Downsized and Supercharged Hybrid-Pneumatic Engine
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Transcript of Downsized and Supercharged Hybrid-Pneumatic Engine
Downsized and Supercharged Hybrid-Pneumatic Engine C. Dönitz, C. Onder, I. Vasile, C. Voser, L. Guzzella
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Nothing New (the Parsey Locomotive, 1847)
Source: http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm
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Dickson Locomotive, 1899
Source: http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm
Mass 16 t, storage 40 bar, working 10 bar, volume 4.8 m3
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Compressed Air as Fuel?
η3= 81%
η2= 44%
η1= 90%
Ptank=300 barTtank= 300 K
η4= 80%
0.25ηtot
Necessary energy in air tank 70 MJ, which corresponds to 320 kg air mass and 200 kg tank mass (kevlar composite) and 925 l tank volume.
Compare that to BEV: plug-to-wheel efficiency of ηtot= 0.75 and 150 kg battery mass (Li-ion batteries with 100 Wh/kg useful energy density).
45 MJ/100km
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Pneumatic Hybrid Powertrains?
Internal combustion engine as range extender: too many components and poor fuel economy
Hybrid pneumatic engine: 1 main energy supply 1 energy buffer 1 energy conversion device
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Directly vs. Indirectly Connected Air Tank
Indirectly Connected Air Tank:
+ Only limited changes in valve actuation system needed
+ No major cylinder head changes− Mode changes difficult/restricted− Reduced actual pumping
compression ratio
Directly Connected Air Tank− Add charge valve actuation to
system− Cylinder head redesign+ Mode changes easy+ Pumping compression ratio not
compromised
Adapted from:A. Fazeli, A. Khajepour, C. Devaud, and N. Lashgarian Azad. A new air hybrid engine using throttle control. SAE Paper 2009-01-1319
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0.1
0.2
0.25
0.3
0.330.350.36
• “downsizing” V-6 R-3
0.10.2
0.25
0.30.330.35
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• “supercharging”
T
n
Replace a V-6 by an R-3 with turbocharger
Downsizing and Supercharging (DSC)
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input
output
idle input
0
full loadoutput
full load inputxx=0.37=0.37
xx=0.17=0.17
Willans Behavior
xx=0.27=0.27
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Problems DSC
?
Drivability
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The Hybrid Pneumatic Engine (HPE) Idea
Previous work by Herrera (1998), Schechter (1999), and Higelin (2001)
Air tank as energy buffer
Recuperation and pneumatic driving
Pneumatic modes are 2-stroke based, all valves variable
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Comparison Valve Actuation Modes
2-stroke modes require variable actuation for all valves 4-stroke concept is cheaper and less complex
IV – Intake Valve
EV – Exhaust Valve
CV – Charge Valve
– ETH Modes
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The ETH DSC HPE Concept
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Operating Modes
Engine Mode
Torque Uses Gasoline
Air Tank Pressure Usage
Pump - no ↑↑ vehicle braking
Pneumatic Motor
+ no ↓↓ rapid pneumatic engine start (avoids idling) & cruising
Conv. Combustion
+ yes →→ most often used engine mode
Super-charged
+ yes ↓↓ transients only, overcoming turbo lag
Recharge (>= 4 cyl.)
+ yes ↑↑ e.g. 2 cylinders pump, 2 cylinders burn,
shifting operating point
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a) b) c)
Additional Engine Modes
a) Pump mode: throttle always open
b) Pneumatic motor mode: closes throttle for higher torque
c) Supercharged mode: air injection at start of compression
- Recharge mode: 2 cylinders conventional, 2 cylinders pump
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Simulation Vehicle & Engine Parameters
Base vehicle weight 1450 kg, engine weight: 67kg/l Rated power: 100kW for all engines, baseline is 2.0l NA
gasoline engine Auxiliaries consume 400 W Gearbox: manual, 5-speed, η=93% Mid-size vehicle, Tank volume 30 liters Effect of reduced compression ratio on engine efficiency
considered Variable valve actuation energy accounted for according
to number of used EHVS.
