A double working condition variable flow drip irrigation system with irrigation and salt driving functions and a hydraulic design method thereof

Abstract

The application discloses a double-working-condition variable-flow drip irrigation system with irrigation and salt driving functions and a hydraulic design method thereof, and belongs to the technical field of agricultural water-saving irrigation and saline-alkali land treatment. The system comprises a water source supply unit, a head hub unit, a water distribution pipe network unit and a partitioned wheel irrigation control unit, and a plurality of variable-flow irrigation emitters are sealingly installed at the water distribution tail ends of the water distribution pipe network unit. The method comprises the following steps: constructing a double-working-condition hydraulic characteristic mathematical model of the variable-flow irrigation emitter; performing double-working-condition hydraulic calculation on the capillary scale and solving the limit laying length; constructing a matrix iterative hydraulic calculation model of the tree-shaped pipe network of the irrigation plot; dividing the micro wheel irrigation plot based on the double-working-condition hydraulic constraint; and formulating a wheel irrigation system of the double-working-condition variable-flow drip irrigation system. The application changes the "salt compression by large water flooding during the dormant period" in the existing irrigation mode into "salt driving by large-flow drip irrigation during the dormant period", so that the low-efficiency large water flooding is replaced by a higher leaching efficiency, thereby achieving the water-saving and salt control purposes.

Description

Technical Field

[0001] This invention belongs to the field of agricultural water-saving irrigation and saline-alkali land management technology, and relates to irrigation systems and their design methods. Specifically, it relates to a dual-condition variable flow drip irrigation system that combines irrigation and salt removal functions and its hydraulic design method. Background Technology

[0002] Southern Xinjiang is not only a major production area for specialty fruits and forests in my country, but also a typical region where the contradiction between water scarcity and soil salinization is most acute. Currently, fruit farmers generally adopt an irrigation model of "drip irrigation during the fruit tree's growing season + flood irrigation during dormancy to suppress salt." While this model achieves water conservation through drip irrigation during the fruit tree's growing season, it still relies on traditional flood irrigation for salt leaching during dormancy. Because flood irrigation has low salt leaching efficiency and high water consumption, the water consumed for salt leaching directly offsets or even exceeds the water savings from drip irrigation, leading to an increase rather than a decrease in total agricultural water consumption in the region. At the same time, long-term flood irrigation may also raise the groundwater level, causing secondary soil salinization, thereby further exacerbating the drought and water shortage and soil salinization situation in southern Xinjiang's orchards.

[0003] If the existing irrigation model of "flood irrigation during dormancy to suppress salt" is replaced with "high-flow drip irrigation during dormancy to remove salt," that is, adopting a variable-flow drip irrigation model of "low-flow drip irrigation during the fruit tree growing season + high-flow drip irrigation during dormancy to remove salt," it is expected to solve the predicament of the fruit industry in southern Xinjiang. The core advantage of this model is that: during the growing season, low-flow drip irrigation precisely meets the water needs of fruit trees, while during the dormancy season, the directional water flow generated by high-flow drip irrigation actively "drives" soil salts away from the root zone of fruit trees to the periphery, replacing inefficient flood irrigation with higher leaching efficiency, thereby achieving the goal of water conservation and salt control.

[0004] Therefore, there is an urgent need to develop a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions, as well as its hydraulic design method, to provide water-saving and salt-controlling drip irrigation technology solutions for the characteristic forestry and fruit industry in southern Xinjiang, and promote the sustainable development of the regional forestry and fruit industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a dual-condition variable flow drip irrigation system and its hydraulic design method that combines irrigation and salt removal functions. This solves the technical problems of low salt removal efficiency and low water utilization rate during the dormant period flood irrigation under the existing technology of "drip irrigation during the fruit tree growing season + flood irrigation during the dormant period to suppress salt" mode, and the fact that long-term flood irrigation can easily raise the groundwater level and cause secondary soil salinization.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A dual-condition variable flow drip irrigation system that combines irrigation and salt removal functions includes a water supply unit, a headworks unit, a water distribution network unit, and a zoned rotation irrigation control unit. The water distribution network unit has several variable flow emitters sealed at its distribution end.

[0007] Specifically, the variable flow water emitter is a pipe-mounted structure, including a dual-channel water emitter body with a water emitter cover installed on top. An elastic diaphragm is provided in the cavity formed by the two, and a linear opening is provided at the center of the elastic diaphragm.

[0008] Specifically, the bottom of the dual-channel irrigation device body is provided with a flow channel, including a side flow channel inlet, a flow channel body, a side flow channel outlet, and an irrigation device outlet; according to function, the flow channel is divided into an independent small-flow irrigation flow channel and a large-flow salt-dissipating flow channel, wherein: the small-flow irrigation flow channel is a labyrinth-type energy-dissipating flow channel; the large-flow salt-dissipating flow channel is a straight-through flow channel without energy-dissipating structure, and an elastic diaphragm is sealed and fixed within the flow cross section of the flow channel to completely block it.

