Numerical Study on Effects of Different Corrugated Height and Initial Crossflow on Impingement Jet Heat Transfer

Abstract More efficient gas turbines are required to realize a decarbonized society. To improve gas turbine performance, it is important to increase turbine inlet temperature and to decrease the mass flow rate of turbine cooling air. Impingement cooling is a well-known and effective heat transfer method, and it is commonly used to cool high temperature turbine components. One of the key problems found with impingement cooling is that crossflow created by upstream impingement negatively impacts the performance of downstream jets. Literature shows that corrugated style impingement geometries are a reliable and effective way to manage crossflow. However, the internal space of the airfoil is limited, limiting the maximum corrugated height. Therefore, it is important to establish the impact of corrugated height in crossflow mitigation, to understand the key flow mechanisms and to consider the effects in high crossflow scenarios found in larger impingement hole arrays. In this study, the effect of corrugated height and initial crossflow on impingement jet heat transfer are numerically investigated. To quantify performance, pumping power and Nusselt number are compared between flat plate, low corrugated and high corrugated impingement geometries. A control volume methodology is implemented to evaluate the contributions of crossflow and impingement to overall loss. Vortical structures are visualised to analyse the key mechanisms by which crossflow interacts with succeeding impingement jets. Impingement jet diameter, jet to jet pitch and distance from impingement plate to target plate are kept the same for each geometry. Calculations are performed for Reynolds numbers of 10,000 and a SST k-ω turbulence model is used. The results of the study show that for the low crossflow condition, Nusselt number enhancement is 5–10% and increases up to 20% under the high crossflow condition, even at a small corrugated height. Improved cooling allows designers to decrease the mass flow rate of cooling air, enabling improved gas turbines efficiency.