Dissertation
Dissertation > Aviation, aerospace > Aviation > Aero-engine ( propulsion system ) > Air jet engine

Pattern Classification of Combustion Modes in Scramjet

Author QuLiang
Tutor BaoWen
School Harbin Institute of Technology
Course Power Machinery and Engineering
Keywords hypersonic scramjet supersonic combustion numerical analysis mode-transition
CLC V235
Type Master's thesis
Year 2008
Downloads 190
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It is very important to develop the hypersonic vehicle in aeronautic and astronautic in 21st century. The hypersonic vehicle is the most important progress following with stealth technology in military domain. The scramjet, which is the propulsion of hypersonic vehicle, has become the focus in many military developed countries. Flight test is more expensive and is taken only as a final means for verification. With the development of computer technology and the advancement of numerical calculation, Computational Fluid Dynamics (CFD) has been applied widely in simulation engine’s chemical non-equilibrium flow fields and has emerged as an extremely valuable and cost-effective engineering tool in engine design and flow field analysis. CFD can be used to do analytical research of aerodynamic parameters in relatively short time, to provide detailed flow field characteristics, to remedy the limitation of wind tunnel test and measurements, and to offer the foundation for improving the configuration of engine.Firstly, the numerical simulation platform of hypersonic combustor was established. The finite-rate chemical kinetics model and the K-E turbulence model are used to simulate the flow field and performance of combustor. The numerical simulation method was introduced in detail and it was validated by the experimental data. By comparison simulation results and the experimental data, the models used in the numerical simulation and the simulation results are valid and correct. The effects of Mach number of the free stream on the inner flow field and wall pressure distributions were discussed, which provided the basis of the pattern classification of hypersonic combustion.Secondly, at the different flight Mach, the investigation of fuel was carried out in the combustor .With one-dimensional analysis method, the flow field parameters, the total pressure loss coefficient and combustion efficiency were estimated in terms of the measured wall static pressure data. For the dual-mode ramjet/scramjet research, the mode transition is one of the key techniques. The combustion mode transits from supersonic combustion to subsonic combustion as the equivalent ratio of fuel-air decreases from less to more. The cavities integrated fuel injector, mixer and flame holder can improve mix and combustion of the fuel and air, and the combustion efficiency.Then, the dual-mode scramjet can apply to the wide range of the flight Mach number from the supersonic to hypersonic. Different optimal operation mode should be adopted for different flight conditions, thus, heating process has to be sophisticatedly adjusted. So it is important to judge the characteristics of different mode, the 2-D inner steady flow of hypersonic combustor was numerically simulated in different free stream conditions and the way of fuel injection, performance of air flow in supersonic combustion was analyzed, and basis on the wall pressures four different combustions mode including pure supersonic combustion, supersonic combustion, subsonic combustion and unstart were defined and analyzed. The feature selection of different combustions mold patterns classification and the classification hyperplane were performed based on“numerical experimental”data by the SVM-RFE algorithm. The physical significance of the classification criterions was explained. The classification criterion was validated by the else data which prove the validity.Finally, the study of the catastrophe theory of the basic principles and the basic characteristics of catastrophe model, but also based on the analysis of "critical point" collection of the catastrophe theory of modeling. According to flow in different conditions, the different equivalent ratio of fuel-air when the multi-fuel mix (or even by orthogonal experimental design) under the numerical simulation results, a large number of examples, find the catastrophe character of flow, based on the catastrophe theory, analyze the catastrophe character of combustion pattern .

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