TRANSIENT EMISSIONS TESTING OF BIODIESEL IN A DDC 6V-92TA DDEC ENGINE

Prepared By

Christopher A. Sharp

FINAL REPORT

Prepared for

National Biodiesel Board 1907 Williams Street

Jefferson City, MO 65110-4898

October 1994

Approved:

Em&Ions Research Dlvlslon

Charles T. Hare, Dlrector Department of Emissions Research Automotive Products and

Emlsslons Research Divlslon

TABLE OF CONTENTS

LIST OF FIGURES . . . . . . . . . iii

LIST OFTABLES ..................................................... iv

EXECUTIVESUMMARY ............................................... v

I. INTRODUCTION ................................................ 1

II. DESCRIPTION OF PROGRAM .......................... : .......... 2

A. TestEngine ............................................... 2 B. Test Fuels and Oil .......................................... 2 C. Test Procedures ............................................ 2

III. TESTRESULTS ................................................. 5

A. Baseline, ECM, andInjection Timing Tests ........................ 5 B. Additive Screening Tests .................................... 12 C. Testing with Catalyst ....................................... 13

Iv. SUMMARY AND CONCLUSIONS .................................. 27

APPENDICES

A TEST FUELS B INDMDUAL TRANSIENT TEST PRINTOUTS C CERTIFICATION DATA PACKS

ii

LIST OF FIGURES

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Transient Test Cell Installation of the 1988 6V-92TA DDEC II Engine ........ 3

Graphic Representation of the Heavy-Duty Transient Cycle ................ 4

Transient Torque-Map Data for Baseline, ECM, and Timing Tests ........... 7

Composite Transient Emissions from Baseline, ECM, and Timing Tests ....... 9

Composite Transient Particulate Composition for Baseline, ECM, andTimingTests ............................................... 10

FTP Smoke Test Data for Baseline, ECM, and Timing Tests .............. 11

Transient Torque-Map Data for Addtitive Screening Tests ................ 15

Average Hot-Start Transient Emissions from Additive Screening Tests ...... 17

Hot-Start Particulate Composition for Additive Screening Tests ............ 18

Transient Torque-Map Data for Tests with Catalyst ..................... 20

Composite Transient Emissions for Tests with Catalyst .................. 23

Composite Transient Particulate Composition for Tests with Catalyst ....... 24

FTP Smoke Test Data for Tests with Catalyst ......................... 25

Comparison of Composite Transient Emissions, Baseline 2-D Versus 2-D with Timing Retard and Catalyst .................................. 26

1u

LIST OF TABLES

Table &@

1 Transient Torque-Map Data for Baseline, ECM. and Timing Tests ........... 6

2 Transient Emissions Results for Baseline, ECM, andriming Tests ........... 8

3 Cetane Analysis Results .......................................... 13

4 Transient Torque-Maps for Additive Screening Tests .................... 14

5 Transient Emissions Results from Additive Screening Tests ................ 16

6 Transient Torque-Maps for Tests with Catalyst ........................ 19

7 Transient Emissions Results for Tests with Catalyst .................... 21

iv

EXECUTIVE SUMMARY

A test program was conducted at Southwest Research Institute (SwRII to evaluate the use of biodiesei in a Detroit Diesel Corporation 6V-92TA electronically controlled transit bus engine in terms of its effects on the exhaust emissions of the engine. Biodiesel was blended with an emissions grade, low sulfur, 2-D diesel fuel at a ratio of 20/80 percent by volume respectively. This blend, referred to herein as B20, was examined in the engine both by itself, and in conjunction with other engine, fuel, and/or aftertreatment modifications to determine what combination achieved the best overall reductions in regulated exhaust emissions. The Table on the following page summarizes the results of transient emission tests conducted during the program.

