Air tank for relieving pipeline positive pressure and application method thereof

Abstract

The invention provides an air tank for relieving the positive pressure of a pipeline and an application method thereof, a first connecting pipe and a second connecting pipe are arranged between the bottom of the air tank for relieving the positive pressure of the pipeline and a pressure pipeline in a communicating mode, and a one-way damping device is installed in the first connecting pipe. The invention discloses an air tank for relieving pipeline positive pressure and an application method thereof, a double-connecting-pipe air tank with different bottom connection forms is designed, through combination with a one-way damping device, the impedance loss of the bottom of the air tank and the on-way loss of connecting pipes are changed, and the difficulty of water flowing into and out of the air tank is controlled; the water level of the air tank is adjusted, and the situation that the positive pressure in the pipeline exceeds the standard is effectively relieved. According to the method, under the condition that the size of the air tank is not changed, the phenomena that the pressure in the pipeline exceeds the standard and the water level of the air tank exceeds the range are avoided by adjusting the sizes of the connecting pipe and the valve, certain economic benefits are achieved, and support is provided for safe and stable operation and optimization of a pump station water conveying system.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline positive pressure relief, and in particular to an air tank for relieving pipeline positive pressure and an application method thereof. Background Art

[0002] The primary purpose of long-distance water transmission systems is to redistribute water resources and improve their utilization. Due to complex topographical and geological conditions, pumping stations are required to pressurize water pipelines to facilitate water transmission over both high and low terrain. During the operation of these pipeline systems, various issues may arise. Among them, transient flow caused by sudden changes in flow within the pipeline poses a significant threat to the stability of the water transmission system. Air tanks can effectively protect against pressure transients, mitigating the sudden changes in pressure waves within the pipeline system.

[0003] When designing air tanks, pipe size, material, geometry, surge variations, and generation patterns should be considered to mitigate water hammer transmission during transient events. Therefore, when simulating hydraulic transients in pressurized water transmission systems incorporating air tanks, various parameters, such as pipe friction and the air tank-to-pipe connection type, need to be calibrated to determine the optimal air tank size. Pipe friction and impedance affect the water level variation in the air tank, and the connecting pipe between the air tank and the water pipeline affects the pipeline's head loss and impedance loss. However, the bottom connection type of the air tank and its impact are rarely discussed.

[0004] Theoretically, the water hammer protection effectiveness of an air tank is proportional to its volume. However, due to technical and economic constraints, the air tank's size must be controlled. To maximize both positive and negative pressure protection, air tank parameters must be determined through trial calculations and rational design. In some terrain-specific situations, particularly high-drop pumping station water supply systems, air tanks can provide effective water hammer protection. However, this can also lead to a rapid surge in the pressure wave, causing the positive pressure in the water supply system to exceed the specified level. In some projects, the maximum pressure at the bottom of the air tank is mitigated by increasing the air tank's volume or installing other protective measures such as overpressure relief valves and vent valves. However, the former significantly increases economic costs and is necessary for positive pressure protection, but is somewhat wasteful for negative pressure protection. The latter is technically challenging to implement and manage, requiring the appropriate timing and pattern of valve opening and closing, and also raises safety and management issues regarding the handling of water releases.

[0005] It can be seen from this that it is necessary to design an economical and feasible positive pressure relief solution. Without increasing the volume of the air tank, it can not only effectively ensure the protection of negative pressure but also effectively reduce the positive pressure. It can effectively serve the actual engineering and has certain application scenarios. Summary of the Invention

[0006] In view of the defects of the prior art, the present invention provides an air tank for relieving pipeline positive pressure and an application method thereof, which can effectively solve the above problems.

[0007] The technical solution adopted in the present invention is as follows:

[0008] The present invention provides an air tank for relieving positive pressure in a pipeline, comprising an air tank body, a one-way damping device (4.4), a first connecting pipe (4.5) and a second connecting pipe (4.6);

[0009] The first connecting pipe (4.5) and the second connecting pipe (4.6) are respectively connected between the bottom of the air tank body and the pressure pipe (5), and the one-way damping device (4.4) is installed in the first connecting pipe (4.5); when the air tank body replenishes water to the pressure pipe (5), the one-way damping device (4.4) is in a fully open state; when the pressure pipe (5) replenishes water to the air tank body, the one-way damping device (4.4) is in a fully closed state.

