Influence of the Inner and Outer Secondary Air Ratios on the Combustion Characteristic and Flame Shape of a Swirl Burner with a Prechamber

Abstract

The swirl burner with a prechamber was used in a 14 MW pulverized-coal combustion experiment to investigate the influence of inner and secondary air ratios (ISA/OSA) on the combustion characteristic and flame shape in this work. The temperatures and species concentrations in the prechamber were measured via the flue gas analyzer and thermocouples. The flame shape beyond the prechamber outlet was captured by using a high-speed camera. The results showed that the combustion efficiency was increased and low nitrogen combustion was achieved by adopting the swirl burner with a prechamber. The high temperature corrosion and slagging phenomenon did not occur in the prechamber. The influence of ISA/OSA on temperature and species concentration profiles at different areas in the prechamber was different. The flame shape size exhibited an inflection point with increasing ISA/OSA. Considering, comprehensively, the temperature peak, near wall temperature, oxygen-free zone, CO concentration, flame length, flame diameter, and divergence angle, the case of ISA/OSA =1 : 2 had great processing on combustion efficiency and NOx emission. Thus, ISA/OSA = 1 : 2 was selected as the optimized case under experiment conditions.