1. GT2009-59108 Turbocharger: Engine Induced Excitations Kostandin Gjika Engineering& Technology Fellow Honeywell Turbo Technologies ASME TURBO EXPO 2009, Power for Land, Sea and Air Luis San Andrés Mast-Childs Professor Fellow ASME Turbocharger Nonlinear Response with Engine-Induced Excitations: Predictions and Test Data ASME Paper GT 2009-59108 Ash Maruyama Research Assistant (05-07) Texas A&M University Sherry Xia Rotordynamics Manager Honeywell Turbo Technologies Supported by Honeywell Turbocharger Technologies (HTT) Accepted for journal publication

2. GT2009-59108 Turbocharger: Engine Induced Excitations Increase internal combustion (IC) engine power output by forcing more air into cylinder Aid in producing smaller, more fuel-efficient engines with larger power outputs Turbochargers:

3. GT2009-59108 Turbocharger: Engine Induced Excitations RBS With Fully Floating Bearing RBS With Semi Floating Bearing RBS With Ball Bearing RBS: TC Rotor Bearing System(s) Desire for increased IC engine performance & efficiency leads to technologies that rely on robust & turbocharging solutions

4. GT2009-59108 Turbocharger: Engine Induced Excitations Bearing Types: Shaft Ball Bearing Squeeze Film Inner Race Locking Pin Outer Race Ball-Bearing Shaft Inner Film Outer Film Oil Feed Hole Floating Ring Locking Pin Semi-Floating Ring Bearing (SFRB) Floating Ring Bearing (FRB) Low shaft motion Relatively expensive Limited lifespan Economic Longer life span Prone to subsynchronous whirl

5. GT2009-59108 Turbocharger: Engine Induced Excitations Shaw & Nussdorfer (1949): Test results show superior performance of FRBs over plain journal bearings Tatara (1970): Initially unstable FRB-supported test rotor becomes stable at high speeds, ring speed reaches constant speed Li & Rohde (1981): Numerically show FRB-supported rotors whirl in stable limit cycles Trippett & Li (1984): Shows lubricant viscosity changes cause unusual floating-ring speed behavior, isothermal analysis is incorrect ENGINE INDUCED Vibrations: Literature Review Kirk et al. (2008): Measure shaft motions of TC on FRB attached to diesel ICE. Engine-attributed low frequency amplitudes comparable to TC subsynchronous amplitudes. Little to no insight on RBS analysis Ying et al. (2008): TC-RBS NL analysis with engine foundation excitation. Rotor response is quite complicated showing chaos at the lowest shaft speed. Little to no insight on test data

6. GT2009-59108 Turbocharger: Engine Induced Excitations TAMU-HTT VIRTUAL TOOL for Turbocharger NL Shaft Motion Predictions XLTRC 2® based with a demonstrated 70% cycle time reduction in the development of new CV TCs. Since 2006, code aids to developing PV TCs with savings up to $150k/year in qualification test time Predicted shaft motion ASME DETC2007-34136 Measured shaft motion

7. GT2009-59108 Turbocharger: Engine Induced Excitations TC linear and nonlinear rotordynamic codes – GUI based Measure ring speeds with fiber optic sensors Realistic thermohydrodynamic bearing models Novel methods to estimate imbalance distribution and shaft temperatures Literature Review: San Andres and students Tools for shaft motion prediction with effect of engine excitation needed –benchmarked by tests data 2004IMEchE J. Eng. Tribology 2005ASME J. Vibrations and Acoustics ASME DETC 2003/VIB-48418 ASME DETC 2003/VIB-48419 2007ASME J. Eng. Gas Turbines Power ASME GT 2006-90873 2007ASME J. Eng. Gas Turbines Power ASME GT 2005-68177 2007ASME J. Tribology IJTC 2006-12001 2007ASME DETC2007-34136

8. GT2009-59108 Turbocharger: Engine Induced Excitations Objectives: TAMU-HTT publications show unique -one to one- comparisons between test data and nonlinear predictions Refine rotordynamics model by including engine-induced housing excitations Deliver predictive tools validated by test data to reduce the need for costly engine test stand qualification Further understanding of complex TC behavior quantification

9. GT2009-59108 Turbocharger: Engine Induced Excitations TC rotor & bearing system 2 shaft model RBS with Semi Floating Bearing

10. GT2009-59108 Turbocharger: Engine Induced Excitations Rotor finite element model: 2 shaft model Shaft measurements (STN 3) & predictions Rotor: 6Y gram SFRB: Y gram Static gravity load distribution Compressor Side: Z Turbine Side: 5Z Compressor TurbineSFRB Thrust Collar Validate rotor model with measurem ents of free-fee modes (room Temp) C T u

