Central recirculation zone induced by the DBD plasma actuation

Gang Li,Yanji Xu,Gang Xu,Zhijun Lei,Cunxi Liu,Jinhu Yang,Xi Jiang

doi:10.1038/s41598-020-70116-9

Abstract

Central recirculation zone (CRZ) is commonly formed in the near field of the injector exit by the vane swirler and used to stabilize the flame. In our experiment, a CRZ induced by the DBD plasma actuation was observed in the low swirl burner configuration for the first time, which clearly demonstrated that the mechanism of the combustion control by the plasma swirler is mainly through the aerodynamic effect. Three dielectric barrier discharge (DBD) actuators are placed in a circular array around the axis to generate ionic wind in the circumferential direction of the injector. Characteristics of the flow field have been measured using Laser Doppler Anemometry. It is found that a central recirculation zone with the shape of an ellipsoid is formed in the non-reacting flow field with the plasma actuation. The position of the upstream stagnation point was determined by the strength of the actuation. Although the CRZ disappears in the reacting flow field as the result of combustion heat release, the influence of the discharge on the flame lift-off height is noticeable. The results demonstrate that swirl enhancement by the plasma swirler is feasible, flexible and effective as a non-intrusive measure for flow control.

Highlights

Central recirculation zone (CRZ) is commonly formed in the near field of the injector exit by the vane swirler and used to stabilize the flame
A CRZ induced by the dielectric barrier discharge (DBD) plasma actuation was observed in our burner configuration for the first time, which clearly demonstrated that the mechanism of the combustion control by the plasma swirler is mainly through the aerodynamic effect
The results show that the swirl as well as the axial adverse pressure gradient are increased because of the plasma actuation and the induced reverse flow is sufficiently strong to result in a CRZ, but the increase is not big enough to cling the CRZ

Summary

Introduction

Central recirculation zone (CRZ) is commonly formed in the near field of the injector exit by the vane swirler and used to stabilize the flame. Swirling flow is widely used in premixed combustion to enhance flame stability through the induced central recirculation zone (CRZ) or the central velocity decay. The latter is the feature of low swirl injector (LSI) where the central velocity decay induced by flow divergence keeps the lifted flame stable[17].

Results

Conclusion