Comparison of Three Schemes of Two-Photon Laser-Induced Fluorescence for CO Detection in Flames

Abstract

Two-photon excitation laser-induced fluorescence of carbon monoxide suffers from interference from mainly C2 and strong pressure quenching. This paper presents an investigation of three excitation/detection schemes for two-photon excitation laser-induced fluorescence on carbon monoxide. The schemes are evaluated for pressure and quenching partner dependencies and C2 interference. Three different emission bands lie in the Hopefield-Birge system: The Angstrom B1Σ+ → A1Πu band, with two-photon excitation through B1Σ+ ← X1Π around 230 nm; the Herzberg band C1Σ+ → A1Πu, with two-photon excitation through, C1Σ+← X1Π, around 217 nm; and the third positive group b3Σ→a3Π, also with excitation of B1Σ ← X1Π around 230 nm. The measurements are performed in laminar premixed flames with various equivalence ratios as well as in a high-pressure cell, where pressure and species concentrations are varied in order to investigate the fluorescence quenching dependence.