The role of corrugated impingement cooling geometries at high temperature ratios for future gas turbines

Gas turbines are likely to be crucial in decarbonisation through their role in the transition to sustainable fuels and for enabling flexible operation power stations. In designing for the new demands of future gas turbines, there is a drive to improve efficiency and reduce manufacturing cost. In order to improve efficiency, designers seek to reduce cooling air mass flow rate, resulting in high temperature ratios between the metal temperature and cooling air. Manufacturing cost can be lowered by reducing the dependence on film cooling, which also leads to higher temperature ratios. Impingement cooling is well-known as an effective heat transfer method, and it is commonly used to cool high temperature turbine components. A key problem for impingement cooling is that high temperature ratios negatively impacts jet performance. Literature shows that corrugated style impingement geometries are a reliable and effective way to manage crossflow in low temperature ratio conditions. This study numerically explores the application of corrugated geometries for a range of high temperature ratio and crossflow conditions. The study evaluates temperature ratios of 1.1 to 2.0 and uses a working fluid of air. Calculations are performed for a Reynolds number of 10,000 and an SST k- turbulence model is used. Impingement jet diameter, jet to jet pitch and distance from impingement plate to target plate are kept the same for each structure. Increasing temperature ratio is found to increase crossflow momentum and cause jet distortion, reducing performance of the flat plate geometry by up to 30%. By mitigating the detrimental effects of crossflow and restoring idealised impingement, corrugated geometries enhance the effectiveness of impingement cooling by up to 47% compared to the flat case at high temperature ratio and crossflow conditions.