Patent Application
20210140928
This application claims the benefit of priority to Japanese Patent Application Number 2019-205008 filed on Nov. 12, 2019. The entire contents of the above-identified application are hereby incorporated by reference.
The disclosure relates to a rubbing detection device for a rotary machine and a method for detecting rubbing of a rotary machine.
Rubbing of a rotary machine has been detected by detecting shaft vibration of a rotary shaft. In the rotary machine, rubbing occurs between a rotary shaft and a seal or other component due to thermal deformation of a casing. This rubbing generates heat, which causes thermal bending of the rotary shaft, thereby generating shaft vibration of the rotary shaft. Rubbing leads to an increase in shaft vibration and deterioration in sealing performance of the rotary machine. Thus, it is desirable to detect rubbing at an earlier stage.
JP 58-034326 A describes a rubbing detection device for a rotary machine. In this device, sound detecting sensors are attached to bearings disposed at either end of a rotary shaft of the rotary machine to detect high-frequency signals. These high-frequency signals obtained through detection are made to pass through a bandpass filter to extract a rubbing signal. The presence or absence of rubbing is identified, and a portion where rubbing occurs is detected based on a difference in phase between the individual high-frequency signals.
JP 63-179222 A describes a rubbing-location determining device in which, even when a phase difference between outputs from acoustic emission (AE) sensors attached to bearings of both ends of a rotary shaft of a rotary machine exceeds 180°, the position where rubbing occurs is determined by adding a comparison between magnitudes of amplitudes of individual outputs.
A steam turbine or other rotary machine deals with a large noise signal resulting from steam flow and so on. In such rotary machines, when amplitude of an AE signal of rubbing from an AE sensor is used as an index, the amplitude of the AE signal of rubbing is smaller than the amplitude of the noise signal resulting from steam flow and so on, and is hidden by the noise signal resulting from steam flow and so on. This leads to a problem in which the AE signal of rubbing cannot be detected.
The present disclosure has been made in view of the problem described above, and an object of the present disclosure is to provide a rubbing detection device for a rotary machine and a method for detecting rubbing of a rotary machine, which efficiently detect rubbing of a rotary machine with higher accuracy.
A means to solve the problem described above provides a rubbing detection device for a rotary machine, including an AE sensor configured to acquire an AE signal of the rotary machine, a calculation unit configured to calculate a rubbing detecting index based on information relating to a phase of the AE signal, and a determination unit configured to determine presence or absence of rubbing from the rubbing detecting index.
A means to solve the problem provides a method for detecting rubbing of a rotary machine, the method including the steps of acquiring an AE signal from a rotary machine, calculating a rubbing detecting index based on information relating to a phase of the AE signal, and determining presence or absence of rubbing in terms of the rubbing detecting index.
According to the disclosure, it is possible to detect rubbing of a rotary machine prior to the occurrence of shaft vibration of a rotating shaft, and also possible to efficiently detect rubbing of a rotary machine with high accuracy.
The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Below, embodiments of the disclosure will be described in detail with reference to the drawings. The embodiments described below deal with a case where a rotary machine is a steam turbine, but the rotary machine according to the disclosure is not limited to a steam turbine.
Steam, which is a working fluid W that has flowed in from an inflow port 42 of the casing 40, passes by the rotor blades 32 arranged on the rotating shaft 30 inside the casing 40. This steam acts on the rotor blades 32 to impart rotational force to the rotating shaft 30. The stator blades 44 arranged in the casing 40 regulate the flow of steam. The steam that has passed by the rotor blades 32 flows out from an outflow port 46.
As illustrated in
The AE sensor 110 is configured as a sensor for detecting acoustic emission (AE; high-frequency output), and outputs a detected AE wave as an AE signal S. The AE sensor 110 is mounted to the bearing portion 20 and is connected to the input-output unit 120.
