A forced air supply system for a water turbine and its working method

Abstract

This invention relates to a forced air supply system and operating method for a hydro-turbine, comprising the following steps: S1, acquiring real-time unit load, head, and unit stability indicators; S2, comparing the acquired data with the threshold values ​​for head and load when the unit is in the vibration zone to determine whether the unit is currently in the vibration zone; S3, comparing the real-time acquired unit stability indicator data with the unit stability indicator threshold values ​​when the unit is in a stable state to determine whether the unit stability indicators exceed the limits; S4, supplying air to the unit, continuously increasing the opening of the air valve, and acquiring the unit stability indicators in real time until the unit stability indicators are within the threshold values; S5, finding the optimal value of the unit stability indicators when the unit is in a stable state by adjusting the opening of the air valve. This invention enables the unit's air supply volume to be automatically adjusted according to changes in unit load, effectively improving the tailrace vortex zone and enhancing the unit's operational stability and efficiency.

Description

Technical Field

[0001] This invention relates to the field of turbine air supply technology, and in particular to a forced air supply system for a turbine and its operating method. Background Technology

[0002] To improve my country's energy structure and reduce the environmental impact of the power industry, new energy sources, represented by wind power and photovoltaic power generation, have become a new development trend in recent years. Hydropower, as the only technologically mature green, renewable, and clean energy source, plays a major role in peak shaving and frequency regulation due to its rapid response and environmental friendliness. To meet electricity demand at different times, the output of the generating units frequently changes with the system load requirements; therefore, the turbines often operate within a relatively wide range of operating conditions. When the turbines of a hydropower station operate in areas deviating from their design operating conditions, a pressure pulsation zone exists in the tailrace vortex zone, causing varying degrees of vibration within the tailrace.

[0003] By injecting air through the top cover, the pressure distribution in the flow field can be altered. The gas displaces the liquid flow field, reducing the ratio of its circumferential velocity component to its axial velocity component. This makes the axial velocity distribution in the cross section more uniform, effectively reducing the vortex eccentricity and suppressing pressure pulsation. At the same time, the air injection also changes the pressure gradient distribution in the flow field. As air is introduced into the tailpipe, the pressure distribution in the tailpipe becomes more uniform, the reverse pressure gradient along the flow direction decreases, and the vortex belt shedding caused by vortex separation transforms into a columnar vortex belt. Simultaneously, the radial cross-sectional pressure gradient distribution also becomes more uniform, thereby suppressing the generation of pressure pulsation.

[0004] Currently, there are two main methods for turbine air supply. One is natural air supply, where one end of the air supply pipe leads to the atmosphere and the other end to the draft tube. When the turbine deviates from its design operating conditions, vortices are generated in the draft tube, causing a pressure drop. When the pressure is lower than atmospheric pressure, a pressure difference is created between the atmosphere and the draft tube, allowing air to enter the draft tube along the air supply pipe. This affects the pressure and pressure gradient within the draft tube, but the amount of air supplied is difficult to control, failing to achieve the desired effect. The other method is forced air supply, which uses an air compressor to deliver high-pressure gas to the draft tube. When the pressure inside the draft tube is higher than atmospheric pressure, the atmosphere cannot enter the draft tube due to the pressure difference, necessitating this method of air supply. While this air replenishment method solves the problem of high pressure in the tailrace tube preventing natural air replenishment, its air replenishment volume cannot be automatically adjusted according to changes in turbine unit load. This results in problems such as insufficient air replenishment under a certain load, ineffective suppression of tailrace tube pressure pulsation, and excessive air replenishment reducing turbine efficiency. Furthermore, the air replenishment volume cannot reach the optimal level under a certain load, preventing the unit from operating stably under optimal conditions and affecting unit efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing forced air supply method, which cannot automatically adjust with the change of turbine unit load, resulting in insufficient air supply to the turbine unit under a certain load, insignificant effect on suppressing tailrace pressure pulsation, excessive air supply reducing turbine efficiency, and failure to achieve optimal air supply under a certain load, thus failing to enable the unit to operate stably under optimal conditions and affecting unit efficiency. Therefore, the present invention provides a forced air supply system and working method for a turbine.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for forced air injection in a water turbine includes the following steps:

