Heat Transfer Analysis of Turbine Blade Cooling using Ribbed Passages through CFD Simulations

Abstract

Gas turbines convert from Thermal energy into Mechanical energy. It is a type of internal combustion engine, generally used in ships, power aircraft, trains, generators, and tanks. The equipment consists of an upstream compressor coupled with a turbine at the rear end, with a combustor in between. Atmospheric air flowing into the compressor is brought at a higher pressure. The addition of Heat energy to the high-pressure air by spraying it with fuel in the combustor section, thus igniting it and producing a high-temperature flow. The thermal efficiency of the gas turbine is directly proportional to the turbine inlet temperature. Today the combustion and turbine technology has improved to such an extent that the operating temperature at the turbine inlet is higher than the melting temperature of the turbine material. Different techniques are used to cope with this problem. One of the most commonly used methods is internal cooling of turbine blades. Conventionally air from the compressor is used for this purpose but due to higher heat capacity, steam can be used as coolant. This increases the possibility to increase the gas temperature. In case of a combined cycle power plant, the availability of steam provides a good opportunity to be used as coolant. This thesis presents computational fluid dynamics based numerical work concentrated on the flow and heat transfer on two pass rectangular channels with and without rib tabulators. The effect of variation in the Aspect ratio was studied for these channels. Their effect on heat transfer was studied for smooth as well as ribbed channels. The result show that for a smooth channel the reduction in width of the inlet pass does not affect the heat transfer enhancement at the inlet and outlet pass regions. In case of ribbed channels, heat transfer decreases at the tip and bend bottom with decrease in width of the inlet pass.