[0010] Preferably, the first connecting pipe (4.5) and the second connecting pipe (4.6) have the same length and diameter.

[0011] Preferably, one end of the first connecting pipe (4.5) communicating with the air tank body, and one end of the second connecting pipe (4.6) communicating with the air tank body, both have an impedance hole (4.3).

[0012] Preferably, the interior of the air tank body has an air bag (4.1) at the top and a water body (4.2) at the bottom.

[0013] The present invention also provides a water delivery system, comprising the air tank for relieving the positive pressure of the pipeline, an upper reservoir (1), a water pump (2), a flow regulating valve (3), a pressure pipeline (5) and a lower reservoir (6);

[0014] The water level of the upper reservoir (1) is lower than that of the lower reservoir (6); the upper reservoir (1) and the lower reservoir (6) are connected via the pressure pipe (5); in the pressure pipe (5), the water pump (2), the flow regulating valve (3) and the air tank for relieving the positive pressure of the pipeline are arranged in sequence according to the direction of water flow from the upper reservoir (1) to the lower reservoir (6).

[0015] The present invention also provides an application method of an air tank for relieving positive pressure in a pipeline, which is applied to the water delivery system and includes the following steps:

[0016] When the water supply system is operating normally, the flow regulating valve (3) is fully open, the water level of the air tank (4) that relieves the positive pressure in the pipeline remains unchanged, and the water pump (2) delivers the water in the upper reservoir (1) to the lower reservoir (6) through the pressure pipe (5);

[0017] When the water pump (2) suddenly loses power, the pressure behind the pump drops rapidly, and the flow regulating valve (3) is quickly closed to 0 degree of opening. During the process of the pressure drop wave transmitting to the downstream, the air tank (4) starts to operate and replenishes water into the pressure pipe (5) behind the pump;

[0018] When the pressure reduction wave is transmitted to the lower reservoir (6), the water delivery system starts to flow back and becomes a reverse pressure increase wave. When the pressure increase wave is transmitted to the air tank (4) in the direction of the upper reservoir (1), the pressure pipe (5) replenishes water into the air tank (4).

[0019] Preferably, during the transmission of the pressure reduction wave to the downstream, the air tank (4) starts to operate to replenish water into the pressure pipe (5) after the pump, specifically:

[0020] During the process of the pressure reduction wave being transmitted downstream, when the pressure reduction wave reaches the bottom of the air tank (4), the air bag (4.1) begins to expand, and the water body (4.2) replenishes water into the pressure pipe (5). Under the influence of this water flow direction, the one-way damping device (4.4) is in a fully open state. Therefore, water flows through the first connecting pipe (4.5) and the second connecting pipe (4.6) to replenish water into the pressure pipe (5), and the impedance holes (4.3) of the first connecting pipe (4.5) and the second connecting pipe (4.6) both generate head loss.

[0021] Preferably, when the water body (4.2) replenishes water in the pressure pipe (5), a head loss coefficient α and an impedance loss coefficient β shown in formula (2) are generated:

[0022]

[0023] Where: L is the length of the pressure pipe; A is the area of ​​the pressure pipe; φ is the flow coefficient through the impedance orifice; D is the diameter of the pressure pipe; g is the acceleration of gravity; L c1 is the length of a single connecting pipe; d c1 is the diameter of a single connecting pipe; A c1 is the cross-sectional area of ​​a single connecting pipe; A st1 is the area of ​​a single impedance hole.

[0024] Preferably, when the boost wave is transmitted to the air tank (4) in the direction of the upper reservoir (1), the pressure pipe (5) replenishes water into the air tank (4), specifically:

[0025] When the boost wave is transmitted to the bottom of the air tank (4), the air bag (1) begins to compress, and the pressure pipe (5) replenishes water into the water body (4.2). Under the influence of this water flow direction, the one-way damping device (4.4) is in a fully closed state, so that water flows into the water body (4.2) only through the second connecting pipe (4.6), and the water flows through the impedance hole (4.3) at the end of the second connecting pipe (4.6), generating a head loss; due to the presence of the one-way damping device (4.4), the water flow can only flow into the air tank (4) from one connecting pipe, the head loss at the connecting pipe increases, and thus the maximum pressure at the bottom of the air tank is reduced; due to the presence of the one-way damping device (4.4), the difficulty of the water flow flowing into the air tank (4) during the pipeline boosting process is increased, thereby limiting the significant rise of the water level in the air tank (4) and effectively controlling the water level fluctuation of the air tank.

