Friction determination device and friction determination method for rotary machine

Abstract

A friction determination device is a device for determining friction in a rotating machine having a rotating part that is supported by a bearing so as to be rotatable with respect to a stationary part. This device acquires an AE signal from an AE sensor attached to a stationary part. With respect to the AE signal, a maximum value and a minimum value are determined for an envelope line obtained by performing envelope line processing with respect to a time change of the AE signal by signal analysis. And calculates a first frequency spectrum corresponding to a first time period including a maximum value in the time change, a second frequency spectrum corresponding to a second time period including a minimum value in the time change, and an average frequency spectrum of the first frequency spectrum and the second frequency spectrum. The first signal strength ratio is calculated as the ratio of the signal strength in a frequency band higher than the reference frequency in the first frequency spectrum to the signal strength in the entire frequency band of the average frequency spectrum. The second signal strength ratio is calculated as the ratio of the signal strength in a frequency band higher than the reference frequency in the second frequency spectrum to the signal strength in the entire frequency band of the average frequency spectrum. A first index, which is the ratio of the first signal strength ratio to the second signal strength ratio, is calculated. The presence or absence of friction is determined on the basis of the first index.

Description

TECHNICAL FIELD

[0001] The present application relates to a friction determination device and a friction determination method for a rotating machine.

[0002] This application claims priority based on Japanese Patent Application No. 2023-083194 filed on May 19, 2023 in the Japan Patent Office, and the contents thereof are incorporated herein. BACKGROUND

[0003] In a rotating machine such as a steam turbine, which has a rotating portion that can rotate with respect to a stationary portion, the gap between the stationary portion and the rotating portion can narrow due to thermal deformation of the machine room during operation, and thus friction can sometimes occur in which the rotating body contacts the stationary portion. The occurrence of friction is a major cause of performance degradation due to an increase in shaft vibration or an increase in the gap in the rotating machine. Therefore, a technology that can detect the occurrence of friction at an early stage and provide feedback on the operation of the rotating machine is required. In recent years, in particular, there is a tendency to reduce the gap in rotating machines for the purpose of coping with rapid load changes or improving performance, and thus the risk of such friction is expected to further increase.

[0004] As a method for determining the occurrence of friction, a technology using an AE (Acoustic Emission) sensor capable of detecting an AE signal is known. The AE sensor can be easily added, and has the ability to detect a wide range of friction, so it is expected to meet the need to quickly and easily evaluate the occurrence of friction by detecting the occurrence or position of friction in a rotating machine during operation.

[0005] However, in a rotating machine such as a turbine, fluid flows inside, so a large amount of noise can be mixed into the AE signal detected by the AE sensor provided in the rotating machine, which can lead to a decrease in the accuracy of friction determination. Thus, it is a problem to accurately determine friction in a noisy environment. In order to address this problem, a method is proposed in Patent Literature 1. In this document, first, based on the insight that the ratio of a contact signal indicating friction to a noise signal (SN ratio) becomes high in a high frequency band (for example, around 175 kHz) by filtering the AE signal acquired from the AE sensor, a band-pass filter is used to extract only the AE signal in the high frequency band. Next, the phase of the rotating synchronous component is calculated from the extracted AE signal, and it is determined that friction has occurred based on the fact that the phase converges. More specifically, an index for quantifying the convergence of the phase is calculated, and a case where the index exceeds a threshold value is automatically determined as the occurrence of friction.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Publication No. 2021-076533 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In the above-described Patent Literature 1, it is determined that friction occurs when the phase calculated from the AE signal acquired from the AE sensor mounted to the stationary portion of the rotating machine converges. However, depending on the mounting position of the AE sensor in the rotating machine, the phase of the AE signal can sometimes exhibit behavior in which it always converges regardless of the presence or absence of friction. In this case, in the above-described method, it is difficult to determine the occurrence of friction in the rotating machine.

