JP2010014100A - Blade erosion monitoring method and blade erosion monitoring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately monitor erosion by a simple system structure and simple processing, in regard to the erosion of a moving blade in a rotary machine such as a steam turbine. <P>SOLUTION: This blade erosion monitoring method measures variation pressure at a fixed point 14 set in a flow passage opposed to the front edge side of the moving blade 4 in a turbine stage 2 of a monitoring object by a pressure measuring device 11, and monitors the blade erosion by determining the occurrence of limit erosion on the moving blade by determining the fixed point variation pressure provided thereby based on a preset erosion limit determining reference value on the fixed point variation pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to monitoring erosion generated on a moving blade in a rotary machine having blades, and more particularly to erosion monitoring suitable for a steam turbine such as that used in a steam turbine plant such as a power plant.

  A rotary machine such as a steam turbine or a gas turbine generally has a plurality of stages in the axial direction, each of which includes a moving blade and a stationary blade. A rotating machine having blades (moving blades and stationary blades) with such a paragraph structure has a problem that erosion occurs in the blades according to the characteristics of each paragraph, and the blades are damaged by the erosion.

  In the following, a steam turbine will be described as a typical example of a rotating machine. In the case of a rotor blade of a low-pressure turbine, erosion in the steam turbine generates wet steam in the low-pressure turbine, and water droplets in the wet steam are generated from the rotor blade. It is caused by colliding with the suction surface (surface on the rotation direction side). Such erosion caused mainly by wet steam is likely to occur in the subsequent rotor blade. On the other hand, in the high and medium pressure turbine, the first stage blades are easily damaged by erosion. This is because the erosion in the high and medium pressure turbine is solid particle erosion. In other words, solid particle erosion is erosion caused by solid fine particles (solid particles) generated in a boiler or the like under conditions of high vapor velocity colliding with the wing, and the collision of solid particles with the wing is more in the first stage than in the latter stage. Because it becomes.

  Such erosion progresses gradually, and if left unattended, there may be a situation where it is difficult to continue the operation of the steam turbine due to damage to the blades caused by erosion. Therefore, it is necessary to monitor the wing erosion. In other words, the progress of wing erosion in the required paragraph is properly monitored, and when erosion has progressed to a critical state that may lead to wing breakage, etc. It is necessary to be able to cope with such as replacing the normal wing with a limit wing.

  For this reason, various techniques have been proposed that enable automatic wing erosion monitoring. For example, in the “steam turbine blade life monitoring device” of Patent Document 1, erosion per unit time using steam flow, pressure, wetness, relative speed of blades and water droplets, and absolute velocity of water droplets in an operating steam turbine. The amount is calculated, and the total amount of erosion from the amount of erosion per unit time to the present is calculated.

  In addition, in the “rotating blade erosion preventing device for steam turbine” of Patent Document 2, the erosion speed of the moving blade is obtained by using the diameter of water droplets in the steam, the steam wetness, and the steam pressure in the steam turbine in operation. An alarm is issued when the speed exceeds the set upper limit.

  Further, in the “turbine blade erosion monitoring device” of Patent Document 3, the erosion amount is predicted by optically measuring the surface shape of the moving blade with a steam turbine in operation.

  Further, in the “steam turbine nozzle erosion monitoring method” of Patent Document 4, the main steam flow rate and the rotor blade inlet pressure are calculated using the pressure before the steam control valve, the steam control valve opening, and the pressure after the steam control valve in the operating steam turbine. Furthermore, the maximum value of the blade pressure difference is determined using the main steam flow rate and the blade inlet pressure, and whether the blade stress maximum value calculated based on the maximum value of the blade pressure difference is within a predetermined value. The erosion is monitored as determined.

Japanese Patent Publication No.56-12682 JP-A-61-207804 JP 63-246673 A Japanese Patent Publication No. 5-88416

  Regarding blade erosion monitoring, various techniques for enabling automatic monitoring have been proposed, as in the examples of Patent Documents 1 to 4 described above. However, none of these conventional techniques has been put into practical use. The reason for this is not necessarily clear, but it is thought that the device structure and the processing in the monitoring are too complicated, and that the problem remains in the monitoring accuracy.

