Study On Emission Characteristics Of Particulate Matter Emitted From Diesel Engine Fueled With Blending Biodiesel

As the energy shortage and environmental pollution problems are gradually prominent,it has become a hotspot to look for new alternative fuels recently.Biodiesel is a kind of clean energy with high hexadecane,low sulfur content,little aromatic hydrocarbons,which makes it a ideal alternative for diesel fuel and it can be directly used on diesel engines.Therefore,the research on the combustion characteristics of biodiesel and the emission characteristics of particulate matter have academic significance and engineering application value.In this paper,4F20 TCI diesel engine was used as the research object to build the engine bench system to analyze the effect of blending biodiesel(B0,B5,B10,B20)on engine combustion and particulate emission characteristics.The influence of biodiesel on the change of in-cylinder pressure and heat release rate was analyzed by combustion analyzer.The exhaust emission analyzer was used to study the conventional emission characteristics of biodiesel.With the increase of the proportion of biodiesel,the maximum explosion pressure increased,the corresponding crankshaft angle was advanced and the peak value of premixed combustion was reduced.At middle and low load,biodiesel had little effects on the conventional emission characteristics.With the increase of biodiesel blending ratio,the emission of CO,HC and soot decreased gradually and the NOx emission increased gradually..The samples were collected based on the microporous uniform deposition type collision impactor(MOUDI),and the size distribution of the particles was obtained by weighing the sampled particles with the microgrid balance.With the increase of the load,the increment concentration of the particulate matter increases,and the mass concentration of the particulate matter was shifted to the smaller size range.The mass of the particulate matter decreased with the increase of the biodiesel blending ratio,especially when at high load,and biodiesel obviously improved the accumulation of particulate matter while the coarse particles changed little.The SOF samples were prepared by particle sample pretreatment and the SOF fractions were analyzed by gas chromatography-mass spectrometry(GC-MS).With the increase of biodiesel blending ratio,the content of SOF components in particulate matter was gradually increased.The SOF components mainly included alkanes,aromatic hydrocarbons,phenols,acids and esters,among which the proportion of alkanes was the largest and ranged from 55% to 72%.With the increase of the proportion of biodiesel,acid and ester substances increased,alkanes,aromatic hydrocarbons and phenols decreased,the number of carbon atoms distribution was more concentrated.The number of carbon atoms in B0 particles SOF was between C12 ~ C24,while the B20 particles SOF carbon atoms mainly between C15 ~ C22.The effects of biodiesel on the microstructure and graphitization of particulate matter were analyzed by scanning electron microscopy,transmission electron microscopy and laser Raman spectroscopy.The emissions of the four fuels were aggregated by a certain number of primary particles,which were bonded to each other and finally exhibited a cluster or tabular morphology.Under the full load condition,with the increase of the biodiesel blending ratio,the average particle size of the primary particles was gradually decreased,and the local overlapping phenomenon was intensified.Raman spectra have two peaks,D and G peaks were corresponding to the positions of 1354cm-1 and 1586cm-1 respectively.With the increase of biodiesel blending ratio,the degree of graphitization of the particles decreased,and as the load increases,the graphitization degree of the particles increased.