The effects of ethanol-gasoline blends on combustion and performance in a DI-HCCI engine

In this study, the effects of two stage direct injection (TSDI) strategy were investigated on the combustion and performance of an engine fueled with ethanol-gasoline blends. A diesel engine was converted to an electronically controlled HCCI engine. For each injection the injection timings and fuel quantity were adjusted to get desired mixture formation in the cylinder. The first injections were selected to be during the intake stroke and second injections were at the end of the compression stroke by using different injection ratios. Three different fuels (gasoline, E10 and E20) were used at the same energy input and constant engine speed conditions. The results showed that the maximum pressure rise rate (MPRR) increased with earlier start of first injection (SOI₂) timing by using ethanol-gasoline blends. It was found that start of second injection (SOI₂) timing has strong effects on the HCCI combustion and performance parameters when compared to the SOI₁ timing although injection ratio (IR) and fuel blends were changed. The maximum cylinder gas pressure (P_max), indicate mean effective pressure (imep) and thermal efficiency can be directly controlled by using the SOI₂ timing at high and low equivalence ratio conditions. It was observed that the operating ranges of the ethanol-gasoline fuel blends were extended, as the MPRRs of these blends were decreased with the use of optimum injection parameters at high equivalence ratio.