A method and system for testing the sealing performance of a tubular falling film evaporator

Abstract

The present application relates to the technical field of sealing test, and specifically to a sealing test method and system for a tubular falling film evaporator, the method comprising: determining the harmonic energy intensity of any frequency to be analyzed based on all suspected fundamental frequencies of any frequency to be analyzed, and the energy amplitudes of all suspected fundamental frequencies at the same frequency corresponding to the frequency spectrum of a normal flow rate signal; and determining the harmonic credible weight in combination with the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed; determining the velocity attenuation characteristic value of the tubular falling film evaporator based on the discrete degree of all elements in the attenuation characteristic sequence, and the average distribution of all elements in the velocity attenuation sequence, and testing the sealing of the tubular falling film evaporator. The present application improves the accuracy of sealing detection of a tubular falling film evaporator by extracting features from velocity monitoring data.

Description

Technical Field

[0001] The present application relates to the technical field of sealing test, and in particular to a sealing test method and system for a tubular falling film evaporator. Background Art

[0002] The tubular falling film evaporator is a highly efficient liquid evaporation and separation device. The core equipment of the tubular falling film evaporator is the film cloth, which can form a thin film on the inner wall of the pipe for the liquid to be evaporated, and heat the liquid inside the pipe with steam to promote its evaporation and achieve evaporation and separation of the liquid. In the process of the film cloth forming a thin film inside the pipe, the sealing performance of the liquid valve at the feed end is particularly important. Once the sealing performance of the liquid valve fails, it may not only cause liquid leakage and environmental pollution, but also destroy the stability of the air pressure environment inside the evaporator, affect the film effect of the film cloth, and then affect the steam output efficiency.

[0003] In the traditional valve sealing test method, it is usually necessary to monitor the flow rate at the inlet of the tubular falling film evaporator to evaluate the sealing condition of the liquid valve. Abnormal changes in flow rate may indicate valve sealing failure, and corresponding response measures need to be taken immediately. However, at the same time, the loss of control of the liquid pump may also cause abnormal flow rate. Therefore, the specific fault type cannot be quickly and accurately determined by flow rate detection alone, which reduces the accuracy of the sealing detection of the tubular falling film evaporator. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a method and system for testing the sealing performance of a tubular falling film evaporator. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for testing the sealing performance of a tubular falling film evaporator, the method comprising the following steps:

[0006] Obtain the liquid flow rate data at the inlet of the tubular falling film evaporator at each sampling time;

[0007] Based on the liquid flow rate data at each collection moment and the preset threshold range, the abnormal moment is determined, all the liquid flow rate data within the preset time before the abnormal moment are formed into a normal flow rate signal, and the liquid flow rate data of the same preset time period are collected from the abnormal moment backward to form an abnormal flow rate signal;

[0008] A time-frequency conversion algorithm is used to obtain the respective spectra of the normal flow velocity signal and the abnormal flow velocity signal. In the spectrum of the abnormal flow velocity signal, all the frequencies to be analyzed and all the fundamental frequencies of any frequency to be analyzed are determined based on the distribution characteristics of the energy amplitudes at all frequencies. All the fundamental frequencies of any frequency to be analyzed are recorded as suspected fundamental frequencies. The harmonic energy intensity of any frequency to be analyzed is determined by combining the energy amplitudes of all the suspected fundamental frequencies of any frequency to be analyzed at the same frequencies corresponding to the frequency spectrum of the normal flow velocity signal; and the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal is determined by combining the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed.

[0009] Based on the difference between the normal flow velocity signal and the abnormal flow velocity signal, the flow velocity attenuation sequence is determined; the harmonic credible weights of all frequencies to be analyzed in the spectrum of the abnormal flow velocity signal are combined into a harmonic weight sequence; based on the harmonic weight sequence and the flow velocity attenuation sequence, the attenuation characteristic sequence is determined, and based on the discrete degree of all elements in the attenuation characteristic sequence and the average distribution of all elements in the flow velocity attenuation sequence, the flow velocity attenuation characteristic value of the tubular falling film evaporator is determined, and the sealing of the tubular falling film evaporator is tested.

