uniiea diares neaiiri tiiucis nosen ui li Environmental Protection Laboratory February 1 980

AgerKy Research Triangle Park NC 2771

Research and Development

Carbonaceous

Aerosol

Generator for

Inhalation Studies
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This report has been assigned to the ENVIRONMENTAL HEALTH EFFECTS RESEARCH series. This series describes projects and studies relating to the toler- ances of man for unhealthful substances or conditions. This work is generally

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studies. In addition to toxicology and other medical specialities, study areas in- clude biomedical instrumentation and health research techniques utilizing animals — but always with intended application to human health measures.

This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161.
CARBONACEOUS AEROSOL GENERATOR FOR INHALATION STUDIES

by

Thomas G. K. Lee & George VJ. I'^ulholland

National Bureau of Standards

Washington D. C. 20234

Interagency Agreement No.

EPA - 78-D-X0170

Project Officer

Judith Graham

Health Effects Research Laboratory, F'PA 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
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.

11
FO REWARD

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 toxicology, 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 radiation 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
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

I./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; 0— 0.08 ym,

baled on a low pressure inertial impactor; median elementary particle — 0.023 ym and median agglomerate particle 0.54 ym, based on transmission 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
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
FIGURES

No. Page

1 Cross-sectional view of the combustion chamber

2 Combustion chamber and connections

3 Control panel of the generator

4 Calibration curves for acetylene and oxygen flow meters . .

5 Calibration curve for nitrogen flow meter

6 Calibration curve for air flow meter

7 Calibration curve for dilution air gauge

8 Cross-sectional view of the light-scattering photometer . .

3

9 Output stability of the soot generator at 6.5 mg/m . . . .

10 Repeatability of the generation rate with on and off

cycling of the generator

11 Comparison of runs 2A and 2B at high concentration levels

12 Photometer reading as function of mass concentration

of the aerosol

25

26

27

28

29

30

31

32

33

34

35

36

13 Typical number-size distribution of generated aerosol

after dilution (30:1) based on EAA measurements . .

14 7olume-size distribution on the diluted aerosol based

on data given in figure 13

15 Number-size distribution of aerosol based on EAA

measurement from flame burning under non-sooting

condition

16 Photomicrographs of carbonaceous ae;rosol under lower

magnification

17 Photomicrographs of carbonaceous aerosol under high

magnification

TABLES

1 Properties of Carbonaceous Aerosol 42

2 Comparison of Diesel and Generator Aerosol 43

vi
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 gener^^or is to be 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

2 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 of 30 L/min with a variable concentration between 5 and 10 mg/m . This need for a high

conversion ratio a^^ 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 vrith

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

2 in the gas phase of the aerosol.

1
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 detennined by a low

pressure cascade impactor developed by Hering 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.

2
SECTION 2

CONCLUSIONS AND RECOMMENDATIONS

A stable, repeatable carbonaceous aerosol generator has been

developed for animal inhalation studies with a carbon conversion

ef f iciency^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 ym.

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 vleld

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.

3
SECTION 3

DESIGN OF CARBONACEOUS AEROSOL GENERATOR

DESIGN AND CONTROLS

The carbonaceous aerosol generator was designe^ 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 ^uel 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 ^urner 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 O

2

, about 5 cm /min, is preraixed vTith 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 tf>e tee

fitting located between the combustion chamber exit and the dilution

air line in order to minimize the wall loss of the aerosol. Apparently

the high velocity aerosol exiting from the nozzle entrained air through

these holes and thus minimized the wall loss of the particles at the

critical area.

The entire stainless steel combustion chamber was heated and

maintained at a temperature of about 40° C by eight small beaters

embedded in thick chamber walls. It was found that the temperature

control of the chamber was necessary to minimize long term drift in

aerosol generation rate. Heating of the chamber wall by the flame is

a major cause for the drift.

4
CONTROL PANEL

The key features of the control panel are shown in fipure 1. Flowmeters (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 ^ for the fuel

and oxygen flowmeters are based on calibration using a soap bubble

flowmeter. Calibration curves in figures 5 and b 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, v?hich 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 27 T./min,

which corresponds to a reading of 0.68 cm H„0 (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 temperature. The digital meter for monitoring the exhaust temperature is

also interfaced to the audible alarm, which will trigger if the temperature 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 commerciallyavailable, light-scatter ing-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 r^ass generation rate and stability over the range from 3 to ]2

mg/m . A connector on the front of the control panel Interfaces the

photometer to a recorder.

5
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 ^erosols 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

6
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^/(M2V2)

where

^ = mass concentration of aerosol in mg/m

= total aerosol flow ^n m /min; typically 0.030

M

2 = mg carbon in one cm of fuel (0^98 for acetylene at 25° C and 1 atmosphere pressure

2 (l . 01 x 10 Pa))

V

2 = fuel flow rate in cm /min.