[0011] At least one embodiment of the present application, which has been made in view of the above circumstances, has an object to provide a rotating machine friction determination device and a rotating machine friction determination method capable of accurately determining the presence or absence of friction based on an AE signal.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] To solve the above-described problems, a rotating machine friction determination device according to at least one embodiment of the present application,

[0014] for determining friction in a rotating machine having a rotating portion supported by a bearing so as to be rotatable with respect to a stationary portion,

[0015] the rotating machine friction determination device includes:

[0016] an AE signal acquisition portion configured to acquire an AE signal from an AE sensor mounted to the stationary portion;

[0017] a signal analysis portion configured to determine a maximum value and a minimum value from an envelope obtained by performing envelope processing on a time variation of the AE signal, and calculate a first average frequency spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average frequency spectrum corresponding to a second time period in which the minimum value is included in the time variation;

[0018] a first signal intensity ratio calculation portion configured to calculate a first signal intensity ratio as a ratio of a signal intensity in a frequency band higher than a reference frequency in the first average frequency spectrum with respect to a signal intensity in all frequency bands of the first average frequency spectrum;

[0019] a second signal intensity ratio calculation portion configured to calculate a second signal intensity ratio as a ratio of a signal intensity in a frequency band higher than the reference frequency in the second average frequency spectrum with respect to a signal intensity in all frequency bands of the second average frequency spectrum;

[0020] a first index calculation section configured to calculate a first index as a ratio of a first signal intensity ratio to a second signal intensity ratio;

[0021] a friction determination section configured to determine the presence or absence of the friction based on the first index.

[0022] To solve the above problem, a friction determination method for a rotating machine having a rotating portion supported by a bearing so as to be rotatable relative to a stationary portion,

[0023] determines the presence or absence of friction in a rotating machine having a rotating portion supported by a bearing so as to be rotatable relative to a stationary portion,

[0024] The friction determination method includes the following steps:

[0025] obtaining an AE signal from an AE sensor mounted to the stationary portion;

[0026] determining a maximum value and a minimum value from an envelope obtained by performing envelope processing on a time variation of the AE signal;

[0027] calculating a first average frequency spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average frequency spectrum corresponding to a second time period in which the minimum value is included in the time variation;

[0028] calculating a first signal intensity ratio as a ratio of a signal intensity in a frequency band higher than a reference frequency in the first average frequency spectrum to a signal intensity in an entire frequency band in the first average frequency spectrum;

[0029] calculating a second signal intensity ratio as a ratio of a signal intensity in a frequency band higher than the reference frequency in the second average frequency spectrum to a signal intensity in the entire frequency band in the second average frequency spectrum;

[0030] calculating a first index as a ratio of the first signal intensity ratio to the second signal intensity ratio; and

[0031] determining the presence or absence of the friction based on the first index.

[0032] Effects of Invention

[0033] According to at least one embodiment of the present application, a friction determination device and a friction determination method for a rotating machine capable of accurately determining the presence or absence of friction based on an AE signal can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a cross-sectional structure diagram of a rotating machine according to an embodiment.

[0035] Figure 2 is Figure 1a structure block diagram of the friction determination device.

[0036] Figure 3 is a flowchart showing steps for calculating the 1st index.

[0037] Figure 4 is a graph showing an example of the time variation of the AE signal.

[0038] Figure 5 is a graph showing the 1st average spectrum and the 2nd average spectrum corresponding to the time variation of the AE signal. Figure 4

[0039] Figure 6 is an example of the time progression of the amplitude, the phase, the 1st index (30 seconds average), and the 1st index (2 minutes average) of the AE signal.

[0040] Figure 7 is a flowchart showing the calculation method of the 2nd index based on the 2nd index calculation section. Figure 2

[0041] is a graph showing the amplitude of the AE signal per rotation number. Figure 8

[0042] is a flowchart showing the determination flow in the friction determination section of the friction determination device. Figure 9 Figure 2

[0043] Figure 10 is a flowchart showing a modification of the friction determination device. Figure 9 DETAILED DESCRIPTION

[0044] Hereinafter, several embodiments of the present application will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangement, and the like of the structures described as embodiments or shown in the drawings are not intended to limit the scope of the present application thereto, but are merely illustrative.

[0045] First, a rotating machine that is a determination target of the friction determination device according to at least one embodiment of the present application will be described. Figure 1 is a cross-sectional structure diagram of the rotating machine 1 according to one embodiment.

[0046] The rotating machine 1 has a stationary portion 2 and a rotating portion 4 that is rotatable with respect to the stationary portion 2. The stationary portion 2 is a housing of the rotating machine 1, and is stationary with respect to the outside. The rotating portion 4 is supported to be rotatable via a bearing 5 housed in a bearing housing 6, and is drivable by an arbitrary power. Like the stationary portion 2, the bearing housing 6 is stationary with respect to the outside.

