Air tank with adjustable air chamber top elevation

Abstract

The invention relates to an air tank with an adjustable air chamber top elevation, which comprises a vertical tank body, the lower part of the tank body is a water chamber, the bottom of the tank body is communicated with a water delivery pressure pipeline through a connecting pipe, a piston in sliding fit with the inner wall of the tank body is arranged in the tank body, and at least one sealing structure is arranged on the contact surface of the piston and the inner wall of the tank body. The space, between the water chamber and the piston, of the upper portion of the tank body is an air chamber, a piston rod connected with the piston penetrates through a penetrating hole in the top of the tank body and extends to the position above the tank body to be connected with a driving mechanism, the driving mechanism is electrically connected with a controller, and the controller is electrically connected with a water pump in a pump station pressurization water conveying system. The control signal is sent out, the driving mechanism is controlled to drive the piston to move downwards, after the normal state is recovered, the driving mechanism is controlled to drive the piston to reset, and at least one vent hole is formed in the top of the tank body. On the premise that the surge amplitude of the air tank is met, the extreme value of the bottom pressure of the air tank can be further improved, and therefore the extreme value of the pressure along the line in the hydraulic transition process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air tank in pump station pressurized water delivery system, and particularly relates to an air tank with adjustable air chamber top elevation. BACKGROUND

[0002] In long-distance water delivery projects with high lift and small flow, air tanks are often used to solve the water hammer problem after the water pump is powered off. Air tanks are widely used because of their convenient operation, maintenance, installation and management, and the design and use experience is relatively rich. Common types of air tanks include vertical air tanks and horizontal air tanks, and vertical air tanks are more widely used.

[0003] The initial absolute pressure of the air chamber of the air tank and the air chamber height not only determine the surge amplitude in the air tank, but also determine the bottom pressure amplitude of the air tank, thereby affecting the pressure envelope along the pipeline. The greater the initial absolute pressure of the air chamber of the air tank, that is, the lower the initial operation water level of the air tank, the smaller the surge amplitude in the air tank, and the greater the bottom pressure amplitude. Therefore, when designing the size of the air tank, the surge amplitude in the air tank and the bottom pressure amplitude of the air tank need to be considered comprehensively, and the appropriate initial operation water level and air chamber height of the air tank are selected from the economic point of view.

[0004] The top elevation of the air chamber of the existing air tank is fixed. In addition, in order to fully reflect the water hammer pressure to ensure that the maximum and minimum pressure along the pipeline meets the specification requirements, the existing conventional air tank type often needs a larger size. SUMMARY

[0005] In order to solve the above problems, the purpose of the present application is to provide an air tank with adjustable air chamber top elevation, which can further improve the extreme value of the bottom pressure of the air tank under the premise of meeting the surge amplitude in the air tank, thereby improving the extreme value of the pressure along the pipeline in the hydraulic transition process.

[0006] To achieve the above purpose, the following technical solutions are adopted in the present application: The air tank with adjustable air chamber top elevation comprises a vertical tank body, the lower part of the tank body is a water chamber, the bottom of the tank body is connected with a water delivery pressure pipeline through a connecting pipe, a piston is installed in the tank body and slidably matched with the inner wall of the tank body, at least one sealing structure is arranged on the contact surface between the piston and the inner wall of the tank body, the space between the water chamber and the piston in the upper part of the tank body is an air chamber, a piston rod connected with the piston extends to the upper part of the tank body through a perforation in the top of the tank body and is connected with a driving mechanism, the driving mechanism is electrically connected with a controller, the controller is electrically connected with a water pump in a pump station pressurized water delivery system, the controller sends a control signal after receiving a water pump power-off signal, controls the driving mechanism to drive the piston to move downward, and controls the driving mechanism to drive the piston to reset after the normal state is restored, and at least one air hole is arranged on the top of the tank body.

[0007] As a specific embodiment, the cross-sectional area of the connecting pipe is greater than or equal to 15% of the cross-sectional area of the water pressure pipeline.

