Notched Abradable Blade Tip Coating for Turbomachine Gap Control

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Solution Overview

Problem

Existing turbomachinery systems face challenges in maintaining minimal radial gaps between rotor blades and the housing to prevent steam leakage and droplet impact erosion, with conventional abrasive coatings failing under high mechanical forces.

Innovation Solution

A blade tip with a designed abrasive rubbing layer featuring notches and a porous structure made of graphite or hexagonal boron nitride, which wears away upon contact with the housing to optimize gap size and minimize damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional abrasive coatings are applied to the housing to minimize radial gaps, then gap losses are reduced, but the coatings fail under high mechanical forces from droplet impact erosion

Engineering Contradiction:

Improveradial gap lossesVSAvoidcoating durability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

Instead of applying the abrasive coating to the stationary housing (conventional approach), the invention applies the abradable coating to the rotating blade tip. This inversion allows the housing to remain hard and erosion-resistant while the blade tip provides the necessary abrasion capability, solving both the gap loss and durability problems simultaneously.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The blade tip coating is designed as a composite structure combining a metallic substrate with an abradable coating layer (such as bronze or aluminum-based materials). This composite approach provides both the mechanical strength needed to withstand centrifugal forces and the softness required for controlled abrasion against the housing.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If the radial gap is made smaller to reduce losses, then energy efficiency improves, but the risk of blade tip contact and damage increases

Engineering Contradiction:

Improveradial gap lossesVSAvoidblade tip damage risk

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The invention converts the potentially harmful blade tip contact into a beneficial process by designing the coating to wear away controllably during contact. The friction and impact that would normally cause damage instead serve to maintain the optimal radial gap through controlled material removal from the blade tip coating.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The abradable coating on the blade tip is designed as a consumable layer that gradually wears away during operation. This disposable coating layer protects the expensive blade substrate while maintaining the radial gap, sacrificing a relatively inexpensive material to prevent damage to critical components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Loss of energy

If a rubbing layer is applied to the blade tip to minimize radial play, then gap losses are reduced, but the rubbing layer may generate excessive debris under high mechanical forces

Engineering Contradiction:

Improveradial gap lossesVSAvoiddebris formation

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The abradable coating is applied selectively only to the blade tip region where contact with the housing occurs, rather than coating the entire blade. This localized application ensures that debris generation is confined to a small area and does not affect the overall blade performance or generate excessive debris in the turbine flow path.

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 solution effectively reduces radial gap losses and prevents damage by controlled material removal, adapting to variations in blade length and housing ovality while ensuring small debris formation.

Implementation Method 1

the rubbing layer is designed such that during operation, upon contact with the housing inner wall, the rubbing layer is worn away

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

a blade tip with a designed abrasive rubbing layer featuring notches and a porous structure

Methodology Applied

Scientific EffectPorosity: Porosity

Data Source

PatentEP4388180B1Blade for turbomachine and method for producing a blade, the blade comprising a tip with notches on an abradable coating surface

Publication Date: 2025.11.12 SIEMENS ENERGY GLOBAL GMBH & CO KG

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AI summary

The invention relates to a blade (1) for a continuous flow machine, wherein the blade (1) is formed along a radial direction (3) and has a blade tip (4) and a blade cross-sectional profile with a pressure side (5) and a suction side (6), wherein the blade (1) has a blade tip surface (7) which is opposite a housing inner wall during operation, wherein the blade tip surface (7) has an abradable coating (8), wherein the abradable coating (8) is formed in such a way that a wearing away of the abradable coating (8) takes place during operation, when coming into contact with the housing inner wall, wherein the abradable coating (8) is formed with an abradable coating surface (11), wherein notches (12) are arranged in the abradable coating surface (11).