Study on the combustion characteristics and ignition limits of the methane homogeneous charge compression ignition with hydrogen addition in micro-power devices

Based on the single process of free piston in micro HCCI free piston power device, the parameters such as the combustion characteristics of methane hydrogenation homogeneous charge compression ignition, the free piston movement process, the ignition time of the mixture gas, the changes of temperature and pressure in micro-combustion chamber, and the power capability of the device are compared and analyzed by combining the experiment method with the numerical simulation method. The experimental results are basically consistent with the numerical results. The research shows: when the initial equivalence ratio is 0.5, the blending of hydrogen can widen the ignition limit of mixed fuel, advance the ignition time of the mixture gas and reduce the starting energy needed for the device. At the same time, adding hydrogen to methane will reduce the maximum temperature and the maximum pressure of the micro-combustion chamber, make the burning flame more stable and alleviate the detonation phenomenon of the combustion of mixture gas. However, the addition of hydrogen to methane will result in the decrease of the final speed of the free piston, the increase of the time required for a single stroke, the decrease of the power capacity of the device, and the indicator thermal efficiency is also reduced. Only the proper hydrogen blending ratio can be used to expand the combustion boundary and improve the reliability of the combustion process while ensuring the capability of the micro power device.