Central Planetary Gearset for Turbojet Fan Rotation
Solution Overview
Problem
Existing turbojet fan rotation systems face issues with bulk, weight, and accessibility during maintenance due to the conventional placement of reduction gears, which also fail to effectively absorb the forces generated by the fan's rotation.
Innovation Solution
A planetary gearset reduction gear system is positioned at the center of the fan, with a central sun gear connected to the low-pressure shaft, a satellite for rotation movement transmission, and an outer planet gear directly attaching the fan blades, allowing for reduced bulk and weight while simplifying maintenance access and force absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the reduction gear is placed below the inlet casing in the conventional position, then the fan can be driven in rotation, but the system has considerable bulk and weight and does not allow easy accessibility during maintenance operations
Solution Approach 1:
The reduction gear is inverted from its conventional position below the inlet casing to a central position within the fan structure. This inversion places the reduction gear at the geometric center of the fan, surrounded by the fan blades rather than positioned externally, thereby reducing overall system bulk and improving accessibility from all directions during maintenance operations.
Solution Approach 2:
The reduction gear structure is merged with the fan structure by positioning the outer planet gear as a central hub to which the fan blades are directly attached. This merging eliminates the need for separate mounting structures and reduces the overall bulk and weight of the system while maintaining functional independence of the reduction gear.
2Productivity
If a planetary gearset is used in the conventional configuration, then rotation transmission is achieved, but the system has considerable bulk and does not allow simple and rapid access to the reduction gear assembly
Solution Approach 1:
The planetary gearset is reconfigured by inverting the position of the outer planet gear from an external ring gear to a central hub structure. This inversion maintains the rotation transmission function while dramatically reducing the radial bulk of the system and allowing maintenance personnel to access the reduction gear assembly from all directions without disassembling surrounding components.
Solution Approach 2:
The reduction gear assembly is repositioned from a peripheral arrangement to a central three-dimensional configuration within the fan structure. This dimensional change allows the satellite carrier and planets to be arranged around the central sun gear in a compact configuration that reduces overall bulk while maintaining efficient rotation transmission.
3Power
If the reduction gear is positioned externally to the fan, then the fan can be driven, but the system does not allow absorption of the considerable forces generated by the rotation of the fan
Solution Approach 1:
The outer planet gear is merged with the fan hub structure, creating a unified load-bearing assembly. The fan blades are directly attached to the outer planet gear, which serves as the central hub. This merging allows the reduction gear structure itself to absorb and distribute the considerable centrifugal forces generated by fan rotation, rather than requiring separate external mounting structures.
Solution Approach 2:
The reduction gear structure is pre-configured with the outer planet gear as a central hub designed to withstand centrifugal forces before the fan blades are attached. This preliminary structural preparation ensures that the force absorption capability is built into the reduction gear design itself, allowing it to handle the loads generated during operation without requiring additional reinforcement.
4Ease of manufacture
If the outer planet gear is designed as a separate component, then assembly is simplified, but the system has considerable bulk and does not allow force absorption
Solution Approach 1:
The outer planet gear is merged with the fan hub to create a unified load-bearing structure. This merging reduces the number of separate components and connections required, simplifying assembly while simultaneously reducing the overall bulk and weight of the system. The unified structure also provides inherent force absorption capability.
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 configuration reduces the system's bulk and weight, enhances resistance to centrifugal forces, and facilitates easier maintenance by positioning the reduction gear centrally and allowing direct blade attachment to the outer planet gear, improving accessibility and mechanical resilience.
Implementation Method 1
a planetary gearset which is situated in the center of the fan and which comprises: a central sun gear; an outer planet gear attached to the fan; at least one satellite arranged between the central sun gear and the outer planet gear for a transmission of a rotation movement between the central sun gear and the outer planet gear
Implementation Method 2
the outer planet gear comprising, on the one hand, an internal portion which meshes with the satellite, and on the other hand an external portion to which are directly attached the blades of the fan
Data Source
AI summary
The invention relates to a system for rotating a fan (2) of a turbojet engine (1) about a first rotation axis Ω, including a reduction gear (3) made up of a planetary gearset placed at the centre of the fan (2), which includes: a central sun gear (31); an outer planet gear (33) attached to the fan (2); at least one satellite gear (32) arranged between the central sun gear (31) and the outer planet gear (33) in order to transmit a rotary movement between the central sun gear (31) and the outer planet gear (33); characterised in that the outer planet gear (33) includes an inner portion (33a) which meshes with the satellite gear (32), as well as an outer portion (33b) to which blades (21) of the fan (2) are directly attached.