Micro-spraying hose on-way pressure distribution prediction method based on numerical simulation

Abstract

The invention discloses a micro-spraying belt on-way pressure distribution prediction method based on numerical simulation, which comprises the following steps: S1, acquiring an upstream water head and upstream flow of an ith spraying hole, and analyzing through a numerical simulation result to obtain an on-way water head loss coefficient between an (i-1) th spraying hole and the ith spraying hole; s2, the upstream water head of the ith spray hole is calculated, and the outlet flow of the ith spray hole is calculated according to an orifice outflow formula; s3, the downstream flow and the downstream speed of the ith spray hole are calculated according to the outlet flow of the ith spray hole; s4, calculating the downstream water head of the ith spray hole according to the upstream water head of the ith spray hole; and S5, the upstream flow and the downstream water head of the (i + 1) th spray hole are calculated by repeating the methods from S1 to S4, and the on-way pressure and flow distribution of the whole micro-spraying belt are obtained. According to the method, numerical simulation research is carried out on the micro-spraying hose, a traditional calculation mode is broken through, and a refined modeling method considering factors such as the actual hole pitch and the wall thickness of the micro-spraying hose is provided.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-spraying belt quality detection, and in particular relates to a method for predicting pressure distribution along a micro-spraying belt based on numerical simulation. Background Art

[0002] Micro-sprinkler tape, also known as nozzle tape or water spray tape, creates a jet stream by perforating a plastic hose at a predetermined spacing and arrangement. As an effective supplement to efficient, water-saving agricultural irrigation technology, micro-sprinkler tape offers advantages such as low operating pressure, low cost, easy installation and movement, simple manufacturing, and strong anti-clogging properties. It is suitable for irrigation operations in various terrains and for a variety of crops.

[0003] To meet water-saving irrigation requirements, micro-sprinkler strips must achieve high irrigation uniformity. This means minimizing the variation in flow rate between nozzles to ensure even water distribution across the entire strip. Ideally, all nozzles should have the same flow rate, but actual flow rate is affected by pressure. To calculate the pressure at each nozzle, the total head of the micro-sprinkler strip must be determined, and the flow rate and head loss must be calculated segment by segment along the water flow direction.

[0004] Calculating head loss in micro-sprinkler strips is complex due to the presence of sprinklers and is difficult to solve analytically. Most studies still use empirical formulas, which can result in significant errors. Numerical simulations using CFD software can significantly shorten research time and reduce costs. Therefore, using CFD simulations to study pressure variations within micro-sprinkler strips and develop a predictive model for pressure distribution along the strips is crucial for optimizing strip installation length and ensuring uniform crop irrigation. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for predicting pressure distribution along a micro-sprinkler strip based on numerical simulation, which solves the problem of large error in calculating head loss of the prior art micro-sprinkler strip.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for predicting the pressure distribution along the micro-spray belt based on numerical simulation, comprising the following steps:

[0007] S1. Obtain the upstream head and upstream flow rate of the i-th nozzle, and obtain the head loss coefficient along the nozzle between the i-1-th nozzle and the i-th nozzle through numerical simulation results analysis;

[0008] S2, calculate the upstream head of the i-th nozzle hole, and calculate the outlet flow rate of the i-th nozzle hole according to the orifice outflow formula;

[0009] S3, calculating the downstream flow rate and downstream velocity of the i-th nozzle according to the outlet flow rate of the i-th nozzle;

[0010] S4, calculating the downstream water head of the i-th nozzle hole according to the upstream water head of the i-th nozzle hole;

[0011] S5. Repeat the methods of S1 to S4 to calculate the upstream flow rate and downstream water head of the i+1th nozzle hole, and obtain the pressure and flow rate distribution along the entire micro-spray strip.

[0012] Furthermore: In S1, the head loss coefficient λ between the i-1th nozzle and the i-th nozzle is i The specific expression is:

[0013] λ i =f λ-Re (Re i )

[0014] Where, Re i is the upstream Reynolds number of the i-th nozzle, f λ-Re (·) is the first fitting formula obtained through analysis of numerical simulation results;

[0015] Re i =u i D / ν

[0016] Where u i is the upstream velocity of the i-th nozzle, D is the diameter of the micro-spray band, and ν is the kinematic viscosity coefficient of water.

