Experimental studies of soot formation for petro- and renewable diesels

The soot formation characteristics of hydro-processed renewable diesel (HRD), biodiesel, and petroleum diesel were studied in a non-premixed counter-flow laminar flame configuration. This investigation is discussed herein in terms of soot morphology, soot volume fraction (SVF), smoke point (SP), and threshold sooting index (TSI) measurements. It was found that both alternative diesel fuels (ie, HRD, and biodiesel) were similar in terms of the soot particle diameter, whereas petroleum diesel was found to exhibit the greatest soot particle formation. Additionally, the soot particle diameter and SVF were both sensitive to the variations of the reactant concentration by as much as 28%, and 86%, respectively. The sooting tendencies of the tested fuels were found to be proportional to their respective aromatic concentrations. In addition, the fuel containing higher hydrogen-to-carbon ratio (ie, HRD) had a lower SVF. The TSI indices reported that both HRD and biodiesel had a similar tendency to form soot, and the highest TSI index was petro-diesel. The SVF has good correlations with the SP results.