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Aerothermal investigations of tip leakage flow in axial flow turbines-part III : TIP cooling


Reference:

Newton, P. J., Lock, G. D., Krishnababu, S. K., Hodson, H. P., Dawes, W. N., Hannis, J. and Whitney, C., 2009. Aerothermal investigations of tip leakage flow in axial flow turbines-part III : TIP cooling. Journal of Turbomachinery: Transactions of the ASME, 131 (1), 011008.

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Official URL:

http://dx.doi.org/10.1115/1.2950060

Abstract

Contours of heat transfer coefficient and effectiveness have been measured on the tip of a generic cooled turbine blade, using the transient liquid crystal technique. The experiments were conducted at an exit Reynolds number of 2.3 x 10(5) in a five-blade linear cascade with tip clearances of 1.6% and 2.8% chord and featuring engine-representative cooling geometries. These experiments were supported by oil-flow visualization and pressure measurements on the tip and casing and by flow visualization calculated using CFX, all of which provided insight into the fluid dynamics within the gap. The data were compared with measurements taken from the uncooled tip gap, where the fluid dynamics is dominated by flow separation at the pressure-side edge. Here, the highest levels of heat transfer are located where the flow reattaches on the tip surface downstream of the separation bubble. A quantitative assessment using the net heat flux reduction (NHFR) revealed a significant benefit of ejecting coolant inside this separation bubble. Engine-representative blowing rates of approximately 0.6-0.8 resulted in good film-cooling coverage and a reduction in heat flux to the tip when compared to both the flat tip profile and the squealer and cavity tip geometries discussed in Part I of this paper Of the two novel coolant-hole configurations studied, injecting the coolant inside the separation bubble resulted in an improved NHFR when compared to injecting coolant at the location of reattachment.

Details

Item Type Articles
CreatorsNewton, P. J., Lock, G. D., Krishnababu, S. K., Hodson, H. P., Dawes, W. N., Hannis, J. and Whitney, C.
DOI10.1115/1.2950060
Uncontrolled Keywordsnovel cooling strategy, turbine tip, heat transfer
DepartmentsFaculty of Engineering & Design > Mechanical Engineering
Research CentresAerospace Engineering Research Centre
RefereedYes
StatusPublished
ID Code14322
Additional InformationProceedings paper from the 52nd ASME Turbo Expo 2007. Montreal, Canada, 14-17 May, 2007

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