[0017] Further: In S2, calculate the upstream water head h of the i-th nozzle orifice,i,1 The specific expression is:

[0018]

[0019] Where h orifice,i-1,2 is the downstream head of the i-1th nozzle, h f,i is the head loss along the path between the i-1th nozzle and the i-th nozzle, l ori is the nozzle spacing, g is the acceleration due to gravity;

[0020] Calculate the outlet flow rate q of the i-th nozzle i The specific expression is:

[0021]

[0022] Where μ i is the flow coefficient of the i-th nozzle, A i is the area of the i-th nozzle hole.

[0023] Further: In S3, the downstream flow rate Q of the i-th nozzle is calculated i+1 and downstream velocity u i+1 The specific expression is:

[0024] Q i+1 =Q i -q i

[0025]

[0026] Where Q i is the upstream flow rate of the i-th nozzle.

[0027] Further: In S4, the downstream head h of the i-th nozzle is calculated orifice,i,2 The specific expression is:

[0028]

[0029] Where h ζ,i is the local head loss, f ζ-Re (·) is the second fitting formula obtained through analysis of numerical simulation results.

[0030] The beneficial effects of the present invention are:

[0031] (1) This invention provides a method for predicting pressure distribution along a micro-spray strip based on numerical simulation. This numerical simulation study of the micro-spray strip breaks through traditional calculation methods and proposes a refined modeling method that considers factors such as the actual hole spacing and wall thickness of the micro-spray strip. During model construction, special attention was paid to the difference between the diameter of the small holes and the main channel, and simulation accuracy was enhanced by densifying the small hole grid.

[0032] (2) In the analysis of pressure changes in micro-spray strips, the present invention proposes a more detailed calculation method by dividing the head loss into along-the-line head loss and local head loss. By calculating the corresponding coefficients and using the results obtained by numerical simulation, a quadratic relationship with the Reynolds number was successfully fitted. This innovative result greatly simplifies the calculation of coefficients under different Reynolds numbers in practical applications, improves calculation efficiency and reduces errors. Traditional methods usually ignore this detailed correlation, while the present invention provides a theoretical basis for the precise design of micro-spray strips under different flow rates and flow conditions.

[0033] (3) The present invention further analyzes the relationship between the longitudinal and local head loss coefficients and the Reynolds number. The study shows that as the Reynolds number increases, the two coefficients gradually decrease and tend to be stable. This phenomenon reveals the changing law of flow resistance of micro-spray strips under high flow rates, which is of great significance for optimizing the design of micro-spray strips. Traditional design methods generally rely on simplified assumptions, while the present invention reveals these complex flow characteristics through detailed numerical simulations, providing a more accurate basis for the design optimization of micro-spray strips in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of a method for predicting pressure distribution along a micro-spray belt based on numerical simulation.

[0035] Figure 2 To predict the predicted value and test value of the pressure along the micro-spray belt under the head pressure of 0.06MPa.

[0036] Figure 3 To predict the predicted value and test value of the pressure along the micro-spray belt under the head pressure of 0.08MPa.

[0037] Figure 4 To predict the predicted value and test value of the pressure along the micro-spray belt under the head pressure of 0.010MPa. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0039] like Figure 1 As shown, in one embodiment of the present invention, a method for predicting pressure distribution along a micro-spray belt based on numerical simulation includes the following steps:

[0040] S1. Obtain the upstream head and upstream flow rate of the i-th nozzle, and obtain the head loss coefficient along the nozzle between the i-1-th nozzle and the i-th nozzle through numerical simulation results analysis;

[0041] S2, calculate the upstream head of the i-th nozzle hole, and calculate the outlet flow rate of the i-th nozzle hole according to the orifice outflow formula;

[0042] S3, calculating the downstream flow rate and downstream velocity of the i-th nozzle according to the outlet flow rate of the i-th nozzle;

[0043] S4, calculating the downstream water head of the i-th nozzle hole according to the upstream water head of the i-th nozzle hole;

[0044] S5. Repeat the methods of S1 to S4 to calculate the upstream flow rate and downstream water head of the i+1th nozzle hole, and obtain the pressure and flow rate distribution along the entire micro-spray strip.

