The influence law of the film percentage and injection on gas film cooling effect of the liquid oxygen/methane attitude control engine

Abstract

At present, the performance and thermal protection requirements of the attitude control engine as the power source for spacecraft attitude maintenance and adjustment are gradually becoming higher. In the field of gas film cooling, the influence law related to heat and mass transfer for attitude control engines with the liquid oxygen (LOX) /methane remains unclear. In the present study, the discrete phase model, the eddy-dissipation concept model and the 18-step methane simplification mechanism were used to simulate gas film cooling. The influences of the percentage, injection form and incidence angle of a gas film on the structure and cooling effect were analyzed. With the increase in gas film percentage, the maximum cooling efficiency increases and the increment shows a decreasing trend. In adopting the gas film injection scheme of round orifices, attention must be paid to the edge area of the gas film, where the cooling effect is easy to occur under poor conditions. Changing to the circumferential seam cooling scheme can significantly improve the thermal protection of the injection panel. The reflux area near the wall absorbs the methane in the core area close to the wall, which reduces the convective heat transfer coefficient near the wall. As the gas film incidence angle increases, the area with higher mass fraction of methane moves toward the head. The law of different parameters on the cooling effect is obtained by taking into account the interaction between the gas film and the mainstream. The gas film incidence angle cannot be lower than 10°, and a gas film incidence angle between 15° and 20° should preferably be taken. Such findings can facilitate the further development of attitude control engines with liquid oxygen and liquid methane and can guide the design of attitude control engines with gas film cooling.