Component modes synthesis applied to a thermal transient analysis

							             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
                                          generate ad hoc
                                          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
          • 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)

                                   
                    
                         
                ~  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

                              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