[0047] ​​​​A gap D is provided between the stationary portion 2 and the rotating portion 4 (more accurately, the gap D is mainly formed between the innermost circumferential portion of the stationary blade possessed by the stationary portion 2 and the outermost circumferential portion (tip end) of the movable blade possessed by the rotating portion 4, but can also reach between the stationary portion 2 in which the stationary blade is mounted and the rotating portion 4 in which the movable blade is mounted). The rotating portion 4 is driven by introducing the working fluid W from the outside to the gap D. The working fluid W that has driven the rotating portion 4 is discharged to the outside via an unillustrated discharge path. When the rotating machine 1 is in operation, at least one of the stationary portion 2 or the rotating portion 4 can be deformed due to the influence of heat or the like, so that the gap D is reduced, generating friction. This friction can be detected from an AE signal detected by the AE sensor 10 described later.

[0048] The rotating machine 1 includes a plurality of units U arranged along the axial direction (extending direction) of the rotating portion 4. In the present embodiment, the rotating machine 1 has a first unit Ua and a second unit Ub as the plurality of units U. The number of units possessed by the rotating machine 1 can be arbitrary.

[0049] The first unit Ua and the second unit Ub share the rotating portion 4 and each have an independent stationary portion 2 (a first stationary portion 2a and a second stationary portion 2b). That is, the first unit Ua is composed of the first stationary portion 2a and the rotating portion 4, and the second unit Ub is composed of the second stationary portion 2b and the rotating portion 4.

[0050] The rotating portion 4 is a rotor that can be rotated by an arbitrary motive force, and in the present embodiment, is given the motive force by the above-described working fluid W. The rotating portion 4 can be configured in one piece, or can be configured by a plurality of components divided in the axial direction and joined to each other by a joint portion. In the latter case, the plurality of components can be configured by different materials from each other.

[0051] In the rotating machine 1, for example, steam can be used as the working fluid W, and each unit U can be configured as a steam turbine. In this case, the flow path of the working fluid W can be independent in each unit U, or each unit U can be connected in series or in parallel. For example, in the case where the flow path of the working fluid W in each unit U is connected in series, the first unit Ua can be a high-pressure turbine, and the second unit Ub can be a high-pressure turbine that can be driven by steam from the high-pressure turbine.

[0052] In addition, an inlet portion 8 for introducing the working fluid W from the outside to the gap D and an outlet portion (not illustrated) for discharging the working fluid W that has completed work in the gap D to the outside are provided on each unit U. Specifically, a first inlet portion 8a for introducing the working fluid W to a first gap Da is provided on the first unit Ua, and a second inlet portion 8b for introducing the working fluid W to a second gap Db is provided on the second unit Ub.

[0053] Further, the rotating machine 1 has at least one bearing 5 (radial bearing) for supporting the rotating portion 4. In the present embodiment, as the bearings 5, there are bearings 5a, 5b, and 5c. The bearing 5a is provided at one end side of the rotating portion 4, the bearing 5b is provided at an intermediate position of the rotating portion 4 (specifically, between the first stationary portion 2a constituting the first unit Ua and the second stationary portion 2b constituting the second unit Ub), and the bearing 5c is provided at the other end side of the rotating portion 4 (the side opposite to the bearing 5a). The rotating portion 4 is supported so as to be rotatable by these multiple bearings 5.

[0054] Further, as described above, the bearings 5a, 5b, and 5c are each housed by a bearing housing 6 that is stationary with respect to the outside.

[0055] The AE sensor 10 is a structure for detecting an AE (Acoustic Emission) signal, which is installed on a structure stationary with respect to the outside in the rotating machine 1. In the present embodiment, the AE sensor 10 is installed on the bearing housing 6 that houses the bearing 5b. The rotating machine 1 generates an AE wave, for example, by causing a seal or the like installed on the stationary portion 2 that has undergone thermal deformation to rub against the rotating portion 4. The AE wave generated at the rubbing site, for example, propagates as an elastic wave in the stationary portion 2 and the rotating portion 4, and is detected as an AE signal by each AE sensor 10 provided to the rotating machine 1. The AE wave generally has a frequency in the acoustic wave region of several tens of kHz to several MHz.

[0056] Further, the AE sensor 10 can be installed on the bearing housing 6 that houses the bearing 5a or 5c, or on the first stationary portion 2a or the second stationary portion 2b.