The B20 blend was tested both in the baseline engine cotiguration, and again with injection timing retarded by one degree. The test results indicated that, at base injection timing, the use of B20 resulted in a little over a ten percent reduction in HC and CO emissions, and a five percent increase in NV, emissions. Total particulate emissions did not change when B20 was used. The composltlon of the total particulates did shift toward a higher fraction of SOF and lower emissions of carbon soot. When B20 was tested with one degree of timing retard, the CO returned to the 2-D baseline level, while NO, was slightly below the baseline level. Total particulates increased about five percent over baseline, with the increase noted in the soot portion of the total particulates. This indicated that, on this engine, the timing retard counteracted most of the benefit of using B20, and that some other solution beyond a simple timing retard was necessary to counteract the NO, increase.

As an alternative to retarding the timing to reduce NO,, two fuel additives for use in B20 were tested. The two selected additives were both cetane improvers; 2-ethylhexyl nitrate (EHN), and di-t-butyl peroxide (DTBP). The two additives were blended separately into B20, as recommended by the manufacturers, to achieve a ten number increase in cetane number. While EHN achieved the desired increase in cetane number with the recommended treat level, DTBP did not respond in B20 as predicted. However, enough cetane increase was obtained with DTBP to determine if the additive had any sign&ant effects on exhaust emissions. Testing was conducted at standard injection timing only. Transient test results indicated that neither cetane improver had any significant effects on the regulated exhaust emissions of the test engine. The trends observed when switching from 2-D fuel to a cetane- improved B20 were the same as those noted for a B20 fuel alone. It should be noted that B20 fuel without additive had a higher cetane number (51) than base 2-D fuel (46).

Another strategy to reduce emissions was to use a diesel oxidation catalytic converter in conjunction with B20 fuel, to determine if the combination could achieve better emissions reductions than either the catalyst or B20 alone. This test was performed both at standard timing, and with the one degree retard of injection timing. Transient test results indicated that the combination of B20 and a catalyst achieved larger emission reductions than the catalyst alone. With this combination at standard timing, NO, was about seven percent higher than the 2-D baseline, but HC, CO, and total particulates were reduced by 65,41, and 46 percent respectively. The one degree timing retard reduced NO, back to the baseline level, with HC, CO, and particulates controlled to levels 59, 34, and 41 percent below the baseline levels, respectively. The level of particulate reduction achieved with the combination

”

SUMMARY OF TRANSIENT TEST RESULTS FROM ALL TEST CONFIGURATIONS

5.

I

Test Injecting Translent Emlsslons, glhphr

SOF BSFC, work, Type Fuel Tlmlng Catalyst HC co NO, PM % lb-hp-hr hphr

Composite FTP 2-D Standard No 0.60 1.60 6.52 0.20 56 0.452 20.1

Composite FTP 820 Standard No 0.53 1.39 6.93 0.20 71 0.457 20.1

Composite FTP I320 1” Retard No 0.55 1.59 6.20 0.21 64 0.469 19.6

Average Hot-Starl 2-D Standard No 0.66 1.56 6.63 0.20 64 0.449 19.7

Average Hot-Start B20+DTBP Standard No 0.57 1.39 9.36 0.20 70 0.460 19.6

Average Hot-Start B20+EHN Standard No 0.62 1.32 9.46 0.20 71 0.46 19.4

Composite FTP 820 Standard Yes 0.21 0.95 9.12 0.11 53 0.465 19.6

Composite FTP 820 1” Retard Yes 0.25 1.05 6.35 0.12 44 0.467 19.7

Composite FTP 2-D 1” Retard Yes 0.29 1.21 6.18 0.14 35 0.467 19.7

was somewhat better than the roughly 30 percent reduction obtained with the catalyst alone. The improved particulate reduction, associated with the use of B2Q in combination with the catalyst, is likely due to the fact that B20 appears to cause a shift in particulate composition toward a lower soot fraction and higher SOF. It is the SOF portion of the total particulates that an oxidation catalyst is most effective in reducing. A final test with the catalyst was performed with 2-D fuel at retarded timing, to verify that regulated emissions would still be below baseline levels if the engine were accidentally fueled on 2-D alone instead of B20. The results with one degree timing retard indicated that while emissions reductions from baseline with 2-D and a catalyst were not as great as with B20 and a catalyst, the regulated emissions were still below the baseline levels (standard timing, 2-D fuel, no catalyst).

