Fuel Effects on RCCI Combustion: Considerations. Scott Curran, Zhiming Gao, Jim Szybist, and Robert Wagner

Transcription

1 Fuel Effects on RCCI Combustion: Performance and Drive Cycle Considerations Scott Curran, Zhiming Gao, Jim Szybist, and Robert Wagner Oak Ridge National Laboratory 2014 CRC Workshop on Advanced Fuels and Engine Efficiency February 2014

2 Combustion will be an important part of the solution with end game objective to maximize vehicle efficiency with compliant emissions Adapted d from DOE presentation, tti Gurpreet Singh et al. Charge must end up in this region after combustion is complete Need to manage the combustion process to avoid soot and NOx formation SI PPC RCCI while at the same time avoiding CO and UHC emissions CIDI Gasoline PFI Diesel DI Low = Prevents Auto Ignition Backup Slide for LTC Landscape Fuel Reactivity 2 High = Promotes Auto Ignition

3 Reactivity Controlled Compression Ignition Dual Fuel Partially Premixed Combustion Technique Reactivity controlled compression ignition (RCCI) allows increased heat release control A low reactivity fuel is introduced early and premixed with air A high reactivity fuel is injected into the premixed charge before ignition RCCI increases engine operating range for premixed combustion Global fuel reactivity (phasing) Fuel reactivity gradients (pressure rise) Equivalence ratio and temperature stratification RCCI offers both benefits and challenges to implementation of LTC Diesel like efficiency or better Ultra Low NOx and soot Controls and emissions challenges Port injection low reactivity fuel, i.e. Gasoline/ E85 (orange) Direct injection high reactivity fuel, i.e. Diesel/ B20 (blue) Adapted from Hanson, UW-M Engine Research Center Gasoline PFI Diesel DI Low = Prevents Auto Ignition Fuel Reactivity High = Promotes Auto Ignition 3

4 Advanced combustion modes must match with the LD drive cycles to have maximum improvement on fuel economy and emissions Emissions regulations and fuel economy for light duty vehicle are prescribed over transient drive cycles (EPA Federal Driving Schedules) Emissions standards are set by EPA for criteria air pollutants NO X, NMOG, CO, PM Steady state advanced combustion brake efficiency emissions from steady state points do not directly equate to drive cycle performance (i.e. fuel economy and emissions) Urban Dynamometer Driving Cycle Highway Fuel Economy Test US06 SC03 80 MPH Commonly called the "LA4" or "the city test" and represents city driving conditions Represents highway driving conditions under 60 mph High acceleration aggressive driving schedule one of two "Supplemental FTP tests FTP with Air Conditioner driving schedule one of two "Supplemental FTP tests 4

5 ORNL s comprehensive approach to advanced combustion research includes fuel effects and engine system integration 2007 GM 1.9 L multi cylinder diesel engines OEM (CR 17.5) and modified RCCI pistons (CR 15.1) (backup slide) Dual fuel system with PFI injectors OEM diesel fuel system with DI injectors Microprocessor based control system Aftertreatment integration & emissions characterization Modular catalysts / regulated and unregulated emissions Particulate matter characterization Vehicle systems simulations using Autonomie Experimental engine maps used for drive cycle simulations Comparison between 2009 PFI, diesel and diesel/rcci Multi mode (RCCI to conventional diesel combustion) used for areas of the drive cycle outside the RCCI operating range ORNL RCCI Multi-Cylinder 1.9L GM 1 Autonomie, Developed by Argonne National Lab for U.S. DOE, Modeled Fuel Economy 5

6 Current RCCI Operation Includes Most of Light Duty Drive Cycle RCCI Calibration B20/UTG96 UDDS Points High BTE within LD drive cycle RCCI 42.5 ULSD CN46 CDC 42.3 Peak BTE region of speed/load map Light duty drive cycle (UDDS) RCCI mapped with focus on efficiency and lowest possible emissions Peak kbte within light duty drive cycle range (better than peak BTE of 1.9L 9LGM diesel) Detailed RCCI map shows insights into future development opportunities and challenges Aftertreatment integration (low exh T), drive cycle simulations (load coverage) Load expansion challenges are under investigation for maximizing BTE Cyclic dispersion, exhaust residuals, thermodynamic analysis of loss mechanisms 6