[0008] S1. Real-time acquisition of unit load, head, and unit stability indicators;

[0009] S2. Compare the load and head obtained in real time in S1 with the threshold values ​​of head and load when the unit is in the vibration zone, respectively, to determine whether the current load and head of the unit are in the vibration zone. If not, return to step S1; if yes, proceed to step S3.

[0010] S3. Compare the unit stability index data obtained in real time in S1 with the unit stability index threshold when the unit is in a stable state, and determine whether the unit stability index is within the threshold. If not, return to step S1. If yes, the unit is in the vibration zone, then proceed to step S4.

[0011] S4. Replenish the unit with air, open and continuously increase the opening of the air valve, then obtain the unit stability index corresponding to the current air valve opening in real time and compare it with the unit stability index threshold to determine whether the unit stability index is within the threshold. If not, continue to increase the opening of the air valve and continue to compare the real-time obtained unit stability index data with the unit stability index threshold. If yes, the unit is in stable operation and proceed to step S5.

[0012] S5. Continue to adjust the opening of the air valve. By acquiring the unit stability index corresponding to the opening in real time and comparing it with the unit stability index corresponding to the previous air valve opening, find the optimal value of the unit stability index when the unit is in a stable state, determine the optimal opening of the air valve, and provide stable air replenishment to the unit.

[0013] Preferably, in step S5, based on the air valve opening in step S4, the air valve opening is further increased, and the real-time unit stability index first decreases and then increases. When it increases, the air valve opening is then continuously decreased, and the real-time unit stability index first decreases and then increases. When it increases, the above steps are repeated until the real-time unit stability index changes uniformly. The air valve opening corresponding to the minimum value of the unit stability index measured in real time is taken as the optimal value. Then, the adjustment of the air valve opening is stopped, and the unit is stably replenished with air.

[0014] Preferably, in steps S4 and S5, the air valve opening adjustment mode is as follows: the compressed air flow rate in the air valve is 0.01% of the turbine's rated flow rate, and is converted into the air valve opening degree through the air valve's flow characteristics, and the time interval for each air valve opening degree adjustment is 1-2 minutes.

[0015] Preferably, in step S4, if the real-time acquired unit stability index data is less than the unit stability index threshold, and the difference between the unit stability index and the maximum value of the unit stability index threshold is within 5%, then proceed to step S5.

[0016] Preferably, the real-time load, head, and stability indicators of the unit are only acquired after the unit has been running stably for a certain period of time.

[0017] A forced air supply system for a water turbine includes a data acquisition and processing subsystem, a controller, an air supply component, and an air supply pipe, wherein the air supply component is electrically connected to the controller.

[0018] One end of the aforementioned air supply pipe is connected to the air outlet of the aforementioned air supply component, and the other end is connected to the inner cavity of the turbine and installed on the turbine top cover;

[0019] An air valve is connected to the aforementioned air supply pipe, the aforementioned air valve is electrically connected to the aforementioned controller, and the aforementioned controller is electrically connected to the aforementioned data acquisition and processing subsystem;

[0020] The aforementioned data acquisition and processing subsystem is electrically connected to the unit status monitoring subsystem to obtain unit load, head, and unit stability indicators in real time.

[0021] Preferably, the above-mentioned air supply pipe includes a main pipe and branch pipes. The air valve is installed on the main pipe. The air inlet of the main pipe is connected to the air outlet of the air supply component. There are multiple branch pipes. The air inlet of any one of the branch pipes is connected to the main pipe. The multiple branch pipes are evenly distributed circumferentially on the turbine top cover.

[0022] Preferably, a check valve is also connected to the main pipeline, and the check valve is located downstream of the air valve.

