A method and device for determining water hammer protection mode

Abstract

The present invention relates to the technical field of water hammer protection, and provides a method and device for determining a water hammer protection mode. The present invention is directed to a floating pump station water delivery system, and firstly, by systematically analyzing the factors that should be considered in the water hammer protection of the floating pump station water delivery system, the most unfavorable working condition that may be caused by an accidental pump stop in the water delivery system is determined; then, the accidental pump stop water hammer under different accident conditions is calculated respectively, and the required water hammer protection measures are selected each time according to the calculation results, so as to obtain a water hammer protection mode that can still achieve protection under the most unfavorable working condition of the whole, which greatly improves the protection effect against the pump stop water hammer and the efficiency of determining the water hammer protection mode, and solves the problems of excessive reliance on manual experience, low efficiency, and failure to achieve the expected water hammer protection effect when determining the water hammer protection mode in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of water hammer protection, and in particular to a method and device for determining a water hammer protection mode. Background Art

[0002] Due to the typical characteristics of the terrain being "high mountains and low water", water diversion projects in Yunnan Province often need to draw water from reservoirs with large water level fluctuations, so there are many floating ship pump station water delivery systems in Yunnan Province. Large water level fluctuations mean a large fluctuation in the net head. There are movable parts such as floating ships and rocker arms in the water intake device, and water hammer protection is more complicated. Engineering practice shows that for pump station water delivery systems under complex terrain in plateau mountainous areas, accidental pump stop water hammer is one of the main causes of pipe burst accidents and threats to the safe operation of pump station water delivery systems. Specifically, when the pump station suddenly stops pumping, the speed of the water flow will suddenly fluctuate greatly, and the pressure will also fluctuate greatly; because of the inertia of the pressurized water flow, the water flow shock wave will have a destructive effect on the pipe wall. This destructive effect is like a hammer hitting, which will damage the flow components of the pump station and even cause the pipe wall to rupture, thereby endangering the safe operation of the pump station, and then seriously affecting the safe operation of the pump station water delivery system.

[0003] Therefore, in order to reduce the damage of water hammer to the water delivery system of the pump station, the pump station must take some measures (for example, installing water hammer eliminators, etc.) to eliminate or reduce the water hammer phenomenon. At present, the commonly used pump stop water hammer measures in engineering include water replenishment type, air replenishment type, water discharge and pressure reduction type and other protective measures, each of which has its own advantages and disadvantages. Compared with other domestic water diversion projects, the long-distance water diversion project in Yunnan Province has the characteristics of high head, large fluctuation of water level of water source, dense pump station group, many water supply objects, and complex pipeline flow distribution.

[0004] However, the current water hammer protection for the floating pump station water delivery system does not take into account comprehensive factors, and the stability of the floating boat and the rocker arm under the impact of water hammer is not considered enough, and it is impossible to adaptably determine the pump stop water hammer measures for different regions and terrains; and for the water hammer protection of large-scale water diversion projects, it is often necessary to take more than one measure, and multiple measures cannot be simply superimposed, resulting in the fuzzy determination of the measures to be taken by relying on subjective opinions such as manual experience. In this case, the corresponding measures are very likely to be ineffective and fail to achieve the expected water hammer protection effect after implementation; and when the water hammer protection effect is poor and / or the water hammer protection effect needs to be improved, there is a lack of guidance for effect positioning and problem troubleshooting based on multiple measures. The overall water hammer protection mode of the water diversion project (that is, multiple measures for water hammer protection) needs to be repeatedly adjusted, and it may even be difficult to achieve the expected water hammer protection effect, which greatly increases the relevant manpower, material resources and time costs of building a water delivery system (which can be understood as a water diversion project). This type of floating pump station water delivery system lacks a relatively unified water hammer protection mode. Therefore, a solution for determining a water hammer protection mode with a clear process is urgently needed.

[0005] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in the field of this technology. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method and device for determining a water hammer protection mode. Its purpose is to greatly improve the protection effect against pump stop water hammer and the efficiency of determining the water hammer protection mode by designing a water hammer protection mode determination scheme with a clear process for the water delivery system of a floating pump station, and solve the problems of excessive reliance on manual experience, low efficiency, and failure to achieve the expected water hammer protection effect when determining the water hammer protection mode in the prior art.

[0007] The present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for determining a water hammer protection mode, wherein the water hammer of the water delivery system caused by pump stop under different accident conditions is calculated respectively; at least one water hammer protection measure required for the water delivery system is determined according to the calculation results; and the water hammer protection mode required for the water delivery system is determined according to the at least one water hammer protection measure; the method for determining the water hammer protection mode comprises:

[0009] Operate the stable operating units in the water delivery system according to the designed number of units, and determine the most unfavorable operating condition based on the first reference operating condition; wherein the first reference operating condition is that all the stable operating units of the designed number of units have pump stops due to accidents, and the pump outlet check valves refuse to move;

[0010] The water hammer caused by pump stoppage in an accident is analyzed under the most unfavorable working condition, and the water hammer protection mode of the water delivery system is determined.

[0011] In a second aspect, the present invention further provides a device for determining a water hammer protection mode, which is used to implement the method for determining a water hammer protection mode according to the first aspect, and the device for determining a water hammer protection mode comprises:

[0012] At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the processor to execute the method for determining the water hammer protection mode described in the first aspect.

[0013] In a third aspect, the present invention further provides a non-volatile computer storage medium, wherein the computer storage medium stores computer executable instructions, which are executed by one or more processors to complete the method for determining the water hammer protection mode described in the first aspect.

