Low-oscillation control method and system for long-distance pipeline low-pressure water delivery system

Abstract

The invention discloses a low-oscillation control method and system for a long-distance pipeline low-pressure water delivery system, and relates to the technical field of long-distance water diversion engineering. The method comprises the following steps: determining a pressure envelope line of the water delivery system when a middle pressure reducing valve is not arranged; drawing up a low-pressure water delivery range, and designing a pressure bearing and a middle pressure reducing valve position for a pipeline; a shunt valve or a tail end valve which is in joint control with the middle pressure reducing valve is determined; adjusting working conditions and the initial flow and the target flow of the corresponding water distribution ports are set; according to the water supply flow requirement and the pipeline design pressure bearing requirement, the initial opening degree and the target opening degree of a middle pressure reducing valve, a shunt valve and a tail end valve are determined; and based on the working condition setting condition, the low-oscillation joint control mode of the middle pressure reducing valve, the shunt valve and the tail end valve is analyzed according to the type of the valve actuator, and the valve joint control adjusting principle is determined. On the premise that the water supply requirement is met, the working pressure of partial areas of the long-distance pressure water conveying system can be reduced, the service life of a pipeline is prolonged, and the safety of the pipeline is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of long-distance water diversion and regulation engineering, and in particular to a low-oscillation control method and system for a long-distance pipeline low-pressure water transmission system. Background Art

[0002] Long-distance pressurized water transmission systems are increasingly favored in water diversion projects due to their high water transmission efficiency and minimal environmental impact. To reduce construction costs, long-distance, fully pressurized water transmission pipelines are often laid along the undulating terrain. To facilitate user adjustments, water flow control facilities are often located at the ends of the main and distribution pipelines. The pipeline's designed pressure is determined by the maximum possible pressure during operation. During normal operation, the actual pressure is lower, leaving the pipeline with a greater margin of strength. For long-distance water diversion projects, the greater the pipeline's designed pressure, the higher the construction cost and the greater the project investment. Furthermore, the water supply pressure at the pipeline's starting point is often determined based on the water supply requirements of the entire system, resulting in higher actual pressure in low-lying areas. For existing projects, prolonged operation of pipelines near their design limits significantly reduces their lifespan and can easily lead to accidents such as pipe bursts. Summary of the Invention

[0003] The purpose of the present invention is to provide a low-oscillation control method and system for a long-distance pipeline low-pressure water transmission system, which can reduce the working pressure in some areas of the long-distance pressurized water transmission system while ensuring water supply demand, thereby reducing the pipeline design strength and cost, extending the pipeline life, and improving pipeline safety.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A low-oscillation control method for a long-distance pipeline low-pressure water transmission system, comprising:

[0006] A hydraulic transient process model is used to calculate a water delivery system when a middle pressure reducing valve is not provided, and a pressure envelope of the water delivery system when the middle pressure reducing valve is not provided is determined; the pressure envelope of the water delivery system includes a maximum pressure envelope and a minimum pressure envelope under a set operating condition;

[0007] Based on the pressure envelope of the water transmission system, the low-pressure water transmission range, pipeline design pressure, and the location of the central pressure reducing valve are formulated; the low-pressure water transmission range is the area where the maximum pressure in the original pipeline layout is too high, but after reducing the maximum pressure, the water supply demand of the water diversion port can still be met; the pipeline design pressure is the difference between the maximum pressure slope line and the terrain elevation line;

[0008] Determine the water diversion valve or terminal valve that is controlled in conjunction with the middle pressure reducing valve;

[0009] Set the regulating working conditions and the corresponding starting flow and target flow of each water outlet;

[0010] Determine the initial and target openings of the middle pressure reducing valve, water diversion valve, and terminal valve based on the water supply flow requirements and pipeline design pressure requirements;

[0011] Based on the working condition settings, the low-oscillation joint control mode of the middle pressure reducing valve, water diverter valve and terminal valve is analyzed according to the valve actuator type to determine the valve joint control adjustment principle; the working condition settings include the starting flow and target flow of each water diversion port, as well as the starting opening and target opening of the middle pressure reducing valve, water diverter valve and terminal valve.

