Biodiesel, the mono alkyl ester of long chain fatty acids derived from renewable lipid resources was evaluated for use as a blending agent with with low sulfur petroleum diesel fuel. Blending with heavy alkylates were also investigated. The engine selected was a L10E Cummins diesel engine. The regulated EPA exhaust emission of the engine were evaluated before and after changing the injection timing of the engine. EPA exhaust emissions were also evaluated after increasing the concentration of biodiesel and heavy alkylate while reducing the low sulfur diesel fuel used when fueling the engine. In general, the engine performed well and power changed very little during the testing. All EPA regulated emissions were reduced below that observed when fueling with baseline low sulfur diesel fuel as a result of timing changes and/or fueling with heavy alkylate blends.
INTRODUCTION
Biodiesel is a domestically produced renewable fuel that can be an option for strengthening United States energy security by reducing dependence on imported oil (1). The use of vegetable oil as a fuel for the compression ignition engine is not a new idea. Rudolph Diesel used peanut oil to fuel the diesel engine during the late 1800s. Petroleum based diesel fuel has been the fuel of choice for the diesel engine for many years. However, methyl esters of animal and vegetable oils (biodiesel) are again being re-evaluated for use as a fuel for modern diesel engines due to their cleaner burning tendencies, other environmental benefits, and energy security reasons.
Heavy alkylate is a by-product of the alkylation process used in most modern refineries to create isooctane, a high octane, clean burning component for gasoline. In the future, reformulated gasolines will be required to have reduced levels of higher boiling components. The use of high boiling heavy alkylate with biodiesel/petroleum diesel blends could serve to relieve a potential problem for petroleum refineries.
PURPOSE AND OBJECTIVES
The purpose of this study was to compare biodiesel (transesterified soybean oil) and biodiesel/heavy alkylate blends with conventional petroleum diesel fuel (petrodiesel) when fueling a Cummins L10E. Specifically, the National Biodiesel Board sponsored a research effort at BDM-Oklahoma (NIPER) to measure and compare: 1) regulated EPA exhaust emissions 2) engine performance and 3) two NOX reducing strategies (timing retard and use of heavy alkylate).
METHODS
A Cummins L10E (electronic control) engine was tested using an engine dynamometer under transient conditions at the Department of Mechanical and Aerospace Engineering at West Virginia University. This is a 1991 emissions certified engine.
The engine was a 1992 Cummins L10E, four-stroke, turbocharged, six-cylinder engine of in-line configuration. This direct injection engine has a 10 liter displacement and is rated at 280 horsepower at 2000 rpm with a peak torque of 900 lb-ft at 1200 rpm. The engine electronic control module (ECM) used when testing at standard injection timing was a standard control module used with the Cummins L10E engine. A different ECM was re-programmed by Cummins Engine Company to determine EPA regulated exhaust emissions when the injection timing of the engine was retarded by 3o.
EPA regulated emissions, oxides of nitrogen (NOx), total hydrocarbons (THC), carbon monoxide (CO), and particulate matter (PM) were recorded using CFR 40 Federal Test Procedures (FTP). FTPs and smoke tests were conducted for different configurations of fuel, engine, and exhaust after treatment conditions. Variables such as air and fuel temperature and relative humidity were carefully monitored and controlled. Three hot starts (at 6/7 weighting) and one cold start (at 1/7 weighting) were measured using the following fuels:
DF = conventional low sulfur 2D petroleum diesel fuelB20 = a blend of 20% biodiesel with 80% DF B20A20 = a blend of 20% biodiesel and 20% heavy alkylate with 60% DF B30A15 = a blend of 30% biodiesel and 15% heavy alkylate with 55% DFA 30% biodiesel/ 70% DF blend (B30) was also used to fuel the engine. However, the B30 testing only consisted of three hot starts since this test was added late in the testing program. The chemical composition of the base fuels can be found in Table 1.
Table 1. Chemical Properties of Biodiesel and Reference Diesel fuel.
