Abstract
Considering nonlinear variation of working fluid’s specific heat with its temperature, finite-time thermodynamic theory is applied to analyze and optimize the characteristics of an irreversible Atkinson cycle. Through numerical calculations, performance relationships between cycle dimensionless power density versus compression ratio and dimensionless power density versus thermal efficiency are obtained, respectively. When the design parameters take certain specific values, the performance differences of reversible, endoreversible and irreversible Atkinson cycles are compared. The maximum specific volume ratio, maximum pressure ratio, and thermal efficiency under the conditions of the maximum power output and maximum power density are compared. Based on NSGA-II, the single-, bi-, tri-, and quadru-objective optimizations are performed when the compression ratio is used as the optimization variable, and the cycle dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density are used as the optimization objectives. The deviation indexes are obtained based on LINMAP, TOPSIS, and Shannon entropy solutions under different combinations of optimization objectives. By comparing the deviation indexes of bi-, tri- and quadru-objective optimization and the deviation indexes of single-objective optimizations based on maximum power output, maximum thermal efficiency, maximum ecological function and maximum power density, it is found that the deviation indexes of multi-objective optimization are smaller, and the solution of multi-objective optimization is desirable. The comparison results show that when the LINMAP solution is optimized with the dimensionless power output, thermal efficiency, and dimensionless power density as the objective functions, the deviation index is 0.1247, and this optimization objective combination is the most ideal.
Highlights
More and more thermodynamic research have focused on the optimal performance of given thermodynamic process and the optimal configuration of a thermodynamic process with a given target extremum, which is defined as finite-time thermodynamics (FTT) [1,2,3,4]
By comparing the deviation indexes obtained under various conditions, the results show that the solution obtained by Multiobjective optimization (MOO) is more desirable, and the deviation indexes are smaller
The results of the η, maximum specific volume ratio and pressure ratio obtained under the maximum power density (Pd) criterion are compared with those under the maximum P
Summary
More and more thermodynamic research have focused on the optimal performance of given thermodynamic process and the optimal configuration of a thermodynamic process with a given target extremum, which is defined as finite-time thermodynamics (FTT) [1,2,3,4]. For the Atkinson cycle (AC), when the working fluid’s (WF’s) specific heats (SHs) are constants [55,56,57,58,59,60,61,62], linear [63,64,65,66,67,68,69], and nonlinear [70,71,72,73,74,75,76] variable with its temperature, many scholars have analyzed and investigated its performance characteristics (PC) by taking into account the different cycle design parameters with different optimization objectives. Shi et al [62] further considered FL, HTL, and IIL on the basis of reference [55], and studied the influence of three losses on the Pd PC of an irreversible. Used P, Pd , E density and exergy loss rate as objective functions to perform MOO of Brayton cycle hybrid system. Carried out MOO on the total pumping and entropy exergy cost of product as optimization objectives.power
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