Effect of biodiesel blends on the particle size distribution (PSD) of exhaust aerosol and the mechanism of nanoparticle formation were investigated with a modern common rail light-duty diesel engine. The results showe...Effect of biodiesel blends on the particle size distribution (PSD) of exhaust aerosol and the mechanism of nanoparticle formation were investigated with a modern common rail light-duty diesel engine. The results showed that PSD of diesel included two modes:nucleation mode (NM) and accumulation mode (CM). The criterion diameter of the two modes is 50 nm. Only CM was observed for all fuels under the condition of 50 N.m,2000 r/min. When the engine torque was higher than 150 N.m,log-modal PSD of diesel shifted to bimodal. At higher loads,if the biodiesel blend ratio was below 60%,the PSD of biodiesel blends still included the two modes. However,no NM particles were found for pure biodiesel. At lower loads,only CM was found in PSD of all fuels. Significant reduction of CM particles was found for biodiesel blends compared with diesel. Discussion on the mechanism of nanoparticle formation indicated that for the light-duty diesel engine with oxidation catalysts,fuel consumption and exhaust temperature increased with increasing the engine loads,and SO2 was converted to SO3 by catalyst which,in its hydrated form,could act as the precursor for biodiesel NM formation. Therefore,sulfur level of biodiesel blends dominates the nanoparticle formation in light-duty diesel engine with oxidation catalysts.展开更多
The design of fuel nozzle orifices at micrometer scales is crucial for generating desired fuel spray patterns, and consequently optimizing fuel combustion and emission in internal combustion engines. Although there ha...The design of fuel nozzle orifices at micrometer scales is crucial for generating desired fuel spray patterns, and consequently optimizing fuel combustion and emission in internal combustion engines. Although there have been several recent advancements in the characterization of orifice internal geometries, quantitative studies on the orifice internal wall surface characteristics are still challeges due to the lack of effective measuring methods. A new method for quantifying the internal wall surface characteristics of fuel nozzle micro-orifices is presented in this study to achieve a better understanding and prediction of spray characteristics: Firstly, by using the synchrotron X-ray micro CT technology, a three-dimensional digital model of the fuel nozzle tip was constructed. Secondly, a data post-processing technique was then applied to unfold the orifice internal wall surface to a flat base plane. Finally, the conventional surface characteristic quantification techniques can be used to evaluate the wall surface characteristics. Two diesel nozzles with identical orifice geometry design but different hydraulic grinding time were measured using this method. One nozzle was hydro-ground for 2 s while the other was not. The internal wall surfaces of the two orifices were successfully unfolded to base planes and their surface characteristics were respectively analyzed. The surface fluctuation data were perfectly reproduced by a Gaussian distribution function. The standard deviations of the distribution demonstrate the fluctuation range and the distribution of the entire surface fluctuation profiles. As an effective parameter to evaluate the hydraulic grinding process and the spray behaviors, the standard deviation was considered feasible for the analysis of the orifice internal wall surface characteristics.展开更多
Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film eva...Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film evaporation characteristics of 90# gasoline, 93# gasoline and 0# diesel with different initial thicknesses were investigated at different en- vironmental fluxes and heating rates. The influences of heating rate, film thickness and environmental flux on fuel film evaporation for these fuels were found. The results showed that the environmental conditions in TGA were similar to those for fuel films in the in- ternal combustion engines, so data from TGA were suitable for the analysis of fuel film evaporation. TGA could simulate the key influencing factors for fuel film evaporation and could investigate the basic quantifi- cational effect of heating rate and film thickness. To get a rapid and sufficient fuel film evaporation, suffi- ciently high wall temperature is necessary. Evapora- tion time decreases at a high heating rate and thin film thickness, and intense gas flow is important to promoting fuel film evaporation. Data from TGA at a heating rate of 100℃/min are fit to analyze the diesel film evaporation during cold-start and warming-up. Due to the tense molecular interactions, the evapora- tion sequence could not be strictly divided according to the boiling points of each component for multi- component dissolved mixture during the quick evaporation process, and the heavier components could vaporize before reaching their boiling points. The 0# diesel film would fully evaporate when the wall temperature is beyond 250℃.展开更多
基金Supported by the National Hi-Tech Research and Development Program of China ("863" Project) (Grant No. 2006AA11A1A2)the Program of Shanghai Chief Subjects (Grant No. B303)
文摘Effect of biodiesel blends on the particle size distribution (PSD) of exhaust aerosol and the mechanism of nanoparticle formation were investigated with a modern common rail light-duty diesel engine. The results showed that PSD of diesel included two modes:nucleation mode (NM) and accumulation mode (CM). The criterion diameter of the two modes is 50 nm. Only CM was observed for all fuels under the condition of 50 N.m,2000 r/min. When the engine torque was higher than 150 N.m,log-modal PSD of diesel shifted to bimodal. At higher loads,if the biodiesel blend ratio was below 60%,the PSD of biodiesel blends still included the two modes. However,no NM particles were found for pure biodiesel. At lower loads,only CM was found in PSD of all fuels. Significant reduction of CM particles was found for biodiesel blends compared with diesel. Discussion on the mechanism of nanoparticle formation indicated that for the light-duty diesel engine with oxidation catalysts,fuel consumption and exhaust temperature increased with increasing the engine loads,and SO2 was converted to SO3 by catalyst which,in its hydrated form,could act as the precursor for biodiesel NM formation. Therefore,sulfur level of biodiesel blends dominates the nanoparticle formation in light-duty diesel engine with oxidation catalysts.
