A Study Of The Combustion And Emisson Characteristics Of Diesel Engines Runing Methanol/Fischer-Tropsch Diesel Blended Fuels

F-T diesel is the good prospect of clean alternative fuel engine, possesses the advantages of soft combustion and low emissions, but the production cost is higher. Mixing a certain proportion of methanol in F-T diesel oil can not only effectively reduce NOx and carbon smoke emission, also can reduce the cost of fuel.With isooctyl alcohol as a cosolvent, made up three different proportions of methanol/F-T diesel blended fuel with different methanol mass fraction in the fuel, according to the proportion of methanol respectively for M5F、M10F and M15F. In4100QBZL diesel engine test bench, test speed characteristics and load characteristics under various speed of the0#diesel oil, the F-Tdiesel, M5F, M10F and M15F at80%of oil throttle opening. Research shows that:On combustion characteristics, F-T diesel fuel’s ignition delay period is shorter, low exothermic peak, the main combustion duration is long, but the diffusion combustion rate quickly, the maximum cylinder pressure was reduced by3.6%on average, the maximum pressure rise rate was reduced by25.5%on average, burning more downy; In terms of engine performance, after burning F-T diesel engine, performance dropped by10%, equivalent oil consumption rate reduction in small load is between5%～15%, in high load is between1%～2.2%; In terms of emissions, after burning F-T diesel NOx emissions was reduced by an average of14.5%, the smoke emissions was reduced by an average of35.6%; On combustion characteristic, compared with the F-T diesel oil, methanol/F-T diesel blended fuel’s ignition delay period is longer, the peak heat large,the main combustion was extended, heat release rate at the diffusion combustion period is same with F-T diesel in low load, in high load is lower than the F-T diesel, the peak pressure in cylinder and pressure rise rate increased, the combustion state got rough; When engine burning M5F, M10F and M15F, powe performance declined, the equivalent fuel consumption rate in high load is same with F-T diesel, CO emission increases slightly, but not higher than that of0#diesel, NOx emission is reduced, the average amplitude is:10.9%,11.4%and8.6%, and carbon smoke emission is reduced, the average amplitude is5%,31%and56%;Experimental data showed that F-T diesel oil is a kind of clean alternative fuel of diesel engine. To some extent, the addition of methanol increased burning rough, but because of its low cost and NOx and soot reduction capability, so adding a certain proportion of methanol is a better alternative.Due to the effect of the proportion of methanol on NOx emission reduction is uncertain, the article selects M10F, based on the software FIRE further discusses the M10F hybrid mechanism to reduce NOx emissions. Research shows that:adding10%methanol diesel to the F-T diesel,the maximum of NO concentration field increases, high concentration area is larger, but the average is lower than F-T diesel. Methanol effect on NO emission of diesel engine is always two sides, but there is a best addation rate, enables the NO emission of diesel engine lowest.