[0008] As a specific embodiment, the sealing structure adopts a combination structure of a Stoff seal ring and two guide rings on both sides, an intermediate sealing groove is formed in the middle of the outer side of the piston for installing the Stoff seal ring, the Stoff seal ring is installed in the intermediate sealing groove and in contact with the inner wall of the tank body, and an outer sealing groove is formed on the upper and lower sides of the intermediate sealing groove for installing the guide rings on both sides, the guide rings are installed in the outer sealing groove and in clearance fit with the inner wall of the tank body.

[0009] As a specific embodiment, the driving mechanism is a linear driving mechanism, which drives the piston to move up and down.

[0010] As a specific embodiment, the piston and the piston rod are both made of rigid material.

[0011] As a specific embodiment, the top of the tank body is provided with a pressure measuring hole, a pressure sensor is arranged in the pressure measuring hole, the pressure sensor is electrically connected with the controller, the pressure sensor detects the pressure on the inside of the pressure measuring hole in real time and sends it to the controller, the controller receives the pressure signal sent by the pressure sensor and judges whether the detected pressure is greater than the local atmospheric pressure, when the detected pressure is greater than the local atmospheric pressure, the controller controls the driving mechanism to drive the piston to move up and reset against the top surface in the tank body.

[0012] As a specific embodiment, the diameter of each air hole is 1 / 10 of the pipe diameter of the water pressure pipeline.

[0013] As a specific embodiment, a layer of flexible material is arranged on the top surface of the piston corresponding to the positions of the air holes and the pressure measuring hole.

[0014] As a specific embodiment, the controller is provided with an alarm module, which sends an alarm when the piston moves up and resets due to air leakage of the air tank.

[0015] As a specific embodiment, the preliminary estimation of the piston down time of the air tank is determined according to the length of the water delivery pipeline before the air tank, that is, air tank piston down time-pump off time = air tank before water delivery pressure pipeline length / water hammer wave speed; the preliminary estimation of the piston down length of the air tank is determined according to the length of the water delivery pipeline after the air tank, that is, air tank piston down length < 2x air tank after water delivery pressure pipeline length / water hammer wave speed; the preliminary estimation of the piston down amount of the air tank is determined according to the initial water level of the air tank, the surge amplitude in the air tank and the installation elevation of the bottom of the air tank, that is, air tank piston down amount ≤ air tank initial water level-air tank surge amplitude-air tank bottom installation elevation-safety water depth; the piston down time, the piston down length and the piston down amount of the air tank are finally determined by adjusting the preliminary estimation values through transient flow numerical simulation.

[0016] The air tank with adjustable air chamber top elevation has the following beneficial effects: The air tank with adjustable air chamber top elevation further improves the extreme value of the bottom pressure of the air tank under the premise of meeting the surge amplitude of the air tank, thereby improving the extreme value of the line pressure in the hydraulic transition process.

