0
Research Papers

Experimental and Computational Study of the Effect of Momentum-Flux Ratio on High-Pressure Nozzle Guide Vane Endwall Cooling Systems

[+] Author and Article Information
Francesco Ornano

Department Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: francesco.ornano@eng.ox.ac.uk

Thomas Povey

Department Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 2, 2017; final manuscript received August 15, 2017; published online September 26, 2017. Editor: Kenneth Hall.

J. Turbomach 139(12), 121002 (Sep 26, 2017) (14 pages) Paper No: TURBO-17-1100; doi: 10.1115/1.4037756 History: Received August 02, 2017; Revised August 15, 2017

High-pressure (HP) nozzle guide vane (NGV) endwalls are often characterized by highly three-dimensional (3D) flows. The flow structure depends on the incoming boundary layer state (inlet total pressure profile) and the (static) pressure gradients within the vane passage. In many engine applications, this can lead to strong secondary flows. The prediction and design of optimized endwall film cooling systems is therefore challenging and is a topic of current research interest. A detailed experimental investigation of the film effectiveness distribution on an engine-realistic endwall geometry is presented in this paper. The film cooling system was a fairly conventional axisymmetric double-row configuration. The study was performed on a large-scale, low-speed wind tunnel using infrared (IR) thermography. Adiabatic film effectiveness distributions were measured using IR cameras, and tests were performed across a wide range of coolant-to-mainstream momentum-flux and mass flow ratios (MFRs). Complex interactions between coolant film and vane secondary flows are presented and discussed. A particular feature of interest is the suppression of secondary flows (and associated improved adiabatic film effectiveness) beyond a critical momentum flux ratio. Jet liftoff effects are also observed and discussed in the context of sensitivity to local momentum flux ratio. Full coverage experimental results are also compared to 3D, steady-state computational fluid dynamics (CFD) simulations. This paper provides insights into the effects of momentum flux ratio in establishing similarity between cascade conditions and engine conditions and gives design guidelines for engine designers in relation to minimum endwall cooling momentum flux requirements to suppress endwall secondary flows.

Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Langston, L. S. , 1980, “ Crossflows in a Turbine Cascade Passage,” J. Eng. Power, 102(4), pp. 866–874. [CrossRef]
Sieverding, C. H. , and Van den Bosche, P. , 1983, “ The Use of Coloured Smoke to Visualize Secondary Flows in a Turbine Cascade,” J. Fluid Mech., 134, pp. 85–90. [CrossRef]
Sharma, O. , and Butler, T. , 1987, “ Predictions of Endwall Losses and Secondary Flows in Axial Flow Turbine Cascades,” ASME J. Turbomach., 109(2), pp. 229–236. [CrossRef]
Thomas, M. , Kirollos, B. , Jackson, D. , and, Povey, T. , 2013, “ Experimental and CFD Studies of NGV Endwall Cooling,” ASME Paper No. GT-2013-95639.
Harasgama, S. P. , and Burton, C. D. , 1992, “ Film Cooling Reasearch on the Endwall of a Turbine Nozzle Guide Vane in a Short Duration Annular Cascade: Part 1—Experimental Technique and Results,” ASME J. Turbomach., 114(4), pp. 734–740. [CrossRef]
Friedrichs, S. , Hodson, H. P. , and Dawes, W. N. , 1999, “ The Design of an Improved Endwall Film-Cooling Configuration,” ASME J. Turbomach., 121(4), pp. 772–780. [CrossRef]
Gao, Z. , Narzary, D. , and Han, J. C. , 2009, “ Turbine Blade Platform Film Cooling With Typical Stator-Rotor Purge Flow and Discrete-Hole Film Cooling,” ASME J. Turbomach., 131(4), p. 041004. [CrossRef]
Thole, K. A. , and Knost, D. G. , 2005, “ Heat Transfer and Film-Cooling for the Endwall of a First Stage Turbine Vane,” Int. J. Heat Mass Transfer, 48(4–5), pp. 5255–5269. [CrossRef]
Sinha, A. K. , Bogard, D. G. , and Crawford, M. E. , 1991, “ Film Cooling Effectiveness Downstream of a Single Row of Holes With Variable Density Ratio,” ASME J. Turbomach. 113(4), pp. 442–449. [CrossRef]
Thole, K. A. , Sinha, A. K. , and Bogard, D. G. , 1990, “ Mean Temperature Measurements of Jets with a Crossflow for Gas Turbine Film Cooling Application,” Third International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC-3), Honolulu, HI, Apr. 1–4, pp. 69–85.
Ekkad, S. V. , Han, J. C. , and Du, H. , 1998, “ Detailed Film Cooling Measurements on a Cylindrical Leading Edge Model: Effect of Free-Stream Turbulence and Coolant Density,” ASME J. Turbomach., 120(4), pp. 799–807. [CrossRef]
Bogard, D. G. , and Thole, K. A. , 2006, “ Gas Turbine Film Cooling,” J. Propul. Power, 22(2), pp. 249–270. [CrossRef]
Pedersen, D. R. , Eckert, E. , and Goldstein, R. , 1977, “ Film Cooling With Large Density Differences Between the Mainstream and the Secondary Fluid Measured by the Heat-Mass Transfer Analogy,” ASME J. Heat Transfer, 99(4), pp. 620–627. [CrossRef]
Shiau, C. C. , Chen, F. C. , Han, J. C. , Azad, S. , and Lee, C. P. , 2016, “ Full-Scale Turbine Vane Endwall Film Cooling Effectiveness Distribution Using Pressure-Sensitive Paint Technique,” ASME J. Turbomach. 138(5), p. 051002. [CrossRef]
Thomas, M. , and Povey, T. , 2016, “ Improving Turbine Endwall Cooling Uniformity by Controlling Near-Wall Secondary Flows,” Proc. Inst. Mech. Eng., Part G, epub.
Thomas, M. , 2014, “ Optimization of Endwall Film-Cooling in Axial Turbines,” Ph.D. thesis, University of Oxford, Oxford, UK.
Roach, P. E. , 1987, “ The Generation of Nearly Isotropic Turbulence by Means of Grids,” Int. J. Heat Fluid Flow, 8(2), pp. 82–92. [CrossRef]
Moffat, R. J. , 1988, “ Describing the Uncertainties in Experimental Results,” Exp. Therm. Fluid Sci., 1(1), pp. 3–17. [CrossRef]
Day, C. R. B. , Oldfield, M. L. G. , and Lock, G. D. , 2000, “ Aerodynamic Performance of an Annular Cascade of Film Cooled Nozzle Guide Vanes Under Engine Representative Conditions,” Exp. Fluids, 29(2), pp. 117–129. [CrossRef]
Nemdili, F. , Azzi, A. , Theodorodis, G. , and Jubran, B. A. , 2008, “ Reynolds Stress Transport Modeling of Film Cooling at the Leading Edge of a Symmetrical Turbine Blade Model,” Heat Transfer Eng., 29(11), pp. 950–960. [CrossRef]
Shalash, K. M. , El-Gabry, L. A. , and Abo El-Azm, M. M. , 2013, “ Numerical Modelling of Slot Film Cooling Using a Wall Function,” ASME Paper No. GT2013-94127.
Cresci, I. , Ireland, P. , Bacic, M. , Tibbott, I. , and Rawlinson, A. , 2015, “ Velocity and Turbulence Intensity Profiles Downstream of a Long Reach Endwall Double Row of Film Cooling Holes in a Gas Turbine Combustor Representative Environment,” ASME Paper No. GT2015-42307.
Mazzoni, C. , Luque, S. , and Rosic, B. , 2015, “ Capabilities of Thermal Wall Function to Predict Heat Transfer on the NGVS of a Gas Turbine With Multiple Can Combustors,” ASME Paper No. GT2015-43515.

