Lean Combustion 2004, TomarDiluted and Stoichiometric Combustion of Dual Fuel (Methane and Gas Oil) Engine with HCCI ConceptOkayama University (Japan)Eiji TomitaNobuyuki KawaharaBackground- Increasing thermal efficiency (reducing CO2)- Reducing pollutant emissionsHCCI : low NOx, no smokeLean Slow speed, Dilutedlow temperaturecombustion stoichiometricThree-way catalyst EGRStratified chargespark-ignitionDual fuel(normal injection)Dual Fuel(Early injection)PREDICPCCISCCIHCCIHomogeneouschargespark-ignitionFlamepropagationAutoignitionTimeExperimental method-Dual fuel engine (methane + diesel fuel)high octane number high cetane numberusing a DI diesel engine- Early injection (40-50°BTDC) : HCCI conceptlow NOx, no smokebut rapid combustion with high NOx in high load -EGR (N2-dilution)achieving mild combustion in high load- Stoichiometric combustion- ROHR and Exhaust emissionsCompression ratio: 17.7:1Injector: 4 holes (φ 0.26mm), Spray angle: 150°Combustion chamber: Deep dishSingle cylinder,4 stroke cycleDirect injection (diesel fuel)+ induction from intake port(methane)Bore x stroke: 92 x 96 mmDisplacement: 638 cm3Engine specifications and combustion chambern =1000rpmθinj=TDC~50°BTDC(Pilot injection)φt =0.4~1.1α=0~37.5%Experimental apparatus and methodExhaustVaporizerGasfuelLightoilInjectionpumpmetermeterNOxHCmeterSmokeFlowmeterSurgetankDatarecorderGapsensorPressureCrankangleTDCmeterThermoTimingbeltDynamometerGasfuelmeterFlowSurgetankHeaterIntakeMixairOilWaterExhaustGasfuelAirMixerFlowmeterIntakeSurgetankVaporizerMethaneGasMixerTiming beltDynamometerExhaustInjection pumpLight oilSurge tankHeaterDatarecorderNOxmetermeterHCSmokemeterThermo meterFlow meterHeaterMixerLight oilSurge tankInjectionPumpDatarecorderNOXHCSmokemeterThermometerTiming beltAirAirMethaneMethanegasgasExhaustExhaustgasgasFlow meterN2gasFlow meterNN2 2 gasgasPressure and ROHR without EGRNormal injection timingEarly injection timingLow temperature reaction due to diesel fuelOne peak with retard combustionExhaust emissions and thermal efficiency w/o EGRφt=0.5Smoke=0Early injection- Low NOx, low HC, Low CO- Low cycle-to-cycle fluctuation- High thermal efficiencyNormal injectionEarly injectionθinj=50°BTDC(mgo=4 mg/cycle, α=0 %)Pressure and ROHR with increasing load w/o EGRIncrease in load--> - increase and advancein Pmax and (dQ/dθ)max- decrease in effective workSmoke=0Exhaust emissions and thermal efficiency w/o EGRIn φt <0.5, combustion is incomplete and bad.In φt>0.5, NOx increases while HC and CO are lower, andcombustion becomes stable.-60 0 600246810θ, °ATDCn = 1000rpmmgo =4mg/cycleθinj = 50°BTDCφt = 0.6P, MPaα= 16.7 %α= 9.1 %α= 0 %-60 0 60020406080100θ, °ATDCdQ/dθ, J/degn = 1000rpmmgo =4mg/cycleθinj = 50°BTDCφt = 0.6α= 9.1 %α= 16.7 %α= 0 %Pressure and ROHREGR ratio, α=0, 9.1%, 16.7%α0 9.1 16.7 23.1 25.9 28.6 33.3Methane+010002000300040005000NOx, ppm0500010000HC, ppmC1*051015200.40.50.60.70.80.9 1Smoke, %φt00.10.20.30.4CO, %nozzle : 150°n : 1000 rpmθinj : 40°Oil : 4mg/cyclα 0 9.1 16.7 23.1 25.9 28.6 33.3Methane+0102030400.4 0.5 0.6 0.7 0.8 0.9 1.0ηi, %05101520CV(Pi), %φtnozzle : 150°n : 1000 rpmθinj : 40°Oil : 4mg/cycleIncreaseα=33%DecreaseExhaust emissions, thermal efficiency and CV(Pi) with EGRAlmost zero levelEGR ratio was changed according to equivalence ratio.θinj=40°BTDC(early injection)IncreaseOperating range of stoichiometric conditionsθinj (°BTDC) 10 20 40 50 40mgo(4mg/cycle)44448Methane0102030400102030405060θinj, ° BTDCα，%0n = 1000 rpmφ t = 1.00013509Smoke,%00003106Smoke=0Smoke could be seen due tofuel-rich region in normalinjection .In early injection,smoke level is almost zero and operating range becomes narrow.When diesel fuel increases, the operating range in φt=1.0 becomes wider.- When the injection timing of diesel fuel is advanced, the range of equivalence ratio for the engine operation becomes narrow. - However, the engine can operate even instoichiometric mixture owing to EGR. - Under the condition of stoichiometric mixture,smoke can be seen when the injection timing is20°BTDC though smoke is not seen when theinjection timing is 40 and 50°BTDC. - This is because there is no rich region of fuel dueto the diffusion of the diesel fuel in the