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Methanol and biodiesel are the oxygenated alternative fuels of diesel engine, which can effectively reduce particulate emissions of diesel engines. However, due to the low cetane number of methanol, it is difficult for methanol to ignite in diesel engine. The addition of cetane number improver is an effective method to improve the ignition performance of diesel engine fuels. In order to study the effects of different cetane number improvers on diesel engine emission pollutants, three kinds of cetane number improvers, such as alkyl nitrates, naphthyl nitrates and ethers were chosen and added to the methanol / biodiesel blend fuel with the mixing ratios of 0.3%, 0.3%, and 3%, respectively. The effects of the cetane number improvers on the physical and chemical properties of methanol/biodiesel blend were investigated. The engine bench test was carried out on the 186F diesel engine without adjusting the structure of the diesel engine during the test. The in-cylinder pressure and exhaust temperature of the diesel engine fueled with methanol/biodiesel blend was measured at 1 800, 3 000 r/min, 25%, and 100% load, then the ignition delay and combustion duration were calculated. The variation of pollutants such as HC, CO, NOX and smoke emitted from the diesel engine at 1 800 and 3 000 r/min, 10%, 25%, 50%, 75% and 100% loads were measured. The effects of cetane number improvers on diesel engine exhaust pollutants were investigated. The results showed that the addition of cetane number improvers had little effects on the density, viscosity and other physical and chemical properties of the methanol/biodiesel blend, but the cetane number of the blend was obviously increased. Because of the low decomposition activation energy of the cetane number improvers, the improvers can help the blend to shorten the chemical delay period. With the addition of cetane number improvers to the methanol/biodiesel blend, the in-cylinder pressure peak was increased, the ignition delay was shortened, and the combustion duration was prolonged. In addition, the corresponding crankshaft angle of in-cylinder pressure peak was advanced. When the amount of improvers was equal, the ignition delay period of alkyl nitrates mixture was the shortest among the three cetane number improvers. When the diesel engine changed from 25% load to 100% load, the exhaust temperature was increased by 194-235 K at the same speed. While the diesel engine speed had smaller effects on the exhaust temperature and the variation range was −3.24%-3.45%. With the addition of cetane number improvers, the HC and CO emission were increased, especially at higher engine load. However, the addition of cetane number improvers can reduce the NOX and the smoke. When the diesel engine was at 3 000 r/min, 100% load, NOX was reduced by 12.90%, 6.45%, 3.87% with the addition of alkyl nitrate, naphthenic nitrates and ethers respectively, and the smoke was reduced by 11.76%, 17.65%, 38.24%. The addition of cetane number improver in methanol/biodiesel blends not only can improve the ignition characteristics of the fuels, but also reduce NOx and particulate emissions. [ABSTRACT FROM AUTHOR]

Abstract: Methanol and biodiesel are the oxygenated alternative fuels of diesel engine, which can effectively reduce particulate emissions of diesel engines. However, due to the low cetane number of methanol, it is difficult for methanol to ignite in diesel engine. The addition of cetane number improver is an effective method to improve the ignition performance of diesel engine fuels. In order to study the effects of different cetane number improvers on diesel engine emission pollutants, three kinds of cetane number improvers, such as alkyl nitrates, naphthyl nitrates and ethers were chosen and added to the methanol / biodiesel blend fuel with the mixing ratios of 0.3%, 0.3%, and 3%, respectively. The effects of the cetane number improvers on the physical and chemical properties of methanol/biodiesel blend were investigated. The engine bench test was carried out on the 186F diesel engine without adjusting the structure of the diesel engine during the test. The in-cylinder pressure and exhaust temperature of the diesel engine fueled with methanol/biodiesel blend was measured at 1 800, 3 000 r/min, 25%, and 100% load, then the ignition delay and combustion duration were calculated. The variation of pollutants such as HC, CO, NOX and smoke emitted from the diesel engine at 1 800 and 3 000 r/min, 10%, 25%, 50%, 75% and 100% loads were measured. The effects of cetane number improvers on diesel engine exhaust pollutants were investigated. The results showed that the addition of cetane number improvers had little effects on the density, viscosity and other physical and chemical properties of the methanol/biodiesel blend, but the cetane number of the blend was obviously increased. Because of the low decomposition activation energy of the cetane number improvers, the improvers can help the blend to shorten the chemical delay period. With the addition of cetane number improvers to the methanol/biodiesel blend, the in-cylinder pressure peak was increased, the ignition delay was shortened, and the combustion duration was prolonged. In addition, the corresponding crankshaft angle of in-cylinder pressure peak was advanced. When the amount of improvers was equal, the ignition delay period of alkyl nitrates mixture was the shortest among the three cetane number improvers. When the diesel engine changed from 25% load to 100% load, the exhaust temperature was increased by 194-235 K at the same speed. While the diesel engine speed had smaller effects on the exhaust temperature and the variation range was −3.24%-3.45%. With the addition of cetane number improvers, the HC and CO emission were increased, especially at higher engine load. However, the addition of cetane number improvers can reduce the NOX and the smoke. When the diesel engine was at 3 000 r/min, 100% load, NOX was reduced by 12.90%, 6.45%, 3.87% with the addition of alkyl nitrate, naphthenic nitrates and ethers respectively, and the smoke was reduced by 11.76%, 17.65%, 38.24%. The addition of cetane number improver in methanol/biodiesel blends not only can improve the ignition characteristics of the fuels, but also reduce NOx and particulate emissions. [ABSTRACT FROM AUTHOR]

With three EGR rates of 0, 10％ and 20％, the characteristics of exhaust particles with butanol／diesel blend of B10 in diesel engine were investigated by thermogravimetric test. The effect of EGR rate on the pyrolysis and combustion characteristics of particles were discussed. The variation characteristics of ignition temperature, burnout temperature component percentage were also analyzed. The activation energy of oxidation reaction of the soot in particles was calculated based on CoatsRedfern non isothermal method with different EGR rates. The results show that with the increasing of EGR rate, the ignition temperature of particles is decreased with increased burnout temperature， and the volatile particles in percentage are decreased with gradually increased volatile components with high boiling point and fixed carbon particle fractions. Compared with B10 particles, the percentage of fixed carbon particles in B10EGR20％ particles is increased by 23.6％, and the activation energy of particles is decreased gradually. Compared with B10 particles, the activation energy of B10EGR10％ and B10EGR20％ particles are reduced by 0.9 kJ·mol-1 and 1.7 kJ·mol-1, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Diesel particulate is one of the main sources of atmospheric particulate matter PM2.5, which seriously harms human health. With the emission regulations become increasingly stringent, higher requirements have been put forward, not only on the quality of particulate emissions but also on the particle number. The change trend of particle size distribution and oxidation characteristics of the diesel particulate are analyzed, in order to understand the change process of the diesel engine particles in the exhaust pipe. For further reduction of the diesel engine exhaust particulate, the post processing technologies have been widely used, such as diesel particulate filter(DPF). A lot of carbon dioxide(CO2), water vapor, hydrocarbon(HC) and particulate matter and other components are contained in the diesel engine exhaust, and the temperature, pressure and other parameters of the exhaust gas flow changed in the exhaust pipe of the diesel engine. The exhaust particulate matter was also accompanied by condensation and oxidation reduction and other physical and chemical processes, and as a result the physical and chemical characteristics of particles also changed. The particle size distribution and oxidation characteristics of the particles were important for the particle capture efficiency and regeneration. The particle size distribution along the direction of movement of the exhaust gas flow and different positions was measured by using the engine exhaust particle size spectrometer(EEPS). Along the direction of the exhaust gas particles at different sites during the pyrolysis process, pyrolysis kinetic parameters, ignition temperature and burnout characteristics index were