[0012] Optionally, a setting method for the position of the middle pressure reducing valve is: the middle pressure reducing valve is set at a set position, the pressure at the set position is reduced by a set distance, and the relevant hydraulic parameters of the middle pressure reducing valve are determined.

[0013] Optionally, determining the water diversion valve or the terminal valve to be controlled in conjunction with the middle pressure reducing valve specifically includes:

[0014] According to the preliminary proposed arrangement plan for the middle pressure reducing valve, a constant flow hydraulic calculation is used to analyze the adjustment amount of other valves when the terminal valve or any water diversion valve is adjusted, a sensitivity analysis is performed on the individual adjustment of each valve, and the water diversion valve or the terminal valve with a sensitivity greater than a preset sensitivity threshold is selected as the valve that must be controlled in conjunction with the middle pressure reducing valve; the preliminary proposed arrangement plan for the middle pressure reducing valve includes the pressure envelope of the water supply system, the low-pressure water supply range, the designed pressure of the pipeline and the position of the middle pressure reducing valve.

[0015] Optionally, determining the initial opening and target opening of the middle pressure reducing valve, the water diversion valve, and the terminal valve according to the water supply flow and the pipeline design pressure requirement specifically includes:

[0016] According to the water supply flow rate and pipeline design pressure requirements, the starting openings of the middle pressure reducing valve, water diversion valve and terminal valve are A0, B0 and C0 respectively, and the target openings are A1, B1 and C1 respectively. The adjustment amplitudes of each opening are dA (A1-A0), dB (B1-B0) and dC (C1-C0) respectively.

[0017] Optionally, the valve actuator types include variable speed actuators and fixed speed actuators.

[0018] Optionally, when the valve actuator type is a variable speed actuator, the adjustment time is determined by isochronous adjustment of the joint control valve; when the valve actuator type is a constant speed actuator, the number of adjustment segments is determined by constant speed multi-stage adjustment of the joint control valve.

[0019] Optionally, the low-oscillation joint control mode includes variable speed joint control and multi-stage constant speed joint control; the multi-stage constant speed joint control includes at least one-stage constant speed joint control, two-stage constant speed joint control and three-stage constant speed joint control.

[0020] The present invention also provides a low-oscillation control system for a long-distance pipeline low-pressure water delivery system, comprising:

[0021] A water delivery system pressure envelope determination module is used to calculate the water delivery system when the middle pressure reducing valve is not installed using a hydraulic transition process model, and determine the water delivery system pressure envelope when the middle pressure reducing valve is not installed; the water delivery system pressure envelope includes a maximum pressure envelope and a minimum pressure envelope under a set operating condition;

[0022] A preliminary plan development module is used to determine the low-pressure water delivery range, pipeline design pressure, and mid-section pressure reducing valve location based on the water delivery system's pressure envelope. The low-pressure water delivery range is defined as the area where the maximum pressure in the original pipeline layout is too high, but which still meets the water supply needs of the diversion port after reducing the maximum pressure. The pipeline design pressure is the difference between the maximum pressure slope and the terrain elevation line.

[0023] Joint control judgment module, used to determine the water diversion valve or terminal valve to be controlled in conjunction with the middle pressure reducing valve;

[0024] The flow setting module is used to set the adjustment working conditions and the corresponding starting flow and target flow of each water outlet;

[0025] The valve opening determination module is used to determine the starting and target openings of the middle pressure reducing valve, water diversion valve, and terminal valve according to the water supply flow requirements and pipeline design pressure requirements;

[0026] The joint control module is used to analyze the low-oscillation joint control mode of the middle pressure reducing valve, the water diverter valve and the terminal valve based on the operating condition setting and the valve actuator type, and determine the valve joint control adjustment principle; the operating condition setting includes the starting flow and target flow of each water diversion port, and the starting opening and target opening of the middle pressure reducing valve, the water diverter valve and the terminal valve.