[0026] Preferably, when the pressure pipe (5) replenishes water into the water body (4.2), a head loss coefficient α and an impedance loss coefficient β shown in formula (3) are generated:

[0027]

[0028] Where: L is the length of the pressure pipe; A is the area of ​​the pressure pipe; φ is the flow coefficient through the impedance orifice; D is the diameter of the pressure pipe; g is the acceleration of gravity; L c1 is the length of a single connecting pipe; d c1 is the diameter of a single connecting pipe; A c1 is the cross-sectional area of ​​a single connecting pipe; A st1 is the area of ​​a single impedance hole

[0029] The air tank for relieving pipeline positive pressure and its application method provided by the present invention have the following advantages:

[0030] The present invention solves the problem of excessive pressure in the water supply system pipeline. Without increasing the volume of the air tank, by providing a double-connected pipe air tank and a one-way damping device, the maximum pressure of the water supply system can be effectively reduced and large fluctuations in the water level in the air tank can be suppressed, thereby ensuring the safe and stable operation of the water supply system and saving project investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the water delivery system provided by the present invention including an air tank for relieving positive pressure in the pipeline;

[0032] Figure 2 This is a schematic structural diagram of the double-connected-tube air tank combined with a one-way damping device provided by the present invention;

[0033] Figure 3 This is a diagram showing the pressure change process at the bottom of the air tank under different protection schemes after the water pump loses power;

[0034] Figure 4 This is a diagram showing the flow rate changes in and out of the air tank under different protection schemes after the water pump loses power;

[0035] Figure 5 The following is the envelope diagram of the minimum pressure of the water delivery system under different protection schemes after the water pump loses power;

[0036] Figure 6 The following is the envelope diagram of the maximum pressure of the water supply system under different protection schemes after the water pump loses power.

[0037] Among them: 1-upper reservoir; 2-water pump; 3-flow regulating valve; 4-air tank; 5-pressure pipe; 6-lower reservoir; 4.1-air bag; 4.2-water body; 4.3-impedance hole; 4.4-one-way damping device; 4.5-first connecting pipe; 4.6-second connecting pipe. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] The present invention discloses an air tank for alleviating positive pressure in pipelines and its application method. A dual-connection-tube air tank with different bottom connection forms is designed. By combining it with a one-way damping device, the impedance loss at the bottom of the air tank and the loss along the connecting pipe are changed, thereby controlling the difficulty of water flowing into and out of the air tank, thereby regulating the water level in the air tank and effectively alleviating excessive positive pressure in the pipeline. This method can avoid excessive pressure in the pipeline and excessive water level in the air tank by adjusting the size of the connecting pipe and valve without changing the volume of the air tank. This method has certain economic benefits and provides support for the safe, stable operation and optimization of the water delivery system of the pump station.

[0040] like Figure 1 and Figure 2 As shown, the present invention provides an air tank for relieving positive pressure in a pipeline, comprising an air tank body, a one-way damping device 4.4, a first connecting pipe 4.5 and a second connecting pipe 4.6;

[0041] The first connecting pipe 4.5 and the second connecting pipe 4.6 are respectively connected between the bottom of the air tank body and the pressure pipe 5, and the one-way damping device 4.4 is installed in the first connecting pipe 4.5; when the air tank body replenishes water to the pressure pipe 5, the one-way damping device 4.4 is in a fully open state; when the pressure pipe 5 replenishes water to the air tank body, the one-way damping device 4.4 is in a fully closed state.

[0042] In a specific embodiment, the first connecting tube 4.5 and the second connecting tube 4.6 have the same length and diameter. The end of the first connecting tube 4.5 that connects to the air tank body, and the end of the second connecting tube 4.6 that connects to the air tank body, both have an impedance hole 4.3. The interior of the air tank body has an air bag 4.1 at the top and a body of water 4.2 at the bottom.

