柴油机不可逆循环性能分析及优化

Performance Analysis and Opti mization of Irreversible Diesel Cycle

建立了不可逆diesel循环的热力学模型 ,对diesel循环进行了有限时间热力学分析。推导出在内可逆、内外均不可逆时diesel循环在给定热力学模型下输出功率与热效率之间的关系式 ,并证明了内可逆diesel循环有一最大输出功率 ,而此时循环热效率即为著名的CA效率 ,并求出了最大输出功率表达式 ,证明了在具有最大输出功率时循环压缩比及预胀比有确定的关系。当具有内外双重不可逆时 ,相应公式只是对内可逆时的公式用不可逆系数I进行修正 ,即用ITL 代替原公式中的TL 即可。给出了计算实例 ,并通过实例计算分析了内不可逆系数、热源温度对最大输出功率、热效率的影响及循环压缩比、预胀比对热效率的影响。本文的研究对内燃机的设计和性能评估有理论意义。

In the paper, a thermodynamic model based on co nsidering internal and external irreversible air standard Diesel internal combu stion engine cycle is established, and the finite time thermodynamic problem of Diesel cycle is studied. It is borne out that there is a maximum power output fo r internal reversible Diesel cycle and the cycle's thermal efficiency is the wel l known CA thermal efficiency. The interrelation between the maximum power outp ut and the optimal thermal efficiency is presented, and expressions of both maxi mum power output and the optimal thermal efficiency are derived, and the determi nate interrelation between cycle parameters μ and ρ is proved at the m aximum power output. When both internal and external cycles exist, the correspon ding formula is revised only by use of the internal irreversible factor I. The effect of heat source temperature T H and internal irreversible f actor I on the maximum power output and thermal efficiency and the effect of cycle parameters μ and ρ on the thermal efficiency are analyzed in an example. The formula derived in the paper is of significance to the design and performance estimation of the internal combustion engine.