Development of an All-Fiber-Coupled, Pulsed, Ultraviolet Laser-Induced-Fluorescence (UV-LIF) Detection System for OH Radicals in Practical Combustion Devices
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An all-fiber-coupled, pulsed, ultraviolet, laser-induced-fluorescence (UV-LIF) detection system for hydroxyl radicals (OH) is developed for use in practical combustion devices that operate in harsh environments. The system is designed to transmit the required excitation-pulse energy through long optical fibers (up to 10 m) for both point and planar LIF (PLIF). First, we investigate the fundamental transmission characteristics of nanosecond (ns)-duration, high-power laser pulses at a 283-nm OH-excitation wavelength for state-of-the-art, commercial, UV-grade optical fibers. Detailed studies carried out on the fibers include 1) damage threshold, 2) optical-transmission stability under long-term, high-power, UV laser irradiation, 3) beam quality at the output, and 4) nonlinear effects during beam propagation. Based on these studies, an all-fiber-coupled ns-UV-LIF excitation/detection system for OH is developed. Single-laser-shot PLIF imaging of OH in flames is also demonstrated using fiber-based excitation. Development of such fiber-based diagnostics and imaging systems constitutes a major step forward in transitioning laser-diagnostic tools from research laboratories to practical combustion facilities. Copyright 2012 by the American Institute of Aeronautics and Astronautics, Inc.
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50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition
