In-situ measurement of water-vapor in fire environments using a real-time tunable diode laser based system. (March 2021)

• Record Type: Journal Article
• Authors: Ghanekar, Shruti; Rajasegar, Rajavasanth; Traina, Nicholas; Mitsingas, Constandinos; Kesler, Richard M.; Horn, Gavin P.; Zevotek, Robin; Kerber, Stephen; Lee, Tonghun
• Is Part Of: Fire safety journal. Volume 120(2021)
• Publication Date: 2021-03
• Subjects: Tunable diode laser -- Near-infrared -- Absorption spectroscopy -- Water-vapor measurement -- Training fires -- Fire suppression -- Smoke obscuration; Fire prevention -- Periodicals; Incendies -- Prévention -- Recherche -- Périodiques; Fire prevention -- Research; Periodicals; 628.92205
• DOI: 10.1016/j.firesaf.2020.103114
• Languages: English
• ISSNs: 0379-7112

Abstract

Abstract: A robust tunable diode laser absorption spectroscopy (TDLAS) based system is developed and deployed to make real-time water-vapor concentration measurements in quasi-controlled live-fire experiments conducted in firefighter training props. This system targets the 1392.5 nm (7181.15 cm −1 ) water-vapor absorption line while employing a multi-tier detection sensitivity scheme that allows for measurements at multiple locations in fire environment through varying smoke obscuration levels. Temperature-corrected absorbance values are compared to HITRAN simulations to quantify water-vapor concentration. Upon validation in laboratory setting, the impact of firefighter hose stream application on water-vapor concentration is studied. Comparative effects of training structures (metal, concrete and drywall-lined) and fuel-loads (pallet/straw, lightweight furnishings and pallet/straw/oriented-strand-board (OSB)) on water-vapor concentration are characterized. Despite small increase in water-vapor concentration due to suppression, the post-suppression concentrations are found to be comparable or lower than the corresponding maximum pre-suppression concentrations in all scenarios except the metal structure. Irrespective of the structure, highest temperature and water-vapor concentrations are measured with pallet/straw/OSB fuel-load. Under identical fuel-loads, the drywall structure scenarios generate highest water-vapor concentration. Peak water-vapor concentrations are measured post-suppression in typical training structures (near-floor and crawling levels), but prior to suppression in the structure/fuel package combination that simulated a typical residential fire scenario. Highlights: TDLAS based system for water-vapor measurement through varying smoke obscuration. Pre- and post-suppression concentrations comparable except in metal structure. Highest temperature and water-vapor concentration for pallet/straw/OSB as fuel load. Non-conforming water-vapor trends in metal structure compared to other structures.