A vertical water turbine main shaft center hole guide type air supplement valve fault detection method

Abstract

The application discloses a kind of vertical water turbine main shaft center hole guide type air supply valve fault detection method, it is related to the technical field of hydroelectric generation, to the problem that in prior art, due to guide type air supply valve installation in water turbine main shaft center hole, the merits and demerits of its state cannot be directly checked on in-service unit, and then whether fault occurs cannot be judged, the application is judged by whether natural air supply phenomenon can occur continuously in part load rotating vortex zone of hydroelectric generating set, and whether the water leakage of water turbine main shaft center hole of unit in shutdown state increases, realizes the fault detection of water turbine main shaft center hole guide type air supply valve arranged in water turbine main shaft center hole on in-service unit.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydroelectric power generation, in particular to a vertical water turbine main shaft center hole guide type air supplement valve fault detection method. BACKGROUND

[0002] Hydroelectric power generation is a process in which water energy is converted into mechanical energy by a water turbine, and the mechanical energy is converted into electric energy by a water turbine generator. The water turbine generator set has the characteristics of mature technology and wide application range, and has become the most widely used hydroelectric power generation equipment type. The Francis turbine and the axial fixed-paddle turbine are the most common and widely used types of water turbines. In the process of converting water energy into mechanical energy by the Francis turbine and the axial fixed-paddle turbine, the water turbine as a prime mover must be operated in a wide load range according to the needs of the power grid, and cannot always be operated near the optimal efficiency point. As a single-regulation water turbine, due to the limitation of its own form, when the Francis turbine and the axial fixed-paddle turbine deviate from the optimal efficiency point, the flow state in the flow passage will deteriorate, and a typical phenomenon is that a rotating vortex band is generated at the outlet of the runner under partial load conditions. The pressure in the rotating vortex band region drops sharply, and a rotating vortex band extending from the outlet of the runner to the draft tube is generated. The rotating vortex band is the main cause of the increase of the pressure fluctuation in the draft tube of the Francis turbine and the axial fixed-paddle turbine. The increase of the pressure fluctuation in the draft tube of the Francis turbine and the axial fixed-paddle turbine often causes the increase of the vibration swing value of the water turbine generator set, which seriously affects the safe and stable operation of the unit. The conventional treatment method is to design the water turbine main shaft as a hollow through structure with a center hole. A one-way air supplement valve is installed at the center hole of the water turbine main shaft. When the unit is operated under partial load conditions, the pressure at the outlet of the runner caused by the rotating vortex band drops to a set value, and the one-way air supplement valve is opened. Since the atmospheric pressure is higher than the pressure in the rotating vortex band region, air enters the low-pressure region of the rotating vortex band through the center hole of the water turbine main shaft. With the supplement of air, the pressure in the rotating vortex band region shows a rising trend. Once the pressure in the rotating vortex band region recovers to a value higher than the set value of the one-way air supplement valve, the one-way air supplement valve is closed, and air no longer supplements the rotating vortex band region. This process is called natural air supplement in the industry. As long as the Francis turbine and the axial fixed-paddle turbine generator set is operated in the rotating vortex band region, the natural air supplement phenomenon will continue to occur, and the above-mentioned one-way air supplement valve will repeatedly open and close to ensure that the pressure in the rotating vortex band region does not drop too sharply, thereby avoiding the increase of the pressure fluctuation in the draft tube of the water turbine, preventing the increase of the vibration swing value of the water turbine generator set, and ultimately achieving the purpose of ensuring the safe and stable operation of the unit.

