Research On Working Process Of The 85% H₂O₂-PE Hybrid Rocket Motor

Because of their low-cost, high safety and reliability, flexible energy management and shutdown-restart ability, hybrid rocket motors have received increasing attention from the space propulsion specialist all over the world. Owing to the dissimilar combustion mode, their working process is different form that of solid rocket motors and the liquid rocket engines. Through the tests of the 85% H2O2-PE hybrid rocket motor, the operation process of the hybrid motor has been studied in the dissertation. The main aspects are as follows:1. The pressurized 85% H2O2-PE hybrid rocket motor test system has been designed and built up for the research work. The hot firing tests and the shutdown-restart of the motor were successfully performed.2. The catalytic decomposition of 85% hydrogen peroxide, the pyrolysis of the polyethylene fuel and the energy performance of the H2O2-PE hybrid rocket motor were all discussed. A catalytic bed made of silver-plated nickel screens was designed and fabricated. The formulation of coating and the coating processing have been obtained through a lot of hydrogen peroxide catalytic decomposition tests. The research of propellant energy performance indicates that the special impulse and characteristic velocity are significantly depended on O/F ratio and weakly depended on chamber pressure. The best theoretical O/F ratio is 8.1. The motor special impulse can be enhanced with the best O/F ratio reduced by increasing the concentration of hydrogen peroxide or adding aluminum powder in the fuel.3. The heat conduction model of the PE fuel with the surface melting and pyrolyzing is developed for the H2O2-PE hybrid rocket motor. Combining with the energy fluxes balance above fuel surface, the simulation and calculation of transient heat conduction of the PE fuel with liquid layer while melting and pyrolyzing are considered by use of the moving coordinates. The calculated regression rate of the PE fuel approximately tallies with the same kind of hybrid rocket motor test data from the abroad. The result of analysis shows that the convective heat flux has main effect on fuel pyrolyzing and vaporizing, the liquid layer of PE fuel can increase the regression rate but also can cause unstable burning.4. The combustion flow in the 85% H2O2-PE hybrid rocket motor has been researched. The numerical simulation of the motor cold flow field and the mixing process of various kinds of gases are performed by PISO algorithm. The combustion model of the oxidizing gas and the fuel pyrolytic gas in themotor was also developed. The simulation of combustion flow is performed under various O/F ratios and different motor chamber structures. The simulations results show that the average combustion temperature is much lower in fuel-rich state and little higher in oxygen-rich state near the best O/F ratio. By extending the post-chamber length the oxidizing gas and the fuel pyrolytic gas can burn completely and the average combustion temperature can be prominently increased. The fuel-rich recirculation zone close to the head of combustion chamber is very important for the combustion. Burning will be incomplete and average combustion temperature will significantly decrease when the sudden-expansion section in the head of the chamber is taken out.5. The internal ballistics and the throttling performance of 85% H2O2-PE hybrid rocket motor loaded with tube grain are studied. The hot firing data of two test motors have been carefully analyzed. The results of research indicate that the pressure, the thrust and the fuel regression rate of the motor decrease while the O/F ratio increasing with the burning time lasting. The special impulse reduces when throttling. The reasons for higher oxidizer flow rate, lower fuel regression rate and lower motor performance in both hot firings are discussed. Several necessary improvements for the test system are suggested.6. The low frequency burning oscillation of the 85% H202-PE hybrid rocket motor is discussed. The FFT spectral analysis of the pressure osci...