Design And Optimization Research On Scramjet System Scheme

In this thesis, thermodynamic analysis method and sub-system models for scramjet engine design are established, preliminary scheme of scramjet engine system is designed and inner flowpath optimization of the based scheme is performed.In the aspect of thermodynamic analysis of scramjet, modified stream thrust analysis model and exergy analysis model are developed, and applied for the scramjet design. The results show that: 1)The compression efficiency is a critical parameter that effects the scramjet performance seriously. The combustion efficiency has important influence on the engine performance compared with the combustor drag force. Both of the nozzle expansion efficiency and the exit pressure effect the scramjet performance seriously, and trade-off should be done between the performance and geometry size to determine the nozzle exit pressure. 2) There does exist the optimal inlet exit temperature under the assumption of constant static heat addition, but it has weak effect on the scramjet performance. 3) The exhaust loss accounts for the main loss of the whole system, and combustion process results in the major exergy destruction in the inner flowpath.In the aspect of scramjet system scheme design, flow chat of scramjet system scheme design is discussed, and the inlet design model and quasi-one dimensional model of scramjet are established. Scramjet feeding system model and the system mass models are also established. With these models, scramjet inner flowpath and feeding system are designed, and the scramjet system dry mass is obtained. The impact of cracked fuel decomposition, cross-section area variation and fuel injection on the heat release are discussed.Finally, the optimization of the inner flow-path is performed, with Simulated Annealing Algorithm. Based on the results, exergy analysis is performed. The comparison of the based and optimized engine scheme shows that :1)The optimized engine scheme produced 40% more thrust than the based engine scheme. 2) The improved thrust relies on the large fuel/air ratio under a supersonic combustion, stronger compression in the inlet and isolator, average distributed fuel injections and proper cross-section area variation of the combustor. 3)The exergy destruction is mainly concentrated in area where the majority of the heat is released.