Research On Engine Test And Numerical Simulation Of N-pentanol-diesel Fuel

The research of clean and renewable energy for vehicles is one of the main directions of energy conservation and emission reduction in vehicle industry.Alcohol fuel can be used in diesel engine and gasoline engine.The chemical formula of n-pentanol is C₅H₁₂O,which contains more oxygen and has lower ignition temperature,viscosity and corrosion risk.Alcohol fuel can be obtained from natural fermentation of engineering microorganisms and glucose biosynthesis,which is considered to be one of the most potential alternative fuels to petroleum fossil energy.In this study,the effects of n-pentanol diesel fuel on the combustion and emission characteristics of diesel engine were studied by the method of verifying the bench test and numerical operation.Firstly,the influence of load,ratio of n-pentanol and intake oxygen concentration on combustion and emission of n-pentanol-diesel fuel was studied by engine bench test.The results show that with the increase of n-pentanol ratio,the ignition delay time increases,the crest of average pressure and instantaneous heat release rate in cylinder increase,the emissions of NO_xand Soot reduce,and the emission of HC increase;With the increase of load,the crest in-cylinder pressure and heat release rate of pure diesel,H30 and H45 fuel increase,while the CO emission decreases.The CO emission of n-pentanol-diesel is higher than that of pure diesel at medium and low load condition,while the CO emission of n-pentanol-diesel is lower than that of pure diesel at high load.With the increase of oxygen concentration,the BTE values of the three fuels increase.The emissions of CO,HC and Soot increase and the emission of NO_xdecreases with the decrease of oxygen concentration.Then,the main components and reaction paths of the combustion process of n-pentanol-diesel fuel were studied from the perspective of chemical kinetics with CHEMKIN.The results show that the initial reaction of n-pentanol is mainly the dehydrogenation of n-pentanol with H,OH and HO₂.The formation of QOOH by the isomerization of ROO affects the reaction rate of the numerical system.With the increase of oxygen concentration,the crest value of OH quality fraction increases,which promotes the chain initiation process of n-pentanol and the key reactions to promote ignition are NC₅H₁₁OH+OH<=>a C₅H₁₀OH+H₂O and NC₅H₁₁OH+OH<=>e C₅H₁₀OH+H₂O,and the ignition delay time decreases.Reducing the oxygen concentration in the intake air will reduce the oxidation of CO.When the ratio of n-pentanol increases,the quality fractions of HO₂ and OH increase,and the rates of ROO generation components(C₅H₁₀OH-3O₂,C₅H₁₀OH-5O₂)in the chemical reaction path of c C₅H₁₀OH and e C₅H₁₀OH decrease,the temperature sensitivity coefficients of NC₅H₁₁OH+OH<=>a C₅H₁₀OH+H₂O and C₄H₉<=>C₂H₅+C₂H₄increase,and the ignition delay time decreases.Finally,the combustion process of n-pentanol-diesel fuel in diesel engine was arithmetically simulated by using CONVERGE,and the effects of n-pentanol ratio and oxygen concentration in intake air on the combustion and emission characteristics of n-pentanol-diesel fuel were further studied.The results show that with the increase of intake oxygen concentration,the in-cylinder temperature at CA50 increases,and the crest values of quality fraction of H₂O₂,OH,HO₂,CH₂O and CH₂CHO in the main components increase.As intake oxygen concentration reduces,the quality fraction of CO increases at CA50 time,the quality fractions of A4,C₂H₂and Soot decrease,and the quality fractions at CA90 of Soot,A4,C₂H₂increase first and then decrease.When the intake oxygen concentration decreases,the crest values of quality fraction of Soot,A1,A4 and C₂H₂increase first and then decrease.With the increase of n-pentanol ratio,the start time of NC₇H₁₆consumption was put off,and the crest values of Soot,A1,A4 and C₂H₂decrease,and the quality fractions of Soot,A4 and C₂H₂at CA90 gradation reduce.Therefore,adding n-pentanol to diesel can reduce A4 generation,thus reducing Soot emission.