7 DOE FLT Research Bio fuels Enabling RCCI Range Expansion Unique properties of biofuels can be taken advantage of for dual fuel RCCI operation Commercially available biofuels replacements for both the PFI fuel and DI fuel were found to have properties that enable load expansion in RCCI. Biofuels allows for improved efficiency through RCCI load expansion and direct petroleum displacement through substitution btit Load expansion to cover the entire drive cycle operating map with high efficiency and low NOx and Soot is also important for addressing market barriers to eventual LTC implementation. Ethanol blends Allow for load expansion through combination of increased Octane, charge cooling and radical sinking Biodiesel Blends Biofuels allows for increased ratio of PFI fuel to DI fuel without sacrificing emissions or stability Combination of the two offers additional benefits Backup Slides for Details on B20 and Ethanol Blends 7

8 RCCI Mapping Completed w/ Multiple Fuel Combinations RCCI mapped with focus on efficiency and lowest possible emissions (Q3 Joule Milestone) Self imposed constraints of pressure raise rate (10bar/deg upper load) and CO limit (5000 PPM lower load) Current RCCI map requires mode switching to cover light duty drive cycles 100% coverage oflow temperature combustion is necessary to avoid mode switching (RCCI to CDC) and additional emissions controls which would have negative impacts on fuel economy and costs High load notes Constraint on MPRR and combustion noise High load increased compared to previous maps resulting in possible fuel efficiency gains RCCI Multi-Mode Map [E30 and ULSD] ULSD CN46 CDC Low load notes CDC used for lower engine loads due to similar efficiencies and NOx with much lower HC and CO than RCCI (Very low NOx CDC in this range ~ PCCI like) Further development opportunities RCCI Emissions concerns Not able to achieve lower NOx than CDC without sacrificing BTE Sub 200 C exhaust temps with high HC and CO represents clear challenges with current oxidation catalysts Backup Slides for Mapping Details 8

9 Biofuel blends potential path to enabling low temperature combustion Motivation i 100% coverage of low temperature combustion is necessary to avoid mode switching and additional emissions controls which would have negative impacts on fuel economy and costs UDDS= City ULSD/UTG 96 RCCI UDDS Points HWFET = Highway RCCI range with conventional fuels * Mixed mode LTC RCCI and PCCI may be required 9

10 Biofuel blends potential path to enabling low temperature combustion Motivation i 100% coverage of low temperature combustion is necessary to avoid mode switching and additional emissions controls which would have negative impacts on fuel economy and costs UDDS= City B20/UTG 96 RCCI UDDS Points HWFET = Highway Expanded RCCI range with conventional gasoline and B20 diesel blend RCCI range with conventional fuels Drive Cycle Coverage (non idling) B20/UTG UDDS 72% HWFET 88% * Mixed mode LTC RCCI and PCCI may be required 10

11 Biofuel blends potential path to enabling low temperature combustion Motivation i 100% coverage of low temperature combustion is necessary to avoid mode switching and additional emissions controls which would have negative impacts on fuel economy and costs UDDS= City ULSD/E30 RCCI UDDS Points HWFET = Highway RCCI range expansion with E30 RCCI range with conventional fuels Drive Cycle Coverage (non idling) B20/UTG ULSD/E30 UDDS 72% 52% HWFET 88% 74% * Mixed mode LTC RCCI and PCCI may be required 11

12 Current RCCI map requires mode switching to cover light duty drive cycles Fuel Economy Improvement depends on drive cycle coverage and BTE difference With multi mode operation, low load RCCI is important for % cycle coverage but requires high BTE delta to increase fuel economy and to make up for high h HC/CO and low Exhaust temps B20/ UTG 96 MPG L PFI, L CI DI, E30 RCCI, B20 RCCI, L PFI, L CID DI, E3 0 RCCI, B20 RCCI, L PFI, L CIDI I, E30 RC CCI, B20 RC CCI, ULSD/ E UDDS HWFET US06 2.4L 4LPFI 1.9L 9LCIDI E30 RCCI B20RCCI Drive Cycle Coverage B20/UTG ULSD/E30 UDDS 72% 52% HWFET 88% 74% Backup Slide for Details on Each Simulation Comparison 12

13 RCCI Challenges Include Lower Exhaust Temps with High HC/CO emissions BTE Difference vs. CDC High HC and CO Similar to PFI engine out Gasoline range and diesel range species with increased aldehydes etc CDC Low exhaust temperatures Areas < 200⁰ C Exh Temp Exh Temp (C) Species Co onc (ppb) RCCI HC Speciation T<200⁰C Back up Slide Emissions Drive cycle simulations 13

