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International Heat Transfer Conference 13

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

EFFECT OF UNSTEADY WAKE ON SHOWERHEAD FILM COOLING PROTECTION FOR A GAS TURBINE BLADE

S. P. Mhetras
Texas A&M University College Station, USA

Je-Chin Han
Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A&M University College Sation, TX 77843-3123, USA

DOI: 10.1615/IHTC13.p21.100
12 pages

Abstract

The effect of showerhead film cooling along the span of high pressure turbine blade in a 5 bladed linear, stationary cascade on film cooling effectiveness was investigated using the Pressure Sensitive Paint (PSP) technique. Film injection at the leading edge through 3 rows of cylindrical holes drilled at 30° to the surface was examined and the extent of the coolant traces on the pressure and suction sides of the blade from showerhead film injection was determined. The coolant is injected at three different average blowing ratios of 0.6, 0.9 and 1.2. Presence of wake due to an upstream vane was simulated by placing a set of rods upstream of the test blade. The wake was controlled by using a rod diameter of 4.8mm. The wake rods were clocked by changing their stationary positions in front of the test blade to simulate a progressing wake. Effect of wake was recorded at four phase locations with equally spaced intervals. The free stream Reynolds number, based on the axial chord length and the exit velocity, was 750,000 and the inlet and the exit Mach numbers were 0.27 and 0.45, respectively resulting in a blade pressure ratio of 1.15. Turbulence intensity level at the cascade inlet was 6% with an integral length scale of around 5cm. Results show that the presence of turbulence and upstream wake can damage the film coolant coverage on the blade. Varying blowing ratios can also have a significant impact on film-cooling effectiveness distribution with a blowing ratio of 0.9 showing highest effectiveness.

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Measurement of fluid temperature with an arrangement of three thermocouples