A simple method for the quantitative assessment of soot production rate

Abstract

Sooting tendency has been characterized with various empirical approaches such as smoke height and Threshold Sooting Index (TSI), that can be regarded as qualitative, as well as Yield Sooting Index (YSI), that is semiquantitative since it relies on the measurements of at least the peak soot volume fraction in the flame. All these techniques have the convenience of being easy to implement and of relying on inexpensive equipment. In the present work we present a comparatively easy but quantitative alternative to determine the soot production rate in counterflow flames. The approach is rooted in the use of: a) soot volume fraction measurements by pyrometry, b) the well established one-dimensional computational modeling of such flames for the determination of temperature and velocity profiles and c) the use of the soot governing equation. The technique is applied to several aliphatics, including methane, propane, ethylene, propene and acetylene. Soot production rate per unit flame area for the tested aliphatics ranges between 10−4 and 10−7 g/(cm2s) and, when normalized with respect to the carbon flux, between 10−5 and 10−2. On a logarithmic scale it correlates linealry with the peak temperature for all fuels. Soot yield scales as alkanes< alkenes < alkynes, with acetylene showing the highest sooting tendency even in flames at relatively low temperatures.