200 T T T

a
fo}

EMA DPM, mg/m?
8

1
50 100 150 200 250

(0) 1

LABORATORY DPM, mg/m?

Figure 7.—DPM by EMA versus laboratory-grade instruments for six engine load-speed conditions at nor-
mal engine operation for tests 102 and 104, (Slope = 0.83; correlation coefficient = 0.92.)

800 T T T

D

8
T
1

EMA DPM, mg/m3
cs
8
T
1

200 4

1 nt 1
ie) 200 400 600 800

LABORATORY DPM, mg/m?

Figure 8.—DPM by EMA vereus laboratory-grade instruments for six engine load-speed conditions at re-
stricted engine alr intake operation for test 103. (Slope = 0.85; correlation coefficient = 0.99.)


UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

atm.

°C

ftelbf

hp

in HO

kg/h

absolute

atmosphere, standard
degree Celsius
centimeter

foot pound (force)
hour

horsepower

inch

inch of water (pressure)
kelvin

Kilogram per hour
kilopascal

Ib/h
L/min

mg/m?*

r/min

vol pet
wt pet

pound per hour

liter per minute
milligram per cubic meter
minute

millimeter

newton meter

percent

part per million
revolution per minute
second

volume percent

weight percent



40 1

30F

EMA A/F

20-

10 20

30 40

LABORATORY A/F

Figure 12.—A/F by EMA versus laboratory-grade instruments for six engine load-speed conditions at re-

stricted engine alr intake operation for test 103. (Slope = 0.83; correlation coefficient = 0.97.)

SUMMARY

In conclusion, the EMA can sample and dilute hot,
moist, diesel exhaust, filter the dilute sample for deter-
mination of the DPM concentration, and provide an ex-
haust sample to portable CO, CO,, NO, and NO, instru-
ments at a known dilution ratio. Raw exhaust CO and
CO, concentrations obtained by measuring the dilute
exhaust concentrations with portable instruments and
multiplying by the known dilution ratio were compared
with laboratory-grade-instrument measurements and were
within about +14 pet for CO and +20 pet for CO,.

Variability in measured DPM, CO, and CO, concentra-
tions is attributed primarily to a problem associated with
condensate flowing from the exhaust system into the sam-
ple probe. In some instances, condensation droplets were
visually observed on the filter holder. This source of
variability has now been eliminated by making sure that
gravity tends to empty rather than fill the probe. This
involves simply making sure that the end of the probe is
always lower than the first few inches of length.

Filter plugging was found to reduce the raw exhaust
flow rate, thereby increasing the dilution ratio above the

calculated value and giving minor errors in some of the
calculated raw exhaust concentrations. A simple proce-
dural modification by which to determine the actual di-
lution ratio involves the collection of two bags of dilute
exhaust, one with and one without the particulate filter.
The correct dilution ratio can be obtained by multiplying
the calculated value by the ratio of the CO, concentration
without the filter to the CO, concentration with the filter,
Recent tests indicate that this new procedure has elimi-
nated this source of error.

An intake air restriction fault was applied to the en-
gine to determine if the EMA could detect the effects of
this fault by measuring an increase in emissions. Results
show that the EMA-measured CO and DPM concentra-
tions are considerably higher than those for the normal
engine condition, indicating that an engine fault was
present.

Additional laboratory testing has been undertaken to
verify the accuracy and precision of the EMA after making
the recommended changes.


exhaust concentration of NO, was measured using a
Beckman model 955 chemiluminescence analyzer, and the
dilute exhaust NO, concentration was measured using a
CSI Meloy model NA 510-2 chemiluminescence analyzer.

ENGINE CONDITIONS

A single test series involved using the EMA to measure
the concentrations of DPM, CO, and CO, at six engine
modes (table 2), while simultaneous measurements were
made using laboratory-grade instruments.

Table 2—Six steady-state operating conditions
representing LHD duty cycle (9)

‘Mode Engine speed Load, pet
1. Peak torqu 50
2. do, 7
3. do. 100
4. Rated .. 50
5. do, 75
6. do, 100

These engine load and speed combinations were selected
based on earlier measurements (9) made on a commercial,
diesel-powered load-haul-dump (LHD) vehicle while a
simulated mucking operation in an underground mine was
performed. Modes 1 to 6 represent different parts of the
LHD cycle, as follows: (1) with the bucket empty, (2)
mucking at the face, (3) backing out of the drift with the
bucket loaded, (4) traveling to the dumpsite, (5) dumping
the load, and (6) traveling from the dumpsite to the drift
with the bucket empty.