[0017] The air tank with adjustable air chamber top elevation effectively alleviates the decrease of the bottom pressure of the air tank by using the piston pressurization, thereby reducing the pressure rise after the reflection, reducing the pressure fluctuation in the pipeline and ensuring the stability and safety of the water delivery pressure pipeline after the pump station unit is powered off. The device can save engineering cost while keeping the initial water level of the air tank unchanged, without increasing the air chamber height of the air tank and the cross-sectional area of the air tank, and can improve the extreme value of the line pressure in the hydraulic transition process. The device can be applied to the air tank water hammer protection design in long-distance water supply projects and can provide reference value for the air cushion surge chamber in power stations. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a structural schematic diagram of the air tank with adjustable air chamber top elevation of the present application; Figure 2 FIG. 2 is a structural schematic diagram of the air tank when the piston is rotated and pressed to the target position; Figure 3 FIG. 3 is a structural schematic diagram of the piston sealing structure of the new air tank; Figure 4 FIG. 4 is a top view schematic diagram of the air tank with adjustable air chamber top elevation of the present application; Figure 5 FIG. 5 is a plan layout of a long-distance water delivery system; Figure 6 FIG. 6 is a related size schematic diagram of the new air tank of the present application; Figure 7The pressure tube water head and the pipe center line height in the constant flow condition of the simulation water delivery system in the application example; Figure 8 The air chamber top elevation change process line of the air tank in the application example; Figure 9 The bottom pressure change process line of the conventional air tank and the new type air tank of the application; Figure 10 The partial enlarged view of the bottom pressure change process line of the conventional air tank and the new type air tank of the application; Figure 11 Another partial enlarged view of the bottom pressure change process line of the conventional air tank and the new type air tank of the application; Figure 12 The water level change process line of the conventional air tank and the new type air tank of the application; Figure 13 The partial enlarged view of the water level change process line of the conventional air tank and the new type air tank of the application; Figure 14 The air chamber pressure change process line of the conventional air tank and the new type air tank of the application; Figure 15 The partial enlarged view of the air chamber pressure change process line of the conventional air tank and the new type air tank of the application; Figure 16 Another partial enlarged view of the air chamber pressure change process line of the conventional air tank and the new type air tank of the application; Figure 17 The maximum pressure envelope line of the conventional air tank and the new type air tank of the application; Figure 18 The partial enlarged view of the maximum pressure envelope line of the conventional air tank and the new type air tank of the application; Figure 19 The minimum pressure envelope line of the conventional air tank and the new type air tank of the application; Figure 20 The partial enlarged view of the minimum pressure envelope line of the conventional air tank and the new type air tank of the application. DETAILED DESCRIPTION

[0019] The application will be further described in detail below in combination with the drawings and specific embodiments: Referring to Figures 1 to 4 , the air tank with adjustable air chamber top elevation comprises a vertical tank body 11, and the lower part of the tank body 11 is a water chamber.

[0020] The bottom of the tank body 11 is communicated with the water delivery pressure pipeline 2 through a connecting pipe 21, and the cross-sectional area of the connecting pipe 21 is greater than or equal to 15% of the cross-sectional area of the water delivery pressure pipeline 2.

[0021] A through hole is formed in the middle of the top surface of the tank 11. A piston 12 is installed in the tank 11 and is in sliding contact with the inner wall of the tank 11. At least one sealing structure 121 is provided on the contact surface between the piston 12 and the inner wall of the tank 11. See Figure 3 The sealing structure 121 can be a combination of a Stoff seal ring and two guide rings. A middle sealing groove is formed in the middle of the outer side of the piston 12 for installing the Stoff seal ring. The Stoff seal ring is installed in the middle sealing groove and is in contact with the inner wall of the tank 11. Two guide rings are installed in the outer sealing grooves formed on the upper and lower sides of the middle sealing groove of the piston 12 and are in clearance fit with the inner wall of the tank 11.

[0022] The space between the water chamber and the piston 12 in the upper part of the tank 11 is a gas chamber for containing compressed gas. The height of the gas chamber can be changed by the up and down displacement of the piston 12.

[0023] The piston rod 122 connected with the piston 12 extends through the through hole in the top of the tank 11 to the upper side of the tank 11 and is connected with the linear driving mechanism 13. The linear driving mechanism 13 can be a mechanism directly or indirectly outputting linear motion with a motor as the power source. The linear driving mechanism 13 is electrically connected with a controller, and the controller is electrically connected with a water pump in the pressurized water supply system of the pump station. After receiving the signal of the water pump being powered off, the controller sends a control signal to control the linear driving mechanism 13 to drive the piston 12 to move downward. After the normal state is restored, the controller controls the linear driving mechanism 13 to drive the piston 12 to return to the original position.

[0024] The piston 12 and the piston rod 122 are made of rigid materials.

[0025] See Figure 4 At least one air hole 111 and one pressure measuring hole 112 are provided on the top of the tank 11 outside the through hole. In this embodiment, three air holes 111 and one pressure measuring hole 112 are provided, which are arranged in pairs with the through hole as the center and are uniformly distributed on the outer periphery of the through hole. The diameters of the air holes 111 and the pressure measuring hole 112 are 1 / 10 of the diameter of the water delivery pressure pipeline 2.

