Fault detection method for guide type gulp valve of vertical water turbine spindle center hole

Abstract

The invention discloses a fault detection method for a guide type gulp valve of a vertical water turbine spindle center hole, relates to the technical field of hydroelectric generation, and aims to solve the problem that whether a fault occurs or not cannot be judged since the guide type gulp valve is mounted at the water turbine spindle center hole and the state of the guide type gulp valve cannot be directly checked on an in-service unit in the prior art. Whether the water-turbine generator set continuously generates a natural air supply phenomenon in a partial load rotating vortex zone area or not and whether the water leakage amount of a central hole of a main shaft of a water turbine is increased or not when the set is in a shutdown state are judged; the fault detection of the water turbine main shaft center hole guide type gulp valve arranged at the water turbine main shaft center hole on an in-service unit is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of hydropower generation, and particularly to a fault detection method for a vertical turbine main shaft center hole guided air inlet valve. Background Art

[0002] Hydropower generation is a process of converting water energy into mechanical energy by a water turbine and then converting the mechanical energy into electrical energy by a hydrogenerator set. Hydrogenerator sets, with their mature technology and wide application range, have become the most widely used type of hydropower generation equipment. Francis turbines and fixed-pitch axial-flow turbines are the most common and widely used types of water turbines. During the process of converting water energy into mechanical energy by Francis turbines and fixed-pitch axial-flow turbines, as the prime mover, the water turbine must operate within a wide load range according to the needs of the power grid and cannot always operate near the optimal efficiency point. As single-regulated water turbines, due to their own form limitations, when Francis turbines and fixed-pitch axial-flow turbines operate away from the optimal efficiency point, the flow state in the flow passage deteriorates. A typical phenomenon is that a rotating vortex band will be generated at the runner outlet under partial load conditions. The pressure in the rotating vortex band region drops sharply, generating a rotating vortex band extending from the runner outlet to the draft tube. The rotating vortex band is the main cause of the increased pressure pulsation in the draft tubes of Francis turbines and fixed-pitch axial-flow turbines. The increase in the pressure pulsation in the draft tubes of Francis turbines and fixed-pitch axial-flow turbines often leads to an increase in the vibration and swing values of the hydrogenerator set, seriously affecting the safe and stable operation of the unit. The conventional treatment method is to design the water turbine main shaft as a hollow through-type structure with a center hole. A one-way air inlet valve is installed at the center hole of the water turbine main shaft. When the unit operates under partial load conditions and the pressure at the runner outlet drops to the set value due to the rotating vortex band, the one-way air inlet valve opens. 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 replenishment of air, the pressure in the rotating vortex band region shows an upward trend. Once the pressure in the rotating vortex band region returns above the set value of the one-way air inlet valve, the one-way air inlet valve closes and air no longer enters the rotating vortex band region. This process is called natural air replenishment in the industry. As long as Francis and fixed-pitch axial-flow hydrogenerator sets operate in the rotating vortex band region, the natural air replenishment phenomenon will continuously occur, and the above one-way air inlet valve will continuously repeat the above opening and closing actions to ensure that the pressure in the rotating vortex band region does not drop too sharply, thereby avoiding the increase in the pressure pulsation in the water turbine draft tube, and further preventing the safety hazard of the increase in the vibration and swing values of the hydrogenerator set, ultimately achieving the purpose of ensuring the safe and stable operation of the unit.

