JP2011157894A - Method and device for predicting cavitation erosion quantity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for predicting a cavitation erosion quantity in a fluid machine, enabling easy prediction of the cavitation erosion quantity. <P>SOLUTION: The method includes mounting a vibration acceleration sensor on the fluid machine, calculating impact pressure due to the bubble collapse of cavitation from a value for vibration acceleration measured by the vibration acceleration sensor, calculating the intensity of the cavitation occurring in the fluid machine from the impact pressure due to the bubble collapse of the cavitation, estimating cavitation energy distribution using cavitation impact force as a parameter from the intensity of the cavitation, calculating the total of cavitation energy having a threshold value or greater which causes the erosion of a material for the fluid machine in the energy distribution, calculating a maximum erosion velocity in the fluid machine from a relationship between the total of the cavitation energy and a previously found maximum erosion velocity, and predicting a maximum cavitation erosion quantity from the maximum erosion velocity and a time for operating the fluid machine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cavitation erosion amount prediction method and a prediction apparatus for a fluid machine, and is particularly suitable for a prediction method and a prediction system for a cavitation erosion amount in a fluid machine such as a pump or a water turbine.

  With the recent reduction in size and weight of fluid machines, the operating conditions of liquid turbo pumps (hereinafter referred to as pumps) have become increasingly severe. This is because a large flow rate can be generated by a low-cost small pump by operating the pump at a higher speed.

  However, when the pump is operated at a high speed, a phenomenon called cavitation described below occurs in the liquid inside the pump, and the inside of the pump may be damaged by cavitation erosion that occurs accordingly.

  Cavitation is a phenomenon in which, when a portion having a pressure lower than the vapor pressure of the liquid is generated in the liquid, vapor bubbles are generated in the portion. When bubbles due to cavitation suddenly return to liquid at the high pressure part, shock pressure is locally generated at the part, and the pressure may act on the inner wall or blade surface of the pump and erode the surface of the part. . This is cavitation erosion. It is said that the strength of cavitation generated in the pump is proportional to the cube of the peripheral speed of the pump blades. Therefore, as described above, cavitation erosion when the pump is operated at high speed is related to maintenance of pump performance and life management. It becomes a very important problem from the viewpoint.

  As a conventional method for predicting the amount of cavitation erosion of a fluid machine, there is a method disclosed in Japanese Patent Laid-Open No. 2003-269313 (Patent Document 1). This method of estimating the amount of cavitation erosion is based on the impact pressure applied to the runner or the surface of the running water, and the magnitude of the impact pressure applied to the actual surface of the water turbine and pump turbine, the runner of the similar model or similar model, or the surface of the running water. A method of detecting the amount of cavitation erosion from the magnitude of the impact pressure detected by a sensor, an underwater microphone or an AE sensor has been used.

  Another method for predicting the amount of cavitation erosion is disclosed in Japanese Patent Application Laid-Open No. 2007-327455 (Patent Document 2). This method of predicting the amount of cavitation erosion consists of a soft metal at the predicted cavitation erosion position, and by operating a model fluid machine, the surface of the soft metal is dented due to the cavitation collapse pressure. The amount of deformation is quantitatively measured, and the amount of cavitation erosion is predicted based on the measured amount of deformation of the depression.

  Furthermore, as a conventional method for calculating an impact pressure due to bubble collapse of cavitation using a vibration acceleration sensor, there is a method disclosed in Japanese Patent Application Laid-Open No. 2007-170981 (Patent Document 3). In this method, a plurality of vibration acceleration sensors are attached to a device in which cavitation occurs in the working fluid, the attenuation rate of pressure waves propagating from the cavitation generation position to each vibration acceleration sensor position, the transmittance at the interface of different media, the sensor installation part Using a predetermined resistance coefficient calculated in consideration of the wall thickness, density, and the like, a plurality of measured vibration acceleration values are subjected to least square approximation processing to extract the impact pressure due to bubble collapse of cavitation.

