Gasoline Engine Performance and Emissions Future Technologies and Optimization

Gasoline Engine Performance and Emissions Future Technologies and Optimization Paul Whitaker - Technical Specialist - Ricardo 8 th June 2005 RD. 05/52402.1

Contents Fuel Economy Trends and Drivers USA and Europe Production Advanced Gasoline Technologies Boosting for Downsizing Technologies Lean Boost Direct Injection EGR Boost Direct Injection 2-stroke / 4-stroke Switching Optimization of Advanced Gasoline Combustion Systems Example: Optimization of a CAI enabled flexible valvetrain engine Summary and Conclusions RD. 05/52402.1 2

Fuel Economy Trends and Drivers USA and Europe Overall fleet fuel economy deteriorating Significant Truck market share increase (now 48%) Significant increase in vehicle weight Emissions legislation limiting dieselization Increased pressure for improved fuel economy CO 2 legislation? stricter CAFE? High Fuel Prices? Significant improvements since 1995: Increased diesel fleet (25% to 45% in last 5 years) Some improved gasoline engines 2002 & 2003 data shows levelling off Diesels near saturation OEMs currently face significant commercial challenges Further improvements in gasoline powertrain efficiency will be required that are cost effective and attractive to consumers Source: EPA Light-Duty Automotive Technology and Fuel Economy Trends: 1975 Through 2004 RD. 05/52402.1 3

Production Advanced Gasoline Technologies Stratified Charge SIDI Failed to deliver fuel economy promise Work continues on central injection (2 nd generation) NOx challenge difficult to overcome in US Homogeneous =1 SIDI Fuel economy, emissions & performance benefits Synergies with many other technologies Less complicated/expensive than stratified, lower risk Cylinder Deactivation Fuel economy potential similar to Stratified SIDI Relatively easy and inexpensive to implement Particularly suitable for OHV engines Easier to apply to V8 than V6 engines Advanced NVH technologies required for full benefit Continuously Variable Cam Phasing Most widely adopted advanced gasoline technology? Fuel economy, emissions & performance benefits Best benefits are from dual independent phasing Phaser speed/controls can limit benefits Fully Mechanical VVA Unthrottled operation, throttled across intake valve Potential friction reduction from reduced valve lift Complex mechanical system Only in production with BMW Baseline: V8 PFI Gasoline Engine Without EGR, Cost of $2,000, 500,000 units p.a. Emissions and performance benefits must also be considered Dual VCP Cylinder Deactivation Homogeneous SIDI Full VVA PFI Cost Benefit vs HSDI Stratified SIDI Better Worse RD. 05/52402.1 4

Contents Fuel Economy Trends and Drivers USA and Europe Production Advanced Gasoline Technologies Boosting for Downsizing Technologies Lean Boost Direct Injection EGR Boost Direct Injection 2-stroke / 4-stroke Switching Optimization of Advanced Gasoline Combustion Systems Example: Optimization of a CAI enabled flexible valvetrain engine Summary and Conclusions RD. 05/52402.1 5

Lean Boost DI (LBDI) Control Octane requirement by direct injection lean operation at full load enables high compression ratio Stratified operation at part load Fuel economy approaching diesel Lower cost and weight Real world fuel economy benefit IMEP [%] 200 180 160 140 120 100 80 60 Naturally aspirated Ignition retard stability limit Increasing MAP Lean stability limit 40 20 0 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Excess Air Factor RD. 05/52402.1 6

Lean Boost DI demonstrator has delivered downsizing benefits - Fully lean operation at all conditions delivers the fuel economy of a diesel with gasoline NVH and lower cost LBDI delivers fuel economy through downsizing, boosting & lean operation with high compression ratio Octane requirement controlled by: direct injection lean operation at full load stratified lean DI operation at part load 3.5 3 2.5 2 1.5 1 Risk Index Camless EMV MPI Base SIDI SIDI HCCI VCR Boosted DI Benefit Index LBDI 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 1.1l LBDI maximises hardware value: Higher power than 1.6 l (+5%) Higher torque than 1.6 l (+20%) Higher economy NEDC >20% better 132 g/km EUDC CO 2 Matched or better acceleration Economy over wide operating range RD. 05/52402.1 7

EGR Boost Direct Injection Intercooler Fixed Geometry Turbocharger SIDI V6 Engine Cost penalty 30% Throttle 3-way Catalyst Fuel economy benefit 12% EGR Boost Technical risk medium/high EGR Valve Intercooler Fixed Geometry Turbocharger EGR Cooler Uses cooled EGR as a dilutant to reduce octane requirement Enables high CR boosted operation Lambda=1 operation with Three-way Catalyst RD. 05/52402.1 8

DI Gasoline 2 / 4 Stroke Switching Concept improves efficiency through extreme downsizing 2 stroke operation provides enhanced low speed torque Very high low speed torque - 220 Nm/litre Ultimate fun to drive (torque and revs) HCCI at part load? LNT required for 2 stroke mode only (not required for typical urban or motorway driving) RD. 05/52402.1 9

