Numerical Simulation Study On Jet Characteristics Of Annular Venturi Ejector Group Under Restricted Conditions

Staged combustion and high-intensity flue gas internal circulation are the core technologies for realizing ultra-low nitrogen combustion of natural gas,which can simplify the structure of the denitration system as much as possible,reduce the cost of denitration and reduce greenhouse gas emissions.And the realization of the dual carbon goal is of great significance.Based on the actual structure and heat transfer conditions of a 0.8 MW boiler in a factory,the correlation law between the jet characteristics determined by the burner structure and the circulation characteristics in the flue gas furnace is mainly studied.Based on the double-blocking model theory,a basic calculation model for the annular Venturi injector group was established.Fluent was used to simulate the main jet and backflow characteristics under the combined action of the central rotating jet and the annular Venturi group jet in a confined space to explore the fuel grading and distribution.The effect of ratio,Venturi structure,Venturi group arrangement,and central swirl structure on furnace flow field characteristics（temperature field,velocity field,concentration field）.The research results show that increasing the fuel distribution ratio in the annular jet area can reduce the combustion temperature in the central jet area,use the central combustion flue gas to dilute the O₂concentration on the flame cover,and effectively build the central jet ultra-low nitrogen combustion conditions from the reaction temperature and atmosphere.Too little gas in the area will lead to unstable combustion,so there is an optimal fuel grading ratio;the central jet cyclone has an optimal breaking angle,and the breaking angle is too large or too small,which will lead to the deterioration of the recirculation characteristics in the ignition zone,aggravating the The local high temperature will destroy the combustion stability at the same time;the use of two-stage Venturi ejector can fundamentally strengthen the effect of flue gas return in the low temperature area of the furnace.After the gas classification method is determined,the structure,quantity and overall arrangement of the Venturi ejector are determined.The characteristics of the gas jet itself,the interaction characteristics of the gas jet and the central jet,and the entrainment characteristics of the gas jet to the flue gas in the low temperature region ultimately determine the temperature and O₂concentration level of the annular jet gas combustion flame front;in the Venturi injector structure,Under the good coordination of quantity and overall arrangement,by reasonably strengthening the internal circulation of flue gas,the construction of ultra-low NO_Xcombustion flow field conditions for outer ring gas can be achieved.The use of large-scale fine gas classification and high-intensity flue gas internal circulation synergy technology can achieve low NO_Xcombustion effect below 10mg/Nm³.The nitrogen oxide concentration was reduced by 97.84%.Fig.56;Table 7;Reference 56...