SAMCEF for ROTORS Chapter 3.2: Rotor modeling This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 1
Table of contents Introduction Introduction 1D Model 2D Model 3D Model 1D Models: Beam-Spring- Modeler Beam definition Springs Rotors and rotation speed Material Damping Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 2
Table of contents 2D Models: Fourier multi-harmonic Modeler Behavior: volume Fourier Rotors and rotation speed Material Assembly Damping Mesh Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 3
Table of contents 3D Models Modeler Behavior Rotors and rotation speed Material Assembly Damping Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 4
Table of contents Super-elements Introduction Rotor Damping Boundary Super-element generation Importing a rotor super-element Positioning Rotation speed and damping Parts Introduction Rotation speed This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 5
Introduction 1.Introduction 2.1D Model 3.2D Model 4.3D Model Summary Introduction 1D Model 2D Model 3D Model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 6
Introduction 1.Introduction 2.1D Model 3.2D Model 4.3D Model Introduction One or several flexible rotors can be modeled with different rotational speeds and a free orientation in space. Three kinds of rotor are available: - The 1D model: rotors are modeled using beams, springs and lumped mass elements. - The Fourier model: rotors are modeled using 2D Fourier multi-harmonic elements. - The 3-D model: quasi-axi-symmetrical rotors are described by volume elements (hexahedra, prisms or tetrahedral) or shell elements. These three can be mixed This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 7
Introduction 1.Introduction 2.1D Model 3.2D Model 4.3D Model 1D model The 1D model: rotors are modeled using beams, springs and lumped mass elements. The geometrical support: straight lines defined by edges, wires and vertices. Beam elements have circular or hollow circular cross sections for analysis in a no rotating frame elements are isotropic about the rotor axis Isotropic springs are used to model parts where the beam model is no longer valid as conical parts. Advantages/Disadvantages: This kind of model is the most classical one and is very useful in the preliminary design phase of machines such as aircraft engines, turbo-pumps, etc... but it is not always adequate for a detailed analysis of such structures. It leads to good approximations of the first eigen-frequencies and critical speeds of the system as well as of reactions at the bearings level, but it is not very convenient to obtain local information such as an accurate description of the dynamic stresses in the shaft. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 8
Introduction 1.Introduction 2.1D Model 3.2D Model 4.3D Model 2D model The Fourier model: rotors are modeled using 2D Fourier multi-harmonic elements. For rotor dynamics application, harmonics with 0 and 1 diameter are taken into account in order to describe axial deformation, torsion and bending with gyroscopic coupling The geometrical support for volume model: faces. The geometrical support for shell model: edge, wire The 2-D model has to be localized in a structural plane X-Y, Y-Z or X-Z. Advantages/Disadvantages: This model allows the development of finer of a large class of rotating equipments. It is very appropriate for the modeling of axial machines with high number of blades. It also allows a better modeling of conical shafts. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 9
Introduction 1.Introduction 2.1D Model 3.2D Model 4.3D Model 3D model The 3-D model where quasi-axi-symmetrical rotors are described by elements (hexahedra, prisms or tetrahedral) or shell elements The geometrical support for volume model: solids. Advantages/Disadvantages: Using this 3D approach, we can of course analyze general, in particular non axisymmetric, but keeping in mind that the basic assumption in SAMCEF for Rotors is precisely that the rotating system is axi-symmetric; thus, this major assumption might be more or less violated depending on the degree of axisymmetry of the structure; a disk with 60 blades for instance is almost axisymmetric so that the SAMCEF for Rotors predicted results will still be acceptable, but in case of a wind turbine rotor, made of 3 blades only, you are then pretty far away from axi-symmetric conditions and the results are to be interpreted accordingly. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 10
1D Model: Beam Spring Lumped Inertia 1.Introduction 2.1D Model 3.2D Model 4.3D Model Summary Modeler Beam definition Springs Lumped Inertia Rotors and rotating speed Material Damping Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 11
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Modeler The idealized geometry of such kind of rotor is just a straight line with different vertices. Vertices have to be defined where rotor cross sections are changing, at centers of mass of rigid disks or at boundaries of springs. The rotor axis orientation is free. The shaft line is made of one or several wires. Each wire is made of one or several edges. These geometrical entities will be used as support in order to assign data On edge of one wire modeling a shaft This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 12
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Beam definition The beam behavior is defined in the Analysis Data. For rotors, two types are allowed as the system is described in a no rotating frame: -The circle; -The closed hollowed circle. The direction is required in order to know the X element s axis orientation. The geometrical support is either a wire or an edge. (or a set of edges, wires ) This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 13
1D Models: Beam-Springs- Beam definition (2) The beam behavior Symbol 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh The final rotor model can be visualized as a solid model: (Beam aspect show) This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 14