[0027] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0028] The present invention discloses a low-oscillation control method and system for a long-distance pipeline low-pressure water transmission system. The method comprises: using a hydraulic transition process model to calculate the water transmission system when a central pressure reducing valve is not provided, determining the pressure envelope of the water transmission system when the central pressure reducing valve is not provided; based on the pressure envelope of the water transmission system, formulating the low-pressure water transmission range, the pipeline design pressure and the position of the central pressure reducing valve; determining the water diversion valve or terminal valve to be controlled in conjunction with the central pressure reducing valve; setting the adjustment working conditions and the corresponding starting flow and target flow of each water diversion port; determining the starting opening and target opening of the central pressure reducing valve, the water diversion valve and the terminal valve according to the water supply flow requirement and the pipeline design pressure requirement; based on the working condition setting, analyzing the low-oscillation joint control mode of the central pressure reducing valve, the water diversion valve and the terminal valve according to the valve actuator type, and determining the valve joint control adjustment principle. The present invention can reduce the working pressure of some areas of the long-distance pressurized water transmission system while ensuring water supply demand, thereby reducing the pipeline design strength and cost, extending the pipeline life, and improving the pipeline safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is the low oscillation control flow chart of the central terminal joint control low-pressure water delivery system in this embodiment;

[0031] Figure 2 This is a schematic diagram of the central terminal joint control low-pressure water delivery system in this embodiment;

[0032] Figure 3 This is a schematic diagram of the terminal control pressure envelope of this embodiment;

[0033] Figure 4 Schematic diagram of the combined control pressure envelope of the middle terminal in this embodiment;

[0034] Figure 5 Schematic diagram of the terminal control pressure wave propagation in this embodiment; wherein, part (a) is a schematic diagram of the terminal valve opening; part (b) is a schematic diagram of the terminal valve closing;

[0035] Figure 6 Schematic diagram of the middle and end joint control pressure wave propagation in this embodiment; wherein, part (a) is a schematic diagram of the middle and end valves being opened simultaneously; part (b) is a schematic diagram of the middle and end valves being closed simultaneously;

[0036] Figure 7 This is a schematic diagram of the speed change isochronous adjustment of this embodiment;

[0037] Figure 8 Schematic diagram of the opening adjustment and flow process of the first stage of constant speed in this embodiment; wherein, part (a) is a schematic diagram of the opening adjustment of the first stage of constant speed; part (b) is a schematic diagram of the flow process;

[0038] Figure 9 Schematic diagram of the two-stage fixed speed adjustment opening and flow process of this embodiment; wherein, part (a) is a schematic diagram of the two-stage fixed speed adjustment opening; part (b) is a schematic diagram of the flow process;

[0039] Figure 10 The diagram of the opening and flow rate process of the three-stage constant speed adjustment in this embodiment is shown in Figure 1. Part (a) is the opening diagram of the three-stage constant speed adjustment; Part (b) is the flow rate process diagram. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] The purpose of the present invention is to provide a low-oscillation control method and system for a long-distance pipeline low-pressure water transmission system, which can reduce the working pressure in some areas of the long-distance pressurized water transmission system while ensuring water supply demand, thereby reducing the pipeline design strength and cost, extending the pipeline life, and improving pipeline safety.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The present invention provides a low-oscillation control method for a long-distance pipeline low-pressure water transmission system, comprising:

[0044] Determine the pressure envelope of the water delivery system when no central pressure reducing valve is installed; the specific process includes:

[0045] According to the original pipeline layout, the maximum and minimum pressure values ​​(i.e., pressure envelope) at each location of the pressure water supply system under various transient process conditions.

[0046] Determine the low-pressure water transmission range, pipeline design pressure, and mid-section pressure reducing valve location. The low-pressure water transmission range refers to areas where the maximum pressure in the original pipeline layout is too high, but can still meet the water supply needs of the diversion outlet after reducing the maximum pressure. These areas are often located in concave areas, and the pressure reducing valve is usually placed near the starting point of the concave area.

