A method for water hammer protection in a pump station pressurization combined with gravity flow water conveyance system

Abstract

This invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance systems, comprising the following steps: designing a pump station pressurization combined with gravity flow water conveyance system, including an upper reservoir, a water pump, a pump outlet valve, an air tank, an elevated water tank, several sets of pressure reducing valves and energy dissipation boxes, a flow regulating valve, and a lower reservoir; when a sudden power outage occurs during pumping, the pump outlet valve, each pressure reducing valve, and the flow regulating valve are controlled according to the aforementioned action strategy, so that the pump outlet valve, each pressure reducing valve, and the flow regulating valve operate according to the aforementioned action strategy to achieve water hammer protection. This invention solves the water hammer protection problem in the pressurization section and gravity flow section of the pump station, effectively protecting the pipeline safety of complex water conveyance systems. It also provides a method for arranging pressure reducing valves and energy dissipation boxes, and proposes reasonable operating rules for all valves, which can directly guide engineering design.

Description

Technical Field

[0001] This application relates to a water hammer protection method, specifically a water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system. Background Technology

[0002] Long-distance, inter-basin water transfer projects are an effective way to redistribute water resources. However, hydraulic transients in pipelines can endanger pipeline safety, making effective water hammer protection a key research challenge. Long-distance pressurized water transmission projects typically include two methods: pumped-station pressurization and gravity flow. With the development of water hammer protection theory, more complex water transmission modes have emerged in practical engineering, namely, pumped-station pressurization combined with gravity flow. The water transmission characteristics of different sections in complex water transmission systems differ and influence each other. Water hammer protection for such systems cannot be simply understood as the sum of protection for the pumped-station section and the gravity flow section. In addition to focusing on the safety of each pipeline section, it is also necessary to discuss the protection of connecting sections within the system. Therefore, developing water hammer protection for such water transmission systems has significant practical implications.

[0003] Generally, this type of water conveyance system features an initial rise followed by a fall, with localized high points in the intermediate section. To overcome these high points, pumping stations are needed to pressurize the rising section of the pipeline; the falling section, due to the large head difference, can rely on gravity for flow. These two elements constitute a complex water conveyance system combining pumping station pressurization and gravity flow. When a pump experiences a power outage, the initial water pressure at the localized high point is low, and downstream water cannot flow back, easily leading to negative pressure disruption. To avoid this, elevated water tanks are typically installed at the localized high points for protection. The elevated water tanks, through water level fluctuations, convert the elastic potential energy of the water caused by water hammer waves into gravitational potential energy, regulating the pipeline flow rate. This not only alleviates water hammer pressure but also ensures a smooth flow of water into the downstream pipeline.

[0004] Relying solely on elevated water tanks to protect against sudden power outages of the water pumps would require a large volume, which would increase construction difficulty and operational risks at high altitudes. Therefore, designing a safe and reliable system protection scheme and operating method that allows water hammer protection measures to simultaneously meet the pressure control standards of both the pump station's pressurization section and gravity flow section has become an urgent problem to solve. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance system, which can effectively solve the above problems.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance systems, comprising the following steps:

[0008] Step S1: Design a water conveyance system that combines pump station pressurization with gravity flow;

[0009] Step S1.1, the water conveyance system includes an upper reservoir (1), a water pump (2), a pump outlet valve (3), an air tank (4), an elevated water tank (6), several sets of pressure reducing valve energy dissipation box combinations, a flow regulating valve (11), and a lower reservoir (12);

[0010] Step S1.2, the elevated water tank (6) is arranged at a local high point between the upper reservoir (1) and the lower reservoir (12); a pump station pressurization section is formed between the upper reservoir (1) and the elevated water tank (6); a gravity flow section is formed between the elevated water tank (6) and the lower reservoir (12);

[0011] Step S1.3: In the pressurization section of the pump station, and near the upper reservoir (1), the water pump (2), the pump outlet valve (3), and the air tank (4) are arranged in sequence along the water flow direction; in the gravity flow section, several sets of pressure reducing valve energy dissipation box combinations are arranged along the water flow direction, and the flow regulating valve (11) is arranged near the lower reservoir (12);

[0012] Step S1.4: Determine the initial state parameters of each pressure reducing valve, each energy dissipation box, and the flow regulating valve (11) in the water transmission system;

[0013] Step S2: Determine the operating strategies of the downstream valve (3), each pressure reducing valve, and the flow regulating valve (11) in the system after the power is cut off from the water pump.

[0014] Step S3, the water conveyance system starts to operate according to the initial state parameters. Under normal operation, the air tank (4), the high-level water tank (6), each pressure reducing valve, each energy dissipation box and the flow regulating valve (11) do not operate.

