Experimental and Numerical Analysis of Multiple Impingement Jet Arrays for an Active Clearance Control System

Abstract

The turbine blade tip clearances control in large aeroengines is currently performed by means of impinging fan air on the outer case flanges. The aim of the present study is to evaluate both the heat transfer coefficient and the adiabatic thermal effectiveness characteristics of an enginelike ACC system, and in particular, to comprehend the effects of the undercowl flow on the impingement jets. The considered geometry replicates the impingement tubes and the bypass duct used in active control clearance systems. The tube's internal diameter is D = 12 mm, the cooling hole's diameter is d = 1 mm, and the spanwise pitch is Sy/d=12. In order to simulate the undercowl flow, the impingement arrays are inserted inside a tunnel that replicates the typical shape of a real engine bypass duct. Tests were conducted varying both the mainstream Reynolds number and the jets Reynolds number in a range typical of realengine operative conditions (Rej=200010000, خ²=1.051.15). Numerical calculations are finally proposed to point out if CFD is able to confidently reproduce the experimental evidences.