Compound Variable Elliptical Airfoil Fillet for Gas Turbine Stress Reduction

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Solution Overview

Problem

Gas turbine blades and vanes experience high operating stresses due to thermal and mechanical loads, particularly at the transition regions between airfoil and platform surfaces, where sharp geometry changes concentrate stress.

Innovation Solution

A compound fillet with two conic surfaces is introduced at the airfoil-platform intersection, providing a smooth transition to reduce stresses. The fillet's conic surfaces are designed to vary in size and shape to manage stress levels, with a method that calculates and adjusts parameters to ensure acceptable stress levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a sharp geometry transition is used between airfoil and platform, then manufacturing is simpler, but stress concentration increases

Engineering Contradiction:

Improveease of manufactureVSAvoidstress concentration

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The patent applies curvature by replacing the sharp geometry transition with a compound fillet featuring concave and convex curved surfaces. This curved transition zone eliminates stress concentration while maintaining manufacturability through standard fillet formation processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent changes the geometric parameters at the airfoil-platform junction by introducing a compound fillet with specific concave and convex curvature radii. This parameter modification optimizes stress distribution while accommodating manufacturing constraints.

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If a compound fillet with varying conic surfaces is used, then stress distribution improves, but manufacturing complexity increases

Engineering Contradiction:

Improvestress distributionVSAvoidfillet geometry complexity

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent segments the fillet geometry into distinct concave and convex conic surfaces with different curvature characteristics. This segmentation allows each surface to be optimized for stress distribution while maintaining overall manufacturability through systematic design.

Inventive Principle:

Principle #1Segmentation

3Reliability

If stress levels are reduced through fillet design, then component reliability improves, but design and manufacturing time increases

Engineering Contradiction:

Improvecomponent reliabilityVSAvoiddesign and manufacturing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent employs systematic parameter variation in the fillet design, optimizing curvature radii and conic surface parameters to achieve stress reduction. This parameter-based approach balances reliability improvement with reasonable design and manufacturing time by providing a systematic design methodology.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8206095B2Compound variable elliptical airfoil fillet

Publication Date: 2012.06.26 ANSALDO ENERGIA SWITZERLAND AG

AI summary

A gas turbine engine blade or vane having a first platform, an airfoil, and a compound fillet extending about a region where the airfoil joins the first platform is disclosed. The compound fillet has a first conic surface and a second conic surface, with the first conic surface tangent to the airfoil and to an offset platform surface and the second conic surface tangent to the first conic surface and the first platform. The two conic surfaces are of different sizes, with different radii, and the conic surfaces can vary in size about the periphery of the joint between the airfoil and the first platform.