  Thus, at present, an automatic monitoring method cannot be used. For this reason, methods are used to determine the occurrence of limit erosion by disassembling and visually observing the steam turbine during periodic inspections of the plant or measuring the nozzle area. There is a need to. However, in recent years, there is a tendency to increase the need to increase the operation efficiency of the plant by performing continuous operation for a longer period without stopping the plant even during periodic inspection. In order to meet such needs, it is necessary to be able to monitor erosion even when the steam turbine is in operation. However, at present, the progress of erosion is judged by listening to the sound of the steam turbine that is in operation. In fact, it has been impossible to identify the occurrence of limit erosion with high accuracy.

  For this reason, there is an increasing demand for automatic monitoring methods. To meet this demand, a simple system is used to monitor the critical erosion of blades, especially for blades that are affected by erosion with high accuracy. It is required to be able to do with structure and simple processing.

  The present invention has been made against the background of the above demands, and its problem is to monitor the erosion of moving blades in a rotating machine such as a steam turbine with high accuracy by a simple system structure and simple processing. It is to be able to do it.

  A high pressure part having a pressure higher than that of the surroundings is formed at the leading edge of the moving blade by the collision of working fluid such as steam. Assuming that this high pressure portion is called a blade leading edge high pressure portion, attention is paid to this blade leading edge high pressure portion.

  The blade leading edge high pressure portion forms a pressure distribution centered on the vicinity of the leading edge of the blade. Therefore, the pressure at the fixed point set appropriately in the flow path facing the leading edge side of the moving blade in the monitored paragraph depends on the distance between the fixed point and the pressure distribution center of the high pressure portion of the moving blade leading edge. Influenced by the edge high pressure part. Then, the influence of the fixed pressure on the fixed point by the blade leading edge high pressure part is brought about by a characteristic change pattern accompanying the rotational motion of the blade. Therefore, the fixed point pressure is a fluctuating pressure whose magnitude changes in correlation with the rotational motion of the moving blade. That is, the fixed pressure is caused by the fluctuating pressure caused by the high pressure portion of the blade leading edge. This fluctuating pressure is called a fixed point fluctuating pressure.

  On the other hand, erosion of the moving blade occurs at the leading edge of the moving blade, and mainly occurs at the tip side leading edge. In addition, the erosion of the moving blade usually occurs in substantially the same manner for each moving blade in the paragraph. Therefore, the leading edge of each moving blade that has caused erosion retreats according to the progress of the erosion, and the pressure distribution center of the high pressure portion of the moving blade leading edge for each moving blade also retreats uniformly. As a result, the distance between the pressure distribution center of the blade leading edge high pressure part and the fixed point where the fixed point fluctuating pressure is detected increases, and the influence of the blade leading edge high pressure part on the fixed point fluctuating pressure accordingly decreases. Become. That is, the fluctuation range of the pressure at the fixed point fluctuation pressure becomes small.

  By using the relationship between the erosion in the moving blade, the blade leading edge high pressure section, and the fixed point fluctuating pressure, the fixed blade fluctuating pressure, more specifically, the pressure fluctuation width at the fixed fluctuating pressure can be used as an index. It is possible to determine the critical erosion of the system with high accuracy, and the only data that needs to be acquired and processed during the operation of the moving blade is the fixed-point fluctuating pressure, which simplifies the system structure and processing. It becomes possible.

  In the present invention, the above-described problems are solved based on the idea as described above. Specifically, in a blade erosion monitoring method for monitoring the occurrence of limit erosion on the moving blade in a rotary machine having one or more stages in the axial direction, the moving blade and the stationary blade in the monitored paragraph Measure the fluctuating pressure at a fixed point set in the flow channel facing the leading edge side of the gas, and determine the fixed point fluctuating pressure obtained based on the erosion limit judgment reference value preset for the fixed fluctuating pressure. Then, the monitoring is performed by determining the occurrence of the limit erosion for the moving blade in the monitoring target paragraph.

  As described above, erosion of the moving blade mainly occurs at the tip side leading edge. Therefore, in the blade erosion monitoring method as described above, it is preferable that the fixed point is set at a position facing the tip-side front edge of the moving blade.

