| The swirl nozzle is widely used as a liquid distributor in the horizontal tube falling film evaporator.The flow and uniformity of the liquid distribution will directly affect the falling film effect and heat transfer efficiency.In this paper,the flow field characteristics of a new type of swirl nozzle with a spiral guide structure on the top are studied.This paper studies the flow field characteristics of a new type of swirl nozzle with a spiral guide structure on the top.Through a combination of numerical simulation and experimental research,the characteristics of the internal and external flow field distribution of single-nozzle spray and the influencing factors of four-nozzle interference spray are analyzed.With the help of Fluent software,the VOF multiphase flow model and the Realizable k-εturbulence model are selected to simulate the spray process of the swirl nozzle under stable spray conditions.And the distribution law of the velocity field and pressure field in the spray area is obtained.Under stable spray conditions,the water moves in a swirling motion close to the wall of the swirling chamber,and the external air at the center of the swirling chamber flows back into the swirling chamber from the outlet to form an air column.The shape of the air column is affected by the spiral guide structure.The top is thinner and tends to the side with the smaller space volume,and the bottom is thicker and the degree of eccentricity is smaller.The surface of the air column is convex with the same direction of rotation.The effective spray area of the external flow field appears as a hollow ring.There are two peaks in the circumferential spray density,which are located near 30° and 210°.Increasing the inlet velocity will cause the deterioration of the circumferential spray uniformity.The influence of the area is small.Under the same inlet conditions,the spray uniformity of the spiral nozzle is better than that of the optimized prototype cone nozzle.Based on the flow field distribution characteristics of a single nozzle,a four-nozzle interference spray experiment was carried out to analyze the influence of inlet pressure,interference distance,and spray height on interference spray.The collision of the droplets will cause fusion,oscillation and fragmentation,and the size of the droplets will be reduced,making the effect of air resistance greater than the inertial force and changing the falling position.Increasing the inlet pressure can increase the speed of droplets,shorten the distance of liquid film breaking,accelerate the process of droplet breaking,and facilitate interference.However,excessive inlet pressure will cause a large number of droplets to accumulate in the center.The interference distance determines the overlap range of the effective spray area.Keeping the interference area under the spray coverage of the four nozzles can increase the probability and frequency of droplet collisions.Spray height affects spray range and droplet size.However,when the spray height is too low,the degree of droplet fragmentation is low,and the droplet collision frequency is too high,and it is difficult for the droplets to pass through the interference center to cover the entire spray area.Under the same interference conditions,the interference spray effect of spiral nozzles is better than that of truncated cone nozzles. |
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