studied, and particle pyrolysis reaction rate and degree of difficulty were analyzed by using the device of thermogravimetry/differential simultaneous thermal analyzer. According to the experiment data, along the direction of the exhaust gas flow, the number of nucleation particles decreased, the number of aggregated particles increased, and the particle size of aggregated particles became larger. It showed that in SOF(soluble organic fraction) evaporation stage and soot oxidation process, the particle weight loss rate increased, and the weight loss peak temperature decreased; along with the diesel engine exhaust gas flow direction, when reducing the temperature of the gas, the content of H2O in particles increased from 1.3% to 2.46%, the content of SOF increased from 38.21% to 42.05%, the soot percent content decreased from 57.84% to 52.24%, and the ash content increased from 3.01% to 3.25%; the pre-exponential factor of particle was reduced from 7.93×1012 to 4.67×1012 and the activation energy could be reduced from 157.3 to 127.9, the ignition temperature decreased from 546 to 501 ℃, which was reduced by about 8.2%, the combustion characteristic index increased from 8.16×10-9 to 1.62×10-8, and the burnout characteristics index was risen by 14.5%. Therefore, based on the study of the particle size distribution and oxidation characteristics which came from the small non-road diesel engine exhaust pipe of particles, it can be concluded that along the exhaust gas flow direction, with lower exhaust temperature, the burnout performance of the particle gets improved and effectively raises the regeneration of particle collector. [ABSTRACT FROM AUTHOR]

Pollutant emissions of diesel engine are mainly particulate matters, nitrogen oxide (NOx), hydrocarbon (HC), carbon moNOxide (CO), etc. The NOx, sulfide and particulate matters can form aerosol in the atmosphere, which is one of main causes leading to fog and haze. The concentration of small and medium scale particles such as PM2.5 and NOx is increasing with the wide application of diesel engine. The fog and haze weather occurs frequently, which has negative impacts on human health. It is quite necessary to carry out research on reducing particulate matters emitted from diesel engine. The diesel particulate matters and NOx emissions can be effectively controlled by adding the oxygen-containing fuel in the reaction process combined with the technology of the exhaust gas recirculation (EGR), which yet has multiple effects on the microstructure and oxidation behavior of the diesel engine particulate matters. In order to analyze and comprehend the effect of particle structure and fractal characteristics, a particulate matter sampling device was employed to collect the diesel engine particulate matters, which took oxygenated fuels combined with the technology of EGR into consideration. And the effects of different EGR rate (0%, 10% and 20%) on the particulate matters, which were produced in the combustion of N-butanol/diesel blended fuel with 10% N-butanol (N10), were studied with the thermal field emission scanning electron microscope (SEM) and high resolution electron microscopy (TEM), and the results were analyzed by the image technology. To be specific, the changing rule of physical structure parameter including the particulate matter microstructure, the average particle size of particulate matter group and the fractal dimension were analyzed, as well as the fringe separation distance and the fringe length distribution of basic carbon particles. It could be well observed that there was obvious clusters structure of particulate matters formed by combustion under 3 different conditions: N10EGR0, N10EGR10% and N10EGR20%. What was more, the range of particulate matter size was mainly concentrated between 30 and 70 nm which showed the normal single peak distribution. And the size of particulate matters demonstrated the pattern moving to larger figures gradually with the EGR rate increasing. Also the average size of particulate matter of N10EGR20% increased by 19% compared to N10EGR0. The gradual decreasing of box dimension indicated the fact that the intergranular degree of clusters gradually weakened. On the other hand, the basic carbon particles under different EGR conditions presented the similar structures, which looked like spherical carbon layer fingerprints. The basic carbon particulate matters were composed of 2 parts, the basic kernel layer and the shell. The basic kernel layer was the amorphous carbon structure, and the shell was the structure of graphite crystallite. Moreover, with the increasing of the EGR rate, the basic kernel