rotor dynamics v14 open days feb 2012
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ansysTRANSCRIPT
© 2011 ANSYS, Inc. February 22, 20121
ANSYS Release 14.0Rotordynamics
Steve Varnam
ANSYS UK
© 2011 ANSYS, Inc. February 22, 20122
There is a wide range of Dynamics capabilities available within the ANSYS Structural Mechanics product portfolio:
ANSYS Dynamics
Nonlinear Transient
DynamicsModal Harmonic Response
Modal Superposition
Linear Transient
DynamicSpectrum Harmonic Response
Response Spectrum Random Vibration
Rigid Body Dynamics Flexible Dynamics
Dynamics capabilities - review
© 2011 ANSYS, Inc. February 22, 20123
Modal and Harmonic many releases ago
Full Transient 11.0
Random Vibration 11.0
Response Spectrum 12.0
Harmonic mode-sup linked to modal 13.0
Perturbation Method 13.0
Mode-sup Transient 14.0
Rotordynamics 14.0
Recent Analysis Type Migration to WB Mechanical
© 2011 ANSYS, Inc. February 22, 20124
Dynamics in WB Mechanical
11.0
Full transient 11.0
14.0
12.013.0
© 2011 ANSYS, Inc. February 22, 20125
Different licence levels support different capabilities
ANSYS Dynamics
Nonlinear Transient
Dynamics
(ST+)
Modal
(DS+)
Harmonic Response
(ST+)
Modal Superposition
Linear Transient
Dynamic (PR+)Spectrum
Harmonic Response
(PR+)
Response Spectrum
(PR+)
Random Vibration
(ST+)
Rigid Body Dynamics
(Standalone)
Flexible Dynamics
(ST+)
Dynamics capabilities – Licence levels
© 2011 ANSYS, Inc. February 22, 20126
• Rotordynamics analysis requires a licence level of Structural or above.
Rotor Dynamics – Licence Level
© 2011 ANSYS, Inc. February 22, 20127
Rotordynamics - Motivation
ANSYS Mechanical users need to be able to quickly create shaft geometriesas well as analyze dynamic characteristics of rotating systems
Industrial fan (Venti Oelde)
© 2011 ANSYS, Inc. February 22, 20128
Background
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•The general equation of motion in matrix form is:
•Different analysis types solve different forms of this equation:
– Modal analysis: F(t) is set to zero, and [C] is usually ignored.
– Harmonic Response analysis: F(t) and u(t) are both assumed to be harmonic in nature, i.e, X sin(wt), where X is the amplitude and w is the frequency in radians/sec.
– Flexible Dynamic analysis: The complete, general form of the equation is solved.
© 2011 ANSYS, Inc. February 22, 20129
Background
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• For Rotor Dynamics, this equation becomes:
•Where the additional terms are:
– G : The gyroscopic matrix, which depends on the rotational velocity (or velocities) of the analysis model.
– B : The rotating damping matrix, also depends upon the rotational velocities. It modifies the apparant stiffness of the model and can produce unstable motion.
© 2011 ANSYS, Inc. February 22, 201210
Background
Typical applications include:
• High speed machinery such as turbine engine rotors, computer disk drives, etc.