[0014] Different from the prior art, the present invention has at least the following beneficial effects:

[0015] The present invention proposes a method for determining a water hammer protection mode based on the most unfavorable working condition for a floating vessel pump station water delivery system. First, based on a systematic analysis of the factors that should be considered for water hammer protection of a floating vessel pump station water delivery system, the most unfavorable working condition that may be caused by an accidental pump stop is determined; then, the water hammer of an accidental pump stop under different accident conditions of the water delivery system is calculated respectively, and the corresponding water hammer protection measures to be taken are selected each time according to the calculation results, and then each water hammer protection measure is comprehensively evaluated and selected to obtain a water hammer protection mode that can still achieve protection under the most unfavorable working condition; the present invention greatly improves the protection effect against pump stop water hammer and the efficiency of determining the water hammer protection mode, and solves the problems of excessive reliance on manual experience, low efficiency, and failure to achieve the expected water hammer protection effect when determining the water hammer protection mode in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a schematic diagram of the overall process of a method for determining a water hammer protection mode provided by an embodiment of the present invention;

[0018] Figure 2 is a flow chart of step 10 of an embodiment of the present invention;

[0019] Figure 3is a flow chart of step 101 of an embodiment of the present invention;

[0020] Figure 4 It is a schematic diagram of the change process of the relative flow rate and relative speed of a water pump under different water inlet levels provided by an embodiment of the present invention;

[0021] Figure 5 It is a schematic diagram of a process of water head change of a pump outlet pressure measuring tube under different water inlet levels provided by an embodiment of the present invention;

[0022] Figure 6 It is a schematic diagram of a pressure envelope under a conventional moment of inertia and a maximum net head provided by an embodiment of the present invention;

[0023] Figure 7 It is a schematic diagram of the change process of the relative flow rate and relative speed of a water pump under different rotational inertia provided by an embodiment of the present invention;

[0024] Figure 8 It is a schematic diagram of a process of water head change of a pump outlet pressure measuring tube under different rotational inertias provided by an embodiment of the present invention;

[0025] Fig. 9 It is a schematic diagram of the change process of the relative flow rate and relative speed of a water pump under different initial flow rates provided by an embodiment of the present invention;

[0026] Fig.10 It is a schematic diagram of a process of water head change of a pump outlet pressure measuring tube under different initial flow rates provided by an embodiment of the present invention;

[0027] Fig.11 It is a schematic diagram of the change process of the relative flow rate and relative speed of the water pumps under different numbers of stopped pumps provided by an embodiment of the present invention;

[0028] Fig.12 It is a schematic diagram of a pump outlet pressure change process under different numbers of pumps stopped provided by an embodiment of the present invention;

[0029] Fig.13 is a flow chart of step 20 of an embodiment of the present invention;

[0030] Fig.14 It is a schematic diagram of a change process of the pressure at the rear point of a pump outlet check valve under different closing rules of a pump outlet valve provided by an embodiment of the present invention;

[0031] Fig.15 It is a schematic diagram of a change process of a relative flow rate and a relative speed of a pump under the condition of whether an air tank is provided or not provided in an embodiment of the present invention;

[0032] Fig.16 It is a schematic diagram of a process of water head change at a water pump outlet pressure measuring tube under the condition of whether an air tank is provided or not provided in an embodiment of the present invention;

[0033] Fig.17 is a flow chart of step 203 of an embodiment of the present invention;

[0034] Fig.18 is a flow chart of step 2031 of an embodiment of the present invention;

[0035] Fig.19 It is a schematic diagram of the architecture of a device for determining a water hammer protection mode provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0038] The terms "first", "second", etc. in the present invention are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0039] In the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0040] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Embodiment 1:

[0042] Pump stations must take some measures to eliminate or reduce water hammer phenomena, such as installing water hammer eliminators, setting up air chambers at pump outlets, and rationally designing the pipeline layout of the pump station water delivery system. These measures can effectively reduce water hammer pressure and protect the safe operation of the pump station water delivery system. Common pump stop water hammer protection measures include two-way surge towers, one-way surge towers, air tanks, air valves, etc.

[0043] In order to avoid relying on subjective opinions such as manual experience to vaguely determine the water hammer protection mode of the water delivery system of a pump station in a plateau mountainous area, Embodiment 1 of the present invention provides a method for determining a water hammer protection mode, which calculates the water hammer of the water delivery system under different accident conditions; determines at least one water hammer protection measure required for the water delivery system based on the calculation results; determines the water hammer protection mode required for the water delivery system based on the at least one water hammer protection measure; Figure 1 As shown, the method for determining the water hammer protection mode includes:

[0044] Step 10: Operate the stable operating units in the water delivery system according to the designed number, and determine the most unfavorable operating condition based on the first reference operating condition; wherein the first reference operating condition is that all the stable operating units of the designed number of units stop pumping due to an accident, and the pump outlet check valve refuses to move.

[0045] Among them, a stable operating unit refers to a water pump unit whose performance parameters such as flow rate, head, power, etc. remain relatively stable and have a small fluctuation range under normal operating conditions.

[0046] The calculation of the water hammer caused by the pump stopping accident in the embodiment of the present invention refers to the calculation and analysis of the entire pipeline water delivery system, including the points inside the pipeline and the hydraulic elements (boundary points) in the water pump water delivery device connected to the pipeline. It should be noted here that the prior art such as the method for calculating the water hammer caused by the pump stopping accident is well known to those skilled in the art, and will be referred to in the prior art and will not be expanded in the subsequent embodiments, and it should not be regarded as unclear in the present invention.

[0047] Step 20: Analyze the water hammer caused by pump stoppage under the most unfavorable working condition, and determine the water hammer protection mode of the water delivery system.

[0048] In the prior art, determining the water hammer protection mode of a water delivery system often relies solely on the technicians' experience with common pump-stop water hammer protection measures. However, the terrain, water source and water level conditions, water quality protection requirements, and construction capital costs of each water delivery system often vary greatly, and the water hammer protection mode is very likely to require the use of more than one pump-stop water hammer protection measure. In this case, simply judging and combining the advantages and disadvantages of each common pump-stop water hammer protection measure often fails to discover and eliminate the possible correlation effects between the pump-stop water hammer protection measures, resulting in the failure to achieve the expected water hammer protection effect.