[0003] Meanwhile, in consideration of improving the cavitation performance of the water turbine and reducing the energy level of the pressure pulsation of the water turbine, generally speaking, the tail water level of the Francis turbine and the axial fixed paddle turbine generator set is higher than the installation height of the rotor of the water turbine generator, that is, if no corresponding measures are taken, under the condition of the shutdown of the unit, the high pressure water at the runner of the water turbine will overflow at the generator rotor through the central hole of the main shaft. Generally, in engineering, the above problem is solved by setting a one-way air supplement valve at the central hole of the main shaft and assisting with the structure of the overflow water pipe specially set at the central hole of the main shaft of the generator rotor. In theory, under the condition of the shutdown of the unit, the one-way air supplement valve prevents the pressure water in the flow passage of the water turbine from entering the central hole of the main shaft of the water turbine; even if the one-way air supplement valve cannot completely prevent the pressure water in the flow passage of the water turbine from entering the central hole of the main shaft of the water turbine due to the structure of the one-way air supplement valve, only a small amount of leakage water enters the central hole of the main shaft of the water turbine, and the leakage amount is very small. The overflow water pipe structure set at the central hole of the main shaft of the generator rotor is to provide a channel for the above-mentioned leakage water. However, due to the limitation of the structure, the overflow capacity of the overflow water pipe at the central hole of the main shaft is designed according to the above-mentioned leakage water amount, and the margin will not be large. Once the one-way air supplement valve fails, the leakage amount of the one-way air supplement valve increases too much, the leakage water cannot be discharged smoothly, and even the leakage water overflows to cause the water flooding of the generator.

[0004] There are many types of one-way air supplement valves for the central hole of the main shaft of the water turbine, but the most widely used is the guide type air supplement valve. Since the guide type air supplement valve is installed at the central hole of the main shaft of the water turbine, the state of the guide type air supplement valve cannot be directly checked on the in-service unit, and whether a fault occurs cannot be determined. SUMMARY

[0005] The purpose of the present application is to solve the problem in the prior art that since the guide type air supplement valve is installed at the central hole of the main shaft of the water turbine, the state of the guide type air supplement valve cannot be directly checked on the in-service unit, and whether a fault occurs cannot be determined, and to provide a fault detection method for the guide type air supplement valve for the central hole of the main shaft of the vertical water turbine.

[0006] The technical scheme adopted by the present application to solve the above technical problem is:

[0007] A fault detection method for the guide type air supplement valve for the central hole of the main shaft of the vertical water turbine, comprising the following steps:

[0008] Step 1: liquid level meter one 31 and liquid level meter two 32 are arranged in the central hole 3 of the main shaft of the water turbine generator, and the elevation of the liquid level meter one 31 is higher than that of the liquid level meter two 32;

[0009] Step 2: start the water turbine generator set, determine whether natural air supplement occurs, if natural air supplement occurs, execute step 3, otherwise, the guide type air supplement valve 5 fails;

[0010] Step three: keep natural air supplement for a set time;

[0011] Step four: stop the water turbine generator set, and obtain the time difference between the triggering times of the liquid level meter one 31 and the liquid level meter two 32;

[0012] Step five: obtain the flow diameter of the water turbine main shaft center hole 3 and the elevation difference between the liquid level meter one 31 and the liquid level meter two, and combine the time difference obtained in step four to obtain the actual leakage water quantity of the water turbine main shaft center hole 3;

[0013] Step six: obtain the theoretical leakage water quantity of the water turbine main shaft center hole 3, and determine whether the leakage water quantity of the water turbine main shaft center hole 3 increases according to the theoretical leakage water quantity of the water turbine main shaft center hole 3 and the actual leakage water quantity of the water turbine main shaft center hole 3, if the leakage water quantity increases, the guide type air supplement valve 5 fails, otherwise, the guide type air supplement valve 5 does not fail.

[0014] Further, the actual leakage water quantity of the water turbine main shaft center hole 3 is represented as:

[0015]

[0016] wherein, is the leakage water quantity of the water turbine main shaft center hole, is the flow diameter of the main shaft center hole 3, is the vertical distance between the liquid level meter one 31 and the liquid level meter two 32, is the time difference between the triggering times of the liquid level meter one and the liquid level meter two.

[0017] Further, in step six, the specific steps for determining whether the leakage water quantity of the water turbine main shaft center hole 3 increases are:

[0018] According to the theoretical leakage water quantity of the water turbine main shaft center hole 3 and the actual leakage water quantity of the water turbine main shaft center hole 3, the relative change rate of the leakage water quantity of the water turbine main shaft center hole 3 is obtained, and whether the leakage water quantity of the water turbine main shaft center hole 3 increases is determined according to the relative change rate of the leakage water quantity of the water turbine main shaft center hole 3;

[0019] The relative change rate of the leakage water quantity of the water turbine main shaft center hole 3 is represented as:

[0020]

[0021] wherein, is the relative change rate of the leakage water quantity of the water turbine main shaft center hole, is the theoretical leakage water quantity of the water turbine main shaft center hole.

