The simulation of engine cooling circuits by coupling Flowmaster

The simulation of engine cooling circuits
by coupling Flowmaster with other
simulation tools
Dr. B. Beyer / W. Maister / Dr. C. Lund
Volkswagen AG
Flowmaster Users‘ Group Meeting 2003
1/18
Dr. Beyer / Maister / Dr. Lund
Overview
1. Using Excel and VBA-scripts for automated Flowmaster calculations
and result analysis
2. Using VBA-scripts for coupling Flowmaster with other simulation
tools
3. Coupled simulation of an engine cooling system with Flowmaster
and a Kuli air side model
4. Comparison of simulation results and
measurements
Flowmaster Users‘ Group Meeting 2003
2/18
Dr. Beyer / Maister / Dr. Lund
Automation of Flowmaster calculations
Flowmaster calculations can be controlled by using Visual Basic Scripts.
Example: Controlling Flowmaster with an all-purpose Excel script which
uses GUI automation.
Program steps:
1. Open a Flowmaster network
2. Transfer the input values from the Excel sheet to Flowmaster
3. Create a new results list entry in Flowmaster
4. Run Flowmaster
5. Transfer the desired results from Flowmaster to Excel for evaluation purposes
Flowmaster Users‘ Group Meeting 2003
3/18
Dr. Beyer / Maister / Dr. Lund
Controlling FM with Excel: Defining input values
Project
name
Element definition
Network
name
Parameter definition
Columns: Individual input values
for each Flowmaster run
(overwriting original values)
Flowmaster Users‘ Group Meeting 2003
4/18
Dr. Beyer / Maister / Dr. Lund
Controlling FM with Excel: Reading results
Nu
m
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r
of
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re
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tr y
Specifying results which
shall be transferred to Excel
Columns: Results for each of the
Flowmaster runs
Flowmaster Users‘ Group Meeting 2003
5/18
Dr. Beyer / Maister / Dr. Lund
Example: Polo 1,9l TDI 74 kW coolant cycle
Main components
of the coolant cycle:
• pump
radiator
• pressure losses of all
components
• pipes, bends, T-pieces
oil cooler
• thermostat
engine
cabin heater
pump
expansion
tank
thermostat
Flowmaster Users‘ Group Meeting 2003
6/18
Dr. Beyer / Maister / Dr. Lund
coolant flow / flow at rated
speed [%]
Comparison of measurement and simulation
pump
120
simulation
100
80
80
60
60
40
40
20
20
0
0
20
40
60
80
100
cabin heater
120
60
40
40
20
20
0
0
0
20
40
60
80
rotational speed / rated speed [%]
100
40
60
80
100
80
100
simulation
measurement
80
60
20
engine oil cooler
100
measurement
80
0
120
simulation
100
simulation
measurement
100
measurement
0
coolant flow / flow
at rated speed [%]
radiator
120
0
20
40
60
rotational speed / rated speed [%]
Polo 1,9l TDI 74 kW coolant cycle
Flowmaster Users‘ Group Meeting 2003
7/18
Dr. Beyer / Maister / Dr. Lund
Thermal management of a vehicle
passenger compartment
evaporator
gear oil
cooler
grill
heater
engine oil
cooler
engine
oil pump
gear
box
⇒ Many systems are
influencing each other
waterpump
servo
steering
Domains involved in thermal
management:
• coolant cycle
• air conditioning / heating
• charge air
• exhaust gas
• air flow through the engine
compartment
• servo oil cooling
• engine oil cooling
• gear oil cooling
⇒ Interaction should be
considered in the simulation
thermostat
TC
exhaust pipe
charge air inlet
engine compartment
air outlet
⇒ An automatic coupling of
the simulation tools for the
miscellaneous systems
would simplify the analysis
of the whole system
Flowmaster Users‘ Group Meeting 2003
8/18
Dr. Beyer / Maister / Dr. Lund
Flowmaster automation by using the COM interface
Flowmaster provides two main areas of automation:
1. GUI automation
Allows to control Flowmaster by scripts very similar to the way it is used manually.
Advantage: All input values and output values can be easily accessed, calculation results
are stored in the result list as usual.
Disadvantage: The iteration process itself can‘t be influenced.
2. Analysis automation
Allows to acces the analysis while it is running.
Advantage: The script can interact with Flowmaster in each iteration step. Hence it is
possible to provide external calculated values within the iteration process.
Disadvantage: It is more difficult to access input values and results. Calculation results
can be stored in the result list by overwriting old results only.
Flowmaster Users‘ Group Meeting 2003
9/18
Dr. Beyer / Maister / Dr. Lund
Coupling Flowmaster to other programs
• For coupling Flowmaster with other software it is often necessary that the
programs are interacting within the iteration steps.
• Intervention within the iteration steps is possible only if „analysis automation“ is
used.
• The intricate setting of input values and reading of results when using „analysis
automation“ can be eliminated by combining both analysis methods and doing
the pre-/postprocessing with GUI automation.