[0009] Specifically, the labyrinth-type energy dissipation channel has a width of 0.5–0.7 mm, a depth of 0.5–0.7 mm, a length of 8.3–9.3 mm, a tooth height of 0.7–0.9 mm, a tooth root distance of 0.5–0.7 mm, and a tooth angle of 55–65°. Preferably, the labyrinth-type energy dissipation channel has a width of 0.6 mm, a depth of 0.6 mm, a length of 8.8 mm, a tooth height of 0.8 mm, a tooth root distance of 0.6 mm, and a tooth angle of 60°.

[0010] Specifically, the elastic diaphragm has a diameter of 9–11 mm and a thickness of 1.2–1.8 mm; the linear opening length is 3.0–4.0 mm. Preferably, the elastic diaphragm has a diameter of 10 mm and a thickness of 1.5 mm; the linear opening length is 3.5 mm.

[0011] This invention also protects a hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described above, the method comprising the following steps: Step 1: Construction of a mathematical model for the hydraulic characteristics of a variable flow irrigation system under dual operating conditions: Step 1.1, Determination of critical pressure threshold under dual operating conditions: Based on the indoor hydraulic performance test results of the variable flow emitter, the pressure range for irrigation operating conditions and the pressure range for salt removal operating conditions are divided.

[0012] Step 1.2, Construction of the piecewise flow-pressure function model under dual operating conditions: Using the general power function model of micro-irrigation variable flow emitter, the flow-pressure relationship of the two operating conditions is fitted respectively to construct a piecewise hydraulic characteristic mathematical model (as shown in Example 1).

[0013] Step 2: Hydraulic calculations under dual working conditions at the capillary scale and determination of the ultimate laying length: Step 2.1, Calculation of total capillary head loss: The friction head loss and local head loss along the pipe are calculated using Equations 2 and 3 of the embodiment, respectively. The sum of the two is the total capillary head loss. Step 2.2, recursive calculation of pressure and flow distribution along the capillary tube: Taking the capillary tube inlet as the starting node, the capillary tube is divided into N calculation units at equal intervals along the water flow direction. Each unit corresponds to one variable flow emitter. Based on the energy conservation equation, a recursive formula for the inlet head of the i-th variable flow emitter is established (as shown in Example 4).

[0014] Step 2.3, Evaluation of capillary hydraulic performance and determination of ultimate laying length: The relative flow deviation rate is used as the control index for the irrigation quality and ultimate laying length of the system. The capillary design ultimate laying length is calculated and obtained by using Example 5.

[0015] Step 3: Construction of the iterative hydraulic calculation model for the tree-like pipe network matrix of the irrigation area: Step 3.1, Generalization and matrix definition of irrigation community pipe network topology: Taking a typical tree-like pipe network as the object, the pipe junction point is defined as a node, a single pipe segment is defined as a pipe element, and the variable flow emitter on the capillary pipe is the end outflow node.

[0016] Step 3.2, Definition of acyclic directed bus topology: Define the node-pipe element association matrix, node head matrix, pipe element flow matrix, and end node flow matrix respectively.

[0017] Step 3.3, Matrix definition of the core control equations of the pipeline network: For the dual-condition characteristics of the variable flow drip irrigation system, matrix forms of the node flow continuity equation, pipe element head loss equation, and terminal outflow equation are constructed respectively.

[0018] Step 3.4, Dual-condition matrix iterative solution: Combining field topology features, input the pipeline network topology, pipe material parameters, and dual-condition hydraulic characteristic model, set the total inlet head of the pipeline network, iteration convergence accuracy, and iteration number, and independently iterate and solve for irrigation and salt removal conditions respectively, output the hydraulic distribution results of the entire pipeline network under the two conditions, and evaluate the hydraulic performance of the system.

[0019] Step 4: Divide micro-irrigation plots based on dual-condition hydraulic constraints: Step 4.1, determine the core constraints of the rotational irrigation plots: take the salt removal condition as the core control condition and the system flow deviation rate as the core control index; at the same time, adopt the following conditions to constrain the maximum area of ​​the micro-rotational irrigation plots: the total water supply flow of a single rotational irrigation plot does not exceed the rated water supply flow of the head pressurization equipment of the system as the flow constraint, and the capillary laying length in a single rotational irrigation plot does not exceed the limit laying length as the layout constraint. The single irrigation plot of the traditional drip irrigation system is divided into several independent micro-rotational irrigation plots with hydraulic conditions that do not interfere with each other.

[0020] Step 4.2, Micro-irrigation zone division: Based on the iterative hydraulic calculation model of the pipeline matrix, calculate the upper limit of the maximum control area of ​​a single irrigation zone. Each micro-irrigation zone is equipped with an independent electrically controlled on / off valve to form an independent hydraulic unit.

[0021] Step 4.3, Hydraulic isolation design of the irrigation sub-areas: Each micro-irrigation sub-area is equipped with an independent pressure transmitter and an electrically controlled on / off valve on its inlet branch. All valves are connected to the intelligent control module at the top of the system to achieve independent control of the water supply and working pressure of the sub-areas, ensuring that the hydraulics of each micro-irrigation sub-area do not interfere with each other during the irrigation process.