JP 2003-269313 A JP 2007-327455 A JP 2007-170981 A

  The conventional technique disclosed in Patent Document 1 is a method for estimating the amount of cavitation erosion based on the magnitude of impact pressure detected during operation of an actual machine, a similar model, or a similar model. However, it was difficult to obtain the amount of erosion. That is, it is generally troublesome to detect an impact pressure with an impact pressure sensor, an underwater microphone or an AE sensor during operation of an actual machine, a similar model, or a similar model.

  In the prior art disclosed in Patent Document 2, a soft metal is provided in a model fluid machine, the amount of dent deformation on the surface of the soft metal is measured, and the amount of cavitation erosion is calculated based on the amount of dent deformation. Since it is to be predicted, the work of installing a soft metal and measuring the amount of depression deformation is troublesome.

  The prior art disclosed in Patent Document 3 only calculates the impact pressure due to bubble collapse of cavitation using a vibration acceleration sensor, and cannot predict the amount of erosion due to cavitation in a fluid machine.

  An object of the present invention is to construct a prediction method and a prediction device for a cavitation erosion amount of a fluid machine that can easily predict the cavitation erosion amount in a short time.

According to a first aspect of the present invention for achieving the above-described object, a vibration acceleration sensor is attached to a fluid machine that is a target for predicting the amount of erosion due to cavitation, and the vibration acceleration value measured by the vibration acceleration sensor is used. Remove certain frequency regions,
Using a predetermined resistance coefficient calculated in consideration of the attenuation rate of the pressure wave propagating from the cavitation generation position to the vibration acceleration sensor mounting position, the transmissivity at the interface between different media, and the wall thickness and density of the sensor mounting part, Calculate the impact pressure due to bubble collapse,
Calculate the cavitation strength generated in the fluid machine from the impact pressure due to bubble collapse of the cavitation,
Estimating the cavitation energy distribution using the cavitation impact force as a parameter from the calculated cavitation strength generated in the fluid machine,
In the cavitation energy distribution, the sum of cavitation energy above a threshold value causing erosion to the material of the fluid machine is calculated,
Calculate the maximum erosion rate in the fluid machine from the relationship between the sum of cavitation energy above a threshold value causing erosion to the material and the maximum erosion rate obtained in advance,
The maximum erosion amount due to cavitation in the fluid machine is predicted from the maximum erosion speed and the operation time of the fluid machine.

Moreover, in the prediction method of the amount of cavitation erosion described above,
Based on the threshold database for each material, calculate the sum of cavitation energy above the threshold that causes erosion of the material of the fluid machine in the cavitation energy distribution, and sum the cavitation energy for each material. The maximum erosion rate in the fluid machine is obtained based on a database of the relationship between the maximum erosion rate and the maximum erosion rate.

A second aspect of the present invention is a vibration acceleration sensor,
An amplifier for amplifying the output signal of the vibration acceleration sensor;
An AD converter that samples the output signal of the amplifier at a high speed;
A fast Fourier transformer that calculates a vibration acceleration value obtained by removing a specific frequency range by performing a fast Fourier transform on the vibration acceleration waveform output from the AD converter;
A computer that records the vibration acceleration value output from the fast Fourier transformer;
The computer includes an extraction means for extracting a cavitation bubble impact pressure from the recorded vibration acceleration value, a strength calculation means for obtaining a cavitation strength from the cavitation bubble impact pressure, and a cavitation impact force as a parameter from the cavitation strength. The estimation means for estimating the cavitation energy distribution, the total calculation means for calculating the sum of the cavitation energy above the threshold value that causes erosion in the material in the cavitation energy distribution, and the erosion in the material. The erosion rate calculating means for obtaining the maximum erosion rate from the relationship between the sum of the cavitation energy above the threshold value to be obtained and the maximum erosion rate obtained in advance, and the maximum erosion rate by inputting the operating time of the fluid machine. Is the erosion amount calculation means to find the maximum erosion amount? And having a comprising data processing means.

