Laser-Engraved Ceramic Coating for Gas Turbine Thermal Runaway

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Solution Overview

Problem

Conventional alumina rotor coatings in gas turbine engines suffer from thermal runaway events due to high conductivity, leading to rotor shaft burn through and unscheduled engine removals, as they generate excessive heat during rub events with vanes, causing thermal expansion and increased rub forces.

Innovation Solution

A ceramic layer with a hardness of at least 7 on the Mohs scale, such as quartz, cubic zirconia, or diamond, is applied to gas turbine engine components and processed with a laser to create a surface with pyramids, reducing the surface area to less than 5% of the base, which abrades the vane tips and reduces the need for abradable coatings, thereby preventing thermal runaway.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional alumina rotor coatings are used, then the coating provides thermal protection, but the high conductivity causes thermal runaway events during rub, leading to rotor shaft burn through

Engineering Contradiction:

Improvethermal protectionVSAvoidthermal runaway prevention

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent changes the material parameter from conventional alumina to a composite ceramic coating with specific properties (hardness of at least 7 on Mohs scale, controlled porosity, specific composition ratios). This parameter change reduces thermal conductivity while maintaining thermal protection, preventing thermal runaway during rub events.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite ceramic coating material that combines multiple ceramic phases with different thermal and mechanical properties. This composite structure provides both thermal protection and reduced thermal conductivity, eliminating the thermal runaway problem while maintaining the necessary protective functions.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the ceramic layer surface is laser engraved to reduce surface area, then abradability is improved and vane tip wear is reduced, but the manufacturing process complexity increases

Engineering Contradiction:

Improveabradability and vane tip protectionVSAvoidlaser engraving process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The laser engraving process is performed as a preliminary action during manufacturing, creating the desired surface topology before the coating is deployed in service. This preliminary action establishes the abradability characteristics and reduces vane tip wear potential from the outset, rather than requiring corrective actions later.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the need for mechanically abradable coatings with a laser-engraved ceramic surface that provides controlled abradability through its surface topology. The laser engraving creates a surface structure that achieves the desired abradability without requiring the coating material itself to be mechanically soft or porous.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 ceramic layer effectively prevents thermal runaway by abrading the vane tips, reducing air leakage, and maintaining engine efficiency without causing damage to the rotor shaft, thus avoiding burn through and unscheduled engine removals.

Implementation Method 1

processed with a laser to have a laser engraved surface in which the top of the surface has less than about 5% of the surface area of the base of the ceramic layer

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

abrasive cutter formed by thermal spray and post treatment... the seal member is coated with a ceramic layer... which abrades the vane tips

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 3

Abrasive cutter formed by thermal spray and post treatment... THERMAL SPRAY COATING PROCESS FOR COMPRESSor SHAFTS

Methodology Applied

Scientific EffectThermal spray: Plasma Spray

Data Source

PatentUS8770927B2Abrasive cutter formed by thermal spray and post treatment

Publication Date: 2014.07.08 RTX CORP

AI summary

A seal for a gas turbine engine component having an airfoil with a radial outward end and a radial inward end, one of which is bare metal. A seal member is adjacent to the bare metal end of the airfoil wherein the seal member is coated with a abrasive layer having a laser engraved surface with the top of the surface has less than about 5% of the surface area of the base of the abrasive layer.