Abstract: In order to increase the thermal efficiency of the existing gas engines, a new engine system with regenerator equipped with big & small air cylinders and big & small pistons is proposed by analyzing the characteristics of stirling engine and conventional engines. When gas in the small cylinder is compressed, water is sprayed into it to reduce compression consuming. After being preheated in the regenerator, the compressed gas enters into the big cylinder and mixes with the fuel that has been injected into the big cylinder, and then combusts and does work. After doing work, the gas releases heat in regenerator and is discharged into air. The performance prediction model of the new engine system is constructed on the basis of an in-depth analysis of the new engine system. With this mathematic model, the thermal-efficiency of the new engine system is calculated under the conditions of different compression ratios, different maximal working temperatures and different piston efficiency. Compared with the conventional otto cycle and diesel cycle under the same conditions, the new engine system has higher thermal efficiency, at most 20% higher than that of the conventional gas engines. Further more, the thermal efficiency of the new engine increases with the efficiency increasing of the regenerator, at most 10%.

Key words: Cylinder, New engine system, Piston, Stirling engine, Thermal circuit, Thermal efficiency