Optimization of Synthetic Oxygenated Fuels for Diesel Engines

Transcription

1 Optimization of Synthetic Oxygenated Fuels for Diesel Engines C. T. Bowman, R. K. Hanson, H. Pitsch, D. M. Golden Mechanical Engineering Department R. Malhotra SRI International A. Boehman Penn State University GCEP Research Symposium October 3,

2 Presentation Outline Background and Motivation Why Oxyfuels? Project Goals Research Tasks and Approach Results Future Directions 2

3 U. S. Combustion-Generated CO 2 Emissions Total = 1638 x 10 9 kg C/yr (2005) GCEP Residential 6% Commercial 4% Ship 3% Electric Power Generation - 39% Transportation 33% Industrial 18% Heavy Duty Truck and Rail - 23% Aircraft 12% Automobile and Light Truck 62% EIA

4 386 in 2004 Fossil fuels will be a dominant energy carrier in the 21 st century. 4

5 Automotive Engine/Fuel Performance Assessment Projected Growth in Bio-Transportation Fuels NiMH Battery Electric FC (PEM) Hybrid - hydrogen FC (PEM) Hybrid - methanol Total Energy Use - MJ/km FC (PEM) Hybrid - gasoline SI Hybrid - CNG 7 6 Ad. CI Hybrid - diesel fuel Ad. SI Hybrid - gasoline 5 4 Advanced CI - diesel fuel 3 Advanced SI - gasoline Current SI -gasoline MIT Energy Lab, 2000 Carbon Emissions - gc/km MIT Energy Lab,

6 Reduction of GHG emissions from transportation sources will require implementation of a variety of strategies: Improvements in overall efficiency of vehicle/fuel systems advanced diesel engines and diesel-hybrids Use of synthetic or renewable fuels to replace or supplement petroleum-based fuels or as performance-improving additives oxygenated liquid fuels can reduce PM and NO emissions from diesel engines and may be synthesized from a variety of feedstocks, including coal and biomass 6

7 Project Goals GCEP Investigate the impact of oxygenated fuel structure on combustion and emissions performance under diesel combustion conditions - Identify functionalities most suitable for clean-burning diesel fuels - Conduct experiments and modeling to provide insight into the mechanisms by which fuel structure impacts combustion behavior - Explore processing strategies to produce synthetic oxygenated hydrocarbons from various feedstocks on a refinery scale 7

8 Screening Structures for Effectiveness in Soot Suppression Compound Structure Compound Structure Alcohols 1 Methanol CH 3- OH 2 Ethanol CH 3 CH 2- OH 3 Butanol CH 3 CH 2 CH 2 CH 2 -OH 4 Hexanol CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 -OH Ketones 19 Acetone CH 3 C(=O)CH Pentanone CH 3 CH 2 C(=O)CH 2 CH Pentanone CH 3 CH 2 CH 2 C(=O)CH 3 22 Acetophenone CH 3 C(=O)C 6 H 5 Ethers 5 Diethyl ether CH 3 CH 2 -O-CH 2 CH 3 6 Dimethoxymethane CH 3 O-CH 2 -OCH 3 7 2,2-Dimethoxy propane CH 3 O-C(CH 3 ) 2 -OCH 3 8 Ethyleneglycol dimethyl ether CH 3 O-CH 2 CH 2 -OCH 3 9 Diethyleneglycol methyl ether CH 3 O-CH 2 CH 2 - O-CH 2 CH 2 -OH 10 Triethyleneglycol methyl ether CH 3 O-CH 2 CH 2 - O-CH 2 CH 2 -O-CH 2 CH 2 -OH Aldehydes 23 Butanal CH 3 CH 2 CH 2 C(=O)H 24 Pentanal CH 3 CH 2 CH 2 CH 2 C(=O)H 25 Hexanal CH 3 CH 2 CH 2 CH 2 CH 2 C(=O)H Misc Ethylhexyl nitrate CH 3 CH 2 CH 2 CH 2 CH(CH 2 CH 3 )CH 2 -ONO 2 27 Di-t-butyl peroxide (CH 3 ) 3 C-O-O-C(CH 3 ) 3 Esters 11 Methyl acteate CH 3 C(=O)OCH 3 12 Methyl propanoate CH 3 CH 2 C(=O)OCH Nitropentane CH 3 CH(NO 2 )CH 2 CH 2 CH 3 29 Amyl nitrate CH 3 CH 2 CH 2 CH 2 CH 2 -ONO 2 30 Amyl nitrite CH 3 CH 2 CH 2 CH 2 CH 2 -ONO 13 Ethyl propanoate CH 3 CH 2 C(=O)OCH 2 CH 3 16 Methyl butanoate CH 3 CH 2 CH 2 C(=O)OCH 3 17 Ethyl butanoate CH 3 CH 2 CH 2 C(=O)OCH 2 CH 3 18 Diethyl carbonoate CH 3 CH 2 -O-C(=O)-O-CH 2 CH 3 8

