Differential pressure transmitter and differential pressure flowmeter gas-liquid two-phase flow calculation method and system

Abstract

The application belongs to the technical field of flow meter calibration, and discloses a differential pressure transmitter and differential pressure flow meter gas-liquid two-phase flow calculation method and system; the method comprises the following steps: installing a differential pressure flow meter on a gas-liquid two-phase flow pipeline, connecting a differential pressure transmitter to the pressure tapping of the differential pressure flow meter; collecting the real-time output current of the differential pressure transmitter and statistically analyzing it to mark the saturation risk state; when it is detected that the saturation risk state jumps from 1 back to 0, recording the output current in the sampling time length at a preset sampling rate to obtain a recovery waveform, statistically analyzing and calculating the waveform features according to the recovery waveform; based on a preset fingerprint table, inquiring the permanent offset corresponding to the waveform features, compensating the output current converted into an engineering differential pressure value to obtain a corrected differential pressure value; combining fluid density and device parameters to calculate and obtain gas phase mass flow and liquid phase mass flow; the application solves the long-existing precision error of differential pressure type two-phase flow measurement under wide working conditions and dynamic flow patterns.

Description

Technical Field

[0001] This invention relates to the field of flow meter calibration technology, and more specifically, to a method and system for calculating the gas-liquid two-phase flow of differential pressure transmitters and differential pressure flow meters. Background Technology

[0002] In industrial production processes, gas-liquid two-phase flow is a common flow pattern, and accurate measurement of its flow parameters is crucial for process control, optimization, and safety assurance. Currently, differential pressure flow measurement methods are widely used in single-phase fluid flow measurement due to their advantages of simple structure, low cost, and high reliability. However, in gas-liquid two-phase flow measurement scenarios, drastic changes in the flow pattern can cause instantaneous and significant fluctuations in the differential pressure signal. Traditional differential pressure flow measurement devices have a fixed range; when the differential pressure surge exceeds the upper limit of the range, the differential pressure transmitter output enters the saturation region. Existing technologies mainly rely on pre-selecting a large range margin to avoid saturation, but this sacrifices measurement resolution and accuracy in the low flow range. Furthermore, brief saturation events can cause irreversible offsets in the transmitter's internal circuitry or sensor unit, resulting in a residual deviation in the output signal after the saturation event ends. This causes all subsequent flow readings to remain consistently high or low, forming a hidden system error.

[0003] In view of this, the present invention proposes a method and system for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and a differential pressure flow meter to solve the above problems. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art and to achieve the above objectives, the present invention provides the following technical solution: a method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and a differential pressure flowmeter, comprising:

[0005] A differential pressure flow meter is installed on the gas-liquid two-phase flow pipeline, and a differential pressure transmitter is connected to the pressure tap of the differential pressure flow meter; the acquisition and analysis module in the differential pressure flow meter acquires the real-time output current of the differential pressure transmitter, performs statistical analysis, and marks the saturation risk state based on the analysis results;

[0006] When the saturation risk state is detected to change from 1 back to 0, the output current within the sampling time is recorded at a preset sampling rate to obtain the recovery waveform. Based on the statistical analysis of the recovery waveform, the waveform characteristics used to quantitatively describe the dynamic speed of the recovery process are calculated.

[0007] Based on the permanent offset corresponding to the waveform characteristics queried from the preset fingerprint table, the output current is converted into an engineering differential pressure value. The engineering differential pressure value is then compensated based on the permanent offset to obtain the corrected differential pressure value.

[0008] Based on the corrected differential pressure value, combined with the fluid density and device parameters, the gas phase mass flow rate and liquid phase mass flow rate are calculated.

[0009] Furthermore, methods for obtaining a preset fingerprint table include:

[0010] Install the differential pressure transmitter to be calibrated on the standard pressure calibration device, and connect the power supply and signal output of the differential pressure transmitter to be calibrated to the data logger.

[0011] Apply a preset reference differential pressure value to the differential pressure transmitter to be calibrated. After the output current of the differential pressure transmitter to be calibrated stabilizes, record the output current at this time as the standard output current.

