Strategy for Turbine Blade Solid Meshing Using HyperMesh

Copyright © Siemens Industrial Turbomachinery AB 2007. All rights reserved.

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.

November 11


RCTM Oleg Rojkov

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

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RCTM Oleg Rojkov


HyperMesh. Gas Turbine Design

SGT-800B Gas Turbine

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RCTM Oleg Rojkov


HyperMesh. Gas Turbine Design

Compressor/Rotor Combustor Turbine

Core Engine Development

Design

Aerodynamics

Heat Transfer &

Secondary Air System

Mechanical Integrity

Hot gas parameters

Cooling air parameters

Project Team

• Project leader

• Aero

• Cooling

• Design

• MI

• Aero - Geometry of gas channel, 3D

distribution of gas parameters

• Cooling – Cooling scheme

• Design – 3D CAD model

• MI – 3D meshing

• Cooling – Conjugated hydralic/heat

transfer analysis

• MI – LCF, TMF, creep, oxidation,

frequency analyses

Cooled blade design process

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RCTM Oleg Rojkov


HyperMesh. Cooled Blade Overview

Blade with Multi-channel and Matrix

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HyperMesh. Cooled Blade Overview

Blade with Film cooling and Matrix

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HyperMesh. CAD Formats

CAD formats used in SIT AB

•NX

•VDA

•JT

• IGES (2D models only)

•Parasolid

Manual control of

cleanup tolerance

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RCTM Oleg Rojkov


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

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RCTM Oleg Rojkov


HyperMesh. Geometry and FE Model Structure

Partitioning the blade root

Geometrical components

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RCTM Oleg Rojkov


HyperMesh. Geometry Cleaning and Meshing

Geometry cleaning

•Repair collapsed surfaces

•Remove cracks

•Suppress dummy edges

•Make additional trims

Release points

Stitch edges

Additional trims,

suppress edges

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RCTM Oleg Rojkov



Partitioning root for mapped and free meshing

Offset lines of fir-tree contour

and simplify, if needed

Blade root

Trim back surface with

offset contour

Extrude (Drag) trimmed contour along root

and mutually intersect with all front surfaces

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RCTM Oleg Rojkov



Blade root

Volume for mapped meshing Tracks of disc contact surfaces

Partitioning root for mapped and free meshing

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RCTM Oleg Rojkov



Blade root

Finalizing volumes for mapped meshing

Some additional trims and partitions Only some trims of source surfaces for mapping

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RCTM Oleg Rojkov



Blade root

Shell mapped meshing

• 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

Switch off smoothing

The main attention to contact surfaces

and transition fillets

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RCTM Oleg Rojkov



Blade root

Solid mapped meshing

4-teeth root mapped in several steps 2-teeth root, each side mapped in one step

Mainly, “General” method for solid

mapping was used

“One volume” method for solid

mapping was used

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Blade root

Transition from mapped to free mesh

Shell coating of mapped mesh inner side Split quads to trias

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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)

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RCTM Oleg Rojkov



Film holes

• 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

Independent control of the mesh density in axial and

circular directions.

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RCTM Oleg Rojkov



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)

Mesh surfaces near cooling

holes (R-trias)

Mesh long channels

(R-trias)

Mesh the rest of

surfaces with free trias

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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)

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RCTM Oleg Rojkov



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

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Disc Partitioning 4-teeth disc for mapped meshing

Tracks of blade root

contact surfaces

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Disc Partitioning 2-teeth disc with air supply hole for mapped meshing

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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

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Disc

Solid mapping

• Map disc attachment and

transitions with General method

• Map the rest with Spin method

• Equivalence coincident nodes

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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

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HyperMesh. Additional Tasks

Standard tasks in HyperMesh

• Creating contact groups

• Applying constraints or creating

node sets for constraints

Master surfaces of contact Slave surfaces of contact

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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

• Two UNSORTED (“ordered” in

HyperMesh) node sets for axial

symmetry of disc used in EQUATION

• 3D layer of elements for TBC (thermal

barrier coating)

Merged nodes

Midside node on diagonal

Mesh with TBC layer TBC thickness distribution

Strategy for Turbine Blade Solid Meshing Using HyperMesh

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