Hydraulic ram pump stopping safety protection system and protection method based on hydraulic model

Abstract

The invention relates to the technical field of pump station safety protection, and discloses a hydraulic model-based hydraulic ram pump stopping safety protection system and method. The hydraulic model-based hydraulic ram pump stopping safety protection system comprises a parameter collection module, a hydraulic model establishment module, a hydraulic model checking module and a hydraulic ram protection optimization module, and outputting a water hammer protection optimization strategy for the most unfavorable transient condition. The positive pressure of a pipeline water hammer can be reduced by optimizing the two-stage closing rule of a hydraulic control butterfly valve and increasing the rotational inertia of a water pump unit aiming at the pump stop water hammer risk of a municipal pump station system, the positive pressure and the negative pressure of the pipeline water hammer can be effectively reduced by installing an air valve at a proper position, and the valve closing total duration and the quick closing duration are fixed. Along with the reduction of the quick-closing angle, the maximum water hammer pressure of the pipeline is firstly reduced and then increased; and when the valve closing total duration and the quick closing angle are fixed, the maximum water hammer pressure of the pipeline is continuously increased along with the increase of the quick closing time.

Description

Technical Field

[0001] The present invention relates to the technical field of pump station safety protection, and in particular to a water hammer pump stop safety protection system and a protection method based on a hydraulic model. Background Art

[0002] Research shows that water hammer is the most common and harmful factor affecting the safe and stable operation of municipal water distribution systems. Water hammer is widely found in municipal water supply projects, building water supply and drainage projects, and other engineering fields. In severe cases, water hammer can cause municipal pumping stations to be flooded, pipes to burst, equipment and buildings to be damaged, seriously affecting urban production, life, and public safety, and causing a waste of water resources.

[0003] In order to avoid destructive water hammer in municipal water supply projects under extreme operating conditions, it is necessary to conduct safety assessment and verification of the most unfavorable operating conditions of municipal pump stations. In view of the uncontrollable risks in actual experiments, it is increasingly important to use accurate calibrated hydraulic models to verify extreme operating conditions. This has important practical significance for supporting the safe and reliable operation of municipal water supply projects, promoting the high-quality development of national intelligent water network construction, urban renewal, and underground pipeline safety, and ensuring urban economic development and social stability. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a water hammer pump stop safety protection system and protection method based on a hydraulic model, which has the advantages of safety protection and solves the above-mentioned technical problems.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a hydraulic pump stop safety protection method based on a hydraulic model, comprising a pump station system, a two-stage closing hydraulically controlled butterfly valve and an air valve, wherein the pump station system comprises a full characteristic curve of the water pump, a speed change equation and a head balance equation, and further comprises the following steps:

[0008] S1. Establish a hydraulic model and set boundary conditions, wherein the hydraulic model includes model establishment parameters and water hammer calculation expressions;

[0009] S2, collecting the hydraulic model parameters in step S1;

[0010] S3. Analyze the local sensitivity and global sensitivity of hydraulic model parameters, including pipeline flow, pipeline friction coefficient, water hammer wave velocity, unit rotational inertia, air valve intake and exhaust coefficient, maximum water hammer pressure, minimum water hammer pressure at the pump outlet, and maximum reverse speed of the pump;

[0011] S4. Perform steady-state hydraulic model calibration and transient hydraulic model calibration based on the hydraulic model;

[0012] S5. Evaluate different transient conditions based on the hydraulic model, determine the most unfavorable transient condition, and output the water hammer protection optimization strategy for the most unfavorable transient condition.

[0013] The water hammer calculation expression in step S1 includes a water hammer wave velocity expression and a water hammer basic equation, and its specific expression is as follows:

[0014] Water hammer wave speed:

[0015]

[0016] Among them, α represents the water hammer wave velocity, K represents the bulk elastic modulus of the fluid, ρ represents the fluid density, D represents the pipe diameter, E represents the elastic modulus of the pipe wall material, and e represents the pipe wall thickness;

[0017] Basic equation of water hammer:

[0018] Equations of motion:

[0019]

[0020] Continuity equation:

[0021]

[0022] Among them, H represents the head lift, V represents the flow velocity in the pipe, f represents the friction coefficient of the pipeline, a represents the angle between the pipeline and the horizontal plane, α represents the water hammer wave velocity, x represents the position coordinate, D represents the pipe diameter, g represents the gravitational acceleration, t is the time variable, sin represents the sine function, and the motion equation and continuity equation both reflect the changing laws of the flow velocity and water body in the water hammer field in the form of partial differential equations, and the characteristic line method is used for instantaneous solution.

[0023] The boundary conditions in step S1 include upstream and downstream boundaries, which are expressed as follows:

[0024]

[0025] in, represents the head pressure at node 1 at the upstream end of pipeline j at any time, H s Indicates the upstream water level, The head pressure at any time at the upstream node n of pipeline j, H d Indicates the downstream grid water level.

