Experiment And Simulation On Combustion And Emission Performance Of Biodiesel/N-butanol Fuel Blends

Energy shortage and environmental pollution are two major threats to humanity today and have become urgent issues to be solved.Diesel engine is a large consumer of oil energy.And the exhaust emissions of diesel engines are also serious problems.In recent years,n-butanol/biodiesel blend fuels have received extensive attention from researchers because of their excellent properties.In this paper,two different blend ratios of n-butanol/biodiesel blend fuels were prepared according to the volume ratio,whose physicochemical properties were measured as well.Combustion characteristics,economic characteristics,emissioncharacteristicsandultrafineparticles?UFPs?of n-butanol/biodiesel blend fuels were studied with the experiments in a common rail six-cylinder diesel engine at different engine loads.Based on the created model of test conditions,the mesh of the combustion chamber was established by using the software AVL FIRE.The combustion processes of four different fuels?BD0,BD100,BD90N10,BD80N20?were simulated with FIRE and the fuel mass fraction,temperature,O₂ mass fraction,NO mass fraction,Soot mass fraction of the four fuels in the cylinder with crank angle were studied.The results show:?1?Compared with biodiesel,with the increasing proportion of n-butanol,the density,viscosity,low calorific value,coagulation point and cold filter point of the blended fuel have decreased,and the oxygen content has increased;?2?At lower load,the injection is divided into two stages:pre-injection and main injection.At higher load,it is a single injection.The BD0 has the longest ignition delay,and the BD100 has the shortest ignition delay.After the addition of n-butanol,ignition delay of the blend fuels were gradually prolonged;with the increase of the n-butanol blend ratio,the combustion speed of the mixed fuel was accelerated,the combustion duration was shortened,and the average temperature in the cylinder increased;At low load,in the pre-injection stage,the peak heat release rates?PHRR?and the peak pressure rise rates?PPRR?of the blend fuels are lower and later than those of biodiesel.In the main injection stage,the peak combustion pressure?PCP?,PHRR and PPRR of the blend fuels are higher than those of biodiesel;but at high load,the PCP,PHRR and PPRR of the blend fuels are lower than those of biodiesel.?3?The BSFC of butanol-biodiesel blend fuels is higher than biodiesel;At low load,the BTE of butanol-biodiesel blend fuels is lower than biodiesel;but at high load,the BTE of butanol-biodiesel blend fuels is higher than biodiesel.?4?Compared with biodiesel,with the increase of n-butanol blend ratio,the NO_X emissions of butanol-biodiesel blend fuels have different rules at different loads,while HC,CO,and soot all have a certain reduction.?5?The number concentration of UFPs reduces obviously by the addition of butanol in biodiesel,furthermore,the geometric mean diameters of UFPs decrease with the increased butanol proportion.With the increasing of engine loads,the number concentration peaks of UFPs gradually transfer from the size range of nucleation mode particles?NMPs?to the size range of accumulation mode particles?AMPs?.Compared to diesel,biodiesel and blend fuels exhibit higher percentage of NMPs number concentration and lower percentage of AMPs number concentration.?6?Simulation results show that the butanol-biodiesel blend fuels has higher in-cylinder combustion temperature and oxygen concentration.While decreasing Soot emissions,NO emissions have increased,and the simulation results are basically consistent with the test results.