[0047] Determine the diverter valve or terminal valve that must be controlled in conjunction with the middle pressure reducing valve; the specific process includes:

[0048] In order to reduce pressure oscillations in the low-pressure water supply area, the valve of the middle pressure reducing valve must be adjusted at the same time when adjusting the water diversion valve or the end valve. Usually, these valves are directly connected to the low-pressure water supply area and the water supply flow is large. When adjusting them using traditional methods, it is easy to induce large pressure oscillations.

[0049] Determine the starting flow and target flow of each water outlet under the regulation condition; the starting flow and target flow of each water outlet are: according to the water supply scheduling plan, the starting flow is the flow of each water outlet at the beginning of scheduling, which may be the flow of the water outlet that is currently supplying water, or the starting flow assumed during the transition process calculation; and the target flow is the flow of the water outlet after the water supply scheduling plan adjusts it to be stable.

[0050] Determine the starting opening and target opening of the middle pressure reducing valve, water diverter valve or terminal valve; specifically, from the perspective of constant flow, in theory, in order to simultaneously meet the water supply flow demand of the water diversion port and the pressure limit requirement of the low-pressure water supply area, there are many groups of opening combinations for the starting opening and target opening of the middle pressure reducing valve, water diverter valve or terminal valve, which can be determined after comprehensive consideration from the perspectives of ease of adjustability, pressure safety margin, and recommended valve adjustment range.

[0051] Determine the low-oscillation joint control method for the central pressure reducing valve, water diversion valve, or terminal valve. This involves analyzing the oscillation amplitude in the low-pressure water delivery area under various joint control methods and determining the appropriate joint control method based on safety, adjustment operation time, and convenience. Based on the propagation patterns of pressurization and decompression waves between the central pressure reducing valve and water diversion valve, recommended joint control methods include variable speed joint control, one-stage constant speed joint control, two-stage constant speed joint control, and three-stage constant speed joint control.

[0052] Verify the rationality of hydraulic parameters in low-pressure areas, summarize joint control rules and formulate valve joint control adjustment principles.

[0053] Based on the above technical solution, the following Figures 1-10 The embodiments shown are used to illustrate the specific implementation of the above steps in detail.

[0054] The embodiment of the present invention is Figure 2 Take the diagram of the low-pressure water supply system with flow regulating valve as an example. Figure 3 and 4 In this longitudinal cross-section, the entire water supply system is supplied from the left side. A pressure reducing valve is installed in the middle of the main pipeline, and several water diversion valves or terminal valves are installed according to water supply needs. Pressure regulating facilities such as pressure relief valves and surge tanks are often installed after the pressure reducing valve to further enhance safety. The pipeline pressure drops sharply after the central pressure reducing valve, indicating a low-pressure water supply area.

[0055] The pressurized water supply system usually uses terminal control to adjust the water supply flow to multiple users. There is no control device in the middle of the pipeline. The maximum and minimum pressure envelopes are as follows: Figure 3 To ensure water transmission safety, the pipeline's minimum operating pressure must be greater than the minimum permissible pressure (the minimum pressure slope is higher than the pipeline elevation), and the pipeline's design pressure must not be lower than the maximum pressure (the difference between the maximum pressure slope and the pipeline elevation). This results in higher pipeline design pressures in low-lying areas, leading to higher pipeline construction costs. Figure 4 As shown in the figure, if the design pressure can be appropriately reduced while meeting the water supply capacity and water supply safety, the pipeline design pressure can be reduced, thereby reducing the project cost.

