AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Evaluation of Semi-Empirical Soot Formation Models in Strained, Oxygen-Enriched Flames
PHILLIP R. JOHNSON, Benjamin M. Kumfer, Washington University in St. Louis
Abstract Number: 395 Working Group: Combustion
Abstract Soot is carbonaceous particulate formed during hydrocarbon combustion. Its presence in industrial boilers and furnaces plays an important role for radiation heat transfer and its emission to the atmosphere affects both the environment and human health. For these reasons, soot volume fraction is often included in CFD combustion models of industrial systems. The complexity of modeling in such applications has led to the widespread use of semi-empirical models rather than computationally-expensive detailed models. Many of these models were developed for a particular application and validated under fuel-air combustion conditions with a specific characteristic mixing time; their use in a different contexts, such as oxy-combustion, can lead to inaccurate predictions. In this study, commonly used semi-empirical soot models and their ability to respond to oxygen enrichment and variable-strain conditions are evaluated. As reported in the literature, a soot-producing flame can become non-sooting (blue) with the combination of oxygen enrichment and fuel dilution, even while maintaining constant flame temperature. In addition, soot-producing flames may become blue with increasing strain rate. In this work, a series of counter-flow flames are modeled which span the sooting-to-non-sooting transition. Flames are modeled using the OPPDIF code and results are post-processed to include soot formation rates and particle transport . Results indicate that these models do not adequately capture the sooting-to-non-sooting transition and thus will be inaccurate under conditions of oxy-combustion or variable strain.