Towards Characterization of Soot Morphology, Composition, and Optical Properties From Large Pool Fires

Abstract

The thermal hazard posed by large hydrocarbon fires is dominated by the radiative emission from high temperature soot. Since the optical and morphological properties of soot are not well known, especially in the infrared, efforts to characterize these properties are underway. Measurements of optical properties and morphology in large fires are important in heat transfer calculations, interpretation of laser-based diagnostics, and to build revised soot property models for fire field models. This research utilizes extractive measurement diagnostics to characterize soot morphology, composition, and optical properties in pool fires. The fires of interest are realistic in size, and considerably larger than recent studies, from transitionally turbulent to fully turbulent JP-8 pool fires. For measurement of the extinction coefficient, soot extracted from the flame zone is transported to a transmission cell where measurements are made using both visible and infrared lasers. Soot morphological properties are obtained by analysis via transmission electron microscopy of soot samples obtained thermophoretically within the flame zone, overfire region, and in the transmission cell. Soot composition, including carbon-to-hydrogen ration and PAH concentration, is obtained by analysis of soot collected on filters. In addition to providing insight into optical properties, soot samples obtained allow researchers to determine that the soot morphology is not affected by the transport to the transmission cell. This paper describes the diagnostics and presents some preliminary data for soot morphology, composition, and optical properties measurements within the flame zone of pool fires.