Study On Two-phase Flow Of Ignition Jet And Propagation Characteristics Of Ignition Gas In Modular Charge

Modular charge is the most ideal and advanced charge technology at present,it can greatly improve the performance of artillery in all aspects.The firing process of modular charge has an important influence on the interior ballistic performance and firing safety of artillery,primer as the key component to complete the ignition process,it is also of great significance to study the output capacity of primer jet after firing.In this dissertation,the propagation of primer jet in the ignition tube,the ignition of starting mix and the propagation of ignition gas in modular charge box are modeled and simulated.The main research contents and achievements are as follows:(1)The combustion model of primer and one-dimensional two-phase flow model of primer jet propagating in ignition tube are established,on the basis of solving the firing and combustion process of primer by the fourth-order Runge-Kutta method,CTVD method was used to calculate the propagation process of the primer two-phase jet in the ignition tube,the variation rules of jet pressure,two-phase velocity and voidage at different positions of the ignition tube are obtained.The results show that under the action of gas pressure,underexpansion primer jet propagates downstream,gas phase velocity is faster than solid phase velocity,a strong pressure wave exists in the jet head;gas phase first reflects on the boundary fixed wall and interacts with particles of solid phase gunpowder whose motion lags behind to strengthen its combustion.When solid particles in the jet move to the right boundary,they accumulate and burn at the right end.These phenomena will cause pressure fluctuation and reverse pressure gradient effect in the ignition tube.(2)Considering the two-dimensional expansion of primer jet outlet,a two-dimensional two-phase flow model of primer jet expansion in combustible ignition tube is established,CTVD method is extended to the numerical calculation of two-dimensional model by using the dimension splitting method.The calculation results show that the difference between the diameter of the primer jet outlet and the ignition tube causes obvious two-dimensional effect in the initial stage of the jet,radial direction pressure wave can enhance the axial propagation of jet;The radial direction effect of primer jet basically disappears after a period of development,especially after a certain distance from primer nozzle.The motion law of the jet in the combustible ignition tube is basically consistent with the one-dimensional model,but because the diameter of the combustible ignition tube is larger than the diameter of the jet outlet,the holistic pressure is lower,the solid phase is more dispersed and the particle velocity is faster,which is helpful to accelerate the fire transfer speed.(3)A two-dimensional two-phase flow model considering the combustion of starting mix and combustible ignition tube and the flow of gas through the fire hole was established.By solving and calculating the model,the propagation characteristics of ignition gas in unit modular charge is analyzed,and the variation rules of main parameters such as pressure,axial and radial two-phase velocity and voidage in combustible ignition tube and module cartridge are obtained,as well as the time of hole breaking.The results show that in the axial direction,the first eight fire holes will rupture in time sequence,and the last two fire holes will rupture ahead of time under the influence of reflected pressure wave,which indicates that a certain intensity of the end cap of the ignition tube can help shorten the time of all the ignition holes rupture;opening fire holes in the combustible ignition tube can delay and reduce the random tearing of the combustible ignition tube due to excessive pressure.In a relatively short time,the ignition temperature of the propellant near the fire holes can basically reach,which indicates that the axial ignition consistency of the modular cartridge is good.(4)Based on the above model and calculation method,the propagation characteristics of ignition gas in six modular charges are analyzed,it can be seen : the combustible ignition tube of the modular box near the primer is first affected by the primer jet,and the pressure rises rapidly;however,the starting mix moves downstream under the action of the jet,which causes the sequential ignition of the ignition tube in the following modules.With the combustion of the starting mix,the pressure of the ignition tube in the following five module boxes increases gradually,and is higher than that near the primer.Due to the long ignition tube,it takes a long time for all the fire holes to break,and the time for the particles in each modular cartridge to reach the ignition temperature is quite different,so it is difficult to achieve the ignition of six modular cartridges at the same time.