Investigation On Propagation Characteristics Of The Continuous Rotating Detonation Wave With The Pintle Injector

Continuous rotating detonation may be one of the causes of high frequency tangential combustion instability of liquid rocket engines.The two are similar in frequency and direction.In the liquid rocket engine,the mixture of flue and oxidizer on the wall is very easy to induce rotational knock in the high temperature environment.Based on findings to date,The structure of energy release area of pintle injector has stable area with different gas parameters.Which is helpful to restrain acoustic instability.In this paper,a variable configuration injector is used in the hollow chamber to realize the transition from the continuous rotating detonation injection method to the pintle injector method.The effect of the pintle injector on the rotating detonation wave is studied by means of experiments and numerical simulation.Explore whether the pintle is designed to suppress trangential combustion instability of liquid rocker engines by suppressing rotating detonation.The hydrogen/air cold flow mixing numerical simulation is carried out in the calcution domain of the same configuration with the combustion chamber,and the double reflux region structure similar to the flow fleid of the pintle injector.The flow fleid results show that with the increase of injector depth and the smaller injector diameter,the length of the reflux zone increases.And when the injector diameter is too small,because of the gas flow is too small,the mainstream will bend from wall to center.Experiments on different injection configurations is carried out under different nozzle shrinkage ratio,equivalent ratio and ignition mode.The results show that the detonation is the most stable mode,reducing the injection diameter and increase the injection depth will make the detonation wave propagation mode more complex.The ignition of isobaric sequential ignition can only be ingition successfully when the nozzle shrinkage ratio is 8,and the mode of propagation will change from detonation wave to isobaric combustion when the injection configuration is transitioned from the extenal ring injection to the injection form of the pintle,and the propagation mode will change from the detonation wave to sawtooth wave finally to the isobaric combustion.It is concluded that the pintle injector can suppress continuous rotating detonation.Bycomaring the FFT main frequency of combustion chamber with the acoustic natural frequency of combustion chamber,it is found that under arbitrary injection configuration,the FFT result of hot-jet ignition always agree well with the correspondind natural frequency,indicating that for small hollow combustion chamber,hot-jet ignition is easy to form a rotating wave.