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1 Luis San Andrés Mast-Childs Professor, Fellow ASME Texas A&M University On the Effect of Thermal Energy Transport to the Performance of (Semi) Floating.

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Presentation on theme: "1 Luis San Andrés Mast-Childs Professor, Fellow ASME Texas A&M University On the Effect of Thermal Energy Transport to the Performance of (Semi) Floating."— Presentation transcript:

1 1 Luis San Andrés Mast-Childs Professor, Fellow ASME Texas A&M University On the Effect of Thermal Energy Transport to the Performance of (Semi) Floating Ring Bearing Systems for Automotive Turbochargers ASME Turbo Expo 2012 June 11-15, 2012, Copenhagen, Denmark Accepted for journal publication GT

2 2 Authors Supported by Honeywell Turbocharger Technologies (HTT) Thermal Energy Transport to the Performance of (Semi) Floating Ring Bearing Systems for Automotive Turbochargers Vince Barbarie Avijit Bhattacharya Kostandin Gjika Honeywell Turbo Technologies Torrance, CA Honeywell Turbo Technologies, Thaon-les-Vosges, France Luis San Andrés Turbomachinery Laboratory Texas A&M University GT

3 3 Fully Floating Bearing Semi Floating Bearing Ball Bearing Types of bearing supports Increased IC engine performance & efficiency demands of robust turbocharging solutions The driver: Oil lubricated bearings are economic with longer life span; but prone to harmful subsynchronous whirl & depend on engine oil condition. Low shaft motion, expensive, limited lifespan

4 4 Major challenges extreme operating conditions: - Low Oil Viscosity, e.g. 0W30 or 0W20 - High Oil Temperature (up to 150°C) - Low HTHS (2.9); Low Oil Pressure (1 bar), - Increased Max. Turbocharger Speed 5 kHZ - Variable Geometry Turbo Technology & Assisted e-power start up - High Engine Vibration Level - More Stringent Noise Requirements Need predictive too to reduce costly engine test stand qualification Thermal management & reduce thermal loading

5 5 TC linear and nonlinear rotordynamic codes – GUI based – including engine induced excitations Realistic bearing models: thermohydrodynamic Novel methods to estimate imbalance distribution and shaft temperatures NL analysis for frequency jumps (internal & combined resonances) and noise reduction Measured ring speeds with fiber optic sensors Literature Review: TAMU work Predictive tool for shaft motion benchmarked by test data 2004IMEchE J. Eng. Tribology 2005ASME J. Vibrations and Acoustics ASME DETC 2003/VIB ASME DETC 2003/VIB ASME J. Eng. Gas Turbines Power ASME GT ASME J. Eng. Gas Turbines Power ASME GT ASME J. Tribology IJTC ASME DETC ASME J. Eng. Gas Turbines Power ASME GT IFToMM Korea

6 6 VIRTUAL TOOL for TC NL shaft motions Tool demonstrated 70% cycle time reduction in the development of new CV TCs. Since 2006, code aids to develop PV TCs with savings up to $1 XX k/year in qualification test time ASME DETC Predicted shaft motionMeasured shaft motion TC testing is expensive and time consuming Predictive tool saves time and resources

7 7 Thermal energy analysis in TCs complicated b/c of a)Hot gas -work and heat flow from turbine b)Cold gas +work and heat flow from the compressor c)internal heat flow across shaft from T to C and radially thru bearings d)Mechanical drag power in bearings e)Heat flow to/from casing to ambient (convective and radiant) Conjugate heat transfer in TCs Engine lubricated bearings: (a) low friction-load support (b) oil carries away heat (cooling)

8 8 turbine compressor Heat flows & energy transfer in a TC Hot air (energy) in -Hot air (energy) out Heat conducted (casing) Heat conducted (shaft) Cold air (energy) in Compressed hot air (energy) out Heat conducted (casing) Bearing drag power generation Oil in Oil out Baines, N., Wygnant, K., Dris, A., 2010, J Eng Gas Turb. Power, Heat conducted (casing) work

9 9 a)Lumped parameter models with empirical formulas for heat transfer coefficients and simplified formulas for drag power, flow & heat flow in the lubricated bearings b)Current 3D modeling stresses on solids with over-simplified coupling to the lubricant flows Thermal energy analyses in TCs use avoid oil coking, optimize flow rates, ensure proper clearances, eliminate seizure. Engineered thermal management to avoid severe thermal loading with improved reliability of bearing system: GOAL