layer was arranged more disorderly and the shell carbon particulate matters presented more irregular graphite crystal structure. To summarize, the average fringe separation distance of basic carbon particles was increased gradually as well as the average tortuosity distribution, and the average fringe length distribution was decreased with the increasing of EGR rate. The oxidation activity of particulate matters was improved with the adoption of EGR. This study can provide a theoretical reference for the formation mechanism of particulate matters and the measures to reduce the particulate matter emission of diesel engine by oxygenated fuel and the technology of EGR together. [ABSTRACT FROM AUTHOR]

Particulate matter emitted from diesel engine is a factor that makes PM2.5 (particulate matter with a diameter of lower than 2.5 μm) increase, which is related to several adverse health effects including respiratory tract inflammation and cancer. Particulate matter is classified to 3 size modes, i.e. the nucleation mode (<50 nm), the accumulation mode (100-1 000 nm) and the coarse mode (>1 000 nm). As is known to all, particulate matter with smaller size does more harm to human than particulate matter with larger size. It is very necessary to carry out research on reducing particulate matter emitted from diesel engine, especially particulate matter with smaller size. It has been demonstrated that there is graphene structure in particulate matter emitted from diesel engine and graphene structure is related to particulate matter removal. Micro-orifice uniform deposition impactor which was produced in MSP company in America was used to collect diesel particulate matter with 3 size ranges, which were 0.18-0.32 μm, >0.32-0.56 μm and >0.56-1 μm respectively. Raman spectroscopy, a fast and nondestructive method, was used to test crystal structure of carbon material. Near edge X-ray absorption spectra, a nondestructive method, was adopted to characterize molecular structure and valence state of carbon atom by using synchrotron radiation technique. DXR Raman spectrometer and soft X-ray microscopy beamline station were used to analyze the defect type of graphene structure, degree of graphitization, crystallite size of graphene, neighboring graphene spacing, molecular structure and valence state of carbon atom. The results showed that the ratio of D1 peak to D2 peak ranged from 3.34 to 4.01, which indicated that the defect type of graphene structure in diesel particulate matter mainly was graphene edge defect. With the size of particulate matter decreasing, the proportion of graphene edge defect increased. When the size of particulate matter increased, width at half maximum of D1 peak increased by 2.8 and 6.7 cm-1, indicating that the material type in particulate matter increased and the chemical heterogeneity of particulate matter was higher. The ratio of D1 peak to G peak decreased by 14.67% and 27.17% respectively with particulate matter changing from small size to the other 2 bigger sizes, which indicated that the proportion of order graphene in diesel particulate matter increased and led to higher graphitic-like structure and degree of graphitization. When the size of particulate matter increased, the relative intensity of D3 peak decreased by 13.73% and 39.22%, respectively. That was to say the proportion of amorphous carbon especially organic ingredients reduced. The length of C-C bond in graphene lattice had no relationship with the size of diesel particulate matter. The length of C-C bond in graphene lattice of diesel particulate matter with 3 size ranges was about 0.142 nm. When the size of particulate matter increased, the crystallite size of graphene increased and the neighboring graphene spacing decreased, which indicated the oxidative reactivity of particulate matter reduced and the energy in the process of oxidizing diesel particulate matter increased. The types of surface functional groups in particulate matter had no relationship with the size of diesel particulate matter. There were many types of surface functional groups which were “graphene” C=C, C=C, aliphatic C=C, phenolic C-OH, ketones C=O, aliphatic C-H and carboxy C=O respectively. With the size of particulate matter increasing, aliphatic C=C, aliphatic C-H, carboxy C=O in diesel particulate matter decreased and “graphite” C=C, phenolic C-OH, ketones C=O in diesel particulate matter increased. This study can provide reference for the perfection of the formation mechanism of diesel particulate matter with different size range and for the optimization of particulate matter removal device. [ABSTRACT FROM AUTHOR]