Research On The Evaporation Characteristics Of Biodiesel-Diesel-Methanol Micro-Emulsion Fuel Droplets

It has become the focus of research by domestic and foreign scholars that developing efficient and clean alternative fuels with the energy shortages and environmental pollution.As typical renewable energy,biodiesel has a high viscosity,and long-term use of diesel engines will cause many problems.The effective way to solve these problems is the micro-emulsion method.The use of micro-emulsification technology to blend biodiesel,diesel,and methanol can form an isotropic micro-emulsion fuel.Good atomization and evaporation characteristics are the basis for improving the combustion efficiency of diesel engines.At present,most of the research on micro-emulsified fuel is only carried out from the whole machine and macro spray combustion level,and the evaporation process of fuel droplets is still insufficiently understood.This paper takes biodiesel-diesel-methanol micro-emulsion fuel as the research object and uses a combination of experiments and simulation to explore the evaporation characteristics of biodiesel-diesel-methanol micro-emulsion fuel from the microscopic droplet level.Firstly,select suitable emulsifiers,and formulate three kinds of micro-emulsified fuels for experiments with different methanol volume fractions,BD95M5,BD85M15,and BD75M25.A hanging drop evaporation test device was built,a droplet evaporation image processing program was developed,and uncertainty analysis was carried out for errors that may occur during the test.Secondly,the research on the single droplet evaporation characteristics of biodiesel-dieselmethanol micro-emulsion fuel was carried out,and the normalized diameter square,temperature,and droplet morphology change laws during the droplet evaporation process were obtained.The study found that the BD85M15 droplets have completely different evaporation modes at different ambient temperatures.The droplet evaporates smoothly at an ambient temperature of 573 K,while bubble formation,expansion and micro-explosion appear inside the droplet at an ambient temperature of 773 K.The micro-explosion causes the mother droplet to break and produce a part of the sub droplets,which increases the evaporation surface area of the droplet and the evaporation rate.Subsequently,the factors affecting the evaporation characteristics of single droplet micro-emulsion fuel were studied.The data indicate that with the volume fraction of methanol,the initial volume and ambient temperature increase,the micro-explosion degree is enhanced to some extent.The stronger the micro-explosion,the more sub droplets are produced,the greater the reduction in mother droplet volume,the faster the evaporation rate of the droplets.Finally,using the infinite heat conduction model,the evaporation process of the threecomponent droplet is numerically simulated.The components of biodiesel and diesel are complex.In the simulation process,biodiesel was replaced by n-hexadecane and diesel was replaced by n-dodecane.Comparing the simulated values with experimental values under different ambient temperatures,the results show that the model can partially reflect the evaporation characteristics of micro-emulsion fuel droplets.