Experimental Study And Numerical Simulation Of Cook-off Characteristic For Composite Solid Propellant

The cook-off process of AP/HTPB composite solid propellant is researched with both experiment and numerical simulation on the background of the thermal safety of the solid rocket motor. The main research contents are as follows:(1) A small-scale cook-off experimental apparatus of solid propellant is designed, in which the composite solid propellant AP/HTPB is taken as a loading object, and the influence of the insulating material is considered. Both fast and slow cook-off tests are carried out using K-type thermocouple of nickel chrome-nickel silicon and the data recorder. The results show that the initial ignition position of AP/HTPB is occurred on the surface of propellant grain at the condition of fast cook-off, and in the center of propellant grain for the slow cook-off.(2) A two-dimensional unsteady cook-off model of AP/HTPB composite propellant is established according to the apparatus, and compared with the experimental results. The results show that the theoretical calculation results are in good agreement with the experimental data, which implies that the calculated model and method are reasonable and feasible.(3) The cook-off model of AP/HTPB propellant proposed in this paper is used to simulate the slow cook-off and fast cook-off behavior of the solid rocket motor with CFD software. The results show that the initial ignition locations of the solid motor are occurred in the annular region on the inner wall of the propellant at the longitudinal distance of about lmm under the condition of slow cook-off, and the initial ignition location moves from the central to the grain shell end surface with the increase of heating rate. But at the condition of fast cook-off, the initial ignition position of the solid motor is occurred in an annular region on the outer wall of propellant close to the nozzle. The ignition delay period is shortened quickly, and the ignition temperature is gradually increased with the improvement of the flame temperature.(4) A two-dimensional steady microscopic combustion model of AP/HTPB composite propellant is established to study its burning characteristics after cook-off response. Numerical simulation for the microscopic flame structure and burning property is carried out under different pressures. The results show that the overall combustion flame structure develops from a premixed structure to a typical diffusion one gradually with the increase of ambient pressure. Moreover, the heat feedback of the flame heat release for the burning surface strengthens and the flame core closes to the surface gradually.