[0049] Since the water delivery system of the pump station in the plateau mountainous area that draws water from the reservoir often adopts the water delivery mode of "pump station pressurization + gravity flow", it usually has the characteristics of large fluctuation of water source water level, high head of the water intake pump station and relatively short pump pressure water delivery pipeline. Therefore, the present invention proposes a method for determining the water hammer protection mode based on the most unfavorable working condition for the floating pump station water delivery system. First, on the basis of a systematic analysis of the factors that should be considered for water hammer protection of the floating pump station water delivery system, the most unfavorable working condition that may be caused by accidental pump stop is determined; then, by respectively calculating the accidental pump stop water hammer of the water delivery system under different accident conditions, the corresponding water hammer protection measures to be taken are selected each time according to the calculation results, and then the various water hammer protection measures are comprehensively evaluated and selected to obtain a water hammer protection mode that can still achieve protection under the most unfavorable working condition; the present invention greatly improves the protection effect against pump stop water hammer and the efficiency of determining the water hammer protection mode, and solves the problems of excessive reliance on manual experience, low efficiency, and failure to achieve the expected water hammer protection effect when determining the water hammer protection mode in the prior art.

[0050] It should be noted that the prior art such as calculation of water hammer caused by accidental pump stop is well known to those skilled in the art and will not be expanded in the subsequent embodiments, and it should not be regarded as unclear in the present invention.

[0051] Embodiment 2:

[0052] Embodiment 2 of the present invention is a further preferred embodiment of the method for determining the water hammer protection mode of Embodiment 1. In order to better illustrate the method for determining the water hammer protection mode of the present invention, step 10 of the method for determining the water hammer protection mode of the embodiment of the present invention is further refined as follows: Figure 2 As shown, the step 10 includes:

[0053] Step 101: Analyze the water hammer caused by pump stoppage under the first reference condition, and determine the first influencing factor corresponding to the net head, the second influencing factor corresponding to the moment of inertia, the third influencing factor corresponding to the initial flow rate, and the fourth influencing factor corresponding to the number of pumps stopped.

[0054] Step 102: Obtain the most unfavorable operating condition according to the first influencing factor, the second influencing factor, the third influencing factor and the fourth influencing factor.

[0055] For example, from the perspective of the maximum reverse speed of the water pump and the water hammer pressure of the pipeline, this water supply system takes the most unfavorable operating condition of all three pumps stopped, maximum net head, and single design rotational inertia.

[0056] The embodiment of the present invention is aimed at the floating vessel pump station water delivery system. On the basis of systematically analyzing the factors that should be considered for water hammer protection, the most unfavorable working condition is proposed. With the stable operating unit operating according to the designed number of units and the pump outlet check valve refusing to operate as the reference working condition, the influence of the net head (water source water level), the unit's moment of inertia, the initial flow rate and the number of pumps stopped on the water hammer caused by accidental pump stop is analyzed, and then the most unfavorable working condition for water hammer protection is determined.

[0057] The following is a description of the specific steps to determine the most unfavorable working conditions. Figure 3 As shown, step 101 includes:

[0058] Step 1011: The initial flow of the stably operating unit is set to the design flow value, and the water hammer caused by the accidental pump stop is calculated under the first reference condition to obtain the first influencing factor under the same initial flow and different water inlet levels to analyze the influence of the net head on the water hammer caused by the accidental pump stop.

[0059] The design flow value is selected by technicians in this field according to the specific usage scenario; the "design flow" in the pump stop water hammer analysis refers to the amount of liquid that the water delivery system should deliver per unit time, which is determined during the engineering design. The design flow affects the water flow velocity in the pipeline, thereby affecting the magnitude of the pump stop water hammer pressure and the reverse speed of the water pump unit; if the design flow is large, a large water hammer pressure will be generated during an accidental pump stop, which may cause damage to the pipeline system.

[0060] The embodiment of the present invention provides a specific example of determining the water hammer protection mode of a water delivery system. The method for determining the water hammer protection mode of the embodiment of the present invention is described below based on the specific example:

[0061] The project draws water from the Xiaowan Power Station Reservoir, with a dead water level of 1166m and a normal water storage level of 1240m. A two-stage water pumping station is set up, with the first-stage pumping station (mobile dock pumping station) located 1km east of Wanyaolong Village in the Xiaowan Reservoir area and about 350m away from the second-stage pumping station. It has a designed head of 125m, a water lifting flow of 1.62m3 / s, and an installed capacity of 3×1000kW (3 in use and 0 in reserve). The forebay of the second-stage pumping station (ground pumping station) is arranged at the top of the Ertai slope at an elevation of 1290.00m.

[0062] The first-level pump station is a floating pump house, which consists of three sections of rocking cantilever, a hosting dock, and a pump house connected to each other, and the entire reservoir area is used as an inlet pool. The lengths of the single-section rocking cantilever are 48m, 55m, and 55m respectively. The cantilevers are connected through the hosting dock. One end of the shore cantilever is connected to the pump house and the other end is connected to the shore anchor pier. The three sections of the rocking cantilever are all single DN1200 steel pipes; and then connected to the secondary pump station inlet pool through a single DN1100 pressure pipeline of about 156m.

[0063] The performance parameters of the water pump units used in the first-level pumping station are shown in the following table.