  As described above, the blade-induced fluctuating pressure is produced in a unique pattern accompanying the rotational motion of the blade. The pattern correlates with the rotational speed of the moving blade and the number of moving blades (the number of moving blades in the monitored paragraph). Therefore, as the fixed point fluctuating pressure, the fluctuating pressure of the frequency related to the rotating speed of the moving blade and the number of moving blades, specifically, the fluctuating pressure of the BPF frequency obtained as (number of moving blades) × rotating speed (rpm) / 60 is used. By doing so, more accurate monitoring becomes possible. Therefore, in the present invention, in the blade erosion monitoring method as described above, the fixed-point fluctuating pressure is calculated from the number of rotating blades and the number of moving blades in the monitored paragraph (number of moving blades) × number of rotations (rpm ) / 60, it is preferable to use the fluctuation pressure of the BPF frequency obtained as / 60.

  Fixed point fluctuating pressure is also affected by the pressure ratio before and after the monitored paragraph. The effect of the pressure ratio before and after the paragraph does not cause a serious injury when the fixed-point fluctuating pressure is used as a judgment index for limit erosion. However, by allowing the influence of the pressure ratio before and after the paragraph to be eliminated, more accurate monitoring becomes possible. For this reason, in the present invention, the blade erosion monitoring method as described above is preferably configured such that the paragraph longitudinal pressure ratio in the monitored paragraph is reflected in the erosion limit determination reference value.

  Usually, the erosion limit judgment reference value in the blade erosion monitoring method as described above is set based on a test or analysis such as a model test or a fluid analysis performed under the same conditions as the moving blade to be monitored. Therefore, in the present invention, in the blade erosion monitoring method as described above, the erosion limit determination reference value is obtained by a test or analysis performed on the erosion limit moving blade in which the limit erosion has occurred or a corresponding moving blade. A preferred mode is to set based on the fixed-point fluctuation pressure.

  The blade erosion monitoring system used in the blade erosion monitoring method as described above includes a pressure measurement device that measures the fixed point fluctuating pressure, a determination reference value storage device that stores the erosion limit determination reference value, and the pressure measurement device. The fixed point fluctuating pressure is determined on the basis of the erosion limit determination reference value, so that an erosion limit determination device that determines the occurrence of the limit erosion of the moving blade in the monitored paragraph is provided.

  According to the present invention as described above, it is possible to monitor erosion of moving blades in a rotary machine such as a steam turbine with high accuracy, and it is possible to simplify the system structure and processing.

  Hereinafter, modes for carrying out the present invention will be described. FIG. 1 schematically shows a configuration of a blade erosion monitoring system 1 according to the first embodiment together with a relationship with a turbine stage 2 to be monitored. For convenience of explanation, a general configuration of the turbine paragraph 2 will be described first. In this embodiment, it is assumed that a general steam turbine in which a plurality of paragraphs are provided from upstream to downstream with respect to the flow of steam as the working fluid is a monitoring target, and turbine stage 2 is the final stage of the low-pressure turbine. .

  The turbine stage 2 includes a stationary blade 3 and a moving blade 4 that form a pair. The stationary blade 3 is fixedly supported by a stationary blade outer wall (external diaphragm) 5 and is stationary, and is disposed upstream of the paragraph. The stationary blade 3 has an inner diaphragm 6 attached to the inner end thereof, and a seal fin 7 for reducing a leakage flow from the main flow of the steam passing through the stationary blade 3 and the moving blade 4 is provided on the inner diaphragm 6. ing. On the other hand, the moving blade 4 is implanted in the rotor 8 and is in a rotatable state, and is disposed on the downstream side of the paragraph. The moving blades 4 are provided in a plurality so as to be arranged at regular intervals in the circumferential direction of the rotor 8, and are connected to adjacent moving blades in the circumferential direction via a connecting cover 9 attached to the tip. ing.

In the turbine stage 2, the stationary blade 3 is a throttle channel. Therefore, the steam that has passed through the stationary blade 3 is accelerated by converting the heat energy into kinetic energy. Then, the steam flows into the moving blade 4 to give a rotating force to the moving blade 4 and generate power in the rotor 8 to which the moving blade 4 is connected. The steam flowing out of the moving blade 4 has lost energy. Therefore, the pressure ratio (P _out / P _in ) before and after the paragraph is smaller than 1.

