A low-temperature Coriolis mass flowmeter online calibration system

Abstract

The invention discloses an online calibration system for a low-temperature Coriolis mass flowmeter, which relates to the technical field of flowmeter calibration. The invention draws characteristic lines in a constructed plane rectangular coordinate system, calculates the cooling slope, the heating slope and the trend slope ratio, analyzes the trend slope ratio of the temperature performance value and the cold and hot trend line slopes, constructs a data pair with the trend slope ratio and the cold and hot trend line slope type, matches the corresponding temperature correction coefficient through a database, and then calculates the ratio of the temperature correction value to the temperature reference value, and the environment correction value to the environment reference value respectively. The density adjustment index is obtained by summing the temperature weight and the environment weight, and then the corresponding density adjustment coefficient is matched to correct the measured density. The system solves the problems in the prior art that the temperature data cannot be accurately evaluated and the density cannot be effectively corrected, and the trend change of temperature is ignored when evaluating the temperature data, resulting in the accuracy of the calibration not being guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of flowmeter calibration, and in particular to an online calibration system for a low-temperature Coriolis mass flowmeter. Background Art

[0002] The Coriolis mass flowmeter is an instrument that uses the Coriolis force generated by the fluid flowing in a vibrating tube, which is proportional to the mass flow rate, to measure mass flow. In the chemical, energy and other industries, Coriolis mass flowmeters are often used to accurately measure the mass flow rate of fluids.

[0003] However, the online calibration system for Coriolis mass flowmeters in the prior art still has the following deficiencies in practical applications:

[0004] When dealing with cryogenic media, their density will change significantly due to temperature changes. When the temperature rises, the molecular thermal motion intensifies, the volume expands, and the density decreases; when the temperature drops, the volume contracts and the density increases. However, existing systems are often unable to accurately evaluate temperature data and effectively correct density. In addition, when evaluating temperature data, they ignore temperature trend changes, resulting in a lack of calibration accuracy.

[0005] In addition, in low-temperature environments, frost is prone to form on the surface of the vibrating tube. The additional mass of the frost will change the vibration characteristics of the vibrating tube, causing the actual measured value of the flow meter to deviate from the true flow rate. However, the existing system lacks effective monitoring of frosting conditions and targeted secondary correction measures, resulting in a decrease in measurement accuracy and an inability to meet the demand for high-precision measurement of low-temperature fluid flow in industrial production.

[0006] Therefore, a low-temperature Coriolis mass flowmeter online calibration system is introduced. Summary of the Invention

[0007] In view of this, the present invention provides an online calibration system for a low-temperature Coriolis mass flowmeter to solve the problems raised in the above-mentioned background technology.

[0008] The object of the present invention can be achieved by the following technical solution: a low-temperature Coriolis mass flowmeter online calibration system, comprising:

[0009] Calibration setting module: preset r calibration points. After reaching each calibration point, the temperature data of the low-temperature medium upstream and downstream of the vibration tube and the ambient temperature of the outer wall of the vibration tube within the set measurement window are recorded and transmitted to the calibration calculation module;

[0010] Calibration calculation module: receives the temperature data of the cryogenic medium upstream and downstream of the vibration tube within the set measurement window and the ambient temperature of the outer wall of the vibration tube, performs a comprehensive evaluation, and corrects the density of the cryogenic medium based on the evaluation results;

[0011] Calibration optimization module: Real-time monitoring of the vibration acceleration signal of the vibrating tube, which is converted into displacement amplitude through integration. The displacement amplitude is comprehensively analyzed to obtain the warning amplitude index. If the warning amplitude index within a certain sliding window is greater than the set threshold, the frost warning is triggered and the corresponding steps are executed to perform a secondary correction on the density of the low-temperature medium.

[0012] In some embodiments, the receiving of temperature data of the cryogenic medium upstream and downstream of the vibrating tube within the set measurement window and performing comprehensive evaluation is specifically as follows:

[0013] Extract the temperature data of the cryogenic medium upstream and downstream of the vibrating tube within the set measurement window, calculate the average of the upstream and downstream temperature data at the same time point, and obtain the temperature performance value of the cryogenic medium at each time point within the set measurement window;

[0014] For the temperature performance values ​​at each time point, the average value is taken to obtain the comprehensive temperature value of the low-temperature medium in the set measurement window; the temperature correction coefficient obtained by analysis is multiplied by the comprehensive temperature value to obtain the temperature correction value.