[0015] Step S4: When the water pump suddenly experiences a power outage, the pump downstream valve (3), each pressure reducing valve, and the flow regulating valve (11) are controlled according to the action strategy, so that the pump downstream valve (3), each pressure reducing valve, and the flow regulating valve (11) operate according to the action strategy to achieve water hammer protection.

[0016] Furthermore, each of the pressure reducing valve and energy dissipation box assemblies includes a pressure reducing valve and an energy dissipation box; the pressure reducing valve is arranged adjacent to the front end of the energy dissipation box and its relative position to the energy dissipation box is fixed. The fluid is first depressurized by the pressure reducing valve and then smoothly enters the energy dissipation box for energy dissipation.

[0017] Furthermore, step S1.4 specifically includes:

[0018] Step S1.4.1: Assume that N sets of pressure reducing valve energy dissipation box combinations are arranged in the gravity flow section, and are sequentially named as the first pressure reducing valve energy dissipation box combination, the second pressure reducing valve energy dissipation box combination, ..., the Nth pressure reducing valve energy dissipation box combination in the direction of gradually moving away from the high-level water tank (6); For the i-th pressure reducing valve energy dissipation box combination, it includes the i-th pressure reducing valve and the i-th energy dissipation box, i = 1, 2, ..., N;

[0019] Step S1.4.2: Determine the head ΔH that needs to be eliminated for each i-th pressure reducing valve energy dissipation box combination. i The initial water level h of each i-th energy dissipation tank Ei ;

[0020] Step S1.4.3, combining the topographic parameters of the water conveyance system, uses the following formula to determine the layout location of the i-th pressure reducing valve energy dissipation box assembly:

[0021]

[0022] in:

[0023] L i The distance between the arrangement position of the i-th pressure reducing valve energy dissipation box assembly and the high-level water tank (6);

[0024] ΔH1 is the head that needs to be eliminated by the first pressure reducing valve energy dissipation box assembly;

[0025] ΔH i The head that needs to be eliminated for the i-th pressure reducing valve energy dissipation box assembly;

[0026] H s The elevation of the high-level water tank (6);

[0027] Z s The height of the center line of the pipe in the high-level water tank (6);

[0028] h Ei Let be the initial water level of the i-th energy dissipation tank;

[0029] θ h The angle between the gravity flow section and the horizontal plane;

[0030] θ v The angle between the hydraulic gradient line of the gravity flow section and the horizontal plane;

[0031] Step S1.4.4, determine the initial opening degree of each i-th pressure reducing valve:

[0032] Since the head that the i-th pressure reducing valve and energy dissipation box combination needs to dissipate is ΔH i Obtain the head ΔH that can be eliminated by the i-th energy dissipation box. i,消 Therefore, the head ΔH that needs to be eliminated by the i-th pressure reducing valve is obtained. i,减 =ΔH i -ΔHi,消 According to the head ΔH that needs to be eliminated by the i-th pressure reducing valve. i,减 Determine the initial opening degree of the i-th pressure reducing valve;

[0033] Step S1.4.5: Determine the initial opening of the flow control valve (11) located at the end:

[0034] The energy H to be eliminated by the flow control valve (11) is obtained by using the following formula. V :

[0035]

[0036] Wherein: H d L is the water level of the lower reservoir (12); L is the distance from the upper reservoir (6) to the lower reservoir (12);

[0037] According to the energy H that needs to be eliminated by the flow control valve (11) V The initial opening degree of the flow regulating valve (11) is determined.

[0038] Step S1.4.6, thereby obtaining the initial state parameters, including the head ΔH that needs to be eliminated for each i-th pressure reducing valve energy dissipation box combination. i The initial water level h of each i-th energy dissipation tank Ei The arrangement of each i-th pressure reducing valve energy dissipation box combination, the initial opening of each i-th pressure reducing valve and the initial opening of the flow regulating valve (11).

[0039] Furthermore, formula (4) for the arrangement of the i-th pressure reducing valve energy dissipation box assembly is derived as follows:

[0040] The pressure head H of the i-th energy dissipation box Ei for:

[0041]

[0042] The centerline height of the pipe at the i-th energy dissipation box is Z. Ei for:

[0043] Z Ei =Z s -L i ×sinθ h (2)

[0044] in: h f =L i ×cosθ h ×tanθ v h f The first intermediate variable related to the hydraulic gradient line;

[0045] The internal water pressure h at the i-th energy dissipation boxEi for:

[0046] h Ei =H Ei -Z Ei (3)

[0047] By combining equations (1) to (3), we can obtain:

[0048]

[0049] This step is now complete.

