Exergy Analysis of Ideal Thermodynamic Cycle for the Four Stroke Free Piston Engine (FPE)

Abstract

A novel thermodynamic cycle of four-stroke free piston engine (FPE) is proposed in this presentation. Combining with lengthened expansion and exhaust stroke, the shortened intake stroke and compression stroke are supplemented with supercharger and intercooler. The thermodynamic cycle simulation of free piston engine is extended to perform the exergy analysis. In order to demonstrate the advantage of FPE, the results of FPE are compared with the conventional Otto cycle engine. Exergetic terms such as exergy transfer with work, exergy transfer with heat, irreversibility, fuel chemical exergy and total exergy of the cycle, are computed based on principles of the second law. Exergy analysis shows that compression ratio and expansion ratio have considerably affected the second law efficiency. With the increasing of compression ratio, supercharge ratio and expansion ratio, the second-law efficiency is remarkably increased. Furthermore, under the same compression end pressure, the larger supercharge ratio is more favorable than the larger compression ratio, because it can not only increase the exergy efficiency, but also improve the output power.