Abstract
Gas turbine blades are cooled internally and externally and one widely used blade cooling technique is film cooling. In this type of cooling, relatively cool air is injected from the inside of the blade to the outside surface which forms a protective layer between the blade surface and hot gas streams. The present study is an attempt to establish the effect of blowing ratio and pressure ratio numerically on film cooling effectiveness in a typical nozzle guide vane with single hole on both pressure and suction surface of the vane. The commercially available CFD code FLUENT has been used after validating it against the experimental results reported in literature. Pressure ratio was varied from 1.1 to 1.2 with density ratio 2.0. Results obtained from the numerical investigation show that with increase in pressure ratio at constant blowing ratio, there was an increase in film cooling effectiveness. It is found that film spread is more on the pressure side as compared to suction side.
Highlights
The gas turbine industry is doing every hard work possible to take the gas turbine engine performance to greater heights
These guide vanes are the prime facie of high temperature high pressure gas coming out of combustion chamber when used for high pressure turbine
The present study investigates the effect of pressure ratio on film cooling effectiveness in a typical nozzle guide vane with single hole on both pressure and suction surface of the vane using CFD
Summary
The gas turbine industry is doing every hard work possible to take the gas turbine engine performance to greater heights. Three blowing rates was investigated by them for a model with three straight holes spaced diameters apart, with density ratio near unity They found that the high free stream turbulence increases the area averaged effectiveness at high blowing rates, but decreases it at low blowing rates. The present study investigates the effect of pressure ratio on film cooling effectiveness in a typical nozzle guide vane with single hole on both pressure and suction surface of the vane using CFD. The model constants C1ε, C2ε, Cμ, σk and σε have the following default values: These default values have been determined from experiments with air and water for fundamental turbulent shear flows including homogeneous shear flows and decaying isotropic grid turbulence They have been found to work fairly well for a wide range of wall-bounded and free shear flows. Discretization of the Geometry In the present work, a portion of the vane was modeled along with entry and exit lengths to make a proper flow domain (Fig. 1)
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