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

R D Brum,G S Samuelsen

doi:10.1007/bf00776179

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.

Highlights

Turbulent and swirling flows with recirculation are found in many engineering systems, notable of which are gas turbines, boilers, furnaces, and incinerators
The degradation of fuel quality, the interest in disposal of hazardous waste, and the requirement for enhanced fuel utilization are each demanding a greater understanding of the turbulent transport and mixing in this class of flows
The present paper addresses this need with the following objectives: (1) To establish the flow structure, including the spatial distribution of Reynolds stress (u' w'), of a swirl-stabilized flow in a model laboratory combustor; (2) To establish the effect of reaction on the flow structure; (3) To examine the isotropy of the flow and, in particular, the turbulent stress at the interface of a swirling and non-swirling stream; (4) To examine the small-scale and global-scale dynamics associated with strongly swirl-stabilized, reacting and non-reacting flows

Summary

Introduction

Turbulent and swirling flows with recirculation are found in many engineering systems, notable of which are gas turbines, boilers, furnaces, and incinerators. The degradation of fuel quality, the interest in disposal of hazardous waste, and the requirement for enhanced fuel utilization are each demanding a greater understanding of the turbulent transport and mixing in this class of flows. To enhance the level of understanding, detailed measurements of the flow structure are required to develop physical insight and refine numerical codes. The experimental data base for turbulent swirling flows was recently analyzed in three separate studies The availability of detailed and spatially-resolved flowfield data is limited

Methods

Results

Conclusion