Computational Analysis of Pin-Fin Arrays Effects on Internal Heat Transfer Enhancement of a Blade Tip Wall

Abstract

Cooling methods are strongly needed for the turbine blade tips to ensure a long durability and safe operation. Improving the internal convective cooling is therefore required to increase the blade tip life. A common way to cool the tip is to use serpentine passages with 180-deg turns under the blade tip cap. In this paper, enhanced heat transfer of a blade tip cap has been investigated numerically. The computational models consist of a two-pass channel with a 180-deg turn and various arrays of pin fins mounted on the tip cap, and a smooth two-pass channel. The inlet Reynolds number is ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible, and nonrotating. Details of the 3D fluid flow and heat transfer over the tip walls are presented. The effects of pin-fin height, diameter, and pitches on the heat transfer enhancement on the blade tip walls are observed. The overall performances of ten models are compared and evaluated. It is found that due to the combination of turning, impingement, and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of 2.67 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 30%. Results show that the intensity of heat transfer enhancement depends upon pin-fin configuration and arrangement. It is suggested that pin fins could be used to enhance the blade tip heat transfer and cooling.

Heat Transfer Research in Sweden: Historical and Current Activities

“…The most recent work on tip cooling of gas turbine blades have received good recognition [41][42][43].…”

Numerical predictions of augmented heat transfer of an internal blade tip-wall by hemispherical dimples

“…Therefore, the agreement between the calculated Nusselt number and experimental data is the main criterion for selecting a turbulence model. In previous works, several turbulence models have been evaluated to simulate the turbulent heat transfer of a smooth-tip two-pass channel [29][30][31]. Based on those evaluations, the Realizable k À e turbulence model is selected for the computations in this work.…”

“…Even though similar works of the heat transfer augmentation in two-pass channels with shaped pin-finned tips can be found in the experimental work by Bunker [28] and the numerical simulations by the authors [29][30][31][32], no available details of the heat transfer and flow field on dimpled tips are available. Furthermore, most previous studies were concerned about the heat transfer on the leading or/and trailing walls of two-pass channels, and very limited information is available for tip-walls.…”

Review of Heat Transfer Augmentation for Cooling of Turbine Blade Tip by Geometrical Modifications to the Surfaces of Blade

“…The use of ribs in the internal passages of the turbine blades, the provision of arrays of pins on the turbine blade tip and the provision of dimples to the internal tip cap of the turbine blades has shown a significant increase in the heat transfer of turbine blades as far as the computations and experimental results are considered. Yet another attempt was made by Gongnan Xie et al [3] to numerically simulate the serpentine passages of turbine blade to evaluate the heat transfer but this time considering the provision of pin fins to the internal tip cap of the turbine blades. The averaged heat transfer is similar to that determined by Bunker experimentally.…”

“…It was found that the heat transfer was doubled compared to smooth tip by provision of dimples on the surface of internal tip cap of the turbine blades. In yet another analysis Gongnan Xie [3] carried out numerical simulations for six different arrangements of the guide rib/vanes in a two pass serpentine passage. The guide ribs/vanes were placed at different locations inside the passage and their effect on the heat transfer coefficient was examined numerically using computational fluid dynamics technique.…”