Numerical analysis of hydrogen peroxide injection effect on the combustion characteristics of a staged combustion aft-injected hybrid rocket motor

The staged combustion aft-injected hybrid rocket motor is a novel propulsion system that utilizes an independent fuel-rich solid propellant gas generator, with high performance and promising application prospects. However, its performance is significantly influenced by the hydrogen peroxide injection scheme. Therefore, a three-dimensional numerical model based on the Euler-Lagrange framework for multiphase turbulent flow and combustion is established. Based on the validated model, the detailed flow and combustion characteristics are carefully discussed. It is found that the combustion flow field exhibits distinct partition characteristics. And the recirculation zones appearing in the motor head enhance mixing combustion. Then, the effects of axial injection angles and axial/swirl injection ratios on the combustion flow field and motor performance are investigated. The results indicate that the larger the axial injection angle, the deeper and earlier the mixing of hydrogen peroxide and primary combustion gas occurs, thereby enhancing the combustion efficiency and specific impulse. To achieve better motor performance, the axial injection angle should not be less than 30°. Additionally, a smaller axial/swirl injection ratio leads to more droplets accumulating near the wall, resulting in incomplete mixing evaporation and hence motor performance loss. However, this also significantly decreases the temperature near the motor head and wall, which positively impacts the motor's thermal protection. This study suggests that the axial/swirl injection ratio should be controlled around 4:1, as the specific impulse decreases by only 2.3 %. This paper provides valuable guidance for the design of injection schemes for the staged combustion aft-injected hybrid rocket motor.