Effects Research Laboratory, Environmental Protection Agency (EPA) to
develop a combustion type carbonaceous aerosol generator and to
characterize the -resulting aerosol. The generator is to he used by
EPA for animal lung deposition studies using C tagged radioactive
fuel.
This report describes the carbonaceous aerosol generator and
includes information on test repeatability, the size distribution of
the generated aerosol, number and mass concentration of particulates,
carbon-hydrogen ratio, and the concentration of CO and CO gases in
the aerosol stream. Detailed assembly and operation instructions for
the generator are also included in the appendix.
During the development of the generator, EPA added the requirement
that the generator have a carbon conversion efficiency of fuel to
particulate in the order of 5% or higher and a maximum particulate
generation rate of about 0.3 mg/min at a flow of 30 L/min with a
variable concentration between 5 and 10 mg/m . This need for a high
conversion ratio and low output generation became obvious because of
the high cost of C labeled fuels, which are necessary for making
lung deposition studies in animals.
A major thrust of the generator development was concerned with
meeting this added requirement. Our early work indicated that the 57
conversion efficiency could be obtained using a diffusion flame with
propane fuel; however, the particulate generation rate was a factor 20
higher than the desired level. Much of the subsequent work was concerned
with finding the best combination of nozzle design, combustion conditions,
and additives to yield high conversion of fuel to particulate at a low
fuel burning rate. In other words, the goal is to promote sooting in a
very small flame. It was found that an acetylene diffusion flame with
a small amount of premixed oxygen or N_0 yielded the best result
though the efficiency is still somewhat less than the desired value.
All subsequent discussion will be confined to acetylene diffusion
flame with premixed oxygen.
The second part of this study was concerned with the physical and
chemical characterization of the carbonaceous aerosol. Since the
carbonaceous aerosol is to be used to simulate the particles of diesel
smoke, it is important to know the characteristics of the carbonaceous
aerosol so that comparison between the two may be made. The chemical
analysis consisted of an analysis of carbon-hydrogen ratio of the
particulate and analyses for CO and CO,-, in the gas phase of the aerosol.
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All of the techniques used by Dolan et al. [1] and ""uk et al. [2]
in their physical measurements of the size distribution of diesel
particulate were applied in the measurements of the carbonaceous
aerosol from the generator, including electrical aerosol analyzer (EAA) ,
scanning and transmission electron microscopy, and cascade impactors.
In addition, the aerodynamic size distribution was determined by a low
pressure cascade impactor developed by Bering et al. [3] with a 50%
efficiency cut-off on the last stage of 0.05 ym, which is almost a
factor of 10 smaller than ambient pressure cascade impactors currently
available.
Numbers in brackets refer to literature references at the end of this
paper.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
A stable, repeatable carbonaceous aerosol generator has been
developed for animal inhalation studies with a carbon conversion
efficiency of fuel to particulate of up to 2.5% at a mass concentration
of 10 mg/m and a flow rate of 30 L/min.
The particle size as measured by the EAA, cascade impactors, and
electron microscopy and the carbon content in the particulate agree
reasonably well with the results based on the high-temperature diesel
exhaust.
The median aerodynamic particle size based on the low pressure
impactor measurement is about 0.08 ym for the generated aerosol. This
is perhaps the first aerodynamic classification of a carbon agglomerate
type aerosol in the size range below 0.2 urn.
If the conversion efficiency of the present generator is shown to
be too low for long-term economic use with a radioactive tagged fuel,
there are two other alternative generator designs that might yield
higher efficiency. Details for their designs are presented in the
discussion section of the report. A second area where additional
research is needed concerns the characterization of the size
distribution and shape of the carbonaceous aerosol. The advantages
of using a low pressure impactor and a diffusion battery for such a
study are also presented in the discussion section of the report.
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SECTION 3
DESIGN OF CARBONACEOUS AEROSOL GENERATOR
DESIGN AND CONTROLS
The carbonaceous aerosol generator was designed to generate a low
concentration of carbonaceous aerosol (5 to 10 mg/m ) so as to be
suitable for animal inhalation experiments without further dilution
though at the same time yielding a high conversion ratio of fuel to
aerosol. The generator design allows considerable flexibility in the
choice of combustion conditions including type of fuel, diameter of
burner nozzle, use of fuel additives and diffusion air, and the temperature
of the combustion chamber.
The generator consists of three parts: combustion chamber,
control panel, and monitoring photometer.
COMBUSTION CHAMBER
The inside and outside views of the combustion chamber are shown
in figures 1 and 2. The fuel enters the burner through the bottom of
the chamber at a flow rate of about 15 cm /min. The 1.7 mm-ID nozzle
of the brass burner is located 20 mm above the base of the chamber.
The diffusion air mixture enters through a sintered porous bronze
cylinder, 6 mm thick, at a flow rate of-about 1 L/min. In the final
design a small amount of 0 , about 5 cm /min, is premised with the
acetylene fuel. Diffusion air is diluted with nitrogen to a final
mixture of about 16% oxygen in order to increase the efficiency of
soot production. The combustion is initiated by a spark generated
from a high voltage wire located next to the burner tip.
The pressure in the combustion chamber was maintained at about 29
Pa (0.3 cm H_0) above ambient with an exit orifice to prevent the high
volume of dilution air from affecting the generation rate of aerosol.
Eight 1.4 mm-ID holes were drilled on the circumference of t>
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CONTROL PANEL
The key features of the control panel are shown in figure 3. Flow-
meters (rotameter) are used for monitoring the flow of fuel, fuel additive,
air and N_. Because of the small flow rates for fuel and fuel additive,
a bubble flowmeter is required for accurate calibration and is included
with the control cabinet. Calibration curves in figure A for the fuel
and oxygen flowmeters are based on calibration using a soap bubble
flowmeter. Calibration curves in figures 5 and 6 for nitrogen and air
flowmeter are based on data supplied by the manufacturer.
