Effects of aluminum and aluminum hydride additives on the performance of hybrid rocket motors based on 95% hydrogen peroxide

Abstract

This paper aims to study experimentally and numerically the effects of aluminum (Al) and aluminum hydride (AlH3) additives on the performance of HRMs. A steady-state numerical model of HRM is established, which adopts the 95% hydrogen peroxide (HP) as the oxidizer. A firing test is completed for the certification of the numerical simulation model, the results illustrate that the regression rate of addition of 38% AlH3 and 20% Al increases by 55.6% compared with pure hydroxyl-terminated polybutadiene (HTPB). A good agreement exists between the simulation regression rate and the experimental data. The deviations of thrust and pressure are less than 3.3% and 3.7%, respectively. Specifically, the error of the regression rate is only 0.3%, indicating that the accuracy of adopting numerical simulation method to predict the characteristics of the HRM is acceptable. Several steady-state simulations based on the different content of AlH3 and Al are performed to investigate the effects on regression rate and combustion performance of the HRM. Due to the addition of H2, the thermal conductivity increases with the decrease of the mass fraction of AlH3, which leads to the increase of the regression rate. The regression rate of the fuel with 8% AlH3 and 50% Al increases by 35.5% than the fuel with 58% AlH3, demonstrating that the effect of Al on the regression rate enhancement is more than that of AlH3. The theoretical specific impulse increases with the mass fraction of AlH3. However, it is owing that the part of H2 does not participate in the reaction with O2 and the oxidizer to fuel ratio (O/F) is far from the optimal O/F, the specific impulse is lower than the theoretical specific impulse.