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Research Papers

Redesign of High-Lift Low Pressure Turbine Airfoils for Low Speed Testing

[+] Author and Article Information
Michele Marconcini

Filippo Rubechini, Roberto Pacciani, Andrea Arnone

“Sergio Stecco” Department of Energy Engineering,  University of Florence, via di Santa Marta, 3, 50139 Firenze, Italy

Francesco Bertini

 Avio S.p.A., via I Maggio, 99, 10040, Rivalta di Torino (TO), Italy

J. Turbomach 134(5), 051017 (May 11, 2012) (8 pages) doi:10.1115/1.4004474 History: Received March 08, 2011; Accepted June 17, 2011; Published May 10, 2012; Online May 11, 2012

Low pressure turbine airfoils of the present generation usually operate at subsonic conditions, with exit Mach numbers of about 0.6. To reduce the costs of experimental programs it can be convenient to carry out measurements in low speed tunnels in order to determine the cascades performance. Generally speaking, low speed tests are usually carried out on airfoils with modified shape, in order to compensate for the effects of compressibility. A scaling procedure for high-lift, low pressure turbine airfoils to be studied in low speed conditions is presented and discussed. The proposed procedure is based on the matching of a prescribed blade load distribution between the low speed airfoil and the actual one. Such a requirement is fulfilled via an artificial neural network (ANN) methodology and a detailed parameterization of the airfoil. A RANS solver is used to guide the redesign process. The comparison between high and low speed profiles is carried out, over a wide range of Reynolds numbers, by using a novel three-equation, transition-sensitive, turbulence model. Such a model is based on the coupling of an additional transport equation for the so-called laminar kinetic energy (LKE) with the Wilcox k-ω model and it has proven to be effective for transitional, separated-flow configurations of high-lift cascade flows.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

T106C single-block O-type grid 549 × 101

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Figure 2

T106C cascade airfoil pressure coefficient distributions at low speed LS and high speed HS (M2s  = 0.65) conditions: (a) Re2s  = 2.1 × 105 , (b) Re2s  = 1.2 × 105 , and (c) Re2s  = 0.5 × 105

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Figure 3

T106C cascade: kinetic energy loss coefficient for the HS (M2s  = 0.65) and LS flow conditions

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Figure 4

Comparison between T106C airfoil and airfoils redesigned for low speed operation (see Table 1)

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Figure 5

T106C cascade low speed airfoil redesign with different target distributions: (a) pressure coefficient, (b) isentropic velocity ratio, and (c) isentropic Mach ratio, fully turbulent flow (Re2s  = 2.5 × 105 )

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Figure 6

Local Reynolds number at maximum separation-bubble-thickness Res,M and reattachment Res,R locations compared with the Hatman and Wang correlation [33]

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Figure 7

Kinetic energy loss coefficient for the HS and LS flow as a function of (a) the isentropic exit Reynolds number and (b) the streamwise distance Reynolds number at the separation onset

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Figure 8

Pressure coefficient distributions for the T106C HS (M2s  = 0.65) and the LS A airfoil: (a) Re2s  = 2.5 × 105 , (b) Re2s  = 1.6 × 105 , and (c) Re2s  = 0.8 × 105

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Figure 9

Skin friction coefficient distributions for the T106C HS (M2s  = 0.65) and the LS A airfoil for Re2s  = 1.6 × 105

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Figure 10

Pressure coefficient contours for Re2s  = 1.6 × 105 : (a) T106C HS and (b) LS A

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Figure 11

Turbulence level contours superimposed to flow streamlines in the bubble region for HS Re2s  = 1.6 × 105 : (a) T106C HS and (b) LS A

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