Fault detection method, system and device for plate heat exchanger

Abstract

The invention relates to the field of heat exchanger fault detection, in particular to a fault detection method, system and device for a plate heat exchanger. The method comprises the following steps: firstly, acquiring a temperature signal of each metal sheet of the plate heat exchanger and a time-domain signal about vibration, fusing the time-domain signals of two adjacent metal sheets according to the fluctuation difference between the time-domain signals and the temperature signals of the two metal sheets adjacent to a target gasket, and then carrying out frequency-domain conversion on the fused time-domain signals; obtaining a frequency domain signal of the target gasket; and acquiring the overall amplitude of the target gasket only under temperature interference, and performing damage detection on the gasket according to the amplitude difference between the frequency domain signals of the target gasket and other gaskets at the same frequency and the difference between the amplitude of the frequency domain signal of the target gasket at each frequency and the overall amplitude. The method can reduce the interference of the vibration signal generated by the temperature change on the vibration characteristic analysis generated by the gasket damage, and improves the accuracy of the damage detection of the plate heat exchanger gasket.

Description

Technical Field

[0001] The present invention relates to the field of heat exchanger fault detection, and particularly to a fault detection method, system and device for a plate heat exchanger. Background Art

[0002] A plate heat exchanger is a heat exchange device widely used in various industrial fields. It separates two fluids at different temperatures through a series of corrugated metal plates, and realizes heat exchange through the space between the plates. The sealing gasket is a key component in the plate heat exchanger, which can prevent fluid leakage to avoid pollution and equipment damage, and helps to ensure the heat exchange efficiency, avoid equipment damage and extend the service life of the equipment. Therefore, detecting whether the sealing gasket is damaged is crucial for maintaining the normal operation of the heat exchanger.

[0003] Since the fluid leakage caused by gasket damage will generate vibration signals. In the related art, usually, the vibration signals of the heat exchanger gasket in the time domain are monitored and collected, and then they are converted into frequency domain signals through Fourier transform, and then the frequency components in the spectrum are analyzed to identify the characteristics related to gasket damage. However, since the working principle of the plate heat exchanger is to cause temperature changes through heat exchange, and the temperature changes will cause the thermal expansion or contraction effect of the metal plates, resulting in slight bending or deformation of the metal plates, thus generating vibration signals. These vibration signals generated by temperature changes will overlap with the vibrations generated by fluid leakage caused by sealing gasket damage in the spectrum, thereby interfering with the vibration characteristics generated by fluid leakage caused by gasket damage and reducing the accuracy of detecting the damage of the heat exchanger gasket. Summary of the Invention

[0004] In order to solve the technical problem that the vibration signals generated by temperature changes will interfere with the vibration characteristics generated by fluid leakage caused by gasket damage and reduce the accuracy of detecting the damage of the heat exchanger gasket, the purpose of the present invention is to provide a fault detection method, system and device for a plate heat exchanger, and the specific technical solutions adopted are as follows: The present invention proposes a fault detection method for a plate heat exchanger, and the method includes: Obtaining the temperature signal and the time-domain signal about vibration of each metal plate of the plate heat exchanger during the working process; Taking any gasket of the plate heat exchanger as the target gasket, and taking the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket. According to the difference in the fluctuations between the time-domain signal and the temperature signal of each reference metal plate, obtaining the fusion weight of the time-domain signal of each reference metal plate at each moment; According to the fusion weight of the time-domain signal of each reference metal plate at each moment, fusing the time-domain signals of the reference metal plates and then performing frequency-domain conversion to obtain the frequency-domain signal of the target gasket; Based on the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket, obtain the overall amplitude of the target gasket only under temperature interference; based on the amplitude difference between the frequency-domain signals of the target gasket and other gaskets except the target gasket at the same frequency, and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude, obtain the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency; based on the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies, obtain the damage possibility of the target gasket; Perform damage detection on each gasket based on the damage possibility of each gasket.

[0005] Furthermore, the obtaining of the fusion weight of the time-domain signal of each reference metal sheet at each moment includes: Take any one of the reference metal sheets as the target reference metal sheet; Based on the calculation formula of the effective coefficient, obtain the effective coefficient of the time-domain signal of the target reference metal sheet at each moment. The calculation formula of the effective coefficient is: where, represents the effective coefficient of the time-domain signal of the target reference metal sheet at the th moment; represents the standard deviation of the amplitudes of all moments between the th moment and the th moment of the time-domain signal of the target reference metal sheet, ; represents the standard deviation of the temperature data of all moments between the th moment and the th moment of the temperature signal of the target reference metal sheet; represents the number of other moments except the th moment; represents the exponential function with the natural constant as the base; represents the normalization function; Perform normalization processing on the effective coefficient of the time-domain signal of the target reference metal sheet at each moment to obtain the fusion weight of the time-domain signal of the target reference metal sheet at each moment. Among them, the sum value of the fusion weights of the time-domain signals of the two reference metal sheets of the target gasket at the same moment is equal to the value 1.

