Numerical Simulation Of Vortex Distribution And Combustion Characteristics In A Square Box Type Furnace

With the development of large-scale petrochemical industry,the square box type heating furnace has been widely used.At the same time,the flow field,heat transfer and combustion characteristics in the square box furnace have become an important research focus in the petrochemical industry to reduce energy consumption and emissions.In the current literature,the research on combustion and heat transfer in the radiation chamber of large-scale tubular heating furnace in petrochemical industry has some foundation,but the research on the influence of eddy current distribution on combustion and heat transfer in the internal flow field after the radiation chamber is large-scale has not been reported.In this paper,the numerical simulation method is mainly used to analyze the vortex distribution characteristics in the radiation chamber of the large square box furnace and its influence on combustion and heat transfer,which has important theoretical reference for the development of energy saving and emission reduction technology of the tube furnace.In this paper,first of all,the numerical simulation method is used to study systematically the characteristics of vortex distribution and the influence of combustion characteristics in the radiation chamber of the square box furnace,and the results are compared with the actual operation data.The two data are close to each other,which verifies the reliability of the calculation model and method.In this paper,the operating conditions and burner structure of a single combustion unit are compared,and the effects of operating conditions and burner structure parameters on the vortex distribution and the combustion characteristics of the furnace during combustion are analyzed.The results show that when the excess air coefficient is 1.15 and the air preheating temperature is 500 K,the vortex distribution in the furnace is more stable and the range of action is wider,and the temperature distribution in the furnace is more conducive to heat transfer.When the diameter of the nozzle is 4mm and 6mm,the vortex action range in the furnace is wider,but the radiation heat transfer is not ideal due to the lower temperature;when the diameter of the nozzle is 5mm,although the distribution of the vortex in the furnace is uneven,the radiation heat transfer effect is better due to the higher temperature.When the nozzle angle increases to 55 °,there is almost no vortex in the middle and upper part of the furnace,and the heat transfer performance in the furnace is the worst.By adjusting the operating conditions and selecting the appropriate burner structure parameters,the vortex can be controlled stably distributed near the furnace wall,which is conducive to the heat transfer process in the furnace.Based on the research of single combustion unit,a three-dimensional full-scale geometric model of square box type heating furnace is built,and the numerical calculation is carried out with the verified model and parameters.The results show that the vortex is always present in the combustion process of the furnace,and new smoke vortices are generated along with the flame combustion,which promote the formed vortices to spread to the whole furnace gradually,until the combustion tends to be stable,a relatively stable symmetrical vortices distribution is formed above the furnace.Affected by the vortex disturbance,the high-temperature flue gas is concentrated in the vortex distribution range and diffuses outwards with the vortex as the center.Due to the "?" arrangement of furnace tubes,which plays a role of isolation,the combustion in each unit furnace is relatively independent and the results are symmetrical.