Characterization of exhaust emissions from palm oil-based and soybean oil-based biodiesel fueled heavy-duty transit buses

Abstract

Characterization of Exhaust Emissions from Palm Oil-Based and Soybean Oil-Based Biodiesel Fueled Heavy-duty Transit Buses Trampas Jay Efaw Biodiesel blends offer a renewable energy fueling option for compression-ignition internal combustion engines. Typically, biodiesel blended at or less than 20% (B20), by volume, will exhibit substantial reductions in diesel particulate matter (PM), while not significantly impacting oxides of nitrogen (NO X) emissions. Additionally, operation on biodiesel blended at B20 levels or less has not been associated with substantial fuel economy penalties. A study was conducted, wherein two transit buses were utilized to quantify the emissions and performance effects associated with the use of biodiesel fuels, derived from palm oil and soybean oil. Evaluation of the two fuels was accomplished through chassis dynamometer, using West Virginia University"s Transportable Heavy-Duty Vehicle Emissions Testing Laboratory (THDVETL) as well as on-board, in-use testing, using WVU"s Mobile Emissions Measurement System (MEMS). Performance, fuel economy, and emissions data were collected from both test vehicles, while they were each operated on three candidate fuelsultra-low sulfur diesel (ULSD-baseline), soybean oil-based B20 biodiesel, and palm oil-based B20 biodiesel. Two buses, unit 04208, powered by a 2004 DDC Series 60 engine, and unit 05108, powered by a 2005 Cummins ISM engine, were utilized for the evaluation. Both vehicles were outfitted with exhaust oxidation catalysts, and the engines employed exhaust gas recirculation (EGR) as a NO X reduction strategy. Vehicle chassis dynamometer tests indicated that B20 blends exhibited 5-7% improvement in fuel economy, with similar vehicle-averaged reductions in fuel consumption realized for both biodiesel blends. NO X emissions measured from the tests for the Cummins bus were actually lower for B20 fuels than for the ULSD baseline fuel. NO X emissions recorded for the DDC bus were slightly higher for B20 biodiesel operation (1-2%). PM was reduced substantially (20-30%) for operation on both biodiesels for both vehicles, with slightly higher reductions in PM being realized for operation with palm oil-based B20. Hydrocarbon (HC) and Carbon Monoxide (CO) data were inconclusive due to the presence oxidation catalysts. During in-use vehicle evaluations, both biodiesel blends exhibited slight differences in fuel economy when compared to ULSD. An anomalous result for the DDC bus was reported, wherein fuel economy for the palm oil-based B20 was 20% improved over the ULSD baseline. However, brake-specific fuel consumption was consistent with other tests, indicating that much less work was performed by the vehicle during that particular instance of operation. Similar to the results obtained during vehicle chassis dynamometer evaluations, NO X emissions were actually reduced when operating with B20 blends for the Cummins bus, and only slightly increased for the DDC bus iii ACKNOWLEDGEMENTS First I would like to thank my committee members Dr. Ben Shade, Dr. Gr...