Turbomachine Rotor Flange Adhesion via Surface Roughness and Coating

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Solution Overview

Problem

Turbomachine rotor parts experience excessive stress and reduced lifetime due to relative slip movements between flanges, leading to increased weight and stress when trying to enhance clamping force, which is not always feasible due to space and material constraints.

Innovation Solution

A method involving milling of bearing faces to modify surface roughness and coating with a thin, hard, high-friction material to increase adhesion between rotor parts, primarily using a ceramic titanium nitride layer to enhance frictional torque transmission and reduce shear stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the clamping force of the nuts is increased to reduce relative slip movements between flanges, then the adhesion between flanges is improved, but the weight of the rotor increases significantly

Engineering Contradiction:

Improveadhesion between flangesVSAvoidweight of the rotor

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The invention changes the surface parameters of the flange faces by machining them with a specific roughness profile (crests and furrows) and coating them with a hard material layer. This modifies the friction characteristics at the interface, allowing high adhesion with lower clamping forces, thereby avoiding the need to increase bolt size or number which would increase rotor weight.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention applies a hard coating material specifically to the bearing surfaces of the flanges, creating a localized region with enhanced friction and wear resistance. This local modification of surface properties increases the coefficient of friction at the critical interface without requiring global reinforcement of the entire rotor structure, thus avoiding weight increase.

Inventive Principle:

Principle #3Local quality

2Reliability

If the number or diameter of bolts is increased to enhance clamping force, then the adhesion between flanges is improved, but the stresses in the disks increase due to closer orifices and greater centrifugal forces

Engineering Contradiction:

Improveadhesion between flangesVSAvoidstresses in the disks

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

By changing the surface roughness and material properties of the flange faces through machining and coating, the invention increases the coefficient of friction at the interface. This allows the same adhesion force to be achieved with lower clamping forces, reducing the load on bolts and the stress concentration around orifices in the disks.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If sand-blasting is used to increase roughness of bearing faces, then the coefficient of friction is improved, but the roughness cannot be well controlled and is not protected under compression

Engineering Contradiction:

Improvecoefficient of frictionVSAvoidcontrol of roughness morphology

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention uses controlled machining processes (milling or turning) to create a specific roughness profile with defined crests and furrows, rather than random roughness from sand-blasting. This provides precise control over the surface morphology. Additionally, a hard coating is applied to protect this controlled roughness structure from being flattened or damaged under compression and friction during operation.

Inventive Principle:

Principle #35Parameter changes

4Power

If the clamping force is increased to transmit torque by friction, then the torque transmission is improved, but the device complexity increases

Engineering Contradiction:

Improvetorque transmissionVSAvoidcomplexity of fastening system

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The invention modifies the surface parameters of the flange faces (roughness and material hardness) to increase the coefficient of friction. This allows effective torque transmission by friction without requiring increased clamping force, thereby avoiding the need for larger or more numerous bolts and keeping the fastening system simple.

Inventive Principle:

Principle #35Parameter changes

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 method effectively doubles the coefficient of friction between rotor parts, extending their lifetime by 1.3 times, allowing for a reduction in the number of bolts or their size, thereby reducing weight and stress without increasing the rotor's overall weight or stress.

Implementation Method 1

coating the or each machined face in a thin layer of a material that is hard and that has a high coefficient of friction

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The thin film may be deposited on the machined face by chemical gas or vapor deposition

Methodology Applied

Scientific EffectChemical Vapour Deposition: Chemical Vapour Deposition

Data Source

PatentUS8881395B2Method for increasing the coefficient of adhesion between two parts rotating as one with a rotor

Publication Date: 2014.11.11 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A method for increasing the coefficient of adhesion between two parts that rotate as one with a rotor, for example a turbomachine rotor, those parts pressing against one another via pressing faces. The method includes milling at least one of the pressing faces so as to modify its surface finish and increase its roughness, then covering the or each machined face with a thin layer of a material that is hard and has a high coefficient of friction.