Moreover, in the prediction apparatus for the cavitation erosion amount described above,
Furthermore, a database of threshold values for each material and a database of the relationship between the sum of cavitation energy for each material and the maximum erosion rate are provided, and the total calculation means includes the cavitation based on the threshold database for each material. The sum of the cavitation energy above a threshold value causing erosion to the material of the fluid machine in the energy distribution is calculated, and the erosion rate calculation means includes the sum of the cavitation energy for each material and the maximum erosion rate. The maximum erosion speed in the fluid machine is obtained on the basis of the database of the relationship.

  According to the method for predicting the amount of cavitation erosion of a fluid machine according to the present invention, a cavitation bubble impact can be obtained by simply attaching a vibration acceleration sensor to the outer surface of the fluid machine without disassembling the fluid machine to be predicted. Since the cavitation strength can be calculated directly from the pressure, it is possible to easily predict the amount of cavitation erosion.

  According to the cavitation erosion prediction apparatus of the present invention, the data processing means for extracting the cavitation bubble impact pressure from the vibration acceleration value built in the computer from the measured vibration acceleration value of the fluid machine, the cavitation bubble impact pressure and Data processing means for obtaining cavitation strength, data processing means for estimating cavitation energy distribution from cavitation strength using cavitation impact force as a parameter, and cavitation exceeding the threshold value that causes erosion of material in this cavitation energy distribution Data processing means for calculating the sum of energy, data processing means for obtaining the maximum erosion rate from the relationship between the sum of cavitation energy exceeding the threshold value causing erosion to the material and the maximum erosion rate obtained in advance, Bi station by it is possible to predict the maximum erosion rate, the operating time of the fluid machine, the maximum erosion rate makes predicting the maximum erosion amount of cavitation device can be provided.

It is sectional drawing of the pump which uses water as a working fluid which is an example of the application object of one Example of this invention. It is a block diagram which similarly shows the system of signal processing. It is a block diagram which similarly shows a data processing means. It is explanatory drawing of the vibration acceleration distribution similarly obtained from the Example. It is explanatory drawing showing the mode of the pressure wave at the time of a plane pressure wave permeate | transmitting the interface of a different medium. It is a figure which shows an example of the pressure propagation path | route of the bubble impact pressure of another Example. It is the figure which plotted vibration acceleration using the pressure propagation coefficient. It is explanatory drawing of the relationship between the cavitation impact force measured in one Example, and frequency. It is explanatory drawing which similarly shows the energy which is concerned in cavitation erosion by the relationship between cavitation impact force and frequency.

  Specific embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of a pump 5 using water as a working fluid, which is an example of an application target of the embodiment of the present invention, and is also a diagram illustrating an example of a pressure propagation path of bubble impact pressure. FIG. 1 shows an example in which the impeller 1 is rotated by a main shaft 2, sucks water from a suction pipe 3, discharges it into a discharge casing 4, pumps water, and attaches four vibration acceleration sensors. Four vibration acceleration sensors 10a to 10d are installed on the outer surfaces of the suction pipe 3 made of carbon steel and the discharge casing 4 made of cast iron. Under certain operating conditions of the pump 5, cavitation (not shown) occurs near the front edge of the impeller 1, and cavitation bubbles collapse on the blade surface of the impeller 1 to generate impact pressure.

  Here, the generation position of the bubble impact pressure is assumed to be one point P, and the pressure propagation path from the point P to each of the vibration acceleration sensors 10a to 10d is assumed to be a one-dimensional linear path indicated by a dotted line. For example, in the case of the vibration acceleration sensor 10c, if the point on the flow surface of the discharge casing 4 in the middle of the path is Q and the installation position of the vibration acceleration sensor 10c on the surface of the discharge casing 4 is R, the pressure wave is the underwater propagation path PQ, solid The vibration acceleration sensor 10c is reached via the propagation path QR.

