Experimental Research And Theoretical Calculation Of Biodiesel Density And Surface Tension

With the decrease of energy reserves and the aggravation of environmental pollution caused by its combustion,the development and efficient utilization of clean alternative energy has become the focus of many scientists and organizations.Biodiesel has become an important part of alternative energy because of its excellent environmental protection and biodegradability.Especially for biodiesel,the accurate data of density and surface tension are very important for the production and use of biodiesel and the research of combustion atomization in diesel engines.Therefore,this paper studied the density and surface tension of fatty acid methyl ester and ethyl ester of biodiesel through experiment and theoretical calculation,to provide data and model support for the study of its spray,combustion and emission process in the engine.The main work of this paper includes the following four aspects:1.The density data of 8 fatty acid methyl esters and 6 fatty acid ethyl esters at the temperature range of 293.15 K to 363.15 K were measured by Anton Padma 5000 M vibration tube densimeter under atmospheric pressure,and the correlation formula was fitted to the data.The average absolute deviation and maximum relative deviation between the experimental value of fatty acid methyl ester and fatty acid ethyl ester and the calculated value of the correlation formula were 0.01% and-0.06%,0.01% and-0.05%,respectively.2.The ST 5000 surface tension measuring system was used to measure the surface tension data of 6 fatty acid methyl esters and 5 fatty acid ethyl esters in the temperature range of293.15 K to 373.15 K under atmospheric pressure,and the correlation formula was fitted to the data.The average absolute deviation and maximum relative deviation of the surface tension between the experimental values of fatty acid methyl ester and fatty acid ethyl ester and the calculated values of the correlation formula are 0.11% and 0.33%,0.08% and-0.24%,respectively.3.On the basis of the experiment,the theoretical calculation model of the density of fatty acid esters was established by splitting,assigning and solving the contribution values of the groups of 14 fatty acid esters.Then,the density of the modeled 14 fatty acid esters was calculated by the model and compared with the experimental data.The average relative deviation and the maximum relative deviation of 14 fatty acid ester densities were 0.44% and 0.92%,respectively.In order to verify the extrapolation of the theoretical model,a total of 36 data points of 4 fatty acid esters were selected for verification.The average relative deviation was 0.70%,and the maximum relative deviation was 1.65%.The results show that this method can accurately estimate the density of fatty acid esters.4.On the basis of the experiment,the surface tension of 11 fatty acid esters was theoretically calculated by means of group contribution method,and the theoretical calculation model of surface tension was finally obtained.The surface tension of 11 fatty acid esters was calculated by using the model and compared with the experimental data.The average relative deviation and the maximum relative deviation of surface tension of 11 fatty acid esters were0.60% and-2.59%,respectively.In order to verify the extrapolation of the theoretical model,a total of 30 data points of 6 fatty acid esters were selected for verification.The average relative deviation was 0.87%,and the maximum relative deviation was-1.72%.The results show that this method can estimate the surface tension of fatty acid esters more accurately.