Influences of the hub lobes on combustion instabilities in a coaxial staged combustor
In response to the combustion instability of a coaxial staged combustor,the addition of lobe to the first and second main stage combustion hubs of a tower swirlers was studied.The differences in cold velocity field of combustors under different structures were compared through experimental results.The large eddy simulation method was applied to obtain the global heat release rate fluctuation spectrum of the combustor,as well as the vorticity and heat release rate within a pulsation period.Finally,the velocity and heat release rates of different combustors were analyzed using dynamic mode decomposition.Adding lobes to the first main stage hub could reduce the frequency of strong vortices,and the pulsation amplitude of the heat release rate was 4％of the global average heat release rate,about 45％lower than the prototype combustor.The heat release rate mode exhibited high-frequency small amplitude.Adding lobes to the second main stage led to an increase in the maximum vortex intensity.The pulsation amplitude of the heat release rate with a main frequency of 471 Hz reached more than 30％of the global average heat release rate,and periodic flashbacks occurred,which was not conducive to the stable operation of the combustion chamber.
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