The rotary machine 10 generates the AE wave when, for example, a seal or the like attached to the casing 40 that has thermally deformed rubs with the rotating shaft 30. For example, the AE wave generated at a portion R where rubbing occurs propagates through the surface of the rotating shaft 30 as an elastic wave and is detected by the AE sensor 110 through the bearing portions 20. The AE wave typically has a frequency that falls in a sound-wave region ranging from several tens of kHz to several MHz. The AE signal S acquired by the AE sensor 110 contains the frequency of the AE wave generated as a result of rubbing and the frequency of a noise signal N resulting from steam flow and so on.
The AE sensor 110 includes an element that detects vibration of the AE wave and outputs the vibration as a voltage, and an amplifier that amplifies the voltage output from the element and outputs the amplified voltage as an electrical signal. The AE sensor 110 is configured integrally with the rubbing detection device 100 in the present embodiment. However, the AE sensor 110 may be configured as a standalone sensor device.
The rotational speed meter 112 detects the rotational speed of the rotating shaft 30 to output a rotational speed f to the input-output unit 120. The rotational speed meter 112 includes, for example, a dog attached to the rotating shaft 30, and a detector that detects the dog. The rotating shaft 30 rotates one turn and the dog is input once to the rotational speed meter 112. Then, the rotational speed meter 112 outputs the rotational speed f based on the input. The rotational speed f output from the rotational speed meter 112 is synchronized with the AE signal S and acquired from the control unit 140. The rotational speed meter 112 may also be configured such that output is performed to the AE sensor 110 and the output is obtained by the control unit 140 from the input-output unit 120 via the AE sensor 110.
The input-output unit 120 notifies the control unit 140 of the AE signal S input from the AE sensor 110 and the rotational speed f of the rotating shaft 30 output from the rotational speed meter 112. The AE signal S and the rotational speed f are recorded as data in the recording unit 130. In a case where the AE sensor 110 is configured as a single unit, the AE sensor 110 may be configured such that information can be input to or output from a recording medium such as a USB memory, so that the information is input to or output from the AE sensor 110 and the rotational speed meter 112 through the recording medium. The input-output unit 120 includes a keyboard, a mouse, and a display monitor, which are not illustrated.
The recording unit 130 holds programs and data. The recording unit 130 is configured, for example, as a hard disk drive (HDD).
The control unit 140 uses programs and data recorded in the recording unit 130 to perform a predetermined computing process on the AE signal S input from the AE sensor 110. The control unit 140 includes a signal acquisition unit 142, a filter processing unit 144, a data processing unit 156, a rotation-synchronization-component calculation unit 158, an index calculation unit 160, a threshold value calculation unit 162, and a determination unit 164. The control unit 140 includes a central processing unit (CPU) and executes various types of computing processes using the CPU to perform functions of each of the units.
The signal acquisition unit 142 acquires the AE signal S from the AE sensor 110. The signal acquisition unit 142 executes a program recorded in the recording unit 130 to acquire the AE signal S from the AE sensor 110. The AE signal S acquired by the signal acquisition unit 142 is recorded as data in the recording unit 130. The AE signal S is acquired at predetermined intervals. For example, the AE signal S is acquired at an interval of once every several seconds. At a single data acquisition, the signal acquisition unit 142 acquires data during a period of time in which the rotating shaft rotates two rotations to four rotations.
The filter processing unit 144 executes a program recorded in the recording unit 130 to perform a filter process on the AE signal 5, and outputs an AE signal Sf that has been subjected to the filter process. The filter processing unit 144 includes a filter with a predetermined frequency component being set as a passband. The passband of the filter in the filter processing unit 144 includes any of frequency bands ranging from several tens of kHz to several MHz, which corresponds to a frequency component included in the AE signal S.
