Burner Ring Fixing Device for Turbojet Afterburner Combustion
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Solution Overview
Problem
Conventional methods for fixing a burner ring onto flameholder arms in an afterburner combustion chamber of a turbojet engine face challenges due to high temperatures causing thermal expansion, making it difficult to use bolts and requiring a solution that is simple, economical, and thermally protected, especially in a confined space without special tooling.
Innovation Solution
A device that uses locking pieces between parallel plates of the flameholder arms to immobilize the burner ring sectors, with cylindrical rods and pins for axial and rotational immobilization, allowing for three-dimensional expansion without spikes or projections, and can be easily fitted and removed without special tooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional bolts are used to fix the burner ring, then the fixation is simple, but the thermal expansion causes the fixing to fail
Solution Approach 1:
The fixing device uses flexible elements (springs or elastomeric materials) that can dynamically adapt to thermal expansion of the burner ring sectors. The flexible elements maintain continuous contact with the sectors while allowing radial expansion, preventing fixation failure under thermal conditions.
Solution Approach 2:
The device changes the physical state of the fixing elements by using materials with different thermal expansion coefficients or phase-change materials that alter their mechanical properties with temperature. This allows the fixing mechanism to remain effective across the temperature range from ambient to 2000K.
2Reliability
If special tooling is used for fixation, then the fixation is secure, but the operation becomes complex and difficult in confined space
Solution Approach 1:
The fixing device is designed to be self-contained with all necessary components (locking elements, flexible elements, mounting structures) integrated into a single assembly that can be installed by simple insertion and engagement actions. The device performs its own fixation function without requiring external special tooling or complex assembly procedures.
Solution Approach 2:
The fixing device is divided into modular components (individual fixing elements for each burner ring sector) that can be independently installed and removed. This segmentation allows the complex fixation function to be achieved through multiple simple operations rather than one complex special tooling operation.
3Stability of the object's composition
If the burner ring sectors are rigidly fixed, then the fixation is stable, but the thermal expansion causes stress and potential failure
Solution Approach 1:
The fixing device replaces rigid constraints with dynamic, flexible elements that can deform elastically under thermal expansion. The flexible elements (springs or elastomeric materials) absorb the expansion stresses through their deformation capability, maintaining both stability and stress resistance simultaneously.
Solution Approach 2:
The device incorporates flexible elements that are pre-loaded to provide cushioning against thermal expansion. The flexible elements are designed to absorb and distribute the stresses generated by thermal expansion before these stresses can cause damage to the burner ring sectors or fixation structure.
4Reliability
If locking pieces with spikes are used, then the fixation is secure, but the spikes act as flameholders in afterburning mode
Solution Approach 1:
The device converts the potential harm of needing secure fixation (which would require spikes or protrusions) into a benefit by using the opposite approach: smooth, rounded surfaces that are actually beneficial for flame flow. The locking pieces use curved geometries that match the burner ring sectors while being completely free of flame-trapping protrusions, thus eliminating the harmful flameholding effect.
Solution Approach 2:
The locking pieces are designed with entirely curved and rounded surfaces that conform to the curvature of the burner ring sectors. This spheroidality provides secure mechanical engagement through surface contact while ensuring no sharp edges or protrusions exist that could trap flames during afterburning operation.
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 device effectively secures the burner ring sectors while allowing for thermal expansion, preventing translational and rotational movement, and is simple to install and remove, ensuring secure fixation without thermal damage or the need for specialized tools.
Implementation Method 1
the temperature in the turbojet engine afterburner combustion chamber is approximately 1100° K in the absence of afterburning and reaches about 2000° K in afterburning mode. The burner ring is therefore subjected to very high temperatures and to significant radiation which gives rise to significant thermal expansion of its components.
Implementation Method 2
Each locking piece comprises a through passage directed radially respectively with respect to the axis of the afterburner combustion chamber and housing a cylindrical rod, the ends of which are engaged in the aforementioned orifices in the plates of the flameholder arm.
Implementation Method 3
the rod comprises a housing to accommodate a pin, a first end of which is immobilized in terms of rotation and in terms of translation in said housing
Data Source
AI summary
Device for fixing a burner ring onto flameholder arms (14) in an afterburner combustion chamber of a turbojet engine, the burner ring being formed of ring sectors (12) placed more or less end to end and the ends of which are housed and guided between two circumferentially-directed parallel plates (34, 36) of the flameholder arms (14) and are immobilized between these plates (34, 36) by locking pieces (52) which are themselves held between the plates (34, 36) by immobilizing means (54, 56) engaged in aligned orifices (58, 60, 64) in the plates (34, 36) and in the locking pieces (52).