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Strategy for Turbine Blade Solid Meshing Using HyperMesh Oleg Rojkov Siemens Industrial Turbomachinery AB Turbine Mechanical Integrity Department Abstract The gas turbine development process has tendency for the time shortening of the whole development cycle. The design phase takes the most of time and efforts involving several engineering disciplines in the process and passing through several iterations. The analysis of the turbine components during design phase is based on 3D models which can be rather sophisticated, like cooled blades and vanes. The FE 3D meshing process becomes the compromise between the time of model creation, the model size and the quality taking into account the specific requirements of different disciplines. The Turbine Mechanical Integrity Department in Siemens Industrial Turbomachinary AB started to use HyperMesh as the meshing tool in 2007. The experience of solid meshing in HyperMesh worked out a general approach of cooled turbine blade model creation to satisfy both time restrictions and model quality, which can be considered as the solid meshing strategy. Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Strategy for Turbine Blade Solid Meshing Using HyperMesh Contents • Gas turbine design • Cooled blade overview • CAD formats used in SIT AB Finspång for importing to HyperMesh • Requirements to the blade FE model • Geometry and FE model structure • Geometry cleaning and model meshing • Blade root • Cooling holes • Blade core • Airfoil, platform and shank • Disc • FE model modification • Additional tasks after meshing Page 2 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Gas Turbine Design SGT-800B Gas Turbine Page 3 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Gas Turbine Design Core Engine Development Compressor/Rotor Combustor Turbine Hot gas parameters Cooling air parameters Design Aerodynamics Cooled blade design process • Aero - Geometry of gas channel, 3D distribution of gas parameters • Cooling – Cooling scheme Project Team • Project leader • Aero • Cooling • Design – 3D CAD model Heat Transfer & Secondary Air System Mechanical Integrity • Design • MI – 3D meshing • MI • Cooling – Conjugated hydralic/heat transfer analysis • MI – LCF, TMF, creep, oxidation, frequency analyses Page 4 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Cooled Blade Overview Blade with Multi-channel and Matrix Page 5 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Cooled Blade Overview Blade with Multi-channel and Matrix Page 6 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Cooled Blade Overview Blade with Film cooling and Matrix Page 7 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Cooled Blade Overview Blade with Film cooling and Matrix Page 8 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. CAD Formats CAD formats used in SIT AB • NX • VDA • JT • IGES (2D models only) • Parasolid Manual control of cleanup tolerance Page 9 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. FE Mesh Requirements FE mesh requirements • 2nd order elements • Fine mesh at known critical locations • Keep fillets in blade core • Mapped mesh with quad faces in contact areas of blade attachment (recommendation from ABAQUS) • Node to node connectivity of contact areas between blade and disc (cooling group requirement) • Controllable mesh density across and along film holes • Mapped mesh in disc (preferable) • Axial symmetry of FE mesh on disc segment cuts (preferable) • The same mesh for Cooling and MI analysis (preferable) • Possibility of geometry modification Page 10 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry and FE Model Structure Partitioning the blade root Geometrical components Page 11 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Geometry cleaning • Repair collapsed surfaces • Remove cracks Release points • Suppress dummy edges • Make additional trims Stitch edges Additional trims, suppress edges Page 12 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Partitioning root for mapped and free meshing Offset lines of fir-tree contour and simplify, if needed Page 13 November 11 Trim back surface with offset contour Extrude (Drag) trimmed contour along root and mutually intersect with all front surfaces Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Partitioning root for mapped and free meshing Volume for mapped meshing Tracks of disc contact surfaces Page 14 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Finalizing volumes for mapped meshing Some additional trims and partitions Page 15 November 11 Only some trims of source surfaces for mapping Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Shell mapped meshing Switch off smoothing The main attention to contact surfaces and transition fillets • Choose mapping directions • Mesh contact surfaces and fillets with quads and all smoothing options switched off • Mesh guiding surfaces with quads to avoid mesh inconsistency between volumes Page 16 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Solid mapped meshing 4-teeth root mapped in several steps Mainly, “General” method for solid mapping was used Page 17 November 11 2-teeth root, each side mapped in one step “One volume” method for solid mapping was used Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Transition from mapped to free mesh Shell coating of mapped mesh inner side Page 18 November 11 Split quads to trias Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade root Free solid meshing • Mesh the rest of root surfaces with trias using free and R-trias methods • Check trias for free edges, quality (Jacobian and Min angle), duplicates, penetration • Repair bad trias if needed (Cleanup and Replace methods) • Mesh with tetras using “Tetra mesh” method and all trias fixed • Check tetras quality (Jacobian and Volume skew) to fit ABAQUS quality requirements • Repair bad tetras (mainly, Node edit->Align node) Page 19 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Film holes Independent control of the mesh density in axial and circular directions. • Split holes at least in 2 surfaces in axial direction to have mappable quad surfaces • Mesh holes with R-trias and all smoothing options switched off Page 20 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Blade core (inner channels) The structured mesh of the core is preferable for cooling model because of the hydraulic net attaching Mesh matrix and internal cooling holes (R-trias) Page 21 Mesh surfaces near cooling holes (R-trias) November 11 Mesh long channels (R-trias) Mesh the rest of surfaces with free trias Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Airfoil, platform and shank Shell meshing • Fillets near blade root (R-trias) • Sealing strips grooves (R-trias) • Transition fillets of airfoil (R-trias) • Shank (free or R-trias) • Surfaces with cooling holes (free mesh) • Trailing edge and airfoil (R-trias) • The rest of surfaces (free or R-trias) Page 22 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Airfoil, platform and shank Solid meshing • Check free edges for inner, outer, cooling holes and transition shells • Check shells quality and repair, if needed • Mesh with tetras using “Tetra mesh” method and all trias fixed • Check quality of tetras and repair, if needed Page 23 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Disc Partitioning 4-teeth disc for mapped meshing Tracks of blade root contact surfaces Page 24 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Disc Partitioning 2-teeth disc with air supply hole for mapped meshing Page 25 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Disc • Choose mapping directions • Partition disc taking into account axial symmetry and mesh density transitions • Mesh source mapping surfaces with any method and guiding surfaces with quads and smoothing options turned off • Mesh source surfaces of Spin volumes with any method Page 26 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Geometry Cleaning and Meshing Disc Solid mapping • Map disc attachment and transitions with General method • Map the rest with Spin method • Equivalence coincident nodes Page 27 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Model Modification Free mesh modification • Delete tetra mesh of modified component • Delete shell mesh on modified surfaces • Insert new geometry • Remesh modified surfaces and create tetra mesh Example of inserting 3 holes in platform Page 28 November 11 Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Additional Tasks Standard tasks in HyperMesh • Creating contact groups • Applying constraints or creating node sets for constraints Master surfaces of contact Page 29 November 11 Slave surfaces of contact Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM Strategy for Turbine Blade Solid Meshing Using HyperMesh. Additional Tasks Non-standard tasks solved with external tools • BIQUAD MPC or EQUATION to bind diagonal nodes in transition from tetra to mapped solids Midside node on diagonal • Two UNSORTED (“ordered” in HyperMesh) node sets for axial symmetry of disc used in EQUATION Merged nodes • 3D layer of elements for TBC (thermal barrier coating) Mesh with TBC layer Page 30 November 11 TBC thickness distribution Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved. Oleg Rojkov RCTM
