Laser Vibrometry for Real-Time Combustion Stability Diagnostic

Laser-based diagnostics for combustion monitoring are promising sensing techniques for the upcoming generation of build-in gas turbines measurement and control devices. Their principles are usually based on direct measurement of line-of-sight transmission, absorption, scattering or re-emission of laser light through the flame. We discuss here how a similar method based this time on interferometry can provide a refined analysis on dynamics of injected reactants and flame stability. Measurements are performed on a resonant premixed air/methane flame using Laser Vibrometry (LV). A method for detection of combustion instability within the primary zone is described, and dual LV measurements performed over the full flame cross section provide a refined analysis of the flow patterns. This technique, originally dedicated to structural dynamics, shows a high potential for low-cost and rapid flow characterisation during the benchmark tests of a gas turbine combustor. The discussion ends on feasibility for embarking Laser Vibrometry as a real-time combustion monitor.