Skip to main content Accessibility help
×
Home

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

  • S. K. Krishnababu (a1), H. P. Hodson (a1), W. N. Dawes (a1), P. J. Newton (a2) and G. D. Lock (a2)...

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.

Copyright

References

Hide All
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 154161.
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 6479.
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 8792.
4. Chyu, M.K., Metzger, D.E. and Hwan, C.L. Heat transfer in shrouded rectangular cavities, J Thermophysics, 1987, 1, pp 247252.
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.
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 300309.
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 643651.
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 284292.
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.
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.
11. Moore, J. and Tilton, J.S. Tip leakage flow in a linear turbine cascade, ASME J Turbomachinery, 1988, 110, pp 1826.
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 162169.
13. Wadia, A.R. Numerical solution of 2-D and 3-D rotor tip leakage models, AIAA J, 1985, 23, (7), pp 10611069.
14. Sjolander, S.A. and Cao, D. Measurements of the flow in an idealised turbine tip gap, ASME J Turbomachinery, 1995, 117, pp 578584.
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.
16. Yaras, M.I. and Sjolander, S.A. Prediction of tip leakage losses in axial turbine, ASME J Turbomachinery, 1992, 114, pp 204210.
17. Atkins, N., Thorpe, S. and Ainsworth, R. Unsteady effects on Transonic turbine blade-tip heat transfer, 2008, ASME Paper GT2008-51177.
18. Schultz, D.L. and Jones, T.V. Heat transfer measurements in short duration hypersonic facilities, Agardograph, 1973, 165.
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 1422.
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 2328.
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 256263.
22. Dawes, W. The development of a solution-adaptive 3D Navier-Stokes solver for turbomachinery, 1991, 27th AIAA Joint Propulsion Conference, Sacramento, CA, USA.
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.
24. Durbin, P.A. On the k-ε stagnation point anomaly, Int J Heat and Fluid Flow, 1996, 17, pp 8990.
25. Rodi, W. and Scheuerer, G. Scrutinising the k-ε turbulence model under adverse pressure gradient conditions, J Fluids Engineering, 1986, 108, pp 174180.
26. Wilcox, D.C. Turbulence modeling for CFD, DCW Industries, 1993, La Canada, CA, USA.
27. Medic, G. and Durbin, P.A. Toward improved prediction of heat transfer on turbine blades, ASME J Heat Transfer, 2004, 124, pp 193199.
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 337353.
29. Deckker, B.E.L. and Chang, U.F. An investigation of steady compressible flow through thick orifices, Proc. ImechE, 1966, 180.
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.

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed