Design And Research Of Cavitation Jet Nozzle With Rotating Impeller

As an emerging technology,the cavitation jet technology is widely used in the field of wastewater treatment.It has the advantages of simple operation,environmental protection and energy saving,and low cost of use and so on.As the core component of the cavitation jet system,the design level of the nozzle directly determines the effect of the cavitation jet in the treatment of wastewater.At present,the cavitation nozzle has the problem of low cavitation rate in the wastewater treatment process,which leads to the unsatisfactory result of the cavitation jet on the wastewater treatment.Therefore,improving the nozzle cavitation rate is the primary problem that needs to be solved.In order to solve the problems,this topic has studied the structural characteristics of the cavitation nozzle and completed the Cavitation jet nozzle with rotating impeller(CJNWRI)structure design.The main research contents of this topic are:The theoretical analysis of CJNWRI is carried out.Based on relative coordinate system,fluid is regarded as ideal,fluid flow is regarded as steady flow and adiabatic flow,the mathematical model of internal flow field of CJNWRI is established,and the velocity and pressure functions of impeller and outlet section are obtained,which lays a theoretical foundation for the design of CJNWRI.Combining the fluid network theory with the empirical formula,the structure size of CJNWRI is preliminarily determined.The model construction,structure optimization and simulation analysis of CJNWRI are completed.Firstly,the numerical simulation of CJNWRI structure parameters combination level is carried out based on orthogonal experiment,and the maximum void fraction of flow field under different combination levels is obtained.Then the range analysis method is used to process the results,and the optimal CJNWRI structure size is obtained.Then,the internal flow field of CJNWRI with the optimal size was simulated by FLUENT software,and the air holdup distribution,velocity and pressure nephogram of the flow field in the nozzle were obtained.The cavitation area and cavitation effect were defined,and the rationality of CJNWRI was demonstrated.Finally,in order to optimize the boundary conditions,the effects of impeller rotation speed,blade number and inlet pressure on the cavitation performance of CJNWRI were studied,and the optimal rotation speed and blade number were 1000 rpm and 5 pieces respectively;When the inlet pressure is below 0.8MPa,the cavitation performance is proportional to the inlet pressure.The experiment of CJNWRI is carried out,and the theoretical analysis and simulation calculation results are verified.The data acquisition instrument and the pressure sensor are combined to build an experimental operation platform for experimental research.The experiment process is mainly divided into two parts.In the first part,the impact force and optimal target distance of CJNWRI and angular cavitation nozzle are measured.The results show that when the inlet pressure is 0.6MPa,the maximum impact force of the cavitation jet produced by CJNWRI is 14.4768 N,and the maximum impact force produced by the angular cavitation nozzle is 12.3432 N.The former is significantly higher than the latter.and the optimal target distance of the former is about 20 mm larger than the latter.In the second part,the impact force and optimal target distance of CJNWRI are obtained by changing the inlet pressure.The results show that the impact force and optimal target distance increase with the increase of pressure.The design and research of CJNWRI in this subject not only improves the cavitation rate produced by the cavitation nozzle,but also has far-reaching significance for the application of cavitation jets in wastewater treatment.