Effect of synergistic impact gas injection device on secondary combustion in boron-based ducted rockets

The combustion efficiency of the afterburner has an important effect on the overall performance of the ducted rocket. In some difficult working conditions with low incoming air temperature or high flight altitude, it is more difficult to achieve efficient combustion in the afterburner. Therefore, this paper mainly solves the problem of low primary gas combustion efficiency in the afterburner of boron-based ducted rockets when the incoming air temperature is low. The flow field can be improved by optimizing the gas injection mode, so as to improve the combustion efficiency. In this paper, a synergistic impact gas injection device associated with angles of two directions is designed. By controlling the self-impact angle α of gas/gas, and the mutual-impact angle β of gas/air, efficient mixing and combustion is realized. Through numerical simulation, the mixing degree and combustion efficiency, as well as the contours of B₂O₃ mass fraction are obtained, and the influence regularities and flow field characteristics are analyzed. The selection scheme of the optimal injection device is verified by a ground direct-connected experiment. Finally, through the jet observation experiments, the gas ejection form from the synergistic impact gas injection device is observed. The research of this paper shows that when the mutual-impact angle β is small, the larger the self-impact angle α is, the higher the mixing degree and combustion efficiency will be. When the mutual-impact angle β is large, each self-impact angle α has a high mixing degree and combustion efficiency. When the self-impact angle α is 40° or the mutual-impact angle β is 35°, the mixing can be completed in advance before the gas reaches the afterburner outlet. The higher the average mixing degree, the higher the combustion efficiency. This paper provides an innovative and efficient method for promoting combustion in the afterburner.