Study On The Effects Of Iron-based Fuel Borne Catalyst On Combustion And Soot Emission Characteristics Of Diesel Engine

In recent years,the global extreme climate events occur frequently and the ecological environment is deteriorating day by day.Various countries have issued stringent emission regulations to limit the emissions of diesel engine pollutants which is as one of the main factors of environmental problems.The simple aftertreatment technology is gradually unable to meet the emission regulations easily,the problem of diesel engine emission pollution from the source can be solved by improving the physical and chemical properties of fuel and optimizing the combustion in cylinder.Fuel borne catalyst(FBC)can achieve efficient and clean combustion without changing the structure of diesel engine,so it has attracted a lot of researchers'attention.More and more analysis and exploration of fuel borne catalyst are gradually carried out in the world.Based on the diesel engine test bench platform and combustion visualization system,this paper has studied the combustion process,emission pollution and soot generation process of the conventional Fe-FBC from the diesel engine market.The particle size distribution(PSD),micro-morphology and structure,oxidation activity and SOF composition of the particles from Fe-FBC fuel have been carried out and analyzed in-depth based on the particle physical and chemical properties testing instrument.Fe-FBC fuel was prepared according to the Fe element mass ratio of 200 mg/kg,400 mg/kg and 600 mg/kg before the test,and labeled as Fe200,Fe400 and Fe600 respectively.The combustion characteristics and emission performance of Fe-FBC fuel were studied by combustion analyzer and exhaust gas analysis system when the engine were fuelled with diesel and three kinds of Fe-FBC fuel.The results show that Fe-FBC can effectively promote the chemical reaction of combustion and significantly improve the combustion rate and thermal efficiency of fuel;Fe-FBC has a better inhibition effect on HC,CO and smoke emissions,and the effect of emission reduction is more significant with the increase of Fe-FBC content.The HC and CO emissions of different concentrations of Fe-FBC fuel are reduced by 4.7%~13.3%and 1.4%~7.8%respectively under various conditions.The smoke drops of Fe200,Fe400 and Fe600 fuel reaches the maximum under the condition of full load,which are 13.7%,20.4%and 24.0%respectively.The inhibition effect of Fe-FBC on NO_x emission is not obvious.When the diesel engine is operated under high load,Fe-FBC can significantly reduce the emissions of formaldehyde,acetaldehyde,1,3-butadiene,ethylene,acetylene,PAHs and other unconventional pollutants.However,adding Fe-FBC to the diesel under low and medium load will lead to more emissions of 1,3-butadiene,ethylene and ethyne.The combustion visualization platform of diesel engine was modified by endoscope system,and the combustion flame images of diesel engine fuelled with Diesel,Fe200 and Fe400 fuel were taken with the platform.The flame temperature and soot concentration in the cylinder were calculated based on the two-color method,and the area distribution in the soot generation process was analyzed.The results show that with the increase of Fe-FBC content in diesel,the ignition time of fuel is a little advanced,the flame development speed is accelerated,the combustion degree is more violent,the maximum combustion temperature in the cylinder is significantly increased,and the combustion duration is slightly shortened.The amount of smoke in the cylinder is always kept at a low concentration during the whole combustion process,and the proportion of smoke area in the combustion chamber decreases significantly with the increase of Fe-FBC content in diesel,which indicates that Fe-FBC can continuously inhibit the formation of smoke and promote the catalytic oxidation of smoke during the combustion process.Engine Exhaust Particle Sizer(EEPS),Scanning Electron Microscope(SEM),Thermal Gravimetric Analyzer(TGA)and Gas Chromatography-Mass Spectrometer(GC-MS)were used to analyze the physical and chemical properties of the particle size distribution,micro-morphology and structure,oxidation activity and SOF components of different fuel.The results show that the particle size is smaller,the total number of particles is slightly increased,and the total mass of particles is significantly reduced while the engine fuelled with Fe-FBC fuel.Compared with diesel,the particle structure of Fe400 tends to be sparse and loose,and has lower box-counting dimension.With the increase of Fe-FBC content,the starting temperature of oxidation reaction of particle decreased,and the oxidation activity at low temperature increased significantly.The addition of Fe-FBC changes the composition of SOF in the particles,especially reduce the type and content of PAHs,and transform PAHs with high benzene ring number to low ring number.In addition,Fe-FBC also reduces the compounds with high carbon atom number in the component of SOF,lowering the toxicity of the particles.