Impact of BEV Powertrain architectures on energy consumption in various driving cycles Stackpole Powertrain International GmbH C O N F I D E N T I A L
Authors Sanketh Jammalamadaka Student worker SJammalamadaka@stackpole.com Dipl.-Ing. Philipp Schaeflein Business Development Manager PSchaeflein@stackpole.com Dr.-Ing. Philipp Kauffmann Research and Innovation Manager PKauffmann@stackpole.com Contact: Stackpole Powertrain international GmbH Campus-Boulevard 30, 52074 Aachen Tel.: +49 241 4636 7033 Fax: +49 241 4636 7050 info-aachen@stackpole.com 2
BEV and HEV market projection 1,40E+07 1,20E+07 1,00E+07 8,00E+06 6,00E+06 4,00E+06 2,00E+06 Reduction EVT DCT CVT Automatic AMT 0,00E+00 CY 2017 CY 2018 CY 2019 CY 2020 CY 2021 CY 2022 CY 2023 CY 2024 Source: IHS September 2017 Variety of different powertrain concepts are competing against each other in xev powertrain, not clear which technology will conquer the market System Simulation can help to understand technological advantages of various concepts. 3
Technology analysis of EV powertrains Tesla Model S BMW i3 Existing EV powertrain solutions use 2-stage cylindrical gear sets due to low complexity and low production volume Number of stages 1 2 3 4 Type of stage spur gear planetary gear combination Number of speeds 1 2 3 4 Ratio 7 8 9 10 11 12 Type of lubrication Injection oil bath Total Ratio: 7-10 4
BMW i8 s two-speed concept 1 2 3 4 2 3 1 9 8 5 7 4 6 Wheel Wheel 5 1: PLCD sensor 2: Gearshift fork 3: Input shaft 4: First gear 5: Intermediate shaft 6: Differential 7: Breather 8: Second gear 9: Gear selector 1: First gear 2: Second gear 3: Selector sleeve 4: Final drive 5: Differential 1st gear ratio: 11.38 2nd gear ratio: 5.85 5 The reduction transmission is inferior, which might lead to a replacement in future pure electric vehicles
Our motivation for system simulation 1 Is it possible to model energy consumption of BEV with GT- Suite? 2 3 What are the loss contributors in the standard driving cycle? How does the energy consumption losses differ in urban, suburban and rural driving conditions? 4 5 How does behaviour of BEV differ from ICE Vehicle? Can addition of second gear improve energy consumption in different cycles? 6
Our motivation for system simulation 1 Is it possible to model energy consumption of BEV with GT- Suite? 7
Reference BEV Vehicle model Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance Factor μ tire 0,01 Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient C d 0,29 Vehicle Frontal Area A f 2,38 m 2 Auxiliary Power Consumption - 750 W Note:Auxiliary power consumption is approximated to consumption of power electronics and control unit to operate the powertrain. Lights, horn, cooling and heating systems are not considered. 8
Reference BEV Powertrain model Maximum Power P max 125 kw Electric Motor Maximum Torque T max 250 Nm Maximum Speed N max 11400 RPM Efficiency ƞ EM Efficiency Map Battery Capacity - 60 Ah Number of speeds n 1 Transmission Gear Ratio i - Efficiency ƞ T - 9
Transmission efficiency map Number of Speeds n 1 Transmission Gear Ratio i 9,665 Efficiency ƞ T Efficiency Map Transmission Efficiency BMW i3 transmission efficiency test results. Tests conducted in collaboration with IKA, RWTH Aachen. Efficiency [%] 98.2 98 97.8 97.6 97.4 Efficiency at 40 C Tq=50 Tq=100 Tq=150 Tq=250 97.2 97 96.8 96.6 0 500 1000 1500 2000 2500 3000 Speed [rpm] 10
Benchmarking simulation results Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance μ tire 0,01 Factor Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient C d 0,29 BMW i3 NEDC cycle power consumption BMW i3 official specification 12,9 kw-h/100km System simulation 12,2 kw-h/100km Vehicle Frontal Area Electric Motor Transmission A f 2,38 m 2 P max T max N max ƞ EM 125 kw 250 Nm 11400 RPM Efficiency Map n 1 i 9,665 ƞ T Efficiency Map Model is Validated 11