[0043] Applying the above air tank for relieving pipeline positive pressure, the present invention also provides a water delivery system, including the air tank for relieving pipeline positive pressure, and further including an upper reservoir 1, a water pump 2, a flow regulating valve 3, a pressure pipe 5 and a lower reservoir 6;

[0044] The water level of the upper reservoir 1 is lower than that of the lower reservoir 6. The upper reservoir 1 and the lower reservoir 6 are connected by the pressure pipe 5. In the pressure pipe 5, the water pump 2, the flow regulating valve 3, and the air tank for relieving the positive pressure in the pipeline are arranged in sequence according to the direction of water flow from the upper reservoir 1 to the lower reservoir 6. Therefore, the flow regulating valve 3 and the air tank for relieving the positive pressure in the pipeline are both arranged after the pump.

[0045] The air tank and water delivery system for relieving pipeline positive pressure provided by the present invention have the following characteristics:

[0046] (1) The air tank for relieving the positive pressure in the pipeline adopts a double-connected pipe air tank, which is arranged at the outlet of the water pump 2. A one-way damping device 4.4 is provided on one of the connecting pipes of the double-connected pipe air tank, while the one-way damping device 4.4 is not provided on the other connecting pipe;

[0047] (2) When the water delivery system is operating normally, the double-connected pipe air tank and the one-way damping device 4.4 do not operate;

[0048] (3) When the water pump 2 suddenly loses power, the pressure behind the pump drops rapidly, and the double-connected pipe air tank quickly replenishes water into the pressure pipe 5;

[0049] (4) When the pressure reduction wave is transmitted to the lower reservoir 6, the water supply system begins to flow back. Due to the presence of the one-way damping device 4.4, the water flow can only flow into the air tank from the connecting pipe without the one-way damping device 4.4. The head loss at the connecting pipe increases, thereby reducing the maximum pressure at the bottom of the air tank.

[0050] In this step, the critical positive pressure at the bottom of the air tank is determined by subtracting a safety margin from the pipeline's pressure tolerance. In the event of a power outage, the water system must maintain no negative pressure, and the positive pressure in the pipeline must not exceed the pipeline's pressure tolerance. Typically, the transient pressure control standard for the water system is that the maximum pressure in the pipeline does not exceed 1.3 to 1.5 times the maximum pressure during steady-state operation, and the minimum pressure in the pipeline is no less than 0 m.

[0051] (5) Due to the presence of the one-way damping device 4.4, the difficulty of water flowing into the air tank during the pressure increase process of the pressure pipe is increased, which limits the sharp rise of the water level in the air tank and effectively controls the water level fluctuation in the air tank.

[0052] The present invention will be further described below with reference to the accompanying drawings.

[0053] like Figure 1 As shown, the water delivery system of the present invention comprises: an upper reservoir 1, a water pump 2, a flow regulating valve 3, an air tank 4, a pressure pipe 5 and a lower reservoir 6; wherein the flow regulating valve 3 and the air tank 4 are both arranged after the water pump 2. Its application method is:

[0054] Step S1: When the water delivery system is operating normally, the flow regulating valve 3 is in a fully open state, the water level in the air tank 4 remains unchanged, and the water pump 2 delivers the water from the upper reservoir 1 to the lower reservoir 6 through the pressure pipe 5;

[0055] Step S2: When a power outage suddenly occurs in water pump 2, the pressure downstream of the pump drops rapidly. To prevent water from flowing back into the pump 2 and causing a water pump failure, the flow regulating valve 3 needs to be quickly closed to 0 degrees. As the pressure drop wave propagates downstream, the air tank 4 starts to operate, replenishing water into the pressure pipe 5 downstream of the pump.

[0056] In step S3, when the pressure reduction wave is transmitted to the lower reservoir 6, the water delivery system starts to flow back and turns into a reverse pressure boost wave. When the reverse pressure boost wave is transmitted to the upper reservoir 1 and reaches the air tank 4, the pressure pipe 5 replenishes water into the air tank 4.

[0057] like Figure 2 As shown, the air tank 4 is a double-connecting pipe air tank, and its design includes: an air bag 4.1, a water body 4.2, an impedance hole 4.3, a one-way damping device 4.4, a first connecting pipe 4.5, and a second connecting pipe 4.6.

