Comparison of droplet size distribution experiments between complete fluidic sprinkler and impact sprinkler

Abstract: Sprinkler is the key equipment of sprinkler irrigation system. The hydraulic performance of sprinkler is directly influenced by the quality and efficiency of irrigation. The fluid at the impact sprinkler (PY) outlet is single-phase water, and that at the complete fluidic sprinkler (PXH) outlet is gas-liquid two-phase flow. In order to explore the distribution regularity and difference of the 2 types of sprinkler droplets, based on the laser raindrop spectrometer measuring technique (laser precipitation monitor, LPM), the experimental study on droplet size distribution of PY and PXH sprinkler was carried out, and the volume weighted method was used to analyze the water droplets frequency distribution, cumulative frequency and medium diameter variation at different distances from sprinklers. The working pressures were 150, 200, 250, 300 and 350 kPa, respectively. The results showed that the droplets frequency of the PXH sprinkler was generally less than the PY sprinkler, and the droplet distribution range of PXH sprinkler was wider than the PY sprinkler under different pressures. Under the low pressure conditions, the droplet distribution of PXH sprinkler was more continuous and uniform. The droplets frequency distribution of PXH and PY sprinkler conformed to logarithmic normal distribution and normal distribution respectively. With the distance from the sprinkler increasing, the slope of the droplet cumulative frequency curve decreased gradually. With the working pressure increasing, the slope of the droplet cumulative frequency curve at different distance from the sprinkler decreased gradually, and the droplet cumulative frequency variation for the PXH sprinkler was more uniform. The droplet cumulative frequency distribution of the 2 kinds of sprinklers conformed to the index function distribution, and when the distance from sprinkler was short, the fitting accuracy of the PXH sprinkler was higher than the PY sprinkler. At the distance of 2 and 4 m from the sprinkler, the correlation coefficients of the fitting function of the PXH sprinkler were respectively 0.9% and 3.5% higher than the PY sprinkler. At the distance of 6 and 8 m from the sprinkler, the correlation coefficients of fitting function of the PY sprinkler were respectively 3.3% and 1.2% higher than the PXH sprinkler. The median diameter increased with the distance from the sprinkler, and the median diameter decreased with the increasing of the working pressure. Under the same working pressure, with the distance from the sprinkler increasing, the increase percentage of the droplet median diameter for the PXH and PY sprinkler gradually became larger. Under the same pressure and the same position, the droplet median diameter of the PY sprinkler was less than the PXH sprinkler. The function of the relationship between median diameter, working pressure and distance from the sprinkler was established. Under the condition of 150 kPa and 7 m far from the sprinkler, the median diameter of PXH sprinkler was 66.2% higher than the PY sprinkler. Under the condition of low pressure, the droplet size distribution of the PXH sprinkler was more continuous and uniform at different distances from the nozzle, which was conducive to water crops and make the force uniformly distributed. The results provide the reference for the study of the jet motion model and the external spraying characteristics.