Gas turbine vane attachment

Abstract

Base hooks of a vane includes an approximate two times thicker radial geometry, with dimensioning and tolerancing that results in a line-line to loose fit on the forward OD hook surface and the aft ID hook surface. Tolerances thus stack up on the opposite, non-critical surfaces of the hooks (the forward ID hook surface and the aft OD hook surface). The base of the vane is curved to match that of the casing. An interface between the vane base and the casing groove includes a metal alloy liner. Also, a wear coating is provided on the vane attachment hooks. The liner protects the casing groove from wear damage, while the hook coating and the liner provide a wear coupling between the vane base and the casing that provides a barrier between the vane bases and the casing to decrease the wear rate.

Description

BACKGROUND OF THE INVENTION[0001]The subject matter disclosed herein relates to gas turbine engines and, more particularly, to the attachment of vanes within a casing of a compressor of a gas turbine engine.[0002]Stator vanes located in the back-end stages of a compressor are typically configured as singlets (one airfoil per attachment), and have a square base that includes an attachment hook on the forward and aft sides of the base. The hooks are commonly constructed with a straight geometry such that when they are slid into the radial compressor casing grooves, the resulting reaction load distribution is concentrated at discrete (determinable) point locations or contact zones. This is due in part to the fact that the base of a vane is planar while the casing grooves are curved to some extent. During operation at load, the stators are subject to an unsteady aerodynamic vibratory environment that causes vibration motion to be transmitted to the constraint points in the base hooks. I...

AI Technical Summary

Benefits of technology

[0006]According to another aspect of the invention, a material interface is provided between the vane base and the casing groove. The material interface includes a metal alloy liner that interfaces between the base of the vane and the associated casing in which the vane is disposed. Also, a wear coating is provided on the vane attachment hooks. The liner protects the casing groove from wear damage, while the combination of the hook coating and the liner provide a wear coupling between the base of the vane and the casing. The wear coupling provides a barrier between the vane bases and the casing to decrease the wear rate.

Problems solved by technology

During operation at load, the stators are subject to an unsteady aerodynamic vibratory environment that causes vibration motion to be transmitted to the constraint points in the base hooks.

In addition, the responsive mode of vibration can result in a concentration of vibratory stress near these same attachment points.

These hook attachment points experience fretting related damage, including fretting wear and fretting fatigue, which significantly shortens the design life of the vane.

If the stator hook damage becomes excessive before repair, the stator airfoils can clash into the rotating stages in front of the stators, resulting in catastrophic damage to the flowpath components.

However, while this solution may provide extended operation capability, it does not address the root cause of the problem.

Another stopgap measure is to attach adjacent vanes together in packs through welding or bolting, which again does not address the root cause of the problem.

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