Conjugate Heat Transfer and Thermal Stress in an Impingement Cooling Unit for Gas Turbine Vane

Impingement cooling is widely used in gas turbines because of its excellent local heat transfer capability, and it plays an important role in the next generation of double-wall cooling technology. However, it induces inhomogeneous temperature fields as well as thermal stress fields. In this paper, the conjugate heat transfer and thermal stress characteristics are investigated for an impingement unit including a single round nozzle and solid plate with uniform heat flux on the heated surface through an experimentally validated numerical approach. The studied operating parameter are Reynolds number (from 10000 to 30000), nozzle-to-plate distance ratio (from 2 to 10), and thickness of solid plate (108 mm and 50 mm). The results show that the Nusselt number distribution along radius may have two maxima at a small impingement distance which is driven by the mismatch of maximum wall shear stress location and maximum near-wall turbulence kinetic energy location. Considering the uneven heat transfer distribution as a boundary condition of solid thermal conduction, thermal conduction would reform the heat flux which makes the uniform heat flux boundary condition on the heated surface into uneven heat flux distribution on the impinged surface. The temperature can be lowered and distributed more evenly by increasing the thermal conductivity of the plate. In contrast, the temperature can be lowered but distributed more unevenly by reducing the thickness of the plate. The flat plate expands into a shape with a thin center and thick edges due to the uneven temperature field. This research illuminates the coupling mechanism between convective heat transfer, solid heat conduction, and thermal stress, which has significance for the prediction of gas turbine vane metal fatigue life.