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# Component modes synthesis applied to a thermal transient analysis by alextt

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```									             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

•   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                            Critical nodes

Caa               
 Ta  K aa K ao  Ta  Q a 
               T   K         T   Q Tgas 
Coo    o   oa Koo   o   o 

Non-critical nodes

Politecnico
di Torino
Component modes synthesis
methodology - 2
• Thanks to:
– Static reduction              To   Koo 1Koa Ta 
– nodes eigenvector             To   o ho 

Coo To  Koo To   0


• {To} linear superposition of {Ta} and {ho}
To   K oo 1K oa Ta   o ho 

Politecnico
di Torino
Component modes synthesis
methodology - 3

• The reduced model is developed

                 

~  Ta  ~  Ta 
C    K    Q Tgas 
~
ho 
      ho 

– If all the eigenvectors {ho} are used, no reduction
is achieved

Politecnico
di Torino
Code Integration - 1
MSC.Patran Thermal
1       Generate Thermal Model

2
MSC.Patran
Nastran bdf

3
MSC.Nastran
Politecnico di Torino             Thermal Matrix Reduction
Code
4

Politecnico
di Torino
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

• 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
– 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)

                    


~  Ta  ~  Ta  ~
C    K    Q Tgas 
 ho 
       ho 

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

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

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