[0022] Further, the specific steps for determining whether the leakage water quantity of the water turbine main shaft center hole 3 increases according to the relative change rate of the leakage water quantity of the water turbine main shaft center hole 3 are:

[0023] like and If the leakage rate is high, it is determined that the leakage rate of the turbine main shaft center hole 3 has increased; otherwise, it is determined that the leakage rate of the turbine main shaft center hole 3 is normal.

[0024] Furthermore, in step two, the determination of whether natural air replenishment has occurred is performed by a flow indicator 4 installed in the central hole 3 of the spindle.

[0025] Furthermore, the time set in step three is 10 minutes.

[0026] Furthermore, the hydro-generator is either a mixed-flow or axial-flow fixed-blade type.

[0027] The beneficial effects of this invention are:

[0028] This application achieves fault detection of the turbine main shaft center hole guided air supply valve located at the turbine main shaft center hole on in-service units by judging whether natural air supply phenomenon will continue to occur in the rotating vortex zone of the turbine generator unit under partial load, and whether the leakage of water in the turbine main shaft center hole increases when the unit is shut down. Attached Figure Description

[0029] Figure 1 This is a flowchart of the application process;

[0030] Figure 2 A schematic diagram of the turbine's operating range and rotating vortex zone;

[0031] Figure 3 This is a schematic diagram of the structure of this application;

[0032] Figure 4 A schematic diagram of the overall structure of a guide-type air supply valve;

[0033] Figure 5 Diagram of the sealing structure of a guide-type air supply valve;

[0034] Figure 6 A schematic diagram of the air supply state for the guided air supply valve. Detailed Implementation

[0035] It should be noted that, where there is no conflict, the various embodiments disclosed in this application can be combined with each other.

[0036] Specific Implementation Method 1: The fault detection method for the guide-type air supply valve of the main shaft center hole of a vertical turbine as described in this implementation method includes:

[0037] Step 1: Start the hydro-generator unit;

[0038] Step 2: The hydro-generator unit operates stably in the rotating vortex zone 101;

[0039] Step 3: Determine whether natural gas replenishment has occurred using the flow indicator 4: If natural gas replenishment has occurred, proceed to Step 4; otherwise, proceed to Step 10.

[0040] Step 4: Maintain natural Qi replenishment for 10 minutes;

[0041] Step 5: Shut down the hydro-generator unit;

[0042] Step Six: Level gauge 232 is triggered and timing begins;

[0043] Step 7: Level gauge 31 is triggered, and the timing ends;

[0044] Step 8: Calculate the leakage rate of the turbine main shaft center hole:

[0045] Step Nine: Determine if the leakage rate of the turbine main shaft center hole has increased: If the leakage rate of the turbine main shaft center hole has increased, proceed to Step Ten; otherwise, proceed to Step Eleven.

[0046] Step 10: The pilot-operated air supply valve 5 malfunctions;

[0047] Step 11: The pilot-operated air supply valve 5 is functioning normally.

[0048] The corresponding meanings of the reference numerals in the figure are as follows: 1-Roller, 2-Main shaft, 3-Main shaft center hole, 4-Flow indicator, 5-Guide air supply valve, 12-Roller outlet end of main shaft center hole, 31-Level gauge one, 32-Level gauge two, 51-Valve plate, 52-Guide rod, 53-Locking nut, 54-Valve seat, 55-Return spring, 56-Piston, 57-Cover, 58-Pressure sleeve assembly, 59-Tightening 100-Turbine operating range, 101-Rotating vortex zone, 511-Clamping screw, 512-Pressure plate, 513-Sealing ring, 514-Valve plate sealing surface, 541-Main guide sleeve, 542-Valve seat sealing surface, 571-Screw, 572-Gland, 573-Auxiliary guide sleeve, 581-Adjusting sleeve, 582-Gasket, 583-Anti-loosening nut A, 584-Anti-loosening nut B.

