A Model For Base Pressure Analysis Of Base Bleed Projectile/Missile And Simulated Calculation

The base bleed technology using solid propellant combustion to increase base pressure to achieve drag reduction or generate thrust is widely used in the projectile, rocket, missile and other high supersonic aircraft, such as the base bleed unit and solid rocket motor. It is an important study to predict the drag reduction ratio and the thrust coefficient by accurately calculating the base pressure characteristics. All of them are a kind of important characteristic parameters of base bleed projectile and rocket motor, and has obvious relationship between base pressure and free flow pressure.The paper is based on a large amount of base bleed experimental results which is used to calculate the drag reduction rate and the thrust coefficient by establishing a relationship and engineering algorithm between the base pressure ratio and the base bleed parameters. In the paper, the main studies are:(1)The semi-empirical model about base pressure ratio of the base bleed unit is established by comparing prior wind tunnel test data and semi-empirical formula. The model considering the base bleed parameter I, the base bleed gas temperature T,and free flow Mach number Max to the influence of the base pressure ratio is deduced. The model could be used when the base bleed parameter is less than 0.005, which could meet the requirements of accuracy and the design requirement in large range.(2) According to the subsonic base bleed and one-dimensional isentropic flow assumption, the interior ballistic model of base bleed unit is established which can simulate and calculate the affection of interior ballistic parameters of base bleed unit by the spinning speed; The 6D freedom base bleed exterior ballistic model is established. The drag reduction ratio could be calculated rapidly by solving the exterior and interior ballistic models of base bleed projectile simultaneously without offering the function of drag reduction ratio. The calculated result is suitable for the engineering necessary accuracy.(3) In order to predict and calculate rapidly the drag reduction ratio of base bleed unit and the thrust coefficient of rocket motor, the simulated calculation module based on the relationship of engineering calculation model and base pressure ratio model is developed by Matlab. The module consists of mainly three parts:the base bleed interior ballistic calculated module, base pressure ratio calculated module of the base bleed unit and the base pressure ratio calculated module of the solid rocket motor;(4) The affection of base pressure ratio under the conditions of the different free flow temperature, Mach number and the structure parameters by inputting a different base bleed unit and rocket motor parameters. The simulated results were compared with the prior wind tunnel test data, which show this method has high calculation precision and can meet the demand of engineering calculation.