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

P J Newton, Gary D Lock, S K Krishnababu, H P Hodson, W N Dawes, J Hannis, C Whitney

Research output: Contribution to journalArticlepeer-review

27 Citations (SciVal)

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.
Original languageEnglish
Article number011008
Number of pages12
JournalJournal of Turbomachinery: Transactions of the ASME
Volume131
Issue number1
Early online date2 Oct 2008
DOIs
Publication statusPublished - Jan 2009
Event52nd ASME Turbo Expo 2007 - Montreal, Canada
Duration: 1 Jan 2009 → …

Keywords

  • novel cooling strategy
  • turbine tip
  • heat transfer

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