Our motivation for system simulation 1 2 Is it possible to model energy consumption of BEV with GT-Suite? What are the loss contributors in the standard driving cycle? 12
Single speed reference BEV Energy loss contributors Vehicle Mass m vehicle 1300 kg 14 P max 125 kw 12 Electric Motor Transmission T max N max ƞ EM 250 Nm 11400 RPM Efficiency Map n 1 i 9,665 Energy Loss [kw-h/100km] 10 8 6 4 ƞ T Efficiency Map 2 Drag F drag ρ C d A f v 2 / 2 0 Rolling Resistance Auxiliary Loss F tire m vehicle. g. μ tyre. Cos(α) Time dependent -2 NEDC Powertrain Loss 2,2 Drag 4,1 Driving Cycle NEDC Rolling Resistance 3,7 Power Consumption (kw-h/100km) 12,2 Auxiliary Load 2,2 Regenerative Braking -0,8 13
Our motivation for system simulation 1 2 3 Is it possible to model energy consumption of BEV with GT- Suite? What are the loss contributors in the standard driving cycle? How does the energy consumption losses differ in urban, suburban and rural driving conditions? 14
Three representative driving cycles NYCC New York City Cycle Urban Cycle NEDC New European Driving Cycle Sub Urban Cycle HWFET Highway Fuel Economy Test Cycle Rural Cycle < 45 kph < 120 kph < 50 kph > 46 kph 15
Energy loss split-up in representative driving cycles 16 Vehicle Mass m vehicle 1300 kg Electric Motor Transmission Driving Cycle Power Consumption (kwh/100km) P max T max N max ƞ EM 125 kw 250 Nm 11400 RPM Efficiency Map n 1 i 9,665 ƞ T Efficiency Map Drag F drag ρ C d A f v 2 / 2 Rolling Resistance Auxiliary Loss F tire m vehicle. g. μ tyre. Cos(α) Time dependent Power consumption in various driving cycles NYCC NEDC HWFET 14 12,2 12,6 Global Energy Loss in % Powertrain Losses [%] NYCC NEDC HWFET 21 18 17 Drag [%] 5 34 46 Rolling Resistance [%] 27 30 29 Auxiliary Load [%] 47 18 8 Regenerative Braking [%] 100 90 80 70 60 50 40 30 20 10 0-10 -9-7 -5
Our motivation for system simulation 1 2 3 Is it possible to model energy consumption of BEV with GT- Suite? What are the loss contributors in the standard driving cycle? How does the energy consumption losses differ in urban, sub-urban and rural driving conditions? 4 How does behaviour of BEV differ from ICE Vehicle? 17
Energy consumption sensitivity comparison: BEV vs. ICE Vehicle Mass m vehicle 1300 kg Electric Motor P max T max N max 125 kw 250 Nm 11400 RPM NYCC Deviation from NEDC consumption is less for BEV compared to NA SI engine, as a result of unstable driving conditions supported by regenerative braking. Transmission ƞ EM Efficiency Map n 1 i 9,665 ƞ T Efficiency Map HWFET NA SI engines have minimum energy consumption in stable driving conditions. 200 % of energy consumption with NEDC as reference 150 100 50 BEV Simulation NA SI engine NYCC NEDC HWFET 18 Source: Impact of Conventional and Electrified Powertrains on Fuel Economy in Various Driving Cycles by Sarp Mamikoglu, Jelena Andric, and Petter Dahlander, Chalmers University of Technology
Our motivation for system simulation 1 2 3 Is it possible to model energy consumption of BEV with GT- Suite? What are the loss contributors in the standard driving cycle? How does the energy consumption losses differ in urban, suburban and rural driving conditions? 4 5 How does behaviour of BEV differ from ICE Vehicle? Can addition of second gear improve energy consumption in different cycles? 19
Gear shift strategy Gears upshift speed is 60kph and down shift speed is 55kph Driving cycle Number of gear shifts NYCC 0 NEDC 4 HWFET 4 < 45 kph < 120 kph < 50 kph > 46 kph 20
Optimization of gear ratios NYCC Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance Factor μ tire 0,01 9,665 Energy consumed per cycle [kw-h ] Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient C d 0,29 Vehicle Frontal Area A f 2,38 m 2 Electric Motor P max T max N max 125 kw 250 Nm 11400 RPM ƞ EM Efficiency Map 21
