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.

Numerical investigation of heat transfer and flow characteristics of a double-wall cooling structure: Reverse circular jet impingement

“…9 b. This more even pressure gradient results in a marginally increased average Nu, but still creates highest Nu values towards jet 5, the explanation for a lack of high Nu at jet 1 in proximity to the inlet is caused by an increased crossflow over the jet 1 nozzle inlet in the main plenum [27], [28].…”

“…Thus, heat transfer of a single reverse jet impingement has been experimentally investigated by using a wind tunnel with heated air and applying the Transient Liquid Crystal technique to validate the numerical work, as explained in the next two sections. The experimental test-rig setup has been illustrated particularly in previous work [27], [28].…”

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

“…Of note, this research is an expansion of one aspect of a larger investigation into the optimisation of cooling air usage in a double-wall structure previously introduced [25], with the aim to maximise the internal heat transfer enhancement, whilst considering the required cooling air. Fundamentally, this enhancement of heat transfer can generally be achieved in one of three ways: decreasing the boundary layer thickness, increasing the boundary layer turbulence, or decreasing the boundary layer viscosity.…”