United States Air and Radiation EPA420-R-97-002
Environmental Protection December 1997
Agency
Office of Mobile Sources
&EPA Exhaust Emissions From A
Heavy-duty Diesel Engine
Equipped With A High
Pressure Common Rail
Fuel Injection System
> Printed on Recycled Paper
-------
TECHNICAL REPORT
EXHAUST EMISSIONS FROM A HEAVY-DUTY DIESEL ENGINE EQUIPPED WITH A
HIGH PRESSURE COMMON RAIL FUEL INJECTION SYSTEM
by
Jaime Pagan
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Mobile Sources
Engine Programs and Compliance Division
December, 1997
NOTICE
This technical report does not necessarily represent final EPA decisions or positions. It is intended to present
technical analysis of issues using data which are currently available. The purpose in the release of such reports is to
facilitate the exchange of technical information and to inform the public of technical developments which may form
the basis for a final EPA decision, position or regulatory action.
-------
I. INTRODUCTION
In October, 1997 the Environmental Protection Agency (EPA) promulgated new exhaust
emission standards for heavy-duty engines'. The new standards, to become effective in the year
2004, will help reduce exhaust emissions for oxides of nitrogen (NOx) to approximately 2 g/bhp-
hr while maintaining the current standard for paniculate matter at 0.1 g/bhp-hr. Although these
lower emission levels will present a challenge in the design of new engines, there are
technologies available that will allow emission reductions without significantly affecting
performance and fuel economy.
Over the last several years, advances in the development of electronic controls and high-
pressure fuel injection systems have allowed manufacturers more flexibility in the control of the
delivery of the fuel during the combustion event and higher injection pressures. High injection
pressures, for example, allow better air/fuel mixing, which result in reduced formation of
particulate matter. Common-rail fuel injection systems are one example of the type of
technologies that are being introduced in the market and that allow both better engine
performance and low emissions2,3.
Common-rail injection systems today are attracting a lot of attention due to their
flexibility by allowing the control of many engine parameters independently. In that type of
system the fuel is accumulated in a rail at high pressures and the injection pressure is increased
by varying the amount of fuel discharged by the supply pump4. Contrary to conventional fuel
injections systems, the common-rail type allows to vary the injection pressures independent of
engine speed and load. In in-line fuel systems the injection pressure results from the metered fuel
quantity being pushed through the nozzle orifice by a piston with a velocity that is proportional to
the engine speed5. The flexibility in varying fuel injection pressures and fuel quantity allow
common-rail systems to produce higher injection pressures and higher torque at low speeds than
systems using in-line pumps. Another advantage of common-rail systems is that, since the
injectors use electromagnetic valves or solenoids, strategies such as rate shaping, pilot injection
or even post injection can be used to further improve performance and exhaust emissions6.
We have obtained baseline emissions data over a variety of transient and steady state
cycles from a heavy-duty diesel engine that utilizes a common-rail fuel injection system. Data
show that even though this engine emits NOx and PM levels that are than the 1998 U.S. heavy-
duty emission standards on the Federal Test Procedure, the steady-state data show that the engine
is capable of achieving NOx emission levels in the order of 3 g/bhp-hr.
H. TESTING PROCEDURES
A. Engine.
The engine was in new condition and already undergone break-in. The engine is naturally
aspirated, with a total displacement of 7.9 liters and its rated power is 193 hp at 2900 rpm. The
-------
engine was setup in a heavy-duty engine test cell at EPA's National Vehicle and Fuel Emissions
Laboratory (NVFEL). Inlet depression was set at -7.9 in H:O at rated point and the exhaust
backpressure at 6.4 in. Hg at rated point. The fuel used for this study was diesel No. 2. The fuel
specifications are included in the Appendix.
B. Test cycles
The following transient test cycles were performed:
a. Heavy-duty Federal Test Procedure (FTP): cold and hot start.
b. Crawler-tractor cycle
c. Backhoe loader cycle
d. Composite cycle
Cycles b., c. and d. were developed by Southwest Research Institute under separate
contracts with the Engine Manufacturers Association (EMA) and the EPA. Although there are no
final reports currently available with detailed information about the development of the cycles,
the torque and speed traces are shown in the Appendix. The FTP was run by following the
procedure outlined in the Code of Federal Regulations (CFR) Title 40, Part 86, Subpart N. Both
the ISO 13 mode (UN-ECE R49) test and the Cl (8 mode), which are described in the ISO 8178-
4 document, were also performed. In addition, a set of 56 steady-state modes were run twice to
develop an emissions map under the torque curve of the engine. Each steady-state mode was run
for approximately five minutes, followed by three minutes of exhaust emissions measurements.
