Research On Working Characteristics Of Variable Flow Gas Generator In Solid Ducted Rocket

Solid ducted rocket has a dominant position in the field of tactical missile because of its simple structure and reliable performance,however,the traditional solid ducted rocket is difficult to change the thrust,which limits the flexibility of the missile because of the lack of thrust adjustment capacity.Variable flow gas generator enables the solid ducted rocket to retain its original advantage and also has the ability to change thrust.In this paper,the working characteristics of the variable flow gas generator of solid ducted rocket was studied in terms of adjustment principle and system design,working process numerical simulation,steady numerical simulation and unsteady numerical simulation.(1)The derivation of the formula for calculating the balance pressure was listed on the basis of the internal ballistic formula,variable flow principle was analysed.The design of the nozzle was completed by the expected range of pressure adjustment.The components of the variable flow system was briefly described.A method for calculating the equivalent area of the throat is established.(2)Based on the basic hypothesis of the working process of gas generator,a steady state numerical simulation model of gas generator is established,and the influence of tip contour,location and structure of pintle and nozzle on the performance of gas generator and the plume of gas generator were studied.The conservation equation of dynamic grid was derived.The dynamic grid calculation model for the simulation of pintle motion in the unsteady numerical calculation of gas generator was established by using the layer method.The result of numerical calculation was compared with the experiment.The influence of the driving speed of the pintle,the free volume of the gas generator and the pressure exponent on the working characteristics of the gas generator was studied.(3)By comparing the equivalent throat area response speed of different pintle tip contour and analysing with the flow field of gas generator and comparing the performance of gas generator,it was known that the circular arc pintle performs well,which was the optimal configuration of gas generator.Large diameter pintle cause large flow losses,and with the increase of the diameter of the pintle,the top of the pintle will become higher temperature,the heavier the degree of ablation,which was not conducive to the use and design of the pintle.The change in the pintle tip contour causes the difference in the back pressure of the nozzle to cause the difference in the position of the Mach disk in the plume flow field.(4)The faster the pintle moves,the faster the pressure response,but the pressure hysteresis phenomenon will be produced.Meanwhile,it may be accompanied by the"negative regulation" phenomenon of thrust.By comparison with the steady calculation,it was found that the unsteady simulation results were almost the same as the steady simulation when the pintle speed was small When the free volume of the gas generator became larger,the time of the pressure to reach the balance was longer and the negative adjustment regulation phenomenon of the thrust is more serious.The main influencing factors of the pressure response velocity vary with the free volume of the gas generator.The change of pressure exponent doesn't affect the trend of combustion chamber pressure and gas generator thrust.With the increase of pressure exponent,the regulation ratio of pressure and thrust increases.