Combustion Chamber Tile Stiffness via Asymmetric Pedestal Patterns
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Solution Overview
Problem
Conventional annular gas turbine engine combustion chamber tiles suffer from cracking due to weak lines formed by regular patterns of pedestals or effusion cooling apertures, leading to potential failure under thermal and pressure loading, necessitating periodic inspection and replacement.
Innovation Solution
The tiles are arranged with pedestals or effusion cooling apertures in predetermined patterns such as Fermat's spiral, pentagonal, or regular hexagonal patterns with interconnecting members or slots, providing uniform stiffness in all directions and eliminating direct lines of weakness across the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If regular patterns of pedestals or effusion cooling apertures are used on tiles, then manufacturing is simplified and cooling is effective, but weak lines are formed that reduce structural strength and lead to cracking
Solution Approach 1:
The patent applies asymmetry by transitioning from regular, symmetric patterns of pedestals and effusion cooling apertures to irregular, non-repeating patterns. This eliminates the formation of continuous weak lines that occur in regular patterns, thereby maintaining manufacturing simplicity while significantly improving tile structural strength and resistance to cracking under thermal and pressure loading.
2Temperature
If regular hexagonal patterns with pedestals are used, then cooling coverage is uniform, but direct lines of weakness form between pedestal rows reducing tile reliability
Solution Approach 1:
The patent eliminates the regular hexagonal pattern that creates straight lines of weakness between pedestal rows. By using irregular spacing and positioning of pedestals and effusion cooling apertures, the design maintains effective cooling coverage while preventing the formation of continuous weak lines, thereby significantly improving tile reliability and reducing cracking susceptibility.
3Use of energy by moving object
If effusion cooling apertures are arranged in regular patterns, then coolant distribution is consistent, but weak sections are created that reduce bending stiffness
Solution Approach 1:
The patent transitions from regular patterns of effusion cooling apertures to irregular patterns that eliminate continuous weak lines. This asymmetric arrangement maintains consistent coolant distribution efficiency while significantly improving bending stiffness by preventing the formation of weak sections that occur in regular patterns.
4Productivity
If tiles are subjected to thermal and pressure loading in combustion chamber, then engine operation is enabled, but cracks form along weak lines leading to potential failure
Solution Approach 1:
The patent applies asymmetry to the arrangement of pedestals and effusion cooling apertures to eliminate regular patterns that create weak lines. This design enables continued engine operation under thermal and pressure loading while significantly improving tile reliability by preventing crack formation along weak lines, thereby reducing potential failure.
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 arrangement enhances the structural integrity and reliability of the tiles by eliminating weak sections, potentially increasing their working life and reducing maintenance needs by minimizing the frequency of boroscope inspections for cracks.
Implementation Method 1
The pedestals provide cooling of the heat shield and/or tile by conducting heat away from the heat shield and/or tile and the heat is transferred to coolant flowing around and between the pedestals
Implementation Method 2
each tile on the inner annular wall is provided with a plurality of effusion cooling apertures which extend through the tile to provide a film of coolant on the radially outer, hot, surface of the tile
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
An annular combustion chamber wall arrangement comprises an annular wall (46) and a plurality of tiles (48A) and each tile (48A) is secured to and is spaced from a further annular wall (46). The first surface (49) of each tile (48A) faces the annular wall (46) and the second surface (49B) of each tile (48A) faces away from the annular wall (46). Each tile (48A) has a plurality of pedestals (78) extending away from the first surface (49) towards the annular wall (46) and/or a plurality of effusion cooling apertures (82) extending through the tile (48A) from the first surface (49) to the second surface (49B). At least one of the tiles (48A) has the pedestals (78) and/or the effusion cooling apertures (82) arranged in a predetermined pattern (110) which provides the tile (48A) with a more uniform stiffness in all directions to reduce the possibility of cracking of the tile (48A). In one predetermined pattern (110) the pedestals (78') are arranged in a Fermat's (parabolic) spiral with the pedestals (78') arranged with Fibonacci number ordering.