The Flow Pattern And Pressure Transient Characteristics Of Regenerative Annular Furnace At Cold State

For an innovative application of HTAC (High Temperature Air Combustion) technology at annular furnace, an experimental investigation was performed about the flow pattern of the furnace and the transient and steady characteristics of the pressure of the annular furnace. Air was used as modeling medium. According to the theory of modeling, natural gas was used as indicator to simulate the distribution of flue gas in furnace. All the results provide parameters for designers to guarantee safe operation and optimal designing of the furnace.The results of the flow field experiment show that the airflow from the burner nozzle formed a vortex in the furnace; the airflow is apt to get to the opposite wall and then be sucked from the opposite burner if the flow rate gets higher. But it would not happen at the first opposite burner. With different flow rate, it usually happened at the second or the third burner. Furthermore, among all the three heating zones, closer to the holding zone, harder the flue gas can be sucked by the opposite burner. It indicated that the flue gas from holding zone could not reach to the furnace tail. However, most of the flue gas from the front heating zone were sucked by the behind ones. So it could prolong the time of the gas staying in the furnace. It is helpful for the gas complete combustion at high temperature.From the smoke tracing experimental results of the furnace, the gas in the furnace flows clockwise from the holding zone to the first heating zone, and then to the tail. In this process, the velocity of the mainstream gets higher gradually. It is helpful for the new steel billet to get a good condition of convection heat transfer. And this flow pattern can form a good temperature field for the countercurrent heating condition.From the burner nozzle to the smoke vent, the velocity profiles of flue gas change fast, the fuel and the air can not fill up all of zones near the nozzle. Farther to the burner nozzle, more gently the velocity profiles in the section of the area is,. At the same time, there is a vortex in each side of the nozzle, and the gas velocity in the vortex is very slow. The velocity distribution at the main working zones of the furnace is quite even. It is good to form a steady temperature field and pressure field.According to the distribution of the natural gas in the furnace, the velocity of the mixed gas in the first heating zone is higher than the third heating zone, and the gas is better-mixer in the first heating zone. The concentration of natural gas near the inlet nozzle is higher than other zones. In the mainstream area, the distribution of the natural gas is gentler than the inlet zones. The natural gas and the air are mixed very well. All of these are favorable to combustion and to form a steady temperature field in the furnace. However, there is a little natural gas near the opposite smoke vent. It indicates that there will not be a lot of fuel gas getting into the regenerator to form post combustion which will waste the fuel and destroy the regenerator. Due to the upstream inflow, the concentration of the natural gas is diluted. The downstream fuel becomes difficult tracing. It is bad for the flame structure. It can be settled by enforce the flame rigidity of the downstream burners.