[0010] Preferably, the abnormal moment is the collection moment corresponding to when the liquid flow rate data exceeds a preset threshold range.

[0011] Preferably, the determining of all frequencies to be analyzed and all suspected fundamental frequencies of any frequency to be analyzed includes:

[0012] Taking half of the preset sampling frequency as the highest frequency of the abnormal flow velocity signal, and taking the frequency corresponding to the maximum energy amplitude in the spectrum of the abnormal flow velocity signal as the inherent fundamental frequency;

[0013] For the spectrum of the abnormal flow velocity signal, between the natural fundamental frequency and the highest frequency, the frequency that is an integer multiple of the natural fundamental frequency and has a peak energy amplitude is taken as the frequency to be analyzed;

[0014] Between the natural fundamental frequency and the highest frequency, the integer multiples of the frequencies of the possible fundamental waves of any frequency to be analyzed are equal to the frequency to be analyzed.

[0015] Preferably, the expression for the harmonic energy intensity of any frequency to be analyzed is: ; In the formula, represents the harmonic energy intensity of the frequency r to be analyzed; Represents the energy amplitude of the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal at the same frequency in the spectrum of the normal flow velocity signal; represents the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal; r represents the frequency to be analyzed in the spectrum of the abnormal flow velocity signal; Represents the number of all suspected fundamental waves of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal.

[0016] Preferably, the method for determining the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal is:

[0017] In the spectrum of the abnormal flow velocity signal, the range of the harmonic energy intensity of all frequencies is calculated, and the difference between the maximum value of the harmonic energy of all frequencies and the harmonic energy intensity of any frequency to be analyzed is calculated, and the ratio of the difference to the range is used as the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal.

[0018] Preferably, the method for determining the flow velocity attenuation sequence is:

[0019] In the normal flow rate signal, the ratios between the liquid flow rate data at the same frequencies as the frequencies to be analyzed in the abnormal flow rate signal are calculated, and the ratios between all the liquid flow rate data constitute a flow rate attenuation sequence.

[0020] Preferably, the method for determining the attenuation characteristic sequence is:

[0021] The product of each element in the harmonic weight sequence and the element at the corresponding same position in the velocity attenuation sequence is calculated, and all the products constitute an attenuation characteristic sequence.

[0022] Preferably, the velocity attenuation characteristic value of the tubular falling film evaporator is a ratio of the discreteness of all elements in the attenuation characteristic sequence to the mean value of all elements in the velocity attenuation sequence.

[0023] Preferably, the process of testing the sealing performance of the tubular falling film evaporator is:

[0024] If the flow rate attenuation characteristic value is less than the preset value, the valve seal of the tubular falling film evaporator fails, otherwise, the valve seal of the tubular falling film evaporator is normal.

[0025] In a second aspect, an embodiment of the present application further provides a sealing test system for a tubular falling film evaporator, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned methods when executing the computer program.

[0026] This application has at least the following beneficial effects:

[0027] In view of the problem that valve seal failure cannot be quickly identified and distinguished during the fault test of a tubular falling film evaporator, this embodiment proposes a sealing test method for a tubular falling film evaporator, including:

[0028] The present application determines the abnormal moment based on the liquid flow rate data at each collection moment and the preset threshold range, and all the liquid flow rate data within the preset time before the abnormal moment constitute the normal flow rate signal, and collects the liquid flow rate data of the same preset time from the abnormal moment, and constitutes the abnormal flow rate signal, which has the beneficial effect of accurately extracting the flow rate characteristics;