[0003] Meanwhile, considering improving the cavitation performance of the turbine and comprehensively reducing the level of pressure pulsation energy of the turbine, generally speaking, the tail water level of Francis and fixed - blade axial - flow turbine - generator units is higher than the installation elevation of the turbine - generator rotor. That is to say, if no corresponding measures are taken, when the unit is in the shutdown state, the high - pressure water at the runner of the turbine will overflow at the generator rotor through the central hole of the main shaft. Generally, in engineering, a one - way air - inlet valve is set at the central hole of the main shaft and supplemented by a special overflow water - pipe structure at the central hole of the main shaft at the generator rotor to solve the above - mentioned problem. Theoretically, when the unit is in the shutdown state, the one - way air - inlet valve prevents the pressure water in the turbine flow passage from entering the central hole of the turbine main shaft; even if, due to the structural reasons of the one - way air - inlet valve, it cannot completely prevent the pressure water in the turbine flow passage from entering the central hole of the turbine main shaft, only a very small amount of leakage water enters the central hole of the turbine main shaft, and the leakage volume is also very small. The overflow water - pipe structure set at the central hole of the main shaft at the generator rotor is considered to provide a drainage channel for the above - mentioned leakage water. However, due to structural limitations, the flow - through capacity of the overflow water - pipe at the central hole of the main shaft is designed according to the above - mentioned leakage water volume, and the margin is not very large. Once an accident occurs to the one - way air - inlet valve and the leakage volume of the one - way air - inlet valve increases too much, the drainage of the leakage water will be blocked, and even the leakage water will overflow, causing an accident of flooding the generator.

[0004] There are many types of one - way air - inlet valves for the central hole of the turbine main shaft, but the most widely used is the guided air - inlet valve. Since the guided air - inlet valve is installed at the central hole of the turbine main shaft, it is impossible to directly check its state on the in - service unit, and thus it is impossible to determine whether a fault has occurred. Summary of the Invention

[0005] The object of the present invention is to provide a method for detecting faults of a guided air - inlet valve for the central hole of a vertical turbine main shaft, aiming at the problem in the prior art that since the guided air - inlet valve is installed at the central hole of the turbine main shaft, it is impossible to directly check its state on the in - service unit, and thus it is impossible to determine whether a fault has occurred.

[0006] The technical solution adopted by the present invention to solve the above - mentioned technical problems is as follows:

[0007] A method for detecting faults of a guided air - inlet valve for the central hole of a vertical turbine main shaft includes the following steps:

[0008] Step 1: Install a first liquid level gauge 31 and a second liquid level gauge 32 in the central hole 3 of the main shaft of the hydro - generator, and the elevation of the first liquid level gauge 31 is higher than that of the second liquid level gauge 32;

[0009] Step 2: Start the hydro - generator unit and determine whether natural air intake occurs. If natural air intake occurs, execute Step 3; otherwise, the guided air - inlet valve 5 has a fault;

[0010] Step 3: Maintain natural air supply within the set time;

[0011] Step 4: Stop the water turbine generator set, and respectively obtain the triggering times of level gauge 1 31 and level gauge 2 32 to get the time difference;

[0012] Step 5: Obtain the flow - through diameter of the main shaft center hole 3 of the water turbine, as well as the elevation difference between level gauge 1 31 and level gauge 2, and combine with the time difference obtained in Step 4 to get the actual leakage water volume of the main shaft center hole 3 of the water turbine;

[0013] Step 6: Obtain the theoretical leakage water volume of the main shaft center hole 3 of the water turbine, and judge whether the leakage water volume of the main shaft center hole 3 of the water turbine increases based on the theoretical leakage water volume and the actual leakage water volume of the main shaft center hole 3 of the water turbine. If it increases, the guided air - intake valve 5 fails; otherwise, the guided air - intake valve 5 does not fail.

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

[0015]

[0016] where Q M is the leakage water volume of the main shaft center hole of the water turbine, D is the flow - through diameter of the main shaft center hole 3, L is the vertical distance between level gauge 1 31 and level gauge 2, and t is the time difference for triggering level gauge 1 and level gauge 2.

[0017] Further, in Step 6, the specific steps for judging whether the leakage water volume of the main shaft center hole 3 of the water turbine increases are as follows:

[0018] Based on the theoretical leakage water volume and the actual leakage water volume of the main shaft center hole 3 of the water turbine, obtain the relative change rate of the leakage water volume of the main shaft center hole 3 of the water turbine, and judge whether the leakage water volume of the main shaft center hole 3 of the water turbine increases according to the relative change rate of the leakage water volume of the main shaft center hole 3 of the water turbine;

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

[0020]

[0021] where ΔQ is the relative change rate of the leakage water volume of the main shaft center hole of the water turbine, and Q T is the theoretical leakage water volume of the main shaft center hole of the water turbine.