  FIG. 2 is a block diagram showing a signal processing system according to the embodiment of the present invention. Note that even one vibration acceleration sensor to be attached can be evaluated. Output signals from the vibration acceleration sensors 10a to 10d installed on the outer surface of the suction pipe 3 and the discharge casing 4 of the pump 5 in FIG. 1 are taken in and amplified by the amplifiers 11a to 11d, respectively. The resonance frequency of the vibration acceleration sensors 10a to 10d is 20 kHz or more. Output signals from the amplifiers 11a to 11d are sampled at high speed by the A / D converter 20 at a sampling frequency of 40 kHz or more. The output signal from the A / D converter 20 is taken into the fast Fourier transformer 21 and fast Fourier transform processing is performed. Moreover, a specific frequency band is filtered with respect to the frequency component below 20 kHz after Fourier transform. For this filtering, a 1 kHz high-pass filter and a 10 kHz low-pass filter are used, but it is possible to change to a filter corresponding to another frequency band according to the cavitation. Further, the fast Fourier transformer 21 calculates an overall value of the filtered signal and outputs it as a measured value of vibration acceleration. This vibration acceleration is recorded in the computer 22.

  The computer 22 includes data processing means 23 including various programs 31 to 36 and various databases 41 to 42 shown in FIG. The data processing means 23 incorporates means 31a to 36a (details will be described later) for executing the various programs 31 to 36 described above.

  The above-mentioned various programs are “program 31 for extracting cavitation bubble impact pressure from vibration acceleration measurement value”, “program 32 for calculating cavitation strength from cavitation bubble impact pressure”, and “cavitation impact force from cavitation strength as parameters. The program includes a program 33 for estimating a cavitation energy distribution, a program 34 for obtaining a sum of cavitation energy above a threshold, a maximum erosion rate calculation program 35, and an erosion amount calculation program 36.

  The various databases are composed of a “threshold database 41 for each material” and a “database 42 for the relationship between the total cavitation energy for each material and the maximum erosion rate”.

Hereinafter, the basic concept of the data processing means 23 of the present invention will be described. First, a description will be given using the “program 31 for extracting the cavitation bubble impact pressure from the vibration acceleration measurement value” in step S31 shown in FIG. FIG. 4 is an example of the vibration acceleration distribution obtained from the application target and signal processing method of the present invention described in FIGS. Under the influence of the structure and material of the suction pipe 3 and the discharge casing 4, the vibration acceleration values obtained from the vibration acceleration sensors 10a to 10d vary greatly. Also, the measurement error of each vibration acceleration is large. The vibration acceleration α2 of the vibration acceleration sensor 10b is about four times the vibration acceleration α3 of the vibration acceleration sensor 10c, and it is inappropriate to evaluate the cavitation bubble impact pressure based on the vibration acceleration of one sensor. Therefore, cavitation bubble impact pressure is extracted based on the following idea. As shown in FIG. 1, it is assumed that the bubble impact pressure p _c in one point P occurs, propagates as a plane pressure wave in the initial amplitude p _c, the frequency f (constant). When the pressure wave propagates through the medium i the path length L _i (water or solids) in sound velocity C _i, the wave number contained in the path length L _i becomes L _i f _i / C _i. If the attenuation coefficient of this medium is δ _i , the amplitude of the pressure wave after propagating through the path length L _i

Attenuates twice. On the other hand, when a plane pressure wave passes through the interface between different media i and i + 1 as shown in FIG.

Double. Here, τ _p is the transmittance, and Z _i = ρ _i C _i is the acoustic impedance. Therefore, when propagating through multiple (n types) media, the amplitude of the pressure wave reaching the acceleration sensor is

It is represented by In the case of FIG. 1, n = 2, i = 1 (underwater propagation path PQ), and i = 2 (solid propagation path QR). Further, when considering a pressure propagation path different from FIG. 1 as shown in FIG. 6, the maximum value of the amplitude of the pressure wave propagating through a plurality of different paths from point P to point R is

It can be expressed as Since it is possible to assume many pressure propagation paths, j = 1, 2,..., But when only the pressure propagation paths shown in FIGS. Corresponds to the case of FIG.