  As described above, turbine stage 2 is the final stage of the low-pressure turbine. Therefore, in the turbine paragraph 2, the steam is wet steam and contains water droplets. FIG. 2 shows the relationship between the rotational speed U of the moving blade 4, the absolute speeds V and Vd of the steam and water droplets at the stationary blade outlet, and the relative speeds W and Wd of the steam and water droplets at the moving blade inlet. Since the speed of the water droplet is smaller than that of the steam, the inflow direction to the moving blade 4 is different between the steam and the water droplet. That is, with respect to the positive pressure surface 10p and the negative pressure surface 10m of the moving blade 4, the water droplets are biased to flow toward the negative pressure surface 10m with respect to the steam. In the turbine stage 2, which is the final stage, the blade length of the moving blade 4 is long, and therefore the peripheral speed on the tip side is large. Therefore, the moving blade 4 usually generates erosion mainly at the leading edge on the tip side. It is.

  Next, the blade erosion monitoring system 1 will be described. The blade erosion monitoring system 1 includes a pressure measurement device 11, a determination reference value storage device 12, and an erosion limit determination device 13.

  The pressure measuring device 11 is a fixed-point fluctuating pressure that is used as an index in the limit erosion determination of the moving blade 4 performed by blade erosion monitoring (this is in the flow path facing the leading edge side of the moving blade 4 in the turbine stage 2 to be monitored). Is used to measure the fluctuating pressure generated at the fixed point 14 set as described below. The measurement of the fixed point fluctuation pressure by the pressure measuring device 11 is performed by converting the pressure detection signal obtained as a voltage signal by the pressure sensor 15 that detects the pressure at the fixed point 14 to obtain the actually measured pressure value. Therefore, the measured pressure value related to the fixed-point fluctuating pressure is output from the pressure measuring device 11 as a time history waveform of the fluctuating pressure (see FIG. 5).

  Here, the fixed point 14 is set in relation to the erosion generated in the moving blade 4. As described above, erosion of the rotor blade 4 mainly occurs at the leading edge on the tip side. However, the tip portion of the rotor blade 4 is prevented from colliding with steam and water droplets by the connecting cover 9, so that erosion does not occur much. Considering this, it is preferable to set the fixed point 14 at a position facing the tip side front edge at a position slightly closer to the base side from the tip of the moving blade 4, and this embodiment also does so. Along with this, the pressure sensor 15 is provided on the inner peripheral surface of the stationary blade outer wall 5 so that the pressure at the fixed point 14 can be detected effectively.

  The determination reference value storage device 12 is used to store, for each paragraph to be monitored, an erosion limit determination reference value obtained as described later with respect to a fixed point fluctuating pressure as an index in the limit erosion determination.

  The erosion limit determination device 13 determines the occurrence of limit erosion for the rotor blade 4 in the turbine stage 2. The determination is made by comparing the measured pressure value relating to the fixed point fluctuation pressure provided from the pressure measuring device 11 with the erosion limit determination reference value fetched from the determination reference value storage device 12, and when it is determined that the limit erosion has occurred. This is appropriately output as an alarm or the like.

  In the following, the method for obtaining the erosion limit determination reference value will be described. First, the relationship between the blade leading edge high pressure portion and the fixed point fluctuating pressure, which is the background for deriving the erosion limit determination reference value, will be described.

  As shown in FIG. 3, a high pressure part having a pressure higher than that of the surroundings due to the collision of steam, that is, a moving blade leading edge high pressure part 16 is formed at the leading edge of the moving blade 4. The blade leading edge high pressure portion 16 forms a pressure distribution centered on the vicinity of the leading edge of the blade 4 and exerts the influence on the upstream side as well. Note that the moving blade 4 in FIG. 3 is shown as an inspection cross section for erosion of the moving blade 4 (corresponding to the fixed point 14 in the cross section along the line AA in FIG. 2).

  FIG. 4 schematically shows the relationship between the blade leading edge high pressure portion 16, the fixed point 14, and the pressure sensor 15 that detects the pressure at the fixed point 14. 4A shows a case where the moving blade 4 is in a normal state, and FIG. 4B shows a case where limit erosion has occurred in the moving blade 4.

