Investigation On Spray Characteristics Of Swirling Solid Nozzle

The centrifugal nozzle is often used as the dispensing device for the falling film evaporation device of seawater desalination.The spray uniformity will directly affect the thermal characteristics of the droplets after the film formation,then determine the thermal efficiency and stability of the whole evaporation device.In this paper,the internal flow field and external spray characteristics of the centrifugal nozzle with a groove channel at the top section are studied.The spray density distribution of the single-nozzle and multi-nozzle interference spray are reasonably analyzed combined with internal flow field,The research contents are as follows(1)By VOF method the internal flow field characteristics of centrifugal nozzle is studied,the filling process and stable process of fluid flow in the nozzle are analyzed.The tangential velocity get improved in swirl chamber,axial velocity get improved in convergent section and straight pipe section,and the divergent section greatly improve the radial velocity of the fluid.The influence of flow channel to the nozzle internal flow field is analyzed,which is of certain guiding significance for the optimization and transformation of centrifugal nozzle;(2)The spray density of single centrifugal nozzle was studied by experiments.Combining with the internal structure of the nozzle,the influences of inlet pressure and spray height on the external spray characteristics were analyzed.The experimental results show that the spray area of centrifugal nozzle is irregular circle,the spray density is small in the central and marginal areas and large between two areas.Proper increase of nozzle inlet pressure and spray height is conducive to droplet crushing and diffusion,The proportion of spray density stable area in the whole spray area is greatly increased,and the uniformity of spray density is improved;(3)Based on the optimal spray height of single nozzle obtained,the four nozzles are arranged according to the principle of "peak and valley superposition",and the interference spray density distribution is obtained by changing inlet pressure and interference distance.The results show that the interference spray improve the spray density distribution,the spray density uniformity is further improved by adjusting the inlet pressure and interference distance,which provides some theoretical guidance for improving the distribution uniformity of horizontal tube falling film evaporator.