Influence of mass-flow ratio of inner to outer secondary air on gas–particle flow near a swirl burner

•The recirculation zone decreases with increasing mass-flow-rate ratio.•Particle concentration in the central zone of burner is high.•Particle volume flux profile has two peaks and two troughs.•The burner exhibits better combustion characteristics at mass-flow-rate ratio of 0.43.

The influence of mass-flow-rate ratio of inner to outer secondary air on gas–particle flow characteristics was determined in the near-burner region of a centrally fuel-rich swirl coal combustion burner. Velocity and particle volume flux profiles and normalized particle number concentrations were obtained. Peaks in tangential mean velocity and three-dimensional root-mean-square fluctuation velocities were found to decrease as the mass-flow-rate ratio increased. Moreover, the peaks in the mean axial velocities and particle volume flux near the wall increased, whereas those near the chamber axis decreased. Simultaneously, both recirculation zone and swirl number decreased as the mass-flow-rate ratio increased.

Graphical abstractParticle volume flux profiles for three mass-flow-rate ratios.Figure optionsDownload full-size imageDownload as PowerPoint slide