Figures

Grahic Jump Location
Fig. 1

Computer-aided design model and components of the super-scale platform cooling facility: (a) front view and (b) rear view. A—vane and platforms, B—rear cameras, C—front cameras, D—combustor simulator, E—tailboards, F—hub cassette, and G—casing cassette.

Grahic Jump Location
Fig. 2

(a) NGV cascade viewed from upstream, (b) detail of the casing endwall, (c) casing film cooling pattern, and (d) vane hub and casing cooling hole inclinations angles

Grahic Jump Location
Fig. 3

CFD-predicted single vane capacity at six pressure ratios fitted with isentropic trend

Grahic Jump Location
Fig. 4

Fields of view: (a) upstream endwall and (b) downstream endwall

Grahic Jump Location
Fig. 5

Typical calibration curve of detector signal as a function of the surface temperature (thermocouple)

Grahic Jump Location
Fig. 6

Contours of the absolute uncertainty (to 95% confidence) in η as a function of T∞/Tc and η

Grahic Jump Location
Fig. 7

Range of momentum flux ratio for endwall cooling systems at typical engine conditions

Grahic Jump Location
Fig. 8

(a) Surface mesh detail, (b) film cooling hole mesh detail, and (c) computational domain

Grahic Jump Location
Fig. 9

Measured normalized radial total pressure profile at the combustor–NGV interface

Grahic Jump Location
Fig. 10

Film effectiveness distribution along the vane exit line obtained during the grid independency study. The flow conditions were MFR = 3.3% and I = 3.89.

Grahic Jump Location
Fig. 11

Endwall adiabatic film effectiveness contours (upstream view) for 0.40 < I < 6.40

Grahic Jump Location
Fig. 12

Endwall adiabatic film effectiveness contours (upstream view) for 11.65 < I < 26.99

Grahic Jump Location
Fig. 13

Endwall adiabatic film effectiveness contours (downstream view) for 0.40 < I < 26.99

Grahic Jump Location
Fig. 14

Measured tangential distribution of adiabatic film effectiveness downstream the first cooling row (line 1)

Grahic Jump Location
Fig. 15

Measured tangential distribution of adiabatic film effectiveness downstream the second cooling row (line 2)

Grahic Jump Location
Fig. 16

Measured tangential distribution of adiabatic film effectiveness on vane midpassage (line 3)

Grahic Jump Location
Fig. 17

Measured tangential distribution of adiabatic film effectiveness on vane outlet line (line 4)

Grahic Jump Location
Fig. 18

Comparison of adiabatic film effectiveness between CFD and experiment for I = 6.40 (MFR = 4.3%): (a) experimental results, (b) CFD prediction, and (c) comparison at vane inlet and outlet lines with indication of experimental uncertainty, uη

Grahic Jump Location
Fig. 19

Comparison of adiabatic film effectiveness between CFD and experiment for I = 11.65 (MFR = 6.3%): (a) experimental results, (b) CFD prediction, and (c) comparison at vane inlet and outlet lines with indication of experimental uncertainty, uη

Grahic Jump Location
Fig. 20

Laterally averaged adiabatic film effectiveness on lines 1–4 as a function of the momentum flux ratio: experiment (solid markers) and CFD (open markers)

Grahic Jump Location
Fig. 21

(a) Normalized total pressure radial profile, (p0−p0*)/(p0,in−p2ave), for different momentum flux ratios and (b) axial and pitchwise location of the radial traverse

Grahic Jump Location
Fig. 22

Normalized total pressure contours at vane inlet and coolant streamline traces: case with low I (a) and high I (b)

Grahic Jump Location
Fig. 23

PS view of Lambda 2-criterion for (a) I = 0.40 and (b) I = 11.65

Grahic Jump Location
Fig. 24

SS view of Lambda 2-criterion and total pressure loss coefficient, cp0, for (a) I = 0.40 and (b) I = 11.65

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In