Research On The Influence Of The Inner Surface Structure Of The Nozzle On Jet Cavitation Characteristics

The cavitation water jet cleaning technology has the characteristics of good cleaning quality,fast cleaning speed,no environmental pollution and almost no corrosion to the cleaning material.At present,it has been widely applied in coal mining,oil drilling and ship cleaning.As it is the place where jet cavitation occurs,the structure of the nozzle directly affects the cleaning effect.In this paper,the inner surface structure of the cavitation nozzle was selected as the research object.Based on the theory of cavitation dynamics,fluid mechanics and tribology,by using the theoretical analysis,numerical simulation and experiment method,the action mechanism of the inner surface structure of the cavitation nozzle on the cavitation process was deeply analyzed.Firstly,the characteristics,mechanism of production and development status of cavitation water jet technology were introduced,and the application and importance of cavitation water jet technology in the field of ship cleaning are emphasized.Then the research made by scholars at home and abroad in the field of cavitation water jet was also briefly reviewed.After that,the significance of the research and the content of the research were expounded.Secondly,the physical model of the convergent cavitation nozzle was built,then,the nozzle internal flow field were analyzed by using the computational fluid dynamics method and FLUENT software,in the process of numerical,the calculation mixture multiphase flow model and k-ε turbulence model were selected.After that,the configuration position of the inner surface of the convergent cavitation nozzle was determined.According to the surface structure configuration method,the configuration of the inner surface of the convergent nozzle was constructed.By changing the location,the spacing,the amount and the size of the bulge respectively in the process of simulation,the influence of the inner surface structure of the nozzle on cavitation characteristics was analyzed from many aspects.Thirdly,based on the bubble dynamics,and according to the Rayleigh equation,the effect of pressure fluctuation caused by the surface structure on the growth and collapse of the cavitation bubble was analyzed by using the method of numerical calculation.And then,the evolution rule of the cavitation bubble near the different bulge configurations was obtained.Next,numerical simulation method was applied to the study on the structure optimization of the inner surface of the nozzle,according to the order that the type design of the bulge configuration at first,and then the size design of the bulge configuration,the shape design of the bulge configuration at last.Then,a design rule of structural configuration for accelerating nozzle cavitation was preliminarily put forward.The best structural configuration of cavitation was obtained under given working conditions.Finally,the cavitation nozzles with different internal surface roughness were designed and processed for the experiment.The performance of the cavitation water jet was indirectly evaluated by the erosion effect using the “standard specimen erosion method”.The results show that the cavitation performance of the cavitation nozzle increases with the increase of the roughness of the inner surface within a certain range.it proves that the cavitation performance of the cavitation nozzle can be optimized by changing the inner surface structure.