Study On Electrostatic Spray Of Ethanol-Biodiesel Blend Fuel

Biodiesel is renewable,environmentally friendly,and easily biodegradable.It is a high-quality fuel that can replace traditional fossil energy.However,its use in internal combustion engines is also insufficient.Internal combustion engines mainly rely on the atomized combustion of liquid fuels to provide power.The high viscosity of biodiesel leads to insufficient atomization,which seriously affects combustion efficiency and emission characteristics.In this study,blending different ratios of ethanol-biodiesel mixed fuel was selected as the research object,and the two methods of blending ethanol and applying electrostatic field were explored to synergistically improve the atomization characteristics of biodiesel.The main research contents and conclusions are as follows:（1）Design and build an electrostatic spraying visualization experiment platform to visualize the different electrostatic spraying modes of ethanol,biodiesel and their mixed fuels.Various modes such as drop,pulsation,spindle,cone jet,offset jet,multiple jets and offset multiple jets have been obtained.With the increase of the ethanol blending ratio,the droplet mode area of the mixed fuel gradually becomes larger,the pulsation mode area gradually decreases,and the spindle mode appears.The addition of ethanol makes the electrostatic atomization mode more abundant,but the formation and maintenance of the cone jet mode is more difficult.The area of the multi-jet mode increases with the increase of the ethanol blending ratio,and the offset jet mode under biodiesel transitions to form an offset multi-jet.In addition,according to the dimensional analysis,the electrostatic atomization mode phase diagram is drawn for ethanol,biodiesel,and ethanol blending amounts of 5%and 20%,respectively.The phase diagram provides a basis for finding the operating range of the specific mode.（2）A two-dimensional axisymmetric model of the capillary nozzle under the action of an electric field is established,and the spatial electric field and velocity field distribution are numerically simulated using the level set method.The results show that there are obvious velocity gradients and potential gradients at the gas-liquid two-phase interface,and when the electric field is strong,vortexes appear near the capillary nozzle to promote the development of the meniscus in a cone shape.According to the experiment and simulation results,the increase of the non-dimensional flow α makes the cone tip of the cone jet elongate,and the electric charge will be highly concentrated to maintain the force balance of the meniscus.The increase of the dimensionless voltage β makes the cone angle larger,and the cone meniscus area decreases to maintain the force balance.In addition,the parameters determining the stability of the cone jet mode are the thickness of the surface charge layer r^*and the dimensionless voltageb β.（3）The spraying characteristics of ethanol-biodiesel and its mixed fuel is studied by a visual experiment platform.The results show that when the ethanol blending ratio is 20%,the particle size distribution of the mixed fuel electrostatic atomization is improved significantly,which is close to the ethanol particle size distribution range.In cone jet mode,the particle size of biodiesel meets the particle size prediction formula,d d₀=k_d（Q Q₀）^{1 2},and there is a linear relationship between the cone jet diameter d_jet of ethanol and mixed fuel and the thickness of the surface charge layer r^*,d_jet0.4r^*.The Coulomb force between the droplets increases due to the increase of the conductivity,and the maximum deviation half angle increases with the increase of the ethanol blending ratio.Therefore,the addition of ethanol and the application of an electrostatic field significantly improve the atomization effect of the mixed fuel.