A device and method for measuring surge characteristics of a one-way tower in a long-distance water supply system

Abstract

The present invention discloses a device and method for measuring surge characteristics of a one-way tower in a long-distance water supply system. The present invention first determines hydraulic boundary parameters according to the layout of the water supply pipeline of the long-distance water supply system; then determines the initial flow of the water supply system through a flow meter, measures the water head of the pressure measuring tube at the bottom of the one-way tower with a pressure measuring meter, and measures the initial water level of the one-way tower with a water level measuring meter; then uploads the measured data to a calculation unit, and calculates the lowest water level of the one-way tower in the transient process. The present invention can omit tedious numerical modeling and simulation work, provide important support for the safe operation of long-distance water supply projects, and has great application prospects.

Description

Technical Field

[0001] The invention relates to a device and method for measuring surge characteristics of a one-way tower in a long-distance water supply system, belonging to the technical field of long-distance water delivery engineering. Background Art

[0002] The surge chamber is an important water hammer pressure relief device, which is widely used in long-distance water supply projects. When the water pump suddenly loses power, the surge chamber can replenish elastic potential energy into the water pipeline in time to prevent the water pressure in the pipeline from dropping below the local vaporization pressure, thereby avoiding the phenomenon of water column separation. The bottom of the connecting pipe at the bottom of the surge chamber is directly connected to the water pipeline, and its steady-state water level is equal to the internal water pressure at that point. In some places with high internal water pressure, the height of the surge chamber can be as high as tens of meters, which brings great challenges to design and construction.

[0003] To solve this problem, engineers installed a one-way check valve at the bottom connecting pipe of the surge chamber. The function of the check valve is to ensure that the water in the one-way tower can only flow in one direction, that is, it can only flow from the one-way tower to the water pipeline. Due to the existence of the check valve, the water level of the one-way tower does not have to be consistent with the initial pressure measuring pipe head line at this point, so the height of the one-way tower can be greatly reduced, and it has been widely used in long-distance water supply projects. However, if the hydraulic parameters (initial water level and cross-sectional area) of the one-way tower are improperly designed, it is very likely that the water level of the one-way tower will be lower than the bottom elevation of the one-way tower during the water replenishment process, causing pipeline air intake bursts, severe vibrations of the water pump unit and other engineering accidents. Therefore, it is of great significance to conduct theoretical research on the water level change characteristics of the one-way tower during transient flow and determine the minimum water level of the one-way tower to ensure the safe operation of water conservancy projects.

[0004] At present, there is no direct reference calculation formula for the transient minimum water level of a one-way tower in the transition state of a hydraulic system. In actual water supply projects, the minimum water level of a one-way tower is generally calculated by programming simulation of the overall water supply system based on the characteristic line method. This type of method requires absolute reliability in programming, and the calculation work is complicated and time-consuming, making it difficult to provide effective and timely guidance for the project operation stage.

[0005] Therefore, a device and a method for measuring surge characteristics of one-way towers in long-distance water supply systems are proposed, which is of great significance to the design and operation of long-distance water supply projects containing one-way towers. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to propose a device and method for measuring surge characteristics of a one-way tower in a long-distance water supply system, which can avoid the tedious modeling and simulation work brought about by the numerical simulation method while ensuring the safe operation of the long-distance water supply system, and can provide reasonable and effective theoretical guidance for the design and operation of the water supply system.

[0007] Technical solution: In order to solve the above technical problems, the present invention adopts the following technical solution:

[0008] The present invention first provides a device for measuring surge characteristics of a one-way tower in a long-distance water supply system, comprising a one-way tower, an inlet pool for supplying water to the one-way tower, and an outlet pool connected to the one-way tower through a water supply pipeline, a water pump is installed between the inlet pool and the one-way tower, a connecting pipe is provided at the bottom of the one-way tower, a check valve is provided at the bottom of the connecting pipe and behind the water pump, a flow meter is installed between the inlet pool and the water pump, a pressure gauge is provided at the connection between the two check valves and the water supply pipeline, a water level gauge is provided inside the one-way tower, and the flow meter, the pressure gauge and the water level gauge are all connected to a computing unit for data.