  The pressure at the fixed point 14 is affected by the moving blade leading edge high pressure portion 16 according to the distance between the fixed point 14 and the pressure distribution center 17 of the moving blade leading edge high pressure portion 16. The effect of the moving blade leading edge high pressure portion 16 on the pressure at the fixed point 14 is a characteristic change pattern accompanying the rotational movement of the moving blade 4, specifically, when the moving blade 4 passes a position facing the fixed point 14. It is brought about by the change pattern that becomes the maximum and becomes small before and after that. Therefore, the pressure at the fixed point 14 becomes a fluctuating pressure whose magnitude changes in synchronization with the moving blade 4 periodically passing through the position opposed to the fixed point 14 by its rotational movement.

  FIG. 5 shows an example of a time history waveform from the pressure measuring device 11 obtained by detecting the fluctuating pressure at the fixed point 14, that is, the fixed point fluctuating pressure by the pressure sensor 15. FIG. 5A shows a case where the moving blade 4 is in a normal state, and FIG. 5B shows a case where limit erosion occurs in the moving blade 4.

  As shown in FIG. 4A, when the moving blade 4 is normal, the center 17 and the fixed point 14 of the moving blade leading edge high pressure portion 16 face each other at a distance Da. On the other hand, as shown in FIG. 4 (b), when a missing portion 18 is generated due to erosion at the leading edge of the moving blade 4, the leading edge of the moving blade 4 retreats according to its progress state, and accordingly the moving blade The center 17 of the leading edge high pressure portion 16 is also retracted with respect to the fixed point 14. As a result, the center 17 of the moving blade leading edge high pressure portion 16 and the fixed point 14 face each other at a distance Db (> distance Da), and the influence of the moving blade leading edge high pressure portion 16 on the fixed point fluctuating pressure accordingly. Becomes smaller. In the state where the limit erosion occurs in the moving blade 4, as shown in FIG. 5, the amplitude (pressure fluctuation width) of the time history waveform from the pressure measuring device 11 is sufficiently higher than that in the normal state of the moving blade 4. It becomes small with a significant width. Therefore, it is possible to determine the limit erosion with high accuracy by using the difference in amplitude between the time history waveform of FIG. 5A and the time history waveform of FIG. 5B. The erosion limit criterion value is set based on this.

  To set the erosion limit judgment reference value, the erosion of the moving blade 4 needs to be quantified. FIG. 6 schematically shows an example of erosion occurring in the moving blade 4. In addition, the moving blade 4 in FIG. 6 is shown as a test | inspection cross section similarly to the case of FIG. 6 (a) shows a normal moving blade 4, and FIG. 6 (b) shows an erosion moving blade 4e that is damaged due to a part of the leading edge lost due to erosion generated at the leading edge. (c) shows an erosion missing portion 18 (see also FIG. 1) missing from the erosion blade 4e.

  For such erosion, hereinafter, the erosion amount is defined by the area of the erosion missing portion 18, and the erosion amount is used as a quantitative value representing the degree of erosion. Further, the erosion amount of the limit erosion that is the erosion that has progressed to a limit state that may lead to the breakage of the rotor blade 4 is referred to as the erosion limit amount.

  As described above, the fluctuating pressure at the fixed point 14 changes the pressure in correlation with the rotation of the moving blade 4. Therefore, for setting the erosion limit determination reference value, it is preferable to use the fluctuating pressure of the frequency related to the rotational speed of the moving blade 4 and the number of moving blades in the turbine stage 2. Specifically, it is preferable to use a fluctuation pressure of a BPF (Blade Passing Frequency) frequency (hereinafter, also referred to as BPF fluctuation pressure as appropriate) obtained as (number of blades) × rotation speed (rpm) / 60. By doing so, more accurate monitoring becomes possible.

  FIG. 7 shows an example of data when the measured pressure value of the fixed point fluctuating pressure output from the pressure measuring device 11 is subjected to frequency analysis at the BPF frequency. When frequency analysis is performed at the BPF frequency, the fluctuation pressure becomes maximum at the BPF frequency, but the BPF fluctuation pressure of the erosion limit blade is sufficiently smaller than that of the normal blade.

