基于平衡和非平衡权重算法的柴油机有机朗肯循环多目标优化

Multi-Objective Optimization of Organic Rankine Cycle for Diesel Engine Based on Balanced and Unbalanced Weight Algorithm

对非共沸混合工质的柴油机ORC系统进了研究,提出了一种基于平衡和非平衡权重的热力学高维多目标优化(EMO)方法。研究表明,使用非共沸混合物,可提高换热器中工质和热源的匹配度,苯/甲苯(质量比:60%/40%)的输出功率(W_(net))比纯工质提高5.4%~19.2%。敏感性参数分析表明,随着蒸发温度的增大,W_(net)先增大后减小,热效率(η_(th))单调增加,总[火用]损(I_(zon))单调减少。由于W_(net),η_(th)和I_(zon)相互矛盾,不存在同时满足这三个指标的运行参数,为此开展高维EMO,利用RPD-NSGA-Ⅱ进行多目标优化并通过TOPSIS进行分析。当基于η_(th),W_(net)和I_(zon)的平衡权重进行选择,最佳η_(th),W_(net)和I_(zon)分别为24.07%,72.36 kW和44.66 kW,而柴油机废气能量回收率(ηg)为12.5%;当基于W_(net)和η_(th)的非平衡权重进行选择,最佳η_(th)和W_(net)分别为22.42%和81.44 kW,对应的I_(zon)为52.33 kW,ηg为14.07%。可见,基于不同权重的选取能够给出更多的工程选择。

The ORC system of a diesel engine with the non-azeotropic mixture was investigated and a high-dimensional evolutionary multi-objective optimization(EMO)method was proposed based on balanced and unbalanced weights.The results indicate that using non-azeotropic mixtures in the ORC system enhances the match between the working fluid and heat source in the heat exchanger.Compared with the pure working fluid,the output power(W_(net))of benzene/toluene(60%/40%mass ratio)increases by 5.4%~19.2%.According to the sensitivity parameter analysis,W_(net) first increases and then decreases,the thermal efficiency(η_(th))monotonically increases,and the total exergy destruction(I_(zon))monotonically decreases when the evaporation temperature increases.The W_(net),η_(th),and I_(zon) indicators are mutually exclusive,and so there is no operating parameter that satisfies all three indicators simultaneously.Consequently,a high-dimensional EMO method is employed,and multi-objective optimization is performed using RPD-NSGA-Ⅱand analysis is conducted by TOPSIS.Based on the balanced weight approach,the optimal values forη_(th),W_(net),and I_(zon) are 24.07%,72.36 kW and 44.66 kW respectively with a diesel exhaust gas energy recovery rate(ηg)of 12.5%.On the other hand,choosing unbalanced weights of W_(net) andη_(th) results in the optimalη_(th) and W_(net) of 22.42%and 81.44 kW,which corresponds to the I_(zon) andηg of 52.33 kW and 14.07%.Accordingly,the use of different weight combinations presents more engineering choices.