Analysis Of Impact Effect Of Gas Jet Of Airborne Missile/Rocket Weapon On Helicopter

As the conventional firepower equipment of modern armed helicopters,airborne missile/rocket weapons are generally launched by burning solid propellant to produce hightemperature and high-pressure gas,which is accelerated by Laval nozzle.During the launch of rocket missiles and other flight off orbit,it will cause surface material damage and great dynamic impact effect when the moving gas jet directly impacts the carrier body.Its changeable impact flow field will also indirectly affect the flight channel of the helicopter and pose a serious threat to flight safety.Taking the launch system of airborne rocket missile of armed helicopter as the research object,this paper deeply studies the multifaceted impact effect of gas jet on helicopter during the launch of airborne rocket weapon by using numerical simulation method and appropriate assumptions.The main research contents are as follows:(1)By simplifying the launch model of helicopter airborne rocket nest,combined with the three-dimensional unsteady flow field numerical calculation method and dynamic grid technology,the gas jet impact flow field of rocket launch under typical attack attitude is numerically simulated,and the variation law of initial shock wave on multiple positions after the nozzle end cover is opened is analyzed,the influence of helicopter attack attitude on the flow field of rocket accompanying gas jet and the change law of impact load during the whole launch process are compared.The results show that the reflection effect of the fuselage wall on the initial shock wave greatly improves the overpressure load at the wall,and the alternating positive and negative pressure of the initial shock wave causes the load change from + 23.7k Pa to-7.15 k Pa on the fuselage;In the process of leaving the tube,the nozzle gas will produce a muzzle shock wave flow field similar to that in the process of gun firing;The lift and lateral force of the helicopter in hovering attitude are easy to fluctuate,which has a great impact on the stability and firing density of the helicopter.(2)Aiming at the multiple firing state of airborne rocket nest,the impact flow field of rocket ejection flow under no-load and intermediate launch conditions with the change of air facing surface structure is simulated and calculated,and compared with the change of flow field during launch under full load.At the same time,the influence of gas jet superposition on impact effect during continuous launch is analyzed.The results show that when the missile position is close to the empty launch tube,part of the gas jet from the tube will pass through it and generate a secondary jet shock wave behind it.The shock wave intensity is the highest when it is launched in the no-load state,and the peak curve of overpressure on the corresponding fuselage changes to double peak type;The peak value of the initial shock wave overpressure on the fuselage decreases linearly with the distance between the nozzle axis and the fuselage,and the average change rate is-71.6k Pa/m;The superposition effect of gas jet has a significant effect on the negative pressure load during continuous fired.(3)The launch model of guideway airborne air to ground missile is established,the difference of dynamic impact load between the missile limit mounting and the actual combat launch is analyzed,and the changes of impact flow field under the rocket multi tube launch mode and the air to ground missile guideway launch mode are compared.The results show that when the distance between the typical missile carrier position and the fuselage is doubled,the peak value of overpressure load on the fuselage is reduced to 1/3,and the linear change rate is-22.48 k Pa/m.The overpressure load on the wall caused by the initial shock wave of rocket gas is greatly related to the nozzle diameter and wall distance;The decrease of the total pressure in the combustion chamber causes the core structure of the jet to shrink inward,and creates a negative pressure zone around it,resulting in additional lateral force load fluctuations on the helicopter fuselage.