14 RCCI offers >20% fuel economy improvement all 2009 PFI engines evaluated PFI map matches 0 60 time of 1.9L diesel engine 0 60 time matched to 2.7L vehicle with best fuel economy from 2.4L engine ORNL chassis dyno and EPA fuel economy data mined for other PFI engine sizes Figure shows how city (UDDS/FTP) fuel economy trends with displacement More complete comparison against best in class PFI engines ORNL and EPA FTP (UDDS) 2009 PFI Fuel Economy Data 1 RCCI 1.9 CIDI Fuel Economy Data Modeled Fuel Economy RCCI % Fuel Economy Improvement Engine Size 18L 1.8L 24L 2.4L 27L 2.7L 40L 4.0L UNIT MPG MPG MPG MPG UDDS 33.1% 31.1% 45.8% 59.2% HWFET 41.6% 36.8% 45.7% 55.4% US % 38.4% 47.4% 38.2% SC % 27.7% 41.9% 52.0% 1 Data for small to full-size passenger cars with varying vehicle weight Backup Slide for Matching 0 60 Performance 14

15 Takeaways Many renewable fuels have unique properties which can enable/expand high efficiency engine operation and improve performance as compared to conventional fuels. Advanced combustion techniques such as RCCI can increase engine efficiency and lower NOx and PM emissions. RCCI uses in cylinder blending of twofuels withdifferent fuel reactivity (octane/cetane) to allow increased control over combustion compared to other advanced combustion methods that use a single fuel Biodiesel blends lower pre mixed ratio needed for meeting emissions and performance targets Lower reactivity and charge cooling effects of ethanol allow for load expansion but can limit low load stability RCCI offers increasedcontrol control for adaptationof of LTC modes to market variations in fuel The ability for RCCI to compensate for full range of market fuels has not been explored Understanding d of sensitivity to fuel effects will be critical in developing engine controls and emissions controls RCCI Premixed Ratio

16 Acknowledgements Kevin Stork, Steve Przesmitzki, Gurpreet Singh, Ken Howden, and Leo Breton of the United States Department of Energy Vehicle Technologies Program for funding a significant portions of the research in this presentation Many, many contributors spanning the ORNL Sustainable Transportation Program including all of the Fuels, Engines and Emissions Research Center 16

17 Contact Scott Curran Backup Slides 17

18 Recent References and Further Information Curran, S., Hanson, R., Wagner, R., and Reitz, R., "ff "Efficiency and Emissions Mapping of RCCI in a Light Duty Diesel Engine," SAE Technical Paper , Hanson, R., Curran, S., Wagner, R., and Reitz, R., "Effects of Biofuel Blends on RCCI Combustion in a Light Duty, Multi Cylinder Diesel Engine," SAE Int. J. Engines 6(1): , 2013, doi: / Curran S.J., Gao, A., and Wagner, R.M., Reactivity Controlled Compression Ignition Drive Cycle Emissions and Fuel Economy Estimations Using Vehicle Systems Simulations, Vehicle Systems Analysis Tech Team Meeting, Aug 7, 2013, Southfield, MI. Curran, S.J., Wagner, R.M., and Gao, Z., Recent Advances in Multi Cylinder Advanced Combustion on Light Duty Compression Ignition Engines, Presentation, 35th Annual International Energy Agency Task Leaders Meeting (San Francisco, CA: July 2013). Curran, S.J., Storey, J.M., Dempsey, A.B., Eibl, M., Wagner, R.M., and Gao, Z., Recent Advances in Multi Cylinder Advanced Combustion on Light Duty Compression Ignition Engines, Presentation, Advanced Engine Combustion Program Review (Southfield, MI: Aug 2013). Curran S.J., Gao, A., and Wagner, R.M., Reactivity Controlled Compression Ignition Drive Cycle Emissions and Fuel Economy Estimations Using Vehicle Systems Simulations, VSATT Meeting (Southfield, MI: Aug 2013) Daw, S., Gao, Z., Prikhodko, V., Curran, S., Wagner, R., Modeling Emissions Controls for RCCI Engines, Engine Research Center Symposium, June, 2013 [invited]. Szbyist J.P., Gasoline like Fuel Effects on Advanced Combustion Regimes, Project ID: FT008, May 16, 2013 Arlington, VA. Curran, S.J., Gao, Z., and Wagner, R.M., Light Duty Reactivity Controlled Compression Ignition Drive Cycle Fuel Economy and Emissions Estimates, Presentation at the Advanced Engine Combustion (AEC) Working Group Meeting, Livermore, CA; Feb Curran, S.J., Wagner, R.M., and Gao, Z., Background on RCCI and B20 RCCI Results With Both Gasoline and Ethanol Blends, Presentation, 2012 National Biodiesel Board Biodiesel Technical Workshop, (October 30 31, 2012, Kansas City, MO. [invited] Curran, S.J., Gao, Z., and Wagner, R.M., Light Duty Reactivity Controlled Compression Ignition Drive Cycle Fuel Economy and Emissions Estimates, Poster, 2012 U.S. DOE Directions in Engine Efficiency and Emissions Research Conference, (October 15 19, 2012, Dearborn, MI). 18