[0056] However, the installation of a pressure reducing valve in the middle also greatly increases the difficulty of system regulation. Figure 5 As shown in the figure, the pressure fluctuation pattern of the traditional terminal control pressure water supply system is relatively simple when regulating the flow at the water diversion port, that is, a pressure drop wave is generated when the valve is opened, and a pressure increase wave is generated when the valve is closed. Since the pipeline design has a certain margin of pressure, it is only necessary to adjust the flow according to the pre-set adjustment speed during operation. After the middle pressure reducing valve is installed, Figure 6 As shown, the design pressure of the pipeline behind the valve drops significantly. When the water diverter valve or the end valve is opened, a pressure reduction wave is formed, and when the middle pressure reducing valve is opened, a pressure increase wave is formed behind the valve. If the middle valve and the end or water diverter valve are adjusted in an alternating manner, pressure increase and pressure reduction waves will appear alternately behind the middle valve. The pipeline is sometimes over-pressured and sometimes negatively pressured, and the pressure and flow oscillate severely, which is very likely to cause accidents such as pipe burst.

[0057] The present invention proposes a method for jointly controlling the middle valve and the end valve (or water diversion valve) to reduce pressure oscillation in the low-pressure water supply area based on the law of pressure wave transmission. According to the method provided by the present invention, the low oscillation control includes the following steps:

[0058] 1. Determine the pressure envelope of the water delivery system when no central pressure reducing valve is installed:

[0059] According to the principle of mass conservation, the difference in mass between the water flowing out of and into the control volume during the period dt should be equal to the change in mass of the water in the control volume during the same period, resulting in the one-dimensional unsteady flow continuity equation:

[0060]

[0061] Where H is the pressure tube head (or the height of the hydraulic grade line calculated from a certain reference); V is the average flow velocity in the cross section; θ is the angle between the pipe axis (flow direction) and the horizontal line, i.e., the inclination angle, which is positive when the height increases in the positive x direction; a is the water hammer wave velocity, which includes the fluid and pipe wall characteristics; x and t are independent variables.

[0062] According to Newton's second law, the one-dimensional unsteady flow momentum equation considering the effect of friction is:

[0063]

[0064] Where g is the acceleration due to gravity, f is the Darcy-Weisbach drag coefficient, and D is the pipe diameter. Absolute values ​​are used to ensure that frictional resistance always opposes the flow velocity.

[0065] According to the continuity equation and taking into account the compressibility of water and the elasticity of the pipe wall, the following expression for the water hammer wave velocity is obtained:

[0066]

[0067] Where, is the propagation speed of sound waves in water. When the water temperature is 10 O C, and the pressure is between 1 and 25 atmospheres. When a0 is 1435 m / s, E is the elastic modulus of water. O C, and the pressure is one standard atmosphere. E=2.1×10 9 Pa; E0 is the elastic modulus of the pipe wall; δ is the pipe wall thickness (m). For general steel pipes, D / δ≈100, E / E0≈0.01, and a≈1000m / s.

[0068] The hydraulic transition process model refers to meshing the entire calculation pipeline and solving the differential equations 1 to 3 simultaneously to obtain the pressure and flow process of each hydraulic unit in the pipeline. The maximum and minimum pressure curves at each point in the entire process are the pressure envelope.

[0069] like Figure 3 As shown in the figure, a series of calculations were performed using a hydraulic transition process model for a water supply system without a central pressure reducing valve, yielding maximum and minimum pressure envelopes under various operating conditions. Since the maximum pipeline pressure when the valve is closed during normal operation is typically higher than the maximum static pressure, the maximum pressure slope curve often exhibits an increasing curve along the pipeline. The minimum pressure slope curve, on the other hand, often reflects the open condition of the terminal valve when the pressure system is supplying water at full capacity, and thus exhibits a decreasing curve along the pipeline.

[0070] 2. Draft the low-pressure water transmission range, pipeline design pressure, and the position of the middle pressure reducing valve, etc.:

[0071] Depend on Figure 3It can be seen that near stake number 50km, there is a significant difference between the pipeline's maximum pressure slope and the terrain elevation line, resulting in a high pipeline design pressure (the difference between the maximum pressure slope and the terrain elevation line). To reduce the pipeline design pressure, a central pressure reducing valve can be added at this location to lower the pipeline design pressure. The preliminary plan proposes installing the pressure reducing valve near stake number 50km, lowering the maximum pressure slope by approximately 20m. Based on this, the relevant hydraulic parameters of the central pressure reducing valve were initially selected.

