A free-piston engine generator (FPEG) is a new type of energy converter, which eliminates the crankshaft and connecting rod\nmechanism. In order to achieve efficient energy conversion, the two-stroke thermodynamic performance optimization of a single cylinder\nfree-piston engine generator is investigated in this paper. Firstly, the components, four-stroke thermodynamic cycle, two stroke\nthermodynamic cycle, and prototype system of the FPEG are presented in detail. The one-dimensional flow simulation\nmodel of the FPEG is created based on the gas dynamics equation, Weber combustion function, and heat transfer function, and\nthen the model is validated by the data tested from the prototype system. According to the four-stroke experimental results of the\nFPEG, an effective power of 4.75kW and a peak pressure of 21.02 bar have been obtained. Then, the two-stroke thermodynamic\ncycle is simulated and compared under the different control parameters of intake air pressure, injection timing, ignition timing,\nand valve timing through the simulation model. The optimized results show that an indicated thermal efficiency of 27.6%, an\nindicated power of 6.7 kW, and a maximal working frequency of 25 Hz can be achieved by the prototype system, when the two stroke\nthermodynamic cycle is used.
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