[0015] In some embodiments, the specific analysis process of the temperature correction coefficient is:

[0016] The temperature performance value at each time point is input into a pre-constructed plane rectangular coordinate system, where the horizontal axis represents the set measurement window and the vertical axis represents the temperature performance value at each time point;

[0017] Draw the numerical points corresponding to the temperature performance values ​​at each time point in the plane rectangular coordinate system, and connect adjacent numerical points to obtain the characteristic line;

[0018] Calculate the slope of the characteristic line and the angle between the characteristic line and the horizontal line. When the angle between the characteristic line and the horizontal line is acute, mark the slope of the characteristic line as the cooling slope. When the angle between the characteristic line and the horizontal line is obtuse, mark it as the heat rise slope. Sum all the values ​​of the cooling slope to obtain the total cooling value and mark it as Z1. Sum all the values ​​of the heat rise slope and take the absolute value to obtain the total heat rise value and mark it as Z2.

[0019] The trend slope ratio Z3 is obtained by calculating the ratio using the total cooling drop value Z1 as the numerator and the total heat rise value as the denominator;

[0020] Connect the first numerical point and the last numerical point in the plane rectangular coordinate system to obtain a line segment and mark the line segment as the hot and cold trend line. Calculate the slope of the hot and cold trend line and the angle with the horizontal line. When the angle between the hot and cold trend line and the horizontal line is acute, mark the slope of the hot and cold trend line as the cold trend slope, and the value of the cold trend slope is represented by the symbol L1. When the angle between the hot and cold trend line and the horizontal line is obtuse, mark the slope of the hot and cold trend line as the hot trend slope, and the absolute value of the hot trend slope is represented by the symbol L2.

[0021] Identify the slope types of the cold and hot trend lines, which include cold trend slope and hot trend slope, and construct a data pair with the trend slope ratio Z3, expressed as (Z3, Le), where e is equal to 1 or 2; input the constructed data pair into a pre-constructed database for matching to obtain the temperature correction coefficient.

[0022] In some embodiments, the constructed data pair is input into a pre-constructed database for matching, specifically:

[0023] Extracting reference data pairs corresponding to the data pairs from a pre-built database, each reference data pair including the slope type of the hot and cold trend lines and the data pair value range, and each reference data pair corresponding to a set of temperature correction coefficients;

[0024] The slope type of the hot and cold trend lines of the constructed data pairs is matched with the slope type of each group of reference data pairs. After the match is successful, the data pair value ranges of the constructed data pairs and each group of reference data pairs are further matched, that is, the Z3 and Le of the constructed data pairs are matched with the Z3 value range and Le value range of the reference data pairs respectively. After the match is successful, the temperature correction coefficient is extracted.

[0025] In some embodiments, the density of the cryogenic medium is corrected based on the evaluation result, specifically:

[0026] The ambient temperature of the outer wall of the vibrating tube within the set measurement window is extracted, and the average value is calculated to obtain the ambient correction value; the temperature correction value is ratioed to the set temperature reference value, that is, the temperature correction value is used as the numerator and the temperature reference value is used as the denominator to obtain the temperature reference ratio; the ambient correction value is ratioed to the set ambient reference value, that is, the ambient correction value is used as the numerator and the ambient reference value is used as the denominator to obtain the ambient reference ratio;

[0027] Multiply the temperature reference ratio and the environment reference ratio by the set temperature weight and environment weight respectively, and then sum them to obtain the density adjustment index; pre-construct the index value ranges of each group corresponding to the density adjustment index, and each index value range corresponds to a density adjustment coefficient;

[0028] The obtained density adjustment index is matched with the value range of each group of indexes to determine the density adjustment coefficient, and the initial measured density value of the cryogenic medium is multiplied by the density adjustment coefficient to obtain the density of the cryogenic medium after correction.

[0029] In some embodiments, the comprehensive analysis of the displacement amplitude to obtain the warning amplitude index is specifically:

[0030] The mean A and standard deviation B of the displacement amplitude data in the sliding window are calculated using formulas (1) and (2) respectively. The formulas are expressed as follows: ; where i represents the number of each time point, n is the total number of time points, represents the displacement amplitude at each time point;

[0031] Using the mean A as the denominator and the standard deviation B as the numerator, the ratio calculation is performed to obtain the warning amplitude index.