The average mass concentration of the aerosol foreruns 2A and 2B (table 1

and curves in figure 11) was fou^d 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.

7
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 monitored 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 ^ass 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 O

2

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.

2 It was found that acetylene began sooting^at a lower 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 a&rosol particles, on the order of 0.01 pm 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 flameproduced particles are presented in the next section.

3 With the addition of a small amount of premixed ©

2

j 3 to 4 cm /min,

to the acetylene diffusion flame, a sudden increase in aerosol concentration 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 O

2

. 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 ]0

to 15% stoichiometric O

2

. By using the ©2 additive Tn 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 N

2O had an effect similar to that of 0_ though a somex^hat

higher flow rate of N

2 O is required compared to O

2

.

8
The preheating of the fuel to about 100° r seemed to have a minor

effect on the soot generation efficiency. The heating of the combustion

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 characteristics 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 distribution 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 D where N is the ^ number concentration of aerosol per cubSc centimeter. The basic data

are the current corresponding to N versus voltage corresponding to . 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 usi^g th^ sensitivity factors in Liu and Pui [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, ^'he auantities 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 partScle size Fange log D^ to log D + A log D , respectively.

The size distributions (number and volume) ^are plottei 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 lA)

.

9
I

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 deviltion, a . These quantities are defined

below for the number distribution: ^

log D

gn

n

I i=l

AN . log P . N

log agn

?

(log - log

i=l N

1/2

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 o are listed in table 2 both for the generated

carbonaceous aerosol Ind 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 pm. It is seen that there is a good agreement for the geometric mean volume diameter for the diesel particulate and the carbonaceous aerosol from the generator.

The size distribution of the aerosol was found to he relatively

independent of the combustion conditions in the generator provided that

the ^otal mass concentration of the soot was jji 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 particulate increased from

5.6 (0.14 ym) to 9.1 mg/m (0.15 ym) . As mentioned in the previous

section aerosol produced under a non-sooting condition has small particles,

D =0.01. As a result, the mass concentration is low and number con- cintration 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 ym, 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
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 percentage (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 last 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 ThermoSystem electrostatic precipitator. Preliminary work v’ith a scanning

electron microscope indicated that the particles had an agglomerate

type structure not unlike those produced by the carbon Mack 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 narticle

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, niscussion of

measurement error is given in Appendix 2.

Elemental analysis of the aerosol collected showed a carbonhydrogen ratio of 99 to 1 or more for carbon. The analysis was performed

by a commercial contractor (Schwarkopf Nicroanalytical) on about ^ mg

11
particulate samples on glass fiber filter by measuring the amount of

CO

2 and H

2O 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 carbcn 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 measurements 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 operation 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 known

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 is clear

from the results in talkie 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, I, which is defined by

dN/dt = r

Fro^^thi^ equation and the data in table 1, one finds that F = 4.1 x

10 cm /s. As defined above F is an average coagulation coefficient,

though in reality 7 depends on particle size, charge, and perhaps on

shape. Because of thg relatively h^gh concentration of the carbonaceous

aerosol, about 3 x 10 particles/cm , the coagulation effect may he

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. At this concentration, the particle size will increase

by about 10% in five minutes.

12
Gas Analysis

An analysis of the CO and CO

2 in the aero^pl strearr. vas made

because of the potential interference of the r in paseous <^om

with the particulate analysis. Using a long-path-length infrared gas

cell, it was found that the concentrations of CO

2

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 C02» 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 measurement method. Quantitative results could be obtained even with the

s^^ll 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 ym 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 pm 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

Dolan, D. F., Kictelson, D. B. and Whitby, K. T. , Measurement

of die.'-=l exhaust particle size distributions, presented at The

Americ-r 'cciety of Mechanical Engineers, November 30-December

-4, 1975, Houston, Texas.

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

Hering, S. V., Flagan, R. C. and Friedlander, S. K. , Design and

evaluation of new lov-pressure impactor. Environmental Science

and Technology, Vol. 12, 667 (1978)

loossi, Reza, Physical and chemical properties of combustion

generated soot, Ph.D. thesis. University of California (1978)

Wright, Franklin J., Effect of oxygen on the carbon forming

tendencies of diffusion flames. Fuel, 53, 332 (1974)

Liu, Benjamin Y. E. and Pui, David Y. H. , On the performance of

the electrical aerosol analyzer, J. Aerosol Science, 6, 249 (1974)

Hering, S. V., Friedlander, S. K. and Collins, J. J., Design

and evaluation of a new lov-pressure impactor, II, Environmental

Science and Technology, Vol. 13, 184 (1979).

Anderson, A. A., New sampler for collection, sizing, and enumeration of viable airborne particles, J. Bacterial, Vol. ^6, 471-484

(1953) or lACFM Ambient Particle Size Sampler.

