Variable-Pitch Fan Module Axial Trunnion Bearing Layout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fan modules with variable-pitch blades face challenges in managing radial and axial dimensions, leading to increased mass and dynamic inefficiencies due to the arrangement of pitch change systems, speed reducers, and bearings, which results in higher loads and vibrations.
Innovation Solution
A fan module design with a planetary gear reduction system, where the first bearing is upstream and the second bearing is downstream of the speed reducer, and an annular pin connects the fan rotor to the lubrication enclosure, allowing for reduced axial and radial dimensions, improved dynamic behavior, and efficient integration of the pitch change system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pitch control system, speed reducer, and bearings are arranged within the annular housing, then the fan module structure is integrated, but the radial and axial dimensions increase leading to increased mass
Solution Approach 1:
The patent relocates the pitch control system from the radial annular housing to the axial direction by extending the trunnion axially upstream. This dimensional reorganization allows the control system to be positioned in the axial space above the rotor rather than consuming radial housing space, thereby reducing both radial and axial dimensions while maintaining structural integration.
2Device complexity
If the pitch control system and bearings are positioned within the annular housing, then the components are compactly arranged, but the cantilever mass on bearings increases leading to worse dynamic performance
Solution Approach 1:
The patent extracts the pitch control system from the traditional annular housing arrangement and relocates it to an axial position upstream of the rotor. This separation removes the control system mass from the rotating assembly, reducing the cantilever mass on the bearings and improving dynamic performance while maintaining compact component arrangement.
3Productivity
If the fan rotor diameter is increased to achieve lower compression ratio, then propulsive efficiency improves, but the operational constraints on fan blades between ground and flight conditions increase
Solution Approach 1:
The patent implements variable-pitch capability on large-diameter fan blades, allowing the blade angle to be dynamically adjusted between ground and flight operating conditions. This dynamic adaptation enables the blades to optimize performance across the full operating range despite the increased diameter and associated operational constraints.
4Speed
If the bending deformation mode frequency shifts towards lower frequencies closer to maximum fan speed, then the natural frequency changes, but dynamic loads and clearance consumption increase
Solution Approach 1:
The patent addresses the harmful effect of reduced bending mode frequency by reducing the cantilever mass through strategic component relocation. This mass reduction increases the natural frequency of the bending mode, creating a beneficial frequency separation from the maximum operating speed and thereby reducing dynamic loads and clearance consumption.
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a fan module (3) comprising variable-pitch blades, said fan module (3) including: a fan rotor (20) bearing the blades (23) of the fan (4, 400a, 400b), each mounted to pivot about a pitch axis (A); a fan shaft (21) extending along a longitudinal axis X inside the fan rotor and driving the fan rotor in rotation; a power shaft (11) driving the fan shaft in rotation by means of a planetary gear speed reducer (50); at least a first and a second bearing (69, 71) for guiding the rotation of the fan rotor, housed inside a lubrication chamber (60); and a system (32) for varying the pitch of the fan blades, comprising a connecting mechanism (33) connected to the blades of the fan and a control means (34) acting on the connecting mechanism (33). According to the invention, the first bearing (69) is disposed upstream of the speed reducer (50) and the second bearing (71) is disposed downstream of the speed reducer (50), the fan rotor (20) being connected to the fan shaft (21) by means of an annular trunnion (59) extending at least along an upstream portion of the lubrication chamber (60).