Flashback investigations in a premixed swirl burner by high-speed laser imaging

摘要

This work addresses the field of lean premixed combustion to reduce NOx emissions in gas turbines. Experimental investigations of the associated flame flashback phenomenon inside the nozzle of a typical swirl burner with bluff-body by means of planar multi-kilohertz laser diagnostics provide insights into the mechanism of flame upstream propagation. Flashback is induced by increasing the swirl strength or equivalence ratio. Besides the recording of global burner stability maps, the simultaneous application of 2C and 3C Particle Image Velocimetry and Planar Laser-Induced Fluorescence of the OH radical allows measuring the flame tip-conditioned flow field at a high spatial and temporal resolution close to the wall. The temporal evolution of flashback is tracked from the conditioned high-speed data and is supplemented by chemiluminescence and wall pressure measurements. The results exclude thermo-acoustic effects as driving forceand conclude in the formulation of a new hypothesis for upstream flame propagationin premixed swirl burners with central bluff-body.