The structure of the trapped-vortex cavity and radial flameholder can maintain stable combustion under severe conditions, such as sub-atmospheric pressure and high inlet velocity. This article reports a complete study of combustion characteristics for this design. The flow field of the physical model was obtained by numerical simulation. The pilot combustion characteristics, including the combustion process, combustion efficiency, and wall temperature distribution, were studied by experiments. The pilot combustion can be divided into three modes under different fuel flow rates and inlet conditions. In “cavity maintained(CM)” mode, pilot flame exists at both sides of the cavity zone, rotating with the main vortex. In “cavity-flameholder maintained(CFM)” mode, the combustion process occurs both inside the cavity and behind the flameholder. While in “flameholder maintained(FM)” mode, the cavity will quench, and the combustion is maintained by the radial flameholder only. Due to the difference in the flow field, the flame pattern and propagation direction vary under different combustion modes. The combustion efficiency, influenced by combustion modes, shows an increase-decrease-increase curve. The wall temperature distribution is also affected; the cavity wall temperature decreases under large fuel flux while the temperature of the burner-back plate continues to rise to a maximum value.
