Diesel Engine and the Environment - Clean Shipping Technology

ENVIRONMENTThe Diesel Engine and the EnvironmentDavid SteffensWartsila North America, Inc.Session Chair – Wayne Cole, Cole EngineeringSeptember 16-17, 2003Houston, Texas

IntroductionThe diesel engine and the environment- rules and regulations- emission reduction technologiesReturn to Session Directory

Typical composition of diesel engine WFI-M exhaust Marine gasTogether> 99.5%Nitrogen N 2 : 76%Oxygen O 2 : 13%Carbon dioxide CO 2 : 5% Low due to high efficiencyWater H 2 O: 5%Sulphur oxides SO X Fuel choice relatedCarbon monoxide CO Low due to good combustionHydrocarbons C X H y Low due to good combustionParticlesLow at steady state operationInfluenced by fuel ash andsulphur contentVisible smoke FSN Low load related (

Exhaust compounds and their environmental impactNO x:– acid rain, acidification– ozone/smog formation in the lower atmosphere(potential damage on vegetation and human health)Particulates:– some considered carcinogenic– blackening with sootSO x:– acid rain, acidification– potential detrimental effect on human healthCO:– ozone/smog formation in the lower atmosphereHydrocarbons:– ozone/smog formation in the lower atmosphere– some considered carcinogenic– contribute to the greenhouse effectCO 2:– the major greenhouse gasReturn to Session Directory

Diesel NO XFormationThermal NO X formation (65-75%)Nitrogen source:combustion airFormation process: extremely complex including hundreds ofdifferent reactionsStrong temperature influence (exponential)Return to Session Directory

20181614121086420Thermal NO x FormationNO x Equilibrium Concentration20040060080010001200140016001800200022002400Local Temperature (K)Relative NOx -ConcentrationReturn to Session Directory

Typical NO x -Emissions for DifferentTypes of EnginesTypical NO x Emissions in g/kWh:138840.651.3DieselLiquid FuelGasDieselLean BurnGas EngineReturn to Session Directory

14NOx emissions of different prime moversoperating on MGO1210NOx g/kWh86420Diesel engine withSelective CatalyticReductionAeroderivative gasturbineDiesel engine withDirect WaterInjectionDiesel engineReturn to Session Directory

Emission reductionTechnologies to reduce emissions:• Primary Methods - During Combustion• Secondary Methods - After CombustionReturn to Session Directory

Primary NO xcontrol - diesel enginesAvailable today - Combustion ModificationEmission rating– Adjustment of fuel injection timing/TC specification–NO x reduction potential: 10 - 20 %– Simple and cheap– Increased fuel consumption and thermal loadLow NO x combustion– Rearranged diesel cycle–NO x reduction typically: 25 - 35 %–NO x well below the IMO limit– Unchanged or improved fuel consumptionReturn to Session Directory

Primary NO xcontrol - diesel enginesAvailable today - Water InjectionWater-in-fuel emulsions– Humidification of the combustion process–NO x reduction potential typically: 20 %– Limitations• emulsion stability• fuel injection system capacity• poor engine performance in “non-water” operational mode• cavitation risk in injection systemDirect water injection– Humidification of the combustion process–NO x reduction typically: 50 - 60 %– Improved thermal load and engine cleanlinessReturn to Session Directory

Low NO XCombustion Engine DesignRearranged diesel cycle– Very late fuel injection start– Higher compression ratio– Early inlet valve closing (4-stroke)– Late exhaust closing (2-stroke)– Optimized combustion chamber– Optimized fuel injection pressureResults– Lower combustion temperatures– Shorter duration at high temperaturesConclusions–NO X reduction typically 25-35%– Unaffected fuel consumptionReturn to Session Directory

Low NO x CombustionApplication: All Fuel TypesConventional DesignEngine Maximum Firing PressureLow NO x DesignEngine Maximum Firing PressurePressure riseinduced fromcombustionPressure riseinduced fromcombustionCylinder PressurePressure riseinduced fromcompressionCylinder PressurePressure riseinduced fromcompression-90 -60 -30 0 30 60 90 120 -90 -60 -30 0 30 60 90 120TDCTDCReturn to Session Directory

Implementation of Low NO x Combustion onWärtsilä Vasa 32bRelative NO x EmissionsRelative Spec. Fuel Cons.100%100%97%80%Compr.RatioWV32Σ = 12WV32LNΣ = 13.8WV32Σ = 12WV32LNΣ = 13.8Return to Session Directory

DisadvantagesFeatures of fuel-water emulsions– Increased camshaft torque and cam load.– Full load of engine not possible at high water ratios due tolimitations in the fuel injection equipment.– Same nozzles not optimal for operation with and withoutemulsion.– Negative impact on injection equipment reliability andlifetime.– Increased fuel viscosity, higher preheating temperaturesneeded.Advantages– Improved low load smoke.– Lower NOx. The NOx limitation is limited to about 20%,because unlimited water amounts cannot be kept in a stableemulsion.Return to Session Directory