11. GT2009-59108 Turbocharger: Engine Induced Excitations Free-free mode natural frequency & shapes: Measured and predicted free-free natural frequencies and mode shapes agree: rotor model validation measuredPredicted% diff KHz - First1.7991.8231.3 Second4.9384.5597.7

12. GT2009-59108 Turbocharger: Engine Induced Excitations (Semi) Floating Bearing Ring : Actual geometry (length, diameter, clearance) of inner and outer films, holes size and distribution Supply conditions: temperature & pressure Lubricant viscosity varies with temperature and shear rate (commercial oil) Side hydrostatic load due to feed pressure Temperature of casing Temperature of rotor at turbine & compressor sides derived from semi-empirical model: temperature defect model XL BRG® thermohydrodynamic fluid film bearing model predicts operating clearance and oil viscosity (inner and outer films) and eccentricities (static and dynamic) as a function of shaft & ring speeds and applied (static & dynamic) loads.

13. GT2009-59108 Turbocharger: Engine Induced Excitations –TC speed ranges from 48 krpm – 158 krpm –Engine speed ranges from 1,000 rpm – 3,600 rpm –25%, 50%, 100% of full engine load –Nominal oil feed pressure & temperature: 2 bar, 100°C Operating conditions from test data: Compressor Housing Air Inlet Engine Proximity Probes (X, Y) TC Engine Test Facility Stand

14. GT2009-59108 Turbocharger: Engine Induced Excitations (S)FRB Predictions : Peak film temperatures Supply temperature Inner film Outer film Increase in power losses (with speed) lead to raise in inner film & ring temperatures. No effect of engine load

15. GT2009-59108 Turbocharger: Engine Induced Excitations (S)FRB Predictions : Oil effective viscosity Supply Viscosity: 8.4 cP Inner film outer film LUB: SAE 15W-40 Increased film temperatures determine lower lubricant viscosities. Operation parameters independent of engine load Lubricant type : SAE 15W - 40

16. GT2009-59108 Turbocharger: Engine Induced Excitations Clearance thermal growth relative to nominal inner or outer cold radial clearance (S)FRB Predictions : Film clearances nominal clearance Inner film outer film Inner film clearance grows and outer film clearance decreases – RING grows more than SHAFT and less than CASING. Material parameters are important

17. GT2009-59108 Turbocharger: Engine Induced Excitations TC housing acceleration measurements: TC center housing and compressor housing accelerations measured with 3-axes accelerometers for three engine loads: 25%, 50%, 100% of full engine load accelerometers

18. GT2009-59108 Turbocharger: Engine Induced Excitations TC housing acceleration analysis: Δt Max Time # points in FFT Δf Max FFT freq. [μs][s]--[Hz] 2003.02,0482.442,500 Last 2,048 (out of 15,000) time data points converted to frequency spectrum via Fast Fourier Transformations (FFTs) Combined manifold & TC system natural frequencies Center Housing Comp. Housing m/s 2 100% engine load ~300 Hz ~570 Hz 1000 rpm 3600 rpm

19. GT2009-59108 Turbocharger: Engine Induced Excitations TC housing acceleration analysis: Combined manifold & TC system natural frequencies Center Housing Comp. Housing m/s 2 100% engine load ~300 Hz ~570 Hz 1000 rpm 3600 rpm 2, 4, and 6 times engine (e) main frequency contribute significantly 1e order frequency does not appear

20. GT2009-59108 Turbocharger: Engine Induced Excitations Center and compressor housings do not vibrate as a rigid body m/s 2 TC housing total acceleration 100% engine load Compressor housing Center housing

21. GT2009-59108 Turbocharger: Engine Induced Excitations Displacement transducers Displacement transducers record shaft motion relative to compressor housing Rotordynamics model outputs absolute shaft motion shaft motion relative to compressor housing needs of casing motion Integration of housing accelerations into rotordynamics model Note: TC Housing accelerations and TC shaft motions NOT recorded simultaneously

22. GT2009-59108 Turbocharger: Engine Induced Excitations Housing accelerations into model Basic assumptions –TC housings move as a rigid body –TC housing vibrations transmitted through bearing connections –Each bearing transmits identical housing vibrations

23. GT2009-59108 Turbocharger: Engine Induced Excitations Rotordynamics model Z Vector of rotor & ring displacements & rotations along (X, Y) at the DOFs of interest M, K, D, G (  ) – Matrices of rotor & ring inertias, stiffness, damping & gyroscopics at the rated rotor speed (  ) F ext(t) Imposed time varying forces acting on the rotor & ring, such as imbalances, aerodynamics, side loads F B(t) Vector of bearing reactions forces including engine vibration excitation Shaft motion (ring motion – base motion)