10 10 SFRB system in engine-oil lubricated TC turbine compressor Semi- floating ring bearing Compressor side bearing oil supply holes to inner and outer films Oil supply holes to inner film Turbine side bearing Outer film with ½ moon groove Oil supply at P sup, T sup Anti-rotation pin shaft casing Oil discharges at ambient pressure P a Lubricant flow paths into bearings on turbine and compressor sides

11 11 Definitions: X,Y: fixed (inertial) coordinate system g : direction of gravity  Circumferential coordinate  X g Ring rotation RR 0º Oil supply hole D Ro DBDB Y Z LoLo outer film shaft Ring Casing Y ½ moon groove LGLG Shaft rotation  inner film LiLi Shaft Z : axial coordinate L o : axial length of outer film L i : axial length of outer film L G : axial length of ½ moon groove D Ro : Ring outer diameter D Ri : Ring inner diameter D J : Shaft (journal) diameter D B : Bearing casing inner diameter D B -D Ro : outer film diametral clearance D Ro -D J : inner film diametral clearance D Ri DJDJ Geometry & coordinate system for typical SFRB

12 12 Kinematics of journal and ring Nomenclature:  : journal rotational speed  R: ring rotational speed  Circumferential (angular) coordinate c o : radial clearance outer film c i : radial clearance inner film h o : outer film thickness h i : inner film thickness e R X, e R Y : Ring center eccentricity components e X, e Y : Shaft (journal) center eccentricity components e J X, e J Y : Eccentricity of journal relative to ring X Y OROR eReR eJeJ e   RR ring journal ring rotation Journal rotation Inner film thickness = e eReR eJeJ + Outer film thickness

13 13 Shaft, T S Casing, T C Ring, T R(r) Inner film, T i( ,z) Outer film, T o( ,z)  RR T Ri T Ro TRMTRM RoRo RiRi RMRM P i,T i P o,T o TSTS TCTC Oil inlet, P sup, T sup Feed hole Inlet ½ moon groove z RsRs RcRc P A, ambient pressure PAPA z Axial view of inner and outer films: nomenclature

14 14 Hydrodynamic pressure generation Nomenclature P : film pressure h : film thickness  : viscosity, fn ( T ) Major assumptions : Laminar flow without fluid inertia effects Average viscosity across film thickness Inner film Outer film  journal rotational speed  R ring rotational speed  circumferential coordinate Z axial coordinate R J : Shaft (journal) radius R B : Bearing casing inner diameter Reynolds equations for inner & outer films TRMTRM R ing P i,T i P o,T o TSTS Casing T C shaft

15 15 shaft Ring TSTS casing Outer film Inner film T Ri T Ro TCTC TiTi ToTo Heat flow from shaft Mechanical drag power Heat flow into ring Mechanical drag power Heat flow into casing Flow outer Flow inner Heat flow carried by oil Heat flows & power in a FRB 

16 16 Nomenclature T i: inner film temperature T J, T Ri : shaft (journal) and ring ID temperatures h J, h Ri : heat convection coefficients with circ. and axial mass flow rates: Inner film mechanical energy dissipation: Thermal energy transport in inner film TRMTRM P i,T i P o,T o TSTS Casing T C shaft

17 17 TRMTRM P i,T i P o,T o TSTS Casing T C shaft Thermal energy transport in outer film Nomenclature T o : outer film temperature T B, T Ro : bearing casing and ring OD temperatures h B, h Ro : heat convection coefficients with circ. and axial mass flow rates: Outer film mechanical energy dissipation:

18 18 Heat conduction in semi-floating ring Nomenclature T R: ring temperature T J, T Ri : shaft (journal) and ring ID temperatures h J, h Ri : heat convection coefficients k R : ring material conductivity q R : heat flow Major assumptions : Steady state, no heat flow in axial direction, No effect of ring rotation r 

19 19 Heat conduction in semi-floating ring Major simplification Radial heat conduction only r  TRMTRM R ing P i,T i P o,T o TSTS Casing T C shaft Nomenclature T R: ring temperature Q R : radial heat flow k R : ring material conductivity

20 20 1Reynolds/Colburn Analogy), Nu=3 Pr Kays and Crawford - constant wall temperature, Nu =7.54 3Kays and Crawford - constant wall heat flux, Nu =8.22 4Haussen - thermally developing constant wall temperature, Nu > Shah - thermally developing constant wall heat flux, Nu > Stephan - Simultaneous developing, constant wall temp, Nu >3.66 7Stephan - Simultaneous developing constant wall heat flux, Nu > Heat flow: Q = h A (T S – T i ) A: wetted area for heat transfer h: heat convection coefficient, a function of Nusselt #, oil conductivity and hydraulic diameter (=clearance). Nusselt # =depends on flow conditions (Prandtl # and Reynolds #) TiTi TsTs Heat convection Models

21 21 Numerical method of solution a)Finite element method for Reynolds Eqns. b) Control volume method for energy transport Eqns. Includes balance of drag torques, material properties f(T), bearing clearance changes due to temperature rise, etc.