[0022] Step 5: Establishing a rotation irrigation schedule for the dual-condition variable flow drip irrigation system: Step 5.1, Formulation of the rotation irrigation system under the growing season: Under the irrigation conditions, the system working pressure is low and the total water supply flow demand is small. Multiple micro-irrigation plots are used for synchronous and continuous irrigation to shorten the irrigation cycle and meet the water demand of fruit trees during the growing season.

[0023] Step 5.2, Formulation of the rotation irrigation system for salt removal during dormancy: Under salt removal conditions, the system operates under high pressure and has a large total water supply flow requirement. A single-group micro-irrigation cell is used to implement a time-sequential independent rotation irrigation method to ensure that the operating pressure and flow deviation rate of each irrigation cell always meet the design requirements.

[0024] The present invention also has the following technical features: Specifically, in step 3.2, the node-to-pipe element association matrix is: 1-th order matrix This represents the total number of pipeline nodes. The total number of pipe elements; the node head matrix is The column matrix is ​​of order, where each element represents the working head of a node; the pipe element flow matrix is... The flow matrix is ​​an ordered column matrix, where each element represents the flow rate of a pipe element; the flow matrix of the terminal node is... An ordered column matrix, where each element represents the total outflow of all variable flow emitters.

[0025] Specifically, in step 3.3, based on the law of conservation of mass, the sum of the inflow flow at any node of the pipeline network is equal to the sum of the outflow flow and the end outflow, thereby constructing the matrix form of the node flow continuity equation (as shown in Example 6).

[0026] Specifically, in step 3.3, since the head loss of the pipe element is equal to the head difference between the two ends of the pipe element, the head between the elements in the matrix is ​​calculated based on this and the method in step 2.2 is used to construct the matrix form of the pipe element head loss equation (as shown in Example 7).

[0027] Specifically, in step 3.3, it is known that the terminal outflow is determined by the working head of the node and the hydraulic characteristic model of the corresponding working condition. Based on this, the head between elements in the matrix is ​​calculated using the method in step 1.2, and the matrix form of the terminal outflow equation is constructed.

[0028] Compared with the prior art, the present invention has the following technical effects: This invention uses the system hydraulic performance under high-flow salt removal conditions as the core control constraint, the system irrigation flow deviation rate as the core control index, and combines key parameters such as the rated flow rate of the dual-condition variable flow emitter under high-flow conditions, capillary head loss, local head loss, dripper spacing, and capillary maximum laying length to comprehensively determine the maximum control area of ​​the micro-irrigation plot. It adopts multi-component time sequence to irrigate the micro-irrigation plots independently, which can simultaneously meet the dual-condition stable operation requirements of continuous synchronous irrigation of the entire irrigation plot under low-flow irrigation conditions and time sequence rotation irrigation of each micro-irrigation plot under high-flow salt removal conditions without changing the overall layout of the main pipeline network.

[0029] This invention replaces the existing irrigation model of "flood irrigation during dormancy to suppress salt" with "high-flow drip irrigation during dormancy to remove salt". That is, it adopts a variable flow drip irrigation mode of "low-flow drip irrigation during the fruit tree growing season + high-flow drip irrigation during dormancy to remove salt", so as to replace the inefficient flood irrigation with higher leaching efficiency, thereby achieving the purpose of water saving and salt control. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the dual-condition variable flow drip irrigation system of the present invention, which combines irrigation and salt removal functions.

[0031] Figure 2 This is a structural design drawing of the dual-condition variable flow water emitter of the present invention, which combines irrigation and salt removal functions.

[0032] Figure 3 This is a schematic diagram of the internal flow field of the dual-condition variable flow water emitter of the present invention, which combines irrigation and salt removal functions.

[0033] Figure 4 This is a flow-pressure relationship curve of the dual-condition variable flow water emitter of the present invention, which combines irrigation and salt removal functions.

[0034] Figure 5 This is a flowchart illustrating the hydraulic design of the dual-condition variable flow drip irrigation system with both irrigation and salt removal functions of the present invention.

[0035] Figure 6 The diagram shows the calculation results of the maximum capillary laying length for a single micro-irrigation plot.

[0036] Figure 7 This is a distribution diagram of flow deviation rate under different combinations of pipeline parameters in a single micro-irrigation plot.

[0037] The meanings of the labels in the diagram are as follows: 1-Water supply unit, 2-Head hub unit, 3-Water transmission and distribution network unit, 4-District irrigation control unit, 5-Variable flow irrigation device.

[0038] 101 - Water source, 102 - Water supply pipe.

[0039] 201-Water pump, 202-Main water pipe, 203-Sand filter, 204-Disc filter, 205-Venturi fertilizer applicator.

[0040] 301 - Main pipe, 302 - Branch pipe, 303 - Capillary pipe.

[0041] 501-Dual-channel water emitter body, 502-Water emitter top cover, 503-Elastic diaphragm, 504-Linear opening.

[0042] 50101-Side flow channel inlet, 50102-Flow channel body, 50103-Side flow channel outlet, 50104-Water outlet of the water dispenser.

