Studies Of The Spray Characteristics Of Blended Fuel In Diesel Engine

The upcoming emission regulations for Diesel engines will become more restrictive. This has made it necessary to develop new diagnostic tools and methods that allow to btain a more accurate knowledge about the chemical and physical phenomena that occur during the atomization, evaporation and ignition of the fuel spray. At the same time, Development of the new generation of combustion theory and technology makes the differences between diesel and gasoline engine technologies become smaller and smaller. Different combustion strategies are used in modern engine according to the different composition of blended fuel. So it must fully understand the combustion characteristic of blended fuel.The object of this study is the main components of distillate coming from crude oil at the four temperature ranges of40-240℃,40-270℃, and40-300℃. By the use of PLIF techniques, the features of these blended fuel are investigated including the spray, The result shows:the volatility (boiling point of90%distillation) of the blended fuel has a notable influence on the spray penetration.The maximum spray penetration of the two blended fuels that have the biggest difference of volatility differ nearly14%.and the spray penetration of four kinds of blended fuels gradual increase along with time. Considering a mixing-limited vaporization process, entrained ambient mass per fuel mass is inversely proportional to the fuel density, and thereby, high fuel density causes a decrease in ambient-to-fuel ratio, which increases spray penetration;The ambient density also has a notable influence on spray penetration of the blended fuel spray. A higher ambient density results in a larger decrease of the spray penetration. However, the volatility of the blended fuel has smaller influence on the spray cone, the spray cone increased only5%while volatility of blended fuel increase55%, and with the increment of the ambient density and injection pressure the influence of the volatility upon the spray cone is letting up.Spray cone increase with increase ambient density and injector diameter, but the influence is very small.Injection pressure doesn’t show an evident influence on the spray cone. The spray cone of four kinds of blended fuels all show the same trend of enlarged first then decrease and keep constant at last. Four blended fuel of the near-field spray angle first decreased and then maintain a relatively stable value until the spray end, far-field spray angle first decreased and then remain unchanged after increasing trend, but the entirechanges in the far-field pray cone angle is very small; far-field spray cone angle than the near-field spray cone angle of15°～18°or so. Penetration has increased with increasing injection pressure;The impact of nozzle diameters is greater on the far-field spray cone than the near-field spray cone; the higher injection pressure, the smaller impact of the volatility penetration; In the process of changes in the nozzle diameter,the volatility and viscosity of blended fuel had no notable impact on the spray cone. reduce nozzle diameter from0.18mm to0.10mm, the near-fieldspray cone narrowed by about4to5°, the far-field spray-cone narrowed by about6to8°, the impact of fuel volatile on the spray penetration growth rate respectively15.31%,15.23%and13.85%, the near-field spray cone growth rate respectively,14.18%,12.5%and11.7%, the near-field spray cone growth rate is10.8%,9.8%,9.6%, respectively.