[0050] Furthermore, formula (6) is derived as follows:

[0051] Since the total head ΔH to be eliminated is composed of the combination of each group of pressure reducing valves and energy dissipation boxes, as well as the flow regulating valve (11), we have formula (5):

[0052]

[0053] Wherein: H f =L×cosθ h ×tanθ v H f It is the second intermediate variable related to the hydraulic gradient line;

[0054] By transforming formula (5), we obtain formula (6).

[0055] Furthermore, step S4 specifically involves:

[0056] When the water pump suddenly loses power, the pressure after the pump drops rapidly, the air tank (4) quickly replenishes water into the pipeline and quickly closes the valve (3) after the pump.

[0057] After the pump valve (3) is closed, the high-level water tank (6) continues to replenish water to the gravity flow section. To prevent the high-level water tank (6) from leaking, all pressure reducing valves and flow regulating valves (11) are closed at the same time. Due to the presence of the energy dissipation box, the large pressure change caused by the closure of the gravity flow section valve is alleviated, and the reliability of the system is increased.

[0058] Furthermore, the minimum water level of the elevated water tank (6) is determined by a safety value.

[0059] Furthermore, in the event of a sudden power outage during pumping, the water supply system is required to maintain a constant pressure above the pipeline pressure standard, ensuring that the system does not experience negative pressure.

[0060] The water hammer protection method provided by this invention for a pump station pressurization combined with gravity flow water conveyance system has the following advantages:

[0061] This invention solves the water hammer protection problem in the pressurization section and gravity flow section of pumping stations, effectively protecting the pipeline safety of complex water conveyance systems. It also provides a method for arranging pressure reducing valves and energy dissipation boxes, and proposes reasonable operating rules for all valves, which can directly guide engineering design. Attached Figure Description

[0062] Figure 1 A schematic diagram of the layout of a water conveyance system that combines pressurization at the pumping station with gravity flow;

[0063] Figure 2 This is a diagram showing the pressure envelope of the water conveyance system in the pumping station section under different protection schemes after a power failure of the water pump.

[0064] Figure 3 The pressure envelope diagram of the gravity flow section water conveyance system under different protection schemes after the water pump loses power;

[0065] Figure 4 This diagram illustrates the water level changes in the high-level water tank under different protection schemes after a power outage of the water pump.

[0066] Figure 5 The diagram shows the changes in water level and pressure in the No. 1 energy dissipation tank under different protection schemes after the water pump loses power.

[0067] Figure 6 The diagram shows the changes in water level and pressure in the No. 2 energy dissipation tank under different protection schemes after the water pump loses power.

[0068] in:

[0069] 1-Upper tank; 2-Water pump; 3-Post-pump valve; 4-Air tank; 5-Pressure pipeline; 6-High-level water tank; 7-1# pressure reducing valve; 8-1# energy dissipation box; 9-2# pressure reducing valve; 10-2# energy dissipation box; 11-Flow regulating valve; 12-Lower tank. Detailed Implementation

[0070] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0071] This invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance systems. It proposes a water hammer protection measure combining an air tank, a pressure reducing valve, and an energy dissipation box. An air tank is installed in the pump station section, and a pressure reducing valve and energy dissipation box are installed in the gravity flow section. Through a series connection of elevated water tanks, water hammer protection is implemented for complex water conveyance systems. The arrangement of the pressure reducing valve and energy dissipation box in such water conveyance systems is also described, along with a reasonable valve closing method. This water hammer protection method effectively prevents pipeline overpressure caused by pump power failure and effectively avoids leakage of the elevated water tank.

[0072] See Figure 1 This invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance system, comprising the following steps:

[0073] Step S1: Design a water conveyance system that combines pump station pressurization with gravity flow;

[0074] Step S1.1, the water conveyance system includes an upper reservoir 1, a water pump 2, a post-pump valve 3, an air tank 4, an elevated water tank 6, several sets of pressure reducing valves and energy dissipation boxes, a flow regulating valve 11, and a lower reservoir 12;

[0075] Specifically, each of the pressure reducing valve and energy dissipation box assemblies includes a pressure reducing valve and an energy dissipation box; the pressure reducing valve is arranged adjacent to the front end of the energy dissipation box and its relative position to the energy dissipation box is fixed. The fluid is first depressurized by the pressure reducing valve and then smoothly enters the energy dissipation box for energy dissipation.

[0076] Step S1.2: The elevated water tank 6 is arranged at a local high point between the upper reservoir 1 and the lower reservoir 12; a pump station pressurization section is formed between the upper reservoir 1 and the elevated water tank 6; a gravity flow section is formed between the elevated water tank 6 and the lower reservoir 12.