[0043] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0044] It should be noted that all components used in this invention, unless otherwise specified, are components known in the art.

[0045] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0046] Example 1 This embodiment presents a dual-condition variable flow drip irrigation system that combines irrigation and salt removal functions, such as... Figure 1 As shown, the system includes a water supply unit 1, a head hub unit 2, a water transmission and distribution network unit 3, and a zoned irrigation control unit 4. Several variable flow irrigation devices 5 are sealed and installed at the water distribution end of the water transmission and distribution network unit 3.

[0047] As one specific solution in this embodiment, such as Figure 1 As shown, the water supply unit 1 includes a water source 101, which is well water or surface water. The outlet of the water source 101 is connected to the inlet of the water supply pipe 102, and the outlet of the water supply pipe 102 is connected to the inlet of the head hub unit 2.

[0048] As one specific solution in this embodiment, such as Figure 1As shown, the head hub unit 2 includes a water pump 201. The inlet of the water pump 201 is connected to the water source 101 through the water supply pipe 102. The outlet of the water pump 201 is connected to the inlet of the sand filter 203 through the water transmission main pipe 202. The outlet of the sand filter 203 is connected to the inlet of the disc filter 204. The outlet of the disc filter 204 is connected to the inlet of the Venturi fertilizer applicator 205. The outlet of the Venturi fertilizer applicator 205 is connected to the inlet of the water transmission and distribution network unit 3.

[0049] As one specific solution in this embodiment, such as Figure 1 As shown, the water distribution network unit 3 is a three-level tree-like network composed of main pipe 301, branch pipe 302, and capillary pipe 303. The inlet end of the main pipe 301 is connected to the Venturi fertilizer applicator 205. Several outlet ends of the main pipe 301 are connected to the inlet ends of several branch pipes 302 respectively. Several outlet ends of each branch pipe 302 are connected to the inlet ends of several capillary pipes 303 respectively. Several outlet ends are opened at equal intervals on the capillary pipe 303. A variable flow irrigation device 5 is sealed and installed at each outlet end. The outlet end of the variable flow irrigation device 5 leads to the micro-irrigation area.

[0050] As a specific embodiment, the zonal irrigation control unit 4 consists of several independent electrically controlled opening and closing valves installed on the branch pipe 302. All electrically controlled opening and closing valves are connected to the head hub unit 2 for signal communication and are used to independently control the water supply and operation of the corresponding micro-irrigation zone.

[0051] As one specific solution in this embodiment, such as Figure 2 As shown, the variable flow water emitter 5 is a pipe-mounted structure, including a dual-channel water emitter body 501, with a water emitter cover 502 installed on its top. An elastic diaphragm 503 is provided in the cavity formed by the two, and a linear opening 504 is provided at the center of the elastic diaphragm 503.

[0052] As one specific solution in this embodiment, such as Figure 2 As shown, the bottom of the dual-channel irrigation device body 501 is provided with a flow channel, including a side flow channel inlet 50101, a flow channel body 50102, a side flow channel outlet 50103, and an irrigation device outlet 50104. According to function, the flow channel can be divided into an independent small-flow irrigation flow channel and a large-flow salt-dissipating flow channel. The small-flow irrigation flow channel is a labyrinth-type energy-dissipating flow channel. The large-flow salt-dissipating flow channel is a straight-through flow channel without energy-dissipating structure. The elastic diaphragm 503 is sealed and fixed in the flow cross section of the flow channel to completely block it.

[0053] As one specific solution in this embodiment, such as Figure 2As shown, the labyrinthine energy dissipation channel has a width of 0.6 mm, a depth of 0.6 mm, a length of 8.8 mm, a tooth height of 0.8 mm, a tooth root distance of 0.6 mm, and a tooth angle of 60°.

[0054] As a specific embodiment, the elastic diaphragm 503 has a diameter of 10 mm and a thickness of 1.5 mm, and is made of food-grade silicone rubber methyl vinyl silicone rubber with a hardness of 55HA; the linear opening 504 has a length of 3.5 mm.

[0055] like Figure 3 As shown, under irrigation conditions, due to the low pressure, the water flow pressure cannot overcome the pre-tightening force of the elastic diaphragm. The linear opening 504 of the elastic diaphragm remains closed, the high-flow salt-discharging channel is in a closed state, and the water flows into the low-flow irrigation channel through the side channel inlet 50101 and flows out from the side channel outlet 50103 to meet the low-flow irrigation water demand of the fruit tree during its growth period.

[0056] like Figure 3 As shown, under the salt removal conditions, due to the high pressure, the high-pressure water flow acts on the water-facing surface of the elastic diaphragm, driving the elastic diaphragm 503 to produce elastic deformation. The linear opening 504 is opened and forms an effective flow section, and the large-flow salt removal channel is fully open. It flows out from the water outlet 50104 of the irrigation device at high speed and large flow rate, realizing the function of large-flow rinsing and salt removal of the soil in the crop root zone.

