The effects of swirl number on the combustion characteristics in an internally-staged combustor

Abstract

The three-dimensional turbulent swirling flame in an internally-staged combustor is numerically investigated. Four cases over a range of swirl intensities are explored by the Flamelet Generated Manifold model in this paper. Special attention is paid to analyzing the variation of the flow field, temperature, major species concentrations and emissions. The results clearly show the effects of swirl number on the size of the center recirculation zone, fuel distribution and combustion characteristics. When the third premixed stage swirl number increases from 0.6 to 1.2, the axial length of the center recirculation zone decreases by 3.7%, while the radial length increases by 6.9%. The characteristics of the flow field play an important role in the spatial distribution of the fuel, which further affects the temperature distribution in the combustor. The backflow effect is enhanced, resulting in a greater concentration of fuel at the outlet of the swirler. After the maximum temperature is reached at the exit position of the pilot stage, the temperature decreases compared to the peak temperature downstream as the proportion of premixed combustion mode increases. This creates a high concentration region of OH at the outlet of the pilot stage injector and the heat release region is squeezed upstream. At the same time, the volume of the high-temperature region downstream of the pilot stage is reduced. In addition, as the swirl number of the third premixed stage increases from 0.6 to 1.2, the emissions of NO and CO decrease by 28.7% and 75%, respectively.

Optimum swirl angle of natural gas combustion in domestic cooker burner with various output port

“…On the other hand, the combustor with diverging and diverging-converging structure can enhance liftoff velocity. Zhao et al, 11 investigated the three-dimensional turbulent swirling flame in an internally-staged combustor numerically. When the third premixed stage swirl number increases from 0.6 to 1.2, the axial length of the center recirculation zone decreases by 3.7%, while the radial length increases by 6.9%.…”

CFD investigation of air-oil two-phase flow in oil jet nozzle

“…The computational fluid dynamics (CFD) method is always widely used to visually understand the fluid flow in real case studies. [10][11][12][13][14][15] Under oil jet lubrication, oil liquid is sprayed from the nozzle exit into the air and finally reaches the lubrication areas of target parts. Clearly, the oil jet lubrication process belongs to a typical liquid-gas two-phase flow behavior.…”