Dynamic Analysis of a Launching Process of a Compressed Air Driven Weapon

Vibration and Shock Dynamics Analysis of a Compressed Air-Driven Weapon Launching Process He Lei, Shang Xingchao, Zhou Kedong, Jiang Yuanqing 2, Zhang Zuoyou 2, Sun Quanling 2 (1. School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; 2. Chinese Weapons The Second Research Institute, Beijing 102202, China) The working principle of pneumatic launching weapon with compressed air as the power source; based on the theory of gas dynamics and Hertz contact theory, the variable mass thermodynamic model and friction model are established, thus establishing the launch process. Kinetic model. The model was simulated by MATLAB/Simulink, and the variation of gas state parameters and projectile motion parameters under constant pressure gas source conditions was obtained. Based on this, structural parameters and power source parameters were analyzed for pneumatic launch. The impact of the weapon launch process. The research results have theoretical guiding significance for the development and design of compressed air driven pneumatic launch weapons.

Conventional weapons generally use gunpowder as their launching energy. However, as the situation of modern warfare continues to change and become more complicated, different requirements are imposed on the energy form of weapons. Many weapons and equipment using new energy sources have been developed, such as electromagnetic guns and sound waves. Weapons, etc. In the field of light weapons, most of the riot guns used to launch shotguns, tear gas, stun guns, etc., like traditional automatic weapons, emit energy from the burning of gunpowder, so the structure of the ammunition is more complicated. Compared with the traditional propellant gas emission, the pneumatic launching weapon has a simple projectile structure, no need for bottom fire, propellant and shell, low production cost, adjustable launch energy, suitable for variable speed and variable pitch launch, stable launch process and impact overload on the projectile. Small; no need to launch drugs, no pollution to the environment when launching, and many other advantages. At present, the foreign use of compressed gas as a launching energy transmitter is more famous, the FN303 low-killing launcher of the Belgian FN company, the American Jackel launching system, etc., and has been applied in the actual combat of anti-terrorism self-defense, the effect is very good, but According to the search results, there are few reports on the theoretical study of the internal ballistic process. In the field of pneumatic launch, Wang Jingui et al. established the internal ballistic model of gas gun in gas gun research. Zhao Junli et al. 63 studied the practical internal ballistic technology of compressed gas gun on the basis of classical internal ballistics.

The gas gun internal ballistic theory often only considers the gas expansion work process and ignores the influence of the gas filling process. When considering the energy loss, a secondary work coefficient is introduced to take the friction into account. In this paper, a variable mass thermodynamic model of aerodynamic emission process aeration and gas expansion work is established. The frictional resistance model of the launch process is derived by using Hertz contact theory, and a complete compressed air driven weapon launch process dynamics model is established. Through the numerical calculation, the thermodynamic parameters of the launching process and the variation law of the projectile motion parameters are obtained, which are provided for the theoretical research and weapon development of pneumatic launching weapons.

The first author, He Lei, associate professor, born in 1973, Heraeus, etc.: a dynamic analysis of the launching process of a compressed air-driven weapon. 1 Structure and working principle The structure of a pneumatic weapon is as shown, the compressed gas power source is connected to the launch valve. After the elastic tool is used to supply the spherical rubber projectile into position, the launch valve is opened, the pressure in the launch tube rises, and the pressure acts on the projectile. When the frictional force is overcome, the projectile accelerates and the ball moves to the position of the film to obtain a fixed speed. Shoot out the film.

There is congestion in the flow. Although the gas velocity at the supersonic gas flow outlet is large, the maximum gas flow rate depends on the critical section in the pipe. The flow rate of gas has different 2.1 gas dynamics theory under supersonic and subsonic conditions. 2.1.1 It is assumed that the flow of the conditional gas in the membrane is a complex opening and boundary changing process. To simplify the model, the following assumptions are made: (2) Since the launching process time is very short, the heat exchange between the system and the outside world is neglected, and this process is considered to be an adiabatic isentropic process; (3) neglecting the influence of gas viscosity, that is, there is no friction between the gas and the pipe wall; (4) Regardless of the cohesive force between gas molecules and the volume of the molecule itself, it is considered that the gas is an ideal gas; the flow; (6) because the direction of the gas jet is 90° from the direction of the projectile motion, regardless of the movement of the gas jet to the projectile influences.

