Quick Look
Preliminary Exhaust Gas
Recirculation Tests on a Mack E7G
Natural Gas Engine, 03-9321
Principal Investigator
James Chiu
Inclusive Dates: 05/31/02 - 09/30/02
Background - The Department of Energy's Office of Transportation Technology and Office of Heavy Vehicle Technologies are initiating the Next-Generation Natural Gas Vehicle Program to encourage the development of commercially viable medium- and heavy-duty natural gas vehicles. These new vehicles will incorporate advanced alternative fuel vehicle technologies and should meet future emissions standards of 0.27 gram/kilowatt-hour (g/kW-hr) or 0.2 gram/brake horsepower-hour (g/bhp-hr) for oxides of nitrogen (NOx) emissions. One alternative fuel technology utilizes chemically correct combustion (CCC) diluted with exhaust gas recirculation (EGR), combined with a three-way catalyst (TWC) for exhaust after treatment. Using this technology, team members conducted preliminary tests to determine if the resulting efficiency and emissions performance made the technology viable.
Approach - The objective of this project was to obtain efficiency and emissions data using CCC with high rates of EGR on a heavy-duty on-highway natural gas engine. The test engine was modified to operate at CCC with high rates of EGR. The engine calibration was modified to operate at the correct air/fuel ratio, and an external EGR system was connected to the engine. EGR was controlled manually by an EGR control valve. Then steady-state tests were conducted to determine efficiency and emissions with this technology. At each steady-state condition, operational data and engine out emissions were collected at various EGR rates and ignition timings.
Accomplishments - The engine was successfully operated using CCC with EGR. Steady-state data were collected to show that there was no efficiency penalty but, in some cases, an efficiency improvement compared to other low emissions natural gas engine technologies. The steady-state data points were also used to predict efficiency and emissions for the Environmental Protection Agency's transient emissions test cycle. Assumptions concerning the TWC efficiency were applied to the final results. As a result of this study, it was concluded that this technology results in increased efficiency as compared to current lean burn technology at the low 0.27 g/kW-hr (0.2 g/bhp-hr) NOx emissions levels and should be able to meet future emissions requirements. In addition, a transient acceleration test was conducted to show that the simple EGR system used on this engine could also be used in a vehicle.
