CFD Based Study of Gas Turbine Blade Cooling

Abstract

Over the years, many techniques have been employed to improve the aerothermal efficiency of gas turbines. The hot gases inlet temperature greatly affects the work output and therefore, efficiency of the turbine. To overcome the metallurgical constraints associated with maximum blade temperature, different methods have been devised to keep it under the permissible levels. The current thesis explores convective cooling of the blades by the means of internal passages. Other methods like ceramic blades have their own limitations in terms of brittle failure, and thermal barrier coatings are almost always used in conjunction with convective cooling. Conjugate heat transfer (CHT) simulations have been performed on a 65 mm gas turbine blade section with cooling cavity, using ANSYS CFX 2019 FVM solver. Cooling performance and pressure loss characteristics of the cavity have been analysed by increasing number of protrusions on the cavity walls from 0 to 88. The results and plots suggest that an increase in the coolant advection causes a reduction in blade maximum temperature, but the temperature reduction obtained with successive velocity increments follows a diminishing trend. However, the pressure loss associated with the coolant flow follows an increasing trend with increasing slope. Increment in the number of protrusions results in a similar trend, with successive addition of protrusions resulting in greater rise in coolant pressure loss.