Sectorised CMC Combustor with Elastic Seals

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Solution Overview

Problem

The existing configurations for annular combustion chambers in gas turbines, particularly those using ceramic matrix composite (CMC) materials, face challenges in manufacturing complexity, dimensional variations between metal and CMC parts, and inadequate sealing, leading to increased costs and potential instability under high stresses.

Innovation Solution

The proposed solution involves dividing the combustion chamber into circumferentially arranged sectors made of single-piece CMC material, with elastically deformable connecting elements between metal casings and CMC walls, and a crown connecting the sectors, which reduces manufacturing complexity and absorbs dimensional variations, while providing effective sealing and axial stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the combustion chamber is made as a single complex CMC component, then thermal resistance and high-temperature performance are improved, but manufacturing complexity and cost increase significantly

Engineering Contradiction:

Improvehigh-temperature performanceVSAvoidmanufacturing complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The combustion chamber is divided into multiple CMC sectors that can be manufactured separately using simpler tools and processes, then assembled together to form the complete annular structure. This segmentation reduces the complexity of individual manufacturing steps while maintaining the thermal performance benefits of CMC material throughout the entire chamber.

Inventive Principle:

Principle #1Segmentation

2Strength

If metal casings and CMC combustion chamber walls are directly connected, then structural integrity is improved, but thermal expansion differences cause dimensional variations and potential failure

Engineering Contradiction:

Improvestructural integrityVSAvoiddimensional stability

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The connecting elements are designed with elastic properties that allow them to deform and accommodate the different thermal expansion coefficients of metal and CMC materials. This parameter change from rigid to elastic connection maintains structural integrity while absorbing dimensional variations caused by thermal effects.

Inventive Principle:

Principle #35Parameter changes

3Strength

If rigid support structures are used to hold CMC tiles, then structural support is improved, but the structure occupies significant volume and requires additional sealing casings

Engineering Contradiction:

Improvestructural supportVSAvoidsupport structure volume

Core Design Contradiction:

StrengthVSVolume of stationary object

Solution Approach 1:

The support structure is integrated directly with the CMC sectors themselves, which are made as single-piece monolithic components. This merging eliminates the need for separate rigid support structures and external sealing casings, reducing overall volume while maintaining structural support through the inherent strength of the CMC material.

Inventive Principle:

Principle #5Merging (Combining)

4Stress or pressure

If chamber sectors are allowed to move independently under high stress, then stress distribution is improved, but axial position stability is lost

Engineering Contradiction:

Improvestress distributionVSAvoidaxial position stability

Core Design Contradiction:

Stress or pressureVSStability of the object's composition

Solution Approach 1:

The connecting elements are designed to be elastically deformable, allowing chamber sectors to move dynamically in response to stress while automatically returning to their proper axial positions. This dynamic elasticity provides both stress distribution and position stability, unlike rigid connections that would either fail or constrain thermal expansion.

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 configuration significantly reduces manufacturing costs, effectively absorbs thermal dimensional variations, and ensures stable assembly under high stresses, enhancing the operational reliability of gas turbines.

Implementation Method 1

elastically deformable parts supporting the combustion chamber between the inner metal casing and the outer metal casing... the differential dimensional variations between metal casings and the CMC combustion chamber walls can be easily and effectively absorbed by the elastic deformation of the connecting elements

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

there is provided a crown in one piece in contact with the chamber bottom sectors and to which the chamber sectors are connected

Methodology Applied

Scientific EffectMechanical connection: Mechanical Fastener

Data Source

PatentEP2107308B1Sectorised CMC combustor for a gas turbine

Publication Date: 2017.09.06 SNECMA PROPULSION SOLIDE

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AI summary

The chamber assembly has a combustion chamber placed between internal and external metallic casings (15, 25). The chamber has internal and external walls and a chamber base linked to the walls to form an assembly divided into chamber sectors (100) between which a sealing joint (13) is placed. Each sector has internal and external wall sectors (110, 120) and a bottom chamber wall sector (130). Elastically deformable connection pieces (17, 27) connect the casings respectively at the sectors (110, 120). A single ring (32) contacts with the sector (130), and is connected to the chamber sectors. The chamber sector is made from a single ceramic matrix composite piece. The sealing joint includes a fibrous structure made of refractory fibers, and is partially densified by a ceramic matrix.