Transcript Component Modes Synthesis applied to a thermal transient

Politecnico di
Torino
Component modes synthesis applied
to a thermal transient analysis
of a turbine disc
Botto, D. - Politecnico di Torino - Mechanics Department
Troncarelli, E. - MSC.Software Italia
Overview
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•
•
•
•
•
Temperature Monitoring Algorithm
Component Modes Synthesis
Integration of MSC’s and Politecnico’s Codes
Turbine disc thermal analysis
Error vs. Modal Shapes Choice
Final Remarks
Politecnico
di Torino
Temperature monitoring algorithm
• Thermal FE model development
• Reduction of the size of the problem
• Critical nodes temperature on line calculation
– Critical nodes: locations that are expected to
determine the fatigue life of the component.
• Agreement with FE solution
– Errors limited to 10 K
Politecnico
di Torino
Component modes synthesis
methodology - 1
• Full FE model
CT  KT  QTgas 
• Partitioned model
Caa


 T a  K aa K ao  Ta  Q a 
  
    Tgas 


Coo  To  Koa Koo  To  Qo 
Non-critical nodes
Politecnico
di Torino
Critical nodes
Component modes synthesis
methodology - 2
• Thanks to:
– Static reduction
– nodes eigenvector
To   Koo 1Koa Ta 
To   o ho 
Coo T o  Koo To   0
• {To} linear superposition of {Ta} and {ho}
To   Koo 1Koa Ta   o ho 
Politecnico
di Torino
Component modes synthesis
methodology - 3
• The reduced model is developed



~  T a  ~  Ta 
~
C    K    Q Tgas 
ho 
 h o 
– If all the eigenvectors {ho} are used, no reduction
is achieved
Politecnico
di Torino
Code Integration - 1
1
MSC.Patran Thermal
Generate Thermal Model
2
MSC.Patran
generate ad hoc
Nastran bdf
3
Politecnico di Torino
Code
Politecnico
di Torino
MSC.Nastran
Thermal Matrix Reduction
4
Code Integration - 2
• MSC.Patran manages Thermal Super Element
– MSC.Patran Thermal and MSC.Nastran codes
– Politecnico di Torino code
• MSC.Patran Thermal customization
– Stiffness Thermal Matrix
• Richard Haddock -MSC LA-
• Easy of Use GUI
Politecnico
di Torino
Turbine disc model
• Developed by
– Fiat Avio with MSC.Patran
• Characterised by:
– Axi-symmetry hypothesis
– triangular elements - CTRIAX
(about 6000 dof)
– Constant material properties
– Constant film coefficients
– 16 gas nodes (Input)
– 5 critical nodes (Output)
Analysis
•
Mission Profile
– Double ‘Accel-Decel’
•
Gas Temperatures
– Related to the mission
profile (input data)
•
Nodal Temperatures
– Time integration with
MSC.Thermal
Politecnico
di Torino
Model reduction
From the “complete” model (more than 6000 dof)
CT  K T  QTgas 
To the reduced model (105 dof)

 
~  T a  ~  Ta  ~
C    K    Q Tgas 
 ho 
 h o 

Why first modal shapes ?
Because they correspond to the highest decay times
Politecnico
di Torino
Error (5th critical node)
Complete vs Reduced (105 dof) Model Error
The error mainly affects
the beginning of the ramp
CMS is steeper than FEM
Null error in Steady-state
Politecnico
di Torino
2nd modal shape
Politecnico
di Torino
4th modal shape
Politecnico
di Torino
15th modal shape
Politecnico
di Torino
27th modal shape
Politecnico
di Torino
Error (5th critical node)
Complete vs Reduced (35 dof) Model Error
Politecnico
di Torino
Conclusions
• Component Modes Synthesis allows size
reduction of a FE model
– The error can be controlled
• steady-state temperatures are matched exactly
• during transient the error can be limited by adding more
modal shapes
– The method can be useful
• To Develop Monitoring Algorithms running in real time
• For faster computing allowing a larger number of
simulations
Politecnico
di Torino
Thank You
Politecnico
di Torino