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Springs Springs are used in a 1D model to described parts of the rotor where the beam representation is no longer adequate. The spring connects two vertices and equivalent stiffness properties have to be defined. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 15
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Springs (2) If one vertex doesn t belong to an edge or a wire but only to a point, this point is not a datum. On the other hand, if one end of the spring has to be connected to a wire or an edge, the corresponding vertex is the vertex of the wire or of the shaft. This point is not a datum Spring 1 Spring 2 This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 16
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh are used to model rigid disks. The moments of inertia are defined in a system of axes linked to the lumped inertia where the Z axis is the symmetry axis. The frame button allows the definition of the X and Y inertia axes orientation in the structural system of axes. The moment of inertia about X and Y inertia axes have to be identical. If the user selects the option rotor, the rotation speed of the lumped inertia corresponds to the rotation speed to the associated rotor and the system of axes linked to the lumped inertia is automatically computed then : -Tensor 11 and 22 of mass inertia correspond to the diametral moment of inertia -Tensor 33 correspond to the polar moment of inertia The geometrical support is a vertex. If the vertex doesn t belong to an edge or a wire but only to a point, this point is not a datum. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 17
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Rotors and rotation speed With 1D, it is better to define the rotor either immediately on the geometrical support (wires, set of edges) or at least before the definition of lumped inertia and springs. It is then possible to assign lumped inertia or springs to existing rotors. When the geometrical support is made of several edges or wires, their orientation has to be identical in order to have a correct definition of the rotor axis. The rotor is spinning in the direct manner about an axis going from the first vertex to the second vertex defining an edge or a wire of the 1D model. With 1D model, the axis of rotation is the line of the geometrical model. It is possible to explicitly define a rotor number. It is interesting when different geometrical supports define the same rotor This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 18
1D Models: Beam-Springs- Rotors and rotation speed (2) 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 19
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Rotation speed (3) In the frequency domain (critical speeds analysis, harmonic response), it is not necessary to explicitly define the rotation speed if it is equal to the sweeping frequency. If it is not the case, The rotation speed has to define as a function of the frequency. In the time domain, the rotation speed has always to be defined as a function of time. It may be constant. The function tool may be used to define rotational speed laws. Based on the kind of analysis, abscissa units are either in Hertz or time units Based on the kind of analysis, abscissa units are either in Hertz or time units This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 20
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Material It is necessary to define a material for the beams. The material is elastic. The geometrical support is the edge or the wire of the corresponding geometrical model. The software ensures the units coherency. Values are verified. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 21
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Damping Proportional damping allows introduction of dissipation in some parts of the model. It is not a material model but an equivalent one taking into account friction effect in assemblies for example. It can be unique per rotor or differ from one geometrical support to the other. In the frequency domain, viscous or hysteretic damping is available. In the time domain, only viscous damping may be defined. Proportional damping is either described when the rotor is defined or when the behavior is defined. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 22
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Damping (2) Hysteretic damping is either defined by stiffness or flexibility proportionality factor When the damping is viscous, circulatory forces are taken into account for rotors. This table summarizes the different proportional damping capabilities for 1D model rotor: Analysis Type Hysteretic Viscous Variable Viscous Critical Speed (Campbell) Algorithm Bi-iteration Harmonic Response Transient S.E. generation This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 23
1D Models: Beam-Springs- 2.Beam definition 3.Springs 4. 5.Rotors & rotation speed 6.Material 7.Damping 8.Mesh Mesh The mesh module allows the generation of the beam elements after definition of the mesh density on the geometrical supports. It is possible to check the orientation of the elements with respect to the rotor axis. Number of nodes or elements can be accessed. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 24
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Summary Modeler Behavior: volume Fourier Rotors and rotating speed Material Lumped Inertia Assembly Damping Mesh Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 25
2D Models: Fourier multi-harmonic Modeler The idealized geometry of these axi-symmetrical rotors is based on set of faces in a meridian plane. The adopted plane has to be a structural one XY, ZX or YZ. 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 26