[0057] Next, a friction determination device 100 for determining friction in the rotating machine 1 having the above-described structure will be described. The friction determination device 100 is constituted by, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. Further, as an example, a series of processes for realizing various functions are stored in the storage medium or the like in the form of a program, and various functions are realized by reading out the program to the RAM or the like by the CPU and performing information processing / operation processing. Further, the program can be applied in a manner of being installed in advance in the ROM or other storage medium, or in a manner of being provided in a state of being stored in a computer-readable storage medium, or in a manner of being distributed via a wired or wireless communication unit, and the like. The computer-readable storage medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, and the like.

[0058] Figure 2 is Figure 1 a structure block diagram of the friction determination device 100. The friction determination device 100 is provided with an AE signal acquisition section 102, a signal analysis section 103, a first signal intensity ratio calculation section 104, a second signal intensity ratio calculation section 106, a first index calculation section 108, a second index calculation section 110, and a friction determination section 112.

[0059] The AE signal acquisition section 102 is a structure for acquiring an AE signal. As described above, the AE sensor 10 is attached to the stationary portion 2 in the rotating machine 1, and the AE signal acquisition section 102 acquires an AE signal detected by the AE sensor 10. In particular, the AE signal acquisition section 102 is configured to be able to determine the time variation of the AE signal by acquiring the AE signal continuously in time.

[0060] The signal analysis section 103 is a structure for performing spectral analysis on the time variation of the AE signal. The first signal intensity ratio calculation section 104 and the second signal intensity ratio calculation section 106 are structures for calculating the first signal intensity ratio POA / OA1 and the second signal intensity ratio POA / OA2 from the results of the spectral analysis. Also, the first index calculation section 108 is a structure for calculating the first index I1 from the first signal intensity ratio POA / OA1 and the second signal intensity ratio POA / OA2.

[0061] Here, with reference to Figures 3-5 , the method of calculating the first signal intensity L1 and the second signal intensity L2 and the first index I1 from the time variation of the AE signal will be described in detail. Figure 3 is a flowchart showing the steps for calculating the first index I1, Figure 4 is a graph showing an example of the time variation of the AE signal, Figure 5 is a graph showing the first average spectrum S1 and the second average spectrum S2 corresponding to the time variation of the AE signal of Figure 4 .

[0062] First, the AE signal is acquired by the AE signal acquisition section 102 over a predetermined period, whereby the time variation of the AE signal is obtained (step S100). With respect to the time variation of the AE signal, a corresponding envelope is obtained by performing envelope processing (step S101), and the maximum value and the minimum value are determined (step S102). An example of the time variation of the AE signal is shown in Figure 4 , showing the maximum value Vm (peak portion) and the minimum value Vn (valley portion) determined from the envelope obtained by the envelope processing. The maximum value Vm and the minimum value Vn appear alternately in time series.

[0063] The signal analysis section 103 obtains a first average spectrum S1 by performing frequency transformation (e.g., Fourier transformation) as spectral analysis on a first time period T1 that includes the maximum value Vm in the time variation of the AE signal (step S103). The first average spectrum S1 is obtained by averaging the spectra calculated for each of the maximum values Vm determined in step S102. The first time period T1 is defined as a prescribed period that includes the maximum value Vm, but for example, can be set such that the start time t1 and the end time t2 of the first time period T1 and the time tm1 at which the maximum value Vm is obtained satisfy the following equation.

[0064] tm1= (t1 + t2) / 2

[0065] Next, the signal analysis section 103 obtains a second average spectrum S2 by performing frequency transformation (e.g., Fourier transformation) as spectral analysis on a second time period T2 that includes the minimum value Vn in the time variation of the AE signal (step S104). The second average spectrum S2 is obtained by averaging the spectra calculated for each of the minimum values Vn determined in step S102. The second time period T2 is defined as a prescribed period that includes the minimum value Vn, but for example, can be set such that the start time t3 and the end time t4 of the second time period T2 and the time tm2 at which the minimum value Vn is obtained satisfy the following equation.

[0066] tm2= (t3 + t4) / 2

[0067] Next, the first signal intensity ratio calculation section 104 calculates the first signal intensity ratio POA / OA1 from the first average spectrum S1 obtained in step S103 (step S105). In step S105, the first signal intensity ratio POA / OA1 is calculated as the ratio of a partial overall value POA corresponding to the signal intensity in a frequency band higher than the reference frequency fref in the first average spectrum S1 to an overall value OA corresponding to the signal intensity in the entire frequency band of the first average spectrum S1.

