HEAT TRANSFER IN AN IMPINGEMENT COOLING SYSTEM FOR TURBINE AIRFOILS WITH A SPARSE DISTRIBUTION OF HOLES

摘要

An experimental investigation of an engine representative Inter-Turbine Duct (ITD) vane with a very sparse distribution of impingement holes along the aerofoil surfaces was conducted using a transient liquid crystal technique. The low jet Reynolds numbers tested drove long crystal phase change times, which required special care when taking measured temperatures for processing the data to obtain accurate local heat transfer coefficients (HTC). Three jet Reynolds numbers (Re) around the design case were measured so that its local influence could be found. HTC results in terms of surface distribution and surface averaged values are presented and compared with some available literature correlations. Finally, an assessment is made of the extension of the local areas of influence where either impingement or duct flow prevails. The correlations which should be used in each of these influence areas are also identified and used to bound experimental results wihtin those limits.