Combustion And Emission Characteristics Of Diesel Engine Fueled With Hydrogenated Biodiesel-Ethanol-Diesel Ternary Blend

With the increasingly serious energy crisis and environmental pollution,biodiesel,ethanol and other biological alternative fuels are attracting more and more attention from researchers.Biodiesel can be made from a wide range of feedstocks.Among them,biodiesel with a low saturation has poor oxidation stability and thus its storage period is limited.Catalytic transfer hydrogenation can effectively increase the saturation of biodiesel and make up for the defects of oxidation stability.However,a large amount of trans-methyl oleate?trans-C18:1?and methyl stearate?C18:0?are generated during the hydrogenation process,resulting in a deterioration of the cold flow property of biodiesel.To achieve the balance between oxidation stability and cold flow property,ultrasonic was applied to adjust the selectivity of trans-C18:1 and C18:0 products in the catalytic transfer hydrogenation of biodiesel.In addition,ethanol with a low kinematic viscosity can be used to compensate the high kinematic viscosity of hydrogenated biodiesel,and meanwhile it owns a good miscibility with the blend of biodiesel and diesel.Therefore,hydrogenated biodiesel-ethanol-diesel ternary blends were constructed,and their oxidation,combustion and emission characteristics were studied.The specific research contents are as follows:?1?Ultrasonic was adopted to assist the catalytic transfer hydrogenation of biodiesel in aqueous environment.The operating parameters of the ultrasonic generator are 180W and 40 kHz.The mixture of deionized water,isopropanol and cottonseed biodiesel with a mass ratio of 100:32:7was put into the flask where the amount of Raney nickel catalyst was defined as 13wt%of cottonseed biodiesel.The hydrogenation reaction was performed at 85?with a constant stirring of 600 r/min.The iodine value of the hydrogenated biodiesel after the 30-minute ultrasonic-assisted hydrogenation reached 77.4,which was close to that?71.6?after the 80-minute traditional reaction.Compared with traditional hydrogenation,trans-C18:1 and C18:0 compostions under ultrasonic-assisted hydrogenation were reduced by 21.3%and 20.5%,respectively.It was revealed that the saturation of biodiesel was slightly reduced under the ultrasonic hydrogenation process and thus some oxidation stability was forfeited,however,the reduction in trans-C18:1 and C18:0effectively improved the cold flow property.The partially hydrogenated cottonseed methyl ester assissted by ultrasonic?UPHCME?had the smaller cetane number,lower heating value and kinematic viscosity than the partially hydrogenated cottonseed methyl ester in traditional process?PHCME?.Both of them almost shared the same oxygen content.?2?The oxidation kinetics of the fuel blends of UPHCME,ethanol and diesel were investigated by thermogravimetry.The oxidation characteristics of the hydrogenated biodiesel-diesel binary blends?HB10,HB20,HB30?and the hydrogenated biodiesel-ethanol-diesel ternary blends?HB5E5,HB10E10,HB15E15?were studied using TGA/DSC1 synchronous thermal analyzer.Compared with diesel,the initial weightlessness temperature,final weightlessness temperature and peak weightlessness temperature of each blend were lagged,except for HB5E5which advanced its initial weightlessness temperature.The peak value of the weight loss rate for each blend was lower in comparision to diesel.Compared with the binary blends,the initial weightlessness temperatures,final weightlessness temperatures and peak weightlessness temperatures for the ternary blends were advanced,and their peaks of weightlessness rate were lowered.The oxidation kinetic parameters of each blend were calculated using Coats-Redfern integration method.The activation energies of oxidation for fuel blends were lower than those of diesel.The ternary blends exhibited the higher activation energies of oxidation than the binary blends.?3?The combustion and emission characteristics of fuel blends were performed on a common rail diesel engine with four cylinders.The engine was operated steadily under the brake mean effective pressures(p_me)of 0.23MPa,0.47MPa,0.70MPa and 0.93MPa,repectively,at the maximum torque speed of 1800 r/min.Compared with diesel,hydrogenated biodiesel and ethanol owned the smaller lower heating values,which contributed to the higher equivalent specific fuel consumptions of fuel blends and their lower effective thermal efficiencies.The binary blend and ternary blend almost shared the same equivalent specific fuel consumption and effective thermal efficiency,which can be attributed to the combined effects of cetane number,kinematic viscosity and latent heat of vaporization for ethanol.At p_me=0.93 MPa and 0.47 MPa,the hydrogenated biodiesel with a high cetane number advanced the ignition timings of binary blends,resulting in the less formation of the premixed mixture.Moreover,the small lower heating value and high kinematic viscosity of hydrogenated biodiesel contributed to the lower maximums of cylinder pressures and maximums of heat release rates for binary blends in the main combustion term,compared with diesel.The heat released from the initial combustion term overcame the disadvantage of the latent heat of vaporization for ethanol.Meanwhile,the good volatilization performance and oxygen attribute resulted in the higher maximums of cylinder pressures and maximums of heat release rates for ternary blends in the main combustion term,compared with diesel.The HC and CO emissions of ternary blends were higher than those of binary blends,whose differences decreased with the increase of load.The NO_x emissions of fuel blends were prone to be influenced by load.At p_me=0.23MPa and 0.47MPa,the NO_x emissions of ternary blends were lower than those of binary blends,which was opposite to the trend of NO_x emissions at p_me=0.70MPa and 0.93MPa.Ternary blends exhibited the lower smoke emissions than binary blends.In this paper,the ultrasonic-assisted catalytic transfer hydrogenation on biodiesel was studied.The physicochemical properties of partially hydrogenated biodiesel in ultrasonic processing were investigated.The oxidation,combustion and emission characteristics of the hydrogenated biodiesel-ethanol-diesel ternary blend were researched.The ultrasonic-assisted hydrogenation craft could possess a certain engineering reference value on the mass production of partially hydrogenated biodiesel.The application study of hydrogenated biodiesel-ethanol-diesel ternary blend could supply the important basic data for broadening the fuel application approach and exploring the clean and efficient combustion mode.