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

[0023] If ΔQ≥15% and Q M-Q T If > 0, it is determined that the leakage water volume of the central hole 3 of the turbine main shaft increases; otherwise, it is determined that the leakage water volume of the central hole 3 of the turbine main shaft is normal.

[0024] Further, in step two, it is judged whether natural air replenishment occurs through the flow indicator 4 arranged in the central hole 3 of the main shaft.

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

[0026] Further, the hydrogenerator is a Francis turbine or a fixed - blade axial - flow turbine.

[0027] The beneficial effects of the present invention are:

[0028] This application realizes the fault detection of the guided air - replenishing valve for the central hole of the turbine main shaft arranged at the central hole of the turbine main shaft on the in - service unit by judging whether natural air replenishment continuously occurs in the partial - load rotating vortex zone of the hydro - generator unit and whether the leakage water volume of the central hole of the turbine main shaft increases when the unit is in the shutdown state. Description of the Drawings

[0029] Figure 1 is the flow chart of this application;

[0030] Figure 2 is the schematic diagram of the operation range of the turbine and the rotating vortex zone;

[0031] Figure 3 is the schematic structural diagram of this application;

[0032] Figure 4 is the schematic diagram of the overall structure of the guided air - replenishing valve;

[0033] Figure 5 is the seal structure diagram of the guided air - replenishing valve;

[0034] Figure 6 is the schematic diagram of the air - replenishing state of the guided air - replenishing valve. Detailed Embodiments

[0035] It should be specifically noted that, without conflict, the various embodiments disclosed in this application can be combined with each other.

[0036] Detailed Embodiment 1: A method for detecting the fault of the guided air - replenishing valve for the central hole of the vertical turbine main shaft described in this embodiment 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 air replenishment has occurred through the flow indicator 4. If natural air replenishment has occurred, proceed to Step 4; otherwise, proceed to Step 10.

[0040] Step 4: Maintain natural air replenishment for 10 minutes.

[0041] Step 6: Shut down the hydro-generating unit.

[0042] Step 6: The second liquid level gauge 32 is triggered and starts timing.

[0043] Step 7: The first liquid level gauge 31 is triggered and the timing ends.

[0044] Step 8: Calculate the leakage water volume of the central hole of the turbine shaft.

[0045] Step 9: Determine whether the leakage water volume of the central hole of the turbine shaft has increased. If the leakage water volume of the central hole of the turbine shaft has increased, proceed to Step 10; otherwise, proceed to Step 11.

[0046] Step 10: The guided air intake valve 5 fails.

[0047] Step 11: The guided air intake valve 5 is normal.

