| The atomization process of dual medium nozzle is a way to atomize the liquid column or liquid film of liquid working medium with the help of high-speed air flow such as air or steam,which can make the liquid rupture more thoroughly,so as to obtain higher atomization quality than single-phase spray atomization.Recently,due to the higher requirements for atomization quality in many industries,the traditional single-phase spray atomizer is not competent.Therefore,dual medium nozzle atomization has been widely used and promoted in many fields such as petroleum,chemical industry,electric power,tobacco and so on.In this paper,using the method of numerical simulation,taking the dual medium nozzle of steam working medium as the research object,by constructing the two-phase continuous phase flow field and DPM discrete state two-way coupling numerical model,the effects of different steam inlet pressure,different liquid flow and different dual medium nozzle structure on the aerodynamic performance and particle size characteristics of nozzle atomization are studied.The results show that:In the continuous phase flow field of dual medium nozzle,with the increase of steam pressure,the maximum flow velocity has little difference,ranging from1010m/s to 1100m/s,but the range of high-speed area increases slightly,the atomization diffusion angle decreases,and the injection distance increases slightly;With the increase of liquid flow rate,the maximum velocity changes greatly.When the flow rate of organic liquid becomes 0.01kg/s,the maximum velocity is about800m/s,while when the flow rate of organic liquid becomes 0.05kg/s,the maximum velocity is about 1100m/s.The difference between them is about 40%.The spraying distance increases and the atomization diffusion angle increases;Changing the structural parameters of the dual medium nozzle has a great impact on the flow field,and the maximum flow rate varies between 900m/s and 1100m/s.through the comparative analysis of the vapor-liquid flow area between the structures,it is obtained that the size of the organic liquid injection distance is mainly affected by the flow area of the liquid path.The larger the flow area of the liquid path,the spray distance decreases accordingly,and the atomization diffusion angle of the organic liquid is mainly affected by the flow area of the gas path.The larger the flow area,the larger the atomization diffusion angle.When discrete droplet particles are added into the continuous phase flow field,with the increase of steam pressure,the Sauter average diameter of droplet particles as a whole gradually decreases,and the median particle size of particles changes little,all of which are 0.93μm～0.98μm,There is no obvious change in particle size uniformity;The Sauter average diameter of droplet particles is the smallest when the organic liquid flow rate is 0.0375kg/s.With the increase of liquid flow rate,the atomization particle size uniformity becomes better,but when the organic liquid flow rate increases to 0.0375kg/s,the atomization particle size uniformity has reached a better level;The dual medium nozzle structure has a great influence on the atomization characteristics.Under structure 2(the central tube retreats 2mm and the needle valve retreats 10mm),the Sauter average diameter of droplet particles is the smallest,the median diameter is the smallest and the particle uniformity is the best.Through the analysis of the change of gas-liquid flow area of each structure,it is concluded that if it is necessary to obtain a better atomization effect,It is necessary to ensure a small flow area of the steam path(the position of the central pipe is not easy to move backward too much when the steam and liquid paths are kept fully closed),and at the same time,the liquid path side needs to maintain a normal opening(the position of the needle valve is not easy to move backward too little when the gas and liquid paths are kept fully closed,and it is appropriate to move backward about 10mm). |
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