9 Screening Structures for Effectiveness in Soot Suppression ASTM D-1322 Smoke Point Method Smoke height Smoke height is inversely proportional to sooting tendency. 9

10 Screening Structures for Effectiveness in Soot Suppression Decreasing sooting propensity Smoke Height mm base fuel (65% n-heptane / 35% toluene) 15.0 BP15 (low sulfur diesel fuel) Wt% Oxygen Methanol Ethanol Butanol Hexanol EthyleneglycolDME Methyl acetate Diethyl ether Dimethoxymethane Dimethoxypropane Methyl propanoate Ethyl propanoate Methyl butanoate Ethyl butanoate Diethyl carbonoate Acetone 2 Pentanone 3-Pentanone Ethyl acetate DiethyleneglycolDME Butanal Pentanal Hexanal 10

11 Screening Structures for Effectiveness in Soot Suppression (Structural Group Additivity Analysis) TSI MW SP Total reduction [TSI units ] From HC part of additive From dilution by additive From O part of additive (Y O = 4 wt%) 11

12 Screening Structures for Effectiveness in Soot Suppression Effectiveness of soot suppressing additives depends on the mass of oxygen in the fuel blend and on molecular structure. Additive effectiveness scales as aldehydes > ketones > esters ethers > alcohols 12

13 Screening Structures for Effectiveness in Soot Suppression Compound Structure Compound Structure Alcohols 1 Methanol CH 3- OH 2 Ethanol CH 3 CH 2- OH 3 Butanol CH 3 CH 2 CH 2 CH 2 -OH 4 Hexanol CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 -OH Ketones 19 Acetone CH 3 C(=O)CH Pentanone CH 3 CH 2 C(=O)CH 2 CH Pentanone CH 3 CH 2 CH 2 C(=O)CH 3 22 Acetophenone CH 3 C(=O)C 6 H 5 Ethers 5 Diethyl ether CH 3 CH 2 -O-CH 2 CH 3 6 Dimethoxymethane CH 3 O-CH 2 -OCH 3 7 2,2-Dimethoxy propane CH 3 O-C(CH 3 ) 2 -OCH 3 8 Ethyleneglycol dimethyl ether CH 3 O-CH 2 CH 2 -OCH 3 9 Diethyleneglycol methyl ether CH 3 O-CH 2 CH 2 - O-CH 2 CH 2 -OH 10 Triethyleneglycol methyl ether CH 3 O-CH 2 CH 2 - O-CH 2 CH 2 -O-CH 2 CH 2 -OH Aldehydes 23 Butanal CH 3 CH 2 CH 2 C(=O)H 24 Pentanal CH 3 CH 2 CH 2 CH 2 C(=O)H 25 Hexanal CH 3 CH 2 CH 2 CH 2 CH 2 C(=O)H Misc Ethylhexyl nitrate CH 3 CH 2 CH 2 CH 2 CH(CH 2 CH 3 )CH 2 -ONO 2 27 Di-t-butyl peroxide (CH 3 ) 3 C-O-O-C(CH 3 ) 3 Esters 11 Methyl acteate CH 3 C(=O)OCH 3 12 Methyl propanoate CH 3 CH 2 C(=O)OCH 3 13 Ethyl propanoate CH 3 CH 2 C(=O)OCH 2 CH 3 16 Methyl butanoate CH 3 CH 2 CH 2 C(=O)OCH 3 17 Ethyl butanoate CH 3 CH 2 CH 2 C(=O)OCH 2 CH Nitropentane CH 3 CH(NO 2 )CH 2 CH 2 CH 3 29 Amyl nitrate CH 3 CH 2 CH 2 CH 2 CH 2 -ONO 2 30 Amyl nitrite CH 3 CH 2 CH 2 CH 2 CH 2 -ONO 18 Diethyl carbonoate CH 3 CH 2 -O-C(=O)-O-CH 2 CH 3 13