Figure 1 shows the specific map points tested under the engine's torque curve.
Exhaust emissions were sampled from a dilution tunnel and recorded continuously. The
emission sampling procedure is described in 40 CFR Part 86 Subpart N. Brake specific NOx,
HC and PM emissions, in g/bhp-hr, were determined from the gas concentrations that were
measured continuously. The efficiency and fuel consumption results were obtained from carbon
balance calculations. The following carbon balance equations were used:
12.011 .
- 12.01 l + l.OOScc
453.6
-------
where a is the hydrogen to carbon ratio, Gs is the total mass of carbon, in grams, and M is the
mass of fuel consumed, in pounds.
350
300 -
7 250 -|
£
£ 200
3
S" 150
2
100
50
n -
+ + + + +
+
• • J • •
X XXX X
X V X X
. x x x x x
A A * **A ^ ^
• •••"•• •
• • * ••• 4 •
;• 25% torque i
• 40% torque .
A 50% torque
X 60% torque
X 75% torque
• 85% torque
+ 100 % torque
500 1000 1500 2000 2500 3000
speed (rpm )
Figure 1. Steady-state emission points under the engine's torque curve.
EL RESULTS AND DISCUSSION
The table below shows the emissions results from the transient test cycles. The backhoe,
crawler and composite cycles results are the average of three runs. The reproducibility of the
results was good as shown in the Appendix, and the standard deviation was consistently within 5
percent of the average values. The Hot Start of the FTP was performed twice and the brake
specific results were also within 5 percent from the averaged values.
-------
Cycle
Backhoe
Crawler
Composite
FTP (HS)
FTP (CS)
bhp-hr
4.5
16.6
20.9
12.2
12.2
NOx
(g/bhp-hr)
5.14
3.42
4.11
4.48
4.67
HC
(g/bhp-
hr)
0.89
0.37
0.41
0.60
0.62
PM
(g/bhp-hr)
0.20
0.16
0.19
0.22
0.25
BSFC
(Ib/bhp-hr)
0.376
0.320
0.377
0.406
0.428
Efficiency
0.37
0.43
0.37
0.34
0.32
g NOx/kg
of fuel
30.1
23.6
24.0
24.3
24.1
Table I. Emission results for various transient cycles.
It is worth noting that the 43% thermal efficiency calculated for the Crawler cycle was
much higher than the efficiencies on the other transient cycles. Furthermore, the thermal
efficiency determined from steady-state data reaches a maximum of 42% at one point only. Since
the overall fuel consumption, and as a result the thermal efficiency, during the Crawler cycle was
very consistent for all three cycles run, it is not possible to explain at this point the reason for
such high thermal efficiency. Results for the 13 mode and ISO Cl steady state cycles are shown
in Table H The weighted brake-specific NOx and PM values were similar for both cycles as can
be seen from the Table. Detailed emissions data is presented in the Appendix.
Cycle
ISOC1 (8 mode)
ISO 13 mode
NOx (g/bhp-hr)
4.66
4.73
HC (g/bhp-hr)
0.29
0.29
PM (g/bhp-hr)
0.28
0.34
Table II. Emission results from two steady-state cycles.
Results from the steady state modes sampled under the torque curve were plotted as
contour graphs. Figures 2 to 6 show the brake-specific emissions, fuel consumption and thermal
efficiency plots. As shown in Figure 2, the lowest NOx values occur from 1300 to almost 2000
rpm across almost the entire operating torque range. The lowest NOx value was 2.61 g/bhp-hr at
1725 rpm and 153 ft-lb. The PM emissions map shown in Figure 3 exhibit its lowest values at
low speeds and high loads. Overall, however, PM emissions are higher than the current 0.1
g/bhp-hr U.S. standard. Both the BSFC and thermal efficiency maps display, as expected, similar
trends: the lowest BSFC's and highest efficiencies occur at the low speed-high torque regions
while the opposite is true at the high speed-low torque region.
-------
400
350-
300-
^250
0)
§200
150-
100-
50
500
1000
1500 2000
speed (rpm)
Figure 2. NOx emissions (g/bhp-hr) map.
2500
3000
400
350 -
300 -
^ 250 -
-------
400
350 -
300 -
4 250 -
-------
400
350-
300-
£ 250-
o>
3
O"
200-
150-
100-
50
).45
•0.55'
500
1000
1500 2000
speed (rpm)
Figure 6. Brake-specific fuel consumption (in Ib/bhp-hr) map.