On the other hand, the density and path length of the solid part (nth medium) where the sensor is installed are ρ _m and L _m (distance between PQs in FIG. 1), and the measured vibration acceleration is α _m (m = 1, 2,...) Then, in this model pump, since the pressure wave hardly attenuates in the solid part where the sensor is installed, the solid part vibrates under the pressure of ρ _m × L _m × G _m . Since this pressure is equivalent to the pressure represented by equation (4),

It can be expressed. Here, if the pressure propagation coefficient R _t is defined by the following equation,

It becomes. As equation (6) shows, the pressure propagation coefficient R _t is a resistance coefficient that depends on the physical properties and shape of the material. Assuming that the bubble impact pressure _pc is constant under certain operating conditions, in this theory, proportional α _m is measured according to the value of R _t from equation (7).

  In this model pump, since vibration acceleration β caused by flow phenomena other than motor vibration and cavitation is also added, equation (7) is

It is corrected to the shape of If this is plotted by taking the alpha _m R _t, the vertical axis to the horizontal axis as shown in FIG. 7, each measurement point in theory is located on a straight line passing through the sections beta, the slope is equivalent to p _c .

Next, in step S32 in FIG. 3, the cavitation bubble impact pressure is converted into the cavitation strength using the “program 32 for calculating the cavitation strength from the cavitation bubble impact pressure”. Here, cavitation strength refers to cavitation energy per unit time / unit area. Cavitation intensity I (W / m ^2), the unit area generated with the collapse of the cavitation bubble collapse, the energy per unit time, from the value of the bubble impact pressure p _c obtained in (8), It can be calculated using the following formula.

Here, ρ _w (kg / m ³ ) is the density of water, and c _w (m / s) is the underwater sound speed.

  In this way, in step S32 of FIG. 3, the cavitation strength can be calculated directly from the cavitation bubble impact pressure by the program 32. Therefore, the cavitation strength can be obtained simply by attaching the vibration acceleration sensor to the outer surface of the fluid machine. It is done.

  Next, in step S33 of FIG. 3, the energy of the cavitation impact force generated in the fluid machine from the cavitation strength using the “program 33 for estimating the cavitation energy distribution using the cavitation impact force as a parameter from the cavitation strength”. Estimate the distribution.

  To construct this program, it is necessary to generate cavitations with different strengths in the fluid using a cavitation tester, etc., and obtain an approximate expression for the cavitation energy distribution using the cavitation strength and cavitation impact force as parameters. Examples of testing machines that meet this purpose include jet testing devices defined in ASTM (American Society for Testing and Materials) G134-95 and magnetostrictive vibration devices defined in ASTM G32-03. (Not shown). In this apparatus, a cavitation energy distribution using the cavitation impact force as a parameter is measured by applying a cavitation impact force to a sensor (not shown). An example of the measurement result is shown in FIG. The program 33 for estimating the relationship of the cavitation energy distribution using the cavitation impact force as a parameter from the cavitation strength is obtained by acquiring the cavitation energy distribution using the cavitation impact force as a parameter shown in FIG. 8 for various cavitation strengths. .

  Although the cavitation energy acting on the fluid machine can be estimated as described above, not all of this cavitation energy is involved in cavitation erosion. This is because there is a minimum cavitation impact force that causes cavitation erosion for each material, and the impact force is referred to as a “threshold value”. This is illustrated in FIG. This "threshold value" can be measured by the above-described jet test or the like, and the value for each material is stored in the "threshold value database 41" in FIG. From the database 41, the “threshold value” for the material of the fluid machine is determined. That is, in step S34 of FIG. 3, among the energy distributions estimated by the program 33 using the “program 34 for calculating the sum of cavitation energy above the threshold value”, the cavitation energy above the “threshold value” is calculated. Calculate the sum.