Four series of comparison tests were performed over a
4-day period, but condensation problems in the EMA’s
sample probe limited the amount of meaningful data that
were collected. Only data from tests 102, 103, and 104 are
presented. Tests 102 and 104 were performed over a
2-day period under normal engine conditions. During test
103, a large intake air restriction was applied to the engine
to simulate a clogged air filter. This broadened the
pollutant level ranges and provided an opportunity to
determine if the EMA could detect this engine fault.

EMISSIONS MEASUREMENT APPARATUS
TEST PROCEDURE

Sampling of particulate and gaseous emissions with the
EMA involved inserting the particulate filter and connect-
ing the filter holder and gas-sampling bag to the ejector
and dilution tunnel. The motive gas valve was opened and

the time recorded. A thermocouple positioned in line, im-
mediately upstream from the suction nozzle, measured the
exhaust temperatures. These temperatures were recorded
manually at 5-s intervals, and the average temperature was
used in the calculation of the exhaust flow rate entering
the nozzle. When the predetermined sampling time was
complete (20 to 90 s), the motive gas valve was closed and
the sample bag and particulate filter were removed. The
concentrations of CO and CO, in the bag were read out
immediately by portable, battery-powered Ecolyzer 2600
electrochemical CO and Fuji ZFPS NDIR CO, instru-
ments. The particulate filter was stored in a petri dish and
conditioned 24 h in a controlled, relative humidity environ-
ment prior to reweighing, a procedure similar to that,
which had been followed in determining the filter tare
weights. NO and NO, were not measured during these
tests because of inadequate calibration gases.

From two to five repeat samples were taken at cach
engine load-speed condition. The total available EMA
sampling time at each load-speed condition was deter-
mined by the time required to load the particulate filter
used for sampling the laboratory's dilution system, typically
about 20 to 30 min.

PROCEDURAL MODIFICATIONS MADE
DURING TESTS

The EMA was initially suspended directly below the
ceiling-mounted engine exhaust pipe to make it accessible
during tests. This location was later found unacceptable
because condensation from the exhaust pipe dripped into
the suction port of the ejector between tests, causing large
variability in the DPM weights. This variability occurred
even though the filters were conditioned (that is, allowed
to come to equilibrium in a controlled, relative humidity
environment) prior to reweighing, indicating that sub-
stances other than water, such as high-boiling-point hydro-
carbons, were present. To correct this problem, a valve
was inserted between the exhaust pipe and ejector suction
inlet. Even with the valve closed between tests, variable
results were observed.

The sample procedure was further modified by incorpo-
rating a pretest purge. This involved opening the suction
inlet valve and turning on the motive nitrogen gas for 5 s
ptior to installing the filter and gas collection bag, then
installing the filter and bag and immediately beginning the
test. The objective was to remove any condensed material
that had dripped into the suction line prior to collecting
the samples. This procedure greatly reduced the amount
of visible condensation material.


INTRODUCTION

Diesel equipment is gaining popularity in underground
coal mines‘ and is almost universally used in underground
noncoal mines. From 1980 through 1990, the estimated
number of underground coal mines using diesels has more
than tripled to more than 200, and the number of diesels
has quadrupled to more than 2,300. An estimated 6,000
pieces of diesel equipment are used in underground non-
coal mines, The increased use is related to the recognition
that diesel-powered vehicles are more flexible, which can
contribute to increased productivity when compared to
their electrically powered counterparts.

However, the use of diesel equipment in underground
mines is controversial. The National Institute of Occupa-
tional Safety and Health (NIOSH) has recommended that
"whole diesel exhaust be regarded as a "potential occu-
pational carcinogen," as defined in the Cancer Policy of the
Occupational Safety and Health Administration." NIOSH
further stated that "though the excess risk of cancer in
diesel-exhaust-exposed workers has not been quantitatively
estimated, it is logical to assume that reduction in ex-
posure to diesel exhaust in the work place would reduce
the excess risk" (7) In 1989, the International Agency for
Research on Cancer also classified diesel exhaust as "ptob-
ably carcinogenic to humans" (2), In 1988, the U.S. Mine
Safety and Health Administration (MSHA) was directed
by an advisory committee to establish a DPM standard

and regulations to minimize exposure to all diesel
pollutants in underground coal mines (3).

Diesel-exhaust-pollutant concentrations underground
are dependent upon the quantity of ventilation air and ex-
haust emission rates. Inadequate maintenance, improper
adjustments, and wear of the diesel engine, and other fac-
tors may cause changes in diesel-exhaust-emission rates,
For example, measurements have shown that an improper-
ly tuned diesel engine can increase concentrations of some
pollutants by a factor of 10 (4). A method for detecting
changes in emissions caused by poor maintenance and
weat is needed to determine when corrective action is re-
quired, Additionally, such measurethents would assure
that tailpipe emissions control systems are functioning
correctly.