[0032] In some embodiments, after the frost warning is triggered, corresponding steps are executed to perform a secondary correction on the density of the cryogenic medium, specifically:

[0033] S1: Obtain a thermal image of the vibrating tube at the time when the frost warning is currently triggered, set a low temperature threshold, and mark the area below the low temperature threshold in the thermal image as a frosted area;

[0034] S2: Identify the boundaries of the frosted areas and obtain the areas and locations of the frosted areas; if the number of frosted areas is one, execute step S3; if the number of frosted areas is greater than one, execute step S4.

[0035] In some embodiments, if the number of frosted areas is one, step S3 is executed. The specific process of step S3 is:

[0036] S3: Calculate the average temperature of each temperature distribution point in the frosted area to obtain a frosted temperature value, mark the area of ​​the thermal image other than the frosted area as a normal area, calculate the average temperature of each temperature distribution point in the normal area to obtain a normal temperature value; subtract the frosted temperature value from the normal temperature value to obtain a frosted temperature difference;

[0037] Based on the frosting temperature difference and the physical properties of the low-temperature medium, the frost thickness d is calculated. The formula is expressed as ;in is the heat flux, is the thermal conductivity of the frost layer, is the frost temperature difference;

[0038] Based on the area and thickness d of the frosted area, calculate the additional mass m of frosting using the formula m=pe×S×d, where S represents the area of ​​the frosted area and pe is the density of the frost.

[0039] The frosting additional mass m is equivalent to the density increment of the low-temperature medium, and the mass flow measured by the Coriolis flowmeter is corrected twice. The result of the secondary correction is expressed as ;in Indicates the mass flow value directly measured by the Coriolis mass flowmeter. Indicates the mass flow measurement value after secondary correction; They represent the baseline density and density increment of the cryogenic medium respectively.

[0040] In some embodiments, if the number of frosted areas is greater than one, step S4 is executed. The specific process of step S4 is:

[0041] S4: number each frosted area, denoted by k, where k = 1, 2, ..., f, where f is the total number of frosted areas;

[0042] Get the centroid coordinates for each frosted area Similarly, step S3 calculates the frosting additional mass; the vibrating tube is divided into various component areas, the centroid coordinates of each frosting area are mapped to the corresponding component area, and the sum of the frosting additional mass in each component area is calculated to obtain the regional mass sum;

[0043] The regional mass sum in each component region is marked as Cg, where g is the number corresponding to each component region. Each group of experimental cases is extracted from a pre-built database. Each group of experimental cases includes the simulated frosting area, regional mass sum, and density increment of each component region.

[0044] From each group of experimental cases, the experimental cases with the same medium type as the current one are selected as the cases to be matched. The Euclidean distance formula is used to calculate the distance bt between the regional mass sum Cg in each component area and the regional mass sum of each group of cases to be matched; the formula is expressed as ; Where N is the total number of component regions, Sg represents the sum of the regional qualities of each component region in the case to be matched;

[0045] The distance bt of each group of cases to be matched is compared with the set distance reference value, and the cases to be matched that are smaller than the distance reference value are screened and the density increment is extracted. The average value of the extracted density increments is calculated as , and similarly, step S3 performs a secondary correction on the mass flow measured by the Coriolis flowmeter.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention draws characteristic lines in a constructed plane rectangular coordinate system, calculates the cooling slope, the heating slope and the trend slope ratio, analyzes the trend slope ratio of the temperature performance value and the slope of the hot and cold trend line, constructs a data pair of the trend slope ratio and the hot and cold trend line slope type, matches the corresponding temperature correction coefficient through a database, and then respectively calculates the ratio of the temperature correction value to the temperature reference value, and the environment correction value to the environment reference value. The density adjustment index is obtained by summing the temperature weight and the environment weight, and then the corresponding density adjustment coefficient is matched to correct the measured density. This solves the problem that the prior art cannot accurately evaluate temperature data and effectively correct density, and ignores the trend change of temperature when evaluating temperature data, resulting in a lack of guarantee of calibration accuracy.

[0048] The present invention collects vibration signals through an acceleration sensor, calculates the warning amplitude index, triggers a frost warning when the index exceeds a threshold, and marks the frosted area with infrared thermal imaging to achieve real-time monitoring of frost.

