Flow Separation Control for LowPressure Turbine LPT Blade using Vortex Generator Jets VGJs

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Flow Separation Control for Low-Pressure Turbine
(LPT) Blade using Vortex Generator Jets (VGJs)
Amit Kasliwal, Karman Ghia and Urmila Ghia
Computational Fluid Dynamics Research
Laboratory Department of Aerospace
Engineering Department of Mechanical, Nuclear
and Industrial Engineering University of
Cincinnati Cincinnati, OH 45221
Presented at 58th Annual Meeting of the Division
of Fluid Dynamics Chicago, Illinois November
20-22, 2005
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Outline

• Motivation
• Goals
• Methodology
• Results
• Results for flow past a circular cylinder ReD
  13,400 with spanwise distance of
• Results with or without control for cylinder flow
  at ReD 13,400 with spanwise distance of 0.15D.
• Controlled and uncontrolled LPT flow at Re
  25,000 with spanwise distance of 0.15ax.
• Conclusion and Future work

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Motivation

• Most fluid flows observed in nature and
  encountered in engineering applications
  involve separation.
• Generally flow separation is detrimental, for
  example it imposes considerable limitation on
  operating characteristics of aircraft wings,
  helicopter blades, turbine blades etc.
• Thus, in detail study of flow separation
  becomes important to minimize its undesirable
  effects.
• Separated flow past a circular cylinder at ReD
  13,400 and LPT cascade flow at Re 25,000
  are considered in the present study.

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Goals

• To explore the separated flow physics and to
  test VGJs flow control strategy for the cylinder
  case Re 13,400 and apply it later to low
  pressure turbine cascade problem to minimize
  separation.
• To apply the VGJ separation control study for
  LPT cascade problem and minimize separation.

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Methodology

• Governing Equations
• Three-dimensional, unsteady, full Navier-Stokes
  equations
• Numerical Solution Technique
• Implicit approximate-factorization algorithm of
  Beam and Warming
• Time Integration Second-order accurate
  implicit method based on three-point backward
  discretization, with Newton-like sub-iteration

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Methodology (contd.)

• Spatial Discretization
• Fourth-order accurate compact-difference
  formulations.
• Filtering
• Sixth-order filtering is used to remove the
  non- physical oscillations caused by
  higher-order accurate schemes
• FDL3DI, a flow solver from AFRL at WPAFB, which
  incorporates the aforementioned methodology.

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Methodology (contd) Boundary Conditions

• Surface
• No-slip (u, v, w 0)
• Isothermal wall (Twall constant)
• (4th order accurate)
• (Equation of state)

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Methodology (contd) Boundary Conditions

• Far Field
• Inflow Uniform flow
• u 1.0, v 0.0, w 0.0, ,
  
• Outflow Zeroth-order extrapolation
• zdirection
• Periodicity

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Cylinder Flow at ReD 13,400 with Spanwise
distance
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Grid Employed for Re 13,400

• 3.9M points on 24 blocks, 48 points in
  z-direction
• Five point overlap between blocks
• 1st grid point spacing 6.9 x 10-5
• Outflow boundary extends to 30 D

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Effect of Grid Refinement, ReD 13,400
0.3M grid points
4M grid points
Grid overlaid on z-vorticity contours for the
coarse grid and fine grid (Re 13,400).
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Lift Coefficient Time History
Lift coefficient time history for cylinder flow
at Re 13,400.
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Q-Criterion
Q-criterion isourfaces for cylinder flow at Re
13,400 (Q 4).
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Separation Control for Cylinder flow at ReD
13,400 with Spanwise distance 0.15D
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VGJs Parameters
VGJ hole
Z0.15
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Boundary Conditions for VGJs
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Coefficient of Drag for Controlled and
Uncontrolled Cases
Comparison of coefficient of drag for controlled
and uncontrolled cases.
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Instantaneous z-vorticity contours animation on
z-mid plane
Controlled flow
Uncontrolled flow
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Time- and Spanwise-Averaged Total Pressure at x/D
5.0
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Flow Separation control for LPT blade with
spanwise distance 0.15 at Re 25,000 using VGJs
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LPT Grid and Boundary Conditions
12-block structured-grid for LPT generated using
GridPro
Without Control Uniform inflow at an angle of
350 to the horizonal at the inlet. Zeroth-order
extrapolation at the outlet. No slip, Isothermal
wall, Pressure Neumann boundary
condition Periodicity in spanwise and crossflow
directions.
Control Jet are placed at 65 axial chord. Jet
parameters same as cylinder case except pulsation
frequency F 1.33.
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Time- and Spanwise-Averaged Surface Cp
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Time- and Spanwise-Averaged z-vorticity for
Controlled and Uncontrolled Cases
Uncontrolled
Controlled
27 reduction in loss coefficient
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Summary and Future Work

• VGJs were found to be successful in minimizing
  separation losses for LPT Cascade flow.
• Increase the upstream location of inlet.
• Conduct a detailed parametric study to understand
  the effect of Jet parameters on separation
  reduction
• Finally, understand the mechanism responsible for
  reduction of separation losses.

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Thank you! Questions ?
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Time- and Spanwise-Averaged Surface Cp for
Controlled and Uncontrolled Cases
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Low Pressure Turbine (LPT) Flow Configuration
Outlet
Flow entering at an angle of 55? to the vertical
Flow configuration for flow through LPT linear
cascade
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LPT Multi-Block Structured Grid
Block-layout for LPT structured-grid
12-block structured-grid for LPT
12-block structured-grid generated using GridPro
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Coefficient of Lift for Controlled and
Uncontrolled Cases
Comparison of coefficient of lift for controlled
and uncontrolled cases.
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Uavg (1-Uavg) at x/D 5.0
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Time- and Spanwise-Averaged Surface Cp for
Controlled and Uncontrolled Cases
Comparison of time- and spanwise-averaged surface
coefficient of pressure for controlled and
uncontrolled case.