The filter processing unit 144 according to the present embodiment includes a bandpass filter with a plurality of different frequency bands being set as a passband. The filter processing unit 144 according to the present embodiment includes a first bandpass filter 146, a second bandpass filter 148, a third handpass filter 150, a fourth handpass filter 152, and a fifth handpass filter 154. The first bandpass filter 146 is a filter having a passband ranging from 75 kHz to 100 kHz. The second handpass filter 148 is a filter having a passband ranging from 100 kHz to 125 kHz. The third bandpass filter 150 is a filter having a passband ranging from 125 kHz to 150 kHz. The fourth bandpass filter 152 is a filter having a passband ranging from 150 kHz to 175 kHz. The fifth bandpass filter 154 is a filter having a passband ranging from 175 kHz to 200 kHz. The bandpass filter is a filter that reduces components other than the passband by a predetermined ratio, for example, by 90% or more. In addition, it is only necessary that the filter processing unit 144 is able to perform a filter process on the AE signal S with frequency used as a reference. The filter processing unit 144 may employ a low-pass filter that only passes frequency components at or below a predetermined frequency, and a high pass filter that only passes frequency components at or above a predetermined frequency.
The data processing unit 156 executes a program recorded in the recording unit 130 to perform a predetermined envelope process, re-sampling, and an average-value zero process on the AE signal S or the AE signal Sf that has been subjected to the filter process. In the envelope process, an envelope process is performed on the AE signal S or the AE signal Sf to output an AE signal Sr in which a high-frequency component is removed. In the re-sampling process, re-sampling at a predetermined frequency is performed on the AE signal Sr that has been subjected to the envelope process to output an AE signal Sp that has been subjected to re-sampling. In the average-value zero process, a process of zeroing an average is performed on the AE signal S. This average value is an average of amplitudes in each cycle and serves as a synchronous average. After the process, an AE signal Sz that has been subjected to the average-value zero process is output.
The rotation-synchronization-component calculation unit 158 executes a program recorded in the recording unit 130 to perform frequency analysis on the AE signal Sz. The rotation-synchronization-component calculation unit 158 performs frequency analysis to convert the AE signal Sz, which is a time series function, into a frequency function expressed as amplitude for each frequency, and outputs a rotational-order analysis result F in which frequency is expressed in terms of rotational orders (
The index calculation unit 160 executes a program recorded in the recording unit 130 to calculate a rubbing detecting index D for information relating to a phase of the AE signal S. The rubbing detecting index D is determined as a temporal distribution, as illustrated in
Rubbing detection index=1/(1+(dispersion of phase of AE signal){circumflex over ( )}0.5) (1)
For example, the dispersion of phase of the first order component of the rotational speed C is used to calculate the rubbing detecting index D. Specifically, the dispersion of phase of the first order component of the rotational speed C is determined as the dispersion of a first order component of the rotational speed extraction phase P obtained by performing predetermined sampling on a phase of the first order component of the rotational speed C. The first order component of the rotational speed extraction phase P is acquired by using, as a phase, shift of the cycle of the first order component of the rotational speed C with respect to the cycle of the rotational speed f acquired by the rotational speed meter 112. The first order component of the rotational speed extraction phase P is acquired by, for example, performing sampling of five to ten rotational points at intervals of several seconds.
The threshold value calculation unit 162 executes a program recorded in the recording unit 130 to acquire a threshold value T used to determine the presence or absence of rubbing in terms of the rubbing detecting index D. The threshold value T is calculated from, for example, cumulative probability of the rubbing detecting index D in a state where rubbing does not occur, as illustrated in
The determination unit 164 executes a program recorded in the recording unit 130 to determine the presence or absence of rubbing in terms of the rubbing detecting index D. The presence or absence of rubbing is determined by comparing the rubbing detecting index D with the threshold value T. The determination unit 164 may be configured so as to output the presence of rubbing, for example, on a display monitor in a case where the rotary machine 10 is determined to have rubbing. The time at which the rubbing detecting index D is detected to exceed the threshold value T can be estimated as a time of occurrence of rubbing. The determination unit 164 may be configured, for example, so as to output the presence of rubbing to the rotary machine 10 to provide feedback in a case where it is determined that rubbing is occurring in the rotary machine 10.