One of the three magnehelic gauges on the front of the control
panel is used for monitoring the flow rate of dilution air, which may
be varied between 8 and 32 L/min by the valve located at the lower
right hand corner of the panel. A dilution air flow of 77 L/min,
which corresponds to a reading of 0.68 cm HO (66 Pa) on the magnehelic
gauge, was used for most experiments. A calibration curve for dilution
air flow rate versus meter reading for the orifice meter is shown in
figure 7.
The second magnehelic gauge is used to monitor the combustion
chamber pressure. The middle gauge is coupled to an audible alarm,
which can be set to alarm if the chamber pressure is either higher or
lower than the preset values.
Other features of the control panel include an ignition button
for the fuel, a temperature controller for the combustion chamber, and
digital meters to monitor exhaust gas temperature and chamber temper-
ature. The digital meter for monitoring the exhaust temperature is
also interfaced to the audible alarm, which will trigger if the temper-
ature drops below 50° C indicative of a flame-out condition. A six
foot umbilical cord is provided to allow separation of the burner from
the control panel.
MONITORING PHOTOMETER
The monitoring photometer, illustrated in figure 8, is a commercially-
available, light-scattering-type smoke detector modified to provide an
analog output. The chamber of the detector has also been modified to
allow steady-state flow through. The photometer is used for monitoring
the mass generation rate and stability over the range from 3 to 12
mg/m . A connector on the front of the control panel interfaces the
photometer to a recorder.
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SECTION 4
EXPERIMENTAL
PERFORMANCE OF GENERATOR
Stability
The output stability of the generator«is shown in figure 9 for
an aerosol concentration of about 6.5 mg/m . The background reading
with no smoke present is 0,2 volts as shown in figure 9. The photometer
output increases rapidly to about 1.13 volts when the fuel is ignited.
It is noted that the output is relatively stable over a 35 minute
period though there is a slight downward concentration drift of about
7% after 30 minutes. In earlier work, drift was found to result from
an incandescent carbon deposit on the high voltage ignition wire or
on the nozzle. By trimming the ignition wire and substituting a
brass burner for the stainless steel burner, the deposit no longer
formed and the drift was greatly reduced.
Repeatibility
Figure 10 gives an indication of the repeatability of the generator.
The generator is on for 15 minutes, off for 10 minutes, and on again for
about 10 minutes. It is critical that the fuel and additive needle
valves remain in the same position when the burner is turned on and
off, because the sooting rate is very sensitive to any change in the
flow rate or valve position. Only the on-off toggle valves should be
used during the on and off cycling of the generator. To assure good
repeatability, the fuel and oxygen lines should be purged for at least
15 minutes if valves upstream of the regulator are shut off.
Figure 11 compares the photometer output for two test runs to
show the degree of repeatability and long term (> 30 min) stability
of the generator at a high concentration level. The record for run
2A is placed on top of run 2B. The mass concentrations of the
aerosol, determined by the filter collection method-for a 10 minute
sampling period for each run, were 9.1 and 9.3 mg/m for 2A and 2B
respectively. Geometric mean sizes of Aerosols from the above
runs which have been diluted in the 1.8 m chamber are given in
table 1.
The results from figure 11 and table 1 show that the generator
can provide a reasonably consistent aerosol both in geometric mean
size as well as in concentration over a 30 minute period.
Generation Rate
The mass concentration of the aerosol is measured by a gravimetric
analysis technique. The aerosol is collected downstream of the
photometer on a 47 mm diameter teflon filter (0.5 ym pore unbacked
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Fluoropore filter, Millipore Corp., Bedford, Massachusetts 01730)*
with the sampling flow rate controlled by a critical orifice at 10
L/min. The collection time was adjusted so that the aerosol sample
collected was about 1 mg.. This required 10 minutes for a mass
concentration of 10 mg/m . Figure 12 shows measurements of the mass
concentration of aerosol and the net photometer output covering the
range of interest. Correlation between the two quantities appears
linear. The photometer output thus provides a convenient method for
monitoring the aerosol concentration and generator stability. The
net photometer output in figure 12 was obtained with a 10 inch span
Esterline recorder corrected for impedance mismatch and based on the
difference of readings recorded with and without the aerosol. Figures
9, 10, and 11 show arbitrary units only. Other photometer/recorder
systems may also be used provided that a gravimetric calibration is
performed. The photometer assembly should be cleaned by directing a
flow of clean air into the photometer chamber after two hours of
generator operation.
Carbon Conversion Efficiency
As pointed out in the introduction, a quantity of prime importance
in this study is the fuel to aerosol conversion efficiency, defined
as the percentage of the carbon in the fuel converted to particulate
matter. The following formula is useful for calculating the conversion
efficiency, E:
E = 100 (mg aerosol generated per minute)/(mg carbon in fuel
consumed per minute)
= 100 M V /(M V )
i _L _L ^- Z,
where _
M = mass concentration of aerosol in mg/m
V- = total aerosol flow in m /min; typically 0.030
M = mg carbon in one cm of fuel (0.98 for acetylene at 25° C and 1
atmosphere pressure (1.01 x 10 Pa))
V_ = fuel flow rate in cm /min.
The average mass concentration of the aerosol for runs 2A and 2B (table 1
and curves in figure 11) was found to be 9.2 mg/m . Using this together
with the fuel flow rate of 13 cm /min, one obtains a conversion efficiency
of 2.2%.
*
Certain commercial equipment, instruments, or materials are identified
in this paper in order to adequately specify the experimental
procedure. In no case does such identification imply recommendation
or endorsement by the National Bureau of Standards, nor does it
imply that the material or equipment is necessarily the best available
for the purpose.
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A dominant characteristic of this carbonaceous aerosol generator,
as well as others such as the premixed acetylene flat flame burner
developed by Toossi [4], is the suddenness of the onset of sooting.
Using a prototype combustion chamber, it was found that a 257 increase
in fuel flow resulted in a 150 fold increase in aerosol output as moni-
tored with an electrical aerosol analyzer. Because of this precipitous
increase in aerosol concentration with fuel flow, it is not convenient
to vary the soot concentration by simply varying the fuel flow. Instead,
the mass concentration of the aerosol is varied over the range 5 to 10
mg/m by changing the percentage of air in the air nitrogen mixture of
the diffusion air. The lower the percent of 0~ the higher the aerosol
concentration. Varying the dilution air may also be used to change the
concentration.
