Experimental and numerical analysis of a novel high turndown ratio utility swirl burner

To meet deep peak shaving demands, the minimum stable combustion load rate for coal–fired power plant boilers must reach 35%–20 %. Current faulty coal–fired boilers without auxiliary fuel only reach about 50 %, falling short of this requirement. This study develops a novel high turndown ratio utility swirl burner (HTRU burner). The effects of gap air flow on burner's aerodynamic and velocity fields is investigated using a scaled–down cold test platform. Results show that the gap air controls the recirculation zone shape and size. Gap air flows of 0%–8% create an annular recirculation zone, while flows above 8 % form a larger central recirculation zone. Increasing gap air flow from 0 % to 24 % shifts the primary and secondary air mixing point closer to the burner outlet, with maximum recirculation ratio achieved at 16 % gap air flow. A numerical simulation is conducted for a 700 MW faulty coal–fired boiler, with all burners in the lower layer replaced by HTRU burners. The results show that at 20 % load, the boiler with only HTRU burners in operation can maintain stable combustion. Furnace temperatures in the main combustion zone exceed 1050 °C for gap air flow of 0 %, 16 % and 24 %. At 16 % gap air flow, both the average furnace temperature and burner outlet temperature reach their peak, while NOx emissions remain relatively low. At 24 % gap air flow, the temperature field of a single burner exhibits noticeable skewness.