Numerical investigation of the impact of dual spark plug coordinated ignition strategy on the combustion process in a free piston engine generator

The unique motion profile of Free Piston Engine Generators (FPEG) results in a brief dwell period at the top dead centre (TDC). Effectively achieving swift combustion within the cylinder during this limited interval is an urgent challenge that needs to be solved. In this study, a three-dimensional simulation model of FPEG was established and the model underwent calibration utilizing experiment data. Subsequently investigating the impacts of varying ignition positions, distinct spark plug spacing, and distribution on the combustion of the FPEG when subjected to the dual spark plug ignition configuration. The research results show that with the advancement of the ignition position, the maximum combustion duration of the dual spark plug FPEG was shortened by 34 %. With a reasonable spark plug spacing, the dual spark plug FPEG could shorten the flame propagation distance, which is conducive to the realization of constant volume combustion. When the dual spark plugs were arranged on both sides of the auxiliary intake port, the peak pressure in the cylinder could reach up to 49.5 bar. When the dual spark plugs were arranged in the main intake port and the auxiliary intake port, the indicated thermal efficiency reached 34.7 %.