| Fuel | |||
| Chemical Property | Low Sulfur Reference Diesel Fuel | Biodiesel | Heavy Alkylate |
| Specific Gravity, g/ml | 0.850 | 0.887 | 0.755 |
| Sulfur, ppmw | 434 | 6 | 6 |
| Flash point,0C | 76 | 164 | 40 |
| Pour point,0C | -24 | ND | ND |
| Cloud point,0C | -13 | 6 | <-51 |
| Viscosity, cst 40 0C | 2.6 | 4.2 | 1.3 |
| Distillation, 0C IBP 10% 20% 50% 90% EBP | 173 226 238 267 316 344 | 264* 332 333 335 337 350* | 120 162 167 178 209 265 |
| Hydrocarbon Type Vol. %, FIA Aromatics Oelfins Saturates |
33 1 66 |
ND** ND** ND** |
6 1 93 |
| Cetane No. | 44 | 67 | 38 |
** = Not Determined, ASTM test method invalid for biodiesel
ND = Not Determined for this testing
At each change of fuel, the fuel filter was changed and the fuel lines were drained. The engine was warmed on the new fuel to purge any of the remaining previous test fuel from the engine's fuel system. The engine was then torque-mapped and prepared for transient testing. Although a torque-map was run at each fuel change to evaluate engine performance, all testing was run using a transient cycle generated from the first torque-map that was conducted using the base 2-D fuel on the first day of testing. This was done to minimize day-to-day variability and allow for better comparison between test fuels.
RESULTS
The results of the testing are in general agreement with biodiesel studies that have been conducted on other two and four stroke diesel engines (2,3,4,5,6,7). As the biodiesel blend concentration increased, the total hydrocarbons (THC), carbon monoxide (CO) and particulate matter (PM) declined while the oxides of nitrogen (NOx) emissions increased slightly. Each targeted EPA emission (NOx, HC, CO, & PM, as well as Opacity (Smoke)) are discussed and compared independently in the text that follows.
Power/Work Performed
Maximum power and peak torque were slightly affected by fuel and timing changes. The maximum changes from baseline occurred with the B20A20 blend which caused approximately 2% loss in maximum power and toque. The cycle work was reduced by about the same percentage for this fuel (Table 2).
Table 2. Cycle -work (Hp-hr) performed when fueling a Cummins L10E with biodiesel and biodiesel/heavy alkylate blends at West Virginia University (hot start data only).
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| Hp-hr @ Standard timing | 19.48 | 19.43 | 19.17 | 19.50 | 19.13 |
| % Change from DF . | N/A | -.02 | -1.6 | +0.1 | -1.8 |
Cycle-work (Hp-hr) comparison after changing timing.
| Engine Configuration | DF | B20 | % Change from DF |
| Hp-hr @ Standard timing | 19.48 | 19.43 | -0.02 |
| Hp-hr @ Retarded timing (3o) | 19.40 | -0.40 |
15) 15 percent, 20) 20 percent
Total Hydrocarbons
Each blend tested clearly reduced the THC emissions of the engine. The engine produced higher THC when fueled on alkylate and biodiesel blends when compared to the biodiesel blends alone. Retarding the timing provided no change in THC emissions. The data reported for standard timing, with the exception of the heavy alkalyte blends, more closely follows the data that has been reported previously in the literature (2,5).
Table 3. Total Hydrocarbon Emissions (g/HP-hr) produced when fueling a Cummins L10E with biodiesel and biodiesel/heavy alkylate blends at West Virginia University.
Full FTP conducted at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| THC, Std. timing | 0.27 | 0.25 | 0.25 | N/A | 0.24 |
| % Change from DF | N/A | -7.4 | -7.4 | N/A | -11.1 |
Averages from 3 hot starts at standard timing.
| Averages from 3 hot starts | DF | B20 | B20 A20 | B30 | B30 A15 |
| Standard timing | 0.27 | 0.25 | 0.26 | 0.23 | 0.24 |
| % Change from DF | N/A | -7.4 | -3.7 | -14.8 | -11.1 |
Full FTP at standard and retarded timing (3o ).
| Fuel | DF | B20 | |
| Timing | Std | Std | Re-tarded |
| grams/brake Hp-hour | 0.27 | 0.25 | 0.25 |
| % Change From DF | -7.4 | -7.4 | |
15) 15 percent, 20) 20 percent
Carbon Monoxide Emissions
The trends observed concerning CO when testing the engine clearly indicate that as the level of biodiesel in the blend increases, that CO levels emitted by the engine declines. The addition of the Alkylate to the biodiesel blend produced even greater CO emissions reductions. As noted in Table 4, CO reductions ranged from approximately 16 - 26 percent when fueling the unmodified L10E with biodiesel, biodiesel blends, and biodiesel-heavy alkylate blends.
Retarding the timing increased the CO emissions in comparison to the test results that were observed when operating at standard timing.
Table 4. Carbon monoxide emission s (g/HP-hr) produced when fueling a Cummins L10E biodiesel and biodiesel/heavy alkylate blends at West Virginia University.
