Gas Turbine Cooled Vane Stiffening Element
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Solution Overview
Problem
Cooled gas turbine blades experience mechanical stress concentrations at the edges of feed bore openings, which can reduce blade life and do not effectively improve vibration behavior.
Innovation Solution
A planar or essentially planar stiffening element extending beyond the immediate vicinity of the feed bore is integrated on the blade shank, connecting to the underside of a platform with rounded corners, and designed to enclose the feed bore, reducing local stress and enhancing vibration behavior by increasing the natural frequency of the first flap vibration mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a bead is provided around the opening of the feed bore to reduce stress peaks, then blade service life is improved, but vibration behavior is not effectively improved
Solution Approach 1:
The stiffening element extends in the longitudinal direction of the blade over the entire length of the shank, transitioning from a localized circular bead to an extended planar structure that spans the shank length. This dimensional extension allows the element to simultaneously address local stress concentrations at the feed bore opening and global vibration characteristics of the blade, resolving the contradiction between service life improvement and vibration behavior.
Solution Approach 2:
The stiffening element serves multiple functions: it reduces stress peaks at the feed bore opening to extend blade service life, and simultaneously improves vibration behavior by increasing the natural frequency of the first flap vibration mode. This multi-functionality resolves the contradiction by making a single structural modification that addresses both previously separate concerns.
2Reliability
If the overall thickness of the blade shank is increased to improve vibration behavior, then natural frequency increases, but blade mass increases
Solution Approach 1:
Instead of uniformly increasing the overall thickness of the blade shank, the invention introduces a localized stiffening element with a specific geometric configuration (planar or essentially planar with rounded corners) that provides targeted reinforcement. This local quality approach increases the natural frequency and improves vibration behavior without the penalty of uniformly increasing blade mass throughout the entire shank.
3Strength
If a stiffening element is provided around the feed bore opening, then stress peaks are reduced, but manufacturing complexity increases
Solution Approach 1:
The stiffening element is integrally formed with the blade shank as a single piece, merging the reinforcement feature into the base structure. This integration eliminates the need for separate manufacturing steps to attach a discrete stiffening component, thereby reducing manufacturing complexity while still providing the stress peak reduction benefit.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a vane (10) for a gas turbine comprises a vane blade (11) that extends in a vane longitudinal direction (19), said vane transitioning at the lower end to a shaft (13) that ends in a vane base (14) for fastening of the vane (10) to a vane support, in particular a rotor disc, wherein devices for cooling the vane (10) are disposed inside the vane blade (11), said devices being fed with a cooling medium, in particular cooling air, through a feed hole (17) located on the side of the shaft (13), and wherein means (18) for reducing spikes in mechanical stress are provided in the area of the feed hole (17). In such vanes, an improved vibration behavior is achieved at the same time in that the means for reducing spikes in the mechanical stress comprise a flat stiffening element (18) that reaches out beyond the direct surroundings of the feed hole (17).