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Research Papers

Influence of Blade Loading Profile on Wake Dynamics in High-Pressure Turbine Cascades

[+] Author and Article Information
Benjamin T. Luymes, Qiang An

Institute for Aerospace Studies,
University of Toronto,
Toronto, ON M3H 5T6, Canada

Adam M. Steinberg

Institute for Aerospace Studies,
University of Toronto,
Toronto, ON M3H 5T6, Canada
e-mail: adam.steinberg@gatech.edu

Xuefeng Zhang, Thomas Vandeputte

Global Research Center,
General Electric,
Niskayuna, NY 12309

1Corresponding author.

2Present address: School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30313.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 10, 2018; final manuscript received July 31, 2018; published online September 28, 2018. Editor: Kenneth Hall.

J. Turbomach 140(10), 101004 (Sep 28, 2018) (8 pages) Paper No: TURBO-18-1153; doi: 10.1115/1.4041141 History: Received July 10, 2018; Revised July 31, 2018

The influences of blade loading profile on wake convection and wake/wake interaction were studied in two different blade designs for high-pressure (HP) turbines (front-loaded (FL) and aft-loaded (AL)), installed in linear cascades. A high-speed moving bar (HSMB) apparatus replicated wake shedding, and a closed loop wind tunnel produced engine-relevant Mach numbers (Ma = 0.7) and Reynolds numbers (Re = 3 × 105). The FL blades had approximately 10% greater total pressure loss when operated with unsteady wake passage. Phase conditioned particle image velocimetry (PIV) measurements were made in the aft portion of the blade channel and downstream of the blade trailing edge. The turbulence kinetic energy (TKE) in the wake was approximately 30% higher for the FL blades when the wake entered the measurement field-of-view. The pressure field in the upstream region of the FL blade design is believed to induce high magnitude strain rates—leading to increased TKE production—and more aggressively turn and dilate the unmixed wake—leading to increased mixing related losses. The higher TKE for the FL blades largely dissipated, being approximately equal to the AL wake by the time the wake reached the end of the blade passage. The interaction of the convected wake with the wake from the blade trailing edge caused periodic vortex shedding at the second harmonic of the convected wake frequency. This interaction also modulated the strength of the trailing edge wake. However, little difference was found in the modulation amplitudes between different cases due to similar strengths of the convected wakes in this region. The higher wake TKE in the upstream portion of the blade channel for the FL blades, therefore, is expected to be the cause of the higher total pressure loss.

FIGURES IN THIS ARTICLE
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Copyright © 2018 by ASME
Topics: Wakes , Blades , Convection
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Figures

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Fig. 2

Representative blade geometries and Mach number distributions

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Fig. 1

Experimental facility, consisting of linear cascade and high-speed moving bar apparatus within the closed-loop wind tunnel at GE Global Research Center. The exploded box shows the blade cascade and the wake generating bars at the leading edge.

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Fig. 6

Comparison of TKE Production levels with the alignment of principal stresses and strain rates for AL blade geometry, phase 4

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Fig. 4

Turbulent kinetic energy levels within the blade channels during transient wake convection

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Fig. 5

Production of TKE within the blade channels during transient wake convection

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Fig. 3

Transient wake passage through both blade cascades at a Reynolds number of Re = 3 × 105. Top row: perturbation velocity, up|i. Middle row: TKE, K|i. Bottom row: TKE production, P|i.

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Fig. 7

Phase-conditioned reduced vorticity with superimposed perturbation velocity vectors at a fixed phase of the trailing edge vortex shedding at Re = 3 × 105. Other trailing edge phases were qualitatively and quantitatively similar. (a) AL geometry and (b) FL geometry.

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Fig. 8

Integral comparison of turbulent properties between test conditions. Values are averaged over the cascade wake period and the mean over the convected wake period is subtracted from each phase to show fluctuations: (a) strain rate magnitude, (b) TKE production, and (c) TKE.

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