Measurement of the Size Distribution of Smoke Particles through Direct Sampling at the Exit of a Steady-State Tube Furnace

Abstract

The size distribution of smoke particles, influenced by varying fire conditions, constitutes a significant research focus in the firefighting domain concerning fire detection and the impact on lung deposition which is a major contributor to both short- and long-term casualties among residents and firefighters. Currently, the ISO/TS 19700 method is commonly employed to measure characteristics of combustion products, including composition and concentration, primarily for gaseous substances. However, due to measurement challenges, limited research results exist on particulate substances using this method, and outcomes vary significantly among researchers. The particle size distribution which is the typical characteristics of particulate materials is crucial factor leading to discrepancies in measurements at the combustion furnace outlet. This distortion is influenced by factors such as particle collision, temperature changes, and residence time in the mixing chamber installed for cooling and dilution. This study unveils the disparity in particle size distribution between using a mixing chamber and direct sampling. A solution is proposed by replacing the mixing chamber at the outlet of the steady-state tube furnace specified in the existing ISO/TS 19700 method with a direct sampling approach. Smoke particles generated under combustion conditions at various temperatures and equivalence ratios were directly sampled at the furnace exit. These samples underwent a two-stage dilution process, and the real-time particle size distribution was measured using an electrostatic low-pressure impactor. This approach minimizes distortion of the particle size distribution attributable to the mixing chamber.