Film Cooling Performance of Tripod Antivortex Injection Holes Over the Pressure and Suction Surfaces of a Nozzle Guide Vane

Abstract

Film cooling performance of the antivortex (AV) hole has been well documented for a flat plate. The goal of this study is to evaluate the same over an airfoil at three different locations: leading edge suction and pressure surface and midchord suction surface. The airfoil is a scaled up first stage vane from GE E3 engine and is mounted on a low-speed linear cascade wind tunnel. Steady-state infrared (IR) technique was employed to measure the adiabatic film cooling effectiveness. The study has been divided into two parts: the initial part focuses on the performance of the antivortex tripod hole compared to the cylindrical (CY) hole on the leading edge. Effects of blowing ratio (BR) and density ratio (DR) on the performance of cooling holes are studied here. Results show that the tripod hole clearly provides higher film cooling effectiveness than the baseline cylindrical hole case with overall reduced coolant usage on the both pressure and suction sides of the airfoil. The second part of the study focuses on evaluating the performance on the midchord suction surface. While the hole designs studied in the first part were retained as baseline cases, two additional geometries were also tested. These include cylindrical and tripod holes with shaped (SH) exits. Film cooling effectiveness was found at four different blowing ratios. Results show that the tripod holes with and without shaped exits provide much higher film effectiveness than cylindrical and slightly higher effectiveness than shaped exit holes using 50% lesser cooling air while operating at the same blowing ratios. Effectiveness values up to 0.2–0.25 are seen 40-hole diameters downstream for the tripod hole configurations, thus providing cooling in the important trailing edge portion of the airfoil.