Flow Characteristics and Hydraulic Performance of a Gun-Type Impact Sprinkler with and without Aeration

Abstract

A water jet aeration method was used to address the problem of high water application rates for rotating impact sprinklers operating at low pressures at the distal end of the wetted radius that cause uneven water distribution. Based on a Jinlong Spray Irrigation Co. model PY20 impact sprinkler, a gas suction component was adopted to form an aeration impact sprinkler. The performance characteristics of the impact sprinkler with and without aeration were compared at operating pressure levels of 200 and 300 kPa. Additional tests on the water jet breakup characteristics of the two impact sprinkler types were conducted using high-speed photography techniques. The initial aeration lengths of the aeration impact sprinkler and two jet breakup lengths of both the aeration impact sprinkler and original impact sprinkler were studied. The experimental results demonstrated that the wetted radii of both impact sprinkler types were nearly the same at the same operating pressure and flow rate. The aeration method increased the water application rate at the midpoint of the wetted radius. At a lower operating pressure of 200 kPa, Christiansen’s uniformity coefficient increased to 68.5% for the aerated sprinkler and from 65.4% for the nonaerated impact sprinkler. The aeration impact sprinkler produced a larger average droplet diameter than that of the original impact sprinkler in the middle of the sprinkler profile, while the average droplet diameter toward the distal end of the profile was smaller. For the aeration impact sprinkler under operating pressure levels of 200 and 300 kPa, the aeration durations were 0.0137 and 0.007 s, and the initial aeration lengths were 7.7 and 8 mm, respectively. The jet breakup lengths were lower for the aeration impact sprinkler than for the original and increased with increasing operating pressure for both sprinkler types. The experimental results proved that the aeration impact sprinkler is not only feasible for agricultural irrigation, but it improves important performance characteristics at low operating pressures compared to a standard impact sprinkler.