[0049] The present invention calculates the frosting temperature difference, thickness and additional mass of a single frosting area, which is equivalent to the density increment, and calculates the corrected flow rate through a formula to eliminate the interference of the frosting additional mass on the vibration characteristics;

[0050] The present invention maps multiple frosted areas to each component area according to the centroid coordinates, calculates the regional mass sum, and uses the Euclidean distance to match experimental cases of the same medium in the database, extracts the density increment mean for secondary correction, and avoids errors caused by the same total mass but different distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Further details, features and advantages of the present application are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0052] Figure 1 It is a principle block diagram of the present invention;

[0053] Figure 2 It is a changing trend diagram of the temperature performance value in the present invention. DETAILED DESCRIPTION

[0054] Several embodiments of the present application will be described in more detail below with reference to the accompanying drawings so that those skilled in the art can implement the present application. The present application can be embodied in many different forms and for many different purposes and should not be limited to the embodiments described herein. These embodiments are provided to make the present application comprehensive and complete and to fully convey the scope of the present application to those skilled in the art. The embodiments do not limit the present application.

[0055] Unless otherwise defined, all terms (including 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. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0056] See also Figure 1-Figure 2 As shown, a low-temperature Coriolis mass flowmeter online calibration system includes a calibration setting module, a calibration calculation module and a calibration optimization module;

[0057] The calibration setting module is used to preset r calibration points according to the actual working conditions. After reaching each calibration point, it records the temperature data of the low-temperature medium upstream and downstream of the vibration tube and the ambient temperature of the outer wall of the vibration tube within the set measurement window and transmits them to the calibration calculation module;

[0058] Supplementary instructions: Select at least three calibration points (such as 10%, 50%, and 90% of the range) to cover the commonly used flow range; the stable measurement time of a single calibration point should be no less than 5 minutes to ensure the stability of the low-temperature medium state (temperature, pressure) and flow rate;

[0059] The temperature is collected by high-precision platinum resistors placed upstream and downstream of the vibrating tube; infrared temperature sensors are placed on the outer wall of the pipeline to collect ambient temperature;

[0060] The calibration calculation module is used to receive the temperature data of the cryogenic medium upstream and downstream of the vibration tube within the set measurement window and the ambient temperature of the outer wall of the vibration tube, and perform a comprehensive evaluation, and correct the density of the cryogenic medium based on the evaluation results;

[0061] It should be noted that the density of cryogenic media is sensitive to temperature;

[0062] When the temperature of the low-temperature medium increases, the molecular thermal motion intensifies, the volume expands, and the density decreases; when the temperature decreases, the volume shrinks and the density increases;

[0063] Specifically:

[0064] Extract the temperature data of the cryogenic medium upstream and downstream of the vibrating tube within the set measurement window, calculate the average of the upstream and downstream temperature data at the same time point, and obtain the temperature performance value of the cryogenic medium at each time point within the set measurement window;

[0065] For the temperature performance values ​​at each time point, the average value is taken to obtain the comprehensive temperature value of the low-temperature medium within the set measurement window; the temperature performance values ​​at each time point are input into a pre-constructed plane rectangular coordinate system, with the horizontal axis representing the set measurement window and the vertical axis representing the temperature performance value at each time point;

[0066] Draw the numerical points corresponding to the temperature performance values ​​at each time point in the plane rectangular coordinate system, and connect adjacent numerical points to obtain the characteristic line;

[0067] Calculate the slope of the characteristic line and the angle between the characteristic line and the horizontal line. When the angle between the characteristic line and the horizontal line is acute, mark the slope of the characteristic line as the cooling slope. When the angle between the characteristic line and the horizontal line is obtuse, mark it as the heat rise slope. Sum all the values ​​of the cooling slope to obtain the total cooling value and mark it as Z1. Sum all the values ​​of the heat rise slope and take the absolute value to obtain the total heat rise value and mark it as Z2.

[0068] The trend slope ratio Z3 is obtained by calculating the ratio using the total cooling drop value Z1 as the numerator and the total heat rise value as the denominator;

[0069] Connect the first numerical point and the last numerical point in the plane rectangular coordinate system to obtain a line segment and mark the line segment as the hot and cold trend line. Calculate the slope of the hot and cold trend line and the angle with the horizontal line. When the angle between the hot and cold trend line and the horizontal line is acute, mark the slope of the hot and cold trend line as the cold trend slope, and the value of the cold trend slope is represented by the symbol L1. When the angle between the hot and cold trend line and the horizontal line is obtuse, mark the slope of the hot and cold trend line as the hot trend slope, and the absolute value of the hot trend slope is represented by the symbol L2.