EFFECT OF VARIOUS PARAMETERS ON THE GENERATION RATE
The effects of a number of parameters on the conversion efficiency
were measured. These parameters included the type of fuel, the addition
of various oxidizing agents to the fuel, diameter of burner tip, and the
temperature of the fuel and air.
„ It was found that acetylene began sooting.,at a Dower flow rate (40
cm /min) than the flow rate for propane (65 cm /min). The conversion
efficiency is high under these conditions. For example, the.,conversion
efficiency for acetylene is about 9%^at a flow rate of 40 cm /min with a
mass concentration of about 120 mg/m , which is about ten times higher
than needed for inhalation experiments with animals.
3
As a sidelight, it was found that acetylene fuel at 30-,cm /min
without additive produced a high number concentration ( 10 /cm ) of
very small aerosol particles, on the order of 0.01 ym diameter; however,
the mass concentration of the aerosol was low, less than 0.1 mg/m .
These small particles always seem to be produced when the fuel flow rate
is below the sooting point. Detailed physical characteristics of flame-
produced particles are presented in the next section.
With the addition of a small amount of premixed 0-, 3 to 4 cm /min,
to the acetylene diffusion flame, a sudden increase in aerosol concentra-
tion and particle size was observed at fuel flow as low as 13 to 14
cm /min. The use of 0? as an additive was motivated by a discussion
with Y. Manheimer-Timnat from Technion, Haifa, Israel, in which he
mentioned that the height of a flame at which sooting occurred greatly
decreased with the addition of a small amount of 0 . Wright [5] has
reported that the efficiency of conversion of fuel to particulate is
greatly enhanced in ethylene and benzene with the addition of about 10
to 15% stoichiometric 0 . By using the Q~ additive In the fuel, the
fuel flow rate can be reduced to a half or less of that required without
the additive for a given soot generation rate. It was also found that
the addition of N20 had an effect similar to that of 0? though a somewhat
higher flow rate of NO is required compared to 0?.
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The preheating of the fuel to about 100° C, seemed to have a minor
effect on the soot generation efficiency. The heating of the comhustion
chamber and diffusion air mixture tends to decrease sooting efficiency,
though temperature control was found necessary to ensure generation
stability.
The inside diameter of the burner nozzle was found to have little
effect on the magnitude of the fuel flow rate at which sooting commenced.
For ethylene fuel, changing the burner diameter from 1.8 to 8 mm resulted
in only a 10% change in the fuel flow rate required for sooting. The
onset of sooting was noted by the visible black stream rising from the
flame.
While the size of the burner nozzle did not have a large effect on
the sooting point, the thermal properties of the material used for
making the tip were found to be important when using acetylene.
Nozzles constructed of stainless steel tended to increase carbon
deposition, which eventually resulted in clogging, while those made
from brass did not have this problem. The selection of inside diameter
for the nozzle (or flow velocity) was based mainly on the ease of fuel
ignition by the high voltage electrode located at a given distance
from the nozzle.
PHYSICAL AND CHEMICAL CHARACTERIZATION OF THE CARBONACEOUS AEROSOL
It is generally recognized that the particle size distribution is
the most important quantity for determining the lung deposition charac-
teristics of an aerosol. Particle measurement techniques used in the
two studies of diesel particulate cited earlier were used in the present
work [1] [2].
The primary instrument used for monitoring the particle size distri-
bution was the electrical aerosol analyzer (EAA), which measures an
effective particle size based on electrical mobility. The data are
presented in terms of the particle number distribution (AN/A log D ) and
particle volume distribution (AV/Alog D )versus P where N is the
number concentration of aerosol per cubic centimeter. The basic data
are the current corresponding to N versus voltage corresponding to "n .
An example of the output from the instrument is included in the top
portion of figure 11 (the multipeaked curve) for eight discrete voltage
settings. The size distributions are derived from the current versus
voltage data using the sensitivity factors in Liu and T>ui [6] for the
case Nt = 1 x 10 (cm )(sec). A log-log plot is necessitated by the
wide range in particle size and concentration. The Quantities AN and AV
refer to the number of aerosol particles in the particle diameter size
range log D to log D + A log D and to the volume of aerosol particles
in the particle size range log D to log D + A log D , respectively.
The size distributions (number and volume) are plotted in figures 13 and
14 for the case of the carbonaceous aerosol diluted in a 1.8 m chamber.
The undiluted aerosol stream has a mass concentration of 5.6 mg/m
(Run 1A).
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It is convenient to characterize a size distribution in terms of
the geometric mean diameter, D , and the breadth of the size distribution
by the geometric standard deviation, a . These quantities are defined
below for the number distribution:
, - " AN. log D
log D = E i
o
1=1 N
11 (lo D lo D 2 AN "' 1/2
log a
gn
1-1 N
where N is the total number of particles and AN. is the number of
particles in the ith interval. A similar definition applies for the
volume distribution except that N in the equations above is replaced
with V.
Comparison of Diesel and Generator Aerosol
The parameters D and a are listed in table 2 both for the generated
carbonaceous aerosol and for the average diesel smoke for an Oliver/
Waukesha F310 DEL six cylinder open diesel engine [1] . The parameters
for the diesel smoke are based on particles in the size range of about
0.07 to 1 urn. It is seen that there is a good agreement for the geo-
metric mean volume diameter for the diesel particulate and the carbona-
ceous aerosol from the generator .
The size distribution of the aerosol was found to be relatively
independent of the combustion conditions in the generator provided that
the total mass concentration of the soot was in the range of 3 to 15
mg/m . For example, in table 1 the value of D changed by only about
0.01 ym as the total mass,.concentration of parriculate increased from
5.6 (0.14 urn) to 9.1 mg/m (0.15 ym) . As mentioned in the previous
jsection aerosol produced under a non-sooting condition has small particles,
D =0.01. As a result, the mass concentration is low and number con-
centration is high. The number size distribution for this case is
plotted in figure 15.
