1 Cooling System Architecture Design for FCS Hybrid

1 Cooling System Architecture Design for FCS Hybrid Electric Vehicle Sungjin Park, Dohoy Jung, Zoran Filipi, and Dennis Assanis The University of Michigan In collaboration with Thrust Area 5 ARC

2 Outline • Background • Motivation and Challenges • Objectives • SHEV Configuration • Cooling System Component Modeling • Cooling System Architecture • Results and Discussion • Summary and Future Plan ARC

Army Ground Vehicle Propulsion Challenges 1. Cooling 2. Cooling 3. Cooling 4. Fuel Effects 5. Filtration The Army vehicle cooling point is high tractive effort to weight under desertlike operating conditions (ex. 5 ton wheeled vehicle ~0. 6 while 15 ton tracked vehicle ~0. 7 both at 120 F ambient) This slide is from the keynote by Dr. Pete Schihl during the 2007 ARC annual conference ARC 3

4 Future Combat System (FCS) • Series Hybrid Electric Vehicle (SHEV) is under development for the automotive platform of FCS. – Improved fuel economy – Greater electric power requirements for advanced weapon system – Exportable electric power – Enhanced low speed maneuverability – Low acoustic signature and stealth operation – Pulse power necessary to drive weapon/mobility/communication/protective systems – Better maintenance: non-mechanical coupling of the power generation unit with drive train architecture ARC

5 Case Study Objectives • Develop a guideline/methodology for cooling system architecture selection for the SHEV • Develop cooling system models for optional architectures. • Explore and demonstrate proper architectures and strategies for thermal management of hybridized powertrain • Optimize the cooling system and component design for performance, size and minimal parasitic loss ARC

6 Motivation and Challenges • SHEVs need additional components – Generator, Motor, Battery, and Power bus • SHEVs also have a dedicated cooling system for the hybrid components with different requirements • Cooling system design for SHEV requires more strategic approach – Multiple cooling circuits due to additional components – Different operating temperature and driving modes • Numerical approach is an efficient way for complicated HEV cooling system design and development. ARC

Vehicle Cooling system for Future Combat System (FCS): Challenges • Heavy-duty operation (20 ton, 400 -500 hp vehicle) • Severe military operation under extreme ambient conditions • Shielded cooling system for survivability • Complicated cooling system architecture in SHEV due to the additional heat sources with various requirements • Vehicle cooling system operation and performance varies with powertrain operation, control, and driving conditions. ARC Control SHEV Cooling System Heat generation @grade load (k. W) Target Temp. Engine 190 120 Oil cooler 40 125 Charge air cooler 13 - Motor 27 95 Generator 65 95 Power bus 5. 9 70 Component (o. C) Battery 12 45 Conventional Cooling System 7

8 Objectives • Develop an efficient cooling system architecture for the SHEV and Optimize the cooling system design using numerical approach: – Configure a SHEV model using VESIM – Model the components of the cooling system for SHEVs – Develop cooling system model integrating the components models – Evaluate the cooling system designs and architectures – Optimize the cooling system • SHEVs need effective cooling system design that has least impact on fuel economy and cost ARC

9 SHEV Configuration (VESIM) Engine Motor Generator Power Bus Engine Controller ARC 2 x 200 HP (149 k. W) 400 HP (298 k. W) 18 Ah / (lead-acid) 120 modules Vehicle 20, 000 kg (44, 090 lbs) Maximum speed Vehicle (298 k. W) Battery Motor 400 HP 45 mph (72 kmph)

10 Power Management of Hybrid Vehicle Discharging mode Charging/Electric Drive mode • Battery is the prime power source • Engine/Generator is the prime power source • When power demand exceeds • When battery SOC is lower than battery ability, the engine is limit, engine supplies additional activated to supplement power to charge the battery demand • Once the power demand is determined, engine is operated at most efficient point ARC Braking mode • Regenerative braking is activated to absorb braking power • When the braking power is larger than motor or battery limits, friction braking is used

SIMULINK Based Vehicle Cooling System Simulation (VCSS) 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 three-way valve 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) ARC 11

