Experimental and numerical work at Ghent University on methanol combustion in SI engines

Transcription

1 Experimental and numerical work at Ghent University on methanol combustion in SI engines Prof. Sebastian Verhelst Ghent University 1

2 WHY METHANOL? 2

3 UGent ICE research focus: background Starts from a vision on long term energy supply and energy carrier for transportation Long term energy supply: selection of candidates based on Sustainability, of energy source and of harvesting technology (includes e.g. recyclability) Scalability, i.e. abundance of energy source, and of resources needed for building the harvesting technology Conclusion: CSP (concentrated solar power) best choice 3

4 UGent ICE research focus: background Long term solution for transport? Options for energy carrier and powertrain? Sustainability: closed cycle for energy carrier and powertrain materials Scalability: resources for energy carrier and powertrain Compact: need sufficient energy & power density 4

5 Conclusions for sustainable transportation Energy carrier: need for renewable (solar), liquid fuels Efficient, so practical and cheap distribution and storage Powertrain: internal combustion engine Cheap to produce: Easy to produce From abundantly available, recyclable materials Relatively little energy needed for production Fuel flexible High power density Still potential for efficiency improvement 5

6 Candidate fuels Simple molecules are preferred Production is more efficient Conversion (end-use) can be controlled more easily (η, emissions) Abundantly available building blocks: C, H, O, N, Thus, most simple fuels: Hydrogen, H 2 (at p atm, liquid at 20K) Methane, CH 4 (at p atm, liquid at 91K) Ammonia, NH 3 (at T atm, liquid at 8.6 bar) Methanol, CH 3 OH (liquid) Dimethylether (DME), CH 3 OCH 3 (liquid at 5.3 bar) LIQUIDS 6

7 Case: methanol Can be produced in different ways Biomass, fossil fuels, synthesize using renewable energy Liquid Cheap tanks, cheap distribution Miscible with gasoline and ethanol Evolution of infrastructure possible High engine efficiencies possible High octane number, heat of vaporization, Also building block for synthetic hydrocarbons (MTO) Has been a focus for UGent since

8 UGent work on methanol as an engine fuel PhD Jeroen Vancoillie [1] Problem statement: no simulation tools for engines operating on light alcohols (MeOH/EtOH) Complexity of engines optim. solely relying on expts. undoable Unique fuel properties tools optimized for gasoline etc. Special working conditions e.g. EGR%, charging pressures, Contents Conversion of engine test benches, measurement database Fundamental data: laminar burning velocity, autoignition delays Evaluation of turbulent combustion velocity models Engine cycle simulations, normal + knocking operation 8

9 UGent work on methanol, cont. MSc theses, postdoc stay Extension of measurement database (incl. effects H 2 O) Vehicle calculations PhD Louis Sileghem [2] Problem statement: introduction of methanol through use as blend component (cfr. presentation James Turner, Univ. Bath); no simulation tools for engines on alcohol blends Non-linear behaviour burning velocity, knocking behaviour, Contents: measurements; blending/mixing rules for burning velocities, auto-ignition delays; engine simulations 9

10 Engine tests EXPERIMENTAL WORK 10

11 Properties MeOH gasoline & implications Properties: Methanol Gasoline High heat of vaporization 325 High octane number 95 High flame speed (kj/kg) 109 RON 1100 Laminar burning velocity at NTP (cm/s) Potential Even for gasoline-optimized engine max. achievable engine load higher when using alcohols Increase in volumetric eff. due to high degree of charge cooling Spark timing less knock limited due to elevated knock resistance and higher flame speeds Options for dedicated engines: High compression ratio High EGR ratios Lean operation 11

12 Experimental work: flex-fuel 2 converted ( flex-fuel ) PFI engines [3,4] With same operating strategy: Relative efficiency benefits MeOH vs. gasoline order of 10% More isochoric combustion Less flow, cooling and dissociation losses Reductions of engine-out NOx levels of 5 10 g/kwh Lower combustion temperatures Alternative load control strategies WOT, lean; or WOT+EGR: relative eff. benefits of 5% vs. throttling Possible due to higher dilution tolerance of MeOH Also lower NOx, due to further lowering of combustion temperatures 12

13 Experimental work: dedicated methanol [3,4] VW TDI, CR 19.5:1 Replaced diesel injectors with spark plugs, mounted methanol PFI system Reproduced EPA work (Brusstar et al.) and expanded to lower loads Faster, more stable combustion High CR, turbocharged, high turbulence More dilution tolerance Wider range (down to 3 bar BMEP) Lower in-cylinder temperatures Cooling & dissociation losses Knock/pre-ignition ; Engine-out NOx 13

14 Experimental work: dedicated methanol [3,4] 42% BTE (%) Diesel-like peak BTE Part load efficiency gains up to 20% (compared to throttled operation) NOx (ppm) Vast engine-out NOx reductions (ppm) Unstable combustion CoV > 10% (EGR 50 m%) 14

