Failure problem diagnosis and structure optimization design method for piston type proportional fertilization pump

Abstract

The invention provides a piston type proportional fertilization pump failure problem diagnosis and structure optimization design method. According to the method, pump inlet and outlet flow and pressure difference are monitored through a performance test platform, head loss, fertilizer absorption amount and fertilizer absorption efficiency are calculated, and whether the pump fails is judged. The sizes of key parts of new and old products are measured through CT scanning, internal blockage and abrasion conditions are observed in combination with disassembly, and failure reasons are deeply analyzed by applying the CFD technology. The method comprises the following steps: designing a plurality of groups of size models for a failure part, constructing a simplified flow field geometric model through NX UG12.0, dividing grids through ANSYS-Mesh, performing FLUENT numerical simulation analysis, extracting the real-time movement speed of a piston in combination with a UDF compiling code, and calculating and scoring performance parameters of each group of models. And finally, selecting an optimal key component size through weight scoring. The method integrates performance testing, CT scanning, disassembly observation and CFD technologies, can accurately diagnose the failure problem, effectively improves the structure of the pump, remarkably improves the performance of the lift pump, and is of great significance to the reliability and the service life of the lift pump.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural irrigation equipment, and in particular to a method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilization pump. Background Art

[0002] As an important part of the water-fertilizer integration system, the role of the fertilization device is crucial. The main function of the fertilization equipment is to dissolve fertilizer and apply fertilizer. At present, the commonly used ones in China mainly include differential pressure fertilization tanks, venturi fertilizer applicators, fertilizer applicators, and proportional fertilization pumps. The proportional fertilization pump is directly installed on the water supply pipeline. It does not require electricity and can be driven and operated only by water pressure. Quantitative and proportional is its typical feature. The ratio of the suction fertilizer flow rate and the inlet flow rate is not affected by pressure and pipe network, and it can operate under low pressure. However, its operating environment is diverse and its internal structure is complex. It is very easy to cause internal blockage and wear of the product during use, which in turn causes product failure. At the same time, due to its complex movement principle and structure, this has caused a major challenge for the structural improvement design of failed products. At present, some scholars in China have conducted research on piston-type proportional fertilization pumps, but they mainly focus on the new structural design of the product and its manufacturing method. There is still a lack of structural improvement design methods for failed piston-type proportional fertilization pump products.

[0003] At present, some scholars have explored and developed new products of piston-type proportional fertilizer pumps, such as Li Hong et al. of Jiangsu University (application publication number: CN105265084A) who disclosed a hydraulically driven fixed-proportion fertilizer pump product. This product proposed a new configuration of sliding seal and obtained the operating efficiency and service life of the device by monitoring the force and loss of the reciprocating motion of the piston through CFD, and finally selected a group of optimal piston combinations. Li Bo et al. of Henan Xishui Mechanical Equipment Sales Co., Ltd. (application publication number: CN117181040A) disclosed a hydrodynamic proportional mixing pump and manufacturing process. This product uses the working principle of water pressure driving piston movement, and uses CFD technology to observe the influence of different spring and sealing ring materials on piston movement resistance and service life, and finally selects the optimal product structure. However, the current research mainly focuses on selecting the optimal structure through cavity negative impact monitoring, and does not detect and highlight the optimization of key components that affect product performance. The failure problem of piston-type proportional fertilizer pumps during operation still exists, and there is still a lack of diagnostic methods for its failure problems and structural improvement design methods for the causes of failure.

[0004] Based on this, the present invention proposes a method for improving the design of piston-type proportional fertilizer pump products. Specifically, a diagnostic method combining experimental testing with CFD analysis and CT observation technology is proposed for the failure of piston-type proportional fertilizer pumps, and on this basis, a structural improvement design method is proposed for the failed piston-type proportional fertilizer pump in combination with CFD technology to reduce internal equipment losses and improve product efficiency. Summary of the invention

[0005] (I) The problem to be solved by the present invention is: at present, it is difficult to diagnose the failure problem of the piston-type proportional fertilization pump after it fails, and it is impossible to analyze the failure cause caused by its structure, and it is impossible to optimize and transform the proportional fertilization pump.