[0026] The hydraulic model parameters in step S2 include actual measured parameters and parameters to be calculated, wherein the actual measured parameters include the length, diameter, wall thickness, roughness coefficient, resistance coefficient, material elastic modulus, factory specifications, models and characteristic parameters of the valve, altitude, cavitation pressure, and air temperature of the pipeline at the current moment; the parameters to be calculated include pipeline resistance coefficient, water pump moment of inertia, and water pump characteristic curve; the pipeline resistance coefficient is calculated using the Hezen-Williams formula, and the water pump moment of inertia is usually based on factory parameters. When data is missing, the expression is as follows:

[0027] J T =J1+J2+J3

[0028]

[0029] J2=J1×10%

[0030] Among them, J1, J2, and J3 represent the motor moment of inertia, the pump impeller moment of inertia, and the additional inertia flywheel moment of inertia, respectively. T represents the rotational inertia of the water pump unit, N represents the motor speed, D represents the inertia diameter, G represents the equivalent weight of the load in the motor-driven system, and the water pump characteristic curve adopts the Suter full characteristic curve with a similar specific speed in the Wanda database.

[0031] The local sensitivity of the hydraulic model parameters in step S3 is analyzed by Morris screening method, and the mean value of the result of Morris screening method is selected as the sensitivity discrimination parameter S, which is specifically expressed as:

[0032]

[0033] Among them, y i+1 represents the target result simulated by the i+1th group of parameter values, y i represents the target result simulated by the i-th group of parameter values, y0 represents the target result simulated by the initial parameter values, P i represents the percentage change of the i-th group of parameters relative to the initial parameter value, P i+1 represents the percentage change of the i+1th group of parameters relative to the initial parameter value, n represents the nth group of data, and finally the ranking expression of the maximum water hammer pressure sensitivity to the model is as follows:

[0034] S 水锤波速 >S 管线流量 >S 转动惯量 >S 摩阻系数 >S 空气阀进排气系数

[0035] The ranking expression of the sensitivity of the minimum water hammer pressure at the pump outlet to the model is as follows:

[0036] S 转动惯量 >S 管线流量 >S 水锤波速 >S 摩阻系数 >S 空气阀进排气系数

[0037] The ranking expression of the sensitivity of the maximum reverse speed of the pump to the model is as follows:

[0038] S 水锤波速 >S 摩阻系数 >S 管线流量 >S 转动惯量 >S 空气间进排气系数

[0039] Among them, S * Indicates *sensitivity.

[0040] The global sensitivity of the hydraulic model parameters in step S3 is analyzed using the Sobol sensitivity analysis method, and finally the global sensitivity expression of the maximum water hammer pressure to the model is obtained as follows:

[0041] S T水锤波速 >S T转动惯量 >S T管线流量 >S T摩阻系数 >S T空气阀进排气系数

[0042] The global sensitivity expression of the minimum water hammer pressure at the pump outlet to the model is as follows:

[0043] S T管线流量 >S T转动惯量 >S T水锤波速 >S T摩阻系数 >S T空气阀进排气系数

[0044] The global sensitivity expression of the maximum reverse speed of the pump to the model is as follows:

[0045] S T水锤波速 >S T摩阻系数 >S T转动惯量 >S T管线流量 >S T空气阀进排气系数

[0046] Among them, S T* Indicates the global sensitivity of *.

[0047] The steady-state hydraulic model verification in step S4 specifically adjusts the pipeline flow, the friction coefficient along the pipeline and the local resistance coefficient of the pipeline, and after the adjustment, the deviation between the simulated values ​​of the steady-state flow and steady-state pressure and the corresponding monitored values ​​of the two is compared to determine the parameter value.

[0048] The transient hydraulic model verification in step S4 specifically adjusts the water hammer wave velocity and the moment of inertia, and determines the parameter value by comparing the deviation between the simulated value and the monitored value of the water hammer pressure variation curve at the key position.

[0049] The transient operating conditions specifically include 4 different transient operating conditions, specifically:

[0050] Transient condition 1: Transient hydraulic transition process after a power outage and pump stop during stable operation of a single large pump

[0051] Transient operating condition 2: Transient hydraulic transition process after power failure and pump stop when two large and one small water pumps are running stably

[0052] Transient operating condition 3: Transient hydraulic transition process after power failure and pump stop when two large pumps are running stably

[0053] Transient operating condition 4: The transient hydraulic transition process after a power outage and pump stop when three water pumps, one large and two small, are running stably;

[0054] The most unfavorable transient operating condition determined is transient operating condition four. The output water hammer protection optimization strategy is specifically: adding air valves, increasing the unit's rotational inertia and optimizing the valve closing rule. The optimized valve closing rule is fast closing 2s, slow closing 18s, fast closing 71°, slow closing 19°, increasing the rotational inertia of both large and small pumps by 50%.

