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

Abstract

<p indent="0mm">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.