19 Modeled RCCI Drive Cycle Fuel Economy Modeling results show up to a 22 28% improvement in fuel economy with RCCI over UDDS compared to 2009 PFI baseline on same vehicle Fuel Econom my (MPG) RCCI fuel economy in diesel equivalent MPG 0 Modeled Fuel Economy over US Light Duty Drive Cycles 2.4L PFI, L CIDI, 35.7 RCCI, L PFI, 9L CIDI, 55.3 RCCI, L PF FI, L CIDI, 33.8 RCCI, 35.9 PFI, L UDDS HWFET US06 SC03 1.8L PFI 2.4L PFI 2.7L PFI 4.0L PFI 1.9L CIDI RCCI 9L CIDI, RCCI, 37.4 Modeled Fuel Economy Improvements with RCCI %Fuel Economy Improvement With RCCI 2009 PFI 2.4L PFI Diesel 1.9L CIDI UDDS (city) + 31% + 10% HWFET (highway) + 37% + 10% US06 (high speed) + 38% + 6% SCO3 (air cond FTP) + 28% + 8% Modeling provides insight into fuel needs under mixed mode mode RCCI operation Amount of drive cycle spent in RCCI mode Total amount of diesel fuel used (or secondary fluid) Fuel split during RCCI operation 19

20 Modeled RCCI Drive Cycle Fuel Economy B20 Map Modeling results show up to a to 59% improvement in fuel economy with RCCI over UDDS compared to 2009 PFI (SI) baseline on same vehicle (4.0L PFI baseline) Modeled Fuel Economy over US Light Duty Drive Cycles PFI Diese el RC CCI PFI Diesel RCCI PFI Diesel RCC CI Modeled Fuel Economy Improvements %Fuel Economy Improvement With RCCI Vs. PFI Vs. Diesel UDDS (city) + 59% + 14% lhwfet (highway) + 53% + 15% PFI Diesel RCCI US06 (high speed) + 39% + 8% NY City (stop and go) + 67% + 13% RCCI fuel economy improvements despite lack of complete drive cycle coverage Further development underway (fuels, hardware, controls) Results based on steady state engine data Does not address transient operation Does not address aftertreatment effectiveness On going research at ORNL 14% improvement over UDDS coverage allowed with biodiesel as compared to RCCI with gasoline and diesel fuel 20

21 RCCI offers >20% improvement all 2009 PFI engines evaluated PFI map matches 0 60 time of 1.9L diesel engine 0 60 time matched to 2.7L vehicle with best fuel economy from 2.4L engine ORNL chassis dyno and EPA fuel economy data mined for other PFI engine sizes Figure shows how city (UDDS/FTP) fuel economy trends with ihdisplacement More complete comparison against best in class PFI engines ORNL and EPA FTP (UDDS) 2009 PFI Fuel Economy Data 1 RCCI 1.9 CIDI Fuel Economy Data Modeled Fuel Economy RCCI % Fuel Economy Improvement Engine Size 18L 1.8L 24L 2.4L 27L 2.7L 40L 4.0L UNIT MPG MPG MPG MPG UDDS 33.1% 31.1% 45.8% 59.2% HWFET 41.6% 36.8% 45.7% 55.4% US % 38.4% 47.4% 38.2% SC % 27.7% 41.9% 52.0% 1 Data for small to full-size passenger cars with varying vehicle weight Backup Slide for Matching 0 60 Performance 21

22 RCCI High Efficiency with Low NOx and Soot Low NOx Trade off of BTE and ultralow NOx Drive Cycle Simulations will revel the level of NOx aftertreatment FSN needed to Meet Tier 2 Bin 5 and Bin 2 standards RCCI NOx Diesel NOx High Low Near zero smoke number Previous results show PM is also reduced Indicates very little elemental carbon in PM (Not zero PM) Implications for possible effectiveness of DOC to further reduce PM RCCI Soot Diesel Soot 22

23 Biodiesel blends allow stable operation with higher premixed gasoline ratio without impacting COV of IMEP or HC/CO emissions For fixed diesel SOI timing, biodiesel blends advanced combustion phasing Differences in NTC region heat release and duration Allows higher ratio of gasoline Allows increased stability for high levels of ethanol Have examined gasoline with ULSD, B5 and B20 Blends SME with Cetane number of ULSD with Cetane number of 42.5 and 46.5 UTG 96 with RON of 97.2 CN 42 ULSD CN 46 ULSD Noise Limited Combustion Phasing Diesel SOI = 60 CA btdc f Biodiesel blends allow combustion phasing to be maintained despite increasing amount of gasoline while observing MPRR limit of 100kPa/deg RCCI 2500 RPM, 8.0bar BMEP 23