[0068] Then, the second signal intensity ratio calculation section 106 calculates the second signal intensity ratio POA / OA2 from the second average spectrum S2 obtained in step S104 (step S106). In step S106, the second signal intensity ratio POA / OA2 is calculated as the ratio of a partial overall value POA corresponding to the signal intensity in a frequency band higher than the reference frequency fref in the second average spectrum S2 to an overall value OA corresponding to the signal intensity in the entire frequency band of the second average spectrum S2.

[0069] Next, the first index calculating section 108 calculates the first index I1 as a ratio of the first signal intensity ratio POA / OA1 to the second signal intensity ratio POA / OA2, (POA / OA1) / (POA / OA2) (step S107). Hereinafter, a case where the first index I1 thus calculated is an index effective in the friction determination will be described.

[0070] In a case where the phase of the AE signal converges, the amplitude of the AE signal varies in synchronization with the rotation speed. Specifically, a peak portion (around the maximum value Vm) where the amplitude is large in the time variation of the AE signal corresponds to a signal at the time of contact, and a valley portion (around the minimum value Vn) where the amplitude is small corresponds to a signal at the time of non-contact. As shown in FIG. 6, if the first average spectrum S1 and the second average spectrum S2 are calculated by applying Fourier transform to the AE signal corresponding to the peak portion and the valley portion, the first average spectrum S1 corresponding to the time of contact (the time of friction) becomes larger in signal intensity than the second average spectrum S2 corresponding to the time of non-contact in a high frequency band (for example, around 175 kHz). An index that numerically represents such a characteristic is the first index I1. Figure 5

[0071] Figure 6 is an example of a time progression of the amplitude of the AE signal, the phase, the first index I1 (30-second average), and the first index I1 (2-minute average). In this example, in the periods ta, tb, and tc, the amplitude of the AE signal increases, and convergence of the phase is confirmed, thereby suggesting that friction has occurred. On the other hand, if the behavior of the first index I1 is focused on, the first index I1 also temporarily increases in the periods ta, tb, and tc. This indicates that the first index I1 is effective as an index for the friction determination. In particular, regarding the first index I1, the 2-minute average is more obvious in the behavior in the periods ta, tb, and tc than the 30-second average, and the usefulness as an index for the friction determination is also improved.

[0072] In addition, in a period other than the periods ta, tb, and tc, the phase always shows a tendency to converge, indicating that it is not sufficient as an index for the friction determination.

[0073] In addition, in Figure 6 , since the amplitude of the AE signal increases at the time of occurrence of friction, there is also an idea that the friction determination can be performed without using the first index I1. However, the amplitude of the AE signal varies depending on the output (load) of the rotating machine 1. Therefore, in the friction determination in the rotating machine 1 including the transient state, by using the first index I1 instead of the amplitude of the AE signal, it is possible to perform the friction determination with more favorable precision.

[0074] Returning to Figure 2 ​, the second index calculating section 110 is a structure for calculating a second index I2 indicating the phase convergence in the time variation of the AE signal. Specifically, the second index I2 is calculated by using the variance σ of the phase of the AE signal from the following equation.

[0075] Second index I2 = 1 / (1 + σ0 5)

[0076] Here, with reference to Figure 7 , the specific calculation method of the second index I2 will be described. Figure 7 is a flowchart of the calculation method of the second index I2 of the second index calculating section 110 based on Figure 2

[0077] First, the second index calculating section 110 performs filter processing based on a prescribed filter on the AE signal acquired by the AE signal acquiring section 102, and outputs the AE signal that has been subjected to the filter processing in a manner that the frequency component with respect to the passband of the filter is extracted (step S200). The filter processing is performed using a band-pass filter that takes a prescribed frequency band of the AE signal as the passband.

[0078] Next, the second index calculating section 110 performs data processing on the AE signal or the AE signal that has been subjected to the filter processing by performing envelope processing, resampling processing, and average zero processing (step S201). Specifically, in the envelope processing, the AE signal or the AE signal after the filter processing is subjected to the envelope processing, and the AE signal that has been subjected to the envelope processing is output. In the resampling processing, the AE signal after the envelope processing is subjected to the resampling, and the AE signal that has been subjected to the resampling processing is output. In the average zero processing, the AE signal after the resampling is subjected to the processing that makes the average value of the amplitudes in each cycle zero, and the AE signal that has been subjected to the average zero processing is output.

