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 Thrust Area 4 University of Michigan The University of Michigan ARC

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

3 Motivation and Challenges • Cooling system is critical issue for combat vehicle’s survivability • Series Hybrid Electric Vehicle for FCS. Power Bus/ Controller ICM Motors Generator • 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 ARC + Battery Engine Sprocket Component Heat generation (k. W)* Control Target T (o. C) Operation Engine 187 120 A Motor 27 95 B Generator 62 95 A Charge air cooler 8 - A Oil cooler 27 130 A Power bus 27 70 C Battery 12 45 D Group

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 ARC

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

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

7 Cooling System Architecture Development Architecture C Operation Group of Heat Sources Component Operation group Engine A Generator A Charge air cooler A Oil cooler A 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. ARC

8 Vehicle Cooling System Simulation (VECSS) Component Models Component Approach Heat Exchanger Thermal 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 model Generator Lumped thermal mass model Power 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 model Charge air cooler Thermal resistance concept 2 -D FDM Generator Motor Power Bus Coolant pump A/C Condenser Radiator 1 Charge Air Cooler Engine Oil Cooler Coolant pump ARC Thermostat Radiator 2 Fan & cooling air

9 SHEV Configuration (VESIM) Vehicle Specification Engine Motor Generator 400 HP (298 k. W) 2 x 200 HP (149 k. W) 400 HP 18 Ah / (lead-acid) 120 modules Maximum speed Motors Generator + Battery Engine (298 k. W) Battery Vehicle Power Bus/ Controller ICM Sprocket Generator Power Bus Engine 20, 000 kg (44, 090 lbs) Battery Motor 55 mph (90 kmph) Controller Framework from the ARC Case Study: Integrated hybrid vehicle simulation (SAE 2001 -01 -2793) ARC Vehicle

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 ARC

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 Heat rejection at radiator: Therefore, Scaling Factor (a) 11 Heat generation (k. W)* Temp. difference 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 Component (T-Tamb) * Grade load condition at 48. 8 C ambient temperature Hybrid vehicle cooling system criteria for initial scaling ARC

Component Sizing Step 2 : Radiator Packaging • Radiator occupies largest area • The radiator size is limited by the physical dimensions of the vehicle( 20 ton 0 ff-road tracked vehicle ~ light tank) • Packaging constraint is determined by considering vehicle size and radiator size of compatible vehicle (radiators are confined in 1. 2 x 0. 75 rectangle) • The heights of all radiators are fixed at 0. 75 m for the convenience of radiator assembly ARC 12

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 100 mm Radiator Test Device Radiator ARC 13

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 Temp. Heat generation (k. W)* difference Engine 187 71. 2 2. 62 Motor 27 46. 2 0. 58 Generator 62 46. 2 1. 34 Charge air cooler 8 41. 2 0. 19 Oil cooler 27 81. 2 0. 33 Power bus 27 21. 27 Component Heat rejection at radiator: Therefore, or Pump scaling: q / DT (T-Tamb) * Grade load condition at 48. 8 C ambient temperature Hybrid vehicle cooling system criteria for pump scaling ARC

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 o. C (120 F) Maximum Speed (Governed) Grade Load (30 mi/h, 7%) ARC Grade Load (20 mi/h, 12%) 15

Component Sizing Step 4 : Severe Condition Simulation • Detailed design is conducted by trial and error test under severe condition (20 mph, 12% grade) 1 • Higher coolant temperature close to control target temperature of component is recommended to reduce the radiator size 2 • Temperature distribution in components / Coolant temperature change in cooling circuit 1 2 ARC 16

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

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

19 Cooling System Power Consumptions 58% A B C 42% A B C 66% 33% 70% Improvement of Power Consumption by Cooling System Redesign ARC 30%

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 ARC

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. ARC

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

23 Thank you for your attention ARC