Simulation And Calculation Of Thermal Separation Between Firststage And Second Stage Of Rocket

Since the 1950 s,carrier rockets,as the main tool for human exploration of space,have made rapid technological advances.In the whole process of rocket design and development,two-stage or multi-stage connection is often used to improve the carrying capacity of the rocket,and the separation technology is one of the core technologies of each model.The separation technology co vers many aspects such as structure,material,power and control,etc.During the thermal separation process,the shock wave structure in the intermediate zone is complex with extremely high instability,which will have a strong interference to flight due to the interaction with various characteristic deviations of the arrow body and other factors.The thermal and mechanical environment in the separation process will directly affect the success or failure of separation.Therefore,in-depth study on the process and mechanism of thermal separation between stages is of great significance to improve the success rate of launch of carrier rockets and promote the rapid development of space science and technology.Rocket interstage heat separation is a physical process flow and movement of mutual coupling,break up one of them to study hard to avoid attend separately,this paper proposes a technique based on C language compiler six degrees of freedom UDF,in order to realize the coupling calculation method of thermal separation of multistage rocket interstage of the results of the simulation are carried out.The research method is adopted from the shallow to the deep.Starting from the simplified interstage pressure containment condition,variables such as containment pressure and nozzle length are introduced to explore the flow field distribution before separation and solve the relevant calculation problems in the early stage.On this basis,establish the arrow separation air and ground simulation calculation model,from two aspects: macro and micro flow movement,inspection from pressure-out to separate the whole process of the change of the flow field in detail,probe into its full motion law,and predict the safety of the separation process,provide the theoretical reference to the design and test for the future.The study found that in the process of pressure-out,high-temperature zone between the stages before and after the reflection,cause the nozzle exit temperature and heat flux of rapid ascension,at the same time with the movement of the shock wave in the expansion and transformation,the boundary layer separation induced by shock wave,make big changes around the wall stress produces,among them,the wall is the most sensitive level between area,around 0.5 ～ 0.8 times the width of the axial pressure changes frequently,peak of about 0.78 MPa.If the pressure of larynx is properly increased,the surface impact of the first stage can be significantly increased and the separation time can be shortened.The shortening of nozzle is beneficial to the uniformity of pressure in the interstage area,which can reduce the maximum pressure value on the wall surface and reduce its fluctuation range.After the interstage unlocking begins to separate,the shock waves in the inters tage area are completely pushed out of the nozzle after two back and forth oscillations.The interaction between the transverse jet flow and the high-speed incoming flow causes oblique shock waves in front of the separation joint,resulting in flow separat ion,and the separation area gradually spreads backward.In addition,the impact of gas on the front head is the main source of stress of a substage.When the shock wave position turns,the axial stress of the arrow body of the two stages appears an extreme value accordingly.When t=0.12 s,the secondary nozzle is completely withdrawn from the interstage area.In addition to axial force,the instability of the gas and the asymmetric arrangement of the interstage structure will also cause the torque in y and Z directions of a sub-stage.When t=0.20 s,a sub-stage will produce a pitch of 0.65° and a yaw of 0.46°.Compared with the first stage,the position and attitude of the second stage are relatively stable,and its movement is mainly reflected in the axial displacement.Excluding the influence of external high-speed incoming flow,the displacement and acceleration of a substage will have greater fluctuations under the ground test condition,but the overall force decreases,among which the maximum force on the front head decreases by 31%.