Effect of Pin Base-Fillet on Heat Transfer Enhancement of an Internal Blade Pin-Finned Tip-Wall

Abstract

A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip-cap. Improving internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip has been investigated numerically. The computational models consist of a two-pass channel with 180-deg turn and pin-fins mounted on the tip-cap, and a smooth two-pass channel. On the other hand, In particular manufacture, the casting process does not make a perfect cylinder pin, a fillet needs to be placed at the endwall. In order to make the conditions of simulations as close to real practice as possible, it is desirable to examine the effect of fillet on the tip heat transfer. Therefore, in the present study, the effect of pin base-fillet on heat transfer enhancement of a blade pin-finned tip-wall is investigated numerically. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible and stationary. It is found that the pin-fins make the counter-rotating vortices towards pin-fin surfaces, resulting in continuous turbulent mixing near the pin-finned tip. Due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of as much as 2.66 higher than that of a smooth tip. Besides, with base-fillets the heat transfer enhancement is increased by about 10% while almost no additional pressure loss is resulted. It is suggested that the pin-fins could be used to enhance blade tip heat transfer and cooling.