[0058] In step S2, during the transmission of the pressure reduction wave to the downstream, the air tank 4 starts to operate to replenish water into the pressure pipe 5 after the pump, specifically:

[0059] During the transmission of the pressure reduction wave downstream, when the pressure reduction wave reaches the bottom of the air tank 4, the airbag 4.1 begins to expand, and the water body 4.2 replenishes water into the pressure pipe 5. Under the influence of this water flow direction, the one-way damping device 4.4 is in a fully open state. Therefore, water flows through the first connecting pipe 4.5 and the second connecting pipe 4.6 to replenish water into the pressure pipe 5, and the impedance holes 4.3 of the first connecting pipe 4.5 and the second connecting pipe 4.6 both generate head loss.

[0060] In step S3, when the boost wave is transmitted to the air tank 4 in the direction of the upper reservoir 1, the pressure pipe 5 replenishes water into the air tank 4, specifically:

[0061] As the pressure wave propagates toward the upper reservoir 1, or upstream, when it reaches the bottom of the air tank 4, the airbag 1 begins to compress, and the pressure pipe 5 replenishes water into the water body 4.2. Under the influence of this water flow direction, the one-way damping device 4.4 is fully closed. Therefore, water flows into the water body 4.2 only through the second connecting pipe 4.6. The water flows through the impedance hole 4.3 at the end of the second connecting pipe 4.6, generating head loss. Due to the presence of the one-way damping device 4.4, the flow rate of water through the impedance hole 4.3 increases, and the water can only flow into the air tank 4 through a single connecting pipe. The head loss at the connecting pipe increases, effectively suppressing the rise in maximum pressure at the bottom of the air tank. The presence of the one-way damping device 4.4 increases the difficulty of water flowing into the air tank 4 during the pipeline pressurization process, limiting the significant rise in the water level in the air tank 4 and effectively controlling the water level fluctuation in the air tank. This design effectively alleviates the positive pressure of the water supply system through a simple design without affecting the negative pressure protection effect of the air tank.

[0062] According to the Darcy-Weisbach formula, the head loss can be divided into two parts, namely the head loss along the pressure pipe and the impedance loss at the bottom of the air tank. Different connection forms between the air tank and the pressure pipe will affect the values ​​of the head loss coefficient α and the impedance loss coefficient β along the pressure pipe, which are calculated using formula (1):

[0063]

[0064] Where: L is the length of the pressure pipe, m; A is the area of ​​the pressure pipe, m 2 ; r is the roughness of the pressure pipe; φ is the flow coefficient through the impedance orifice; D is the diameter of the pressure pipe, m; g is the acceleration of gravity, m / s 2 ; A st is the impedance orifice area.

[0065] Compared to conventional air tanks, in the present invention, in step S2, when water body 4.2 is replenishing pressure pipe 5, a double-connecting pipe air tank is equipped with an additional impedance hole. Therefore, the impedance holes 4.3 of both connecting pipes generate head loss. At the same time, since the connecting pipes have a certain length, the head loss along the connecting pipe section is increased. Therefore, the head loss coefficient α and impedance loss coefficient β shown in formula (2) are generated:

[0066]

[0067] Where: L c1 is the length of a single connecting pipe, m; d c1 is the diameter of a single connecting pipe, m; A c1 is the cross-sectional area of ​​a single connecting pipe, m 2 ; A st1 is the area of ​​a single impedance hole, m 2.

[0068] In the present invention, in step S3, when the pressure pipe 5 is replenishing water into the water body 4.2, as shown in FIG. Figure 2 As shown, a single damping device 4.4 is added to one of the connecting pipes, the first connecting pipe 4.5. Water flows only through the second connecting pipe 4.6 to replenish the water body 4.2. Therefore, during the system pressurization process, the water in the pressure pipe 5 can be restricted from flowing into the air tank 4, thereby reducing the increase in the positive pressure in the pipe. During the process of system pressure increase, the head loss coefficient α and impedance loss coefficient β shown in formula (3) are generated:

[0069]

[0070] In order to verify the accuracy of the theoretical analysis and study the impact of this new device on air tank surge, a model will be established based on an actual water transfer project to simulate the surge changes of the air tank during hydraulic transients.