0.83f dA c
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Baseline Engine as Willans Machine
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Engine Scaling
Account for reduced internal efficiency when reducing the compression ratio due to supercharging
Values obtained using engine process simulation
engine ε k(ε)
2.0l NA 10.5 1
1.6l TC 9.5 0.978
1.4l TC 9.5 0.978
1.2l TC 9.0 0.966
1.0l TC 9.0 0.966
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Variable Valve Actuation Energy
,, ,
/ 4Hyd Hyd i Hyd i Hydi CV EV IV
T V p z
[bar] min max 8 ,50 ,200Hyd Tankp p
Valve # per Zylinder
yHyd type
Charge Valve CV 1 5 mm V0.5
Intake Valves IV 2 10 mm V0.7
Exhaust Valves EV 2 10 mm V0.7
Energy demand for EHVS is added to demanded torque Hydraulic pump efficiency of ηHyd=0.6 assumed
zi is the number of variably actuated valves per 2 revolutions
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MVEG-95, 1550 kg vehicle
Simulations (1): Fuel Economy
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QSS & Dynamic Programming
Additional degree of freedom, additional state: Internal energy of air tank
Use quasi-static simulation (QSS) and engine mode maps and reduce to
Dynamic Programming: One state: tank pressure One input: engine mode choice Disturbance: drive cycle Cost: fuel consumed
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Simulations (2): Influence Tank Volume
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Simulations (3): Overcoming the Turbo-lag
Simulation for 1500 kg vehicle in 4th gear with 0.75 liter engine
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PFI/stoich gasoline engine Asymmetric turbo charger
Variable valve actuation system for CV only Air tank (cold tank strategy)
Engine Type
Additional Hardware:
Main Ideas
Strong downsizing to improve fuel economy
Connect pressurized air tank directly to engine cylinders: enables excellent driveability
The ETH DSC HPE Test Engine
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Hardware (1): Modified Engine MPE750
engine data
manufacturer Weber Automotive GmbH (WENKO)
displaced volume 0.75 liter
# cylinders 2, parallel twin 360°
compression ratio 9.0
fuel gasoline port fuel injection
# valves 2 IV, 2 EV per cylinder
turbocharger Garrett GT 12 (C) – 14(T)
rated power 61 kW
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Hardware (2): Modified Engine MPE750
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Electro-Hydraulic Valve Actuation System
21.04.23
EHVS provides fully variable valve actuation for the CV:
opening closing
K. Mischker and D. Denger. Requirements for a fully variable valvetrain and realization with the electro-hydraulic valvetrain system EHVS. VDI-Fortschritt-Berichte, 12(539), 2003.
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Hardware (3): Engine on testbench
Air tank 30 liters, steel, not insulated for cold-tank strategy
Engine equipped with GT12 compressor & GT14 turbine
Electricwastegate actuator
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… or come and visit us!
A (virtual) lab visit
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Hardware (4): Engine Control Systems
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Engine Controls:Vehicle Emulation Control Architecture
Dynamometer controls torque (behaves like a vehicle in drive cycle)
Engine controls speed
Supervisory control determines engine mode f(pT)
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Measurements (1): The Supercharged Mode
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Measurements (2): The Supercharged Mode
Test at constant intake pressure (550 mbar)
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Measurement (3): Overcoming the Turbolag
N = 2000 rpm
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Measurements (4): Rapid Pneumatic Start
Rapid engine start enables start/stop operation and thus the elimination of idling.
Pneumatic engine start < 350ms for pT= 10 bar.
