1995-09-01

Pressure Modulated Injection and Its Effect on Combustion and Emissions of a HD Diesel Engine 952059

The paper describes the concept selection, design and performance of a fuel injection equipment (FIE) which provides high flexibility in shaping the injection rate. With this injection system standard and boot shaped injection rates as well as pilot injections and post injections can be achieved throughout the hole speed and load range. Special emphasis was drawn to realize boot rate shaping by pressure modulation rather than by throttling the fuel flow (i.e.: the system is operated with fully opened needle during the whole injection period and no throttling device limits the fuel flow in front of the nozzle to reduce the injection rate).Initial engine tests on a single cylinder research engine with 2 liter displacement were carried out at one operating point (1000 rpm, 200 mm3/str = 75% of full load fueling). Boot and pilot (split) injection rate shaping strategies are compared to a standard injection without rate shaping. At constant smoke and BSFC the boot injection shows a considerable improvement potential in NOx emissions of up to -14%, or NOx and BSFC can be reduced simultaneously by -9% and -7 respectively. The results with pilot injection are less promising than the results with boot injection. Furthermore, they are sensitive to pilot timing and to injection pressure as well as fueling during pilot injection.

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