Rotordynamics in ANSYS - register.ansys.com.cnregister.ansys.com.cn/ansyschina/minisite/201411_em/motordesign... · Rotordynamics in ANSYS - Outline Introduction . ANSYS Rotordynamics

© 2011 ANSYS, Inc. June, 2012 1

Rotordynamics in ANSYS

ASME Turbo Expo 2013 Dave Looman Tech. Support Mgr.

© 2011 ANSYS, Inc. June, 2012 2

Rotordynamics in ANSYS - Outline

Introduction ANSYS Rotordynamics capabilities by analysis type Continuing Rotordynamics Enhancements Benchmark Studies & Industrial Applications Summary and Questions

Image Courtesy of Beckman Coulter, Inc.

© 2011 ANSYS, Inc. June, 2012 3

Benefits of Using ANSYS for RotorDynamics

Complete Solution in ANSYS… • CAD import and automatic meshing • Library of elements types • Analysis types - including prestress • Dedicated post-processing

Image Courtesy of Electric Machinery Co.

© 2011 ANSYS, Inc. June, 2012 4

…Benefits of Using ANSYS for RotorDynamics

Complete Solution in ANSYS… • Multi-spool dynamics simulation • 3D model of supporting structure and/or disks • Direct connection to bearing codes – ROMAC • Direct connection to other ANSYS tools

Geometry, Mesh,

Simulation, …

Optimization and Design Exploration

Tools

Parameters: Geometry, Bearing Stiffness, …

© 2011 ANSYS, Inc. June, 2012 5

Rotordynamics Analyses: Modal, Harmonic, Transient

ASME Turbo Expo 2013

© 2011 ANSYS, Inc. June, 2012 6

Modal Analysis

Orbit Plot

Mode Information Frequency Stability Damping Ratio Log Decrement

Deformed Shape Animation

Images Courtesy of Electric Machinery Co.

Specify Rotational Velocities

© 2011 ANSYS, Inc. June, 2012 7

Modal Analysis – Campbell Diagram

Critical Speed Whirl Direction Stability

© 2011 ANSYS, Inc. June, 2012 8

Modal Analysis - Log Decrement Plot

UNSTABLE

STABLE

• The logarithmic decrement plot is used to measure stability

0 Log Dec Line

Mode 3 becomes unstable

© 2011 ANSYS, Inc. June, 2012 9

• Critical Speed Map can be used to show the evolution of the critical speeds of the rotor with respect to the bearing stiffness

Modal Analysis - Critical Speed Map

Critical Speed Map generated by the CRITSPEEDMAP macro

© 2011 ANSYS, Inc. June, 2012 10

Harmonic Analysis – Unbalance Response

Centrifuge

Image Courtesy of Beckman Coulter, Inc.

Phase Angle

Amplitude

© 2011 ANSYS, Inc. June, 2012 11

Harmonic Analysis - Orbit plots

In a plane perpendicular to the spin axis, the orbit of a node is an ellipse

It is defined by three characteristics: semi axes A , B and phase ψ in a local coordinate system (x, y, z) where x is the rotation axis

Angle ϕ is the initial position of the node with respect to the major semi-axis A.

PRINT ORBITS FROM NODAL SOLUTION LOCAL y AXIS OF ORBITS IN GLOBAL COORDINATES 0.0000E+00 0.1000E+01 0.0000E+00 LOAD STEP= 1 SUBSTEP= 4 RFRQ= 0.0000 IFRQ= 2.5606 LOAD CASE= 0 ORBIT NODE A B PSI PHI ymax zmax 1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3 0.38232 0.38232 0.0000 0.0000 0.38232 0.38232 4 0.70711 0.70711 0.0000 0.0000 0.70711 0.70711 5 0.92301 0.92301 0.0000 0.0000 0.92301 0.92301

© 2011 ANSYS, Inc. June, 2012 12

Transient Analysis – Stability Verification

Unstable Orbits

Stable Orbits

© 2011 ANSYS, Inc. June, 2012 13

Rotordynamic Features Features

Campbell Diagram

Unbalance response to synchronous and asynchronous excitations

Visualize and printout the orbits characteristics

Animation

© 2011 ANSYS, Inc. June, 2012 14

Basic Features

Features

Support Line, Mass, Solid, Shell Elements

Support for Axiharmonic Element

Dedicated bearing element COMBI214

© 2011 ANSYS, Inc. June, 2012 15

Dedicated Bearing Element

Element Description Characteristics cross terms

Nonlinear characteristics

COMBIN14 Uniaxial spring/damper None None

COMBI214 2D spring/damper Unsymmetric Function of Ω and Eccentricity

MATRIX27 General stiffness and damping matrices

Unsymmetric None

MPC184 Multipoint constraint Symmetric for linear, none for nonlinear

Function of the displacement

Sample COMBI214 Table Input *DIM,KYY,TABLE,3,1,1,OMEGS KYY(1,0) = OMEGA1,OMEGA2,OMEGA3

