Late Intake Valve Closing and Exhaust Rebreathing in a V8 Diesel Engine for High Efficiency Clean Combustion

DEER Conference 2010

High-Efficiency Clean Combustion Engine Designs for Compression Ignition Engines GM-DOE AGREEMENT No. DE-FC26-05NT42415

Manuel A. Gonzalez D. General Motors Powertrain. Advanced Diesel September 29, 2010

Advanced Diesel DEER Conference 2010 1 Outline

● Objectives ● Technical Approach & Hardware ● Discussion of Variable Compression Ratio - Late Intake Valve Closing & Two Stage Turbo Charging ● Discussion of Internal EGR - Exhaust Rebreathing ● Estimated overall driving cycle impacts ● Summary ● Acknowledgements

Advanced Diesel DEER Conference 2010 2 Objectives ● Investigate the use of variable valve actuation (VVA) as a means to improve the efficiency of a light duty diesel engine approaching and exceeding Tier 2 Bin 5 NOx emission levels Multi-cylinder engine testing using a “simple mechanism” VVA system – steady state engine-out emission targets combined with aftertreatment technology for beyond Tier 2 Bin 5 tailpipe targets and enhanced fuel economy ─ Late Intake Valve Closing (LIVC) Study ─ Exhaust Rebreating Study

● Barriers addressed To operate at Low Temperature Combustion (LTC) conditions using “VVA simple mechanisms” for control of effective compression ratio and internal EGR (IEGR) Expand the useful range of the Early Premixed Charge Compression Ignition (PCCI) LTC mode in order to reduce fuel consumption To reduce engine out emissions To minimize the fuel energy required to raise exhaust gas temperature for catalyst efficiency and regeneration

Advanced Diesel DEER Conference 2010 3 VVA Strategies

Strategy Valve profiles Observations

Late Intake Valve • Too limiting for engine breathing Closing (both reducing volumetric efficiency and valves) torque

• Effective compression ratio control • Reduces volumetric efficiency Late Intake Valve • LIVC with extended duration, same Closing (one expansion ratio with reduced valve) compression ratio (improved efficiency) Intake Re- • Higher heat losses than exhaust rebreathing breathing (Intake valve re- • More difficult to open than exhaust opening during valve exhaust stroke) • Only one exhaust valve lift profile PISTON / VALVE need to be changed APPROACH DIAGRAM Exhaust Re- • Multiple profiles possible and PISTON MOTION breathing combined with intake - exhaust INTAKE VALVE EXHAUST VALVE (Exhaust valve re- pressure control opening during • Easier to be opened than intake intake stroke) valve • Less heat losses than intake rebreathing 0 100 200 300 400 500 600 700

Advanced Diesel DEER Conference 2010 4 Technical Approach - Hardware

Multi Cylinder Engine – VVA Study • Late Intake Valve Closing (phasing of one valve per cylinder) • Exhaust Rebreathing (re-opening of one valve per cylinder) with single and two stage turbocharging

Concentric Secondary exhaust Camshafts and phaser Two-stage turbocharging opening profile

Configuration/Displacement V8 4.5 liters Compression Ratio 16.0:1 Bore x stroke 88 mm x 92 mm Valve Train DOHC - 4v

Outboard intake with integrated Intake Configuration cam cover intake manifold

EGR Syste m Cooled external

In Vee exhaust with manifold Exhaust System Base integrated into head Engine Testbed Emissions Syste m DOC, Urea SCR and DPF

Advanced Diesel DEER Conference 2010 5 VVA - Late Intake Valve Closing 17 Exhaust Veffective Intake 16.5 CR = Intake phasing effective VTDC 16

15.5 Effective Valve Lift Valve compression 15 ratio in LIVC 14.5 operating range Effective Compression ratio

Crank angle 14 BDC Intake 0 70 LIVC phasing capability up to 90 ca degrees LIVC (crankangle degrees)

Two stage system, concentric camshaft and phaser in multi-cylinder engine head

Engine operating map for LIVC study

Advanced Diesel DEER Conference 2010 6 Exh Int Turbocharging for LIVC

 1-D Modeling for LMK 4.5L V8 Diesel Engine

Target: 70 ca deg phasing of one intake valve matching AFR and EGR

Two stage charging selected

Base VGT LIVC0 HP FG and LP FG LIVC70 Base VGT LIVC70 HP VGT and LP FG LIVC70 Base VGT Closed LIVC70 HP FG and LP VGT LIVC70