[0072] 3. Determine the water diversion valve or terminal valve that must be controlled in conjunction with the middle pressure reducing valve:

[0073] Based on the preliminarily proposed center pressure reducing valve layout, a steady-flow hydraulic calculation is used to analyze the adjustment of other valves when adjusting the terminal valve or a water diverter valve. A sensitivity analysis is performed on the individual valve adjustments, and the water diverter valve or terminal valve with the greater sensitivity is selected as the valve that must be controlled in conjunction with the center pressure reducing valve. In this example, the valves selected for control in conjunction with the center valve are the water diverter valve and the terminal valve shown in the figure. A steady-flow equation is defined as one in which the time term in the unsteady flow control equation is zero.

[0074] 4. Determine the starting flow and target flow of each water outlet under the regulation working condition:

[0075] For a specific regulation condition, the starting flow and target flow of each water diversion port must be determined first. In this example, the starting flow distribution of the water diversion valve or terminal valve is 118.2m 3 / h and 127.2m 3 / h, and the target flow rates are 0.0m 3 / h and 127.2m 3 / h, that is, the purpose of regulation is to close the water diversion valve and keep the water supply flow of the terminal valve unchanged.

[0076] 5. Determine the starting and target openings of the middle pressure reducing valve, water diverter valve or terminal valve:

[0077] Based on the water supply flow rate and pipeline design pressure requirements, a constant flow calculation determined the starting openings of the center, diversion, and terminal valves to be 80%, 45%, and 60%, respectively. The target openings were 50%, 0%, and 45%, respectively, and the adjustment ranges were 30%, 45%, and 15%, respectively.

[0078] 6. Determine the low oscillation joint control mode of the middle pressure reducing valve, water diverter valve or terminal valve:

[0079] according to Figure 6 The middle and end parts jointly control the pressure wave propagation mechanism. The ideal adjustment process should be variable speed isochronous adjustment. At this time, the pressure increase wave and the pressure reduction wave can mostly offset each other, thereby reducing the pipeline fluctuation amplitude. Figure 7As shown in the figure, variable speed isochronous regulation means that the multiple valves involved in the joint control take the same amount of time to adjust from their initial opening to their target opening. Since the three valves have adjustment ranges of 30%, 45%, and 15%, respectively, if the adjustment times are the same, the adjustment speed ratio should be 2:3:1.

[0080] However, the existing flow regulating valves are mostly regulated by constant speed actuators, which cannot achieve the same adjustment time for multiple valves with different amplitudes, and the formation of Figure 8 (a) is the constant speed adjustment method. Figure 8 As shown in (b), due to inconsistent regulation speeds, the difference between the pressure-increasing wave and the pressure-reducing wave widens, resulting in greater pipeline fluctuations. At this point, the constant-speed multi-stage regulation method proposed in the present invention can be used. That is, when one-stage regulation cannot meet the low oscillation requirement, try using two-stage regulation. When two-stage regulation also cannot meet the low oscillation requirement, try using three-stage regulation until the low oscillation requirement is met. By increasing the number of segments, the impact of the uncoordinated opening between valves during a single-stage regulation process can be reduced. Figure 9 As shown in the figure, when the constant speed two-stage adjustment is adopted, the fluctuation amplitude of the end valve is significantly reduced, while when the constant speed three-stage adjustment is adopted ( Figure 10 ), the fluctuation amplitude of the terminal valve is further reduced. When analyzing the transition process of the actual scheduling plan, an appropriate fixed-speed segmented adjustment scheme can be selected based on the allowable fluctuation value of the pipeline design pressure.

