Soot, Precursor Particle and Higher Hydrocarbon Production in FlamesEPA Grant Number: R828167
Title: Soot, Precursor Particle and Higher Hydrocarbon Production in Flames
Investigators: Pfefferle, Lisa , Fillipov, Andrei , McEnally, Charles
Current Investigators: Pfefferle, Lisa , McEnally, Charles
Institution: Yale University
EPA Project Officer: Shapiro, Paul
Project Period: August 1, 2000 through July 31, 2002 (Extended to July 31, 2003)
Project Amount: $224,170
RFA: Exploratory Research - Engineering, Chemistry, and Physics) (1999) RFA Text | Recipients Lists
Research Category: Engineering and Environmental Chemistry , Water , Land and Waste Management , Air
Two of the most important unresolved issues relating to soot production are: 1) what is the mechanism for soot nucleation and how is it affected by individual PAH; and 2) what is the relative importance of nucleation versus surface growth? We will focus on the initial steps of soot production to determine the role of the liquid-like particles that precede soot both to understand how they are formed and their fate in the combustion environment. We will also directly address the relative importance of mass growth of mature soot from conversion of the precursor particles and from surface growth under a wide range of conditions. Precursor particles are difficult to measure and have not been considered in most studies. Determination of soot surface area is also difficult due to the complex morphology of soot particles. We will address these problems by development of methodologies for primary particle size measurement of both mature and precursor particles and by using our doped flame methodologies to decouple soot nucleation and growth processes from the other complex mechanisms occurring in the flames.
The capability to rapidly measure a wide range of both gas phase species and particulate types is of key importance for this study where a large array hydrocarbon species, combustion products, and both clear and mature soot particles are present throughout the flame. A distinctive capability of our laboratory is the ability to combine rapid and concurrent gas phase and particulate phase measurements over a wide range of conditions in soot laden diffusion flames. We will use VUV-MS and REMPI to simultaneously measure both combustion intermediates and products in a broad mass range (0-2000 amu) and LIF to provide OH concentrations. Soot will be probed using laser-induced incandescence (LII) to extract the soot concentration and primary particle size distribution. These measurements will be complemented by absorption and fluorescence measurements and the thermophoretic sampled particle diagnostic with TEM analysis (TPD/TEM). Since these techniques are based on the measurement of different physical properties, comparison of profiles made for the same conditions reveal changes in the nature of particulates throughout the flame.
In the proposed work we obtain a more complete characterization of the soot inception process in diffusion flames. Simultaneous measurement of both soot and soot precursors along with a map of stable species and OH radical will be important in testing mechanisms in the literature and pointing up areas where information is particularly needed. Characterization of precursor particles will be important for both risk assessment and management as the precursor particle emissions are currently uncontrolled and may provide more health risk than mature soot.