Computational Analysis of Gas Turbine Blade Cooling System

Cooling of gas turbine blades is a major consideration because they are subjected to high temperature, working conditions. Several methods have been suggested for the cooling of blades and one such technique is to have radial holes to pass high velocity cooling air along the blade span. The forced convection heat transfer from the blade to the cooling air will reduce the temperature of the blade to allowable limits. Finite element analysis is used in the present work to examine steady state thermal & structural performance for N155 Inconnel 718 nickel-chromium alloys. Four different models consisting of solid blade and blades with varying number of holes (5, 9 & 13 holes) were analyzed in this paper to find out the optimum number of cooling holes.

The analysis is carried out using ANSYS software package.  While comparing these materials, it is found that Inconnel 718 is better suited for high temperature applications. On evaluating the graphs drawn for temperature distribution, von-mises stresses and deflection, the blade with 13 holes is considered as optimum. This conclusion was drawn based on the fact that the induced stresses are minimum and the temperature of the blade is close to the required value of 800 C. Any further increase in the number of holes will bring down the temperature below the required value of 8000 C.