[0070] Identify the slope types of the cold and hot trend lines, including cold trend slope and hot trend slope, and construct a data pair with the trend slope ratio Z3, expressed as (Z3, Le), where e is equal to 1 or 2;

[0071] Extracting reference data pairs corresponding to the data pairs from a pre-built database. Each reference data pair includes the slope type of the hot and cold trend lines and the data pair value range. Each reference data pair corresponds to a set of temperature correction coefficients. The temperature correction coefficient range is set to 0.895-1.136.

[0072] Supplementary note: if the slope type of the hot and cold trend lines is a cold trend slope and the value of Z3 is large, the probability of matching 1.136 is higher. The specific setting is made by technicians based on experimental data;

[0073] Match the slope type of the hot and cold trend lines of the constructed data pair with the slope type of each reference data pair. After the match is successful, further match the data pair value ranges of the constructed data pair with each reference data pair, that is, match the Z3 and Le of the constructed data pair with the Z3 value range and Le value range of the reference data pair respectively. After the match is successful, extract the temperature correction coefficient; multiply the temperature correction coefficient by the temperature comprehensive value to obtain the temperature correction value;

[0074] In addition, when the temperature change trend is gradually decreasing, the temperature comprehensive value is further adjusted downward to make the correction value more in line with the actual temperature change. For example, if the temperature comprehensive value is -160℃ and the trend is continuously decreasing, it is adjusted to -162℃ to compensate in advance for the impact of subsequent temperature drop on density.

[0075] If the temperature trend is gradually increasing, the opposite is true;

[0076] Extract the ambient temperature of the outer wall of the vibration tube within the set measurement window, calculate the average value and obtain the environmental correction value;

[0077] Calculate the ratio of the temperature correction value to the set temperature reference value, that is, the temperature correction value is used as the numerator and the temperature reference value is used as the denominator to obtain the temperature reference ratio;

[0078] Calculate the ratio of the environmental correction value to the set environmental reference value, i.e., the environmental correction value is used as the numerator and the environmental reference value is used as the denominator, to obtain the environmental reference ratio;

[0079] Multiply the temperature reference ratio and the environment reference ratio by the set temperature weight and environment weight respectively, and then sum them to obtain the density adjustment index; the sum of the temperature weight and the environment weight is one, and the temperature weight is greater than the environment weight;

[0080] Supplementary note: the vibration tube is assumed to work in a low temperature environment;

[0081] Pre-construct the index value ranges for each group of density adjustment indices, and each index value range corresponds to a density adjustment coefficient. The density adjustment coefficient range is set between 0.954 and 1.127. The larger the density adjustment index, the higher the probability of matching 1.127.

[0082] The obtained density adjustment index is matched with the value range of each group of indexes to determine the density adjustment coefficient, and the initial measured density value of the cryogenic medium is multiplied by the density adjustment coefficient to obtain the density of the cryogenic medium after correction;

[0083] The calibration optimization module uses the deployed acceleration sensors to monitor the vibration acceleration signal of the vibrating tube in real time, converts it into displacement amplitude through integration, and performs a comprehensive analysis of the displacement amplitude to obtain the warning amplitude index. If the warning amplitude index within a certain sliding window is greater than the set threshold, a frost warning is triggered and the corresponding steps are executed to perform a secondary correction on the density of the low-temperature medium.

[0084] To supplement, install accelerometers (sensitivity ≥ 100 mV / g, frequency response 0.1-1000 Hz) at both ends or in the middle of the vibration tube to collect the vibration acceleration signal of the vibration tube and convert it into displacement amplitude (unit: μm) through integration. Continuous sampling at a frequency above 100 Hz ensures that high-frequency vibration details are captured. A sliding window (e.g., 500 data points, 5 seconds in duration) is used to calculate the real-time amplitude.

[0085] The specific process of calculating the warning amplitude index is as follows:

[0086] The mean A and standard deviation B of the displacement amplitude data in the sliding window are calculated using formulas (1) and (2) respectively. The formulas are expressed as follows: ; where i represents the number of each time point, n is the total number of time points, represents the displacement amplitude at each time point;

[0087] Using the mean A as the denominator and the standard deviation B as the numerator, the ratio calculation is performed to obtain the warning amplitude index;

[0088] After the frost warning is triggered, the corresponding steps are executed, specifically:

[0089] S1: A low-temperature infrared thermal imager is deployed around the flow meter to cover the entire surface of the vibrating tube. A thermal image of the vibrating tube at the time when the frost warning is triggered is obtained. A low-temperature threshold is set, and areas below the low-temperature threshold in the thermal image are marked as frosted areas.

