2014.10.10 Measurement and Prediction Technology of Cooling Capability for Hybrid Drivetrain Components Tadashi Yamada TOYOTA MOTOR CORPORATION
Contents 1, Introduction 2, Cooling mechanism of the Hybrid drivetrain 3, Measurement technology 4, Prediction technology(cfd) 5, Improvement of cooling capability (Case study) 6, Summary
1, Introduction Design of the HV unit Realize the aim performance by control a flow of the oil, and reduction the rebellion Cooling performance Important in securing the fuel economy of the vehicle, function and durability of the unit Difficult to achieve an aim in severe heat environment in the engine room Aim performance Cooling Lubrication Power transmission / control Rebellion Stirring loss Oil leak Vibration / Noise Substance transportation Conventional HV unit development Unit design Vehicle design Prototype Unit evaluation Full vehicle evaluation Repeat a practical vehicle evaluation (Wind Tunnel) Needs to front loading
2, Cooling mechanism of the hybrid drive unit Heat condition of HV unit Inside Oil flow Heat transfer 1To outside air 2To water jacket 3To oil cooler 4To neighbor parts Heat generation 1Motor generator (iron, copper loss) 2Gear engage 3Bearing friction 4Oil stirring Heat transfer path MG/Gear/Bearing Oil Cooler To oil heat generation Oil heat generation To case To case Conduction in the case Outside air LLC Neighbor parts Cooling capability depends on inside oil flow and outside wind flow Heat transfer path is complicated, and difficult to grasp it Target technology Measurement Enable the measurement in a unit simple substance Prediction Enable the prediction of temperature and heat flux
3, Measurement technology (Thermal VRS bench) Measurement evaluation technology that simulated a practical vehicle running condition The VRS bench which realizes the drive of the unit simple substance Simulate practical vehicle driving condition Measure torque loss Measure electrical power loss + Thermoregulation wind tunnel Simulate practical vehicle driving condition Control and measure outside air cooling and water cooling + Developed multi points measurement technology of unit surface temperature and heat flux BTS HV 制 御 装 置 新 HV HV Control 制 御 装 置 Device (TTDC) Torque Sensor インバーター Inverter Motor:M3 吸 収 モーター (Driven) (M3) Torque トルク 計 Rev 回 転 計 Electrical power loss Sensor 回 転 計 Wind Control Device 風 洞 (Temperature) 制 御 装 置 ( 三 機 ) (Velocity) Motor:M1 駆 動 モーター (M1) (Drive) Torque トルク 計 Rev Outlet Duct Velocity Temp 風 速 / 温 度 センサ Velocity 風 速 Temp / 温 度 センサ / 熱 流 速 センサ Heat Flux Inlet Duct Velocity Temp 風 速 / 温 度 センサ Wattmeter 電 力 計 Thermal Control Device 温 調 装 置 (ATF) (ATF) (LLC) (LLC) Motor:M2 (Driven) 吸 収 モーター (M2) Torque トルク 計 Rev 回 転 計 Wind Tunnel T/A Surface: Temperature/Heat Flux Wind : Velocity/Temperature 風 速 / 温 度 センサ / 熱 流 速 センサ Thermal Sensor Thermal VRS bench enabled : Measurement evaluation of each part heat flux and temperature in the environment that simulated the practical vehicle (Without needing practical vehicle)
4, Prediction technology (CFD) Temperature prediction : Inside oil flow, outside airflow and coupled solid analysis Driving condition Specifications Gear/Bearing heat source (mechanical loss) Oil flow CFD Inner surface heat transfer Coefficient Solid heat CAE MG heat source (iron loss, copper loss) Electromagnetic field CAE Air flow CFD Outer surface heat transfer coefficient Film air temperature Oil temperature as unknown value Calculate until energy is in balance To calculate in a short term : At first calculate inside oil flow and outside air flow separately Finally perform in coupled heat calculation
4, Prediction technology (CFD) Approach to Inside oil flow [Required function] Multi phase flow of oil and the air. (free surface) Moving/rotation objects such as gear (moving boundary) Calculate time averaged heat transfer coefficient [Realization method in the CFD] Free surface is considered by VOF (Volume Of Fluid) method. Combination of Moving mesh and Grid interface (Really rotate gear). By integration of the user defined function, the heat transfer coefficient that was averaged by time is calculated from the transient flow. The method that become basic of this technology had been already developed (Reported in 2011JSAE, 2013ANSYS user meeting)