[0057] like Figure 4 As shown, the flow-pressure relationship curve of the variable flow emitter 5 provided in this embodiment exhibits two levels of output flow within the irrigation and salt-removal pressure ranges; when the operating head exceeds the flow change interval, the output flow of the variable flow emitter 5 increases from 1.38 L / h to 5.11 L / h. Furthermore, within the irrigation pressure range, the flow coefficient... and flow index The values ​​are 0.87 and 0.22 respectively; the flow coefficients are within the pressure range of the salt removal operation. and flow index The values ​​are 1.67 and 0.45 respectively.

[0058] As a specific and preferred embodiment, the head hub unit 2 integrates a pressurized water supply module, a precision pressure regulation module, a multi-stage filtration module, and an intelligent control module. Specifically: the pressurized water supply module provides continuous and stable water supply power for the stable operation of the system under dual operating conditions; the precision pressure regulation module performs closed-loop precise control of the system's water supply pressure, achieving seamless and stable switching between conventional irrigation working pressure and high-flow salt-removal start-up pressure, precisely matching the graded start-up pressure characteristics of the variable-flow emitter 5; the multi-stage filtration module performs multi-stage purification of the irrigation water source, preventing physical blockage of the dual-channel variable-flow emitter 5 and ensuring long-term stable system operation; the intelligent control module communicates with all the electrically controlled on / off valves of the zoned irrigation control unit 4, automatically switching the system's irrigation and salt-removal operating conditions according to the water requirements and root zone salt regulation needs of the fruit trees at different growth stages.

[0059] Example 2 This embodiment presents a hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions, as described in Embodiment 1. The design process is as follows: Figure 5 As shown, the method includes the following steps: Step 1: Construction of a mathematical model for the hydraulic characteristics of a variable flow irrigation system under dual operating conditions: Step 1.1, Determination of critical pressure thresholds for dual operating conditions: Based on the indoor hydraulic performance test results of the variable flow emitter, the pressure range for irrigation operating conditions is divided into 6–10 mH2O, and the pressure range for salt removal operating conditions is 12–16 mH2O.

[0060] Step 1.2, Construction of the piecewise flow-pressure function model under dual operating conditions: Using the general power function model of micro-irrigation variable flow emitters, the flow-pressure relationship under the two operating conditions is fitted to construct a piecewise hydraulic characteristic mathematical model (as shown in Equation 1 below): Formula 1.

[0061] In the formula: The flow rate of the variable flow emitter is expressed in L / h. The working head at the inlet of the variable flow irrigation device is measured in meters (m). , These are the flow coefficient and flow regime index under irrigation conditions, respectively, obtained by fitting hydraulic test data within the irrigation pressure range. , These are the flow coefficient and flow regime index under salt displacement conditions, respectively, obtained by fitting hydraulic test data within the salt displacement pressure range.

[0062] Step 2: Hydraulic calculations under dual working conditions at the capillary scale and determination of the ultimate laying length: Step 2.1, Calculation of total capillary head loss: The total capillary head loss includes friction head loss along the pipe and local head loss. For the on-pipe installation structure of the variable flow emitter, the following formulas 2 and 3 are used for calculation: ① The head loss along the flow path is corrected using the Darcy-Weisbach equation combined with the multi-outlet coefficient method, which is adapted to the variable flow characteristics of capillary tubes with multiple outlets: Equation 2.

[0063] In the formula: This represents head loss along the friction path, expressed in meters (m). m is the fluid viscosity. 2 / s; The flow velocity for each pipe segment, in meters (m). 3 / s; The inner diameter of each pipe segment, in meters (m). The distance between variable flow emitters or between each pipe section is measured in meters (m). The specific values ​​of the various indices in the above formula have been obtained by fitting the hydraulic performance test data of the variable flow emitters.

[0064] ② The local head loss is calculated by fully considering the installation structure of the pipe-mounted variable flow irrigation device, using the following formula: Formula 3.

[0065] In the formula: This represents local head loss, expressed in meters (m). This is the ratio of the pipe's cross-sectional area; The flow velocity for each pipe segment is expressed in m / s. This is the acceleration due to gravity, measured in m / s². 2 ; The value of is the Reynolds number, which is obtained by fitting the hydraulic performance test data of the variable flow emitter under irrigation and salt removal conditions, respectively.

[0066] Step 2.2, Recursive Calculation of Pressure and Flow Distribution along the Capillary: Taking the capillary inlet as the starting node, the capillary is divided into N equal-distance calculation units along the water flow direction (each unit corresponds to one variable flow emitter). Based on the energy conservation equation, a recursive formula for the inlet head of the i-th variable flow emitter is established: Formula 4.

[0067] In the formula: The inlet working head of the i-th variable flow emitter is in meters; The working head is designed for the capillary inlet, in meters. The head is 10 mH2O for irrigation and 16 mH2O for salt removal. , These represent the cumulative head loss along the capillary inlet to the i-th variable flow emitter, and the local head loss, respectively, in meters (m). Using the dual-condition flow-pressure piecewise function model from step 1.2, the actual flow rate of the i-th variable flow emitter is calculated simultaneously. .