FSNMEC Test on W6L46CR, Vaasa2-19 December 2002INFLUENCE OF WATER EMULSION ON FSNStandard Nozzle: 12x0.64x160°, Fuel: HFO0.800.700.60FSN0.500.400.30W/F ratio = 0, without MECW/F ratio = 0, with MECW/F ratio = 0.1W/F ratio = 0.2W/F ratio = 0.30.200.100.000 10 20 30 40 50 60 70 80 90 100 110Engine load [%]Return to Session Directory

NO xemissionsMEC Test on W6L46CR, Vaasa2-19 December 2002INFLUENCE OF WATER EMULSION ON NO x EMISSIONSStandard Nozzle: 12x0.64x160°, Fuel: HFOReference NOx: Without MEC1.000.95Relative NO0.900.85100% load85% load75% load50% load0.800.750.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35W/F ratioReturn to Session Directory

Return to Session DirectoryThe principle of Direct Water Injection

Direct Water InjectionWatertankWaterControlHigh pressure unitwater pumpFlow fuseSolenoidvalveFuelTFuel needleWater needleReturn to Session Directory

Return to Session DirectoryDirect Water Injectiontypical water/fuel timing and duration

Emission Control Technologies - Tomorrow’s solutionsFuture Technologies:•CASS (Combustion Air Saturation System)Return to Session Directory

CASSCASSCompressor“Intercooler”/heaterWater injectionReceiverWater injectionThe hot air after the compressor is cooledto the saturation point by injecting watermistHeatAfter heating in the “charge air cooler” themixture is again saturated by injecting ofmore waterHeating of the air by HT-waterReturn to Session Directory

Efficiency of humidification methodsRelative NO xformation1.11.00.90.80.70.60.50.40.30.20.1Direct WaterInjectionCombustion Air HumidificationW20W320.5 1.0 1.5 2.0Water/Fuel flow ratioReturn to Session Directory

Predicted NOx behavior with different controlmethods on Wärtsilä 46NOx15Fuel Water Emulsion10CASSFWE + CASS550 100 150 200 250Water amount as % of fuel consumptionReturn to Session Directory

Secondary NO xcontrol - diesel enginesAvailable todaySelective catalytic reduction (SCR)–NO x reduction typically: 85 - 95 %– Urea/water solution injected– Integrated part of the engine package– Exhaust temperature window 330 - 450 °C at HFO operation– Investment and operating costs relatively highCompact SCR– Combined silencer and SCR unit– Minimized sizeReturn to Session Directory

Return to Session DirectoryPrinciple of Selective Catalytic Reduction

SCR Reactions With Urea• Before Entering the Reactor:(NH 2 ) 2 CO + H 2 O 2 NH 3 + CO 2• In the Reactor:4 NO + 4 NH 3 + O 2 4 N 2 + 6 H 2 O6 NO 2 + 8 NH 3 7 N 2 + 12 H 2 OReturn to Session Directory

Retrofit of Compact SCRBirka Princess at Lloyd WerftSCR plants have beenretrofitted in several passengerships in existing engine casing= no lost space!A Compact SCR occupies alittle more space than a normalsilencer which it replaces.Return to Session Directory

Smokeless Diesel EngineParticle Emissions– Particle emissions are seen as smoke– More prevalent at low loads and start-upSmoke Reduction Methods– Common rail fuel injectionReturn to Session Directory

Smokeless Diesel EngineTargets for the Smokeless Engine• No visible smoke at start-up• No visible smoke at any load• NO x emissions to be reduced• CO 2 emissions to be reduced even lower by furtherimprovements in efficiencyReturn to Session Directory

Conventional vs common rail fuel injectionConventional injectionsystemMechanical./hydrauliccontrol at the injectorsCommon Rail InjectionElectronic / hydrauliccontrol of injectionConstant fuelpressureFuel pressureproduced each timeby the injection pumpReturn to Session Directory

Return to Session DirectoryWÄRTSILÄ COMMON RAIL SYSTEM

Common Rail advantages• Smokeless operation at all loads and speeds.• Smokeless start of the engine.• Smokeless load pick-up ramps.• NOx reduction down to 3…4 g/kWh with humidificationpossible without visible smoke.• Improved total fuel economy.• Flexibility for different fuels without hardware modifications(heavy fuel, diesel oil, gas turbine fuel, water-fuel emulsion).• Improved safety and comfort because more engines can bekept running with still good fuel economy and no smoke.Return to Session Directory

Wärtsilä 46 Common RailFSN status at engine laboratory and delivery test runFilter smoke number0.50.450.40.350.30.250.20.150.10.050Production enginesMay 2002 and forupgrading*THIS ISSMOKELESSBest lab.resultswith modifiedpiston shape*0 10 20 30 40 50 60 70 80 90 100 110*Engine load (%)Conventional injection**Return to Session Directory