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Numerical and experimental investigation of tip leakage flow and heat transfer using idealised rotor-tip models at transonic conditions

Published online by Cambridge University Press:  03 February 2016

S. K. Krishnababu ,
H. P. Hodson ,
W. N. Dawes ,
P. J. Newton  and
G. D. Lock
S. K. Krishnababu
Affiliation:
Whittle laboratory, Department of Engineering, University of Cambridge, Cambridge, UK
H. P. Hodson
Affiliation:
Whittle laboratory, Department of Engineering, University of Cambridge, Cambridge, UK
W. N. Dawes
Affiliation:
Whittle laboratory, Department of Engineering, University of Cambridge, Cambridge, UK
P. J. Newton
Affiliation:
[email protected], Department of Mechanical Engineering, University of Bath, Bath, UK
G. D. Lock
Affiliation:
[email protected], Department of Mechanical Engineering, University of Bath, Bath, UK
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Abstract

The effect of tip geometry on discharge coefficient and heat transfer is investigated both experimentally and numerically using idealised models of an unshrouded rotor blade. A flat tip was compared with two squealer-type geometries (a cavity and suction-side squealer) under the transonic conditions expected in the gas turbine engine. Heat transfer measurements were performed using a transient liquid crystal technique while a duplicate test section was used for measuring the pressure field. Computations were carried out using an unstructured, fully compressible, three-dimensional RANS (Reynolds averaged Navier Stokes) solver. Initial computations performed using a low Reynolds number k-ε model demonstrated the inability of the model to predict the Nusselt number with reasonable accuracy. Further computations performed using a low Reynolds number k-ω model improved the predictions dramatically. The computed discharge coefficient and the average Nusselt number over the blade tip agreed well with the experiments. Three upstream-total to exit-static pressure ratios were used to create a range of engine-representative Mach numbers. Both experimental and numerical studies at the lower pressure ratio of 1·3 (exit Mach number ~ 0·65) established the cavity geometry as the best performer from an aerodynamic perspective by reducing the discharge through the tip. However, from the heat transfer perspective, both the peak Nusselt number and the average heat transfer to the tip were higher than the flat tip. At the higher pressure ratios of 1·85 and 2·27 (corresponding to exit Mach numbers ~ 0·98 and 1·12) the discharge coefficient and heat transfer to the tip increases. This paper explores the fluid dynamics associated with these flows and shows that the highest heat transfer is caused by reattachment and flow impingement. The fluid dynamic computations provide insight into the experimental measurements and were successfully compared with simple analytical models.

Type
Research Article
Information
The Aeronautical Journal , Volume 113 , Issue 1141 , March 2009 , pp. 165 - 175
Copyright
Copyright © Royal Aeronautical Society 2009 

