Angled Oil Feed in Planetary Gearbox Friction Bearings

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Solution Overview

Problem

Friction bearings in gas turbine engines experience high thermal deformations and inefficient lubrication due to limited oil availability and high operating temperatures, leading to reduced load-bearing capability and increased power losses.

Innovation Solution

A friction bearing design for planetary gearboxes with an oil feed system that directs lubricant at an angle to minimize lateral proliferation and maximize centric delivery to the tightest lubrication clearance, utilizing the Coanda effect to displace hot oil with fresh lubricant, ensuring improved viscosity and load-bearing capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If high volumetric oil flows are supplied to the friction bearing, then the cooling and lubrication effect is improved, but the power losses and fuel consumption increase

Engineering Contradiction:

Improvebearing temperatureVSAvoidpower losses

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent applies local quality by directing oil flow specifically to the tightest lubrication clearance where it is most needed, rather than uniformly distributing oil throughout the bearing. The oil feed pocket is positioned to deliver lubricant precisely to the region of highest temperature and friction, improving cooling efficiency while minimizing overall oil consumption and associated power losses.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs preliminary action by pre-positioning the oil feed pocket and feed lines to deliver lubricant before the oil reaches its least effective position. The oil is directed into the bearing clearance at an optimized location and angle, ensuring that fresh, cool oil reaches the tightest clearance region first, maximizing its cooling and lubricating effect before the oil becomes heated and less effective.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If oil is directed radially into the bearing clearance, then the lubrication is simplified, but the oil spreads laterally and does not reach the tightest lubrication clearance effectively

Engineering Contradiction:

Improvelubrication system complexityVSAvoidlubrication effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies asymmetry by positioning the oil feed pocket and feed lines asymmetrically within the bearing structure, rather than using a symmetric radial arrangement. The feed line is directed at a specific angle relative to the bearing axis to target the tightest lubrication clearance, creating an asymmetric flow pattern that improves oil delivery effectiveness to the critical region while maintaining reasonable system complexity.

Inventive Principle:

Principle #4Asymmetry

3Strength

If the bearing clearance is made tighter to increase load-bearing capability, then the lubrication efficiency improves, but the oil becomes significantly heated by shear friction

Engineering Contradiction:

Improveload-bearing capabilityVSAvoidoil temperature

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent employs preliminary action by introducing fresh, cool oil into the tightest lubrication clearance before the oil undergoes significant heating from shear friction. The strategically positioned oil feed pocket ensures that new lubricant reaches the high-shear region continuously, replacing heated oil before it can degrade the lubrication film and bearing performance.

Inventive Principle:

Principle #10Preliminary action

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 enhances the load-bearing capability of friction bearings by maintaining lower temperatures and improved lubrication, reducing power losses and the need for high volumetric oil flows, thus optimizing the lubrication system and reducing fuel consumption.

Implementation Method 1

The fed lubricant is exploited to be transported in a targeted manner into the bearing clearance that converges as a function of the loading in the circumferential direction by the Coanda effect

Methodology Applied

Scientific EffectCoanda effect: Coanda Effect

Implementation Method 2

The lubricant in the region of the tightest lubrication clearance is significantly heated by the shear friction prevalent there

Methodology Applied

Scientific EffectViscous heating: Viscous Heating

Data Source

PatentUS12188519B2Friction bearing, and method for lubricating and cooling a friction bearing

Publication Date: 2025.01.07 ROLLS ROYCE DEUT LTD & CO KG

AI summary

A friction bearing of a planetary gearbox, has first and second rotatably connected components. Oil adjacent an oil feed pocket of the first component is directed into the bearing clearance between the components. The oil is directed into the pocket by a first line that opens into the pocket. The profile of the line conjointly with the radial direction of the bearing clearance encloses an angle to direct the oil from the line into the oil feed pocket, the angle being approximately 5°-60° to the radial direction of the bearing clearance and in the main rotation direction of the second component in relation to the first component, or at an angle of approximately 5°-20° to the radial direction of the bearing clearance and in the circumferential direction of the bearing clearance and counter to the main rotation direction of the second component to the first component.