Key parameters and influence analysis of Marine S-CO2 Brayton cycle power generation system under off-design conditions

Utilizing the flue gas of ship main engine for waste heat power generation by S-CO2 Brayton cycle is an effective way to realize the energy saving and emission reduction of ships and the greening of the shipping industry. As the load of ship main engine will change under different sailing conditions, leading to changes in the temperature and mass flow of flue gas from the main engine, which makes the overall operating state of the S-CO2 Brayton cycle power generation system change. Reasonable control of turbine inlet temperature, compressor inlet temperature, compressor inlet pressure and flow split ratio is an effective way to ensure a good performance of the S-CO2 Brayton cycle under different states of flue gas. To determine the control objects and controlled parameters of the S-CO2 Brayton cycle under unsteady heat source, the mathematical model of the core components of the system, such as heat exchanger, turbine and compressor, and the steady-state simulation program of the S-CO2 recompression Brayton cycle were established in this paper. Based on analyzing the influence of key thermodynamic parameters on the performance of S-CO2 Brayton cycle, taking maximizing the output power of the system as the objective of optimization, the optimal operating key parameters of the S-CO2 Brayton cycle system under different main engine conditions are determined, which provides a numerical basis for the operation control of marine S-CO2 Brayton cycle power generation system.