1. Turbine Over-speed Aerodynamics
David John R
Academic Supervisor: V. Pachidis
Industrial Supervisor: S. Brown, A. Rowe
RAeS Annual Lecture Competition, Cranfield, 14th July 2016
©2016 Cranfield University, School of Aerospace, Transport & Manufacturing, Propulsion Engineering Centre The information presented here is the property of the Cranfield University Rolls-Royce UTC in Gas Turbine Performance Engineering and may not be copied or communicated
to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Cranfield University and Rolls-Royce plc.

2. Overview Engine Over-speed Event Turbine Behaviour
Hi-fidelity, Event based Characterization
Methodology
Axial Displacement & Secondary Air System
Damage to Rotor Shroud tip as design modification
Flow Physics
Implementation in Model
Conclusion
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3. Shaft Over-speed Failure [1]
Engine Over-speed Event
Qantas A380 Flight 32 – 4th November 2010
Shaft Over-speed Failure [1]
[1] ATSB Report dated June 2013 on Qantas Flight 32 Incident on November 2010
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4. Engine Over-speed Event
Compressor reverse flow, stall, possible surge
Secondary air system behaviour
Turbine displacement and entanglement
Decoupling
Turbine rapid acceleration
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5. Engine Over-speed Event – Modelling
High Pressure Spool Failure Engine Over-speed Model
Predict Speed of Rotor with time after shaft failure
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6. f Turbine Solver in Over-speed model HP Rotor airfoil Torque
HP Turbine Mass Flow Function
IP Turbine Mass Flow Function f
Speed function
Pressure Ratio
Typically carried out for clean configuration
Scaling factors used for tip clearance - ~ 1%
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7. Hi Fidelity Event based Characterisation
Axial displacement of shrouded rotors
Modelling of Rim and Tip Seal
Secondary Flows from rim seals
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8. Axial Displacement Thermo-mechanical Friction model Contact and Wear
Developed from non-linear structural dynamic analyses
[2] Psarra, A., Pachidis, V. and Pilidis, P., 2009, January. Finite Element Turbine Blade Tangling Modelling Following a Shaft Failure. In ASME Turbo Expo 2009: Power for Land, Sea, and Air (pp ). American Society of Mechanical Engineers.
[3] Gonzalez, A. and Pachidis, V., 2014, June. On the Numerical Simulation of Turbine Blade Tangling After a Shaft Failure. In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition (pp. V07BT33A026-V07BT33A026). American Society of Mechanical Engineers.
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9. Axial Displacement
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10. Flow Path Change
0 mm
10 mm
15 mm
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11. SAS network Validated Transient Model Sinks, Sources, Links
Heat transfer effects
Validated Transient Model
Sinks, Sources, Links
[4] Gallar, L., Calcagni, C., Pachidis, V. and Pilidis, P., 2009, January. Development of a One-Dimensional Dynamic Gas Turbine Secondary Air System Model—Part I: Tool Components Development and Validation. In ASME Turbo Expo 2009: Power for Land, Sea, and Air (pp ). American Society of Mechanical Engineers.
[5] Calcagni, C., Gallar, L. and Pachidis, V., 2009, January. Development of a One-Dimensional Dynamic Gas Turbine Secondary Air System Model—Part II: Assembly and Validation of a Complete Network. In ASME Turbo Expo 2009: Power for Land, Sea, and Air (pp ). American Society of Mechanical Engineers.
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12. Flow Property Change
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13. 3D RANS Study – HP Turbine
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14. 3D RANS Characterisation – HP Turbine
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15. Aerodynamic Analyses at different displacements
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Grid Convergence Studies

16. Flow Physics
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17. Flow Physics
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18. Flow Physics
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19. Change in Parameters Cranfield, 14th of July 2016
[6] L Pawsey, D John, V Pachidis, 2016, June. Turbine Overspeed- On the Aerodynamic Performance of an Unlocated HP Turbine Rotor. Manuscript submitted to XXIII International Symposium on Air Breathing Engines, Manchester, England
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20. Implementation in Model
Improved accuracy in prediction with implementation of displacement characteristics
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21. Engine Over-speed Event – Modelling
Certification
EASA – ‘Hazardous Engine Effects’ – Free Running Turbine Over-speed
Acceptable Means of Compliance E 850
Analyses based in service / test experience
Certification Memorandum – More reliable Analytical Models to predict shaft failure event
[6] L Pawsey, D John, V Pachidis, 2016, June. Turbine Overspeed- On the Aerodynamic Performance of an Unlocated HP Turbine Rotor. Manuscript submitted to XXIII International Symposium on Air Breathing Engines, Manchester, England
[7] Certification specifications for engines CS-E - Amendment 3. Technical report, European Aviation Safety Agency, 2010
[8] Certification memorandum - turbine over-speed resulting from shaft failure. Technical report, European Aviation Safety Agency, 2012
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22. Damage to Rotor Shroud tip
0 mm
10 mm
15 mm
Trigger Unbalance after shaft failure
Contact between Rotor Tip & Casing
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23. Aerodynamic Analyses with Damaged Tip
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24. Flow Physics
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25. Flow Physics
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26. Flow Physics
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27. Change in Parameters
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28. Implementation in Model
Reduction in terminal speed with damaged shroud tip
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29. Engine Over-speed Event – Modelling
Design of Turbine Rotor Sub-assemblies
Over-speed and Burst margins
Sizing of Rotor Disks
Reduction in Overall Weight of System
Improved T/W ratio and Specific Fuel Consumption
[9] L Pawsey, D John, V Pachidis, 2016, July. Turbine Overspeed- On the Aerodynamic Performance of an Unlocated HP Turbine Rotor with Worn Seals. Manuscript under review.
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30. Conclusion
Integrated Structural, Secondary Air System and Aerodynamic Methodology
Hi-Fidelity Event based Characterisation of Turbines
Greatly improved accuracy in terminal speed prediction - Ease of certification
Use of analyses methodology to explore design variants to reduce terminal speed of rotor - Carry over benefits to design
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