[0055] The present invention also provides a water hammer pump stop safety protection system based on a hydraulic model, which is used to run the above-mentioned water hammer pump stop safety protection method based on a hydraulic model, including a parameter collection module, a hydraulic model establishment module, a hydraulic model verification module and a water hammer protection optimization module. The parameter collection module is used to collect parameters in the hydraulic model establishment process, and send the collected formulas to the hydraulic model establishment module. The hydraulic model establishment module establishes the model through model establishment parameters and water hammer calculation expressions, and analyzes the local sensitivity and global sensitivity of the hydraulic model parameters. Thereafter, the hydraulic model verification module performs steady-state hydraulic model verification and transient hydraulic model verification on the model established by the hydraulic model establishment module. Finally, the water hammer protection optimization module determines the most unfavorable transient operating condition, and outputs a water hammer protection optimization strategy for the most unfavorable transient operating condition.

[0056] Compared with the prior art, the present invention provides a water hammer pump stop safety protection system and protection method based on a hydraulic model, which has the following beneficial effects:

[0057] 1. The present invention aims at the risk of water hammer during pump stop in the municipal pump station system. It can reduce the positive pressure of pipeline water hammer by optimizing the two-stage closing rule of the hydraulically controlled butterfly valve and increasing the rotational inertia of the water pump unit. Installing an air valve at a suitable position can effectively reduce the positive and negative pressures of pipeline water hammer. Under the conditions that the total valve closing time and the quick closing time are fixed, the maximum water hammer pressure of the pipeline first decreases and then increases with the decrease of the quick closing angle; when the total valve closing time and the quick closing angle are fixed, the maximum water hammer pressure of the pipeline continues to increase with the increase of the quick closing time.

[0058] 2. The present invention points out through the research results of the correlation of hydraulic model parameters that the water hammer wave velocity, pipeline flow and resistance coefficient are positively correlated with the maximum water hammer pressure, and the unit moment of inertia is negatively correlated with the maximum water hammer pressure; the unit moment of inertia is positively correlated with the minimum water hammer pressure at the water pump outlet, and the pipeline flow, resistance coefficient and water hammer wave velocity are negatively correlated with the minimum water hammer pressure at the water pump outlet; the water hammer wave velocity, pipeline flow and resistance coefficient are positively correlated with the maximum reversal speed of the water pump, and the unit moment of inertia is negatively correlated with the maximum reversal speed of the water pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a schematic diagram of the first-order and full-order sensitivity of different simulation parameters to the maximum water hammer pressure of the present invention;

[0060] Figure 2 It is a schematic diagram of the first-order and full-order sensitivity of different simulation parameters to the minimum water hammer pressure at the outlet of the water pump according to the present invention;

[0061] Figure 3 It is a schematic diagram of the first-order and full-order sensitivity of different simulation parameters to the maximum reverse speed of the water pump according to the present invention;

[0062] Figure 4 This is a schematic diagram of the principle of high-frequency pressure collection and analysis in step S2 of the present invention;

[0063] Figure 5 It is a schematic diagram of the process of the present invention;

[0064] Figure 6 It is a schematic diagram of the system framework of the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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.

[0066] See also Figure 1-6A safety protection method for stopping a water hammer pump based on a hydraulic model includes a pump station system, a two-stage closing hydraulically controlled butterfly valve and an air valve. The pump station system includes a full characteristic curve of the water pump, a speed change equation and a head balance equation.

[0067] The hydraulically controlled butterfly valve is a two-stage closing valve widely used in water pipelines. Among them, the heavy hammer hydraulically controlled butterfly valve is opened by hydraulic drive and closed by the potential energy of the heavy hammer. It has the characteristics of complex structure, large project investment, and high maintenance requirements. Therefore, it is generally used in pump station systems with high head, large flow, large water hammer pressure rise or high automation requirements.

[0068] The air valve is a special valve used in water pipelines. It is usually installed at the outlet pipe of a water pump and at a local high point of a long-distance water pipeline. It exhausts air at high speed when filling with water; it continuously removes a small amount of dissolved gas in the water when the pipe is full; it inhales air at high speed when the pipeline is drained to prevent negative pressure from forming in the pipeline.

[0069] The following steps are also included:

[0070] S1. Establish a hydraulic model and set boundary conditions, wherein the hydraulic model includes model establishment parameters and water hammer calculation expressions;

[0071] The water hammer calculation expression in step S1 includes the water hammer wave velocity expression and the water hammer basic equation, and its specific expression is as follows:

[0072] Water hammer wave speed:

[0073]

[0074] Among them, α represents the water hammer wave velocity, K represents the bulk elastic modulus of the fluid, ρ represents the fluid density, D represents the pipe diameter, E represents the elastic modulus of the pipe wall material, and e represents the pipe wall thickness;

[0075] Basic equation of water hammer:

[0076] Equations of motion:

[0077]

[0078] Continuity equation:

[0079]

[0080] Among them, H is the head lift, V is the flow velocity in the pipe, f is the friction coefficient of the pipeline, a is the angle between the pipeline and the horizontal plane, α is the water hammer wave velocity, x is the position coordinate, D is the pipe diameter, g is the gravitational acceleration, t is the time variable, sin is the sine function, and the equation of motion and continuity equation both reflect the changing laws of flow velocity and water body in the water hammer field in the form of partial differential equations, and the characteristic line method is used for instantaneous solution.