[0071] The total length of the water pipeline in this embodiment is about 3300.0m, and the designed water supply flow rate is 1.00m 3 / s, using DN800 steel pipe for water transportation. Figure 1 The design water level of upper reservoir 1 is 5.00m, the water level of lower reservoir 6 is 40.00m, and the actual head of pump 2 in the pumping station is 52.63m. If a sudden power outage occurs in pump 2, the water delivery system must meet both positive and negative pressure requirements, with the positive pressure control standard at 64.4m and the negative pressure control standard at 0m. If protective measures are not implemented in the event of a sudden power outage in pump 2, the pipeline pressure will drop below -10m, generating vapor pressure and causing serious damage to the pipeline. Therefore, it is necessary to install an air tank 4 after the pump and close the flow control valve 3 after the pump.

[0072] This embodiment designs three air tank protection schemes:

[0073] Plan A is a conventional protection plan, that is, the air tank is directly connected to the pressure pipe, and there is no connecting pipe between the air tank and the pressure pipe.

[0074] Solution B is a double-connecting pipe air tank protection solution, that is, the air tank is connected to the pressure pipe through two connecting pipes;

[0075] Solution C is similar to Solution B, but a one-way damping device 4.4 is added to one of the connecting pipes. Solution C is the solution provided by the present invention. Figure 2 The air tank parameters for the three solutions are shown in Table 1. To maximize the water hammer protection effect of the air tank, the pump downstream valve was considered to be rapidly closed. The flow control valve downstream of the pump closed in a straight line over a 5-second period.

[0076] Table 1 Statistics of initial parameters of air tank

[0077]

[0078] Table 2.4 Numerical simulation results

[0079]

[0080] From Table 2 and Figures 3 to 6 It can be seen that the lowest water levels of Schemes A, B, and C are almost the same. Compared with Scheme A, the highest water level of Scheme C drops by 0.23m. In Scheme C, at t=65s, due to the presence of the one-way damping device, the flow rate from the pipeline to the air tank is reduced by 0.09m 3 / s. The maximum pressure changes of Scheme A and Scheme B are almost the same, but the minimum pressure of Scheme B is reduced by 0.90m. The double connecting pipe increases the head loss of the connecting pipe section, so the minimum pressure at the bottom of the air tank and the minimum pressure along the pipeline are reduced. As shown in Table 2, the volume of the air tank in Scheme B is reduced by 0.18m 3 . Under the conditions of Plan C, although the volume of the air tank is reduced, the maximum pressure is reduced by 6.56m. Due to the presence of the one-way damping device, the boost wave cannot be completely reflected at the connecting pipe. The presence of the one-way damping device can reduce the maximum pressure of the pipeline to a limited extent, limit the volume of water flowing into the air tank, and at the same time appropriately optimize the volume of the air tank. It can be seen that the method of the present invention can effectively alleviate the positive pressure of the pipeline without increasing the volume of the air tank, thereby saving engineering investment.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An air tank for relieving positive pressure in a pipeline, characterized in that: It comprises an air tank body, a one-way damping device (4.4), a first connecting pipe (4.5) and a second connecting pipe (4.6); The first connecting pipe (4.5) and the second connecting pipe (4.6) are respectively connected between the bottom of the air tank body and the pressure pipe (5), and the one-way damping device (4.4) is installed in the first connecting pipe (4.5); when the air tank body replenishes water to the pressure pipe (5), the one-way damping device (4.4) is in a fully open state; when the pressure pipe (5) replenishes water to the air tank body, the one-way damping device (4.4) is in a fully closed state.

2. The air tank for relieving pipeline positive pressure according to claim 1, characterized in that: The first connecting pipe (4.5) and the second connecting pipe (4.6) have the same length and diameter.

3. The air tank for relieving pipeline positive pressure according to claim 1, characterized in that: One end of the first connecting pipe (4.5) communicating with the air tank body, and one end of the second connecting pipe (4.6) communicating with the air tank body, both have an impedance hole (4.3).

4. The air tank for relieving pipeline positive pressure according to claim 1, characterized in that: The interior of the air tank body is provided with an air bag (4.1) at the upper part and a water body (4.2) at the lower part.

5. A water delivery system, characterized in that: An air tank for relieving pipeline positive pressure according to any one of claims 1 to 4, further comprising an upper reservoir (1), a water pump (2), a flow regulating valve (3), a pressure pipeline (5) and a lower reservoir (6); The water level of the upper reservoir (1) is lower than that of the lower reservoir (6); the upper reservoir (1) and the lower reservoir (6) are connected via the pressure pipe (5); in the pressure pipe (5), the water pump (2), the flow regulating valve (3) and the air tank for relieving the positive pressure of the pipeline are arranged in sequence according to the direction of water flow from the upper reservoir (1) to the lower reservoir (6).