[0064]

[0065] The inlet and outlet water levels of the water delivery system are as follows:

[0066]

[0067] The layout of the water delivery system is "3 machines and 1 pipe". The rocker arm between the floating ship and the anchor pier on the shore is a DN1200 steel pipe; the anchor pier on the shore to the outlet pool is a single DN1100 steel pipe. The characteristic parameters of the water delivery pipeline are as follows:

[0068]

[0069] The embodiment of the present invention first calculates the water hammer of the accidental pump stop according to the water hammer model under the first reference working condition (all three units are stopped and the pump outlet check valve refuses to move) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; The water level of the outlet pool is 1289.60m; the lowest water level is the power frequency operation; the highest water level is the variable frequency operation. The calculation results under the same initial flow and different water levels are shown in the following table:

[0070]

[0071] The starting point on the shore is the end point of the rocker arm (pile number F0+000). Figure 4 When the valve is not closed, the relative flow rate and relative speed of the pump change at different water inlet levels; Figure 5 When the valve is not closed, the water head change process of the pump outlet pressure measuring tube at different water inlet levels; Figure 6 It is the pressure envelope under normal rotational inertia and maximum net head when the valve is not closed.

[0072] According to the above calculation results, the first influencing factor under the same initial flow rate and different water inlet levels is as follows:

[0073] Under the conditions that the water level and initial flow rate of the outlet pool are the same and the water levels of the inlet pool are different, after the pump is stopped due to an accident, the higher the net head, the faster the speed and flow rate of the pump will drop, the earlier the unit will flow back and reverse, and the greater the maximum reverse speed; the greater the drop in the pump outlet pressure, the greater the maximum water hammer pressure in the pipeline, and the smaller the minimum water hammer pressure.

[0074] Step 1012: setting the initial flow of the stably operating unit to the design flow value, calculating the water hammer caused by pump shutdown under the first reference condition, and obtaining the second influencing factor under different rotational inertia.

[0075] Since increasing the unit's rotational inertia will increase the motor size and manufacturing cost, require a larger installation space, and require a larger starting torque, increasing the unit's rotational inertia is not suitable for certain water delivery projects. There is no need to determine the second influencing factor under different rotational inertias. The analysis of water hammer caused by accidental pump shutdown is carried out according to the equipment manufacturer's designed rotational inertia.

[0076] Determine the second influencing factor. For example, the embodiment of the present invention then calculates the water hammer of the accidental pump stop according to the water hammer model under the first benchmark operating condition (all three units are stopped and the pump outlet check valve refuses to move) and the design flow; wherein, the water level of the outlet pool is 1289.60m; the minimum water inlet level is 1166.00m; and the power frequency operation.

[0077] The calculation results under different moments of inertia are shown in the following table; Figure 7 When the valve is not closed, at the highest net head and at different moments of inertia, the relative flow rate and relative speed of the pump change; Figure 8 When the valve is not closed, at the highest net head and at different moments of inertia, the water head change process of the pump outlet pressure measuring tube.

[0078]

[0079] According to the above calculation results, the second influencing factor under different moments of inertia is as follows:

[0080] After the pump is stopped due to an accident, the smaller the moment of inertia, the faster the speed and flow of the pump will drop, the earlier the unit will flow back and reverse, and the greater the maximum reverse speed; the greater the drop in pump outlet pressure, the greater the maximum water hammer pressure in the pipeline, and the smaller the minimum water hammer pressure.

[0081] Step 1013: Calculate the water hammer caused by pump shutdown in an accident under the first reference condition to obtain the third influencing factor under different initial flow rates.

[0082] For example, the embodiment of the present invention then calculates the water hammer of the accidental pump stop according to the water hammer model under the first reference working condition (all three units are stopped and the pump outlet check valve refuses to move) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Maximum inlet water level 1240.00m; Initial operation at different speeds and flows.

[0083] The calculation results under different initial flow rates are shown in the following table:

[0084]

[0085] like Fig. 9 When the valve is not closed, at the lowest net head and at different initial flows, the change process of the relative flow rate and relative speed of the pump; Fig.10When the valve is not closed, at the lowest net head and at different initial flow rates, the head change process of the pump outlet pressure measuring tube is shown.

[0086] According to the above calculation results, the third influencing factor under different initial flow rates is as follows:

[0087] After the pump is stopped due to an accident, the greater the initial flow rate and the greater the inertia of the water body, the later the unit will flow back and reverse, but the maximum reverse speed will be basically the same; the greater the drop in pump outlet pressure, the smaller the minimum water hammer pressure, but the maximum water hammer pressure in the pipeline will be basically the same.

[0088] Step 1014: setting the initial flow of the stably operating unit to the design flow value, calculating the water hammer caused by pump shutdown in an accident, and obtaining the fourth influencing factor under different numbers of pump shutdowns.

[0089] For example, the embodiment of the present invention then calculates the water hammer of the accidental pump stop according to the water hammer model under the first reference working condition (all three units are stopped and the pump outlet check valve refuses to move) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Minimum water inlet level 1166.00m; Power frequency operation.

[0090] The calculation results under different numbers of pumps stopped are shown in the following table:

[0091]

[0092] like Fig.11 When the valve is not closed, at the highest net head and with different numbers of pumps stopped, the relative flow and relative speed of the water pump change; Fig.12 When the valve is not closed, the pump outlet pressure changes under the highest net head and different numbers of pumps stopped.

[0093] According to the above calculation results, the fourth influencing factor under different numbers of pump stoppages is as follows:

[0094] After an accident occurs and the pump is shut down, the fewer the number of pumps that are shut down, the earlier the backflow and reverse rotation of the shut-down unit will occur, and the greater the reverse rotation speed after stabilization; but the smaller the outlet pressure of the shut-down pump, the smaller its maximum reverse rotation speed; the smaller the maximum water hammer pressure in the pipeline, the greater the minimum water hammer pressure.

[0095] It should be noted that the maximum net head, minimum net head, etc. are determined by those skilled in the art according to the specific conditions of the water delivery system. The method for obtaining the specific parameter values ​​corresponding to the relevant concepts is well known to those skilled in the art and will not be expanded in the subsequent embodiments. It should not be regarded as an unclear determination of the present invention.