[0029] The present application adopts a time-frequency conversion algorithm to obtain the respective spectra of the normal flow velocity signal and the abnormal flow velocity signal. In the spectrum of the abnormal flow velocity signal, all frequencies to be analyzed are determined based on the distribution characteristics of the energy amplitudes at all frequencies to obtain all suspected fundamental frequencies of any frequency to be analyzed, and the harmonic energy intensity of any frequency to be analyzed is determined in combination with the energy amplitudes of all suspected fundamental frequencies of any frequency to be analyzed at the same frequencies corresponding to the frequency spectrum of the normal flow velocity signal; based on the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed, the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal is determined, which has the beneficial effect of eliminating the interference caused by the leakage point;

[0030] The present application determines a flow velocity attenuation sequence based on the difference between a normal flow velocity signal and an abnormal flow velocity signal; the harmonic credible weights of all frequencies to be analyzed in the spectrum of the abnormal flow velocity signal are combined into a harmonic weight sequence; based on the harmonic weight sequence and the flow velocity attenuation sequence, an attenuation characteristic sequence is determined; based on the discrete degree of all elements in the attenuation characteristic sequence and the average distribution of all elements in the flow velocity attenuation sequence, the flow velocity attenuation characteristic value of the tubular falling film evaporator is determined; the sealing of the tubular falling film evaporator is tested, and the beneficial effect is that the accuracy of the sealing detection of the tubular falling film evaporator is improved.

[0031] The present application improves the accuracy of sealing detection of a tubular falling film evaporator by extracting data features generated by valve sealing failure in flow rate monitoring data. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A flow chart of the steps of a method for testing the sealing performance of a tubular falling film evaporator provided in one embodiment of the present application;

[0034] Figure 2 A schematic diagram of a harmonic trustworthy weight extraction process provided for an embodiment of the present application;

[0035] Figure 3 A schematic diagram of a flow velocity attenuation characteristic value extraction process provided by an embodiment of the present application;

[0036] Figure 4 A flow chart of a seal failure detection process provided for one embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of the sealing test method and system of a tubular falling film evaporator proposed in the present application, its specific implementation method, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0038] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0039] The following is a detailed description of a method and system for testing the sealing performance of a tubular falling film evaporator provided by the present application in conjunction with the accompanying drawings.

[0040] See also Figure 1 , which shows a flow chart of the steps of a method for testing the sealing performance of a tubular falling film evaporator provided by an embodiment of the present application, the method comprising the following steps:

[0041] Step S1: Acquire the liquid flow rate data of the tubular falling film evaporator at each sampling time.

[0042] When testing the valve sealing performance through flow monitoring, the liquid flow at the inlet of the tubular falling film evaporator is usually detected to complete abnormal detection. When the flow exceeds the predetermined range, it is considered that the flow is abnormal. Failure of the valve sealing performance of the tubular falling film evaporator will cause abnormal liquid flow, so the valve sealing failure can be preliminarily tested based on this.

[0043] Therefore, a liquid flow meter is installed at the inlet of the tubular falling film evaporator to obtain the liquid flow rate data at the inlet of the tubular falling film evaporator at each sampling time, wherein the preset sampling frequency of the liquid flow rate data is set to f.

[0044] It should be noted that the values ​​of the preset sampling frequency f are all manually set. In this embodiment, the value of the sampling frequency f is 100 Hz. The implementer can also set it by himself according to the specific situation. This embodiment does not make any special limitation.

[0045] Furthermore, in the traditional valve sealing test method, the valve sealing is preliminarily detected through flow abnormality, and the flow abnormality is usually detected by setting a threshold. When the liquid flow rate data exceeds the preset threshold range, it is considered that the liquid flow is abnormal. At this time, the collection time corresponding to the liquid flow rate data is recorded as the abnormal time.

[0046] It should be noted that the value of the preset threshold range is artificially set. In this embodiment, the value of the preset threshold range is , the unit is meter per second, and the implementer can also set it according to the specific situation. This embodiment does not impose any special limitation.

[0047] Furthermore, all liquid flow rate data within a preset time period before the abnormal moment are combined into a normal flow rate signal, and liquid flow rate data of the same preset time period are collected from the abnormal moment backwards to form an abnormal flow rate signal.

