Effects of Ignition Timing and Compression Ratio on Performance of GDI Engines

The influence of different ignition timings and compression ratios on the combustion characteristics and performance of a gasoline direct injection GDI engine operating on gasoline and liquefied petroleum gas (LPG) fuels at a constant speed of 3000 rpm were numerically investigated. For this reason, a model was created and developed using the AVL Boost program (fully integrated IC engine simulation software). The results of this study showed that the effective power and effective torque were decreased for engines fueled with LPG compared to those of gasoline for all selected ignition timings. Also, brake specific fuel consumption was higher for LPG fuel than for gasoline fuel, but brake mean effective pressure, maximum cylinder pressure, and maximum cylinder temperature were higher for gasoline fuel than for LPG fuel. Increasing the compression ratios resulted in an increase in the effective power, effective torque, brake mean effective pressure, peak cylinder pressure, and peak cylinder temperature, but it also resulted in a decrease in the specific fuel consumption for both fuels.