Muzzle Stability Analysis And Multi-objective Optimization Of Gatling Gun

With the development of air firepower and the improvement of missile technology,it requires the gatling gun to develop towards a higher firing speed and rotation speed.In continuous firing,the gun will be subjected to high frequency,high strength impact load and thermal load caused by the temperature difference inside the barrel.Continuous impact load and thermal load will reduce the muzzle stability and increase the muzzle vibration response.Muzzle vibration will change the initial direction of projectile at the moment of muzzle exit,and then affect the firing accuracy of Gatling gun.Therefore,improving the muzzle stability of Gatling gun under continuous firing has become the focus of research.In order to solve the above problems,the whole gun dynamic finite element model is established according to the basic theory of gun firing.On the basis of the classical interior ballistics theory,the bore force of gun firing is solved.Based on the dynamic model and Block Lanczos method,the modal parameters of the firing system of the Gatling gun are calculated,and the modal frequencies which have great influence on the muzzle stability are obtained.The modal analysis results show that the second and third modal frequencies of the rotating parts,the first three modal frequencies of the cradle and the first seven modal frequencies of the bracket should be kept away from the firing frequency to prevent the muzzle stability from decreasing.The finite element implicit integration algorithm is used to solve the muzzle vibration response of Gatling gun under continuous impact load,which can provide reference for multi-objective optimization design of Gatling gun.The heat conduction equation of gun barrel during continuous firing is solved by finite element method,and the temperature response characteristics of gun barrel are analyzed.In continuous firing,the temperature gradient of barrel along radial direction is much larger than that along axial direction.The muzzle vibration response of barrel under continuous thermal load is calculated by means of thermo solid coupling.Under continuous thermal load,the muzzle vibration response of gatling gun is mainly reflected in the axial direction of barrel.The cooling characteristics of the barrel under different cooling methods are analyzed through the heat transfer model of the cross section of the barrel.Chromium plating cooling on the inner barrel can quickly reduce the inner wall temperature in the initial stage of continuous firing,but it can not solve the problem of temperature accumulation in the barrel.The interlayer cooling method can take away 20% of the total heat input from the inner wall when firing 100 rounds continuously,which can slow down the increasing trend of the inner wall temperature with the firing times and solve the problem of temperature accumulation in the barrel.Based on the quasi two-phase flow model of interior ballistics,the one-dimensional quasi two-phase flow equations are solved by using Mac Cormack difference scheme,and the distribution of flow field parameters at any time is obtained.The distribution of flow field parameters at the moment when the projectile exits the muzzle is taken as the initial condition of muzzle flow field simulation in the aftereffect period.The muzzle flow field in aftereffect period is simulated by finite volume method.The characteristics of muzzle flow field with brake and the influence of blow hole structure on muzzle flow field are analyzed.Blowing holes can reduce the pressure and temperature of the flow field inside the brake,and reduce the forward force of the brake.The influence of muzzle brake on muzzle stability is analyzed by means of unidirectional thermal fluid solid coupling.The results show that the quality of the brake has a great influence on the lateral displacement of the muzzle,and the hole blowing can reduce the influence of the brake on the axial displacement of the muzzle.The design matrix of multi-objective optimization experiment is determined by central composite design.The explicit functional relationship between the design variables and muzzle vibration response is constructed by using the second-order response surface model,and the improved multi-objective genetic algorithm is selected to optimize the design variables,so as to obtain the Pareto of the target variables.The corresponding design variables are selected in Pareto to improve the muzzle stability of gatling gun.