[0048] The meanings corresponding to the reference numerals in the figure are as follows: 1 - runner, 2 - main shaft, 3 - central hole of the main shaft, 4 - flow indicator, 5 - guided air intake valve, 12 - outlet end of the runner of the central hole of the main shaft, 31 - first liquid level gauge, 32 - second liquid level gauge, 51 - valve plate, 52 - guide rod, 53 - locking nut, 54 - valve seat, 55 - return spring, 56 - piston, 57 - cover body, 58 - compression sleeve assembly, 59 - fastening bolt, 100 - operating range of the water turbine, 101 - rotating vortex band area, 511 - fastening screw, 512 - pressing 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] Francis and fixed - blade axial - flow turbines operate within the range marked as 100 of the turbine operating range. Within the turbine operating range 100, under partial - load conditions, there is a region where a rotating vortex rope is generated at the runner outlet and the pressure drops sharply, which is called the rotating vortex rope region 101. When the hydro - generator unit operates in the rotating vortex rope region 101, due to deviation from the optimal design condition, a rotating vortex rope will be generated and the pressure pulsation in the draft tube of the turbine will increase. The increase in the pressure pulsation of the turbine draft tube will cause the vibration and swing value of the hydro - generator unit to increase, thus becoming a potential hazard to the safe operation of the unit. The most commonly used method in engineering to reduce the turbine pressure pulsation caused by the rotating vortex rope is natural air admission. Natural air admission is a process of injecting air into the runner outlet end 12 of the main - shaft center hole at the outlet of the runner 1 according to the characteristic that the pressure at the runner outlet end 12 of the main - shaft center hole of the Francis and fixed - blade axial - flow turbines with a rotating vortex rope is much lower than the atmospheric pressure through the natural air - admission system of the turbine. The natural air - admission systems of conventional Francis and fixed - blade axial - flow turbines are designed according to the following principle: A pilot - operated air - admission valve 5 is installed on the center hole 3 of the turbine main - shaft 2. The pilot - operated air - admission valve 5 is a one - way valve that only allows air to enter the turbine flow passage 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 most widely used air - admission valve on Francis and Kaplan turbines is the pilot - operated air - admission valve. The structure of the pilot - operated air - admission valve is as Figure 4 and Figure 5As shown in the figure: The guided air replenishing valve 5 is composed of main functional components such as a valve plate 51, a guide rod 52, a valve seat 54, a return spring 55, a piston 56, a cover body 57, and a compression sleeve assembly 58. The guide rod 52 drives the valve plate 51 to move up and down to achieve the functions of air replenishment and sealing respectively: For air replenishment, when the hydro-generating unit operates in the rotating vortex belt area 101, air enters the water turbine flow channel from the generator end 6 of the main shaft center hole towards the runner outlet end 12 of the main shaft center hole; for sealing, when the unit is in the shutdown state, it prevents a large amount of high-pressure water at the runner outlet end 12 of the main shaft center hole from overflowing 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 through a locking nut 53, and the other end of the guide rod 52 is connected to the piston 56 through the compression sleeve assembly 58. The main guide sleeve 541 and the auxiliary guide sleeve 573 provide radial positioning for the guide rod 52, and the return spring 55 always provides an upward restoring force for the guide rod 52, making the valve plate 51 tend to move upward. The valve seat 54 and the cover body 57 are connected together through fastening bolts 59. The return spring 55 is located in the enclosed space formed by the valve seat 54 and the cover body 57, and the piston 56 is located above the return spring 55 in this enclosed space. The return spring 55 is located in the enclosed space formed by the valve seat 54, the cover body 57, and the piston 56, and the center lines of the guide rod 52 and the return spring 55 coincide. The guide rod 52 can move axially along the main guide sleeve 541 on the valve seat 54, and the main guide sleeve 541 plays a guiding role. A screw 571 fastens the gland 572 to the cover body 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, the piston 56, and the compression sleeve assembly 58 move axially, the main guide sleeve 541 and the auxiliary guide sleeve 573 play a guiding role. The return spring 55 is in a compressed state, and the piston 56 is always subjected to the upward elastic force of the return spring 55. The compression sleeve assembly 58 is composed of an adjustment sleeve 581, a gasket 582, a locknut A 583, and a locknut B 584. It can not only connect the piston 56 and the guide rod 52 together, but also adjust the elastic force of the return spring 55 by adjusting the axial position of the piston 56. A compression screw 511 fixes the sealing ring 513 on the sealing working surface A 514 of the valve plate 51 through a pressing plate 512. The valve plate sealing surface 514 and the valve seat sealing surface 542 can be pressed together. The working principle of the guided air replenishing valve is as follows: The upward elastic force of the return spring 55 acting on the piston 56 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 tightly on the valve seat sealing surface 542, and the guided air replenishing valve 5 closes to form an effective seal.When the water turbine operates in the rotating vortex band area 101, since the pressure in the spiral cavity of the rotating vortex band of Francis and fixed - blade axial - flow turbines is much lower than the atmospheric pressure, the water pressure at the runner outlet end 12 of the main shaft central hole will be significantly reduced, and the pressure difference between the generator end 6 and the runner outlet end 12 of the main shaft central hole increases, resulting in an increasing downward pulling force on the valve plate 51. When the upward elastic force of the return spring 55 of the pilot - type air - admission valve 5 in the central hole 3 is less than the downward pulling force on the valve plate 51, the valve plate 51 will move downward, forming a gap between the valve plate sealing surface 514 and the valve seat sealing surface 542, and the pilot - type air - admission valve 5 is opened. Air enters the spiral cavity of the rotating vortex band from the central hole 3 along the direction from the generator end 6 to the runner outlet end 12 of the main shaft central hole, as shown by the arrow in. Figure 6 As the air is continuously replenished, the local pressure at the runner outlet end 12 of the main shaft central hole 3 will rise accordingly, the pressure difference between the generator end 6 and the runner outlet end 12 of the main shaft central hole will gradually decrease, and the downward pulling force formed by the pressure difference between the generator end 6 and the runner outlet end 12 of the main shaft central hole acting on the valve plate 51 will also decrease. When the downward pulling force acting on the valve plate 51 is less than the upward elastic 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 against the valve seat sealing surface 542. The tight combination state of the valve plate sealing surface 514 and the valve seat sealing surface 542 isolates the generator end 6 to the runner outlet end 12 of the main shaft central hole on the central hole 3, forming an effective seal, which not only ensures that external air cannot enter the water turbine flow passage, but also prevents the water in the water turbine flow passage from overflowing a large amount at the generator end 6 of the main shaft central hole from the runner outlet end 12 of the main shaft central hole under the action of the tail water level higher than the installation elevation of the water - turbine generator rotor when the unit is in the shutdown state.

