Simulink Based Vehicle Cooling System Simulation;

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Simulink Based Vehicle Cooling System Simulation
Series Hybrid Vehicle Cooling System
Simulation 13th ARC Annual Conference May 16,
2007 SungJin Park, Dohoy Jung, and Dennis N.
Assanis University of Michigan
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Outline

• Introduction
• Motivation
• Objectives
• Simulation and Integration
• Hybrid vehicle system modeling VESIM
• Cooling system modeling
• Configuration of HEV cooling system
• Summary

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Vehicle thermal management and cooling system
design

• Motivation
• Additional heat sources (generator, motor, power
  bus, battery)
• Various requirements for different components
• Objective
• Develop the HEV Cooling System Simulation for the
  studies on the design and configuration of
  cooling system
• Optimize the design and the configuration of the
  HEV cooling system

Conventional Cooling System
HEV Cooling System
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Overview of Cooling System Simulation

• Cooling system model use simulation data from the
  hybrid system model
• Minimizes computational cost for optimization of
  design and configuration

Driving schedule
HEV Cooling System Model
Hybrid Propulsion System Model VESIM
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Hybrid propulsion system configuration and VESIM
Engine 400 HP (298 kW)
Motor 2 x 200 HP (149 kW)
Generator 400 HP (298 kW)
Battery (lead-acid) 18Ah / 25 modules
Vehicle 20,000 kg (44,090 lbs)
Maximum speed 45 mph (72 kmph)
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Hybrid vehicle power management
Charging mode
Braking mode
Discharging mode

• Battery is the primary power source
• When power demand exceeds battery capacity, the
  engine is activated to supplement power demand

• Engine / generator is the primary power source
• When battery SOC is lower than limit, engine
  supplies additional power to charge the battery
• Once the power demand is determined, engine is
  operated at most efficient point

• Regenerative braking is activated to absorb
  braking power
• When the braking power is larger than motor or
  battery limits, friction braking is used

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Vehicle simulation
Vehicle driving cycle
Vehicle simulation model VESIM
Cycle simulation results ( engine / generator /
motor / battery)
Motor Speed
Battery SOC
Engine Speed
Generator Speed
Generator Torque
Engine BMEP
Motor Torque
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Cooling system modelingConfigurations
Configuration A
HEV Cooling System Model in Matlab Simulink
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Guide Lines of Cooling system configuration
Criteria for system configuration

• Radiators for different heat source components
  are allocated in two towers based on operation
  group
• The radiators are arranged in the order of
  maximum operating temperature
• Electric pumps are used for electric heat sources
  
• The A/C condenser is placed in the cooling tower
  where the heat load is relatively small
• Battery is assumed to be cooled by the
  compartment A/C system due to its low operating
  temperature (Lead-acid 45oC)

Component Heat generation (kW) Control Target T (oC) Operation group
Engine 190 120 A
Motor / controller 27 95 B
Generator / controller 65 95 A
Charge air cooler 13 - A
Oil cooler 40 125 A
Power bus (DC/DC converter) 5.9 70 C
Battery 12 45 D
Grade Load condition The heat sources that generate heat simultaneously during driving cycle are grouped together. Maximum speed condition / Lead-acid Grade Load condition The heat sources that generate heat simultaneously during driving cycle are grouped together. Maximum speed condition / Lead-acid Grade Load condition The heat sources that generate heat simultaneously during driving cycle are grouped together. Maximum speed condition / Lead-acid Grade Load condition The heat sources that generate heat simultaneously during driving cycle are grouped together. Maximum speed condition / Lead-acid
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Configurations
Configuration C
Configuration B
Power Generation
Vehicle Propulsion
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Modeling Approach
Component Approach Implementation
Heat Exchanger Thermal resistance concept 2-D FDM Fortran (S-Function)
Pump Performance data-based model Matlab/Simulink
Cooling fan Performance data-based model Fortran (S-Function)
Thermostat Modeled by a pair of valves Fortran (S-Function)
Engine Map-based performance model Matlab/Simulink
Engine block Lumped thermal mass model Matlab/Simulink
Generator Lumped thermal mass model Matlab/Simulink
Power bus Lumped thermal mass model Matlab/Simulink
Motor Lumped thermal mass model Matlab/Simulink
Oil cooler Heat exchanger model (NTU method) Matlab/Simulink
Turbocharger Map-based performance model Matlab/Simulink
Condenser Heat addition model Matlab/Simulink
Charge air cooler Thermal resistance concept 2-D FDM Fortran (S-Function)
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Modeling Approach Heat source

• Heat Input and Exchange Model for Engine Block
  and Electric Components
• Lumped thermal mass model
• Heat transfer to cooling path (Qint) and to outer
  surface (Qext radiation and natural convection)
• Engine
• Map based engine performance model
• Heat rejection rate as a function of speed and
  load is provided by map
• Turbo Charger
• Map base turbo charger performance model
• The temperature and flow rate of the charge air
  as functions of speed and load are provided by
  map

Schematic of Heat Exchange Model at Engine and
Electric components
Engine heat rejection rate
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Modeling ApproachHeat sources (cont.)