An EMA that dilutes diesel exhaust and allows meas-
urement of DPM, CO, CO,, NO, and NO, concentrations
was developed by MTU under contract to the U.S. Bureau
of Mines.’ The EMA enables the exhaust of diesel en-
gines to be monitored on a regular basis so that engines
producing excessive exhaust pollutants can be identified
and taken out of service for maintenance. As part of the
Bureau’s program to improve safety of the underground
worker, this report (1) describes the design and operation
of the EMA and (2) presents results of preliminary labora-
tory tests designed to evaluate the accuracy of EMA
measurements,

EMISSIONS MEASUREMENT APPARATUS DILUTION SYSTEM

The EMA dilution system (fig. 1) is designed to instan-
taneously dilute and cool a sample of hot, moist diesel ex-
haust with nitrogen or air at a predetermined dilution
tatio® The dilute sample is then passed through a pre-
weighed particulate filter, and a portion of the filtered
exhaust is collected in a gas-sampling bag for later
analysis.

Instantaneous dilution simulates the situation where
hot, raw diesel exhaust is rapidly emitted into the mine air.
Because most chemical reactions are temperature and con-
centration dependent, instantaneous dilution and resultant
cooling would be expected to greatly reduce the effect of
such reactions on the measured concentrations.

“Information obtained from R. W. Waytulonis, Twin Cities Research
Center, in 1990.

SItalic numbers in parentheses refer to items in the list of referenes
at the end of this report.

“Dilution ratio as used here is defined as the volume of the dilute
mixture per unit volume of exhaust at the same temperature and
pressure.

The DPM concentration is determined gravimetrically.
The concentrations of CO, CO,, NO, and NO, are meas-
ured by connecting the gas-sampling bag to portable
instruments immediately after collecting the sample.
Measurements for NO and NO, are made first because the
bag concentrations change over time (5). NO, is difficult
to measure accurately because of the difficulty of
preparing calibration standards.

The EMA is designed to be used during a stationary
test of an underground mine vehicle and not on vehicles
during production from actual mining operations. In-mine
tests are conducted by operating the engine under high
load at a single speed with the vehicle parked. This test
condition is achieved by depressing the vehicle’s brake,
engaging the transmission in high gear, and pressing the
accelerator pedal to the floor. It represents the condition
of maximum torque on the engine. It is repeatable and
operates the engine at a low air-to-fuel mass ratio (A/F)
that results in the production of high CO and DPM

Work done by MTU under Bureau of Mines contract J0199125.


APPARATUS FOR MEASURING DIESEL TAILPIPE EMISSIONS
IN UNDERGROUND MINES

By D. H. Carison,' T. R. Taubert,? and J. H. Johnson®

ABSTRACT

The U.S. Bureau of Mines and Michigan Technological University (MTU) are collaborating to de-
velop an apparatus for measuring diesel tailpipe emissions in underground mines. A tailpipe emissions
measurement apparatus (EMA) is described that dilutes diesel exhaust and measures the concentrations
of diesel particulate matter (DPM), CO, CO,, NO, and NO, at known dilution ratios.

The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory-
grade instruments. Concentrations of CO and CO, measured by the EMA were usually within + 14 pet
of concentrations measured by laboratory-grade instruments for CO and +20 pct for CO,, EMA-
measured DPM concentrations were, on average, 29 pct lower than those measured by laboratory-grade
instruments, with the differences being fairly consistent. The CO and CO, differences are related to the
method of calculating the EMA’s dilution ratio, and the difference in DPM concentrations is attributed
to thermophoretic and/or condensation losses related to the EMA’s unheated sample probe.
Preliminary analysis of data obtained with a heated sampling probe and modifications in the sampling
procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

\Senior research engineer, Michigan Technological University, Houghton, MI.
?Mechanical engineer, Twin Cities Research Center, U.S. Bureau of Mines, Minneapolis, MN.
Presidential professor, Michigan Technological University.


4

REFERENCES

1. National Institute of Occupational Safety and Health. Carcin-
ogenic Effects of Exposure to Diese! Exhaust. Current Intelligence Bull.
50, Dep. Health and Human Serv. (NIOSH) Publ. 88-116, 1988, 30 pp.

2. International Agency for Research on Cancer (Lyon, France).
TARC Monographs on the Evaluation of Carcinogenic Risks to Humans
—Diesel and Gasoline Engine Exhausts and Some Nitroarenes. V. 46,
1989, 458 pp.

3. U.S. Mine Safety and Health Administration. Report of the Mine
Safety and Health Administration Advisory Committee on Standards and
Regulations for Diesel-Powered Equipment in Underground Coal Mines.
Rep. to Secretary Labor, July 1988, 90 pp.

