RANS based numerical simulation of a GCH4/GO2 rocket engine combustion chamber with film cooling and improvement of wall heat flux prediction

Abstract

Methane/Oxygen rocket engine is becoming one of the most promising rocket engines today due to its cost-effectiveness and reusability. In the design process of rocket engines, cooling system is a crucial part and film cooling is a very important method. The accurate prediction of heat transfer characteristics is crucial for the design and development of rocket engines using film cooling. In this paper, a numerical framework based on the Reynolds Averaged Navier-Stokes (RANS) method and the Eddy Dissipation Concept (EDC) reaction model is established, verified and applied to simulations of single- and multi-injector combustion chamber with film cooling. Besides, a single injector combustion experiment with film cooling is carried out to verify the numerical framework. The investigation indicates that flow and chemistry reactions near the wall coupled influence the wall heat load significantly, and the coupled wall function exploited by Direct Numerical Simulation (DNS) is modelled and embedded on the numerical frame in order to consider these coupling effects. The results of single injector chamber investigation show that by considering the chemical reactions near the wall the wall heat flux reduced 50% and agree much better to the experimental data, which indicates that coupled wall function is more effective at predicting wall heat flux than general wall functions in a chamber with film. In addition, the results also denote that the coupled wall function only acts in the near-wall region and has no effect on the main flow. Furthermore, after being verified in the single injector combustion chamber experiment, the numerical framework is applied to a multiple-injector case. The results indicate that the wall heat flux in multi-injector combustion chamber is 75% lower than the general wall functions, Afterwards, the effect of the film on the chemical enthalpy term near the wall, as well as the coupling effect of the turbulent flow and the temperature gradient near the wall are discussed. Finally, the analysis of the vorticity in the multi-injector chamber shows that the film weakens the vorticity in the front section of the combustion chamber, and subsequently affects the expansion of the flame.