Study Of The Combustion And Particulate Emissions Properties Of Butanol/Diesel Blends

Energy crisis and environmental pollution are the two direct global problems which threat the existence of human beings,the healthy and rapid development of automobile industry is also facing the technical challenges come from these problems.From the birth of the first internal combustion engine,internal combustion engine is used as the main power source of the moving vehicles around the world,but with the increasingly strict motor vehicle emission regulations,the development of internal combustion engine is also presently undergoing a severe test.To explore the technologies to achieve high efficiency clean combustion of compression ignition engine,this paper studied butanol,the new type alternative fuel,from two aspects of fuel properties and boundary conditions.Explored the combustion and particulate emission characteristics of different oxygen content and different bonding forms butanol/diesel blended fuels from the aspect of fuel-oxygen.Based on a light compression ignition engine,this paper built a measurement and control system which is suitable for the analysis of the combustion and pollutant emissions.Obtained stable,different oxygen content test fuels with n-butanol and diesel mixed together;obtained butanol/diesel blends,which have same oxygen content,different molecular structure,using n-butanol,sec-butanol and iso-butanol mixed with diesel respectively.The experimental research about the butanol /diesel fuels was performed with the control of the boundary conditions such as combustion phase,injection pressure and the inlet oxygen concentration,the results showed that:A certain proportion of n-butanol in the diesel fuel has a significant effect on the combustion and pollutant emissions of the compression ignition internal combustion engine.N-butanol/diesel fuel is beneficial to increase the proportion of premixed combustion of compression ignition engine.With the increase of n-butanol addition ratio,the combustion delay period is prolonged,the combustion duration is shortened,the smoke opacity and particulate matter are reduced,The proportion of nuclear particles in the medium and light load is increased,and the proportion of nuclear particles in the large load is reduced while the NOx emission is not changed greatly.Under moderate load,the engine emissions can be further reduced by optimizing the combustion phase and the fuel injection pressure.In this study,the optimum CA50 of n-butanol / diesel blends at medium load is 5° CA ATDC,the most excellent fuel injection pressure of 100 MPa,under this condition,the engine indicates the highest thermal efficiency,exhaust smoke extinction smoke value is relatively low,CO and NOx emissions at the same low level,and exhaust particles have a small proportion of nuclear mode particles.N-butanol/diesel mixed fuel is conducive to reducing the requirements of high injection pressure for diesel engine,too high fuel injection pressure will not only have a little reduction of soot emissions,but also will make a further increase of the NOx emissions,while increasing the proportion of nuclear mode particles.By the introduction of EGR to further reduce the intake oxygen concentration,it is conducive to significantly reduce the NOx emissions of n-butanol / diesel fuel with no obvious increase of the soot emissions at the same time,and in heavy load conditions,the appropriate increase of the oxygen content of butanol / Diesel fuel mixture can increase the tolerance to EGR,increase the proportion of butanol and reduce the intake oxygen concentration is conducive to the improvement of the exhaust smoke and NOx emissions.The n-butanol with the straight chain structure is more favorable for the activation and combustion than the s-butanol and i-butanol,and it has a better smoke reduction effect.Under different load,the exhaust smoke of n-butanol / diesel fuel is the smallest,The NOx concentration of the three isomers was not significantly different,and the total amount of total particulates in the medium and heavy load was slightly decreased with the sequence of n-butanol/diesel,sec-butanol/diesel and i-butanol/diesel while the proportion of nuclear mode particles is slightly higher in this order.In addition,the intake oxygen concentration has a great influence on the combustion,emission and exhaust particulate properties of butanol isomers / diesel blends,and n-butanol is more sensitive to oxygen concentration.With the decrease of oxygen concentration,the NOx emissions of the three butanol isomers-diesel blends were significantly decreased,and the increase proportion of smoke opcity of isobutanol-diesel blends was significantly higher than n-butanol/diesel blends by 20%-40%,while the peak concentration of emission particulates of n-butanol with the chain structure is more susceptible to EGR.