[0006] (II) Technical solution

[0007] A method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilization pump comprises the following steps:

[0008] S1: Failure determination of proportional fertilization pump: Connect the piston proportional fertilization pump to be tested and a brand new piston proportional fertilization pump of the same model to the proportional fertilization pump performance test platform respectively, open the water inlet valve 2, water pump 3, branch water inlet valve 7, branch water outlet valve 9, main line valve 8, return valve 16, monitor the inlet and outlet flow and pressure difference through the water inlet flow meter 6 and water outlet flow meter 10, water inlet pressure gauge 5 and water outlet pressure gauge 11, and calculate the head loss P 损 , the amount of fertilizer absorbed Q 吸肥 and fertilizer absorption efficiency μ 吸肥 If the fertilizer absorption amount or fertilizer absorption efficiency of the piston-type proportional fertilizer pump decreases by 10% and the head loss increases by 10%, the piston-type proportional fertilizer pump to be tested is judged to be a failed product;

[0009] S2: Failure structure detection: Perform CT scanning and measurement on the failed product and the new product respectively, observe and obtain the dimensions of their key components and the dimensions of the new and old products, then dismantle the failed piston proportional fertilizer pump, observe the blockage and wear of the internal key components, and then perform CFD technology diagnosis, and combine the comprehensive performance test, CT scanning measurement, and disassembly observation results to determine the failure location and cause of failure;

[0010] S3: Improved modeling of the product structure of the failed piston proportional fertilizer pump: Simplify the product model of the failed piston proportional fertilizer pump, design multiple sets of dimensions for the failed parts, use NX UG12.0 software to build a simplified flow field geometry model of the failed piston proportional fertilizer pump product of equal proportion, perform structured meshing in ANSYS-Mesh, import it into FLUENT for numerical simulation analysis, extract the real-time motion speed of the piston and compile the piston motion in combination with UDF compilation code, set the output inlet and outlet pressure, flow rate, and flow field cloud map at each time step;

[0011] S4: Structural optimization judgment: Calculate the head loss P of the corresponding product models of different groups according to the output results of CFD technology 损 , fertilizer absorption amount Q and fertilizer absorption efficiency μ, and calculate N respectively through weight scoring pi 、N qi and N μi , where the total amount of fertilizer absorbed is Nq―total =10, total score of fertilizer absorption efficiency N μ―total =10, calculate the total score N of the i-th group i :

[0012] N i =N pi +N qi +N μi

[0013] Finally, the total score results of n groups are sorted and the total score result N is selected. i The highest set of treatments was identified as the optimal critical component size.

[0014] Preferably, the proportional fertilization pump performance test platform in S1 includes a water tank 1, a water pump 3, a flow sensor 4, a water inlet pressure gauge 5, a water inlet flow meter 6, a water outlet pressure gauge 11, a water outlet flow meter 10, a fertilizer liquid barrel 13 and a distribution box 17. The two ends of the water tank 1 are connected by a pipeline. On the pipeline, an inlet valve 2, a water pump 3, a flow sensor 4, a main line valve 8, a water outlet valve 15 and a return valve 16 are installed in sequence. Between the flow sensor 4 and the main line valve 8, the main line valve 8 and the water outlet valve Three-way connectors are installed between the doors 15, and the three-way connectors are connected through branch pipes. A branch water inlet valve 7, a water inlet flow meter 6, a water inlet pressure gauge 5, a piston-type proportional fertilizer pump 12, a water outlet pressure gauge 11, a water outlet flow meter 10 and a branch water outlet valve 9 are installed in sequence on the branch pipes. A fertilizer liquid barrel 13 is placed corresponding to the piston-type proportional fertilizer pump 12. The fertilizer liquid barrel 13 is connected to the water storage tank 1 through a return pipe. A float valve 14 is installed on the return pipe, and a distribution box 17 supplies power to the electrical equipment.

