Partial Ceramic Coating on Gas Turbine Blade Outer Air Seal

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Solution Overview

Problem

Conventional blade outer air seal members in gas turbine engines face challenges with thermal expansion and contraction due to high temperatures, leading to potential degradation and early wear of ceramic coatings, which can expose underlying metal to excessive heat and stress, causing cracking and degradation.

Innovation Solution

The design incorporates cooling passages with strategically located inlets and outlets to maintain the blade rub area at a desired temperature, and tapered ceramic coatings to reduce thermal mechanical fatigue, while eliminating the need for abradable coatings by positioning cooling fluid directly over the blade rub area, thus minimizing thermal stress and extending the lifespan of the seal member.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the blade outer air seal is made of strong oxidation-resistant metal alloy to withstand large pressures and hot gas flow, then the strength and reliability are improved, but the weight and complexity of the cooling system increase

Engineering Contradiction:

ImprovestrengthVSAvoidcooling system complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies porous ceramic coating materials on the blade outer air seal surface. The porous structure provides thermal insulation properties while maintaining structural integrity, reducing the need for complex internal cooling systems while still protecting the underlying metal alloy from excessive heat and oxidation

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent uses composite material structure combining metal alloy base material with ceramic coating layers. The metal alloy provides mechanical strength and oxidation resistance, while the ceramic coating provides thermal insulation and environmental protection, creating a multi-functional composite structure that reduces cooling system complexity

Inventive Principle:

Principle #40Composite materials

2Temperature

If thermal barrier coating is applied to protect the underlying metal alloy from heat, then the temperature resistance is improved, but the coating is susceptible to thermal mechanical fatigue and early wear

Engineering Contradiction:

Improvetemperature resistanceVSAvoidcoating durability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent modifies the thermal and mechanical parameters of the coating system by using porous ceramic materials with specific thermal conductivity, porosity, and mechanical properties. These parameter changes allow the coating to withstand thermal mechanical fatigue while maintaining temperature protection, preventing early wear and degradation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different coating characteristics in different regions of the blade outer air seal. The porous ceramic coating provides localized thermal insulation where needed while maintaining structural integrity in critical areas, enhancing both temperature resistance and coating durability through spatially varying properties

Inventive Principle:

Principle #3Local quality

3Temperature

If cooling passages are incorporated to maintain desirable seal temperature, then the temperature control is improved, but the structural complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvetemperature controlVSAvoidmanufacturing ease

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent uses porous ceramic coating as an alternative to traditional internal cooling passages. The porous structure provides passive thermal management through its inherent thermal insulation properties, eliminating the need for complex internal cooling channels while maintaining desirable seal temperature and simplifying manufacturing

Inventive Principle:

Principle #31Porous materials

4Adaptability or versatility

If abradable coating is used to allow blade contact, then the blade contact tolerance is improved, but the coating degrades early and exposes underlying metal to excessive heat

Engineering Contradiction:

Improveblade contact toleranceVSAvoidcoating lifespan

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The patent combines metal alloy base material with porous ceramic coating to create a composite structure that tolerates blade contact while protecting against heat. The composite provides both mechanical compliance for blade contact and thermal protection, extending coating lifespan without sacrificing adaptability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent creates localized properties in the coating system where the porous ceramic structure provides both contact tolerance and thermal protection in the same region. This local quality approach eliminates the need for separate abradable and thermal barrier layers, preventing early degradation and extending coating lifespan

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

This solution effectively manages thermal expansion and contraction, reduces thermal mechanical fatigue, and prevents early degradation of the seal member by ensuring consistent cooling of the blade rub area, thereby enhancing the durability and longevity of the blade outer air seal member.

Implementation Method 1

cooling passages with strategically located inlets and outlets to maintain the blade rub area at a desired temperature

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

cooling fluid flowing through the cooling passages to cool the blade outer air seal member

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

The gas path surface of the blade outer air seal may include a thermal, environmental or corrosion resistance coating system to help protect the underlying metal alloy

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 4

Conventional blade outer air seal members in gas turbine engines face challenges with thermal expansion and contraction due to high temperatures

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 5

positioning cooling fluid directly over the blade rub area, thus minimizing thermal stress

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Data Source

PatentEP3103967B1Blade outer air seal having partial coating

Publication Date: 2019.07.31 UNITED TECH CORP

Figure 1~3
Figure 4A~4B
Figure 5~6

AI summary

A blade outer air seal member (32) includes a distinct body (40) that has two circumferential sides (42), a leading edge (44a) and a trailing edge (44b), and a gas path side (46a) and a radially outer side (46b) opposite the gas path side (46a). A ceramic coating (48) is initially disposed on a portion of the gas path side. The ceramic coating (48) includes a forward coating portion and an aft coating portion. The gas path side (46a) has a bare area (52) axially separating the forward coating portion and the aft coating portion. The bare area (52) excludes any of the ceramic coating (48). One or more cooling passages (60) have an outlet (62) that opens at the bare area (52). The cooling passage (60) extends in the body (40) in an axial direction under the ceramic coating (48).