Zhiqin Li

In this paper, a tesla-shaped emitter is proposed based on the structure of the “tesla valve” as the source of inspiration, so that the water flow in the channel would produce a variety of energy dissipation phenomena, such as diversion, hedging, and mixing, to explore the hydraulic performance and energy dissipation mechanism of the tesla-shaped emitter. The channel structure parameters were taken as factors, and 16 groups of orthogonal tests were arranged. Based on CFD technology, the pressure–flow relationship curve slope, flow ratio between the main channel and secondary channel, flow field, and head loss of the emitter were calculated and analyzed for different combinations of structural parameters. Based on a significance level α = 0.05 test, the main channel inlet section length (L₃) had a significant impact on the curve slope, and the secondary channel length (L₁) and main channel inlet section length (L₃) had a significant impact on the flow. The multiple linear regression mathematical models between the channel structure parameters and the curve slope and the flow were constructed. The larger the ratio between the main channel and the secondary channel flow, the better the hydraulic performance of the emitter. The channel unit loss coefficient increased linearly with the increase of the emitter inlet pressure, and its value ranged from 4.5769 to 8.1716, with an excellent energy dissipation effect. The hedge mixing of the water flow was the core of the energy dissipation of the tesla-shaped emitter. By appropriately increasing the inlet size of the main channel and other elements to increase the main channel flow and optimize the flow ratio between the main channel and the secondary channel, the mixing was improved, which consequently improved the hydraulic performance of the emitter.

As a key component of a drip irrigation system, the performance of drip irrigation emitters is determined by the flow channel structures and parameters. In this paper, a novel Y-shaped labyrinth-channel emitter was proposed, and the influence of the hydraulic performance was researched under different waist-arc angles (α) and ratios of crown height to chord length (a:b). The flow characteristics and energy dissipation mechanisms of water in the emitter were analyzed by using fluid dynamics software. The analysis showed that, keeping the ratio of crown height to chord length unchanged and with an increase in the waist-arc angle from 90° to 180°, the pressure-drop ratio before and after the water flow through the vortex area increased, and the hydraulic performance of the emitter was improved, specifically: the design flow could be reduced by 6.02–26.7%, and the slope of the curve could be reduced by 9.83–28.1%. The smaller the ratio of crown height to chord length, the weaker the influence of waist-arc angle was on the design flow and hydraulic performance. Keeping the waist-arc angle unchanged, there was a decrease in the ratio of crown height to chord length from 6:30 to 1:30, the vortex strength inside the emitter channel increased, and the hydraulic performance was improved: the design flow could be reduced by 7.56–23.5%, and the slope of the curve could be reduced by 5.43–20.5%. The bigger the waist-arc angle, the weaker the influence of the ratio of crown height to chord length was on the design flow and the hydraulic performance, even to the point of having no effect. When the Y-shaped emitter was close to the pressure-flow curve slope of the commonly-used triangular-channel emitter, the hydraulic performance of the two was similar, and the former could increase the channel width by 25%, as compared to the latter, or shorten the channel length by 44.3%. The results showed that the Y-shaped emitter had better hydraulic performance compared with the triangular-flow-channel emitter commonly used today. Therefore, the Y-shaped emitter has broad application prospects in water-saving irrigation.

A In this paper, a Y-shaped labyrinth channel emitter is proposed to explore the influence of the waist arc’s angle(α) and crown-to-chord ratio(a:b) on the hydraulic performance of its was investigated. Numerical simulation using CFD software for fluid dynamics to obtain the pressure ~ flow relationship’s curve and slope and flow field diagram, compare and analyze the slope of pressure ~ flow curve, design flow and flow field diagram of the emitter with different waist arc’s angle and crown-to-chord ratio.Research shows that, (1) When the waist arc’s angle of Y-shaped emitter is 90°, and the crown-to-chord ratio is 6:30, the slope of curve is close to the triangular channel emitter currently commonly used, which has same cross-sectional size and runner length. (2) Keep the crown-to-chord ratio unchanged, with the increase of waist arc’s angle, the slope of curve and the design flow are reduced, the pressure drop ratio before and after the water flow through the low-speed vortex area increases, and the hydraulic performance of emitter is improved. (3) The smaller the crown-to-chord ratio, the weaker the influence of waist arc’s angle on the design flow and hydraulic performance. (4) Keep the waist arc’s angle unchanged, with the decrease of crown-to-chord ratio,the slope of curve and the design flow are reduced, the vortex strength inside the emitter channel increases, and the hydraulic performance is improved; (5) The bigger the waist arc’s angle, the weaker the influence of crown-to-chord ratio on the design flow and hydraulic performance, even no effect. (6) When the Y-shaped emitter is close to the pressure ~ flow curve’s slope of the commonly used triangular channel emitter, the hydraulic performance of the two is similar, the former can increase the runner width by 25% compared to the latter, or shorten the runner length by 44.3%.

In this paper, a split-flow channel layout with one (group) inlet and two (group) outlets is adopted, based on computational fluid dynamics technology, and compared with the current commonly used channel with one (group) inlet and one (group) outlet emitter. On the premise of the same outlet spacing, the pressure–flow relationship curve and slope of the split-flow emitter were analyzed under the three channel layouts of non-return, single-sided re-entry, and bilateral re-entry, with different channel widths and lengths. When exploring the influence of the channel layout and size on the hydraulic performance of split-flow emitters, the results showed that when the split-flow emitter with a non-return channel is adopted and the hydraulic performance is not reduced, the single-side channel length is half that of the one-in-one-out emitter, meaning the channel width needs to be reduced by 15%. When the channel layout is a single-sided channel re-entry, the hydraulic performance is better than that of the one-in-one-out emitter; if the hydraulic performance of the two remains unchanged, the channel width can be increased by 10% or the single-sided channel length can be reduced by 20%. When the channel layout is a bilateral channel re-entry, the channel width can be increased by nearly 30% if the hydraulic performance of the 2 is consistent, and the single-side channel length is increased by about 50%. When the split-flow emitter adopts a non-return channel layout, the channel width needs to be reduced to ensure the hydraulic performance is consistent. If the layout of single-sided channel re-entry or bilateral channel re-entry is adopted, the hydraulic performance is better than that of the one-in-one-out emitter and the hydraulic performance of the two is consistent. Thus, the channel length can be reduced or the channel width increased, which is beneficial for improving the anti-clogging performance of the emitter.

The rectangular labyrinth emitter is taken as the study object in this article, as we added internal teeth to vortex-free and vortex areas in its lateral channel or lengthened the vertical channel, to change the channel structure. Using the computational fluid dynamics (CFD) method simulates the water flow field, to get the relationship between flow rate and pressure, and the vortexes distribution in channel. The aim of this study is to explore the reasons for the influence of structural change on hydraulic performance of the emitter through the analysis of vortex intensity and its distribution from the perspective of the vortex. The results show that the relative error of simulated results and experimental data was 1.02–2.11%. Adding internal teeth to vortex-free areas in lateral channel can improve hydraulic performance of the emitter; adding them to vortex areas can reduce it. The increase in vortex number and intensity in flow field is the internal reason for the improvement of the emitter’s hydraulic performance. The channel structure changes promote the formation of a larger velocity gradient, and the increase in the velocity gradient in flow field exacerbates vortex formation. Changing channel structure to improve the emitter’s hydraulic performance can promote an increase in the number and intensity of vortexes in the channel.