Study On The Effects Of Gas-Liquid Components On The Properties And Spray Characteristics Of Micro-Nano Bubble Flowing Fuel

In the context of "carbon peak and carbon neutrality",new clean fuels and optimization of the activated atmosphere in the cylinder have become important technical means for efficient and clean combustion.Low carbon,high efficiency,and near zero emissions have become new trends and new demands in the development of internal combustion engines in China.Based on the characteristics of high oxygen content and high stability of bulk micro/nano bubbles,this paper proposes to use fuel as the liquid carrier,and use micro-nano bubble preparation technology before fuel injection to prepare/premix gas in the form of micro-nano bubbles into liquid fuel to form " bulk micro-nano bubbly flow fuel ",The high oxygen content of bubbles in micro-nano bubbly flow fuel and the bubble breaking during spray are used to improve the oil-gas mixing ratio and the spray breaking degree during the injection process.Relying on the Natural Science Foundation of Jilin Province(20220101212JC),this paper takes micro-nano bubbly flow fuel as an entry point,and conducts research on the properties of micro-nano bubbly flow fuel and spray characteristics.The specific work is as follows:Based on the self-designed fuel preparation device for micro-nano bubble flow based on porous membrane tube and Venturi tube cavitation method,the properties of nano bubble flow fuel were characterized by NS300 nanoparticle tracer,contact angle meter,etc.The study found that the concentration of nanobubbles in the micro-nanobubble flow fuel initially increases and then decreases as the preparation/premixing time of the fuel preparation device based on the porous membrane tube is increased,and the bubble concentration reaches the peak value at 20 minutes.The particle size of nano-bubbles presents multi-peak distribution,and the bubble concentration between the peaks has little difference.The concentration peak gradually moves towards the larger particle size,and the average particle size of nano-bubbles gradually increases.With the increase of the pore size of the porous membrane tube,the concentration and average particle size of the nanobubbles in the fuel increase within the same preparation time.In the fuel preparation device based on Venturi tube,with the increase of preparation/premixing time,the concentration of nano-bubbles in the micro-nano bubble flow fuel first increases and then decreases,and the bubble concentration reaches the peak at 5 minutes.The particle size of the nano-bubbles presents a single or double peak distribution,and the average particle size gradually decreases with the preparation time.With the cavitation intensity of Venturi tube decreases,the concentration of nano-bubbles in micro-nano bubble flow fuel gradually decreases,the concentration peak gradually moves towards the larger particle size,and the average particle size of nano-bubbles gradually increases.After standing for 24 hours,there are still about65%-72% nanobubble concentrations in the fuel.During this process,the average particle size and concentration of nanobubbles decrease with standing time.In terms of micro-nano bubbly flow fuel spray,the spray characteristics of micro-nano bubbly flow fuel under different premixing time,preparation pressure,injection pressure and environmental ambient pressure under normal pressure and pressurized preparation conditions were studied.The results show that the conventional diesel premixed with micro nano bubbles at normal pressure can promote the radial diffusion of fuel,increase the fuel spray cone angle and the maximum spray width,inhibit the axial penetration of fuel,reduce the spray penetration,and increase the spray projection area.The greater the bubble concentration,the more obvious the promotion effect on the spray cone angle and projection area,and the inhibition effect on the spray penetration.Pressurized premixing will further increase the fuel spray cone angle,further reduce the spray penetration,and the spray projection area between the fuels is almost equal and lower than the spray projection area of the micro nano bubbly flow fuel under the same condition of atmospheric premixing.On the other hand,if the ambient pressure increases,the fuel spray’s penetration distance and projection area will decrease,while the spray cone angle will increase.Within the range of ambient pressure selected in the experiment,the maximum spray width is little affected by ambient pressure.At the same time,the increase of ambient pressure weakens the influence of premixed micro and nano bubbles on fuel spray characteristics to some extent.Micronano bubble flow fuel is more suitable for engines with low compression ratio.With the increase of injection pressure,the fuel spray penetration,the maximum spray width and the spray projection area all increase.The increase of injection pressure will reduce the inhibition of bubble breaking on the penetration.Gray correlation analysis was used to evaluate the factors influencing spray penetration depth and spray cone angle.The injection pressure had the greatest influence,followed by the ambient pressure,and finally the premixing time and the preparation pressure.