Research On The Influence Of Bell-type Nozzle Characteristic Size On Its Resistance Characteristics Based On Fluent Numerical Simulation

Circulating fluidized bed boilers have been widely used in China due to their high combustion efficiency,wide fuel adaptability and excellent environmental performance.The air distribution system is an important component of a circulating fluidized bed boiler,and its function is to achieve fluidized combustion of the fuel in the furnace.The nozzle is a key component of the air distribution system,which ensures that the primary wind has appropriate resistance when entering the fluidized bed boiler to obtain a more uniform air distribution effect,ensuring safe,stable and economic operation of the circulating fluidized bed boiler.It is of great significance to carry out in-depth research on the factors affecting the resistance characteristics of the nozzle.In view of the influencing factors of the resistance characteristics of the bell-type nozzle,a 300MW circulating fluidized bed boiler bell-type nozzle in a power plant in Xinjiang was used as a prototype.Based on the Fluent numerical simulation software,single variable model with three characteristic size of outlet pore thickness,annulus width and inner core orifice diameter was built.From the perspective of the internal flow field,the influence of feature size on the resistance characteristics is deeply explored,and guiding opinions for the structural optimization of the hood are proposed.Studies have shown that the diameter of the inner core tube has a significant influence on the resistance characteristics,and a small dimensional change will cause a large change in the drag coefficient.The influence of the annulus width on the resistance is mainly reflected in the limitation of the outflow of the inner core tube orifice and the influence of the inlet angle of the vent cap and the concentration of the watershed.The thickness of the outlet of the hood has little effect on the drag coefficient,the main influence is the limitation on the outflow angle and the control of the recirculation.As the thickness increases,the limiting effect on the outflow direction is enhanced.In actual production,the hood characteristic size parameters can be adjusted and optimized according to specific resistance requirements.