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Daimler Trucks
Thermal Management Concept Investigations of the new
Heavy Duty Engine Platform using GT-Cool/GT-Power
GT-Suite-Conference
Frankfurt/M., 20.10.2008
Matthias Schmid
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 2Daimler Trucks
Agenda
• Overview Heavy Duty Engine Platform
• Overview thermal management investigations
• Model setup
• GT-Power model
• GT-Cool model
• Results
• Conclusion
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 3Daimler Trucks
First version of the new Heavy Duty Engine Platform:Detroit Diesel DD15 (EPA07)
• Configuration: 6 cylinder in-line
• Displacement: 14.8l
• Bore: 139mm
• Stroke: 163mm
• Max. Power: 418kW (560hp)
• Max. Torque: 2509Nm (1850 lb-ft)
• Thermostat & fan: inlet controlled
• Following displacements: 10.6l, 12.8l, 15.6l
• The new platform will replace the successful BR500 & OM457 (Mercedes-Benz), S60 (Detroit
Diesel) and 6M70 (Mitsubishi Fuso).
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 4Daimler Trucks
Goal of the thermal management investigations:“How to save fuel?”
• Reduce “real” engine friction with higher oil temperature between the friction surfaces
• Reduced coolant flow (pump clutch)
• Higher coolant temperature (heated thermostat)
• Higher (overall) oil temperature (oil thermostat)
• Reduce coolant pump power consumption due to lower coolant flow
• 2-stage clutch (magnetic)
• Stage less clutch (viscous)
• Reduce oil pump power due to lower pressure rise (with oil thermostat)
• Higher oil temperature (lower oil viscosity)
• Eliminate pressure loss of oil cooler at low oil temperatures
• Optimize the fan controller for inlet controlled system
• Implement set point dependency of engine speed and load
• The maximum capability of the cooling system must not be reduced; transient behavior of the
modified system must be acceptable to avoid temperature peaks. Change of emissions must be
considered.
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 5Daimler Trucks
Indirect coupled GT-Power/GT-Cool model setup
Engine State
•Speed
•Load
•Fuel cons. map
Vehicle*
•Speed
•Gear
•road grade
Cooling system
•Temperature
•Pump power
•Fan power
GT-Power result file
•Gas side boundary
conditions
Oil circuit
•Temperature
•Pump power
Control system
•Coolant pump
•Fan
•Thermostat
Friction power
calculation
*Results from LDYN (Daimler Trucks software for longitudinal dynamics simulation)
Fuel consumption
•total
•specific
„Output“
„Input“
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 6Daimler Trucks
GT-Power model
• GT-Power model calculates stationary in-cylinder gas side boundary conditions:
• Engine fired mode
• Engine brake mode
• Results are adjusted with
steady-state measurement results
(heat release rate).
• Indirect coupling provides sufficient accuracy;
calculation speed of GT-Cool model is
real time or faster.
• Direct coupling is not recommended:
• Solver too slow for long distance simulations.
• Heat release rate (transient mode) ≠ Heat release rate (steady-state mode)
►complex burn rate model necessary
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 7Daimler Trucks
GT-Cool model – Coolant circuit (main window)
Vehicle
Accessory
cooling
Cooling
air path
Coolant
distributor
Coolant
collector
Coolant
thermostat
EGR-Cooler
Engine state part
Cylinder 1-6
Surge tank
Friction
• Layout similar to real engine
• Includes
• coolant system with 3D-cylinders
• Interfaces to all sub-models
• Interface to GT-Power result file
• Cooling air path
• Vehicle
• Engine state part
• Accessory heat input via map
interpolation.
• Accurate calibration of water jacket parts
(material, thickness, surface roughness)
necessary for adequate liner
temperatures.