[0015] Preferably, the head loss P in S1 损 , the amount of fertilizer absorbed Q 吸肥 and fertilizer absorption efficiency μ 吸肥 The calculation is as follows:

[0016] P 损 =P 进口 ―P 出口

[0017] Q=Q 出口 ―Q 进口

[0018]

[0019] Among them, P 进口 is the inlet pressure monitored by the water inlet pressure gauge 5, P 出口 is the outlet pressure monitored by the outlet pressure gauge 11, Q 进口 is the inlet flow rate monitored by the inlet flow meter 6, Q出口 It is the outlet flow rate monitored by the outlet water flow meter 10.

[0020] Preferably, the CFD technical diagnosis described in S2 includes the following steps: using NX UG12.0 software to establish three-dimensional models of the measured dimensions of key components of the failed product and the new product, and then dividing them through the ANSYS-Mesh mesh model, substituting them into FLUENT for operation analysis, setting Mixture as a multiphase flow model, the standard k-ε model as a turbulence model, the boundary conditions as a total pressure inlet, a static pressure suction port and a static pressure outlet, the wall surface as a no-slip wall surface, and after enabling the dynamic mesh, inputting the UDF code to output the inlet and outlet pressures, inlet and outlet flow rates and velocity cloud maps of each time step.

[0021] Preferably, the principle formula of the UDF compilation code in S3 is:

[0022] ΔF 水压 =ΔP 上下差 *A

[0023] ΔF 总 =ΔF 水压 +ΔF 弹簧

[0024]

[0025] Where m is the piston mass, unit: kg; Δt is the instantaneous velocity, unit: s.

[0026] Preferably, the weights in S4 are used to score the head loss N of the i-th group. pi The score is calculated as follows:

[0027]

[0028] Among them, N pi Score the head loss for group i;

[0029] N p―total is the total score of head loss, with a value of 10;

[0030] P 损i is the head loss of the ith group, unit: MPa.

[0031] Preferably, the weights in S4 are used to score the fertilizer intake of group i, N qi The score is calculated as follows:

[0032]

[0033] Among them, N qi Score the fertilizer absorption of group i;

[0034] Nq―total is the total score of fertilizer absorption, with a value of 10;

[0035] Q i is the fertilizer absorption amount of group i, unit: L / h.

[0036] Preferably, the weights in S4 are used to score the fertilizer intake of group i, N qi The score is calculated as follows:

[0037]

[0038] Among them, N μi Score the fertilizer absorption efficiency of group i;

[0039] N μ―total is the total score of fertilizer absorption efficiency, with a value of 10;

[0040] μ i is the fertilizer absorption efficiency of group i, unit: %.

[0041] Beneficial effects of the present invention:

[0042] The present invention provides a variable speed drip irrigation belt recycling machine. The present invention proposes a diagnostic method for the failure problem of a piston-type proportional fertilizer pump. The failure of the piston-type proportional fertilizer pump is analyzed by comparing the hydraulic and fertilization performance tests of new products and failed products. The internal key dimensions are measured in combination with CT scanning analysis. After the equipment is disassembled, the wear and blockage of each component are observed. After the key difference dimensions are substituted into the model, the internal flow field differences are observed in combination with CFD technology. The cause of the failure of the piston-type proportional fertilizer pump is analyzed, and a diagnostic method for the failure problem of the piston-type proportional fertilizer pump is established. Based on the above-mentioned diagnostic method for the failure problem of the piston-type proportional fertilizer pump, the present invention proposes an improved design method for the structural problem of the failed piston-type proportional fertilizer pump product. The dimensions of the key failure parts obtained by the diagnostic method of the failure problem are respectively set up with orthogonal experiments, and the internal multi-field flow of the orthogonal groups of piston-type proportional fertilizer pumps of different sizes is analyzed by CFD dynamic grid technology. The head loss, fertilizer absorption amount, and fertilizer absorption efficiency are combined for scoring comparison, and the optimal failure key component dimensions are screened out to construct a structural improvement design method for the failed piston-type proportional fertilizer pump product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1A structural diagram of a proportional fertilization pump performance test platform provided in an embodiment of the present invention;