[0006] Furthermore, the obtaining of the frequency-domain signal of the target gasket includes: Using the fusion weights of the time-domain signals of the two reference metal plates of the target gasket at each moment, the amplitudes of the time-domain signals of the two reference metal plates are weighted and summed at each moment to obtain the fusion amplitude of the target gasket at each moment, and the signal composed of the fusion amplitudes of the target gasket at all moments is used as the fusion time-domain signal of the target gasket with respect to vibration; Perform a Fourier transform on the fusion time-domain signal of the target gasket with respect to vibration to obtain the frequency-domain signal of the target gasket.

[0007] Further, the obtaining of the overall amplitude of the target gasket only under temperature interference includes: Construct an overall amplitude function for each gasket, and the overall amplitude function is: where, represents the overall amplitude function of the -th gasket, and its independent variable is the serial number corresponding to the -th gasket; , , and respectively represent four unknown parameters; represents the natural constant; Construct an error function according to the amplitudes of the same frequency of the frequency-domain signals of all gaskets and the overall amplitude function. The error function contains , , and four unknown parameters; Use the least squares method to minimize the error function and calculate the , , and numerical values of the four unknown parameters, and substitute the numerical values of the , , and four unknown parameters and the serial number corresponding to the target gasket into the overall amplitude function to obtain the overall amplitude of the target gasket only under temperature interference.

[0008] Further, the constructing of the error function includes: Perform a negative correlation mapping on each frequency value of the frequency-domain signal to obtain the reference weight of each frequency of the frequency-domain signal; Construct an error function, and the error function is: where, represents the error function; Represents the reference weight of the th frequency of the frequency-domain signal; Represents the amplitude of the frequency-domain signal of the th gasket at the th frequency; Represents the overall amplitude function with respect to the th gasket; Represents the number of frequencies included in the frequency-domain signal. The number of frequencies included in the frequency-domain signal of each gasket is equal; Represents the number of gaskets.

[0009] Furthermore, the obtaining of the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency includes: Taking any frequency of the frequency-domain signal as the target frequency, and taking the absolute value of the difference in amplitude between the frequency-domain signals of the target gasket and each other gasket at the target frequency as the amplitude difference value between the frequency-domain signals of the target gasket and each other gasket at the target frequency; Taking the average value of the amplitude difference values between the frequency-domain signals of the target gasket and all other gaskets at the target frequency as the amplitude difference degree of the frequency-domain signal of the target gasket at the target frequency; Taking the absolute value of the difference between the amplitude of the frequency-domain signal of the target gasket at the target frequency and the overall amplitude of the target gasket as the degree of non-temperature interference of the frequency-domain signal of the target gasket at the target frequency; Combining the amplitude difference degree and the degree of non-temperature interference to obtain the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency.

[0010] Furthermore, the obtaining of the damage possibility of the target gasket includes: Taking the product value of each frequency value of the frequency-domain signal of the target gasket and the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency as the adjusted damage performance degree of the frequency-domain signal of the target gasket at each frequency; Normalizing the average value of the adjusted damage performance degrees of the frequency-domain signal of the target gasket at all frequencies to obtain the damage possibility of the target gasket.

[0011] Furthermore, the damage detection of each gasket includes: Taking the gasket with the damage possibility greater than the preset possibility threshold as the damaged gasket.

[0012] The present invention also proposes a fault detection system for a plate heat exchanger, and the system includes: A data acquisition module for acquiring the temperature signal of each metal plate of the plate heat exchanger during the working process and the time-domain signal regarding vibration; The first analysis module is configured to use any gasket of the plate heat exchanger as the target gasket, and use the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket. According to the difference in the fluctuations between the time-domain signal and the temperature signal of each reference metal plate, the fusion weight of the time-domain signal of each reference metal plate at each moment is obtained; according to the fusion weight of the time-domain signal of each reference metal plate at each moment, the time-domain signals of the reference metal plates are fused and then subjected to frequency-domain conversion to obtain the frequency-domain signal of the target gasket; The second analysis module is configured to obtain the overall amplitude of the target gasket only under temperature interference according to the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket; according to the amplitude difference between the frequency-domain signals of the target gasket and other gaskets except the target gasket at the same frequency, and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude, obtain the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency; according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies, obtain the damage possibility of the target gasket; The damage detection module is configured to perform damage detection on each gasket based on the damage possibility of each gasket.

[0013] The present invention also provides a fault detection device for a plate heat exchanger. The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of any one of the fault detection methods for a plate heat exchanger are implemented.

