Influence Of Double Internal Tooth Parameters On Hydraulic Performance Of Labyrinth Irrigation Device

Water is the resource on which human society depends and it is also a strategic economic resource for human progress and development.However,with the economic development and rapid population growth,the shortage of water resources has become a common problem faced by all mankind.China is one of the countries that are seriously deprived of water in the world.At the same time,due to the widespread existence of water pollution and waste of water resources,China's water resources are in a tight supply and demand situation.Therefore,in order to alleviate the shortage of water resources in our country,improve the water utilization rate and realize the balance between supply and demand of water resources,China must implement water-saving technologies in an all-round way.As a large agricultural country,China has a huge amount of irrigation water every year,and agricultural water accounts for about 73%of the total national water use.However,China still uses the traditional flood irrigation technology,and the waste of water resources is very serious.Therefore,promoting water-saving irrigation technology is an important measure for the rational distribution of water resources and the high yield of crops.At present,drip irrigation is one of the more advanced irrigation technologies,and its absorption rate for crop water resources is higher than irrigation techniques such as pipe irrigation and sprinkler irrigation.Among them,the emitter is the key part of the drip irrigation system,and the labyrinth flow path has better energy dissipation effect for the water flow by virtue of its complicated side wall structure,and is the best structural form of the drip irrigation emitter.At present,scholars at home and abroad have studied more labyrinth flow channels,but most of them have a cross-sectional area of about 1 mm,and their anti-clogging performance is poor.In order to improve the anti-clogging of the emitter and optimize its hydraulic performance,the internal teeth were added to the vertical and horizontal runners of the rectangular labyrinth emitter,and a rectangular labyrinth channel emitter with double internal teeth was formed by the change of the physical model in the runner.In a unit labyrinth flow path,the teeth in the vertical flow path are located on the upper left side and the lower right side,and the lower left side and the upper right side from the direction of the water flow.The internal tooth positions of the lateral flow path are vortex side and non-vortex side.In this paper,the physical test method is used to verify the influence of the relative position of the internal teeth on the hydraulic performance and the change of the internal tooth to its hydraulic performance.Using the numerical modeling method,the E-type double internal-tooth rectangular labyrinth channel emitters with section sizes of 1.5×1.5 mm,1.7×1.7mm,2.0×2.0 mm,and 2.5×2.5 mm are named as E_1.5,E_1.7,E_2.0,E_2.5.5 type emitters;G-type common rectangular labyrinth water emitters whose flow path width and depth are consistent with the width of the corresponding double internal teeth rectangular labyrinth water fountain plus teeth,respectively named as G_1.5,G_1.7,G_2.0,and G_2.5.5 emitters;runner width is the same as the width of the corresponding double internal teeth emitter,and the depth of the runner is the same as the width of the corresponding double internal teeth emitter without teeth,respectively named F_1.5,F_1.7,F_2.0,and F_2.5.5 emitters for simulation studies.The relationship between the hydraulic performance in the flow channel,the relative position of the internal teeth,the height of the internal teeth,the distance between the internal teeth and the dimension of the cross section of the emitter is mainly studied.Finally,the pressure-flow curve,flow coefficient,and flow index of each emitter can be analyzed.The effect of tooth parameters and section dimensions on its hydraulic performance.Through the above analysis,the following conclusions can be drawn:1)The flow rates in the E,F,and G-shaped labyrinthine flow channels are consistent with changes in the pressure head,showing a positive correlation.2)The sensitivity change of the internal teeth parameter to the flow index of the double internal teeth rectangular labyrinth emitter is:internal tooth relative position>internal tooth height>internal tooth spacing;among them,the variation of internal index and internal tooth height has significant influence on the change of flow index,internal tooth spacing has little effect on the change of the flow index.In particular,in the E1.5-type labyrinthine flow path,the internal tooth position has the most significant effect on the flow index.3)In the double internal tooth rectangular emitter,the internal tooth parameters influence the flow coefficient in the following order is:internal tooth height>internal tooth spacing>internal tooth relative position;and these three internal tooth parameters all have significant influence on the flow coefficient.4)In the E_1.5,E_1.7,E_2.0.0 and E_2.5.5 emitters,the minimum flow index internal tooth parameter level combination is A₁B₁C₃,that is,the inner teeth were added to the upper left side and lower right side of the vertical flow channel and the transverse flow path without vortex,the internal tooth spacing was 29.4%of the flow channel width,and the internal tooth height was 52.9%of the flow channel width.And the minimum flow coefficient combination was A₁B₁C₄,that is,the inner teeth were added to the upper left side and lower right side of the vertical flow channel and the transverse flow path without vortex,the internal tooth spacing was 29.4%of the flow channel width,and the internal tooth height was64.7%of the flow channel width.5)For a double internal tooth rectangular emitter and an ordinary rectangular labyrinth emitter,the flow coefficient increases with the size of the runner section,and the flow index decreases as the section size increases.Analyze from the degree of change,the influence of the section size on the flow coefficient is higher than its effect on the flow index.6)For double internal tooth rectangular labyrinth emitters of the same type and different cross-sectional dimensions,the flow at the same pressure decreases with the reduction of the cross-sectional dimension;according to the pressure-flow curve,the smaller the cross-section size,the more gradual the curve,that is,the flow change smaller with the pressure,and the emitter has better hydraulic performance.7)Through the numerical simulation of the E,F and G types of emitters,it can be concluded that the pressure flow curve of the G-type emitter is the most gentle,that is,the fluctuation of the flow with pressure is the smallest,but the flow index is in the largest,and the flow coefficient is smallest in the three emitters;the F-type emitter has the steepest pressure flow curve and the worst hydraulic performance.This shows that the hydraulic performance of the emitter is not only related to the flow state index,but also to the flow coefficient,and these two factors should be comprehensively considered.8)The smoothness of the pressure-flow curve of the E-type emitter is second only to the G-type emitter,but its cross-sectional area is larger than that of the G-type emitter.The anti-clogging performance of the E-type emitter can be expected to be better than that of the G-type emitter.It can be inferred that the E-type double internal tooth labyrinth flow channel emitter has better hydraulic performance.