[0048] It should be noted that the value of the preset time length is artificially set. In this embodiment, the value of the preset time length is 5s. The implementer can also set it by himself according to the specific situation. This embodiment does not impose any special restrictions. The length of the normal flow rate signal is the same as the length of the abnormal flow rate signal.

[0049] In particular, if the abnormal moment is less than the preset time period, the moment will not be considered.

[0050] Step S2: Use a time-frequency conversion algorithm to obtain the respective frequency spectra of the normal flow velocity signal and the abnormal flow velocity signal. In the frequency spectrum of the abnormal flow velocity signal, based on the distribution characteristics of the energy amplitudes at all frequencies, determine all the frequencies to be analyzed and all the suspected fundamental frequencies of any frequency to be analyzed, and combine the energy amplitudes of all the suspected fundamental frequencies of any frequency to be analyzed at the same frequencies corresponding to the frequency spectrum of the normal flow velocity signal to determine the harmonic energy intensity of any frequency to be analyzed, and combine the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed to determine the harmonic credible weight of any frequency to be analyzed in the frequency spectrum of the abnormal flow velocity signal.

[0051] When there is no abnormal flow in the tubular falling film evaporator, the measured flow rate data corresponds to the normal flow rate signal. At this time, the flow rate is controlled by the water pump, that is, the normal flow rate signal contains the control information of the water pump on the flow rate. This part can be used as fingerprint information to determine whether the water pump maintains control over the flow rate; when there is an abnormal flow, if the valve sealing fails, the water pump is still working normally. Therefore, the abnormal flow rate signal at this time still has the fingerprint information of the water pump; when the abnormal flow is caused by a water pump failure, this part of the fingerprint information is eliminated.

[0052] Therefore, by analyzing the distribution characteristics of the energy amplitude at all frequencies, all frequencies to be analyzed are determined to obtain all suspected fundamental frequencies of any frequency to be analyzed, and the harmonic energy intensity of any frequency to be analyzed is determined in combination with the energy amplitudes of all suspected fundamental frequencies of any frequency to be analyzed at the same frequency in the spectrum of the normal flow rate signal; based on the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed, the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow rate signal is determined to effectively identify the harmonic interference caused by the failure of valve sealing and improve the credibility of the flow rate measurement data, specifically:

[0053] S201: Using a time-frequency conversion algorithm to obtain respective frequency spectra of a normal flow velocity signal and an abnormal flow velocity signal.

[0054] The normal flow velocity signal and the abnormal flow velocity signal are respectively used as the input of the time-frequency conversion algorithm, and the frequency spectrum of the normal flow velocity signal and the abnormal flow velocity signal is output;

[0055] It should be noted that there are many commonly used time-frequency conversion algorithms. In this embodiment, fast Fourier transform is used to obtain the frequency spectra of normal flow velocity signals and abnormal flow velocity signals. The implementer may also use other methods such as wavelet transform. Regarding the selection of time-frequency conversion algorithm, this embodiment does not impose any special restrictions.

[0056] Among them, fast Fourier transform is a well-known technology in the field of signal processing, and the specific process of converting time domain signals into frequency domain is not repeated here.

[0057] S202: In the spectrum of the abnormal flow velocity signal, based on the distribution characteristics of the energy amplitudes at all frequencies, determine all the frequencies to be analyzed and all the fundamental frequencies of any frequency to be analyzed, record all the fundamental frequencies of any frequency to be analyzed as suspected fundamental frequencies, and determine the harmonic energy intensity of any frequency to be analyzed by combining the energy amplitudes of all the suspected fundamental frequencies of any frequency to be analyzed at the same frequencies corresponding to them in the spectrum of the normal flow velocity signal.

[0058] When the valve sealing of the tubular falling film evaporator fails, although the flow rate is still controlled by the water pump, resulting in a small difference between the abnormal flow rate signal and the normal flow rate signal; however, a leakage point appears in the valve at this time, and the leakage point will interfere with the flow rate, resulting in the abnormal flow rate signal having not only a characteristic part that is similar to the normal flow rate signal, but also a characteristic part caused by the interference of the leakage point.

