Effects of Fuel Injection Parameters on Low Temperature Diesel Combustion Stability 2010-01-0611
Low temperature diesel combustion (LTC) exhibits ultra low NOx and smoke emissions, but currently it has the problems of increased CO and THC emissions, and higher combustion instability compared to conventional diesel combustion. This study evaluated the effects of fuel injection parameters on combustion stability in a single cylinder research diesel engine running at low and intermediate speeds and loads under LTC operating conditions. The LTC operation was achieved using high rates of EGR.
In this work, the fuel injection timing and injection pressure were varied to investigate their effects on combustion stability at fixed engine speed and total fuel quantity. The cylinder pressure and THC emissions were measured during the tests. The THC emissions and the coefficient of variability of IMEP (CoV(IMEP)) were used to assess combustion stability. The relationship between these two parameters was also evaluated.
Changes to the fuel injection parameters influenced combustion stability and the associated THC emissions. Early injections were considered leading to fuel impingement, which was exacerbated by higher injection pressures. At low loads, combustion stability and THC emissions appeared to be correlated, indicating that unstable combustion was leading to increases in unburned fuel. For the intermediate load conditions, the CoV(IMEP) was low and relatively insensitive to the fuel injection process. However, THC emissions were high and were significantly affected by the changes of the fuel injection parameters.