[0045] Figure 2 A simplified structural diagram of a proportional fertilization pump provided in an embodiment of the present invention;

[0046] Figure 3 The performance of the new product and failed product piston proportional fertilizer pump provided by the embodiment of the present invention

[0047] Figure 4 Internal flow field cloud diagram of new products and failed products provided by embodiments of the present invention

[0048] Figure 5 Comparative analysis of actual measurement and CFD simulation performance provided by the embodiment of the present invention

[0049] Figure 6 CFD numerical simulation of hydraulic and fertilization performance of piston proportional fertilization pump provided in the embodiment of the present invention

[0050] Icons: 1. Water storage tank; 2. Water inlet valve; 3. Water pump; 4. Flow sensor; 5. Water inlet pressure gauge; 6. Water inlet flow meter; 7. Branch water inlet valve; 8. Main line valve; 9. Branch water outlet valve; 10. Water outlet flow meter; 11. Water outlet pressure gauge; 12. Piston-type proportional fertilizer pump; 13. Fertilizer liquid barrel; 14. Float valve; 15. Water outlet valve; 16. Return valve; 17. Distribution box; 18. Water inlet; 19. Piston; 20. Water inlet valve port; 21. Drive chamber; 22. Water outlet valve port; 23. Water outlet; 24. Fertilizer suction chamber. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1-Figure 6 As shown, a method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilization pump includes the following steps:

[0053] S1: Failure determination of proportional fertilization pump: Connect the piston proportional fertilization pump to be tested and a brand new piston proportional fertilization pump of the same model to the proportional fertilization pump performance test platform respectively, open the water inlet valve 2, water pump 3, branch water inlet valve 7, branch water outlet valve 9, main line valve 8, return valve 16, monitor the inlet and outlet flow and pressure difference through the water inlet flow meter 6, water outlet flow meter 10, water inlet pressure gauge 5 and water outlet pressure gauge 11, and calculate the head loss P 损 , the amount of fertilizer absorbed Q吸肥 and fertilizer absorption efficiency μ 吸肥 If the fertilizer absorption amount or fertilizer absorption efficiency of the piston-type proportional fertilizer pump decreases by 10% and the head loss increases by 10%, the piston-type proportional fertilizer pump to be tested is judged to be a failed product;

[0054] The performance test platform of the proportional fertilization pump in S1 comprises a water tank 1, a water pump 3, a flow sensor 4, a water inlet pressure gauge 5, a water inlet flow meter 6, a water outlet pressure gauge 11, a water outlet flow meter 10, a fertilizer liquid barrel 13 and a distribution box. The two ends of the water tank 1 are connected by a pipeline. On the pipeline, an inlet valve 2, a water pump 3, a flow sensor 4, a main line valve 8, a water outlet valve 15 and a return valve 16 are installed in sequence. Between the flow sensor 4 and the main line valve 8, the main line valve 8 and the water outlet valve 15 A three-way connector is installed between them, and the three-way connector is connected through a branch pipe. A branch water inlet valve 7, a water inlet flow meter 6, a water inlet pressure gauge 5, a piston-type proportional fertilizer pump 12, a water outlet pressure gauge 11, a water outlet flow meter 10 and a branch water outlet valve 9 are installed in sequence on the branch pipe. A fertilizer liquid barrel 13 is placed corresponding to the piston-type proportional fertilizer pump 12. The fertilizer liquid barrel 13 is connected to the water storage tank 1 through a return pipe. A float valve 14 is installed on the return pipe, and a distribution box 17 supplies power to the electrical equipment.