[0012] While maintaining the preset reference differential pressure value, an impact pressure P is applied to the differential pressure transmitter to be calibrated for a duration of t1; the output current is sampled from before the application of the impact pressure P to obtain the waveform of the entire process; the sampling duration is maintained for the preset maximum duration.

[0013] Statistical analysis was performed on the recovery phase of the entire waveform to extract waveform features from the recovery phase.

[0014] Take the output current at the moment of recovery completion as the steady-state value, calculate the difference between the steady-state value and the standard output current, and obtain the permanent offset;

[0015] Change the impact parameters and preset baseline differential pressure value, recalculate the corresponding permanent offset, and obtain R sets of data pairs; where the impact parameters include impact pressure and duration; the data pairs are waveform features and corresponding permanent offsets; construct a two-dimensional lookup table with each waveform feature as the query index and the corresponding permanent offset as the query result, summarize the two-dimensional lookup tables corresponding to all waveform features, and obtain the preset fingerprint table.

[0016] Furthermore, when the rate of change of the output current of the differential pressure transmitter to be calibrated is lower than the rate of change threshold, the output current of the differential pressure transmitter to be calibrated is determined to be stable.

[0017] Furthermore, methods for obtaining the corrected differential pressure value include:

[0018] Calculate the product of the permanent offset and the disturbance attenuation function to obtain the disturbance amount, and calculate the difference between the engineering differential pressure value and the disturbance amount to obtain the corrected differential pressure value.

[0019] Furthermore, methods for obtaining gas phase mass flow rate and liquid phase mass flow rate include:

[0020] Calculate the product of the corrected differential pressure and the gas density to obtain the fourth product. Calculate the product of the second root of the fourth product and the instrument coefficient to obtain the apparent gas flow rate.

[0021] Calculate the ratio of apparent gas flow rate to initial total mass flow rate to obtain the flow rate ratio. Calculate the product of the flow rate ratio and the correction factor to obtain the gas mass content.

[0022] Calculate the ratio of gas phase mass content to gas density to obtain the third ratio. Calculate the difference between value 1 and gas phase mass content. Calculate the ratio of the difference to liquid phase density to obtain the fourth ratio. Calculate the sum of the ratios of the third and fourth ratios. Then calculate the ratio of value 1 to the sum of the ratios to obtain the true mixed density.

[0023] Calculate the product of numerical value 2, the actual mixing density and the corrected differential pressure value to obtain the fourth product. Calculate the quadratic root of the fourth product and the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube to obtain the total mass flow rate.

[0024] Calculate the product of the gas phase mass content and the total mass flow rate to obtain the gas phase mass flow rate;

[0025] Calculate the difference between the total mass flow rate and the gas phase mass flow rate to obtain the liquid phase mass flow rate.

[0026] Furthermore, methods for obtaining the initial total mass flow rate include:

[0027] Calculate the product of numerical value 2, initial density and corrected differential pressure to obtain the third product. Calculate the quadratic root of the third product and the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube to obtain the initial total mass flow rate.

[0028] Furthermore, methods for labeling saturation risk states based on analysis results include:

[0029] Calculate the rate of change of the real-time output current. When the real-time output current exceeds the saturation threshold and the rate of change exceeds the positive threshold, or when the real-time output current exceeds the saturation threshold for more than W sampling periods, the saturation risk state is marked as 1. When the saturation risk state is 1, continuous monitoring is performed. If the real-time output current does not exceed the saturation threshold and the rate of change is lower than the negative threshold, and this is maintained for a preset period of time, the saturation risk state is reset to 0.

[0030] Furthermore, methods for calculating the rate of change of real-time output current include:

[0031] Calculate the arithmetic mean of the real-time output current corresponding to the first Q sampling points to obtain the average current value; obtain the average current value corresponding to the Q sampling points in the previous sampling period, calculate the current difference between the average current value and the average current value in the previous sampling period, calculate the ratio of the current difference to the sampling period to obtain the rate of change.