Next, a method for detecting rubbing of a rotary machine will be described. As illustrated in
The rubbing detection device 100 acquires the AE signal S (Step S10). The rubbing detection device 100 uses the signal acquisition unit 142 to acquire the AE signal S.
The rubbing detection device 100 performs a filter process using a predetermined filter on the acquired AE signal S to output the AE signal Sf that has been subjected to the filter process so as to have a frequency component in connection with the passband of the filter (step S20). The filter process is performed by using a bandpass filter having a predetermined frequency band of the AE signal S being set as a passband. The rubbing detection device 100 performs the filter process by using the filter processing unit 144.
The rubbing detection device 100 performs the envelope process, the re-sampling, and the average-value zero process on the AE signal S or the AE signal Sf that has been subjected to the filter process, to thereby perform data processing (Step S30). In the envelope process, the rubbing detection device 100 performs the envelope process on the AE signal Sf that has been subjected to the filter process or the AE signal S, and outputs the AE signal Sr that has been subjected to the envelope process. In the re-sampling process, the rubbing detection device 100 performs re-sampling on the AE signal Sr that has been subjected to the envelope process, and outputs the AE signal Sp that has been subjected to the re-sampling process. In the average-value zero process, the rubbing detection device 100 performs, on the AE signal Sp that has been subjected to re-sampling, a process of zeroing the average value of the amplitude in each cycle, and outputs the AE signal Sz that has been subjected to the average-value zero process. The rubbing detection device 100 performs the data processing by using the data processing unit 156.
The rubbing detection device 100 performs frequency analysis on the AE signal Sz that has been subjected to the average-value zero process, and outputs the rotational-order analysis result F in which frequency is expressed in terms of rotational orders, as illustrated in
The rubbing detection device 100 acquires the first order component of the rotational speed C based on the rotational-order analysis result F, and calculates the rubbing detecting index D in terms of the first order component of the rotational speed extraction phase P acquired by performing sampling of the first order component of the rotational speed C (Step S50). The rubbing detection device 100 performs the index calculation by using the index calculation unit 160.
Next, the rubbing detection device 100 calculates the threshold value T for the calculated rubbing detecting index D (Step S60). The rubbing detection device 100 performs threshold calculation by using the threshold value calculation unit 162.
The rubbing detection device 100 determines the presence or absence of rubbing in terms of the calculated rubbing detecting index D (Step S70). The rubbing detection device 100 determines the presence or absence of rubbing by comparing the calculated rubbing detecting index D with the threshold T. When the rubbing detecting index D exceeds the threshold value T, the rubbing detection device 100 determines that rubbing exists (YES in Step S70). When the rubbing detecting index D is less than or equal to the threshold value T, the rubbing detection device 100 determines that rubbing does not exist (NO in Step S70). The rubbing detection device 100 makes the determination by using the determination unit 164.
In a case where the filter processing unit 144 includes a plurality of filters as in the present embodiment, the rubbing detection device 100 performs the processes of Step S20 to Step S70 in parallel for each of the filters. The rubbing detection device 100 outputs the AE signal Sf processed by each of the filters in Step S20, and performs processing on each AE signal Sf.
In a case where, for example, there are N filters, the rubbing detection device 100 outputs N pieces of AE signals Sf that have been subjected to the filter process (Step S20). The rubbing detection device 100 performs data processing on the N pieces of AE signals Sf that have been input, and outputs N pieces of AE signals Sp that have been subjected to re-sampling (Step S30). The rubbing detection device 100 performs frequency analysis on the N pieces of input AE signals Sz, and outputs N pieces of rotational-order analysis results F (Step S40). The rubbing detection device 100 acquires the first order component of the rotational speed extraction phase P based on the N pieces of inputted rotational order analysis results F, and calculates N pieces of rubbing detection indices D (Step S50). The rubbing detection device 100 calculates N pieces of threshold values T for the N pieces of input rubbing sensing indices D (Step S60). For the N pieces of input rubbing sensing indices D and the N pieces of input threshold values T, the rubbing detection device 100 compares each of the rubbing sensing indices D and threshold values T corresponding to the rubbing sensing indices D. When any of the rubbing sensing indices D exceeds the corresponding threshold value T, the rubbing detection device 100 determines that rubbing exists (YES in Step 70). When all the rubbing sensing indices D are less than or equal to the corresponding threshold value T, the rubbing detection device 100 determines that no rubbing exists (NO in Step S70).
