RECENT DEVELOPMENTS IN LEAN-BURN IC ENGINES

RECENT DEVELOPMENTS INLEAN-BURN IC ENGINESR.L. EvansDepartment of Mechanical EngineeringThe University of British ColumbiaVancouver, B.C., CANADATHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

THE “PARTIALLY STRATIFIED-CHARGE” ENGINE• Spark-ignited combustion• Main mixture is homogeneous & ultra-lean• Enriched mixture near spark plug• Engine control strategy is critical• Natural Gas or gasoline fuelTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

How it works…1. Ultra-leanhomogeneouscharge of naturalgas and airTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

How it works…1. Ultra-leanhomogeneouscharge of naturalgas and air2. Fuel is injected in theregion of the sparkplugTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

How it works…1. Ultra-leanhomogeneouscharge of naturalgas and air2. Fuel is injected in theregion of the sparkplug3. Flame kernel forms,and propagatesthrough lean airfuelchargeTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

ADVANTAGES OF PARTIAL CHARGESTRATIFICATION• Engine operates in “fuel control” mode, similarto a Diesel engine• Limited use of throttling increases efficiency• Only one fuel is required• No requirement for on-board gas compression• No need for expensive and complex fuelinjection equipmentTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Partially Stratified-Charge Control ConceptTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Partially-Stratified Charge Spark Plug• Lean homogeneous maincharge of fuel and air• Injection of fuel nearignition source• Spark initiates stableflame in fuel-rich area• Flame propagates rapidlythrough lean chargeTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

UBC Ricardo Hydra Test Engine FacilityTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

BSFC vs. Air-fuel RatioInjection Duration Optimisation(WOT, 2500 rpm, EOI at MBT-10)300.0BSFC (g/kW-hr)290.0280.0270.0260.0250.0Homogeneous-charge25 deg. inj. duration30 deg. inj. duration35 deg. inj. duration240.0230.0220.01.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80Relative Air-Fuel RatioTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Total Hydrocarbons vs. Air-fuel Ratio(WOT, 2500 rpm, 35 deg. Injection pulse width)40.00tHC-wet (g/kW-hr)35.0030.0025.0020.0015.0010.00Homogeneous-chargeEOI at MBT-5EOI at MBT-10EOI at MBT-155.000.001.40 1.50 1.60 1.70 1.80Relative Air-Fuel RatioTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

CO vs. Air-fuel Ratio(WOT, 2500 rpm, 35 deg. Injection pulse width)14.00CO-dry (g/kW-hr)12.0010.008.006.004.00Homogeneous-chargeEOI at MBT-5EOI at MBT-10EOI at MBT-152.000.001.40 1.50 1.60 1.70 1.80Relative Air-Fuel RatioTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Mass-Burned Fraction Comparison(WOT, 2500 rpm)100%Mass Fraction Burned (%)Homogeneous fuelling,RAFR = 1.65(MBT Spark = -54)PSC fuelling, RAFR = 1.65(MBT Spark = -50)75%50%25%0%-60 -40 -20 0 20 40 60Crank Angle DegreesTHE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Bsfc & BMEP vs. Lambda(WOT, 2000 rpm)3008275BMEP6250BSFC422510% extension of leanlim it w ith P S C22001 1.2 1 .4 1 .6 1.8Lam bda (m ass basis)0THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Bsfc vs. BMEP(WOT, 2000 rpm)30027510% more load controlthrough PSC leaning at W ideOpen Throttle (W OT)250225W OT, Leaning, no PSCW O T , Leaning, w ith P S C2004 6 8BMEP (bar)THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

10NOx vs. BMEP(2000 rpm, Injection at MBT -10)98PSCNo PSC (May 21)BS NOx (g/kW-h)76543245%, L1.5235%, L1.3545%, L1.49Wide Open Throttle,Lambda 1.55100 1 2 3 4 5 6 7 8BMEP (bar)Wide Open Throttle,Lambda 1.68THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

Combustion Stability(WOT, 2000 rpm)765432EngineMisfiresNo PSC - Lambda 1.6110TDCWith PSC - Lambda 1.74-5 0 5 10 15 20-1Crank angle of Pmax (deg)THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

COV of IMEP vs. Lambda302520HomogeneousPSC1510501.0 1.2 1.4 1.6 1.8Lam bda (m ass basis)THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

CONCLUSIONS• Partially stratified-charge approach extended the leanlimit, and reduced Bsfc by up to 10% at a given airfuelratio• PSC approach reduced NOx emissions at part-loadconditions• Combustion stability is improved with PSC approach• PSC may be one component of a multi-componentoperating strategy due to “convergence”THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004

The End !Any Questions?THE UNIVERSITY OF BRITISH COLUMBIAECI – Lean Combustion Technology IIDepartment of Mechanical Engineering R.L. Evans - April, 2004