15 Experimental work: dedicated methanol Dedicated engines: diesel-like efficiencies while using cheap aftertreatment systems Used engine bench results in vehicle driving cycle calculations [5] Efficiency % NOx emissions NEDC FTP NEDC NOx g/km FTP75 NOx g/mi Vehicle 5, MeOH, Throttle Vehicle 6, MeOH, WOT_EGR Vehicle 5, MeOH, Throttle Vehicle 6, MeOH, WOT_EGR 15

16 Experimental work: DI engines Naturally asp. DI: Hyundai 2.4L at Argonne Nat. Lab [11] Tested MeOH vs. gasoline, EtOH, BuOH, E85, M56 Stock ECU load limitations (~injection duration; λ=1) Low-mid load: 2.7 %pt BTE increase on MeOH vs. gasoline High load: 5.6 %pt (BTE=40%, i.e. -20% CO 2 ) Turbocharged DI: Volvo 1.6L T3 MoTeC M1 ECU In progress 16

17 Burning velocity measurements and computations FUNDAMENTAL WORK 17

18 Building blocks for engine cycle simulations Laminar burning velocity u l Groups chemical effects on combustion Function of pressure, temperature, mixture composition 50% higher than for gasoline faster combustion, higher efficiency Lack of reliable u l data for methanol at engine-like conditions Calculated u l using carefully selected chemical kinetics scheme Built correlation for use in engine code [6] Validated correlation Flat flame burner at Lund University [7] Spherical flames at Leeds University [1] 18

19 Evaluation of u l correlation + u t models [8] 19

20 Building blocks for engine cycle simulations, cont. Autoignition delay time τ Determines resistance to engine knock Function of pressure, temperature, mixture comp. RON 109 higher efficiency: either through increased CR or wider use of MBT Again, lack of data Calculated τ using the same chemical kinetics scheme as for u l Built correlation for use in engine code [9] 20

21 u l & τ correlations; engine simulation framework NUMERICAL WORK 21

22 Multizone thermodynamic engine model i.e. quasi-dimensional approach Compromise between accuracy and computational effort Framework for testing u l & τ correlations Power cycle: in-house GUEST code (Ghent University Engine Simulation Tool) Gas dynamics: GT-Power Findings [10] Puddling model necessary: low volatility Evaporated fraction low compression slope underestimated Evaporated fraction high volumetric efficiency overestimated 22

23 Engine cycle simulations Evaluation of u l &τ correlations, and u t models, against experimental database obtained on 2 engines with variation of: throttle position fuel-air equivalence ratio spark timing engine speed Normal & knocking combustion [10] knocking: puddling model & in-cylinder heat transfer to be revisited 23

24 Summary UGent contributions on methanol-fueled ICEs Measurement database on a range of SI engines Correlations for u l, δ l, τ for use in engine simulation Validation of engine cycle simulations against expt. database To be improved In-cylinder heat transfer models (work in progress at UGent) Proper modeling of evaporative cooling In progress or starting MeOH in downsized engine Dual-fuel operation: MeOH in diesel engine 24

25 Outlook LEANShips: Low Energy And Near to zero emissions Ships EU Horizon 2020 Mobility for Growth innovation action 48 partners, 8 demonstrator platforms UGent: WP05 leader Demonstrating the potential of methanol as an alternative fuel (6 partners) Conversion of high speed marine diesel engine to dual fuel operation with methanol LCA of methanol in shipping Tools for dissemination and market uptake (pilots) 25

26 References 1. Jeroen Vancoillie, Modeling the combustion of light alcohols in spark-ignition engines, PhD Ghent University, download link 2. Louis Sileghem, Modeling the combustion of alcohol blends in SI engines, Ghent University, PhD defense July Vancoillie J et al, Experimental evaluation of lean-burn and EGR as load control strategies for methanol engine, SAE Vancoillie J et al, The Potential Of Methanol As A Fuel For Flex-Fuel And Dedicated Spark-Ignition Engines, Applied Energy 102: , Naganuma K et al, Drive Cycle Analysis of Load Control Strategies for Methanol Fuelled ICE Vehicle, SAE Vancoillie J et al, Laminar burning velocity correlations for methanol-air and ethanol-air mixtures valid at SI engine conditions, SAE Vancoillie J et al, The temperature dependence of the laminar burning velocity of methanol flames, Energy&Fuels 26: , Vancoillie J et al, The turbulent burning velocity of methanol-air mixtures, Fuel 130:76-91, Vancoillie J et al, Development and Validation of A Knock Prediction Model for Methanol-Fuelled SI Engines, SAE Vancoillie J et al, Development and validation of a quasi-dimensional model for methanol and ethanol fueled SI engines, Applied Energy 132: , Sileghem L et al, Experimental investigation of a DISI production engine fuelled with methanol, ethanol, butanol and iso-stoichiometric alcohol blends, SAE

27 Thank you for your attention! Sebastian Verhelst 27