[0009] The present invention also provides a method for calculating the surge characteristics of a one-way tower using the one-way tower surge characteristics measuring device in a long-distance water supply system, the method comprising the following steps:

[0010] S1. According to the layout of the water supply pipeline of the long-distance water supply system, the length and area of ​​the water supply pipeline, the roughness coefficient of the pipeline, the cross-sectional area of ​​the one-way tower and the area parameters of the connecting pipe are determined respectively. The length and area of ​​the water supply pipeline are defined as variables L and A. The roughness coefficient of the water supply pipeline is determined by the steady-state friction method and is defined as variable n. The cross-sectional area and the connecting pipe area of ​​the one-way tower refer to the water flow area at the top of the one-way tower and the area of ​​the connecting pipe at the bottom, respectively, and are defined as variables A. s and A zk ;

[0011] S2. Determine the initial flow rate of the water delivery system by a flow meter, measure the water head of the pressure measuring pipe at the bottom of the one-way tower by a pressure measuring meter, and measure the initial water level of the one-way tower by a water level measuring meter;

[0012] S3. The measurement data obtained in step S1 and step S2 are uploaded to the calculation unit to calculate the lowest water level of the one-way tower in the transient process. The calculation and analysis method of the calculation unit includes the following steps:

[0013] S3.1. Calculate the initial pressure head difference of the one-way tower based on the piezometric head at the bottom of the one-way tower and the initial water level of the one-way tower;

[0014] S3.2. According to the pipe roughness coefficient n, length L and area A of the water pipeline; the area A of the connecting pipe zk , calculate the hydraulic resistance coefficient of the water pipeline and the hydraulic resistance coefficient of the one-way tower connecting pipe respectively;

[0015] S3.3. According to the hydraulic resistance coefficient obtained in step S3.2, the relevant vibration parameters of the water delivery system are calculated respectively, and the relevant vibration parameters include the transient vibration small parameter, the initial vibration angular frequency, the initial amplitude, and the initial vibration phase angle;

[0016] S3.4. According to the relevant vibration parameters obtained in step S3.3, determine the water replenishment flow equation of the water delivery system containing the one-way tower, and determine the end time of water replenishment by taking the time when the water replenishment flow is 0 as the judgment condition;

[0017] S3.5 Integrate the water replenishment flow equation according to the water replenishment end time obtained in step S3.4 to obtain the minimum water level of the one-way tower.

[0018] Further, the initial pressure head difference ΔH of the one-way tower described in step S3.1 of the connecting pipe T The calculation formula is:

[0019] ΔH T =H s -Z T

[0020] In the formula, H S is the water head of the piezometer at the one-way tower, measured by a pressure gauge, in meters; Z T is the initial water level of the one-way tower, in m, measured by a water level meter.

[0021] Furthermore, the calculation formula of the hydraulic resistance coefficient β of the water pipeline in step S3.2 is:

[0022]

[0023] Where d is the diameter of the water pipeline, in meters;

[0024] The hydraulic resistance coefficient β of the one-way tower connecting pipe described in step S3.2 S The calculation formula is:

[0025]

[0026] In the formula, It is an empirical coefficient, generally ranging from 0.6 to 0.8.

[0027] Furthermore, the calculation formula of the transient vibration small parameter ε in step S3.3 is:

[0028]

[0029] Where g is the acceleration due to gravity, in m / s 2 ;

[0030] The calculation formula of the initial vibration angular frequency ω0 in step S3.3 is:

[0031]

[0032] The initial amplitude a0 described in step S3.3 is calculated as:

[0033]

[0034] Where Q0 is the initial flow rate of the pipeline, in m 3 / s, measured by flow meter;

[0035] The initial amplitude phase angle described in step S3.3 The formula is:

[0036]

[0037] Furthermore, the water replenishment flow equation of the water delivery system containing a one-way tower in step S3.4 is:

[0038]

[0039] Where Q(t) is the water replenishment at time t, t is the propagation time in seconds, and ξ is the water hammer wave propagation attenuation coefficient, which is generally 5×10 -6 ; m is the number of times the water hammer wave propagates in the pipeline, int(*) is the rounding down function, a is the water hammer wave speed, 1000m / s;

[0040] Furthermore, the minimum water level Z of the one-way tower in step S3.5 is min The calculation formula is:

[0041]

[0042] Wherein, Z0 is the initial water level of the one-way tower, measured by the water level meter in step S2, and the unit is m; T is the value satisfying Q(T)=0.

