Study On The Steady-state Characteristics Of Marine Two Stage Regenerative Recompression S-CO₂ Brayton Cycle

In recent years,the technology of ship’s waste heat utilization has become one of the important directions of the development of green ships,and the two-stage regenerative and recompressive supercritical carbon dioxide Brayton cycle has great potential in the field of thermal power generation technology with the advantages of high efficiency,compact equipment,clean working medium and so on.But at present,there are still some deficiencies in the research of supercritical carbon dioxide Brayton cycle waste heat power generation system in system Thermodynamics Simulation and component level simulation.In this paper,the steady-state thermodynamic simulation of marine S-CO₂Brayton cycle power generation system with two-stage regenerative recompression is carried out,and the influence of important parameters of the cycle on the cycle performance is analyzed.On this basis,the influence of heat exchanger heat transfer capacity on the system performance is studied.The main research work and innovation of this paper are as follows:1、The performance of marine S-CO₂ Brayton cycle with two-stage regenerative recompression was studied.Based on FORTRAN platform,the mathematical model of the core equipment of S-CO₂ Brayton cycle thermodynamic system and the simulation model of steady-state operation at design point are established.The sensitivity analysis of the main input parameters of the model is carried out by using Spearman rank correlation coefficient method,and the key parameters of the cycle design point are analyzed based on this.The results show that there is an optimal outlet pressure value and the optimal shunt coefficient value to maximize the thermal efficiency,and the main compressor inlet temperature has more obvious influence on the thermal efficiency than the turbine inlet temperature.2、The performance of marine S-CO₂ Brayton cycle with two-stage regenerative recompression under non design conditions is studied.The design and calculation models of compressor,turbine and high and low temperature regenerator are developed.The equipment dimensions and parameters suitable for 300 k W S-CO₂closed Brayton cycle are obtained.The influences of the inlet temperature of main compressor,the inlet pressure of main compressor and the inlet temperature of turbine on the cycle performance under non design point conditions are analyzed.The results show that the low-temperature design can not produce the rated power output value under the condition of lower inlet pressure of the main compressor,and the high-temperature design can exceed the maximum pressure limit under the condition of higher inlet pressure.3、The heat transfer performance of the high and low temperature recuperator was studied.According to the heat transfer characteristics of the fluid in the pipeline,the correlations of heat transfer and pressure drop in the high and low temperature regenerator are fitted,and the calculation and analysis program of the heat exchanger is developed,which further improves the accuracy of the model.The effects of total heat transfer coefficient of high and low temperature regenerators on the minimum temperature difference,effectiveness,heat transfer,cycle heat efficiency and output work of the regenerators are analyzed.The research on the steady-state characteristics of marine S-CO₂ Brayton cycle with two-stage regenerative recompression is of great significance to the design,manufacture,operation control and practical application of marine thermal power generation system.