| Fluid throat nozzle technology is an emerging thrust vector control technology,generally through the secondary fluid injection,the mainstream and secondary flow interaction,making the mainstream of the throat flow area and throat shape change.Compared with the conventional thrust vector control technique adopted in the solid rocket motor,it has the advantage of not needing to drive the drive servo mechanism such as the hosel,reducing the size and quality of the structure,and having no moving parts,so the reliability is enhanced.In the solid rocket engine combustion chamber,there are not only a variety of gain factors that cause sound energy,but also various damping factors,which can cause loss of sound energy and make the pressure oscillation gradually decay.The most important damping factors in solid rocket motors are nozzle damping,particle damping,wall damping,structural damping,and head cavity damping,among which nozzle damping has a strong damping effect on axial acoustic instability combustion.In the solid rocket engine,the sound energy loss caused by the nozzle often accounts for more than half of the total loss of sound energy.Therefore,it is of great significance to study the damping characteristics of the nozzle in order to predict and suppress the unstable combustion of the solid rocket motor.At present,more and more damping experiments and simulations have been carried out for ordinary nozzles at home and abroad.The application of secondary flow in the throat nozzle will certainly affect the damping of the nozzle.At present,A special study of the damping of jet nozzles.In order to investigate the influence of the secondary flow of the fluid throat on the nozzle damping,the main work and content of this paper are as follows:Based on the cold flow experimental engine as the basic model,the numerical simulation method of the standard model and the standard wall function are used to simulate the nozzle damping with secondary jet.Based on the steady-state wave attenuation method,To stabilize,the pressure oscillation in the gas gathering chamber is activated by the application of a stable sine wave signal,and the pressure change recorded by the appropriate monitoring point is selected to calculate the damping of the nozzle under the secondary flow injection.Through the design of multiple sets of injection conditions,change the jet secondary flow and the mainstream flow ratio,control other conditions remain unchanged,the number of simulation tests.The simulation results show that the secondary jet of the nozzle has a significant effect on the damping of the rocket engine nozzle,and the damping of the rocket engine nozzle decreases with the increase of the choke effect of the secondary jet.At the end of the excitation wave,the larger the secondary jet flow is,the smaller the effective throat area is,and the slower the attenuation of pressure oscillating wave is,the smaller the damping effect is.Through the design of three injection angle of the secondary flow nozzle,the secondary flow and the mainstream of 30 °,60 °,90 ° angle jet,using the corresponding geometric model,the analysis of three kinds of injection angle of the operating conditions,the secondary flow The results show that the variation trend of damping with secondary flow rate is the same,that is,the damping ratio increases with the increase of the secondary flow ratio.But it does not get the simple rule that the injection angle affects the damping.A large-aspect-ratio cylindrical combustor was designed and connected with a nozzle with a secondary jet.The experimental study on the pressure oscillation response of the combustion chamber under pulsed excitation was carried out and several sets of controlled experiments were carried out.After the secondary jet is injected into the chamber,the pulse excitation path is opened and the attenuation curve of pressure oscillation in the gas gathering chamber is recorded.By varying the pressure of the secondary jet,the nozzle damping of the engine under various operating conditions is compared.The results show that the nozzle damping decreases with the increase of the secondary flow ratio.Based on the cold flow experimental engine as the basic model,the numerical simulation method of two-phase flow VOF model and the standard wall function are used to simulate the damping of the nozzle with liquid secondary jet.The steady-state attenuation method is also used,The damping of the nozzle in the liquid secondary jet is calculated.At the same time,the design of liquid secondary flow engine cold flow experimental system to measure the fluid throat nozzle damping.The results show that the liquid secondary flow has similar characteristics to that of the gas secondary flow,and the conclusion is that the choke capacity is much less than that of the air when the secondary flow is water under the same secondary flow mass flow rate.The experimental results show that : The effective throat area ratio is the same,the liquid secondary flow nozzle damping ratio greater than the gas. |
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