变冷却条件下超临界二氧化碳动力系统瞬态特性研究OA

[Objective]The supercritical carbon dioxide Brayton cycle(SCBC)is an important technological development direction in the field of thermal power generation.The study of its dynamic process is of great significance to the application of this system.In this paper,a dynamic analysis model of the SCBC power system is established to analyze the transient characteristics when the cooling condition is changed.[Methods]For compressors and turbines,the steady-state model is used.For heat exchangers,a dynamic model is established based on the steady-state finite volume(FV)model,to analyze the transient characteristics of the system when cooling conditions change.[Results]The research result shows that after changing the cooling flow rate of the precooler,the system reaches a stable state at the latest within about 200 seconds.The main compressor is highly sensitive to changes in the flow rate on the water side of the precooler.When the flow rate of the precooler drops to 50%of the minimum value,the efficiency of the main compressor decreases by approximately 0.5%.Increasing the flow rate on the water side of the precooler can improve the operating efficiency of the compressor.When the flow rate linearly increases to 175%within 25 seconds,the main compressor tends to stabilize after 75 seconds,and the efficiency increases by 0.8%.But at this point,the state of the compressor inlet is already very close to the surge line.After 200 seconds,the recompressor becomes stabilized,and its efficiency increases by 0.2%.The net output power of the system stabilizes after 300 seconds,and the thermal efficiency of the system decreases by 0.3%.[Conclusion]As the inlet temperature(306 K)of the main compressor is close to the critical temperature of CO2,increasing the flow rate on the cold side of the precooler can easily cause the inlet temperature of the compressor to be lower than the critical temperature,affecting the stable operation of the compressor.Reducing the flow rate on the cold side of the precooler will lead to a decrease in the net output power of the system and a reduction in thermal efficiency.Therefore,adjusting the flow rate in the precooler can rapidly change the total power consumption of the compressor,thereby quickly influencing the net output power of the system.This study provides a reference for designing reasonable control strategies when disturbances occur in the cooling water side of the precooler for RCBC systems,aiming to shorten the system response time and mitigate detrimental fluctuations.