Full FTP conducted at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| THC, Std. timing | 1.46 | 1.22 | 1.12 | N/A | 1.08 |
| % Change from DF . | N/A | -16.4 | -23.3 | N/A | -26.0 |
Averages from 3 hot starts at standard timing.
| Averages from 3 hot starts | DF | B20 | B20 A20 | B30 | B30 A15 |
| Standard timing | 1.43 | 1.22 | 1.11 | 1.11 | 1.06 |
| % Change from DF . | N/A | -14.7 | -22.4 | -22.4 | -25.9 |
Full FTP at standard and retarded timing (3o ).
| Fuel | DF | B20 | |
| Timing | Std | Std | Re-tarded |
| grams/brake Hp-hour | 1.46 | 1.22 | 1.23 |
| % Change From DF | -16.4 | -15.7 | |
DF ) Diesel Fuel, B) Biodiesel, A) Heavy Alkalyte
15) 15 percent, 20) 20 percent
Oxides of Nitrogen Emissions
Oxides of nitrogen emissions followed trends that are reported in the literature. As the concentration of biodiesel increased, the oxides of nitrogen emissions increased. An analysis of the data indicates that the B20A20 fuel blend effectively reduced the oxides of nitrogen emissions below that of baseline diesel fuel. As noted in Table 5, the increase in the oxides of nitrogen emissions while fueling the unmodified L10E with a 20 percent biodiesel blend was 3.7 percent. Retarding the timing was an effective way of reducing NOX emissions when fueling with the biodiesel blends.
Table 5. Oxides of Nitrogen emissions (g/HP-hr) produced when fueling a Cummins L10E with biodiesel and biodiesel/heavy alkylate blends at West Virginia University.
Full FTP conducted at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| NOX Std. timing | 5.01 | 5.17 | 4.97 | N/A | 5.12 |
| % Change from DF . | N/A | +3.2 | -0.7 | N/A | +2.2 |
Averages from 3 hot starts at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| Standard timing | 4.99 | 5.17 | 4.92 | 5.05 | 5.08 |
| % Change from DF . | N/A | +3.7 | -1.3 | +1.2 | +1.8 |
Full FTP at standard and retarded timing (3o ).
| Fuel | DF | B20 | |
| Timing | Std | Std | Retarded |
| grams/brake Hp-hour | 5.01 | 5.17 | 4.61 |
| % Change From DF | +3.2 | -7.9 | |
DF ) Diesel Fuel, B) Biodiesel, A) Heavy Alkalyte
15) 15 percent, 20) 20 percent
Particulate Matter Emissions
The PM reductions noted for biodiesel blends in unmodified engines follow those reported in the literature (2,3,4,5). Reductions in PM were noted when testing the engine when fueled with B20. The addition of the 20% heavy alkylate to the B20 blend further reduced the particulate matter emissions. However, the addition of 15% heavy alkylate with the B30 blend increased the particulate matter emissions (using hot start data). The reason for this is unclear and deserving of further study. As expected, retarding the timing with the B20 blend increased the particulate matter but still provided results that were below baseline diesel (-4.8%). As noted in Table 6, fueling an unmodified L10E with a B20 blend produced a 12-30 percent reduction in PM, depending on the blend that was tested.
Table 6. Particulate Matter emissions (g/HP-hr) produced when fueling a Cummins L10E with biodiesel and biodiesel/heavy alkylate blends at West Virginia University.
Full FTP conducted at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| Std timing | 0.105 | 0.092 | 0.078 | N/A | 0.073 |
| % Change from DF . | N/A | -12.4 | -25.7 | N/A | -30.4 |
Averages from 3 hot starts at standard timing.
| Fuel | DF | B20 | B20 A20 | B30 | B30 A15 |
| Std timing | 0.104 | 0.089 | 0.077 | 0.069 | 0.072 |
| % Change from DF . | N/A | -14.4 | -26.0 | -33.7 | -30.7 |
Full FTP at standard and retarded timing (3o ).
| Fuel | DF | B20 | |
| Timing | Std | Std | Re-tarded |
| grams/brake Hp-hour | 0.105 | 0.092 | 0.100 |
| % Change From DF | -12.4 | -4.8 | |
DF ) Diesel Fuel, B) Biodiesel, A) Heavy Alkalyte
15) 15 percent, 20) 20 percent
Opacity (Smoke)
Smoke levels with the B20 fuel were lower than with the base diesel fuel. This was consistent for the various combinations of injection timing and exhaust treatment for the B20 tests. It should be noted that the smoke levels were quite low in all tests, including the DF fuel. The current EPA emission standards for smoke are 20, 15 and 50 percent respectively for the acceleration mode, lugging mode, and peaks.
