| Water-saving irrigation plays an important strategic role in the shortage of water for agricultural production in China.Solar sprinkler irrigation has the advantages of no pollution and no external power supply,which can achieve the effects of energy saving&emission reduction and water-saving irrigation.However,the hydraulic performance of solar sprinkler irrigation system is rare,and the combination of solar energy technology and water-saving irrigation technology is still insufficient,limiting the development of solar sprinkler irrigation system.In this paper,the experimental analysis,theoretical calculation and comprehensive evaluation were used,the hydraulic characteristics of the fixed solar sprinkler irrigation system in different solar intensity range were studied,and the optimal allocation measures of sprinkler in different solar intensity range were proposed.The main research contents and conclusions were as follows:(1)To explore the variation rules between the system spraying hydraulic performance and solar intensity,the solar intensity was taken as the influencing factor,the pump outlet flow rate,pump outlet pressure,wetted radius,water distribution and combination uniformity coefficient of the system were taken as the evaluation indexes,the hydraulic performance experiments were carried out.The results show that,when the solar intensity was between 200 to 900 W/m~2,with the increase of the solar intensity,the pump outlet flow rate and pressure increased exponentially.The wetted radius was stable at about 9.2m,and the combination uniformity coefficient of the system was more than 76%.When the solar intensity was more than 900 W/m~2,the pump outlet flow rate,pressure,wetted radius and water distribution remained invariant,and the combination uniformity coefficient of the system was more than 88%.It can be seen that the fixed solar sprinkler irrigation system can work normally when the solar intensity was more than 200 W/m~2.When the solar intensity was more than 900 W/m~2,the system reached the best working condition.(2)The droplet distribution experiments were carried out under different solar intensity by using Laser Precipitation Monitor.The rules of droplets distribution in fixed solar sprinkler irrigation system were obtained,the measurement and calculation methods of energy conversion efficiency of the system were put forward.The results showed that,1)With the increase of solar intensity,the droplet average diameter at the same distance from the sprinkler becomed smaller,and the range of variation gradually decreased.When the solar intensity was 225.7 W/m~2,the droplet average diameter was the largest.2)With the increase of solar intensity,the droplet average velocity decreased at the same distance from sprinkler,and the distance between the maximum droplet velocity and the sprinkler increased.The larger the solar intensity was,the smaller the maximum droplet velocity was.3)With the increase of solar intensity,first the kinetic energy per unit volume increased,then decreased,and finally tended to be stable after3m of the sprinkler.4)With the increase of droplet average diameter,the average kinetic energy of single droplet increased,and the range of variation gradually decreased;the influence of solar intensity on the average kinetic energy of single droplet was mainly concentrated on the small diameter droplets which were near the sprinkler.5)The fluctuation range of kinetic energy intensity was relatively small when the solar intensity was between 300.8 to 1018.8 W/m~2;when the solar intensity were 225.7 W/m~2and 1145 W/m~2,the variation range of kinetic energy intensity at the end of the range was relatively large and unstable,which was easy to cause soil hardening and form surface runoff.6)The energy conversion efficiency of fixed solar sprinkler irrigation system was between 24.59%to 37.21%.With the increase of solar intensity,first the energy conversion efficiency tended to keep constant,then decreased,and finally keeped constant.When the solar intensity was between 225.7 W/m~2 to 416 W/m~2,the energy conversion efficiency was the highest,the value was about 36%.(3)Five solar intensity ranges were simulated,and the two-dimensional video disdrometer was used to measure and calculate the hydraulic characteristics of the fixed solar sprinkler system,which was using three different types of sprinklers.The range of solar intensity was taken as the influencing factor,the wetted radius,combination uniformity coefficient of the system,kinetic energy per unit volume of droplets,combination uniformity coefficient of kinetic energy intensity and the conversion efficiency of solar energy were taken as the evaluation indexes,the three types of sprinklers of fixed solar sprinkler irrigation system were comprehensively evaluated by principal component analysis method.The sprinkler with the highest score under the special solar intensity range was selected.The optimal configuration scheme of fixed solar sprinkler irrigation system for different solar intensity areas was provided.The innovation is that the hydraulic performance and water drop distribution rules of the fixed solar sprinkler system were explored,the energy conversation efficiency calculation method of the fixed solar sprinkler was established,and optimal configuration schemes of the fixed solar sprinkler system for different solar intensity areas were provided. |
PDF Full Text Request