vii

I. INTRODUCTION

This final report contains the results of two related test programs conducted at Southwest Research Institute (SwRD on behalf of the National Biodiesel Board (NBB). The objective of both test programs was to examine the use of biodiesel, specilically methyl soyate, used with typical diesel fuel, in a diesel transit bus engine as a means of reducing exhaust emissions. Engine moditications, the use offuel additives, and aftertreatment were examined in conjunction with biodiesel. All test work was conducted using a 1988 Detroit Diesel Corporation W-92TA DDEC II coach engine provided by Bi-State Transit Company of St. Louis, Missouri. Foseen Manufacturing and Development procured a specially programmed electronic control module (ECM) fmm DDC for use in this program. This special ECM was used briefly, and then the original ECM was used for the remainder of the program. Fuel additives in the form of cetane improvers were provided by ARC0 Chemical Company and Ethyl Corporation. A diesel oxidation catalyst was supplied by Engelhard.

Testing during this program was conducted with the understanding that potentially the data would be submitted to the EPA for certification under the Urban Bus Retrofit and Rebuild Program. Therefore, detailed supporting documentation for all test work has been prepared as a part of this project.

II. DESCRIPTION OF PROGRAM

A. Test Envine

The test engine was a 1988 model year DDC 6V-92TA DDEC II coach engine, which was a two-stroke, six cylinder engine of “V” configuration having 552 cubic inches displacement, and was turbocharged and aftercooled. This engine was supplied by the Bi- State Transit Company of St. Louis, MO. The as-received engine employed no exhaust aftertreatment, and was rated at 300 horsepower at a speed of 2100 rpm. Peak torque was 1020 lb-ft at an engine speed of 1200 rpm. Transient test cell installation of the engine is shown in Figure 1. Engine control input was achieved by means of a throttle potentiometer supplied by DDC to interface with the electronic control system of the engine. This 6V-92TA employed a standard DDEC II electronic control module (ECM). Two ECM programs were used on the 6V-92TA during this program, the “baseline” program unit that came with the engine, and another program that was obtained through Foseen Manufacturing and Development programmed with a “modified” engine calibration. This modified calibration incorporated a new injection timing map wherein timing was retarded at selected high speed and high load conditions.

B. Test Fuels and Oil

Several test fuels were used during the course of this program. The fuel used as base stock for blending was an emissions grade 2-D diesel obtained from Phillips Petroleum, Lot No. S-464, and coded SwRI EM-1852-F. Properties for this base fuel are given in Appendix A. Biodiesel used for this program was obtained from Interchem. The test blend was an 80- 20 blend by volume of the base 2-D fuel and biodiesel, respectively. This blend is referred to as B20 in this report. For the additive test work, two batches of B20 were blended with two different cetane improvers. One cetane improver used was 2-ethylhexyl nitrate (EHN), blended at 0.5 percent by volume into B20. The second cetane improver was di-t-butyl peroxide (DTBP), blended at 0.7 percent by volume. Lubricating oil used was Texaco URSA Super 40.

C. Test Procedures

Emissions of interest were measured over the heavy-duty transient Federal Test Procedure (FTP), following procedures given in CFR Title 40, Part 86, Subpart N, and CFR Title 40, Subpart 87. The FTP outlines specific requirements for setting up the test engine and mapping the engine’s full torque capabilities over its operating speed range. Engine- specific performance data are used, along with a normalized EPA transient cycle, to define a transient command cycle for test engine operation. The 20-minute transient command cycle illustrated in Figure 2 shows the rapid changes in speed and torque the engine must produce.