[0026] A layer 123 of flexible material such as rubber is provided on the top surface of the piston 12 corresponding to the positions of the air holes 111 and the pressure measuring hole 112. Alternatively, a layer 123 of flexible material covering the entire or most of the top surface of the piston 12 is provided on the top surface of the piston 12.

[0027] A pressure sensor is arranged in the pressure measuring hole 112 and electrically connected with the controller. The pressure sensor detects the pressure inside the pressure measuring hole 112 in real time and sends the pressure to the controller. The controller receives the pressure signal sent by the pressure sensor and determines whether the detected pressure is greater than the local atmospheric pressure. When the detected pressure is greater than the local atmospheric pressure (at this time, the tank has air leakage), the controller controls the linear driving mechanism 13 or the rotary driving mechanism to drive the piston 12 to move upward and reset against the top surface of the tank 11. The flexible material layer 123 on the top surface of the piston 12 seals each air vent hole 111 and the pressure measuring hole 112, ensuring the safety and reliability of the air tank and preventing air leakage due to the failure of the sealing structure 121 of the piston 12, thereby preventing the occurrence of air tank failure.

[0028] Preferably, the controller is provided with an alarm module. When the piston 12 moves upward and resets due to air leakage of the air tank, the alarm module issues an alarm.

[0029] Considering that the air tank may be arranged in the middle of the pump station pressurized water delivery system, the piston 12 of the novel air tank of the present application should be pressed down at the moment when the depressurization wave reaches the air tank, so as to ensure that the depressurization process of the pump-off water hammer and the pressurization effect achieved by the piston 12 are superimposed to prevent unnecessary negative pressure or overpressure damage to the pipeline. The preliminary estimation of the piston 12 down time of the air tank can be determined according to the length of the water delivery pipeline before the air tank, i.e., air tank piston 12 down time-pump off time = air tank before water delivery pressure pipeline length / water hammer wave speed.

[0030] The piston 12 down time of the air tank should be considered to avoid the superposition of the positive pressure wave generated by the outlet reflection, causing the pipeline to be overpressured. The preliminary estimation of the piston 12 down time of the air tank can be determined according to the length of the water delivery pipeline after the air tank, i.e., air tank piston 12 down time < 2 x air tank after water delivery pressure pipeline length / water hammer wave speed.

[0031] The preliminary estimation of the piston 12 down amount of the air tank should ensure that the down amount does not cause the air tank to leak air. The preliminary estimation of the piston 12 down amount of the air tank can be determined according to the initial water level of the air tank, the surge amplitude in the air tank, and the installation elevation of the bottom of the air tank, i.e., air tank piston 12 down amount ≤ air tank initial water level-air tank surge amplitude-air tank bottom installation elevation-safety water depth.

[0032] The piston 12 down time of the air tank, the piston 12 down time, and the piston 12 down amount are finally determined by adjusting the preliminary estimated values through transient flow numerical simulation.

[0033] A long-distance water delivery project containing the novel air tank of the present application adopts a "two-in-one standby" pump unit arrangement. Referring to Figure 5, the long-distance water conveyance system includes an intake sump 3, a pumping station, an air tank 1, a water conveyance pressure pipeline 2, and an outlet sump 4. The pumping station pumps the water in the intake sump 3 through the water conveyance pressure pipeline 2 to the outlet sump 4. The air tank 1 is installed behind the pumping station and is connected to the water conveyance pressure pipeline 2. The pumping station installs 3 centrifugal pumps 5, 2 are put into normal use, and 1 is used as a spare. The single-unit design flow rate is 3.25 m³ / s, the design head is 186.00 m, the rated speed is 750 r / min, and a check valve 6 is provided behind each centrifugal pump 5. The specific calculation conditions are as follows: upstream design water level, downstream design water level, two pump units operate at the design head, and two pump units stop pumping simultaneously due to power failure. The piezometric head and the elevation of the pipe centerline under the steady-state condition of the pipeline behind the pump are as Figure 7 shown.