[0049] Mixed-flow and axial-flow fixed-blade turbines operate within the turbine operating range marked 100. Within this operating range, under partial load conditions, there exists a region called the rotating vortex zone 101, characterized by a rapidly decreasing pressure due to the generation of a rotating vortex band at the runner outlet. When the turbine-generator unit operates within this rotating vortex zone 101, the deviation from optimal design conditions leads to the generation of a rotating vortex band and increased pressure pulsation in the turbine's tailrace. This increased pressure pulsation in the tailrace causes an increase in the turbine-generator unit's vibration swing, posing a potential safety hazard. The most commonly used engineering method to reduce turbine pressure pulsation caused by the rotating vortex band is natural air injection. Natural air injection utilizes the characteristic that the pressure at the runner outlet 12 of the main shaft center hole at the outlet of the rotating vortex band in mixed-flow and axial-flow fixed-blade turbines is significantly lower than atmospheric pressure. Air is introduced into the runner outlet 12 of the main shaft center hole through the turbine's natural air injection system. Conventional natural air supply systems for mixed-flow and axial-flow fixed-propeller turbines are designed according to the following principles: A guide-type air supply valve 5 is installed on the center hole 3 of the turbine main shaft 2. This guide-type air supply valve 5 is a one-way valve, allowing air to enter the turbine flow channel only through the center hole 3 from the generator end 6 of the main shaft center hole to the runner outlet end 12 of the main shaft center hole. Currently, the guide-type air supply valve is the most widely used air supply valve in mixed-flow and axial-flow fixed-propeller turbines. The structure of the guide-type air supply valve is as follows: Figure 4 and Figure 5As shown: The guided air supply valve 5 consists of main functional components such as valve plate 51, guide rod 52, valve seat 54, return spring 55, piston 56, cover 57, and clamping sleeve assembly 58. The guide rod 52 drives the valve plate 51 to move up and down, realizing the functions of air supply and sealing respectively: air supply, when the hydro-generator unit is running in the rotating vortex zone 101, air flows into the turbine channel from the generator end 6 of the main shaft center hole to the runner outlet end 12 of the main shaft center hole; sealing, when the unit is stopped, prevents high-pressure water at the runner outlet end 12 of the main shaft center hole from overflowing in large quantities at the generator rotor through the main shaft center hole 3. The lower end of the guide rod 52 is connected to the valve plate 51 via a locking nut 53, while the other end of the guide rod 52 is connected to the piston 56 via a clamping sleeve assembly 58. The main guide sleeve 541 and auxiliary guide sleeve 573 provide radial positioning for the guide rod 52, while the return spring 55 consistently provides an upward restoring force to the guide rod 52, giving the valve plate 51 a tendency to move upwards. The valve seat 54 and the cover 57 are connected by fastening bolts 59. The return spring 55 is located in the enclosed space formed by the valve seat 54 and the cover 57, with the piston 56 located above the return spring 55 within this enclosed space. The return spring 55 is located within the enclosed space formed by the valve seat 54, the cover 57, and the piston 56, with the centerline of the guide rod 52 coinciding with that of the return spring 55. The guide rod 52 can move axially along the main guide sleeve 541 on the valve seat 54, with the main guide sleeve 541 serving a guiding function. Screw 571 secures the gland 572 to the cover 57, and the auxiliary guide sleeve 573 is nested on the gland 572. The center lines of the main guide sleeve 541 and the auxiliary guide sleeve 573 coincide. When the guide rod 52, piston 56, and clamping sleeve assembly 58 move axially, the main guide sleeve 541 and the auxiliary guide sleeve 573 act as guides. The return spring 55 is under compression, and the piston 56 is always subjected to the upward elastic force of the return spring 55. The clamping sleeve assembly 58 consists of an adjusting sleeve 581, a washer 582, a lock nut A 583, and a lock nut B 584. It can connect the piston 56 to the guide rod 52 and adjust the elastic force of the return spring 55 by adjusting the axial position of the piston 56. The clamping screw 511 fixes the sealing ring 513 to the sealing working surface A 514 of the valve plate 51 through the pressure plate 512. The valve plate sealing surface 514 and the valve seat sealing surface 542 can be pressed together. The working principle of the pilot-type air replenishment valve is as follows: the return spring 55 acting on the piston 56 exerts an upward force, which drives the valve plate 51 to move upward through the guide rod 52, so that the sealing ring 513 on the valve plate sealing surface 514 is pressed against the valve seat sealing surface 542, and the pilot-type air replenishment valve 5 closes, forming an effective seal.When the turbine operates in the rotating vortex zone 101, the pressure within the spiral cavity of the rotating vortex zone in mixed-flow and axial-flow fixed-blade turbines is much lower than atmospheric pressure. This results in a significant decrease in water pressure at the runner outlet 12 of the main shaft center hole, increasing the pressure difference between the generator end 6 and the runner outlet 12. This creates a continuously increasing downward pull on the valve plate 51. When the upward force of the return spring 55 of the guide-type air supply valve 5 in the center hole 3 is less than the downward pull on the valve plate 51, the valve plate 51 moves downward, creating a gap between the valve plate sealing surface 514 and the valve seat sealing surface 542. The guide-type air supply valve 5 opens, allowing air to enter the spiral cavity of the rotating vortex zone from the center hole 3 along the direction from the generator end 6 to the runner outlet 12. Figure 6 As indicated by the middle arrow, with the continuous replenishment of air, the local pressure at the spindle center hole 3 rotor outlet end 12 will increase accordingly. The pressure difference between the spindle center hole generator end 6 and the spindle center hole rotor outlet end 12 will gradually decrease, and the downward force formed by the pressure difference between the spindle center hole generator end 6 and the spindle center hole rotor outlet end 12 on the valve plate 51 will also decrease. When the downward force acting on the valve plate 51 is less than the upward force of the return spring 55, the valve plate 51 will move upward under the push of the return spring 55, pressing the sealing ring 513 tightly onto the valve seat sealing surface 542. The tight fit between the valve plate sealing surface 514 and the valve seat sealing surface 542 isolates the generator end 6 of the main shaft center hole 3 from the runner outlet end 12 of the main shaft center hole, forming an effective seal. This ensures that external air cannot enter the turbine flow channel and prevents water in the turbine flow channel from overflowing from the runner outlet end 12 of the main shaft center hole through the center hole 3 to the generator end 6 of the main shaft center hole when the unit is stopped, even under the influence of the tailwater level which is higher than the installation elevation of the turbine generator rotor.

