Downsized and Supercharged Hybrid-Pneumatic Engine

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Downsized and Supercharged Hybrid-Pneumatic Engine C. Dönitz, C. Onder, I. Vasile, C. Voser, L. Guzzella

Nothing New (the Parsey Locomotive, 1847)

Source: http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm

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

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

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

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

0.330.350.36

• “downsizing” V-6 R-3

0.10.2

0.30.330.35

• “supercharging”

Replace a V-6 by an R-3 with turbocharger

Downsizing and Supercharging (DSC)

output

idle input

full loadoutput

full load inputxx=0.37=0.37

xx=0.17=0.17

Willans Behavior

xx=0.27=0.27

Problems DSC

Drivability

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

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

The ETH DSC HPE Concept

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

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

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

Baseline Engine as Willans Machine

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

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

MVEG-95, 1550 kg vehicle

Simulations (1): Fuel Economy

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

Simulations (2): Influence Tank Volume

Simulations (3): Overcoming the Turbo-lag

Simulation for 1500 kg vehicle in 4th gear with 0.75 liter engine

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

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

Hardware (2): Modified Engine MPE750

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.

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

… or come and visit us!

A (virtual) lab visit

Hardware (4): Engine Control Systems

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)

Measurements (1): The Supercharged Mode

Measurements (2): The Supercharged Mode

Test at constant intake pressure (550 mbar)

Measurement (3): Overcoming the Turbolag

N = 2000 rpm

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

Optimization Results Pneumatic Modes

Pump mode: operating area strongly limited

Pneumatic motor mode: only for low engine speeds

Measurements (4): Recuperation Efficiency

maxTeff

Δmair

⎝ ⎜

⎠ ⎟p.mot

× maxΔmairTeff

⎝ ⎜ ⎜

⎠ ⎟ ⎟pump

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

Experiment: VW Polo, MVEG-95

Engine Mode Determined Using DP

Experiment: Nissan Micra, FTP

Engine Mode Determined Using DP

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)

Result Overview, MVEG-95

Vehicle VW Polo (2005)

VW Polo (2009)

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 %**

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

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)

Thank you for your attention!

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

Reproduceability of Measurements

Mean measured fuel consumption (g)

Deviations from mean values (exemplary, 3 measurements per cycle)

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

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.

Downsized and Supercharged Hybrid-Pneumatic Engine

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