Analysis of the Effect of Blade Cooling on Gas-Turbine Performance

Abstract

This paper is an analytical study of the effects on specific air consumption and thermal efficiency of three types of blade-cooling systems. The methods considered are: (a) Air forced-convection cooling; (b) air transpiration cooling; (c) liquid forced-convection cooling. The analysis was applied to a simple gas-turbine power plant containing a cooled turbine and an uncooled turbine both of which were composed of an infinite number of infinitesimal stages. Certain general design parameters were chosen for each coolant system and the effect of variation of these parameters on power-plant performance was studied. The three cooling methods also were compared against one another for otherwise identical conditions in the basic power plant. The results of this work make it possible to predict, in a semiquantitative manner, the effect of cooling-system design on power-plant performance. In particular, the results of this paper show that for well-designed cooling systems operating at design conditions, appreciable net gains in performance can be realized by increasing turbine-inlet temperature beyond the temperature which the uncooled blades can withstand.