Advanced Diesel DEER Conference 2010 7 Charging

● Modeling air BSFC (g/Kw-h) . AFR matching 280.0 handling only reached  1-D modeling base 270.0 when using a engine and VVA High Pressure 260.0 VGT not using system 1200/2.8 rpm/bar VNT closing 250.0 BMEP  Charging hardware which have 240.0 1400/5.6 rpm/bar detrimental selection BMEP 230.0 BSFC 1600/10.9 rpm/bar performance 220.0 BMEP Single VGT Single VGT Single VGT HP 2-stage . Experimental Baseline 70 deg LIVC 70 deg 70 deg LIVC work also have LIVC; VGT shown

0.75

0.765 Closed 0.705 0.66 0.72 emissions 0.735 0.66 0.78

0.675 0.72

0.63 0.69

0.705 0.765 0.75 benefits with a 0.735

0.645

0.63 0.66 0.78 0.615 645 0.6 0.645 06 0.585 615 0.6750.69 0.75 0.57 0.63585 0.5550.54 0.555 57 0.63 0.54 controlled 0.5250.510.465 0.66 0.525 0.60.4950.48 0.69 0.51 0.6150.5850.57 0.645 0.4950.465 Pressure ratio Pressure 0.6750.63 0.48 reduction in AFR

Corrected Flow

Advanced Diesel DEER Conference 2010 8 Effective Compression Ratio 1600 rpm/4.8 bar BMEP Normal combustion on Cylinder Pressure Coolant @ 88C, Bypass OFF Constant NOx 1.2 g/kg Ca50 12 atdc fix

80 80

65 65

50 50

35 35

20 20

5 5 AHRR (J/cad) Cyl Press (bar)

-10 -10 1

0.5

. Peak cylinder pressure reduction resulted by LIVC Curr Inj 0 implementation for lower effective compression ratio -40 -20 0 20 40 60 80 SCE 1600 rpm x 4.2 bar LIVC60 EINOx 0.3 g/kg-f Early PCCI (blue color, LIVC70) and late PCCI . Start of injection can be advanced for constant combustion phasing to compensate . Coef of Variation of combustion phasing increases for longer ignition delay with LIVC, cam phasing control stability and impact of changing flow dynamics of individual cylinders

Advanced Diesel DEER Conference 2010 9 1600 rpm/4.8 bar BMEP Variation of main engine parameters at Normal combustion Coolant @ 88C, Bypass OFF different LIVC phasing and constant NOx < 1.2 g/kg EINOx Ca50 12 atdc fix Fix 70% VNT position

Advancing SOI for constant phasing 5

20 DELTA MAIN INJECTION [°CA 18 AFR drops with less efficient charging 16 144 AIR FUEL RATIO [-] 136

38 Flow to intake manifold 128

36 120 AIR_FLOW [kg/h]

34 EGR [%] Less EGR at constant NOx 32 LIVC0 LIVC40 LIVC50 LIVC60 LIVC70 LIVCdegrees [-]

Advanced Diesel DEER Conference 2010 10 1600 rpm/4.8 bar BMEP Variation of main engine parameters at Normal combustion Coolant @ 88C, Bypass OFF different LIVC phasing and constant NOx < 1.2 g/kg EINOx Ca50 12 atdc fix Fix 70% VNT position

2.7

2.4 Lower temperature profile for higher HCs

2.1

1.8 255 HYDROCARBONS [g/kg]

252

249

246 BSFC [g/kWh] Optimum BSFC determined by Phasing, Heat transfer, Friction

1 3 243

1 Higher oxygen accesibility SMOKE [FSN]

SMOKE RATIO by lower effective compression ratio and variable swirl 0 0 LIVC0 LIVC40 LIVC50 LIVC60 LIVC70 LIVC degrees [-]

Advanced Diesel DEER Conference 2010 11 Base and LIVC 50 ca degreees AFR, BSFC, HC, Smoke 1200 rpm/3.9 bar BMEP Normal combustion with LIVC Phasing Coolant @ 88C, Bypass OFF