[0050] Guided-type air replenishment valves are generally not prone to failure. Occasional failures of guided-type air replenishment valves manifest as jamming of the moving parts during air replenishment and seal failure during shutdown.

[0051] The jamming phenomenon of the kinematic pair under the air replenishment state can be divided into the following two situations: In the first situation, once the kinematic pair between the guide rod 52 and the main guide sleeve 541 jams, the guide rod 52 cannot move axially along the main guide sleeve 541. This will directly cause the guide air replenishment valve 5 to fail to open and form a normal air replenishment state when the turbine is running in the rotating vortex zone 101. It will be unable to suppress the sharp drop in pressure in the rotating vortex zone, which will lead to an increase in the pressure pulsation of the turbine tailrace pipe, and ultimately cause an increase in the vibration swing value of the turbine generator unit, making it impossible to ensure the safe and stable operation of the unit. In the second scenario, if the guide rod 52 and the auxiliary guide sleeve 573 become stuck, the guide rod 52 will not be able to move axially along the auxiliary guide sleeve 573. This will directly cause the guide-type air supply valve to fail to open and form a normal air supply state when the turbine is running in the rotating vortex zone 101. This will prevent the turbine from suppressing the sharp drop in pressure in the rotating vortex zone, which will lead to an increase in the pressure pulsation of the turbine's tailrace pipe. Ultimately, this will cause an increase in the vibration swing value of the turbine generator unit, making it impossible to guarantee the safe and stable operation of the unit.