基金supported by the National Natural Science Foundation of China(Grant Nos.91441125,51106113,51006075)the Key Project of the Shanghai Synchrotron Radiation Facility(Grant No.2016-SSRF-ZD-004512)Tongji University Outstanding Young Talents Project(Grant No.2015KJ037)
文摘The design of fuel nozzle orifices at micrometer scales is crucial for generating desired fuel spray patterns, and consequently optimizing fuel combustion and emission in internal combustion engines. Although there have been several recent advancements in the characterization of orifice internal geometries, quantitative studies on the orifice internal wall surface characteristics are still challeges due to the lack of effective measuring methods. A new method for quantifying the internal wall surface characteristics of fuel nozzle micro-orifices is presented in this study to achieve a better understanding and prediction of spray characteristics: Firstly, by using the synchrotron X-ray micro CT technology, a three-dimensional digital model of the fuel nozzle tip was constructed. Secondly, a data post-processing technique was then applied to unfold the orifice internal wall surface to a flat base plane. Finally, the conventional surface characteristic quantification techniques can be used to evaluate the wall surface characteristics. Two diesel nozzles with identical orifice geometry design but different hydraulic grinding time were measured using this method. One nozzle was hydro-ground for 2 s while the other was not. The internal wall surfaces of the two orifices were successfully unfolded to base planes and their surface characteristics were respectively analyzed. The surface fluctuation data were perfectly reproduced by a Gaussian distribution function. The standard deviations of the distribution demonstrate the fluctuation range and the distribution of the entire surface fluctuation profiles. As an effective parameter to evaluate the hydraulic grinding process and the spray behaviors, the standard deviation was considered feasible for the analysis of the orifice internal wall surface characteristics.
文摘Thermogravimetric analysis (TGA) was compared with the petrochemical distillation meas- urement method to better understand the character- istics of fuel film evaporation at different wall tem- peratures. The film evaporation characteristics of 90# gasoline, 93# gasoline and 0# diesel with different initial thicknesses were investigated at different en- vironmental fluxes and heating rates. The influences of heating rate, film thickness and environmental flux on fuel film evaporation for these fuels were found. The results showed that the environmental conditions in TGA were similar to those for fuel films in the in- ternal combustion engines, so data from TGA were suitable for the analysis of fuel film evaporation. TGA could simulate the key influencing factors for fuel film evaporation and could investigate the basic quantifi- cational effect of heating rate and film thickness. To get a rapid and sufficient fuel film evaporation, suffi- ciently high wall temperature is necessary. Evapora- tion time decreases at a high heating rate and thin film thickness, and intense gas flow is important to promoting fuel film evaporation. Data from TGA at a heating rate of 100℃/min are fit to analyze the diesel film evaporation during cold-start and warming-up. Due to the tense molecular interactions, the evapora- tion sequence could not be strictly divided according to the boiling points of each component for multi- component dissolved mixture during the quick evaporation process, and the heavier components could vaporize before reaching their boiling points. The 0# diesel film would fully evaporate when the wall temperature is beyond 250℃.
