Flame stability limits of premixed low-swirl combustion

Yinli Xiao,Zhibo Cao,Changwu Wang

doi:10.1177/1687814018790878

Yinli Xiao, Zhibo Cao + Show 1 more

Open Access

https://doi.org/10.1177/1687814018790878

Copy DOI

Abstract

The objective of this study is to gain a fundamental understanding of the flow-field and flame behaviors associated with a low-swirl burner. A vane-type low-swirl burner with different swirl numbers has been developed. The velocity field measurements are carried out with particle image velocimetry. The basic flame structures are characterized using OH radicals measured by planar laser-induced fluorescence. Three combustion regimes of low-swirl flames are identified depending on the operating conditions. For the same low-swirl injector under atmospheric conditions, attached flame is first observed when the incoming velocity is too low to generate vortex breakdown. Then, W-shaped flame is formed above the burner at moderate incoming velocity. Bowl-shaped flame structure is formed as the mixture velocity increases until it extinct. Local extinction and relight zones are observed in the low-swirl flame. Flow-field features and flame stability limits are obtained for the present burner.

Highlights

Swirl flame–stabilized methods are widely adopted in gas turbine combustors to increase the combustion intensity and reduce the required length
Because the key flow-field features are preserved at different flow velocities, the particle image velocimetry (PIV) measurements are all conducted under the same incoming velocity
The width of the recirculation zone decreases due to the increase of the adverse pressure gradient. For this low-swirl burner, flow field exhibits three distinct types depending on the swirl number

Summary

Introduction

Swirl flame–stabilized methods are widely adopted in gas turbine combustors to increase the combustion intensity and reduce the required length. Most practical combustors employ high swirl number injectors, and strong recirculation zones are formed in the primary combustion zone to provide a stable heat source.[1] it significantly increases the residence time of reactants and the pollutant emissions. Low-swirl combustion (LSC), as a novel lean premixed combustion method, has gained attentions since it was originally developed by RK Cheng[2] for fundamental studies. LSC is an approach to achieve ultralow NOx emissions and operates based on a premixed flame wave propagation concept. The divergent flow pattern is formed downstream of the low-swirl injector. The velocity decays linearly along the axial direction and the flame is stabilized where the turbulent combustion speed equals the local velocity

Objectives

Results

Conclusion