40 numerical simulation of blade casing rub interaction · numerical simulation of blade / casing...

European Workshop on New Aero Engine ConceptsMunich, 30 June – 1 July 2010

Numerical simulation of blade / casing rub interaction

NEWAC is an Integrated Project Co-funded by the European Commission within the Sixth Framework Programme(2002-2006) under Thematic Priority 4 Aeronautics and Space.

Olivier Beaupain, Techspace-AeroPP Jeunechamps, JP Ponthot University of Liège, Belgium


Partners involved

•University of Liège, LTAS-MN²L Aerospace & Mechanical Engineering department, Belgium •Techspace-Aero (WP leader), Belgium• Snecma, Villaroche, France• Sulzer METCO, Zurich, Switzerland


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Technical approach : Overview

• Original numerical wear method• Validation of wear method on Sulzer rub test• Finite element simulation of a blisk test


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Original numerical wear method : framework

• Framework to numerically describe wear process:

No new global Degrees Of Freedom into the system

Focus on the blade/casing geometrical interaction (not on the local abradable behavior)


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abradable behavior)

Define a wear profile on the contact tool (constant during any time step)

Use of constant wear profile to compute contact forces and achieve iterative equilibrium

Update wear at the end of the step (post processing operation)

⇒ Increase of CPU cost remains under control


Original numerical wear method : Definition of wear surface

Abradable contact surface feature:- Must consist of 1 or several contact surfaces- Contact surface limited by a 4-lines wire- Contact surface can be a plane, a ruled surface, a


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- Contact surface can be a plane, a ruled surface, a Coons, a revolution surface…

Meshed abradable contact surface

4 lines wire


Original numerical wear method: definition of wear surface

Meshing of contact side:Transfinite meshWear cells = Quads (bilinear Coons)

Wear points:ξ, η in side isoparametric spaceInitial and final wear stored at each wear point

Contact side for wear

Blade topWear cell


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wear pointCorrection of penetration of blade in abradable (≡ Gap) by interpolation inside each wear cellGeometrical wear law used:

newWear = α(gap - oldWear)α = wear parameter to be identifiedgap = penetration of blade in abradable, function of contact pressure.

eta

ksi

Meshed contact side in isoparametric space

Wear point

Wear cell


Original numerical wear method : Detection of wearedpoints

• Detecting all active contact nodes at times tand t+∆t )

• Searching for every active “blade contact Edge” (edge of blade FEM mesh for which nodes are in contact at time t and t+ ∆t).

X,Y,Z space


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• Defining a “wear quad” including all wear points to be weared between t and t+ ∆t

•For each wear point:• Compute if wear point is inside the wear quad• Compute local coordinate (ksi,eta) in wear quad space• Evaluate gap by bilinear interpolation• Update wear

eta

ksi

Blade edge at t Blade edge at t+ ∆t

Wear isoparametric space


Original numerical wear method : Simple pin test application


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Validation on Sulzer rub test : Description of test

• Experimental data:• Rotation Speed : 3800RPM corresponding to tip speed of 200m/s• Incursion rate : 0.05mm/s• Incursion depth: 1mm

• Numerical model:


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• Numerical model:• 2268 finite elements• Elastic-plastic model for blade behavior• Wear model parameters:

Penalty factor PFriction coefficient µWear parameter α

• CPU cost: between 1 and 2 days for 100 revolutions


Validation on Sulzer rub test : correlation test

• Contact periodicity:• Experimental: essentially contact at every revolution (sometimes after 2 revolution)• Finite element: contact at every revolution (bright

Experimental Finite element


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every revolution (bright blue lines correspond to top tours)

• Blade vibration modes OK

1st mode 2rd mode 3th mode 4th mode

Experimental 200Hz 900Hz 1150Hz 2300Hz

Finite element 250Hz 850Hz 1200Hz 1900Hz


Validation on Sulzer rub test : onset of divergence for some wear parameters values, change in frequency modes

2 revolutionsbefore divergence

Beginningof divergence


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Divergence 2 revolutionsafter divergence

New frequenciesappear

Important bending of blade


• 56 blades• 13000 volumic elements• Overlength blade:

– 25 elements along height– 22 elements along width– 2 elements along thickness

• Other blades:

Simulation of blisk test Overlength blade


• Other blades:– 8 elements along height– 11 elements along width– 2 elements along thickness

• Blisk imposed rotation at the some nodes• Initial unbalancing by applying a concentrated

mass of 29.4g.cm• Incompatible mesh between blades and blisk ⇒

sticking contact considered (tied interface)• Casing geometry: Revolution surface

01/04/2010P.P. Jeunechamps, J.P. Ponthot, LTAS-MN²L, ULg

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Imposed displacement

Initial unbalance


y (mm) z (mm) Orientation (°)

SG1 208.7 21.2 90

SG2 222.7 17.3 -45

SG3 217.3 10.0 90

SG4 216.3 26.6 45

y

Simulation of blisk test : Strain gauges position


Leading edgeTrailing edge

SG2

SG1

SG2

SG1

SG2

SG1

SG4

SG3

Trailing edgeLeading edge

01/04/2010 13P.P. Jeunechamps, J.P. Ponthot, LTAS-MN²L, ULg


Simulation of blisk test : Evolution of wear footprint


01/04/2010P.P. Jeunechamps, J.P. Ponthot, LTAS-MN²L, ULg

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Simulation of blisk test : Evolution of contact forces between overlength blade and casing ⇒⇒⇒⇒ irregular contact forces (bright blue lines corresponding to top tours)


250 contact revolutions

750 contact revolutions 1000 contact revolutions500 contact revolutions

Full signal



Conclusions and future work

• New numerical model able to accurately describe blade / casing interaction and able to describe the onset of divergence

• Wear model: only one simple wear model is implemented (geometry based). More sophisticated material models for abradable can be implemented but these models require relevant physical experiments to identify wear constitutive model parameters



• Blisk test:– No onset of periodic wear footprint due to the perfect circular casing

geometry ⇒ insert elliptic casing or initial wear of abradable material– To be correlated with future experimental test

• CPU cost to be improved, even if wear computation cost remains low with respect to blisk computation

40 numerical simulation of blade casing rub interaction · numerical simulation of blade / casing...

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