The second method of size analysis is based on aerodynamic size
classification with the Anderson cascade impactor [8] . The aerodynamic
particle size is the effective size for a unit density sphere. The
concentration of particles on each stage was determined gravimetrically.
In one experiment 98% of the carbonaceous aerosol by mass was found to
be less than 1.1 ym aerodynamic diameter, 91% less than 0.7 vim, and 78%
less than 0.4 ym. As in the case of the FAA, the results with the
impactor were found to be similar for a range of generator conditions.
For example, for three different experiments performed over a six week
period the range in the percent of total particulate less than 0.4 ym
varied from 79% to 86%.
10
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As shown in table 2, there is reasonable agreement in the percent
of aerosol less than 1.1 ym for the generator aerosol and the high
temperature (> 300°C) exhaust from a 3150 caterpillar diesel engine
[2]. At the lower exhaust temperature, there is a notably larger per-
centage (between 6 and 19%) that is greater than 1.1 ym in aerodynamic
particle size.
The conventional cascade inertia impactors are not capable of
detailed size classification of the aerosol of interest, because a
major fraction of the aerosol is below the minimum sizing range of the
impactor. A recently developed low pressure impactor [7] was used to
measure the aerodynamic particle size down to 0.05 ym. Because of the
low flow rate and small nozzle size, the samples collected were too
small to be measured gravimetrically. Visual observation of the
opacity of the deposited aerosol on the collection surface indicated
that the major fraction of the aerosol was deposited on the ]ast two
stages, corresponding to particles sizes of 0.075 to 0.05 ym. This
was found to be the case for both coated (silicone stopcock grease)
and uncoated collection surfaces. By comparing the opacity of the
last two stages, it was found that the major deposition was on stage 7
(0.075 ym).
The third technique for particle sizing was electron microscopy.
The samples were collected on microscope cover slides and on 2.3 mm
diameter copper specimen grids with a carbon coating using a Thermo-
System electrostatic precipitator. Preliminary work with a scanning
electron microscope indicated that the particles had an agglomerate
type structure not unlike those produced by the carbon black industries
[9] but the resolution was not adequate for analyzing detailed structure.
As shown in figures 16 and 17, transmission electron microscopy clearly
indicates that the aerosol particles are made up of an agglomeration
of nearly spherical elementary particles of about 0.023 ym in diameter.
There is qualitative similarity between this picture and those presented
in the diesel study by Vuk et al. Their rather extensive particle
analysis showed that the mean elementary particle size based on number
is 0.026 ym. The mean size refers to the particle size at the 50%
point; that is, half of the number of particles are larger and half
smaller than the mean. The elementary particle size for the generator
was found to be about 0.023 ym based on sizing 108 particles. As a
measure of the agglomerate particle size, the hypothetical diameter of
the largest sphere which can cover the entire agglomerate was used.
The mean largest sphere diameter, 0.54 ym, given in table 2 is seen to
far exceed the particle size measured by the other methods. Vuk et
al. found for diesel particulates that the largest sphere diameter
exceeds the aerodynamic particle size by a large amount just as in the
case for the carbonaceous aerosol from this generator. Hiscussion of
measurement error is given in Appendix 2.
Elemental analysis of the aerosol collected showed a carbon-
hydrogen ratio of 99 to 1 or more for carbon. The analysis was performed
by a commercial contractor (Schwarkopf Microanalytical) on about A mg
11
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particulate samples on glass fiber filter by measuring the amount of
CO- and H?0 produced by the combustion of the samples. Results from
duplicate samples agreed within 0.5%. As shown in table ?, the diesel
particulate at high exhaust temperature was found to have almost as
high a carbon content, 98%. At lower exhaust temperatures, the percent
carbon drops, presumably because of an increased amount of condensed
hydrocarbons [2].
Aerosol Size and Repeatability
Table 1 shows the consistency in the concentration and geometric mean
size of some sample carbonaceous aerosols obtained in this study. The
results are given for two concentrations (1 and 2) with duplicate mea-
surements and a third measurement to determine the effect of coagulation.
All results except for the mass concentration were obtained using the
electrical aerosol analyzer. Each experiment required 30-40 minute opera-
tion of the generator to allow time for the collection of two filter
samples (10 to 15 minutes each) and for time to measure the size
distribution with the electrical aerosol analyzer. The necessary
dilution of the aerosol for operation of the EAA was obtained by
directing the aerosol into a 1.8 m dilution chamber for a Vnown
period of time (23 minutes). The results indicate that the generator
has the stability and repeatable aerosol size characteristic for
animal exposure study in a flow through system.
Effect of Particle Coagulation
The third experiment showed the effect of aging on the concentration
and size distribution. As the particles collide and coagulate due to
Brownian motion, the number concentration will decrease and the particle
size will increase. This process does not affect the total mass of the
suspended particles but it does affect the number concentration and
particle size. That coagulation as an important aging mechanism ±s clear
from the results in tf.^le 1 (run 3) where it is seen that the number
concentration drops by 20% while the volume (mass) concentration remains
about the same after 32 minutes. It is also seen in table 1 that
there is a slight increase in the mean particle size.
The fundamental quantity for coagulation is the coagulation
coefficient, T, which is defined by
dN/dt = T N2
From this equation and the data in table 1, one finds that T = 4.1 x
10 cm /s. As defined above T is an average coagulation coefficient,
though in reality T depends on particle size, charge, and perhaps on
shape. Because of the relatively high concentration of the carbonaceous
aerosol, about 3 x 10 particles/cm , the coagulation effect may be
important in affecting the particle size if the generator output is
run into an accumulator for some length of time before entering the
animal chamber. A'- this concentration, the particle size will increase
by about 10% in five minutes.