[0014] The present invention has the following beneficial effects: In view of the fact that the vibration signals generated by temperature changes will interfere with the vibration characteristics caused by gasket damage leading to fluid leakage, reducing the accuracy of detecting gasket damage in heat exchangers. Therefore, first, the temperature signals of each metal plate of the plate heat exchanger and the time-domain signals regarding vibration are obtained. The obtained fusion weights reflect the reference value of the amplitude at each moment of the time-domain signal of each reference metal plate during subsequent signal fusion, enabling the fused time-domain signal to better represent the time-domain signal regarding vibration of the target gasket and accurately obtaining the frequency-domain signal of the target gasket. Since the vibration signals generated by temperature changes will interfere with the vibration signals generated when the target gasket is damaged, resulting in the inability of the frequency-domain signal of the target gasket to accurately express its vibration characteristics when damaged. Therefore, first, the overall amplitude obtained is used to reflect the overall level of the amplitude of the frequency-domain signal of the target gasket under the influence of only temperature, facilitating subsequent reduction of the interference of temperature changes on damage analysis. Since when the damage of the target gasket and temperature changes are not considered, the amplitudes of the same frequency of the frequency-domain signals of each gasket tend to be consistent, and the greater the difference between the amplitude of the frequency-domain signal of the target gasket at a certain frequency and the overall amplitude, it indicates that the influence of temperature changes on the frequency-domain signal at this frequency is smaller. At the same time, when the consistency of the amplitudes of the frequency-domain signals between the target gasket and other gaskets at this frequency is poor, it indicates that the target gasket exhibits obvious damage characteristics at this frequency. Therefore, the damage manifestation coefficient can be used to reflect the degree of damage of the target gasket shown by the frequency-domain signal at each frequency, thereby reducing the interference of the vibration signals generated by temperature changes on the analysis of the vibration characteristics caused by gasket damage. Furthermore, the damage possibility is used to reflect the possibility of damage to the target gasket, and the damage detection of each gasket is carried out through the damage possibility, improving the accuracy of damage detection. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 Flowchart of a fault detection method for a plate heat exchanger provided by an embodiment of the present invention; Figure 2 Schematic diagram of the temperature signals of two adjacent metal plates provided by an embodiment of the present invention; Figure 3 Schematic diagram of the time-domain signals regarding vibration of two adjacent metal plates provided by an embodiment of the present invention; Figure 4Schematic diagram of the fused time-domain signal of the target gasket with respect to vibration provided by an embodiment of the present invention; Figure 5 Schematic diagram of the frequency-domain signal of the target gasket provided by an embodiment of the present invention. Detailed implementation manners

[0017] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the drawings and preferred embodiments to detail the specific implementation manners, structures, features and effects of a fault detection method, system and device for a plate heat exchanger proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0019] The following specifically describes the specific solutions of a fault detection method, system and device for a plate heat exchanger provided by the present invention with reference to the drawings.

[0020] Please refer to Figure 1 , which shows a flowchart of a fault detection method for a plate heat exchanger provided by an embodiment of the present invention. The method includes: Step S1: Obtain the temperature signal and the time-domain signal with respect to vibration of each metal plate of the plate heat exchanger during the working process.

[0021] A plate heat exchanger usually consists of metal plates, channels, sealing gaskets, etc. The sealing gasket is generally installed between adjacent metal plates to play a role in fluid isolation and sealing, ensuring that the fluids in each channel do not mix or leak.

[0022] In the embodiment of the present invention, an acceleration sensor and a temperature sensor are first installed on each metal plate. The time-domain signal with respect to vibration of each metal plate of the plate heat exchanger during the working process is collected through the acceleration sensor, that is, the vibration signal in the time domain. Please refer to Figure 3 , which shows a schematic diagram of the time-domain signal with respect to vibration of two adjacent metal plates provided by an embodiment of the present invention. Among them, the time-domain signal includes amplitudes at different times. Then, the temperature signal of each metal plate of the plate heat exchanger during the working process is collected through the temperature sensor. Please refer to Figure 2 , which shows a schematic diagram of the temperature signal of two adjacent metal plates provided by an embodiment of the present invention. Among them, the temperature signal includes temperature data at different times.

[0023] It should be noted that the data acquisition frequencies of the acceleration sensor and the temperature sensor are the same. In an embodiment of the present invention, the data acquisition frequencies of both are set to 100 Hz. The specific value of the data acquisition frequency can also be set by the implementer according to the specific implementation scenario, and is not limited herein.

[0024] It should be noted that after multiple metal plates of the plate heat exchanger are arranged, channels will be formed, and the fluid will flow in the channels. In the embodiment of the present invention, for the convenience of calculation and analysis in subsequent steps, after the fluid enters from the channel, the gaskets of the plate heat exchanger are numbered in the order of fluid flow. For example, after the fluid enters from the channel, the serial number of the first gasket it flows through is set to the value 1, the serial number of the second gasket it flows through is set to the value 2, and so on.

[0025] Step S2: Take any gasket of the plate heat exchanger as the target gasket, and take the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket. According to the difference in the fluctuations between the time-domain signal and the temperature signal of each reference metal plate, obtain the fusion weight of the time-domain signal of each reference metal plate at each moment; according to the fusion weight of the time-domain signal of each reference metal plate at each moment, fuse the time-domain signals of the reference metal plates and then perform frequency-domain conversion to obtain the frequency-domain signal of the target gasket.

[0026] In the embodiment of the present invention, it is necessary to analyze the vibration characteristics of the gasket to detect whether the gasket is damaged and causes fluid leakage. Therefore, first take any gasket of the plate heat exchanger as the target gasket. Since the sensors are arranged on the metal plates in the embodiment of the present invention, it is necessary to analyze the vibration signal of the gasket by using the vibration signal of the metal plate. When analyzing the vibration signal of the target gasket, the two metal plates adjacent to it are in direct contact with the target gasket. Therefore, the two metal plates adjacent to the target gasket have the greatest reference value, and thus the two metal plates adjacent to the target gasket can be used as the reference metal plates of the target gasket.

