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Downsized and Supercharged Hybrid-Pneumatic Engine

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.

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Downsized and Supercharged Hybrid-Pneumatic Engine

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

  2. Nothing New (the Parsey Locomotive, 1847) Source: http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm

  3. Dickson Locomotive, 1899 Mass 16 t, storage 40 bar, working 10 bar, volume 4.8 m3 Source: http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm

  4. Compressed Air as Fuel? 45 MJ/100km η2= 44% η4= 80% Ptank=300 bar Ttank= 300 K η1= 90% η3= 81% 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).

  5. 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

  6. 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

  7. • “downsizing” V-6R-3 • “supercharging” 0.36 0.35 0.33 0.3 0.25 0.2 0.1 Downsizing and Supercharging (DSC) Replace a V-6 by an R-3 withturbocharger 0.3 0.33 0.36 0.35 0.25 0.2 0.1 7

  8. x=0.27 Willans Behavior output x=0.37 full load input full load output x=0.17 0 input idle input

  9. Problems DSC ? Drivability

  10. 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

  11. 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

  12. The ETH DSC HPE Concept

  13. Operating Modes

  14. Additional Engine Modes Pump mode: throttle always open Pneumatic motor mode: closes throttle for higher torque Supercharged mode: air injection at start of compression - Recharge mode: 2 cylinders conventional, 2 cylinders pump a) b) c)

  15. 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 efficiencyconsidered • Variable valve actuation energy accounted for according to number of used EHVS.

  16. Baseline Engine as Willans Machine

  17. Engine Scaling • Account for reduced internal efficiency when reducing the compression ratio due to supercharging • Values obtained using engine process simulation

  18. Variable Valve Actuation Energy • 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

  19. Simulations (1): Fuel Economy MVEG-95, 1550 kg vehicle

  20. 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

  21. Simulations (2): Influence Tank Volume

  22. Simulations (3): Overcoming the Turbo-lag Simulation for 1500 kg vehicle in 4th gear with 0.75 liter engine

  23. The ETH DSC HPE Test Engine Main Ideas • Strong downsizing to improve fuel economy • Connect pressurized air tank directly to engine cylinders: enables excellent driveability • PFI/stoich gasoline engine • Asymmetric turbo charger Engine Type Additional Hardware: • Variable valve actuation system for CV only • Air tank (cold tank strategy)

  24. Hardware (1): Modified Engine MPE750

  25. Hardware (2): Modified Engine MPE750

  26. Electro-Hydraulic Valve Actuation System • EHVS provides fully variable valve actuation for the CV: opening closing 15.09.2014 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.

  27. 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

  28. A (virtual) lab visit … or come and visit us!

  29. Hardware (4): Engine Control Systems

  30. 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)

  31. Measurements (1): The Supercharged Mode

  32. Measurements (2): The Supercharged Mode Test at constant intake pressure (550 mbar)

  33. Measurement (3): Overcoming the Turbolag N = 2000 rpm

  34. Measurements (4): Rapid Pneumatic Start pT = 10 bar • Rapid engine start enables start/stop operation and thus the elimination of idling. • Pneumatic engine start < 350ms for pT= 10 bar.

  35. Optimization Results Pneumatic Modes • Pneumatic motor mode: only for low engine speeds • Pump mode: operating area strongly limited

  36. Measurements (4): Recuperation Efficiency

  37. 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

  38. Experiment: VW Polo, MVEG-95

  39. Engine Mode Determined Using DP

  40. Experiment: Nissan Micra, FTP

  41. Engine Mode Determined Using DP

  42. 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)

  43. Result Overview, MVEG-95

  44. Result for FTP, Nissan Micra Data sources: Touring Club Switzerland www.tcs.ch, EMPA Switzerland, OEM webpages

  45. Electric Hybridization vs. DSC HPE Concept HPE: Estimated added cost for EHVS & tank: 1500 CHF (conservative) DSC & pneum. hybridization electric hybridization For normalization: base rated power 61 kW base weight 1080 kg (Prius base weight 1250 kg)

  46. Thank you for your attention!

  47. Compressed Air in a Series Hybrid? comp. 20 kW 1-stage adiabatic tank, ~50 l pneum.motor 60 kW ICE 20 kW ptank=20-30 bar Ttank= 700-800 K 45 MJ / 100km η4= 81% η5= 80% η3= 80% η1= 35% COP = 1 η2= 80% pneum.motor 60 kW comp. 20 kW 2-stages air tanks ~50 l and ~10 l ICE 20 kW ptank~ 80 bar Ttank= 400 K Expand and heat up 45 MJ / 100km η5= 80% η13= 95% η4= 81% η11= 35% COP = 0.5 η12= 80% η23= 50% Q21= 65% η22= 50%

  48. Reproduceability of Measurements Mean measured fuel consumption (g) Deviations from mean values (exemplary, 3 measurements per cycle)

  49. 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

  50. 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.

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