Session: 12-12-01: Gas Turbine Heat Transfer and heat exchanger

Paper Number: 165816

Y-Shaped Hole for Film Cooling 

The geometry of film-cooling holes strongly affects film-cooling adiabatic effectiveness.  Thus, many investigators have explored and developed geometries to improve film cooling. These include compound-angle holes, shaped holes, and vortex generators.  

This study seeks to further improve one-type of shaped hole, one that is referred to as laidback-fan-shaped holes (https://doi.org/10.1115/1.1860562).  These shaped holes increase film-cooling effectiveness by expanding the hole’s cross-sectional area to spread the cooling jet laterally and by having a convex surface on one side of the hole to minimize lift off.  However, penetration of the cooling flow downstream of the hole is reduced because increasing cross-sectional area decreases the cooling flow’s momentum. The momentum-preserving W-shaped hole (https://doi.org/10.1115/GT2007-27600) was developed to increase lateral spreading as well as increase its downstream penetration by protruding the middle part of the hole so that the cross-sectional area does not increase as the hole widens to preserve momentum of the cooling flow.  In this study, the design concept embedded in the W-shaped hole was refined to create the Y-shaped hole to further enhance the momentum of the cooling flow to promote both lateral spreading and downstream penetration.

To assess the usefulness of the Y-shaped hole developed, a combined computational and experimental study was performed to examine the film-cooling of a flat plate that is exposed to a flow of hot gas with the film-cooling flow issuing from one row of Y-shaped holes and with the coolant supplied by a plenum.  The hot gas above the plate and the coolant are both air.  Parameters studied include blowing ratio (BR= 0.75 and 1.0) and temperature ratio (TR= 1.07 and 1.9).  On the blowing ratio, it is based on the maximum mass flux in the film-cooling hole.

The computational part of this study is based on steady Reynolds-Averaged Navier-Stokes (RANS) with the Shear-Stress Transport (SST) turbulence model for a thermally-perfect gas with temperature-dependent viscosity and thermal conductivity. The experimental part of this study was conducted by using a conjugate heat transfer test rig with a plenum, where cooling flow is introduced. Measurements made include velocity and temperature profiles upstream and downstream of the film-cooling holes as well as the temperature at several locations on the hot and cold sides of the film-cooled flat plate. The computational study was validated by comparing computed results with those from measurements at BR= 0.75 and 1.0 and TR = 1.9.

Computational and experimental results are presented to show the effects of BR and TR on the flow structures and how those structures improve the adiabatic effectiveness of film cooling.

Presenting Author: Robert Gillespy Purdue University

Presenting Author Biography: Robert Gillespy is a MS. student in the School of Aeronautics and Astronautics at Purdue University.

Authors:

Robert Gillespy Purdue University
Jason Liu NASA Marshall Flight Center
Tom I-P. Shih Purdue University
Douglas Straub National Energy Technology Laboratory
Justin Weber National Energy Technology Laboratory