12
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Gas Analysis
An analysis of the CO and CO in the aerosol stream was made
because of the potential interference of the C in gaseous form
with the particulate analysis. Using a long-path-length infrared gas
cell, it was found that the concentrations of C0? and CO were P40
ppm and 10 ppm respectively for the case of an acetylene flow rate
of about 14 cc/min. From a carbon balance, one finds that about
90% of the carbon in the fuel is converted to C09, 1% to CO and the
remainder to particulate.
13
-------
SECTION 5
DISCUSSION
The prototype generator developed appears to be well suited for
lung deposition studies because of its constant output and consistent
particle size distribution. However, the conversion efficiency of the
generator may still be too low for long-term economical use with a
radioactive tagged fuel. There are a couple of alternative generator
designs that might yield higher efficiency. One method is to use
liquid aromatic fuels such as benzene or toluene. These fuels have
been shown to have a high conversion efficiency to particulate [5].
Another possible method widely used in the carbon black industry [9]
is to generate the particulate by the thermal decomposition of the
fuel in the absence of oxygen. Professor Flagan at California Institute
of Technology has a tube furnace that might be available for making
a preliminary study of the feasibility of such a technique.
A second area where additional research is needed concerns the
characterization of the size distribution of the carbonaceous aerosol.
For agglomerate type particles such as the carbonaceous aerosol, there
is no theory for relating the particle size parameter of one instrument
based on one aerosol property such as the electrical mobility, to the
particle size based on another property such as aerodynamic size
classification. In table 2 it is seen that the aerodynamic particle
size from the low pressure impactor is a factor 4 smaller than the
electrical mobility volume particle size. This difference is not
simply an instrument calibration effect, because good agreement was
found between the low pressure impactor and the EAA in the 0.05 to
0.1 ym diameter size range by Hering et al [7] using spherical sulfuric
acid aerosol.
Even though the low pressure impactor results are qualitative at
this point, the magnitude of the discrepancy with other methods
justifies a carefully designed study with this newly developed measure-
ment method. Quantitative results could be obtained even with the
small amount of particulate deposited in each impaction stage by using
C labeled fuel and sensitive radiation detectors. This method has
the advantage over the other two techniques for particle deposition
studies that it measures the aerodynamic particle size, which is known
to be an important parameter for particle deposition in animals [10] .
The low-pressure impactor by itself will not answer all the
questions regarding particle deposition. The diffusion of particles
in the respiratory tract passages becomes an important mechanism of
deposition for sufficiently small particle sizes. In a study of
aerosol deposition at the bifurcation of airways under conditions
simulating flow in the lung, Bell [11, 12] found that the major
mechanism of aerosol deposition for spherical particles less than
0.1 urn in diameter is diffusion. Over the size range from 0.1 ym to
1, ym there is a transition from diffusional to inertial deposition
(impaction). A proposed deposition and retention model for aerosol
14
-------
in the respiratory tract developed by a special task group on lung
dynamics set up by Committee II of the International Commission of
Radiological Protection [13,10] indicates that a significant fraction
of particles smaller than 0.1 ym diameter are deposited by diffusion
in the pulmonary and T-bronchial region of the lungs.
These studies suggest that diffusional deposition might be an
important mechanism for the deposition of carbonaceous aerosols in
the lungs. It is not possible to predict the diffusion coefficient
of the carbonaceous aerosol, because the relation between particle
diffusion coefficient and the aerodynamic diameter is unknown for
cluster and chain type agglomerates. Therefore, we suggest that the
diffusion coefficient of the carbonaceous aerosol be determined. This
can be done by using a diffusion battery together with a condensation
nuclei counter.
While the particle size of the aerosols from diesel exhaust and
from the generator are similar, the morphology (including shape and
surface area) of the particulates has not been compared in the present
work.
15
-------
SECTION 6
REFERENCES
1 Dolan, D. F., Kittelson, D. B. and Whitby, K. T., Measurement
of diec»l exhaust particle size distributions, presented at The
America "ociety of Mechanical Engineers, November 30-December
4, 1975, Houston, Texas.
2 Vuk, C. T., Jones, M. A. and Johnson, J. H., The measurement
and analysis of the physical character of diesel particulate
emissions, presented at the Society of Automotive Engineers
Congress and Exposition, February 23-27, 1976, Detroit, Michigan
3 Hering, S. V., Flagan, R. C. and Friedlander, S. K., Design and
evaluation of new low-pressure impactor, Environmental Science
and Technology, Vol. 12, 667 (1978)
4 Toossi, Reza, Physical and chemical properties of combustion
generated soot, Ph.D. thesis, University of California (1978)
5 Wright, Franklin J., Effect of oxygen on the carbon forming
tendencies of diffusion flames, Fuel, 53, 332 (1974)
6 Liu, Benjamin Y. H. and Pui, David Y. H., On the performance of
the electrical aerosol analyzer, J. Aerosol Science, 6, 249 (1974)
7 Hering, S. V., Friedlander, S. K. and Collins, J. J., Design
and evaluation of a new low-pressure impactor, II, Environmental
Science and Technology, Vol. 2J3, 184 (1979).
8 Anderson, A. A., New sampler for collection, sizing, and enumera-
tion of viable airborne particles, J. Bacterial, Vol. 76, 471-484
(1958) or IACFM Ambient Particle Size Sampler.
9 Donnet, J. B. and Voet, H., Carbon black, physics, chemistry and
Elastomer Reinforcement, Marcel Jekler, Inc., 1976.
10 Air sampling instruments for evaluation of atmospheric contaminants,
Sec. G, American Conference of Government Industrial Hygienists(1972).
11 Bell, K. A., Aerosol deposition in models of a human lung bifurcation,
Ph.D. thesis in chemical engineering, California Institute of
Technology (1978).
12 Friedlander, S. K.,"Smoke, Dust and Haze',' p. 119, John Wiley
and Sons, 1977.
13 Report of task group on lung dynamics to ICRP Committee, Deposition
and retention models for internal dosimetry of the human respiratory
tract. Health Physics, 12, 173 (1966).