While the engine is operated over the 20-minute test cycle, torque and speed responses of the engine are compared to the command cycle to ensure FTP compliance. Simultaneously, engine exhaust gases are diluted with conditioned air, and emissions of interest are determined. Measured emissions are divided by the level of work performed during the test, and the heavy-duty engine emissions are reported in terms of pollutant mass per unit work. When both cold-start and hot-start data are available, a composite emission level is determined, essentially by combining one-seventh of the cold-start level and six-sevenths of the hot-start level.

2

FIGURE 1. TRiW3IENT TEST CELL INSTALLATION OF THE 1988 6V-9ZTA DDEC II ENGINE

1

400 600 800 1000, 1200 Time (seconds)

iz 0 / d-.-J , w u U’ / L-

ma-20 1

0 200 400 600 800 1000 1200 7me (seconds)

FIGURE 2. GRAPHIC REPRESENTATION OF THE HEAVY-DUTY TRANSIENT CYCLE

Emissions measured during this program included total hydrocarbons (THC), carbon monoxide (CO), oxides of nitrogen (NO,), and particulate matter (PM). Hydrocarbons were measured using continuous sampling techniques employing a heated flame ionization detector (HFID). CO and CO, were determined using proportional dilute gaseous samples analyzed using non-dispersive infrared (NDIR) instruments. NO, was measured continuously during the transient cycle via an NO, chemiluminescence instrument. In addition, particulate samples were collected and analyzed to determine total particulate mass and the soluble organic fraction @OF).

Total PM levels were determined by collecting particulate matter on a set of 9Omm Pallflex filters, which were weighed both before and after the transient test. Soluble organic fraction (SOF) was determined by analyzing particulate samples collected on 90mm filters. SOF analysis was conducted using a solvent comprised of a 30-70 mixture by volume of toluene and ethanol.

III. TEST RESULTS

A. Baseline, ECM. and Injection Timine Tests

Installation of the test engine in transient test Cell 11 was completed on August 30, 1994. Following initial startup and verification of the installation, the engine was torque- mapped and prepared for transient testing. It was tested first at standard timing with both the 2-D base fuel and B20. The new ECM was installed and tested with B20, but problems with the new program resulted in the new ECM being removed and the baseline ECM being reinstalled. The engine was then tested using B20 with injection timing retarded one degree.

Torque-map data for the baseline engine configuration is given in Table 1, along with the results from torque-maps generated using B20, the new ECM, and a one-degree injection timing retard. The initial torque-map indicated that maximum engine power was 283 hp, which is about five percent lower than the engine’s nominal power rating. Previous experience with this particular test engine during other NBB programs had demonstrated a similar power level, so this lower power level was deemed characteristic for this unit. Torque-map data for the baseline configuration, runs on B20, and the timing tests are illustrated in Figure 3. Transient test results for these test configurations are given in Table 2, and the corresponding composite emissions are also shown in Figure 4. Individual transient test results are included in Appendix B. Detailed sets of data for all tests that can be submitted to EPA for certification purposes are given in Appendix C.

Emission levels for the baseline engine with the base 2-D fuel indicated composite emissions were well within the 1988 EPA standards. In addition, test results were similar to those observed during previous test programs with this engine. Transient composite NO, and particulate levels were 8.5 g’hp-hr and 0.20 g/hp-hr respectively. Particulate compositions for the baseline, B20, and retarded timing tests are shown in Figure 5. SOF analysis of particulate filters from the baseline engine with 2-D fuel indicated that roughly 60 percent of the total particulates were soluble organics. This result again was similar to previous test data observed for this engine. Smoke test results are shown in Figure 6. Smoke emission levels for the baseline engine with 2-D fuel were also well below EPA standards for a 1988 engine.