[0045] Based on the OpenFOAM computing platform, this paper constructs a high-precision three-dimensional numerical model of the flow within a single-nozzle micro-sprinkler strip. This model systematically analyzes the internal pressure variations and proposes a predictive model for pressure distribution along the strip. This model can be used to optimize the length of micro-sprinkler strips and ensure uniform irrigation for crops, providing theoretical support for the refined design of micro-sprinkler strips.

[0046] In this embodiment, the flow rate of the micro-spray belt head is Q0, the head pressure is p0, the diameter of the micro-spray belt is D, and the cross-sectional area of the main flow channel of the micro-spray belt is A. m =πD 2 / 4, the nozzle spacing is l ori , the area of the i-th nozzle is A i , the flow coefficient is μ i (Assuming μ i is a constant), the outflow is q i , the upstream flow rate of the i-th nozzle is Q i , downstream flow is Q i+1 =Q i -q i , upstream speed is u i =Q i / A m , downstream velocity is u i+1 =Q i+1 / A m , the upstream Reynolds number is Re i =u i D / ν, downstream Reynolds number is Re i+1 =u i+1 D / ν, upstream head is h orifice,i,1 , downstream head is h orifice,i,2 , the local head loss coefficient is ζ i 、Local head loss is h ζ,i =h orifice,i,2 -h orifice,i,1 , the head loss coefficient along the path between the i-1th nozzle and the i-th nozzle is λ i , head loss along the way h f,i =h orifice,i,1 -h orifice,i-1,2 , where u0=u1=Q0 / (A m ), h orifice,0,1 =h orifice,0,2 =p0 / ρg, and the distance between the first nozzle and the head is also l ori .

[0047] In S1, for h orifice,i-1,2 and Q i is known, so u i and Re iIt is also known that the head loss coefficient λ along the way is obtained according to the numerical simulation results. i and upstream Reynolds number Re i The first fitting formula, the head loss coefficient λ between the i-1th nozzle and the i-th nozzle i The specific expression is:

[0048] λ i =f λ-Re (Re i )

[0049] Where, Re i is the upstream Reynolds number of the i-th nozzle, f λ-Re (·) is the first fitting formula obtained through analysis of numerical simulation results;

[0050] Re i =u i D / ν

[0051] Where u i is the upstream velocity of the i-th nozzle, D is the diameter of the micro-spray band, and ν is the kinematic viscosity coefficient of water.

[0052] In this embodiment, for h orifice,i-1,2 and Q i is known, so u i and Re i It is also known that the head loss coefficient λ along the way is obtained according to the numerical simulation results. i and upstream Reynolds number Re i The first fitting formula of .

[0053] In S2, calculate the upstream head h of the i-th nozzle orifice,i,1 The specific expression is:

[0054]

[0055] Where h orifice,i-1,2 is the downstream head of the i-1th nozzle, h f,i is the head loss along the path between the i-1th nozzle and the i-th nozzle, l ori is the nozzle spacing, g is the acceleration due to gravity;

[0056] Calculate the outlet flow rate q of the i-th nozzle i The specific expression is:

[0057]

[0058] Where μ i is the flow coefficient of the i-th nozzle, A i is the area of the i-th nozzle hole.

[0059] In S3, the downstream flow rate Q of the i-th nozzle is calculated i+1 and downstream velocity u i+1 The specific expression is:

[0060] Q i+1 =Q i -q i

[0061]

[0062] Where Q i is the upstream flow rate of the i-th nozzle.

[0063] In S4, calculate the downstream head h of the i-th nozzle orifice,i,2 The specific expression is:

[0064]

[0065] Where h ζ,i is the local head loss, f ζ-Re (·) is the second fitting formula obtained through analysis of numerical simulation results.

[0066] like Figures 2-4 As shown in this embodiment, the method of the present invention is used to predict the pressure distribution along the micro-spray belt under three head pressures. Compared with the test measurement values, the predicted values and the test values under different head pressures are relatively close. The maximum error occurs at 40m~60m, but is less than 4%. It shows that the prediction model can accurately predict the pressure distribution along the micro-spraying belt.