[0055] The head loss P 损 , the amount of fertilizer absorbed Q 吸肥 and fertilizer absorption efficiency μ 吸肥 The calculation is as follows:

[0056] P 损 =P 进口 ―P 出口

[0057] Q=Q 出口 ―Q 进口

[0058]

[0059] Among them, P 进口 is the inlet pressure monitored by the water inlet pressure gauge 5, P 出口 is the outlet pressure monitored by the outlet pressure gauge 11, Q 进口 is the inlet flow rate monitored by the inlet flow meter 6, Q 出口 It is the outlet flow rate monitored by the outlet water flow meter 10.

[0060] S2: Failure structure detection: Perform CT scanning and measurement on the failed product and the new product respectively, observe the dimensions of their key components and the dimensions of the new and old products, then disassemble the failed piston proportional fertilizer pump, observe the blockage and wear of the internal key components, and then perform CFD technical diagnosis, and combine the comprehensive performance test, CT scanning measurement, and disassembly observation results to determine the failure location and failure cause; the CFD technical diagnosis includes the following steps: use NX UG12.0 software to establish a three-dimensional model of the measured dimensions of the key components of the failed product and the new product, and then divide them through the ANSYS-Mesh mesh model, substitute them into FLUENT for operation analysis, set Mixture as a multiphase flow model, the standard k-ε model as a turbulence model, the boundary conditions are total pressure inlet, static pressure suction port and static pressure outlet, the wall is a non-slip wall, and after enabling the dynamic mesh, enter the UDF code to output the inlet and outlet pressures, inlet and outlet flow rates and velocity cloud maps of each time step.

[0061] S3: Improved modeling of the product structure of the failed piston proportional fertilizer pump: Simplify the product model of the failed piston proportional fertilizer pump, design multiple sets of dimensions for the failed parts, use NX UG12.0 software to build a simplified flow field geometry model of the failed piston proportional fertilizer pump product of equal proportion, perform structured meshing in ANSYS-Mesh, import it into FLUENT for numerical simulation analysis, extract the real-time motion speed of the piston and compile the piston motion in combination with the UDF compilation code, set the output inlet and outlet pressures, flow rates, and flow field cloud diagrams at each time step; the principle formula of the UDF compilation code is:

[0062] ΔF 水压 =ΔP 上下差 *A

[0063] ΔF 总 =ΔF 水压 +ΔF 弹簧

[0064]

[0065] Where m is the piston mass, unit: kg; Δt is the instantaneous velocity, unit: s.

[0066] S4: Structural optimization judgment: Calculate the head loss P of the corresponding product models of different groups according to the output results of CFD technology 损 , fertilizer absorption amount Q and fertilizer absorption efficiency μ, and calculate N respectively through weight scoring pi 、N qi and N μi , where head loss N pi The score is calculated as follows:

[0067]

[0068] Among them, N pi Score the head loss for group i;

[0069] N p―total is the total score of head loss, with a value of 10;

[0070] P 损i is the head loss of the ith group, unit: MPa.

[0071] Fertilizer absorption amount N qi The score is calculated as follows:

[0072]

[0073] Among them, N qi Score the fertilizer absorption of group i;

[0074] N q―total is the total score of fertilizer absorption, with a value of 10;

[0075] Q i is the fertilizer absorption amount of group i, unit: L / h.

[0076] Fertilizer absorption amount N qi The score is calculated as follows:

[0077]

[0078] Among them, N μi Score the fertilizer absorption efficiency of group i;

[0079] N μ―total is the total score of fertilizer absorption efficiency, with a value of 10;

[0080] μ i is the fertilizer absorption efficiency of group i, unit: %.