[0081] The boundary conditions in step S1 include the upstream and downstream boundaries, which are expressed as follows:

[0082]

[0083] in, represents the head pressure at node 1 at the upstream end of pipeline j at any time, H s Indicates the upstream water level, The head pressure at any time at the upstream node n of pipeline j, H d Indicates the downstream grid water level

[0084] S2, collecting the hydraulic model parameters in step S1;

[0085] The hydraulic model parameters in step S2 include actual measured parameters and parameters to be calculated, wherein the actual measured parameters include the length, diameter, wall thickness, roughness coefficient, resistance coefficient, material elastic modulus, factory specifications, models and characteristic parameters of the valve, altitude, cavitation pressure, and air temperature of the pipeline at the current moment. The parameters to be calculated include the pipeline resistance coefficient, the moment of inertia of the water pump, and the water pump characteristic curve. The pipeline resistance coefficient is calculated using the Hezen-Williams formula, and the moment of inertia of the water pump is usually based on the factory parameters. When the data is missing, the expression is as follows:

[0086] J T =J1+J2+J3

[0087]

[0088] J2=J1×10%

[0089] Among them, J1, J2, and J3 represent the motor moment of inertia, the pump impeller moment of inertia, and the additional inertia flywheel moment of inertia, respectively. T represents the rotational inertia of the water pump unit, N represents the motor speed, D represents the inertia diameter, G represents the equivalent weight of the load in the motor-driven system, and the water pump characteristic curve adopts the Suter full characteristic curve with a similar specific speed in the Wanda database;

[0090] As far as water hammer protection is concerned, the monitoring indicators of municipal pump stations and pipeline systems mainly include two categories: system hydraulic parameters and equipment operating parameters. Among them, hydraulic parameters include flow, pressure and water level; equipment operating parameters include hydraulic butterfly valve closing rules, water pump speed, motor power and pipeline amplitude. By monitoring the above parameters, the monitoring data can help to scientifically evaluate whether the daily operating conditions of the pump station meet safety requirements; on the other hand, the monitoring data can be used to determine whether the factory parameters of key components such as water pumps and butterfly valves are accurate, which helps to accurately establish the initial hydraulic model. A high-frequency water hammer monitoring system is used, which consists of a perception module, a recording and analysis module, and a communication module. It mainly collects water hammer transient pressure at high frequency, generally not less than 200Hz, and is supplemented by monitoring pipeline flow, vibration and equipment operating status. For example, for water pump units, the main monitoring is the time when the water pump starts to reverse, reaches the maximum reversal, and the maximum reversal speed of the water pump, to determine whether the reversal speed and time of the water pump meet the standards after the pump is stopped under extreme working conditions (not exceeding 1.2 times the rated speed, and the reversal time is less than 2 minutes); for hydraulically controlled butterfly valves, the main monitoring is the water hammer pressure rise value of the pipeline after the pump is stopped and the displacement and time rules of the hydraulically controlled butterfly valve weight hammer, to determine whether the check valve is damaged in long-term operation and whether the opening and closing rules are offset; for air valves, the main monitoring is the pressure and liquid level at the air valve, to evaluate the operating status of the air valve and to determine whether suction and exhaust occur in the pipeline; for pipelines, the main monitoring is the pipeline vibration speed and the flow rate at the end of the pipeline after the pump is stopped, to evaluate the impact of pipeline vibration on the water supply and distribution system;

[0091] Water hammer monitoring of pump stations and pipeline systems is mainly aimed at locations prone to pipe bursts or other key locations in the system, such as the inside of the pump room, the hump of the pipeline, the joints where the pipeline material changes, and near tunnels and railways. Among them, pressure monitoring points are generally selected at the inlet and outlet of the water pump, the outlet of the check valve, the inlet of the air valve and the control valve, and nodes set according to the needs of hydraulic analysis, such as the lowest point of the pipeline elevation; flow monitoring points are generally selected at the outlet main pipe of the pump station, the starting end of the water pipeline, and the starting end of the branch pipe; pipeline vibration monitoring points are generally selected at the outlet main pipe of the pump station, the inlet of the control valve, etc.

