Experimental Study On Effect Of Gasoline Blending With N-butanol On Particulate Emission In A Direct Injection Engine

Under the background of energy crisis and environmental pollution,it is vital to find renewable and clean energy.N-butanol can be one kind d of biomass fuel which can be produced by fermentation method,and because of containing oxygen it could promote combustion,therefore,it can be used as an alternative fuel of gasoline to automobile.In this thesis,the influence of gasoline blending with n-butanol on particulate emission by different mixing methods was studied.Experiments could be divided into two parts:single injection of fuel?GNDI?and fuel dual injection?G-NxDI and N-Gx DI?.The mixing method of gasoline and n-butanol was volume ratio for GNDI.Energy ratio was used for dual injection to obtain special fuel mixture.Experimental involved variables included n-butanol blending volume ratio?NBr?,?,timing of spark ignition,timing of fuel injection,pressure of fuel injection,speed and load.The index of particulate emission includes particle mass concentration?PM?,particle number concentration?PN?and their size distribution.The conclusions are summarized as follows.Firstly,theoretical heat analysis was carried out on the mixing mode of volume ratio,and it showed that heat release rate decreased with increasing ratio of n-butanol to gasoline.The heat of NDI reduced by 0.83%compared with GDI.However,the experiment results showed that both cylinder pressure and IMEP increased firstly and then decreased with increasing NBr at?=1,and 20%NBr had the maximum IMEP value,it rised by 0.28%compared with GDI.The followings were experimental conclusions about particle obtained from experiments.?1?Under the same NBr,particle changed from accumulation mode to nucleation mode with?increasing,PN always decreased firstly and then increased with?increasing.And there was one best?to obtain the lowest particle number,moreover,the optimum?decreased with NBr increasing and it was at 1.0-1.1.When?was at 0.9-1.0,PN decreased firstly and then increased after increasing NBr,and there was one best NBr to achieve the lowest particle number.However,when?was higher than 1.0,PN increased continuously with?increasing.Along with increasing sparking timing,particle shifted from nucleation mode to accumulation mode,GDI's PN increased,while the PN of N₂₀DI increased firstly and then decreased.Other Nx DI'PN reduced continuously because of the obvious decreasing of nucleation mode particle.?2?Under the same NBr,particle changed from nucleation mode to accumulation mode with rising rotational speed,and the change trends of PN were same,decreased firstly and then rised with increasing speed under different NBr.And there was one optimum rotational speed to obtain the minimum PN,but different NBr has different optimum rotational speed.With increasing load,particle changed from nucleation mode to accumulation mode.And the change trend of PN was same,decreased firstly and then rised with rising load under different NBr.And there was one optimum load to obtain the minimum PN,and the optimum load increased continuously with increasing NBr?3?Under the same NBr,particle changed from accumulation mode to nucleation mode with the advance of fuel injection timing,while PN decreased firstly under different NBr before increasing.There was one optimum injection timing to make PN minimum,and the optimal injection timing was at 90o-105oCA BTDC.And with the increasing NBr,the optimum injection timimg was delayed.As injection pressure increased,particle shifted from accumulation mode to nucleation mode,GDI'PN decreased continuously.NDI'PN increased continuously with rising injection pressure.While with increasing injection pressure when NBr was at 20%-80%,PN rised firstly and then decreased,and there was one optimum injection pressure to obtain minimum PN,while the optimum pressure decreased continually with increasing NBr.?4?Under the same NBr,PM decreased with?increasing,and increased continuously with the advance of sparking timing.PM rised continuously with the increasing of speed or load.PM decreased continuously with injection pressure increasing or the advance of injection timing.Although under different?,sparking timing,rotational speed,load,fuel injection timing and injection pressure,PM always decreased continuously with increasing NBr.?5?As NBr increased and the other variables remained constant,PN increased continuously under these conditions,rotational speed was at 1000 r/min,load was at MAP=30 kPa,injection pressure was higher than 7MPa or?>1.However under other operating conditions,even though under different sparking timing,?,rotational speed,load,fuel injection timing and injection pressure,PN decreased firstly and then increased with NBr increasing,and there always existed optimum NBr to make PN minimum.While the optimum NBr would change according to different experimental conditions,however it always was at 20%-40%.Although PM decreased continuously with NBr rising,however,PN increased obviously under high NBr.Thus gasoline blending with 20%-40%volume ratio n-butanol will be an useful method to reduce particle number and particle matter.The second part was about dual-fuel dual injection,two fuels were mixed according to different fuel direct injection ratio?DIr?and injection method.Firstly,energy error calibration was performed on mixing mode of energy ratio,it was within acceptable range.Then we analyzed particle number,particle matter and their particle size distribution.In dual injection,cylinder pressure and IMEP decreased continuously with DIr increasing,then PN increased after first decreased,and there was one optimal DIr to make PN minimum,PM increased continuously.After considering IMEP and particulate emission,40%DIr was considered as the best direct injection ratio.Particle size distributions of dual injection were different with DIr increasing,the particle size distribution of N-Gx DI shifted from nucleation mode to accumulation mode.However,the particle size distribution of G-NxDI still presented nucleation mode distribution due to fuel characteristics.And under the same DIr,the particulate emission of N-GxDI was always lower than G-NxDI's particle.When DIr was below 60%,PM of dual injection was at very low level,almost could be negligible compared with GNDI.When DIr was larger than 60%,the PM of N-GxDI and G-NxDI increased rapidly,but N-GxDI increased more significantly,and was about 3 times higher than that of G-Nx DI.Comparing these three injection modes,GNDI had the lowest IMEP under different DIr or NBr,N-GxDI's IMEP value was slightly higher than GNDI's,G-NxDI had the highest IMEP value?except for DIr or NBr was at 100%?.Depending on IMEP,PN,and PM,N-GxDI combined 40%DIr was considered the best injection method,because it owned the minimum particulate emission.Compared with GDI at?=1,PN of N-GxDI combined 40%DIr could be reduced by 51.07%and PM could be negligible.However compared with GPI,this injection mode also had to sacrifice 1%IMEP value,but its IMEP value was still higher than GDI.