• Oil Cooling Circuit
• Heat addition model heat is directly added to
  the oil
• Heat rejection rate as a function of speed and
  load is provided by map
• Condenser
• Heat addition model heat is directly added to
  the cooling air
• Constant value is used for heat rejection rate

• Charge air coolers
• 2-D FDM-based model
• In contrast to radiator, heat transfer occurs
  from air to coolant
• Generator
• Heat generation is calculated using a 2D look-up
  table indexed by speed and input torque
• Lumped thermal mass model

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Modeling ApproachHeat sources (cont.)

• Motors
• Heat generation is calculated using a 2D look-up
  table indexed by speed and input torque
• Lumped thermal mass model
• Power bus
• Power bus regulates the power from electric power
  sources and supply the power to electric power
  sink
• Heat generation is determined by battery and
  motor power
• Lumped thermal mass model

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Modeling ApproachHeat sinks

• Heat exchanger (radiator)
• Design variables
• Core size
• Water tube depth, height, thickness
• Fin depth, length, pitch, thickness
• Louver length, height, angle, pitch
• Based on thermal resistance concept
• 2-D Finite Difference Method

Structure of a typical CHE
Design parameters of CHE core
Empirical correlation for ha (by Chang and Wang)
Staggered grid system for FDM
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Modeling ApproachHeat sinks(cont.)

• Oil cooler
• Finned concentric pipe heat exchanger model for
  Oil Cooler
• Counter flow setup
• NTU approach is used to calculate the exit
  temperature of two fluids

Schematic of Heat Exchange at Engine and Electric
components
NTU Method
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Modeling ApproachDelivery media (Coolant)

• Coolant Pumps
• The coolant flow rate is calculated with
  calculated total pressure drop by cooling system
  components and the pump operating speed
• Performance map is used to calculate the coolant
  flow rate
• The mechanical pump is driven by engine and
  electric pump is driven by electric motor

Efficiency
Flow rate
Efficiency
Flow rate
Performance Maps of Mechanical Pump
Performance Maps of Electric Pump
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Modeling ApproachDelivery media (Coolant)

• Thermostats
• Two way valve with Hysteresis characteristics
• Coolant flow rate to re-circulate circuit and
  radiator are determined by the pressure drops in
  each circuit

T/S valve lift with hysteresis
Valve lift curve of T/S
Coolant flow calculation based on pressure drop
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Modeling ApproachDelivery media (Oil/Air)

• Oil Pump
• Map based gear pump model for Oil Pump
• Cooling fans
• Total pressure drop is calculated from the air
  duct system model based on system resistance
  concept
• Performance map is used to calculate the air flow
  rate

Map Based Gear Pump Model
Condenser
Fan Shroud
Grille
Radiator 1,2
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Test conditions

• Test condition for sizing components and
  evaluating cooling system configuration
• The thermal management system should be capable
  of removing the waste heat generated by the
  hardware under extreme operating condition
• Grade load condition is found to be most severe
  condition for cooling system

Off-Road
Maximum Speed
Grade Load
Ambient Temperature 40 oC
Road profile of off-road condition
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Configuration testGrade Load (30 MPH, 7 )
Engine Speed
Engine BMEP
Battery SOC
Grade Load
Max. SOC 0.7 Min. SOC 0.6 Initial SOC 0.6
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Configuration A and B

• Config. A could not meet the cooling requirements
  of electric components

Configuration B
Configuration A
Generator
Generator
Motor
Motor
PowerBus
PowerBus
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Configuration A and B
Configuration B
Configuration A

• Performance of one CAC in Config. B was better
  than that of two CAC in Config. A

CAC1
CAC
CAC2
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Configuration B and C
Configuration C
Configuration B

• Config. C is designed by adding a coolant by-pass
  line to Oil Cooler in Config. B
• Power consumption of pump is reduced by 5 adding
  the bypass circuit

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Summary

• The HEV Cooling System Simulation is developed
  for the studies of the cooling system design and
  configuration
• The HEV cooling systems are configured using the
  simulation
• In hybrid vehicle, the heat rejection from
  electric components is considerable compared with
  the heat from the engine ( Grade Load heat from
  electric components 98kW, heat from engine
  module 240kW)
• Proper configuration of cooling system is
  important for hybrid vehicle components, because
  the electric components work independently and
  have different target operating temperatures
• Parasitic power consumption by the cooling
  components can be reduced by optimal
  configuration design
• Optimization study of cooling system is conducted
  using developed model (Symposium II, Optimal
  design of electric-hybrid powertrain cooling
  system)

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Acknowledgement

• General Dynamics, Land Systems (GDLS)

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Thank you!