Flowmaster Users‘ Group Meeting 2003
10/18
Dr. Beyer / Maister / Dr. Lund
Process of a coupled Flowmaster calculation
Start the Flowmaster iteration with
start values for the variables
Perform a Flowmaster
iteration step
Did
Flowmaster
converge?
yes
no
Transfer of
parameters
Perform a complete external calculation
Transfer of results
Result
analysis
Flowmaster Users‘ Group Meeting 2003
11/18
Dr. Beyer / Maister / Dr. Lund
Example: Coupling of Flowmaster and Kuli
Heat rejection of
the engine, oil
cooler etc.
heat
Experimental datas from
vehicle or engine test bench *)
*)
Coolant cycle
1D-Flowmaster model of
the whole coolant cycle
heat
Air
1D-Kuli model of the
engine compartment
may be replaced by
calulation results
Flowmaster Users‘ Group Meeting 2003
12/18
Dr. Beyer / Maister / Dr. Lund
Flowmaster model for a coupled simulation
Values read from Flowmaster and
values written to Flowmaster during
the iteration process:
radiator
oil heat
oil cycle
cabin
heater
reading inlet temperature
reading inlet pressure
engine
heat
writing heat duty
writing pressure loss
pump
reading coolant mass flow
expansion
tank
thermostat
Flowmaster Users‘ Group Meeting 2003
13/18
Dr. Beyer / Maister / Dr. Lund
Kuli model for a coupled simulation
Kühlwasserkreislauf
inlet pressure
coolant mass flow
COM
Aus
Aus
COM
Druck
Massenstrom
inlet temperature COM
Aus
fan speed (fan 1)
Aus
COM
345 mm
Antriebsdrehzahl
Aus
P
Aus
Ein
radiator
type
Dateiauswahl
COM heat
flow
1.Rechenglied
Wärmeleistung IM
pressure
loss
Ein 1
Eintrittsdruck IM
Austrittsdruck IM
Ein 2
-
Aus
Ein
COM
Kühlluftmassenstrom (Summe der Beträge)
COM air
flow
blue = value set before calculation
red = data written to Kuli during iteration
green = data read from Kuli during iteration
black = result read from Kuli after calculation
Antriebsdrehzahl
COM
Simulationsparameter
Aus
COM
Air side model
fans
SP
cp-value
grill
Fahrgeschwindigkeit
ambient
temperature
Ein
Ein
290 mm
vehicle velocity
Aus
Aus
Temperatur
fan speed (fan 2)
Ein
KF
COM
1.P-Regler
Wasserkühler
Ein
Aus
Umgebungstemperatur
press.
loss of
engine
radiator comp.
Aus
COM
cp-values
condenser
Flowmaster Users‘ Group Meeting 2003
14/18
Dr. Beyer / Maister / Dr. Lund
Calibration of the air side model
constant coolant
flow rate
3. Determination of the engine
compartment pressure loss
which leads to this air flow rate.
pressure difference
2. Determination of the
corresponding air flow rate in
the radiator performance
map.
heat duty / ITD
1. Determination of the
radiator heat duty for a
choosen operating
point by measuring the
radiator inlet and outlet
temperature as well as
the coolant flow rate in
a vehicle.
1
3
pressure loss
of the engine
compartment
air flow rate
2
air flow rate
1
Pressure rise of fan and
airstream
2
Pressure loss sum for all
known components
3
Pressure loss of the entire
„air path“
Flowmaster Users‘ Group Meeting 2003
15/18
Dr. Beyer / Maister / Dr. Lund
All-purpose Excel sheet for a coupled simulation
Setting the
transfer direction
Value name used
in FM and Kuli
Definition of values transferred during iteration
Setting start values of
Flowmaster
Setting start values of
Kuli
Flowmaster results
Kuli results
Flowmaster Users‘ Group Meeting 2003
16/18
Dr. Beyer / Maister / Dr. Lund
Comparison of measurement and coupled simulation
Velocity [km/h]
60
120
vmax
120
120
vmax
Hill climbing [%]
12
7
0
7
7
0
off/on
off/on
off/on
on
on
off
Fans
Modifications
-
Radiator inlet
temperature:
used for model
calibration
upper grill closed
40% reduction of lower grill
area
Deviation of the
simulation from
measurement [K]
0.4
0.6
-1.5
Flowmaster Users‘ Group Meeting 2003
17/18
Dr. Beyer / Maister / Dr. Lund
Conclusions
• The COM interface allows an interactive coupling between Flowmaster and other
software which is providing a corresponding interface.
• When Excel is used for programming the coupling it is possible to define input
tables which allow an easy modification of the data exchange between the
programs (no change of the source code necessary).
• A 1D-simulation of the coolant cycle and the air flow through the engine
compartment has shown that the coupling is working reliably and that accurate
results can be obtained.
• Other tools may be coupled to Flowmaster additionally (e.g. engine process
simulation).
Flowmaster Users‘ Group Meeting 2003
18/18
Dr. Beyer / Maister / Dr. Lund