[0023] Preferably, a gas flow meter is also connected to the main pipeline, and the gas flow meter is electrically connected to the controller.

[0024] Preferably, the above-mentioned air replenishment component includes an air compressor and an air tank, the air outlet of the air compressor is connected to the air inlet of the air tank, and the air outlet of the air tank is connected to the air replenishment pipe.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. By monitoring the real-time load and head, and then adjusting the air valve to supply air to the unit, the amount of air supplied to the unit can be automatically adjusted according to the changes in the unit load.

[0027] 2. Because the stability index is a direct indicator of whether the unit is stable, by using the air valve opening and the unit stability index as feedback closed-loop regulation control loop, the air opening can be quickly adjusted so that the air supply can bring the unit's stability index within the threshold range, allowing the unit to quickly reach a stable operating state. Moreover, this adjustment is gradual and will not affect the unit's operating state due to a sharp increase in the air supply.

[0028] 3. Under real-time load, by finding the optimal value of the stability index, the optimal value of the air valve opening can be found, and the optimal air supply can be determined, so that the unit can operate in the optimal state, thereby improving the unit's operational stability and efficiency. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a diagram illustrating the system operation method in an embodiment of the present invention;

[0031] Figure 2 This is an overall schematic diagram of an embodiment of the present invention;

[0032] Figure 3 This is a graph showing the change in air supply volume and unit stability index over time after the air valve is opened in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Air supply assembly; 11. Air compressor; 12. Air tank; 2. Main pipeline; 3. Branch pipeline; 4. Air valve; 5. Check valve; 6. Gas flow meter; 7. Turbine top cover. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] This invention provides a method for forced air supply to a water turbine, such as... Figure 1 As shown, it includes the following steps:

[0039] S1. Real-time acquisition of unit load, head, and unit stability indicators;

[0040] S2. Compare the load and head obtained in real time in S1 with the threshold values ​​of head and load when the unit is in the vibration zone, respectively, to determine whether the current load and head of the unit are in the vibration zone. If not, return to step S1; if yes, proceed to step S3.

[0041] S3. Compare the unit stability index data obtained in real time in S1 with the unit stability index threshold when the unit is in a stable state, and determine whether the unit stability index is within the threshold. If not, return to step S1. If yes, the unit is in the vibration zone, then proceed to step S4.

[0042] S4. Replenish the unit with air, open and continuously increase the opening of the air valve, then obtain the unit stability index corresponding to the current air valve opening in real time and compare it with the unit stability index threshold to determine whether the unit stability index is within the threshold. If not, continue to increase the opening of the air valve and continue to compare the real-time obtained unit stability index data with the unit stability index threshold. If yes, the unit is in stable operation, then proceed to step S5.

[0043] S5. Continue adjusting the air valve opening. By acquiring the unit stability index corresponding to the opening in real time and comparing it with the previous air valve opening value, find the optimal value of the unit stability index when the unit is in a stable state. Determine the optimal air valve opening and provide stable air replenishment to the unit. Specifically, based on the air valve opening in step S4, continue increasing the air valve opening. The real-time unit stability index first decreases and then increases. While increasing, continuously decrease the air valve opening. The real-time unit stability index first decreases and then increases. Repeat the above steps until the real-time unit stability index changes uniformly. The optimal value is the air valve opening corresponding to the minimum real-time measured unit stability index. Then stop adjusting the air valve opening and provide stable air replenishment to the unit. Specifically, as follows... Figure 3 As shown, point a represents the threshold value of the unit stability index, specifically, the horizontal vibration peak of the top cover is 90µm and the vertical vibration peak is 110µm. Point A0 is the point where the stability index initially exceeds the standard. Point A1 is the real-time stability index value point in step S4 leading into S5. Then, the opening of the air valve is continuously increased from Q1 to Q3. The real-time unit stability index first decreases and then increases. The real-time unit stability index decreases from A1 to A2, and then increases from A2 to A3. While increasing, the opening of the air valve is continuously decreased from Q3 to Q5. The real-time unit stability index first decreases and then increases, that is, the unit stability index decreases from A3 to A4, and then increases from A4 to A5. Then, the above steps are repeated until the minimum value of the unit stability index is found, which is the optimal value A*, and is also the optimal value of the supplementary air volume Q*.