[0050] Generally speaking, the pilot - type air - admission valve is not prone to failure. The occasional failures of the pilot - type air - admission valve 5 are manifested as the jamming of the moving pair in the air - admission state and the sealing failure in the shutdown state.

[0051] The jamming phenomenon of the moving pair in the air-supply state can be divided into the following two situations: In the first situation, once the jamming phenomenon occurs between the moving pair of the guide rod 52 and the main guide sleeve 541, the guide rod 52 cannot make axial movement along the main guide sleeve 541, which will directly lead to the failure of the guide air-supply valve 5 to open and form a normal air-supply state when the turbine is operating in the rotating vortex belt area 101, and the rapid drop in pressure in the rotating vortex belt area cannot be suppressed, which in turn leads to an increase in the pressure pulsation of the turbine tail water pipe, and finally causes the vibration swing value of the turbine generator set to increase, and the safe and stable operation of the unit cannot be guaranteed. In the second case, a jam occurs between the guide rod 52 and the auxiliary guide sleeve 573, and the guide rod 52 cannot make axial movement along the auxiliary guide sleeve 573, which will directly lead to the failure of the guide air supply valve to open and form a normal air supply state when the turbine is operating in the rotating vortex belt area 101, and the failure to suppress the sharp drop in pressure in the rotating vortex belt area, which in turn leads to an increase in the pressure pulsation of the turbine tail water pipe, and finally causes the vibration swing value of the turbine generator set to increase, making it impossible to ensure the safe and stable operation of the unit.

[0052] The sealing failure phenomenon in the shutdown state can also be divided into the following two situations: In the first situation, once the return spring 55 has material defects, processing defects or heat treatment defects, fatigue fracture will occur under the action of the alternating stress in the air replenishment state, causing the return spring 55 to break, causing the upward elastic force on the combination of the piston 56, the guide rod 52 and the valve plate 51 to disappear, and the valve plate sealing surface 514 cannot be pressed together with the valve seat sealing surface 542. The gap between the valve plate sealing surface 514 and the valve seat sealing surface 542 cannot be closed, and the sealing effect on the water pressure at the turbine runner fails, resulting in the water at the turbine runner under the action of pressure. The accident occurs that a large amount of water overflows from the generator rotor through the main shaft center hole 3 in a short time. In the second case, also due to long-term alternating effects, the sealing ring 513 ages and fails or is partially damaged in large size. At this time, although the valve plate sealing surface 514 and the valve seat sealing surface 542 are pressed together, there is no guarantee that an effective seal will be formed between the valve plate sealing surface 514 and the valve seat sealing surface 542. An accident may occur in which a large amount of water at the turbine runner overflows through the main shaft center hole at the generator rotor in a short time.

