Research On Acoustic Energy Resonance Test And Simulation Analysis Technology Of Solid Rocket Motor

With the continuous improvement of missile performance requirements,solid rocket motors with high loading,high pressure,large aspect ratio,and composite high-energy propellants have become a development trend.However,in the process of motor test run,unstable combustion phenomenon occurs from time to time,which is difficult to be solved by traditional methods,and has a great influence on the motor design and technical development.According to the relationship between the pressure oscillation frequency and the natural frequency of the motor acoustic cavity,unstable combustion can be divided into acoustically unstable combustion and non-acoustic unstable combustion.The acoustically unstable combustion is a problem that often occurs and is not easy to completely solve.Based on the problem of acoustically unstable combustion,from an acoustic point of view,through experimental research,numerical simulation and theoretical analysis,the influence of structural characteristics on motor stability is explored,and the whole machine analysis model is established to explore the acoustic resonance law of solid rocket motor with wing column charge,which provides reference for motor design and prediction of unstable combustion.The main research contents are as follows:(1)Based on the theory of acoustic unstable combustion and acoustic theory,using acoustic excitation as disturbance and provides energy,considering the structural damping,wall damping,nozzle damping and acoustic energy loss inside the acoustic cavity,using the acoustic response transfer function to characterize the stability of the acoustic cavity,the experimental method and system are established to explore the acoustic resonance law of solid rocket motor.And the influence of excitation position,front head structure,submerged cavity volume and aspect ratio on the stability of acoustic cavity is studied.(2)Transforming the gain/damping factor in motor into simulation boundary and condition,using the acoustic response to characterize the stability of the acoustic cavity,the acoustic resonance simulation analysis method is established.The acoustic impedance of nylon material,insulation material,charge material and nozzle wall material is measured by standing wave tube test to characterize the absorption effect of sound field boundary on sound wave;the pressure coupling admittance function of propellant is obtained by T-shaped burner test to characterize the sound energy gain provided by burning surface;the fluid medium parameters are obtained by internal flow field calculation to consider its influence on acoustic characteristics and performance of acoustic cavity.The simulation models corresponding to acoustic resonance test,vki model motor cold flow test and motor hot test are established.The simulation calculation is carried out and the results are compared to verify the simulation methods from different aspects.(3)Based on acoustic resonance simulation analysis method and steady-state wave attenuation method,the numerical simulation method of the motor nozzle damping is established.The calculation results show that: Nozzle damping is independent of the location of the monitoring point,the intensity of the sound source and the mean pressure of the combustion chamber;increasing the nozzle throat to port area ratio,reducing nozzle convergence angle and motor length are beneficial to increase nozzle damping;motor head cavity and end cavity both weaken nozzle damping,and the weakening degree of end cavity is significantly higher than that of head cavity;The submerged cavity reduces the acoustic power transmission coefficient of the nozzle throat,resulting in a decrease in nozzle damping.(4)For the wing post-charged solid motor,the influence of the working time and the position of the wing post on the natural sound frequency and mode shape of the acoustic cavity is explored.The whole machine analysis model is established,and using the acoustic response to characterize the motor stability,the influence of wing post position and working time on acoustic characteristics and stability of the acoustic cavity is explored.The results show that: the natural frequencies of each order of the acoustic cavity change with the change of the position of the wing and the working time,but the change is small when the length of the acoustic cavity remains unchanged;the motor is more prone to unstable combustion in the middle and later stages,and the stability of the motor with the rear wing charge structure is the lowest at the same time.