[0077] Step S1.3: In the pressurization section of the pump station, and near the upper reservoir 1, the water pump 2, the pump outlet valve 3, and the air tank 4 are arranged sequentially along the water flow direction; in the gravity flow section, several sets of pressure reducing valve energy dissipation box combinations are arranged along the water flow direction, and the flow regulating valve 11 is arranged near the lower reservoir 12.

[0078] Therefore, the post-pump valve 3 and air tank 4 are both located after the water pump 2, the flow regulating valve 11 is located before the lower tank 12, and each set of pressure reducing valve energy dissipation box assemblies is arranged on the pressure pipeline between the high-level water tank 6 and the flow regulating valve 11. For example, two sets of pressure reducing valve energy dissipation box assemblies are arranged: the first pressure reducing valve energy dissipation box assembly and the second pressure reducing valve energy dissipation box assembly. The first pressure reducing valve energy dissipation box assembly includes pressure reducing valve 7 and energy dissipation box 8, and the second pressure reducing valve energy dissipation box assembly includes pressure reducing valve 9 and energy dissipation box 10. Pressure reducing valve 7 and energy dissipation box 8, and pressure reducing valve 9 and energy dissipation box 10 are adjacent to each other.

[0079] Step S1.4: Determine the initial state parameters of each pressure reducing valve, each energy dissipation box, and the flow regulating valve 11 in the water supply system;

[0080] This step is specifically as follows:

[0081] Step S1.4.1: Assume that N sets of pressure reducing valve energy dissipation box assemblies are arranged in the gravity flow section, and are sequentially named as the first pressure reducing valve energy dissipation box assembly, the second pressure reducing valve energy dissipation box assembly, ..., the Nth pressure reducing valve energy dissipation box assembly in the direction of gradually moving away from the high-level water tank 6; for the i-th pressure reducing valve energy dissipation box assembly, it includes the i-th pressure reducing valve and the i-th energy dissipation box, i = 1, 2, ..., N;

[0082] It should be noted that, in order to protect the pipeline pressure downstream of the pressure reducing valve as much as possible and reduce the change in water level in the energy dissipation tank, this invention innovatively combines the pressure reducing valve and the energy dissipation tank. The pressure reducing valve is placed very close to the energy dissipation tank, working together with the end flow regulating valve to eliminate excess head. This invention does not limit the number of pressure reducing valve and energy dissipation tank combinations in the pipeline; the attached diagram only shows an example of two pressure reducing valve and energy dissipation tank combinations. The specific number of pressure reducing valve and energy dissipation tank combinations is set according to project requirements. When N sets of pressure reducing valve and energy dissipation tank combinations are arranged in the pipeline, the pipeline is thus divided into N+1 sections.

[0083] Step S1.4.2: Determine the head ΔH that needs to be eliminated for each i-th pressure reducing valve energy dissipation box combination. i The initial water level h of each i-th energy dissipation tank Ei ;

[0084] Specifically, the head ΔH that each i-th pressure reducing valve energy dissipation box combination needs to eliminate is... i The initial water level h of each i-th energy dissipation tank Ei It can be set according to the needs of the project.

[0085] Step S1.4.3: Based on the topographic parameters of the water conveyance system, determine the location of the i-th pressure reducing valve energy dissipation box assembly.

[0086] Specifically, the pressure head H of the i-th energy dissipation box... Ei for:

[0087]

[0088] The centerline height of the pipe at the i-th energy dissipation box is Z. Ei for:

[0089] Z Ei =Z s -L i ×sinθ h (2)

[0090] in: h f =L i ×cosθ h ×tanθ v h f The first intermediate variable related to the hydraulic gradient line;

[0091] The internal water pressure h at the i-th energy dissipation box Ei for:

[0092] h Ei =H Ei -Z Ei (3)

[0093] By combining equations (1) to (3), we can obtain:

[0094]

[0095] in:

[0096] L i The distance between the location of the i-th pressure reducing valve energy dissipation box assembly and the elevated water tank 6;

[0097] ΔH1 is the head that needs to be eliminated by the first pressure reducing valve energy dissipation box assembly;

[0098] ΔH i The head that needs to be eliminated for the i-th pressure reducing valve energy dissipation box assembly;

[0099] H s The elevation of the high-level water tank 6;

[0100] Z s The height of the centerline of the pipe in the high-level water tank 6;

[0101] h Ei Let be the initial water level of the i-th energy dissipation tank;

[0102] θ h The angle between the gravity flow section and the horizontal plane;

[0103] θ v The angle between the hydraulic gradient line of the gravity flow section and the horizontal plane;

[0104] Using formula (4), the distance L between the arrangement position of each i-th pressure reducing valve energy dissipation box assembly and the high-level water tank 6 is obtained. i Thus, the arrangement position of each i-th pressure reducing valve energy dissipation box assembly is determined.