2500
3000
It was attempted to compare the emission test results from this engine with other
commercially available engines of similar displacement and power rating. Unfortunately there
are almost no naturally-aspirated heavy-duty engines currently available since most engines sold
in the U.S. for the heavy-duty truck market are turbocharged.
IV. SUMMARY AND CONCLUSIONS
We have obtained baseline emission data from a common-rail heavy-duty diesel engine.
The engine uses a very flexible common-rail fuel injection system that is controlled electronically
and is capable of. very high injection pressures. For the transient cycles, the brake-specific
emissions were relatively high when compared to the 1998 US highway standard of 4.0 g/bhp-hr
NOx. On the FTP, for example, the resulting NOx emission level was 4.48 g/bhp-hr. PM
emissions were also high relative to the 0.1 g/bhp-hr U.S. standard. Steady-state emissions and
efficiency maps were also produced from the test data. The maps show that the lowest NOx
region (of about 3.0 g/bhp-hr) occur at intermediate speeds, while at rated speed the NOx can
increase to 4.15 g/bhp-hr at full load.
V. REFERENCES
1. Federal Register, Vol. 62, No. 203, October 21, 1997, pp.54694-54730.
-------
2. S. Ashley, "Diesel Cars Come Clean", Mechanical Engineering, Vol. 119, No.8. August 1997.
pp. 52-56, ASME.
3.G. Stumpp and Mario Ricco, "Common Rail-An Attractive Fuel Injection System for
Passenger Car DI Diesel Engines", SAE 960870.
4. Y. Yamaki, et al, "Application of Common Rail Fuel Injection System to a Heavy-Duty Diesel
Engine", SAE 942294.
5. See endnote 2-S. Ashley, "Diesel Cars Come Clean", 1997.
6.W. Boehner and K. Hummel, "Common Rail Injection System for Commercial Diesel
Vehicles", SAE 970345.
VI. ACKNOWLEDGMENTS
Special thanks to the Engine Testing Group in the Testing Services Division at U.S.
EPA's National Vehicles and Fuel Emissions Laboratory for their technical suppport of this
project. Also we appreciate the help of Dr. Joe Norbeck, from the University of California-
Riverside for his suggestions and comments on this report.
-------
VI. Appendix
Al.BackhoeCycle
A2. Crawler Tractor Cycle
A3. Composite Cycle
A4. Fuel Specifications
A5. Steady-state emissions data.
A7. ISO 13 mode and Cl data.
A8. Transient cycle data.
10
-------
Backhoe Cycle
'110
Speed
Torque I
time (sec.)
-------
Crawler Tractor Cycle
120
100
o>
3
•o
o
N
E
i_
o
i ;..
i ,
in o in o in
cvjiONOCMinNOcvj
co •«* ^ •* i- m m
m
h-
m
o m
o CM
(O (O
o m o
if> t~~ O
to
-------
Composite Cycle
130
110
-1 0
:—Speed (
Torque j
time (sec.)
-------
Certificate of Analysis
PHILLIPS CHEMICAL COMPANY
A DIVISION Of PHILUPS PETBOtEUM COMPANY
SPECIALTY CHEMICALS
P O. BOX 968
BORGER. TX 79008-09M
0.05 SULFUR DIESEL FVEL
LQTM48X
TESTS
Conation
SpMftleQnvtty,60/«0
APIOravtty
Sulfur, Wt%
Ft««h Pott*. *F, PM
Pour Point f
Cloud Point, '?
ViaeMtty, c* 40C
C«rbon,wt%
Hydreg*n,wt%
A*h,wt%
NMHMI of Combustion,
BTUrtb.
RESULTS
1A
C«tMwlnd«
354
.034
171
-9
0
2.67
0.01
18434
8
47 J
Rtport
Rtport
32-37
130 Un.
Rtport
2JJ-3.4
Report
Rtport
Report
15 Un.
TO BE REPORTED LATER
DISTT t ATIOM. 'f
IBP
5%
10%
20%
30%
40%
50%
60%
70%
80%
90%
95%
EP
Loss
RMMU*
HYDROCARBON TYPg. VOL%
Aronurttc*
OMlM
DATE OF SHIPMEMT
Oft-16-96
CUSTOMER ORDER NO.
6A-1011-NTLX
INWREQN. NO.
660279
CONTAINER NO.
TRLRM58
METHOD
A3TMO-130
ASTMD-4062
ASTMD-12M
ASTMD-2822
ASTMO-W
ASTMO-97
ASTM 0-2500
ASTMD-448
ASTM 0-482
ASTM 0-3338
ASTM 0-227*
ASTM 0*78
ASTM 0-613
ASTM 0*6
374
410
427
453
472
4M
502
516
533
555
5W
815
842
04
0.7
3X0
340-400
400-480
470-540
560-630
610-890
27Mln.