[0079] Next, the second index calculating section 110 performs frequency analysis on the AE signal that has been subjected to the average zero processing, and outputs the rotational number analysis result F in which the frequency is expressed by the rotational number, as shown in Figure 8 Figure 8 is a chart showing the amplitude of the AE signal for each rotational number.

[0080] ​​Next, the second index calculation unit 110 obtains the rotational speed component C from the rotational speed analysis result F and calculates the second index I2 using the above equation using the variance σ of the phase P extracted from the rotational speed component C obtained by sampling the phase of the rotational speed component C (step S203). This variance σ is calculated for the phase P extracted from the rotational speed component C obtained by performing predetermined sampling on the phase of the rotational speed component C. The phase of the phase P is obtained as the deviation of the period of the rotational speed component C from the period of the rotational speed of the rotating part. For example, the phase P extracted from the rotational speed component C is obtained by sampling at 5-10 points at intervals of several seconds.

[0081] The friction determination unit 112 is configured to determine the presence or absence of friction based on at least one of the first indicator I1 and the second indicator I2. The friction determination may be based on either the first indicator I1 or the second indicator I2, or may be based on both the first indicator I1 and the second indicator I2.

[0082] Here, the friction determination method performed by the friction determination unit 112 will be described in detail. Figure 9 Yes Figure 2 Flowchart of the determination process in the friction determination unit 112. Figure 9 In the illustrated embodiment, the friction determination unit 112 determines the presence or absence of friction based only on the first index I1.

[0083] First, the friction determination unit 112 obtains the first index I1 calculated by the first index calculation unit 108 (step S300 ). The first index calculation unit 108 successively calculates the first index I1, and the friction determination unit 112 obtains the first index I1 from the first index calculation unit 108 each time.

[0084] Next, the friction determination unit 112 acquires a first threshold value corresponding to the first index I1 (step S301 ). The first threshold value may be a calculated value based on the operating state of the rotary machine 1 or a predetermined value pre-stored in a storage device.

[0085] Next, the friction determination unit 112 determines whether the first indicator I1 obtained in step S300 is greater than the first threshold value obtained in step S301 (step S302). If the first indicator I1 is greater than the first threshold value (step S302: Yes), the friction determination unit 112 determines that friction is present (step S303). On the other hand, if the first indicator I1 is less than the first threshold value (step S302: No), the friction determination unit 112 determines that there is no friction (step S304). As described above, friction determination using the first indicator I1 is effective regardless of phase convergence, enabling highly accurate friction determination.

[0086] Figure 10Yes Figure 9 In this modification, the friction determination unit 112 determines the presence or absence of friction based on both the first index I1 and the second index I2.

[0087] First, the friction determination unit 112 obtains the first index I1 calculated by the first index calculation unit 108 and the second index I2 calculated by the second index calculation unit 110 (step S400). The first index calculation unit 108 and the second index calculation unit 110 successively calculate the first index I1 and the second index I2. The friction determination unit 112 obtains the first index I1 from the first index calculation unit 108 and the second index I2 from the second index calculation unit 110 each time.

[0088] Next, the friction determination unit 112 obtains a first threshold value and a second threshold value corresponding to the first index I1 and the second index I2, respectively (step S401). The first threshold value and the second threshold value may be calculated based on the operating state of the rotating machine 1 or may be predetermined values ​​pre-stored in a storage device.

[0089] Next, the friction determination unit 112 determines whether the first indicator I1 or the second indicator I2 obtained in step S400 is greater than the first threshold value or the second threshold value obtained in step S401 (step S402). When at least one of the first indicator I1 or the second indicator I2 is greater than the first threshold value or the second threshold value (step S402: yes), the friction determination unit 112 determines that there is friction (step S403). On the other hand, when the first indicator I1 and the second indicator I2 are both below the first threshold value and the second threshold value (step S402: no), the friction determination unit 112 determines that there is no friction (step S404). In this way, by using both the first indicator I1 and the second indicator I2, compared with the reference Figure 9 Compared with the above example, friction determination can be performed with higher accuracy.

[0090] Furthermore, constituent elements in the above-described embodiments may be appropriately replaced with well-known constituent elements within a scope not departing from the spirit of the present invention, and the above-described embodiments may be appropriately combined.

[0091] The contents described in each of the above-mentioned embodiments can be understood, for example, as follows.