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Modeler (2) It is necessary to split the geometry into a set of faces when material properties or damping are different. These faces have to be glued or sewed in order to obtain one opened shell. When importing external CAD description, it is necessary to clean or repair the initial geometry in order to obtain the idealized one. Imported geometry Corresponding idealized geometry This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 27
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Volume Fourier The behavior is assigned to the opened shell. When the finite element mesh is generated, it corresponds to Fourier multi harmonic elements. These elements are iso-parametric elements with several harmonics. Here, harmonics with 0 and 1 diameter are taken into account for rotor dynamics. Harmonic 6 is added in order to access to results in meridian planes located every 15 degrees. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 28
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Rotors and rotation speed It is now necessary to define the rotor axis. For example, Z if the meridian plane θ=0 corresponds to the ZY structural plane and if Z is the axis of symmetry. Regarding the rotation speed, the definition is identical as for 1D This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 29
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Material It is necessary to assign a material for the volume Fourier model. The material is elastic. The geometrical supports are faces or opened shells of the corresponding geometrical model. Orthotropic material may be defined where components 1,2,3 are the radial, axial and circumferential directions. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 30
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model are used to model rigid rotating components. For example, small blades can be assumed rigid in a lower frequency range where analysis has to be performed. This set of blades can be characterized by its total mass, diametral and polar moments of inertia about the axis of symmetry. The lumped inertia properties can be assigned to one vertex or a Fourier node near the blade location. The idealization is as follows: the Fourier node under the vertex is automatically linked to a 3D node on the axis by a junction element (FOU3 element). The displacements and rotations of these 3D nodes on the axis are the mean displacements and rotations of the annulus described by the Fourier node Graphical model Final idealize model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 31
2D Models: Fourier multi-harmonic (2) 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model If the user selects the option rotor: The idealization is activated (previous slide) The rotation speed of the lumped inertia = rotation speed to the associated rotor The system of axes linked to the lumped inertia is automatically computed : -Tensor 11 and 22 of mass inertia correspond to the diametral moment of inertia -Tensor 33 correspond to the polar moment of inertia This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 32
2D Models: Fourier multi-harmonic 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model Damping Proportional damping allows introduction of dissipation in some parts of the model. It is not a material model but an equivalent one taking into account friction effect in assemblies for example. It can be unique per rotor or differ from one geometrical support (faces, opened shell) to the other. The damping modeling capabilities for 2D Fourier model are identical to the ones available for 1D. Analysis Type Hysteretic Viscous Variable Viscous Critical Speed (Campbell) Algorithm Bi-iteration Harmonic Response Transient S.E. generation This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 33
2D Models: Fourier multi-harmonic Assembly It is possible to describe internal boundary conditions within the rotor like assemblies including sleeves or flanges. 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 34
2D Models: Fourier multi-harmonic Mesh The mesh module allows the generation of quadrangular and triangular 2D elements after definition of the mesh density on the geometrical supports 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 35
2D Models: Fourier multi-harmonic Mesh (2) This mesh can be edited. 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 36
2D Models: Fourier multi-harmonic Idealized model A final 2D rotor model based on Fourier multi harmonic elements looks like this: 2.Behavior: volume Fourier 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Assembly 8.Mesh 9.Idealized model The corresponding idealized FE model including FOU3 junction elements, lumped inertia and internal links is as follows: (Drawing obtained with the FE editor SAMCEF BACON) This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 37
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh Summary Modeler Behavior Rotors and rotating speed Material Lumped Inertia Damping Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 38
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh Modeler The idealized geometry of 3D rotors is based on set of solids or 3D faces. The whole idealized geometrical model has to be axi-symmetrical about any direction. For example, based on a 2D opened shell, it is possible to generate compound of solids of revolution. It is then possible to assign different material or damping properties to the internal solids. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 39
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh Behavior The volume behavior is either assigned to the compound of solids or per solid. When the finite element mesh is generated, it corresponds to hexahedron, tetrahedron or prismatic iso-parametric elements. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 40