24. GT2009-59108 Turbocharger: Engine Induced Excitations Housing accelerations into model 0 Fourier coefficient decomposition of housing acceleration time data Double time integration Procedure: Find first 10 Fourier coefficients (amplitude and phase) of center housing acceleration and input into rotordynamics model. Run nonlinear time transient analysis and find absolute shaft motion response. Subtract compressor housing displacements to obtain shaft motion relative to compressor

25. GT2009-59108 Turbocharger: Engine Induced Excitations RBS damped natural frequencies 1 st elastic mode cyl. turb. bear. ringing mode cyl. comp. ringing mode conical mode 1X Critical speed 100% engine load

26. GT2009-59108 Turbocharger: Engine Induced Excitations RBS response to imbalance 100% engine load Differences between predictions and test data attributed to inaccurate knowledge of imbalance distribution Test data NL pred. C T u

27. GT2009-59108 Turbocharger: Engine Induced Excitations Transient time NL rotor response XL TRC 2 ® Nonlinear numerical integration of equation of motion (time- marching ) with bearing forces evaluated at each time step. Gear stiff method Component mode synthesis Post processing in frequency domain (Virtual Tools) Integration parameters CPU ~ 30’ per shaft speed ΔtMax Time # time steps Δf Max FFT freq. [μs][s]--[Hz] 78.1112,80046,400 Results (amplitudes at) compressor nose vertical direction shown relative to maximum conical motion at the compressor shaft end

28. GT2009-59108 Turbocharger: Engine Induced Excitations Housing accelerations induce broad range, low frequency shaft whirl motions Test data shows broad frequency response at low frequencies (engine speeds) Waterfalls of shaft motion at compressor end 100% engine load 1000 rpm 3600 rpm

29. GT2009-59108 Turbocharger: Engine Induced Excitations Good correlation with test data for all shaft speeds Total shaft motion at compressor end (amplitude) 100% engine load Test data NL pred. Amplitude pk-pk (-) Rotor speed (RPM)

30. GT2009-59108 Turbocharger: Engine Induced Excitations Good agreement b/w predictions and test data from 1750 – 2750 rpm Subsynchronous amplitudes vs engine speed 100% engine load Test data NL pred. Engine speed (RPM) Amplitude 0-pk (-)

31. GT2009-59108 Turbocharger: Engine Induced Excitations 2e and 4e orders engine frequency contribute the most to shaft motions 14e order is due to shaft self-excited vibration (whirl from bearings) Subsynchronous amplitudes vs engine orders 100% engine load Test data NL pred. Orders of main engine speed Amplitude 0-pk (-)

32. GT2009-59108 Turbocharger: Engine Induced Excitations System (manifold & TC) natural frequency ranges ~570 Hz ~300 Hz Subsynchronous frequency vs. rotor speed 2e frequency shown in test data and preds 4e frequency tracks rotor conical mode Subsynchronous frequencies ~ super- harmonics of conical mode 2e order freq. 4e order freq. Group 1 (0.5 C) Group 2 (2C) Group 3 (4C) Test 1X Subsynchronous frequency (Hz) Rotor speed (RPM)

33. GT2009-59108 Turbocharger: Engine Induced Excitations Subsynchronous freq. vs. IC engine speed Subsynch. freqs. are multiples of IC engine frequency Higher engine order frequencies not predicted 100% engine load Test NL Subsynchronous frequency (Hz) Engine speed (RPM) TC manifold nat freq.

34. GT2009-59108 Turbocharger: Engine Induced Excitations Engines induce significant and complex, low frequency subsynchronous whirl in turbochargers 2e and 4e order frequencies contribute significantly to housing acceleration Center housing and compressor housing do not vibrate as a single rigid body Engine super-harmonics excite TC rotor damped natural frequencies. Whirl frequencies are multiples of engine speed Conclusions Good agreement between predictions and test data validates the nonlinear rotordynamics model!

35. GT2009-59108 Turbocharger: Engine Induced Excitations Recommendations Validation against test data from different TCs is needed Housing accelerations and TC shaft motion must be recorded simultaneously and for longer periods of time (smaller frequency step size) Work completed in 2008 Understand why higher order subsynchronous frequencies are not predicted Update model to account for unequal housing excitations at each bearing location

36. GT2009-59108 Turbocharger: Engine Induced Excitations Acknowledgments Learn more at http://phn.tamu/edu/TRIBgroup Honeywell Turbocharging Technologies (2000-2008) TAMU Turbomachinery Laboratory Turbomachinery Research Consortium (XLTRC 2® ) Questions?