[0067] As can be seen from the above, this invention improves the accuracy of flow analysis within micro-sprinkler strips through CFD numerical simulation, significantly improving prediction accuracy compared to traditional empirical formulas. The calculated optimal laying length effectively reduces pressure loss, enhancing the applicability of the micro-sprinkler strips. By optimizing the spacing between nozzles, the pressure distribution along the strips becomes more uniform, significantly improving spray uniformity. Furthermore, the numerical simulation of the flow resistance characteristics and patterns within micro-sprinkler strips can also be applied to other micro-irrigation equipment, such as drip irrigation tapes.

[0068] Economic effect: Due to the optimization of pressure distribution, irrigation water waste is reduced, water-saving effect is significant, and water resource utilization rate is improved; by optimizing the laying length and nozzle arrangement, equipment investment cost is reduced.

[0069] Social Impact: This method is applicable to a variety of terrains and crop types, particularly in arid and water-scarce regions, and can significantly improve the sustainability of agricultural production. By reducing water waste, it promotes the development of water-saving agriculture, meeting the needs of green agriculture and modern farmland management.

[0070] The present invention not only improves the design theory of micro-sprinkler strips, but also provides a scientific basis for agricultural water-saving irrigation, and has important engineering application value.

[0071] In the description of the present invention, it should be understood that the terms "center", "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "radial", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, the features defined by "first", "second", and "third" may explicitly or implicitly include one or more of such features.

Claims

1. A method for predicting pressure distribution along a micro-spraying belt based on numerical simulation, characterized in that: The following steps are involved: S1. Obtain the upstream head and upstream flow rate of the i-th nozzle, and obtain the head loss coefficient along the nozzle between the i-1-th nozzle and the i-th nozzle through numerical simulation results analysis; S2, calculate the upstream head of the i-th nozzle hole, and calculate the outlet flow rate of the i-th nozzle hole according to the orifice outflow formula; S3, calculating the downstream flow rate and downstream velocity of the i-th nozzle according to the outlet flow rate of the i-th nozzle; S4, calculating the downstream water head of the i-th nozzle hole according to the upstream water head of the i-th nozzle hole; S5. Repeat the methods of S1 to S4 to calculate the upstream flow rate and downstream water head of the i+1th nozzle hole, and obtain the pressure and flow rate distribution along the entire micro-spray strip.

2. The method for predicting pressure distribution along the micro-spraying belt based on numerical simulation according to claim 1 is characterized in that: In S1, the head loss coefficient λ between the i-1th nozzle and the i-th nozzle i The specific expression is: λ i =f λ-Re (Re i ) Where, Re i is the upstream Reynolds number of the i-th nozzle, f λ-Re (·) is the first fitting formula obtained through analysis of numerical simulation results; Bid i s i D / ν Where u i is the upstream velocity of the i-th nozzle, D is the diameter of the micro-spray band, and ν is the kinematic viscosity coefficient of water.

3. The method for predicting pressure distribution along the micro-spraying belt based on numerical simulation according to claim 2 is characterized in that: In S2, calculate the upstream head h of the i-th nozzle orifice,i,1 The specific expression is: Where h orifice,i-1,2 is the downstream head of the i-1th nozzle, h f,i is the head loss along the path between the i-1th nozzle and the i-th nozzle, l ori is the nozzle spacing, g is the acceleration due to gravity; Calculate the outlet flow rate q of the i-th nozzle i The specific expression is: Where μ i is the flow coefficient of the i-th nozzle, A i is the area of the i-th nozzle hole.

4. The method for predicting pressure distribution along the micro-spraying belt based on numerical simulation according to claim 3 is characterized in that: In S3, the downstream flow rate Q of the i-th nozzle is calculated i+1 and downstream velocity u i+1 The specific expression is: Q i+1 =Q i -q i Where Q i is the upstream flow rate of the i-th nozzle.

5. The method for predicting pressure distribution along the micro-spraying belt based on numerical simulation according to claim 3 is characterized in that: In S4, calculate the downstream head h of the i-th nozzle orifice,i,2 The specific expression is: Where h ζ,i is the local head loss, f ζ-Re (·) is the second fitting formula obtained through analysis of numerical simulation results.

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