[0081] Total score of fertilizer absorption N q―total =10, total score of fertilizer absorption efficiency N μ―total =10, calculate the total score N of the i-th group i :

[0082] N i =N pi +N qi +N μi

[0083] Finally, the total score results of n groups are sorted and the total score result N is selected. i The highest set of treatments was identified as the optimal critical component size.

[0084] Example 1

[0085] Connect the failed product and the new product to the position of the piston proportional fertilizer pump 12 in the test platform, and open the water inlet valve 2, water pump 3, branch water inlet valve 7, branch water outlet valve 9, main line valve 8, and return valve 16. The water will enter the pipeline from the water inlet valve 2, flow through the branch and the pipeline, and then flow into the water tank from the return valve 16. The inlet and outlet flow rates and inlet and outlet pressure differences of the failed product and the new product are respectively monitored by the inlet flow meter 6, outlet flow meter 10, inlet pressure gauge 5, and outlet pressure gauge 11 corresponding to the inlet and outlet pressure differences, and the following are obtained through analysis: Figure 3 The performance of the new product and the failed product piston proportional fertilizer pump is shown. It was found that the head loss of the failed product increased by 22.9%, the fertilizer absorption decreased by 16.8%, the fertilizer absorption efficiency decreased by 17.16%, and it could not operate under low and high pressure conditions. At the same time, CT scanning and measurement were performed on the failed product and the new product. Analysis found that there were large differences between the new and old products in the four key dimensions of the water outlet valve port, the water inlet valve port, the piston length and the piston diameter. After disassembling the failed product and observing its internal components, it was found that the internal components had a lot of blockage and wear.

[0086] NX UG12.0 software was used to build three-dimensional models of the new product and the failed product piston proportional fertilizer pump, and then the ANSYS-Mesh mesh model was used to divide the mesh model and substituted into FLUENT for operation analysis. Mixture was set as a multiphase flow model, the standard k-ε model was set as a turbulence model, the boundary conditions were the total pressure inlet, the static pressure suction port and the static pressure outlet, and the wall was a non-slip wall. After the dynamic mesh was enabled, the UDF code was compiled using the following formula:

[0087] ΔF 水压 =ΔP 上下差 *A

[0088] ΔF 总 =ΔF 水压 +ΔF 弹簧

[0089]

[0090] Output the inlet and outlet pressure, inlet and outlet flow and velocity cloud diagrams at each time step, and obtain the following Figure 4 The internal flow field cloud diagram shown and the analysis results Figure 5 The comparison chart between actual measurement and CFD numerical simulation shows that the deviation between the simulation results and the actual measurement results is within 10%. Therefore, it is determined that the CFD numerical simulation results can be used to prove that the blockage and wear deformation of the product after failure causes the size difference of key components, which in turn causes the degradation of its various performances and changes in internal flow.

[0091] By combining the performance changes found in experimental tests, changes in key components in CT scans, internal component observations and CFD analysis results, it was comprehensively determined that the failure of the piston proportional fertilization pump lies in the water inlet valve port, water outlet valve port, piston diameter and piston length.

[0092] according to Figure 2 The simplified flow field model constructed using NX UG12.0 software is shown in Figure 2 As shown, water flows in from the water inlet 18 and into the cavity of the piston 19. After the water pressure acts on the piston surface, the fertilizer liquid is sucked from the fertilizer absorption cavity 24, and enters the drive cavity 21 from the water inlet valve port 20 to be mixed with the movement of the piston, and flows out of the piston from the water outlet valve port 22. Finally, the mixed liquid flows out of the product from the water outlet 23.

[0093] Substitute the data into FLUENT for analysis. For the different parts that are diagnosed to cause performance degradation, namely the inlet valve port, outlet valve port, piston diameter and piston length, three sizes are set for each part for orthogonal processing. The processing settings are shown in the following table.

