SIMULATION AND EVALUATION OF ENGINE FRICTION EUROPEAN GT CONFERENCE, FRANKFURT/MAIN, OCTOBER 9TH, 2017 Prof. Dr.-Ing. Peter Steinberg, BTU Cottbus M.Sc. Oleg Krecker, PhD candidate, BMW
AGENDA 1 2 3 4 Motivation and objective Modelling of friction related components Validation Conclusion and further developments Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 2
01 MOTIVATION AND OBJECTIVE Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 3
Temperature [ C] Correlation & validation Friction MOTIVATION other losses mech. power Real boundary conditions High Transient cycles Total engine fired Test 1-cylinder fired (floating liner) Total engine / strip-down Friction Measurement data (motored and fired) Speed Simulation data Thermal engine model 1D Simulation warm up & fuel consumption within driving cycles Low 150 Low Single components motored High Warm up Cylinder Bridge Temperature, NEDC m.th_zst_1_2_05 Data resolution & reproducibility escv zu Mean 0D/1D Simulation Friction Total engine GT-Suite Final result: Piston assembly Crankshaft TH_ZST_1_2_05 [ C] 100 50 escv auf Mean Impact on CO 2 - emissions Cylinder head + chain drive Oil + vacuum pump Belt drive TH_ZW_A02_035 [ C] 0 0 200 400 600 800 1000 1200 Zeit [s] Time [s] m.th_zw_a02_035 150 100 50 0 0 200 400 600 800 1000 1200 Zeit [s] escv zu Mean escv auf Mean Predictive evaluation of concepts and trends in engine friction reduction. As simple as possible and as complex as necessary. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 4
Requirements OBJECTIVE Closeness of basic conditions to reality Fast prediction High Transient cycles Agile transferability Total engine fired 1-cylinder fired (floating liner) Relative comparison Total engine / strip-down Physical evaluation Low Low Single components motored High Possible measuring resolution & reproducibility Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 5
02 MODELLING OF FRICTION RELATED COMPONENTS Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 6
IDENTIFICATION OF MAJOR FRICTION SOURCES Chain drive & hydraulic components Guides and tensioner Oil & vacuum pump VANOS Chain Cylinder head unit Camshaft bearings Valvetrain and VALVETRONIC High pressure pump Crank train Piston Liner system Conrod and crankshaft bearings Balancer shaft Front end accessory drive Multiple v-belt Auxiliaries, e.g. alternator Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 7
CAPABILITIES IN GT SOME EXAMPLES Complex kinematics (var. valve lift) & independent definition of each friction contact Surface properties Inlet camshaft and VALVETRONIC of a 3-cylinder engine Crank train of a 4-cylinder engine Dynamic beam modelling and hydrodynamic bearing solution Detailed piston and liner geometry Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 8
03 VALIDATION Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 9
CRANKSHAFT VALIDATION AND CALIBRATION Model underestimates friction Area of good correlation Model overestimates friction Friction torque deviation between measurement and simulation is shown (strip-down crankshaft). At high speeds >3500 RPM the model lacks in accuracy more effort in calibration is necessary. Good correlation in usual speed ranges (<2500 RPM) of driving cycles fuel consumption area of interest. Model calibration on temperature, oil flow and friction torque. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 10
Friction Torque [Nm] Friction Torque [Nm] CRANKSHAFT MODEL TRANSFERABILITY (CASE STUDY ON BEARING CLEARANCE) Friction Crankshaft only, 90 C 0 1000 2000 3000 4000 5000 6000 Speed [RPM] 0 1000 2000 3000 4000 5000 6000 Speed [RPM] 1 Clearance 20µm Messung measured Clearance 20µm Simulation simulation Clearance 60µm Messung measured Clearance 60µm Simulation simulation Investigation on transferability at changing boundary conditions (bearing clearance). Experiment on strip-down test rig and variation of clearance: Minimum = 20 µm Maximum = 60 µm GT setup: Bearing mobility method Crankshaft 3D beam dynamic Tuning of oil temperature model Model shows good agreement of frictional losses with changing clearances. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 11
PISTON ASSEMBLY TOTAL FRICTION OF PISTON SKIRT + RINGS (FLOATING LINER) Measurement A w/o bore distortion & skirt geom. B with bore distortion & skirt geom. Study shows the importance of proper geometry definition in the piston-liner system (convexity, ovality, distortion). Unsteady peaks occur due to high contact pressure on partial areas at the skirt. Current investigation on thermal FE skirt calculation and development of a work around by modifying skirt geometry. also V2019 will include an elastic deformation model for the skirt to improve friction prediction. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 12
Friction Torque [Nm] Friction Torque distribution [%] CYLINDER HEAD UNIT EXAMPLE: EXHAUST CAMSHAFT AND VALVETRAIN Camshaft and Valvetrain Friction, exhaust side, 90 C Strip-Messung Measurement Bezug AZ3.2 Simulation 90% Friction Camshaft Torque Bearings - CamShaft 80% Bearings 0 1000 2000 3000 4000 5000 6000 Speed [RPM] 100% 70% 60% 50% 40% 30% 20% 10% Friction distribution, exhaust side, 90 C 0% 750 1000 1500 2000 3000 4000 5000 Speed [RPM] Hyd. Lash Adjuster Reibmoment HVA Valve Pad Reibmoment Ventilfuß Valve Guide Reibmoment Ventilführung Cam Follower Friction Torque - Cam-Follower Contacts absolut Roller Bearing MWälz; Part Mittelwert State of measurement: camshafts are driven by chain, valvetrain rocker arms are partly removed dynamic chain movement might interfere result fidelity (4500/5000 RPM) Percentage distribution of friction contacts is a current state estimation. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 13
Simulation Experiment TOTAL ENGINE SIMULATION AND ADDITIONAL MEASUREMENTS Strip-Down Test, 90 C Gap due to: Missing simulation of chain friction Belt drive friction needs a bit more tuning Deviation in piston assembly Total Engine Test Rig Transmission Oil- & Vacuum Pump Water pump Acc. Belt Drive Inlet Camshaft + Valvetrain Exhaust Camshaft + Valvetrain Balancer Shaft Piston Skirt Piston Rings Small End Bearing Big End Bearing Main Bearings Seals Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 14
04 CONCLUSION AND FURTHER DEVELOPMENTS Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 15
Further developments CONCLUSION AND FURTHER DEVELOPMENTS Conclusion GT offers a variety of capabilities to model entire engine friction losses. Main models of friction related engine components are set up, validated and calibrated but some effort is necessary for physical reasonable interpretation of simulation results! Good agreement on simulation and measurement data correlation. Sophisticated fusion of subsystem models. Further measurements for detailed subsystem friction analysis. Optimizing studies on friction reduction. Investigation on load and temperature and its impact on overall engine friction. Slick workflow model set up, parameter studies and post processing. Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 16
THANK YOU! Simulation and Evaluation of Engine Friction Oleg Krecker October 9th 2017 Slide 17