The interaction between characteristic flow structures and diffusion flame
Date Issued
2012
Date
2012
Author(s)
Chen, Chuan-Sheng
Abstract
The interaction between characteristic flow structures formed by a bluff-body burner and diffusion flame reactions had been experimentally investigated. This interaction could be attributed to the coupled effects of both flow vorticity and heat release in the combustion field. The objectives aim to unveil how the interaction produces different combustion efficiency distribution and to characterize spatial patterns in fluctuating heat release for future control purposes.
In this study, the different kinds of characteristic flow structures were created by adjusting the air co-flow outlet velocity, while the outlet velocity of central jet, consisting of pure propane, was fixed. The reacting flow field was characterized using 1kHz high-speed particle imaging velocimetry (PIV), while the corresponding combustion pattern was investigated exploiting employing implementing C2* and CH* chemiluminescence which detecting the spontaneous light emitted by the flame.
The results showed that the flame intensity and reaction frequency differed from each location, including the recirculation zone, vortex pair shear layer and buoyancy toroidal vortex active zone, because of the various flow characters. At the recirculation zone, there were complicated vorticity structures with wide spectrum distribution acted. The vorticity structure enhanced the air-fuel mixing and heat transfer efficiency at different frequency, providing a set of suitable environments for chemical reactions. As a result, a series of complex reactions would happen in various intensity and frequency at the recirculation zone. Furthermore, the heat release from the recirculation zone would induce the flow buoyancy instability, dominating the creation of toroidal vortexes which contain much more complicated vorticity structures; consequently, these structures caused the reaction to proceed at a wide range of reaction rates, even at a high frequency response. This flow-flame interaction mechanism significantly influences the combustion efficiency of non-premixed bluff-body burner.
Subjects
flow-flame interaction
diffusion flame
chemiluminescence
PIV
spectrum analysis
Type
thesis
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