Optical Study On The Spray And Combustion Characteristics Of Diesel Ethanol Cyclopentanol Blends In A Constant Volume Chamber And An Optical Engine

In recent years,facing with the increasingly severe energy crisis and environmental pollution in the development of internal combustion engines,the search for alternative fuels and the realization of efficient and clean combustion of internal combustion engine have become focus of researchers.Among the many second generation biofuels produced from lignocelluloses,cyclopentanol with a cyclic structure has a great potential as an oxygen-containing alternative biofuel for automobiles.However,the greater density and viscosity of cyclopentanol affect the low-temperature fluidity and atomization performance of the fuel to a certain extent.The viscosity and density of ethanol are low and the evaporation is good.Replacing diesel or cyclopentanol with a certain proportion of ethanol(10%)can not only improve the physical and chemical properties of fuel,but also improve atomization and reduce soot emissions.Based on the above ideas,diesel cyclopentanol binary mixed fuel(D80CP20)was prepared according to volume ratio by using diesel as the basic fuel(D100),and ternary mixed fuels(D80CP10E10 and D70CP20E10)were prepared by replacing cyclopentanol or diesel with a certain volume ratio of ethanol(10%).This paper firstly studied the differences in physical and chemical characteristics between different fuels,and high-speed photography and two-color method were used to study the spray characteristics,combustion characteristics and the KL factors representing the soot emissions of four fuels under different injection pressures(100,120 and 100MPa)and different injection timings(6,9,12 and 15° crank angle before top dead center(°CA BTDC)),based on constant volume combustion chamber and optical engine test platform.The research results were as follows:(1)The cetane number and lower heating value of the blended fuels were lower than diesel,but the density,heat of evaporation and surface tension of the blended fuels,compared to diesel,had different degrees of improvement.Compared with D80CP20,although the cetane number and heating value of D80CP10E10 and D70CP20E10 slightly decreased,the decrease in kinematic viscosity and the increase in oxygen content in fuels had a positive effect on improving fuel atomization and reducing soot emissions.(2)The addition of cyclopentanol can effectively improve the quality of atomization,although the atomization effect of fuels were slightly worse than D80CP20 after replacing cyclopentanol or diesel with a certain proportion of ethanol,ethanol had the advantage of evaporation,and the atomization level can be improved by increasing the injection pressure.In a word,D80CP20 was slightly better than D80CP10E10 and D70CP20E10 in improving fuel atomization,and D80CP10E10 was better than D70CP20E10.(3)Replacing cyclopentanol or diesel with a certain proportion of ethanol had greater potentiality in reducing soot emissions than D80CP20,and D70CP20E10 had the lowest soot emissions.Compared with D100,the soot emissions of D80CP10E10 and D70CP20E10 decreased by 89%-98.3%、94%-98.4%,respectively.(4)The exotherm of combustion reduced with the addition of cyclopentanol and ethanol,which was due to the decrease of diffusion combustion ratio and low calorific value.Compared with D80CP20,at a higher injection pressure,replacing cyclopentanol with a certain proportion of ethanol had a better effect on heat release.(5)The experimental results in optical engine showed that D80CP20 had higher cylinder pressure and heat release rate than D80CP10E10 and D70CP20E10 under all operating conditions,and increased injection pressure and advanced injection timing can effectively drop the adverse effects of cyclopentanol and ethanol on cylinder pressure and heat release rate.D80CP20 always had the largest flame combustion area.In addition,Replacing cyclopentyl with a certain proportion of ethanol(D80CP10E10)was less adverse effects than replacing diesel(D70CP20E10).(6)Addition of cyclopentanol and ethanol can effectively reduce soot emissions.Compared with D80CP20,the whole combustion process of D80CP10E10 had a lower level of soot emissions,but considered the influence of cylinder pressure and heat release rate,D80CP20 can be regarded as a future alternative fuel,especially under the condition of injection pressure of 140 MPa and injection timing of 15° CA BTDC.