• Seals - very small rotor-stator clearances
• Flexible bearing supports
• Rotor Instability
Rotordynamics analysis aims at:
• Finding Critical Speeds (Campbell diagrams)
• Calculating unbalance response
• Calculating response to base excitation
• Predicting Rotor Whirl and system stability
• Simulating transient start-up and shutdown
© 2011 ANSYS, Inc. February 22, 201211
Structural Elements for Rotordynamics
Element Type Detail
Structural Mass MASS21
3D Beam BEAM188BEAM189
3D Pipe PIPE288PIPE289
Structural Shell SHELL181SHELL281
3D Structural SolidSOLID185SOLID186SOLID187
General Axisymmetric Solid SOLID272SOLID273Elements supporting Coriolis
© 2011 ANSYS, Inc. February 22, 201212
Bearing Modeling
Specific Bearing Element
Bearing element choice depends on:• Shape (1D, 2D, 3D)• Cross terms• Nonlinearities
© 2011 ANSYS, Inc. February 22, 201213
Modal Analysis
Orbit Plot
Complex Frequency Printout
Specify the rotational velocity and activate
the Coriolis effect
Deformed Shape
Animation
© 2011 ANSYS, Inc. February 22, 201214
Modal Analysis – Campbell
Set up a Multiple Load Step Modal Analysis
Frequencies - Whirls - Stability
Critical Speeds
Logarithmic Decrement
© 2011 ANSYS, Inc. February 22, 201215
Harmonic Analysis – Unbalance Response
Specify the Unbalance Force on Inner Spool
Orbit PlotUnbalance Response
© 2011 ANSYS, Inc. February 22, 201216
Transient Analysis 1
Start-up and Stop Simulation
Transient Response
Specify the RotationalVelocity/Time History
© 2011 ANSYS, Inc. February 22, 201217
Transient Analysis 2
Stability Verification
Transient Orbits
Specify a Short Duration Force
© 2011 ANSYS, Inc. February 22, 201218
Documentation - Verification Manual
Verification Tests
VM247
© 2011 ANSYS, Inc. February 22, 201219
Rotordynamics Analysis Guide
Analysis Guide specific to Rotordynamics
© 2011 ANSYS, Inc. February 22, 201220
Technology Demonstration Guide
© 2011 ANSYS, Inc. February 22, 201221
Workbench Implementation – new at v14
• Geometry creation in Design Modeler
• Analyze dynamic characteristics of rotating systems with the effects of damping, Coriolis and different rotational velocities
• Identify Critical Speeds with Campbell Plots
• Supported for solid and line bodies
© 2011 ANSYS, Inc. February 22, 201222
Geometry Creation
Geometries can be imported from a CAD system or imported from a simple text file definition as used in preliminary design
© 2011 ANSYS, Inc. February 22, 201223
Modal Analysis Enhancement
Turn on damping
DampedUndamped
No damping
Added solvers
DampingControls
© 2011 ANSYS, Inc. February 22, 201224
Damped Modal Analysis (cont)
Note the output table is in engineering terms(damped frequency, stability, etc.), not mathematical ones(real/imaginary eigenvalue)
© 2011 ANSYS, Inc. February 22, 201225
Animation with Decay
Toggle to turn on/off time decay during animation for damped modal analysis
Control the number of cycles to visualize the effects of decay
© 2011 ANSYS, Inc. February 22, 201226
Rotational velocity with Coriolis effect
Rotational velocity enabled in Modal analysis
Option to turn on Coriolis Effect
© 2011 ANSYS, Inc. February 22, 201227
Campbell Diagram
Basic setup for Campbell Diagram- Tabular Rotational velocity- Damped solve- Turn on Coriolis Effect- Turn on Campbell Diagram- Minimum 2 solve points
Specify rotational velocity for the number of points
© 2011 ANSYS, Inc. February 22, 201228
Campbell Diagram (cont)
© 2011 ANSYS, Inc. February 22, 201229
Campbell Diagram (cont)
© 2011 ANSYS, Inc. February 22, 201230
Fast Critical Speed Map
The new APDL Math feature extends the APDL scripting environment of Mechanical APDL:
• extraction of data from ANSYS files (FULL, EMAT, MODE, and SUB)
• powerful matrix/vectors manipulation routines
• direct access to solvers
• Speed up dependant upon number of rotational velocity steps required to identify critical speeds.
