| Drip irrigation belt is currently one of the faster-growing water-saving irrigation equipment in China and has the characteristics of low cost and convenient installation.It can effectively improve the effective utilization coefficient of irrigation water throughout the country and has gradually become one of the generally accepted water-saving methods in agriculture across the country.At present,a lot of researches have been carried out on products development,hydraulic performance and application design of drip irrigation belt.However,relatively little research has been done on the physical structure of channel of drip irrigation belt and its influence on anti-blocking performance.Through the investigation of drip irrigation belt products,this paper collects and analyzes the main models and use conditions of domestic and foreign drip irrigation belts,as well as related hydraulic performance,and conducts structural parameter test tests,pressure flow test,and anti-blocking test of muddy water sediment concentration and salinity of irrigation water.According to the fluid-related theory and experimental data,the working pressure of drip irrigation belts,muddy water sediment concentration,irrigation salinity,interval use,and structure parameters of patch channel of the emitter were studied to determine the anti-blocking performance of drip irrigation belt important factors and structural parameters of the emitter.Finally,by meshing the geometry of the drip-irrigator,setting the boundary conditions,establishing the CFD model of the emitter,analyzing the hydraulic performance and anti-blocking and dissipating performance of the flow channel of the emitter,and optimizing the physical parameters of the flow channel to obtain the conclusion of the tooth pitch and convection index is positively correlated and negatively correlated with the outflow.It also provides theoretical support for future research on the emitters production of drip irrigation belt.The main research results are as follows:(1)Carried out physical parameter measurement and analysed of influencing factorors of on emitter drip irrigation belt.Collected 18 kinds of patch drip irrigation belt commonly used at home and abroad,and scanned the flow channel using structured light scanning technology to generate 3D stereo images.The geometric and physical parameters that characterize the flow channel were analyzed,and 8 structural parameters were screened and the UG and Spaceclaim 3D modeling software were used to test the structure parameters of the emitter 3D patch image.Principal component analysis of the 8 structural parameters was carried out,and the impact of channel parameter of the emitter was analyzed.The scores were ranked as follows: spacing between the teeth(score 33.265)> Minimum channel width(score 31.883)> tooth height(score 29.579)> Maximum channel width(score 28.717)> the number of teeth(score 28.670)> the circumference of runner(score 28.469).In addition,by conduction pressure flow tests on 13 drip irrigation belts,it was found that the range of flow coefficient is 3.487-14.631,the range of the convection index is 0.401-0.565,and the average convection index is 0.486,which is close to 0.5.Therefore,the flow pattern of the drip irrigator flow channel is turbulent.(2)Experimental study on the anti-blocking performance of drip irrigation belts with emitter.The anti-blocking tests of muddy water sediment rate and irrigation water salinity were carried out respectively,and it was found that the working pressure was negatively correlated with the clogging rate,and the water quality(sand content,salinity)and interval use were positively correlated with the clogging rate.Analysis of variance of the sand content rate,mineralization degree and interval use,because the main component of muddy water sand content test is that soil sediment is not easily soluble in water,and the main component of salinity test is that salt is easily soluble in water.It was found that the effect of interval use on salinity was greater than that of muddy water sediment concentration.Finally,the correlation analysis was conducted on the test data with sand content of 5g/L,and it was found that the correlation between the channel structure parameters and the average water discharge on emitter of drip irrigation belt as: number of teeth > spacing between the teeth > Minimum channel width > Maximum channel width > tooth height.Besides,the first four structural parameters with the largest correlation coefficient were selected to establish a regression expression.(3)Based on CFD software,the numerical simulation of hydraulic performance on emitter of drip irrigation belt was carried out.CFD(FLUENT)software was used,and the mesh size was 0.025 mm.The turbulence model was selected as the calculation model,and the standard wall function was selected as the near-wall processing function.Two boundary conditions were set: no water outlet hole and water outlet hole were added to the patch channel storage tank,and the model of the drip channel flow channel was established.Numerical simulation of No.5 drip irrigation belt(NFD 16 × 300-1.38-0.18),pressure(0.02-0.15 MPa)and flow rate,and verification with test data,the error ranges are-6.45% ~ 8.22%,-4.73% ~ 5.48%.The average errors are 3.01% and 2.68% respectively.The numerical simulation flow results are basically consistent with the experimental flow results.Therefore,the numerical simulation model of the No.5 belt established by CFD(FLUENT)has higher accuracy,and it is found that the numerical simulation results of adding water outlet holes in the water storage tank are closer to the results of physical tests.Finally,through the cloud map analysis of pressure field and velocity field generated by numerical simulation,it was found that a lot of vortices were generated between the sawtooth and the sawtooth,which reduced the flow velocity in the flow channel and affected the anti-blocking performance of the emitter.(4)The optimization scheme of the tooth pitch of the emitter of the drip irrigation belt was designed,and the scheme was optimized.From the two aspects of the hydraulic performance and anti-blocking energy dissipation performance of drip irrigation belt emitter,the physical parameters(tooth pitch)with greater influence were selected,and an optimization scheme was designed and analyzed.After physical optimization of the No.5(NFD 16 × 300-1.38-0.18)patch emitter,using Soildworks software to gradually reduce the tooth pitch size of the emitter,three optimization schemes were designed to reduce the tooth pitch to 0.1,0.2,0.29 mm.After numerical optimization of the three optimization scheme of the structured patch flow channel after optimization,it was found that the convection index decreased and the hydraulic performance improved.It was found that the convection index of Scheme 3 was 0.395,a decrease of 14.50%,and the total flow rate increased by 12.11%.Compared with Scheme 1 and Scheme 2,the hydraulic performance improvement of Scheme 3 was greater than the reduction of energy dissipation effect.Analysis of the channel velocity cloud map found that a lot of inter-tooth vortices were reduced,and the kinetic energy and anti-blocking performance of the patch channel on emitter were also improved.Therefore,Option 3 is the optimal solution.At the same time,the results obtained by physical optimization are consistent with the results of a negative correlation between tooth spacing and drip irrigation flow in the results of physical experiments. |
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