Investigating the effects of molecular structure on the combustion and emissions of fuels from alcohols

Transcription

1 Investigating the effects of molecular structure on the combustion and emissions of fuels from alcohols Dr. Paul Hellier, Dr. Pavlos Aleiferis and Professor Nicos Ladommatos UCL Fuels and Combustion FPC2014 Future Powertrain Conference

2 utline 1. Future fuels 2. Experimental methodology Ultra low volume fuel system 3. Fatty acid ester alcohol moiety 4. Symmetrical carbonate esters 5. Genetically modified microorganisms 6. Conclusions

3 Approach Liquid fuel Feedstock Process Product Fossil fuel rganic matter Intense heat and pressure over millions of years Current bio-fuels Future fuels Agricultural crops with food value Lignocellulosic biomass, photosynthetic micro-organisms, waste streams Conversion of sugars, starch, and fatty acids with varying net C 2 performance Various possible routes of biological and thermo-chemical conversion Refined to meet performance and environmental requirements in ICE Designed to emulate existing fossil fuels?

4 Biomass to liquid SI Fuels Sugars Fermentation ABE IBE Ethanol Butanol (C2 4)

5 Biomass to liquid Lignocellulosic Pretreatment biomass Physical Chemical Biological Sugars Fermentation ABE IBE SI Fuels Ethanol Butanol (C2 4)

6 Alcohols for SI ptical Spray Chamber Fundamentals ptical Engine Link Droplet Size & Velocity Flame Propagation ptical Nozzle Computational Fluid Dynamics Exhaust Emissions C 2, Economy Cavitation & Flash Boiling Spray/Flow Interactions Legislative Requirements Fuel Exploitation Novel Engines

7 Alcohols for CI Lignocellulosic Pretreatment biomass Physical Chemical Biological Sugars Fermentation ABE IBE SI Fuels Ethanol Butanol (C2 4)? CI Fuels?

8 Experimental approach Testing logical series of chemistries in which a specific molecular structural property is incrementally altered while others are kept constant. 1 double bond H 3 C CH 2 Carbon chain length = 12 High assay single component fuels may be of limited supply or require expensive synthesis.

9 Engine facility Single cylinder research diesel engine. Ricardo Hydra with Ford Duratorq 2.0 L head. Common rail (Bosch CP3) with solenoid valve DI injector (Delphi DFI 1.3). Gaseous emissions: Horiba MEXA 9100 HEGR. Particulate emissions: Cambustion DMS 500 Spectrometer.

10 Solution Bypass Free moving pistons High pressure valve Diesel reservoir Fossil diesel Pressure vessel Test fuel Filter Common rail Injector Exhaust High pressure pump Pressure sensor DAQ Emissions analysis Particulates analysis Engine

11 Experimental conditions Constant injection timing: 1200 rpm and 450 bar fuel injection pressure 4 bar IMEP (variable injection timing ~ μs) SI = 7.5 CAD BTDC Variable SC Constant ignition timing: 1200 rpm and 450 bar fuel injection pressure 4 bar IMEP (variable injection timing ~ μs) Variable SI SC = TDC

12 Experimental conditions Constant ignition delay timing: Addition of 2 EHN to control duration of ignition delay 1200 rpm and 450 bar fuel injection pressure 4 bar IMEP (variable injection timing ~ μs) Fixed SI SI = 7.5 CAD BTDC Variable SC SC at TDC Variable SI SC at TDC SI

13 Fatty acid ester alcohol moiety

14 Thermo-gravimetric analysis CN = ~ 100 H CN = 61.7

15 Alcohol moiety particulates Boiling point, viscosity xygen content

16 Carbonate esters H + C Inorganic base H catalyst Symmetrical carbonate esters more than double alcohol mass. Production method potentially utilises C 2 (1,2). 1. Tian, J. S.; Miao, C. X.; Wang, J. Q.; Cai, F.; Du, Y.; Zhao, Y.; He, L. N. Green Chemistry 2007, 9, Fujita, S. i.; Bhanage, B. M.; Ikushima, Y.; Arai, M. Green Chemistry 2001, 3,