[0034] Currently, the research on the hydraulic transient process generally focuses on one-dimensional numerical simulation. The following uses an application example to numerically simulate the above conditions through program calculation. By studying the pressure at the bottom of the air tank, the water level in the air tank, the pressure in the air chamber of the air tank, and the maximum and minimum pressure envelopes, the practicability of the new air tank of the present invention in improving the extreme values of the along-line pressure in the hydraulic transient process and other aspects is further analyzed.

[0035] The mathematical model of the new air tank of the present invention is similar to the mathematical model of the conventional air tank, and mainly realizes the transformation of the mathematical model by controlling and changing the elevation of the top of the air chamber.

[0036] It is assumed that the air in the closed pressure air tank satisfies the ideal gas state equation. Since the transient process is very rapid, the air expansion or compression process is close to the adiabatic condition, which is in line with the actual situation for an air tank with a small volume.

[0037] Its main equations are as follows: (1) In the formula: H A is the absolute pressure of the gas in the air tank; V is the volume of the gas in the air tank; n is the exponent of the gas state equation, 1 < n < 1.4, and the average value 1.2 is adopted in the design calculation; C is a constant related to the initial state of the gas in the air tank.

[0038] (2) In the formula: H P is the pressure at the connection node between the air tank and the pipeline, which is the relative pressure; k is the value of the hydraulic loss coefficient at the connection node between the air tank and the pipeline, and different values should be taken according to the sign of Q S when flowing in and out; Q S is the flow rate flowing into the air tank; Z is the water level in the air tank; H B is the local atmospheric pressure, which is related to the local elevation; the meanings of other symbols are the same as before.

[0039] (3) where dz is the water level change in the time range dt; A C is the cross-sectional area of the air tank; other symbols have the same meaning as before.

[0040] (4) where Q U is the flow rate at the upstream node of the air tank; Q D is the flow rate at the downstream node of the air tank; other symbols have the same meaning as before.

[0041] C+: (5) C-: (6) where H P is the pressure at the connection node of the air tank and the pipeline; C p and B p are intermediate variables, C p and B p are calculated by equation (7); C M and B M are intermediate variables, C M and B M are calculated by equation (8); other symbols have the same meaning as before.

[0042]

[0043] (7)

[0044] (8) where H i-1 and H i+1 are the water heads at the nodes before and after the calculation node at the previous time; Q i-1 and Q i+1 are the flow rates at the nodes before and after the calculation node at the previous time; B is the characteristic impedance of the pipeline, which is calculated by equation (9); R is the head loss coefficient, which is calculated by equation (10); other symbols have the same meaning as before.

[0045] (9) where a is the water hammer wave speed; g represents the acceleration due to gravity; A represents the cross-sectional area of the pipeline; other symbols have the same meaning as before.

[0046] (10) where f is the Darcy-Weisbach friction loss coefficient; ∆x is the average length of the pipeline; D is the diameter of the pipeline; other symbols have the same meaning as before.

[0047] Equations (1) to (10) are used to solve the pressure and flow of the pressure air tank node, and the air tank gas volume, pressure and water level change process can be solved.

[0048] Air tank surge amplitude It can be estimated by the following formula: (11)

[0049] Air tank bottom pressure change amplitude It can be estimated by the following formula: (12)

[0050] In the formula: v0 is the initial flow rate in the pipeline after the pump; L is the length of the water conveying pipeline after the air tank; f is the cross-sectional area of the pipeline; g is the gravitational acceleration; A C is the air tank cross-sectional area; σ is an intermediate variable, which is calculated by formula (13).

[0051] (13) In the formula: m is the ideal gas polytropic index, which is 1.0 for isothermal change and 1.4 for adiabatic change, and is 1.2 in numerical calculation; p0 is the absolute pressure of the air tank; l0 is the initial air chamber height of the air tank.

