Research Of The Scramjet Active Cooling System Scheme Based On Thermoelectric Conversion

This dissertation,in the context of scramjet application,studies the scamjet active cooling system scheme based on thermoelectric conversion.According to the scramjet cooling problem,the available work of the heat is analyzed,three schemes including direct,indirect and combination type are proposed,the performance of the system scheme is studied and compared.The purpose is fulfilling the scramjet cooling requirements.Firstly,the scramjet wall heat transfer is analyzed according to the working process and the energy balance.The heat exergy calculation model,the exergy balance equations of the closed system and the steady flow system are proposed.The total heat and the available work are calculated,and the potential work of the scramjet wall heat is obtained.The available cold source is analyzed for active cooling system scheme.Three system schemes are proposed including direct,indirect and combination type.The structure and working processes of different schemes are analyzed.Discuss the matching requirements of the fuel cooling and combustion process by analyzing the influence between the fuel cooling process and fuel combustion process.The performance parameters of the active cooling system schemes are proposed.The mathematical analysis models of the system schemes are established,which include semiconductor thermoelectric generator(TEG),thermodynamic cycle and TEG-turbine type system.Comparison of endothermic ending temperature,maximum working temperature,Dimensionless Figure of Merit(ZT)and pressure ratio on the performance of the schemes are discussed to compare the schemes influencing trend.The heat transfer and conversion of direct thermoelectric conversion(TEG)system scheme is analyzed.The method of the coupled heat transfer process analyzing is proposed.The performance parameters are obtained for fulfilling the scramjet cooling requirements under the scramjet certain working condition.In the light of the scheme of indirect system,the thermodynamic process analysis method is put forward to analyze the closed Brayton cycle,Rankine cycle and fractional expansion thermodynamic cycle system schemes thermodynamic processes.The performance parameters are obtained for fulfilling the scramjet cooling requirements under the scramjet certain working condition.Based on the study of TEG system scheme heat transfer and conversion,the performance of TEG-TURBO type system is analyzed.The expansion process of fuel turbo is discussed.The performance parameters are obtained under the scramjet certain working condition.Three active cooling system schemes based on thermoelectric conversion are compared in the same external factors.It is concluded that the fractional expansion thermodynamic cycle system scheme with He as the working fluid in engine active cooling can be have more advantages.The exergy transfer models of indirect(closed Brayton cycle)system scheme and TEG-TURBO type system scheme are put forward to study the exergy changing problem of the scheme heat transfer and conversion.The exergy change of the scheme thermodynamic process is analyzed,and the total exergy loss and exergy efficie ncy of the system are obtained to give a way for improving the system scheme performance.In this paper,the research result provides new ideas for active cooling system design of the scramjet with working long time.It also provides guidance for power requirement and electrical source system design of hypersonic vehicle with flying long time.