Performance Of Palm Oil-diesel-ethanol Microemulsion Fuel In Diesel Engine

In addition to providing high thermal efficiency,diesel engine also brings high NOx and smoke emission,which leads to environmental pollution and seriously threatens human health.Alternative diesel fuels,revolutionary in-cylinder combustion strategies and exhaust post-treatment systems are used to meet stringent emissions regulations.However,there are many problems in the engine exhaust emission aftertreatment systems due to high cost,poor durability and high fuel consumption.Also,diesel particulate filter(DPF),lean NOx trap(LNT)technology,selective catalysis reduction(SCR)system and other exhaust emission post-treatment technologies will increase fuel consumption.However,the in-cylinder combustion strategy is only in the laboratory stage and cannot be applied in practice.combustion strategy is still in the laboratory stage and cannot be applied in practice.Universal concerns about degradation in ambient environment,stringent emission legislations,depletion of petroleum reserves,security of fuel supply and global warming have motivated research and development of engines operating on alternative combustion concepts,which also have capability of using renewable as well as conventional fuels.The most feasible way to meet the growing energy demand in transportation with no increase of the greenhouse gas emissions is by utilizing alternative fuels.Therefore,great attention has been paid to diesel alternative fuels.Vegetable oil is considered as the most potential alternative fuel because of its wide sources and renewable,which has attracted the attention of many scholars and research institutions at home and abroad.However,vegetable oils have very high viscosities,low volatilities,and often freeze at low temperatures.Thus,the long-term use of neat vegetable oils causes engine durability problems such as coking of injector nozzles and sticking of piston rings,and using microemulsification is a simple and economical solution.Based on the above analysis,this paper studies the physical and chemical properties,combustion and emission characteristics,which is used the microemulsion method and selecting palm oil from vegetable oil,of W/O microemulsified fuel prepared with compound emulsifier under the action of palm oil/diesel oil as oil phase(O)and ethanol as water phase(W).The optimum emulsifier was selected at first,the oleic acid and 1-butanol were mixed according to certain proportion,then three kinds of emulsifier were prepared,the ratio of oleic acid and 1-butanol was 6:4,7:3 and 8:2,respectively.The three kinds of emulsifier were used to emulsify PD30 Exx and PD50Exx(P,D and E represents palm oil,diesel and ethanol,respectively.30 and 50 represents the ratio of palm oil/based-oil,xx represents the proportion of ethanol).It was found that the amount of emulsifier was the least when the emulsifier effect was satisfied,which the ratio of oleic acid to n-butanol was 8:2.Therefore,that emulsifier was used in this paper.Then the main physical and chemical properties of the microemulsion fuel were measured,including density,kinematic viscosity,heating value,sodilify point and cold filter plug point,and other physical and chemical properties such as surface tension and stoichiotric air-fuel ratio were calculated by empirical formula.The test results show that the density and surface tension of the microemulsion fuel are higher than that of pure diesel fuel.At the same temperature,the viscosity of the microemulsion fuel is far less than that of pure palm oil,but close to that of diesel oil.In the microemulsion fuel,the higher the proportion of ethanol,the smaller the heating value.With the increase of the proportion of ethanol and palm oil,the stoichiotric air-fuel ratio decreases.Then the load characteristics of diesel,PD30E10,PD30E30,PD50E10 and PD50E30 fuel were tested on a six-cylinder high pressure common rail diesel engine,the main injection and pre-injection were combined under small and medium loads,the main injection method was adopted under large loads,and the fuel economy,combustion characteristics and emission characteristics were analyzed.It was found that the ignition delay of microemulsion fuels was longer than that of diesel,and it became longer with the increase of the proportion of ethanol.The in-cylinder pressure of the microemulsion fuels is also lower than that of diesel fuel,and the temperature of all fuels increases with the increasing of speed and load.In the pre-injection stage,the peak value of heat release rate(HRR)of diesel fuel is larger than that of microemulsion fuels,while it is higher in the main injection stage.When the engine load and speed increase,CA50 will shift.In the micro-emulsified fuel,the greater the proportion of ethanol and palm oil,the shorter the combustion duration of the fuel and the higher the CA50.With the increase of engine load,the Break Specific Fuel Consumption(BSFC)decreases and the Break Thermal Efficiency(BTE)increases.The CO and NOx emissions of microemulsion fuels are higher than that of diesel,but the number of Particulate Matter(PM)is smaller,and there is no significant difference in the smoke emissions.With the increase of load,the number and concentration of CO and Particulate Matter(PM)emissions decreased,and NOx and soot emissions increased.