In a Rotordynamics analysis, APDL Math can be used to obtain the critical speed map directly
© 2011 ANSYS, Inc. February 22, 201231
Fast Critical Speed Map
APDL Math script – see CRITICALSPEEDMM.MAC
0][ 2 MK w 0GjMM with
*SMAT, K, D, IMPORT, FULL, file.full, STIFF*SMAT, M, D, IMPORT, FULL, file.full, MASS*SMAT, G0, D, IMPORT, FULL, file.full, DAMP
*SMAT, zMG0, Z, COPY, M*AXPY,, alpha, G0, 1,, zMG0*SMAT, zK, Z, COPY, K
/SOLUANTYPE, MODALMODOPT, UNSYM, 6*EIGEN, zK, zMG0,, EiV, EiMFINI
loo
p o
n b
ear
ing
stif
fne
ss
Solve
© 2011 ANSYS, Inc. February 22, 201232
Import/Export of Bearing Characteristics
ANSYS provides an interface that allows to import bearing characteristics from an external file – see IMPORTBEARING.MAC
© 2011 ANSYS, Inc. February 22, 201233
Industrial Applications
ANSYS Rotordynamics
© 2011 ANSYS, Inc. February 22, 201234
Industrial Application #1:Centrifugal Compressor
Two Tilting Pad Bearings with dynamic coefficients
Eight Stage Centrifugal Compressorused for natural gas re-injection at an
offshore drilling site
© 2011 ANSYS, Inc. February 22, 201235
Industrial Application #1:Centrifugal Compressor
Tilting Pad Bearing: 5 identical pads Analyzed with THPAD (ROMAC)
Macro ImportBearing.mac
ET, 1, COMBI214R, 1, %KYY%, %KZZ%, %KYZ%, %KZY%, %CYY%, %CZZ% RMORE, %CYZ%, %CZY%
© 2011 ANSYS, Inc. February 22, 201236
Industrial Application #1:Centrifugal Compressor
Campbell Diagram: Bearings with Variable Characteristics
(undamped)
© 2011 ANSYS, Inc. February 22, 201237
Industrial Application #1:Centrifugal Compressor
Unbalance Response – Bearings with Variable Characteristics (damped)
Configuration 1
Configuration 2
unbalance 3.4 oz.in @ 0 deg
unbalance 3.4 oz.in @ 0 deg
unbalance 3.4 oz.in @ 180 deg
© 2011 ANSYS, Inc. February 22, 201238
Industrial Application #2:Chiller
Free-Free Testing Apparatus used for initial model calibration
Courtesy of Trane, a business of
American Standard, Inc.
Centrifugal Compressor Shaft for a Chiller
© 2011 ANSYS, Inc. February 22, 201239
Industrial Application #2:Chiller
Courtesy of Trane, a business of American Standard, Inc.
Solid Model of Compressor Shaft plus Chiller Assembly in ANSYS
Workbench
© 2011 ANSYS, Inc. February 22, 201240
Industrial Application #2:Chiller
Housing and entire
chiller assembly
represented by a CMS
superelement
Finite element model of
rotor and impellers
Courtesy of Trane, a business of American Standard, Inc.
CMS SuperelementRepresentation
© 2011 ANSYS, Inc. February 22, 201241
Industrial Application #2:Chiller
Impeller
Bearing
locations
Outline of CMS
superelement
Courtesy of Trane, a business of American Standard, Inc.
Chiller Assembly Details
© 2011 ANSYS, Inc. February 22, 201242
Industrial Application #2:Chiller
Courtesy of Trane, a business of American Standard, Inc.
Chiller Shaft Assembly Modes
Deformed ShapeShaft + CMS Supporting Structure
© 2011 ANSYS, Inc. February 22, 201243
Industrial Application #3:Hard Disk Drive
ANSYS 4 disk modelDisk thickness = 0.8mm
Total mass = 87.5gSpin = 755 rd/s7855 elements
3 disks HDD sketch
© 2011 ANSYS, Inc. February 22, 201244
Industrial Application #3:Hard Disk Drive
Campbell Diagram for 1 disk
© 2011 ANSYS, Inc. February 22, 201245
Summary
The previous slides have described the elements of completerotordynamics analysis, with ANSYS
Key enabling features:– CAD import and automatic meshing– Library of elements– All analysis types (including prestress)– Dedicated post-processing– Multi-spool dynamics simulation– Direct connection to bearing codes– Account for the flexibility of the
supporting structure and/or the disks– Connect directly to other ANSYS tools via
Workbench (Design Explorer)
© 2011 ANSYS, Inc. February 22, 201246
Questions?