Oil flow CFD

2014.10.10
Measurement and Prediction Technology
of Cooling Capability
for Hybrid Drivetrain Components
Tadashi Yamada
TOYOTA MOTOR CORPORATION
Contents
1,
2,
3,
4,
5,
6,
Introduction
Cooling mechanism of the Hybrid drivetrain
Measurement technology
Prediction technology(CFD)
Improvement of cooling capability (Case study)
Summary
1, Introduction
Aim performance
Cooling
Lubrication
Power transmission /
control
Design of the HV unit
Realize the aim performance by control
a flow of the oil, and reduction the
rebellion
Rebellion
Stirring loss
Oil leak
Vibration / Noise
Substance
transportation
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
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
Heat transfer
To
oil
Oil heat
generation
Heat generation
Oil Cooler
Inside
Oil flow
①Motor generator
(iron , copper loss)
②Gear engage
③Bearing friction
④Oil stirring
MG/Gear/Bearing
heat generation
To case
Neighbor parts
outside air
water jacket
oil cooler
neighbor parts
To case
①To
②To
③To
④To
Heat transfer path
Conduction in
the case
Outside air LLC
・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
BTS
Developed multi points measurement
technology of unit surface temperature
and heat flux
Wattmeter
電力計
Outlet
Duct
Velocity
風速
/温度センサ
Temp
HV制御装置
トルク計
Torque
トルク計
Torque
新HV制御装置
HV Control
Device
(TTDC)
回転計
Rev
Thermal Control
温調装置
Device
（ATF)
(ATF)
(LLC)
（LLC）
吸収モーター
Motor:M2
(M2)
(Driven)
Motor:M3
吸収モーター
(Ｍ3)
(Driven)
・Control and measure
outside air cooling and water cooling
+
Wind
Tunnel
インバーター
Inverter
+
Thermoregulation wind tunnel
⇒Simulate practical vehicle
driving condition
Electrical
power loss
Sensor
回転計
Rev
駆動モーター
Motor:M1
(M1)
(Drive)
トルク計
Torque
Velocity
風速
/温度センサ
Temp
/熱流速センサ
Heat
Flux
Rev
回転計
Torque
Sensor
Velocity
風速
/温度センサ
Temp
Inlet Duct
T/A Surface:
Temperature/Heat Flux
Wind :
Velocity/Temperature
風速/温度センサ
/熱流速センサ
Wind Control Device
風洞制御装置
(Temperature) (三機)
Thermal Sensor
(Velocity)
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
Oil flow CFD
Inner surface
heat transfer
Coefficient
Gear/Bearing
heat source
(mechanical loss)
MG heat source
(iron loss,
copper loss)
Electromagnetic
field CAE
Solid heat 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
⑨
⑥，⑤
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/m2℃]
Oil distribution
(Transient)
Heat transfer coefficient
(Time averaged)
4, Prediction technology (CFD)
Outside air flow CFD
Calculation condition of outside air flow
Solver
ANSYS Fluent R15.0.7
Turbulence Model
Realizable k-epsilon
Wall Function
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/m2℃]
Oil distribution
(Transient)
Heat transfer coefficient
(Time averaged)
Temperature (Steady)
4, Prediction technology (CFD)
Validation of temperature prediction
[K]
Temperature [K]
Experiment
Calculation
Upper
Front
Rear
Side
Lower
Front
Rear
Side
Lower
Upper view
Comparison of surface temperature (180km/h)
Experiment
Heat Flux [W/m2]
Calculation
Upper
Comparison of surface heat flux (180km/h) Front view
Side view
Rear view
Distribution of surface temperature
Experiment
Calculation results fit measured
value well
⇒ It enabled analysis of cooling
Oil Temperature [K] .
Calculation
1
2
35km/h
3
4
5
6
100km/h
7
8
9
10
170km/h
Case No.
Comparison of oil temperature
11
mechanism under various driving
condition of the vehicle
5, Improvement of cooling capability
Improvement investigation of cooling capability (Case study)
Before
[K]
[W/m2K]
Oil Temperature [K]
Wind
After
Motor
Cover
Initial
Distribution of temperature
Heat transfer coefficient （Exterior surface）
[W/m2K]
Motor
Cover
Heat transfer coefficient
（Interior surface）
Optimal
Comparison of oil temperature
Motor Cover:
Heat transfer coefficient is high in
outer surface ⇒ Add fin
Heat transfer coefficient is low in
inner surface ⇒ Supply hot oil
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.
Thank you

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