L-Butt Gap Seal for Rotary Machine Leakage

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Solution Overview

Problem

Rotary machines face challenges in maintaining effective seals between components due to varying thermal expansion rates during startup, shutdown, or transient operations, leading to leakage issues that affect performance and efficiency.

Innovation Solution

A seal assembly featuring an array of arcuate segments with 'L' shaped seals disposed at butt gaps, where the 'L' seals have complementary surfaces and configurations to minimize leakage, including radial slots and teeth that align and expand with the segments, ensuring proper contact and sealing across the full operating range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If arcuate segments are used to form a seal between components, then the seal assembly can accommodate thermal expansion and contraction, but leakage occurs at the butt joints between segments during transient operations

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidsealing effectiveness

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The seal assembly is divided into multiple arcuate segments that can independently expand and contract with thermal changes. Each segment is separated into discrete units rather than a continuous ring, allowing differential movement at the butt joints while maintaining overall sealing function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An elastomeric material is introduced as an intermediary substance at the butt joints between arcuate segments. This elastomeric material fills the gaps and maintains sealing contact despite relative movement between segments during thermal expansion and contraction, preventing leakage while accommodating dimensional changes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If tight clearances are created between sealing faces to achieve sealing, then leakage is minimized, but the seal assembly becomes sensitive to thermal expansion variations

Engineering Contradiction:

Improvesealing effectivenessVSAvoidthermal expansion tolerance

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The clearance parameters between sealing faces are designed to vary with thermal conditions. The elastomeric material at the butt joints allows the effective sealing clearance to dynamically adjust as components expand and contract, maintaining optimal sealing gaps across different temperature conditions rather than being fixed.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The seal assembly combines rigid arcuate segments with a flexible elastomeric material at the joints. This composite structure allows the rigid segments to maintain precise sealing faces while the elastomeric portion accommodates thermal dimensional changes, combining the advantages of both material types.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If a single seal design is used for all butt joints, then the device complexity is reduced, but leakage cannot be minimized at both the radially outermost surface and the downstream face

Engineering Contradiction:

Improveseal configurationVSAvoidleakage prevention

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The seal assembly employs different sealing configurations at different locations. The elastomeric material is strategically placed at the butt joints where leakage paths exist, providing enhanced sealing precisely where needed rather than uniformly across all surfaces. This localized approach addresses specific leakage paths without unnecessarily complicating the entire seal design.

Inventive Principle:

Principle #3Local quality

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 seal assembly significantly reduces leakage and enhances sealing capabilities, improving the overall efficiency and performance of rotary machines by maintaining alignment and contact across varying thermal expansion conditions.

Implementation Method 1

During the operation of the rotary machine, and more particularly during startup, shutdown or transient operations, components experience different thermal expansion rates, which in turn governs the spacing between the arcuate segments as the components expand and contract.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS7631879B2"L" butt gap seal between segments in seal assemblies

Publication Date: 2009.12.15 GE INFRASTRUCTURE TECH LLC

AI summary

Disclosed herein is a seal assembly for a rotary machine having a plurality of arcuate segments and at least one seal. The plurality of arcuate segments are arrayed in an annulus and have butt joints, each of the arcuate segments has a radially outermost surface and a downstream face. The at least one seal is arranged to minimize leakage through the butt joints. The at least one seal has a first portion configured to minimize leakage at the radially outermost surface and a second portion configured to minimize leakage at the downstream face.