Lean Gasoline Engine. Focus Group March 31, 2011

Transcription

1 Lean Gasoline Engine Emission Challenges Jim Parks, Dean Edwards, Shean Huff, John Thomas, Kevin Norman, Vitaly Prikhodko, Bill Partridge, Jae-Soon Choi, Paul Chambon, John Storey, Teresa Barone Oak Ridge National Laboratory Teleconference Presentation ti to the CLEERS Focus Group March 31, 2011 This presentation contains information on the experimental studies performed on a lean gasoline vehicle. The presentation also contains information on the data files uploaded to the CLEERS website (see slides 17-19). Further information is contained in the data files. This file updated March 16, 2012 to include information on addition of transient drive cycle data to CLEERS website. Sponsors: Gurpreet Singh and Ken Howden Advanced Combustion Engine Program U.S. Department of Energy

2 Background Relevance: U.S. passenger car fleet is dominated by gasoline-fueled vehicles. Enabling introduction of more efficient lean gasoline engines can provide significant reductions in passenger car fuel consumption thereby lowering petroleum use and reducing greenhouse gases lean gasoline is one of many options being considered, but it is an option that has synergy with other technologies (e.g. HEVs) Experimental Studies: ORNL studied a modern lean gasoline vehicle (BMW 120i) on a chassis dynamometer Fuel saving benefits of the lean combustion were characterized Combustion (AFR, etc.) and emissions data were also collected Database: Engine map data with emissions has been uploaded to the CLEERS website 2 Managed by UT-Battelle

3 Making modest improvements in fuel economy can significantly decrease overall fuel consumption Goals of reduced petroleum consumption and reduced 0.1 greenhouse gas emissions being 0.09 addressed by variety of approaches 0.08 Gallons per Mile Improving from 20 mpg to 22 mpg, 10%, has significant ifi overall impact Saves 300,000,000 barrels gasoline annually 10% fuel economy improvement can be achieved with lean gasoline approach Needs more than TWC for emissions control 3 Managed by UT-Battelle % improvement of 20 MPG vehicle saves 4.5 gallons per 1000 miles 20% improvement of 40 MPG vehicle saves 4.2 gallons per 1000 miles Miles per Gallon (MPG) Lean gasoline vehicles can decrease US gasoline consumption by ~1 million barrels per day

4 Lean Gasoline Engine Late 1990s: interest in lean gasoline engines for fuel economy improvement Port Fuel Injector (PFI) engine technology Newer Spark-Ignited Direct-Injection (SIDI) engine technology advances (also called GDI: Gasoline Direct Injection) NOx emission challenges present significant technological hurdle 2000s: large focus on diesel engine technology and development of lean aftertreatment t t t for diesel application (for new regulations) Late 2000s: renewed interest in lean gasoline engines Wall-guided and spray-guided direct injection technologies with advanced piezo-electric fuel injectors NOx emission challenges still present significant technological hurdle References: SAE , SAE , SAE , SAE , SAE , SAE , SAE , SAE , 2007 CLEERS Workshop (Brinkman), 2009 CLEERS Workshop (Li, Narayanaswamy) 4 Managed by UT-Battelle

5 BMW 120i Lean Gasoline Vehicle Thanks to GM for loan of vehicle Engine Out TWC TWC LNT In LNT LNT Out Engine Specs (N43B20): 2.0-Liter 4-cylinder Lean burn combustion 200 bar direct Injection 170 hp (130 kw) at 6,700 rpm 210 Nm (155 ft-lb) at 4,250 rpm 12:1 compression ratio Dual VVT and EGR 5 Managed by UT-Battelle

6 Lean Engine Operation Gives Primary Fuel Economy Benefit but Does Not Meet U.S. Emission Regulations 2008 BMW 1 Series Fuel Economy Vehicle has multiple l technologies for fuel economy improvement Lean operation offers most significant fuel economy improvement Start/Stop operation and mild hybridization via intelligent alternator control also contribute to fuel economy improvements 2008 BMW 1 Series - NOx Emissions MPG Stoich. Lean Lean with Start/Stop Lean, Start/Stop & Smart Alt FTP HFET US06 mi g/m US Tier II Standard 50k Bin 5 = 0.05(g/mi) EU Standard (new vehicle) Euro4 = 0.13 (g/mi) Stoich Lean Lean & micro hybrid Lean engine improves fuel economy but fails to meet US emission standards FTP HFET US06 6 Managed by UT-Battelle

7 4-15% Fuel Economy Benefit from Lean Combustion but NOx Emissions Problematic during Lean Mode Vehicle designed to meet emissions levels required by European regulations NOx emission levels exceed U.S. Tier II Bin 5, 0.05 g/mile at 50k miles Bin g/mile NOx emissions during lean operation are problematic Particulate matter (PM) emissions may also be of concern with respect to particle number regulations* *see SAE , SAE , SAE , etc. Improved Lean NOx catalysis required for deployment of lean gasoline vehicles 7 Managed by UT-Battelle Drive Cycle Fuel Economy Improvement** Tailpipe NOx emissions (g/s) Lean Stoich NOx Emissions (g/mile) FTP 10.0% 0.11 HFET 14.6% 0.11 US06 4.4% 0.35 **comparing stoichiometric operation to lean

8 A Note on Analytical Tools Used in Study Emissions and Reductant Species UEGOs for both exhaust manifold legs General emissions analyzers at engine out and tailpipe positions Reductant focused emissions analysis at LNT inlet position FTIR (NO, NO 2, N 2 O, NH 3, HCs, CO, etc) Mass Spectrometry (SpaciMS) (H 2, O 2 ) Engine Out 1 2 TWC LNT In LNT Out 3 LNT 4 TWC 8 Managed by UT-Battelle

