Augmented Heat Transfer of an Internal Blade Tip by Full or Partial Arrays of Pin-Fins

Cooling methods are needed for the turbine blade tips to ensure a long durability and safe operation. A common way to cool the tip is to design serpentine passages with 180-deg turn under the blade tipcap taking advantage of the three-dimensional turning effect and impingement like flow. Improved internal convective cooling is therefore required to increase the blade tip life. In the present study, augmented heat transfer of an internal blade tip by pin-fins has been investigated numerically. The computational models consist of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap, and a smooth-tip two-pass channel. The computational domain includes the fluid region and the solid pins as well as the tip regions. Turbulent convective heat transfer between the fluid and pins, and heat conduction within pins and tip are simultaneously computed. The main objective of the present study is to observe the effect of the full and partial pin-fins arrays on heat transfer enhancement of pin-finned tips. Results show that due to the combination of turning impingement and pin-fin crossflow, the maximum heat transfer coefficient of the full and partial pin-finned tip is a factor of 3.0 and 1.8, respectively, higher than that of a smooth tip. Disregarding the increased active heat transfer area, the tip with partial pin-fins array provides around 6% higher heat transfer enhancement than the tip with full pin-fins array. It is suggested that the use of partial pin-fins array is suitable for improving blade tip cooling when the added weight and thereby the increased stress on a blade are considered.