Centrifugal Compressor Forward And Reverse Flow Research

Steady and unsteady numerical simulation methods are used to calculate the forward and reverse flow phenomena in centrifugal compressors.The analysis shows that the reverse flow flows out of the diffuser inlet from the outlet of the diffuser blade passage,and the flow transversely impacts the outlet section of the working impeller blade to form the eddy current,as well as the supersonic flow relative to the working impeller,which results in the large eddy current loss and shock wave loss between the outlet of the working impeller and the inlet of the vane diffuser.The large incidence reverse flow relative to the geometrical structure angle at the outlet of the working impeller blade will also cause a large area of flow separation in the passage of the working impeller blade.Despite the complex flow phenomena such as separation,eddy current and shock wave in reverse flow,the steady flow can be formed by reverse flow,which avoids the local over-temperature of centrifugal compressor due to blowing down,and affects the life and safety of IPU.When the high pressure gas source flows backward,the diffuser blade passage becomes a convergent passage,and there is a critical section in the inlet section.When the gap area of the diffuser outlet baffle is large,the critical section of the diffuser blade passage becomes the throat section,and the change of the gap area of the outlet baffle will not affect the reverse flow.The reverse flow phenomena and characteristics of outlet baffle gap area of 1.2%~3.5% are compared and analyzed.The pressure required for high-pressure air source under different gap area is obtained,which can provide reference for airplane carrying high-pressure air source pressure.In order to reduce the resistance moment of reverse flow in centrifugal compressor,an adjustable guide vane was designed by adjusting the angle of diffuser blade.After adjusting the guide vane,the forward and reverse flow power consumption of centrifugal compressor was greatly reduced,and the loss of eddy current and shock wave was apparently reduced.