SIMULINK Based Vehicle Cooling System Simulation (VCSS) Heat Source Components Component Engine Heat generation model Heat transfer model Map-based performance model Pressure drop model Experimental correlation: Generator Battery is charged and motor is working Lumped thermal mass model Flow in smooth pipe Power bus Motor is working Laminar: Motor is generating Turbulent: Motor Generator: Turbocharger Map-based performance model N/A ARC 12

SIMULINK Based Vehicle Cooling System Simulation (VCSS) Heat Sink Components Component Heat generation model Heat transfer model N/A Thermal resistance concept 2 D FDM [8] Condenser Heat from A/C module is assumed to be constant Heat addition model Charge air cooler N/A Thermal resistance concept 2 D FDM Radiator Heat Source Oil cooler Water side : Air side : Map-based performance model Heat addition model Heat exchanger model (NTU method) [9] Heat Exchanger Pressure drop model Flow in smooth pipe Laminar: N/A Turbulent: Performance data-based model Oil Pump N/A ARC 13

SIMULINK Based Vehicle Cooling System Simulation (VCSS) Delivery Media Components Component Flow rate model Heat transfer model Pressure drop model Performance data-based model Pump N/A N/A Performance data-based model Cooling fan Modeled by a pair of valves Thermostat Lumped thermal mass model ARC 14

15 Cooling System Architecture Development Architecture A (1) Separate cooling circuit is added for electric components. (2) Electric pumps are used for electric heat sources to separate the cooling circuit for electric components from engine module (3) The radiators are arranged in the order of control target temperature of heat source which is cooled by the radiator ARC

16 Cooling System Architecture Development Architecture A Architecture B Component Control target temp. (o. C) Engine 120 Motor / controller 95 Generator / controller 95 Charge air cooler - Oil cooler 125 Power bus 70 Battery 45 Control Target Temp. of Heat Sources (1) Cooling circuit for electric components is further divided into two circuits based on control target temperatures. (2) Electric pumps are used for electric heat sources to separate the cooling circuit for electric components from engine module (3) The radiators are arranged in the order of control target temperature of heat source which is cooled by the radiator. ARC

17 Cooling System Architecture Development Architecture C Component Operation group Engine A Motor / controller B Generator / controller A Charge air cooler A Oil cooler A Power bus C Battery - Operation Group of Heat Sources Cooling Module 1 Cooling Module 2 (1)The heat source components are allocated into two cooling modules based on the operating groups to minimize redundant operation of the cooling fan. (2) The condenser used for the air conditioning of the compartment is placed in the cooling module where the heat load is relatively lower. ARC

SIMULINK Based Vehicle Cooling System Simulation 18 Vehicle Cooling System Simulation (VCSS) Cooling circuit for electric components A/C Condenser Electric Components Parallel Cooling Coolant Circuit pump Radiator 1 Cooling circuit for engine module Parallel Charge Air Cooling Cooler Circuit Engine Block Coolant pump ARC Oil Cooler Thermostat Fan & cooling air Radiator 2

19 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 ARC

20 Cooling System Test Conditions • Three driving were selected to size the components of cooling system and to evaluate cooling system design performance Grade Load Maximum Speed (Governed) Ambient Temperature : 40 o. C Road profile for off-road ARC Off-Road

Power Consumption of Cooling System (Grade load condition) ARC 21

22 Driving Schedule for the Evaluation of Cooling System • Realistic driving schedule is needed to evaluate the cooling system • City + Cross country driving schedule is used Component Operation group Engine A Motor / controller Generator / controller Charge air cooler A Oil cooler A Power bus C Battery - B A Operation Group of Heat Sources City + Cross country Driving Schedule Heat Rejection Rate of Each Component over Driving Schedule ARC

Power Consumption and Cooling Performance during Driving Schedule Electric Component Temperature Power Consumption ARC 23

24 Cooling System Power Consumptions Portion of Cooling System Power Consumption in Engine Power Improvement of Power Consumption by Cooling System Redesign ARC

25 Summary and Future Plan • SHEV model was configured with the previously developed VESIM. • Cooling system model for the SHEV was developed. • The results show that strategic approach to cooling system architectural design of SHEVs can reduce the power consumption and enhance the performance significantly. • Co-simulation of VESIM and Cooling system model is needed to evaluate - Fuel economy impact - Interaction between the powertrain system and cooling system ARC