pT = 10 bar
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Optimization Results Pneumatic Modes
Pump mode: operating area strongly limited
Pneumatic motor mode: only for low engine speeds
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Measurements (4): Recuperation Efficiency
€
maxTeff
Δmair
⎛
⎝ ⎜
⎞
⎠ ⎟p.mot
× maxΔmairTeff
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟pump
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Remark: Recuperation using Alternator
Recuperation: pumping is limited by four-stroke mode In the MVEG-95 ~500 kJ cannot be recuperated by
pumping air in braking phases Excess energy can be used for:
EHVS actuation: 104 kJ needed to drive MVEG-95 (assuming 60% efficiency for the alternator & 60% efficiency for an electric hydraulic pump)
Electric auxiliaries need 300 W at the crankshaft for 1200 s, i.e., 360 kJ are needed for the drive cycle
Fuel consumption can be further reduced
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Experiment: VW Polo, MVEG-95
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Engine Mode Determined Using DP
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Experiment: Nissan Micra, FTP
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Engine Mode Determined Using DP
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Fuel Consumption Measurement Results Engines of approximately same maximum power are compared Comparison to NA SI engines in series production cars
Measured Fuel Consumption Reduction (MVEG-95)
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Result Overview, MVEG-95
Vehicle VW Polo (2005)
VW Polo (2009)
Nissan Micra
Nissan Micra
Toyota Prius II
Engine Vd 1390 ccm 1390 ccm 1240 ccm 1386 ccm 1497 ccm
Rated power 59 kW 63 kW 59 kW 65 kW 57 kW
Weight 1088 kg 1070 kg 1065 kg 1075 kg 1400 kg**
Price (CHF) 19’770 22’600 16’897 20’090 38’950
ECE / EUDC / NEDC (l/100km)
8.3 / 5.2 / 6.3
8.0 / 4.7 / 5.9
7.4 / 5.1 / 5.9
7.9 / 5.4 / 6.3
5.0 / 4.2 / 4.3
Hybrid Pneumatic MPE750 (61kW), 30l Air Tank
ECE / EUDC / NEDC (l/100 km)
4.2 / 4.0 / 4.1
(4.2 / 3.9 / 4.0)*
4.3 / 4.6 / 4.4
4.2 / 4.5 / 4.4
(4.5 / 4.4 / 4.5)**
Fuel savings - 49.4 % / - 23.2 % / - 35.4 %
(- 47.2 % /- 17.5 % /- 31.9 %)*
- 42.6 % /- 10.5 % /- 24.6 %
- 46.3 % /- 16.2 % /- 29.8 %
(- 9.1 % /+ 5.0 % /+ 3.7 %)**
Δ rated power + 3.4 % - 3.2 % + 3.4 % - 6.2 % + 7.0 %**
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Result for FTP, Nissan Micra
Vehicle Nissan Micra (visia)
Engine Vd 1240 ccm
Rated Power 59 kW
Weight 1065 kg
Price (CHF) 16’897
FTP part 1 / 2 / 3 / comb. 6.2 / 6.5 / 5.6 / 6.1 (l/100km)
Hybrid Pneumatic MPE750 (61kW), 30l Air Tank
FTP part 1 / 2 / 3 / comb. 4.8 / 4.4 / 4.6 / 4.6 (l/100km)
Fuel Savings - 22.4 % / - 32.7 % / - 17.9 % / - 24.9 %
Data sources: Touring Club Switzerland www.tcs.ch, EMPA Switzerland, OEM webpages
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Electric Hybridization vs. DSC HPE Concept
DSC & pneum. hybridization
electric hybridization
HPE: Estimated added cost for EHVS & tank: 1500 CHF (conservative)
For normalization:base rated power 61 kWbase weight 1080 kg (Prius base weight 1250 kg)
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Thank you for your attention!
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Compressed Air in a Series Hybrid?
η2= 80% η3= 80%η1= 35%
45 MJ / 100kmη4= 81%
ptank=20-30 barTtank= 700-800 K
η5= 80%
ICE 20 kW comp. 20 kW1-stage
pneum.motor 60 kW
COP = 1
adiabatic tank, ~50 l
0.15ηtot
0.19ηtot
η13= 95%η11= 35% η4= 81%
ptank~ 80 barTtank= 400 K
η5= 80%
ICE 20 kW comp. 20 kW2-stages
pneum.motor 60 kW
COP = 0.5η12= 80%
air tanks ~50 l and ~10 l
Q21 = 65%
45 MJ / 100km
η22= 50% η23= 50%
Expand and
heat up
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Reproduceability of Measurements
Mean measured fuel consumption (g)
Deviations from mean values (exemplary, 3 measurements per cycle)
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Pneumatic Modes Control
Pneumatic Pump Mode: Feedforward only Braking torque is limited a
priori if too high
Pneumatic Motor Mode: Throttle feedforward only Feedback uses as ΔMV2O
as control signal
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Supervisory Control – Dynamic Programming
3 states: tank pressure, old engine mode, and old gear
2 inputs: engine mode, gear switching
allows engine start & gear switching penalty For the MVEG-95, gears are pre-defined, so 2 states and 1 input
results.