[0052] In this application example, the water hammer protection effects of the conventional air tank and the new air tank of the application are compared through hydraulic transition calculation, and the calculation results are shown in Figures 9 to 18 , wherein the initial parameters of the two types of air tanks are: air chamber height l=3m, initial operating water level h=525m, air tank area S=50m2, connecting pipe diameter d=1m (see Figure 6 for size marking of air tank related parameters). The piston of the new air tank of the application adopts a 10s downward pressure of 0.1m, as shown in Figure 8 .

[0053] When the water pump unit is powered off during pumping, the valve after the pump is closed, and the pressure of the pipeline after the pump begins to drop. Because water hammer wave propagates very quickly and the air tank is installed after the pump, when the water hammer just reaches the bottom of the air tank, the new air tank of the application has little difference with the conventional air tank due to the small amount of downward pressure of the piston, and the reflection effect of the air tank on the water hammer wave is not much different, but the bottom pressure drop process is a gradual decline process, and the use of the piston pressurization method can effectively alleviate the air tank bottom pressure drop.

[0054] When the water level in the air tank rises due to the reflected positive pressure wave and the water body backflow, the air chamber pressure increases, but the air tank bottom pressure drop is eased, the air tank bottom pressure rise value is also reduced, and the air chamber maximum pressure is also reduced accordingly.

[0055] By Figures 9 to 14 It can be seen that the new air tank of the application can ensure that the minimum surge of the air tank is not much different from Figure 12 and Figure 13 The minimum surge of the conventional air tank is 523.11m, and the minimum surge of the new air tank of the application is 523.06m, only 0.05m different.

[0056] At the same time, the decrease of the air tank bottom pressure is eased, see Figure 9 and Figure 10 The minimum pressure is increased from 97.72m of the conventional air tank to 99.02m of the new air tank, thereby effectively reducing the maximum pressure of the reflected air tank bottom, see Figure 11 The maximum pressure is reduced from 300.51m of the conventional air tank to 298.49m of the new air tank. The minimum and maximum values of the air chamber pressure are also improved, see Figure 14 and Figure 15 The minimum pressure is increased from 110.83m of the conventional air tank to 112.18m of the new air tank, see Figure 16 The maximum pressure is reduced from 310.80m to 308.89m.

[0057] As can be seen from Figures 17 to 20 The new air tank of the application can effectively improve the extreme value of the pressure along the line during the hydraulic transition process, the minimum pressure is increased from 3.22m of the conventional air tank to 3.97m of the new air tank, and the maximum pressure is reduced from 300.51m of the conventional air to 298.50m of the new air tank.

[0058] Therefore, compared with the conventional air tank, the application can effectively improve the water hammer protection effect of the air tank under the condition that the air tank body parameters are consistent and the minimum surge of the air tank is not much different. By using this advantage, the air tank body can be optimized. Through numerical calculation verification, under the condition of obtaining the same water hammer protection effect, the new air tank of the application can reduce the cross-sectional area by 1m2, i.e. the air tank volume can be reduced by 5.2m3 (air tank height 5.2m), which reduces the volume by nearly 2%. This can greatly reduce the investment of the air tank which has very high economic cost, and has great practical significance.

[0059] The above is only a specific embodiment of the application, and does not limit the patent scope of the application. Any equivalent structural transformation using the content of the application specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

Claims

1. An air tank with adjustable air chamber top elevation, comprising a vertical tank body (11), the lower part of the tank body (11) being a water chamber, the bottom of the tank body (11) being communicated with a water delivery pressure pipeline (2) through a connecting pipe (21), characterized in that: The tank body (11) is internally provided with a piston (12) in sliding cooperation with the inner wall of the tank body (11), and at least one sealing structure (121) is arranged at the contact surface between the piston (12) and the inner wall of the tank body (11); the space between the water chamber and the piston (12) at the upper part of the tank body (11) is a gas chamber; the piston rod (122) connected with the piston (12) extends through the perforation at the top of the tank body (11) to the upper side of the tank body (11) and is connected with a driving mechanism; the driving mechanism is electrically connected with a controller; the controller is electrically connected with a water pump in the pressurized water delivery system of the pump station; after receiving the power-off signal of the water pump, the controller sends a control signal to control the driving mechanism to drive the piston to move downward; after the normal state is restored, the controller controls the driving mechanism to drive the piston to reset; and at least one air vent (111) is arranged at the top of the tank body (11).