[0059] Therefore, when judging the valve sealing performance through the water pump flow characteristics, the leakage point will act as an interference source to interfere with the water pump flow characteristics, resulting in a large degree of dissimilarity between the normal flow rate signal and the abnormal flow rate signal, thereby interfering with the test of valve sealing failure.

[0060] The leakage point, as an interference source, interacts with the original liquid flow rate to generate interference, so the interference signal generated by it is a harmonic of the normal flow rate signal. Therefore, this embodiment can eliminate the flow rate interference generated by the leakage point as an interference source by calculating the harmonic characteristics of the normal flow rate signal for the abnormal flow rate signal.

[0061] When the valve seal of the tubular falling film evaporator fails, the leakage point, as an interference source, will generate harmonics based on the normal flow rate signal, causing interference in the abnormal flow rate signal. Therefore, in the abnormal flow rate signal, by analyzing the energy amplitude corresponding to each suspected fundamental frequency of any frequency to be analyzed in the spectrum of the normal flow rate signal, and each suspected fundamental frequency of any frequency to be analyzed, the harmonic energy intensity of any frequency to be analyzed in the spectrum of the abnormal flow rate signal is determined, specifically:

[0062] (1) For any frequency position to be analyzed, when there is a harmonic at that frequency position, find out all the fundamental frequencies that may cause the harmonics at that frequency position. In other words, if there is a harmonic at that frequency position, then this harmonic must be generated by an integer multiple of a fundamental frequency. The steps to obtain all the fundamental frequencies at any frequency to be analyzed are:

[0063] a. First, determine the maximum frequency. According to the Nyquist theorem, the maximum frequency is usually half of the sampling frequency. In this embodiment, the sampling frequency f is 100 Hz, so the maximum frequency is 50 Hz;

[0064] b. Further, the frequency corresponding to the maximum energy amplitude in the spectrum of the abnormal flow velocity signal (excluding the DC component with a frequency of 0 Hz) is taken as the inherent fundamental frequency;

[0065] c. Further, for the spectrum of the abnormal flow velocity signal, between the natural fundamental frequency and the highest frequency, the frequency that is an integer multiple of the natural fundamental frequency and has a peak energy amplitude is used as the frequency to be analyzed;

[0066] d. Further, for any frequency to be analyzed (r), find all possible fundamental frequencies (h) so that the integer multiple of h is equal to the frequency to be analyzed (r). For the convenience of expression, all fundamental frequencies of any frequency to be analyzed are recorded as suspected fundamental frequencies.

[0067] Assume that the frequency to be analyzed is r=30Hz. Within the frequency range of 2-50Hz, all the suspected fundamental frequencies at the frequency to be analyzed (r) are 2Hz, 3Hz, 5Hz, 6Hz, 10Hz, 15Hz, and 30Hz.

[0068] Among them, the Nyquist theorem and the process of obtaining the fundamental frequency are both well-known technologies, and the specific principles will not be repeated here.

[0069] (2) Further, based on all the suspected fundamental frequencies of any frequency to be analyzed and combined with the energy amplitudes of all the suspected fundamental frequencies of any frequency to be analyzed at the same frequency in the spectrum of the normal flow rate signal, the harmonic energy intensity of any frequency to be analyzed is determined, specifically:

[0070] Harmonic energy intensity of the frequency r to be analyzed The expression is: ; In the formula, Represents the energy amplitude of the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal at the same frequency in the spectrum of the normal flow velocity signal; represents the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal; r represents the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal; Represents the number of all suspected fundamental waves of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal.