[0096] In order to determine at least one pump-off water hammer protection measure in the water hammer protection mode step by step according to a reasonable process, the embodiment of the present invention continues to perform accidental pump-off water hammer analysis based on the most unfavorable working condition, such as Fig.13 As shown, the step 20 includes:

[0097] Step 201: Under the second accident condition, close the pump outlet check valve, calculate the accident pump stop water hammer according to the unit backflow start time, the maximum reverse speed and the maximum water hammer pressure at the pump outlet, and determine the closing rule of the pump outlet check valve.

[0098] Among them, the second accident condition is: the initial flow of the stably operating unit is the design flow value, the moment of inertia of the stably operating unit is the conventional design value, and when the pump station is at the highest net head, the stably operating unit stops pumping due to an accident.

[0099] The conventional design value is selected by those skilled in the art according to the specific usage scenario; in an optional embodiment, the conventional design value is 27 kg·m 2 .

[0100] For example, the embodiment of the present invention then calculates the water hammer of the accident pump stop according to the water hammer model under the second accident condition (initial 3 power frequency operation, all stopped; and the pump outlet check valve is closed) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Inlet water level 1166.00m;.

[0101] like Fig.14 It is the change process of the pressure at the rear point of the pump outlet check valve when the pump outlet check valve is in different closing rules and at different closing rates of the pump outlet check valve; Fig.14 It can be seen that when the check valve at the pump outlet is not closed, the water pump reaches the maximum backflow flow rate 2.4 seconds after the pump is stopped. The calculation results at different initial flow rates are shown in the following table.

[0102] According to the above calculation results, the first change law between the different closing laws of the pump outlet check valve and the maximum reverse speed of the unit, and the second change law between the closing of the pump outlet check valve and the maximum water hammer pressure are obtained as follows:

[0103] (1) Closing the pump outlet check valve can reduce the maximum reverse speed of the unit. The faster the pump outlet check valve closes, the smaller the maximum backflow flow of the unit and the smaller the reverse speed. For this water supply system, when the linear closing time exceeds 4s or the fast closing time of the two-stage closing exceeds 3s, the maximum reverse speed of the unit exceeds 1.2 times the rated speed. (2) Closing the pump outlet check valve has no effect on improving the negative pressure in the pipeline. (3) Closing the pump outlet check valve aggravates the increase in the maximum water hammer pressure. Compared with the working condition of the pump outlet check valve refusing to move, when the pump outlet check valve is closed before the unit starts to flow back but before the maximum backflow flow is reached, the faster the valve is closed, the smaller the maximum water hammer pressure at the rear point of the pump outlet check valve; when the pump outlet check valve is closed after the unit has the maximum backflow flow, the faster the valve is closed, the greater the maximum water hammer pressure.

[0104]

[0105]

[0106] From the perspective of controlling the maximum reverse speed of the unit and protecting the unit, and considering the closing speed of the drive valve and the cost of the drive device, the type of pump outlet check valve recommended for this water supply system is a hydraulically driven axial flow check valve that can be closed quickly.

[0107] Step 202: When closing the check valve at the pump outlet has no effect on improving the negative pressure in the pipeline, measures to be taken to eliminate the negative pressure are determined according to the terrain of the water delivery system and the range of negative pressure elimination required.

[0108] The embodiment of the present invention sets an air tank under the second accident condition, calculates the influence of the air tank on the start time of reverse flow and reverse speed of the unit, and determines whether to take measures to eliminate negative pressure. For example, the embodiment of the present invention then calculates the water hammer of the accident pump stop according to the water hammer model under the second accident condition (initial 3 units running at power frequency, all stopped) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; The water level of the outlet pool is 1289.60m; The water level of the inlet is 1166.00m; An air tank is set at the starting point of the main pipe on the shore (pile number F0+000). The initial water-gas ratio of the air tank is considered to be 1:1, and the size parameters are shown in the following table:

[0109]

[0110] The following table shows the influence of the air tank on the start time of reverse flow and the maximum reverse speed of the unit under the highest net head:

[0111]

[0112]

[0113] When the valve is not closed and the highest net head is reached, Fig.15 The figure shows the change process of relative flow rate and relative speed of the water pump. Fig.16 The figure shows the change process of the water head of the pressure measuring tube at the outlet of the water pump. According to the above calculation results, it can be obtained that the closing of the check valve at the pump outlet has no effect on improving the negative pressure in the pipeline, and protective measures must be set to eliminate the negative pressure in the pipeline. Since the pipeline is located in a mountainous area and the longitudinal section is steep, it is not possible to arrange a pressure regulating tower; the air valve can improve the negative pressure in the pipeline, but the protection range is limited and the flow is complex. Therefore, it is more appropriate to use an air tank for water hammer protection for this water supply system. Under the condition that the check valve at the pump outlet is not closed, after the air tank is set, the time when the water pump starts to flow back is advanced, the maximum reverse speed and maximum backflow flow of the water pump are reduced, the maximum water hammer pressure at the outlet of the water pump is reduced, and the vaporization phenomenon is eliminated.

[0114] Step 203: Determine the water hammer protection mode according to the type of the pump outlet check valve and its closing rule and the negative pressure elimination measures taken.

[0115] When the type of the pump outlet check valve and / or the measures taken to eliminate negative pressure have an impact on each other or there are other special protection requirements, other water hammer protection measures must be set to eliminate the impact. The following takes the setting of an air tank as a negative pressure elimination measure as an example to illustrate this:

[0116] like Fig.17 As shown, when the negative pressure elimination measure is to set an air tank, step 203 includes:

[0117] Step 2031: When it is necessary to reduce the impact of the backflow water on the pump boat and the rocker arm, set an intermediate check valve.

[0118] The embodiment of the present invention calculates and analyzes the impact of the backflow water on the pump boat and the rocker arm and the impact on their stability after the pump outlet check valve is closed and the air tank is set, and determines whether the impact is not negligible; at the same time, it verifies whether the air tank achieves the required water hammer protection effect.

