Needle‐shaped water dispersion devices (NSWDDs) can break the jet and make the sprinkler spray evenly even under low working pressure. However, an inappropriate selection of the depth at which the NSWDD is inserted into the jet will affect the sprinkler pattern radius. To study the effect of the NSWDD insertion depth on the jet breakup, the jet structure, atomization, vorticity, static pressure and velocity distribution are studied using a combination of the lattice Boltzmann method and high‐speed photography. The results show that as the insertion depth increases, the jet structures gradually evolve from liquid films to ligaments, causing the diffusion angle of the jet to increase. Under the same operating pressure, the degree of jet atomization increases with increasing insertion depth. Meanwhile, the velocity pulsation degree on the central axis gradually increases, which will cause the jet to have a shorter air travelling distance. As the insertion depth and the radial position distance from the nozzle outlet increase, the velocity on the radial line first exhibits a symmetrical distribution, then an asymmetric one and finally a symmetric one again. The results can fill the gap in previous research on the effects of the NSWDD on jet breakup.

Improving water distribution uniformity is crucial for the development of high‐performance irrigation sprinklers, and the diffuser's tooth length greatly influences water distribution. Five diffusers with varying tooth I lengths were designed and researched. The expressions for the force acting on tooth I, the hydraulic performance of the sprinkler and the combination uniformity were obtained analytically and experimentally. The results showed that the tooth I force is affected by the working pressure, the ratio between the plate outlet area and the riser pipe flow area, tooth width, entry water depth, trajectory angle and tooth I slope surface angle. Moreover, the components of the tooth I force acting in the vertical, radial and circumferential directions increase with the tooth I length and working pressure. The necessary condition for normal diffuser operation is that the force in the aforementioned three directions should be greater than 0.37, 0.57 and 0.28 N, respectively. Furthermore, when the working pressure is increased by 50 kPa, hereby reducing the rotation time by 10 min and the tooth I length by 1 mm, its water distribution and combination uniformity are optimal. This study provides a basis for designing and operating diffusers and improving sprinkler hydraulic performance.

To improve the performance of sprinklers that work under low pressure, a new type of automatic rotating sprinkler equipped with different water dispersion devices was designed and the jet diffusion angle and hydraulic performance of the new and original sprinklers were compared using experimental methods. The results indicate that, when the working pressure is below 200 kPa, the jet diffusion angle of the new sprinkler with the water dispersion device B is the largest. Although the pattern radius of the new sprinkler is slightly lower than that of the original, it is more effective in improving the combined coefficient of uniformity (CU) at lower working pressures. Specifically, when the working pressure was 100 kPa, the new sprinkler with the water dispersion device B, which has a square inner hole with a side length of 6.2 mm, improved the CU by 54.89% on average. Remarkably, the CU of the new sprinkler with water dispersion device B at a working pressure of 100 kPa was 6.65% higher than that of the original sprinkler at a working pressure of 200 kPa. The research results provide valuable insights into the design of sprinklers to improve the performance of low-pressure sprinkler irrigation systems.