Experimental and numerical study of the development of swirling flow and flame dynamics and combustion characteristics at biomass thermo-chemical conversion

Abstract

The focus of this study is to investigate the main factors determining the development of swirling flow dynamics and to correlate the development of the non-premixed swirling flame characteristics at biomass thermo-chemical conversion with the evolution of the confined swirling flow velocity fields in a pilot device which combines a biomass gasifier and a combustor. This study includes complex experimental study and numerical modelling of the development of velocity fields for confined non-reacting swirling flows and flame, as well as the development of swirling flame velocity fields and combustion characteristics at biomass thermochemical conversion under effects of various inlet conditions, such as the inlet nozzle diameter at the bottom of the combustor, primary and swirling air supply rates in the device. The results show that the development of the swirling flow velocity field first of all is closely related to the inlet nozzle diameter, which for the fixed primary and secondary air supply rates strongly affects the upstream and downstream swirling airflow formation and swirl intensity, which are highly responsible for the mixing of combustible volatiles with the axial air flow, for the ignition and combustion of volatiles. The results also show that the development of the swirling flow velocity field depends on the air supply rate which affects the development of the combustion dynamics and composition of emission through the variation of the downstream flow structure and the air excess ratio in the flame reaction zone.