Ca50 9 atdc fix Fix 72% VNT position 30-42% EGR sweep

24 AFR [-]

21 Consistent

trends are 254 observed at

252 different keypoints

BSFC [g/kWh] 250 6.0

5.6

0.9 LIVC 0 5.2 EITHC [g/kg] LIVC 50

0.6

0.3 Smoke [FSN] Smoke

0.0 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 3.9 EINOX [g/kg]

Advanced Diesel DEER Conference 2010 12 1600 rpm/4.8 bar BMEP Smoke vs AFR at Low NOx Coolant @ 88C, Bypass OFF Two stage HP TC. Ca50 12 atdc fix with LIVC Phasing for Fix 50% VNT position High % EGR sweep PCCI Combustion Modes NOx << 1 g/kg fuel

3.0 1 Early PCCI encounters either SMK_FSN_NOLIVC 0 high smoke or high noise if 2.7 SMK_FSN_NOLIVC 50 using a conventional valve lift SMK_FSN_NOLIVC 60 profile. 2.4 For LIVC, a single injection 2.1 strategy could achieve good overall engine performance. 1.8 By using LIVC, the combustion 0.51.5 phasing can be advanced for better fuel economy.

SMOKE [FSN] 1.2

SMOKE RATIO The AFR can be reduced 0.9 because smoke emissions are lower due to longer ignition 0.6 delay.

0.3 The combustion noise is controlled within the noise

0.00 limits by adjusting the injection 16 17 18 19 20 21 22 23 24 25 timing. Air Fuel Ratio [-]

Advanced Diesel DEER Conference 2010 13 LIVC 50 ca delay - Overall Effects

Impact FTP Cycle  BSFC ~ -0.5%  PM ~ -25%, > 50% at keypoints  HC > +17%

Operating region defined by trade-offs of fuel efficiency and emissions (boundaries: HCs at light loads; loss of ignition delay advantage for mixing at higher loads and AFR drop) Advanced Diesel DEER Conference 2010 14 Internal EGR Exhaust rebreathing events

High Lift - Duration Low Lift - Duration

Valve Lift Valve Baseline Exhaust

Camshaft Angle

● Keypoints operating area selected by HC contribution to cold start FTP cycle ● High/Low Lift and duration profiles ● Valvetrain exhaust implementations opposite to intake helical and tangential ports RPM

Advanced Diesel DEER Conference 2010 15 Internal EGR approach Exhaust Valve Flows 650 rpm/2.2 bar Valve lift lift Valve

. Representative IEGR profiles . Modeling of HC and NOx contributing keypoints

Exhaust Valve Flows 1600 rpm/6.8 bar

Fixed cams for switching profiles options

Advanced Diesel DEER Conference 2010 16 Fix RPM/BMEP keypoints In 200 sec warm-up phase Internal EGR relative to Baseline Coolant @ 40C, Bypass ON NOx ≤ target Base Temp Turbine Inlet Temp increase 700 41 • Turbine In 600 24 41 temperature 500 26 can be 14 400 increased along 43 300 30 15 all the 200 operating range Turbine Inlet

Temperature ( C) ( Temperature 100 • Can induce 0 light-off for the 800/105 1000/112 1200/90 1400/190 1600/150 1600/191 1800/263 2000/333 DOC catalyst • Varies with 70.0 heat transfer, 60.0 AFR by 50.0 Base substitution of External 40.0 Reb cam (Bypass) EGR 30.0 (%) 20.0 • Internal EGR 10.0 amount by

External (Bypass ) (%) EGR 0.0 model based 800/105 1000/112 1200/90 1400/190 1600/150 1600/191 1800/263 2000/333 approach

RPM/TORQUE

Advanced Diesel DEER Conference 2010 17 Fix RPM/BMEP keypoints Internal EGR relative to Baseline In 200 sec warm-up phase Coolant @ 40C, Bypass ON NOx ≤ target

. DOC inlet and Post DOC temperature can 0.0 be further -10.0 increased by HC/CO additional -20.0 conversion (also -30.0 changes in -40.0 turbine operating -50.0 point efficiency) -60.0 . Post DOC Post DOC HC (%) -70.0 performance, (as -80.0 HC % of reduction) is -90.0 favored by less 800/105 1000/112 1200/90 1400/190 1600/150 1600/191 1800/263 2000/333 engine out emissions plus RPM/TORQUE faster light-off and higher conversion by higher operating temperature

Advanced Diesel DEER Conference 2010 18 Fix RPM/BMEP keypoints In 200 sec warm-up phase Impact of IEGR Coolant @ 40C, Bypass ON NOx ≤ target