16
-------
14 Groblicki, P.J. and Begeman, C.R., Particle size variation in
diesel car exhaust, SAE Tech. Paper 790421, Feb. 1979
15 Carpenter, K. and Johnson, J.H. Analysis of physical characteristics
of diesel particulate matter using transmission electron microscope
technique, proceeding Central State Section of The Combustion
Institute, April 1979.
17
-------
APPENDIX A
DETAILED CONSTRUCTION & OPERATION OF THE GENERATOR
Construction, nd Function of Parts in the Combustion Chamber
Body
The body of the generator (figure 1) consisted of the top and bottom
chambers jointed together by bolts and sealed by two(2) copper gaskets
at the mid section. Each gasket is welded to one of the porous cylinders.
In addition to the main chambers, there are the exit and burner sections.
These sections are also sealed to the main chamber by use of copper
gaskets and bolts. Each of the 4 stainless steel sections may be dis-
assembled. Both the exaust nozzle and burner nozzle can also be removed.
Heaters and Thermocouples
Eight 40-watt heaters, connected electrically in parallel, are embedded
in the two(2) chambers. There are three type K thermocouples: the one
located in the bottom chamber is connected to the temperature controller;
the one at the exit section extends 'nto the exit nozzle, the third one
is for monitoring the body temperature of the top chamber.
Air Mixture and Fuel Inlets
The diffusion air mixture is distributed by a swagelock tee to the top
and bottom section of the chamber. The gas is heated as it travels
through the chamber and diffuses through the porous metallic cylinder.
Each chamber can be independently supplied by different mixtures. A
flame arrestor separates the fuel inlet and the downstream fuel line.
High Voltage Ignition and Pressure Monitor.
The burner section contains a H.V. ignition lead and an opening for
monitoring the chamber pressure. The high voltage terminal is
insulated from the chamber by a ceramic tubing. It should be
protected from any impact because of its brittleness. Disconnect
or connect the lead carefully by pulling straight down or inserting
straight up thru the tygon tubing. Any arcing from H.V. lead to
chamber ground would prevent any firing at the nozzle.
Connections
All connections to the chamber should be made carefully according
to line labels. Fuel and air mixture lines should be identified
using odor from C_H or by other means after initiating free flow
and before the final connection.
Connect the ground w^re from the power line to the chamber at one
of the body bolts aL the midsection of the chamber. The bolt may
be loosened and retightened by a proper alien wrench.
18
-------
Control Panel Functions
Line Connections
Both the inlet and outlet gas lines are equipped with Ouick Disconnect
joints located at the side of the control cabinet and identified by
labels. Both the male and female joints contain valves which shut
off the flow after the joint is disconnected.
Gas and Power requirement:
Power: 115 VAC, 10 amp.
Air : 10-15 psi, 30 L/min, filtered
0_ : Bottle, regulated 15 psi, 10 cm /min
N : Bottle, regulated 15 psi, 1 L/min .,
C H : Bottle, regulated (do not exceed) 10 psi, 20 cm /min
Gas Flow Meter and Control
After entering the inlet at the cabinet the gas goes thru the
in-line filters, an on-off toggle valve, a needle control
valve, and finally the rotameters. Dilution air flow is controlled by
a needle valve and monitored by the magnehelic gauge. Because of
high flow volume, a supplemental and disposable filter should be used
upstream of the air inlet.
Calibration curves for each flowmeter are given in the text. A bubble
flowmeter provided with the instrument may be connected at a specific
outlet to check or recalibrate the flowmeter for a specific gas. Once
the needle values for the fuel and 0_ additive are set, avoid changing
the settings.
Temperature Controller and Indicators
A time proportional temperature controller, though designed for type J
thermocouple and Fahrenheit scale, will maintain the chamber about
40°C at a setting of 90. The temperature is displayed by one of the
digital temperature monitor. Controller setting does not correspond
exactly to the desired chamber temperature because the required type J
thermocouple was not used. The digital indicator using Type K thermo-
couple is correct, however.
The exhaust gas temperature is monitored by the other digital
indicator which is connected to the audible alarm. The alarm
will trigger when exhaust temperature drops below 50°C. Other
trigger temperature may also be selected by connecting the
proper channels of the BCD output at the back of the meter.
19
-------
Safety Alarm and Photohelic Gauge
The purpose :i the electrical audible alarm is to warn the operator of
incorrect p -sure conditions in the chamber or flame-out situation.
The alarm i^ - -'vated by the indicated toggle switch at the top part
of the panel. The alarm should be turned on when the generator begins
to operate after the initial ignition and start-up. The center magne-
helic gauge monitoring the chamber pressure is connected to the alarm.
Adjustment knobs at the front of the gauge will bracket the desired
safe operating pressure. Pressure below or in excess of the set points
will trigger the alarm. It is a good practice to move the set points
into alarm position and then back off slightly after the chamber is
warmed up and operating properly.
Magnehelic Gauge Manometer
In addition to the magnehelic gauge which monitors safe operating
pressure, there are two other gauges. One manometer measures the
chamber pressure. Any leakage, malfunction of gas flow rate, or
flame-out will be indicated. The other gauge monitors the orifice
meter which measures flow rate of dilution air. At a pressure drop of
0.68 cm H20 (66 Pa), the flow rate i^. 27 L/min as shown by the calibra-
tion curve.
High Voltage Ignition
A Fenwal direct spark ignition (-05-14) device is used for fuel
ignition at the burner. A momentary contact button (red) when held at
on-position will initiate and maintain the high voltage to the
ignitor inside the chamber. Once ignition is confirmed, the button
should be released. Full ignition is indicated when the exhaust
temperature indicator begins to climb above 70°C and stay at this
value. Special flow rates for N2 and air are needed to start the fuel
ignition (see operating section).
Monitoring Photometer
The monitoring light-scattering photometer contains an ESL (Electro-
Signal Lab) photoelectric smoke detector with analog output from the
photodiode. The input connector (amphenol) has 4 lines: 2 for the 6
volt AC to power the light source and the electronic components, 2 for
the signal on light scattering intensity.
