Angel Wing Abradable Seal for Turbine Clearance Control

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Solution Overview

Problem

The efficiency of rotary machines like steam and gas turbines is compromised due to varying radial clearance between rotor blades and stationary nozzles, leading to excessive cooling air leakage and potential damage from metal-to-metal rubbing, as centrifugal forces and thermal growth cause clearance changes.

Innovation Solution

An abradable seal material is applied to the surface of either the flange portion or seal plate member at the interface between the rotor bucket and stationary nozzle, reducing the radial clearance and preventing direct contact that could cause damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the clearance between the rotor bucket shank and stationary seal structure is increased to prevent metal-to-metal rubbing, then reliability is improved, but cooling air leakage increases and efficiency decreases

Engineering Contradiction:

Improveprevention of metal-to-metal rubbingVSAvoidcooling air leakage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

An abradable seal material is introduced as an intermediary element between the rotor bucket shank and the stationary seal structure. This material allows controlled wear to accommodate clearance variations while maintaining an effective seal, preventing both metal-to-metal contact and excessive cooling air leakage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The seal design incorporates an abradable material that changes its dimensional parameters through controlled wear. As the material wears, it adjusts the clearance dynamically, maintaining optimal sealing performance across varying operating conditions without causing energy loss.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the clearance between the rotor bucket shank and stationary seal structure is decreased to improve efficiency, then cooling air leakage is reduced, but metal-to-metal rubbing and damage increase

Engineering Contradiction:

Improvecooling air leakageVSAvoiddamage from metal-to-metal rubbing

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The abradable seal material serves as a protective intermediary that prevents direct metal-to-metal contact between the rotor bucket and stationary seal. This allows the clearance to be minimized for efficiency while the abradable material absorbs the mechanical stress and wear.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The abradable material is applied in advance to the seal surface, creating a cushioning layer that prevents damage before metal-to-metal rubbing can occur. This protective layer wears away controllably, maintaining the optimal small clearance for efficiency while preventing reliability issues.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If the seal clearance is reduced to improve turbine efficiency, then cooling air leakage decreases, but the seal components are more susceptible to wear and damage during acceleration and deceleration

Engineering Contradiction:

Improveturbine efficiencyVSAvoidseal component lifespan

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The abradable seal material acts as a sacrificial intermediary that protects the main seal components from wear during acceleration and deceleration phases. This allows the clearance to be optimized for efficiency while the abradable material absorbs the impact of dynamic clearance changes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The abradable seal material is designed as a consumable component that can be replaced when worn. This approach allows the use of thin, efficient sealing structures that would otherwise be too fragile, while the abradable layer provides the necessary durability and can be replenished through maintenance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 abradable seal material effectively reduces leakage by tightening the clearance between the rotor and stationary components, minimizing wear and improving turbine efficiency by up to 15-20% while extending the lifespan of seal components.

Implementation Method 1

an abradable seal material is provided on a surface of one of the facing seal components that define a seal gap between a nozzle inner shroud and the shank of an adjacent rotating bucket

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentUS7500824B2Angel wing abradable seal and sealing method

Publication Date: 2009.03.10 GE INFRASTRUCTURE TECH LLC

AI summary

An abradable seal is provided to improve turbine performance by physically reducing the clearance between a flange portion of the nozzle and an opposed angel wing/seal plate member of the bucket. The provision of an abradable seal also mitigates angel wing/seal plate tooth or fin wear by providing for abradable contact without metal to metal hard rub.