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.

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 Cranfield, 14th of July 2016

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 Cranfield, 14th of July 2016

Engine Over-speed Event Compressor reverse flow, stall, possible surge Secondary air system behaviour Turbine displacement and entanglement Decoupling Turbine rapid acceleration Cranfield, 14th of July 2016

Engine Over-speed Event – Modelling High Pressure Spool Failure Engine Over-speed Model Predict Speed of Rotor with time after shaft failure Cranfield, 14th of July 2016

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% Cranfield, 14th of July 2016

Hi Fidelity Event based Characterisation Axial displacement of shrouded rotors Modelling of Rim and Tip Seal Secondary Flows from rim seals Cranfield, 14th of July 2016

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. 73-81). 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. Cranfield, 14th of July 2016

Axial Displacement Cranfield, 14th of July 2016

Flow Path Change 0 mm 10 mm 15 mm Cranfield, 14th of July 2016

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. 457-465). 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. 435-443). American Society of Mechanical Engineers. Cranfield, 14th of July 2016

Flow Property Change Cranfield, 14th of July 2016

3D RANS Study – HP Turbine Cranfield, 14th of July 2016

3D RANS Characterisation – HP Turbine Cranfield, 14th of July 2016

Aerodynamic Analyses at different displacements Cranfield, 14th of July 2016 Grid Convergence Studies

Flow Physics Cranfield, 14th of July 2016

Flow Physics Cranfield, 14th of July 2016

Flow Physics Cranfield, 14th of July 2016

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 Cranfield, 14th of July 2016

Implementation in Model Improved accuracy in prediction with implementation of displacement characteristics Cranfield, 14th of July 2016

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 Cranfield, 14th of July 2016

Damage to Rotor Shroud tip 0 mm 10 mm 15 mm Trigger Unbalance after shaft failure Contact between Rotor Tip & Casing Cranfield, 14th of July 2016

Aerodynamic Analyses with Damaged Tip Cranfield, 14th of July 2016

Flow Physics Cranfield, 14th of July 2016

Flow Physics Cranfield, 14th of July 2016

Flow Physics Cranfield, 14th of July 2016

Change in Parameters Cranfield, 14th of July 2016

Implementation in Model Reduction in terminal speed with damaged shroud tip Cranfield, 14th of July 2016

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. Cranfield, 14th of July 2016

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 Cranfield, 14th of July 2016