[0027] Since metal materials have thermal expansion characteristics, when the temperature rises, the metal plate will expand, causing its shape and size to change. Especially when the temperature fluctuates rapidly, the metal plate will expand and contract rapidly with the temperature change. This rapid expansion and contraction will cause the plate to deform violently, resulting in an increase in the fluctuation of the vibration amplitude. Therefore, the temperature fluctuation is directly proportional to the change in vibration amplitude, that is, the more violent the temperature fluctuation, the more obvious the change in vibration amplitude. Therefore, the more consistent the fluctuation between the time domain signal and the temperature signal of a reference metal plate is, the more the temperature change affects the time domain signal of the reference metal plate. The more consistent and stable the time domain signal of the reference metal plate is, the greater the reference value of the time domain signal of the reference metal plate in the subsequent fusion process. Therefore, the fusion weight of the time domain signal of each reference metal plate at each moment can be obtained according to the difference in fluctuations between the time domain signal and the temperature signal of each reference metal plate, and the difference in amplitudes between the time domain signals of the two reference metal plates at the same moment. The fusion weight reflects the reference value of the amplitude of the time domain signal of each reference metal plate at each moment when the signal is fused subsequently, so that the fused time domain signal can better represent the time domain signal of the vibration of the target gasket and accurately obtain the frequency domain signal of the target gasket.

[0028] Preferably, in one embodiment of the present invention, the method for obtaining the fusion weight of the time domain signal of each reference metal plate at each moment specifically includes: Taking any reference metal sheet as a target reference metal sheet; Based on the calculation formula of the effective coefficient, the effective coefficient of the time domain signal of the target reference metal plate at each moment is obtained. The calculation formula of the effective coefficient is: in, The time domain signal representing the target reference metal plate is The effective coefficient at each moment; The first time domain signal representing the target reference metal plate The moment and The standard deviation of the amplitude at all moments between ; The first The moment and The standard deviation of the temperature data at all times between the moments; Indicates that except The number of moments other than the moment; Expressed as a natural constant An exponential function with base is used for negative correlation mapping processing; denotes a normalization function for normalization processing. In one embodiment of the present invention, the normalization processing can be, for example, maximum-minimum normalization processing, and the normalization in subsequent steps can all adopt maximum-minimum normalization processing. In other embodiments of the present invention, other normalization methods can be selected according to the specific range of values, which will not be elaborated herein.

[0029] It should be noted that all the moments between the th moment and the th moment include the th moment and the th moment.

[0030] Among them, the smaller it is, the greater the consistency between the amplitude fluctuation of the time-domain signal of the target reference metal sheet between the th moment and the th moment, and the temperature data fluctuation of the temperature signal between the th moment and the th moment. Furthermore, it indicates that the amplitude of the th moment of the time-domain signal of the target reference metal sheet has a greater reference value in subsequent signal fusion.

[0031] It should be noted that in other embodiments of the present invention, negative correlation mapping can also be achieved through other basic mathematical operations, which will not be elaborated herein.

[0032] By the same method as above, the effective coefficient of the time-domain signal of each reference metal sheet at each moment can be obtained.

[0033] Furthermore, the effective coefficient of the time-domain signal of the target reference metal sheet at each moment can be normalized to obtain the fusion weight of the time-domain signal of the target reference metal sheet at each moment. Among them, the sum value of the fusion weights of the time-domain signals of the two reference metal sheets of the target gasket at the same moment is equal to the numerical value 1.

[0034] In one embodiment of the present invention, the effective coefficient of the time-domain signal of the target reference metal sheet at each moment can be used as the numerator, the sum value of the effective coefficients of the time-domain signals of the two reference metal sheets at each moment can be used as the denominator, and the ratio is used as the fusion weight of the time-domain signal of the target reference metal sheet at each moment, so as to realize the normalization processing of the effective coefficient of the time-domain signal of the target reference metal sheet at each moment and ensure that the sum value of the fusion weights of the time-domain signals of the two reference metal sheets of the target gasket at the same moment is equal to the numerical value 1.

[0035] As an example, in one embodiment of the present invention, the expression of the fusion weight of the time-domain signal of the target reference metal sheet at each moment can be, for example: Among them, represents the fusion weight of the time-domain signal of the target reference metal sheet at the th moment; represents the effective coefficient of the time-domain signal of the target reference metal sheet at the th moment; represents the effective coefficient of the time-domain signal of another reference metal sheet of the target gasket except the target reference metal sheet at the th moment.

[0036] By the same method as above, the fusion weight of the time-domain signal of each reference metal sheet at the th moment can be obtained. For a certain moment, the relatively larger the fusion weight of the time-domain signal of a certain reference metal sheet at this moment, it indicates that in the process of fusing the time-domain signals of the two reference metal sheets, the reference value of the amplitude of the time-domain signal of this reference metal sheet at this moment is relatively larger. At the same time, when performing damage detection based on the vibration characteristics of the gasket, it is usually necessary to convert the time-domain signal about vibration to the frequency domain. Therefore, according to the fusion weight of the time-domain signal of each reference metal sheet at each moment, the time-domain signals of the reference metal sheets are fused and then frequency-domain conversion is performed to obtain the frequency-domain signal of the target gasket. Subsequently, damage detection of the target gasket can be performed based on the frequency-domain signal.

