A modified Diesel cycle via isothermal heat addition, its endoreversible modelling and multi-objective optimization

Abstract

A new model of thermal cycle, modified Diesel cycle, is constructed via isothermal heat addition. Endorebersible modelling is performed considering heat transfer loss. Power (P), efficiency (η), power density (Pd) and ecological function (E) are deduced and evaluated. Characteristic relationships are deduced by using the finite-time thermodynamics theory. Cycle performances under the conditions of the maximum E, the maximum Pd, the maximum η, and the maximum P are compared. Under the same conditions, four performance functions of modified Diesel cycle and traditional Diesel cycle are compared. Based on the algorithm of NSGA-II, taking four performance indictors as the optimization objectives and the compression ratio as the optimization variable, multi-objective optimizations of the modified and traditional Diesel cycles under different objective combinations are carried out. Three decision-making method are used to select a group of optimal solutions. Compared with traditional Diesel cycle, performances P, η, Pd and E of modified Diesel cycle are improved at least by 8.69 %, 0.97 %, 8.23 %, and 8.64 %, respectively. Modified Diesel cycle with Pd and E for two-objective optimization is optimal, and the minimum deviation index is 0.1336, while the traditional Diesel cycle with P, η and Pd for three-objective optimization is optimal, and the minimum deviation index is 0.1339.