Two-component laser anemometry measurements of non-reacting and reacting complex flows in a swirl-stabilized model combustor

Abstract

Simultaneous two-component velocity measurements are acquired in a model, complex flow swirl-stabilized combustor using a two-color laser anemometer. A time base computer interface enables the direct measurement of Reynolds stress$(\overline {u'w'} )$ as well as mean and rms axial (u,u′) and azimuthal (w,w′) velocities. The peak value of the normalized Reynolds stress$(\overline {u'w'} /u_{rms} w_{rms} )$ approaches 0.25 which is less than values (∼0.40) obtained by others using indirect, non-simultaneous measurement methods in complex flows, but similar to a direct measurement in a dump combustor without swirl. Isotropy is satisfied except in regions of high unidimensional shear, and both turbulence intensity and normalized Reynolds stress are reduced in the absence of reaction. Relatively small-scale form intermittencies, associated with a fluctuation of the stagnation point and a precessing vortex core, serve to reduce the measured values of the normalized Reynolds stress at the centerline by increasing the apparent turbulence intensity. At an elevated fuel loading, a global-scale form intermittency is invoked and, while likely realistic relative to practical devices, may not be a viable condition for time-averaged calculations.