Abstract: [Objective] In view of the deficiencies that spray droplets were wider in flat-fan nozzle of plant protection machinery, and particle size uniformity were insufficient, a new type of nozzle structure based on the coupling of jet and impinging jets was proposed to improve the spray droplet size uniformity and the droplet spectrum.[Method] Using photosensitive liquid phase curing molding process of rapid prototyping manufacturing technology and C-UV9400 stereoscopic light modeling resin material, the flat-fan nozzle and impinging nozzle were produced which had the same exit shape, exit diameter(d₁=1 mm) and groove angle(α=30°). The droplet size and droplet distribution of the two kinds of nozzles were obtained according to the test system for atomizing performance of nozzle, and the uniformity of the particle size was evaluated in terms of the international criteria for distribution span.[Result] At the position 100 mm away from the nozzle exit, when the spraying pressure changed within the range of 0.3-0.8 MPa, it was found that the S value of the distribution span of flat-fan nozzle and impinging nozzle were respectively between 1.65-1.82 and 1.07-1.23, in which the smaller S value stands for better uniform and narrower spectrum, and the spraying performance test system showed that the droplet were more concentrated; the droplet size of flat-fan nozzle tended to be stable when the spraying pressure was greater than 0.6 MPa, and the droplet size of impinging nozzle decreased with the increase of spraying pressure, which indicated that the impinging nozzle had a variable pressure regulating performance with wide pressure regulating range; large droplets will be formed after impact, and larger droplets with a certain speed had better penetration performance and anti-drift ability. Besides, a multiple regression model of droplet size was established to provide a basis for selecting nozzle to achieve a better pest control.[Conclusion] The impinging nozzle based on the coupling of jet and impinging jets had the characteristics of improving particle size uniformity, narrow droplet spectrum, wide range of pressure regulation and better anti-drift ability. It can provide technical support for developing precision sprayer.

Key words: impinging nozzle, impinging jets, droplet size, particle size uniformity, pressure regulating performance