Numerical Investigation of the Impact of Fuel Injection Strategies on Combustion and Performance of a Gasoline Compression Ignition Engine

Gasoline compression ignition is a promising strategy to achieve high thermal efficiency and low emissions with limited modifications to the conventional diesel engine hardware. It is a partially premixed concept which derives its superiority from higher volatility and longer ignition delay of gasoline-like fuels combined with higher compression ratio typical of diesel engines. The present study investigates the combustion process in a gasoline compression ignition engine using computational fluid dynamics. Simulations are carried out on a single cylinder of a multi cylinder heavy-duty compression ignition engine which operates at a compression ratio of 17:1 and an engine speed of 1038 rev/min. In this study, a late fuel injection strategy is used because it is less sensitive to combustion kinetics compared to early injection strategies, which in turn is a better choice to assess the performance of the spray model. Three different injection strategies viz., Pilot-Main-Post, Pilot-Main and Main-Post, are investigated to understand their impact on combustion and performance of the engine. RNG k-ε model is used to describe in-cylinder turbulence and KH RT model is used to simulate the fuel spray breakup. Simulation results with two chemical mechanisms are assessed and compared to experimental data. Overall, the simulation results are found to be in good agreement with the experimental data, both for different injection strategies and varying start of fuel injections. Numerical results are then used to carry out an in-depth investigation of combustion process for different injection strategies and thermal efficiency of the gasoline compression ignition engine.