Session: 12-12 Computational Techniques

Paper Number: 78245

78245 - Film Cooling Hole Shape Effects on Turbine Blade Heat Transfer – Part II: Effects of Mass Flow Rate and Unsteadiness 

Unsteadiness in cooled gas turbines causes highly complicated film cooling flow and can often cause disconnects between film cooling performance and the flat plate film cooling performance used to develop the cooling technology. To provide a detailed analysis of film cooling in a turbine environment, this study incorporates experimental and computational research performed on a high-pressure turbine stage operating at design corrected conditions. Three different turbine blades are investigated, all with identical airfoil shape and differing only in film cooling hole shape. Film cooling hole shapes include round, fan, and advanced anti-vortex shapes, and the performance of these cooling systems installed on the rotating blades are evaluated on time-averaged and unsteady bases for multiple cooling flow rates.

Film cooling hole shape and coolant mass flow are observed to provide different cooling benefits in different areas of the blade. Diffusion characteristics of shaped film cooling holes typically allow for increased film effectiveness at higher coolant flow rates due to the lower cooling gas momentum. Advanced film cooling holes on the pressure surface, however, are observed to cause separation in the diffusing section at the highest blowing ratios due to aggressive expansion. Across the pressure surface, leading edge, and suction surface, advanced film cooling holes show the most response to changing coolant mass flow, and typically have the highest film effectiveness at the highest film cooling flow rate.

Film cooling jets from all cooling holes experience similar motion. Unsteady pressure gradients across the film cooling hole exits on the pressure surface are observed to cause lateral cooling jet motion. Fan and advanced shaped holes cause lateral spread of cooling gas on a steady basis. Coupling unsteady lateral motion with steady lateral spread of the coolant results in a larger blade wall region receiving consistent film coverage. On a time-average basis, this results in much more lateral spread and increased film coverage for shaped film cooling holes.

The results of this study help identify the performance of shaped film cooling holes in turbine environments. The response of different hole shapes to unsteadiness has a significant impact on the time average film cooling coverage. Additionally, the hole shapes respond differently to increased levels of coolant mass flow rate and provide different degrees of film cooling coverage on different parts of the blade. An increased understanding and appreciation of the unsteady performance of various film cooling geometries is a foundational piece of continued technology development.

Presenting Author: Spencer Sperling The Ohio State University

Presenting Author Biography: Bio to be provided later

Authors:

Spencer Sperling The Ohio State University
Louis Christensen The Ohio State University
Randall Mathison The Ohio State University
Hakan Aksoy Honeywell Aerospace
Jong Liu Honeywell Aerospace
Jeremy Nickol Honeywell Aerospace