[0071] Furthermore, according to the harmonic energy intensity of any frequency to be analyzed in the spectrum of the abnormal flow rate signal, it can be understood that the greater the energy amplitude of the fundamental wave, the greater the harmonic energy amplitude. When the valve seal fails in the tubular falling film evaporator, the data of the corresponding frequency is more likely to be interfered by the harmonics generated by the leakage point, and the liquid flow rate data at this time is less reliable. Since the higher the harmonic order, the lower the energy amplitude of the harmonic, the ratio of the fundamental frequency of frequency r to frequency r is used as the reciprocal of the harmonic order. The smaller the reciprocal of the harmonic order, the higher the harmonic order, the smaller the harmonic energy amplitude generated by the hth frequency at the rth frequency position, the lighter the flow rate characteristics at the rth frequency are interfered by the harmonics generated by the leakage point, and the more reliable the data is.

[0072] S203: Determine the harmonic credible weight of any frequency to be analyzed in the frequency spectrum of the abnormal flow velocity signal based on the extreme distribution of the harmonic energy intensities of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed.

[0073] In the spectrum of the abnormal flow velocity signal, the range of the harmonic energy intensity of all frequencies to be analyzed is calculated, and the difference between the maximum value of the harmonic energy of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed is calculated, and the ratio of the difference to the range is used as the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal.

[0074] According to the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal, it can be understood that the greater the difference between the maximum value of the harmonic energy of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed, the greater the range of the harmonic energy intensity of all frequencies to be analyzed, and the greater the harmonic credible weight of the corresponding frequency to be analyzed; conversely, the smaller the difference between the maximum value of the harmonic energy of all frequencies to be analyzed and the harmonic energy intensity of any frequency to be analyzed, the smaller the range of the harmonic energy intensity of all frequencies to be analyzed, and the smaller the harmonic credible weight of the corresponding frequency to be analyzed.

[0075] Preferably, the schematic diagram of the harmonic credible weight extraction process provided in this embodiment is as follows: Figure 2 shown.

[0076] Step S3: Based on the difference between the normal flow velocity signal and the abnormal flow velocity signal, the flow velocity attenuation sequence is determined; the harmonic credible weights of all frequencies in the spectrum of the abnormal flow velocity signal form a harmonic weight sequence, and the elements at the same position of the flow velocity attenuation sequence and the harmonic weight sequence are weighted, and the flow velocity attenuation characteristic value is determined based on the discrete degree of the weighted result and the average distribution of all elements in the flow velocity attenuation sequence.

[0077] When the flow rate of the tubular falling film evaporator is abnormal, it may be due to a water pump failure or a valve seal failure. When the water pump fails, the characteristic information about the water pump in the abnormal flow rate signal disappears compared to the normal flow rate signal, indicating that the water pump no longer controls the water flow; when the valve seal fails, the water pump still controls the water flow, but the raw material leaks due to the seal failure, which leads to a decrease in the overall flow rate. The abnormal flow rate signal still contains characteristic information generated by the water pump control, but the characteristic intensity of this part decreases due to the seal failure. This decrease in characteristic intensity is reflected in the abnormal flow rate signal as follows: the energy amplitude waveform at each frequency position is similar to the normal flow rate signal waveform, but the energy amplitude decreases proportionally.

[0078] Accordingly, based on the difference between the normal flow velocity signal and the abnormal flow velocity signal, and the harmonic credible weights of all frequencies to be analyzed in the spectrum of the abnormal flow velocity signal, the flow velocity attenuation characteristic value is determined, specifically:

[0079] (1) In a normal flow rate signal, the ratios between the liquid flow rate data at the same frequencies as the frequencies to be analyzed in the abnormal flow rate signal are calculated, and the ratios between all the liquid flow rate data constitute a flow rate attenuation sequence.

[0080] (2) Furthermore, the harmonic credible weights of all frequencies to be analyzed in the spectrum of the abnormal flow velocity signal are combined into a harmonic weight sequence.

[0081] (3) Further, the product of each element in the harmonic weight sequence and the element at the corresponding same position in the velocity attenuation sequence is calculated, and all the products constitute the attenuation characteristic sequence.