[0053] Since the guided air supply valve 5 is installed underwater, it is impossible to directly evaluate whether it has a fault through conventional inspection means, and the state of the guided air supply valve 5 can only be evaluated by an indirect detection method.

[0054] When the water turbine operates in the rotating vortex zone 101, the guiding air intake valve 5 opens, and the water turbine is in the air intake state, that is, there is a continuous sufficient air flow in the main shaft central hole 3 from the generator end 6 of the main shaft central hole to the runner outlet end 12 of the main shaft central hole. Once a sticking fault occurs in the moving pair of the guiding air intake valve 5 in the air intake state, it is manifested as that when the water turbine operates in the rotating vortex zone 101, the guiding air intake valve 5 cannot open and cannot form an air intake state, that is, there is no continuous sufficient air flow in the main shaft central hole 3 from the generator end 6 of the main shaft central hole to the runner outlet end 12 of the main shaft central hole. To judge whether there is a continuous sufficient air flow in the main shaft central hole 3 from the generator end 6 of the main shaft central hole to the runner outlet end 12 of the main shaft central hole, a flow indicator 4 is arranged in the main shaft central hole 3. When there is air flow passing through, the flow indicator 4 will send out a signal, and when there is no air flow passing through, there will be no signal sent out. If the guiding air intake valve 5 works normally, when the water turbine operates in the rotating vortex zone 101, due to the large pressure difference between the generator end 6 of the main shaft central hole of the water turbine and the runner outlet end 12 of the main shaft central hole, the valve plate 51 will move downward, forming a gap between the valve plate sealing surface 514 and the valve seat sealing surface 542, and air will continuously flow in the central hole 3 along the direction from the generator end 6 of the main shaft central hole to the runner outlet end 12 of the main shaft central hole in the water turbine flow passage. At this time, the flow indicator 4 arranged in the main shaft central hole 3 will send a signal indicating that air is continuously supplemented into the water turbine flow passage from the main shaft central hole 3; if a sticking fault occurs in the moving pair of the guiding air intake valve 5, when the water turbine operates in the rotating vortex zone 101, although there is a large pressure difference between the generator end 6 of the main shaft central hole of the water turbine and the runner outlet end 12 of the main shaft central hole at this time, due to the sticking phenomenon between the guide rod 52 and the main guide sleeve 541 or between the guide rod 52 and the auxiliary guide sleeve 573, the guide rod 52 is stuck and cannot move, resulting in the valve plate 51 unable to move downward, and the air intake gap cannot be formed between the valve plate sealing surface 514 and the valve seat sealing surface 542. The air intake passage entering the water turbine flow passage in the central hole 3 along the direction from the generator end 6 of the main shaft central hole to the runner outlet end 12 of the main shaft central hole cannot be opened, and a continuous air flow cannot be formed between the generator end 6 of the main shaft central hole and the runner outlet end 12 of the main shaft central hole, and the flow indicator 4 cannot send out a signal indicating that air flow has passed through.

[0055] To sum up, when the water turbine operates in the rotating vortex zone 101, if the flow indicator 4 sends out a signal, it indicates that the guiding air intake valve 5 works normally; otherwise, it indicates that the guiding air intake valve 5 has a fault.

[0056] Generally speaking, the tail water levels of Francis and fixed-pitch axial-flow hydro-generator units are both higher than the installation elevation of the hydro-generator rotor. As a safety measure to prevent a large amount of high-pressure water at the runner outlet end 12 of the main shaft center hole from gushing out along the center hole 3 at the generator end 6 of the main shaft center hole, the guiding air-intake valve 5 must ensure that the valve plate sealing surface 514 is tightly pressed against the valve seat sealing surface 542 to form an effective seal when the unit is in the shutdown state.

