Partial Collar Design Mitigates Turbine Exhaust Strut Cracking

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Solution Overview

Problem

Gas turbine engine exhaust apparatus struts frequently experience cracking due to high thermal gradients, poor weld quality, and vibrations, particularly at weld joints, leading to costly and time-consuming field repairs with potential re-cracking issues.

Innovation Solution

The implementation of a partial collar design at the strut shield interfaces, featuring a first section aligned with the strut shield and a second section aligned with the duct-wall, forming a smooth curve intersection to distribute stresses and reduce weld material proportion, thereby mitigating cracking risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional weld joints are used to attach strut shields to duct-walls, then the structure is simple and easy to manufacture, but cracking occurs frequently due to high thermal gradients and poor weld quality

Engineering Contradiction:

Improvecrack resistanceVSAvoidjoint structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The collar is divided into multiple sections (first section, second section, third section) that can be independently manufactured and then assembled. This segmentation allows each section to be optimized for its specific function while reducing the complexity of manufacturing the entire collar as a single piece, thereby improving reliability without significantly increasing overall device complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The collar acts as an intermediary component between the strut shield and the duct-wall. It distributes thermal and mechanical stresses across multiple attachment points rather than relying on a single weld joint, thereby preventing cracking while adding only moderate structural complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If full perimeter collars are used to attach strut shields, then stress distribution is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvestress distributionVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of providing a collar along the full perimeter of the strut shield, the invention uses partial collars at specific locations (leading edge and/or trailing edge). This partial action is sufficient to achieve the primary objective of stress distribution and crack prevention, while significantly reducing manufacturing complexity and cost compared to full perimeter collars.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The collar is applied locally at the most critical stress points (leading and/or trailing edges of the strut shield) rather than uniformly across the entire perimeter. This local quality approach concentrates the stress-distributing function where it is most needed, improving reliability without the manufacturing burden of full perimeter coverage.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If complex multi-section collars are manufactured as single pieces, then manufacturing precision is improved, but manufacturing time and cost increase

Engineering Contradiction:

Improvecollar geometry precisionVSAvoidmanufacturing efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The collar is segmented into multiple sections that can be manufactured separately using standard manufacturing processes, then assembled together. This segmentation improves productivity by allowing parallel manufacturing and reducing the complexity of single-piece production, while maintaining manufacturing precision through standardized interface designs and fitment requirements.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The partial collar design effectively redistributes stresses, reduces the risk of distortion and weld mismatch, and enhances the equivalent strength of the flowpath cross-section, addressing cracking issues while allowing for easier on-site installation and potentially reducing re-cracking.

Implementation Method 1

An intersection of the first and second sections is formed by a smooth curve defined by a radius configured to distribute stresses at the respective interface

Methodology Applied

Scientific EffectStress distribution:

Data Source

PatentEP3797211B1Turbine exhaust crack mitigation using partial collars

Publication Date: 2023.10.18 SIEMENS ENERGY GLOBAL GMBH & CO KG

Figure 1~2
Figure 3~6
Figure 4

AI summary

An exhaust apparatus (10) for a gas turbine (1) includes an annular duct (12) with a plurality of struts (18) extending at least from an outer duct-wall (14) to an inner duct-wall (16) of the annular duct (12). Each strut (18) is encapsulated in a respective strut shield (20). An interface (22, 24) of the strut shield (20) with a respective duct-wall (14, 16) includes at least one collar (26) extending along a partial length of the perimeter of the strut shield (20) at the respective interface (22, 24). The collar (26) includes a first section (32) extending radially and being aligned with the strut shield (26), and a second section (34) oriented at an angle to the first section (32) and being aligned with the respective duct-wall (14, 16). The first section (32) is attached to the strut shield (20) along a first joint (42) and the second section (34) is attached to the respective duct-wall (14, 16) along a second joint (44). An intersection (40) of the first and second sections (32, 34) is formed by a smooth curve defined by a radius configured to distribute stresses at the respective interface (22, 24).