Aircraft Turbomachine Reducer Bearings With Split Oil Flow Paths
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Solution Overview
Problem
Mechanical reducers for turbomachines, particularly in aircraft, face challenges with the large axial dimension of planet gears due to high torque and centrifugal loads, leading to increased overall dimensions and high power losses from oil circulation requirements in hydrodynamic bearings.
Innovation Solution
The mechanical reducer incorporates hydrodynamic bearings with independent oil supply and evacuation pipelines, allowing precise oil management and reducing the overall dimension by optimizing oil flow and power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hydrodynamic bearings are used to support planet gears under high torque and centrifugal loads, then the load capacity is improved, but the axial dimension of the planet gears increases considerably
Solution Approach 1:
The bearing is divided into two separate hydrodynamic bearings arranged in parallel, each supporting half of the planet gear. This segmentation allows each bearing to be shorter in axial dimension while collectively supporting the full load, resolving the contradiction between load capacity and axial length.
2Strength
If the bearing length is increased to extend the full length of the planet gear, then the load capacity is improved, but the oil flow rate requirement and power losses increase
Solution Approach 1:
By segmenting the bearing into two parallel hydrodynamic bearings, each bearing can be optimized to the minimum necessary length to support its portion of the load. This reduces the total oil flow rate required and minimizes power losses while maintaining adequate load capacity.
3Volume of moving object
If the overall dimension of the reducer is reduced by placing bearings under the toothings, then the compactness is improved, but the bearings become loaded with high torque and centrifugal effects
Solution Approach 1:
The planet gear is divided into two halves, each supported by its own hydrodynamic bearing. This segmentation distributes the bearing load between two separate bearings rather than concentrating it on one long bearing, allowing the bearings to be placed under the toothings for compactness while managing the load effectively.
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 design enhances lubrication and oil evacuation efficiency, resulting in a more compact, reliable, and efficient mechanical reducer with reduced mass and power losses.
Implementation Method 1
a bearing which is carried by the planet carrier and comprises a body engaged in the planet gear and around which is located a film of oil under pressure
Implementation Method 2
The pressurised oil film is interposed between these surfaces and allows that there is no contact between these surfaces
Implementation Method 3
first pipelines for conveying oil from this cavity to at least one external cylindrical surface of the body extending around said second axis
Implementation Method 4
the centrifugal effects applied to the planet gears in the case of an epicyclic reducer
Data Source
AI summary
A mechanical reducer for a turbomachine, in particular for an aircraft, this reducer including a sun gear, a ring gear, planet gears which are meshed with the sun gear and the ring gear, hydrodynamic bearings for guiding the planet gears in rotation, these hydrodynamic bearings being carried by a planet carrier and including cylindrical bodies which include an internal oil circulation cavity and first pipelines for conveying oil from this cavity to at least one external cylindrical surface of the body, wherein each of the cylindrical bodies further includes second oil evacuation pipelines, which are different from the first pipelines, and which extend from said at least one external cylindrical surface to at least one of the longitudinal ends of that body.