Fundamental Study on Pest Control Systems by High Pressure Type Sprinkler in the Orchard (3)

Effect of Nozzle Loss on Water Jet and Coverage Property of Water Jet

Abstract

1. A loss coefficient of a solid cone nozzle for the high pressure type sprinkler became greater according to the increase of Re Number in the range under Re_c and it had a peak near Re_c. ζ_n was considerably affected by the contraction angle δ of a nozzle; namely ζ_n became less against the nozzle that δ was smaller regardless of the nozzle diameter. Considering an aspect ratio, when D_n was less than 2mm, ζ_n became smaller for the nozzle without cylindrical part because the pressure loss was caused by the swirl at this part of the nozzle, but when D_n was bigger than 3mm, ζ_n became greater for the nozzle with cylindrical part.
2. Accompanied air velocity u_a by water jet stream was approximately expressed by a normal distribution, and the air velocity on the axis of water jet stream was shown by 2 kinds of exponential curves. A length of jet stream core was not varied by the difference of ejected pressure for the nozzle that D_n=1mm, but it extended with the increase of ejected pressure against D_n=2mm.
3. When a nozzle was fixed as the ejected angle became 12°, the maximum coverage distance L_m of droplet became greater with the increase of ejected pressure for the nozzle that D_n=2, 3mm, but L_m became less for D_n=1mm. Also, when D_n were 2 and 3mm, L_m/D_n was expressed by the function of Re Number and when D_n was 1mm, it was expressed as the function of Re Number and ζ_n.
4. The trajectory of a droplet which arrived at L_m point was simulated very well under the usage of u_a measured by the experiment. It became clear by another simulation that the coverage property was not hardly influenced by the rotation of the high pressure type sprinkler.