3D Models Rotors and rotation speed It is necessary to define the rotor axis. Regarding the rotation speed, the definition is identical as for 1D. 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 41
3D Models Material It is also possible to store predefined materials in the Data Library and to assign them to solids. 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 42
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh are used to model rigid rotating components. For example, small blades can be assumed rigid in a lower frequency range where analysis has to be performed. This set of blades can be characterized by its total mass, diametral and polar moments of inertia about the axis of symmetry. The lumped inertia properties can be assigned to one vertex located on the axis of symmetry at the center of mass. This vertex is then linked to a circular edge (or cylinder face) of the shaft by a MEAN junction element. In order to obtain an inertia node, the corresponding vertex is not a datum. This vertex will have to be explicitly meshed. The displacements and rotations of the inertia node on the axis are the mean displacements and rotation of the nodes on the circular edge. Idealization This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 43
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh (2) The idealization process is no longer automatic as in the case of the Fourier multi harmonic model. The different steps are as follows: - Create one vertex (not a datum) located on the axis of symmetry of the set of blades - Link this vertex to a circular edge (or cylinder face) of the shaft by a mean junction element (ASSEMBLY)- This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 44
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh (3) Define the lumped mass on the vertex located on the axis. The vertex is not a datum and the point has to be meshed. The inertia is part of the same rotor as the solids. If the user selects the option rotor: The rotation speed of the lumped inertia = rotation speed to the associated rotor The system of axes linked to the lumped inertia is automatically computed : -Tensor 11 and 22 of mass inertia correspond to the diametral moment of inertia -Tensor 33 correspond to the polar moment of inertia This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 45
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh Damping Proportional damping allows introduction of dissipation in some parts of the model. It is not a material model but an equivalent one taking into account friction effect in assemblies for example. It can be unique per rotor or differ from one geometrical support (solid) to the other. The damping modeling capabilities for 3D model are identical to the ones available for 1D. Analysis Type Hysteretic Viscous Variable Viscous Critical Speed (Campbell) Algorithm Bi-iteration Harmonic Response Transient S.E. generation This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 46
3D Models 2.Behavior 3.Rotors & rotation speed 4.Material 5. 6.Damping 7.Mesh Mesh The mesh module allows the generation of hexahedron elements after definition of the mesh density on the geometrical supports if these supports are solids of revolution. It is necessary to impose the same number of layers per solid in order to obtain a continuous mesh. On the other hand, the points on the axis of symmetry supporting lumped inertia have to be meshed. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 47
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Summary Introduction Rotor Damping Boundary Super-element generation Importing a rotor super-element Positioning Rotation speed and damping This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 48
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Introduction When it is necessary to reduce the size of the rotor model, an interesting way is to generate a super-element. The reduction process is based on Craig and Bampton technique. It is first necessary to define the boundary of the super-elements. These boundaries correspond to locations where the super-element will be connected with other joints, where results are directly expected or where loads will be applied. As the reduction technique introduces approximation in the model, it is necessary to add a set of internal normal modes. These modes will improve the dynamic behavior of the reduced model in a given range of frequencies. The selected analysis type from the Analysis Driver has to be Super Element Creation. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 49
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Rotors When generating a super-element, the rotor has to be defined on the geometrical model: - Name for 1D model (rotor number is optional); - Name and rotor axis for 2D and 3D model. The rotation speed has not to be defined and it is not possible to define it. It is specified when the super-element is used. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 50
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Damping Proportional damping can be defined during super-element creation. It can be unique per rotor or differ from one geometrical support to the other. If the super-element will be used in the frequency domain, viscous or hysteretic damping is available. If it will be used in the time domain, only viscous damping has to be defined. Only constant damping is available when generating a super-element.. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 51
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Boundary: 1D Models The boundary of the super-element is defined on the geometrical model. For 1D model, boundaries correspond to retained nodes and the geometrical supports are vertices. The retained nodes are located at vertices where bearings, lumped inertia, unbalances or other boundary conditions will be applied when using the super-element. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 52
