Turbine Fan Hub Pivot Segmentation for Maintenance Access
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Solution Overview
Problem
Existing fan blade pivot systems in turbine engines face challenges such as inadequate sealing, complex maintenance, and overdimensioning due to concurrent force paths, making them difficult to dismantle and maintain, especially in 'open rotor' turbojets with contrarotating propellers.
Innovation Solution
A pivot system for adjustable pitch blades featuring a stud with coupling means, an annular force-decoupling part, outer and inner rolling bearings, a pitch transmission ring, and clamping nuts that separate force paths and allow for unitary assembly, enabling easier maintenance and use of titanium alloys without raceways on the hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If all parts of the pivot are subjected to all centrifugal and aerodynamic forces, then the pivot can withstand stresses in twisting, compression, and stretching, but the parts need to be overdimensioned and the pivot becomes difficult to dismantle
Solution Approach 1:
The pivot is divided into multiple independent parts: a first part subjected to centrifugal forces, a second part subjected to aerodynamic forces, and a third part for pitch control. This segmentation allows each part to be optimized for its specific function rather than being overdimensioned to handle all forces, and facilitates easier dismantling and maintenance of individual components.
2Ease of repair
If the casing upstream from the propeller is opened for maintenance, then the pivots can be accessed and maintained, but the entire oil enclosure installation needs to be rebuilt including pressurization
Solution Approach 1:
The pivot assembly is segmented into removable parts that can be accessed and maintained independently. The pitch transmission ring and other components can be removed without opening the upstream casing, allowing maintenance of single blades without disrupting the entire oil enclosure installation or requiring rebuild of pressurization systems.
3Adaptability or versatility
If two propellers with rotary drive shafts and blade pitch control systems are present, then thrust can be controlled, but access to the pivots of fan blades is greatly restricted
Solution Approach 1:
The pivot components are segmented into modular parts that can be accessed from the downstream side of the propeller assembly. The pitch transmission ring and other elements can be removed independently without requiring disassembly of the upstream propeller or its control systems, maintaining full thrust control capability while improving accessibility for maintenance.
4Reliability
If the pivot uses conventional design with all parts subjected to all forces, then the pivot can function reliably, but it requires concurrent force paths that make the pivot difficult to dismantle
Solution Approach 1:
The pivot is segmented into distinct functional parts with separate force paths: the first part handles centrifugal forces, the second part handles aerodynamic forces, and the third part manages pitch control. This segmentation maintains reliability by ensuring each part is properly designed for its specific load while making the entire assembly easier to dismantle and maintain individually.
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 pivot system effectively manages centrifugal, transverse, and bending forces, simplifies maintenance by allowing individual fan blade access without disassembling the entire propeller assembly, and facilitates the use of titanium alloys, improving durability and reducing maintenance complexity.
Implementation Method 1
an outer rolling bearing having an inside ring mounted to press transversely against the radially outer end of the force-decoupling part
Implementation Method 2
an inner rolling bearing assembled around the radially inner end of the force-decoupling part and held thereby
Implementation Method 3
a stud having, at a radially inner end, coupling means for transmitting a twisting torque
Data Source
AI summary
A pivot for an adjustable-pitch blade for a turbine engine fan hub, the pivot including a stud having coupling device for transmitting a twisting torque and an outside thread, a force-decoupling part positioned around the stud, provided with an outside thread, pressing transversely against the stud at its radially outer end, an outer rolling bearing having an inside ring mounted to press transversely against the force-decoupling part, an inner rolling bearing assembled around the force-decoupling part and held thereby, a pitch transmission ring provided with a coupling device co-operating, with the coupling device of the stud, a first clamping nut screwed onto the outside thread of the force-decoupling part in order to clamp the outer and inner rolling bearings around the fan hub, and a second clamping nut screwed onto the outside thread of the stud in order to provide clamping between the stud, the force-decoupling part, and the pitch transmission ring.