Heat transfer augmentation and cooling of a turbine blade using an innovative converging-diverging ducts - A CFD study

Gas turbines are used in power plants to supply peak loads in hydro-plants and they are also used in jet, aircraft and ships for propulsion. Turbine blades extract energy from high temperature and pressure of combustion gases. In order to endure this extreme condition of temperature, gas turbine blades are often cooled internally. This ensures that the entry temperature of the combustion gases could be increased which in turn increases the thermal efficiency of a gas turbine blade and the turbine could work for a reasonable lifetime. With this desire to increase entry temperature, converging-diverging (CD) ducts are incorporated in the leading edge region as cooling passages for analysis. The CD ducts are used so that fluid passes through several fluid passages which increase its velocity and ultimately provides enhanced cooling of the turbine blades. From the analysis, it is observed that ducts with minor diameter of 7mm, major diameter of 8.5mm, and pitch of 5mm result in better cooling of turbine blades and lead to optimum thermal performance. Moreover, this study also reveals that incorporating turbulators has a significant impact on cooling of turbine blades. Turbulator arrangement with relative roughness (p/e) ratio of 2 for pitch length (ph) of 5mm gives enhanced cooling and it reduces blade wall temperature by 17%.