SUMMARY AND CONCLUSIONS
The results of the testing are in general agreement with biodiesel studies that have been conducted on other unmodified two and four stroke diesel engines. As the biodiesel blend concentration increased, the L10E produced lower levels of total hydrocarbons (THC), carbon monoxide (CO) and
Table 7. Smoke analysis when fueling a L10E Cummins with biodiesel and biodiesel/heavy alkylate blends at West Virginia University.
Full federal smoke test procedure.
| Fuel | DF | B20 | |
| Timing | Std | Std | Retarded (3o) |
| Smoke at Acceleration | 3.1 | 2.1 | 2.0 |
| Smoke at Lugging | 1.8 | 1.0 | 1.8 |
| Smoke at peak of either mode | 6.0 | 4.6 | 4.8 |
particulate matter (PM)(2,3,4,5,6). Specific conclusions that were drawn include:
1. As the concentration of the biodiesel blend increased , the L10E produced lower levels of total hydrocarbon (THC), carbon monoxide (C)), and particulate matter (PM) exhaust emissions. The oxides of nitrogen emissions (NOX ) increased.
2. The addition of 20% heavy alkylate to B20 provided reductions in CO, NOX, and PM. THC emissions were unchanged.
3. The L10E, while fueled with B20 or B30, produced power during the FTP that was nearly equal to that when it was fueled with baseline DF.
4. Oxides of nitrogen emissions on the L10E, when fueled with B20, can be successfully reduced below that of baseline DF by either retarding injection timing or replacing 20 percent of the DF of the B20 blend with heavy alkylate.
RECOMMENDATIONS
The following recommendations were made based on the findings of this investigation:
1. Further investigation concerning the adjustment of engine timing when fueling with biodiesel blends is warranted. Although one of the advantages of biodiesel is its ability to be used in unmodified diesel engines, a small timing change with B20 provided reductions for all EPA regulated emissions.
2. Further research is needed to determine the physical and chemical characteristic(s) of heavy alkylate that resulted in lower levels of NOX emissions when combined with the biodiesel/reference diesel blend.
3. Further research is needed to determine the effects of long term usage of heavy alkylate and its possible inclusion in the diesel fuel pool.
ACKNOWLEDGEMENTS
The L10E is a modern four stroke engine that is used to power transit buses in metropolitan areas across the United States (among other uses). The L10E engine was donated for testing purposes by Bi-State Development Agency, St. Louis, Missouri.
The base diesel fuel and the heavy alkylate were obtained from Phillips Petroleum Company. The biodiesel was secured from Midwest Biofuels of Overland Park, Kansas. The base diesel fuel was chemically analyzed by Phillips Petroleum Company. The biodiesel and heavy alkylate fuels were analyzed by NIPER. The fuels were blended volumetrically at West Virginia University.
REFERENCES
1. Morris, D. 1993. How Much Energy Does it take to Make a Gallon of Soydiesel? The Institute for Local Self-Reliance, Washington, D.C.
2. Borgelt, S.C., T. Kolb, and L.G. Schumacher. 1994. Biodiesel: World Status. In Proceedings of Liquid Fuels, Lubricants, and Additives from Biomass. 67-76. ASAE Publication 06-94. St. Joseph, MI: ASAE.
3. Callahan, T.J.. 1993. Evaluation of Methyl Soyate/Diesel Fuel Blends as a Fuel for Diesel Engines. Final Report Prepared for the American BioFuels Association by Southwest Research Institute. Jefferson City, MO: National Biodiesel Board.
4. Grabowski, M. 1994. Emissions from Biodiesel Blends and Neat Biodiesel From a 1991 Model Series 60 Engine Operating at High Altitude. Final Report Prepared for the National Renewable Energy Laboratory by the Colorado Institute for Fuels and High Altitude Engine Research. Jefferson City, MO: National Biodiesel Board.
5. Schumacher, L. G., S.C. Borgelt, & W.G. Hires. 1992. Fueling a Diesel Engine With Methyl Ester Soybean Oil. Proceedings of an Alternative Energy Conference. Nashville, TN: ASAE.
6. Schumacher, L. G. 1995. Biodiesel Emissions Data from Series 60 DDC Engines. 1995 American Public Transit Association Bus Operations and Technology Conference. Reno, NV.
7. Sharp, C.A. 1994. Transient Emissions Testing of Biodiesel and Other Additives in a DDC Series 60 Engine. Final Report Prepared for the National Biodiesel Board by Southwest Research Institute. Jefferson City, MO: National Biodiesel Board.