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Cooling System Architecture Design for FCS Hybrid Electric Vehicle

Sungjin Park, Dohoy Jung, Zoran Filipi, and Dennis AssanisThrust Area 4

University of MichiganThe University of Michigan

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Outline

• Motivation and Challenges• Objectives• Cooling System Architecture Design• Cooling System Component Sizing• Results and Discussion• Summary and Future Plan

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Motivation and Challenges• Cooling system is critical issue for

combat vehicle’s survivability• Series Hybrid Electric Vehicle for

FCS.• Additional powertrain components

for SHEV– Additional heat sources need

additional cooling circuit, pump, fan , sensors, and controllers

– Complicated cooling system architecture in SHEV due to the additional heat sources with various requirements and various vehicle driving modes

ICM

Sprocket

Motors

Generator

Power Bus/Controller

EngineBattery

+-

ComponentHeat

generation (kW)*

Control Target T

(oC)

OperationGroup

Engine 187 120 AMotor 27 95 B

Generator 62 95 ACharge air

cooler 8 - A

Oil cooler 27 130 APower bus 27 70 C

Battery 12 45 D

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Objectives

• Develop a guideline/methodology for an efficient cooling system architecture selection for FCS SHEV using modeling and simulation capability

• Criteria for cooling system architecture design selection:– Cooling requirements– Parasitic power consumption– Thermal shock (temperature fluctuation)– Packaging

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Cooling System Architecture DevelopmentArchitecture A

- Separate cooling circuit is added for electric components.

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Cooling System Architecture DevelopmentArchitecture A Architecture B

- Cooling circuit for electric components is further divided into two circuits based on control target temperatures.

Control Target Temp. of Heat Sources

ComponentControl

target temp. (oC)

Engine 120

Oil cooler 130

Charge air cooler -

Motor 95

Generator 95

Power bus 70

Battery 45

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Cooling System Architecture Development

- The heat source components are allocated into two cooling modules based on the operating groups to minimize redundant operation of the cooling fan.

Cooling Module 1 Cooling Module 2

Operation Group of Heat Sources

Architecture C

Component Operation group

Engine A

Generator A

Charge air cooler A

Oil cooler A

Motor B

Power bus C

Battery D

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Vehicle Cooling System Simulation (VECSS)

Component ApproachHeat

ExchangerThermal resistance concept

2-D FDM

Pump Performance data-based model

Cooling fan Performance data-based model

Thermostat Modeled by three-way valve

Engine Map-based performance model

Engine block Lumped thermal mass modelGenerator Lumped thermal mass modelPower bus Lumped thermal mass model

Motor Lumped thermal mass model

Oil cooler Heat exchanger model (NTU method)

Turbocharger Map-based performance model

Condenser Heat addition modelCharge air

coolerThermal resistance concept

2-D FDM

cac spec

inler air v elocity

inlet air temperature

turbo charger

f(u)

sum

Ramass

thermodelP

coolant temp, K

inlet air velocity , m/s

inlet air temp, oC

Ramass1

Tcoolout

thermodelP1

RadelP, bar

to f an

outlet air temp, K

radiator2

Ramass

thermodelP

coolant temp, K

inlet air velocity , m/s

inlet air temp, oC

Ramass1

Tcoolout

thermodelP1

RadelP, bar

to f an

outlet air temp, K

radiator 1

coolant m(kg/s)

coolant density ,kg/m3

f low coef f cac

f low coef f egn

coolant f low 1

coolant f low 2

coolant f low 3

m_sum

dp(bar)

parallel coolant circuit2

coolant m(kg/s)

