Predicting Transition in Turbomachinery—Part II: Model Validation and Benchmarking

[+] Author and Article Information
T. J. Praisner, E. A. Grover, M. J. Rice

Turbine Aerodynamics,  United Technologies Pratt & Whitney, 400 Main St., M∕S 169-29, East Hartford, CT 06108

J. P. Clark

Turbine Branch, Turbine Engine Division, Propulsion Directorate,  Air Force Research Laboratory, Building 18, Room 136D, 1950 5th St., WPAFB, OH 45433john.clark3@wpafb.af.mil

J. Turbomach 129(1), 14-22 (Mar 01, 2004) (9 pages) doi:10.1115/1.2366528 History: Received October 01, 2003; Revised March 01, 2004

The ability to predict boundary layer transition locations accurately on turbomachinery airfoils is critical both to evaluate aerodynamic performance and to predict local heat-transfer coefficients with accuracy. Here we report on an effort to include empirical transition models developed in Part I of this report in a Reynolds averaged Navier-Stokes (RANS) solver. To validate the new models, two-dimensional design optimizations utilizing transitional RANS simulations were performed to obtain a pair of low-pressure turbine airfoils with the objective of increasing airfoil loading by 25%. Subsequent experimental testing of the two new airfoils confirmed pre-test predictions of both high and low Reynolds number loss levels. In addition, the accuracy of the new transition modeling capability was benchmarked with a number of legacy cascade and low-pressure turbine (LPT) rig data sets. Good agreement between measured and predicted profile losses was found in both cascade and rig environments. However, use of the transition modeling capability has elucidated deficiencies in typical RANS simulations that are conducted to predict component performance. Efficiency-versus-span comparisons between rig data and multi-stage steady and time-accurate LPT simulations indicate that loss levels in the end wall regions are significantly under predicted. Possible causes for the under-predicted end wall losses are discussed as well as suggestions for future improvements that would make RANS-based transitional simulations more accurate.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Measured-versus-predicted efficiencies for five LPTs at takeoff conditions (a), and for an LPT at takeoff and cruise conditions (b)

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Figure 2

Measured and predicted heat-load distributions at the midspan of an high-pressure turbine vane cascade. Data are from Arts (22).

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Figure 3

Measured and predicted profile losses versus Reynolds number for Pack B. Data are from Bons (25).

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Figure 4

Measured and predicted profile losses plotted versus exit Reynolds number for the Pack D-A and Pack D-F airfoils

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Figure 5

Measured and predicted pressure loadings for the aft region of (a) the Pack D-F airfoil at Re2=56,000 and (b) the Pack D-A airfoil at Re2=160,000. Data are from Sjolander (26).

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Figure 6

Annular cascade loss-versus-span data with fully turbulent and transitional CFD predictions. Data are from Soderberg (1988).

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Figure 7

Measured and predicted (steady and time-accurate) radial turbulence-intensity distributions downstream of the first two stages of a LPT rig. Data are from Binder (27).

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Figure 8

Four-stage LPT rig (Rig A) efficiency-versus-span data at cruise conditions with fully turbulent and transitional steady CFD predictions

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Figure 9

Measured and predicted (time-accurate) efficiency-versus-span results for Rig A. Predictions for two clocking positions of the first stage at cruise conditions are shown.

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Figure 10

Rig A efficiency-versus-span data with time-accurate transitional and turbulent CFD predictions at clocking position 1 at cruise conditions

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Figure 11

Mid-span transition information from the second row of steady and time-accurate simulations of Rig A

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Figure 12

Rig B efficiency-versus-span data at cruise conditions. Time-accurate predictions are shown.

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Figure 13

Measured-versus-predicted integrated efficiencies for five LPTs at takeoff and cruise conditions. Fully turbulent results are shown in (a) and transitional results are shown in (b).

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Figure 14

Measured-versus-predicted mid-span efficiencies for four LPTs. Fully turbulent results are shown in (a) and transitional results are shown in (b).

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Figure 15

Measured-versus-predicted integrated efficiencies for three LPTs. Steady transitional results are shown in (a) and time-accurate transitional results are shown in (b).




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