After the baseline smoke test, the fuel was switched to B20, and the engine was torque-mapped and prepared for transient testing. The torque-map data indicated no measurable change in engine performance with B20, compared to the base 2-D fuel. Transient emissions testing indicated no significant change in composite HC and CO emissions. Composite NO, emissions with B20 were about 5 percent higher than with 2-D fuel, while total particulate emissions showed no sign&ant change. Analysis of the particulate filters from the baseline engine tests using 2-D and B20 indicated that a shift in the composition of the particulate emissions had occurred. The soluble organic fraction @OF) of the total particulate increased by about 15 percent with B20, while insolubles, primarily carbon soot, were decreased by 26 percent with B20, compared to 2-D fuel. The net effect of these two offsetting changes in particulate composition was a negligible change in total particulates. Smoke test results also indicated a small decrease in opacity levels when B20 was used in place of 2-D.

TABLE 1. TRANSIENT TORQUE-MAP DATA FOR BASELINE, ECM, AND TIMING TESTS

, :

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7

TABLE 2. TRANSIENT EMISSIONS RESULTS FOR BASELINE, ECM, AND TIMING TESTS

EL-ZD-Cl 1 2-D 1 Baseline 1 0.57 1 1.91 I 8.18 I 0.21 0.467 20.0 58

BL-2D-H4 2-D Baseline 0.62 1.56 8.50 0.20 0.449 20.1

Composite 1 2-D ( Baseline 11 0.60 1.60 1 8.52 0.20 0.452 1 20.1

BL-2D-Sl 2-D Baseline

EL-B20-Cl 1 820 1 Baseline 11 0.49 1 1.65 ( 8.69 I 0.21 I 0.475 ( 20.1 1 70

0.55 1.36 8.84 0.20 0.451 20.1 71

0.51 1.35 9.10 0.20 0.455 20.1 71

0.54 1.33 8.96 0.20 0.456 20.1 70

0.53 1.39 8.93 0.20 0.457 20.1 71

BL201-Cl 820 Baseline 0.50 1.77 8.03 0.22 0.484 20.0 59

BL201-Hl I 820 I Baseline II 0.56 I 1.56 I 8.22 I 0.21 I 0.467 1 19.8 1 65

BL201-H2 820 Baseline 0.56 1.47 8.16 0.21 0.467 19.7 68

BEOl-H3 I 820 I Baseline II 0.61 I 1.46 I 8.24 I 0.21 1 0.496 1 19.8 ) 69

Composite 820 Basellne 0.55 1.59 8.20 0.21 0.489 19.8 64

BL201-Sl 1 820 1 Baseline

Smoke Ooacitv. % .

A 1 B C

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An attempt was made to alter the timing curve of the engine in order to eliminate the 5 percent NO, increase, without increasing particulate emissions. This was done using a new DDEC II ECM which had been programmed by DDC according to NBB specifications. When the new ECM was installed, a dramatic change was seen in engine performance. Figure 3 shows a relatively large increase in power during the torque-map with the new ECM. This was not expected because the timing change requested by NBB was a timing retard on the order of one degree of camshaft rotation, which should not have caused such a power increase. SwRI confirmed that the proper ECM was installed, and NBB requested that planned test work continue.

Transient emissions testing was conducted with the new ECM using B20 fuel. Composite NO, emissions were only 4.5 g/hp-hr, while particulates increased to 0.27 g/hp-hr. CO emissions also increased significantly, to 1.9 $hp-hr. The engine also suffered a ten (10) percent loss in fuel economy. These results indicated that the new ECM may not have been properly programmed for this particular engine model and year. Further investigation with both DDC and FMD revealed that the ECM had been mistakenly programmed at DDC for a 1991 model year engine, rather than 1988 as requested. Even though the results generated with the new ECM cannot be considered representative of a real application, they are included in this report for completeness. SOF analysis was not performed on particulate filters from this configuration.

Following consultation with DDC, NBB elected to continue testing with the original ECM, and to achieve the desired one degree injection timing retard by another means. The baseline ECM was reinstalled, and the timing retard was accomplished by physically moving the camshaft timing sensor 0.061 inches in the direction of camshaft rotation. This delayed the point at which the ECM recognized top-dead-center by one degree; and therefore, retarded injection timing by one degree. This modification produced a one-degree timing retard across the entire operating range of the engine. Following the timing change, the engine was torque-mapped and prepared for transient testing, still fueled on B20. As shown in Figure 3, the timing change produced no noticeable change in engine performance.

