Effects of heat transfer and variable specific heats of working fluid on performance of a Miller cycle

The performance of an air-standard Miller cycle with heat transfer loss and variable specific heats of working fluid is analysed by using finite-time thermodynamics. The relationships between the work output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between work output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of heat transfer loss and variable specific heats of working fluid on the cycle performance are analysed. The results show that the effects of heat transfer loss and variable specific heats of working fluid on the cycle performance are obvious, and they should be considered in practice for cycle analysis. The results obtained herein may provide guidance for the design of practical internal combustion engines.