工质变比热条件下内燃机循环普适特性

用有限时间热力学的方法分析空气标准不可逆内燃机循环,导出了考虑工质变比热情况下,存在摩擦及传热损失时,由两个加热过程、两个放热过程和两个绝热过程组成的普适的空气标准不可逆内燃机循环的功率与压缩比、效率与压缩比以及功率和效率的最佳特性关系,同时由数值计算分析了工质变比热和循环过程对循环性能的影响特点,比较了工质恒、变比热时循环性能差异。所得结果包含了不可逆往复式Diesel、Otto、Brayton、Atkinson、Dual和Miller 循环的性能特性。

UNIVERSAL PERFORMANCE OF INTERNAL COMBUSTION ENGINES WITH VARIABLE SPECIFIC HEATS OF WORKING FLUID

The performance of a generalized irreversible internal combustion engine cycle model consisting of two heating branches, two cooling branches and two adiabatic branches with heat transfer, friction and variable specific heats of working fluid was analyzed by using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived by numerical example. Moreover, the effects of variable specific heats of working fluid and cycle process on cycle performance are analyzed. The performances of the cycle with variable and constant specific heats of working fluid are compared. The results obtained herein include the performance characteristics of irreversible reciprocating Diesel, Otto, Atkinson, Brayton, Dual and Miller cycles.