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 8Daimler Trucks
Oil circuit
Friction
bearings
Main gallery
Piston heat
Liner heat
Friction
valvetrain
Turbocharger
Turbocompound
Oil panPump
Oil cooler
Oil thermostat
Bypass
Air
compressor
Heat release
Heat input
• The oil circuit must be calibrated with attention to achieve correct heat input:
• Heat transfer coefficient (piston & liner)
• Volume flow (component pressure drop)
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 9Daimler Trucks
Clutch controllerCoolant pump / Fan
• Clutches are gear parts with varying ratio and efficiency
• Necessary clutch ratio is calculated similar to ECU algorithm
• Clutch efficiency is interpolated from measurement results
• Example: Coolant pump clutch
Stage less clutch
2-stage clutchClutch ratio / efficiency
Coolant pump
Engine state
Pulley ratio
Controller window
Main window
Selector (case setup):
• Standard (no clutch)
• 2-stage clutch
• Stage less clutch
Coolant pump clutch
characteristics
pulley speed [rpm]
pum
p im
pelle
r sp
eed
[rpm
]
2-stage clutch high2-stage clutch low
stageless clutchoperation range
identical tostandard pump
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 10Daimler Trucks
Modeling coolant thermostat
• Flexible setup needed for different specifications:
• Standard wax thermostat
• Heated wax thermostat
• Electric valve
• Thermostat build-up consists of 3 parts:
• manual valve (actuated)
• Transfer function for wax behavior (by B. Luptowski / GTI)
• Control function for heating power (optional)
Controller for
heating power
Manual valve
Transfer function
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 11Daimler Trucks
Friction power calculation
• Schwarzmeier‘s formula for calculating the mean friction pressure:
( ) ( ) ( )me
oiloilCW
me
CW
me
CW
m
CW
m
frictionfriction
pnfT
nd
T
ndC
T
p
T
pC
T
c
T
cC
pp
,66,1*
2*
66,1
2
366,1*
*
66,1266,1*
*
66,11
*
+
⋅−⋅⋅+
−⋅+
−⋅+
+=
•C1, C2, C3 : engine specific constants•TCW : Cylinder wall temperature („relevant to friction“)•cm : mean piston speed•pme : mean effective pressure
Source: Schwarzmeier, M.: Reibmitteldruck – Der Einfluß des Arbeitsprozessverlaufs auf den Reibmitteldruck; FVV Vorhaben Nr. 421 Abschlussbericht; FVV-Heft 503; 1992
piston
crankshaft,connecting rod,
valve train
accessory
• Crankshaft / Connecting rod / valve train friction depends on oil temperature & engine speed• Piston friction depends on cylinder wall temperature & engine speed / load
•d : mean bearing diameter (crankshaft, connecting rod)•n : engine speed•Toil : mean oil temperature•* : reference value (from measurement)
How to get cylinder wall temperature?
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 12Daimler Trucks
Cylinder wall temperature calculation
( ) ( ) ( )**** 8,05,16,1 coolantcoolantmememmCWCW TTppccTT −⋅+−⋅+−⋅+=• Schwarzmeier‘s formula (for steady-state engine operation / raw data):
• Wall temperature of 3D-cylinder model (GT-Cool)
Raw data
Similar behavior
►Cylinder wall temperature TCW can be taken from the GT-Cool 3D-cylinder model
Load step
(Results must be smoothed for transient engine mode)
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 13Daimler Trucks
Comparison cylinder liner temperatures: Simulation vs. Measurement results
• Surface temperatures (0mm depth) are approx. 10°C higher than measured values (1mm depth).
• Behavior of calculated cylinder liner temperatures similar to measurement results.
• Limited accuracy of absolute values due to restricted potential of the 1D-model.
n=1240 1/minTCoolant =90°C
0
20
40
60
80
100
120
140
160
180
200
90 100 110 120 130 140 150 160 170 180
T [°C]
h [m
m]
p_me=21,2bar
p_me=5,3bar
Temperature values:Measurement: 1mm below liner surfaceSimulation: on liner surface(General reference value for temperature gradient in liner wall: approx. 10°C/mm)Measurement result range
pme=21,2barpme=5,3bar
Simulation results:
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 14Daimler Trucks
Example: Comparison fan control system
• Standard system
with 1 fixed value
for desired
coolant outlet
temperature.
• Modified system
with dependency
of coolant inlet
temperature and
engine
speed/load leads
to faster
reaction. Smaller temperature peaks
Faster reaction
Less engagement
20.10.2008 - Frankfurt/M. - GT-Suite-Conference 15Daimler Trucks
Conclusion
Advantages of a coupled GT-Power/GT-Cool model:
• delivers sufficient accuracy for concept investigations
• allows predictions (fuel consumption) before hardware parts are available
• gives the possibility to create first validation of ECU-calibration
• allows fast valuation of new concepts without prototype hardware
• supports the experimental (vehicle & engine test bench) development