[0052] The sealing failure phenomenon under shutdown state can also be divided into the following two situations: In the first situation, if the return spring 55 has material defects, processing defects or heat treatment defects, fatigue fracture will occur under the action of alternating stress in the air replenishment state, causing the return spring 55 to break. This causes the upward elastic force on the assembly composed of piston 56, guide rod 52 and valve plate 51 to disappear. The valve plate sealing surface 514 cannot be pressed tightly with the valve seat sealing surface 542, and the gap between the valve plate sealing surface 514 and the valve seat sealing surface 542 cannot be closed. The sealing effect on the water pressure at the turbine runner fails, resulting in a large amount of water at the turbine runner overflowing from the generator rotor in a short time under pressure through the main shaft center hole 3. In the second scenario, due to long-term alternating action, the sealing ring 513 may age and fail or suffer large-scale local damage. In this case, although the valve plate sealing surface 514 and the valve seat sealing surface 542 are pressed together, it is still impossible to guarantee an effective seal between the valve plate sealing surface 514 and the valve seat sealing surface 542. This can also lead to an accident where water at the turbine runner overflows in large quantities at the generator rotor through the central hole of the main shaft in a short period of time.

[0053] Since the pilot-operated air supply valve 5 is installed underwater, it is impossible to directly evaluate whether it has malfunctioned through conventional inspection methods. Only indirect detection methods can be used to evaluate the condition of the pilot-operated air supply valve 5.

[0054] When the turbine is running in the rotating vortex zone 101, the guide-type air supply valve 5 is open, and the turbine is in an air supply state. This means that there is a continuous and sufficient airflow between the generator end 6 of the main shaft center hole 3 and the runner outlet end 12 of the main shaft center hole. If a malfunction occurs where the moving pair of the guide-type air supply valve 5 jams during air supply, the valve will fail to open and air supply will not be established. In other words, there will be no continuous and sufficient airflow between the generator end 6 of the main shaft center hole 3 and the runner outlet end 12 of the main shaft center hole. To determine whether there is a continuous and sufficient airflow between the generator end 6 of the main shaft center hole 3 and the runner outlet end 12 of the main shaft center hole, a flow indicator 4 is installed in the main shaft center hole 3. The flow indicator 4 will emit a signal when airflow is present and will not emit a signal when no airflow is present. If the guided air supply valve 5 is working properly, when the turbine is running in the rotating vortex zone 101, due to the large pressure difference between the generator end 6 of the turbine's main shaft center hole and the runner outlet end 12 of the main shaft center hole, the valve plate 51 will move downwards, creating a gap between the valve plate sealing surface 514 and the valve seat sealing surface 542. Air will then continuously flow into the turbine's flow channel along the direction from the generator end 6 of the main shaft center hole to the runner outlet end 12 of the main shaft center hole within the center hole 3. At this time, the flow indicator 4 installed in the main shaft center hole 3 will send a signal indicating that air is continuously being supplied into the turbine's flow channel from the main shaft center hole 3. If the guided air supply valve 5 experiences a motion pair jamming fault, when the turbine is running in the rotating vortex zone 101, although... However, at this time, there is a large pressure difference between the generator end 6 and the runner outlet end 12 of the turbine main shaft center hole. But due to the jamming between the guide rod 52 and the main guide sleeve 541 or the guide rod 52 and the auxiliary guide sleeve 573, the guide rod 52 is stuck and cannot move, which causes the valve plate 51 to be unable to move downward. The valve plate sealing surface 514 and the valve seat sealing surface 542 cannot form a gas supply gap. The gas supply channel entering the turbine flow channel in the center hole 3 along the direction from the generator end 6 to the runner outlet end 12 of the main shaft center hole cannot be opened. A continuous air flow cannot be formed between the generator end 6 and the runner outlet end 12 of the main shaft center hole, so the flow indicator 4 cannot send a signal that airflow has been detected.

[0055] In summary, when the turbine is running in the rotating vortex zone 101, if the flow indicator 4 sends a signal, it indicates that the guided air supply valve 5 is working normally; otherwise, it indicates that the guided air supply valve 5 has malfunctioned.