[0043] Beneficial effects: The present invention can provide a theoretical basis for the safe operation of the one-way tower of the long-distance water supply system. Compared with the previous method of numerically simulating the transient flow process of the long-distance water supply system through programming to obtain the lowest water level of the one-way tower, the present invention can directly obtain the lowest water level of the one-way tower through the initial hydraulic boundary conditions. Since the cumbersome numerical simulation calculations are omitted, it is more efficient and quick, and has great engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of a water delivery system and a measuring device according to an embodiment of the present invention.

[0045] Figure 2 It is a process framework diagram of an embodiment of the present invention.

[0046] Figure 3 This is a comparison chart of the theoretical and numerical simulation change process lines of the one-way tower water replenishment flow after the water pump loses power.

[0047] Figure 4 This is a comparison chart of the theoretical and numerical simulation change process lines of the one-way tower water level after the pump loses power.

[0048] Figure 5 It is the correlation factor between the numerical simulation and theoretical calculation curves of the one-way tower at different initial water levels.

[0049] Figure 6 It is the correlation factor between the numerical simulation and theoretical calculation curves of one-way towers with different cross-sectional areas.

[0050] Figure 7 It is the correlation factor between the numerical simulation and theoretical calculation curves of the one-way tower with different connecting pipe areas. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings.

[0052] like Figure 1 As shown, the present invention includes a water inlet pool 1, a water pump 2, a check valve 3, a connecting pipe 4, a one-way tower 5, a water pipeline 6, a water outlet pool 7, a flow meter 8, a pressure gauge 9, a water level gauge 10 and a computing unit 11, and is characterized in that: a water pump 2 is installed before the water inlet pool 1 and the one-way tower 5, a check valve 3 is arranged after the water pump 2, a connecting pipe 4 is arranged at the bottom of the one-way tower 5, a check valve 3 is arranged at the bottom of the connecting pipe 4, the one-way tower 5 and the water outlet pool 8 are connected by a water pipeline 6, and the flow meter 8, the pressure gauge 9 and the water level gauge 10 are data-interconnected with the computing unit 11.

[0053] When the water pump 2 is powered off, the pressure reduction wave behind the pump propagates downstream along the pipeline 6. When it is transmitted to the one-way tower 5, part of the pressure reduction wave will be converted into the surge pressure of the one-way tower 5. The pipeline 6 will be protected by the one-way tower 5 to prevent the pipeline pressure from dropping below the negative pressure. A check valve 3 is set after the water pump 2 to prevent the water in the one-way tower 5 from flowing into the water pump 2, causing the water pump 2 to reverse. When the pressure at the bottom of the one-way tower 5 is lower than the initial pressure measuring pipe head line, the check valve 3 at the bottom of the one-way tower 5 will open quickly to replenish water into the pipeline 6 to protect the downstream pipeline. If the initial water level or cross-sectional area of ​​the one-way tower 5 is improperly designed, the lowest water level of the one-way tower 5 during the water replenishment process may be lower than the center elevation of the pipe, and then engineering operation accidents such as pipeline air intake may occur. When the water delivery system is in a transient flow state, the lowest water level of the one-way tower 5 during the water replenishment process is usually unknown. The most common practice at present is to model and numerically simulate the entire water delivery system to determine the lowest water level of the one-way tower. The calculation work often takes several hours and is quite tedious and time-consuming. Therefore, there is an urgent need for a one-way tower surge characteristic measurement device and calculation method in a long-distance water supply system. According to the initial boundary system parameters of the water supply system, the minimum water level of the one-way tower can be determined to reduce the calculation workload.

