The Flame Development Process In GOX/GCH4 Rocket Combustor And It's Impact On The Wall Heat Load

In recent years,with the rise of commercial aerospace,the demand for high performance and low cost liquid rocket engine is increasing,the reusable liquid rocket engine has become an important development direction of the future liquid rocket engine.The oxygen/methane liquid rocket engine has the advantage of excellent cooling performance,high coking temperature and high propulsion performance,and has become one of the most promising reusable engine.Thrust chamber is the key component of liquid rocket engine,in which the combustion and heat transfer process will determine the performance and reliability of the engine directly.In this paper,the CFD method is used to study the thrust chamber of a scaled oxygen/methane rocket engine with seven coaxial shear injectors.The wall heat transfer process,the mixed combustion process and the influence of post thickness of the injector are analyzed in detail,these will provide some guidance for the development of oxygen/methane rocket engine.Firstly,the numerical model for turbulent combustion process in oxygen/methane rocket combustor is established,and the applicability of the numerical method based on RANS framework and EDC finite rate model is verified.We found that the numerical model based on the RANS framework can capture the characteristics of the turbulent combustion process well,but there is an overprediction of nearly 30% for the wall heat load.After that,the defect of the numerical model in predicting the wall heat load is deeply analyzed.It is found that the chemical equilibrium shifting caused by the strong cooling effect will have a significant impact on the wall heat load,and this effect is also coupled with the three-dimensional flow effect in the combustion chamber.By re-modelling the governing equations of reactive flow,the effect of chemical equilibrium shifting under large temperature gradient is taken into account in the new wall function,and finally embedded in the previous calculation model through UDF method.The results show that the new coupled wall function can significantly improve the prediction of the wall heat load,without affecting the mainstream combustion process.Then,the controlling factors of the combustion process of oxygen/methane are analyzed in depth.The scalar dissipation rate,which can measure the rate of the mixing process is established theoretically.Based on this time scale,the internal relationship between the combustion process and the mixing process is analyzed.The results show that the combustion process of gas methane can be divided into four linear stages,and there is a quadratic function relationship between the overall combustion heat release rate and the mixing time scale.Finally,the effects of the injector post thickness on combustion and heat transfer process are discussed.The results show that the increase and decrease of the post thickness will reduce the heat load of the chamber wall through different ways,but the decrease of post thickness will further reduce the thermal load of the faceplate.From the point of view for reducing the overall thermal load of combustion chamber,the injector with small post thickness is preferred.