THEORETICAL ANALYSIS OF COOLING EFFECT ON THE EFFECTIVENESS OF GAS TURBINE BLADES

Document Type : Original Article

Authors

1 Mechanical Power Engineering Department Faculty of Engineering, Minoufiya University,

2 Mechanical Power Engineering Department Faculty of Engineering, Minoufiya University

Abstract

The modem gas turbine engines operate at high pressure ratio and consequently higher entry
turbine temperatures. At high loads, this temperature exceeds the allowable metal-temperature
limits. The turbine blades need to be protected to ensure theft integrity. The efficient cooling
technique such as film cooling is therefore essential to protect the gas turbine blades. The
efficiency of this technique depends on several parameters, such as the injection blowing ratio,
density ratio, mainstream turbulence intensity, mainstream pressure gradient, boundary layer
thickness, injection angle, spacing between holes as well as their arrangement, and the blade
geometry. The main objective of this study was to make a numerical study on the first stage for
both profiles VKI and C3X turbine blades cascade with a leading edge showerhead film-cooling
arrangement by using the commercial code Fluent v. 5.4. The governing equations for steady, t~vo
dimensional, turbulent, compressible flow are integrated over arbitrary two-dimensional control
volumes with the aid of Gauss theorem. The present computational model seeks to a realistic film￾cooled turbine blade. The code is used to study the combination of film and convection cooling.
While most ofthe theoretical studies considered isothermal blade surfaces in thermal calculations
over the blade surfaces. The results indicated that the film cooling enhances adiabatic effectiveness
and decreases the surface heat flux by six times that of uncooling blade. In case of increasing the
blowing ratios or streamwise injection angle, the adiabatic effectiveness decreases gradually. The
effectiveness for combined cooling is higher than that of film cooling only due to the combination
offilm and convection cooling together. Also the film cooling effectiveness for the VKI profile is
higher than that ofthe C3X profile as a result ofthe better design shape of VKI profile. The model
had been validated and tested with previously published experimental and theoretical results.
These comparisons show a satisfactory agreement that permits an extension of the theoretical
study.

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