[0054] The water delivery system and measuring device of this embodiment are as follows Figure 1 The design water level of the water inlet pool 1 is 5.00m. After being pressurized by the water pump 2, the water is transported to the downstream reservoir 7 through the DN2800 water pipeline 6. The design water level of the downstream reservoir 7 is 87.00m, and the design head of the water pump is 84.00m.

[0055] according to Figure 2 The process framework diagram shown in the figure, the calculation implementation steps of this implementation are as follows:

[0056] (1) According to the layout of the water supply pipeline of the long-distance water supply system, the length of the water supply pipeline is 2.00 km and the area is 6.16 m 2 The pipeline roughness is 0.012, and the cross-sectional area of ​​the one-way tower is 9.24m 2 , the connecting pipe area is 2.69m 2 .

[0057] (2) The initial flow rate of the water delivery system is measured by flow meter 8 to be 10.00 m 3 / s, the water head of the pressure measuring tube at the bottom of the one-way tower is measured by the pressure measuring gauge 9 as 88.22m, and the initial water level of the one-way tower is measured by the water level measuring gauge 10 as 68.22m.

[0058] (3) After the above data is measured, it is uploaded to the calculation unit 11 to calculate the lowest water level of the one-way tower during the transient process. The calculation and analysis method steps of the calculation unit are as follows:

[0059] (3.1) The initial pressure head difference of the one-way tower is calculated based on the water head of the pressure gauge at the bottom of the one-way tower and the initial water level of the one-way tower. The initial pressure head difference at the one-way tower 5 is ΔH T =H s -Z T =88.22-68.22=20m.

[0060] (3.2) The calculation formula of the hydraulic resistance coefficient β of the water pipeline is:

[0061]

[0062] Where d is the diameter of the water pipeline, in meters;

[0063] Hydraulic resistance coefficient β of one-way tower connecting pipe S The calculation formula is:

[0064]

[0065] In the formula, It is an empirical coefficient, generally ranging from 0.6 to 0.8.

[0066] According to the hydraulic boundary parameters of the long-distance water supply system mentioned above, the hydraulic resistance coefficient of the water supply pipeline is calculated to be 1.222×10 -2 , hydraulic resistance coefficient β of one-way tower connecting pipe 4 S is 6.944×10 -3 .

[0067] (3.3) According to the hydraulic resistance coefficient, the transient vibration minimum parameter, initial vibration angular frequency, initial amplitude, initial vibration phase angle and other parameters of the water supply system are calculated respectively. The calculation formula is as follows:

[0068] The calculation formula of initial vibration angular frequency ω0 is:

[0069]

[0070] The calculation formula of initial amplitude a0 is:

[0071]

[0072] Where Q0 is the initial flow rate of the pipeline, in m 3 / s, measured by flow meter;

[0073] Initial amplitude phase angle The formula is:

[0074]

[0075] The data of this embodiment is substituted into the above formula to calculate the minimum parameter ε of the transient vibration of the hydraulic system, which is 5.346×10 -3 , the initial vibration angular frequency ω0 is 5.718×10 -2 , the initial amplitude a0 is 15.227, the initial amplitude phase angle It is 1.506.

[0076] (3.4) Based on the relevant vibration parameters, determine the water replenishment flow equation for the water delivery system containing a one-way tower.

[0077] The water replenishment flow equation of the water delivery system containing a one-way tower is:

[0078]

[0079] Where Q(t) is the water replenishment at time t, t is the propagation time in seconds, and ξ is the water hammer wave propagation attenuation coefficient, which is generally 5×10 -6 ; m is the number of times the water hammer wave propagates in the pipeline, int(*) is the rounding down function, a is the water hammer wave speed, 1000m / s;

[0080] The water replenishment end time is determined by taking the moment when the water replenishment flow rate is 0 as the judgment condition. According to the above formula, the water replenishment flow equation of the one-way tower can be determined. After calculation, the water replenishment of the one-way tower 5 ends at t=12.125s.