4. Waytulonis, RW. The Effects of Maintenance and Time-
in-Service on Diesel Engine Exhaust Emissions. Paper in Mine Venti-
lation. Proceedings of the 2nd U.S. Mine Ventilation Symposium/

University of Nevada-Reno/23-25 September 1985. A. A. Balkema,
1985, pp. 609-617.

S. Fawcett, G. J. The Suitability of Polymer Bags for the Sampling
and Storage of Mine Atmospheres, Seam Gases and Diesel Exhaust
Gases Prior to Analysis. Dep. Miner. Resour, New South Wales,
‘Australia, Chem, Lab. Rep. 81/31, 1981, 11 pp.

6. Holtz, J. C. Safety With Mobile Diesel-Powered Equipment
Underground. BuMines RI 5616, 1960, 87 pp.

7. Perry, R. H., and C. H. Chilton (eds.). Chemical Engineers’
‘Handbook. McGraw Hill, Sth ed., 1973, pp. 6-29.

8. Baumgard, K. J, and K.L. Bickel. Development and Effectiveness
of Ceramic Diesel Particle Filters. BuMines IC 9141, 1987, pp. 94-102.

9. Johnson, J. H., E. O. Reinbold, and D. H. Carlson. ‘The Engi-
neering Control of Diesel Pollutants in Underground Mining. Soc. of
Automot. Eng. Tech. Pap. 810684, 1981, 46 pp.

INT.BU.OF MINES,PGH.,PA 29588


@ i) Sample
Activated orifice
aamary =) charcoal a
and HEPA
air filter LFE @ oO Lg 4|Filtered 4
compressed air

Smoke

opacity
meter

Tooas
analyzers

8- by 10-in
filter holder

Engine

Universal dynamometer

To PoP —§
pump

controller

A A

KEY

HEPA
FE

High-efficiency particulate air

c

Laminar flow element

z
3
%

Positive displacement pump.
Pressure

Pressure differential

[XTO)

Temperature

Figure 2.—Schematic of Bureau’s dilution system.

Table 1.—No. 2 diesel fuel specifications

Cetane index 42.4 || Total sulfur ...... wtpet.. 0.39
Gravity, API. 31.5 || Aromatics, FIA.. vol pet... 40.8
IBP 169.4 I] Flash point ......... °C.. 71.0

‘API American Petroleum Institute.
FIA Fluorescent indicator absorption.
IBP Initial boiling point.

The engine was operated under steady-state conditions.
Exhaust was transferred continuously from the 10.2-cm-
diameter (4-in) exhaust pipe to the 15.2-cm-diameter
(6-in) dilution tunnel through a 2.5-cm (1-in) sample line.
The sample line contained a 1.0-cm-diameter (0.41-in) ori-
fice for flow calculations. The temperature and static
pressure of the exhaust and the pressure drop across the
orifice were recorded, and these data were used to calcu-
late the raw exhaust flow rate to the dilution tunnel. In
the dilution tunnel, the raw exhaust was mixed with
dilution air that was cleaned by passage through activated
charcoal and a high-efficiency particulate air (HEPA) filter
to remove organics and DPM. The residence time of the
exhaust in the dilution tunnel was about 1 s under

turbulent flow conditions (Reynolds number = 45,000).
The volume flow rate of primary air mixed with the
exhaust was measured using a Jaminar flow element.

The dilution ratio was typically 22:1 and was calculated
from the raw exhaust and dilution air flow rate’s. The
dilution flow ratio was verified by comparison of the ratio
of the NO, concentration measured in the raw exhaust to
the NO, concentration measured in the dilute exhaust.

A constant mass flow sampler draws a portion of the
dilute exhaust through a preweighed, 20.3- by 25.4-cm
(8- by 10-in) Pallflex TX40HI20-WW glass-fiber filter.
Prior to the initial weighing, the filter is stored overnight
in a desiccator containing Drierite calcium sulfate desic-
cant. Final weighing of the loaded filter followed 2 h of
storage in the same desiccator.

The air and fuel flow rate’s to the engine were
measured continuously and the A/F was calculated. The
air flow rate was measured using a laminar flow element,
and the fuel flow rate was measured using a Flow-Tron
model 22 flow measurement system capable of an accuracy
of +0.23 kg/h (0.5 Ib/h). The raw exhaust concentrations
of CO and CO, were measured using separate Beckman
model 864 nondispersive infrared analyzers. The raw



RI 9422 REPORT OF INVESTIGATIONS/1992

Apparatus for Measuring Diesel Tailpipe
Emissions in Underground Mines

By D. H. Carlson, T. R. Taubert, and J. H. Johnson

UNITED STATES DEPARTMENT OF THE INTERIOR

BUREAU OF MINES



500 T T T T

400 +

300

EMA CO, ppm

200

n 1 L n
100 200 300 400 500 600

LABORATORY CO, ppm

Figure 3.—CO by EMA versus laboratory-grade instruments for six engine load-speed conditions at normal engine operation for
tests 102 and 104. (Slope = 0.85; correlation coetficeint = 0.99.)