[0037] Preferably, in an embodiment of the present invention, the method for obtaining the frequency-domain signal of the target gasket specifically includes: Using the fusion weights of the time-domain signals of the two reference metal sheets of the target gasket at each moment, perform weighted summation on the amplitudes of the time-domain signals of the two reference metal sheets at each moment to obtain the fusion amplitude of the target gasket at each moment, and use the signal composed of the fusion amplitudes of the target gasket at all moments as the fusion time-domain signal of the target gasket about vibration. Please refer to Figure 4 , which shows a schematic diagram of the fusion time-domain signal of the target gasket about vibration provided by an embodiment of the present invention.

[0038] As an example, in an embodiment of the present invention, the expression of the fusion amplitude of the target gasket at each moment can be specifically, for example: Among them, represents the fusion amplitude of the target gasket at the th moment; represents the fusion weight of the time-domain signal of one of the reference metal sheets of the target gasket at the th moment; represents the time-domain signal of the other reference metal sheet of the target gasket at the The fusion weight at a certain moment; The amplitude of the time-domain signal of one of the reference metal sheets of the target gasket at the th moment; The amplitude of the time-domain signal of another reference metal sheet of the target gasket at the th moment.

[0039] Then, perform a Fourier transform on the fusion time-domain signal of the target gasket with respect to vibration to obtain the frequency-domain signal of the target gasket. Among them, the Fourier transform is a well-known technical means in the art, which can transform the time-domain signal into the frequency domain and will not be elaborated here. Please refer to Figure 5 , which shows a schematic diagram of the frequency-domain signal of the target gasket provided by an embodiment of the present invention. Among them, the frequency-domain signal contains amplitudes of different frequencies.

[0040] The frequency-domain signals of each gasket can be obtained by the same method as above. It should be noted that after the frequency-domain conversion of the fusion time-domain signals of each gasket, the frequency ranges and quantities of the frequency-domain signals of each gasket are the same.

[0041] Step S3: Obtain the overall amplitude of the target gasket only under temperature interference according to the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket; obtain the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency according to the amplitude difference between the frequency-domain signals of the target gasket and other gaskets except the target gasket at the same frequency, and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude; obtain the damage possibility of the target gasket according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies.

[0042] When the plate heat exchanger starts to operate, the hot fluid usually enters from one inlet, while the cold fluid enters from another inlet. The two fluids flow in the channels formed by alternately arranged metal plates, passing through each metal plate and the gaskets between the metal plates, and heat exchange is carried out through thin walls between each metal plate. From the initial stage when the fluid enters the channel, due to the large temperature difference between the hot fluid and the cold fluid, the temperature difference between the metal plates is also significant. The large temperature difference makes the heat transfer more rapid, and the temperature fluctuation between the metal plates is more intense, thus causing a strong vibration phenomenon with a large vibration amplitude. As the hot fluid and the cold fluid exchange some heat and continue to flow through the subsequent metal plates, the temperature difference gradually decreases, resulting in a decrease in the vibration frequency and amplitude. Therefore, in the embodiment of the present invention, first, according to the amplitudes of the frequency domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket, the overall amplitude of the target gasket only under temperature interference is obtained. The overall amplitude reflects the overall level of the amplitude of the frequency domain signal of the target gasket only under the influence of temperature, facilitating subsequent reduction of the interference of temperature changes on damage analysis.

[0043] Preferably, in an embodiment of the present invention, the method for obtaining the overall amplitude of the target gasket only under temperature interference specifically includes: As can be seen from the above analysis, after the fluid enters the channel, as the fluid flows through each gasket, the change in the vibration amplitude of the gasket closer to the back is smaller, that is, the change in the vibration amplitude of the gasket with a larger serial number is smaller. Based on this rule, an overall amplitude function for each gasket can be constructed. The overall amplitude function is: Wherein, represents the overall amplitude function of the th gasket, and its independent variable is the serial number corresponding to the th gasket; , , and respectively represent four unknown parameters; represents the natural constant.

[0044] Then, according to the amplitudes of the frequency domain signals of all gaskets at the same frequency and the overall amplitude function, an error function is constructed. Among them, the error function contains , , and four unknown parameters.

[0045] Preferably, in an embodiment of the present invention, the method for constructing the error function specifically includes: For the frequency-domain signal of the gasket, the thermal expansion and contraction effects caused by temperature changes usually concentrate in the low-frequency region. Therefore, the amplitude of the low-frequency part of the frequency-domain signal contributes more to the analysis of the overall amplitude. First, a negative correlation mapping is performed on each frequency value of the frequency-domain signal to obtain the reference weight for each frequency of the frequency-domain signal.

[0046] Then, an error function is constructed, and the error function is: Where, represents the error function; represents the reference weight of the th frequency of the frequency-domain signal; represents the th gasket's frequency-domain signal amplitude at the th frequency; represents the overall amplitude function with respect to the th gasket; represents the number of frequencies included in the frequency-domain signal, and the number of frequencies included in the frequency-domain signals of each gasket is equal; represents the number of gaskets; represents the th frequency value of the frequency-domain signal; represents a preset adjustment parameter used to prevent the denominator from being zero The value range of is set to In one embodiment of the present invention, is set to 0.01. The specific value of can also be set by the implementer according to the specific implementation scenario and is not limited here.