[0081] (3.5) According to the water replenishment end time, the water replenishment flow equation is integrated to obtain the minimum water level of the one-way tower. The minimum water level Z of the one-way tower min The calculation formula is:

[0082]

[0083] Wherein, Z0 is the initial water level of the one-way tower, measured by the water level meter in step S2, in m; T is the value satisfying Q(T) = 0. The equation of the water level change process line of the one-way tower can be determined according to the formula, and the lowest water level of the one-way tower is 60.783m.

[0084] In order to test the accuracy of the method proposed in this patent, the characteristic line method is used to Figure 1 The transient process numerical simulation of the water delivery system is carried out and compared with the method proposed in this patent. The comparison of the water replenishment flow and water level change process lines of the one-way tower 5 after the water pump loses power is shown as follows: Figure 3 and 4 shown.

[0085] Figure 3 This is the flow rate change process line of the one-way tower 5. When the water pump is powered off, the one-way tower 5 quickly replenishes water to the pipeline 6 in a very short time, and the initial water replenishment flow rate is 10.00m3 / s. The water replenishment process has about three main stages, each stage is about 4s. At t = 12.125s, the one-way tower water replenishment is completed, and the one-way tower water replenishment flow calculated by the theoretical method is basically completely consistent with the numerical simulation result.

[0086] Figure 4 is the water level change process line of the one-way tower 5. When the water pump power failure occurs at t=0s, the water level in the one-way tower 5 begins to drop because the check valve 3 at the bottom of the one-way tower 5 opens quickly to replenish water to the pipeline 6. At t=12.125s, the water level of the one-way tower reaches the lowest value. The lowest water level calculated by the present invention is 60.783m, which is completely consistent with the numerical simulation result of 60.783m.

[0087] In order to test the applicability of this patent under different one-way tower parameters (initial design water level, cross-sectional area and connecting pipe area), the sensitivity analysis method is used to test the applicability of the method proposed in this patent. The range of one-way tower parameters is shown in the following table:

[0088] Table 1 Variation range of single-line tower design parameters

[0089]

[0090] In order to evaluate the approximation between the numerical simulation and theoretical calculation curves, the correlation factor method is introduced to quantify the approximation between the numerical simulation and theoretical calculation curves. The correlation factor is defined as follows:

[0091]

[0092] Where: m = numerical simulation data; m' = theoretical calculation data; The larger the R value, the higher the similarity between the two.

[0093] Under different one-way tower parameters, the approximation of the curves obtained by numerical simulation and theoretical calculation is as follows: Figures 5 to 7 It can be seen that by using the method proposed in this patent, the approximation degree of the curves obtained by numerical simulation and theoretical calculation is above 0.950, which can meet the calculation accuracy requirements of the one-way tower under different design parameters, and avoid the tedious modeling and calculation work, and can provide timely and effective guidance for the safe operation of the water transfer project.

Claims

1. A method for calculating surge characteristics of a one-way tower in a long-distance water supply system, wherein the method adopts a one-way tower surge characteristics measuring device in a long-distance water supply system, comprising a one-way tower (5), an inlet pool (1) for supplying water to the one-way tower (5), and an outlet pool (7) connected to the one-way tower (5) via a water pipeline (6), characterized in that: A water pump (2) is installed between the water inlet pool (1) and the one-way tower (5), a connecting pipe (4) is provided at the bottom of the one-way tower (5), a check valve (3) is provided at the bottom of the connecting pipe (4) and after the water pump (2), a flow meter (8) is installed between the water inlet pool (1) and the water pump (2), a pressure meter (9) is provided at the connection between the two check valves (3) and the water pipeline (6), a water level meter (10) is provided inside the one-way tower, and the flow meter (8), the pressure meter (9) and the water level meter (10) are all connected to the computing unit (11) for data connection; the method comprises the following steps: S1. According to the layout of the water supply pipeline of the long-distance water supply system, the length and area of ​​the water supply pipeline (6), the roughness coefficient of the pipeline, the cross-sectional area of ​​the one-way tower (5) and the area parameters of the connecting pipe are determined respectively, wherein the length and area of ​​the water supply pipeline (6) are defined as variables L and A, the pipeline roughness coefficient of the water supply pipeline (6) is determined by the steady-state friction method and is defined as variable n, and the cross-sectional area and the connecting pipe area of ​​the one-way tower (5) refer to the water flow area at the top of the one-way tower and the area of ​​the connecting pipe at the bottom, respectively, and are defined as variables A s and A zk ; S2. The initial flow rate of the water delivery system is determined by a flow meter (8), a pressure meter (9) measures the water head of the pressure gauge at the bottom of the one-way tower, and a water level meter (10) measures the initial water level of the one-way tower; S3. The measurement data obtained in step S1 and step S2 are uploaded to the calculation unit to calculate the lowest water level of the one-way tower in the transient process. The calculation and analysis method of the calculation unit includes the following steps: S3.

