Investigation Of Aeration-impact Sprinklers For Improved Water Distribution In Low Pressure Sprinkler Irrigation

In light of global warming,population growth,and water scarcity,sprinkler irrigation systems with water-and energy-saving characteristics have gained increasing popularity in agriculture.The sprinkler head plays a critical role in such systems,and the impact sprinkler(IS)is particularly susceptible to changes in operating pressure,which can significantly affect its irrigation performance.To address this issue,a novel aeration-impact sprinkler(AIS)was developed and evaluated in this study.The research employed the orthogonal test method to analyze the size influence on suction capacity of the AIS.Indoor and outdoor experiments were conducted to compare the irrigation performances of the IS and AIS,specifically under low operating pressure conditions.A water distribution calculation model was established to study the combined sprinkler irrigation performance,and its predicted values were compared with experimental results.Additionally,a laser raindrop spectrometer was used to measure the sprinkler drop size distribution,while a model predicting the wind drift of droplets was developed.The study also investigated the jet breakup mechanism of the liquid-gas two-phase jet flow using high-speed photography techniques.The main findings and conclusions of the research are as follows:(1)The study proposed a liquid-gas two-phase jet flow and examined the factors influencing the sprinkler’s suction capacity.By coaxially installing a suction pipe within the impact sprinkler tube,the research identified the most important factors affecting the suction capability,including operating pressure,inner diameter of the suction pipe,displacement of the suction pipe,convergent angle of the nozzle,and diameter of the nozzle.The optimal location for the outlet of the suction pipe was found to be 2 mm exterior from the nozzle outlet.These findings provide valuable insights for the practical application of AIS technology in sprinkler irrigation systems.(2)A combined sprinkler irrigation field test was conducted to verify the performance of the AIS under low operating pressure conditions.The study compared water loss,coefficient of uniformity(CU),and distribution uniformity(DU)between the IS and AIS.The AIS demonstrated a higher CU than the IS,enabling it to reach the specified value in the IS standard under low operating pressure.The study also established the consistency between field experiment results and simulation values,with the simulated coefficient of uniformity showing a high degree of agreement with experimental data.The aeration method in the sprinkler water jet was concluded to be a feasible solution for reducing operating pressure.(3)The study investigated the irrigation performance difference between the IS and AIS by studying water droplets.Using the volume-weighted method,the research examined droplet size distribution produced by the two sprinklers and found that the AIS displayed more consistent droplet dispersion under varying pressure levels in windless conditions.The study also observed changes in droplet frequency distribution and median diameter with distance from the sprinkler and operating pressure.The low-pressure,constant droplet size distribution of the AIS makes it preferable for irrigation purposes.(4)A simulation was conducted to quantify and characterize the dynamics of wind drift of inflight droplets.The study revealed that droplet size,initial velocity,wind speed,nozzle height,and wind direction were primary factors affecting droplet drift.The research proposed Cumulative number distribution(CNF)and cumulative volume distribution(CVF)curves,which provided insights into droplet behavior.Drift losses were reported under different pressure and wind conditions,and the simulation results were highly similar to the experimental observations.(5)The influence of riser height on sprinkler performance was investigated in field experiments.The research examined the effects of riser height and nozzle type on various sprinkler characteristics.It was found that an 8.3 mm aeration nozzle coupled with a 7 mm impact sprinkler exhibited superior performance across different riser heights,demonstrating higher rotational speeds and application rates.The aeration sprinkler nozzle also offered more uniform water distribution compared to the impact sprinkler nozzle.(6)The jet breakup characteristics of the IS and AIS were compared and studied using highspeed photography and image processing techniques.The research found that the aeration nozzle had advantages over the original impact nozzle,including lower jet breakup lengths and higher degrees of breakup.An empirical formula was derived to predict the breakup length and range of the jet under varying pressures.In summary,the research findings provide valuable insights into the performance and benefits of the novel aeration-impact sprinkler(AIS)compared to the traditional impact sprinkler(IS).These findings contribute to the practical application of AIS technology in sprinkler irrigation systems,aiming to address the challenges posed by global warming,population growth,and water scarcity.