An air-standard isothermal-heating modified Atkinson-cycle and its performance optimizations with five objectives and NSGA-II

Abstract An endoreversible-model of air-standard modified Atkinson-cycle via isothermal-heat-addition is built in this study, power ( P ), efficiency ( η ), power-density ( P d ), ecological-function ( E ), and efficient-power ( E p ) performances of modified Atkinson-cycle are analyzed and compared firstly. Taking <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mover accent="true"> <m:mi>P</m:mi> <m:mo>̄</m:mo> </m:mover> </m:mrow> </m:math> $\bar{P}$ , η , P d , E and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msub> <m:mover accent="true"> <m:mi>E</m:mi> <m:mo>̄</m:mo> </m:mover> <m:mi>p</m:mi> </m:msub> </m:mrow> </m:math> ${\bar{E}}_{p}$ as objective-functions (OFs), and compression-ratio ( γ ) as optimization variable, the one five-objective optimization, five quadru-objective optimizations, ten tri-objective optimizations, ten bi-objective optimizations and five single-objective optimizations are completed by using NSGA-II furtherly. To find optimal solution, deviation indices ( Ds ) of three decision-making-methods (DMMs) which include Shannon Entropy, LINMAP and TOPSIS are utilized to compare optimization results. Results show that curves P versus η and P d versus η are loop-shaped ones, and curves P versus γ and P d versus γ are parabolic-like ones. With the increases of pre-expansion-ratio ( ρ ) and the maximum-temperature-ratio ( τ ), P d is improved. Modified Atkinson-cycle designed with P d as the OF has smaller size and higher η . Compared with traditional Atkinson-cycle, isothermal heating modified Atkinson-cycle performance is evidently improved, <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mover accent="true"> <m:mi>P</m:mi> <m:mo>̄</m:mo> </m:mover> </m:mrow> </m:math> $\bar{P}$ , η , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mover accent="true"> <m:mi>E</m:mi> <m:mo>̄</m:mo> </m:mover> </m:mrow> </m:math> $\bar{E}$ , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msub> <m:mover accent="true"> <m:mi>P</m:mi> <m:mo>̄</m:mo> </m:mover> <m:mi>d</m:mi> </m:msub> </m:mrow> </m:math> ${\bar{P}}_{d}$ , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msub> <m:mover accent="true"> <m:mi>E</m:mi> <m:mo>̄</m:mo> </m:mover> <m:mi>p</m:mi> </m:msub> </m:mrow> </m:math> ${\bar{E}}_{p}$ are improved by 30.18 %, 7.31 %, 39.57 %, 32.27 %, 47.60 %, respectively. When optimized with 5, 4, 3, or two objectives, the more the number of objectives is, modified Atkinson-cycle has more reasonable design plan and better trade-off design performance . The m