[0047] It should be noted that in other embodiments of the present invention, negative correlation mapping can also be achieved through other basic mathematical operations, which will not be elaborated here.

[0048] Finally, the least squares method is used to minimize the error function, and the numerical values of the four unknown parameters , , and are calculated. Then, the numerical values of the four unknown parameters , , and and the serial number corresponding to the target gasket are substituted into the overall amplitude function to obtain the overall amplitude of the target gasket only under temperature interference. The least squares method is a well-known technical means in the art and will not be elaborated here.

[0049] Under the normal working conditions of the plate heat exchanger, if the vibration effects caused by the damage of the sealing gasket and temperature changes are not considered, then the frequency-domain signal of the gasket is generated by the overall working environment and system dynamic characteristics of the plate heat exchanger. Since all gaskets are subjected to similar fluid flows under the same operating conditions, the pressure fluctuations and turbulence generated when the fluid flows through each channel will have a similar vibration effect on each gasket. In addition, the gaskets are usually arranged symmetrically, and their structures, dimensions, and materials are the same or very similar. These factors make the mechanical loads and vibration sources received by each gasket very similar. Therefore, without considering the damage and temperature effects, the amplitudes of the same frequency of the frequency-domain signals of each gasket tend to be consistent. The greater the difference between the amplitude of the frequency-domain signal of the target gasket at a certain frequency and the overall amplitude, the smaller the influence of the temperature change on the frequency-domain signal at this frequency. At the same time, when the consistency of the amplitudes of the frequency-domain signals between the target gasket and other gaskets at this frequency is poor, it indicates that the target gasket exhibits more obvious damage characteristics at this frequency. Therefore, based on the amplitude difference of the frequency-domain signals between the target gasket and other gaskets except the target gasket at the same frequency, and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude, the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency can be obtained. The damage performance coefficient reflects the degree of damage of the target gasket shown by the frequency-domain signal of the target gasket at each frequency, thereby reducing the interference of the vibration signal generated by the temperature change on the vibration characteristic analysis of the gasket damage and improving the accuracy of the subsequent detection of the gasket damage.

[0050] Preferably, in an embodiment of the present invention, the method for obtaining the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency specifically includes: First, take any frequency of the frequency-domain signal as the target frequency, take the absolute value of the difference in amplitude between the frequency-domain signals of the target gasket and each other gasket at the target frequency as the amplitude difference value between the frequency-domain signals of the target gasket and each other gasket at the target frequency, and take the average value of the amplitude difference values between the frequency-domain signals of the target gasket and all other gaskets at the target frequency as the amplitude difference degree of the frequency-domain signal of the target gasket at the target frequency. The greater the amplitude difference degree, the poorer the consistency of the amplitudes of the frequency-domain signals between the target gasket and other gaskets at the target frequency, and the more likely the frequency-domain signal of the target gasket shows damage characteristics at the target frequency.

[0051] Then, the absolute value of the difference between the amplitude of the frequency-domain signal of the target gasket at the target frequency and the overall amplitude of the target gasket is used as the degree of temperature interference not suffered by the frequency-domain signal of the target gasket at the target frequency. The greater the degree of temperature interference not suffered, the smaller the degree of interference of the amplitude of the frequency-domain signal of the target gasket at the target frequency by temperature changes. At this time, if the degree of amplitude difference of the frequency-domain signal of the target gasket at the target frequency is greater, then the frequency-domain signal of the target gasket at the target frequency is more likely to exhibit damage characteristics rather than temperature change characteristics.

[0052] Therefore, the degree of amplitude difference and the degree of temperature interference not suffered can be combined to obtain the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency.

[0053] In an embodiment of the present invention, the sum value or product value of the degree of amplitude difference and the degree of temperature interference not suffered can be used as the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency, so as to achieve the combination of the two, and no limitation is made here.

[0054] As an example, in an embodiment of the present invention, the expression of the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency can be specifically, for example: Wherein, represents the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency; represents the amplitude of the frequency-domain signal of the target gasket at the target frequency; represents the overall amplitude of the target gasket; represents the degree of temperature interference not suffered by the frequency-domain signal of the target gasket at the target frequency; represents the th other gasket except the target gasket, and represents the amplitude of the frequency-domain signal of the other gasket at the target frequency; represents the target gasket and the th other gasket, and represents the amplitude difference value between the frequency-domain signals of the target gasket and the other gasket at the target frequency; represents the degree of amplitude difference of the frequency-domain signal of the target gasket at the target frequency; represents the number of other gaskets except the target gasket.

[0055] By the above same method, the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency can be obtained, and then according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies, the damage possibility of the target gasket can be obtained.

[0056] Preferably, in an embodiment of the present invention, the method for obtaining the damage possibility of the target gasket specifically includes: Since the damage to the gasket is generally local, such as cracks, wear or local deformation, etc., the fluid leakage caused by these local damages will lead to higher-frequency vibrations, and the damage to the gasket often causes the nonlinear behavior of the system. The nonlinear characteristics can enhance the components of high-frequency signals. For example, when micro-cracks appear on the surface of the gasket, the pressure fluctuations generated by the fluid leakage may cause local nonlinear phenomena such as friction and impact, generating high-frequency vibrations. Therefore, for the frequency-domain signal of the target gasket, the high-frequency damage performance coefficient can better reflect the damage characteristics of the target gasket.

