Effects of Circumferential Heating Variations and Channel Height on Heat Transfer Coefficient of Wetted Surfaces in a Single Inline Row Impingement Channel

Abstract

High performance turbine airfoils are typically cooled with a combination of internal cooling channels and impingement channels. In such applications, the jets impinge against a target surface, and then exit along the channel formed by the jet plate, target plate, and side walls. Local convection coefficients are the result of both the jet impact, as well as the channel flow produced from the exiting jets. Numerous studies have explored the effects of jet array and channel configurations on both target and jet plate heat transfer coefficients. However, little work has been done in examining effects of circumferentially non-uniform heating on all channel walls, which is the kind of thermal boundary condition in real world applications. This paper examines the local and averaged effects of channel height and circumferential heating variations on heat transfer coefficients. High resolution local heat transfer coefficient distributions on target and side wall surfaces were measured using temperature sensitive paint and recorded via a scientific grade charge-coupled device (CCD) camera. Streamwise pressure distributions for both the target and side walls was recorded and used to explain heat transfer trends. Results are presented for average jet based Reynolds numbers between 17,000 and 45,000. All experiments were carried out on a large scale single row, 15 hole impingement channel, with X/D of 5, Y/D of 4, and Z/D of 1, 3 and 5.