Steady-State Emissions Test on a Heavy-Duty On-Highway Class 8 Gasoline Engine, 03-9457Printer Friendly Version
Inclusive Dates: 01/13/04 - 05/13/04
Background - As with all sources of air pollution, cleaner emissions will be required in the future for heavy-duty on-highway truck engines. These future emission regulations could affect the selection of the most cost-effective powertrain system. The current choice for heavy-duty applications is the diesel engine. In the future, the initial and operating costs of the diesel engine are expected to increase. An alternative to the diesel engine is the spark-ignited engine. Currently spark-ignited engines typically have lower power densities and lower efficiencies than diesel engines, but spark-ignited engines can have significantly lower emissions than diesels. In the future where cleaner emissions will be required, the increasing costs to operate a diesel engine may make the spark-ignited engine an economically viable option to the diesel engine. A demonstration of a low-emissions spark-ignited engine was conducted on an emissions Mack E7G engine fueled with natural gas. The low-emissions E7G engine operates at stoichiometry and uses a three-way catalyst to achieve low emissions. It also uses high rates of exhaust gas recirculation, not only at partial loads but also at full load, to improve efficiency, lower combustion chamber temperatures, reduce engine-out NOx emissions, and reduce the tendency to knock. The low-emissions E7G engine meets the year 2010 emissions standards for all regulated emissions with the exception of particulate matter (although it is expected that particulate matter emissions will also meet the 2010 standard with minor engine control programming).
Approach - The objective of this project was to obtain efficiency and emissions data over the 13-mode steady-state emissions test on a low-emissions, heavy-duty, on-highway, class 8 engine operating on a spark-ignited engine fueled with gasoline. To demonstrate this, the low-emissions Mack E7G natural gas-fueled engine was converted to operate on gasoline. The conversion of the engine involved replacing the natural gas fuel system with a gasoline fuel system.
Accomplishments - The Mack E7G engine was converted to run on gasoline, and a 13-mode steady-state test was attempted. Although several practice 13-mode tests were conducted, the engine began to severely knock on mode 8 of the actual test. Only results from the first seven modes are reportable. The results showed significantly lower emissions on a stoichiometric, gasoline-fueled, heavy-duty engine compared to current diesel engines. High power and high efficiencies (for a gasoline engine) should also be possible. Partial-load efficiencies are still lower than a diesel engine, but new technologies such as variable valve actuation should reduce the differences.