2,000, T T T T

EMA CO, ppm

400--

1 1 1 n
te) 400 800 1,200 1,600 2,000

LABORATORY CO, ppm

Figure 4.-CO by EMA versus laboratory-grade Instruments for six erigine load-speed conditions at re-
‘stricted engine air intake operation for test 103. (Slope = 0.99; correlation coefficient = 0.95.)



RESULTS AND DISCUSSION

COMPARISON OF EMISSIONS MEASUREMENT
APPARATUS VERSUS LABORATORY-GRADE
INSTRUMENTS

The data from the EMA measurements are com-
pared with the values from the measurements by
laboratory-grade instruments in table 3 and in figures 3
through 8. Figures 3 and 5 show EMA-measured CO and
CO, concentrations versus those measured by laboratory-
grade instruments for tests 102 and 104. A least squares
regression line is drawn through the data and reveals that
while the data correlate very well, the EMA-measured
concentrations average differences of 8.5 pet for CO and
4.1 pet for CO, from those of the laboratory-grade in-
struments, with most of the EMA values being lower.
One possible explanation for these differences is par-
ticulate filter plugging. The EMA requires sonic flow in
both the motive and exhaust venturi nozzles for equation 1

to accurately calculate flow rate. As the particulate filter
becomes loaded, pressure in the ejector increases, and if
it reaches a high enough value, the critical pressure ratio
is not maintained over the exhaust venturi nozzle and flow
becomes subsonic. This results in higher-than-calculated
dilution ratios and lower gas and particulate concentra-
tions. To identify and correct this condition, the following
approach to sample the exhaust and measure the emission
concentrations has been tried with some success:

1. Collect a bag sample of exhaust gas diluted by the
EMA without the particulate filter installed.

2. Collect a bag sample of exhaust gas diluted by the
EMA with the particulate filter installed,

3. Measure the CO, concentration in the first bag and
measure the concentrations of all gases in the second bag
(CO, CO,, NO, and NO,).

Table 3.—Comparison of tallpipe concentrations measured by EMA and laboratory-
grade instruments with and without engine Intake alr restriction

No intake restriction 38 in H,O intake restriction
Engine condition EMA Laboratory EMA Laboratory
Speed Load, pet Avconc' = §D. Numberof — Mey cone ‘SD Number of cane!
samples ‘samples
CO,

Peak torque .. 50 54 0.0 5 55 68 01 5 62
Do. 75 78 2 2 73 9.0 0 3 84
Do 100 9.0 oY) 2 9.6 11.6 5 4 10.7

Rate 50 53 0 3 5.2 69 o 3 58
Do. 75 66 oO 4 68 9.0 0 3 WW
Do. 100 8.0 0 4 84 WA A 3 9.4

PARTICULATE

Peak torque .. 50 38.9 15.0 4 50.5 45.8 57 6 76.1
Do. 75 59.0 72 2 84.9 102 43 3 142.1
Do. 100 162 1 2 240.6 602 29.8 4 732.7

Rated 50 Wt 21.0 3 99.5 94.6 14.5 3 130.0
Do. 75 73.5 48 3 99.6 86.1 25 3 142.4
Do. 100 66.8 35 4 104.3 100 36 3 144.1

co

Peak torque .. 50 120 07 5 139 240 44 5 223
Do. 75 228 12.0 2 231 497 at 3 485
Do. 100 461 ND 1 531 1,850 4t 3 1,746

Rated 50 200 64 3 23 365 0 2 326
Do. 75 256 83 4 a2 465 65 3 4
Do. 100 282 1 4 302 873 217 3 374

SD Standard deviation,

TEMA average concentrations and laboratory concentrations were measured as follows: for CO,, by percent; for particulate, by milli-
grams per cubic meter; and for CO, by parts per million.


Figure 1.EMA dilution system.

concentrations, Engine faults magnify these concentrations
at this condition, and it has been reported that excessive
CO production can only be detected at a high engine
torque condition (6). The temperature of the transmission
fluid is monitored and maintained within the manu-
facturer’s recommended limits by adjusting the amount of
time the engine is allowed to idle between repeat tests.
Experience has indicated that when sampling times are
less than 1 min, the fluid temperatures are maintained
even after a number of repeat measurements.

