Study on methane HCCI combustion process of micro free-piston power device

Modeling studies were performed to investigate the methane homogenous charge compression ignition (HCCI) of micro free-piston power device. To ensure the success of combustion in micro power device, mixture gas should be compressed ignition by free-piston with certain amount of initial kinetic energy in the starting phase. Through the modeling studies of methane compression ignition process, a mathematical formula was deduced to predict the critical initial kinetic energy value. Simulation results reveal that a critical initial kinetic energy exists, and the homogeneous gas could not be compressed ignition until the piston obtains more energy than the critical initial kinetic energy. The critical initial kinetic energy is affected by micro-combustor geometric parameters, equivalence ratio and leakage. More important, the formula can be used to guide the design of micro free-piston power device.