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Research Papers

The Effects of Inlet Guide Vane-Wake Impingement on the Boundary Layer and the Near-Wake of a Rotor Blade

[+] Author and Article Information
Francesco Soranna, Yi-Chih Chow, Oguz Uzol, Joseph Katz

Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218

J. Turbomach 132(4), 041016 (May 10, 2010) (13 pages) doi:10.1115/1.3149282 History: Received November 25, 2008; Revised March 01, 2009; Published May 10, 2010; Online May 10, 2010

This paper examines the response of a rotor blade boundary layer and a rotor near-wake to an impinging wake of an inlet guide vane (IGV) located upstream of the rotor blade. Two-dimensional particle image velocimetry (PIV) measurements are performed in a refractive index matched turbomachinery facility that provides unobstructed view of the entire flow field. Data obtained at several rotor phases enable us to examine the IGV-wake-induced changes to the structure of the boundary layer and how these changes affect the flow and turbulence within the rotor near-wake. We focus on the suction surface boundary layer, near the blade trailing edge, but analyze the evolution of both the pressure and suction sides of the near-wake. During the IGV-wake impingement, the boundary layer becomes significantly thinner, with lower momentum thickness and more stable profile compared with other phases at the same location. Analysis of available terms in the integral momentum equation indicates that the phase-averaged unsteady term is the main contributor to the decrease in momentum thickness within the impinging wake. Thinning of the boundary/shear layer extends into the rotor near-wake, making it narrower and increasing the phase-averaged shear velocity gradients and associated turbulent kinetic energy (TKE) production rate. Consequently, the TKE increases during wake thinning, with as much as 75% phase-dependent variations in its peak magnitude. This paper introduces a new way of looking at the PIV data by defining a wake-oriented coordinate system, which enables to study the structure of turbulence around the trailing edge in great detail.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Schematic of the axial turbomachine test section. (b) Schematic of IGV blade and rotor blade. Also indicated are the coordinate systems with rotor trailing edge located at (x/c,y/c)=(1,1).

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Figure 2

Distributions of phase-averaged vorticity at four phases. The (x,y) axes are normalized with c. Contour scale is maintained the same at all phases.

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Figure 3

Contours of axial velocity perturbation at phases 1–4 and perturbation velocity vectors locally scaled with the magnitude of the perturbation velocity

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Figure 4

First row: distributions of U¯sw in the (s,n) coordinate system defined by the rotor wake centerline (white lines) at phases 1–4. Second row: distribution of cross stream gradient of U¯sw.

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Figure 5

Distributions of U¯sw and U¯nw at phase 4 near the rotor trailing edge. The arrowed lines indicate streamlines of the phase-averaged velocity vector.

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Figure 6

Profiles of U¯sb at s/c=−0.125,−0.025

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Figure 7

Profiles of U¯sw at s/c=0.014 indicated in Fig. 2

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Figure 8

Profiles of U¯sw at s/c=0.064 indicated in Fig. 2

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Figure 9

Streamwise variation of ((a) and (b)) wake length scale δβ and ((c) and (d)) wake deficit [U¯β(s)−U¯s(s,0)] along the suction and pressure sides at four rotor phases

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Figure 10

Phase-averaged boundary layer profile at phase 2′. The solid line represents the distribution of the potential velocity U¯psb.

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Figure 11

Distribution of δ∗, and θ at phase 2′

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Figure 12

Available terms in the evolution equation of momentum thickness 8

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Figure 13

First three rows: distributions of us′2¯, un′2¯, and us′un′¯ at four rotor phases. Last row: distribution of TKE.

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Figure 14

Top to bottom rows, distributions of production rate of TKE (first row) and the terms contributing to it (Eq. 11): −us′un′¯∂U¯sw/∂n (second row), −us′2¯∂U¯sw/∂s, and −un′2¯∂U¯nw/∂s (third and fourth rows). Data are presented in the (s,n) coordinate system defined by the wake centerline and plotted in the (x,y) grid.

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Figure 15

Profiles of turbulent kinetic energy and its production rate at ((a)and (b)) s/c=0.014 and ((c) and (d)) s/c=0.064

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