Research Of Working Characteristic Of Solid Motor In Water

Launching missile under water has many advantages, for example, good maneuverability, easy concealment and steady attitude. The thrust will have a peak when launching missile under water. The peak of thrust might be harmful for the working process of missile. In this thesis, to reduce the thrust peak, the working process of the solid rocket motor under water is numerically studied. Four aspects of the job are included, namely, numerical study of the thrust for the solid rocket motor under water using both sphere bubble model and quasi one dimension model, setting up the model of end-burning solid motor embedded with wire, proposing several means to depress the thrust peak, and suggesting a new method to adjust the thrust of the solid rocket motor.With the sphere bubble model, the working status of solid rocket motor under water is numerically simulated. From the numerical results, the relationships between thrust peak and parameters of solid motor, such as the area of throat, the burning area, the initial volume of chamber, the depth of water, the opening pressure of nozzle cover and the initial radius of bubble, are numerical studied. It is shown that the burning area and the initial radius of bubble have the great effects upon the thrust peak. The other parameters might have the slight effects upon the thrust peak..Since neglecting axial momentum of gas in the sphere bubble model would cause some errors, we establish the quasi one-dimensional model for simulation of the working status of solid rocket motor under water. In this model, the gas movement in the nozzle and bubble is approximated to be one-dimensional and the flow field of water is assumed to be the potential flow, which is solved using the boundary element method. The results obtained from the quasi one-dimensional model are compared with those of the sphere bubble model. Similarly as the sphere bubble model, it is shown that the thrust peak will decrease when increasing the initial radius of gas bubble or decreasing the mass of the cover at the tail of the nozzle.In order to decrease the thrust peak for launching the missile under the water, we consider the end-burning solid motor embedded with wire. In this thesis, the numerical model for the end-burning solid motor embedded with wire of solid motor is set up. Solving the two-dimensional heat conductivity equation for end-burning grain, the one-dimensional heat conductivity equation for wire and the ordinary differential equation for the gas properties in the chamber, the working process of end-burning solid motor is numerically simulated. From the numerical results, the effects of the thermo-physical properties and the diameter of the wire upon the burning-rate are studied. It is shown that the burning-rate would increase when increasing the thermal conductivity of wire, or increasing melting temperature of wire, or decreasing the specific heat of wire. Especially, the thermal conductivity of the wire affects burning-rate obviously. It is interesting that there exists an optimal wire diameter, where the burning-rate takes the maximum. The reason for the existence of the optimal wire diameter is studied by investigating the effective endothermic ratio.Decreasing the thrust peak has the practical importance. In this thesis, we suggest three methods to decrease the thrust peak. The first method is using the end-burning solid motor embedded with wire to decrease thrust. Numerical research of the first method demonstrate that thrust peak at initial time is less than steady thrust. The second method is making large initial radius of bubble before ignition. Two specific projects for this method are propounded. One project is filling up the chamber with gas beforehand, and the other is using internal gas source. We have studied working characteristic of the former project under different condition, namely, different gas, pressure and depth of water. In addition, effect of missile tail outline on thrust peak is numerical studied. Thrust peak of different tail shape, namely, column shape, elliptical sphere shape and taper shape, are compared with each other. Results show that thrust peak of taper shape is the least.At last, with the special modifications for the end-burning solid motor embedded with wire, a method to adjust the work status of the solid rocket motor is proposed. The thrust would be accommodated by changing the burning rate with the technique of adding the negative quantity of heat to the wire. The feasibility of this method is investigated with the numerical simulations. Numerical results show that this method can adjust the work status of the solid rocket motor in a certain range. After adding the negative heat quantity, there exists a relaxation time for that the chamber pressure reaches stable. The advantage of this method is that control system for adjusting the work status of the solid rocket motor is simple and need not work under high temperature circumstance.