4, Prediction technology (CFD) Problem of the inside oil flow CFD Large scale and complex shape Large number of assy parts Space volumes increase largely A scale is big, and an application of the CFD is difficult Conventional model (differential) 1,300,000 fluid cells 16 parallel CPUs Enabled analysis by: Simplification of the part which does not contribute to heat. Development of the modeling technique and standardization. increasing computer resources and solver licenses HV unit model 5,400,000 fluid cells 256 parallel CPUs
4, Prediction technology (CFD) Inside oil flow CFD Explicit Calculation model(mesh) Calculation condition of inside oil flow Solver ANSYS FLUENT Ver13(Transient) Turbulence Model RNG k-ε Wall Function Enhanced Wall Treatment Multi Phase Method VOF Compressive (Implicit) Number of Element 5,362,144 Vehicle Speed 35 100 170 180(km/h) Implicit Oil distribution
4, Prediction technology (CFD) Result of inside oil flow CFD CFD result : Oil distribution (100km/h)
4, Prediction technology (CFD) Validation of inside oil flow CFD 8 7 1 6,5 9 4 CFD Experiment Comparison of oil distribution (Vol %) CFD expresses oil movement and distribution of experiment exactly Accuracy of CFD is good
4, Prediction technology (CFD) Progress Oil distribution (Transient)
4, Prediction technology (CFD) Progress [W/m 2 ] Oil distribution (Transient) Heat transfer coefficient (Time averaged)
4, Prediction technology (CFD) Outside air flow CFD Calculation condition of outside air flow Solver Turbulence Model Wall Function ANSYS Fluent R15.0.7 Realizable k-epsilon Enhanced Wall Treatment Number of Element 22,000,000 Wind Velocity 5 6 10 12 20(m/s) Wind Temp 40( ) inlet outlet Distribution of wind velocity Comparison of wind velocity Air flow CFD fits measured value well Accuracy of CFD is good
4, Prediction technology (CFD) Progress [W/m 2 ] [ ] Oil distribution (Transient) Heat transfer coefficient (Time averaged) Temperature (Steady)
Temperature [K] 4, Prediction technology (CFD) Validation of temperature prediction Experiment Calculation [K] Upper Front Rear Side Lower Comparison of surface temperature (180km/h) Upper view Heat Flux [W/m2] Experiment Calculation Oil Temperature [K]. Upper Front Rear Side Lower Comparison of surface heat flux (180km/h) Experiment Calculation 1 2 3 4 5 6 7 8 9 10 11 35km/h 100km/h 170km/h Case No. Comparison of oil temperature Front view Side view Rear view Distribution of surface temperature Calculation results fit measured value well It enabled analysis of cooling mechanism under various driving condition of the vehicle
5, Improvement of cooling capability Improvement investigation of cooling capability (Case study) Before After Motor Cover Wind [W/m 2 K] [K] Oil Temperature [K] Distribution of temperature Initial Optimal Comparison of oil temperature Heat transfer coefficient (Exterior surface) Motor Cover [W/m 2 K] Motor Cover: Heat transfer coefficient is high in outer surface Add fin Heat transfer coefficient is low in inner surface Supply hot oil Heat transfer coefficient (Interior surface) Made it possible to improve cooling capability that is effective depending on mechanism
6, Summary Conclusion Thermal VRS bench enabled measurement evaluation of each part heat flux and temperature in the environment that simulated the practical vehicle. CFD enabled analysis of cooling mechanism under various driving condition of the vehicle. Prediction technology made it possible to improve cooling capability that is effective depending on mechanism at the stage of design.
6, Summary Next theme This prediction technology is applied only to a steady running condition (vehicle speed and oil temperature are constant). Continue engineering development toward the prediction of the transient running condition. Development of the one dimension tool which assumed heat transfer characteristic provided in this development technology. Utilization as a cooling capability simple examination tool at early period of design.
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