Submitted to International Gas Turbine Institute 2013 DRAFT GT2013-94289 1 Copyright © 2013 by ASME Numerical Simulation of Flow and Heat Transfer in Rotating Cooling Passage with Turning Vane in Hub Region Hung-Chieh Chu 1 , Hamn-Ching Chen 2 , and Je-Chin Han 1 1 Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843-3123 2 Zachry Department of Civil Engineering, Texas A&M University, College Station, Texas 77843-3136 Email: jc-han@tamu.edu Abstract Numerical simulation of three-dimensional turbulent flow and heat transfer was performed in a multi-pass rectangular (AR=2:1) rotating cooling channel with and without turning vane in the hub region under various flow conditions, with two different Reynolds numbers of 10000 and 25000, two different channel orientations of 45-deg and 90-deg., and the rotation number varies from 0 to 0.2. The present study provides detailed explanation on the dramatic flow change due to the turning vane. The numerical results show that the addition of vane in hub portion does not cause much impact to the flow before the turn. However, it greatly affects flow behaviors and heat transfer characteristics in the turning region and the third passage after the hub turn. Compared to the cases without turning vane, the vane clearly changes local flow pattern, divides the main flow into two separate streams, and alters the flow reattachment location and vortex distribution. The local heat transfer is influenced by this complex flow field and its effects last from the turn portion to the third passage. 1. Introduction In order to improve thermal efficiency, engineers try to increase turbine inlet temperature. However, various cooling technologies are needed in order to prevent the high temperature from devastating the turbine blade. Among these, internal cooling is one method which has been widely used in the gas turbine. The internal cooling channel is a serpentine passage consists of several straight ducts and 180 degree sharp/smooth turns. Turn portions play an important role in this configuration. Ekkad and Han [1] measured heat transfer distribution in two-pass square channels with a 180 degree sharp turn. It was showed that the Nusselt number ratio in second passage is 2-3 times higher than that in the first passage due to the turn effect. Liou and Chen [2] used Laser Doppler Velocimetry (LDV) to investigate heat transfer in a two–pass smooth passage with a 180° sharp turn. Their measurement indicated that the secondary flow induced by the sharp turn enhances the heat transfer in first part of the second passage. In Luo and Razinsky [3], four different turbulence models (V2F, k-ε model, shear stress transport (SST) and Reynolds Stress model (RSM)) were used to predict flow in a U-duct. It was revealed that the round turn reduced secondary flow in comparison with the sharp turn. The complex geometries of internal passage tend to produce high pressure loss. In order to decrease this loss, engineers tried to add a guide vane in the smooth turn portion of the cooling passage. Zehnder et al. [4] investigated the effect of different size vanes in a two-pass channel. According to their experimental and numerical results, Zehnder et al. showed that, with a suitable design, the application of vane in the turn portion can reduce pressure loss while maintaining similar heat transfer level. Chen et al. [5] used liquid crystal method to investigate vane effects in a ribbed two-pass channel. They concluded that the guide vane did not cause big influence to first passage (before turn). However, it indeed caused significant influence to the turn portion and the second passage downstream of the turn. They also noted that, with appropriate arrangement, the vane can meet the requirement on heat transfer and pressure drop. In reality, turbine blades rotate with high rotating speed. This rotation changes flow and heat transfer in internal cooling channel. Wagner and Velkoff [6] measured velocities and pressures in different regions of a rotating duct. It was revealed that the magnitude of the cross-flow velocities and longitudinal vortices are linearly proportional to the rotational speed. Dutta and Han [7] presented their experiment data to show rotation indeed caused influence to heat transfer in a two-pass channel by choosing different Reynolds number (Re=2500 to 25000) and different rotation number (Ro=0.3 to 0.03). Dutta and Han concluded that when the coolant moves from hub portion to tip portion, rotation enhanced heat transfer on trailing surface but decreased heat transfer on leading surface. When the coolant moves from tip portion to hub portion, it caused opposite influence. Huh et al. [8] extended the range of the rotation number to 0.45 to investigate high