[0105] Step S1.4.4, determine the initial opening degree of each i-th pressure reducing valve:

[0106] Since the head that the i-th pressure reducing valve and energy dissipation box combination needs to dissipate is ΔH i Obtain the head ΔH that can be eliminated by the i-th energy dissipation box. i,消 Therefore, the head ΔH that needs to be eliminated by the i-th pressure reducing valve is obtained. i,减 =ΔH i -ΔH i,消 According to the head ΔH that needs to be eliminated by the i-th pressure reducing valve. i,减Determine the initial opening degree of the i-th pressure reducing valve;

[0107] Step S1.4.5: Determine the initial opening of the flow control valve 11 located at the end:

[0108] Since the total head ΔH to be eliminated is composed of the combination of each group of pressure reducing valves and energy dissipation boxes and the flow regulating valve 11, we have formula (5):

[0109]

[0110] Wherein: H f =L×cosθ h ×tanθ v H f It is the second intermediate variable related to the hydraulic gradient line;

[0111] Equation (5) is transformed to obtain equation (6). Using equation (6), the energy H to be eliminated by the flow control valve 11 is obtained. V :

[0112]

[0113] Wherein: H d 1 is the water level of the lower reservoir 12; L is the distance from the upper reservoir 6 to the lower reservoir 12.

[0114] According to the energy H that needs to be eliminated by the flow control valve 11 V The initial opening degree of the flow regulating valve 11 is determined.

[0115] Step S1.4.6, thereby obtaining the initial state parameters, including the head ΔH that needs to be eliminated for each i-th pressure reducing valve energy dissipation box combination. i The initial water level h of each i-th energy dissipation tank Ei The arrangement of each i-th pressure reducing valve energy dissipation box assembly, the initial opening degree of each i-th pressure reducing valve, and the initial opening degree of the flow regulating valve 11.

[0116] Step S2: Determine the operating strategies of the downstream valve 3, each pressure reducing valve, and the flow regulating valve 11 in the system after the water pump is de-energized.

[0117] Step S3: The water supply system starts to operate according to the initial state parameters. Under normal operation, the air tank 4, the high-level water tank 6, each pressure reducing valve, each energy dissipation box, and the flow regulating valve 11 do not operate.

[0118] Step S4: When the water pump suddenly experiences a power outage, the pump downstream valve 3, each pressure reducing valve, and the flow regulating valve 11 are controlled according to the action strategy, so that the pump downstream valve 3, each pressure reducing valve, and the flow regulating valve 11 operate according to the action strategy to achieve water hammer protection.

[0119] Step S4 is as follows:

[0120] When the water pump suddenly loses power, the pressure after the pump drops rapidly, the air tank 4 quickly replenishes water into the pipeline, and the valve 3 after the pump is quickly closed.

[0121] After the pump valve 3 is closed, the high-level water tank 6 continuously replenishes water to the gravity flow section. To prevent the high-level water tank 6 from leaking, all pressure reducing valves and flow regulating valves 11 are closed at the same time. Due to the presence of the energy dissipation box, the large pressure changes caused by the closure of the gravity flow section valves are alleviated, and the reliability of the system is increased.

[0122] In this invention, the minimum water level of the elevated water tank 6 is determined by a safety value. In the event of a sudden power outage during pumping, the water delivery system is required to prevent negative pressure and ensure that the positive pressure in the pipeline does not exceed the pipeline pressure-bearing standard.

[0123] This invention provides a water hammer protection method applicable to pump station pressurization combined with gravity flow water conveyance systems, which can effectively protect the safety of the water conveyance system. The main steps can be described as follows:

[0124] (1) Design water hammer protection measures, install an air tank after the water pump, and install a pressure reducing valve and energy dissipation box in the gravity flow section;

[0125] Specifically, the water conveyance system includes an upper reservoir and a lower reservoir. Between the upper and lower reservoirs, a water pump, a post-pump valve, an air tank, an elevated water tank, a pressure reducing valve, an energy dissipation box, and a flow regulating valve are installed sequentially. The water pump, post-pump valve, and air tank are all located near the upper reservoir, while the flow regulating valve is located near the lower reservoir.

[0126] An air tank is located at the water pump outlet, and an elevated water tank is located at a local high point. The water supply system is divided into a pump station pressurization section and a gravity flow section. A pressure reducing valve is located adjacent to the front end of the energy dissipation box and its relative position to the energy dissipation box is fixed to ensure that the fluid is first depressurized and then enters the energy dissipation box smoothly for energy dissipation. A flow regulating valve is located at the end of the gravity flow.

