Heat Transfer in an Oblique Jet Impingement Configuration With Varying Jet Geometries

Abstract

The experimental and numerical heat transfer results in a trapezoidal duct with two staggered rows of inclined impingement jets are presented. The influence of changes in the jet bore geometry on the wall heat transfer is examined. The goal of this project is to minimize the thermal load in an internal gas turbine blade channel and to provide sufficient cooling for local hot spots. The dimensionless pitch is varied between p/djet=3 − 6. For p/djet=3, cylindrical and conically narrowing bores with a cross section reduction of 25% and 50%, respectively, are investigated. The studies are conducted at 10,000≤Re≤75,000. Experimental results are obtained using a transient thermochromic liquid crystal technique. The numerical simulations are performed solving the RANS equations with FLUENT using the low- Re k- ω -SST turbulence model. The results show that for a greater pitch, the decreasing interaction between the jets leads to diminished local wall heat transfer. The area averaged Nusselt numbers decrease by up to 15% for p/djet=4.5, and up to 30% for p/djet=6, respectively, if compared to the baseline pitch of p/djet=3. The conical bore design accelerates the jets, thus increasing the area-averaged heat transfer for identical mass-flow by up to 15% and 30% for the moderately and strongly narrowing jets, respectively. A dependency of the displacement between the Nu maximum and the geometric stagnation point from the jet shear layer is shown.

Basic Aspects of Gas Turbine Heat Transfer

“…The use of inclined impingement jets on shaped turbulators in irregular shaped passages can also result in very high heat transfer. In a recent study [29,30], and as shown in Figure 25, it was highlighted that directed inclined impingement can result in relatively high heat transfers from the target walls and additionally produces intense convective fluid mixing within the passage. In a turbine blade, such a combination can result in greater total heat removal by the coolant from the hot airofoil walls.…”

Flow And Heat Transfer Characteristics Of Inclined Jet Impingement On A Flat Plate

“…However, the effect of inclination angle of the jet on heat transfer is not studied enough and blind spots still exists. The difficult nature of a turbulent impinging jet flow, a jet issuing out of a pipe or nozzle and then impinging on a target surface with change of flow direction upon impingement, makes it hard to rely on analytical solutions to analyze the heat transfer process between the jet and the target plate [10][11]. A number of studies narrate about the examination of inclined impinging air jet and a flat surface in the literature [12][13][14][15][16][17].…”