[0092] S3, based on the Guizhou Provincial Municipal Pumping Station, there are two pumps (one for use and one for backup). The rated head of a single pump is 220m and the rated flow is 70m 3 / h, rated speed 1475r / min, matching motor power 450kw, efficiency 78%. The diameter of the water pump pressure pipe is DN300mm, and then it is connected to the water lifting main pipe. The main pipe is a steel pipe with a diameter of DN500mm, a wall thickness of 12mm, and a pipe length of 1.35km. An air valve with an intake and exhaust coefficient of 0.72 is arranged at 0+318, 0+705 and 1+010 of the main pipe respectively. A DN300 two-stage hydraulically controlled butterfly valve is installed at the water outlet of the water pump as a check valve. The center elevation of the water pump is 928.8m, the center elevation of the check valve is 930.2m, and the operating water levels of the inlet and outlet pools are 929.8m and 1099.0m respectively. The local sensitivity and global sensitivity of the hydraulic model parameters are analyzed, where the hydraulic model parameters include pipeline flow, pipeline friction coefficient, water hammer wave velocity, unit moment of inertia, air valve intake and exhaust coefficient, maximum water hammer pressure, minimum water hammer pressure at the pump outlet and maximum reverse speed of the pump;

[0093] In step S3, the local sensitivity of the hydraulic model parameters is analyzed using the Morris screening method, and the mean value of the results of the Morris screening method is selected as the sensitivity discrimination parameter S. The specific expression is:

[0094]

[0095] Among them, y i+1 represents the target result simulated by the i+1th group of parameter values, y i represents the target result simulated by the i-th group of parameter values, y0 represents the target result simulated by the initial parameter values, P i represents the percentage change of the i-th group of parameters relative to the initial parameter value, P i+1 represents the percentage change of the i+1th group of parameters relative to the initial parameter value, b represents the nth group of data, and finally the ranking expression of the maximum water hammer pressure sensitivity to the model is as follows:

[0096] S 水锤波速 >S 管线流量 >S 转动惯量 >S 摩阻系数 >S 空气阀进排气系数

[0097] The ranking expression of the sensitivity of the minimum water hammer pressure at the pump outlet to the model is as follows:

[0098] S 转动惯量 >S 管线流量 >S 水锤波速 >S 摩阻系数 >S 空气阀进排气系数

[0099] The ranking expression of the sensitivity of the maximum reverse speed of the pump to the model is as follows:

[0100] S水锤波速 >S 摩阻系数 >S 管线流量 >S 转动惯量 >S 空气间进排气系数

[0101] Among them, S * Indicates *sensitivity.

[0102]

[0103] The global sensitivity of the hydraulic model parameters in step S3 is analyzed using the Sobol sensitivity analysis method. The main steps are as follows:

[0104] In the first step, samples are randomly selected according to the value intervals of the five different variable parameters, and the number of samples is set to 9×(2×5+2)=108;

[0105] In the second step, the 108 sets of sample parameters obtained by random sampling were imported into the hydraulic model and the corresponding simulation results were collected;

[0106] In the third step, the sobol program was used to conduct a global sensitivity analysis of the 108 groups of sample parameters and the corresponding simulation results based on Python software;

[0107] In the fourth step, a graph is drawn based on the obtained results, and finally the global sensitivity expression of the maximum water hammer pressure to the model is obtained as follows:

[0108] S T水锤波速 >S T转动惯量 >S T管线流量 >S T摩阻系数 >S T空气阀进排气系数

[0109] The global sensitivity expression of the minimum water hammer pressure at the pump outlet to the model is as follows:

[0110] S T管线流量 >S T转动惯量 >S T水锤波速 >S T摩阻系数 >S T空气阀进排气系数

[0111] The global sensitivity expression of the maximum reverse speed of the pump to the model is as follows:

[0112] S T水锤波速 >S T摩阻系数 >S T转动惯量 >S T管线流量 >S T空气阀进排气系数

[0113] Among them, S T* represents the global sensitivity of *;

[0114] Combination Figure 1 Among the parameters that affect the maximum water hammer pressure, the water hammer wave velocity (parameter 3) and the moment of inertia of the water pump unit (parameter 4) have the highest full-order sensitivity, followed by the full-order sensitivity of the pipeline flow rate (parameter 1) and the pipeline friction coefficient (parameter 2), and the air valve intake and exhaust coefficient (parameter 5) has the lowest full-order sensitivity. Figure 2 It can be intuitively found that among the parameters that affect the minimum water hammer pressure at the pump outlet, the pipeline flow rate (parameter 1) and the moment of inertia of the pump unit (parameter 4) have the highest full-order sensitivity, followed by the full-order sensitivity of the water hammer wave speed (parameter 3) and the pipeline friction coefficient (parameter 2), and the full-order sensitivity of the air valve intake and exhaust coefficient (parameter 5) is the lowest. Figure 3 It can be intuitively found that among the parameters that affect the maximum reversal speed of the water pump, the water hammer wave speed (parameter 3) has the highest full-order sensitivity, followed by the pipeline friction coefficient (parameter 2), the unit moment of inertia (parameter 4) and the pipeline flow rate (parameter 1). The air valve intake and exhaust coefficient (parameter 5) has the lowest full-order sensitivity.