Donnet, J. B. and Voet, H., Carbon black, physics, chemistry and

Elastomer Reinforcement, I'arcel Jekler, Inc., 1976.

Air sampling instruments for evaluation of atmospheric contaminants.

Sec. G, American Conference of Government Industrial Hygienists (1972)

Bell, K. A., Aerosol deposition in models of a human lung bifurcation

Ph.D. thesis in chemical engineering, California Institute of

Technology (1978).

Friedlander, S. K. ."Smoke, Dust and Haze',' ?. 119, John Wiley

and Sons, 1977.

Report of task group on lung d>-namics 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 jnd 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 disassembled. 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 Into 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 or by other means after initiating free flow

and before the final connection.

Connect the ground wire from the power line to the chamber at one

of the body bolts at the midsection of the chamber. The bolt may

be loosened and retightened by a proper alien wrench.

18
Control Panel Functions

r>

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

Air

°2

""2 C2H2

115 VAC, 10 amp.

10-15 psi, 30 L/min, filtered

^ Bottle, regulated 15 psi, 10 cm /min

Bottle, regulated 15 psi, 1 L/min

^ 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 magnehellc 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 thermocouple 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 of the electrical audible alarm is to warn the operator of

incorrect pr -^sure conditions in the chamber or flame-out situation.

The alarm is a tivated 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 magnehelic 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 H2 O (66 Pa), the flow rate is 27 L/min as shown by the calibration 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 (ElectroSignal 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 calibration is valid. Jarring should be avoided. Recalibration based on

light scattering and filter collection of the aerosol should be performed 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 the 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 O2 and C 2 H2 , 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 lA bottle is

recommended

.

O2 or C 2 H - 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 CpH 2

. Allow gas to

flow for at least 15 minutes, or sufficient time to completely purge

the long line. Do not adjust needle valve, ^low rate should he about

15 cm^/min.

Turn on O 2 from bottle and adjust regulator to 15 psi and open toggle

switch at panel and purge the O 2 line. Do not adjust the needle valve.

If the pressure in the chamber is above 0.3 cm H 2 O (2° Pa) and odor in

the exhaust nozzle shows presence of C 2H 2 (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 temperature 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/m^

Gas °2 ^2 Air Dilution

Air

Float G G ss G

Scale

Reading 22 27 85 45 0.68 cm H

2 O

Pr PR sure Psig

<10 15 15 10-15 10-15

Air may be varied from 55 to 45 in order to vary soot concentration

from 3 to about 10 mg/m^

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 arrestor

should be placed in series at the outlet, downstream of the pressure

regulator. All tubing to the generator inlet should be ]ess than (S 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

N 2 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 MBS. 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 spectroscopy 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 pm 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, ag.

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 10 ORIFICE

COMBUSTION CHAMBER FOR SOOT GENERATOR

Figure 1 Cross-sectional view of the combustion chamber

25
26

Figure 2

Combustion

chamber

and

connections
27

'R^011•ro

nflnpl

of

fViP

PPTlPrfl

t".fvr
28
29

Figure 5

Calibration

curve

for

nitrogen

flow

meter
30
cubO33

bC

•HCO

•rl

•H

re

•HI—i

re CJ0)

S-( 3

bt •H

pt-i

31
32

Fieure

8

Cross-sectional

view

of

the

light-scattering

photometer
>Jd 6

OOL 06

WdOT

001 06 S WdTT

001 06

<AZl

OOt^ 06 - HI ^z wVo57 aj = w « >< ? I001 06

WV2

33

Figure 9

Output

stability

of

the

soot

generator

at

6.5

mg/'
aN/is:xtaj:

WV9

o:;’

I"-:. I 'x.

WV8

Md t lavis

j

oc

VJd9

I ^

>><" \<l

I

. 155^' jAI

o: Wd8

s'?

ov Of;

\yrviS

\ Wd 01

'

I

cot 06 f-.9 OS’ oe 02 01 I) HZl

WV6

•Of

WVOT

<yj

i

o/.

A|

o?

I Of oc

li'lVI?

G'J Of ot

02

f

i

i

I

WdT

OL i»

WdZ

OL <> wde

WV9

34

Figure

10

Repeatability

of

the

generation

rate

with

on

and

off

cycling

of

the
35

Figure

11

Comparison

of

runs

2A

and

2B

at

high

concentration

levels

P’iglire 13 Tvplcal number-size distribution of generated aerosol after dHuffon

(30:1) based on EAA measurements

37
AV/A

log

On,

/imVcm

Dp, pm

Figure 14 Volume-size distribution on the diluted aerosol based on data given

in figure 13

38
Figure 15 Number size distribution of aerosol based on EAA measurement from

flame burning under non-sooting condition

41

Figure

17

Photomicroeraphs

of

carhortapponn;

aarnaAl

nn/^o-r

v-ToK m

*a

r>^ !

