Low-pressure drop size distribution characterization of impact sprinkler jet nozzles with and without aeration

Abstract

Impact sprinkler (20PY2 IS) outlet is a single-phase water flow, and the aeration impact sprinkler (20PY2 AIS) outlet is gas-liquid two-phase flow. The jet dispersing principle of AIS is somewhat different from conventional sprinklers and has advantages and the ability to working well at the low-pressure condition. The experimental study on the droplet size distribution of IS and AIS was carried out by the volume-weighted method to analyze the mean diameter (Dv), median diameter(D50), water droplets frequency distribution, and the cumulative frequency at different distances from sprinklers. Similarly, the velocity of the drop was measured by Laser Precipitation Monitor (LPM) and statically analyzed by using a number-weighted method. The results showed that both the drop diameters Dv and D50 increased with the distance from the sprinkler nozzle but decreased with an increase in the working pressure. Similarly, droplet frequency distribution at a diameter < 3.5 mm of both sprinklers increased with the working pressure. The quantity of larger droplets decreased with an increase in working pressure, and this trend amplified with an increase in the distance from the sprinkler nozzle. Under low-pressure (0.15 MPa, 0.2 MPa, and 0.25 MPa) and the absence of wind conditions, the droplet distribution of the AIS was more uniform and constant than the IS. The droplet's frequency distribution of AIS and IS nozzles was conformed to a logarithmic normal distribution. With the distance from the sprinkler increasing, the slope of the droplet cumulative frequency curve decreased gradually. Under the same pressure and at similar distances from the nozzle, the (D50) of the 20PY2IS was less than the 20PY2AIS, and the functional relationship between median diameter, working pressure, and distance from the sprinkler was established. When the pressure was set at 0.15 MPa and 10 m away from the sprinkler, the droplet's median diameter was 6% higher under AIS than under IS. At the working pressure of 0.25 MPa, the frequency distribution of water droplets under both nozzles was higher, and water droplets are more frequent for a different distance from a sprinkler. Droplet velocity was improved with the decreasing droplet diameter, but due to low pressure, there was not significantly influenced in velocity. The results may deliver a basis for additional efficient exploration of the AIS.