[0056] Generally speaking, the tailwater level of mixed-flow and axial-flow fixed-blade hydro-generator units is higher than the installation elevation of the hydro-generator rotor. The guide-type air supply valve 5 is used to ensure that the high-pressure water at the runner outlet end 12 of the main shaft center hole does not gush out in large quantities along the center hole 3 at the generator end 6 of the main shaft center hole. When the unit is stopped, it is necessary to ensure that the valve plate sealing surface 514 and the valve seat sealing surface 542 are pressed together to form an effective seal.

[0057] The sealing failure phenomenon under shutdown state can also be divided into the following two situations: In the first situation, if the return spring 55 has material defects, processing defects or heat treatment defects, fatigue failure will occur under the action of alternating stress during the gas replenishment state, resulting in fatigue fracture of the return spring 55. This causes the upward elastic force on the assembly composed of piston 56, guide rod 52 and valve plate 51 to disappear, the valve plate sealing surface 514 cannot be pressed tightly with the valve seat sealing surface 542, and the gap formed between the valve plate sealing surface 514 and the valve seat sealing surface 542 cannot be closed. The sealing effect on the water pressure at the outlet end 12 of the main shaft center hole wheel fails, resulting in a large amount of high-pressure water at the outlet end 12 of the main shaft center hole wheel overflowing at the generator rotor in a short time through the main shaft center hole 3. The second scenario involves the aging and failure of the sealing ring 513 due to long-term alternating action, or large-scale localized damage. In this case, although the valve plate sealing surface 514 and the valve seat sealing surface 542 are pressed together, an effective seal cannot be guaranteed between them. This can lead to a situation where pressurized water at the rotor outlet 12 of the main shaft center hole overflows in large quantities at the generator rotor in a short period through the main shaft center hole 3. In short, the sealing failure of the guided air supply valve 5 manifests as follows: after the air supply operation ends and the unit is quickly shut down, the main shaft center hole 3 is filled with air. If water seeps into the main shaft center hole 3 at this time, and the water level, i.e., the leakage rate, changes too rapidly, it indicates that the guided air supply valve 5 has failed to seal. To accurately, quickly, and effectively detect whether the guide-type air supply valve 5 has experienced sealing failure while the turbine is stopped, level gauge 1 (31) and level gauge 2 (32) are respectively placed in the main shaft center hole 3, with an elevation difference between them, where the elevation of level gauge 2 (32) is lower than that of level gauge 1 (31). The cross-sectional area of ​​the main shaft center hole 3 remains constant. By measuring the time it takes for the pressurized water entering the main shaft center hole 3 from the runner outlet 12 of the main shaft center hole to rise from the position of level gauge 2 (32) to the position of level gauge 1 (31), the leakage rate of the turbine main shaft center hole can be calculated using the following formula:

[0058]

[0059] In the formula:

[0060] : Water leakage from the center hole of the turbine main shaft ;

[0061] The flow diameter of the spindle center hole (3) ;

[0062] The vertical distance between level gauge 1 (31) and level gauge 2 (32) ;

[0063] The time difference between triggering level gauge 1 (31) and level gauge 2 (32) .

[0064] For turbine air supply valves of the type 5 (guided type), a certain amount of leakage is allowed in the seal formed between the valve plate sealing surface 514 and the valve seat sealing surface 542. This means a very small amount of high-pressure water from the turbine runner outlet 12 at the main shaft center hole is allowed to overflow along the center hole 3 from the turbine runner outlet 12 to the generator end 6 at the main shaft center hole, and be discharged through a specially designed overflow pipe. When a seal failure occurs during shutdown, because an effective seal cannot be formed between the valve plate sealing surface 514 and the valve seat sealing surface 542, a large amount of pressurized water from the turbine runner outlet 12 at the main shaft center hole will overflow from the main shaft center hole 3 to the generator rotor in a short period. In other words, the water flow rate from the turbine runner outlet 12 to the generator end 6 through the main shaft center hole 3 will far exceed the design allowable value. This indicates a seal failure during shutdown. Generally, a leakage rate exceeding the theoretical design value by 15% in the turbine main shaft center hole is considered a seal failure. To check if the leakage from the central bore of the turbine main shaft has increased, follow these steps:

[0065]

[0066] In the formula:

[0067] Theoretical leakage rate of the central bore of the turbine main shaft. ;

[0068] : The relative change rate of water leakage from the central bore of the turbine main shaft, dimensionless;

[0069] If satisfied and If the condition is met, it is determined that the leakage of water from the central hole of the turbine main shaft has increased; otherwise, it is determined that the leakage of water from the central hole of the turbine main shaft is normal.