24 Ethanol Blends Allow for RCCI Load Expansion Ethanol Blends require higher percentage of diesel fuel At fixed diesel SOI ethanol blends retard combustion phasing DI to PFI fueling ratio changes Lower reactivity of E85 requires higher fraction of diesel / biodiesel Both a chemical octane effect and a charge cooling effect with E85 Cyclic instabilities observed at high load limit for E85 High pressure rise followed by near misfire Minor stochastic perturbations may cause large operational changes due to homogeneity of fuel 2000RPM, 7.0bar BMEP Diesel SOI = 60 CA btdc f 436 kpa/deg rev/min 5% 1000 kpa/deg BTE (%) RCCI (E20/diesel) RCCI (gas/diesel) CDC (diesel) BMEP (bar) 24

25 Current RCCI Operation Includes Most of LD Drive Cycles RCCI mapped with focus on efficiency and lowest possible emissions Peak BTE within light duty drive cycle range (> peak BTE of 1.9L GM diesel) Current RCCI map requires mode switching to cover light duty drive cycles 100% coverage of low temperature combustion is necessary to avoid modeswitching Diesel RCCI RCCI Map overlain on diesel map Urban Dynamometer Driving Cycle Highway Fuel Economy Test US06 New York City Cycle Commonly called the "LA4"" or Represents highway h driving High acceleration aggressive "the city test" and represents conditions under 60 mph driving schedule also called city driving conditions the "Supplemental FTP" Features low speed stop andgo traffic conditions 25

26 Range of Compression Ignition Strategies Includes LTC and HTC Dual Fuel RCCI Diesel HCCI Exhaust Intake 360 HCCI CDC PCCI PFS Majority Premixed PPC Majority Stratified PPC Level of In Cylinder Fuel Stratification at the Start of Combustion 26 0 GCI LTC/HTC

27 Matching Engine Based on 0 60 Performance Current range of engine maps allows matching based on performance to have best comparison against representative 2009 PFI baseline FY 12 Milestone compared modeling results to 4.0L only Specifically asked to be addressed by ACEC and in AMR reviewer notes 0 60 mph acceleration simulations performed with standard performance transmission (non fuel economy optimized transmission) for each vehicle on same mid size sedan 2.7 L PFI engine best match for performance (2.4 L best fuel economy) 1.8 L PFI underpowered for vehicle size 0 60MPH acceleration (default shifting strategy) Engine Distance(M) Time(S) CDC CDC/RCCI peed (mph) PFI PFI PFI PFI Vehicle S Simulated time for 0 60 mph acceleration CDC CDC/RCCI PFI4.0 PFI2.7 PFI2.4 PFI Time (s) 27

28 Corollary Study: Aftertreatment Integration with RCCI Drive cycle simulations help illustrate challenges Estimate emissions and exhaust temperatures over drive cycles Modeled engine out emissions reductions compared to Diesel Modeled CDC and RCCI Mixed Mode Exhaust Temps over UDDS Reductions With RCCI NOx HC CO UDDS* 17% + 240% + 150% HWFET 21% + 300% + 140% US06 8% + 310% + 140% NY City +4% + 220% + 150% Examples 1500 RPM, 55b 5.5bar and 20b 2.0bar BMEP [Model DOC (1.25 L, 100g/Ft^3 Pt, 400 csi)] Experimental Data Showing Challenges with Low Temperature Aftertreatment 1500rpm, 5.5bar BMEP (280C) 1500rpm, 2.0bar BMEP (180C) 28

29 Corollary Study: Aftertreatment Integration with RCCI Drive cycle simulations help illustrate challenges Estimate emissions and exhaust temperatures over drive cycles B20 Map Modeled engine out emissions reductions compared to Diesel Modeled CDC and RCCI Mixed Mode Exhaust Temps over UDDS Reductions With RCCI NOx HC CO UDDS* 17% + 240% + 150% HWFET 21% + 300% + 140% US06 8% + 310% + 140% NY City +4% + 220% + 150% E30 Map Modeled engine out emissions reductions compared to Diesel Reductions With RCCI NO % HC% CO% UDDS 16.0% % +82.5% HWFET 18.6% % % US06 9.5% % +89.1% SC % % +78.6% 29