Turbomachine Fan Hub Blade Pivot With Adjustable Orientation
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Solution Overview
Problem
In turbojets with high bypass ratios, the existing fan blade retention systems are bulky, limiting the minimization of the fan hub diameter and increasing the risk of high-energy debris generation in case of rolling-element failure, which complicates the dimensioning of airplane shielding.
Innovation Solution
A blade pivot with adjustable orientation featuring a ball bearing with four points of contact, an anti-rupture sleeve, and a needle or roller bearing for efficient force distribution and failure protection, ensuring retention of rolling elements even in case of rupture, thereby preventing harmful debris ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner and outer rolling-element bearings are highly spaced radially to minimize transverse forces on the inner bearing, then the inner bearing can be smaller, but the hub diameter increases due to the larger radial spacing required
Solution Approach 1:
The invention divides the force-taking function into two separate bearings: the inner rolling-element bearing takes centrifugal forces, and the outer needle bearing takes transverse forces. This segmentation allows each bearing to be optimized for its specific function, with the needle bearing positioned to efficiently handle transverse loads without requiring excessive radial spacing.
Solution Approach 2:
The invention introduces a new dimensional arrangement by placing the needle bearing in the outer radial position and orienting it to take transverse forces, while the inner bearing handles centrifugal forces. This dimensional reorganization allows compact radial spacing while maintaining adequate transverse force capacity through the needle bearing's geometry and positioning.
2Strength
If a single large inner rolling-element bearing is used to take all centrifugal forces, then the bearing can handle the loads, but the hub diameter increases and tangential space between adjacent blade pivots is restricted
Solution Approach 1:
The invention segments the force-taking functions between two bearings: the inner rolling-element bearing is dedicated to centrifugal forces, while the outer needle bearing handles transverse forces. This segmentation allows the inner bearing to be smaller since it only needs to handle centrifugal loads, reducing the required hub diameter and increasing tangential space between adjacent pivots.
3Volume of moving object
If the rolling-element bearing for taking centrifugal forces is positioned close to the blade root, then the pivot architecture is more compact, but the bearing is at risk of rupture and debris ejection
Solution Approach 1:
The invention implements beforehand cushioning by positioning the needle bearing and its outer ring as a protective barrier between the inner rolling-element bearing and the external environment. In case of inner bearing rupture, the needle bearing structure and outer ring contain the debris, preventing ejection while maintaining compact pivot architecture.
Solution Approach 2:
The needle bearing and its outer ring serve as an intermediary protective structure between the inner rolling-element bearing and the external environment. This intermediary element provides mechanical protection and debris containment without significantly increasing the overall pivot volume, as it utilizes the existing radial space efficiently.
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 solution reduces the bulkiness of the fan hub architecture, enhances compactness, and provides a failsafe mechanism to prevent the ejection of high-energy debris, thus simplifying the dimensioning of airplane shielding and ensuring safer operation.
Implementation Method 1
a ball bearing for taking centrifugal forces having an inner ring mounted transversely supported against an outer shoulder of the stud and an outer ring intended to be mounted transversely supported inside the fan hub
Implementation Method 2
a rolling-element bearing for taking transverse forces having an inner ring and a smooth outer ring intended to be mounted transversely supported inside the fan hub
Data Source
AI summary
The invention relates to a blade pivot with adjustable orientation for a turbomachine fan hub, comprising: a stud having a fastener configured to retain a blade root and coupling means for the transmission of a twist torque; a ball bearing for taking centrifugal forces having an inner ring and an outer ring; a first clamping nut intended to be screwed on an inner thread of the hub to ensure clamping of the outer ring of the ball bearing; a rolling-element bearing for taking transverse forces having an inner ring and a smooth outer ring; a locking ring mounted between these two inner rings to provide for them a respective transverse support; an anti-rupture sleeve carrying the inner ring of the rolling-element bearing for taking transverse forces and the terminal end of which is extended transversely beyond the outer ring of this bearing.