Simulation analysis of low-frequency combustion stability of a hydrogen oxygen gas generator
In view of the obvious pressure oscillations of 200-230 Hz in the hot test of a hydrogen oxygen rocket engine gas generator,a low frequency combustion stability simulation mathematical model was established to analyze whether there is low-frequency unstable combustion phenomenon of limit cycle related to combustion delay.Simulation results under different combustion time delay,pressure drop of injector and combustion chamber volume showed that the oscillations frequency related to the combustion time delay was significantly lower than the test data.The low-frequency fluctuation in the test data may be excited by the acoustic frequency of the feed line.Further analysis showed that the key parameter to determine the stability of the system is the ratio of combustion delay to gas residence time.When the ratio was greater than a critical value,the system became unstable,otherwise the system became stable.Based on the simulation data fitting,a semi empirical formula for calculating the inherent frequency of the system was formed.The inherent frequency of the system decreased with the increase of the sum of combustion delay and gas residence time.The stable boundary of the system under different injector pressure drops was obtained.With the increase of pressure drop ratio,the critical ratio of combustion delay and gas residence time from stable to unstable became larger.
liquid rocket enginelow frequency combustion stabilitygas generatorinherent frequencystable boundary
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