[0057] The seal failure phenomena in the shutdown state can be divided into the following two cases: In the first case, once the return spring 55 has material defects, machining defects, or heat treatment defects, under the action of alternating stress during the air-intake state, fatigue failure will occur, resulting in fatigue fracture of the return spring 55. As a result, the upward elastic force acting on the combined body composed of the piston 56, the guide rod 52, and the valve plate 51 disappears. The valve plate sealing surface 514 cannot be tightly pressed against 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 runner outlet end 12 of the main shaft center hole fails, leading to an accident where a large amount of high-pressure water at the runner outlet end 12 of the main shaft center hole overflows through the main shaft center hole 3 at the generator rotor in a short time. In the second case, also due to long-term alternating action, the sealing ring 513 undergoes aging failure or large-size local damage. At this time, although the valve plate sealing surface 514 is tightly pressed against the valve seat sealing surface 542, it is still impossible to ensure an effective seal between the valve plate sealing surface 514 and the valve seat sealing surface 542. An accident where the pressure water at the runner outlet end 12 of the main shaft center hole overflows through the main shaft center hole 3 at the generator rotor in a short time will also occur. In short, the seal failure of the guiding air-intake valve 5 is manifested as follows: After the air-intake operation is completed and the unit quickly shuts down, the main shaft center hole 3 is in a state filled with air. At this time, if water seeps into the main shaft center hole 3 and the water level, that is, the change in the leakage water volume, changes too quickly, it indicates that the guiding air-intake valve 5 has a seal failure. To accurately, quickly, and effectively detect whether the guiding air-intake valve 5 has a seal failure in the shutdown state, a level gauge 1 31 and a level gauge 2 32 are respectively installed in the main shaft center hole 3, and there is an elevation difference between the level gauge 1 31 and the level gauge 2 32, and the elevation of the level gauge 2 32 is lower than that of the level gauge 1 31. Since the cross-sectional area of the main shaft center hole 3 remains unchanged, as long as the time it takes for the pressure water entering the main shaft center hole 3 from the runner outlet end 12 of the main shaft center hole to rise from the position of the level gauge 2 32 to the position of the level gauge 1 31 is measured, the leakage water volume of the hydro-turbine main shaft center hole can be calculated according to the following formula:

[0058]

[0059] In the formula:

[0060] Q M: Leakage water volume of the central hole of the turbine shaft, m 3 / s;

[0061] D: Flow-through diameter of the central hole (3) of the main shaft, m;

[0062] L: Vertical distance between the first level gauge (31) and the second level gauge (32), m;

[0063] t: Time difference for triggering the first level gauge (31) and the second level gauge (32), s.

[0064] For the air admission valve of the turbine of the guiding air admission valve 5 type, a certain leakage is allowed to exist between the valve plate sealing surface 514 and the valve seat sealing surface 542, that is, a very small amount of leakage is allowed at the runner outlet end 12 of the central hole of the main shaft

[0065] The high-pressure water overflows along the central hole 3 from the runner outlet end 12 of the central hole of the main shaft to the generator end 6 of the central hole of the main shaft and is discharged by a specially provided overflow water pipe. When the seal failure phenomenon occurs in the shutdown state, since an effective seal cannot be formed between the valve plate sealing surface 514 and the valve seat sealing surface 542, an accident will occur where the pressure water at the runner outlet end 12 of the central hole of the main shaft overflows in a large amount in a short time at the generator rotor through the central hole 3 of the main shaft, that is, the water flow rate through the central hole 3 of the main shaft from the runner outlet end 12 of the central hole of the main shaft to the generator end 6 of the central hole of the main shaft will far exceed the design allowable value. At this time, it indicates that the seal failure phenomenon has occurred in the shutdown state. Generally speaking, when the leakage water volume of the central hole of the turbine shaft exceeds 15% of the theoretical design value, it can be determined that the seal has failed. Whether the leakage water volume of the central hole of the turbine shaft increases is executed according to the following procedure:

[0066]

[0067] In the formula:

[0068] Q T : Theoretical leakage water volume of the central hole of the turbine shaft, m 3 / s;

[0069] ΔQ: Relative change rate of the leakage water volume of the central hole of the turbine shaft, dimensionless;

[0070] If the conditions of ΔQ≥15% and Q M -Q T >0 are satisfied, it is determined that the leakage water volume of the central hole of the turbine shaft increases; otherwise, it is determined that the leakage water volume of the central hole of the turbine shaft is normal.

