System Dynamic Simulation And Experimental Study Of Key Components In Solar Air Brayton Cycle

The solar air Brayton cycle power generation system has the advantages of a quick start-up and shut-down speed,low water consumption,high power output quality,and high power generation efficiency when combined with the bottom cycle.It is suitable for peak and frequency modulation of fluctuating renewable energy systems.In this paper,for the solar air Brayton cycle power generation system,four aspects of research work are carried out on the heliostats field,air receiver,thermal power conversion and system optimization.The flux density distribution measurement and simulation of the heliostats field are carried out.Through two flux density distribution measurement methods,the concentrated flux distribution of heliostats is measured.The measuring errors of the two methods are 3.1%and 4.2%,respectively.A flux density distribution model is developed based on the analytical method,and the model is verified by the flux density measurement data.For the concentrating performance of52 heliostats,the average relative error of the simulated and measured flux density at each position on the Lambertian plate is 1.03%,the relative error of the highest flux density is 3.81%,and the relative error of the total received energy is 3.05%.The air receiver test and dynamic simulation research are carried out.In the receiver test,the receiver outlet temperature can reach 888?,when the inlet air pressure of the receiver is 284 k Pa,the pressure loss is only 0.88%.The thermal efficiency and the thermal power of the air receiver can reach 68.9%and 132 k W,respectively.A dynamic model of the tubular air receiver is developed and coupled with the flux density distribution model to form a dynamic simulation model of light and heat coupling.The dynamic model is validated by two air receiver experimental data,and the RMSE of the experimental and the simulated values of the receiver outlet temperature is 1.91%and 3.92%,respectively.The factors that affect the operating characteristics of the air receiver are explored.The two operating strategies of the air receiver are compared.When the average flux density in the receiver aperture is increased from 408 k W/m~2 to 1044k W/m~2,the receiver aperture diameter can be reduced from 0.8 m to 0.5 m,and the thermal efficiency of the air receiver can be increased from 70.0%to 77.6%.A dynamic simulation platform of the micro gas turbine is developed based on the Lumped-volume method.The experimental data from the literature are used to validate the proposed model.The dynamic simulation results are validated,including the startup,load change and shutdown processes of the micro gas turbine in the speed mode.The compared parameters are the turbine outlet temperature,the power output,the rotational speed and the combustor inlet temperature.The results show that the RMSE of these parameters between simulated values and experimental values is within 4.4%.The dynamic simulation and system optimization are carried out for three different types of solar air Brayton cycle systems.When the load of the micro gas turbine is reduced,the air receiver and the thermal storage tank need to be bypassed in time to prevent the shaft from overspeeding because of the large thermal capacity of the air receiver and the thermal storage tank.The thermal storage system can reduce the fluctuation of the combustor inlet temperature from 145?to around 2?when the DNI fluctuates,stabilizing the operation of the micro gas turbine.The steam receiver is arranged around the air receiver aperture,which can increase the average interception efficiency of the receiver from 0.869 to 0.978.The steam injection in the system can improve the performance of the micro gas turbine and increase its response rate when the load is changed.In the intraday dynamic simulation of the system,the usage of the air receiver can reduce the fuel consumption of the micro gas turbine by 50.9%.Steam injection in the system can further reduce the fuel consumption of the micro gas turbine,and the fuel consumption is reduced by 52.8%.This work is expected to provide a reference scheme for the construction of the solar air Brayton cycle power generation system and provide a valuable reference for the research and development of key components.