Investigation on the mixing and combustion characteristics in methane rocket engine with coaxial shear injectors

With the rising of the commercial space launch activities, there is increasingly high demand for high performance and low-cost vehicles, rendering reusable liquid rocket engines become an important direction for future engine development. Among these, the oxygen/methane rocket engine stands out as one of the most promising candidates for reusable applications, owing to the excellent cooling performance, low coking tendency, and low handling cost of methane fuel. The combustion chamber, as the core component of a rocket engine, directly determines the engine's performance through its heat release process. In this study, numerical simulations are conducted based on a scaled gaseous oxygen/methane rocket chamber equipped with seven coaxial shear injectors. The different influence mechanisms of injector–wall and injector–injector interactions on the morphology of the methane diffusion flame are revealed. The controlling factors of the oxygen/methane turbulent diffusion combustion process are analyzed. By establishing the chemical time scale and the mixing time scale, a four-stage linear correspondence between the heat release rate and the mixing rate of methane combustion is obtained, along with a global parabolic relationship between the heat release rate and the square root of the mixing time scale. Finally, the effects of the injector lip thickness on the oxygen/methane mixing and combustion process are evaluated, thereby providing guidance for the development of high-performance oxygen/methane rocket engines.