[0070] The technical solution of this application achieves the accurate determination of the fault of the guide air valve of the center hole of the turbine main shaft; achieves the accurate determination of the fault of the valve plate seal failure of the guide air valve of the center hole of the turbine main shaft; and achieves the accurate determination of the working status of the guide air valve of the center hole of the turbine main shaft of the in-service hydro-generator unit.

[0071] It should be noted that the specific embodiments are merely explanations and illustrations of the technical solution of the present invention and should not be used to limit the scope of protection. Any modifications made in accordance with the claims and specification of the present invention that are only partial should still fall within the protection scope of the present invention.

Claims

1. A method for detecting a failure of a center hole guide type air supply valve of a vertical water turbine main shaft, characterized by The method comprises the following steps: Step one: setting a liquid level gauge one (31) and a liquid level gauge two (32) in the center hole (3) of the main shaft of the hydro-generator, the height of the liquid level gauge one (31) being higher than that of the liquid level gauge two (32); Step two: starting the hydro-generator unit, and determining whether natural air supplement occurs, if the natural air supplement occurs, executing step three, otherwise, the pilot air supplement valve (5) is faulty; Step three: maintaining the natural air supplement for a set time; Step four: stopping the hydro-generator unit, and obtaining the time triggered by the liquid level gauge one (31) and the liquid level gauge two (32) respectively, and obtaining the time difference; Step five: obtaining the flow diameter of the center hole (3) of the main shaft, and the height difference of the liquid level gauge one (31) and the liquid level gauge two, and combining the time difference obtained in step four, to obtain the actual leakage water quantity of the center hole (3) of the main shaft of the hydro-generator; Step six: obtaining the theoretical leakage water quantity of the center hole (3) of the main shaft of the hydro-generator, and determining whether the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator increases according to the theoretical leakage water quantity of the center hole (3) of the main shaft of the hydro-generator and the actual leakage water quantity of the center hole (3) of the main shaft of the hydro-generator, if the leakage water quantity increases, the pilot air supplement valve (5) is faulty, otherwise, the pilot air supplement valve (5) is not faulty.

2. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 1, characterized in that The actual leakage water quantity of the center hole (3) of the main shaft of the hydro-generator is represented as: wherein, is the water leakage amount of the center hole of the main shaft of the water turbine, is the flow diameter of the center hole (3) of the main shaft, is the vertical distance between the liquid level meter one (31) and the liquid level meter two (32), is the time difference of triggering the liquid level meter one and the liquid level meter two.

3. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 2, characterized in that In step six, the specific steps for determining whether the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator increases are as follows: According to the theoretical leakage water quantity of the center hole (3) of the main shaft of the hydro-generator and the actual leakage water quantity of the center hole (3) of the main shaft of the hydro-generator, obtaining the relative change rate of the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator, and determining whether the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator increases according to the relative change rate of the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator; The relative change rate of the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator is represented as: wherein, is the relative change rate of the leakage water quantity of the center hole of the main shaft of the water turbine, is the theoretical leakage water quantity of the center hole of the main shaft of the water turbine.

4. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 3, characterized in that The specific steps for determining whether the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator increases according to the relative change rate of the leakage water quantity of the center hole (3) of the main shaft of the hydro-generator are as follows: If and , it is determined that the water turbine main shaft center hole (3) has increased water leakage, otherwise, it is determined that the water turbine main shaft center hole (3) has normal water leakage.

5. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 1, characterized in that In step two, whether the natural air supplement occurs is determined by the flow indicating signal (4) arranged in the center hole (3) of the main shaft.

6. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 1, characterized in that The set time in step three is 10 minutes.

7. The method for detecting the failure of the air supply valve of the vertical water turbine main shaft center hole guide type according to claim 1, characterized in that The hydro-generator is a mixed-flow type or an axial fixed-paddle type.

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