Research On The Performance Of Supercrtical Carbon Dioxide Closed Brayton Cycle With Finite Cold Sourece And Power Promotion

In view of the huge demand of hypersonic vehicles for power supply in future,this paper develops the Closed Brayton cycle?CBC?power generation system of supercritical carbon dioxide?S-CO₂?based on the wall heat dissipation of scramjet combustion chamber as the energy source.Due to the S-CO₂ Brayton cycle has characteristics such as sudden changes in physical properties near the critical point and low cost,which is regarded as the main research direction of the future thermoelectric cycle power generation system.Based on the premise that fuel is the only source of cooling for hypersonic vehicles,related research is conducted on the performance of simple regenerative S-CO₂ closed Brayton cycle power generation system and the characteristics of compressor components.Based on existing research,the inlet temperature of the S-CO₂ compressor under a limited cooling source is much higher than the general S-CO₂ closed Brayton cycle,which will have a greater impact on the performance of the compressor and the closed Brayton cycle system.Further,the specific impact range of the high inlet temperature characteristics of the compressor was clarified,and the one-dimensional aerodynamic design and three-dimensional numerical simulation analysis of the S-CO₂ compressor were carried out.This article details the one-dimensional aerodynamic design process and three-dimensional numerical value of the S-CO₂ compressor According to the numerical calculation results,an in-depth study on the influence of the compressor flow field characteristics and temperature on the compressor isentropic efficiency is made based on the numerical calculation results.The results show that the compressor designed in this paper has good aerodynamic performance under design conditions,and is qualitative and quantitative.It reveals the impact of the high inlet temperature increase on the compressor's isentropic efficiency,which is more obvious when approaching the critical point of the working fluid.This has a great reference value for the future performance of the airborne thermoelectric conversion power generation system.Due to the wide operating range of the compressor,the aerodynamic performance and three-dimensional flow field characteristics of the compressor under non-design conditions need to be studied.This paper studies the one-dimensional speed of the compressor at 80% and 120% at non-operating point The design characteristic curve and the three-dimensional numerical flow field characteristics show that the compressor has a small separation vortex at the compressor outlet at a small flow rate,which causes a significant increase in entropy in this area.The flow velocity is high,and a condensation area appears at the leading edge of the impeller blade.This area is small in scope and fails to extend to the entire channel,and haslittle effect on the mainstream.According to the analysis of the three-dimensional flow field characteristics of the impeller hub and blades,it is concluded that the compressor still has good aerodynamic performance under non-design conditions,but in order to ensure better aerodynamic performance requirements,the compressor should be operated within the design conditions.Completed the performance analysis of the S-CO₂ simple regenerative Brayton cycle power generation system under the condition of the finite cold source,introduced the regulation of compressor isentropic efficiency with inlet temperature,revised and optimized the model,and compared the ground level with the same parameters.The performance of the closed Brayton cycle system can obtain the performance of the S-CO₂ closed cycle power generation system under a more practical the finite cold source.At the same time,the influence law of the temperature difference on the cold source side of the system on the power generation and thermal efficiency of the circulation system is obtained.As the temperature difference on the cold source side of the system increases,there is an extreme point in the power generation of the circulation system.Aiming at the problem of insufficient power supply of the closed Brayton cycle under the finite cold source,a scheme of a closed Brayton cycle and fuel vapor turbine combined power generation system is further proposed to improve energy utilization and electric power supply.The combined power generation system is based on fuel as the finite cold source.The fuel working fluid after absorbing heat through the cooling channel of the combustion chamber is used as the heat source of the closed Brayton cycle system.The modeling and simulation results show that the power generation power per unit massflow of fuel has been greatly improved.When the inlet temperature is 1000 K and the expansion ratio is 10 of fuel vapor turbine,and the maximum pressure of the closed Brayton cycle is 25 MPa,the combined system can generate power of 322.1 kW.