[0115] The water hammer wave velocity, pipeline flow rate and resistance coefficient are positively correlated with the maximum water hammer pressure, and the unit moment of inertia is negatively correlated with the maximum water hammer pressure; the unit moment of inertia is positively correlated with the minimum water hammer pressure at the pump outlet, and the pipeline flow rate, resistance coefficient and water hammer wave velocity are negatively correlated with the minimum water hammer pressure at the pump outlet; the water hammer wave velocity, pipeline flow rate and resistance coefficient are positively correlated with the maximum reverse speed of the pump, and the unit moment of inertia is negatively correlated with the maximum reverse speed of the pump

[0116] S4. According to a municipal pump station in Hunan Province, the total design flow is 500,000 m3 / d and the design head is 45m. The starting point of the water supply system is the water collection well of the pump station and the end point is the screen pool of the water treatment plant. The water collection well is connected to the water source and has the same water level. The average water level of the water source in the dry season is 27.44m, and the average water level in the flood season is 31m. The average water level of the screen pool of the water treatment plant is 64.7m. At present, the main water hammer protection measures of the pump station are: a hydraulically controlled slow-closing check valve is installed after the pump; an air valve is installed at the switching well and the local high point of the water supply pipeline

[0117] Cooperate with hydraulic model to carry out steady-state hydraulic model calibration and transient hydraulic model calibration;

[0118] The steady-state hydraulic model verification in step S4 specifically adjusts the pipeline flow, the friction coefficient along the pipeline and the local resistance coefficient of the pipeline, and after the adjustment, compares the deviation between the simulated values ​​of the steady-state flow and steady-state pressure and the corresponding monitored values ​​to determine the parameter values.

[0119] The transient hydraulic model calibration in step S4 specifically adjusts the water hammer wave velocity and the moment of inertia, and determines the parameter value by comparing the deviation between the simulated value and the monitored value of the water hammer pressure variation curve at the key position.

[0120] S5. Evaluate different transient working conditions based on the hydraulic model, determine the most unfavorable transient working condition, and output water hammer protection optimization strategy for the most unfavorable transient working condition;

[0121] The transient operating conditions include four different transient operating conditions, namely:

[0122] Transient condition 1: Transient hydraulic transition process after a power outage and pump stop during stable operation of a single large pump

[0123] Transient operating condition 2: Transient hydraulic transition process after power failure and pump stop when two large and one small water pumps are running stably

[0124] Transient operating condition 3: Transient hydraulic transition process after power failure and pump stop when two large pumps are running stably

[0125] Transient operating condition 4: The transient hydraulic transition process after a power outage and pump stop when three water pumps, one large and two small, are running stably;

[0126] When water hammer occurs during pump stop in the four steady-state conditions, the maximum water hammer pressure exceeds 1.5 times the steady-state pressure value, which does not meet the safety requirements of the pump station. Among them, transient condition 4 (maximum flow rate of the pump station system pipeline) is the most unfavorable pump stop condition, and its transient maximum water hammer pressure is 86.8m, which is the maximum value among the four transient conditions, reaching 1.87 times the corresponding steady-state pressure value. The most unfavorable transient condition is determined to be transient condition 4. The output water hammer protection optimization strategy is specifically: adding air valves, increasing the unit's rotational inertia and optimizing the valve closing law. The optimized valve closing law is fast closing 2s, slow closing 18s, fast closing 71°, slow closing 19°, and increasing the rotational inertia of large and small pumps by 50%.

[0127] During transient condition 1, the maximum water hammer positive pressure of the system is 65.4m, the maximum negative pressure along the first and second phase water supply pipelines are -9m and -8m respectively, and the maximum reverse speed of the water pump is 521r / min; during transient condition 2, the maximum water hammer positive pressure of the system is 67.5m, the maximum negative pressure of the first and second phase pipelines both reach -9m, and the maximum reverse speed of the water pump is 617r / min; during transient condition 3, the maximum water hammer positive pressure of the system is 78m, the maximum negative pressure of the first and second phase pipelines are -9m and -8m respectively, and the maximum reverse speed of the water pump is 667r / min; during transient condition 4, the maximum water hammer positive pressure of the system is 86.8m, the maximum negative pressure of the first and second phase pipelines both reach -10m, and the maximum reverse speed of the water pump is 800r / min.

[0128] For transient operating condition 4, a combined protection scheme of adding air valves + increasing the moment of inertia of the unit + optimizing the valve closing rule is proposed, which can effectively eliminate the positive and negative pressure of pipeline water hammer. The optimized valve closing rule is fast closing 2s, slow closing 18s, fast closing 71°, slow closing 19°; the moment of inertia of both large and small pumps is increased by 50%, and the increased moment of inertia of the large pump is 918kg·m2, and the moment of inertia of the small pump is 395kg·m2; two air valves with an intake and exhaust coefficient of 0.72 are added at pile number 0+74.5 of the first phase pipeline and 0+39.0 of the second phase pipeline. After applying this protection strategy, the maximum positive water hammer pressure of the pipeline is 53.5m, which is 1.2 times the steady-state water hammer pressure; the maximum negative pressure of the first and second phase pipelines are -2.9m and -2.1m respectively, both controlled within -3m.

