Effect of Buoyancy, Density Ratio, and Dimple Geometry on Heat Transfer in the Internal Cooling Channel of a Gas Turbine Blade With Dimples

The internal cooling of gas turbine blades features serpentine channels equipped with various turbulence generators, such as dimples, pin-fins, and ribs. These generators are critical for reducing surface temperature and enhancing the heat transfer coefficient. Achieving a balance between high heat transfer and low-pressure drop remains a significant challenge. While offering superior heat transfer, pin-fins result in a high-pressure drop, whereas dimples have gained popularity due to their optimal heat transfer and pressure drop balance. This study focuses on the rotational effects of internal gas turbine blade cooling using dimples, providing insights into the density and buoyancy effects within the cooling channel. Two types of dimples-partial spherical and leaf dimples-were examined experimentally and numerically. Experiments were conducted with a heat flux range of 1,300 to 40,000 W/m2 and a Reynolds number (Re) of 50,000, utilizing an experimental setup capable of rotating up to 1,000 rpm, with tests completed at 900 rpm. The large eddy simulation (LES) technique was employed for numerical analysis. The investigation revealed the influence of buoyancy forces on the heat transfer coefficient within a cooling channel with an aspect ratio of 1:1. Results indicated that the leaf-dimpled channel provided superior heat-transfer enhancement compared to the partially spherical dimpled channel.