[0044] In step S4, if the difference between the unit stability index and the unit stability index threshold is within 5%, the unit can be considered to be in a stable operating state. Once the real-time stability index falls within the threshold range, the optimization process in step S5 is performed, thus simplifying the optimization process in step S5.

[0045] Preferably, in steps S4 and S5, the air valve opening adjustment mode is as follows: the compressed air flow rate in the air valve is 0.01% of the turbine's rated flow rate, and the air valve opening is converted through the air valve's flow characteristics. Because according to the previous CFD flow field calculation, when the make-up air flow rate changes by 0.01% of the turbine's rated flow rate, it has a significant impact on the unit's stability. When the make-up air flow rate changes too little, it will not affect the unit's stability. Moreover, the time interval between each air valve opening adjustment is 1-2 minutes, and the measured unit stability index is relatively accurate.

[0046] In the above method, the system can obtain real-time data on the unit's load, head, and stability indicators from the unit status monitoring subsystem. Only when the load, head, and stability indicators are all within the vibration zone is the system accurately determined to be in the vibration zone, requiring air replenishment. During air replenishment, the air valve opening is adjusted, and the air valve opening is further adjusted based on the real-time acquired unit stability indicators, forming a closed-loop control loop. Ultimately, the unit's stability indicators reach the threshold range, the air valve operates stably for air replenishment, and the unit is in a stable operating state. Specifically, by monitoring the real-time load and head, and then adjusting the air valve to replenish the unit, the amount of air replenished to the unit can be adjusted accordingly. The unit automatically adjusts to changes in load. Since stability indicators are direct measures of unit stability, a closed-loop control system using air valve opening and unit stability indicators as feedback can rapidly adjust the air valve opening to ensure the air supply volume keeps the unit's stability indicators within the threshold range, allowing the unit to quickly reach a stable operating state. This adjustment is gradual and will not affect the unit's operating state due to a sharp increase in air supply volume. Under real-time load, the optimal value of the stability indicator is found, leading to the optimal value of the air valve opening and the optimal air supply volume. This ensures the unit operates in its optimal state, improving both operational stability and efficiency.

[0047] Furthermore, after the unit has been running stably for 3-5 minutes, the real-time load, head, and stability indicators of the unit are acquired. Then, step S2 is performed to determine whether the unit is in the vibration zone, so as to avoid performing gas replenishment operation when the unit is in the start-up or shutdown phase. Specifically, the load deviation is considered to be within ±10% as stable operation.

[0048] Furthermore, the unit's stability indicators that exceeded the standards included tailwater pressure pulsation, top cover XY direction vibration, guide vane arm vibration comparison, and inlet door vibration.

[0049] The above-mentioned air replenishment method corresponds to a turbine forced air replenishment system, such as... Figure 2As shown, the system includes a unit status monitoring subsystem, a data acquisition and processing subsystem, a controller, a gas supply component 1, and a gas supply pipe. The gas supply component 1 is electrically connected to the controller. One end of the gas supply pipe is connected to the outlet of the gas supply component 1 via a flange, and the other end is connected to the inner cavity of the turbine and installed on the turbine top cover 7 via a flange. An air valve 4 is connected to the gas supply pipe via a flange. The air valve 4 is electrically connected to the controller, the controller is electrically connected to the data acquisition and processing subsystem, and the data acquisition and processing subsystem is electrically connected to the unit status monitoring subsystem. Specifically, both the data acquisition and processing subsystem and the unit status monitoring subsystem are existing systems within the power plant.

