1. Cooling System Architecture Design for FCS Hybrid Electric Vehicle
Sungjin Park, Dohoy Jung, Zoran Filipi, and Dennis Assanis
Thrust Area 4
University of Michigan
The University of Michigan

2. Outline Motivation and Challenges Objectives
Cooling System Architecture Design
Cooling System Component Sizing
Results and Discussion
Summary and Future Plan

3. Motivation and Challenges
Sprocket
Motors
Generator
Power Bus/
Controller
Engine
Battery + -
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
Component
Heat generation (kW)*
Control Target T (oC)
Operation
Group
Engine
187
120 A
Motor 27 95 B
Generator 62
Charge air cooler 8 -
Oil cooler
130
Power bus 70 C
Battery 12 45 D

4. 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

5. Cooling System Architecture Development
Architecture A
- Separate cooling circuit is added for electric components.

6. Cooling System Architecture Development
Architecture A
Architecture B
Control Target Temp.
of Heat Sources
Component
Control target temp. (oC)
Engine
120
Oil cooler
130
Charge air cooler -
Motor 95
Generator
Power bus 70
Battery 45
- Cooling circuit for electric components is further divided into two circuits based on control target temperatures.

7. Cooling System Architecture Development
Architecture C
Operation Group of Heat Sources
Component
Operation group
Engine A
Generator
Charge air cooler
Oil cooler
Motor B
Power bus C
Battery D
Cooling Module 1
Cooling Module 2
- The heat source components are allocated into two cooling modules based on the operating groups to minimize redundant operation of the cooling fan.

8. Vehicle Cooling System Simulation (VECSS)
Component Models
Radiator1
Coolant
pump
Engine
Thermostat
Radiator2
Fan &
cooling air
Charge Air Cooler
A/C
Condenser
Oil
Cooler
Power Bus
Motor
Generator
Component
Approach
Heat Exchanger
Thermal resistance concept 2-D FDM
Pump
Performance data-based model
Cooling fan
Thermostat
Modeled by three-way valve
Engine
Map-based performance model
Engine block
Lumped thermal mass model
Generator
Power bus
Motor
Oil cooler
Heat exchanger model (NTU method)
Turbocharger
Condenser
Heat addition model
Charge air cooler

9. SHEV Configuration (VESIM)
Vehicle Specification I C M
Sprocket
Motors
Generator
Power Bus/
Controller
Engine
Battery + -
Engine
400 HP
(298 kW)
Motor
2 x 200 HP (149 kW)
Generator
Battery
(lead-acid)
18Ah /
120 modules
Vehicle
20,000 kg (44,090 lbs)
Maximum speed
55 mph
(90 kmph)
Engine
Generator
Vehicle
Motor
Battery
Controller
Power
Bus
Framework from the ARC Case Study: Integrated hybrid vehicle simulation (SAE )

10. 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
Driving schedule
Hybrid Vehicle Model
Cooling System Model

11. 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
Component
Heat generation (kW)*
Temp. difference
(T-Tamb)
Engine
187
71.2
Motor 27
46.2
Generator 62
Charge air cooler 8
41.2
Oil cooler
81.2
Power bus
21.2
* Grade load condition at 48.8C ambient temperature
Heat rejection at radiator:
Therefore,
Scaling Factor (a)
Hybrid vehicle cooling system criteria
for initial scaling 11

12. 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

13. 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 Test Device
Radiator

14. Component Sizing Step 3 : Pump Scaling
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
Component
Heat generation (kW)*
Temp. difference
(T-Tamb)
q / DT
Engine
187
71.2
2.62
Motor 27
46.2
0.58
Generator 62
1.34
Charge air cooler 8
41.2
0.19
Oil cooler
81.2
0.33
Power bus
21.2
1.27
* Grade load condition at 48.8C ambient temperature
Heat rejection at radiator:
Therefore, or
Pump scaling:
Hybrid vehicle cooling system criteria for pump scaling

15. 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%)

16. 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 1 2

17. Driving Schedule for the Evaluation of Cooling System
Cooling system architectures are evaluated for representative mission.
Heavy duty urban cycle +
Cross country driving schedule

18. Cooling Performance during Driving Schedule
Generator
Motor
Power Bus .
Electric Component Temperature

19. Cooling System Power ConsumptionsA B C
58%
66%
70%
42%
33%
30%
Improvement of Power Consumption by Cooling System Redesign

20. 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

21. 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.

22. Automotive Research Center (ARC) General Dynamics, Land Systems (GDLS)
Acknowledgement
Automotive Research Center (ARC)
General Dynamics, Land Systems (GDLS)
I’d like to thanks to automotive research center and general dynamics land system for their support for this study.

23. Thank you for your attention