Turbulence Amplification With Incidence at the Leading Edge of a Compressor Cascade

The flow structure and turbulence around the leading and trailing edges of a rotor blade operating downstream of a row of inlet guide vanes (IGV) are investigated experimentally. Particle image velocimetry (PIV) measurements are performed in a refractive index matched facility that provides unobstructed view of the entire flow field. Data obtained at several rotor blade phases focus on modification to the flow structure and turbulence in the IGV wake as it propagates along the blade. The phase-averaged velocity distributions demonstrate that wake impingement significantly modifies the wall-parallel velocity component and its gradients along the blade. Due to spatially non-uniform velocity distribution, especially on the suction side, the wake deforms while propagating along the blade, expanding near the leading edge and shrinking near the trailing edge. While being exposed to the nonuniform strain field within the rotor passage, the turbulence within the IGV wake becomes spatially nonuniform and highly anisotropic. Several mechanisms, which are consistent with rapid distortion theory (RDT) and distribution of turbulence production rate, contribute to the observed trends. For example, streamwise (in rotor frame reference) diffusion in the aft part of the rotor passage enhances the streamwise fluctuations. Compression also enhances the turbulence production very near the leading edge. However, along the suction side, rapid changes to the direction of compression and extension cause negative production. The so-called wall blockage effect reduces the wall-normal component.

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Periodic Transition on an Axial Compressor Stator: Incidence and Clocking Effects: Part II—Transition Onset Predictions

Solomon

Walker

Hughes

1999

Journal of Turbomachinery

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Transition onset observations from a 1.5-stage axial compressor outlet stator presented in Part I of this paper are compared with the predictions of conventional transition correlations applied in a quasi-steady manner. The viscous/inviscid interaction code MISES is used to predict the blade surface pressure distributions and boundary layer development. The temporal variation in transition onset is then predicted using ensemble-averaged free-stream turbulence data from the compressor measurements. This simple procedure captures most significant features of the complex transition process on the compressor, and is clearly superior to fixed transition models based on long-term average free-stream turbulence levels. Parallel computations for both natural and bypass transition modes indicate that the natural transition mode tends to dominate on the compressor. This is at variance with turbine airfoil experience, where bypass transition is clearly more important. Comparison of prediction and experiment highlights the significance of leading edge potential flow interactions in promoting periodic wake-induced transition. Viscous/inviscid interactions in the neighborhood of transition can also have an important influence on boundary layer stability and separation phenomena.

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Turbulence Amplification With Incidence at the Leading Edge of a Compressor Cascade

Cited by 3 publications

References 5 publications

Flow Measurement Techniques in Turbomachinery

Flow Measurement Techniques in Turbomachinery

The Effect of Inlet Guide Vanes Wake Impingement on the Flow Structure and Turbulence Around a Rotor Blade

Periodic Transition on an Axial Compressor Stator: Incidence and Clocking Effects: Part II—Transition Onset Predictions

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