Hydraulic Performance And Numerical Analysis Of Flow Field Characteristics For Single Tooth Rectangular Channel Emitter

Many regions on the earth are facing the problem of water shortage, which is more serious in our country. Developing water-saving agriculture, improving utilization and saving the irrigation water are the important issues to promote the sustainable development of agriculture. As an advanced micro-irrigation method, drip irrigation has the merits of energy saving, water saving and high yield, which is one of the most effective agricultural irrigation ways to solve water scarcity problem. Emitter, the key component in drip irrigation system, can consume the pressure of the capillary water about to enter it, making the water slowly, steady, uniformly outflow of it. Structure of the flow channel has great impact on the hydraulic performance of emitters, and hydraulic performance directly determines the irrigation quality. Labyrinth path emitters precisely because of their relatively low complexity and cost of the flow channel boundary is widely used. Most researchers have paid their attention to the impact of flow structure parameters changes on the hydraulic performance, but few studied the design of the tooth-plused in the emitter’s flow channel.In order to improve the flow velocity distribution in the rectangular labyrinth emitters, and enhance energy dissipation efficiency and anti-clogging performance, a kind of internal tooth rectangular channel emitters was presented in thie paper, providing a basis for the production of high-performance hydraulic emitter. Numerical simulation for single-tooth labyrinth channel and traditional rectangular channel were carried out by using the FLUENT software, and pressure~flow relationship, flow velocity distribution, and internal vortex area characteristic index at different locations were obtained. By analyzing the datas above we can get the following conclusions:1) The distribution of mainstream zone and vortex area in flow channel was changed by adding tooth at place of no vortex in the rectangular channel labyrinth emitter, and the flow coefficient and flow index reduced.2) When the ratio of cross-sectional area of the flow channel for place of the tooth-plused and the entrance reaches about 25%, the flow index is smaller than that of the rectangular channel plus front toot. Only in this case, the tooth will improve the hydraulic performance for the single tooth rectangular channel by adding tooth at vortex aera in the rectangular channel labyrinth emitter.3) The hydraulic performance of the single tooth rectangular channel by adding tooth at the bottom wall of the flow channel(no vortex aera) is better than that by adding tooth at the upper wall of the flow channel(vortex aera) in the rectangular channel labyrinth emitter.4) In the same size single tooth rectangular channel, with the increasing of tooth height, the flow coefficient and flow index reduce, the flow fluctuation in emitter declines, and the flow is decreased sensitivity to pressure, which are better for improving the irrigation quality.5) When the ratio of the flow cross section in the channel is consistent, the flow coefficient raises and the flow fluctuation increases with the increasing of tooth height for the reason that the size of flow channel is positively correlated with the tooth height.6) Quantitative comparison of the flow index for the single tooth rectangular channel and the same size rectangular channel was analyzed. Results show that the emitter with maximum extent of flow index decreases is the E15 type(obtained from adding tooth at place of no vortex), whose flow index decreased by13.3%. It is indicated that the larger size of the rectangular labyrinth path emitters, the greater extent of flow index decreases after adding tooth at no vortex area.7) Under the same inlet pressure, head loss coefficient single tooth rectangular channel is larger than the rectangular channel; and the labyrinth path emitters head loss coefficient changes with pressure head stabilized.8) Maintaining the minimum flow sections of the single tooth rectangular channel and the rectangular channel consistently, we found that the vortex area is mainly located at the upper and the bottom wall in rectangular channel, while at both ends of the tooth in single tooth rectangular channel. In addition, for the single tooth rectangular channel, the streamline distribution is denser, the flow rate is higher, the flow turbulence is stronger in vortex area, the number of the vortex is much more, and the area of the vortex is larger. Thus, single tooth rectangular labyrinth emitter has the merit of greater head loss, which means its energy dissipation effect is more significant.