In-cylinder Emissions Reduction Technologies in a
Inclusive Dates: 10/01/01 - Current
Background - Meeting the upcoming U.S.
Environmental Protection Agency 2007 emissions standards is a significant
challenge for the diesel industry and will likely require the use of expensive
exhaust treatment devices. In general, the cost of an exhaust treatment device
is directly proportional to its emission-reduction performance. In-cylinder
emissions reduction methods can be used to reduce greatly the required
performance from the exhaust treatment device. The focus of this program is
reducing NOx emissions using an in-cylinder method called partial
premixed charge compression ignition (PCCI).
Approach - The primary objective of this project is to explore the reduction potential of NOx emissions in a light-duty diesel engine operating under various levels of PCCI. A secondary objective is to develop a better understanding of the processes and limits of PCCI. The PCCI mode of combustion is obtained by injecting a portion of the fuel charge early in the cycle, which is often referred to as a pilot injection, to allow additional time for fuel/air mixing prior to the main fuel injection and combustion event. The test engine for this project has a common rail fuel system that is externally controlled, giving flexible pilot and main injection timing and quantity control. The effects of pilot timing, quantity, and number of injections on engine-out emissions and performance are being studied.
Accomplishments - Tests with a single pilot injection have been performed with five different operating conditions. Pilot timing and quantity were varied during these tests. The results indicated a slight to moderate NOx reduction (up to 35 percent NOx reduction) compared to the baseline engine for most of the conditions. The effects of pilot quantity and start of injection (SOI) on NOx emissions are shown for a medium-speed, light-load test condition (mode 3). The effects of multiple pilot injections will be studied in the next set of experiments.