| Among all kinds of aquatic vegetables, Lotus has the largest planting area. But the harvest of lotus root is difficult and costs much at present. Attributed to this, it’s necessary to develop practical lotus root harvest machine for the market demand. However, optimization of performance parameters is important to the design of harvest machine. Firstly, in this research, the mechanical characteristic of lotus root was investigated systematically, and the influence factors of lotus root harvest by hydraulic scouring, include power of pump, nozzle shape, the direction of the jet flow, scouring time, soil condition, and target distance were analyzed in theory. Secondly, based on the theoretical analysis, a set of lotus root harvest test platform was set up, in which the nozzle moving range, spray angle and installation spacing in a certain range were adjustable. In addition, control system of the platform was designed to control the nozzle forward, backward, left and right automatic reciprocating motion, automatic starting and stop action. At last, tests were carried out on the experimental platform to explore the impact factors of nozzle shape, nozzle diameter, nozzle installation angle, water flow, flow velocity and scouring time to the lotus root harvest effect by hydraulic scouring. The main research contents were as follows:(1) "Elian 5", which was widely cultivated in Hubei province, was used as the research object. The mechanical properties of "Elian 5", include the compressive strength of lotus root body, the axial and radial compressive strength of lotus root block, axial compressive strength of lotus root section, mechanics parameters on axial and radial crushing stress of lotus root body, tensile and bending properties of lotus root joint, etc. were acquired by test. Based on analysis of above mechanical parameters, it concluded that the lotus root body material characteristic was anisotropy, and radial damage was more susceptible than axial, the radial compressive strength scope was 2.22~2.90 MPa, with a mean of 2.71 MPa. Therefore, nozzle outlet water effect on the lotus root pressure must be less than 2.22 MPa when designing the hydraulic parts of test platform. Average bending strength of lotus root joint I, II and III respectively were 1.337 MPa, 1.227 MPa and 1.153 MPa. The fracture force of lotus root joints ranged from 84.466 N to 212.166 N. Therefore, it must be ensured that the continuous radial forces on joints of lotus root, created by mechanical equipment’s nozzle outlet water flow, should not exceed 84 N. The tensile failure force of lotus root joints ranged from 351.366 N ~ 807.533 N, so the continuous axial forces on lotus root’s joint created by mechanical equipment’s nozzle outlet water flow should not exceed 351 N. The minimum value of axial tensile force of joint was bigger than the maximum of radial fracture force. Therefore, lotus root joint was easier to break. The above research provided reference for the selection of key parameters when designing lotus root harvest equipment based on hydraulic scouring.(2) The energy dependence of hydraulic system pipeline was analyzed, and the relationship among pump power, flow rate, head and jet impact force was studied. In addition, the influence factors of lotus root’s harvest effect by hydraulic scouring, include power of pump, nozzle shape, the direction of the jet flow, scouring time, soil condition, and target distance were analyzed in theory, and obtained the relationship between hydraulic parameters, which provided the basis for the designing of lotus root harvest equipment.(3) A set of lotus root harvest test platform was set up, in which the nozzle spacing, installation angle, the width and speed of left and right reciprocating motion, the speed of forward and backward reciprocating motion were all adjustable and could be controlled independently to the automatic control system. The spacing adjustable range of the test platform’s nozzle was 120~300 mm, the angle adjustable range was 0~45°, the length adjustable range of the around movement was 0~300 mm, and the speed adjustable range was 0~480 mm/s, the adjustable speed range of the before and after movement was 0~300 mm/s. In order to explore the impact of nozzle shape on the hydraulic scouring, four kinds of nozzles with different shapes, include round, square, rectangle, and oval were designed. The four kinds of nozzles’ overall length, inlet diameter, outlet area were 80 mm, 50 mm and 314mm2 respectively.(4) Control system of the platform was design to control the nozzle forward, backward, left and right automatic reciprocating motion, automatic starting and stop action. The control system adopted AT89S52 module microprocessor to control the reciprocating sequential of nozzle. PWM modulation circuit of NE555 was used to control motor speed regulation. Forward and backward touch switch was used to control nozzle’s automatic reciprocating motion, automatic start-stop in setting range. A high power driver module PCB was used to drive motor and ensure the system reliability.(5) Performance tests were carried out on the experimental platform to identify the normal working state of it. Single factor tests, based on nozzle shape, installation angle, power, nozzle diameter, scour time respectively, were carried out to explore the impact on hydraulic scouring effect. Results showed that the round nozzle in installation angle of 30 degrees scouring effect best. With the flow of 24.25m3/h, nozzle diameter of 20 mm, nozzle moving of 220 mm, scouring the reciprocating frequency of 3 times, scouring time of 31.146 s, the round nozzle could erosion the lotus root farmland soil with the soil solid degree of 465.3kpa to over 30 cm depth, and could rush up the lotus root with 30 cm depth in the mud to the surface, to obtained better harvest effect. |
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