[0119] Step 2032: Determine the size parameters and target initial water-gas ratio of the air tank according to the longitudinal profile layout of the pipeline and the influence of the air tank on water hammer caused by pump shutdown in an accident.

[0120] Specifically, under the third accident condition, the water hammer caused by the accidental pump stop is calculated to obtain the third variation law between the initial water-gas ratio of the air tank and the maximum water hammer pressure and the minimum water hammer pressure in the pipeline; under the third accident condition, the water hammer caused by the accidental pump stop is calculated to obtain the fourth variation law between the initial water-gas ratio of the air tank and the minimum water depth in the air tank; according to the third variation law and the fourth variation law, the size parameters of the air tank and the target initial water-gas ratio are determined.

[0121] Among them, the third accident condition is: the moment of inertia of the stably operating unit is the conventional design value, the stably operating units all stop pumping due to an accident, and the pump outlet check valve is closed at the preset flow value moment; the preset flow value moment is selected by technical personnel in this field according to the specific circumstances of the water supply system. In an optional embodiment, the preset flow value moment is the 0 flow moment.

[0122] For example, the embodiment of the present invention then calculates the water hammer of the accident pump stop according to the water hammer model under the third accident condition (initial 3 power frequency operation, all stopped) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Inlet water level 1166.00m; Air tank setting method and parameters are the same as above.

[0123] The calculation results are obtained based on the water hammer model; when the intermediate check valve is set and the highest net head is reached, the calculation results of the accident pump stop water hammer under different initial water-gas ratio conditions of the air tank are shown in the following table:

[0124]

[0125] According to the above calculation results, it can be obtained that the initial water-gas ratio of the air tank has a certain influence on the water hammer pressure in the pipeline. The smaller the initial water body, the more gas, and the smaller the pressure fluctuation at the air tank installation point. Therefore, the greater the maximum water hammer pressure from the water pump outlet to the air tank section, the greater the minimum water hammer pressure (air tank upstream point); the better the negative pressure improvement from the air tank to the end of the pipeline; the smaller the minimum water depth in the tank.

[0126] Taking into account the negative pressure conditions in the pipeline and the minimum water depth in the tank, the target initial water-to-air ratio of the air tank of this water delivery system is set to 1:1.

[0127] Step 2033: When the negative pressure of the pipe section from the pump outlet to the intermediate check valve is affected after the intermediate check valve is set, an air valve is set to improve the negative pressure of the pipe section.

[0128] Under the third accident condition and the highest net head, an air valve is set to determine whether the negative pressure state from the air tank to the end of the pipeline needs to be further improved, and at the same time verify that the unit reverse speed and pipeline water hammer pressure under each working condition meet the water hammer protection requirements; in an optional embodiment, a water hammer-proof air valve is set at pile number F0+122.599. The calculation results of the accident pump stop water hammer after adding the air valve are as follows:

[0129]

[0130] The calculation results show that (1) the water pump does not reverse; (2) the maximum water hammer pressure at the point behind the pump outlet check valve is 130.72m, which is 1.05 times its initial constant flow pressure of 124.46m. The pressure rise in the pipe section from the pump outlet to the intermediate check valve is very small, and the minimum water hammer pressure is above +2m; (3) the maximum water hammer pressure at the air tank point is 58.22m, which is 1.18 times its initial constant flow pressure of 49.4m. There is no negative pressure from the intermediate check valve to the end of the pipeline; (4) the minimum water depth in the air tank is 0.443m, which has sufficient safety margin.

[0131] Therefore, an air valve is required.

[0132] Step 2034: Determine the water hammer protection mode according to the type of the pump outlet check valve and the corresponding negative pressure elimination measures, as well as the settings of the intermediate check valve and the air valve. For example, the water delivery system of the embodiment of the present invention adopts the protection mode of "pump outlet axial flow check valve + air tank + intermediate check valve + water hammer air valve". In an optional embodiment, the accidental pump stop water hammer under different initial working conditions is calculated to verify that the unit reverse speed and pipeline water hammer pressure under each working condition meet the water hammer protection requirements.

[0133] The following is a detailed description of the process of determining whether an intermediate check valve is required. Fig.18 As shown, the step 2031 includes:

[0134] Step 20311: Set up an air tank. Under the second accident condition, when the distance between the water pump and the air tank is greater than a preset distance value, and / or when the flow rate of water flowing out of the air tank and flowing in the opposite direction of the upstream water pump is greater than a preset backflow threshold, set an intermediate check valve upstream of the air tank.

[0135] The preset distance value and the preset backflow threshold are selected by those skilled in the art according to the specific conditions of the water delivery system and are not limited here.

[0136] For example, the embodiment of the present invention then calculates the water hammer of the accident pump stop according to the water hammer model under the second accident condition (initial 3 power frequency operation, all stopped) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Inlet water level 1166.00m; Air tank setting method and parameters are the same as above.

[0137]

[0138] The calculation results are obtained based on the water hammer model; under the highest net head, the influence of the closing of the pump outlet check valve on the calculation results of the water hammer of the accidental pump shutdown is shown in the table above:

[0139] The change process of the pump outlet pressure, as well as the change processes of the tank flow rate of the air tank, the upstream flow rate and the downstream flow rate of the air tank can also be calculated.

[0140] According to the above calculation results, it can be obtained that after the air tank is set, when the check valve at the pump outlet is closed, there is no backflow and reversal phenomenon in the water pump; the minimum water depth in the air tank increases, and the maximum water hammer pressure at the pump outlet decreases. However, since there is a pipeline of about 158m (greater than the preset distance value) between the water pump and the air tank, and in the period of 0.7s to 1.0s after the pump is stopped, part of the water flowing out of the air tank (greater than the preset backflow threshold) flows in the reverse direction of the upstream water pump. Therefore, it is necessary to set an intermediate check valve upstream of the air tank. In order to reduce the impact of the backflow water on the pump ship and the rocker arm, an intermediate check valve can be installed at the starting point of the onshore main pipe and upstream of the air tank. In an optional embodiment, in order to facilitate operation management, the check valve adopts a hydraulic valve. In addition, in order to reduce the volume of the air tank, the amount of water flowing in the reverse direction upstream from the water flowing out of the air tank should be reduced.

