NUMERICAL SIMULATION OF GAS TURBINE BLADE COOLING FOR ENHANCEMENT OF HEAT TRANSFER OF THE BLADE TIP

Sushil Sunil Gaikwad, C. R. Sonawane

Abstract: In today’s industrial scenario, Gas Turbine is one of the most important components of auxiliary power plant system. In order maximize the overall performance and efficiency of all modern turbines, which theoretically operate according to Brayton cycle, they are operated at a very high temperature. These temperatures are so high that, which may fall in the region of turbine blade material melting point temperatures. Due to such high temperatures there is a possibility that the turbine blades may get damaged due to produced thermal stresses and presents a possible threat to the turbine system as well as the operators. Hence to ensure safe and reliable working of the turbines an effective and reliable cooling system is necessary. Currently available methods for cooling of the turbine blades include film cooling with impingement cooling for the leading edge, rib turbulated cooling using serpentine passages for the middle portion of the blade and pin fin cooling for the trailing edge of the turbine blades. The cooling mechanism for turbine blades must include cooling for all possible regions which are exposed to hot gas flow. The turbine blade tip is one of the critical regions which are severely exposed to hot gas flow occurring due to the leakage of gases from the clearance gap between the turbine tip and the shroud. Hence the tip of the turbine blade must be cooled effectively to prevent thermal expansion of the turbine blade tip due to heating. This cooling will eventually help to avoid rubbing of blades to the shroud which may cause their wear. In this paper the effect of provision of pins of two different diameters and heights over the turbine blade tip at the corners, on the heat transfer has been investigated. The results obtained were compared with the heat transfer of smooth tip two pass channels. Investigations were carried out at different Reynolds numbers ranging from 200000 to 450000. It was found that if pins are provided at the corners the local heating of the tip at corners is avoided. A heat transfer augmentation of about 1.3 times was observed as compared to a smooth surface with pressure drop of less than 6 %. Hence the proper arrangement and number of pin fins is recommended for augmentation of heat transfer over the turbine blade tip.

Keywords: Turbine Tip Cooling, Turbulence, numerical simulation, hotspots.

DOI: https://doi.org/10.15623/ijret.2014.0309006