2. The air chamber top elevation adjustable air tank of claim 1, wherein: The cross-sectional area of the connecting pipe (21) is greater than or equal to 15% of the cross-sectional area of the water delivery pressure pipe (2).

3. The air chamber top elevation adjustable air tank of claim 1, wherein: The sealing structure (121) adopts a combined structure of a Stoff seal ring and two guide rings; a middle sealing groove is formed in the middle part of the outer side of the piston (12) and used for mounting the Stoff seal ring; the Stoff seal ring is mounted in the middle sealing groove and in contact with the inner wall of the tank body (11); and outer side sealing grooves are formed in the upper and lower sides of the middle sealing groove of the outer side of the piston (12) and used for mounting the two guide rings; the guide rings are mounted in the outer side sealing grooves and in gap cooperation with the inner wall of the tank body (11).

4. The air chamber top elevation adjustable air tank of claim 1, wherein: The driving mechanism is a linear driving mechanism, which drives the piston (12) to move up and down.

5. The air chamber top elevation adjustable air tank of claim 1, wherein: The piston (12) and the piston rod (122) are both made of rigid materials.

6. The air chamber top elevation adjustable air tank of claim 1, wherein: The top of the tank body (11) is provided with a pressure measuring hole (112), a pressure sensor is arranged in the pressure measuring hole (112), the pressure sensor is electrically connected with the controller, the pressure sensor detects the pressure on the inner side of the pressure measuring hole (112) in real time and sends the pressure to the controller, the controller receives the pressure signal sent by the pressure sensor and judges whether the detected pressure is greater than the local atmospheric pressure, when the detected pressure is greater than the local atmospheric pressure, the controller controls the driving mechanism to drive the piston (12) to move upward and reset against the inner top surface of the tank body (11).

7. The air chamber top elevation adjustable air tank of claim 1, wherein: The diameter of each air vent (111) is 1 / 10 of the pipe diameter of the water delivery pressure pipe (2).

8. The air chamber top elevation adjustable air tank of claim 6, wherein: A flexible material layer (123) is arranged on the top surface of the piston (12) corresponding to the positions of the air vent (111) and the pressure measuring hole (112).

9. The air chamber top elevation adjustable air tank of claim 6, wherein: The controller is provided with an alarm module, which sends an alarm when the piston (12) moves upward and resets due to air leakage of the air tank.

10. The air chamber top elevation adjustable air tank of claim 1, wherein: The preliminary estimation of the piston (12) of the air tank is determined according to the length of the water delivery pipeline before the air tank, that is, the piston (12) of the air tank is pressed down at the time - the water pump is powered off at the time = the length of the water delivery pressure pipeline before the air tank / the water hammer wave speed; The preliminary estimation of the piston (12) of the air tank is determined according to the length of the water delivery pipeline after the air tank, that is, the piston (12) of the air tank is pressed down for a period of time < 2 x the length of the water delivery pressure pipeline after the air tank / the water hammer wave speed; The preliminary estimation of the piston (12) down-pressing amount of the air tank is determined according to the initial water level of the air tank, the surge amplitude in the air tank and the installation elevation of the bottom of the air tank, that is, the piston (12) down-pressing amount of the air tank ≤ the initial water level of the air tank - the surge amplitude in the air tank - the installation elevation of the bottom of the air tank - the safety water depth; The piston (12) down-pressing time, the piston (12) down-pressing duration and the piston (12) down-pressing amount are finally determined through transient flow numerical simulation according to the preliminary estimation.

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