| With the development of car industry, the energy crisis problem becomes to be moreand more serious, and it seems to be more critical for our country as we dependent too muchon importing; Environmental pollution problem is getting worse, since last year there is toomuch haze in and it definitely affected people’s life. In view of such a social condition,looking for cleaner and more economical combustion mode has become the developmentdirection of the auto industry. Technology of gasoline engine in cylinder direct injection(GDI) becomes popular in such circumstances, GDI technology compared with traditionalPFI engine has better economical efficiency,and under specific conditions have significantlylower emissions. But in terms of particulate emissions, due to the short mixing time, forminglocal concentration area becomes more likely, so the GDI exhausts more particulateemissions. In order to find more optimal control strategy, and explore further potential ofGDI engine,this paper is going to discuss the characteristic of combustion and exhaustparticulate matter emission from the GDI engine.Research is mainly by experiment means, aiming to use the most direct way to explorethe regularity of the characteristic. Test mainly contains two aspects: the research of GDIengine combustion characteristic and the research of GDI engine particulate emissioncharacteristics. Combustion characteristic is discussed mainly bythe pressure in cylinder,thetemperature in cylinder and the gas emissions: The characterstic of particulate matteremission is mainly discussed through particle number concentration, the concentration of theparticle surface area and particle mass concentration. Experiment is conducted in thecondition of a car’s actual work conditions, the speed of2000r/min and small load condition.Experiments are studying the different air-fuel ratio, ignition advance Angle, injectionadvance Angle and load.By conducting such experiments to find the relative optimizationcontrol strategy. The main conclusions of this paper are the following:1. In experimental conditions,when the air-fuel is14.7, the maximum explosionpressure in cylinder and heat release rate has the highest peak. When the mixture is rare, thepressure and heat release rate in cylinder are decreased, and there is an obvious combustionlag. With the increase of air-fuel ratio, CO and HC emissions decrease; At the beginningNOx emissions increase with the increase of air-fuel ratio, when the air-fuel ratio becomes19.2the emissions of NOx comes to the maximum, then NOx emissions decrease with theincrease of air-fuel ratio.With the increase of Air-fuel ratio from11.8to20.1, the particlenumber concentration turns a bimodal distribution of nuclear modal particle andaccumulation mode into bimodal mode distribution of nuclear model and initial particles,along with the increase of air-fuel ratio it turns to be a kernel mode of nuclear model. Withthe increase of air-fuel ratio, concentration of particle surface area and particle massdecreases obviously. Summary: In experimental conditions,when the air-fuel ratio is14.7the engine power is highest.With the increase of air-fuel ratio,all gas emissions and particleemissons decrease,the average size of particle also decrease.2. When the fuel injection advance Angle is320°CA BTDC，the pressure in thecylinder reach the maximum.Moreove the peak of the heat release rate is much higher andthe time of is also very timely. With the increase of fuel injection advance Angle, CO andHC emissions reduced gradually; At the beginning NOx emissions increase with the increaseof the injection advance angle, when t the injection advance angle becomes320°CA BTDCthe emissions of NOx comes to the maximum, then NOx emissions decrease with theincrease of the fuel injection advance angle.When the fuel injection advance angle decreasefrom340°CA BTDC to260°CA BTDC,the particle number presents bimodal distribution ofnuclear model and the particle number increases when the injection advance angledecreases.When the fuel injection advance angle is220°CA BTDC or200°CA BTDC,particle number concentration appears as the bimodal distribution of nuclear modal andaggregation modal and with the decrease of the fuel injection advance Angle particle numberconcentration increased. With the decrease of the fuel injection advance Angle particlesurface area and the mass concentration are decreased. Summary: In experimental conditions,when the fuel injection advance Angle is320°CA BTDC and engine power isthe highest, but at this point the emissions of NOx is the most; HC and CO emissionsgradually reduce with the increase of fuel injection advance Angle. With the decrease of thefuel injection advance Angle particulate emissions increase in the number, when fuelinjection advance Angle is large the main composition of particles is the nuclear particle,when the injection advance Angle is less than220°CA BTDC emerged a large number ofparticles in the state of accumulation.3. With the increase of the ignition advance Angle, the maximum cylinder pressureincreasing, and combustion occurs earlier.Combining the cylinder pressure curve and heatrelease rate curve, optimum ignition advance Angle is15°CA BTDC. With the increase ofthe ignition advance Angle, CO and HC emissions are coming down. As the ignitionadvance Angle increases, NOx emission is rising, and the NOx emission curve presents thetendency of increase with the two stages. When the ignition moment from5°CA BTDCincreased to15°CA BTDC, particle number concentration increased; When the ignitiontime increased from15°CA BTDC to27°CA BTDC, particle number concentrationdecreased. With the increase of the ignition advance Angle, particle surface areaconcentration decreased, while from the ignition advance Angle is15°CA BTDC thenuclear modal particles’ surface area has increased significantly. With the increase of theignition advance Angle, particle mass concentration decreased.Summary: In experimentalconditions,the ignition advance Angle is15°CA BTDC engine power is highest,.With theincrease of the ignition advance Angle CO and HC emissions gradually reduce while NOxemissions increase gradually; When ignition advance Angle is15°CA BTDC the particlenumber concentration is the biggest, with the increase of the ignition advance Angle particlesurface area concentration and mass concentration declined.4. With the increase of load the pressure and heat release rate in cylinde are increased,when the load is70nm the combustion state is the best within experiment conditions. Withthe increase of load, CO and HC emissions reduced. NOx emissions significantly increasedwith increasing load. When the load is40Nm and50Nm, particle number concentrationshows the bimodal distribution of nuclear mode;When the load is60Nm,70Nm and80Nm, the curve presents bimodal distribution of nuclear modal and aggregation modal.Concentration of particle surface area and mass concentration increased with the increase ofthe load.Summary： In experimental conditions,when the load is70nm engine powerperformance is best; With the increase of load,the emissions ofthe CO and HC reduce whileNOx emissions increased; The number of particles concentration increases with the increaseof load... |
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