Effects Of Fuel Formulation On Surface Functional Groups And Oxidation Reactivity Of Diesel Engines Particulate Matters

The particulate matter (PM) emission control of diesel engine becomes a hotissue in the field of internal combustion engines due to the appearance of hazeweather and other worse pollution incidents. In this paper, the surface function groupsand oxidation reactivity of soot, which generated from diesel fuel (DF), biodiesel (BD)and CTL with multi-operating conditions, were investigated. The results couldprovide a useful theoretical reference for understand of formation mechanism anddevelopment control technology of particulate matters. The major achievements arelisted as follows:1. The concentration of aliphatic C-H function groups of soot which generatedfrom different fuel and operating conditions was analyzed by Fourier transforminfrared spectroscopy. Results reveal that the concentration of aliphatic C-H functiongroups decreased with increasing the load of engine, raising the engine speed resultedin concentration of aliphatic C-H groups decreased and a gradual increase followed.The BD soot possesses the highest concentration of C-H function groups, while theconcentration of CTL soot is much lower.2. The X-ray photoelectron spectroscopy (XPS) was employed to investigate thesurface characteristics of soot. Results show that the main components of sootcollected from diesel engine are carbon and oxygen, and O/C ratio of BD soot ishigher than others, in a range of0.081to0.145. Three kinds of soot share the similartendency of O/C ratio while change operating conditions: the O/C ration have anegative relationship with load, and firstly increases and then decreases withincreasing the speed, besides, the impact of load on O/C ration is more pronouncedthan speed. The concentration of hydroxyl (C-OH) and carbonyl (C=O) groups wereanalyzed and results reveal that: the main component of oxygenated surfacefunctional on soot is hydroxyl groups, while amount of carbonyl groups is small.Increasing engine load lead to a decrease of hydroxyl groups amount, with raisingengine speed a decrease follow by an increase of hydroxyl groups amount in a smallrange was observed. The formulation of fuel has observed influence on the amount ofhydroxyl groups. Highest concentration of hydroxyl groups was observed in BD soot,the CTL soot posted the minimum concentration.3. The light-off and burn-out temperatures of all three kinds of soot range from 394to622.5oC, and the range of apparent activation energies is138.1-172.5kJ/mol.The apparent activation energies of soot have a negative relationship with engine loadand a trend that firstly increased and then decreased with increasing speed. Theoxidation activity of three kinds of particles, in descending order, is: BD>DF>CTL.The aromatic and oxygenated component directly effects concentration of surfacefunction groups of soot, and subsequently effects oxidation reactivity. Aliphatic C–Hand hydroxyl (C-OH) groups post more important position in governing sootoxidation reactivity than carbonyl (C=O) groups.