| Drip irrigation has characteristics of water saving and fertilizer saving as a localized irrigation method.The compensating emitters are used more widely because its flow rate can remain constant when the watering system pressure changes.At present,the pressurecompensating emitters which used commonly at home and abroad are silica gel-type products,which have a complicated structure,a long research and development cycle,and are difficult to recycle.In order to overcome the problem of “recycling difficulty” of silica gel-type pressure-compensating emitters,this study replaces silicone rubber material with thermoplastic elastomer(TPE).Based on the principle of emitter flow compensation and CFD(Computational Fluid Dynamics)numerical calculation method,the structure of the emitter labyrinth channel was designed and optimized with Ansys15.0.This study uses orthogonal design test on some important factors of the emitter,such as tip angle,channel width,channel depth,number of channel quantity,and orthogonal experiment was established to confirm the emitter structure.Use two-color mold injection molding machine to manufacture the emitter,and test the hydraulic performance and anti-clogging performance of the emitter.At the same time,in order to investigate the influence of the elastic compensator on the hydraulic performance of the emitter,the mechanical properties of the elastic sheet were studied according to aging test.The influence of the hydraulic performance of the emitter indicates the relationship between the mechanical tensile index of the elastic sheet and the hydraulic performance of the emitter.The main conclusions are as follows:(1)Developed a design method of the integrated pressure-compensating emitter.According to design requirement,establish a orthogonal experiment of different combinations of variable channel structure parameters,and this paper conducts a simulation analysis on this different emitters by Fluent.Design a emitter structure having a tooth tip angle of 34°,a channel width of 4 mm,a channel depth of 0.4 mm,and a number of channel units of twelve,and carried out the mechanical analysis of the compensating element-elastic piece,found the relationship between the pressure difference of the elastic piece and the hardness of the elastic piece.According to the simulation calculation results,the hardness of the elastic piece was determined to be 35~55HA.(2)Produced and tested the integrated pressure-compensating emitters for hydraulic performance which elastic sheet hardness is 30 and 40 HA.When the elastic sheet is 30 HA,the emitters' flow index is 0.07 which is much lower than that of 0.02,and its compensation is excellent;the starting compensation pressure is 35 kPa,and the compensation interval is between 35 kPa and 300 kPa,which can be applied to the topographic relief areas of arid and semi-arid areas in the northwest of the mountainous.Because of a simple structure which adopts an integrated form,this techniques on emitter's design makes the product properties are fine and time shortened.The cost of a single emitter in mass production is 0.05~0.1 ?,which is 15%~35% of the cost of the traditional "three-piece" one,and the production efficiency is increased by 50%~150%.(3)Compared with the other two general emitters,the integrated pressurecompensating emitter has better anti-clogging performance and smallest runner size and cross section.When the sediment content of the test irrigation is 1.0g/L and the irrigation pressure is 50 kPa.the A30 emitter still has better anti-clogging performance after 20 times of irrigation,;when the irrigation pressure is 100 kPa,the A30 emitter clogging is basically the same as the B emitter of the flow passage cross-sectional area.(4)When the sediment concentration is not more than a certain concentration(for example,1.0g/L),the emitter has better anti-clogging performance.Due to the variability of the channel structure,when the sediment concentration is 0.5 and 0.75g/L,emitter's average relative flow rate is 80% after 25 times of irrigation,and greater than 75% indicates that no serious clogging occurs;When the sediment concentration is 1.00g/L,some emitter's relative flow rate drops below 80% suddenly after the fourth irrigation,and the individual emitter appears completely clogging.Different irrigation pressures on emitter plugging test,the smaller the irrigation pressure,the better the anti-clogging performance of the emitter.we could consider reducing the clogging of the emitter by reducing the system's irrigation pressure.(5)There is a correlation between the tensile index of the elastic sheet and the hydraulic performance of the emitter.In the flexural test of the high-frequency irrigation,the emitter's flow rate will decrease in incipient stage and then stabilize with the increase of the number of irrigation times.Through the tensile test of TPE elastic sheet after different times of watering,it is shown that the amount of permanent deformation in the tensile index has a significant effect on the flow rate of the emitter(P<0.05),and has a negative correlation,that is,the more bigger the permanent deformation is broken,the smaller the flow rate of the emitter;the tensile test of the material after the atmospheric exposure test shows that the tensile elongation at break of the TPE compensating element has a significant influence on the flow rate,flow coefficient and compensation interval of the emitter(P<0.05),showing a negative correlation;but positive correlation with the starting pressure and flow index(P<0.05). |
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