Transient test results from the engine with the one-degree timing retard and B20 fuel indicated that, compared to standard timing with B20 fuel, NO, decreased about eight percent, while total particulates increased five percent. Compared to the baseline test with 2-D fuel, NO, emissions were slightly lower, while totat particulates were slightly higher, and HC and CO emission levels with B20 fuel and retarded timing were very close to baseline levels. SOF analysis indicated that the increase in particulate observed when timing was retarded on degree with B20 fuel was due to an increase in the insoluble fraction, indicating a higher level of soot in the particulate. The SOF with B20 and the one-degree timing retard was similar to the level observed with B20 at standard timing. FTP smoke testing with B20 and retarded timing resulted in smoke levels nearly identical to levels obtained for baseline testing on 2-D.

B. Additive Screening Tests

After characterizing the effects of retarding the timing by one degree, the focus of testing shifted to evaluating additives for use with biodiesel blends. Injection timing was reset to baseline by returning the camshaft timing sensor to its original position. For this portion ofthe test program, only hot-start transient testing was conducted, with two hot-start tests run on each fuel. The two additives tested were both cetane improvers; 2-ethylhexyl

12

nitrate (EHN) and di-t-butyl peroxide (DTBP). Quantities of these cetane improvers were added to B20 as recommended by the manufacturers, individually to achieve a 10 cetane number increase over the cetane number of B20 alone.

C&me analysis of the blends indicated that while the EHN achieved an 11 cetane number increase over standard B20 at the recommended 0.5% treat level by volume, the DTBP achieved only a 6 number increase even at the higher recommended treat level of 0.7% by volume. Table 3 shows cetane analysis results for the various test fuels. The reason for the difference in cetane response is not clear at this time. It should be noted that the B20 fuel had a cetane number of 51, 5 numbers higher than the base 2-D fuel.

TABLE 3. CETANE ANALYSIS RESULTS

Fuel ( 2-D 1 Biodiesel 1 520 1 820 + EHN (0.5%) 1 820 + DTBP (0.7%) 1 ! / , , I

Cetane Number 46 60 51 62 57

Transient testing was conducted on the base 2-D fuel and the two cetane-improved B20 fuels within the same day to eliminate the effects of day-to-day variability. Torque-map data for these three fuels is given in Table 4 and shown in Figure 7. Hot-start transient results for the three fuels are given in Table 5 and illustrated in Figure 8.

Transient torque-maps on all three test fuels indicated no difference in engine performance between the two cetane-improved B20 fuels and the base 2-D fuel. Hot-start emission results for both the EHN- and DTBP-additized fuels indicated no change in particulate emissions compared to 2-D fuel, while NO, increased approtimately seven percent. HC was not affected significantly, while CO decreased slightly with both cetane improvers in B20. Particulate composition for all three fuels is given in Figure 9. Both cetane-improved B20 fuels had a lower level of insolubles than the 2-D fuel, but a higher SOF level, resulting in no net change in total particulates. Overall, the changes noted for the cetane-improved B20 fuels versus 2-D fuel were nearly identical to changes noted when comparing emissions with B20 to emissions with 2-D. Therefore, it appears that neither cetane improver in B20 provided any significant reduction in exhaust emissions from this engine.

C. Testing with Catalvst

After examining the effect of two cetane improvers in B20, the program focused on using a catalytic converter along with B20 fuel to reduce exhaust emissions. A diesel oxidation catalyst was supplied by Engelhard. The catalyst had been aged as part of the previous work performed by SwRI on behalf of Engelhard. After the exhaust system was modified to accommodate the catalyst, the engine was torque-mapped and prepared for transient testing. Testing with catalyst was conducted at standard timing on B20 fuel, and with a one-degree timing retard using both B20 and 2-D base fuel. Transient torque-map data for all testing with the catalyst is given in Table 6 and illustrated in Figure 10. These torque-maps indicated that the catalyst did not have any sign&ant effect on engine performance. Transient test results for all tests conducted with the catalyst are given in Table 7.

