Studies of Carbon Particulates (soot) Derived from the Combustion of Biodiesels
Soot nanostructures formed in open air-flames of canola methyl ester, soybean methyl ester, mixture of soybean methyl ester-animal fats biofuels and diesel fuel are studied using the thermophoretic sampling technique and HR-TEM imaging. Reconstructed evolution of soot particles along the flame centerline in the axial direction shows the existence of two characteristic distinct soot morphologies.
Canola Methyl Ester/Air Flame
Diesel/Air Flame
Low and high resolution TEM images of soot collected from the annular region of the canola methyl ester (CME) air-flame as a function of increasing height (Z). (a-d) represent low resolution TEM images of the primary soot particles extracted thermophoretically at selected axial locations of (a) Z = 9.0, (b) 14.0, (c) 17.0, and (d) 22.0 mm from edge of the fuel nozzle; (e-h) represents higher resolution TEM images of selected areas in (a-d).
Low and high resolution TEM images of collected soot from the annular region of the diesel air-flame as a function of increasing height (Z). (a-d) represent low resolution TEM images of the soot particles extracted thermophoretically at selected axial locations of (a) Z = 9.0, (b) 14.0, (c) 17.0, and (d) 31.0 mm from edge of the fuel nozzle; (e-h) represents higher resolution TEM images of selected areas in (a-d).
Representative HR-TEM images of young and mature soot nanostructure variation from different biodiesels and from diesel fuel near the bottom-flame, intermediate-flame, and tip-flame regions. a1-a3) from a CME air-flame; b1-b3) from the SME air-flame; c1-c3) soot from a mixture of SME-AF air-flame; and d1-d3) soot from a mixture of Diesel air-flame.
Average diameters of primary soot particles measured at different axial locations of the CME, SME, SME-AF and Diesel air-flames. The values in the plot represent the peak values of the average primary soot particle diameter (dp) at each flame location. The soot produced from the CME has the smallest size particle diameter of all the tested biodiesels with a dp value of 27 nm. The peak values of dp for the SME and SME/AF (are larger than those present in the CME) and have a value of 39 and 29 nm, respectively. The soot produced from the Diesel flame has the largest dp value (48 nm) of all the tested liquid fuels. The measurement uncertainty is indicated by the vertical error bars; each bar denotes one standard deviation.
Merchan-Merchan et al. Fuel 102(2012) 525-535