coolant density ,kg/m3

coolant f low 1

coolant f low 2

coolant f low 3

m_sum

dp

parallel coolant circuit1

coolant temp1

coolant mass

oil cooler spec

by pass mass

oil cooler mass

delP

ori fice

0flowrate 1flowrate 2flowrate 3

flow sum

dptemp1

heat rejection rate

pump speed

engine1

heat rejection, kW

cool mass1

coolant temp

Tcool_out

f low coef f a/b/c

engine block

pump speed

pressure rise, bar

coolant temp

coolant mass

pressure rise

cool mass, kg/s

coolant temp, K

coolant density , kg/m3

coolant pump2

T_pb

T_gen

T_mot

motor_rpm

coolant pump motor/controller

pump speed

pressure rise, bar

coolant temp

coolant mass

pressure rise

cool mass, kg/s

coolant temp, K

coolant density , kg/m3

coolant pump 1

coolant temp1

coolant mass

delP

recirculate massradiator masscoolant temp2

Re delPthermo delP

delP1

Remass

Recooltemp

RedelP

Ramass

Racooltemp

RadelP

enginedelP

thermodelP

coolant mass

coolant temp

pressure drop2

collector5

Remass

Recooltemp

RedelP

Ramass

Racooltemp

RadelP

enginedelP

thermodelP

coolant mass

coolant temp

pressure drop2

collector3

T1

T2

m1

m2

Tsum

col lector1

T1

T2

T3

m1m2

m3

Tsum

col lector0

f an speed, rpm

vehicle speed, km/h

inlet air temp, oC

radiator3 spec

radiator2 spec

radiator1 spec

radi out air T1

inlet air v el, m/s 01

inlet air v el, m/s 02

inlet air v el, m/s 03

inlet air temp, oC 1

ai r side, fan

elec_pump_rpm

Coolant_temp

f an_rpm

V_speed

Ta

ai r side input1

rad_ai r_T

To File6

heat_gen

To Fi le3

Terminator2

Terminator

coolant temp1

coolant mass

delP1

delP2

recirculate mass

radiator mass

coolant temp2

Re delP

thermo delP

T/S temp delP_sum

T/S

Load input data

C_m (kg/s)

C_Tin(K)

C_m(kg/s)

C_Tout(K)

Reservoi r4

C_m (kg/s)

C_Tin(K)

C_m(kg/s)

C_Tout(K)

Reservoi r1

coolant f low rate (kg/s)

coolant temp in (K)

coolant temp

pb temp

dp(bar)

Power Bus

coolant f low rate (kg/s)

coolant temp in (K)

oil f low rate (kg/s)

oil temp in (K)

cool mass

Oil cooler dp(bar)

cool temp out

oil temp out

Oil dp(bar)

oil cooler spec

Oil cooler

pump speed

heat

press rise

Toil_in

Toil_out

oil mass

Oil ci rcui t

coolant f low rate (kg/s)

coolant temp in (K)

coolant temp

mc temp

dp(bar)

Motor/controller A,B

f(u)

K2C

f(u) K->oC

coolant f low rate (kg/s)

coolant temp in (K)

coolant temp

gc temp

dp(bar)

Generator/control ler_new

[h_cac]

From5

[h_oc]

From4

[h_eng]

From3

[h_mc]

From2

[h_pb]

From1

[h_gc]

From

0

Display6

0

Display5

0

Display4

0

Display2

0

Display1

f(u)

C2K

inlet air velocity , m/s

inlet air temp, oC

to f an

outlet air temp, K

A/C

cool_mass

coolant temp, K

inlet air velocity , m/s

inlet air temp, oC

coolant density , kg/m3

Tcoolout

f low coef f a/b/c

outlet air temp, K

cac spec

1st charge air cooler

Radiator1

Coolant pump

Engine Thermostat

Radiator2

Fan & cooling air

Coolant pump

Charge Air Cooler

A/CCondenser

OilCooler

Power Bus

MotorGeneratorComponent Models

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SHEV Configuration (VESIM)

Engine400 HP

(298 kW)

Motor 2 x 200 HP (149 kW)

Generator400 HP

(298 kW)Battery

(lead-acid)18Ah /

120 modules

Vehicle 20,000 kg (44,090 lbs)

Maximum speed

55 mph (90 kmph)

Vehicle Specification

Engine

Generator

Vehicle

MotorBattery

Controller

PowerBus

Framework from the ARC Case Study: Integrated hybrid vehicle simulation (SAE 2001-01-2793)

ICM

Sprocket

Motors

Generator

Power Bus/Controller

EngineBattery

+-

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Sequential SHEV-Cooling System Simulation• Operation history of each HEV component from VESIM is fed into

Cooling system Model as input.

• Better computational efficiency compared to co-simulation

Hybrid Vehicle Model Cooling System Model

Driving schedule

-200

-100

0

100

200

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500

time(sec)

0

100

200

300

400

-100

0

100

200

300

400

500

600

700

0 100 200 300 400 500

time(sec)

-1500

-1000

-500

0

500

1000

1500

-200

0

200

400

600

800

1000

1200

1400

0 100 200 300 400 500

time(sec)

-1000

-500

0

500

1000

1500

2000

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500

time(sec)

0

10

20

30

40

50

0 300 600 900 1200 1500 1800Time(sec)

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Component Sizing Step 1 : Initial Scaling

• Radiator and pump are the main component that determines cooling capacity

• Initially, the sizes of radiator and pump are estimated by scaling from well established cooling system

scalscalradhtscalcrefrefradhtrefcscalref TAmTAmqq ,,,,,, ::

scalref

refscal

TqTq

a

2

cmq TAq radht .,

TAmq radhtc .,Therefore,

Heat rejection at radiator:

