Dynamic response characteristics of semi-infinite pressure tube
In the combustion instability experiment,oscillation pressure was usually sampled by the semi-infinite pressure tube,the amplitude of the sampled oscillation pressure was attenuated and the phase was delayed.Therefore,the method of combining theoretical analysis of acoustic propagation in tube,experimental research and numerical simulation was adopted to study the influences of the diameter of the semi-infinite pressure tube and the structure of the mounting seat on the dynamic response characteristics of the semi-infinite pressure tube,and the parameters such as gain and phase difference of the oscillation pressure measured by the semi-infinite pressure tube were analyzed.The results showed that when the length of the semi-infinite pressure tube was insufficient,it caused oscillation in the response curve produced by terminal reflection.Reducing the diameter of the semi-infinite pressure tube could increase the pressure amplitude attenuation,so the length of the semi-infinite pressure tube can be appropriately shortened.Mounting seat structure could lead to the oscillation in the amplitude-frequency characteristics and phase-frequency characteristics of the semi-infinite pressure tube due to the mounting seat reflection,and the larger volume of mounting seat cavity indicated the more stronger oscillation.In addition,the reason of response curve oscillation caused by mounting seat was analyzed by theoretical analysis and numerical simulation.The research content can accurately predict and correct the measurement deviation of the semi-infinite pressure tube,which has reference significance for the measurement of oscillation pressure in the gas turbine combustor.
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