[0090] S2: Identify the boundaries of the frosted areas and obtain the area and location of the frosted areas; if the number of frosted areas is one, execute step S3; if the number of frosted areas is greater than one, execute step S4;

[0091] S3: Calculate the average temperature of each temperature distribution point in the frosted area to obtain a frosted temperature value, mark the area of ​​the thermal image other than the frosted area as a normal area, calculate the average temperature of each temperature distribution point in the normal area to obtain a normal temperature value; subtract the frosted temperature value from the normal temperature value to obtain a frosted temperature difference;

[0092] Based on the frosting temperature difference and the physical properties of the low-temperature medium, the frost thickness d is calculated. The formula is expressed as ;in is the heat flux, is the thermal conductivity of the frost layer, is the frost temperature difference;

[0093] According to the area and thickness d of the frosted area, the additional mass m of frosting is calculated using the formula m=pe×S×d; where S represents the area of ​​the frosted area and pe is the density of the frost, which is 500kg / m 3 ;

[0094] The frosting additional mass m is equivalent to the density increment of the low-temperature medium, and the mass flow measured by the Coriolis flowmeter is corrected twice. The result of the secondary correction is expressed as ;in Indicates the mass flow value directly measured by the Coriolis mass flowmeter. Indicates the mass flow measurement value after secondary correction; They represent the base density of the cryogenic medium and the density increment of the cryogenic medium respectively;

[0095] In addition, when frost forms on the low-temperature medium pipeline, the additional mass of the frost will change the vibration characteristics of the vibrating tube, causing the flow meter's measured value to deviate from the true flow rate. By quantifying the equivalent density increment, the measurement result is corrected to improve the accuracy of flow measurement in low-temperature environments.

[0096] S4: number each frosted area, denoted by k, where k = 1, 2, ..., f, where f is the total number of frosted areas;

[0097] Get the centroid coordinates for each frosted area , similarly, step S3 calculates the frosting additional mass;

[0098] Divide the vibrating tube into various component areas, such as the top, bottom, and middle of the tube; map the centroid coordinates of each frosted area to the corresponding component area, and calculate the sum of the frosted added mass in each component area to obtain the regional mass sum;

[0099] Supplementary explanation: if the frosted area k=1,2 is located at the top of the tube, and k=3 is located at the bottom of the tube, then the total mass of the area at the top of the tube = m1 + m2, and the total mass of the area at the bottom of the tube = m3;

[0100] The regional mass sum in each component region is marked as Cg, where g is the number corresponding to each component region. Each group of experimental cases is extracted from a pre-built database. Each group of experimental cases includes the simulated frosting area, regional mass sum, and density increment of each component region.

[0101] From each group of experimental cases, the experimental cases with the same medium type as the current one are selected as the cases to be matched. The Euclidean distance formula is used to calculate the distance bt between the regional mass sum Cg in each component area and the regional mass sum of each group of cases to be matched; the formula is expressed as ; Where N is the total number of component regions, Sg represents the sum of the regional qualities of each component region in the case to be matched;

[0102] The distance bt of each group of cases to be matched is compared with the set distance reference value, and the cases to be matched that are smaller than the distance reference value are screened and the density increment is extracted. The average value of the extracted density increments is calculated as Similarly, step S3 performs a secondary correction on the mass flow measured by the Coriolis flowmeter;

[0103] In addition, when there are multiple frosted areas, the additional mass of each area is included in the calculation of the sum of the corresponding component areas through numbering, centroid positioning and area mapping. For example, the mass sum of multiple frosted areas on the top of the pipe is treated separately from the mass sum of a single area at the bottom of the pipe. This avoids the correction error caused by "same total mass but different distribution" when frosting multiple areas, and improves the system's adaptability to complex frosting forms. Euclidean distance is used to screen cases with the same medium as the current one, ensuring that the physical properties of the matching cases are consistent with the actual operating conditions, reducing correction deviations caused by medium differences.

