Numerical investigation of heat transfer performance and flows characteristics in turbine blade internal cooling using Pin-Fin arrays coupled with discontinuous ribbed endwall

Abstract

In the scientific domain of cooling techniques research utilizing pin-fins, a number of studies have concentrated on the configurations of pin-fins. However, recent investigations have shifted their focus towards the optimization of endwalls. The objective of this optimization is to better control and maintain vortices, which in turn leads to an increase in heat transfer near the endwall. Further research has taken this a step further by optimizing the lower and upper walls of the unadorned heated channel, resulting in a significant boost in heat transfer efficiency. These studies have also led to the discovery of new heat transfer properties and alterations in the flow structure. This research unveils the findings from an examination into the flow field and heat transfer properties of pin–fin arrays featuring a ribbed endwall, specifically referred to as a Discontinuous Ribbed Endwall (DRE). The investigations are executed using Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ω turbulence model at the mesh parameter of the 20.4 million mesh model is used throughout the work. The study involves a numerical investigation of the heat transfer and pressure drop characteristics of the channel, comparing them with the case of flat endwall across a range of inlet Reynolds numbers, spanning from 7400 to 36000. The entire section of the heated channel is divided into 7 upper surfaces, 7 lower surfaces, and cylindrical surfaces to comprehensively investigate the heat transfer characteristics of both pin-fins and endwalls. The results reveal that the heat transfer regions at the pin-fins and endwalls are expanded and significantly enhanced, particularly causing notable alterations in the flow structure and velocity field. However, the coefficient of friction also increases. The Area-averaged Nusselt Number ($\overline{\mathrm{Nu}}$) and the Heat Transfer Efficiency Index (HTEI) improves from 42.99% to 88.65% and from 36.81% to 73.66% for the DRE compared to the case of flat endwall across the entire range of Reynolds numbers. With Reynolds number 21500, when varying the height parameter of the DRE, the maximum value of the HTEI improves by 84.13%. Other geometric parameters of the DRE, including forward width, behind width, left width, streamwise position, and left position, also undergo changes, with the maximum values of HTEI improving by 73.76%, 75.35%, 80.60%, 75.41% and 74.16%, respectively.