6. An application method of an air tank for relieving positive pressure in a pipeline, characterized in that: The water delivery system according to claim 5 comprises the following steps: When the water supply system is operating normally, the flow regulating valve (3) is fully open, the water level of the air tank (4) that relieves the positive pressure in the pipeline remains unchanged, and the water pump (2) delivers the water in the upper reservoir (1) to the lower reservoir (6) through the pressure pipe (5); When the water pump (2) suddenly loses power, the pressure behind the pump drops rapidly, and the flow regulating valve (3) is quickly closed to 0 degree of opening. During the process of the pressure drop wave transmitting to the downstream, the air tank (4) starts to operate and replenishes water into the pressure pipe (5) behind the pump; When the pressure reduction wave is transmitted to the lower reservoir (6), the water delivery system starts to flow back and becomes a reverse pressure increase wave. When the pressure increase wave is transmitted to the air tank (4) in the direction of the upper reservoir (1), the pressure pipe (5) replenishes water into the air tank (4).

7. The method for using an air tank to relieve pipeline positive pressure according to claim 6, characterized in that: During the transmission of the pressure reduction wave to the downstream, the air tank (4) starts to operate to replenish water into the pressure pipe (5) after the pump, specifically: During the process of the pressure reduction wave being transmitted downstream, when the pressure reduction wave reaches the bottom of the air tank (4), the air bag (4.1) begins to expand, and the water body (4.2) replenishes water into the pressure pipe (5). Under the influence of this water flow direction, the one-way damping device (4.4) is in a fully open state. Therefore, water flows through the first connecting pipe (4.5) and the second connecting pipe (4.6) to replenish water into the pressure pipe (5), and the impedance holes (4.3) of the first connecting pipe (4.5) and the second connecting pipe (4.6) both generate head loss.

8. The method for using an air tank to relieve pipeline positive pressure according to claim 7, characterized in that: When the water body (4.2) replenishes water in the pressure pipe (5), the head loss coefficient α and the impedance loss coefficient β shown in formula (2) are generated: Where: L is the length of the pressure pipe; A is the area of ​​the pressure pipe; φ is the flow coefficient through the impedance orifice; D is the diameter of the pressure pipe; g is the acceleration of gravity; L c1 is the length of a single connecting pipe; d c1 is the diameter of a single connecting pipe; A c1 is the cross-sectional area of ​​a single connecting pipe; A st1 is the area of ​​a single impedance hole.

9. The method for using an air tank to relieve pipeline positive pressure according to claim 6, characterized in that: When the boost wave is transmitted to the air tank (4) in the direction of the upper reservoir (1), the pressure pipe (5) replenishes water into the air tank (4), specifically: When the boost wave is transmitted to the bottom of the air tank (4), the air bag (1) begins to compress, and the pressure pipe (5) replenishes water into the water body (4.2). Under the influence of this water flow direction, the one-way damping device (4.4) is in a fully closed state, so that water flows into the water body (4.2) only through the second connecting pipe (4.6), and the water flows through the impedance hole (4.3) at the end of the second connecting pipe (4.6), generating a head loss; due to the presence of the one-way damping device (4.4), the water flow can only flow into the air tank (4) from one connecting pipe, the head loss at the connecting pipe increases, and thus the maximum pressure at the bottom of the air tank is reduced; due to the presence of the one-way damping device (4.4), the difficulty of the water flow flowing into the air tank (4) during the pipeline boosting process is increased, thereby limiting the significant rise of the water level in the air tank (4) and effectively controlling the water level fluctuation of the air tank.

10. The method for using an air tank to relieve pipeline positive pressure according to claim 9, characterized in that: When the pressure pipe (5) replenishes water into the water body (4.2), the head loss coefficient α and the impedance loss coefficient β shown in formula (3) are generated: Where: L is the length of the pressure pipe; A is the area of ​​the pressure pipe; φ is the flow coefficient through the impedance orifice; D is the diameter of the pressure pipe; g is the acceleration of gravity; L c1 is the length of a single connecting pipe; d c1 is the diameter of a single connecting pipe; A c1 is the cross-sectional area of ​​a single connecting pipe; A st1 is the area of ​​a single impedance hole.

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