In current axial compressor design their presences of pressure waves is largely ignored as the flow is invariably turbulent or contains large amounts of free stream fluctuations.

However, the presence of pressure waves are is largely associated with another physical process, such as turbulent shedding, transition or separation and thus their study can provide some . With this in mind by focusing on the presence of pressure waves some insight into the physical insight into the processes occurring can be gained.

 

Investigations on transonic open aerofoils have shown how wake shedding can result in upstream travelling pressure waves, waves than can drive transition and often show some form of lock in, as suggested early on by Tijdeman \[1977\]. These upstream traveling pressure waves that originate from the trailing edge are termed “Kutta Waves” though they are not obviously present in axial compressors.

 

In a set of high fidelityhigh-fidelity Large Eddy Simulations (LES) of an axial compressor cascade at engine relevant Mach and Reynolds numbers the presence of upstream traveling pressure waves has been observed. The simulations have been performed over a range of operating conditions with different incident free stream disturbances, both discrete wakes and free stream turbulence and a combination of both.

The simulations highlight how the different incident disturbances interact with the boundary layer of the blade resulting in different frequencies of the produced pressure waves. 

 

In the work presented here the induced changes in the flow field, transition and pressure fluctuations are investigated. The study aims to highlight changes in transition and instability that are affected by the type of free stream disturbance.

The changes in loss and time averaged quantities are also presented to compare how different free stream disturbances might affect the dynamical properties and mean quantities differently.


Exploring the Presence of Pressure Waves in Axial Compressor Cascades

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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