NDLI: Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Nasir, S. Bolchoz, T. Ng, W. F. Zhang, L. J. Moon, H. K. Anthony, R. J.
Copyright Year	2008
Abstract	This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105, 1.1 × 106 and 1.5 × 106, respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.
Starting Page	1063
Ending Page	1075
Page Count	13
File Format	PDF
ISBN	9780791848715
DOI	10.1115/IMECE2008-66528
e-ISBN	9780791838402
Volume Number	Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C
Conference Proceedings	ASME 2008 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2008-10-31
Publisher Place	Boston, Massachusetts, USA
Access Restriction	Subscribed
Subject Keyword	Suction Turbulence Cooling Wind tunnels Cascades (fluid dynamics) Reynolds number Pressure gradient Pressure Density Gages Thin films Wall temperature Platinum Chords (trusses) Coolants Film cooling Turbines Boundary layers Heat transfer Mach number
Content Type	Text
Resource Type	Article

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