FLOW RATE CONTROL

The EMA uses an air ejector (7) to mix compressed
nitrogen or air with diesel exhaust. Under test conditions,
the air or nitrogen flows into the ejector’s venturi-shaped
motive nozzle under a pressure that is maintained at more
than twice atmospheric to maintain critical flow conditions
(7). For a nozzle of given diameter under critical flow
conditions, the flow rate (F) is controlled primarily by
controlling the pressure upstream of the nozzle and is not

affected by the downstream pressure. F is calculated by
equation 1:

56.77 X Cy x d? x Py x Ty

Px fT,

T, = temperature at which volume F is ex-
pressed, K,

F (L/min atT,, P,) = »()

where
P, = pressure at which volume F is ex-
pressed, kPa (abs),

Cg = nozzle coefficient of discharge,

d = nozzle throat diameter, cm,
P, = nozzle inlet pressure, kPa (abs),
and T, = nozzle inlet temperature, K.

The low pressure created in the ejector draws a sample
of diesel exhaust into the ejector’s suction chamber. The
EMA’s ejector has a venturi-shaped nozzle in the suction
inlet. The ejector and suction nozzle are sized to give
critical flow conditions in the suction nozzle at upstream
Pressures as low as 1/2 atm. The exhaust flow rate
through the suction nozzle is also calculated using equa-
tion 1, The dilution ratio can be varied by varying the
sizes of the motive and suction nozzles.

Thus, in the EMA, controlled volumes of nitrogen and
exhaust are mixed at known, controllable dilution ratios
(usually about 20 volumes of mixture per volume of
exhaust). The mixture passes through the ejector, then
through a Pallflex T60A20* 64-mm-diameter (2-1/2-in)
Teflon fluorocarbon polymer-coated glass-fiber filter, and
finally through a splitter, which directs a portion of the
dilute exhaust into a Calibrated Instruments five-layer,
gas-sampling bag and rejects the remaining portion.
Usually a 20-s sample collects adequate particulate for
accurate determination of the increase in weight of the
64-mm filter and calculation of the DPM concentration.

EMISSIONS MEASUREMENT APPARATUS LABORATORY TESTS

LABORATORY DESCRIPTION AND PROCEDURES

The evaluation of the EMA dilution system was
performed at the Bureau’s Twin Cities Research Center
(TCRC) diesel engine laboratory (fig. 2), which is de-
scribed in detail in reference 8. A Caterpillar 3304 PCNA
diesel engine was coupled to an eddy current dynamom-
eter that can control engine speed to +1 r/min and engine

load to +0.7 Nem (0.5 ftelbf). The engine is rated at
86 hp at 1,800 r/min and 380 N+m (280 ft+Ibf) torque at
1,200 r/min. A commercially available No. 2 diesel fuel
was used (table 1).

Reference to specific products does not imply endorsement by the
‘U.S. Bureau of Mines.


CONTENTS

Abstract 0... eee e cece eee eens

Emissions measurement apparatus dilution system .
Flow rate control 6.0.6.0... .eeeeseeeeeee
Eniissions measurement apparatus laboratory tests
Laboratory description and procedures ...
Engine conditions ..............00005
Emissions measurement apparatus test procedure .
Procedural modifications made during tests . .
Results and discussion ............ fe eeeee
Comparison of emissions measurement apparatus versus laboratory-grade instruments ..
Calculation of air-to-fuel mass ratio from CO, concentrations measured by emissions measurement
apparatus and laboratory-grade instruments . .
Summary ...
References . .

ILLUSTRATIONS

1. EMA dilution system . .
2. Schematic of Bureau’s dilution system .
3. CO by EMA versus laboratory-grade instruments for six engine load-speed conditions at normal engine
operation for tests 102 and 104 . .
4. CO by EMA versus laboratory-grade instruments for six engine load-speed conditions at restricted
engine air intake operation for test 103 .... 0... ss ccccceeceeeeeeeeeeeeteeeeeteeeeeseees
5. CO, by EMA versus laboratory-grade instruments for six engine load-speed conditions at normal engine
operation for tests 102 and 104.0... ... cee cece cece cece eee e eee e ete e teste teste eee
6. CO, by EMA versus laboratory-grade instruments for six engine load-speed conditions at restricted
engine air intake operation for test 103 6... .. cece cece cece eect eee eeeeeeeeeeteanenses
7. DPM byEMA versus laboratory-grade instruments for six engine load-speed conditions at normal engine
operation for tests 102 and 104 1... .... sec c ee cccee cece eect eee eeteeteeteseeeeeeeeeee
8. DPM by EMA versus laboratory-grade instruments for six engine load-speed conditi
engine air intake operation for test 103
9. A/F by laboratory-grade instruments versus A/F calculated from laboratory
engine load-speed conditions at normal engine operation for tests 102 and 104 ..............0008
10. A/F by laboratory-grade instruments versus A/F calculated from laboratory CO, concentrations for six
engine load-speed conditions at restricted engine air intake operation for test 103 ............0006
11. A/F by EMA versus laboratory-grade instruments for six engine load-speed conditions at normal engine
operation for tests 102 and 104.0... . eee cece eecee eee e eee ee eee tense ee eeaaeetenens
12. A/F by EMA versus laboratory-grade instruments for six engine load-speed conditions at restricted
engine air intake operation for test 103.0... .... 0c cece eee cece e eee eee eee eeeaneeeeenes

