Dr. Terry Alger. Southwest Research Institute. Southwest Research Institute. San Antonio, Texas

Transcription

1 Gasoline Engine Technology for High Efficiency Dr. Terry Alger Southwest Research Institute Southwest Research Institute San Antonio, Texas

2 Losses and Opportunities for Improvement in Gasoline Engines Current trend of downsizing and boosting offers significant challenges for high efficiency powertrains Low CR Large enrichment region Significant thermal losses Particularly challenged in real world driving conditions and on highly loaded cycles Brake Power Combustion Losses Friction Losses Coolant Heat Losses Cycle Losses Pumping Work Exhaust Heat Losses

3 Cooled EGR Impact on Engine Performance Reduced Knock High CR operation enabled Improved combustion phasing Improved Emissions Reduced PM / PN Reduced NO x and CO Significantly Higher Efficiency and Lower Emissions Improved Cycle Efficiency Reduced Heat Transfer Improved Cycle Lower Exhaust Temperatures Eliminates enrichment requirement Enables VGT

4 Knock Suppression with EGR 87 octane to 92 octane has same knock suppression as increasing EGR from 15% to 25% with GDI. 10% EGR ~ 5 point AKI increase ON 93 ON 100 ON MFB [ o atdc] CA50% EGR = 12% ON = 6 EGR = 15% ON = EGR [%]

5 Improved Cycle Efficiencies Through Knock Reduction Modern GDI engine 1500 rpm / 60% load HEDGE concepts applied: Cooled EGR Adv. Ignition (DCO) 2 Stage Boosting Low P EGR system

6 Emissions Reduction With EGR Data from modern GDI 3000 rpm / 75% load

7 Enabling Technologies for High Dilution Applications

8 Engine BMEP [bar] Full Map Fuel Economy Improvement with Cooled EGR 1.6 L GDI Engine 1.6 L GDI Engine (series configuration) 25 % EGR Full map improvement = 22 BSFC [g/kwh] real world and test cycle : 1 CR FE improvement Engine Speed [rpm] Typical improvement over GDI baseline : 6-9% Improvement over TC MPI engine (including adding cam phasers) : 8-11% Improvement over NA MPI baseline : > 11% Engine BMEP [bar] 22 BSFC [g/kw-hr] Engine Speed [rpm]

9 Future Work on LPL EGR Engines SwRI s HEDGE III consortium continues to look at advancements in LPL EGR technologies Synergies with highly variable valvetrains Continuous improvement in subsystems Ignition Boosting Controls Understanding design requirements In-cylinder aerodynamics Engine architecture Dual-loop EGR Optimized pumping work at low and high loads High power density with single TC

10 Synergies with LPL EGR and Variable Valvetrains Primary FE benefit from EGR at part load comes from Increased CR Reduced HT losses Charge property improvements Pumping work improvement limited by dilution tolerance

11 Blended EGR* Dual-loop loop EGR for Pumping Work Optimization 4000 RPM Blended EGR 6000 RPM HPL EGR 2000 RPM LPL EGR HPL EGR At low load At high speed / high load LPL EGR At low speed / high load HPL + LPL EGR At mid-speed / high load *patent pending

12 Challenges Remain Knock / Reduced Reduced Flame Speeds / CR in Boosted Increased Combustion Engines Inefficiencies EGR Tolerance / Combustion Stability High Efficiency Barriers Heat Rejection To increase efficiency even further, several areas of improvement are required for cooled EGR engines

13 Dedicated EGR Improving Efficiency Via In-Cylinder Reforming ɸ > 1.00 ɸ = 1.00

14 Sources of Improvement in D-EGR Knock resistance Pumping work reduction Improvement in Reduced NOx emissions > less reductantneeded for TWC control (leaner combustion in main cylinders) Eliminate main cylinder enrichment 25% EGR reductant needed for TWC control Reformate Improved fuel octane > knock resistance Improved dilution tolerance Use EGR at lower engine temperatures Faster burn velocities / Reduced ignition energy Improvement in NOTE : D-EGR is not an exclusive technology. It can integrated into almost any existing engine architecture (i.e. Atkinson-cycle, VTEC, etc) 14

15 Improving the Fundamentals Enabling High CR and Impacting the Working Fluid Cool combustion + dilution + reformate = higher 1.1 < D < 1.5 Higher = Improved otto

16 Enabling High EGR Tolerance Test Platform 2006 MY 2.4 L Chrysler World Engine 14:1 CR rpm / 2 bar bmep V IMEP [% %] 6 4 Co Cylinder #1 Faster combustion = Improved Stability at 25% EGR

17 Increased Knock Resistance Reformate Impact on Effective RON + Faster Burn Rates = Improved Knock Tolerance [N-m] imited Pea ak Torque Knock L RPM WOT Dedicated Cylinder

18 Improved Torque at High Compression Ratios % EGR 2.0 L TC MPI engine 2000 RPM 12.5:1 CR % EGR 12.6 % [g/kw hr] BSFC % 24.3 % 20% LPL 12.5:1 CR D EGR 12.5:1 CR BMEP [bar] Enables High-Efficiency Downsizing 18

19 Enabling Low Octane Fuel? Knock Limite d Maximum Load at MBT [ bar] % EGR D Phi = 1.2 LPL EGR 12.5:1 CR, 92 AKI LPL EGR 12.5:1 CR, 87 AKI D EGR 12.5:1 CR, 88 AKI 22 % EGR Engine Speed [rpm] 19

20 Reduced Emissions BS SCO [g/kw-hr] BSH HC [g/kw-hr] BSN NOx [g/kw-hr] BSCO BSHC BSNOx Soot Mass D-EGR Equivalence Ratio [-] Engine out Emissions: 2.0 L TC MPI D EGR Engine 2000 rpm 10.5 bar BMEP S oot Mass [mg/ /kw-hr] Combustion efficiency returns to nearly nondilute levels Reformate improves HC and CO emissions NOx emissions increase slightly Still ~ ¼ of non- dilute case Significant PM reduction enabled

21 Solution for the Entire Performance Map BTE~ 40% in a 2.0 L TC GDI application ~ 330 g/kwh at 2000 rpm / 2 bar bmep BTE ~ 42% in a 2.0 L TC MPI application < 330 g/kwh at 2000 rpm / 2 bar bmep

22 D-EGR in a Vehicle > 10% improvement in MPG 13% improvement over the baseline on a US FTP-75 10% improvement on the US HWFET SULEV / Tier III emissions potential Current emissions ~ US LEV III Engineering margin still required for production applications Drivability >= baseline vehicle

23 Summary The use of EGR cooled LPL or H2 enriched D-EGR has significant ifi efficiency i benefits Reduced knock high CR downsizing Improved charge properties Reduced emissions and exhaust temperatures Improved combustion phasing Success demonstrated via early work in LPL EGR leads to new research directions D-EGR EGR + VVA Advanced enabling technologies

24 Contact Information Dr. Terry Alger (m) (w) Southwest Research Institute 24