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Boundary: 2D Models, Fourier multi-harmonic The boundary of the super-element is defined on the geometrical model. But If necessary, the boundary can be defined after meshing of the rotor model and the support can be a set of Fourier nodes. For 2D Fourier, the geometrical support of the boundary either will be an edge or some vertices. It is possible to activate an idealization of the boundary when for example, an edge corresponding to a joint working length is chosen. It is possible to obtain as final boundary node, a 3D node located on the symmetry axis and linked with the Fourier model. When the Center Node option is chosen, the boundary node is one single 3D node on the axis whose displacements and rotations are the mean displacements and rotations of the Fourier nodes on the selected geometrical support, an edge in our example. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 53
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Boundary: 2D Models, Fourier multi-harmonic The Fourier nodes are linked to corresponding 3D nodes on the axis by junction elements (FOU3 elements); The 3D nodes on the axis are linked to the retained node by a MEAN element; Displacements and rotation of the retained 3D node are the mean displacements and rotation of the set of Fourier nodes on the edge; (drawing was not obtained with SAMCEF Field but using the FE editor SAMCEF BACON). This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 54
Super-elements Boundary: 3D In the 3D case, it is also possible either to choose as boundary one 3D node located at the geometrical centre of the support (geometrical entity, set of nodes) or to use the nodes attached to the support. 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 55
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Super-element generation To activate the super-element generation, the Solver module has to be chosen. It is necessary to adopt the Component Modes Condensation algorithm and to specify an upper frequency for the normal modes of the super-element. Usually, the adopted value is equal to 2 times the higher rotation speed of the system where the rotor will be integrated. The super-element contains the reduced matrices and vectors describing the rotor: -Stiffness matrix -Mass matrix -Gyroscopic matrix -Viscous or Hysteretic damping matrix -Complementary Damping - matrix (Circulatory Forces) -Unit Maneuver Loads This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 56
Super-elements Super-element generation (2) These are the results of the super-element generation. The following files describe the super-element: name.sdb and name _dy.u18 : data base and reduced matrices; the other files are needed for recovery 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 57
Super-elements Importing a Rotor super-element Super-elements are imported as specialized parts 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping It is possible to see the geometrical model of the super-element. It is mainly a datum. Only the geometrical supports used to define the super-element boundaries in the generation phase are available as supports for boundary conditions or assembly. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 58
Super-elements Positioning It is possible to apply translation and/or rotation to the super element 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping There are two systems of coordinates: one for the whole model and one for the part (here the super-element). Rotation of super-element is also available for super-element based on Fourier multi harmonic model if the boundary nodes are 3D nodes located on the axis of symmetry. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 59
Super-elements 1.Introduction 2.Rotors 3.Damping 4.Boundary 5.Super-element generation 6.Importing a rotor superelement 7.Positioning 8.Rotation speed and damping Rotation speed and damping Rotation speed After having imported a rotor super-element, the rotation speed data is available in the Data Tree. It can be edited in order to assign a rotationalspeed as well as a rotor number to the superelement. Damping If no damping matrix has been reduced when generating the super-element, it is possible to define proportional damping after import of the super-element. The damping is defined with the rotation speed. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 60
Parts 1.Introduction 2.Rotation speed Summary Introduction Rotation speed This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 61
Parts 1.Introduction 2.Rotation speed Introduction When dealing with multiple rotors systems and when the of each separate rotor are available, an interesting way is to use the part concept. The idea is to import the existing as parts and to perform the assembly. A part is an existing model with its geometry, the analysis data and the FE mesh. The parts can be used: either to gather different, or to create a repetitive model. Practically it s a.sfield file, imported in a new document as a part. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 62
Parts Introduction (2) 1.Introduction 2.Rotation speed Any imported part is gathered in a specific directory. Each imported part keeps its own data tree. On each imported part, the following operations can be performed: Copy /Paste Read only setting or unsetting Editing after activation as current part Positioning (placement, translation, rotation, mirror symmetry) Duplication A model can simultaneously be composed of parts and of geometrical objects included in the main data tree. This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 63
Parts Rotation speed After having imported a rotor as part, the rotation speed data is available in the part data tree. It can be edited in order to assign a rotational-speed as well as a rotor number to the part. 1.Introduction 2.Rotation speed This document is the property of SAMTECH S.A. MEF 101-03-2-A, Page 64