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References

1. Booth, T.C., Dodge, P.R. and Hepworth, H.K. Rotor-tip leakage: part 1-basic methodology, ASME J Engineering for Power, 1982, 104, pp 154–161.Google Scholar
2. Bunker, R.S. A review of turbine blade tip heat transfer, heat transfer in gas turbine systems, Annals of the New York Academy of Sciences, 2001, New York, USA, 934, pp 64–79.Google Scholar
3. Mayle, R.E. and Metzger, D.E. Heat transfer at the tip of an unshrouded turbine blade, Proceedings of Seventh International Heat Transfer Conference, 1986, 3, pp 87–92.Google Scholar
4. Chyu, M.K., Metzger, D.E. and Hwan, C.L. Heat transfer in shrouded rectangular cavities, J Thermophysics, 1987, 1, pp 247–252.Google Scholar
5. Krishnababu, S.K., Dawes, W.N., Hodson, H.P., Lock, G.D., Hannis, J. and Whitney, C. Aero-thermal investigation of tip leakage flow in axial turbines. Part 2: Effect of relative casing motion, 2007, ASME Paper GT2007-27957.Google Scholar
6. Newton, P.J., Lock, G.D., Krishnababbu, S.K., Hodson, H.P., Dawes, W.N., Hannis, J. and Whitney, C. Heat transfer and aerodynamics of turbine blade tips in a linear cascade, J Turbomachinery, 2007, 128, pp 300–309.Google Scholar
7. Heyes, F.J.G., Hodson, H.P. and Dailey, G.M. The effect of blade tip geometry on the tip leakage flow in axial turbine cascade, Asme J Turbo machinery, 1992, 114, pp 643–651.Google Scholar
8. Metzger, D.E. and Rued, K. The influence of turbine clearance gap leakage on passage velocity and heat transfer near blade tips: Part I-sink flow effects on blade pressure side, ASME J Turbomachinery, 1989, 111, pp 284–292.Google Scholar
9. Chen, G., Dawes, W.N. and Hodson, H.P. A Numerical and Experimental Investigation of Turbine Tip Gap Flow, 29th AIAA Joint Propulsion Conference and Exhibit, 1993, Monterey, CA, USA.Google Scholar
10. Rains, D.A. Tip clearance flows in axial flow compressors and pumps, report No. 5, 1954, Hydrodynamics and Mechanical Engineering Laboratories, California Institute of Technology, CA, USA.Google Scholar
11. Moore, J. and Tilton, J.S. Tip leakage flow in a linear turbine cascade, ASME J Turbomachinery, 1988, 110, pp 18–26.Google Scholar
12. Wadia, A.R. and Booth, T.C. Rotor-tip leakage Part II- design optimisation through viscous analysis and experiment, ASME J Engineering for power, 1982, 104, pp 162–169.Google Scholar
13. Wadia, A.R. Numerical solution of 2-D and 3-D rotor tip leakage models, AIAA J, 1985, 23, (7), pp 1061–1069.Google Scholar
14. Sjolander, S.A. and Cao, D. Measurements of the flow in an idealised turbine tip gap, ASME J Turbomachinery, 1995, 117, pp 578–584.Google Scholar
15. Bindon, J.P. Pressure and flow field measurements of axial turbine tip clearance flow in a linear cascade, Report Number CUED/A-Turbo TR123, 1986, Whittle lab, University of Cambridge, Cambridge, UK.Google Scholar
16. Yaras, M.I. and Sjolander, S.A. Prediction of tip leakage losses in axial turbine, ASME J Turbomachinery, 1992, 114, pp 204–210.Google Scholar
17. Atkins, N., Thorpe, S. and Ainsworth, R. Unsteady effects on Transonic turbine blade-tip heat transfer, 2008, ASME Paper GT2008-51177.Google Scholar
18. Schultz, D.L. and Jones, T.V. Heat transfer measurements in short duration hypersonic facilities, Agardograph, 1973, 165.Google Scholar
19. Newton, P.J., Yan, Y., Stevens, N.E., Evatt, S.T., Lock, G.D. and Owen, J.M. Transient heat transfer measurements using thermochromic liquid crystal. Part 1: An improved technique, 2003, Int J Heat and Fluid Flow, 24, pp 14–22.Google Scholar
20. Owen, J.M., Newton, P.J. and Lock, G.D. Transient heat transfer measurements using thermochromic liquid crystal. Part 2: experimental uncertainties, Int J Heat and Fluid Flow, 2003, 24, pp 23–28.Google Scholar
21. Kingsley-Rowe, J., Lock, G.D. and Owen, J.M. Transient heat transfer measurements using liquid crystal: lateral-conduction error, Int J Heat and Fluid Flow, 2005, 26, pp 256–263.Google Scholar
22. Dawes, W. The development of a solution-adaptive 3D Navier-Stokes solver for turbomachinery, 1991, 27th AIAA Joint Propulsion Conference, Sacramento, CA, USA.Google Scholar
23. Lam, C.K.G. and Bremhorst, K.A. Modified form of the k-ε model for predicting wall turbulence, 1981, J Fluids Eng, 103.Google Scholar
24. Durbin, P.A. On the k-ε stagnation point anomaly, Int J Heat and Fluid Flow, 1996, 17, pp 89–90.Google Scholar
25. Rodi, W. and Scheuerer, G. Scrutinising the k-ε turbulence model under adverse pressure gradient conditions, J Fluids Engineering, 1986, 108, pp 174–180.Google Scholar
26. Wilcox, D.C. Turbulence modeling for CFD, DCW Industries, 1993, La Canada, CA, USA.Google Scholar
27. Medic, G. and Durbin, P.A. Toward improved prediction of heat transfer on turbine blades, ASME J Heat Transfer, 2004, 124, pp 193–199.Google Scholar
28. Benson, R.S. and Pool, D.E. The compressible flow discharge coefficients for a two-dimensional slit, Int J Mechanical Science, 1965, 7, pp 337–353.Google Scholar
29. Deckker, B.E.L. and Chang, U.F. An investigation of steady compressible flow through thick orifices, Proc. ImechE, 1966, 180.Google Scholar
30. Willinger, R. and Haselbacher, H. 2000, On the modeling of tip leakage flow in axial turbine blade rows, ASME paper No 2000-GT-633.Google Scholar