Study On Micro-Explosion And Combustion Characteristics Of Biodiesel And Its Blended Fuel With Micro And Nano Particles

As a clean and renewable bioenergy,biodiesel has the advantages of low cost and wide range of sources.The blended fuel formed by blending biodiesel with ethanol in a certain proportion can be used in diesel engines,aircraft engines and other engines,effectively reducing the dependence on traditional fossil energy and improving combustion efficiency.The application of this fuel blend can also significantly reduce the emission of soot precursors,volatile organic compounds and nitrogen oxides during combustion.In addition,micro-nano particles have high specific surface area,thermal conductivity and mass density,and the addition of micro-nano particles is conducive to the evaporation and combustion of mixed fuels,promoting the occurrence of micro-explosion phenomenon,thereby enhancing the combustion characteristics of mixed fuels.This is important for improving the energy density of future hybrid synthetic fuels to meet the needs of next-generation combustion and propulsion systems.The main contents of this article are as follows:The evaporation micro explosion images of biodiesel ethanol mixed with different proportions and contents of coal slurry particles were measured on the atmospheric pressure constant temperature synchronous heating system and tube furnace heating test bench.Based on the obtained images,a method for measuring the volume of micro droplets is proposed.This method uses MATLAB and Photoshop programs to calculate the real-time diameter and area of a single mixed droplet image,analyzes the expansion and evaporation of the mixed droplet based on the droplet diameter.The results indicate that the droplet heating evaporation process can be divided into droplet heating stage(t1),fluctuating evaporation stage(t2),and stable evaporation stage(t3).The addition of coal slurry particles will accelerate the evaporation rate of the mixed droplets.The increase in particle content in the fuel will accelerate the total evaporation rate(K)of the droplets,and the stable evaporation rate(K3)of the droplets also shows a trend of first decreasing and then increasing.In addition,droplets containing 60μm particle size have the fastest evaporation rate at the same particle content.The micro explosion and combustion characteristics of biodiesel ethanol mixture droplets under different aluminum powder particle contents and particle sizes were studied using an atmospheric pressure synchronous heating system under pure oxygen conditions at an ambient temperature of 850℃.The entire evaporation and combustion process of the mixed fuel was fully recorded and analyzed using CCD high-speed photography technology,binary imaging technology,and droplet optimization algorithm.The results indicate that increasing the particle size of aluminum powder in the mixed droplet will promote the micro explosion of the droplet while the content of aluminum powder particles remains unchanged.Within a certain range,when the particle size of aluminum powder is less than 10μm,the combustion duration of the mixed droplets will extend with the increase of aluminum powder content,while when the aluminum powder particles are greater than 10μm,the opposite result will appear.Increasing the content of aluminum powder will also extend the full life of the droplets.A new micro explosion strength calculation model has been established,providing new ideas and methods for comparing the micro-explosion phenomena of fuel droplets with different initial diameters horizontally.For mixed fuels containing micron-sized aluminum powder,the particle content with the best micro explosion strength is around 20%.