No. 2 diesel fuel specifications
Six steady-state operating conditions representing LHD duty cycle .
Comparison of tailpipe concentrations measured by EMA and laboratory-grade instruments with and
without engine intake air restriction 6.0... 0.00... cess eeseceeeeeeeeeeeeeeeeeeenereeens
4, Comparison of A/F’s calculated by EMA and measured and calculated by laboratory-grade instruments
with and without engine intake air restriction .

epee



10

Because there can be no filter plugging while the first
bag is collected, the exhaust flow rate and the dilution
ratio should be equal to that calculated by equation 1.
The exhaust flow rate may decrease with the filter installed
because of plugging with a resulting lower CO, concentra-
tion in the dilute exhaust sample (higher dilution ratio).
The actual dilution ratio can be determined by multiplying
the calculated dilution ratio by the CO, ratio (CO, without
filter divided by CO, with filter) as shown in equation 2.

Cc
DRgor = DRegie 0, W/OFiter 0)
CO? w/ritter
where DRyc DRegje = actual and calculated dilu-
tion ratios, respectively,
and CO, W/Filter> ;
2 W/OFitter = CO concentrations meas-
ured with and without filter

installed, respectively.

Figures 4 and 6 show the relationship between CO and
CO, concentrations measured by the EMA and laboratory-
grade instruments for test 103. Results show that the
concentrations measured by the EMA are higher than
those by laboratory-grade instruments, with average per-
centage differences of 29.1 and 13.2, respectively. This
discrepancy cannot be explained by filter plugging and is,
at present, not understood.

Figures 7 and 8 show the DPM measurements by the
EMA versus those by laboratory-grade instruments for
tests 102 and 104 and test 103, respectively. Analysis in-
dicates that all DPM concentrations measured by the
EMA are lower than those by laboratory-grade instru-
ments, except for mode 4, tests 102 and 104. The average

percentage differences are 22.6 and 30.6. The fact that
EMA-measured DPM concentrations are consistently low-
er than those measured by laboratory-grade instruments is
probably due to DPM losses in the EMA as a result of
cooling, condensation, and thermophoresis. Thermophore-
sis results in particles being repelled by a hot gas and
deposited onto a cold surface. It is likely that these losses
occurred because an unheated sample probe was used.

In the original EMA design, the use of a hot probe was
avoided because the EMA was intended to be used under-
ground where electrical power supplies are limited and
because it was believed that the probe would be heated
sufficiently by the exhaust prior to taking a sample. The
present data indicate that losses are obtained with an in-
sufficiently heated probe; thus, in the future, the probe will
be wrapped with heating tape.

Thermophoresis and/or condensation-related particu-
late deposition on the cold surfaces of the unheated EMA
sampling probe is the apparent cause for particulate
concentrations that were consistently lower than those
obtained by laboratory-grade instruments (about 30 pct
lower on average). A heated probe has been incorporated
in the apparatus, and recent laboratory measurements indi-
cate that the particulate concentrations now agree with the
values by laboratory-grade instruments.

CALCULATION OF AIR-TO-FUEL MASS RATIO

FROM CO, CONCENTRATIONS MEASURED BY

EMISSIONS MEASUREMENT APPARATUS AND
LABORATORY-GRADE INSTRUMENTS

Equation 3 is the mass balance equation developed by
the authors to calculate the CO, A/F’s of the EMA and
laboratory-grade instruments presented in table 4. The
equation assumes complete combustion of fuel to CO, and
water and calculates the engine intake A/F from the wet
exhaust CO, concentration.

Table 4.—Comparison of A/F's calculated by EMA and measured and calculated
by laboratory-grade Instruments with and without engine Intake alr restriction

Engine condition No intake restriction 38 in H,O intake restriction
Load, EMA Laboratory EMA Laboratory
Speed pet  Caleav SD Numberof Measured Ratio from Calcav SD Number of Measured Ratio from
ratio samples ratio calcCO, ratio samples ratio calc CO,
Peak 50 380 (02 5 39.0 373-900 05 5 wa 33.0
Do 7% 20 7 2 29.5 79 2h 3 244 24.4
Do too 226 2 21.4 20 00«17.2 8 4 19.2 18.7
Rated 50 3870 3 43.0 395 296 3 36.4 35.3
Do. 7% 09 4 4 92.9 300 225° 2 3 278 264
Do. 100254 t 4 25.6 241 1802 3 23.0 215

sD ‘Standard deviation.