[0092] (1) A friction determination device for a rotating machine according to one embodiment is for determining friction in a rotating machine having a rotating part supported by a bearing so as to be rotatable relative to a stationary part, the friction determination device for a rotating machine comprising:

[0093] an AE signal acquiring unit, configured to acquire an AE signal from an AE sensor mounted on the stationary unit;

[0094] a signal analysis section for determining a maximum value and a minimum value from an envelope obtained by performing envelope processing on a time variation of the AE signal, and calculating a first average spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average spectrum corresponding to a second time period in which the minimum value is included in the time variation, respectively;

[0095] a first signal intensity ratio calculation section for calculating a first signal intensity ratio as a ratio of a signal intensity in a frequency band higher than a reference frequency in the first average spectrum to a signal intensity in all frequency bands of the first average spectrum;

[0096] a second signal intensity ratio calculation section for calculating a second signal intensity ratio as a ratio of a signal intensity in a frequency band higher than the reference frequency in the second average spectrum to a signal intensity in all frequency bands of the second average spectrum;

[0097] a first index calculation section for calculating a first index as a ratio of the first signal intensity ratio to the second signal intensity ratio; and

[0098] a friction determination section for determining the presence or absence of the friction on the basis of the first index.

[0099] According to the manner of (1) above, the presence or absence of friction is determined on the basis of a time variation of an AE signal detected by an AE sensor attached to a stationary portion of a rotating machine. By performing envelope processing on the time variation of the AE signal, an envelope of the time variation is created, and a maximum value and a minimum value thereof are determined. A first average spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average spectrum corresponding to a second time period in which the minimum value is included in the time variation are calculated, respectively. A first signal intensity ratio is calculated as a ratio of a signal intensity in a frequency band higher than a reference frequency in the first average spectrum to a signal intensity in all frequency bands of the first average spectrum. A second signal intensity ratio is calculated as a ratio of a signal intensity in a frequency band higher than the reference frequency in the second average spectrum to a signal intensity in all frequency bands of the second average spectrum. In this manner, a first index for determining the presence or absence of friction is calculated using the first signal intensity ratio and the second signal intensity ratio. The first index thus calculated reflects information related to the presence or absence of friction independently of a convergence state of a phase calculated on the basis of the time variation. Therefore, by determining the presence or absence of friction on the basis of the first index, friction determination with reliability can be performed.

[0100] (2) In another manner, in the manner of (1) above,

[0101] the friction determination section determines the presence or absence of the friction on the basis of a result obtained by averaging the first index over a prescribed period.

[0102] According to the above-described (2), by averaging the first index calculated as described above over a prescribed period, random components such as noise included in the first index are canceled out. By using the first index from which the random components are removed in this way, a more accurate friction determination can be performed.

[0103] (3) In another aspect, in the aspect of (1) or (2) above,

[0104] Further provided is a second index calculation unit that calculates a second index indicating convergence of phase in the time variation,

[0105] The friction determination unit determines the presence or absence of the friction based on the first index and the second index.

[0106] According to the above-described (3), as described above, by using the first index based on signal intensity and the second index based on phase convergence, a more accurate friction determination can be performed.

[0107] (4) In another aspect, in any one of the aspects of (1) to (3) above,

[0108] The stationary portion is a bearing housing that houses the bearing.

[0109] According to the above-described (4), an accurate friction determination can be performed based on an AE signal detected by an AE sensor provided to the bearing housing.

[0110] (5) A friction determination method for a rotating machine having a rotating portion supported by a bearing so as to be rotatable relative to a stationary portion, the friction determination method comprising the steps of:

[0111] obtaining an AE signal from an AE sensor mounted to the stationary portion;

[0112] determining a maximum value and a minimum value from an envelope obtained by performing envelope processing on a time variation of the AE signal;

[0113] calculating a first average frequency spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average frequency spectrum corresponding to a second time period in which the minimum value is included in the time variation;

[0114] calculating a first signal intensity ratio as a ratio of signal intensity in a frequency band higher than a reference frequency in the first average frequency spectrum to signal intensity in the entire frequency band in the first average frequency spectrum;

[0115] calculating a second signal intensity ratio as a ratio of signal intensity in a frequency band higher than a reference frequency in the second average frequency spectrum to signal intensity in the entire frequency band in the second average frequency spectrum;

[0116] calculating a first index as a ratio of the first signal intensity ratio to a second signal intensity ratio; and

[0117] determining the presence or absence of the friction based on the first index.

