Optimization of a swirl burner with universal low-load stable combustion technology: Investigating flow characteristics, combustion performance, and fuel adaptability

Stable combustion under ultra-low loads is crucial for deep peak-shaving in coal-fired power plants but remains technically challenging. To overcome common problems such as ignition delay, nozzle overheating, and excessive NOx emissions, a novel universal low-load stable combustion technology is proposed, combining laboratory-scale gas-particle experiments and full-scale combustion simulations. A systematic comparison was conducted among a prototype burner (OPCC) and two optimized configurations (GOPCC and GIPCC) under ultra-low-load conditions. Structural optimizations involving gap air introduction markedly strengthened internal recirculation and mixing, elevating the reflux ratio from less than 36 % in OPCC to over 60 % in GOPCC and GIPCC, and increasing swirl number from 11.14 (OPCC) to 16.61 (GOPCC) and 14.92 (GIPCC). This enhanced mixing accelerated primary-air velocity decay, moving ignition positions significantly upstream (from 2.5 m in OPCC to 0.15 m in GOPCC and 1.2 m in GIPCC). Moreover, optimized burners developed a concentrated and uniform flame structure, effectively shifting the high-temperature region away from the nozzle to mitigate overheating risks. When burning lean coal, GOPCC maintained stable combustion with NOx emissions below 40 mg m−3 in the central recirculation zone. These results offer a cost-effective, wide-load-adaptable solution to achieve stable deep peak-shaving across various coal grades.