[0127] (2) Determine the layout of the pressure reducing valve and the energy dissipation box, as well as the initial opening of the pressure reducing valve and the initial opening of the flow regulating valve;

[0128] (3) Determine the action strategy of all valves in the system after the power is cut off when the water pump is pumping water;

[0129] (4) Initial operating state: Under normal operating conditions of the water supply system, all valves are not activated;

[0130] Specifically, under normal operating conditions, the air tank, elevated water tank, pressure reducing valve, energy dissipation box, and flow regulating valve will not operate.

[0131] (5) Verify the water hammer protection effect. After the water pump is de-energized, all valves operate in a regular manner.

[0132] Specifically, when a water pump suddenly experiences a power outage, the pressure after the pump drops rapidly. The air tank quickly replenishes water into the pipeline and rapidly closes the valve after the pump. After the valve closes, the elevated water tank continuously replenishes water to the gravity flow section. To prevent the elevated water tank from emptying, the pressure reducing valve and flow regulating valve of the gravity flow section must be closed promptly. The presence of the energy dissipation box mitigates the significant pressure changes caused by the closure of the gravity flow section valves, increasing the system's reliability.

[0133] The pressure control standard for the transient process of the water conveyance system is that the maximum pressure of the pipeline shall not exceed 1.3 to 1.5 times the maximum pressure of the water conveyance system during steady-state operation, and the minimum pressure of the pipeline shall not be lower than 0m.

[0134] This invention solves the water hammer protection problem in the pressurization section and gravity flow section of pumping stations, effectively protecting the pipeline safety of complex water conveyance systems. It also provides a method for arranging pressure reducing valves and energy dissipation boxes, and proposes reasonable operating rules for all valves, which can directly guide engineering design.

[0135] The following is an example:

[0136] In this example, two sets of pressure reducing valve energy dissipation box assemblies are arranged: the first pressure reducing valve energy dissipation box assembly and the second pressure reducing valve energy dissipation box assembly. The first pressure reducing valve energy dissipation box assembly includes pressure reducing valve #7 and energy dissipation box #8, and the second pressure reducing valve energy dissipation box assembly includes pressure reducing valve #9 and energy dissipation box #10.

[0137] The post-pump valve 3 and air tank 4 are both located after the water pump 2. The flow regulating valve 11 is located before the lower tank 12. The pressure reducing valve 7 and the energy dissipation box 8, the pressure reducing valve 9 and the energy dissipation box 10 are adjacent to each other and are located on the pressure pipeline between the high-level water tank 6 and the flow regulating valve 11.

[0138] Under normal operating conditions, the downstream valve 3, pressure reducing valve 7, pressure reducing valve 9, and flow regulating valve 11 are at their initial openings, while the water levels in air tank 4, elevated water tank 6, energy dissipation box 8, and energy dissipation box 10 remain constant. If pump 2 experiences a sudden power outage, the downstream pressure drops rapidly. To prevent backflow into pump 2 and potential runaway, downstream valve 3 needs to be quickly closed to its zero opening. To prevent air leakage in elevated water tank 6, pressure reducing valve 7, pressure reducing valve 9, and flow regulating valve 11 need to be closed to their zero openings promptly. To effectively reduce water level fluctuations in elevated water tank 6, energy dissipation box 8, and energy dissipation box 10, the operating strategy for pressure reducing valve 7, pressure reducing valve 9, and flow regulating valve 10 is designed to close simultaneously.

[0139] To verify the accuracy of the theoretical analysis and study the effectiveness of this water hammer protection method, a model will be established based on an actual water conveyance project to simulate the water hammer protection effect during a power outage of the water pump.

[0140] In this embodiment, the total length of the water supply pipeline is approximately 9350.0m, with a gravity flow section of 4531m and a designed water supply flow rate of 0.58m³ / h. 3 / s, using a single DN350 steel pipe for water transport. Figure 1 The design water level of the upper reservoir 1 is 2129.00m, the design water level of the elevated water tank 6 is 2141.71m, and the design water level of the lower reservoir 12 is 2141.71m. The actual head of pump 2 is 18.23m. If pump 2 experiences a sudden power outage, the water supply system must simultaneously meet both positive and negative pressure requirements. The control standard for positive pressure is 283.58m, and the control standard for negative pressure is 0m. If no protective measures are implemented after a sudden power outage of pump 2, the pipeline pressure will drop below -10m, generating vapor pressure and causing severe pipeline damage. Therefore, an air tank 4 must be installed after the pump, and the valve 3 after the pump must be closed. Simultaneously, to prevent leakage from the elevated water tank 6, pressure reducing valves 7 (1#), 9 (2#), and the flow regulating valve 11 must be closed promptly.

[0141] This embodiment designs two valve action schemes: Scheme A is a valve closing scheme where the valves close sequentially, and Scheme B is a valve closing scheme where the valves close simultaneously.

