Simultaneous Measurements of Light Hydrocarbons Using Supercontinuum Laser Absorption Spectroscopy

Abstract

Simultaneous measurements of light hydrocarbon species based on near-infrared (near-IR) supercontinuum laser absorption spectroscopy (SCLAS) are demonstrated. SCLAS is a broadband absorption diagnostic technique that provides significant advantages over existing absorption diagnostic techniques. Coupled with a fast spectrum analysis strategy, accurate measurements of multiple hydrocarbon concentrations can be made concurrently. Methane (CH₄), acetylene (C₂H₂), ethylene (C₂H₄), and their mixtures were probed near ambient temperature and pressure conditions. Light hydrocarbons are found in many fuel and energy applications, and a sensor that can accurately and simultaneously probe multiple species' concentrations and temperature would greatly enhance measurement versatility. Absorption spectra of the three hydrocarbon species were measured between 1.5 and 1.7 mu m in this study. These spectra can be very convoluted, where broad absorption features interfere with neighboring features, be it from the same or different species. Species concentrations and temperatures were resolved using a spectrum analysis strategy based on linear regression. Experimental results showed good agreement with test conditions even in the presence of significant spectral overlap.