Whole FTP Cycle Fuel consumption ~ +0.3% Tailpipe Hydrocarbons ~ -20% (-50% first 200 sec of FTP cycle)

. First 200 sec in the warmup phase FTP Cycle – Estimate by weighting factors  Test vehicle weight 7000 lbs. Exhaust Gas temperature Management at low coolant temperature >20 % of the fuel consumed in FTP cycle  Smoke impact constrains for maximum applied engine bmeps

Advanced Diesel DEER Conference 2010 19 Fix RPM/BMEP keypoints Comparing exhaust heating strategies In 200 sec warm-up phase Coolant @ 40C, Bypass ON 300 NOx ≤ target

280 Baseline

260 Baseline w/retarded • injection For matching exhaust 240 Low Lift - Duration

Helical Port temperature, IEGR 220 Low Lift - Duration by exhaust Turbine In temperature (C) temperature In Turbine Tangential Port rebreathing shows promising results 200 for a competitive 320 strategy to retarded

310 timing at idle h) - 300 • Sources of 290 sensitivity to port

BSFC (g/kW location to be 280 subject of detailed 270 investigation 800 rpm / 105 N-m

Advanced Diesel DEER Conference 2010 20 IEGR Strategy / Aftertreatment modeling

Vehicle TVW 7000 lbs ● Phase 1 with highest Temperatures Exh manifold 500 contribution to HC and NOx 450 Pre DOC T overall tail-pipe emission for 400 SCR_Tavg FTP 350 300 ● Increasing exhaust 250 temperature by 40 degrees

Te mp [C] 200 150 . Overall emission for FTP 100 can be reduced by 25% 50 (HC) and 17%(NOx) 0 0 20 40 60 80 100 120 140 160 180 200  Total HC reduction Time [sec] Engine-out plus higher conversion 35%

Advanced Diesel DEER Conference 2010 21 Patent application - Diesel engine with switching roller finger followers for internal EGR control

The application of switching roller finger followers on the exhaust valvetrain of multi-cylinder diesel engines for selectively producing the re-opening of exhaust valves for internal EGR control

EGR Level Exh Valve #1 Exh Valve #2 0 Off Off 1-D Simulation 1 On Off Idle 2 Off On Internal EGR replacing external EGR

3 On On

Ways to apply the system:

• Single Exhaust valve per cylinder - allows one discrete rebreathing profile to be used, switchable

• Both exhaust valves per cylinder - single actuator, allows a higher amount of EGR to be introduced based on a single actuator

• Both exhaust valves per cylinder - dual actuator circuit, allow combinations of internal EGR rate to be achieved (zero, low and high)

• Both Exhaust valves per cylinder - dual actuator circuit, dual lift profiles, flexible control with 3 levels of internal EGR possible (additional control achieved with back pressure regulation)

Advanced Diesel DEER Conference 2010 22 Summary ● Late Intake Valve Closing for Changing Effective Compression Ratio and Exhaust Rebreathing for Internal EGR have been investigated with promising results ● Operating envelope  LIVC operation at part loads for emissions and FE of hot FTP cycle, constrained by charging system capability  IEGR operation from idle to part loads for warm-up and emissions of cold FTP cycle. Max BMEP determined by smoke limitations

VVA Major impacts Benefits / Limitations

Strategies FTP75 FTP75 cycle Profiles Comb Exhaust Intake cycle fuel emissions. NOx PM HC CO noise temp Exhaust cons.

1% * 50% PM LIVC + ++ - - + O reduction reduction 0.3-0.5% Internal ~20% HC increase O - + + O + EGR reduction **

Higher FE *: Depending on charging Key: potentialimprovement capability for LIVC including the + improved benefit for increased **: Compensation by warm-up o neutral strategy and aftertreatment impact DPF regen interval - worse

Advanced Diesel DEER Conference 2010 23 Summary

● Variabe valvetrain techniques have significant impacts on fuel efficiency and emissions with packaging and control challenges for implementation with different alternative valvetrain mechanisms in new engine designs

● Late intake valve closing and exhaust rebreathing provide further optimization opportunities for fuel efficiency and emissions

● Experimental impacts and estimations for the assessment of application are highly dependent on engine architecture and engine performance and emissions targets

Advanced Diesel DEER Conference 2010 24