[0071] The technical solution of this application realizes the accurate determination of the card failure of the guiding air inlet valve in the central hole of the turbine main shaft; realizes the accurate determination of the valve plate seal failure of the guiding air inlet valve in the central hole of the turbine main shaft; and realizes the purpose of accurately determining the working state of the guiding air inlet valve in the central hole of the turbine main shaft of the in-service hydro-generating unit.

[0072] It should be noted that the specific implementation manners are only explanations and descriptions of the technical solution of the present invention, and the scope of the right protection cannot be limited thereby. Those that are only partial changes made according to the claims and the description of the present invention should still fall within the protection scope of the present invention.

Claims

1. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve, characterized in that The following steps are involved: Step 1: a liquid level gauge 1 (31) and a liquid level gauge 2 (32) are arranged in the main shaft center hole (3) of the hydro-generator, wherein the elevation of the liquid level gauge 1 (31) is higher than the elevation of the liquid level gauge 2 (32); Step 2: Start the hydro-generator set and determine whether natural air supply occurs. If natural air supply occurs, execute step 3. Otherwise, the guided air supply valve (5) fails. Step 3: Maintain natural Qi replenishment within the set time; Step 4: The hydro-generator set is shut down, and the triggering time of the liquid level gauge 1 (31) and the liquid level gauge 2 (32) are respectively obtained to obtain the time difference; Step 5: Obtain the flow diameter of the main shaft center hole (3), and the elevation difference between the liquid level gauge 1 (31) and the liquid level gauge 2, and combine the time difference obtained in step 4 to obtain the actual water leakage of the turbine main shaft center hole (3); Step 6: Obtain the theoretical water leakage of the center hole (3) of the main shaft of the turbine, and determine whether the water leakage of the center hole (3) of the main shaft of the turbine increases according to the theoretical water leakage of the center hole (3) of the main shaft of the turbine and the actual water leakage of the center hole (3) of the main shaft of the turbine. If it increases, the guide air supply valve (5) fails; otherwise, the guide air supply valve (5) does not fail.

2. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 1, characterized in that The actual water leakage of the turbine main shaft center hole (3) is expressed as: Among them, Q M is the water leakage of the center hole of the main shaft of the turbine, D is the flow diameter of the center hole (3) of the main shaft, L is the vertical distance between the liquid level gauge 1 (31) and the liquid level gauge 2 (32), and t is the time difference between triggering the liquid level gauge 1 and the liquid level gauge 2.

3. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 2, characterized in that In step 6, the specific steps of judging whether the amount of water leakage from the central hole (3) of the main shaft of the turbine increases are: According to the theoretical water leakage of the center hole (3) of the main shaft of the turbine and the actual water leakage of the center hole (3) of the main shaft of the turbine, a relative change rate of the water leakage of the center hole (3) of the main shaft of the turbine is obtained, and according to the relative change rate of the water leakage of the center hole (3) of the main shaft of the turbine, whether the water leakage of the center hole (3) of the main shaft of the turbine is increased is judged; The relative change rate of water leakage from the turbine main shaft center hole (3) is expressed as: Among them, ΔQ is the relative change rate of water leakage from the center hole of the turbine main shaft, Q T It is the theoretical water leakage of the center hole of the turbine main shaft.

4. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 3, characterized in that The specific steps of judging whether the amount of water leakage from the center hole (3) of the main shaft of the turbine has increased according to the relative rate of change of the amount of water leakage from the center hole (3) of the main shaft of the turbine are: If ΔQ ≥ 15% and Q M -Q T >0, it is determined that the water leakage of the center hole (3) of the main shaft of the turbine is increased; otherwise, it is determined that the water leakage of the center hole (3) of the main shaft of the turbine is normal.

5. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 1, characterized in that In the step 2, whether natural air replenishment occurs is determined by using a flow signaler (4) disposed in the central hole (3) of the main shaft.

6. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 1, characterized in that The time set in step 3 is 10 minutes.

7. A method for detecting faults of a vertical turbine main shaft center hole guided air supply valve according to claim 1, characterized in that The hydro-turbine generator is of mixed flow type or axial flow fixed slurry type.

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