  FIG. 8 is an explanatory diagram of the relationship between the measured cavitation impact force and frequency, and FIG. 9 is an explanatory diagram showing the energy involved in cavitation erosion in the same relationship between the cavitation impact force and frequency.

  Next, in step S35 of FIG. 3, the energy distribution of the cavitation impact force is calculated by the “database 42 of the relationship between the sum of cavitation energies exceeding the threshold and the maximum erosion speed” and the “maximum erosion speed calculation program 35”. The maximum erosion rate is obtained from the sum of the cavitation energy above the threshold that causes erosion in the fluid machine material.

  Furthermore, when the operating time of the fluid machine is input using the “erosion amount calculation program 36” in step S36 of FIG. 3, a predicted value of the erosion amount is calculated.

  In this way, by using the present prediction method of the embodiment, it is possible to accurately predict the life of the designed fluid machine. It is also possible to easily and accurately determine the pump inspection time, repair time or replacement time. Moreover, the amount of cavitation erosion can be easily predicted by simply attaching a vibration acceleration sensor to the outer surface of the fluid machine without disassembling the fluid machine to be predicted.

  The second embodiment is an example of the block diagram of the signal processing method of the present invention shown in FIG. 2. The vibration acceleration sensors 10 a to 10 d, the amplifiers 11 a to 11 d for amplifying the signals, and the output signal for sampling are amplified. An A / D converter 20, a fast Fourier transformer 21 for calculating an overall value (vibration acceleration value) obtained by performing fast Fourier transform processing and filtering processing on an output signal from the A / D converter 20, and a fast Fourier transformer The cavitation erosion amount prediction device is constructed by combining the computer 22 that records the vibration acceleration measurement value output from the control unit 21. As shown in FIG. 2, the computer 22 incorporates data processing means 23. The data processing means 23 includes the following means.

  That is, the “program 31 for extracting cavitation bubble impact pressure from the vibration acceleration measurement value” is executed in step S31 of FIG. 3, the extracting means 31a for extracting the cavitation bubble impact pressure from the vibration acceleration measurement value, and “cavitation” in step S32. The strength calculating means 32a for calculating the cavitation strength from the cavitation bubble impact pressure, which executes the program 32 for calculating the cavitation strength from the bubble impact pressure, and the “cavitation using the cavitation strength from the cavitation strength as a parameter in step S33. The estimation means 33a for estimating the cavitation energy distribution using the cavitation impact force as a parameter from the cavitation strength for executing the program 33 for estimating the energy distribution; Threshold database 41 for each charge ”and“ Program 34 for obtaining the sum of cavitation energy above threshold ”, and a sum calculation means 34a for obtaining the sum of cavitation energy above the threshold; Erosion rate calculating means 35a for obtaining the maximum erosion rate by the "database 42" of the relationship between the sum of the cavitation energies for each and the maximum erosion rate, and the "maximum erosion rate calculation program 35"; It comprises erosion amount calculation means 36a for obtaining the maximum erosion amount from the maximum erosion rate by inputting the operation time of the fluid machine using the calculation program 36 ".

  According to the present embodiment, the amount of cavitation erosion can be easily determined based on the vibration acceleration measurement value from the vibration acceleration sensor by simply attaching the vibration acceleration sensor to the outer surface of the fluid machine without disassembling the fluid machine to be predicted. Can be predicted.

  Moreover, since this measuring device is portable, it can be brought into a place where the pump is actually used, such as a pump station, and the amount of erosion of the pump in operation can be measured.

  DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Main shaft, 3 ... Suction pipe, 4 ... Discharge casing, 10a-10d ... Vibration acceleration sensor, 11a-11d ... Amplifier, 20 ... A / D converter, 21 ... Fast Fourier transform, 22 ... Computer, 23 ... Data processing means, 31 ... Program for extracting cavitation bubble impact pressure from vibration acceleration measurement value, 32 ... Program for obtaining cavitation strength from cavitation bubble impact pressure, 33 ... Cavitation impact force from cavitation strength Program for estimating cavitation energy distribution as a parameter 34: Program for calculating the sum of cavitation energy above a threshold value 35: Calculation program for maximum erosion rate 36: Calculation program for erosion amount 41: For each material Threshold database, 42 ... for each material Database of relationship between sum of cavitation energy and maximum erosion rate, 31a ... extraction means, 32a ... strength calculation means, 33a ... estimation means, 34a ... sum calculation means, 35a ... erosion rate calculation means, 36a ... erosion amount calculation means.

