Research On The Flow Field And Ballistic Characteristics Of The Gas-Steam Ejection

Gas-steam ejection is a common launching technique for underwater launching,which has the advantages of simple structure,stable interior ballistic performance,large thrust,favorable thermal environment,safety and reliability.It is an important research direction of underwater launching.In the process of underwater launching,the interior ballistic parameters and the complex mechanical environment of out-cylinder play the important roles in the safety of the missile launching,which may affect the mechanical ability of the launcher structure.Therefore,it is of great significance for the safety of underwater launching to research the flow field,the ballistic characteristics of in-cylinder and out-cylinder.The paper takes the underwater gas-steam ejection system as the research object,a series of research and exploration are carried out for the gas-water vaporization mechanism,the interior ballistic characteristics,the theoretical calculation,the interior ballistic optimization,the flow field and the load properties of out-cylinder.The contents of this paper are as follows:(1)The numerical model of the in-cylinder process for the gas-steam ejection is established.The high-speed gas jet,the gas-water two-phase flow,the turbulent flow,the species transfers and the dynamic mesh technology are considered in the calculations.With the combustion test of the high pressure chamber,the pressure is obtained.The reliability influence of the mesh density and the numerical methods are evaluated.Furthermore,the mechanism of high temperature gas-water vaporization involved in the ejection process is verified by the experiment which injecting water to rocket flame.The multiphase flow field,the pressure of in-cylinder,the temperature of in-cylinder and the internal ballistics of missile are analyzed.Furthermore,the influence of cooling device on the internal ballistics and the load are researched.The results show that the cooling device can improve the stability of missile and improve thermal environment of launcher.(2)The influence of structure parameters of gas-steam ejection system and the environment parameters on the internal ballistics,the multiphase flow field,the load characteristics are researched.Under different conditions of second nozzle throat size,spray hole diameter,spray hole number,spray hole angle,elbow inlet angle and launch depth,the quantitative analysis is conducted based on the flow field,load and internal ballistics.The effect of structure parameters on hydraulic pressure differential coefficient is obtained.The influence of different depths on missile velocity of out-cylinder is studied.The comprehensive assessment is carried out of the interior ballistic performance under different factors.(3)The theoretical model of ejection system is built based on thermodynamic theory and missile motion equations on the high and low pressure chamber thermal system of gas-steam ejection system.A method for predicting the characteristics of the internal ballistics is proposed.The mass-flow coefficient,pressure coefficient and energy coefficient can be obtained based on the results of CFD simulation.The theoretical calculation results are in good agreement with the experiment values and CFD numerical solutions,which could demonstrate the validity of this method.(4)Based on the theoretical mathematical model of the internal ballistics,the multi-objective optimization model which treats the structure parameters of launcher as design variables and treats the interior ballistic parameters as optimization targets is established.The interior ballistic parameters are optimized by combining the Optimal Latin Hypercube Design and the Multi-Objective Optimization method.The influence of spray hole diameter and cylinder initial height on the interior ballistic target is analyzed.Furthermore,the optimal solution of the internal ballistics is acquired.The results show that gas energy efficiency and launch stability have greatly improved.(5)In view of the process ejecting from cylinder,three-dimensional unsteady numerical model of the process out cylinder for underwater launched missile is established.The boundary pressure change,bubble dynamics,cavitations and dynamic mesh technology are considered in calculations.The effectiveness of the numerical model is verified by the experiment of underwater missile motion.In addition,the flow field characteristics,evolution process of tube mouth bubble,shoulder cavitations and ballistics out cylinder are researched.On the basis,the influence of missile head shapes,open angles,boat speeds and launch depths on the flow field,load and ballistics out cylinder have been studied.