[0068] Step 2.3, Evaluation of capillary hydraulic performance and determination of ultimate laying length: The relative flow deviation rate is used as the control index for the system irrigation quality and ultimate laying length. The calculation formula is as follows: Formula 5.

[0069] In the formula: This refers to the relative flow deviation rate of the capillary tube. , These are the maximum and minimum flow rates of the capillary-mounted variable flow emitter, respectively, in L / h. The rated design flow rate of the variable flow emitter, expressed in L / h, is for irrigation and salt removal conditions. This value is obtained from hydraulic performance test data. Specifically, a trial-and-error method is used to determine the capillary tube's maximum laying length, with a relative flow rate deviation rate not exceeding 20% ​​as a constraint. This method is then used to determine the maximum allowable capillary tube laying length under irrigation and salt removal conditions. , The smaller of the two values ​​is taken as the capillary design limit laying length. ).

[0070] Step 3: Construction of the iterative hydraulic calculation model for the tree-like pipe network matrix of the irrigation area: Step 3.1, Generalization and matrix definition of irrigation community pipe network topology: Taking a typical tree-like pipe network as the object, the pipe junction point is defined as a node, a single pipe segment is defined as a pipe element, and the variable flow emitter on the capillary pipe is the end outflow node.

[0071] Step 3.2, Definition of acyclic directed bus topology: Define the node-pipe association matrix respectively ( A ), node head matrix ( H ), pipe element flow matrix ( Q ) and end-node traffic matrix ( q ). Among them: the node-to-pipe element correlation matrix is 1-th order matrix This represents the total number of pipeline nodes. The total number of pipe elements; the node head matrix is The column matrix is ​​a column matrix, where each element represents the working head of a node, in meters (m); the pipe element flow matrix is... An ordered column matrix, where each element represents the flow rate of a pipe element, in meters (m). 3 / s; the end-node traffic matrix is The matrix is ​​a column matrix, where each element represents the total output flow of all variable flow emitters, in L / h.

[0072] Step 3.3, Matrix Definition of Core Control Equations for the Pipeline Network: For the dual-condition characteristics of the variable flow drip irrigation system, matrix forms of the nodal flow continuity equation, pipe element head loss equation, and terminal outflow equation are constructed respectively. Specifically: ① The continuous equation for node flow is based on the law of conservation of mass. The sum of the inflow at any node in the pipeline network is equal to the sum of the outflow and the outflow at the end. The matrix expression is: Formula 6.

[0073] ② The head loss equation for the pipe element is given, where the head loss equals the head difference between the two ends of the pipe element. The head calculation process between elements within the matrix follows step 2.2, and the specific matrix form is as follows: Formula 7.

[0074] In the formula: This is a column matrix representing the head loss along the pipe element. This is a column matrix representing the local head loss of the pipe element; For the correlation matrix The transpose of .

[0075] ③ The end outflow equation is determined by the working head at the node and the hydraulic characteristic model of the corresponding working condition. The head calculation process between elements in the matrix follows step 1.2.

[0076] Step 3.4, Dual-condition matrix iterative solution: Combining field topology features, input the pipeline network topology, pipe material parameters, and dual-condition hydraulic characteristic model, set the total inlet head of the pipeline network, iteration convergence accuracy, and iteration number, and independently iterate and solve for irrigation and salt removal conditions respectively, output the hydraulic distribution results of the entire pipeline network under the two conditions, and evaluate the hydraulic performance of the system.

[0077] Step 4: Divide micro-irrigation plots based on dual-condition hydraulic constraints: Step 4.1, determine the core constraints of the irrigation plot: take the salt removal condition as the core control condition, and the system flow deviation rate as the core control index (in this embodiment, the system flow deviation rate not exceeding 20% ​​is the hydraulic constraint); at the same time, the following conditions are used to constrain the maximum area of ​​the micro-irrigation plot: the total water supply flow of a single irrigation plot does not exceed the rated water supply flow of the head pressurization equipment of the system as the flow constraint, and the capillary laying length in a single irrigation plot does not exceed the limit laying length as the layout constraint. The single irrigation plot of the traditional drip irrigation system is divided into several independent micro-irrigation plots with hydraulic conditions that do not interfere with each other.

[0078] Step 4.2, Micro-irrigation zone division: Based on the iterative hydraulic calculation model of the pipeline matrix, calculate the upper limit of the maximum control area of ​​a single irrigation zone. Each micro-irrigation zone is equipped with an independent electrically controlled on / off valve to form an independent hydraulic unit.

[0079] Step 4.3, Hydraulic isolation design of the irrigation sub-areas: Each micro-irrigation sub-area is equipped with an independent pressure transmitter and an electrically controlled on / off valve on its inlet branch. All valves are connected to the intelligent control module at the top of the system to achieve independent control of the water supply and working pressure of the sub-areas, ensuring that the hydraulics of each micro-irrigation sub-area do not interfere with each other during the irrigation process.

