Numerical Simulation Research On Unsteady Flow Field In Launching Chamber

When the gun is fired,the gunpowder burns to produce a large amount of high temperature and high pressure gas to form a gas flow field in the chamber.The gas flow field in the chamber is an unsteady,complex flow field including gunpowder burning,material flow,projectile movement and energy conversion,which affects launch safety.Due to the improvement of internal ballistic performance and the development of launching technology,studying the law of motion of the flow field in the bore and influencing factors has certain significance for improving the ballistic performance of weapons and the safety of the launch process.In this paper,based on the characteristics of the transient flow field in the bore,combined with the dynamic grid technology,numerical calculations are carried out for the gas flow field in the bore of a 30 mm gun under different firing conditions.The main research contents and results are as follows:(1)The combustion performance of different variable burning rate propellant is studied through the closed explosive experiment.The results show that the combustion gradual increase can be improved by adjusting the EC content,aspect ratio and aperture of the outer layer.(2)Established a two-dimensional axisymmetric unsteady state theoretical model in the firing chamber,using the secondary development tool UDF of the fluent software,numerically calculated the gas flow field in the chamber of a 30 mm gun at different gas generation rates,and analyzed The characteristics of the gas flow field in the chamber show that the higher the gas generation rate,the faster the projectile velocity increases,the faster the pressure in the chamber rises,the greater the peak value,the faster the pressure drop,and the lower the pressure in the chamber.Stable;and the gas flow field in the chamber is calculated numerically under different loading conditions,and the characteristics of the gas flow field in the chamber are compared and analyzed.The results show that as the charge increases,the speed of gas and projectiles will increase,and the pressure in the chamber will increase.The earlier the peak is reached,and the greater the peak,the greater the fluctuation of the pressure difference between the bore and the bottom of the bomb.(3)Through numerical calculation of the flow field in the bore of a 30 mm gun with or without resistance,the influence of the air resistance in front of the projectile on the flow field characteristics in the bore was studied.The results show that when the projectile is affected by air resistance,the gas and projectile velocity will decrease,and the pressure in the chamber will increase;at the beginning of the movement,the pressure concentration area at the bottom of the chamber spreads slowly to the surroundings as the projectile moves,and the radial pressure gradient The disappearance is slower,and finally the time for the axial pressure gradient in the bore to increase.