Numerical investigation of the effects of discrete guide vanes on the control of heat transfer on the tip surface of a turbine blade

The cooling of the tip surface of a turbine blade is a critical issue with respect to the increase in turbine inlet temperatures. Guide vanes, ribs, pins, dimples, and protrusions have been used by previous researchers in the tip turning region in internal two-pass channels to increase the cooling effect on the tip surface. However, external heat transfer at the tip surface is not uniform. Thus, different local heat transfer measurements are needed for cooling the tip surface. Discrete guide vanes have been suggested to control the cooling effect on tip surfaces. Numerical simulations were performed in six different guide vane cases in a two-pass channel to compare the effects of discrete guide vanes. In a two-pass channel, ribs were installed at 45°. The Reynolds number, which is based on hydraulic diameter and velocity, was fixed at 10,000 in each case. The results indicated that the base case and U-vane case showed high heat transfer at the tip surface of the first channel but low heat transfer at the tip surface of the second channel. Also, the heat transfer on the tip surface was asymmetrical. In comparison, the heat transfer on the tip surface was asymmetrical in discrete guide vane cases. The 1S2S case showed high heat transfer on the tip surface of the second passage pressure side and the 1P2P case showed high heat transfer on the tip surface of the second passage suction side. The arrangement of discrete guide vanes caused different flow characteristics in comparison with the U-vane case. Thus, the design of discrete guide vanes can control heat transfer on the tip surface effectively.