13

TABLE 4. TRANSIENT TORQUE-MAPS FOR ADDITIVE SCREENING TESTS

14

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15

TABLE 5. TRANSIENT EMISSIONS RESULTS FOR ADDITIVE SCREENING TESTS

Test Test Number Fuel Additive

‘*

m

Average 820 EHN

Transient Emlsslons, g/hphr

HC co NO, PM BSFC,

lblhphr

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(trH-dH/9>) S3lb-ln3lltl~d

._.....____..

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17

Jo \ \ \ \

TABLE 6. TRANSIENT TORQUE-MAPS FOR TESTS WITH CATALYST

II Mau No. I 8 I 9 I 10 II Fuel 620 820 2-D

I Injection Timing

Speed, rpm

Standard 1” Retard 1 a Retard

/I 700 600 I 581 588 598 613 594 627

II 800 I 685 I 725 t 748 II 900 776 836 a40

1000 a34 a53 a49

1100 a43 863 862

1200 a53 865 855

1300 a50 a57 852

II 1400 a48 862 a58 II

II II

1500

1600 1

a42

902 I

a73

a24 I

863 1

a42 II

1700 795 796 791

1800 773 769 776

II 1900 I 744 I 741 I 755 II 2000 727 727 738

2100 707 716 714

II 2200 I 206 1 209 I 210 II

/I Reference Work, hwhr I 20.5 20.7 20.8

19

20

TABLE 7. TRANSIENT EMISSIONS RESUTLS FOR TESTS WITH CATALYST

For the initial test with catalyst, the engine was left at standard timing, and B20 fuel was used. Figure 11 shows composite transient emissions for B20 fuel with a catalyst. Then baseline 2-D emission levels are also shown for comparison purposes. At standard timing with B20 fuel and a catalyst, HC, CO, and particuiates were reduced by 65, 41, and 46 percent, respectively, relative to the baseline 2-D configuration. NO, emissions increased by seven (7) percent. Particulate composition for tests with B20 and catalyst is given in Figure 12. Insoluble particulates were reduced with the B20 fuel, and SOF was decreased significantiy due to the catalyst.

Catalyst data released by Engelhard indicate that the catalyst alone on 2-D fuel could be expected to reduce particulate3 by about 30 percent. The combination of B20 and the catalyst appeared to be more effective in reducing total particulates than either of the elements separately. It is likely that the B20 caused a shif? in particulate composition toward higher SOF, which is the portion of the total particulate that an oxidation catalyst is most effective in reducing. Figure 13 shows FTP smoke test results. With B20 and a catalyst, the smoke ievels were essentially the same as those observed during the baseline 2-D tests.

Testing with catalyst and B20 fuel was also conducted with injection timing retarded one degree. This timing retard was accomplished in the same manner as described previously (i.e., moving the camshaft timing sensor), and was intended to offset the NO, increase observed when moving from base 2-D fuel to B20. As before, engine performance appeared unaffected by the timing retard. Transient test results indicated that, compared to the same B20 fuel at standard timing with a catalyst, X0, was reduced by seven (7) percent, while particulates and HC were slightly higher. NO, with B20, retarded timing, and a catalyst was nearly identical tn the original 2-D baseline level. HC, CO, and particulates were 59,34, and 41 percent lower than the 2-D baseline respectively. SOF analysis indicated an increase in insoluble particulate emissions associated with the timing retard. WP smoke emissions were also slightly higher at the retarded timing. The 41 percent reduction in particulates with the catalyst and B20 was better than the 30 percent reduction the catalyst would be expected to achieve from the baseline 2-D level.