22 22 Example Semi FRB for PV turbine bearing Oil: SAE 5W C 213C Shaft (journal) RING CASING Oil inlet Bearing dimensions Inner FilmOuter film Diameter mm length mm Cold clearance7.535  m

23 23 Meshes for inner and outer flow domains X =132 º Y Z Casing ½ moon groove Feed hole x 4 groove journal ring 132 o ½ moon groove Circ. groove Oil supply hole (4x) Axial groove (4 x) Mesh: outer film Mesh: inner film N EX =45, N EY =12 N EX =52, N EY =12  z z Engineered design to improve flow delivery and reduce temperature rise

24 24 (b) Temperature field (C)  z (a) Pressure field (bar)  z T sup =120C T S =213C 240 krpm Feed hole & axial groove Predictions for inner film at Oil heats quickly along axial plane

25 25 Temperatures: maximum in films Shaft Temp inner film outer film exit mixed films Inner film temperature shaft T (< flash T). Outer film relatively cold.

26 26 Temperatures: average in films Inner film much hotter than outer film. Exit mixing lubricant temperature nearly constant > 90 krpm Shaft Temp inner film outer film exit mixed films

27 27 Ring Temperatures: ID, OD and mean Large radial temperature gradient across ring. OD-ID Temperature difference ~ 40 o C. RING material conductivity is important. Shaft Temp (mean radius) RingID RingOD

28 28 Oil viscosity (average): inner & outer films outer film inner film Relative to supply: Inner film viscosity decreases because of increase in film temperature (> T sup ) Thermal effects can not be ignored

29 29 Oil flow rates: inner & outer outer film inner film Flow=1 = out+in Oil flow is minimum at top speed. Outer/inner flow decreases/increa ses because of clearance shrinks/grows + lower oil viscosity

30 30 Heat flows and drag power Low speeds: heat from shaft dominates. High speeds: drag power losses increase. For all conditions lubricant carries more energy that casing soaks. Heat from shaft Drag power (inner film) Heat to lubricant Heat to casing Heat to ring + + =1=

31 31 Width of boxes denotes intensity of heat flows Thermal energy transport and balance Heat from shaft 100% Heat to casing Heat to fluid (i+o) Heat to fluid (i) Heat to fluid (o) Heat to ring 97% 3% 36 % 27 % 74 % 10 % 64 % low speed (45 krpm) Drag Power (inner & outer) Lubricant carries away heat from shaft mainly.

32 32 Width of boxes denotes intensity of heat flows Thermal energy transport and balance Heat from shaft 100% Heat to casing Heat to fluid (i+o) Heat to fluid (i) Heat to fluid (o) Heat to ring 65% 35% 24 % 17 % 83 % 8 % 76 % high speed (240 krpm) Drag Power (inner & outer) Drag power losses increase. Lubricant carries away largest portion of heat flow.

33 33 30 krpm 240 krpm Heat from shaft (W) Inlet plane Exit plane High power low power Low heat flow High heat flow Exit plane Drag power (W) Drag power and heat from shaft Drag power and heat from shaft are large at inlet because of inlet (cold) lubricant.

34 34 Conclusions (a) Heat flow from hot shaft into inner film is large; more so at the inlet plane where oil is cold; (b) The inner film temperature increases quickly (viscosity drops) due large heat flow from shaft and drag shear power; (c) The floating ring has a large radial temperature gradient; (d) At all rotor speeds, the lubricant flows carry more than 70 % of the total energy input. The rest soaks into the TC casing. The bearing design must allow for adequate flow paths to cool components. Tool integrated into sponsor engineering design practice to predict thermal loading and mechanical stresses and to ensure lubricant does not overheat (coking)

35 35 Acknowledgments Thanks to Honeywell Turbocharging Technologies ( ) Learn more at: Questions (?) Copyright© 2012 Luis San Andres


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