[0082] (4) Furthermore, the ratio of the discrete degree of all elements in the attenuation characteristic sequence to the mean value of all elements in the velocity attenuation sequence is taken as the velocity attenuation characteristic value of the tubular falling film evaporator.

[0083] It should be noted that there are many methods for measuring the degree of discreteness of a set of data. In this embodiment, the degree of discreteness of the products at all the same positions is measured by calculating the standard deviation of the products at all the same positions. The implementer may also adopt other methods for measuring the degree of discreteness of data, such as method, discrete coefficient, etc. This embodiment does not impose any special restrictions on the selection of the method for measuring the degree of discreteness of data.

[0084] Furthermore, according to the velocity attenuation characteristic value of the tubular falling film evaporator, it can be understood that the smaller the standard deviation of the attenuation characteristic sequence, the more similar the energy amplitude waveform representing the frequency position in the abnormal flow velocity signal is to the normal flow velocity signal waveform, and the larger the mean of all elements in the flow velocity attenuation sequence, the more the energy amplitude reflects the characteristic of proportional decrease, and the flow anomaly at this time is more likely to be caused by valve seal failure, wherein the weighted standard deviation is calculated using the harmonic weight sequence as the weight, which can eliminate the influence of the harmonic noise at the leakage point on the flow velocity attenuation characteristic; conversely, the larger the standard deviation of the attenuation characteristic sequence, the greater the difference between the energy amplitude waveform representing the frequency position in the abnormal flow velocity signal and the normal flow velocity signal waveform, and the smaller the mean of all elements in the flow velocity attenuation sequence, the less likely the flow anomaly at this time is caused by valve seal failure.

[0085] Preferably, the flow velocity attenuation characteristic value extraction process schematic diagram provided in this embodiment is as follows Figure 3 shown.

[0086] Step S4: Based on the velocity attenuation characteristic value of the tubular falling film evaporator, the sealing performance of the tubular falling film evaporator is tested.

[0087] If the velocity attenuation characteristic value of the tubular falling film evaporator is less than a preset value, the valve seal of the tubular falling film evaporator fails; otherwise, the valve seal of the tubular falling film evaporator is normal.

[0088] It should be noted that the value of the preset numerical value is manually set. In this embodiment, the value of the preset numerical value is 0.2. The implementer can also set it by himself according to the specific situation. This embodiment does not impose any special restrictions.

[0089] So far, this embodiment has completed the rapid test of valve seal failure by extracting the data features generated by valve seal failure in the flow rate monitoring data, thereby improving the accuracy of sealing detection of the tubular falling film evaporator, and accelerating the response speed to seal failure during the use of the tubular falling film evaporator, which is beneficial to improving the overall production efficiency of the tubular falling film evaporator.

[0090] Preferably, the sealing failure detection process flow chart provided in this embodiment is as follows: Figure 4 shown.

[0091] Based on the same inventive concept as the above method, an embodiment of the present application also provides a tubular falling film evaporator sealing test system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned tubular falling film evaporator sealing test methods when executing the computer program.

[0092] It should be noted that the above sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying 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.

