| With the rapid development of waste incineration industry,high-temperature flue gas was produce during incineration process,and directly emission to air is harmful to the environment.Therefore,high-temperature flue gas needs to discharged after the removal of clust by causes the filtration.However,high-temperature flue gas is generally higher than800 ℃,direct filtration and dust removal will cause certain damage to the equipment and affect the service life of the equipment.Therefore,it is very importance to develop an efficiency cooling method to reduce of the outlet temperature.Generally,the high-temperature flue gas needs to be cooled down to 250 ℃.The direct air cooling and indirect cooling method for flue gas can not achieve the goal.Because of its high heat transfer coefficient,wide temperature range and low temperature gradient,spray cooling has broad application prospects in flue gas cooling.Therefore,taking the external mixing air assisted atomizer as the research object,the effects of air supply pressure,atomization water flow rate and spray angle on atomization characteristics including atomized droplet size,droplet concentration and droplet velocity were studied by using ANSYS FLUENT numerical simulation software.Through analyzing the internal flow field of the spray cooler,the purpose further of this research is to improve the cooling efficiency of the high temperature flue gas and provide a theoretical basis for the industrial application of the external mixing air assisted atomizing nozzle.Based on the above diacussions,the main contents of this work are as follows:(1)Aiming at the structure of cooler air assisted atomizing nozzle,the physical model was established,and the mesh was divided by FLUENT MESHING.The numerical model of spray cooling process was established by using turbulence model,heat transfer model,discrete phase model,and component transport model.The corresponding boundary conditions were set up to verify the mesh independence.On this basis,the influence of supply air pressure on the flow field downstream of the nozzle is studied.The results show that the velocity field in the downstream section of the nozzle outlet gradually decreases along the axial direction.According to the streamline diagram,it is found that there exists a recirculation zone where the flue gas enters the cylinder,and the turbulence degree is high,with the totally mixed flue gas and droplets,leading to the benificial effect to the heat transfer of high-temperature flue gas.(2)The influence of nozzle air supply pressure on droplet size,droplet concentration,and droplet velocity in primary and secondary atomization was investigated.The results show that with the increase of air supply pressure,the air flow rate and droplet outlet velocity increase,resulting in the enhancement of the crushing and shearing effect of air on the liquid,the reduction of the average droplet size in the cylinder,the shortening of the jet crushing distance downstream of the nozzle,as well as in the improvement of atomization performance and cooling efficiency.(3)The influence of air pressure,atomization water flow,and spray angle on droplet size and flue gas outlet temperature was studied by response surface methodology.The results show that the droplet size increases with the increase of atomization water flow rate,while the droplet size has no effect on secondly changes with the increase of spray angle.When combined analysis of multiple factors,only the interaction between atomization water flow and spray angle has a significant effect on the temperature of flue gas outlet.The atomized water flow exhibits a higher influence in outlet temperature for the flue gas than that of the air supply pressure,which is greater than that of spray angle. |
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