| China is a country with“rich coal and less oil”.F-T diesel obtained by coal-to-oil indirect liquefaction technology.And because of its low sulfur and aromatic content of F-T diesel,it has gradually become a research hotspot in the field of clean fuels.Compared with diesel,the production cost of F-T diesel is relatively high and the cetane number of F-T diesel is relatively large.In some working conditions,the combustion and emission characteristics of the engine will deteriorate.Ethanol/n-butanol fuels can effectively reduce the emission of smoke in diesel engine because of its own oxygen content,and the cetane number of ethanol/n-butanol is much lower than that of F-T diesel.In combination with F-T diesel,Ethanol and n-butanol can theoretically improve the combustion performance,emission performance and the economy of the engine.In order to intuitively study the combustion and emission characteristics of F-T diesel,three-dimensional simulation of engine combustion and emission process was carried out based on the fuel injection law.The simulation results showed that,compared with the rectangular injection law,the trapezoid injection law had a low initial injection amount,which caused lower pressure and softer combustion in the cylinder.Moreover,under the trapezoidal injection law,the ignition delay period of fuels was longer,the heat release in the premixed stage was smaller,and the soot emission was lower.Compared with the shoe-shaped fuel injection law,the trapezoidal fuel injection law had advanced the center of gravity of the injection,resulting in a higher peak pressure in the cylinder,a smaller amount of heat released during the diffusion combustion phase.The combustion temperature in the cylinder was also relatively lower under the trapezoidal fuel injection law,resulting in lower NO emission of engine.The intersolubility test of F-T diesel and ethanol/n-butanol was carried out.The results showed that the small proportion of ethanol and F-T diesel had better intersolubility.When the proportion of ethanol increased to 10%,the intersolubility was poor and small amount of cosolvent should be added to improve the stability of the blended fuel.The intersolubility of n-butanol and F-T diesel was good,and there was no stratification phenomenon after standing for 30 days.Based on the fuel intersolubility test,five kinds of fuel were prepared,which were pure F-T diesel,F-T diesel respectively blended with 5%and 10%ethanol,F-T diesel respectively blended with 8%and 16%n-butanol,recorded as:FT,E5FT,E10FT,B8FT and B16F.Bench test of F-T diesel blended ethanol/n-butanol was carried out.The results showed that when engine speed was constant,the peak pressure in cylinder of five fuels decreased with the decrease of the load.And the peak pressure of F-T diesel blended with ethanol/n-butanol was significantly higher than that of pure F-T diesel.The peak pressure rise rate of blended fuel pressure was higher than that of F-T diesel under different loads,and the peak value of pressure rise rate increased with the proportion of alcohol in blended fuel.The peak value of instantaneous heat release rate of blended fuel was higher than that of pure F-T diesel under constant engine speed,and increased with the increase of the alcohol proportion.The emission of NO_X and Soot of engine fueled with blended fuel decreased in varying degrees.Under the constant engine speed and full load condition,emission reduction of Smoke of E10FT blended fuel was 55.0%compared with pure F-T diesel.Under the constant engine speed and 50%load condition,emission reduction of NO_X of E10FT blended fuel was as high as 62.6%compared with pure F-T diesel.The emission of CO and HC increased with the increase of alcohol proportion.When the engine is at a constant speed,the brake fuel consumption of the five fuels decreased with increasing load.Moreover,the greater proportion of ethanol/n-butanol in the blended fuel,the higher brake fuel consumption. |
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