A Supersonic Combustion Model With Shock Train For A Scramjet-powered Hypersonic Aircraft

At Present, the research on the hypersonic aircraft based on the air-breathing engine becomes one of the hot subject fields of the aeronautics and astronautics. There are a lot of complex flow structures in the internal flow path of the air-breathing hypersonic vehicle, which contain shock and expansion waves, separated flow, fuel injection, mixing and combustion and some of other aerothermodynamics phenomena. In response to these complex flow phenomena, some calculation methods have been developed based on numerical simulation for the past few years. One-Dimension numerical method has been used widely due to its ability of analyzing the flow field rapidly. A new supersonic combustion model with shock train is built in this paper, and the effects of area change, wall friction, mass injection, fuel mixing, finite-rate chemistry and heat transfer to the combustor walls are included. The major work and conclusions of present paper are as follows:First of all, the knowledge of gas thermodynamics is discussed in depth. The flowing characteristics of Calorically perfect gas, Thermally perfect gas and Chemically reacting mixture of perfect gas in the same operating conditions are analyzed, respectively. Meanwhile, the influence of hydrogen injection to the mainstream has been investigated under different jet-to-freestream momentum flux ratio (or dynamic pressure ratio) conditions. The flow phenomena of mixing and combustion between the hydrogen and mainstream are simulated and the forward-propagation phenomenon of high pressure due to combustion is observed.Second, the former model fails to predict pressure distribution in the isolator accurately without considering the pre-combustion shock train, and it is revised on the basis of pre-combustion shock train model proposed by P.J.Waltrup and F.S.Billig and the hypothesis of combustion with constant static pressure proposed by Heiser W H, Prattdt, Deleyd H, et al. The revised model is coupled with the finite-rate chemistry to describe the flowfield of supersonic combustion.Finally, the new model is used to calculate some published supersonic combustion cases. The results show that the improved model in this paper is capable of explaining the experimental data for different conditions. It also verifies the accuracy of the model.