Theoretical And Experimental Research On The Internal Operation Process Of Hybrid Rocket Engine

Hybrid rocket motors keep the features of low cost, high reliability, and no hazards. In recent years, there has been a resurgence of interest in the development of hybrid rocket engines for advanced launch vehicle applications. But in hybrid rocket motors, the combustion efficiency and regression rate are very slow. Although the aforementioned work has provided considerable information to the understanding of flow and hybrid combustion process in hybrid rocket motors, many fundamental issues regarding the detailed mixing and combustion process, especially the performance of regression rate, still need to be addressed.Of particular importance in the design of hybrid rocket motors is the fuel surface regression rate and the manner in which it varies with operation conditions. In view of this, a research program involving both experimental and numerical approaches is initiated. This thesis is aimed at providing the complete details of the hybrid combustion processes and flowfields in hybrid rocket motors and seeking ways to improve the combustion efficiency in order to provide theoretical basis and direction for the design of hybrid rocket motors. The results attained are as follows.Based on the thermodynamic calculation and theoretical performance analysis, effects of fuel, oxidizer/fuel ratio, combustor pressure on the performance of hybrid rocket motor and temperature of combustor are analyzed. A ballistics model has been developed for the purpose of investigating the influence of fuel grain design on overall performance of hybrid rocket motors. The model, based on steady, one-dimensional compressible flow, includes the capability to handle arbitray wagon-wheel fuel section designs. Results of the ballistics calculations are presented for liquid oxygen as fuel.Aimed at hybrid propellant having low strength and poor combustion performance, development of HTPB propellant is presented. In order to determine the effects of solid-fuel additives on the combustion behavior of HTPB and GOX, many different types of powders are added to the solid fuel. Kinds of intensifiers with active groups are added to enhance curing network of HTPB binder system. The propellant is endowed with excellent performances of different metal content, tensile strength up to 1.8MPa, regression rate>0.3mm/s.Based on the fluid-solid coupling technique and some comprehensive physical processes during working of hybrid rocket motor, a numerical model is developed to predict the regression rate for the solid fuel surface of hybrid rocket motor under different working conditions. The muti-dimensional Favre-averaged compressible turbulent N-S equations are used as the governing equations of the reacting flow, the improved k-εtwo-equation turbulence model is used to simulate the turbulent flow, and Eddy-Dissipation Model is used to simulate the gas combustion. Accuracy of the calculated model is verified by comparison of calculation results with experiment data. The simulation results of model motor show that combustion, flow and regression rate of solid fuel surface of hybrid rocket motor are of inhomogeneity. Information gained from CFD modeling provides future engine designers valuable information regarding the design of hybrid rocket motors combustion chambers.The paper also makes a whole design of experimental hybrid rocket motor system, and discusses the result of motor firing. Technical project and experiment results of multiple start and shutoff of GOX/HTPB hybrid rocket motors are presented. The performance data of hybrid rocket motors are measured. Various kinds of factors, which affect hybrid rocket motors performance, are preliminarily analyzed. The experiments show that multiple-start and shutoff can be realized and its number of times and time intervals can be regulated at ramdom. An innovative igniter based on catalytic decomposition of H₂O₂ is designed and manufcatured. A H₂O₂/HTPB hybrid rocket motor using this igniter was tested. The experiment results demonstrated that this new igniter can successful start the H₂O₂/HTPB hybrid rocket motors.