| The hose reel irrigator is a kind of the intensive irrigation equipment adapting to operating efficiently for large-medium-small scale lands and has many advantages such as high-adaptablity, flexibility and easy-operation, high-automation and less equipment-investment for unit area, which is suitable for Chinese situation. Chinese hose-rell-irrigator industry develops rapidly in recent years, but its variety specifications are few and have not really formed product series. There is a large gap between China and abroad in aspects of key technology research, product quality,performance characteristics,etc. Especially,a large number of the special water turbine of the hose reel irrigator use European technology which was developed over forty years ago, and the problem has been particularly acute in inefficiency. Although a small amount of foreign advanced technologies have been introduced, little research has been done on the basic theory such as optimal design, inner flow mechanism, etc.Also, little foreign open research literature increases the research difficulty.Aimed at the problems mentioned above, this dissertation conducted following innovative research funded by the National Key Research and Development Program(2016YFC0400104-04) "Development on the Hose Reel Irrigator Using the Clean Power for the Integral Control of Water and Fertilization" and Jiangsu Agricultural Science and Technology Support Program (BE2012385) "Research and Development on Low-Energy Intelligent Agriculture Irrigation Equipment with Automatic Reel".The main contents and innovations are as follows:1. Theoretical basis and basic properties of special water turbine with the impulse inlet structure were mastered. In allusion to foreign special water turbine with the special structure of impulse inlet, theoretical basis of water turbine has been studied by theoretical analysis, numeral simulation, and experimental verification.The study found that similarity and linear diffusion law of the main body of the nozzle jet flow in the appropriative water turbine with the special structure were damaged, and this jet flow was a non-free submerged jet; the curving degree of impeller blade type line has the effect on the force. The blade surface with big curvature is under heavy load, while the one with small curvature is under light load;the velocity distributions on different cross-section of the draft tube present flow phenomena of the elbow, for example, inside flow velocity is greater than outside one,and the vortex strip lengthens and increases with the flow rate reducing.The performance characteristics of the foreign special water turbine were predicted and analyzed, and then it was verified by the water turbine performance test rig. All the shaft powers of water turbine at different rotate speeds have the maximum,and the extreme of the shaft power shifts toward the high speed with the head increasing. The peak efficiency of the foreign water turbine is 34%, and the maximum error between performance prediction and experimental data is within 5% according to experimental verification by building the testing apparatus of water turbine performance.2. Determinate method for the shaft power of special water turbine was set up by analyzing variation factors of the load firstly. Variation rules for required traction, traction torque, rotating torque and power of the hose reel have been mastered by analyzing variation factors of the load such as all kinds of ground resistances, translational traction velocity, coiling layer, compose of rotational inertia of traction PE pipe and sprinkler car. The analysis found that the sliding frictional resistance between ground and PE pipe was considerably bigger than the rolling frictional resistance between ground and sprinkler car; the rotating torque is far smaller than traction torque of PE pipe stretching on the ground, and the reel torque can be estimated by using traction torque; the relationship between the required power of reel and the required shaft power of water turbine was established by conducting the efficiency test for transmission system of the hose reel irrigator, and design parameters of water-turbine shaft power were given. The shaft powers of water turbine are not less than 195W 和 125W respectively, when the friction coefficients are selected 0.8 and 0.5 at the common translational velocity of below 40m/h.3. Factors affecting on the efficiency of special water turbine and its inner flow mechanism were mastered.Simulation test and performance prediction were performed for 18 schemes generated from orthogonal experiments by CAD, then the range and variance analyses were conducted. The result reveals that the factors affecting on water-turbine efficiency were, in order, outlet diameter, incline angle of blade outlet, blade number, blade width, inlet installing angle and blade edge clearance by the influence extent. Also, the factor of outlet diameter in the level between 3 and 1 or 2, and the one of blade-outlet incline angle in the level between 1 and 3, have shown highly significant difference. The interior flow analysis for the remarkable influence factor shows that, with the outlet diameter increasing, the fluid flowing from blade passage generates further impact losses, and the low-pressure area in the center of the draft tube is increased to tend to produce the vortex strip and to increase the losses. The bigger the outlet incline angle is, the stronger the guiding effect for the flow is, the fewer the vortex in the blade outlet is. The fluid can flow into the draft tube smoothly, the loss generated from the vortex decreases.The 6 impeller schemes with better performances from 18 impeller schemes have been shaped by 3D printing technology and taken as the objects for the prototype experiment. The tested result is basically consistent with the simulated prediction, and the maximum error is within 6.3% at the flow range of 15 m3/h～22.5m3/h. The best in the 18 impeller schemes is the No. 14 scheme, and its tested maximum efficiency is 38% and increased 6.4% with the foreign appropriative water turbine.4. The optimized design method for the geometric parameters of special water-turbine impeller was built.The GA BP optimization algorithm was adopted to gain the optimized geometric parameters of the impeller, based on the initial input of groups of parameters from the orthogonal test design of water turbine, and to solve some problems in the follow-up work of orthogonal test, such as working inefficiency,etc. Comparing inner flow characteristics of the water-turbine prototype with that of the optimized water turbine,the close relationship between the size or the length of vortex strip in the draft tube and the incline angle of blade outlet were found, the bigger the incline angle is, the smaller the restriction and guiding effect of the blade on the flow are. The flow velocity decreases, and the formation of the vortex strip in the draft tube is restrained. Pressure distribution in the radial cross section and load distribution on the working face of blade show that, except for the flow channel that the nozzle jet flows toward, other areas of water turbine present almost isobaric state,and pressure energy restores in the flow channel. The curving degree of blade-inlet type line has great effect on the blade load, the bigger the curvature is, the more concentrated the blade load is. The impeller torque of optimized water turbine increases 26% approximately with that of the prototype and 10% with that of No. 14 scheme. The maximum efficiency of optimized water turbine reaches 42.5%, and improves 11 percent points with that of the prototype and 4.5 percent points with that of No. 14 scheme. It has been proven that the overall performance characteristics of optimized water turbine have been improved obviously.5. The mechanism of rotor-stator interaction and characteristic of pressure fluctuation were mastered. The CFD unsteady calculation was used to simulate the pressure fluctuation in 13 monitor points located in nozzle zone, runner outer edge,draft tube inlet, draft tube elbow and draft tube outlet. The effect of pressure fluctuation characteristic and rotor-stator interaction on runner working for special water turbine was mastered through the analysis of time-domain and frequency-domain. The research results show that the pressure fluctuation of each monitor point presents stable periodicity, the number of wave crest and valley appeared in pressure fluctuation curve under the whole revolution is the same as the number of runner blade. For prototype water turbine, the blade surface sustained impact force slowly, the direction of water velocity vector confusedly in the blade passageway, the jet flow forked if it was not directly facing a blade passageway, the water flow velocity increased on blade working surface, the pressure and the force decreased on blade working surface during the rotor-stator interaction process. While for the optimized water turbine, the blade profile became curvier, the blade surface sustained stronger impact force more quickly and more intensively, the fluid water smoothly flowed along the blade working surface to the blade outlet with relatively slow velocity,the pressure and the force became greater on blade working surface during the rotor-stator interaction process. |
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