[0104] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-temperature Coriolis mass flowmeter online calibration system, characterized in that: include: Calibration setting module: preset r calibration points. After reaching each calibration point, the temperature data of the low-temperature medium upstream and downstream of the vibration tube and the ambient temperature of the outer wall of the vibration tube within the set measurement window are recorded and transmitted to the calibration calculation module; Calibration calculation module: receives the temperature data of the cryogenic medium upstream and downstream of the vibration tube within the set measurement window and the ambient temperature of the outer wall of the vibration tube, performs a comprehensive evaluation, and corrects the density of the cryogenic medium based on the evaluation results; The specific steps of comprehensive assessment are: Extract the temperature data of the cryogenic medium upstream and downstream of the vibrating tube within the set measurement window, calculate the average of the upstream and downstream temperature data at the same time point, and obtain the temperature performance value of the cryogenic medium at each time point within the set measurement window; For the temperature performance values ​​at each time point, take the average value to obtain the comprehensive temperature value of the low-temperature medium within the set measurement window; multiply the analyzed temperature correction coefficient by the comprehensive temperature value to obtain the temperature correction value; The specific analysis process of the temperature correction coefficient is: The temperature performance value at each time point is input into a pre-constructed plane rectangular coordinate system, where the horizontal axis represents the set measurement window and the vertical axis represents the temperature performance value at each time point; Draw the numerical points corresponding to the temperature performance values ​​at each time point in the plane rectangular coordinate system, and connect adjacent numerical points to obtain the characteristic line; Calculate the slope of the characteristic line and the angle between the characteristic line and the horizontal line. When the angle between the characteristic line and the horizontal line is acute, mark the slope of the characteristic line as the cooling slope. When the angle between the characteristic line and the horizontal line is obtuse, mark it as the heat rise slope. Sum all the values ​​of the cooling slope to obtain the total cooling value and mark it as Z1. Sum all the values ​​of the heat rise slope and take the absolute value to obtain the total heat rise value and mark it as Z2. The trend slope ratio Z3 is obtained by calculating the ratio using the total cooling drop value Z1 as the numerator and the total heat rise value as the denominator; Connect the first numerical point and the last numerical point in the plane rectangular coordinate system to obtain a line segment and mark the line segment as the hot and cold trend line. Calculate the slope of the hot and cold trend line and the angle with the horizontal line. When the angle between the hot and cold trend line and the horizontal line is acute, mark the slope of the hot and cold trend line as the cold trend slope. The value of the cold trend slope is represented by the symbol L1. When the angle between the hot and cold trend line and the horizontal line is an obtuse angle, the slope of the hot and cold trend line is marked as the hot trend slope, and the absolute value of the hot trend slope is represented by the symbol L2; Identify the slope type of the hot and cold trend lines, including cold trend slope and hot trend slope, and construct a data pair with the trend slope ratio Z3, expressed as (Z3, Le), where e is equal to 1 or 2; input the constructed data pair into a pre-built database for matching to obtain the temperature correction coefficient; Calibration optimization module: Real-time monitoring of the vibration acceleration signal of the vibrating tube, which is converted into displacement amplitude through integration. The displacement amplitude is comprehensively analyzed to obtain the warning amplitude index. If the warning amplitude index within a certain sliding window is greater than the set threshold, the frost warning is triggered and the corresponding steps are executed to perform a secondary correction on the density of the low-temperature medium.

2. The low-temperature Coriolis mass flowmeter online calibration system according to claim 1, characterized in that: The constructed data is input into a pre-constructed database for matching, specifically: Extracting reference data pairs corresponding to the data pairs from a pre-built database, each reference data pair including the slope type of the hot and cold trend lines and the data pair value range, and each reference data pair corresponding to a set of temperature correction coefficients; The slope type of the hot and cold trend lines of the constructed data pairs is matched with the slope type of each group of reference data pairs. After the match is successful, the data pair value ranges of the constructed data pairs and each group of reference data pairs are further matched, that is, the Z3 and Le of the constructed data pairs are matched with the Z3 value range and Le value range of the reference data pairs respectively. After the match is successful, the temperature correction coefficient is extracted.

3. The low-temperature Coriolis mass flowmeter online calibration system according to claim 2, characterized in that: The density of the cryogenic medium is corrected based on the evaluation result, specifically: The ambient temperature of the outer wall of the vibrating tube within the set measurement window is extracted, and the average value is calculated to obtain the ambient correction value; the temperature correction value is ratioed to the set temperature reference value, that is, the temperature correction value is used as the numerator and the temperature reference value is used as the denominator to obtain the temperature reference ratio; the ambient correction value is ratioed to the set ambient reference value, that is, the ambient correction value is used as the numerator and the ambient reference value is used as the denominator to obtain the ambient reference ratio; Multiply the temperature reference ratio and the environment reference ratio by the set temperature weight and environment weight respectively, and then sum them to obtain the density adjustment index; pre-construct the index value ranges of each group corresponding to the density adjustment index, and each index value range corresponds to a density adjustment coefficient; The obtained density adjustment index is matched with the value range of each group of indexes to determine the density adjustment coefficient, and the initial measured density value of the cryogenic medium is multiplied by the density adjustment coefficient to obtain the density of the cryogenic medium after correction.

