Elastomeric Annular Seal for Turbomachine Blade Alignment
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Solution Overview
Problem
Turbine engine rotor blades experience misalignment during start-up and shutdown, leading to blade deterioration and reduced turbomachine performance due to centrifugal forces and manufacturing tolerances, which cause radial clearances and vibration issues.
Innovation Solution
An annular elastomeric seal with a specific hardness and shape is used to maintain blade positioning by exerting an elastic force, preventing air leakage and vibration, and allowing circumferential displacement, ensuring blades remain aligned and separated from the outer casing during operation and shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the annular seal is made with higher hardness to maintain blade positioning, then the blade alignment is improved, but the circumferential displacement of blades is restricted
Solution Approach 1:
The patent applies parameter changes by selecting a specific hardness range for the elastomeric seal material (Shore A 40-90, preferably 50-70). This optimized hardness parameter allows the seal to be sufficiently rigid to maintain blade alignment while remaining soft enough to permit necessary circumferential displacement during operation, thus resolving the contradiction between alignment precision and operational flexibility.
2Ease of operation
If the annular seal is made with lower hardness to allow blade displacement, then the ease of operation is improved, but the blade alignment maintenance capability deteriorates
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal hardness range (Shore A 40-90) for the elastomeric seal. Within this range, the seal maintains sufficient elasticity to allow blade displacement during operation while simultaneously providing enough structural rigidity to maintain proper blade alignment, thus balancing operational ease with alignment precision.
3Ease of manufacture
If the blade roots are housed with larger play in the annular groove to facilitate assembly, then the ease of manufacture is improved, but the blade positioning accuracy deteriorates
Solution Approach 1:
The elastomeric seal acts as an intermediary element between the blade roots and the annular groove. It compensates for assembly tolerances and manufacturing variations by providing a compliant interface that maintains accurate blade positioning even when larger plays are present in the groove, thus resolving the contradiction between ease of assembly and positioning accuracy.
4Reliability
If the seal is made to interfere with circumferential sliding to improve sealing, then the sealing performance is improved, but the blade mobility deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the seal's hardness within the Shore A 40-90 range and controlling the interference fit parameters (radial interference between seal outer diameter and groove diameter). These parameter optimizations ensure the seal provides adequate sealing contact with blade platforms while maintaining sufficient elasticity to allow necessary circumferential mobility 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
The annular seal effectively maintains blade alignment, reduces vibration, and prevents air leakage, enhancing turbomachine performance by ensuring blades do not rub against the outer casing during start-up and shutdown, while allowing for correct positioning and circumferential displacement.
Implementation Method 1
the hardness of the elastic seal is determined so that the restoring force exerted by the seal on the blade is low enough to allow circumferential displacement of the blade in the groove and high enough to ensure the correct positioning of the blade
Implementation Method 2
In operation, this seal expands radially outwards under the effect of centrifugal forces and comes into contact with the platforms of the blades
Implementation Method 3
In operation, the annular seal dampens the vibrations of the blades
Data Source
Figure 1
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AI summary
Turbomachine rotor wheel, this wheel comprising a disc (24) carrying blades (16) whose feet (18) are engaged and retained in an annular groove (20) of the disc, these feet being connected to platforms (44) intended to cooperate with an annular seal (54) mounted in an annular groove of the disc, the annular seal (54) exerting on the platforms (44) of the blades an elastic force maintaining the blades (16) in a correct operating position, when the turbomachine is stopped.