Claims (4)

A vibration acceleration sensor is attached to a fluid machine that is a target for predicting the amount of erosion due to cavitation, and a specific frequency region is removed from the value of vibration acceleration measured by the vibration acceleration sensor.
Vibration acceleration using a predetermined resistance coefficient calculated in consideration of the attenuation rate of pressure waves propagating from the cavitation generation position to the vibration acceleration sensor mounting position, the transmissivity at the interface of different media, and the wall thickness and density of the sensor mounting part Calculate the impact pressure due to cavitation bubble collapse from the value of
Calculate the cavitation strength generated in the fluid machine from the impact pressure due to bubble collapse of the cavitation,
Estimating the cavitation energy distribution using the cavitation impact force as a parameter from the calculated cavitation strength generated in the fluid machine,
In the cavitation energy distribution, the sum of cavitation energy above a threshold value causing erosion to the material of the fluid machine is calculated,
Calculate the maximum erosion rate in the fluid machine from the relationship between the sum of cavitation energy above a threshold value causing erosion to the material and the maximum erosion rate obtained in advance,
A method for predicting the amount of cavitation erosion characterized by predicting the maximum amount of erosion due to cavitation in the fluid machine from the maximum erosion speed and the operation time of the fluid machine. In the prediction method of the amount of cavitation erosion according to claim 1,
Based on the threshold database for each material, calculate the sum of cavitation energy above the threshold that causes erosion of the material of the fluid machine in the cavitation energy distribution, and sum the cavitation energy for each material. A method for predicting the amount of cavitation erosion characterized by obtaining a maximum erosion rate in the fluid machine based on a database of a relationship between a maximum erosion rate and a maximum erosion rate. A vibration acceleration sensor;
An amplifier for amplifying the output signal of the vibration acceleration sensor;
An AD converter that samples the output signal of the amplifier at a high speed;
A fast Fourier transformer that calculates a vibration acceleration value obtained by removing a specific frequency range by performing a fast Fourier transform on the vibration acceleration waveform output from the AD converter;
A computer that records the vibration acceleration value output from the fast Fourier transformer;
The computer includes an extraction means for extracting a cavitation bubble impact pressure from the recorded vibration acceleration value, a strength calculation means for obtaining a cavitation strength from the cavitation bubble impact pressure, and a cavitation impact force as a parameter from the cavitation strength. The estimation means for estimating the cavitation energy distribution, the total calculation means for calculating the sum of the cavitation energy above the threshold value that causes erosion in the material in the cavitation energy distribution, and the erosion in the material. The erosion rate calculating means for obtaining the maximum erosion rate from the relationship between the sum of the cavitation energy above the threshold value to be obtained and the maximum erosion rate obtained in advance, and the maximum erosion rate by inputting the operating time of the fluid machine. Is the erosion amount calculation means to find the maximum erosion amount? Cavitation Erosion amount prediction apparatus further comprising a data processing means comprising. In the prediction apparatus of the said cavitation erosion amount of Claim 3,
Furthermore, a database of threshold values for each material and a database of the relationship between the sum of cavitation energy for each material and the maximum erosion rate are provided, and the total calculation means includes the cavitation based on the threshold database for each material. The sum of the cavitation energy above a threshold value causing erosion to the material of the fluid machine in the energy distribution is calculated, and the erosion rate calculation means includes the sum of the cavitation energy for each material and the maximum erosion rate. A cavitation erosion amount predicting apparatus characterized in that a maximum erosion speed in the fluid machine is obtained based on a relational database.

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