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SHAPED FILM COOLING HOLE WITH CURVED PROFILE AND CONTROLLED INTERNAL SURFACE AUGMENTATION.

IP.com Disclosure Number: IPCOM000247527D
Publication Date: 2016-Sep-14
Document File: 3 page(s) / 234K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention relates to a the definition of a particular film cooling hole geometry for gas turbine airfoil and in general for accurately protect a surface exposed to hot gas by injecting coolant that cover it in an efficient way. It is commonly know that film cooling is a crucial technique for assuring an adequate protection to gas turbine components exposed to the highest temperature in gas turbine engines. Coolant (generally air, at a lower temperature than the one outside the component) is conventionally inject through cylindrical holes, due to their manufacturing simplicity, or through holes with a more complex geometry, called "shaped holes". Shaped holes present an enlarged outlet surface and a positive inclination in fluid direction, in order to augment the coolant coverage and to maintain it as much attached as possible to the surface; these improvements from cylindrical geometry allow to increase film cooling performances, reducing the detrimental effect caused by hot gas and coolant mixing. Surface increment in the diffusive zone of shaped holes can negatively affect the performance by slowing down too much the coolant and by consequence decreasing the blowing ratio; furthermore, sudden area variation in the transition from the cylindrical to the diffusive zone can increase hole's pressure losses. This invention relates to a film cooling shaped hole that has a curved profile, reducing pressure losses, and a controlled surface variation, increasing its performances. The goal of the invention is to produce a shaped film cooling hole with great coverage and low mass consumption.

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SHAPED FILM COOLING HOLE WITH CURVED PROFILE AND CONTROLLED INTERNAL SURFACE AUGMENTATION. 

BACKGROUND

This invention relates to a the definition of a particular film cooling hole geometry for gas turbine airfoil and in general for accurately protect a surface exposed to hot gas by injecting coolant that cover it in an efficient way.

It is commonly know that film cooling is a crucial technique for assuring an adequate protection to gas turbine components exposed to the highest temperature in gas turbine  engines. Coolant (generally air, at a lower temperature than the one outside the component) is conventionally inject through cylindrical holes, due to their manufacturing simplicity, or through holes with a more complex geometry, called “shaped holes”. Shaped holes present an enlarged outlet surface and a positive inclination in fluid direction, in order to augment the coolant coverage and to maintain it as much attached as possible to the surface; these improvements from cylindrical geometry allow to increase film cooling performances, reducing the detrimental effect caused by hot gas and coolant mixing.

Surface increment in the diffusive zone of shaped holes can negatively affect the performance by slowing down too much the coolant and by consequence decreasing the blowing ratio; furthermore, sudden area variation in the transition from the cylindrical to the diffusive zone can increase hole’s pressure losses. This invention relates to a film cooling shaped hole that has a curved profile, reducing pressure losses, and a controlled surface variation, increasing its performances. The goal of the invention is to produce a shaped film cooling hole with great coverage and low mass consumption.

BRIEF DESCRIPTION

This invention relates to a film cooling hole geometry based on shaped hole characteristics, like the trapezoidal outlet section and the cylindrical inlet. In this invention, transition from inlet to outlet is not sudden, but smooth, thanks to geometrical CAD functions like loft. The diffuser part of the hole is generated in a way that the surface augmentation is partly compensated by a narrowing in the thickness direction, avoiding an excessive reduction of coolant velocity.

Innovation of this idea is to realize a particular geometry that can reduce pressure losses and increase performance, with a non-conventional shaping. The complexity of the geometry and the direct use of CAD functions makes it ideal for the production with additive manufacturing techniques, like DLMS (Direct Metal Laser Sintering).

The proposed invention is characterized by some parameter that identify the geometry: two different angles defining the inclination of the inlet and the outlet, the position of the mid-plane on which is defined the end of the quasi-cylindrical part, nominal diameter and trapezoid dimensions.

DETAILED DESCRIPTION

This invention relates to...