An Improved Method of Smoke Point Normalization

Abstract

Abstract The most widely used method of normalizing laminar smoke points from different studies has been the threshold sooting index (TSI). TSI has several drawbacks, particularly a nonphysical dependence on fuel molar mass. An improved normalization method, called normalized smoke point (NSP), is introduced here. For each fuel, NSP is a weighted average of the smoke point lengths measured by different studies. NSP eliminates the major TSI drawbacks. NSP values were determined for 112 hydrocarbons by averaging 256 smoke point measurements from 12 past studies. This allows for the most extensive evaluation to date of the effects of fuel type on the smoke points of hydrocarbon diffusion flames. Hydrocarbon sooting propensity generally increases with increasing fuel carbon/hydrogen atom ratio. For n-alkanes, sooting propensity increases with carbon number, however it generally decreases with carbon number for alkenes and 1-alkynes. Sooting propensity generally increases according to alkanes < alkenes < 1-alkynes < aromatics. Keywords: Flame lengthLaminar diffusion flameSootSooting propensityTSI ACKNOWLEDGMENTS The authors thank Dr. Heping Zhang for helpful discussions. This work was sponsored by NASA Glenn Research Center (grant NNX07AO91A) and the China Scholarship Council. Notes a CI is the 95% confidence interval and is shown for fuels considered by more than one study. b Study numbers correspond to those in Table 1.