  The above is the background for deriving the erosion limit determination reference value. Under such background, the erosion limit determination reference value is obtained as follows. First, an erosion limit amount Ec that can be tolerated for the moving blade 4 in the turbine stage 2 to be monitored is determined. In this method, FEM (finite element method) analysis is performed on the shape in which erosion has progressed, and the limit erosion amount at which the maximum stress is less than or equal to the allowable stress is defined as the limit erosion amount Ec. It is assumed that the shape in which erosion has progressed is known in advance by a test.

  Next, a BPF fluctuation pressure Fc (BPF fluctuation pressure function Fc: constant in the case of the present embodiment) is obtained for the erosion limit blade that has caused erosion of the limit erosion amount Ec by model test or fluid analysis. Is used as the erosion limit criterion value.

  In this case, the erosion limit determination device 13 generates the actual measurement value FP by performing frequency analysis of the actual pressure value provided from the pressure measurement device 11 using the BPF frequency. Then, FP <Fc is determined for the BPF fluctuation pressure Fc and the actual measurement value FP relating to the turbine stage 2 taken out from the determination reference value storage device 12, and when the result of the determination becomes affirmative, a limit erosion is generated, which is indicated by an alarm or the like As appropriate.

  Hereinafter, the second embodiment will be described. FIG. 8 schematically shows the configuration of the blade erosion monitoring system 21 according to the second embodiment together with the relationship with the turbine stage 22 to be monitored. The turbine stage 22 targeted in the present embodiment is assumed to be the first stage in a high turbine or an intermediate pressure turbine. However, the configuration of the turbine stage 22 is basically the same as that of the turbine stage 2 in FIG. 1, the blade length is short, and the seal fins 7 are also provided on the stationary blade outer wall 5 facing the connecting cover 9 of the moving blade 4. It is different because it is provided.

  In the high and medium pressure turbine, as described above, the solid particle erosion mainly in the first stage is a problem. Solid particle erosion at the first stage is most likely to occur in the stationary blade 3, but also occurs in the moving blade 4. That is, the solid particles collide with the antinode (positive pressure surface) side of the stationary blade 3 to generate solid particle erosion, and then cause the moving blade 4 to generate solid particle erosion.

  Even in such solid particle erosion, the determination of the limit erosion is the same as in the case of the first embodiment. Therefore, the blade erosion monitoring system 21 includes the pressure measurement device 11, the determination reference value storage device 12, and the erosion limit determination device 23, similarly to the blade erosion monitoring system 1. The pressure measurement device 11 and the determination reference value storage device 12 are the same as those in FIG. The erosion limit determination device 23 corresponds to the erosion limit determination device 13 in FIG. 1, but is different from the erosion limit determination device 13 in that a pressure ratio calculation unit 24 is provided.

The reason why the pressure ratio calculation unit 24 is provided in the erosion limit determination device 23 is that the pressure ratio before and after the paragraph (this is the pressure ratio (P _out / P _in ) described above) can be reflected in the erosion limit determination reference value. This is to prevent the pressure ratio before and after the turbine paragraph 22 from affecting the determination of the limit erosion and to perform monitoring with higher accuracy.

  The fluctuating pressure at the fixed point 14 is also affected by the pressure ratio before and after the paragraph. FIG. 9 is a conceptual diagram showing the relationship between the pressure ratio before and after the paragraph, the erosion amount, and the BPF fluctuation pressure. If the anteroposterior pressure ratio is the same, the larger the erosion amount, the smaller the BPF fluctuating pressure. If the erosion amount is the same, the larger the paragraph front / rear pressure ratio, the smaller the BPF fluctuating pressure.

