Theoretical And Experimental Study On The Fluidic Sprinkler Controlled By Clearance

The research on fluidic sprinkler controlled by clearance was one of the main contents of China National High-tech Program (No. 2004AA2Z4010)"Development and Industrialization of key equipment in new irrigation system".The fluidic sprinkler was characteristic of simple structure, good hydraulic performances, and multi-function, which adapted to the trend of multi-function and energy-saving of sprinkler. So, establishing the design method of the fluidic sprinkler by complete, deep and systemic research on wall-attachment jet theory, performance experiment and reliability test, was of not only great significant for theoretical study, but also of practical value for wide application.Based on the theories of free turbulence jet and wall attachment jet, wall attachment point and core area length in the jet component were calculated and analyzed to guide the design of working area system of the sprinkler. Running control system of the sprinkler was designed based on the theory of running control. A dynamic analysis of running control system was conducted to deduce the structure size, which can get maximum driving moment. The main geometrical parameters that influenced the hydraulic performance of the sprinkler were summarized, and a great deal contrast tests were tried out. The best-combined geometrical parameters for different hydraulic demands were analyzed by orthogonal experiments. Under different running state of the fluidic element, CFD software was applied to simulate the inner flow. The results of numerical simulation, theoretical analysis, and the experimental data were compared with each other. Based on the systematically study of mentioned above, design method of the fluidic sprinkler was established preliminarily for the first time.The main research contents and results were as follows:(1) The working principle and structural characteristics of fluidic sprinkler were introduced. Design parameters of one series including six types were established, with the higher target than the national standard "rotating sprinkler". Each system of the fluidic component, such as steady flow system, liquid seal system, signal incepting and transporting system, working area system had been designed. The unique reverse structure was also put forward.(2) The processes and methods of calculating wall-attachment radius, wall attachment distance varied with the offset ratio were derivated using Attachment Point Model and Control Volume Model respectively. The source program was written and applied to calculate the wall-attachment radius and the distance of fluidic component typed 10PXH and 30PXH preliminarily. The flow in the core area of fluidic component was analyzed by M. Kimura's model for the first time. (3) Based on the research of running-controlled theory of complete fluidic sprinkler, design request of key sizes was put forward to realize stable switch.Wall-attachment controlling and running system of the sprinkler was designed. The design principle of running parameters, such as the location of signal tube, the length of the pipe, the width of gap C, were set forth respectively. The driving moment of the sprinkler was analyzed, and the calculating equations of wall-attachment driving force and moment, friction force and moment were put forward for the first time.The theoretical relationship between the maximum wall-attachment moment and geometrical sizes was deduce using centerline equation of wall-attachment jet flow and momentum equation.Moment equation and angle equation of fluidic sprinkler were educed using rigid body rotating theory.(4) A auto-testing system of sprinkler rainfall distribution based on distributional RS485 bus was established in this paper. The influence to hydraulic performance caused by working pressure and major hydraulic sizes was studied by experiment.The best combination of geometrical sizes according to different performance requests, such as range, water distribution, frequency and wall-attachment moment et.al, was achieved by the orthogonal experiments.(5) Durable test-beds and fretting test-beds were developed to research the stability of fluidic sprinkler, and durable test and fretting test were done. The test result indicated that the lasting long performance of fluidic sprinkler was good because of the safety-running period of 2000 hours. Wearing characteristics will be lucubrated in the future.(6)3-Demesion transient N-S equation was used as control equation, k-εequation model was used to close Reynolds time-averaged equation. VOF method was used to track the shape and location of free face, and PISO method was used to couple the velocity field and pressure field. By the 2-D and 3-D numerical simulations of the flow in sprinkler component under different states, the preliminary flow law of the sprinkler was revealed for the first time. In order to testify the accuracy of numerical simulation, the results of theoretical analysis, experiments and numerical simulations were compared with each other.(7) Design method of the fluidic sprinkler was summarized based on the theoretical calculations and experimental studies. The calculating formulas of the length and offset ratio of working area, the left and right offset ratio of export cover were recommended.