Design And Simulation On The Intake Channel Structure Of Catapult Device

Ejection device because of its easy to conceal,low cost,high security advantages widely used in UAV,carrier-based aircraft,kinetic energy bombs and other ejection process.As the optoelectronic components of the guidance and control system can not withstand the large overload,so in order to launch high-precision kinetic energy bombs,ejection process required lower ejection force.But the normal burning of gunpowder requires a certain pressure environment,so the catapult need to set the high pressure chamber and low pressure chamber.At the same time,the structural design of the intake passage connected to it is particularly important.Firstly,the basic structure of the intake channel is analyzed by using the theory of fluid mechanics,gas dynamics and catapult correlation,A shrink-type intake passage suitable for the exit Mach number of less than 1 and a contraction-expansion type intake passage suitable for the outlet Mach number greater than 1 are obtained,and each type has three preliminary structural schemes.Secondly,through the theoretical analysis of the two intake channels,combined with the ejection process and the ejection requirements,the specific structural parameters such as the inlet,outlet and throat cross section of the contraction type channel and the contraction expansion channel are analyzed and calculated.And the flow state is analyzed,the design state of the intake passage satisfying the ejection requirement is obtained.Finally,through the analysis of the basic characteristics of high and low pressure chambers and their working process,the concrete method of channel modeling and simulation is obtained,and FLUENT fluid simulation software is used to model the initial structure of the channel.Analysis the flow field change and its impact on the low-pressure chamber of the pre-working process pressure,temperature and other parameters,and a detailed analysis of their specific structural parameters.Through the simulation analysis we can see that the contraction type intake channel scheme three,that is,the first parallel after the contraction type of the program is the optimal structure of the contraction channel,in the case of the same length of the intake channel,it reaches the same ejection pressure required less time.And within a certain range parallel to increase the channel length of 1mm will withstand the maximum pressure drop of about0.48%.At the same time it has a positive effect on the temperature of the low-pressure chamber,meet the export Mach number less than 1 of the intake channel structure design requirements.Through the simulation analysis,it can be seen that the parallel contraction and re-expansion scheme is the optimal structure scheme of the contraction-expansion channel.When the channel length is the same,it takes less time to reach the same ejection pressure.And in a certain range Increase the length of the parallel section by 1mm will reduce the maximum pressure on the intake passage by about 0.92%.At the same time it has a positive effect on the temperature of the low-pressure chamber,meet the export Mach number greater than 1 of the intake channel structure design requirements.