A new nonadiabatic procedure of the flamelet/progress-variable approach (NA-FPV approach) is proposed, and the validity is assessed by performing a large eddy simulation (LES) employing the NA-FPV approach for an H2/O2 combustion field in a single element coaxial combustor under a pressurized condition. The results show that the LES employing the NA-FPV approach can successfully predict the heat flux and capture the effects of heat loss through the cooled walls on the combustion characteristics. This procedure is quite useful especially for the numerical simulations of combustion fields with high temperatures, where there remain reactive radicals (e.g., OH, CH) with high concentrations, such as pressurized combustion, supercritical combustion, and oxygen combustion.

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The cooling characteristics of combustion chamber affect the chamber lifetime and engine operating condition significantly and need to be predicted accurately for the engine development. Especially for the LE-X engine, which is being developed in Japan as the first stage engine of the Next Flagship Launch System, the accurate prediction of chamber wall temperature is necessary for the highly reliable rocket engine design, because of its engine cycle features. Both flowfields of combustion gas and coolant affect wall temperature significantly and should be analyzed precisely for the accurate prediction. Because CFD analysis can capture those complicated flowfields directly, it is considered to have the potential for the accurate prediction. Therefore, JAXA and MHI have been working on development of the analysis method for wall temperature prediction based on high fidelity CFD analysis. Although there is a need of further validation and improvement, the fundamental analysis method was established. In the future, the established method will be applied to the LE-X engine development.

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