| As a clean fuel,biomass fuel has attracted much attention in the field of internal combustion engine.The fuel’s high energy density allows it to release more heat during combustion,increasing the power output of the internal combustion engine.In addition,compared with traditional fossil energy,biomass fuels generate less pollutants from thermal degradation,which is more friendly to the environment.There are many kinds of biomass fuels,which furan and Methyl enanthate are part of.Therefore,this study will explore the application potential of furan and methyl heptanate in internal combustion engines.The fuels used in this study were pure diesel fuel,furan/diesel fuel mixture and methyl heptanate/diesel fuel mixture,with the blending ratio of 10%and 20%respectively.Then,the late atomization development and combustion characteristics of diesel fuel and its mixture were studied in constant volume combustor.The atomization development and flame propagation process of test fuel were recorded by high-speed camera.In the test process,the direct shot method and schlieren method were respectively used to capture the atomization area of the test fuel.For the burning area,the direct shot method is used to capture.In this test,four fuel injection pressures(80MPa,100MPa,120MPa and 140MPa)were set to explore the influence of injection pressure on atomization effect and combustion characteristics of the tested fuel.After the images of spray and combustion of fuel are taken,relevant programs are written on MATLAB to extract relevant information from the images.Finally,the extracted information is processed and analyzed to understand the atomization and combustion characteristics of the fuel.The result analysis of late spray development shows that the through-motion velocity decreases obviously after the fuel leaves the nozzle.After 4.0ms,the atomized oil beam moves more slowly.Under 100MPa condition,from 4.25ms to 4.75ms,the penetration distance of D100 spray liquid phase increases only 3.5mm.Moreover,with the increase of injection pressure,the spray liquid phase length of the test fuel tends to be more and more stable.Under the condition of 140MPa,after 3.5ms,the spray liquid phase length of F20 basically fluctuates around 62mm.When furan and methyl heptanate were mixed in diesel oil,the penetration distance of spray liquid phase increased due to the increase of fuel density and the decrease of kinematic viscosity.Compared with the mixed fuel,the spray liquid phase area of pure diesel is larger.Under the condition of 120MPa,the spray liquid phase area of D100 is above 900mm2,while that of F20 is about 850mm2.At the later stage of spray development,the fuel evaporative diffusion in the radial direction is very obvious.At the condition of120MPa from 2.1ms to 3.0ms,the normal distance of D100 fog injection increases from17.95mm to 30.63mm,with an increase ratio of 70%.The mixing of furan and methyl heptanate significantly improved the evaporation and diffusion ability of fuel.Under the four conditions,the penetration distance,average cone Angle and axial distance of the mixed fuel were greater than that of the pure diesel fuel.Moreover,the higher the mixing ratio of furan and methyl heptanate,the larger the average cone Angle of fog injection.Due to the volatilization of furan,the fogging area of F20 is obviously larger than that of D100.At80MPa and 3.0ms,the fogging area of F20 is close to 1400mm~2,while that of D100 is about1000mm~2.With the increase of injection pressure,the fog area of all test fuels increases,the components of evaporative gasification of fuels increase,and the combustible mixture formed by mixing with ambient gases increases.The blending degree of oil and gas is better than that of pure diesel.The gas phase percentage of F20 and ME20 is up to 70%,while that of D100 is up to 55%.In general,the atomization effect of mixed fuel is better than that of pure diesel,especially that of furan/diesel mixed fuel,and most of the characteristic parameters of fog injection are larger than that of pure diesel fuel.The comparison of spray and combustion results shows that the mixed fuel has an obvious blue flame emitting region during combustion,while the pure diesel basically only produces yellow light and white light,almost no blue light.Comparing the results of spray and combustion,it is found that the shape of spray head has great influence on the shape of combustion area,and there is a high correlation between the two.The further analysis of the influence of spray atomization on the combustion process during the free development of spray shows that for all test fuels,the correlation between flame floating length and spray liquid floating length is very weak during the rapid expansion of combustion,and the influence of spray liquid floating length on flame floating length is little,so is the change law of the influence of spray area on flame area.There is a positive correlation between flame area and injection pressure,and the increase of injection pressure leads to the increase of flame area.The flame area of mixed fuel is larger than that of pure diesel,especially under ultra-high injection pressure.At 140MPa,the peak flame area of F20 and ME20 exceeds750mm~2,while that of D100 is around 600mm~2.When the percentage of spray gas phase of the test fuel increases,the flame combustion temperature will increase accordingly.When the percentage of spray gas phase is 60%,the flame combustion temperature of F20 is 2200K,which is nearly 22%higher than that of 30%.The soot particles produced by the combustion of mixed fuel are higher than that of pure diesel fuel.Under the ultra-high injection pressure,this phenomenon is more obvious.Under the condition of 140MPa,the flame KL factor of F20 and ME20 is close to 0,while the flame KL factor of D100 is above 4.In general,when the mixed fuel is burned,its flame area is larger than that of pure diesel,and the fuel components involved in the thermochemical reaction are more,the heat release efficiency is high,and more heat can be released,and the production of soot particles is less,and the emission reduction effect is good. |
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