9 Air-to-Fuel Ratio (AFR) for Operation At low engine loads (<60%), engine 30 operates at lean 28 AFRs of Rich operation of 22 engine at ~12 AFR used for LNT 16 regeneration At high engine loads 10 (>60%), engine operates at stoichiometric AFR AFR Engine Out 2500 rpm 3000 rpm 3500 rpm 4000 rpm 4500 rpm 0% 20% 40% 60% 80% 100% Engine Load 9 Managed by UT-Battelle

10 Catalyst Temperatures Catalyst temperatures vary with operating conditions (data Catal lyst Temperat ture (C) from 3500 rpm 700 shown) 600 Significant 500 differences occur between closecoupled TWCs and underfloor LNT LNT TWC (1&4) TWC (2&3) 0% 20% 40% 60% 80% 100% Engine Load 10 Managed by UT-Battelle

11 NOx Emissions Engine out NOx emissions vary greatly with engine load (3500 rpm data shown) TWCs effectively reduce NOx during stoichiometric operation (>60% loads), and LNT further adds NOx reduction contributions as TWC High concentration of NOx during lean operation (<60% loads) leads to significant tailpipe NOx as LNT NOx control becomes difficult NOx (ppm m) % 20% 40% 60% 80% 100% Engine Load Engine Out (Lean/Stoich) Engine Out (Rich) TWC Out (Lean/Stoich) TWC Out (Rich) LNT Out (Lean/Stoich) LNT Out (Rich) 11 Managed by UT-Battelle

12 NOx Emission Profiles Profiles of NOx concentration at Engine Out and LNT Out positions show NOx breakthrough occurring from LNT during both lean and rich phases of operation (data shown from 3500 rpm and 22% load) Saturation of NOx storage capacity occurs and leads to greater release during regeneration NOx (ppm m) Engine Out (1&4) LNT Out Time (sec) 12 Managed by UT-Battelle

13 Reductants during LNT Regeneration H 2, CO, and NH 3 are main reductants observed during LNT regeneration (data from 3500 rpm shown) H 2 presence at higher levels than CO differs from diesel engine LNT experience base NH 3 is present as expected, but levels are not significant ifi relative to H 2 and CO Red ductant Conce entration (%) H2 (Lean) H2 (Rich) CO (Lean) CO (Rich) NH3 (Lean) NH3 (Rich) NH3 (Rich) x10 0% 20% 40% 60% 80% 100% Engine Load 13 Managed by UT-Battelle

14 Reductant Emission Profiles Profiles of reductants produced during LNT regeneration show uniform Gaussian-type timing of reductant supply (data from 3500 rpm and 32% load shown) H 2 and CO Concentrat tion (%) H2 CO NH (ppm) NH 3 Co oncentration Time (sec) 14 Managed by UT-Battelle

15 TWC Affects Reductant Mix Analysis of CO and H 2 before and after TWCs shows that TWC is affecting mixture of reductants (data from 3500 rpm shown) CO levels drop over TWCs while H 2 levels increase suggesting that TWC is converting CO to H 2 via the Water-Gas-Shift reaction 4.0 entration (%) ductant Conc Re CO H 2 CO (TWC In, Rich) CO (TWC Out, Rich) H2 (TWC In, Rich) H2 (TWC Out, Rich) 0% 20% 40% 60% 80% 100% Engine Load d(%) 15 Managed by UT-Battelle

16 Database Uploaded to CLEERS Website 16 Managed by UT-Battelle

17 Files Uploaded to CLEERS Website Include: This presentation (for reference information) (3) Excel files containing data as function of engine maps [uploaded March 2011] Lean operation Rich operation Merged data set (4) Excel files containing transient drive cycle data [uploaded March 2012] Cold LA4 Hot LA4 HFET US06 Many thanks to Dean Edwards and Paul Chambon for their work on these data sets 17 Managed by UT-Battelle

18 Files Uploaded to CLEERS Website Data includes: Engine data such as AFR, air flow, fuel consumption, etc. Engine out emissions (CO 2, CO, O 2, THC, NOx) TWC Out/LNT In emissions (includes NO/NO 2, some HC speciation) Tailpipe emissions (CO 2, CO, O 2, THC, NOx) Exhaust system temperature and pressure data PM emission data Note: sparse non-replicated PM data (use with caution) Engine map data forced to square data matrices for ease of use in matrix math programs by filling edge regions with max, min, or interpolated values The filled data is noted by the font color red 18 Managed by UT-Battelle

19 A Note on Transmission Factor Details Matlab m-file used for translation of engine shaft work to wheel work (transmission factor) Experiments were performed on vehicle on chassis dynamometer Fixed gear operation for steady-state engine map data A translation factor was applied to determine engine shaft work from the wheel work (measured) M-file generated for translations supplied here for users who may want to perform system level modeling (Autonomie, etc.) 19 Managed by UT-Battelle

20 Conclusions Chassis dynamometer study of a lean gasoline engine vehicle (BMW 120i) Fuel economy improvements from lean operation (vs. stoichiometric) were 4-15% and varied with drive cycle, but U.S. Tier II Bin 5 NOx emission level were exceeded Database of engine emissions and operational parameters a (including emissions s at various points in exhaust system) has been uploaded to CLEERS website Questions: Jim Parks parksjeii@ornl.gov (865) Managed by UT-Battelle