ASTM 0-1319
08/16/96
RF3700
A4
-------
Sleady-slale emissions
Mode
10
11
12
13
14
15
16
17
IB
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
41
42
43
44
45
46
47
Speed (rpm)
600
600
600
600
600
600
600
785
785
785
785
785
785
785
1137
1137
1137
1137
1137
1137
1137
1490
1490
1490
1490
1490
1490
1490
1725
1725
1725
1725
1725
1725
1725
1960
1960
1960
1960
I960
1960
1960
Torque (ft-lb)
85
136
170
204
262
289
340
87
140
175
210
281
297
350
94
150
188
225
275
319
375
92
146
183
220
287
311
98
153
191
229
265
325
382
93
148
185
222
264
315
370
hp
9.7
15.6
196
23.3
29.9
33.0
38.8
13.4
20.9
26.1
31.4
42.0
44.4
52.3
20.3
32.5
40.7
48.7
59.4
69.1
81.3
26.1
41.4
51.9
62.4
81.5
88.3
122.2
31.5
50.2
62.7
75.4
87.1
106.9
125.8
34.8
55.3
69.1
83.0
98.7
117.7
1380
NOx (g/bhp-hr)
4.16
4.63
4.93
5.21
6
6.63
6.34
4.09
4.15
4.33
4.49
5.07
5.18
4.93
3.25
3.14
3.31
3.44
3.76
3.71
3.44
2.79
2.72
2.82
2.86
3.16
3.27
2.81
2.66
2.61
2.62
2.65
2.83
3.02
2.89
3.09
2.96
308
3.1
3.08
3.24
3.24
NOx(g/hr)
40.35
72
96.39
121.3
179.6
219
246.1
55
86.89
113.2
140.8
213
230.1
258
66.12
101.9
134.6
167.6
223.4
256.2
279.6
72.72
112.7
146.3
178.6
257.6
268.7
343.5
83.67
130.9
164.3
199.7
246.6
322.8
363.5
' 107.4
163.8
212.9
257.2
303.9
381.3
447.1
HC (g/bhp-hr)
1
0.53
0.45
0.38
0.31
0.31
0.27
1.37
0.61
0.51
0.41
0.32
0.28
0.21
1.15
0.5
0.38
0.33
0.28
0.23
0.12
1.47
0.72
0.53
0.43
0.26
0.2
0.08
1.46
0.72
0.55
0.38
0.29
0.13
0.01
1.71
0.9
0.63
0.5
0.35
0.2
0.05
PMjg/bh£-hr}
0.316
0.173
0.144
0.131
0.096
0.085
0.108
0.25
0.161
0.155
0.132
0.093
0.086
0.115
0.259
0.157
0.133
0.13
0.115
0.092
0.19
0.366
0503
0.203
0.184
0.103
0.089
0.156
0.374
0.316
0.293
0.189
0.133
0.104
0.181
0.408
0.308
0.213
0.162
0.139
0.126
0.151
fuel cons.
4.3
5.79
6.98
8.15
10.21
11.18
13.29
5.15
7.35
8.94
10.44
13.78
14.54
17.4
8.37
11.68
14.02
16.45
19.91
23.25
27.75
11.38
15.57
18.7
21.97
27.99
30.36
36.13
;14:11 /
19.48
23.21
27.15
31.07
37.88
44.11
16.34
22.03
26.18
30.61
35.89
42.47
49.31
bslc (I
0.44
0.37
0.36
0.35
0.34
0.34
0.34
0.4
0.35
0.34
0.33
0.33
0.33
0.33
0.41
0.36
0.34
0.34
0.33
0.34
0.34
0.44
0.38
0.36
0.35
0.34
0.34
0.35
0.45
0.39
0.37
0.36
0.36
0.35
0.35
0.47
0.4
0.38
0.37
0.36
0.36
0.36
Ih. eflic.
