Rotordynamics in ANSYS 1 ASME Turbo Expo 2013 Dave Looman Tech. Support Mgr.
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. 2
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. 3
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, Parameters: Geometry, Bearing Stiffness, Optimization and Design Exploration Tools 4
Rotordynamics Analyses: Modal, Harmonic, Transient ASME Turbo Expo 2013 5
Modal Analysis Deformed Shape Animation Specify Rotational Velocities Images Courtesy of Electric Machinery Co. Orbit Plot Mode Information Frequency Stability Damping Ratio Log Decrement 6
Modal Analysis Campbell Diagram Critical Speed Whirl Direction Stability 7
Modal Analysis - Log Decrement Plot The logarithmic decrement plot is used to measure stability 0 Log Dec Line UNSTABLE STABLE Mode 3 becomes unstable 8
Modal Analysis - Critical Speed Map Critical Speed Map can be used to show the evolution of the critical speeds of the rotor with respect to the bearing stiffness Critical Speed Map generated by the CRITSPEEDMAP macro 9
Harmonic Analysis Unbalance Response Amplitude Phase Angle Centrifuge Image Courtesy of Beckman Coulter, Inc. 10
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 11
Transient Analysis Stability Verification Unstable Orbits Stable Orbits 12
Rotordynamic Features Features Campbell Diagram Unbalance response to synchronous and asynchronous excitations Visualize and printout the orbits characteristics Animation 13
Basic Features Features Support Line, Mass, Solid, Shell Elements Support for Axiharmonic Element Dedicated bearing element COMBI214 14
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% 15
Interface to THPAD ASCII file generated by ROMAC Tilt Pad Bearing program IMPORTBEARING.MAC supplied by ANSYS imports bearing data for use with COMBI214 16 ANSYS Bearing Element COMBI214
Recent Enhancements - Campbell Diagram in WB Mechanical at 14.0 17
Recent Enhancements Rotordynamics Solver Controls in WB Mechanical at 14.0 Import Shaft Geometry from text file in WB DM at 14.0 18
Recent Enhancements Support for Bearings in WB Mechanical at 14.5 19
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 20
15.0 Enhancement CMS of Rotor QA Test of Full Rotor vs Partial CMS Rotor 21
Industrial Applications and Benchmark Study ASME Turbo Expo 2013 22
ROMAC Benchmark Tilt Pad Bearings Eight Stage Centrifugal Compressor used for natural gas re-injection Tilt Pad Bearings with dynamic coefficients 23
ROMAC Benchmark Description Bearings: - Tilting pad bearings - Velocity dependent stiffness and damping Shaft: - Total length: 2.81m - 35 stations (nodes) - 34 beams - 35 point masses - 15 masses with rotary inertia - 20 masses with no rotary inertia Analyses done: - Critical speed map computation - Unbalanced responses on 1 st and 2 nd bending modes 24
Benchmark Results Critical Speed Map Critical speed map: Critical speed versus bearing stiffness (no damping or cross terms) 25
Benchmark Results Unbalanced Response First bending mode - Unbalanced magnitude = 2.44E-03 N.m - Load applied on station 17 Unbalanced response Second bending mode - Unbalanced magnitude = 2.44E-03 N.m - Load applied on station 11 and 24 with 180 phase 26
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 27
Benchmark Phase 1 Results Campbell Diagram (ANSYS) Campbell Diagram (ROMAC) 28
Centrifugal Compressor Shaft for a Chiller Free-Free Testing Apparatus at Trane 3D model with Mass of attachments Courtesy of Trane, a business of American Standard, Inc. 29
Shell Support Structure with Rotor Components 30 Courtesy of Trane, a business of American Standard, Inc.
Chiller Structure Modeled with CMS SuperElement Finite Element Model of Rotor and Impellers CMS Superelement Courtesy of Trane, a business of American Standard, Inc. 31
Rotordynamics Analysis Guide 32
Technology Demonstration Guide 33
Verification Manual VM247 34 Verification Tests
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 Image Courtesy of Electric Rotordynamics Guide Machinery Co. 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! 35
Faster, more complete and accurate machine analysis with ANSYS ASME Turbo Expo 2013 36