[0129] According to the four transient simulation results, as the number of pumps in the pump station and the flow rate of the pipeline increase, when the pump stops and the water hammer occurs, the maximum positive pressure of the system pipeline continues to increase, the maximum negative pressure of the pipeline continues to increase, and the pump reversal speed also continues to increase. Therefore, transient condition 4 is determined to be the most unfavorable pump stop condition.

[0130] In view of the risk of water hammer during pump stop in municipal pump station system, the positive pressure of pipeline water hammer can be reduced by optimizing the two-stage closing rule of hydraulic butterfly valve and increasing the rotational inertia of water pump unit. Installing air valve at appropriate position can effectively reduce the positive and negative pressure of pipeline water hammer. Under the condition of fixed total valve closing time and fast closing time, as the fast closing angle decreases, the maximum water hammer pressure of pipeline first decreases and then increases; when the total valve closing time and fast closing angle are fixed, the maximum water hammer pressure of pipeline increases with the increase of fast closing time.

[0131] The present invention also provides a water hammer pump stop safety protection system based on a hydraulic model, which is used to run the above-mentioned water hammer pump stop safety protection method based on a hydraulic model, including a parameter collection module, a hydraulic model establishment module, a hydraulic model verification module and a water hammer protection optimization module. The parameter collection module is used to collect parameters in the hydraulic model establishment process, and send the collected formulas to the hydraulic model establishment module. The hydraulic model establishment module establishes the model through model establishment parameters and water hammer calculation expressions, and analyzes the local sensitivity and global sensitivity of the hydraulic model parameters. Thereafter, the hydraulic model verification module performs steady-state hydraulic model verification and transient hydraulic model verification on the model established by the hydraulic model establishment module. Finally, the water hammer protection optimization module determines the most unfavorable transient operating condition, and outputs a water hammer protection optimization strategy for the most unfavorable transient operating condition.

[0132] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A safety protection method for a water hammer pump stop based on a hydraulic model, comprising a pump station system, a two-stage closing hydraulically controlled butterfly valve and an air valve, wherein the pump station system comprises a full characteristic curve of the water pump, a speed change equation and a head balance equation, and is characterized in that: The following steps are also included: S1. Establish a hydraulic model and set boundary conditions, wherein the hydraulic model includes model establishment parameters and water hammer calculation expressions; S2, collecting the hydraulic model parameters in step S1; S3. Analyze the local sensitivity and global sensitivity of hydraulic model parameters, including pipeline flow, pipeline friction coefficient, water hammer wave velocity, unit rotational inertia, air valve intake and exhaust coefficient, maximum water hammer pressure, minimum water hammer pressure at the pump outlet, and maximum reverse speed of the pump; S4. Perform steady-state hydraulic model calibration and transient hydraulic model calibration based on the hydraulic model; S5. Evaluate different transient conditions based on the hydraulic model, determine the most unfavorable transient condition, and output the water hammer protection optimization strategy for the most unfavorable transient condition.

2. The hydraulic pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The water hammer calculation expression in step S1 includes a water hammer wave velocity expression and a water hammer basic equation, and its specific expression is as follows: Water hammer wave speed: Among them, α represents the water hammer wave velocity, K represents the bulk elastic modulus of the fluid, ρ represents the fluid density, D represents the pipe diameter, E represents the elastic modulus of the pipe wall material, and e represents the pipe wall thickness; Basic equation of water hammer: Equations of motion: Continuity equation: Among them, H represents the head lift, V represents the flow velocity in the pipe, f represents the friction coefficient of the pipeline, a represents the angle between the pipeline and the horizontal plane, α represents the water hammer wave velocity, x represents the position coordinate, D represents the pipe diameter, g represents the gravitational acceleration, t is the time variable, sin represents the sine function, and the motion equation and continuity equation both reflect the changing laws of the flow velocity and water body in the water hammer field in the form of partial differential equations, and the characteristic line method is used for instantaneous solution.

3. The water hammer pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The boundary conditions in step S1 include upstream and downstream boundaries, which are expressed as follows: in, represents the head pressure at node 1 at the upstream end of pipeline j at any time, H s Indicates the upstream water level, The head pressure at any time at the upstream node n of pipeline j, H d Indicates the downstream grid water level.

4. The hydraulic pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The hydraulic model parameters in step S2 include actual measured parameters and parameters to be calculated, wherein the actual measured parameters include the length, diameter, wall thickness, roughness coefficient, resistance coefficient, material elastic modulus, factory specifications, models and characteristic parameters of the valve, altitude, cavitation pressure, and air temperature of the pipeline at the current moment; the parameters to be calculated include pipeline resistance coefficient, water pump moment of inertia, and water pump characteristic curve; the pipeline resistance coefficient is calculated using the Hezen-Williams formula, and the water pump moment of inertia is usually based on factory parameters. When data is missing, the expression is as follows: J T =J1+J2+J3 J2=J1×10% Among them, J1, J2, and J3 represent the motor moment of inertia, the pump impeller moment of inertia, and the additional inertia flywheel moment of inertia, respectively. T represents the rotational inertia of the water pump unit, N represents the motor speed, D represents the inertia diameter, G represents the equivalent weight of the load in the motor-driven system, and the water pump characteristic curve adopts the Suter full characteristic curve with a similar specific speed in the Wanda database.