Scaling Factor (a)

scalrefradhtrefcrefrefradhtrefcscalref TaAmaTAmqq ,,,,,, ::

Hybrid vehicle cooling system criteriafor initial scaling

ComponentHeat

generation (kW)*

Temp. difference

(T-Tamb)

Engine 187 71.2

Motor 27 46.2

Generator 62 46.2

Charge air cooler 8 41.2

Oil cooler 27 81.2

Power bus 27 21.2

* Grade load condition at 48.8C ambient temperature

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Component Sizing Step 2 : Radiator Packaging

• Radiator occupies largest area• The radiator size is limited by the physical dimensions of the

vehicle( 20ton 0ff-road tracked vehicle ~ light tank)• Packaging constraint is determined by considering vehicle size

and radiator size of compatible vehicle (radiators are confined in 1.2x0.75 rectangle)

• The heights of all radiators are fixed at 0.75m for the convenience of radiator assembly

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Component Sizing Step 2 : Radiator Thickness

• Radiator thickness is another design factor• Optimal radiator thickness found by cooling power vs heat transfer test• Radiator thickness is designed not to exceed 100mm

Radiator

120

160

200

240

25 50 75 100 125 150Radiator Thickness (mm)

2kW

4kW

1kW

Radiator Test Device

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Component Sizing Step 3 : Pump Scaling

cmq TAq radht .,

TAmq radhtc .,Therefore,

or .,radhtc A

Tqm

Heat rejection at radiator:

Pump scaling:

.,.,, :: radhtref

radhtcrefc ATqA

Tqmm

• If radiator size is changed by the packaging constraint, cooling pump size should be rescaled

• First estimation don’t guarantee the cooling performance for vehicle cooling requirement

Hybrid vehicle cooling system criteria for pump scaling

ComponentHeat

generation (kW)*

Temp. difference

(T-Tamb)q / T

Engine 187 71.2 2.62

Motor 27 46.2 0.58

Generator 62 46.2 1.34Charge air

cooler 8 41.2 0.19

Oil cooler 27 81.2 0.33

Power bus 27 21.2 1.27

* Grade load condition at 48.8C ambient temperature

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Component Sizing Step 4 : Severe Condition Simulation• Three driving conditions were simulated to size the components

of cooling system and to evaluate cooling system design performance

Ambient Temperature : 48.8 oC (120F)

Grade Load(30mi/h, 7%)

Maximum Speed (Governed)

Grade Load(20mi/h, 12%)

0

100

200

300

400

0 300 600 900 1200 1500 1800Time(sec)

55mph 0% : 163kW

30mph 7% : 291kW 20mph 12% : 310kW

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Component Sizing Step 4 : Severe Condition Simulation• Detailed design is conducted by trial and error test under

severe condition (20mph, 12% grade)• Higher coolant temperature close to control target temperature

of component is recommended to reduce the radiator size• Temperature distribution in components / Coolant temperature

change in cooling circuit

1

2

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Driving Schedulefor the Evaluation of Cooling System

Heavy duty urban cycle + Cross country driving schedule

• Cooling system architectures are evaluated for representative mission.

-20

-10

0

10

20

30

0 300 600 900 1200 1500 1800Time(sec)

0

20

40

60

80

-20

-10

0

10

20

30

0 300 600 900 1200 1500 1800Time(sec)

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Cooling Performance during Driving Schedule

Electric Component Temperature

Generator Motor

Power Bus

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Cooling System Power Consumptions

Improvement of Power Consumption by Cooling System Redesign

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5

10

15Architecture AArchitecture BArchitecture C-9.6%

-31.1%

-11.6%-2.2%

Grade Load(12% 20mph)

City + Cross CountryDriving Cycle

Max. Speed(0% 55mph)

-1.7%-20.3%A B C

A B C A B C 0

100

200

300

400

Engine moduleElectric components

Grade Load(12% 20mph)

Max. Speed(0% 55mph)

City + Cross CountryDriving Cycle

58%

66%70%42%

33% 30%

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Summary• SHEV model was configured with the previously developed

VESIM and cooling system model for the SHEV was developed.

• The results show that the cooling system architecture of the SHEV should be developed considering various cooling requirements of powertrain components, power management strategy, performance, and parasitic power consumption.

• It is also demonstrated that a numerical model of the SHEV cooling system is an efficient tool to assess design concepts and architectures of the system during the early stage of system development

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Future Plan

• Co-simulation to study the effect of cooling system on the fuel economy of SHEVs and the interaction between the vehicle and cooling system.

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Acknowledgement

• Automotive Research Center (ARC)• General Dynamics, Land Systems (GDLS)

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Thank you for your attention