ISAIF 10-58, 2012
Turbine blade tip clearances control of large aero-engines is currently performed by impinging fan air on the outer case flanges. The present paper reports a numerical and experimental survey aimed to evaluate the heat transfer coefficient of six arrays of impingement holes drilled on circular ducts. Tested geometry replicate the impingement tubes and the by-pass duct used in active control clearance systems. Tube internal diameter is D=12mm, cooling holes diameter d=1mm, span-wise pitch is Sx/d = 12. In order to simulate the flow of the by-pass duct, the impingement arrays are inserted inside a tunnel that replicates the typical shape of a real engine by-pass duct. Numerical and experimental tests were conducted varying both the mainstream Reynolds number and the jet Reynolds number in a range typical of effective engine operative conditions (Rej=2000-10000, beta=1.01-1.20).