Development of a probe for in-situ measurements of major species in a pool fire using multiplexed near-IR TDLAS

ABSTRACT In this paper we discuss the development of a tunable diode laser absorption spectroscopy probe to simultaneouslymeasure, in situ concentrations of 4 major species (CO. C2H,. Cl-I4. and l-IO) and the gas phase temperature in a pool tire. The difficulty in making these types of measurements is intrinsic to the environment itself. A large fire is composed of veryhot (>1000 K). turbulent gases and highly radiating and absorbing soot particles. Fiber optic cables are used to transport laserradiation into the fire via a water-cooled probe. This paper focuses on probe design issues, such as the optimization of openpath. multipass optics for a turbulent, particulate-laden flow, and the application of high-frequency wavelength modulation spectroscopv to frequency-domain multiplexing of diode lasers. Keywords: diode laser absorption, in situ probe. multiplexing I. INTRODUCTION Large-scale pool fires (see Fig. 1), resulting from the ignition of fuel vapor above a liquid hydrocarbon pool.