[0141] Step 20312: When the air tank and the intermediate check valve are set, the water hammer caused by the pump stopping accident is calculated under the third accident condition to obtain the fifth variation law between the closing rate of the intermediate check valve and the maximum water hammer pressure at the pump outlet.

[0142] Step 20313: Calculate the water hammer caused by the pump stopping accident under the third accident condition, and obtain the sixth variation law between the closing rate and the maximum water hammer pressure at the pump outlet and the minimum water hammer pressure at the rocker arm section.

[0143] Step 20314: Determine the type of the intermediate check valve and its closing rule based on the fifth change rule and the sixth change rule.

[0144] For example, the embodiment of the present invention then calculates the water hammer of the accident pump stop according to the water hammer model under the third accident condition (initial 3 power frequency operation, all stopped; pump outlet check valve closed at 0 flow time, that is, closed about 0.7s after the pump is stopped) and the design flow rate; wherein the moment of inertia J = 27kg·m 2 ; Outlet pool water level 1289.60m; Inlet water level 1166.00m; Air tank setting method and parameters are the same as above; An intermediate check valve is installed upstream of the air tank.

[0145] The calculation results are obtained based on the water hammer model; at the highest net head, the intermediate check valve is about 158m away from the pump outlet. According to the calculation results of the previous working condition without the intermediate check valve, the intermediate check valve begins to close about 0.15s after the pump stops. The calculation results of the accidental pump stop water hammer when the intermediate check valve is closed at different rates are shown in the following table; the closing time of the intermediate check valve has a certain influence on the maximum water hammer pressure at the pump outlet and the negative pressure of the pipe section from the pump outlet to the intermediate check valve. If the intermediate check valve closes quickly and completes the closing before the pump outlet check valve, the pipe section from the pump outlet to the intermediate check valve will have negative pressure or even vaporization pressure; if the intermediate check valve closes too slowly, the pressure at the point behind the pump outlet check valve will increase. The closing rule of the intermediate check valve of this system is set as: the full stroke closing time is 2s linear closing.

[0146]

[0147] In summary, the present invention provides a water hammer protection mode determination scheme with clear process, step-by-step determination and elimination of associated influences, aiming at the characteristics of the water delivery system of the floating vessel pump station in the plateau mountainous area. It avoids the reliance on manual experience in the prior art, and simply makes judgments and superimposes combinations based on the advantages and disadvantages of each common pump-stop water hammer protection measure. It discovers the possible associated influences between the pump-stop water hammer protection measures by analyzing the process and eliminating them by adding measures, thereby greatly improving the protection effect against pump-stop water hammer and the efficiency of determining the water hammer protection mode.

[0148] Example 3

[0149] like Fig.19 , which is a schematic diagram of the architecture of a device for determining a water hammer protection mode according to an embodiment of the present invention. The device for determining a water hammer protection mode according to this embodiment includes one or more processors 21 and a memory 22. Fig.19 A processor 21 is taken as an example.

[0150] The processor 21 and the memory 22 may be connected via a bus or other means. Fig.19 The example of connecting through bus is taken in the following.

[0151] The memory 22 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs and non-volatile computer executable programs, such as the method for determining the water hammer protection mode in Example 1. The processor 21 executes the method for determining the water hammer protection mode by running the non-volatile software programs and instructions stored in the memory 22.

[0152] The memory 22 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices. In some embodiments, the memory 22 may optionally include a memory remotely arranged relative to the processor 21, and these remote memories may be connected to the processor 21 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0153] The program instructions / modules are stored in the memory 22, and when executed by the one or more processors 21, the method for determining the water hammer protection mode in the above embodiment 1 is executed, for example, the method described above is executed. Figure 1-Figure 3 , Fig.13 and Figure 17-Figure 18 It is worth noting that the information interaction, execution process and other contents between the modules and units in the above-mentioned device and system are based on the same concept as the processing method embodiment of the present invention, and the specific contents can be found in the description of the method embodiment of the present invention, and will not be repeated here.

[0154] A person skilled in the art may understand that all or part of the steps in the various methods of the embodiments may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the storage medium may include: a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, etc.

