Gas Turbine Combustion Chamber Sliding Flange Design
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Solution Overview
Problem
Existing combustion chamber arrangements in gas turbine engines face issues with axial movement and stress between inner and outer casings due to thermal expansion, leading to manufacturing difficulties and increased costs, as well as complex assembly and repair processes.
Innovation Solution
The proposed combustion chamber arrangement incorporates axially extending flanges with recesses and fasteners to secure the radially inner and outer cowls and walls, allowing for a bolted construction while enabling the radially inner annular wall to slide relative to the upstream end wall, reducing stress and simplifying assembly and repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the radially inner annular wall is rigidly secured to the annular upstream end wall by a bolted joint, then the structural strength is improved, but the stress induced by thermal expansion and axial movement between inner and outer casings increases
Solution Approach 1:
The radially inner annular wall is designed to slide axially within the annular upstream end wall rather than being rigidly fixed. This dynamic arrangement allows the inner wall to move with thermal expansion while maintaining structural integrity through frictional contact and periodic repositioning, thereby reducing stress accumulation during engine operation cycles.
2Stress or pressure
If the radially inner annular wall is slidably mounted on the annular upstream end wall, then the stress induced by thermal expansion is reduced, but the structural strength decreases
Solution Approach 1:
The sliding mechanism allows controlled axial movement of the radially inner annular wall within the upstream end wall. The frictional contact between the sliding surfaces provides sufficient structural strength while accommodating thermal expansion, eliminating the need for rigid fixation that would generate stress.
3Strength
If the radially inner and outer cowls are integral with the annular upstream end wall produced by casting, then the structural strength is improved, but the ease of manufacture and assembly deteriorates
Solution Approach 1:
The combustion chamber is divided into separate modular components: the annular upstream end wall, the radially inner annular wall, the radially outer annular wall, and the cowls. These segments can be manufactured independently using standard fabrication processes and then assembled together, improving manufacturability and enabling easier repair and replacement of individual components.
Solution Approach 2:
The separate components are prepared and pre-assembled outside the engine, allowing quality control and inspection before installation. This preliminary assembly approach simplifies the overall manufacturing process and facilitates maintenance operations.
4Strength
If the radially inner annular wall is rigidly secured to the annular upstream end wall, then the structural strength is improved, but the ease of repair deteriorates
Solution Approach 1:
The modular design allows the radially inner annular wall to be independently removed from the upstream end wall for repair or replacement without affecting other components. This segmentation significantly improves maintenance efficiency while the frictional sliding contact maintains adequate structural strength during 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
This design reduces manufacturing costs and complexity, enhances assembly and repair efficiency, and minimizes stress induced by axial movement between casings, improving the overall reliability and maintainability of the combustion chamber.
Implementation Method 1
the axial loads applied to the inner casing and the thermal expansion of the inner casing results in considerable movement of the inner casing relative to the outer casing
Data Source
AI summary
A combustion chamber arrangement comprises an annular combustion chamber, an outer casing, an inner casing and a stage of outlet guide vanes arranged at the downstream end of the combustion chamber interconnecting the outer casing and the inner casing. The combustion chamber comprises an upstream wall structure, a radially inner cowl is removably secured to a radially inner axially extending flange by fasteners and a radially outer wall structure and a radially outer cowl are removably secured to a radially outer axially extending flange by fasteners. The flange is slidably mounted on the radially inner wall structure. The flange has at least one recess in its radially inner surface and the fasteners are arranged in the recess in the radially inner surface of the flange. The cowl abuts the radially outer surface of the flange and the radially inner wall structure abuts the radially inner surface of the flange.