[0032] Furthermore, methods for converting the output current into an engineering differential voltage value include:

[0033] Obtain the first count value when the input current is at the lower limit of the current range, and the second count value when the input current is at the upper limit of the current range. Calculate the real-time difference between the output current and the first count value, and calculate the first count difference between the second count value and the first count value. Calculate the ratio of the real-time difference to the first count difference to obtain the first ratio. Calculate the first range difference between the upper limit of the current range and the lower limit of the current range. Calculate the product of the first ratio and the first range difference to obtain the first product. Calculate the sum of the first product and the lower limit of the current range to obtain the current engineering value.

[0034] Calculate the engineering difference between the current engineering value and the lower limit of the differential pressure transmitter output current range; calculate the second count difference between the upper limit of the differential pressure transmitter current range and the lower limit of the differential pressure transmitter current range; calculate the ratio of the engineering difference to the second count difference to obtain the second ratio; calculate the second range difference between the upper limit of the differential pressure range and the lower limit of the differential pressure range of the differential pressure transmitter; calculate the product of the second ratio and the second range difference to obtain the second product; calculate the sum of the second product and the lower limit of the differential pressure range of the differential pressure transmitter to obtain the engineering differential pressure value.

[0035] A differential pressure transmitter and differential pressure flowmeter gas-liquid two-phase flow calculation system, implementing the aforementioned differential pressure transmitter and differential pressure flowmeter gas-liquid two-phase flow calculation method, including:

[0036] Status marking module: A differential pressure flow meter is installed on the gas-liquid two-phase flow pipeline, and a differential pressure transmitter is connected to the pressure tap of the differential pressure flow meter; the acquisition and analysis module in the differential pressure flow meter acquires the real-time output current of the differential pressure transmitter, performs statistical analysis, and marks the saturation risk status based on the analysis results;

[0037] Waveform analysis module: When the saturation risk state is detected to change from 1 back to 0, the output current within the sampling time is recorded at a preset sampling rate to obtain the recovery waveform. Based on the statistical analysis of the recovery waveform, waveform characteristics used to quantitatively describe the dynamic speed of the recovery process are calculated.

[0038] Differential pressure compensation module: Based on the permanent offset corresponding to the waveform characteristics queried by the preset fingerprint table, the output current is converted into an engineering differential pressure value, and the engineering differential pressure value is compensated based on the permanent offset to obtain the corrected differential pressure value;

[0039] Flow calculation module: Based on the correction differential pressure value, combined with fluid density and device parameters, calculates the gas phase mass flow rate and liquid phase mass flow rate.

[0040] The technical effects and advantages of the differential pressure transmitter and differential pressure flowmeter gas-liquid two-phase flow calculation method and system of this invention are as follows:

[0041] This invention achieves reliable detection and capture of instantaneous saturation events caused by abrupt changes in flow pattern in gas-liquid two-phase flow by real-time monitoring of the amplitude and rate of change of the output current of the differential pressure transmitter. Furthermore, by analyzing the recovered waveform of the signal after saturation, characteristic quantities representing its dynamic velocity are extracted. Using a pre-established waveform feature and offset fingerprint database for the differential pressure transmitter, the permanent hardware offset caused by this saturation is accurately queried. Finally, this offset is smoothly compensated back into the differential pressure measurement signal, thus solving the hidden system error that is unavoidable in traditional methods. This allows the system to avoid sacrificing the measurement accuracy and resolution under normal range to prevent saturation, fundamentally solving the long-standing problems of inaccuracy and reliability in differential pressure two-phase flow measurement under wide operating conditions and dynamic flow patterns. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the gas-liquid two-phase flow calculation method of the differential pressure transmitter and differential pressure flow meter of the present invention;

[0043] Figure 2 This is a schematic diagram of the differential pressure transmitter and differential pressure flow meter device of the present invention;

[0044] Figure 3 This is a schematic diagram of the method for calculating and obtaining gas phase mass flow rate and liquid phase mass flow rate according to the present invention;

[0045] Figure 4 This is a schematic diagram of the gas-liquid two-phase flow calculation system of the differential pressure transmitter and differential pressure flow meter of the present invention.