[0057] Therefore, the product value of each frequency value of the frequency-domain signal of the target gasket and the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency can be used as the adjusted damage performance degree of the frequency-domain signal of the target gasket at each frequency. Furthermore, the average value of the adjusted damage performance degrees of the frequency-domain signal of the target gasket at all frequencies is normalized, and the calculation result is limited to the range, so as to obtain the damage possibility of the target gasket.

[0058] As an example, in an embodiment of the present invention, the expression of the damage possibility of the target gasket can be specifically, for example: Wherein, represents the damage possibility of the target gasket; represents the th frequency value of the frequency-domain signal; represents the damage performance coefficient of the frequency-domain signal of the target gasket at the th frequency; represents the adjusted damage performance degree of the frequency-domain signal of the target gasket at the th frequency; represents the number of frequencies included in the frequency-domain signal; represents the normalization function for normalization processing.

[0059] The damage possibility of each gasket can be obtained by the same method as above.

[0060] Step S4: Based on the damage possibility of each gasket, perform damage detection on each gasket.

[0061] The greater the damage possibility of a certain gasket, the more likely it is that the gasket is damaged and causes fluid leakage. Therefore, based on the damage possibility of each gasket, damage detection can be performed on each gasket to improve the accuracy of damage detection of the gaskets of the plate heat exchanger.

[0062] Preferably, in an embodiment of the present invention, the method for performing damage detection on each gasket specifically includes: The gasket with a damage possibility greater than a preset possibility threshold is regarded as a damaged gasket, where the value range of the preset possibility threshold is , in an embodiment of the present invention, the preset possibility threshold is set to 0.6. The specific value of the preset possibility threshold can also be set by the implementer according to the specific implementation scenario, and is not limited herein.

[0063] After detecting the damaged gasket, the damaged gasket can be replaced to prevent further damage to the plate heat exchanger.

[0064] An embodiment of the present invention provides a fault detection system for a plate heat exchanger. The system includes: A first analysis module, which is used to take any gasket of the plate heat exchanger as a target gasket, take the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket, and obtain the fusion weight of the time-domain signal of each reference metal plate at each moment according to the difference in the fluctuation between the time-domain signal and the temperature signal of each reference metal plate; according to the fusion weight of the time-domain signal of each reference metal plate at each moment, fuse the time-domain signals of the reference metal plates and then perform frequency-domain conversion to obtain the frequency-domain signal of the target gasket; A second analysis module, which is used to obtain the overall amplitude of the target gasket only under temperature interference according to the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket; according to the amplitude difference between the frequency-domain signals of the target gasket and other gaskets except the target gasket at the same frequency, and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude, obtain the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency; according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies, obtain the damage possibility of the target gasket; A damage detection module, which is used to perform damage detection on each gasket based on the damage possibility of each gasket.

[0065] An embodiment of the present invention provides a fault detection device for a plate heat exchanger. The device includes a memory, a processor, and a computer program, where the memory is used to store the corresponding computer program, the processor is used to run the corresponding computer program, and when the computer program runs in the processor, it can implement the method described in steps S1~S4.

[0066] It should be noted that: the above sequence of the embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0067] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A fault detection method for a plate heat exchanger, characterized in that, The method includes: Obtaining the temperature signals and time-domain signals regarding vibration of each metal plate of the plate heat exchanger during the working process; Taking any gasket of the plate heat exchanger as the target gasket, taking the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket, and obtaining the fusion weight of the time-domain signal of each reference metal plate at each moment according to the difference in fluctuations between the time-domain signal and the temperature signal of each reference metal plate; performing frequency-domain conversion after fusing the time-domain signals of the reference metal plates according to the fusion weights of the time-domain signals of each reference metal plate at each moment to obtain the frequency-domain signal of the target gasket; Obtaining the overall amplitude of the target gasket only under temperature interference according to the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket; obtaining the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency according to the amplitude difference of the frequency-domain signals between the target gasket and other gaskets except the target gasket at the same frequency and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude; obtaining the damage possibility of the target gasket according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies; Performing damage detection on each gasket based on the damage possibility of each gasket.

2. The fault detection method for a plate heat exchanger according to claim 1, characterized in that, The obtaining of the fusion weight of the time-domain signal of each reference metal plate at each moment includes: Taking any reference metal plate as the target reference metal plate; Based on the calculation formula of the effective coefficient, obtaining the effective coefficient of the time-domain signal of the target reference metal plate at each moment, and the calculation formula of the effective coefficient is: Among them, represents the effective coefficient of the time-domain signal of the target reference metal sheet at the -th moment; represents the standard deviation of the amplitudes of all moments between the -th moment and the -th moment of the time-domain signal of the target reference metal sheet, ; represents the standard deviation of the temperature data of all moments between the -th moment and the -th moment of the temperature signal of the target reference metal sheet; represents the number of other moments except the -th moment; represents the exponential function with the natural constant as the base; represents the normalization function; Normalizing the effective coefficient of the time-domain signal of the target reference metal plate at each moment to obtain the fusion weight of the time-domain signal of the target reference metal plate at each moment, wherein the sum of the fusion weights of the time-domain signals of the two reference metal plates of the target gasket at the same moment is equal to the value 1.