[0094] Control group Treatment Group Water inlet valve 16.5 15、18、19.5 Water outlet valve 14 13.5、14.5、15 Piston diameter 58 56、60、62 Piston length 67 65、69、71

[0095] The above 82 sets of processed data were analyzed, and the inlet and outlet pressures, flow rates and flow field cloud diagrams at each time step were output respectively. Figure 6 Shown are the head loss, fertilizer absorption amount and fertilizer absorption efficiency.

[0096] Calculate N by weight score pi 、N qi and N μi :

[0097]

[0098] The total score N of the i-th group is calculated by the following formula: i :

[0099] N i =N pi +N qi +N μi

[0100] Taking the optimal key component dimensions of the 81 groups of treatments, the outlet valve size of 14.5 mm, the inlet valve size of 18 mm, the piston diameter of 62 mm and the piston length of 71 mm (OUT14.5_IN18_R62_L71) as an example, its P 损i =0.0156MPa, Q i =163.2L / h, μ i =21.73%, calculated N pi =0.1079, N qi =0.1714, Nμi =0.1307, so N i =0.41.

[0101] Finally, the total score results of n groups are sorted and the total score result N is selected. i The highest set of treatments was identified as the optimal critical component size.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilization pump, characterized in that: The method comprises the following steps: S1: Failure determination of proportional fertilization pump: Connect the piston proportional fertilization pump to be tested and a brand new piston proportional fertilization pump of the same model to the proportional fertilization pump performance test platform respectively, open the water inlet valve (2), water pump (3), branch water inlet valve (7), branch water outlet valve (9), main line valve (8), and return valve (16), monitor the inlet and outlet flow and pressure difference through the water inlet flow meter (6), water outlet flow meter (10), water inlet pressure gauge (5), and water outlet pressure gauge (11), and calculate the head loss P 损 , the amount of fertilizer absorbed Q 吸肥 and fertilizer absorption efficiency μ 吸肥 If the fertilizer absorption amount or fertilizer absorption efficiency of the piston-type proportional fertilizer pump decreases by 10% and the head loss increases by 10%, the piston-type proportional fertilizer pump to be tested is judged to be a failed product; S2: Failure structure detection: Perform CT scanning and measurement on the failed product and the new product respectively, observe and obtain the dimensions of their key components and the dimensions of the new and old products, then dismantle the failed piston proportional fertilizer pump, observe the blockage and wear of the internal key components, and then perform CFD technology diagnosis, and combine the comprehensive performance test, CT scanning measurement, and disassembly observation results to determine the failure location and cause of failure; S3: Improved modeling of the product structure of the failed piston proportional fertilizer pump: Simplify the product model of the failed piston proportional fertilizer pump, design multiple sets of dimensions for the failed parts, use NX UG12.0 software to build a simplified flow field geometry model of the failed piston proportional fertilizer pump product of equal proportion, perform structured meshing in ANSYS-Mesh, import it into FLUENT for numerical simulation analysis, extract the real-time motion speed of the piston and compile the piston motion in combination with UDF compilation code, set the output inlet and outlet pressure, flow rate, and flow field cloud map at each time step; S4: Structural optimization judgment: Calculate the head loss P of the corresponding product models of different groups according to the output results of CFD technology 损 , fertilizer absorption amount Q and fertilizer absorption efficiency μ, and calculate N respectively through weight scoring pi 、N qi and N μi , where the total amount of fertilizer absorbed is N q―total =10, total score of fertilizer absorption efficiency N μ―total =10, calculate the total score N of the i-th group i : N i =N pi +N qi +N μi Finally, the total score results of n groups are sorted and the total score result N is selected. i The highest set of treatments was identified as the optimal critical component size.