[0142] The relevant parameters of the air tank are shown in Table 1. To fully utilize the water hammer protection effect of the air tank, a rapid closure of the post-pump valve is considered, with the valve closing in a linear sequence every 5 seconds. The relevant parameters of the pressure reducing valve and the flow regulating valve are shown in Table 2.

[0143] Table 1. Statistics of Initial Parameters for Air Tank Type

[0144]

[0145]

[0146] Table 2. Statistics of initial parameters for pressure reducing valves and flow regulating valves

[0147]

[0148] In other words, in Scheme A, when the water pump 2 suddenly experiences a power outage, starting from the moment the power outage occurs, at second 0, both the downstream valve and the flow regulating valve are simultaneously closed; at second 15, pressure reducing valve #2 is closed; and at second 30, pressure reducing valve #1 is closed.

[0149] In Scheme B, when water pump 2 suddenly experiences a power outage, starting from the moment the power outage occurs, at second 0, the downstream valve, the flow regulating valve, pressure reducing valve #2, and pressure reducing valve #1 are simultaneously shut off.

[0150] Depend on Figure 2It can be seen that the minimum pressure in the pressurization section of the pump station occurs at the bottom of the air tank, with a minimum pressure of 0.79 m and a maximum pressure of 145.79 m. This meets both the requirement of no negative pressure in the pipeline and the maximum pressure control standard (145.79 m < 202.8 m). The minimum pressure in the gravity flow section is 0.00 m, occurring in the section from the elevated water tank to the first energy dissipation box. The minimum pressure in the remaining pipe sections is greater than 0.00 m. The maximum pressure in each section is within the maximum pressure control range (226.10 m < 283.58 m). Schemes A and B have relatively small impacts on the pipeline pressure envelope, with the pressure in Scheme A being slightly lower than that in Scheme B. The difference in minimum pressure in the pressurization section of the pump station is 0.05 m, and the difference in maximum pressure is 0.95 m. The difference in minimum pressure in the gravity flow section is 0.30 m, and the difference in maximum pressure is 0.20 m.

[0151] Depend on Figure 3 and Figure 4 It can be seen that different valve closing methods affect the water level changes in the elevated water tank and the energy dissipation tank. In the two schemes, the maximum drop in water level between the elevated water tank and the energy dissipation tank differs significantly. In Scheme A, the maximum drop in water level of the elevated water tank is greater than in Scheme B, with a difference of 0.27m, approximately 2.7 times that of Scheme B. In Scheme A, the water level in the energy dissipation tank rises by 0.3m, while in Scheme B, the water level change in the energy dissipation tank is less than 0.07m.

[0152] It is evident that the method of this invention can effectively protect the entire water conveyance system. By arranging water hammer protection measures and operating all valves according to the method of this invention, the water level fluctuations in the high-level water tank and energy dissipation box can be effectively reduced, thereby increasing the safety and reliability of the system.

