Performance Optimizations with Single-, Bi-, Tri-, and Quadru-Objective for Irreversible Diesel Cycle.

Shuangshuang Shi,Lingen Chen,Yanlin Ge,Huijun Feng

doi:10.3390/e23070826

Abstract

Applying finite time thermodynamics theory and the non-dominated sorting genetic algorithm-II (NSGA-II), thermodynamic analysis and multi-objective optimization of an irreversible Diesel cycle are performed. Through numerical calculations, the impact of the cycle temperature ratio on the power density of the cycle is analyzed. The characteristic relationships among the cycle power density versus the compression ratio and thermal efficiency are obtained with three different loss issues. The thermal efficiency, the maximum specific volume (the size of the total volume of the cylinder), and the maximum pressure ratio are compared under the maximum power output and the maximum power density criteria. Using NSGA-II, single-, bi-, tri-, and quadru-objective optimizations are performed for an irreversible Diesel cycle by introducing dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density as objectives, respectively. The optimal design plan is obtained by using three solution methods, that is, the linear programming technique for multidimensional analysis of preference (LINMAP), the technique for order preferences by similarity to ideal solution (TOPSIS), and Shannon entropy, to compare the results under different objective function combinations. The comparison results indicate that the deviation index of multi-objective optimization is small. When taking the dimensionless power output, dimensionless ecological function, and dimensionless power density as the objective function to perform tri-objective optimization, the LINMAP solution is used to obtain the minimum deviation index. The deviation index at this time is 0.1333, and the design scheme is closer to the ideal scheme.

Highlights

Assuming the working fluid’s specific heats are constants [14,15,16,17,18,19,20,21,22,23,24] and vary with its temperature [25,26,27,28,29,30,31,32], many scholars have studied the performance of irreversible Diesel cycles with various objective functions, such as power output (P), thermal efficiency (η), and ecological functions (E, which was defined as the difference between the exergy flow rate and the exergy loss)
When taking P, E, and Pd as the optimization objectives to perform tri-objective optimization, the deviation index obtained by the LINMAP solution is smaller, and the design scheme is closer to the ideal scheme
The expression of the Pd of an irreversible Diesel cycle was derived in this paper, and the impacts of τ and three loss issues on the cycle of Pd versus γ and η characteristics were analyzed

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Assuming the working fluid’s specific heats are constants [14,15,16,17,18,19,20,21,22,23,24] and vary with its temperature [25,26,27,28,29,30,31,32], many scholars have studied the performance of irreversible Diesel cycles with various objective functions, such as power output (P), thermal efficiency (η), and ecological functions (E, which was defined as the difference between the exergy flow rate and the exergy loss). Kumar [37] conducted thermodynamic analysis and optimization of a reversible Diesel cycle under the criteria of P, Pd , and effective P when the working fluid’s specific heats were linearly functioning with temperature. That is, LINMAP, TOPSIS, and Shannon entropy, the deviation indexes obtained under different solutions are compared, and the optimized design scheme with the smallest deviation index is obtained

Cycle Model

Maximum Power Density Optimization

Multi-Objective

Figures showoptimization the Pareto frontiers

Findings

Conclusions