[0080] Step 5: Establishing a rotation irrigation schedule for the dual-condition variable flow drip irrigation system: Step 5.1, Formulation of the rotation irrigation system under the growing season: Under the irrigation conditions, the system working pressure is low and the total water supply flow demand is small. Multiple micro-irrigation plots are used for synchronous and continuous irrigation to shorten the irrigation cycle and meet the water demand of fruit trees during the growing season.

[0081] Step 5.2, Formulation of the rotation irrigation system for salt removal during dormancy: Under salt removal conditions, the system operates under high pressure and has a large total water supply flow requirement. A single-group micro-irrigation cell is used to implement a time-sequential independent rotation irrigation method to ensure that the operating pressure and flow deviation rate of each irrigation cell always meet the design requirements.

[0082] Verification of the effect of Example 2: Based on step two, the maximum capillary laying length for a single micro-irrigation plot was calculated, and the results are as follows: Figure 6 As shown in the figure, the hydraulic performance of the dual-condition variable flow drip irrigation system should be limited to meet the salt removal condition, and the spacing between the variable flow emitters should be greater than 1.0m to obtain an acceptable flow deviation rate.

[0083] Furthermore, based on step three and using the 1.0m variable flow emitter spacing determined in step two of this embodiment as input, the flow deviation rate distribution under different pipeline parameter combinations in a single micro-irrigation plot in this embodiment was established, and the results are as follows: Figure 7 As shown in the figure, the combination of capillary and branch pipe lengths under salt removal conditions is the key to determining the hydraulic performance of the dual-condition variable flow drip irrigation system. Furthermore, by appropriately reducing the maximum laying length of the capillary, the branch pipe length can be effectively increased, thereby increasing the actual irrigation area of ​​a single micro-irrigation plot.

[0084] Specifically, by Figure 7 It can be seen that when the capillary tube length and branch tube length are 45m and 65m respectively, the flow deviation rate of a single micro-irrigation plot does not exceed 20%, and the effective irrigation area can reach 4.7 mu.

[0085] Furthermore, based on steps four and five, and using the appropriate capillary length and branch pipe length determined in step three of this embodiment as input, and taking a 100-mu orchard in southern Xinjiang with a main stream spacing of 3.0m and a plant spacing of 1.0m as an example, 23 micro-irrigation plots for the dual-condition variable flow drip irrigation system are obtained, with a rated flow of 35m³ at the headworks. 3 / h, total system water supply flow rate 31.42m³ / h 3 / h.

[0086] During the fruit tree growing season, 23 micro-irrigation plots are irrigated simultaneously and in a continuous manner under irrigation conditions to meet the water requirements of the fruit trees during the growing season. During the fruit tree dormancy period, under salt removal conditions, single micro-irrigation plots are irrigated independently in sequence. Six micro-irrigation plots are operated in parallel by a single irrigation group. The plots within the group are operated in parallel and synchronously, while the plots between groups are irrigated in sequence according to time. A 24-hour continuous irrigation mode is adopted, with a single irrigation group having a single irrigation duration of 4.5 days. The total complete salt removal irrigation cycle of the entire system is 18 days, which is fully adapted to the safe leaching window of 30 days before the soil freezes during the dormancy period of fruit trees in southern Xinjiang.

Claims

1. A dual-condition variable flow drip irrigation system with both irrigation and salt removal functions, characterized in that, Includes several variable flow water emitters (5); The variable flow water emitter (5) is a pipe-on structure, including a dual-channel water emitter body (501), with a water emitter cover (502) installed on its top. An elastic diaphragm (503) is provided in the cavity formed by the two, and a linear opening (504) is provided at the center of the elastic diaphragm (503). The bottom of the dual-channel water emitter body (501) is provided with a flow channel, including a side flow channel inlet (50101), a flow channel body (50102), a side flow channel outlet (50103), and a water emitter outlet (50104). According to their functions, the flow channels are divided into two independent channels: a small-flow irrigation channel and a large-flow salt removal channel. The small-flow irrigation channel is a labyrinth-type energy dissipation channel, while the large-flow salt removal channel is a straight-through channel without an energy dissipation structure. An elastic diaphragm (503) is sealed and fixed within the flow cross section of the channel to completely block it.

2. The dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 1, characterized in that, The labyrinthine energy dissipation channel has a width of 0.5–0.7 mm, a depth of 0.5–0.7 mm, a length of 8.3–9.3 mm, a tooth height of 0.7–0.9 mm, a tooth root distance of 0.5–0.7 mm, and a tooth angle of 55–65°.

3. The dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 1, characterized in that, The elastic diaphragm (503) has a diameter of 9-11 mm and a thickness of 1.2-1.8 mm; the linear opening (504) has a length of 3.0-4.0 mm.

4. A hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: Step 1: Construction of a mathematical model for the hydraulic characteristics of a variable flow irrigation system under dual operating conditions; Step 2: Hydraulic calculation under dual working conditions at the capillary scale and solution for the ultimate laying length; Step 3: Constructing an iterative hydraulic calculation model for the tree-like pipe network matrix of the irrigation area; Step 4: Divide micro-irrigation plots based on dual-condition hydraulic constraints; Step 5: Formulate the rotation irrigation system for the dual-condition variable flow drip irrigation system.

5. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, Step one includes the following steps: Step 1.1, Determination of critical pressure threshold under dual operating conditions: Based on the indoor hydraulic performance test results of the variable flow emitter, the pressure range of irrigation operating condition and the pressure range of salt removal operating condition are divided. Step 1.2, Construction of the piecewise flow-pressure function model under dual operating conditions: Using the general power function model of micro-irrigation variable flow emitter, the flow-pressure relationship of the two operating conditions is fitted respectively to construct a piecewise hydraulic characteristic mathematical model.

6. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, Step two includes the following steps: Step 2.1, Calculation of total capillary head loss: The head loss along the friction and the local head loss are calculated separately, and the sum of the two is the total capillary head loss; Step 2.2, recursive calculation of pressure and flow distribution along the capillary tube: Taking the capillary tube inlet as the starting node, the capillary tube is divided into N calculation units at equal intervals along the water flow direction. Each unit corresponds to one variable flow emitter. Based on the energy conservation equation, a recursive formula for the inlet head of the i-th variable flow emitter is established. Step 2.3, Evaluation of capillary hydraulic performance and determination of ultimate laying length: Using the relative flow deviation rate as the control index for the irrigation quality and ultimate laying length of the system, calculate and obtain the design ultimate laying length of the capillary tube.

7. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, Step three includes the following steps: Step 3.1, Generalization and matrix definition of irrigation community pipe network topology: Taking a typical tree-like pipe network as the object, the pipe junction point is defined as a node, a single pipe segment is defined as a pipe element, and the variable flow emitter on the capillary pipe is the end outflow node; Step 3.2, Definition of acyclic directed bus topology: Define the node-pipe element association matrix, node head matrix, pipe element flow matrix, and end node flow matrix respectively; Step 3.3, Matrix definition of the core control equations of the pipeline network: For the dual-condition characteristics of the variable flow drip irrigation system, matrix forms of the node flow continuity equation, pipe element head loss equation, and terminal outflow equation are constructed respectively. Step 3.4, Dual-condition matrix iterative solution: Combining field topology features, input the pipeline network topology, pipe material parameters, and dual-condition hydraulic characteristic model, set the total inlet head of the pipeline network, iteration convergence accuracy, and iteration number, and independently iterate and solve for irrigation and salt removal conditions respectively, output the hydraulic distribution results of the entire pipeline network under the two conditions, and evaluate the hydraulic performance of the system.

8. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, In step 3.2, the node-to-pipe element correlation matrix is: 1-th order matrix, This represents the total number of pipeline nodes. The total number of pipe elements; the node head matrix is The column matrix is ​​of order, where each element represents the working head of a node; the pipe element flow matrix is... An ordered column matrix, where each matrix element represents the flow rate of a pipe element; The end-node traffic matrix is ​​as follows: An ordered column matrix, where each element represents the total outflow of all variable flow emitters.

9. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, Step four includes the following steps: Step 4.1, determine the core constraints of the rotational irrigation plots: take the salt removal condition as the core control condition and the system flow deviation rate as the core control index; at the same time, adopt the following conditions to constrain the maximum area of ​​the micro-rotational irrigation plots: the total water supply flow of a single rotational irrigation plot does not exceed the rated water supply flow of the head pressurization equipment of the system as the flow constraint, and the capillary laying length in a single rotational irrigation plot does not exceed the limit laying length as the layout constraint. The single irrigation plot of the traditional drip irrigation system is divided into several independent micro-rotational irrigation plots with hydraulic conditions that do not interfere with each other. Step 4.2, Micro-irrigation zone division: Based on the iterative hydraulic calculation model of the pipeline matrix, calculate the upper limit of the maximum control area of ​​a single irrigation zone. Each micro-irrigation zone is equipped with an independent electrically controlled on / off valve to form an independent hydraulic unit. Step 4.3, Hydraulic isolation design of the irrigation sub-areas: Each micro-irrigation sub-area is equipped with an independent pressure transmitter and an electrically controlled on / off valve on its inlet branch. All valves are connected to the intelligent control module at the top of the system to achieve independent control of the water supply and working pressure of the sub-areas, ensuring that the hydraulics of each micro-irrigation sub-area do not interfere with each other during the irrigation process.

10. The hydraulic design method for a dual-condition variable flow drip irrigation system with both irrigation and salt removal functions as described in claim 4, characterized in that, Step five includes the following steps: Step 5.1, Formulation of rotation irrigation system under irrigation conditions during the growing season: Under irrigation conditions, the system working pressure is low and the total water supply flow demand is small. Multiple micro-rotation irrigation plots are used for synchronous and contiguous irrigation to shorten the irrigation cycle and meet the water demand of fruit trees during the growing season. Step 5.2, Formulation of the rotation irrigation system for salt removal during dormancy: Under salt removal conditions, the system operates under high pressure and has a large total water supply flow requirement. A single-group micro-irrigation cell is used to implement a time-sequential independent rotation irrigation method to ensure that the operating pressure and flow deviation rate of each irrigation cell always meet the design requirements.

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