Combustion Chamber Fairing with Internal Tabs for Aerodynamic Repair

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Solution Overview

Problem

Existing combustion chamber designs face performance penalties due to airflow disturbances caused by bolt heads and are difficult to repair due to welds that complicate disassembly and reassembly.

Innovation Solution

The combustion chamber employs internal tabs and caps with circumferentially distributed fixing parts that are welded or brazed, allowing for easy disassembly and repair by grinding welded zones, and uses TIG welding and brazing to maintain structural integrity without disturbing airflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of repair

If bolted assembly is used to join combustion chamber components, then ease of disassembly and repair is improved, but airflow disturbances caused by bolt heads worsen aerodynamic performance

Engineering Contradiction:
Improveease of disassemblyVSAvoidairflow disturbance
Core Design Contradiction:
Ease of repairVSObject-affected harmful factors

Solution Approach 1:

The invention extracts the harmful bolt heads from the external surface of the combustion chamber by moving the fastening mechanism inside the fairing. The tabs and slots with retaining rings are positioned within the fairing structure, eliminating protruding elements that disrupt airflow while maintaining easy disassembly capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The fastening mechanism is nested within the fairing structure. The tabs are positioned inside the fairing, and the retaining rings are housed within the fairing's internal geometry, allowing the fastening system to be contained within the aerodynamic envelope rather than protruding outward.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Object-affected harmful factors

If welds are used to join combustion chamber components, then aerodynamic performance is improved by eliminating bolt heads, but ease of repair worsens due to difficulty in cutting and reassembling welded joints

Engineering Contradiction:
Improveairflow disturbanceVSAvoidease of disassembly
Core Design Contradiction:
Object-affected harmful factorsVSEase of repair

Solution Approach 1:

The invention segments the combustion chamber into modular components (fairing, outer wall, inner wall, bottom wall) that can be independently removed and reassembled. The tab-and-slot design with retaining rings allows each component to be separated without cutting, enabling modular repair and replacement while maintaining aerodynamic smoothness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The retaining rings act as intermediary elements that facilitate the connection between tabs and slots. These removable intermediaries allow for easy disassembly by simply removing the retaining rings, avoiding the need to cut welded joints while maintaining a smooth external surface for aerodynamic performance.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Strength

If multiple welds are used to join fairing and chamber components, then structural integrity is improved, but device complexity worsens due to multiple assembly steps and cost

Engineering Contradiction:
Improvestructural integrityVSAvoidassembly complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The fairing and chamber components are segmented into modular sections connected by tabs and slots. This segmentation allows each component to be manufactured and assembled independently, reducing overall assembly complexity while maintaining structural integrity through the distributed tab-slot connections throughout the structure.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention changes the connection parameter from permanent welding to removable mechanical fastening with retaining rings. This parameter change simplifies the assembly process, reduces manufacturing costs, and enables easy disassembly while maintaining sufficient structural integrity for the application.

Inventive Principle:
Principle #35Parameter changes

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 aerodynamic performance by minimizing airflow disruptions and facilitates maintenance by allowing for seamless disassembly and reassembly of components, improving repairability and reducing reassembly costs.

Implementation Method 1

The tabs attached to the caps are preferably joined to them by brazing. Each tab is joined to the cap using a filler metal whose melting point is lower than the melting point of the materials being joined. The joint is therefore made without melting the metal of the components being joined. Once heated to its melting point, the filler metal penetrates the joints between the parts to be joined by capillary action.

Methodology Applied
Scientific EffectBrazing: Brazing

Implementation Method 2

Once heated to its melting point, the filler metal penetrates the joints between the parts to be joined by capillary action.

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Implementation Method 3

The welding process joining the tabs is preferably a TIG weld, a well-known technique. A high-intensity current passes through a tungsten electrode, forming an electric arc with the parts to be joined. The metal receiving the arc undergoes localized melting. The welding is performed in a neutral gas environment (argon, for example).

Methodology Applied
Scientific EffectTIG welding: Welding

Data Source

PatentEP1717516B1Easily disassembled combustion chamber with improved aerodynamic performance
Publication Date: 2019.04.03 SAFRAN AIRCRAFT ENGINES SAS
  • EP1717516B1 patent drawingFigure 1~3
  • EP1717516B1 patent drawingFigure 2

AI summary

The chamber has a chamber end wall with an injector unit and extending between annular outer and inner walls (12, 13). A fairing (15) has outer and inner caps (16, 17) with respective tongues (25) projecting into an annular cavity. The outer cap and the annular inner wall are assembled together by welding. The tongues are curved so as to touch each other in pairs one against the other, and welded together at their ends.