Experimental and Numerical Heat Transfer Investigation of Impingement Jet Nozzle Position in Concave Double-Wall Cooling Structures

Abstract

In this paper, experimental and numerical study has been carried out to investigate impingement cooling with a row of five circular jets, varied between target positions on a realistic leading edge region of a gas turbine blade geometry. Experimental data is collected from a transient thermochromic liquid crystal measurement technique at the target surface.Numerical study was conducted with the geometry using commercial computational fluid dynamics software to analyse the fluid flow. The unique aims of the study are to observe the effects of variation in jet location, and those specific to realistic target and nozzle geometries.Distributions of local and average Nusselt number show that a location targeting the concave surface at 90° demonstrates an overall higher heat transfer coefficient, especially in the stagnation region, and towards the aerofoil sides, with significantly less swirl. The experiment was performed with the following parameters: distance from nozzle to target of 1.7 to 2.1 jet diameters, pitch between jets of 4.4 jet diameters, and concave target diameter of 8.0 jet diameters. The jet Reynolds number range during this test was 20,000 -40,000. A standard flat target plate impingement test is also experimentally conducted and compared against existing literature for method validation.