Perforated Flexible Seal Strips for Gas Turbine Leakage Control

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Solution Overview

Problem

Gas turbine engines experience fluid leakage due to pressure variations between axially adjacent zones, with existing seals like brush and leaf seals facing performance deterioration and insufficient flexibility to resist pressure gradients.

Innovation Solution

The introduction of flexible seal strips with perforations that increase circumferential flexibility, allowing for improved durability and reduced leakage across adjacent zones by enhancing the seal's ability to resist pressure differentials and maintain contact with the rotating shaft.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If brush seals are used to reduce leakage, then sealing effectiveness is improved initially, but performance deteriorates over time due to bristle brittleness and insufficient rigidity

Engineering Contradiction:

Improvesealing effectivenessVSAvoidservice life

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent changes the material parameter from bristles to seal strips made of flexible material with specific durometer range (40-80 Shore A), providing both initial sealing effectiveness and long-term durability by resisting brittleness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The seal strips are made of composite flexible material that combines circumferential flexibility with axial rigidity, achieving both durability and resistance to pressure gradients simultaneously

Inventive Principle:

Principle #40Composite materials

2Duration of action of moving object

If leaf seals with solid seal strips are used, then durability is improved, but flexibility in the circumferential direction is insufficient

Engineering Contradiction:

Improveservice lifeVSAvoidcircumferential flexibility

Core Design Contradiction:

Duration of action of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent modifies the physical parameter of the seal strip by introducing perforations, which changes the flexibility characteristics to provide increased circumferential flexibility while maintaining axial rigidity for durability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The seal strips incorporate perforations creating a porous structure that allows circumferential bending and flexing, enhancing adaptability to shaft movement while maintaining structural integrity

Inventive Principle:

Principle #31Porous materials

3Strength

If seal strips with high axial rigidity are used, then resistance to pressure gradients is improved, but circumferential flexibility is reduced

Engineering Contradiction:

Improveresistance to pressure gradientVSAvoidcircumferential flexibility

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies different mechanical properties to different directions: the seal strips have high axial rigidity to resist pressure gradients while having high circumferential flexibility to adapt to shaft movement, achieving directional property differentiation

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The seal strip is segmented into multiple sections by perforations, allowing independent circumferential movement of each segment while maintaining overall axial structural integrity for pressure resistance

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 solution effectively reduces fluid leakage and enhances the durability of the seal by allowing for increased flexibility in the circumferential direction while maintaining axial rigidity, thereby improving the thermodynamic efficiency of the gas turbine engine.

Implementation Method 1

At least one of the seal strips comprises a plurality of perforations extending through the at least one seal strip and located between a leading edge and a trailing edge of the at least one seal strip for effecting an increased flexibility of the at least one seal strip adjacent to the tip portion

Methodology Applied

Scientific EffectFlexibility enhancement through perforations:

Implementation Method 2

a radially inner end comprising a tip portion extending widthwise in the axial direction engaged in sliding contact with a peripheral surface of the rotatable shaft

Methodology Applied

Scientific EffectSliding contact: Friction

Data Source

PatentUS9206904B2Seal including flexible seal strips

Publication Date: 2015.12.08 SIEMENS ENERGY INC

AI summary

A seal member for effecting a seal preventing fluid flow in an axial direction through an annular space formed between two relatively moving components including a rotatable shaft and a stator structure. The seal member includes a plurality of flexible seal strips. Each seal strip includes a planar plate extending radially through the annular space and having a radially outer end supported to the stator structure and a radially inner end defining a tip portion extending widthwise in the axial direction engaged in sliding contact with a peripheral surface of the rotatable shaft. At least one of the seal strips includes a plurality of perforations extending through the seal strip and located between a leading edge and a trailing edge of the seal strip for effecting an increased flexibility of the seal strip adjacent to the tip portion.