[0081] 7. Verify the rationality of the hydraulic parameters in the low-pressure area, summarize the joint control rules and formulate the joint control adjustment principles of the valves: carry out a series of transition process working condition analysis, conduct a comprehensive analysis of the relevant layout parameters, summarize the advantages and disadvantages of the proposed scheme; then analyze a variety of low-pressure area layout schemes, comprehensively analyze the reduction in project investment after setting up the low-pressure water supply area and the safety and convenience of the joint control and dispatch of the middle and end terminals, determine the final low-pressure water supply scheme, and formulate the joint control adjustment principles of the adopted scheme. For example, in this example, if Figure 4 Lowering the design pressure behind the intermediate pressure reducing valve to around 240m would reduce pipeline construction costs by approximately 500 million yuan. However, due to the significant reduction in design pressure, pressure fluctuations after the valve must be controlled within 10m, requiring a four-stage regulation system to meet these low-oscillation requirements. However, if the design pressure is reduced to around 250m, pipeline construction costs could be reduced by approximately 300 million yuan. Fluctuations must be controlled within 20m, requiring a two-stage regulation system to meet these low-oscillation requirements, significantly shortening regulation time. Both options reduce pipeline construction costs. Designers can determine the final low-pressure water supply plan by comprehensively analyzing factors such as the reduction in project investment after establishing a low-pressure water supply zone and the safety and convenience of joint control and scheduling at the central and terminal ends. Once the water supply plan is determined, the joint control and regulation principles can be formulated based on the adopted staged regulation scheme.

[0082] Based on this embodiment, it can be seen that this solution has the following beneficial effects:

[0083] By installing a pressure-reducing valve in the middle of a pressure pipeline, this invention significantly reduces the design strength of the pipeline behind the valve, lowering project costs and offering promising economic prospects. For existing pipelines, adding a pressure-reducing valve and adopting a low-pressure water delivery method can extend pipeline life and reduce the likelihood of pipe bursts. Compared to other existing low-pressure water delivery methods, valve-controlled pressure reduction offers faster flow regulation and is easy to deploy, making it convenient for retrofitting existing pipelines.

[0084] The joint control method of the central pressure reducing valve and other water diversion valves proposed in the present invention is based on the principle of superposition of pressurization waves and pressure reducing waves, which can reduce the oscillation of the low-pressure water delivery area during the water diversion outlet adjustment process. The equal time adjustment proposed for the variable speed valve and the segmented adjustment proposed for the fixed speed valve can control the pressure and flow fluctuations within a smaller range.

[0085] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A low oscillation control method for a long-distance pipeline low-pressure water delivery system, characterized in that: include: A hydraulic transition process model is used to calculate the water delivery system when the middle pressure reducing valve is not provided, and a pressure envelope of the water delivery system when the middle pressure reducing valve is not provided is determined; the pressure envelope of the water delivery system includes a maximum pressure envelope and a minimum pressure envelope under a set working condition; Based on the pressure envelope of the water delivery system, the low-pressure water delivery range, pipeline design pressure and the position of the middle pressure reducing valve are formulated; The low-pressure water delivery range is the area where the maximum pressure in the original pipeline layout is too high, but the water supply demand of the water diversion port can still be met after the maximum pressure is reduced; the designed pressure of the pipeline is the difference between the maximum pressure slope line and the terrain elevation line; Determine the water diversion valve or terminal valve that is controlled in conjunction with the middle pressure reducing valve; Set the adjustment conditions and the corresponding starting flow and target flow of each water outlet; According to the water supply flow requirements and pipeline design pressure requirements, determine the starting and target openings of the middle pressure reducing valve, water diversion valve and terminal valve; Based on the operating condition settings, the low oscillation joint control mode of the middle pressure reducing valve, the water diverter valve and the terminal valve is analyzed according to the valve actuator type, and the valve joint control adjustment principle is determined; the operating condition settings include the starting flow and target flow of each water diversion port, and the starting opening and target opening of the middle pressure reducing valve, the water diverter valve and the terminal valve.

2. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 1 is characterized in that: One way to set the position of the middle pressure reducing valve is: the middle pressure reducing valve is set at a set position, the pressure at the set position is reduced by a set distance, and the relevant hydraulic parameters of the middle pressure reducing valve are determined.

3. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 1 is characterized in that: The step of determining the water diversion valve or the terminal valve to be controlled in conjunction with the middle pressure reducing valve specifically includes: According to the preliminary proposed arrangement plan of the middle pressure reducing valve, the adjustment amount of other valves when the terminal valve or any water diversion valve is adjusted is analyzed by constant flow hydraulic calculation, and sensitivity analysis is performed on the individual adjustment of each valve, and the water diversion valve or the terminal valve with a sensitivity threshold greater than the preset sensitivity threshold is selected as the valve that must be controlled in conjunction with the middle pressure reducing valve; the preliminary proposed arrangement plan of the middle pressure reducing valve includes the pressure envelope of the water supply system, the low-pressure water supply range, the designed pressure of the pipeline and the position of the middle pressure reducing valve.

4. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 1, characterized in that: Determining the initial opening and target opening of the middle pressure reducing valve, the water diversion valve and the terminal valve according to the water supply flow and the pipeline design pressure requirements specifically includes: According to the water supply flow rate and pipeline design pressure requirements, the starting openings of the middle pressure reducing valve, water diverter valve and terminal valve are A0, B0 and C0 respectively, the target openings are A1, B1 and C1 respectively, and the adjustment amplitudes of each opening are dA (A1-A0), dB (B1-B0) and dC (C1-C0) respectively.

5. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 1, characterized in that: The valve actuator types include variable speed actuators and fixed speed actuators.

6. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 5, characterized in that: When the valve actuator type adopts a variable speed actuator, the adjustment time is determined by isochronous adjustment of the joint control valve; when the valve actuator type adopts a constant speed actuator, the number of adjustment segments is determined by constant speed multi-stage adjustment of the joint control valve.

7. The low oscillation control method for a long-distance pipeline low-pressure water delivery system according to claim 1, characterized in that: The low-oscillation joint control method includes variable speed joint control and multi-stage constant speed joint control; the multi-stage constant speed joint control includes at least one-stage constant speed joint control, two-stage constant speed joint control and three-stage constant speed joint control.

8. A low oscillation control system for a long-distance pipeline low-pressure water delivery system, characterized in that: include: A water delivery system pressure envelope determination module, used to calculate the water delivery system when the middle pressure reducing valve is not provided by using a hydraulic transition process model, and determine the pressure envelope of the water delivery system when the middle pressure reducing valve is not provided; the pressure envelope of the water delivery system includes a maximum pressure envelope and a minimum pressure envelope under a set working condition; A preliminary scheme formulation module is used to formulate the low-pressure water transmission range, pipeline design pressure and middle pressure reducing valve position based on the pressure envelope of the water transmission system; The low-pressure water delivery range is the area where the maximum pressure in the original pipeline layout is too high, but the water supply demand of the water diversion port can still be met after the maximum pressure is reduced; the designed pressure of the pipeline is the difference between the maximum pressure slope line and the terrain elevation line; A joint control judgment module is used to determine the water diversion valve or the terminal valve to be joint-controlled with the middle pressure reducing valve; The flow setting module is used to set the adjustment conditions and the corresponding starting flow and target flow of each water outlet; The valve opening determination module is used to determine the starting opening and target opening of the middle pressure reducing valve, water diversion valve and terminal valve according to the water supply flow requirements and the pipeline design pressure requirements; The joint control module is used to analyze the low-oscillation joint control mode of the middle pressure reducing valve, the water diverter valve and the terminal valve based on the working condition setting and the valve actuator type, and determine the valve joint control adjustment principle; the working condition setting includes the starting flow and target flow of each water diversion port, and the starting opening and target opening of the middle pressure reducing valve, the water diverter valve and the terminal valve.

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