.4 final test was run using 2-D fuel with retarded timing and with the catalyst in place. This test was run in order to ensure that exhaust emissions would not be increased over baseline levels if this engine configuration were “misfueled” with 2-D fuel, instead of B20. Engine performance over the transient torque-map on 2-D was not significantly different from performance on B20. Figure 14 compares composite emission results with 2-D fuel, the timing change, and a catalyst, to the baseline 2-D levels. HC, CO, and particulate levels were reduced by 51, 24, and 32 percent, respectively, with the catalyst and retarded timing compared to then levels for 2-D in baseline configuration. NO, was also slightly lower due to the retarded timing. The smaller amount of particulate reduction achieved with the catalyst on 2-D fuel was probably due to the smaller fraction of SOF percent in the engine-out total particulates with 2-D fuel. As shown in Figure 11, the insoluble fraction with 2-D fuel was higher than with B20, given the same injection timing and aftertreatment. FTP smoke levels on 2-D were similar to those observed with B20 fuel in the same configuration, although “peak” (C factor) smoke was slightly lower and “lugging” (B factor) smoke was higher.

Following the conclusion of this final test, engine timing was reset to baseline, and the engine was removed from the test cell.

22

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2-D 820 + CAT ’ EVO+RETARDtCAT’ 2-D+RETARD+CAT

CONFIGURATION

FIGURE 12. COMPOSITE TRANSIENT PARTICULATE COMPOSITION FOR TESTS WITH CATALYST

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...........................

...........................

... .._..........._ .........

HC co NOx PM ’ POLLUTANT

FIGURE 14. COMPARISON OF COMPOSITE TRANSIENT EMISSIONS BASELINE 2-D VERSUS 2-D WITH TIMING RETARD AND CATALYST

IV. SUhlMARY AND CONCLUSIONS

Several biodiesel blends were tested in a DDC 6V-92TA DDEC II diesel bus engine, including B20 (a 20 percent blend in 2-D base fuel), and two B20 blends with cetane improvers. A variety of engine and aftertreatment configurations were also tested with biodiesel, including a new ECM, a timing retard, and a diesel oxidation catalyst. Emissions of HC, CO, SO,, particulates, and SOF were measured over the EPA heavy-duty transient cycle in an effort to determine if B20 in combination with a retard of timing, or cetane improver, or catalyst, could reduce the exhaust emissions of the engine.

The use of B20 was examined both with and without an injection timing change. Without timing retard, the B20 fuel caused a reduction in composite CO and HC emissions, but increased NO, slightly. Total particulate emissions did not change when B20 was used, but the total particulate characteristics were altered to have a higher percentage of SOF, and lower insolubles (less soot). No differences in engine performance were observed when B20 fuel was used instead of 2-D. When injection timing was retarded one degree, the NO, emission increase due to change from 2-D to B20 was controlled; but the CO and HC benefits of the fuel substitution were eliminated, and total particulate emissions increased slightly due to an increase in insoluble particulate emissions associated with retarding the timing.

Aa an alternative to retarding the timing, the use of two different cetane improvers was examined as a possible means of controlling the observed NO, increase while preserving the benefits observed for other emissions when B20 was substituted for 2-D. Both a nitrate- based additive (EHN) and a peroxide-based material (DTBP) were used. However, neither cetane improver had a significant effect on any of the transient emissions from the engine.

The use of a catalyst in conjunction with B20 was also investigated to determine ifthe combination might provide a greater benefit in terms of emission reductions than either the catalyst or B20 alone. This was examined both with and without a one-degree timing retard. Results indicated that particulate reductions with B20 and a catalyst were larger than reductions reported for the catalyst alone using 2-D. When B20 is used, total particulate contains a higher fraction of SOF and lower fraction of insolubles relative to when 2-D fuel is used. Compared to emissions with 2-D, particulate reductions for B20 with the catalyst were 46 percent at standard timing, and 41 percent when one degree of timing retard was used to control NO, to baseline 2-D levels.

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