Analysis of the Temperature Distribution in GT Blade Cooled by Compressed Air

As the gas turbine inlet temperature increases, the heat transferred to the turbine blade also increases. The operating temperatures are far above the permissible metal temperatures. Therefore, there is a critical need to cool the blades for safe operation. In the present work the internal cooling of a gas turbine blade is analyzed. The blade has a rectangular 9mm18mm compressed air channel along the blade span. Finite-Difference method is used to predict temperature distribution for blade cross section at different heights from the root. Effect of compressed air mass flow rate, inlet temperature and the temperature of combustion gasses have been considered. The investigations are carried out for both smooth and two opposite ribbed-walls channels. The results are presented and discussed as temperature distribution in various sections of the blade, and also the comparison between ribbed and smooth channel hydrothermal values. Various ribs configurations have been considered in the analysis. Results at rib angles, α of 90°, 60°, 45° and 30° and ribs blockage ratios, e/Dh ranging from 0.042 to 0.078 are compared in terms of Nu and friction factor, f. It is found that maximum Nu number occurs when 60° ribs are introduced in the channel. An enhancement of 149.45% is achieved with penalty of increase in the friction factor by 114.5%.

Keywords: Gas turbine blade, heat transfer enhancement, numerical analysis, ribbed channel, blade cooling.