[0050] Specifically, the data acquisition and processing subsystem obtains data from the unit status monitoring subsystem. Then, the data acquisition and processing subsystem compares the acquired data with the unit stability data set within it to determine whether the unit is in the vibration zone. If the unit is in the vibration zone, the data acquisition and processing subsystem calculates the amount of air replenishment required by the unit at this time and sends a signal to the controller. The controller controls the air valve 4 to open, and the air replenishment component 1 replenishes air through the air replenishment pipe, thereby improving the operating stability of the tailrace vortex and the unit in the original vibration zone and ensuring stable operation of the unit.

[0051] Furthermore, the air supply pipe includes a main pipe 2 and a branch pipe 3, with an air valve 4 installed on the main pipe 2.

[0052] The air inlet of the main pipe 2 is connected to the air outlet of the supplementary air assembly 1. There are multiple branch pipes 3, and the air inlet of any branch pipe 3 is connected to the main pipe 2. The multiple branch pipes 3 are evenly distributed around the turbine top cover 7, so that the gas entering the bladeless area of ​​the runner remains uniform in the circumferential direction, and the generation of pressure pulsation is stably suppressed.

[0053] Furthermore, a check valve 5 is also connected to the main pipeline 2. The check valve 5 is located downstream of the air valve 4 to prevent water and gas from flowing back into the unit and to ensure the normal operation of the branch pipeline 3.

[0054] Furthermore, a gas flow meter 6 is also connected to the main pipeline 2. The gas flow meter 6 is electrically connected to the controller, so that the amount of gas entering the unit can be known in real time. This allows for the real-time display of the relationship between the amount of gas supplied to the branch pipeline 3 and the stability indicators of the unit, facilitating analysis by the staff.

[0055] Furthermore, the air supply component 1 includes an air compressor 11 and an air tank 12. The air outlet of the air compressor 11 is connected to the air inlet of the air tank 12, and the air outlet of the air tank 12 is connected to the air inlet of the main pipeline 2 through a flange. By setting up the air tank 12, a constant initial pressure is achieved in the air tank 12, and air is stably supplied through the air supply pipe.

[0056] The specific operating method of the above-mentioned air replenishment system is as follows: First, the data acquisition and processing subsystem obtains real-time unit load, head, and stability indicators from the unit status monitoring subsystem. Then, it compares the collected data with the head threshold and load threshold set within the data acquisition and processing subsystem when the unit is in the vibration zone, and then determines whether the current unit is in the vibration zone. If the current unit is not in the vibration zone, the data acquisition and processing subsystem does not send a signal to the controller, the unit operates normally, and the data acquisition and processing subsystem continues to collect real-time data for comparison, repeating this process. If the current unit is in the vibration zone, the data acquisition and processing subsystem simultaneously... The subsystem compares the stability index data obtained from the unit status monitoring subsystem with the standard stability index data set within it, and then determines whether the unit stability index is in a stable state. If it is in a stable state, no signal is sent to the control system, and the judgment is continued based on the re-acquired head, load, and unit stability index, and the process is repeated. If the unit stability index exceeds the standard, the data acquisition and processing subsystem calculates the air replenishment amount and then sends a signal to the controller. The controller controls the air compressor 11 to run, and the air valve 4 is opened to the corresponding degree. Then, the gas in the air storage tank 12 is replenished to the turbine through the main pipeline 2 and multiple branch pipelines 3.

