不可逆Otto循环功率密度分析与多目标优化

Power density analysis and multi-objective optimization of an irreversible Otto cycle

基于有限时间热力学理论和NSGA-II算法,对不可逆Otto循环进行了热力学分析和多目标优化.在前人建立的不可逆Otto模型基础上,进一步导出了该循环功率密度的表达式,分析了循环最大温比、传热损失、摩擦损失和内不可逆性损失对循环功率密度与压缩比和功率密度与效率特性的影响;在最大功率与最大功率密度准则下,比较了该循环的热效率、最大比容比和最大压比;基于NSGA-II算法,引入功率、效率、生态学函数和功率密度,对该循环分别进行单、双、三和四目标优化;采用LINMAP,TOPSIS和Shannon entropy三种决策方式,比较了不同优化目标组合下的偏差指数,得到了优化设计方案.当以无因次功率和无因次生态学函数为优化目标进行二目标优化时,采用LINMAP决策方式得到的偏差指数最小,其设计方案更接近于理想方案.

Based on the finite-time thermodynamic theory and NSGA-II, thermodynamic analysis and multi-objective optimization of an irreversible Otto cycle are performed. Further, based on the irreversible Otto model established in previous literature, the expression of cycle power density is obtained. Additionally, the effect of the maximum cycle temperature ratio, heat transfer loss, friction loss,and internal irreversibility loss on the power density performance of the cycle is analyzed. The characteristic relationships among the cycle power density versus compression ratio and power density versus thermal efficiency are obtained. Moreover, the thermal efficiency, maximum specific volume ratio, and maximum pressure ratio of the cycle are compared under the maximum power output and maximum power density criteria. Using NSGA-II, single-, bi-, tri-, and quadru-objective optimizations are performed for the irreversible Otto cycle by taking power output, thermal efficiency, ecological function, and power density as optimization objectives.The optimal design plan is obtained using three decision-making methods: LINMAP, TOPSIS, and Shannon entropy, by comparing the deviation indexes under different objective function combinations. When power output and ecological function are taken as objective functions of bi-objective optimization, the LINMAP solution is used to obtain the minimum deviation index, and the design scheme is close to the ideal scheme.