Film cooling effectiveness was measured on a contoured endwall surface using the pressure sensitive paint (PSP) technique. A double staggered row of holes was adopted to supply cooling air in front of the nozzle leading edges. To simulate realistic engine configuration, a back-facing step was built, which was located upstream from the film injection. Nitrogen gas was used to simulate film cooling flow as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to be from 0.5% to 3.0% of the mainstream mass flow. Film effectiveness distributions were measured on the endwall surface for both smooth (baseline) and back-facing step inlet configurations. For the smooth inlet case, film effectiveness increased nonlinearly with mass flow rate, indicating a strong interference between the cooling jets and the secondary flows. At lower mass flow ratios, the secondary flow dominated the near wall flow field, resulting in a low film effectiveness value. At higher mass flow ratios, the cooling jet momentum dominated the near wall flow field, resulting in a higher film effectiveness. For the back-facing step inlet configuration, the values of film effectiveness were reduced significantly, suggesting a stronger secondary flow interaction. In addition to the comparison between the smooth and back-facing step inlet configurations, comparison to previous data by the authors on a flat endwall was also made.
Turbine Nozzle Endwall Inlet Film Cooling: The Effect of a Back-Facing Step
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Zhang, L, & Moon, HK. "Turbine Nozzle Endwall Inlet Film Cooling: The Effect of a Back-Facing Step." Proceedings of the ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. Volume 5: Turbo Expo 2003, Parts A and B. Atlanta, Georgia, USA. June 16–19, 2003. pp. 203-211. ASME. https://doi.org/10.1115/GT2003-38319
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