In a case where the filter process is not performed in the method for detecting rubbing described above, the rubbing detection device 100 performs the envelope process and subsequent steps on the AE signal 5, and outputs the AE signal Sz that has been subjected to data processing. That is, in the envelope process, the rubbing detection device 100 performs the envelope process on the AE signal S that has not been subjected to the filter process, and outputs the AE signal Sr that has been subjected to the envelope process. In the re-sampling process, the rubbing detection device 100 performs re-sampling on the AE signal Sr that has been subjected to the envelope process, and outputs the AE signal Sp that has been subjected to the re-sampling process. In the average-value zero process, the rubbing detection device 100 performs, on the AE signal Sp that has been subjected to the re-sampling, a process of zeroing the average value of the amplitude in each cycle, and outputs the AE signal Sz that has been subjected to the average-value zero process.
With reference to
From
Furthermore, in the case described above, the signal-to-noise ratio between the AE signal due to rubbing and the noise signal at 10:20, which is the time at which detection is made based on the rubbing detecting index D, was approximately −10 dB. Here, the signal-to-noise ratio is determined as: signal-to-noise ratio=10·log10 ((amplitude of AE signal Sr after the envelope process)/(amplitude of noise signal N after the envelope process)). In addition, the noise signal N due to steam entering the rotary machine is included between 10:30 and 11:15. However, as illustrated in
Next, with reference to
In contrast, the signal-to-noise ratio between the AE signal S of rubbing and the noise signal N was −3.4 dB at a frequency component of 175 kHz. In this case, in order to detect rubbing using the rubbing detecting index D in a more accurate manner, it is preferable to use a frequency component of 175 kHz exhibiting a lower signal-to-noise ratio. Thus, a frequency component including 175 kHz of the AE signal S is acquired as the AE signal Sf by performing a filter process on the AE signal using a bandpass filter having a frequency band of 175 kHz being set as a passband thereof. In this way, in an actual rotary machine, the signal-to-noise ratio between the AE signal S of rubbing and the noise signal N may vary depending on which frequency component is looked at in the AE signal S of rubbing. This leads to a need for performing a filter process with a filter having an appropriate passband.
With reference to
In
As described above, in order to obtain the frequency component in connection with rubbing on the basis of the acquired AE signal 5, it is necessary to perform the filter process to the AE signal S using a bandpass filter having, as a passband thereof, a frequency band having a high signal-to-noise ratio, in other words, a frequency band having a high sensitivity to the AE signal S due to rubbing. However, there may be a case in which a frequency band having a high signal-to-noise ratio cannot be identified in advance. In addition, a frequency band having a high signal-to-noise ratio may also change. In such cases, by providing a bandpass filter having a plurality of different frequency components being set as a passband thereof, it is possible to perform a filter process to the AE signal in passbands including a plurality of different frequency components. This makes it possible to detect the presence or absence of rubbing using the rubbing detecting index D without being influenced by the noise signal N occurring due to usage conditions or usage situations of the rotary machine 10.
The rubbing detection device for a rotary machine according to the first embodiment may be configured such that the determination unit 164 outputs a result of determination, for example, to a display monitor through the input-output unit 120, or outputs a feedback to the rotary machine 10. In addition, in the second embodiment, Step S70 of making a determination may include an output step in which a result of determination as to the presence or absence of rubbing of the rotary machine 10 is outputted from the input-output unit 120 to display it, for example, on a monitor, or may include a feedback step in which a feedback is given from the input-output unit 120 to the rotary machine to perform output.
While preferred embodiments of the invention have been described as above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirits of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-205008 | Nov 2019 | JP | national |