[0118] According to the aspect (5) described above, the presence or absence of the friction is determined based on the time variation of the AE signal detected by the AE sensor installed in the stationary portion of the rotating machine. By performing the envelope processing on the time variation of the AE signal, the envelope line of the time variation is created, and the maximum value and the minimum value thereof are determined. A first average spectrum corresponding to a first time period in which the maximum value is included in the time variation and a second average spectrum corresponding to a second time period in which the minimum value is included in the time variation are calculated, respectively. The first signal intensity ratio is calculated as a ratio of the signal intensity in a frequency band higher than a reference frequency in the first average spectrum to the signal intensity in the entire frequency band of the first average spectrum. The second signal intensity ratio is calculated as a ratio of the signal intensity in a frequency band higher than the reference frequency in the second average spectrum to the signal intensity in the entire frequency band of the second average spectrum. In this aspect, the first index for determining the presence or absence of the friction is calculated using the first signal intensity ratio and the second signal intensity ratio. The first index thus calculated reflects information related to the presence or absence of the friction independently of the convergence state of the phase calculated from the time variation. Therefore, by determining the presence or absence of the friction based on the first index, the friction determination with reliability can be performed.

[0119] Explanation of Symbols

[0120] 1 - rotating machine, 2 - stationary portion, 2a - first stationary portion, 2b - second stationary portion, 4 - rotating portion, 5 - bearing, 6 - bearing housing, 8 - inlet portion, 8a - first inlet portion, 8b - second inlet portion, 10 - AE sensor, 100 - friction determination device, 102 - AE signal acquisition portion, 104 - first signal intensity ratio calculation portion, 106 - second signal intensity ratio calculation portion, 108 - first index calculation portion, 110 - second index calculation portion, 112 - friction determination portion, Ua - first unit, Ub - second unit, D - gap.

Claims

1. A friction determination device for a rotating machine, for determining friction in a rotating machine having a rotating part supported by a bearing so as to be rotatable relative to a stationary part, the friction determination device for a rotating machine comprising: an AE signal acquiring unit, configured to acquire an AE signal from an AE sensor mounted on the stationary unit; a signal analysis unit configured to determine a maximum value and a minimum value of an envelope obtained by performing envelope processing on a time variation of the AE signal, and calculate a first average spectrum corresponding to a first time segment containing the maximum value in the time variation and a second average spectrum corresponding to a second time segment containing the minimum value in the time variation; a first signal strength ratio calculation unit configured to calculate a first signal strength ratio as a ratio of signal strength in a frequency band higher than a reference frequency in the first average spectrum to signal strength in all frequency bands of the first average spectrum; a second signal strength ratio calculation unit configured to calculate a second signal strength ratio as a ratio of signal strength in a frequency band higher than a reference frequency in the second average spectrum to signal strength in the entire frequency band of the second average spectrum; a first index calculation unit configured to calculate a first index as a ratio of the first signal strength ratio to the second signal strength ratio; and The friction determination unit is configured to determine the presence or absence of the friction based on the first index.

2. The friction determination device for a rotary machine according to claim 1, wherein: The friction determination unit determines the presence or absence of the friction based on a result obtained by averaging the first index over a predetermined period of time.

3. The friction determination device for a rotating machine according to claim 1 or 2, further comprising a second index calculation unit for calculating a second index indicating the phase convergence during the temporal change. The friction determination unit determines the presence or absence of the friction based on the first index and the second index.

4. The friction determination device for a rotary machine according to claim 1 or 2, wherein: The stationary portion is a bearing box that accommodates the bearing.

5. A method for determining friction in a rotating machine, the method comprising determining friction in a rotating machine having a rotating part supported by a bearing so as to be rotatable relative to a stationary part, the method comprising the following steps: acquiring an AE signal from an AE sensor mounted on the stationary portion; determining a maximum value and a minimum value of an envelope obtained by performing envelope processing on a temporal change of the AE signal; respectively calculating a first average spectrum corresponding to a first time period containing the maximum value in the time variation and a second average spectrum corresponding to a second time period containing the minimum value in the time variation; calculating a first signal intensity ratio which is a ratio of signal intensity in a frequency band higher than a reference frequency in the first average spectrum to signal intensity in the entire frequency band in the first average spectrum; calculating a second signal intensity ratio which is a ratio of signal intensity in a frequency band higher than a reference frequency in the second average spectrum to signal intensity in the entire frequency band in the second average spectrum; calculating a first index as a ratio of the first signal strength ratio to the second signal strength ratio; and The presence or absence of the friction is determined based on the first index.

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