Performance Modulation of S-CO2 Brayton Cycle for Marine Low-Speed Diesel Engine Flue Gas Waste Heat Recovery Based on MOGA

Liangtao Xie; Jianguo Yang

doi:10.3390/e24111544

Performance Modulation of S-CO₂ Brayton Cycle for Marine Low-Speed Diesel Engine Flue Gas Waste Heat Recovery Based on MOGA

Entropy (Basel). 2022 Oct 27;24(11):1544. doi: 10.3390/e24111544.

Authors

Liangtao Xie¹, Jianguo Yang^{1

2

3}

Affiliations

¹ School of Naval Architecture, Ocean and Energy Power Engineering, Wuhan University of Technology, Wuhan 430063, China.
² Key Laboratory of Marine Power Engineering Technology Transportation Industry, Wuhan 430063, China.
³ National Engineering Laboratory for Marine and Ocean Engineering Power System, Electronic Control Sub-Laboratory for Low-Speed Engine, Wuhan 430063, China.

Abstract

(1) Background: the shipping industry forced ships to adopt new energy-saving technologies to improve energy efficiency. With the timing modulation for the marine low-speed diesel engine S-CO₂ Brayton cycle, the waste heat recovery system is optimized to improve fuel economy. (2) Methods: with the 6EX340EF marine low-speed diesel engine established in AVL Cruise M and verified by the bench test data, the model of the S-CO₂ Recompression Brayton Cycle (SCRBC) system for the low-speed engine flue gas waste heat recovery was developed in EBSILON, and verified by SANDIA experimental data. On this basis, the effects of injection timing and valve timing parameters on the comprehensive performance of the main engine and the waste heat recovery system were investigated. By optimizing the timing modulation parameters through multi-objective genetic algorithm (MOGA) and evaluating the flue gas waste heat recovery from the perspective of thermodynamic performance and emission reduction, the research on the performance modulation method of the S-CO₂ Brayton Cycle for flue gas waste heat in marine low-speed engines has been completed. (3) Results: the SCRBC with waste heat modulation will further increase the total power and efficiency, which in turn brings about a reduction in the fuel consumption rate. The efficiency of the SCRBC system with the addition of waste heat modulation increases by 2.28%, 1.04% and 2.07% at 50%, 75% and 100%, respectively. After adding the residual heat modulation, the maximum annual CO₂ emission reduction of 748.51 × 10³ kg·a^-1 occurred at 50% load; with the exergy analysis, the cooler has the largest system exergy loss of 165 kW, with the exergy loss efficiency of 2.06% under 100% load. (4) Conclusions: the research on the performance modulation method of S-CO₂ Brayton cycle for flue gas waste heat in the marine low-speed engine has been completed, which further improves the efficiency of the system and can be extended to other engines.

Keywords: S-CO2 recompression Brayton cycle; marine low-speed diesel engine; the exergy analysis; thermodynamic performance; waste heat modulation; waste heat recovery of flue gas.

Grants and funding

This paper is supported by the China Ministry of Industry and Information Technology (Marine Low-speed Engine Engineering (Phase I) Development (MIIT Joint Letter No. 21 (2017))).