Optimization of gear ratios NEDC Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance μ tire 0,01 Factor Air Density ρ 1,17 kg/m 3 9,665 9,665 Energy consumed per cycle [kw-h ] Vehicle Drag Coefficient C d 0,29 Vehicle Frontal Area A f 2,38 m 2 Electric Motor P max T max N max 125 kw 250 Nm 11400 RPM ƞ EM Efficiency Map 22
Optimization of gear ratios HWFET cycle Vehicle Mass m vehicle 1300 kg 9,665 Tire Rolling Resistance Factor μ tire 0,01 9,665 Energy consumed per cycle [kw-h ] Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient C d 0,29 Vehicle Frontal Area A f 2,38 m 2 Electric Motor P max T max N max 125 kw 250 Nm 11400 RPM ƞ EM Efficiency Map 23
Optimization of gear ratios 0-100kph time Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance Factor μ tire 0,01 9,665 9,665 Time for 0-100kph [sec] Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient Vehicle Frontal Area C d 0,29 A f 2,38 m 2 Electric Motor P max T max N max ƞ EM 125 kw 250 Nm 11400 RPM Efficiency Map 24
Optimization of gear ratios for balanced power consumption and performance NYCC i s1 =11,5 i s2 = - NEDC Best efficiency i s1 = 6,9 i s2 = 4,1 HWFET Best efficiency i s1 = 8,3 i s2 = 4,1 0-100kph Best performance i s1 = 20,0 i s2 = 8,4 To have a balanced efficiency and performance, gear ratio i s1 =9,667 and i s2 = 4,47 are chosen with Reference and Eco modes. Reference Mode No gear shifts Constant engaged gear ratio i s1 = 9,665 Eco Mode i s1 =9,665 i s2 =4,47 25
Simulation results - Gear ratios selected to balance efficiency and performance Vehicle Mass m vehicle 1300 kg Tire Rolling Resistance μ tire 0,01 Factor Air Density ρ 1,17 kg/m 3 Vehicle Drag Coefficient C d 0,29 Vehicle Frontal Area A f 2,38 m 2 Electric Motor P max T max N max 125 kw 250 Nm 11400 RPM Energy Consumption [kw-h/100km] 15 14 13 12 ƞ EM Efficiency Map 11 NYCC NEDC HWFET Transmission n 1 is1 9,665 i s2 4,47 Reference mode i=9,665 Eco mode i1=9,665, i2=4,47 14 12,2 12,6 14 11,6 11,5 ƞ T Efficiency Map Optimized gear ratio 13,9 11,6 11,5 26
Dual speed transmission energy loss distribution Vehicle Mass m vehicle Electric Motor Transmission P max T max N max ƞ EM 1300 kg 125 kw 250 Nm 11400 RPM Efficiency Map n 2 i s1 9,665 i s2 4,47 ƞ T Efficiency Map Drag F drag ρ C d A f v 2 / 2 Rolling Resistance Auxiliary Loss F tire m vehicle. g. μ tyre. Cos(α) Time dependent Global Energy Loss in % Powertrain Losses [%] NYCC NEDC HWFET 21 14 9 Drag [%] 5 35 51 Rolling Resistance [%] 27 32 32 Auxiliary Load [%] 47 19 8 Regenerative Braking [%] 100 90 80 70 60 50 40 30 20 10 0-10 -9-7 -5 27
Energy loss distribution comparison Global Energy Loss in % Energy loss for single speed transmission Powertrain Losses [%] NYCC NEDC HWFET 21 18 17 Drag [%] 5 34 46 Rolling Resistance [%] 27 30 29 Auxiliary Load [%] 47 18 8 Regenerative Braking [%] 100 90 80 70 60 50 40 30 20 10 0-10 -9-7 -5 Global Energy Loss in % Energy loss for two speed transmission Powertrain Losses [%] NYCC NEDC HWFET 21 14 9 Drag [%] 5 35 51 Rolling Resistance [%] 27 32 32 Auxiliary Load [%] 47 19 8 Regenerative Braking [%] 100 90 80 70 60 50 40 30 20 10 0-10 -9-7 -5 28
Operational points of electric motor NYCC NEDC 250 250 150 150 Torque [Nm] 50-50 -150 0 5000 10000 Torque [Nm] 50-50 -150 0 5000 10000-250 Speed [RPM] -250 Speed [RPM] HWFET 250 Torque [Nm] 150 50-50 -150-250 0 5000 10000 Speed [RPM] Driving Cycle Average Operational Efficiency Of Transmission Single Speed Dual Speed NYCC 75% 75% NEDC 79% 81% HWFET 85% 93% 29
Questions answered 1 2 3 4 5 Is it possible to model energy consumption of BEV with GT- Suite? What are the loss contributors in the standard driving cycle? How does the energy consumption losses differ in urban, suburban and rural driving conditions? How does behaviour of BEV differ from ICE Vehicle? Can addition of second gear improve energy consumption in different cycles? 30
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