Cost/FE Benefit Trade-off Advanced Gasoline Technologies Baseline: V8 PFI Gasoline Engine Without EGR, Cost of $2,000, 500,000 units p.a. Dual VCP RD. 05/52402.1 10 Homogeneous SIDI Cylinder Deactivation Full VVA PFI Stratified SIDI Cost Benefit vs HSDI EGR Boost Better Worse LBDI 2s / 4s Switching SIDI HSDI diesel Emissions and performance benefits must also be considered Downsizing technologies offer the greatest fuel economy potential

Contents Fuel Economy Trends and Drivers USA and Europe Production Advanced Gasoline Technologies Boosting for Downsizing Technologies Lean Boost Direct Injection EGR Boost Direct Injection 2-stroke / 4-stroke Switching Optimization of Advanced Gasoline Combustion Systems Example: Optimization of a CAI enabled flexible valvetrain engine Summary and Conclusions RD. 05/52402.1 11

Increased variability requires a mathematical optimisation technique DoE provides an efficient, robust analytical solution New powertrain configurations have increased challenges in optimisation: More variables More interactions More non-linear responses More emphasis on robustness Design of Experiments can create a virtual engine or powertrain and reduce experimental work leading to: Shorter development times Better, more robust solutions Increased engineering understanding BS HC [g/kwh] 6 5 4 3 2 1 0 2 4 BMEP [bar] 6 8 3 4 5 6 7 8 EVL [mm] 9 10 DoE is now essential for many engine development and calibration tasks Two requisites for successful DoE Good tools, especially for modeling and optimisation Intelligent implementation of DoE process Planning Design Testing Modeling Validation Optimisation RD. 05/52402.1 12

Example Optimisation of a Controlled Auto Ignition enabled gasoline engine using a flexible valve train providing variable lift & phasing on intake & exhaust BMW Valvetronic system applied to intake and exhaust system on 4 cylinder engine RD. 05/52402.1 13

A Design-of-Experiments (DoE) approach using Stochastic Process Modelling (SPM) and optimiser tools identified variable settings for best fuel economy Variables Objectives Definition of of variables v under investigation Inlet valve phasing (IVP) Exhaust valve phasing (EVP) Inlet valve lift (IVL) Exhaust valve lift (EVL) Manifold air pressure (MAP) Estimation of ranges of of each variable Model improvement Generate models Model quality FAIL assessment Responses Modelled BMEP Fuel consumption HC NOx CO COV (Net IMEP) (stability) 50% Mass Fraction Burned Ignition to 10% MFB 10 90 % MFB PMEP Optimum spark timing (MBT) Source: Re-define corner points unsuitable Design experiment Test corner points of of experiment on engine OK Run test sequence on engine Data sets obtained for inlet valve throttled, load ranges 1000-3500 rev/min with inlet throttle wide open. Control variables IVP, EVP, IVL, EVL, MAP PASS Optimise -with constraints Test engine to validate optimum points Poor validation OK End RD. 05/52402.1 14

Comparison of model output and measured data shows good correlation Data shown at minimum fuel consumption 2000 rev/min throttled 2000 rev/min valve lift controlled BSFC [g/kwh] 600 550 500 450 400 350 300 250 DoE model - variable inlet and exhaust lift and phase - unconstrained optimum BSFC Validation test results BSFC [g/kwh] 600 550 500 450 400 350 300 250 200 1000 rev/min valve lift controlled DoE model - variable inlet and exhaust lift and phase - unconstrained optimum BSFC Validation test results 1.0 2.0 3.0 4.0 5.0 6.0 BMEP [bar] BSFC [g/kwh] 200 900 800 700 600 500 400 300 200 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 BMEP [bar] 3500 rev/min valve lift controlled DoE model - variable inlet and exhaust lift and phase - unconstrained optimum BSFC Validation test results 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 BMEP [bar] RD. 05/52402.1 15

Validated optimum settings show that CAI combustion provides significant BSFC gains compared with normal SI operation Results shown for 2000 rev/min load range VCP=Variable Cam Phasing VVL=Variable Valve Lift BSFC [g/kwh] 500 475 450 425 400 375 350 325 300 275 250 Baseline fixed maximum lift and variable inlet and exhaust cam phasing Variable inlet and exhaust phasing and lift CAI operation 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BMEP [bar] SI - Dual VCP SI - Dual VCP + Dual VVL CAI - Dual VCP + Dual VVL Variable inlet and exhaust phasing and lift SI operation RD. 05/52402.1 16

Typical pressure/volume characteristics for CAI operation show recompression in exhaust stroke Negative valve overlap creates recompression cycle Recompression largely reversible Higher trapped mass due to high residuals higher pressures Lower losses across intake valve reduced throttling due to high residuals RD. 05/52402.1 17

CAI combustion provides significant BSFC gains compared with normal SI operation mainly due to pumping work reduction Results shown for 2000 rev/min load range VCP=Variable Cam Phasing VVL=Variable Valve Lift Fuel Consumption Benefit [%] 20 18 16 14 12 10 8 6 4 2 Dual VCP + Dual VVL with SI combustion Dual VCP + Dual VVL with CAI combustion PMEP [bar] 0.0-0.1-0.2-0.3-0.4-0.5-0.6-0.7-0.8-0.9-1.0 Fuel Consumption benefit versus Dual VCP SI - Dual VCP SI - Dual VCP + Dual VVL CAI - Dual VCP + Dual VVL 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 BMEP [bar] 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BMEP [bar] RD. 05/52402.1 18