Applications Of Chemical Equilibrium And Flamelet Model For The Numerical Simulation Of Scramjet

Airbreathing hypersonics studies the technology of aerospace vehicles propelled by airbreathing engine or combined cycle engine for long-distance hypersonic flight in atmosphere layer or trans-atmosphere layer at flight Mach number above 5. The core technology of airbreathing hypersonic is scramjet and airframe/propulsion integrated hypersonic flight vehicle.With the development of computer technology and numerical methods, computational fluid dynamics (CFD) has become one of three means (ground test, flight test and CFD) using in scramjet research, and gradually becomes an economic and efficient mean in a design of scramjet and analysis of flow. Numerical calculation can accomplish analysis of flow parameters in relative short time, providing detailed characteristics of flow field, remedying the deficiency of wind tunnel and measurements and offering basis for continuous improved design of engine configuration.This paper focuses two problems faced in studies of scramjet simulation: The simulation of combustion cost expensive, which have handicaped CFD appliactions in engineering. We have developed a massively parallel CFD code, equilibrium reacting models and flamelet model for hydrocarbon or hydrogen fuels. Massively parallel computations have been completed on Sunway MPP machine, and detailed comparison and analysis of computational result and experimental data have also been done. We firstly use chemical equilibrium analysis method to calculate reacting compositions of scramjet for hydrocarbon fuels, and use flamelet model to simulate the interaction of turbulence and combustion in scramjet combustor for hydrogen fuel.This paper consists of five chapters. The first chapter gives a short introduction including the background of scramjet and research status both at home and abroad; After this, a review of studies of scramjet is also given. We analyse the difficulties and present situation in a simulation of the interaction of turbulence and combustion in scramjet. Finally, the main work of this paper is presented briefly.The second chapter introduces numerical methods, chemical models, physical models and numerical schemes used in our calculation. And We introduces five two-equations turbulence models: (1) low Re k ?ε(Jones & Launder); (2) low Re k ?ω;(3) Menter's BSL;(4) Menter's k ?ωSST; (5) q ?ω(Coakley & Huang,1992). Four benchmark cases are calculated to validate the capabilities of numerical software for turbulence flow in comparison with experimental data. The results show that the numerical software has high resolution and good reliability.The third chapter introduces four methods for simulating chemical equilibrium flow: (1) minimization of Gibbs energy method (Gordon & McBride); (2)element potentials method(Powell & Reynolds); (3) Gibbs function continuation method (Pope); (4)chemical equilibrium analysis method. Computational results show that only chemical equilibrium analysis method can be used to optimizing design for scramjet, and the chemical reatcing is nonequilibrium in scramjet for hydrocarbon fuels.The fourth chapter gives the research of numerical simulating turbulent combustion. Firstly, a review of studies of turbulent combustion models is given. After this, a detailed introduction for flamelet model has been done. The simulation of a hydrogen fueled scramjet (DLR) verified the reliability of the CFD code. Based on this, we conducted a simulation of CARDC's scramjets on SW MPP machine. The numerical results are compared with experimental data and finite-rate reacting model. Computational results show that the interaction of turbulence and combustion in scramjet can't be ignored. Applying flamelet model to simulate turbulent combustion in scramjet is a good choice.The fifth chapter is conclusions. Most of research and innovative points are listed and the outlook of future work is also given.