4*

-f

*1

/*‘\t*>
!

Table 1 Properties of Carbonaceous Aerosola

Run //

1

A

1 B

2 A

2 B

3 (t = 0)

3

(t = 1920s)

Concentration

Number

1 / 3 1/cm

Volume

3 3 ym /cm

Mass

, 3 mg/m

Apparent Density

g/cm^

D

gn

ym agn

Dgv

ym 0 gv

2.58 X 10^ 1.31 X lO'^' 5.6 0.43 0.14 1.7 0.33 1.7

2. 61 1.33 5.9 0.44 0.34 1.7 0.33 1.7

3.30 2.04 9.1 0.45 0.15 1.7 0.34 1.7

3.64 2.07 9.3 0.45 0.15 1.7 0.33 1.7

0.285 0.152 0.15 1.6 0.34 1.8

0.233 0.155 0.16 1.6 0.36 1.8

^All quantities except for the itass 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

gn

0.099^ O.IA

a gn

1.88 1.7

D , pm

gv’

0.32^, 0.1® 0.33

0

gv

1.88 1.7

Impactcr Measurements

Anderson Impactors (ambient)

Mass less than 1.1 pm, % 98-99

Diesel Exhaust temp. > 300° C 9A-96^

Diesel Exhaust temp. < 300° C 81-9A^

Mass less than 0.7 pm, % 91

Mass less than O.A pm, % 78

Lov; Pressure Tmpactor

Estimated median particle size, pm 0.08

Transmission Electron Microscopy

Mean elementary particle size, pm 0.026^, 0.0A6^ D = 0.023 a gn 1 Mean agglomerate size, pm D = 0.5A o gn g Carbon in Aerosol Particles, wt %

Exhaust temp. > 300° C 98^ 99

Exhaust temp. < 300° C 89^

Diesel study given in reference [1]

^Diesel study from reference [2] cBased on 108 particles from lower two photographs in figure 17 '^Bascd on A5 particles from all photographs in figure 16

Reference lA, based on the mean from 5 small diesel engines

^Reference 15, based on the mean of 12,000 particle measurements from

Cateplllar 3150 diesel engine exhaust

43
TECHNICAL REPORT DATA ! (Please read Instrucnons on the reverse before complcnmj

1. REPORT NO. j2- EPA-600/1-80-014 1 l

3. RECIPIENT S ACCESSION NO.

i

1

4. TITLE AND SUBTITLE

Carbonaceous Aerosol Generator for Inhalation Studies

5. REPOar DATE 1 February 1980

6. PERFORMING ORGANIZATION CODE |

7. AUTHORIS)

Thomas G.K. Lee and George W. Mulholland

S. PERFORMING ORGANIZATION REPORT NO. ,

g pcp.FOBMING ORGANIZATION NAME AND ADDRESS

National Bureau of Standards

Washington, DC 20234

10. PROGRAM element NO. 1 1AA815 ;

1 1. CONTRACT/GRANT NO. | lAG No. EPA-78-D-X0170 |

12. SPONSORING AGENCY NAME AND ADDRESS

Environmental Protection Agency

Research Triangle Park, NC 27711

13. TYPE OF.BEPORT AND PERIOD CO VEBEC | Final report 2/78 to 4/i

14. SPONSORING AGENCY CODE

EPA 600/11

T5. SUPPLEMENTARY NOTES 1

1

' - "i 16. ABSTRACT

A carbonaceous aerosol generator designed for inhalation experiments with

f 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 Op to the acetylene fuel greatly increased the efficiency of fuel to | parti culjte'^con vers ion, the maximum value was 2.5%. The aerosol_ size characteristics

| were: D = 0.14 '^m, based on the electrical aerosol analyzer;

^

0.08 wm, based on a

j low pressure inertial impactor; mediam elementary particle =^0.023 urn and mediam i agglomerate particle -0.54 ym, based on transmission electron microscopy. The size

j characteristics of the generated aerosol are compared with diesel exhaust based on i available published data. j|

17. <EY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b.lDENTIFIERS/OPEN ENDED TERMS c. COSAT 1 Field/Group

ll

1

j

Aerosol generator Garb onaceous 06F,T 1

1 Agglomerate Inhalation j Diesel exhaust Toxicology * Diffusion flame

Inhalation

Particulates i Soot

13. DISTRIBUTION STATEMENT " 19. SECURITY CLASS (This Report) 21 . NO. OF PAGES

RELEASE TO PUBLIC

UNCLASSIFIED SO J

1

20. SECURITY CLASS (This page) 22. PRICE I' UNCLASSIFIED 1 = Pofm 2220—1 (Rev. 4 — 77) ^=i=iEvious soition is obsolete i

i 4A

. J

!