| Nowadays,with the optimization of the fuel-related particle control strategy,the oil is becoming more and more important.In this study,the lubricating oil,few popular oil additives like the oil additive package,anti-wear additive and pour point depressant additive,specific element of sulfur and ash content in the oil,was taken into consideration to study the effects of oil compositions on the particle emissions and physico-chemical characteristics,all of these experiments were conducted based on many different techniques.Fast particulate spectrum,transmission electron microscope,Raman spectrum,Thermogravimetric analysis,X-ray Photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to analyze the size distribution,number concentration,morphology,nanostructure,volatile fractions and surface functional groups.The results show that the total number concentration of particle increased with about two times when lubricating oil was involved into the combustion.Especially when the oil additive package and pour point depressant additive were used,there were sharp increase,but the anti-wear additive impacts the accumulation mode particle a lot.In the meantime,the average diameter of the primary particles increased from 22 nm to 26 nm maximum when lubricating oil additives were burnt at low engine speed condition,while decrease from 24 nm to 19 nm minimum at high engine speed condition.The fractal dimension of the aggregates decreased from 1.822 to1.424 for the oil-additive-dosed fuels,which indicates that the spatial structure of the aggregate is loosened.Compare with the pure diesel particles,the fringe length increased from 1.191 nm to 0.947nm,1.139nm and 1.064nm for the additive package,anti-wear additive and pour point depressant additives,respectively.For the separation distance analysis,the results show that it increased from 0.362nm to0.364nm,0.388nm and 0.379nm for the additive package,anti-wear additive and pour point depressant additives,respectively.Similarly,the tortuosity of the fringes also increased from 1.405 to 1.453,1.439 and 1.454,respectively.This means that the inner structure of the particles is less ordered when the oil fractions were burnt along with the fuel.The analysis results from the surface functional groups show that about7%more carbon atom show in sp~3 style compare with pure diesel fuel related particles when the lubricating oil was burnt along.On the other hand,the concentration of the oxygenated functional groups increased about 3.1%for the C-OH.When using the oil with high sulfur concentration,the C-H group concentration decreased but the oxygenated groups increased little bit.However,for the high ash oils,the C-H,C-OH and C=O groups decreased.Lastly,the thermogravimetric analysis data show that at low engine speed condition,the volatile fractions increased about 3%,among which about 15%increase of the low volatile fraction and 12%decrease of the high volatile fraction.The elemental carbon fraction decreased consequently.The more volatile fractions in the oil indicates that there are more unburnt lubricating oil or fuel fractions,and this is in good agreement with the unclear and non-crystallized structure based on the high resolution transmission electron microscope images.In summary,based on the experimental study of all of the oils and oil additives,the results show that the combustion of these oil compositions changes the size distribution and number concentration a lot.The higher volatile fractions in the oil or oil additive-derived particles may be responsible for these changes,and the high oxygenated surface functional groups also indicate that the oxidation reactivity of the oil-derived particles is higher than the pure diesel related particles. |
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