[0155] 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining a water hammer protection mode, characterized in that: Calculating the water hammer caused by pump stop under different accident conditions of the water delivery system respectively; and determining at least one water hammer protection measure required to be taken by the water delivery system according to the calculation results; determining a water hammer protection mode required for the water delivery system according to the at least one water hammer protection measure; The method for determining the water hammer protection mode includes: Operate the stable operating units in the water delivery system according to the designed number of units, and determine the most unfavorable operating condition based on the first reference operating condition; wherein the first reference operating condition is that all the stable operating units of the designed number of units stop pumping due to an accident, and the check valve at the pump outlet refuses to move; Analyze the water hammer caused by pump stop under the most unfavorable working conditions and determine the water hammer protection mode of the water delivery system; Wherein, the stable operation units in the water delivery system are operated according to the designed number of units, and the most unfavorable operating condition is determined based on the first reference operating condition, including: Under the first reference working condition, the water hammer caused by the pump stopping accident is analyzed, and the first influencing factor corresponding to the net head, the second influencing factor corresponding to the moment of inertia, the third influencing factor corresponding to the initial flow rate and the fourth influencing factor corresponding to the number of pumps stopped are determined respectively; Obtaining the most unfavorable operating condition according to the first influencing factor, the second influencing factor, the third influencing factor and the fourth influencing factor; Wherein, the analysis of the water hammer caused by pump stop under the first reference condition, respectively determining the first influencing factor corresponding to the net head, the second influencing factor corresponding to the moment of inertia, the third influencing factor corresponding to the initial flow rate and the fourth influencing factor corresponding to the number of pumps stopped, includes: The initial flow rate of the stably operating unit is set as the design flow rate value, and the water hammer of the pump is calculated under the first reference condition to obtain the first influencing factor under the same initial flow rate and different water inlet levels, so as to analyze the influence of the net head on the water hammer of the pump; The initial flow rate of the stably operating unit is set to the design flow rate value, and the water hammer caused by the pump stopping in an accident is calculated under the first reference condition to obtain the second influencing factor under different moments of inertia; Calculate the water hammer of the pump when it stops due to an accident under the first benchmark condition to obtain the third influencing factor under different initial flow rates; The initial flow rate of the stable operation unit is set to the design flow rate value, and the water hammer of the accidental pump shutdown is calculated to obtain the fourth influencing factor under different numbers of pump shutdowns; Wherein, under the most unfavorable working condition, analyzing the water hammer caused by pump stop accident and determining the water hammer protection mode of the water delivery system includes: Under the second accident condition, close the pump outlet check valve, calculate the accident pump stop water hammer according to the unit backflow start time, the maximum reverse speed and the maximum water hammer pressure at the pump outlet, and determine the closing law of the pump outlet check valve; The second accident condition is: the initial flow of the stable operation unit is the design flow value, the moment of inertia of the stable operation unit is the conventional design value, and when the pump station is at the highest net head, the stable operation unit stops pumping due to an accident; When closing the check valve at the pump outlet does not improve the negative pressure in the pipeline, the negative pressure elimination measures to be taken are determined according to the terrain of the water delivery system and the range of negative pressure elimination required; Determine the water hammer protection mode according to the type of the pump outlet check valve and its closing rule and the negative pressure elimination measures taken; Wherein, when the negative pressure elimination measure is to set an air tank, the water hammer protection mode is determined according to the type of the pump outlet check valve and its closing rule and the negative pressure elimination measure taken, including: When it is necessary to reduce the impact of backflow water on the pump boat and rocker arm, an intermediate check valve is installed; Determine the size parameters and target initial water-gas ratio of the air tank according to the longitudinal section layout of the pipeline and the influence of the air tank on the water hammer caused by pump shutdown in an accident; When the negative pressure of the pipe section from the pump outlet to the intermediate check valve is affected after the intermediate check valve is provided, an air valve is provided to improve the negative pressure of the pipe section; Determine the water hammer protection mode according to the type of the pump outlet check valve and the corresponding negative pressure elimination measures, as well as the settings of the intermediate check valve and the air valve; Wherein, when it is necessary to reduce the impact of the backflow water on the pump boat and the rocker arm, the intermediate check valve is provided, including: An air tank is provided. Under a second accident condition, when the distance between the water pump and the air tank is greater than a preset distance value, and / or when the flow rate of water flowing out of the air tank and flowing in the opposite direction of the upstream water pump is greater than a preset backflow threshold, an intermediate check valve is provided upstream of the air tank.

2. The method for determining the water hammer protection mode according to claim 1, characterized in that: The pump outlet check valve is closed under the second accident condition, and the accident pump stop water hammer is calculated according to the start time of the unit backflow, the maximum reverse speed and the maximum water hammer pressure at the pump outlet, and the closing rule of the pump outlet check valve is determined, including: Under the second accident condition, close the pump outlet check valve, calculate the accident pump shutdown water hammer, and obtain the first change law between the different closing laws of the pump outlet check valve and the start time of the unit backflow and the maximum reverse speed; Under the second accident condition, close the pump outlet check valve, calculate the water hammer caused by pump shutdown, and obtain the second variation law between the closing of the pump outlet check valve and the maximum water hammer pressure; The type of the pump outlet check valve is determined according to the first change rule and the second change rule.

3. The method for determining the water hammer protection mode according to claim 1, characterized in that: Determining the size parameters and the target initial water-gas ratio of the air tank according to the longitudinal profile layout of the pipeline and the influence of the air tank on the water hammer caused by pump shutdown in an accident includes: Under the third accident condition, the water hammer of the pump stop during the accident is calculated, and the third variation law between the initial water-gas ratio of the air tank and the maximum and minimum water hammer pressures in the pipeline is obtained; Under the third accident condition, the water hammer of the pump stopping accident is calculated to obtain a fourth variation law between the initial water-gas ratio of the air tank and the minimum water depth in the air tank; Determining the size parameters of the air tank and the target initial water-gas ratio according to the third variation rule and the fourth variation rule; Among them, the third accident condition is: the moment of inertia of the stably operating unit is the conventional design value, the stably operating unit has an accident and the pump stops, and the pump outlet check valve is closed at the preset flow value.

4. The method for determining the water hammer protection mode according to claim 1, characterized in that: When it is necessary to reduce the impact of the backflow water on the pump boat and the rocker arm, the intermediate check valve is also provided: When the air tank and the intermediate check valve are set, the water hammer of the pump stop during the accident is calculated under the third accident condition, and the fifth variation law between the closing rate of the intermediate check valve and the maximum water hammer pressure at the pump outlet is obtained; Under the third accident condition, the water hammer of the pump stopping accident is calculated to obtain a sixth variation rule between the closing rate and the maximum water hammer pressure at the pump outlet and the minimum water hammer pressure at the rocker arm section; According to the fifth change law and the sixth change law, the type of the intermediate check valve and its closing law are determined.

5. A device for determining a water hammer protection mode, characterized in that: The invention comprises at least one processor and a memory, wherein the at least one processor and the memory are connected via a data bus, and the memory stores instructions executable by the at least one processor, and after the instructions are executed by the processor, the method for determining the water hammer protection mode according to any one of claims 1 to 4 is implemented.

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