5. The hydraulic pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The local sensitivity of the hydraulic model parameters in step S3 is analyzed by Morris screening method, and the mean value of the result of Morris screening method is selected as the sensitivity discrimination parameter S, which is specifically expressed as: Among them, y i+1 represents the target result simulated by the i+1th group of parameter values, y i represents the target result simulated by the i-th group of parameter values, y0 represents the target result simulated by the initial parameter values, P i represents the percentage change of the i-th group of parameters relative to the initial parameter value, P i+1 represents the percentage change of the i+1th group of parameters relative to the initial parameter value, n represents the nth group of data, and finally the ranking expression of the maximum water hammer pressure sensitivity to the model is as follows: S 水锤波速 >S 管线流量 >S 转动惯量 >S 摩阻系数 >S 空气阀进排气系数 The ranking expression of the sensitivity of the minimum water hammer pressure at the pump outlet to the model is as follows: S 转动惯量 >S 管线流量 >S 水锤波速 >S 摩阻系数 >S 空气阀进排气系数 The ranking expression of the sensitivity of the maximum reverse speed of the pump to the model is as follows: S 水锤波速 >S 摩阻系数 >S 管线流量 >S 转动惯量 >S 空气间进排气系数 Among them, S * Indicates *sensitivity.

6. The hydraulic pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The global sensitivity of the hydraulic model parameters in step S3 is analyzed using the Sobol sensitivity analysis method, and finally the global sensitivity expression of the maximum water hammer pressure to the model is obtained as follows: S T水锤波速 >S T转动惯量 >S T管线流量 >S T摩阻系数 >S T空气阀进排气系数 The global sensitivity expression of the minimum water hammer pressure at the pump outlet to the model is as follows: S T管线流量 >S T转动惯量 >S T水锤波速 >S T摩阻系数 >S T空气阀进排气系数 The global sensitivity expression of the maximum reverse speed of the pump to the model is as follows: S T水锤波速 >S T摩阻系数 >S T转动惯量 >S T管线流量 >S T空气阀进排气系数 Among them, S T* Indicates the global sensitivity of *.

7. The hydraulic pump stop safety protection method based on hydraulic model according to claim 1 is characterized in that: The steady-state hydraulic model verification in step S4 specifically adjusts the pipeline flow, the friction coefficient along the pipeline and the local resistance coefficient of the pipeline, and after the adjustment, the deviation between the simulated values ​​of the steady-state flow and steady-state pressure and the corresponding monitored values ​​of the two is compared to determine the parameter value.

8. The hydraulic pump stop safety protection method based on hydraulic model according to claim 7 is characterized in that: The transient hydraulic model verification in step S4 specifically adjusts the water hammer wave velocity and the moment of inertia, and determines the parameter value by comparing the deviation between the simulated value and the monitored value of the water hammer pressure variation curve at the key position.

9. The hydraulic pump stop safety protection method based on hydraulic model according to claim 8 is characterized in that: The transient operating conditions specifically include 4 different transient operating conditions, specifically: Transient condition 1: Transient hydraulic transition process after a power outage and pump stop during stable operation of a single large pump Transient operating condition 2: Transient hydraulic transition process after power failure and pump stop when two large and one small water pumps are running stably Transient operating condition 3: Transient hydraulic transition process after power failure and pump stop when two large pumps are running stably Transient operating condition 4: The transient hydraulic transition process after a power outage and pump stop when three water pumps, one large and two small, are running stably; The most unfavorable transient operating condition determined is transient operating condition four. The output water hammer protection optimization strategy is specifically: adding air valves, increasing the unit's rotational inertia and optimizing the valve closing rule. The optimized valve closing rule is fast closing 2s, slow closing 18s, fast closing 71°, slow closing 19°, increasing the rotational inertia of both large and small pumps by 50%.

10. A hydraulic pump stop safety protection system based on a hydraulic model, used to run the hydraulic pump stop safety protection method based on a hydraulic model as claimed in any one of claims 1 to 9, characterized in that: It includes a parameter collection module, a hydraulic model building module, a hydraulic model verification module and a water hammer protection optimization module. The parameter collection module is used to collect parameters in the hydraulic model building process and send the collected formulas to the hydraulic model building module. The hydraulic model building module builds the model through model building parameters and water hammer calculation expressions, and analyzes the local sensitivity and global sensitivity of the hydraulic model parameters. Then, the hydraulic model verification module performs steady-state hydraulic model verification and transient hydraulic model verification on the model built by the hydraulic model building module. Finally, the water hammer protection optimization module determines the most unfavorable transient working condition, and outputs the water hammer protection optimization strategy for the most unfavorable transient working condition.

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