CMC Combustor Liner Radial Fixation Thermal Growth

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Solution Overview

Problem

Metal fasteners used to secure ceramic matrix composite (CMC) liners in gas turbine combustors lose strength and can melt at high operating temperatures, undermining the desired high-temperature capability of CMCs, as their allowable operating temperature is typically lower than that of the CMCs.

Innovation Solution

A combustor design featuring a metallic combustor shell with a heat shield and CMC liner segments that are radially located without axial fixation, allowing for axial movement to accommodate thermal growth differences, and a cooling system with pressure differential to maintain engagement with the heat shield, minimizing the need for axial fixation and cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metal fasteners are used to secure CMC liners, then the liners can be fixed in position, but the fasteners lose strength and may melt at CMC operating temperatures

Engineering Contradiction:

Improveliner fixation reliabilityVSAvoidfastener strength at high temperature

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces the mechanical fastening system (metal fasteners) with a thermal field-based solution (cooling system). The cooling system creates a temperature gradient that allows the metal shell to expand less than the CMC liner, creating a self-locking interference fit without requiring metal fasteners to secure the liner at high temperatures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the temperature parameter distribution within the system by introducing active cooling to the metal shell. This creates a controlled temperature differential between the shell and the CMC liner, allowing the shell to maintain lower thermal expansion and create a self-locking interference fit that secures the liner without metal fasteners.

Inventive Principle:

Principle #35Parameter changes

2Strength

If metal fasteners and surrounding areas are cooled to maintain fastener strength, then the fasteners can maintain their strength, but this undermines the desired high temperature capability of the CMC

Engineering Contradiction:

Improvefastener strengthVSAvoidCMC operating temperature capability

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent applies local quality by providing cooling only to the metal shell portions that require it for dimensional stability, while allowing the CMC liner to operate at high temperatures. The cooling system is localized to create a temperature gradient where the shell remains cooler (for structural integrity) and the CMC liner remains hotter (for performance).

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the thermal management system, separating the cooling requirements of the metal shell from the CMC liner. The cooling system targets specific regions of the shell to control its thermal expansion independently, allowing the CMC liner to achieve its full high-temperature capability without being constrained by fastener temperature limitations.

Inventive Principle:

Principle #1Segmentation

3Temperature

If CMC liners are used, then operating temperatures can exceed metal alloy maximum use temperatures, but thermal growth differences cause binding stresses when axially fixed

Engineering Contradiction:

Improveoperating temperature capabilityVSAvoidbinding stress from thermal growth

Core Design Contradiction:

TemperatureVSStress or pressure

Solution Approach 1:

The patent transitions from a static fixation system to a dynamic one. The interference fit creates a flexible, self-adjusting connection that accommodates thermal growth differences between the CMC liner and metal shell. The radial locking mechanism allows axial movement while maintaining positional stability, adapting to thermal expansion variations in real-time.

Inventive Principle:

Principle #15Dynamics

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 design enhances the operational temperature capability of CMC liners by allowing for thermal growth accommodation and reducing the risk of binding stresses, while minimizing cooling requirements and maintaining structural integrity.

Implementation Method 1

a cooling system with pressure differential to maintain engagement with the heat shield

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

allowing for axial movement to accommodate thermal growth differences

Methodology Applied

Scientific EffectThermal growth: Thermal Expansion

Data Source

PatentUS11226099B2Combustor liner for a gas turbine engine with ceramic matrix composite components

Publication Date: 2022.01.18 ROLLS ROYCE NORTH AMERICAN TECHNOLOGIES INC

AI summary

A combustor adapted for use in a gas turbine engine includes a metallic combustor shell forming an interior space, a heat shield, and a liner arranged in the interior space of the metallic case. The liner defines a combustion chamber in which fuel is burned during operation of a gas turbine engine.