The photometer has a flow through system with 3/4" OD copper tube
inlet and outlet. The cover may be easily removed for cleaning. Lamp
alignment in the photometer is critical in assuring that the calibra-
tion is valid. Jr^ring should be avoided. Recalibration based on
light scattering and filter collection of the aerosol should be per-
formed if misalignment is suspected.
Deviation from the normal base line output of the photometer when
20
-------
exposed to clean air is an indication of the need for cleaning. For
cleaning, the top cover should be removed and compressed air jet stream
be directed at various points to dislodge fchg deposit.
Hook-Up Procedures
Electrical and Gas Lines
It is essential that the laboratory receptacle for the AC plug of the
generator is polarized in accordance to standard electrical code. All
electrical lines and gas tubings are labeled and should be matched in
completing the connections between the chamber. Inlet tubings from
bottled gases, especially 02 and C2H2, should be installed and tested
carefully.
Slight height adjustment by shimming the cabinet may be needed in
aligning the rigid copper tubing from the cabinet to the mixing tee
section of the combustion chamber.
Compressed Gas Bottles
Air - Filtered and pressure regulated laboratory air from compressed
air line at 30 L/min may be used.
N2 - Compressed regulator-controlled nitrogen in 1A bottle is
recommended.
02 or C2H - Because of very small flow volume needed small bottles 5A
and oA with 2 stage regulator are recommended.
The distance between the gas bottles and the control cabinet should be
short to avoid long time necessary for purging the line during start-up
operation because of the low flow rates.
Operation
Procedures
After all the connections between the gas sources, control cabinet and
combustion burner are made and checked, the following procedure is
suggested for the start-up operation.
The output of the generator should be directed into a well-ventilated
laboratory exhaust system.
Turn knob of controller to a setting of 90 for heating of the chamber.
Turn on dilution air and adjust to 27 L/min.
Turn air on at the toggle switch. Adjust flow rate to a scale reading
of 50.
21
-------
Turn on acetylene from compressed gas bottle, adjust regulator to about
10 psi, open toggle valve at the control panel for C?H2. Allow gas to
flow for at least 15 minutes, or sufficient time to completely purge
the long line. Do not adjust needle valve. "Plow rate should be about
15 em3/min.
Turn on 02 from bottle and adjust regulator to 15 psi and open toggle
switch at panel and purge the 02 line. Do not adjust the needle valve.
If the pressure in the chamber is above 0.3 cm H20 (2« Pa) and odor in
the exhaust nozzle shows presence of C2H2 (before diluting) the burner
is ready for ignition.
Note the chamber and nozzle exhaust temperatures at the indicators.
Turn ignition power switch on and alarm power off.
Push red button to initiate ignition. Release button if nozzle tempera-
ture has reached a high and steady value. Several attempts may be
needed.
Once ignition is confirmed, adjust the gas flow rates to the following
values (scale reading) for soot generation at 10 mg/m3:
Gas
Float
Scale
Reading
Pressure
Psig
n u n
C2H2 02
G G
22 27
<10 15
N2
SS
85
15
Air
G
45
10-15
Dilution
Air
0.68 cm H00
2.
10-15
Air may be varied from 55 to 45 in order to vary soot concentration
from 3 to about 10 mg/m3.
Safety Precaution
Acetylene has a wide flammable and explosive limit (2.5 to 82%).
Standard procedure for handling explosive gas should be observed. No
copper tubing should be in contact with the acetylene. Plame arrester
should be placed in series at the outlet, downstream of the pressure
regulator. All tubing to the generator inlet should be Jess than 6 mm
OD.
Line should be checked for leak after initial connection. Purging of
the lines is necessary after an overnight shut down. Do not ignite
until line is completely purged. Purging also assures that the
regulator has reached equilibrium.
22
-------
To shut the system down, simply decrease the airflow and increase the
N2 flow rate. Shut off all toggle valves after nozzle temperature
indicator has confirmed a condition of flame out. Shut off valves at
the cylinder head. Do not adjust the regulator valves.
Diffusion air must be flowing in the chamber before attempting ignition.
Leads to the H.V. ignition terminal has about 1200 volts. Do not use
other leads and take necessary precautions to avoid shock.
Trouble Shooting and Maintenance
The exit section of the chamber may be removed easily in order to
examine the condition in the burner section by sighting with a
flashlight.
If the burner requires cleaning, remove all connecting lines and
tubings before removing the burner section. In pulling the section
out, be careful not to damage the insulating ceramic tubing covering
the HV wire.
The generator has been in use for sometime at ^BS. No foreseeable
problems were encountered. If any unforeseeable problems arise, please
call the authors at NBS.
23
-------
APPENDIX B
MEASUREMENT ERRORS USING ELECTRON MICROSCOPY TECHNIQUE
There are a number of considerations that go into the determination
of the accuracy of a size distribution measurement by electron microscopy
including the resolution of the microscope, the analysis of the electron
micrographs for particle size, the statistical significance of the
sample size, and the nature of the collection process. Here we present
a brief discussion of these factors and how they affect the accuracy
of the particle size measurements.
The magnification of the transmission electron microscope (TEM)
was determined by measuring the line separation of an optical spectro-
scopy grating with 2160 lines per millimeter versus the intermediate
lens currents of the TEM. The resulting calibration curve has a relative
error of up to + 10%.
The actual particle size measurements were made on the prints from
the microscope negatives by using a micrometer. The micrometer is
graduated to 0.025 mm (0.001 inch). For example, a primary particle
with a diameter of 0.023 ym would correspond to about 3.1 mm on the
print, a magnification of 135,000.
The estimated error in the resolution of the micrometer is only
a few percent compared to the estimated error of + 10% associated with
the uncertainty in determining the exact edge of the particle on the
print.
To accurately determine the size distribution of a polydisperse
particles, a large number of particle must be sized. In their TEM
analysis of diesel exhaust particulate, Vuk et al sized 600 primary
particles to obtain an accurate size distribution. In this study 100
primary particles were sized; this represents a large enough size to
get a good measure of the mean particle size but only a qualitative
estimate of the geometric standard deviation, og.