[0093] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0094] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for testing the sealing performance of a tubular falling film evaporator, characterized in that: The method comprises the following steps: Obtain the liquid flow rate data at the inlet of the tubular falling film evaporator at each sampling time; Based on the liquid flow rate data at each collection moment and the preset threshold range, the abnormal moment is determined, all the liquid flow rate data within the preset time before the abnormal moment are formed into a normal flow rate signal, and the liquid flow rate data of the same preset time period are collected from the abnormal moment backward to form an abnormal flow rate signal; A time-frequency conversion algorithm is used to obtain the respective spectra of the normal flow velocity signal and the abnormal flow velocity signal. In the spectrum of the abnormal flow velocity signal, all the frequencies to be analyzed and all the fundamental frequencies of any frequency to be analyzed are determined based on the distribution characteristics of the energy amplitudes at all frequencies. All the fundamental frequencies of any frequency to be analyzed are recorded as suspected fundamental frequencies. The harmonic energy intensity of any frequency to be analyzed is determined by combining the energy amplitudes of all the suspected fundamental frequencies of any frequency to be analyzed at the same frequencies corresponding to the frequency spectrum of the normal flow velocity signal; and the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal is determined by combining the extreme distribution of the harmonic energy intensity of all frequencies to be analyzed. Based on the difference between the normal flow velocity signal and the abnormal flow velocity signal, the flow velocity attenuation sequence is determined; the harmonic credible weights of all frequencies to be analyzed in the spectrum of the abnormal flow velocity signal are combined into a harmonic weight sequence; based on the harmonic weight sequence and the flow velocity attenuation sequence, the attenuation characteristic sequence is determined; based on the discrete degree of all elements in the attenuation characteristic sequence and the average distribution of all elements in the flow velocity attenuation sequence, the flow velocity attenuation characteristic value of the tubular falling film evaporator is determined, and the sealing of the tubular falling film evaporator is tested; The step of determining all frequencies to be analyzed and all fundamental frequencies of any frequency to be analyzed includes: Taking half of the preset sampling frequency as the highest frequency of the abnormal flow velocity signal, and taking the frequency corresponding to the maximum energy amplitude in the spectrum of the abnormal flow velocity signal as the inherent fundamental frequency; For the spectrum of the abnormal flow velocity signal, between the natural fundamental frequency and the highest frequency, the frequency that is an integer multiple of the natural fundamental frequency and has a peak energy amplitude is taken as the frequency to be analyzed; Between the natural fundamental frequency and the highest frequency, the integer multiples of the frequencies of the possible fundamental waves of any frequency to be analyzed are equal to the frequency to be analyzed.

2. A method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The abnormal moment is the collection moment corresponding to when the liquid flow rate data exceeds a preset threshold range.

3. The method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The expression of the harmonic energy intensity of any frequency to be analyzed is: ; In the formula, represents the harmonic energy intensity of the frequency r to be analyzed; Represents the energy amplitude of the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal at the same frequency in the spectrum of the normal flow velocity signal; represents the hth suspected fundamental frequency of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal; r represents the frequency to be analyzed in the spectrum of the abnormal flow velocity signal; Represents the number of all suspected fundamental waves of the frequency r to be analyzed in the spectrum of the abnormal flow velocity signal.

4. The method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The method for determining the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal is as follows: In the spectrum of the abnormal flow velocity signal, the range of the harmonic energy intensity of all frequencies is calculated, and the difference between the maximum value of the harmonic energy of all frequencies and the harmonic energy intensity of any frequency to be analyzed is calculated, and the ratio of the difference to the range is used as the harmonic credible weight of any frequency to be analyzed in the spectrum of the abnormal flow velocity signal.

5. The method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The method for determining the flow velocity decay sequence is: In the normal flow rate signal, the ratios between the liquid flow rate data at the frequencies that are the same as the frequencies to be analyzed in the abnormal flow rate signal are calculated, and the ratios between all the liquid flow rate data constitute a flow rate attenuation sequence.

6. A method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The method for determining the attenuation characteristic sequence is: The product of each element in the harmonic weight sequence and the element at the corresponding same position in the velocity attenuation sequence is calculated, and all the products constitute an attenuation characteristic sequence.

7. The method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The velocity attenuation characteristic value of the tubular falling film evaporator is the ratio of the discrete degree of all elements in the attenuation characteristic sequence to the mean value of all elements in the velocity attenuation sequence.

8. The method for testing the sealing performance of a tubular falling film evaporator according to claim 1, characterized in that: The process of testing the sealing performance of the tubular falling film evaporator is as follows: If the flow rate attenuation characteristic value is less than the preset value, the valve seal of the tubular falling film evaporator fails, otherwise, the valve seal of the tubular falling film evaporator is normal.

9. A system for testing the tightness of a tubular falling film evaporator, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method for testing the sealing performance of a tubular falling film evaporator as described in any one of claims 1 to 8 are implemented.

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