Aerodynamic Analysis Of Ejection Capsule

In recent years,research on near space vehicle has become a hot spot in both aviation and aerospace fields.When the hypersonic near space vehicle works,the power conversion must be carried out under a certain height and Mach number.The process is often accompanied by a high incidence of accidents.Therefore,it is necessary to study the lifesaving problem of the near space vehicle with a high Mach number.According to the current situation of escape system field at home and abroad,a closed ejection system for near space vehicle is designed.The following research is carried out by using the numerical simulation method:(1)The governing equations and numerical methods which were used in this thesis were discussed,and the numerical calculation method is firstly presented to analyze the wall pressure coefficient of the typical semicircle pillar in a high speed.By comparison,the numerical simulation results agree well with the wind tunnel experiment data which verify the correctness of the numerical method.(2)Then the calculation method is applied to the research of closed ejection system.Based on the calculation conditions of 30 km altitude with Mach number of 4,the flow field distribution of the ejection capsule with different shapes are investigated.The most appropriate shape is determined.On the basis of the selected shape,the variation of seat aerodynamic characteristics at angles of attack from-90° to 90° and the angles of sideslip from 0° to 50° is further calculated.The static stability analysis shows that the closed ejection seat of the unstable device is easy to rotate.(3)Two kinds of hard stabilization devices are designed and installed.A large number of steady calculations are carried out and the results show that the stabilization rod can improve the aerodynamic characteristics of the closed ejection seat in a wide range of attitude angles compared with the stabilization plate,and makes the seat statically stable within the angle of 0~20 degrees,which is suitable for the stable deceleration system of the closed ejection seat.(4)The forces acting on the seat-occupant system during free flight after ejection were analyzed and the six-degree-of-freedom(6DOF)equations for the seat-occupant system were set up.The quasi steady method based on static mesh and the unsteady method based on dynamic mesh are respectively calculated by coupling 6DOF equations and N-S equations with UDF and the dynamic stability and deceleration performance of the seat-occupant system is obtained.The results show that the two methods agree well with each other and both can be used for dynamic calculations of the seat-occupant system.The designed stabilization rod system has a good effect on both pitching-stability and yaw-stability,but poor deceleration performance.