Annular Combustion Chamber Wall Slots for Thermal Expansion
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Solution Overview
Problem
Combustion chambers in gas turbine engines face issues with differential thermal expansion between outer and inner walls, leading to reduced working life due to the lack of effective thermal management solutions.
Innovation Solution
The design incorporates an annular wall structure with integral inner and outer walls, featuring a box-like structure with coolant apertures and slots that extend through the full thickness of the inner wall to accommodate thermal expansion, secured to ring structures and equipped with dilution apertures and a cellular structure for enhanced cooling and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the outer wall and inner wall are made as a single piece unitary structure, then the structural integrity and manufacturing simplicity are improved, but differential thermal expansion between the outer and inner walls causes stress and reduces working life
Solution Approach 1:
The inner wall is segmented by introducing slots that extend through its full thickness, dividing it into sections that can independently expand and contract. This segmentation allows the inner wall to accommodate differential thermal expansion relative to the outer wall while maintaining overall structural integrity, thereby resolving the contradiction between unitary structure benefits and thermal expansion stresses.
2Temperature
If cooling holes are provided in the outer wall for impingement cooling and in the inner wall for effusion cooling, then cooling efficiency is improved, but the complexity of the wall structure increases
Solution Approach 1:
The cooling functions are merged into the wall structure itself by integrating cooling holes directly into both the outer wall and inner wall. The outer wall contains impingement cooling holes that direct coolant jets against the inner wall surface, while the inner wall contains effusion cooling holes that allow coolant to emerge as a film. This integration achieves effective cooling while maintaining relative structural simplicity compared to separate cooling systems.
3Weight of moving object
If the inner wall is made thinner to reduce weight, then the weight is reduced, but the structural strength and ability to withstand thermal stress is compromised
Solution Approach 1:
The inner wall is designed with effusion cooling holes that create a porous structure. This porous configuration reduces the overall weight of the inner wall while the holes themselves serve a dual purpose: they reduce material mass and enable effusion cooling where coolant emerges through the holes to form a protective film on the inner wall surface, thereby maintaining structural strength despite the reduced material thickness.
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 effectively manages thermal expansion, enhances cooling efficiency, and extends the operational life of combustion chamber segments by allowing for differential expansion without stress transmission, thereby improving the overall performance and reliability of the gas turbine engine.
Implementation Method 1
The outer wall is provided with an arrangement of cooling holes to provide impingement cooling of the outer surfaces of the tiles
Implementation Method 2
The tiles are provided with cooling holes to provide effusion, or film, cooling of the inner surfaces of the tiles
Implementation Method 3
the inner wall having at least one slot extending through the full thickness of the inner wall to accommodate differential thermal expansion between the inner wall and the outer wall
Data Source
AI summary
A combustion chamber includes at least one annular wall which includes at least one box like structure and each box like structure includes an inner wall, outer wall, upstream end wall and downstream end wall. The inner wall is spaced radially from the outer wall and the outer wall has a plurality of apertures for the supply of coolant into the box like structure. The inner wall, the outer wall, the upstream end wall and the downstream end wall are integral. The upstream end of the annular wall has features to secure the annular wall to an upstream ring structure and a downstream end of the annular wall has features to mount the annular wall on a downstream ring structure. The inner wall has at least one slot extending through the full thickness of the inner wall to accommodate differential thermal expansion between the inner wall and the outer wall.