Optimization Design And Experimental Study Of Small-Scale Sprinkler Irrigation Systems With Low Energy Consumption And Multi Purposes

The research in this thesis is supported by the National Hi-Tech Research&Development Program (863Program)-Precision Sprinkler Irrigation Technologies and Products (No.2011AA100506), and the Jiangsu Scientific Research and Innovation Program for Graduates in the Universities-Fixed-movable Duple-purpose Hose Sprinkler Irrigation System Based on Minimum Energy Consumption and Best Water Distribution (No. CXZZ110565)The low energy consumption has become one of the focuses in the development of sprinkler irrigation systems under the growing water shortage and energy consumption problem worldwide. In China, the terrain conditions, the crops and the rural economic levels are various across the land. Hence, the diversity in the configuration of Small-Scale Sprinkler Irrigation Systems is a trend. The increasingly shrinking farm labor as a result of urbanization, combined with the large-scale operations of farmland have challenged the present sprinkler irrigation machines with one-line pipe layout which is accompanied with inconvenience in transferring the pipeline to the next location. Therefore, the flexibility in the combination of components and the possibility in the application of larger areas within limited power need to be improved, and the energy consumption needs to be reduced so as to provide some basis for the further promotion of Small-Scale Sprinkler Irrigation Systems. The theoretical simulation and experimental validation were used in the optimization design and experimental study of Small-Scale Sprinkler Irrigation Systems with Low Energy Consumption and Multi Purposes.The main contributions and possible innovations of this work are presented as follows.(1) Development of Small-Scale Sprinkler Irrigation Systems with low energy consumption and multi purposesA Fixed-Movable Multi-Purpose Sprinkler Irrigation System was proposed to improve the flexibility of the small-scale sprinkler irrigation system and the adaptability to the crops. The key parts in the system were designed and produced including a quick-connect coupling for connection of the riser and the pipe tee, and a fixture for the sprinkler and the pipe in the system. A Multiple-Sprinkler Irrigation System with Pairs of Laterals was developed. Theoretical analyses show that it has the minimal operation time, the minimal total cost in the life span, the highest irrigation uniformity coefficient and proper energy consumption compared to the traditional systems with one pipeline or two parallel lines.Eleven kinds of pipe layouts were summarized for different areas according to the combination of different lateral layouts used in the two new irrigation systems, and the mobility of components of the system. These will provide various alternatives of pipe networks for different users and applications.(2) Establishment of comprehensive evaluation model of Small-Scale Irrigation System and investigation on the impact factors of different indicatorsA multi-criteria evaluation model of small-scale irrigation system considering technical, economic, environmental and social aspects with ten sub-criteria and processed with Grey Relational Analysis (GRA) was developed. The Analytical Hierarchy Process (AHP) and entropy method was employed in the evaluation of irrigation systems to take into account the subjective and objective aspects. Analyses indicate that the evaluation model can be adjusted easily and will provide an efficient method for the multi-criteria and multi-objective evaluation of irrigation systems.And the impact factors of the evaluation indicators of irrigation system were explored. For the technical aspect, the impact of working pressure and sprinkler spacing on the overlapping irrigation uniformity were investigated to provide a basis for the optimization of the system. For the economic aspect, the components of Life Cycle Cost of irrigation systems were analyzed. Results show that:the energy consumption accounts for the major part of LCC of the systems, followed by the initial cost and the labor cost. Thus, the configuration optimization of irrigation system is very important to the reduction of cost and energy consumption. For the environmental aspect, the orthogonal design L27(3’3) of four factors on three levels considering the interaction between factors was applied in the study of impacts of configuration parameters on the energy consumption. The results demonstrate that the impact of working pressure at the end sprinkler comes first, followed by that of pipe diameter, the impact of number of sprinklers is also obvious, and that of sprinkler spacing is manifested in the interactions with the other factors. Therefore, the multi-objective optimization of irrigation systems is needed. (3) Hydraulic calculation and multi-objective optimization of Small-Scale Irrigation SystemsThe traditional hydraulic model was improved. And three models were developed according to the co-operation characteristics of pump-pipeline-sprinkler in the Small-Scale Irrigation Systems for there were generally no pressure regulators in the systems. They are the back step method, and the forward method considering the constraint of discharge of pump for the system with one line. And combination of both with the Golden Section Search was first used for the complicated networks. Results show that:the forward method will reflect the characteristics of irrigation pipelines better compared with the back step method. In a sprinkler irrigation system, the outlets are far less and the flow rate for each is far higher compared to a micro-irrigation lateral, thus there is an abrupt pressure drop at some length along the pipeline, not as continuous as that calculated by the back step method. The newly-designed forward-backward method will better meet the requirement of minimal pressure at the end sprinkler on each lateral in a pipe network compared to previous researches.Ant Colony Optimization (ACO) was originally introduced in the optimization of sprinkler irrigation systems for the lowest specific energy consumption and compared with Genetic Algorithm (GA) and the field tests. Results show that the optimal number of sprinklers and pressure profiles along the pipeline calculated with ACO are closer to the experimental results compared to that by GA. The multi-objective optimization model of small-scale irrigation systems was then built with Linear Weight Sum Method based on the analyses of impact factors of indicators.(4) Field experiment on the specific energy consumption and irrigation uniformity of sprinkler irrigation systemThe specific energy consumption and the irrigation uniformity are the major criteria in the environmental and technical aspects, and will reflect the operation condition and the irrigation quality of the system, respectively. Moreover, they are more sensitive to the change of configuration parameters. Hence, the field experiment was carried out on the system typed PC45-4.4equipped with sprinklers15PY to investigate the impact of configuration parameters of system on the energy consumption and irrigation uniformity, to validate the practicability of hydraulic model and optimization method, and to derive the optimal configuration in the test condition. The analyses on the impact factors of energy consumption demonstrate that: the theoretical analysis method is generally practical. But in the field test the energy consumption rises when the pipe diameter is increased for the pressure head of sprinklers provided by the pump are higher. This indicates the interaction between the pump-pipeline-sprinkler, which is neglected in the theoretical analysesThe analyses on the impact factors of irrigation uniformity coefficient show that: for the application of irrigation systems in the areas with wind speed lower than2.7m/s (the maximum value in the experiment), the combination of rectangle layout, proper sprinkler spacing and lateral spacing, and lower pressure can be used to ensure a high irrigation uniformity and a lower energy consumption. But for the application of irrigation systems in the areas with more frequent wind or higher wind speed, the combination of triangle layout, closer sprinkler and lateral intervals and higher sprinkler pressure is suggested to minimize the effect of wind on the irrigation uniformity. The interactions between the impact factors of specific energy consumption and irrigation uniformity are obvious, thus the configuration parameters should be chosen considering different aspects.