3. The fault detection method for a plate heat exchanger according to claim 1, characterized in that, The obtaining of the frequency-domain signal of the target gasket includes: Using the fusion weights of the time-domain signals of the two reference metal plates of the target gasket at each moment to perform weighted summation on the amplitudes of the time-domain signals of the two reference metal plates at each moment to obtain the fusion amplitude of the target gasket at each moment, and taking the signal composed of the fusion amplitudes of the target gasket at all moments as the fusion time-domain signal of the target gasket regarding vibration; Performing Fourier transform on the fusion time-domain signal of the target gasket regarding vibration to obtain the frequency-domain signal of the target gasket.

4. A fault detection method for a plate heat exchanger according to claim 1, characterized in that, The obtaining of the overall amplitude of the target gasket only under temperature interference includes: Constructing an overall amplitude function for each gasket, and the overall amplitude function is: Among them, represents the overall amplitude function of the th gasket, with its independent variable being the serial number corresponding to the th gasket ; , , and respectively represent four unknown parameters; represents the natural constant; Construct an error function based on the amplitudes of the same frequencies of the frequency-domain signals of all gaskets and the overall amplitude function, where the error function contains , , and four unknown parameters; Using the least squares method, minimize the error function and calculate the , , and the values of the four unknown parameters, and substitute the , , and the values of the four unknown parameters and the serial number corresponding to the target gasket into the overall amplitude function to obtain the overall amplitude of the target gasket only under temperature interference.

5. The fault detection method for a plate heat exchanger according to claim 4, characterized in that, The constructing of the error function includes: Performing negative correlation mapping on each frequency value of the frequency-domain signal to obtain the reference weight of each frequency of the frequency-domain signal; Constructing an error function, and the error function is: Among them, represents the error function; represents the reference weight of the -th frequency of the frequency-domain signal; represents the -th shim's amplitude at the -th frequency of the frequency-domain signal; represents the overall amplitude function with respect to the -th shim; represents the number of frequencies included in the frequency-domain signal, and the number of frequencies included in the frequency-domain signal of each shim is equal; represents the number of shims.

6. A fault detection method for a plate heat exchanger according to claim 1, characterized in that, The obtaining of the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency includes: Take any frequency of the frequency-domain signal as the target frequency, and take the absolute value of the difference in amplitude at the target frequency between the target gasket and the frequency-domain signals of each other gasket as the amplitude difference value between the target gasket and the frequency-domain signals of each other gasket at the target frequency; Take the average value of the amplitude difference values at the target frequency between the target gasket and the frequency-domain signals of all other gaskets as the degree of amplitude difference of the frequency-domain signal of the target gasket at the target frequency; Take the absolute value of the difference between the amplitude of the frequency-domain signal of the target gasket at the target frequency and the overall amplitude of the target gasket as the degree of temperature interference-free of the frequency-domain signal of the target gasket at the target frequency; Integrate the degree of amplitude difference and the degree of temperature interference-free to obtain the damage performance coefficient of the frequency-domain signal of the target gasket at the target frequency.

7. A fault detection method for a plate heat exchanger according to claim 1, characterized in that The obtaining of the damage possibility of the target gasket includes: Take the product value of each frequency value of the frequency-domain signal of the target gasket and the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency as the adjusted damage performance degree of the frequency-domain signal of the target gasket at each frequency; Normalize the average value of the adjusted damage performance degrees of the frequency-domain signal of the target gasket at all frequencies to obtain the damage possibility of the target gasket.

8. A fault detection method for a plate heat exchanger according to claim 1, characterized in that, The damage detection of each gasket includes: Take the gasket with the damage possibility greater than the preset possibility threshold as the damaged gasket.

9. A fault detection system for a plate heat exchanger, characterized in that, The system includes: A data acquisition module for acquiring the temperature signal and the time-domain signal regarding vibration of each metal plate of the plate heat exchanger during the working process; A first analysis module for taking any gasket of the plate heat exchanger as the target gasket, taking the two metal plates adjacent to the target gasket as the reference metal plates of the target gasket, and obtaining the fusion weight of the time-domain signal of each reference metal plate at each moment according to the difference in fluctuation between the time-domain signal and the temperature signal of each reference metal plate; according to the fusion weight of the time-domain signal of each reference metal plate at each moment, fuse the time-domain signals of the reference metal plates and then perform frequency-domain conversion to obtain the frequency-domain signal of the target gasket; A second analysis module for obtaining the overall amplitude of the target gasket only under temperature interference according to the amplitudes of the frequency-domain signals of all gaskets at the same frequency and the serial number corresponding to the target gasket; obtaining the damage performance coefficient of the frequency-domain signal of the target gasket at each frequency according to the amplitude difference between the frequency-domain signals of the target gasket and other gaskets except the target gasket at the same frequency and the difference between the amplitude of the frequency-domain signal of the target gasket at each frequency and the overall amplitude; obtaining the damage possibility of the target gasket according to the damage performance coefficients of the frequency-domain signal of the target gasket at all frequencies; A damage detection module for performing damage detection on each gasket based on the damage possibility of each gasket.

10. A fault detection device for a plate heat exchanger, the device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

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