Theory study of exhaust heat recovery by pneumatic and internal combustion combined cycle

In order to improve the efficiency of internal combustion engine,a method of engine exhaust heat recovery through combined pneumatic and internal combustion cycle was proposed.This method used the mixture of exhaust gas and compressed air as working fluid of the pneumatic cycle.The mathematical model of combined cycle working process was built,and the it was used to analyze the influence of the main parameters on the combined cycle performance.The preliminary results show that increasing of the exhaust pressure of internal combustion engine,decreasing of the compressed air proportion,decreasing of the pneumatic engine rotation speed and the stroke/diameter ratio can lead to high exhaust heat recovery rate and high efficiency of combined cycle.The combined cycle can match the working fluid flow rates of the pneumatic cycle and the mixture gas through the regulation of the pneumatic engine rotation speed or the compressed air proportion.