1. Calculate the initial pressure head difference of the one-way tower based on the piezometric head at the bottom of the one-way tower and the initial water level of the one-way tower; S3.

2. According to the pipe roughness coefficient n, length L and area A of the water delivery pipe (6); the area A of the connecting pipe (4) zk , calculate the hydraulic resistance coefficient of the water pipeline and the hydraulic resistance coefficient of the one-way tower connecting pipe respectively; S3.

3. According to the hydraulic resistance coefficient obtained in step S3.2, the relevant vibration parameters of the water delivery system are calculated respectively, and the relevant vibration parameters include the transient vibration small parameter, the initial vibration angular frequency, the initial amplitude, and the initial vibration phase angle; S3.

4. According to the relevant vibration parameters obtained in step S3.3, determine the water replenishment flow equation of the water delivery system containing the one-way tower, and determine the end time of water replenishment by taking the time when the water replenishment flow is 0 as the judgment condition; S3.5 Integrate the water replenishment flow equation according to the water replenishment end time obtained in step S3.4 to obtain the minimum water level of the one-way tower.

2. The method for calculating surge characteristics of a one-way tower according to claim 1, characterized in that: The initial pressure head difference ΔH of the one-way tower described in step S3.1 of the connecting pipe T The calculation formula is: ΔH T =H s -Z T In the formula, H S is the water head of the piezometer at the one-way tower, measured by the pressure gauge (9), in m; Z T is the initial water level of the one-way tower, in m, measured by a water level meter (10).

3. The method for calculating surge characteristics of a one-way tower according to claim 1 or 2, characterized in that: The calculation formula of the hydraulic resistance coefficient β of the water pipeline in step S3.2 is: Where d is the diameter of the water pipe (6), in meters; The hydraulic resistance coefficient β of the one-way tower connecting pipe described in step S3.2 s The calculation formula is: Where g is the acceleration due to gravity, It is an empirical coefficient, ranging from 0.6 to 0.

8.

4. The method for calculating surge characteristics of a one-way tower according to claim 3, characterized in that: The calculation formula of the transient vibration small parameter ε in step S3.3 is: Where g is the acceleration due to gravity, in m / s 2 ; The calculation formula of the initial vibration angular frequency ω0 in step S3.3 is: The initial amplitude a0 described in step S3.3 is calculated as: Where Q0 is the initial flow rate of the pipeline, in m 3 / s, measured by flow meter (8); The initial amplitude phase angle described in step S3.3 The formula is:

5. The method for calculating surge characteristics of a one-way tower according to claim 4, characterized in that: The water replenishment flow equation of the water delivery system containing a one-way tower described in step S3.4 is: Where Q(t) is the water replenishment at time t, t is the propagation time in seconds, and ξ is the water hammer wave propagation attenuation coefficient, which is 5×10 -6 ; m is the number of times the water hammer wave propagates in the pipeline. int(*) is the floor rounding function, a is the water hammer wave speed, 1000m / s.

6. The method for calculating surge characteristics of a one-way tower according to claim 5, characterized in that: The lowest water level Z of the one-way tower in step S3.5 min The calculation formula is: Wherein, Z0 is the initial water level of the one-way tower, measured by the water level meter (10) in step S2, and the unit is m; T is a value satisfying Q(T)=0.

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