2. A method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilization pump, characterized in that: The proportional fertilizer pump performance test platform described in S1 comprises a water tank (1), a water pump (3), a flow sensor (4), a water inlet pressure gauge (5), a water inlet flow meter (6), a water outlet pressure gauge (11), a water outlet flow meter (10), a fertilizer liquid barrel (13) and a distribution box (17). The two ends of the water tank (1) are connected by a pipeline. On the pipeline, a water inlet valve (2), a water pump (3), a flow sensor (4), a main line valve (8), a water outlet valve (15) and a return valve (16) are installed in sequence. Between the flow sensor (4) and the main line valve (8), the main line valve (8) and A three-way connector is installed between the outlet valves (15), and the three-way connector is connected through a branch pipe. A branch water inlet valve (7), a water inlet flow meter (6), a water inlet pressure gauge (5), a piston-type proportional fertilizer pump (12), a water outlet pressure gauge (11), a water outlet flow meter (10) and a branch water outlet valve (9) are installed in sequence on the branch pipe. A fertilizer liquid barrel (13) is placed corresponding to the piston-type proportional fertilizer pump (12). The fertilizer liquid barrel (13) is connected to the water storage tank (1) through a return pipe. A float valve (14) is installed on the return pipe. A distribution box (17) supplies power to the electrical equipment.

3. A method for failure diagnosis and structural optimization design of a piston-type proportional fertilization pump, characterized in that: The head loss P in S1 损 , the amount of fertilizer absorbed Q 吸肥 and fertilizer absorption efficiency μ 吸肥 The calculation is as follows: P 损 =P 进口 ―P 出口 Q=Q 出口 ―Q 进口 Among them, P 进口 is the inlet pressure monitored by the water inlet pressure gauge (5), P 出口 is the outlet pressure monitored by the outlet pressure gauge (11), Q 进口 is the inlet flow rate monitored by the outlet flow meter (6), Q 出口 It is the outlet flow rate monitored by the outlet flow meter (10).

4. A method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilizer pump, characterized in that: The CFD technical diagnosis described in S2 includes the following steps: using NXUG12.0 software to build three-dimensional models of the measured dimensions of key components of failed products and new products, and then dividing them through the ANSYS-Mesh mesh model, and substituting them into FLUENT for operation analysis, setting Mixture as a multiphase flow model, the standard k-ε model as a turbulence model, the boundary conditions as a total pressure inlet, static pressure suction port and static pressure outlet, the wall as a no-slip wall, and after enabling the dynamic mesh, input the UDF code to output the inlet and outlet pressures, inlet and outlet flow rates and velocity cloud maps at each time step.

5. A method for failure diagnosis and structural optimization design of a piston-type proportional fertilization pump, characterized in that: The principle formula of the UDF compilation code described in S3 is: ΔF 水压 =ΔP 上下差 *A ΔF 总 =ΔF 水压 +ΔF 弹簧 Where m is the piston mass, unit: kg; Δt is the instantaneous velocity, unit: s.

6. A method for failure diagnosis and structural optimization design of a piston-type proportional fertilization pump, characterized in that: As described in S4, the head loss N of group i is scored by weight. pi The score is calculated as follows: Among them, N pi Score the head loss for group i; N p―total is the total score of head loss, with a value of 10; P 损i is the head loss of the ith group, unit: MPa.

7. A method for diagnosing failure problems and optimizing the structure of a piston-type proportional fertilizer pump, characterized in that: As described in S4, the weights are used to score the i-th group's fertilizer absorption amount N qi The score is calculated as follows: Among them, N qi Score the fertilizer absorption of group i; N q―total is the total score of fertilizer absorption, with a value of 10; Q i is the fertilizer absorption amount of group i, unit: L / h.

8. A method for failure diagnosis and structural optimization design of a piston-type proportional fertilizer pump, characterized in that: As described in S4, the weights are used to score the i-th group's fertilizer absorption amount N qi The score is calculated as follows: Among them, N μi Score the fertilizer absorption efficiency of group i; N μ―total is the total score of fertilizer absorption efficiency, with a value of 10; μ i is the fertilizer absorption efficiency of group i, unit: %.

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