Theoretical And Experimental Research On The Operation Process Of The Solid Fuel Ramjet

Because of the virtues, such as high specific impulse, self-adaptive control property, simple structure and high security et., the solid fuel ramjet has extensive application foreground on supersonic missile and added-range projectile. The study on the combustion and flow behavior inside the motor is carried out through theoretical study, numerical simulation and experimental study. Moreover, the study on the simulation of the solid fuel ramjet operation process and the optimization of the motor design is carried out.On the basis of the analysis of the decomposition and reaction process of HTPB, the 12 species 17 steps model is used. Because the chemical kinetics velocity and diffusion velocity are in the same magnitude in the solid fuel ramjet, the models, such as the E-A model, fast reaction simplified PDF model and finite reaction velocity simplified PDF model, can not mirror this phenomenon. Comparing with other models, the second-moment model is selected. Thus, the physicomathematical model is established to describe the combustion and flow behavior inside the combustion chamber, the second combustion chamber and the nozzle of the solid fuel ramjet. The three-dimensional Favre-averaged compressible turbulent N-S equations are used as the governing equations of the reacting flow, and the BSL two-equation turbulence equations are used for the turbulent flow, and the chemical non-equilibrium equations are used for the reaction rate, and the second-moment model is used for the turbulent combustion.The key to numerical simulation is the calculation of the fuel regression rate. In many literatures, in order to achieve the fuel regression rate, the convective heat transfer coefficient is calculated to get the heat exchange rate, using many empirical formula and methods. In the thesis, the heat conductivity of the laminar sub-layer on the surface of the grain is calculated, which reflects the physical essence of the heat transferring. But it demands the higher computational accuracy. Time-dependent LU-SGS method and close coupled full implicit finite volume scheme are used. The AUSMPW+ based on the three-order MUSCL difference scheme is used for the inviscid operator, and the maximum eigenvalue splitting method is used to convert matrix operation to algebraic operation in order to shorten the computing time. Based on the above, a numerical simulation computing program is coded. It is analyzed the influence of the parameters, such as the step height, air total temperature, combustion air flux et.For the first time in domestic, the solid fuel ramjet experiments with nonoxidizer propellant are performed. The experiments results prove that the ignition is reliable, and the motor works stably. A new style solid fuel ramjet test system is established adopting the three species combustion-air heater and vertical hose connection mode for the first time in domestic. The accuracy of thrust measurement of this test system is higher than that of the test system adopting the axial labyrinth seal connection mode, and the heater system has the virtues of high reliability and heating efficiency. The effect of factors, such as total air flow rate, the air inlet diameter of the combustion chamber, the ratio of the air flow rate of the combustion chamber to total air flow rate, on the performance is investigated experimentally. The experimental data shows that some parameters, such as the total air/fuel ratio, pressure in the second combustion chamber and specific impulse, decrease as the reduction of total air flow rate. Moreover, the hot gas flow rate increases as the reduction of the air inlet diameter or the increment of the air flow rate of the combustion chamber, which causes the reduction of the total air/fuel ratio and specific impulse.Considering the radiative heat transfer and the effect of the mass addition from the wall on the convective heat transfer coefficient, the fuel regression rate simulation model is established. On the basis of the above, the operation process simulation model of the solid fuel ramjet is established. The simulation program is coded, and is used to analyze the effect of different structure parameters and operating condition on the performance in detail. It is showed that the specific impulse should be the maximum at the design height, not merely considering enhancing the performance of the inlet. The flight velocity must be optimized in the missile overall design procedure. A proper design point can make the thrust stable during the flight. The solid fuel ramjet has good adaptability, for it can adjust thrust with the change of the flight height and velocity.On the base of the simulation analysis, five main parameters are selected as the optimize variables, and the design optimization model of the solid fuel ramjet is established. The optimize results show that the flight range increases 24.8 percent of the non-optimize results.