| The use of chemical pesticides makes environmental problems more and more serious,and some of them even threaten food security.With the improvement of people’s awareness of environmental protection and health,microbial pesticides are becoming more and more important as a substitute of chemical pesticides.However,due to the lack of special spraying technology and equipment,the application of microbial pesticides is limited at present.At present,conventional spray nozzle can be used for microbial pesticide spraying cone fog and fan fog.Compared with conical spray nozzle,fan-shaped spray nozzle has the advantage of a larger spraying range,but it often has a greater impact on microbial activity after spraying.In order to ensure the activity of microbial spraying,this paper studied a kind of external mixing dual-fluid nozzle for spraying microbial pesticides.The nozzle mouth structure is similar to that of the standard fan-shaped spray nozzle,and the spray type is also plane fan-shaped,but it has little influence on microbial activity during spraying.The study of two kinds of liquid atomization mechanism indicates that the two-fluid fanshaped spray nozzle can be divided into small droplets to achieve atomization effect when there is a certain velocity difference between pesticide and high-pressure water.In this paper,the model of the external mixing dual-fluid nozzle is modeled,and the atomization numerical simulation is carried out,and the atomization characteristics are evaluated by the fog type and distributed concentration.The viscosity energy dissipation rate was used as the evaluation standard and basis to judge the degree of microbial damage caused by fluid.The flow field under different boundary conditions was simulated and compared with the conventional fan fog nozzle.The results showed that the hydrodynamic spray nozzle was similar to the conventional fan-shaped spray nozzle,but the extreme value of the viscosity energy dissipation rate was far less than the extreme value of biological damage,which was more suitable for the spraying of microbial pesticides,effectively ensuring the biological activity of microbial pesticides,and higher microbial survival rate.Based on the simulation results,the optimal nozzle parameters for microbial spraying are found out.In this paper,the activity of microbial pesticides after spraying was tested and verified.Based on the survival rate of microorganisms after spraying(V%),the difference of microbial activity between two spray heads was compared.The results showed that dual-fluid fan-shaped spray heads could effectively reduce the mortality rate of microorganisms.At the same time,the spray characteristics of the two-fluid fan-shaped spray nozzle were tested.The spray distribution and its uniformity were evaluated by coefficient of variance(CV),standard deviation(σ)and coefficient of variation(α).The results show that the two-fluid spray nozzle can have good spray characteristics under appropriate pressure.In a word,this article is based on the fog and droplets distribution,as well as the influence on the activity of microbial pesticide double-fluid was studied in vitro mixed sprayer,the simulation and experimental results indicate that can use it instead of the conventional fan-shaped fog spray nozzle,and reduce the mortality of microbes in the nozzle,improve performance of the spray nozzle,improve pesticide effect,improve the efficiency of microbial pesticide spraying,It has certain significance to the environment and human health. |
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