Numerical and experimental study on 95% hydrogen peroxide catalytic ignition of hybrid rocket motors with HTPB-based aluminum additive fuel

This paper attempts to research ignition delay time and ignition process of catalytic hybrid rocket motor (HRM) with 95% hydrogen peroxide (95HP)/HTPB-based aluminum additive fuel. Firing tests are conducted with 95HP and different fuels on lab-scale HRMs. The aluminum weight fractions of four HTPB-based fuels are 38%, 48%, 58% and 65% respectively. Corresponding two-dimensional axisymmetric transient simulations are established to verify the relationship of catalytic ignition delay to fuel grain aluminum weight fraction and to catalytic decomposition temperature. The mono-propellant catalysis experiments of 95HP are carried out and show that the maximum temperature of decomposition products can reach 1140 K. The catalytic ignition delay time of 95HP/HTPB-based fuels is affected by the aluminum additive. When the aluminum weight fraction of the fuels is increased from 38% to 65%, the effective heating time of the ignition is correspondingly increased from 0.250 s to 0.556 s. The flame pictures are taken by the high-speed camera in the firing tests. A large number of sparks appear in the flame when it reaches a stable state, but there is no spark in the flame at the initial stage of ignition. Therefore, it is indicated that the aluminum does not participate in the chemical reaction at the initial stage of ignition, but may change the physical properties of the fuel. Similarly, the simulation results prove that the increase of the aluminum weight fraction of the fuel will increase the ignition delay time while the increase of catalytic decomposition temperature will greatly reduce the ignition delay time.