Based on such a relationship, a model test or fluid analysis is performed on normal blades and erosion limit blades using discrete stage front-rear pressure ratios as variables, which are assumed to occur as operating conditions in an actual plant. The fluctuating pressure is obtained for each pressure ratio before and after the assumed paragraph, that is, discretely, and based on this, the BPF fluctuating pressure calculation function Fc (P _out / P _in ) using the pressure ratio as an argument is obtained, and this is the erosion limit criterion value Used as

In this case, the erosion limit determination device 13 generates the actual measurement value FP by performing frequency analysis of the actual pressure value provided from the pressure measurement device 11 using the BPF frequency. On the other hand, the pressure ratio calculation unit 24 obtains the pre-paragraph pressure ratio at that time. Next, the BPF fluctuation pressure calculation function Fc (P _out / P _in ) related to the turbine stage 22 is extracted from the determination reference value storage device 12, and the pressure ratio calculation unit 24 uses the BPF fluctuation pressure calculation function Fc (P _out / P _in ). seeking seeking BPF fluctuation pressure prediction value Fc by performing the operation a paragraph before or after the pressure ratio at the time as an argument (P _out / P _in). Then, the actual measurement value FP <BPF fluctuating pressure prediction value Fc (P _out / P _in ) is determined. If the result of the determination becomes affirmative, a limit erosion occurs, and this is appropriately output as an alarm or the like.

  As mentioned above, although the form for implementing this invention was demonstrated, these are only representative examples, This invention can be implemented with various forms in the range which does not deviate from the meaning. For example, although the steam turbine is targeted in the above embodiment, the present invention can be applied to any rotating machine that requires erosion monitoring of a moving blade.

It is a figure which shows the structure of the blade erosion monitoring system by 1st Embodiment with the turbine paragraph of the monitoring object. It is explanatory drawing of the speed triangle of the moving blade inlet_port | entrance in a low pressure turbine. It is a pressure contour figure of a moving blade front edge. It is a figure which shows the relationship between a moving blade front edge high pressure part, a fixed point, and a pressure sensor. It is a figure which shows the example of the time history waveform of a fixed point fluctuation pressure. It is a figure which shows the example of the erosion which arises in a moving blade. It is a figure which shows the example of a data at the time of performing frequency analysis of the fixed point fluctuation pressure. It is a figure which shows the structure of the blade erosion monitoring system by 2nd Embodiment with the turbine paragraph of the monitoring object. It is a conceptual diagram of the amount of erosion, pressure ratio before and after a paragraph, and BPF fluctuation pressure.

Explanation of symbols

1, 21 Blade erosion monitoring system 2 Turbine stage 3 Stator blade 4 Rotor blade 11 Pressure measurement device 12 Judgment reference value storage device 13, 23 Erosion limit judgment device 14 Fixed point 24 Pressure ratio calculation unit

Claims (6)

In a blade erosion monitoring method for monitoring the occurrence of limit erosion in the rotating blade in a rotary machine having one or more stages in the axial direction including a stage composed of a moving blade and a stationary blade,
An erosion limit judgment criterion in which a fluctuating pressure at a fixed point set in the flow path facing the leading edge side of the moving blade in the monitoring target paragraph is measured, and the fixed fluctuating pressure obtained by the measurement is preset with respect to the fixed fluctuating pressure. The blade erosion monitoring method, wherein the monitoring is performed by determining the occurrence of the limit erosion of the moving blade in the monitoring target paragraph by determining based on a value.   The blade erosion monitoring method according to claim 1, wherein the fixed point is set at a position facing the tip side front edge of the blade.   As the fixed-point fluctuating pressure, a fluctuating pressure of the BPF frequency obtained from (the number of moving blades) × the number of rotations (rpm) / 60 from the number of rotating blades and the number of the moving blades in the monitored paragraph is used. The blade erosion monitoring method according to claim 1, wherein the blade erosion monitoring method is provided.   The blade erosion monitoring method according to any one of claims 1 to 3, wherein a pressure ratio in the monitoring target paragraph is reflected in the erosion limit determination reference value.   2. The erosion limit determination reference value is set based on the fixed point fluctuating pressure obtained by a test or analysis performed on an erosion limit moving blade in which the limit erosion has occurred or a moving blade corresponding to the erosion limit moving blade. The blade erosion monitoring method according to claim 4. A blade erosion monitoring system used in the blade erosion monitoring method according to any one of claims 1 to 5,
A pressure measuring device that measures the fixed point fluctuating pressure, a determination reference value storage device that stores the erosion limit determination reference value, and the fixed point fluctuating pressure from the pressure measuring device is determined based on the erosion limit determination reference value. A blade erosion monitoring system comprising: an erosion limit determination device for determining occurrence of the limit erosion for the moving blade in the monitoring target paragraph.

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