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Research On Flow Field Characteristics And Anti-clogging Performance Of The Drip Irrigation Emitter

Posted on:2019-05-29Degree:MasterType:Thesis
Country:ChinaCandidate:Y TangFull Text:PDF
GTID:2393330563958763Subject:Mechanical engineering
Abstract/Summary:PDF Full Text Request
The hydraulic performance and anti-clogging performance of the drip irrigation emitter are the important indicators to evaluate the quality of its channel structure design,and also are directly related to the flow field characteristics of the channel.Based on the computational fluid dynamics(CFD),the flow field of the channel was studied.And the effects of using different wall functions and grid partition schemes on the simulation results were analyzed.The result shows that the flow field will have the greater velocity near the wall and higher vortex strength by using enhanced wall treatment(EWT)and setting the boundary layer grid.The influence of the manufacturing shape parameters of the sawtooth type drip irrigation emitter such as the slanting angle of the side wall and the fillet radius of the tooth tip of the channel on its hydraulic performance was studied.Computational fluid dynamics(CFD)also was used to simulate the flow field in the in-line drip irrigation emitter of the triangular type.The shape parameters of the triangular channel were defined,and the influence of each parameter on hydraulic performance of the drip irrigation emitter was also analyzed.As for sawtooth type emitter,the study indicates that the flow rate increases with the increase of the slanting angle of the side wall and the fillet radius of the tooth tip,and the flow index of the drip irrigation emitter can be effectively decreased when the side wall of channel has a 3-4° slanting angle.As for triangular type emitter,the study indicates that the flow rate increases with the increase of the channel height and the fillet radius of the tooth tip,also increasing with the decrease of the angle of the tooth tip and the distance of the opposite tooth tips,and the flow rate changes on the draft angle is not obvious.And the flow index of the drip irrigation emitter decreases with the increase of the draft angle,the angle of the tooth tip and the distance of the opposite tooth tips,also decreasing with the decrease of the fillet radius of the tooth tip,and the flow index is unrelated to the changes of the height of the channel.Through the discrete phase model(DPM),it is found that particles with smaller diameter are easier to follow the main stream of the fluid and enter the eddy regions,but they will have the greater velocity in the flow field.And the particles will accumulate at the entrance,the rounded corners and the regions of the tooth tips.The effect of the curvature of the top and bottom surfaces of the channel on its anti-clogging performance was also studied by the solid-liquid coupling method.The result shows that the drip irrigation emitter which possesses flat top and bottom surfaces has a better anti-clogging performance,comparing to the one whose top and bottom surfaces are curved.Because the particles in the flat type drip irrigation emitter are not easily involved into the vortexes in the channel,they can leave faster than those in the curved one.In order to observe the flow field in drip irrigation emitter channel of the sawtooth type directly,the visualized channel structure of the four plates type of the emitter was designed and manufactured.This device can truly reflect the inlet position relative to the flow channel and consider the effect of energy dissipation of the fluid by the entrance grid.The hydraulic performance experiment was carried out by the visualized channel structure of the four plates type and the triangular type drip irrigation.The difference of the hydraulic performance curves obtained by experiment and simulation is only 5%-10%,which proving the reliability of the simulation analysis.Through particle image velocimetry(PIV)experiment,the flow field in different positions of the visualized channel structure of the four plates type was obtained and analyzed.It is found that the flow field in the emitter mainly consists of the main stream region,the vortex zones and the low speed zones.The main steam region is S type,and the vortexes are distributed on its sides.The gaps between the vortexes and the shape of the channel become the low velocity areas in the flow field,the particles will easily accumulate in those positions.When the working pressure is at 40 kpa,the maximum velocity in the flow field appears around the tooth tips.And the maximum velocity in the tooth tip area is 1.3489m/s,the maximum velocity in the corner region is 1.588m/s.There are the higher strength and larger area of the vortexes in the corner region compare to those in the tooth tip area.The numerical simulation values are highly consistent with the experiment results,and the errors of the maximum velocity of the tooth tip area and the corner region got through experiment and simulation are only about 5.2% and 10.9%.The rationality of numerical simulation of flow field is verified.
Keywords/Search Tags:drip irrigation, flow field, anti-clogging performance, hydraulic performances, channel structure
PDF Full Text Request
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