17 Carbonate esters di butyl carbonate di-methyl carbonate di 1 methyl propyl carbonate Alkyl chain length di-ethyl carbonate di 2 methyl propyl carbonate Branching di-tert-butyl carbonate

18 Constant injection timing Alkyl chain length

19 Low temperature reactivity xygenate of decomposition: RC = R + C 2 RC = R + C 1 st route dominates (3), i.e. in the case of DMC: CH 3 CCH 3 CH 2 + CH 3 + C 2 Increasing alkyl chain length increases availability of weakly bonded secondary H atoms and potential for 6 member transition rings: CH 3 H 3 C CH 3 H 3 C CH 3 Secondary CH 3 Primary 6 member ring 3. Glaude, P. A.; Pitz, W. J.; Thomson, M. J. Proceedings of the Combustion Institute 2005, 30,

20 Alkyl chain length

21 Alkyl chain length Decreasing latent heat of vaporisation

22 Alkyl chain length

23 Alkyl chain length

24 Alkyl chain length Decreasing fuel oxygen content

25 Alkyl chain branching Constant injection timing DnBC D1MPC D2MPC DTBC

26 Low temperature reactivity Increasing alkyl chain branching decreases reactivity: CH 3 H 3 C CH 3 Primary Secondary CH 3 H abstraction from bonded C preferential to secondary C. Methyl branch on bonded C has greater impact on ignition delay.

27 Alkyl chain branching

28 Alkyl chain branching 2 CH 3 Alkyl chain length Cross reactions C- H abstraction Alkyl chain length 1 CH 3 vaph PHRR Nx, C + Nx + Duration of ignition delay -

29 Genetic modification for future fuels Photosynthetic cyanobacteria Compounds secreted from cells Courtesy of Lamya Al-Haj and Dr. Saul Purton, UCL Institute of Structural and Molecular Biology

30 H Geraniol Nerol H Linalool H H Citronellol H Geranial (Citral-A) Citronellene H Citral dimethyl acetal 3,7-dimethyloctan-1-ol Farnesene Geranyl acetate H H H H Squalene Menthol cis vs trans Alcohol group position Degree of saturation Functional group Alkenyl chain length

31 Microbial terpene fuels trans 1 DB cis 2 DB 0 DB C15 C30 -H =

32 Fuel viscosity Squalene high viscosity poorer mixing increased particulates

33 Conclusions Fuel molecular structure determines ignition delay through low temperature reaction kinetics. Ignition delay is most strongly influenced by the reactivity of long alkyl chains. ther elements of molecular structure can: Result in molecule breakdown prior to vaporisation. Impact significantly on ignition delay where the alkyl moiety is of poor ignition quality. Emissions of Nx are thermal and dictated by heat release rates determined primarily by duration of ignition delay. Levels of soot produced increases with removal of fuel and increasing fuel viscosity. Understanding of effects of molecular structure will inform development of future alcohol fuels, eg. from genetically modified organisms

34 Thank you for listening Questions? Acknowledgements: EPSRC UCL Institute of Structural and Molecular Biology All figures and results in this presentation have previously been published in the following journal articles: P. Hellier, L. Al-Haj, M. Talib, S. Purton and N. Ladommatos, Combustion and emissions characterisation of terpenes as biofuels produced by the microalgae Synechocystis, Fuel, Volume 111, September 2013, Pages P. Hellier, N. Ladommatos, R. Allan, and J. Rogerson, Influence of carbonate ester molecular structure on compression ignition combustion and emissions. Energy and Fuels, 27(9), P. Hellier, N. Ladommatos, R. Allan, M. Payne and J. Rogerson, "The Influence of Fatty Acid Ester Alcohol Moiety Molecular Structure on Diesel Combustion and Emissions", Energy and Fuels, 2012, 26 (3), pp