0.31
0.37
0.38
0.39
0.4
0.41
0.4
0.35
0.39
0.4
0.41
0.42
0.42
0.41
0.34
0.38
0.4
0.41
0.41
0.41
0.4
0.32
0.37
0.38
0.39
0.4
0.4
0.4
0.31
0.36
0.37
0.38
0.39
0.39
0.39
0.29
O35
0.36
0.37
038
038
039
g NOx/kg fuel
19.91
27.34
29.07
32.27
38.32
43.17
41.23
22.48
26.29
28.32
29.96
34.74
34.93
32.48
17.37
18.88
20.86
22.46
24.32
23.97
21.67
14.26
16.07
17.02
17.66
20.2
20.76
14.38
13.2
14.84
15.79
16.12
17.54
18.7
1793
14.19
16.03
17.56
1796
1852
1965
1994
-------
Steady-state emissions
48
49
50
51
52
53
54
55
56
57
58
59
61
2312
2312
2312
2312
2312
2312
2312
2900
2900
2900
2900
2900
2900
2900
88
141
177
212
264
300
353
88
141
176
211
264
299
352
38.7
62.1
77.9
93.1
116.4
132.2
155.5
48.6
77.9
97.2
116.5
145.8
165.0
189.4
3.8
3.28
3.31
3.16
3.01
3.21
3.11
9.75
7.66
6.79
6.15
5.26
4.77 '
4.15
147.2
203.7
257.9
294.2
350.4
424.4
483.6
474.1
596.7
660
716.6
766.8
787.1
786
1.96
1
0.69
0.53
0.27
0.14
0.02
1.55
0.89
0.7
0.56
0.3
0.12
0.02
0.541
0.326
0.211
0.204
0.154
0.165
0.237
0.584
0.276
0.212
0.169
0.175
0.212
0.326
19.65
26.56
31.6
36.61
40.79
49.69
58.84
27.33
35.2
40.64
46.61
56.95
64.68 '
74.98
0.51
0.43
0.41
0.39
0.35
0.38
0.38
0.56
0.45
0.42
0.4
0.39
0.39
0.39
0.27
0.32
0.34
0.35
0.39
0.37
0.36
0.25
0.31
0.33
0.34
0.35
0.35
0.36
16.52
17.21
18.27
17.93
18.53
18.67
18.28
37.98
37.2
35.64
33.62
29.63
27.07
23.37
-------
Steady state cycles
IS013 mod£_
Weighted:
IS013 mode
ISOC1
02
189.1
144.8
962
482
19.4
0.1
123.S
93.4
62.0
31.0
12.3
02
NOx
tfvAir
9"" -
11.40
758.87
743.91
650.32
478.90
357.00
14.28
347.40
27820
161.60
86.05
48.63
14.80
417.73
439.41
HC
PM
8.95
0.38
022
0.18
0.40
1.32
20.67
0.22
0.13
026
0.36
0.87
12.76
BSFC
Ib/bhp-tv
6.78
0.41
0.41
0.44
0.60
1.11
11.75
0.36
0.38
0.39
0.48
0.78
6.70
Efficiency
0.02
0.34
0.34
0.31
0.23
0.12
0.01
0.39
0.37
0.36
0.29
0.18
0.02
NOx/kg fuel
17JS
21.8
27.7
34.0
36.7
36.6
212
17.4
17.5
149
12.8
11.2
220
0.34
028
-------
transient cycles
Baseline Emissions Data
Cycle: Crawler
Test No.
NOx (g/bhp-hr)
HC (g/bhp-hr)
CO (g/bhp-hr)
PM (g/bhp-hr)
BSFC (Ib/bhp-hr)
1
3.386
0.386
0.792
0.159
0.313
2
3.408
0.371
0.789
0.167
0.319
3
3.467
0.351
0.803
0.153
0.329
avg.
3.420
0.369
0.795
0.160
0.320
std. dev.
0.042
0.018
0.007
0.007
0.008
Cycle: Backhoe
NOx
HC
CO
PM
BSFC (Ib/bhp-hr)
1
5.196
0.815
2.521
0.201
0.387
2
5.256
0.891
2.496
0.204
0.381
3
4.979
0.960
2.398
0.205
0.361
avg.
5.144
0.889
2.472
0.203
0.378
std. dev.
0.146
0.073
0.065
0.002
0.014
Cycle: Composite
NOx
HC
CO
PM
BSFC (Ib/bhp-hr)
1
4.285
0.423
1.211
0.198
0.382
2
4.159
0.413
1.104
0.186
0.380
3
3.891
0.387
1.181
0.201
0.368
avg.
4.112
0.408
1.165
0.195
0.377
std. dev.
0.201
0.019
0.055
0.008
0.008
Cyde: FTP-HS
NOx
HC
CO
PM
BSFC (Ib/bho-hr)
1
4.532
0.577
1.673
0216
0.409
2 3
4.429
0.626
1.674
0.222
0.403
avg.
4.481
0.602
1.674
0.219
0.406
std. dev.
CycteFTP-CS
NOx
HC
CO
PM
BSFC (Ib/bhp-hr)
1 2
4.671
0.626
1.883
0.251
0.428
3 avg. std. dev.
A8
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