Finally, the sampling of the carbonaceous aerosol into the copper
specimen grids by the electrostatic precipitator may affect the size
distribution. The shape of the deposited particle may be affected by
the charging and the collection process under a high electric field.
there may also be enhanced deposition of particles upon previously
deposited particles because of electrical effects. Such effects would
be significant in regard to the overall agglomerate size (greatest
sphere diameter) but probably would have little effect on the primary
particle size.
Taking into consideration the errors mentioned above., the uncertainty
in particle size measurement using TEM is estimated to be + 20-30%.
24
-------
2.6 ID ORIFICE
POROUS SINTERED
BRONZE
PORE SIZE 20-30H
ALL DIMINSIONS IN MILLIMETER
T. C = THERMOCOUPLE
COMBUSTION CHAMBER FOR SOOT GENERATOR
Figure 1 Cross-sectional view of the combustion chamber
25
-------
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(30:1) based on EAA measurements
37
-------
10
to
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10'
tut
10'
10
0.01
I I
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Figure 14 Volume-size distribution on the diluted aerosol based on data given
in figure 13
-------
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106
10'
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I I I I I I
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0,01
Dp,
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Figure 15 Number size distribution of aerosol based on EAA measurement from
flame burning under non-sooting condition
39
-------
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Table 1 Properties of Carbonaceous Aerosol
Concenttation
1
1
2
2
3
3
Run #
A
B
A
B
(t = 0)
(t = 1920f)
2.
2.
3.
3.
0.
0.
Number
I/cm3
58 x 106
61
30
64
285
233
Volume Mass Aoparent Density D
33 3 3 gn
ym /cm mg/m g/cm ura
1.
1.
2.
2.
0.
0.
31 x 104 5.6 0.43
33 5.9 0.44
04 9.1 0.45
07 9.3 0.45
152
155
0
0
0
0
0
0
.14
.14
.15
.15
.15
.16
o
gn
1
1
1
1
1
1
.7
.7
.7
.7
.6
.6
D
gv
pm
0.33
0.33
0.34
0.33
0.34
0.36
a
gv
1.7
1.7
1.7
1.7
1.8
1.8
All quantities except for the mass concentration were calculated based on data from
the electrical aerosol analyzer. Concentrations in run 1-2 are given in terms of
the original discharge concentration although measurements were made after the aerosols
were diluted in a 1.8 m chamber. Concentrations for run 3 are the chamber concentrations.
42
-------
Table 2 Comparison of Diesel and Generator Aerosol
EAA Measurements Diesel Generator Aerosol
D , ym 0.0993 0.14
gn
a 1.88 1.7
D , ym 0.323, O.le 0.33
gv
a 1.88 1.7
gv
Impactor Measurements
Anderson Impactors (ambient)
Mass less than 1.1 ym, % 98-99
Diesel Exhaust temp. > 300° C 94-96b
Diesel Exhaust temp. < 300° C 81-94b
Mass less than 0.7 ym, % 91
Mass less than 0.4 ym, % 78
Low Pressure Tir.pac ten-
Estimated median particle size, ym 0.08
Transmission Elect r on Hicr oscopy
b f — c
Mean elementary particle size, ym 0.026 , 0.046 D = 0.023 a =1.4
o'l r>
Mean agglomerate s;.2e, ym T) = 0.54 0 = 2.2
gn g
Carbon in Aerosol Particles, wt %
Exhaust temp. > 300° C 98b 99
Exhaust temp. < 300° C 89b
Diesel study given in reference [1]
Diesel study from reference [2]
^
Based on 108 particles from lower two photographs in figure 17
d
Based on 45 particles frcm all photographs in figure ]6
£
Reference 14, based on the mean from 5 small diesel engines
Reference 15, based on the mean of 12,000 particle measurements from
Catepillar 3150 diesel engine exhaust
43
-------
TECHNICAL REPORT DATA
/Please read Instructions on ihc revere before completing*
1. REPORT NO.
EPA-600/^80-014
2.
&. TITLE AND SUBTITLE
Carbonaceous Aerosol Generator for Inhalation Studies
7. AUTHOR(S)
Thomas G.K. Lee and George W. Mulholland
9. PERFORMING ORGANIZATION NAME AND ADDRESS
National Bureau of Standards
Washington, DC 20234
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Research Triangle Park, NC 27711
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
February 1980
6. PERFORMING ORGANIZATION CODE
!
8. PERFORMING ORGANIZATION REPORT NO.
1
10. PROGRAM ELEMENT NO.
1AA815
11. CONTRACT/GRANT NO.
IAG No. EPA-78-D-X0170
13. TYPE OF,B£PORT AND PERIOD COVERED
Final report 2/78 to 4/
14. SPONSORING AGENCY CODE
EPA 600/11
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A carbonaceous aerosol generator designed for inhalation experiments with
animals is described. The3aerosol produced from a modified diffusion flame has a
concentration of 3-10 mg/m at a flow rate of 30 L/min. The addition of a small
amount of 02 to the acetylene fuel greatly increased the efficiency of fuel to
particuiate conversion, the maximum value was 2.5%. The aerosol_ size characteristics
were: D = 0.14 Mm, based on the electrical aerosol analyzer; 5^ 0.08 urn, based on a
low pressure inertia! impactor; mediam elementary particle =0.023 urn and median
agglomerate particle -0.54 urn, based on transmission electron microscopy. The size
characteristics of the generated aerosol are compared with diesel exhaust based on
available published data.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Aerosol generator
Agglomerate
Diesel exhaust
Diffusion flame
Inhalation
Particulates
Soot
Carbonaceous
Inhalation
Toxicology
06F,T
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report/
UNCLASSIFIED
21. NO. OF PAGES
50
20. SECURITY CLASS fThu pagei
UNCLASSIFIED
22. PRICE
Form 2220—1 (Rev. 4—77) ;"*eviou5 SOITION is OBSOLETE
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