Because the working pressure of the pneumatic launching weapon studied in this paper is not high (about 10 MPa), the ideal gas state equation (Clapperon equation) can better describe the state parameters of the gas, and its form is as follows: gas constant. Under adiabatic conditions, the gas state parameters satisfy the adiabatic process equation 7:1.3 gas flow considerations the isentropic flow of the gas along the variable cross-section pipe, in the supersonic gas as the discriminating condition, when the back pressure (the ratio of the outlet pressure P to the inlet pressure) is less than this At the value, the flow is a supersonic flow; when the back pressure is greater than this value, the flow is a subsonic flow.

2.2 Hertz contact theory The spherical rubber projectile will be affected by the friction force when moving in the launch tube. The frictional force depends on the normal contact force between the rubber projectile and the pipe wall. The contact force is caused by the elastic deformation of the rubber projectile due to the existence of the outer dimensions of the rubber projectile and the inner diameter of the pipe wall. Therefore, the key problem in solving friction is the solution of normal contact force. Hertz theory is widely used in the contact model between elastic three-dimensional bodies. 10 12 uses Hertzian contact to establish the contact force model of the ball and raceway in the ball screw, and its rationality is verified by numerical simulation or experiment; 13 using Hertz contact The contact model of the relay contact is studied, and the feasibility and accuracy of the model are verified by the impact test.

The Hertz theory describes the contact force generated by the rigid sphere in three-dimensional contact with the elastic plane. The deformation on the elastic plane is a circular pit with a radius a. The vertical displacement generated by the contact area is the load distribution form where E corp = RdE is Yang. The modulus of elasticity is Poisson's ratio, R is the radius of the sphere, d is the maximum deformation amount M. The section plane, the model of the contact is as shown, the solid line indicates the real object after elastic deformation under the z-direction force. The wall and the dotted line are the original shape of the object. The deformation of the model in this section is the same as the Hertzian contact, and the load distribution is the same, except that the deformation occurs in the sphere and not in the plane. Since the contact area of ​​the model is a circular cylindrical surface, the load of the contact area is integrated: Yang Liming. New non-lethal weapon - OC tear pain ball launcher. Light weapons, 002, 1:16-17. Wang Jingui. Principle and Technology of Gas Guns M. Beijing: National Defense Industry Press, Wang Jingui. Research on super-high speed projectile launching technology of secondary light gas gun. Journal of High Pressure Physics, 1992, 6 (4) Lin Junde, Zhang Xiangrong, Zhu Yurong, et al. Three-stage compressed gas gun technology for ultra-high speed impact experiments. Explosion and shock, 2012, Zhao Junli, Gao Yuefei. Research on practical internal ballistic technology of gas cannons. Journal of Taiyuan University of Technology, 2003, 34(3) Tong Binggang, Kong Xiangyan, Deng Guohua. Gas Dynamics M. Beijing: Higher Education Press, 2012. Lu Jiapeng, Tan Xingliang, Lei Zhiyi. Automatic weapon gas dynamics. Nanjing: Nanjing University of Science and Technology Press, 1989. Niu Sibo, Wang Hongyan, Chi Baoshan, et al. Analysis of double-chamber airbag cushioning characteristics of reloading and recycling system. Vibration and shock, 012, Jiang Hongkui, Song Xianchun. Dynamics research and simulation of the ball screw sub-ball cycle system. Vibration and Shock, 2007, Chen Yong will, Tang Wencheng, Wang Jiechi. Influencing factors and experimental research on the stiffness of ball screw. Vibration and shock, 2013, Li Geng, Chen Jinjiang, Long Chao, et al. Finite element analysis of ball bearing Hertz contact problem based on ANSYS. Mechanical Research and Application, 2011, 5: Yan Guofu, Chen Yinghua, Ren Wanbin. A method for analyzing the impact characteristics of beam structures with Hertzian contacts. Vibration and Shock, 2009, Yang Kai, Zhou Wei, Ma Li. MATLAB basic application and simulation implementation. Chengdu: Southwest Jiaotong University Press, 012.

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