KYY(1,1) = KYY1 , KYY2 , KYY3

R,1, %KYY%

© 2011 ANSYS, Inc. June, 2012 16

Interface to THPAD

IMPORTBEARING.MAC supplied by ANSYS imports bearing data for use with COMBI214

ANSYS Bearing Element COMBI214

ASCII file generated by ROMAC Tilt Pad Bearing program

© 2011 ANSYS, Inc. June, 2012 17

Recent Enhancements -

Campbell Diagram in WB Mechanical at 14.0

© 2011 ANSYS, Inc. June, 2012 18

Recent Enhancements

Rotordynamics Solver Controls in WB Mechanical at 14.0

Import Shaft Geometry from text file in WB DM at 14.0

© 2011 ANSYS, Inc. June, 2012 19

Recent Enhancements

Support for Bearings in WB Mechanical at 14.5

© 2011 ANSYS, Inc. June, 2012 20

Recent Enhancements – Bearing Stiffness and Damping as a function of Eccentricity at 14.0

Transient Analysis of a 3 disk Rotor • Bearing stiffness and damping defined as a function of eccentricity

• Rotational velocity ramped from zero

© 2011 ANSYS, Inc. June, 2012 21

15.0 Enhancement – CMS of Rotor

QA Test of Full Rotor vs Partial CMS Rotor

© 2011 ANSYS, Inc. June, 2012 22

Industrial Applications and Benchmark Study

ASME Turbo Expo 2013

© 2011 ANSYS, Inc. June, 2012 23

ROMAC Benchmark – Tilt Pad Bearings

Eight Stage Centrifugal Compressor used for natural gas re-injection

Tilt Pad Bearings with dynamic coefficients

© 2011 ANSYS, Inc. June, 2012 24

ROMAC Benchmark Description

Shaft: - Total length: 2.81m - 35 stations (nodes) - 34 beams - 35 point masses

- 15 masses with rotary inertia - 20 masses with no rotary inertia

Bearings: - Tilting pad bearings - Velocity dependent stiffness and

damping

Analyses done: - Critical speed map computation - Unbalanced responses on 1st and 2nd bending modes

© 2011 ANSYS, Inc. June, 2012 25

Benchmark Results – Critical Speed Map

Critical speed map: • Critical speed versus bearing stiffness (no damping or cross terms)

© 2011 ANSYS, Inc. June, 2012 26

Benchmark Results – Unbalanced Response

Unbalanced response First bending mode - Unbalanced magnitude = 2.44E-03 N.m - Load applied on station 17

Second bending mode - Unbalanced magnitude = 2.44E-03 N.m - Load applied on station 11 and 24 with 180° phase

© 2011 ANSYS, Inc. June, 2012 27

ROMAC Benchmark - Squeeze film damping

Shaft: Material standard steel 25 nodes and 24 elements l = 0.0254 m each, axis length L = 0.6096 m d = 0.0508 m Disks: d = 0.0508 m Thickness = 0.0508 m at stations 10, 13 and 16 Bearings: Phase 1: Constant Symmetric Properties Kxx = Kyy = 1.7512E+07 N/m Cxx = Cyy = 1.7512E+02 N/m Cxy = Cyx = Kxy = Kyx = 0 Phase 2: Velocity and eccentricity dependent stiffness and damping Kxy = 3.503E+05 N/m = q (Aerodynamic cross-coupling) Kyx = - Kxy Cxx = Cyy = Cxy1 = Cyx1 = 0

© 2011 ANSYS, Inc. June, 2012 28

Benchmark Phase 1 Results

Campbell Diagram (ANSYS) Campbell Diagram (ROMAC)

© 2011 ANSYS, Inc. June, 2012 29

Centrifugal Compressor Shaft for a Chiller

Free-Free Testing Apparatus at Trane

Courtesy of Trane, a business of American Standard, Inc.

3D model with Mass of attachments

© 2011 ANSYS, Inc. June, 2012 30

Shell Support Structure with Rotor Components

Courtesy of Trane, a business of American Standard, Inc.

© 2011 ANSYS, Inc. June, 2012 31

Chiller Structure Modeled with CMS SuperElement

Courtesy of Trane, a business of American Standard, Inc.

CMS Superelement

Finite Element Model of Rotor and Impellers

© 2011 ANSYS, Inc. June, 2012 32

Rotordynamics Analysis Guide

© 2011 ANSYS, Inc. June, 2012 33

Technology Demonstration Guide

© 2011 ANSYS, Inc. June, 2012 34

Verification Manual

Verification Tests

VM247

© 2011 ANSYS, Inc. June, 2012 35

Summary

Key Features: – CAD import and automatic meshing – Library of elements types

– BEAM, SHELL, SOLID, COMBI214 – Analysis types - including prestress

– modal, harmonic, transient – Dedicated post-processing – Multi-spool dynamics simulation – Direct connection to bearing codes - ROMAC – Rotordynamics Guide – Account for flexibility of supporting structure and/or the disks – Continuing enhancements – Connect directly to other ANSYS tools via Workbench platform

– DesignXplorer, nCode DesignLife, etc. – Easy to use!

Image Courtesy of Electric Machinery Co.

© 2011 ANSYS, Inc. June, 2012 36

Faster, more complete and accurate machine analysis…

with ANSYS

ASME Turbo Expo 2013