40
S
= 30h
8
&
:
B 20f
4
10

20

30

40

LABORATORY A/F

Figure 10.—A/F by laboratory-grade instruments versus A/F calculated from laboratory CO, concentrations for six engine load-speed

conditions at restricted engine air intake operation for test 103. (Slope = 0.97; correlation coefficient = 1.0.)

50

40-

EMA A/F

30

1

20

30

LABORATORY A/F

40

50

Figure 11.—A/F by EMA versus laboratory-grade Instruments for six engine load-speed conditions at normal

engine operation for tests 102 and 104, (Slope = 0.84; correlation coefficient = 0.98.)



Library of Congress Cataloging in Publication Data:

Carlson, D. H.

Apparatus for measuring diesel tailpipe emissions in underground mines / by D.H.
Carlson, T.R. Taubert, and J{H. Johnson.

P- _ em, — (Report of investigations / U.S. Dept. of the Interior, Bureau of
Mines; 9422)

Includes bibliographical references (p. 14).

1, Diesel motor exhaust gas—Analysis. 2, Mining machinery. I. Taubert, T. R.
(Todd R.). II. Johnson, J. H. (John H.), 1937- . TIL. Title. IV. Series: Report
of investigations (United States. Bureau of Mines); 9422.

TN23.U43 [T8868] 622 s—de20 [6228] 91-6849 CIP



Report of Investigations 9422

Apparatus for Measuring Diesel Tailpipe
Emissions in Underground Mines

By D. H. Carlson, T. R. Taubert, and J. H. Johnson

UNITED STATES DEPARTMENT OF THE INTERIOR
Manuel Lujan, Jr., Secretary

BUREAU OF MINES
T S Ary, Director


10 T T
- gh 4
8 Oo
a
8
< o
WwW 6F 4

Oo
\ Nl
4 6 8 10

LABORATORY CO», pct

Figure 5.—-CO, byEMA versus laboratory-grade instruments for six engine load-speed conditions at nor-
mal engine operation for tests 102 and 104. (Slope = 0.86; correlation coefficient = 0.98.)

12

EMA COz, pct
tS)
T

@
T

6 1 1 1
4 6 8 10 12

LABORATORY COp, pct

Figure 6.—CO, by EMA versus laboratory-grade Instruments for six engine load-speed conditions at restricted engine alr intake
operation for test 103. (Slope = 1.05; correlation coefficient = 0.98.)



__ (1382 - $2.20)(400 - R%CO,)

AJP =
s (93 + 193R)%CO,

8)

where CO, = percentage by volume of CO, in

exhaust-measured wet basis,

and R = number ratio of atoms of hydrogen to
carbon in fuel.

Q = RH x 0,00004066 x (TDC +273)

~ (TDC - 152)?
xe 4

where RH = relative humidity of air taken into

engine, pet,

and TDC = temperature of air taken into engine,
Q
C.

A/Ps determined by measurements by laboratory-grade
instruments of the engine intake air and fuel mass flow

il

rate’s (abscissa) compare quite well with those obtained by
equation 2 using the CO, concentrations measured by
laboratory-grade instruments (figs. 9-10). Analysis shows
that the A/F measured by laboratory-grade instruments
for both tests was slightly higher, with an average
percentage difference of 5.8 and 3.6, respectively.

Plots of the measured A/F by laboratory-grade
instruments versus the calculated A/F by the EMA
(figs. 11-12) show good correlation and indicate that
the A/F’s are being calculated correctly from the EMA-
measured CO, concentrations, Average percentage differ-
ences of 6.0 and 15.0 were measured.

During test 103, a restriction was applied to the
engine’s air intake system to simulate a dirty intake air
filter and to determine if the EMA could detect this
engine fault, Results show that the EMA-measured CO
and DPM concentrations for test 103 are considerably
higher than those for the normal engine condition (tests
102 and 104) for all six engine modes, indicating that the
EMA was able to detect an engine fault. These increases
were especially noticeable at peak torque speed, the peak
torque where CO and particulate emissions increased by
300 and 270 pet, respectively.

40
‘
<
N
[e}
O
5 30h 4
<
a
{e}
a
¢
a
! l
20 30 40 50

LABORATORY A/F eT
OR ATORVAIE

Figure 9.—A/F by laboratory-grade Instruments versus A/F calculated from laboratory CO, concentrations for alx ‘engine load-speed
conditions at normal engine operation for tests 102 and 104, (Slope = 0.89; correlation coefficient = 0.99.)