[0153] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for water hammer protection in a pump station pressurization combined with gravity flow water conveyance system, characterized in that, Includes the following steps: Step S1: Design a water conveyance system that combines pump station pressurization with gravity flow; Step S1.1, the water conveyance system includes an upper reservoir (1), a water pump (2), a pump outlet valve (3), an air tank (4), an elevated water tank (6), several sets of pressure reducing valve energy dissipation box combinations, a flow regulating valve (11), and a lower reservoir (12). Step S1.2, the elevated water tank (6) is arranged at a local high point between the upper reservoir (1) and the lower reservoir (12); a pump station pressurization section is formed between the upper reservoir (1) and the elevated water tank (6); a gravity flow section is formed between the elevated water tank (6) and the lower reservoir (12); Step S1.3: In the pressurization section of the pump station, and near the upper reservoir (1), the water pump (2), the pump outlet valve (3), and the air tank (4) are arranged sequentially along the water flow direction; in the gravity flow section, several sets of pressure reducing valve energy dissipation box combinations are arranged along the water flow direction, and the flow regulating valve (11) is arranged near the lower reservoir (12). Step S1.4, determine the initial state parameters of each pressure reducing valve, each energy dissipation box, and the flow regulating valve (11) in the water transmission system, specifically as follows: Step S1.4.1, assuming that the gravity flow section is jointly arranged The pressure-reducing valve energy dissipation box assemblies, arranged in order of increasing distance from the elevated water tank (6), are sequentially designated as the first pressure-reducing valve energy dissipation box assembly, the second pressure-reducing valve energy dissipation box assembly, ..., the third... Pressure reducing valve and energy dissipation box assembly; for the first Pressure reducing valve energy dissipation box assembly, including the first Pressure reducing valve and the first Energy dissipation box ; Step S1.4.2, determine each of the following: The pressure reducing valve and energy dissipation box combination needs to eliminate the water head. Each Initial water level of the energy dissipation tank ; Step S1.4.3, combining the topographic parameters of the water conveyance system, uses the following formula to determine the first... Location of the pressure reducing valve and energy dissipation box assembly: （4） in: For the first The distance between the arrangement of the pressure reducing valve energy dissipation box assembly and the elevated water tank (6); The head that needs to be eliminated for the first pressure reducing valve energy dissipation box assembly; For the first The pressure reducing valve and energy dissipation box assembly needs to eliminate the water head; The elevation of the high-level water tank (6); The height of the center line of the pipe in the high-level water tank (6); For the first Initial water level in the energy dissipation tank; The angle between the gravity flow section and the horizontal plane; The angle between the hydraulic gradient line of the gravity flow section and the horizontal plane; Step S1.4.4, determine the initial opening degree of each pressure reducing valve: Due to the The head that needs to be eliminated by the pressure reducing valve and energy dissipation box combination is , obtain the The head that the energy dissipation box can eliminate Thus, the first The pressure reducing valve needs to eliminate the water head. According to the first The pressure reducing valve needs to eliminate the water head. Determine the first The initial opening degree of the pressure reducing valve; Step S1.4.5, determine the initial opening degree of the flow control valve (11) located at the end: The energy to be eliminated by the flow control valve (11) is obtained by using the following formula. : （6） in: The water level of the lower reservoir (12); The distance from the high-level water tank (6) to the lower reservoir (12); According to the energy that needs to be eliminated by the flow control valve (11) The initial opening degree of the flow regulating valve (11) is determined; Step S1.4.6, thereby obtaining the initial state parameters, including each of the following: The pressure reducing valve and energy dissipation box combination needs to eliminate the water head. Each Initial water level of the energy dissipation tank Each The arrangement of the pressure reducing valve and energy dissipation box assembly, and the various components. The initial opening degree of the pressure reducing valve and the initial opening degree of the flow regulating valve (11); Step S2: Determine the operating strategies of the downstream valve (3), pressure reducing valves, and flow regulating valve (11) in the system after the water pump is de-energized. Step S3, the water supply system starts to operate according to the initial state parameters. Under normal operation, the air tank (4), the high-level water tank (6), each pressure reducing valve, each energy dissipation box and the flow regulating valve (11) do not operate. Step S4: When the water pump suddenly experiences a power outage, the pump downstream valve (3), each pressure reducing valve, and the flow regulating valve (11) are controlled according to the action strategy, so that the pump downstream valve (3), each pressure reducing valve, and the flow regulating valve (11) operate according to the action strategy to achieve water hammer protection.

2. The water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, Each pressure reducing valve and energy dissipation box assembly includes a pressure reducing valve and an energy dissipation box; the pressure reducing valve is arranged adjacent to the front end of the energy dissipation box and its relative position to the energy dissipation box is fixed. The fluid is first depressurized by the pressure reducing valve and then smoothly enters the energy dissipation box for energy dissipation.

3. The water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, No. Formula (4) for the arrangement of the pressure reducing valve and energy dissipation box assembly is derived as follows: No. Pressure head of the energy dissipation box for: （1） No. Pipe centerline height at the energy dissipation box for: （2） in: ; , The first intermediate variable related to the hydraulic gradient line; No. Internal water pressure at the energy dissipation box for: （3） By combining equations (1) to (3), we can obtain: （4） This step is now complete.

4. The water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, Formula (6) is derived in the following way: Due to the total head that needs to be eliminated It is composed of a combination of pressure reducing valves and energy dissipation boxes, and a flow regulating valve (11), therefore, we have formula (5): （5） in: , It is the second intermediate variable related to the hydraulic gradient line; By transforming formula (5), we obtain formula (6).

5. A water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, Step S4 is as follows: When the water pump suddenly loses power, the pressure after the pump drops rapidly, the air tank (4) quickly replenishes water into the pipeline, and the valve (3) after the pump is quickly closed. After the pump valve (3) is closed, the high-level water tank (6) continues to replenish water to the gravity flow section. To prevent the high-level water tank (6) from leaking, all pressure reducing valves and flow regulating valves (11) are closed at the same time. Due to the presence of the energy dissipation box, the large pressure change caused by the closure of the gravity flow section valve is alleviated, and the reliability of the system is increased.

6. A water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, The minimum water level of the elevated water tank (6) is determined by a safety value.

7. A water hammer protection method applicable to a pump station pressurization combined with gravity flow water conveyance system according to claim 1, characterized in that, In the event of a sudden power outage during pumping, the water supply system must not experience negative pressure, and the positive pressure in the pipeline must not exceed the pipeline pressure standard.

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