Heat transfer characteristics of pin-fin arrays with coupled trapezoidal ribbed endwalls in gas turbine blade internal cooling channels

Abstract

For internal cooling of the turbine blade, pin-fin arrays located near the blade's trailing edge are essential for enhancing heat transfer and preserving structural integrity. However, the flat end wall of a conventional pin-fin channel tends to generate wake vortices, resulting in low heat transfer regions. To overcome this limitation, a new end wall design, termed the coupled trapezoidal ribbed end wall (CTRE), is proposed to improve overall heat transfer performance. Numerical simulations were performed by solving the Reynolds-averaged Navier-Stokes equations with the k-omega turbulence model. The CTRE design consists of an upstream rib and a downstream rib positioned lower and higher than the pin-fin base, respectively. The recirculating flow generated by the CTRE continuously interacts with the pin-fins and strengthens the horseshoe vortices, thereby expanding the high heat transfer regions. Moreover, the upward flow induced by the downstream rib interacts with the wake flow and weakens the wake vortices, further diminishing the low heat transfer regions behind the pin-fins. Consequently, the CTRE configuration yields a significant enhancement in the average Nusselt number (Nu) and the heat transfer efficiency index (HTEI), while introducing only a slight increase in the friction factor. Specifically, the new end wall design enhances average Nu by approximately 91.88%-103.04% and HTEI by 74.15%-78.05% over a Reynolds number range of Re=7400-36000. Six geometric parameters of the CTRE design were investigated, including the height, long-base length, and short-base length of the upstream and downstream ribs. The results provide valuable insights into the physical mechanisms associated with geometric variations.