14 Experimental and Modeling Studies GCEP Shock tube and flow reactor studies - effect of oxygenates (as pure fuels and additives) on ignition and combustion behavior and on soot formation Detailed modeling of oxygenate combustion chemistry - insight into mechanisms by which oxygenate structures affect combustion and soot formation Engine experiments - effect of oxygenates on engine-out PM and NO x emissions Advanced modeling of diesel engine combustion - interpretation of engine experiments and effect of engine design and operating conditions on performance and emissions 14

15 Ignition Behavior of DME and DME-Heptane mixtures 1% Total fuel in Ar/O 2 φ = 1 P scaled to 1.5 atm (P ) 1000 Inc. DME τ ign [μs] 1% DME Data 1% DME Model.75% DME/.25% Heptane Data.75% DME/.25% Heptane Model Stanford Kinetics Shock Tube 100.5% DME/.5% Heptane Data.5% DME/.5% Heptane Model.25% DME/.75% Heptane Data.25% DME/.75% Heptane Model /T [1/K] DME addition has a small effect on ignition time. Good agreement between ignition time data and simulations. 15

16 Combustion Behavior of DME GCEP Φ = 2 Stanford Flow Reactor DME oxidation may be modeled with existing reaction mechanisms. 16

17 Sooting Characteristics of Heptane and DME-Heptane Mixtures n-heptane P = 20 bar, Φ = 5, [C] total = constant n-heptane/dme Stanford High-Pressure Shock Tube Addition of DME significantly reduces soot yield. 17

18 Sooting Characteristics of Heptane + Oxygenate Mixtures 15 Soot Yield for Heptane+Oxygenates Soot Yield [%] K, 17.5 atm, φ = 5 [C] total /[M] total = [C] oxygenate /[C] total = % Heptane, neat 0.27% Heptane, 0.09% Acetone 0.27% Heptane, 0.07% Butanal 0.27% Heptane, 0.14% DME additive m O /m fuel DME acetone butanal Time [ms] Additive effectiveness scales as butanal > acetone > dimethyl ether 18

19 Effect of Oxygenates on Engine-Out PM Emissions FSPM BG-2 Low FSPM TEOM Low FSPM (g/kg fuel) Penn State 2.5L, 16 valve, DOHC Common Rail, Turbodiesel Engine Research Facility 0 BP15 Hexane DMM Pentanone Butanal Acetone Fuel Oxygenate addition reduces the number and size of the particles Effectiveness depends on oxygen functionality 19

20 Main objectives: Assess the effect of oxygenated fuels in reduction of soot production in realistic diesel engine configurations LES of flow in a simplified piston-cylinder configuration Develop a computational tool to perform large eddy simulation (LES) of flow and combustion in an internal combustion engine Parametric optimization of diesel engine cycle using oxygenated fuels Intake stroke Compression stroke Exhaust stroke End of intake stroke Expansion stroke 20

21 Computational Capabilities GCEP Soot formation Immersed boundary Moving mesh Multi-phase flows LES Solver Premixed combustion Compressible solver Diffusion flames 21

22 Validation against Experimental Data GCEP Imperial College test case Cylinder with a flat head Swept to clearance volume ratio 2.0 Piston driven at 200 rpm 2 stroke cycle (no effective compression stroke) Comparison of Phase Averaged Statistics with the experimental data Intake stroke Exhaust stroke Crank angle location 36 degrees Intake stroke deg x=0.01m deg x=0.02m y(m) 0.02 y(m) Symbols - Numerical Simulation Lines - Experimental Measurement <U>/<V p > <U>/<V p > 22

23 Summary of Important Results Laboratory and engine tests and modeling have been carried out to assess the effectiveness of various oxygenates both as pure fuels and as additives in reducing soot formation under diesel combustion conditions. Results from these studies indicate that oxygenates containing a carbonyl functional group appear to be the most effective in reducing soot formation. 23

24 Future Directions Experimental and modeling studies of additional oxygenates to determine/confirm optimal structures Engine Modeling - additional validation against the Sandia diesel combustion simulator - simulate realistic engine configurations Explore processing strategies to produce optimal synthetic oxygenated hydrocarbons from various feedstocks on a large scale 24