4. The low-temperature Coriolis mass flowmeter online calibration system according to claim 3, characterized in that: The above-mentioned comprehensive analysis of the displacement amplitudes yields the early warning amplitude index, specifically: The mean A and standard deviation B of the displacement amplitude data in the sliding window are calculated using formulas (1) and (2) respectively. The formulas are expressed as follows: ; where i represents the number of each time point, n is the total number of time points, represents the displacement amplitude at each time point; Using the mean A as the denominator and the standard deviation B as the numerator, the ratio calculation is performed to obtain the warning amplitude index.

5. The low-temperature Coriolis mass flowmeter online calibration system according to claim 4, characterized in that: After the frost warning is triggered, the corresponding steps are executed to perform a secondary correction on the density of the low-temperature medium, specifically: S1: Obtain a thermal image of the vibrating tube at the time when the frost warning is currently triggered, set a low temperature threshold, and mark the area below the low temperature threshold in the thermal image as a frosted area; S2: Identify the boundaries of the frosted areas and obtain the areas and locations of the frosted areas; if the number of frosted areas is one, execute step S3; if the number of frosted areas is greater than one, execute step S4.

6. The low-temperature Coriolis mass flowmeter online calibration system according to claim 5, characterized in that: If the number of frosted areas is one, step S3 is executed. The specific process of step S3 is as follows: S3: Calculate the average temperature of each temperature distribution point in the frosted area to obtain a frosted temperature value, mark the area in the thermal image other than the frosted area as a normal area, and calculate the average temperature of each temperature distribution point in the normal area to obtain a normal temperature value; Subtract the frosting temperature value from the normal temperature value to obtain the frosting temperature difference; Based on the frosting temperature difference and the physical properties of the low-temperature medium, the frost thickness d is calculated. The formula is expressed as ;in is the heat flux, is the thermal conductivity of the frost layer, is the frost temperature difference; According to the area and thickness d of the frosted area, calculate the additional mass m of frosting, which can be expressed as m=pe×S×d; Where S represents the area of ​​frost, and pe is the density of frost; The frosting additional mass m is equivalent to the density increment of the low-temperature medium, and the mass flow measured by the Coriolis flowmeter is corrected twice. The result of the secondary correction is expressed as ;in Indicates the mass flow value directly measured by the Coriolis mass flowmeter. Indicates the mass flow measurement value after secondary correction; They represent the baseline density and density increment of the cryogenic medium respectively.

7. The low-temperature Coriolis mass flowmeter online calibration system according to claim 6, characterized in that: If the number of frosted areas is greater than one, step S4 is executed. The specific process of step S4 is: S4: Number each frosted area, denoted by k, where k = 1, 2, ..., f, where f is the total number of frosted areas; Get the centroid coordinates for each frosted area Similarly, step S3 calculates the frosting additional mass; the vibrating tube is divided into various component areas, the centroid coordinates of each frosting area are mapped to the corresponding component area, and the sum of the frosting additional mass in each component area is calculated to obtain the regional mass sum; The regional mass sum in each component region is marked as Cg, where g is the number corresponding to each component region. Each group of experimental cases is extracted from a pre-built database. Each group of experimental cases includes the simulated frosting area, regional mass sum, and density increment of each component region. From each group of experimental cases, the experimental cases with the same medium type as the current one are selected as the cases to be matched. The Euclidean distance formula is used to calculate the distance bt between the regional mass sum Cg in each component area and the regional mass sum of each group of cases to be matched; the formula is expressed as ; Where N is the total number of component regions, Sg represents the sum of the regional qualities of each component region in the case to be matched; The distance bt of each group of cases to be matched is compared with the set distance reference value, and the cases to be matched that are smaller than the distance reference value are screened and the density increment is extracted. The average value of the extracted density increments is calculated as , and similarly, step S3 performs a secondary correction on the mass flow measured by the Coriolis flowmeter.

Images