[0057] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method of operating a water turbine with forced air injection, characterized in that, The method comprises the following steps: S1, real-time acquisition of unit load, water head and unit stability index; S2, comparison of the real-time acquired load and water head in S1 with the threshold value of water head and the threshold value of load when the unit is in the vibration zone, to determine whether the current unit load and water head are in the vibration zone, if not, return to step S1, if yes, enter step S3; S3, comparison of the real-time acquired unit stability index data in S1 with the unit stability index threshold value when the unit is in a stable state, to determine whether the unit stability index is within the threshold value, if not, return to step S1, if yes, the unit is in the vibration zone, then enter step S4; S4, air supplement to the unit, opening and continuously increasing the opening degree of the air valve, then real-time acquisition of the unit stability index corresponding to the current air valve opening degree and comparison with the unit stability index threshold value, to determine whether the unit stability index is within the threshold value, if not, continuously increase the opening degree of the air valve, and continuously compare the real-time acquired unit stability index data with the unit stability index threshold value, if yes, the unit is in stable operation, enter step S5; S5, continuous adjustment of the opening degree of the air valve, to find the optimal value of the unit stability index when the unit is in a stable state by real-time acquisition of the unit stability index corresponding to the opening degree and comparison with the unit stability index corresponding to the previous air valve opening degree, to determine the optimal opening degree of the air valve, and to perform stable air supplement to the unit.

2. The forced air makeup service method of claim 1, wherein, In step S5, based on the air valve opening degree in step S4, continuously increase the opening degree of the air valve, the real-time unit stability index first decreases and then increases, and when it increases, then continuously decrease the opening degree of the air valve, the real-time unit stability index first decreases and then increases, and when it increases; Repeat the above steps, finally the real-time unit stability index changes uniformly, take the air valve opening degree corresponding to the minimum value of the real-time measured unit stability index as the optimal value, then stop adjusting the opening degree of the air valve, and perform stable air supplement to the unit.

3. The forced air makeup service method of claim 1, wherein, In steps S4 and S5, the adjustment mode of the air valve opening degree is as follows: the compressed air flow in the air valve is 0.01% of the rated flow of the hydraulic turbine, and is converted into the opening degree of the air valve through the flow characteristic of the air valve, and the time interval for each adjustment of the opening degree of the air valve is 1-2 min.

4. The forced make-up air working method according to claim 1, characterized in that, In step S4, if the real-time acquired unit stability index data is less than the unit stability index threshold value, and the difference between the unit stability index and the maximum value of the unit stability index threshold value is within 5%, then enter step S5.

5. The forced make-up air working method according to claim 1, characterized in that, The unit stability operation is performed for a certain period of time before the real-time unit load, water head and unit stability index are acquired.

6. The forced air makeup working method of claim 1, implemented with a hydraulic turbine forced air makeup system, characterized in that, The hydraulic turbine forced air supplement system comprises a unit state monitoring subsystem, a data acquisition and processing subsystem, a controller, an air supplement assembly and an air supplement pipe, the air supplement assembly is electrically connected with the controller; One end of the air supplement pipe is in communication with the air outlet of the air supplement assembly, and the other end is in communication with the inner cavity of the hydraulic turbine and is installed on the top cover of the hydraulic turbine; The air supplement pipe is communicated with an air valve, the air valve is electrically connected with the controller, and the controller is electrically connected with the data acquisition and processing subsystem; The data acquisition processing subsystem is electrically connected with the unit state monitoring subsystem, and is used for acquiring unit load, water head and unit stability index in real time.

7. The forced air makeup service method of claim 6, wherein, The air supplement pipe comprises a main pipe and branch pipes, the air valve is arranged on the main pipe, an air inlet of the main pipe is communicated with an air outlet of the air supplement assembly, the number of the branch pipes is plural, an air inlet of any one of the branch pipes is communicated with the main pipe, and the plural branch pipes are uniformly distributed on the turbine top cover in a circumferential direction.

8. The forced air makeup service method of claim 7, wherein, A check valve is further communicated with the main pipe, and the check valve is located downstream of the air valve.

9. The forced air makeup service method of claim 7, wherein, A gas flow meter is further communicated with the main pipe, and the gas flow meter is electrically connected with the controller.

10. The forced make-up air working method according to claim 6, characterized in that, The air supplement assembly comprises an air compressor and an air storage tank, an air outlet of the air compressor is communicated with an air inlet of the air storage tank, and an air outlet of the air storage tank is communicated with the air supplement pipe.

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