Numerical Simulation Of Biodiesel Spray And Applied Research

The high demands for energy together with the non-renewable of the fossil fuel reserves have result in exploration of alternate energy sources. Now more and more people focus on biodiesel because it is renewable, non-toxic, biodegradable etc. So biodiesel is a perfect alternative fuel for diesel engine in the future.The combustion process in diesel engine has a direct effect on engine power, economy and emissions. Moreover the process of fuel injection, atomization and mix with air are the most important factor affecting the combustion process. So it is necessary to research the influence factor and varying trend of fuel spray characteristics. In this paper, the spray characteristic of biodiesel in a constant volume is numerical simulated base on the fundamental of computational fluid dynamics. The influences of ambient pressure, injection orifice diameter, opening pressure of injection nozzle to biodiesel spray characteristics are studied and compared the difference between biodiesel and diesel. The results show that biodiesel has the same trend of spray characteristics as diesel under different conditions, but the effect of atomization is not so good as diesel,the overall sauter diameter is larger than diesel. The biodiesel has a higher viscosity and surface tension than diesel which cause the difference between spray characteristics. Increase the opening pressure of nozzle, reduce the orifice diameter can improve the atomization process.The author also designed and established the experiment sets of biodiesel-diesel double fuels in a diesel engine. With the structure parameters of engine unchanged, the load experiments were done with three different blends of biodiesel. The fuel economy and emission under different load in calibration speed were also measured. The experiment results show that the engine fuel economy decreased after pure diesel blended with biodiesel, mixed fuel consumption is proportional to the amount of biodiesel blended with diesel. The soot, HC, CO emission concentration decreased, but the concentration of NO_X increased. Generally speaking, a more feasible approach to apply biodiesel in diesel engine at present is to blend diesel with a certain percentage of biodiesel. In this way, not only similar power can we get, but also the emission decreas to a low level.