Numerical Analysis of Crossflow and Single Jet Impinging on a Heated Surface With Shaped Groove

Gas turbine performance is strongly affected by firing temperature; raising this parameter has always been one of the major development strategies in gas turbine technology. This trend requires enhancements in materials and cooling techniques in order to keep components temperatures within structural limits and to satisfy expected life requirements. Cooling techniques are proven to be very effective, and it justifies tremendous research efforts. Among these techniques, impingement cooling is widely used, especially in vane cooling. Impingement fluid dynamics is quite complex, and its understanding is still incomplete; moreover further improvements in impingement cooling performance are expected. A great amount of experimental investigations are available on the subject and recently more and more numerical analysis has been performed. Due to advances in computational fluid dynamics (CFD) and availability of commercial codes, numerical investigations are often used in industrial design methodologies. Therefore the present study has been carried out using a commercial code with a two equation turbulence model, as common in industry standard analyses. The aim of this work is to investigate a single jet with cross-flow, at several blowing rates, analysing both flow field and heat transfer. The cross-flow passes through a rectangular duct. The jet is injected on the upper surface from a circular pipe perpendicularly to the duct axis and impacts on the lower surface. Firstly, a comparison of results with experimental data available in literature is provided. This permits to characterize the numerical model, particularly with respect to mesh, boundary conditions, and turbulence model. Then the rectangular duct lower flat surface is replaced by a grooved one. A single groove, horse-shoe shaped and located slightly upstream the impinging region, is used to control the flow field near the impact surface. Effects of the groove on impingement cooling are investigated. Both fluid dynamic and heat transfer analyses are performed. Results show the groove to be effective in driving the flow field interaction between cross-flow and impinging jet; heat transfer is also affected by the groove.