Three Dimensional Chemiluminescence Imaging of Unforced and Forced Swirl Stabilized Flames in a Lean Premixed Multi Nozzle Can Combustor

Abstract

A tomographic image reconstruction technique has been developed to measure the 3D distribution of CH* chemiluminescence of unforced and forced turbulent premixed flames. Measurements are obtained in a lean premixed, swirlstabilized multinozzle can combustor. Lineofsight images are acquired at equally spaced angle increments using a single intensified chargecoupled device camera. 3D images of the flames are reconstructed by applying a filtered back projection algorithm to the acquired lineofsight images. Methods of viewing 3D images to characterize the structure, dynamics, interaction and spatial differences of multinozzle flames are presented. Accuracy of the reconstruction technique is demonstrated by comparing reconstructed lineofsight images to measured lineofsight downstreamview images of unforced flames. The effect of the number of acquired projection images on the quality of the reconstruction is assessed. The reconstructed 3D images of the unforced multinozzle flames show the structure of individual flames as well as the interaction regions between flames. Forced flame images are obtained by phasesynchronizing the camera to the forcing cycle. The resulting 3D reconstructions of forced flames reveal the spatial and temporal response of the multinozzle flame structure to imposed velocity fluctuations, information which is essential to identifying the underlying mechanisms responsible for this behavior.