Laser Ignition of Propane-Air Mixtures Using a Dual-Pulse Technique
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© 2017 by Ciprian Dumitrache, Azer Yalin. A novel laser ignition technique based on dual pulse gas pre-ionization and energy addition is demonstrated for combustion of propane-air mixtures. The method uses an ultraviolet (266 nm) laser pulse to achieve initial gas pre-ionization followed by an overlapped near-infrared (1064 nm) pulse for energy addition into the pre-ionized gas. In this experimental study the dual-pulse technique is contrasted with the more common laser induced breakdown ignition using a single (1064 nm) Q-switched laser. Pressure data collected during the combustion event shows that the dual-pulse technique leads to extension of the lean limit and an increase in combustion energy conversion efficiency as compared to single pulse ignition. The leanest mixture that was successfully ignited using the dual-pulse method had an equivalence ratio of Φ = 0. 6 as opposed to Φ = 0. 7 for single-pulse ignition. Analysis of the pressure curves also shows that the combustion efficiency is higher near the lean limit using the dual-pulse laser ignition technique. Finally, an investigation of the flame speed was conducted by acquiring OH* chemiluminescence images which revealed that flames initiated using the dual-pulse method exhibited less stretching (as compared to singlepulse) which may contribute to the extension of the lean limit.
author list (cited authors)
Dumitrache, C., VanOsdol, R., Limbach, C., & Yalin, A. P.