Turbomachine Blade Root Attachment Using Adjustable Wedge Assembly
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Solution Overview
Problem
Wide chord and large span unducted fan blades experience intense vibratory excitation and bending stress due to turbulent aerodynamic flows, leading to potential damage to the blade root and attachment, which existing deformable spacers fail to effectively mitigate, especially at low fan speeds.
Innovation Solution
An assembly comprising a clip with two wedges and a clamping screw, where the wedges' bearing surfaces are fixed relative to each other, allowing for increased clamping force on the blade root, and the clamping screw's rotation adjusts the force distribution to adapt to manufacturing dispersions and varying aerodynamic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deformable shim is used to tighten the blade root firmly within the attachment recess, then the flapping phenomenon is reduced, but the shim cannot effectively eliminate flapping in variable-pitch, wide-chord, and/or large-span bladed fans where intense aerodynamic forces are encountered even at low fan speeds
Solution Approach 1:
The patent applies the dynamics principle by making the wedge movable in the axial direction through a tensioning device. This allows the clamping force to be dynamically adjusted according to varying aerodynamic conditions and operational requirements, enabling the system to adapt to different flight phases and intensity levels while maintaining reliable blade root attachment.
Solution Approach 2:
The patent applies parameter changes by using a tensioning device that can vary the axial position of the wedge, thereby changing the clamping force parameter. This allows the attachment system to respond to different aerodynamic loading conditions by adjusting the compression force applied to the blade root, improving both reliability and adaptability.
2Productivity
If the blade span is increased to maximize bypass ratio and improve aerodynamic performance, then thrust efficiency is improved, but the blades experience more intense vibratory excitation and bending stress
Solution Approach 1:
The patent applies preliminary action by pre-compressing the blade root against the attachment recess using the wedge and tensioning device before operational loading occurs. This preliminary clamping action creates a pre-load that counteracts the intense vibratory excitation and bending stresses that will occur during operation, allowing longer blade spans to maintain structural integrity while preserving aerodynamic performance.
3Use of energy by stationary object
If a very open timing setting is used during engine start-up to ensure low fan speeds and machine safety, then power consumption is reduced, but the blades experience turbulent aerodynamic flow that generates broadband vibrational excitation and intense bending stress
Solution Approach 1:
The patent applies preliminary anti-action by using the wedge and tensioning device to pre-compress the blade root against the attachment recess before the harmful vibrational excitation occurs during start-up. This pre-applied clamping force creates a counter-action that resists the turbulent aerodynamic flow and vibrational excitation, protecting the blade root from damage even when very open timing settings are used during engine start-up.
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 assembly provides enhanced resistance to blade root damage by applying a greater clamping force and adapting to different operational conditions, effectively reducing flapping phenomena and ensuring secure attachment even under intense aerodynamic forces at low fan speeds.
Implementation Method 1
a clamping screw cooperating with the respective threads of the two wedges so that a rotation of the clamping screw causes a displacement of one of the two wedges relative to the other wedge
Implementation Method 2
two wedges, each wedge comprising: o a first bearing surface to bear against the foot o a second bearing surface opposite the first bearing surface to bear against the fastener when the wedge is received in the recess
Data Source
AI summary
Assembly for a turbomachine blade, comprising: a fastener (9) defining a pocket (10) for receiving a blade root (11), and comprising two flanks defining between them a passage leading into the pocket (10) and forming stops preventing the root (11) from exiting the pocket (10) through the passage, and a shim (26a, 26b) adapted to be received in the pocket (10) with the root (11), the shim (26a, 26b) having a first bearing surface (28a, 28b) for bearing on the root (11) and a second bearing surface (30a, 30b) opposed to the first bearing surface (28a, 28b) for bearing against the fastener (9), the bearing surfaces being fixed in relation to one another and oriented such that a movement of the shim (26a, 26b) in the pocket (10) with respect to the fastener (9) varies the magnitude of a force exerted by the shim (26a, 26b) on the root (11).