[0046] Reference numerals in the attached diagram: 1. Differential pressure flow meter; 2. Differential pressure transmitter; 3. Acquisition and analysis module; 4. Display and output module; 5. Venturi tube; 6. Differential pressure sensor. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1:

[0049] Please see Figure 1 As shown, this embodiment provides a method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and a differential pressure flow meter, including:

[0050] The data acquisition and analysis module acquires the real-time output current of the differential pressure transmitter, performs statistical analysis, and marks the saturation risk state based on the analysis results.

[0051] Methods for labeling saturation risk status based on analysis results include:

[0052] The rate of change of the real-time output current is calculated. When the real-time output current exceeds the saturation threshold and the rate of change exceeds the positive threshold, or when the real-time output current exceeds the saturation threshold for more than W sampling periods, the saturation risk state is marked as 1. When the saturation risk state is 1, continuous monitoring continues. If the real-time output current does not exceed the saturation threshold and the rate of change is lower than the negative threshold, and this is maintained for a preset period, the saturation risk state is reset to 0. The method for calculating the rate of change of the real-time output current includes: calculating the arithmetic mean of the real-time output current corresponding to the previous Q sampling points to obtain the average current value; obtaining the average current value corresponding to the Q sampling points in the previous sampling period, calculating the current difference between the average current value and the average current value in the previous sampling period, and calculating the ratio of the current difference to the sampling period to obtain the rate of change. The saturation threshold is set according to the range of the differential pressure transmitter, such as setting it to 95% of the output current of the full-scale differential pressure of the differential pressure transmitter. The positive threshold is set based on historical data statistics. For example, during normal production after equipment installation, i.e., during the period ensuring no saturation events, the output current change rate data is recorded for more than 24 hours. All collected change rate data are statistically analyzed to calculate their probability distribution, finding the maximum value or 99.9th percentile of the probability distribution. This value represents the maximum positive change rate that normal process fluctuations can produce under this specific application scenario. The positive threshold is set based on the maximum value or 99.9th percentile of the probability distribution. The value of W is set empirically, and can be set to 3-5, mainly used to determine whether saturation has been reached. Similarly, the negative threshold is set during normal stable production by recording the output current change rate dataset for more than 24 hours and calculating the standard deviation of the change rate dataset. In a stable state, the change rate should fluctuate randomly around 0. Its standard deviation characterizes the system's background noise fluctuation level, and the negative threshold can be set based on the standard deviation. The preset time period is set based on the sampling theorem and engineering experience, used to ensure that the criteria are continuously met for a certain duration before state switching. This is to prevent misjudgments caused by noise or transient interference and improve the reliability of state transitions; the sustaining time should cover at least several to dozens of sampling periods to ensure that the judgment is based on a trend rather than individual noise points. Q is set as the ratio of the average time window to the system sampling period. The average time window is set to 1 / 5 to 1 / 2 of the differential pressure transmitter's step response time. The differential pressure transmitter's step response time can be obtained by referring to the differential pressure transmitter's product manual, which is the time required for the differential pressure transmitter output to track a step input change to reach 63.2% of the final value.

[0053] The above steps, by determining in real time whether the system is in a saturation risk state, enable the system to be instantly identified at the moment a saturation impact occurs. The saturation risk state clearly marks the start time of the impact, and the reset condition reliably determines the end of the impact's effect and the start of the recovery process. Locking the start and end times is an absolute necessity for all subsequent analyses. Through an anti-interference design that maintains a rate of change below a negative threshold for a preset period, the system ensures that a state transition is only confirmed when the signal has left the saturation region and recovered to a steady state. This prevents false resets caused by signal fluctuations near the threshold or noise interference, thus ensuring that the recovered waveform captured after a state reset is complete and effective, guaranteeing the accuracy of subsequent feature extraction and offset mapping.

[0054] When the saturation risk state is detected to change from 1 back to 0, the acquisition and analysis module records the output current within the sampling time at a preset sampling rate to obtain the recovered waveform. Statistical analysis is then performed on the recovered waveform to extract waveform features that quantify the dynamic speed of the recovery process. The preset sampling rate is set according to the Nyquist sampling theorem and is no less than twice the highest frequency of the measured signal. The initial saturation recovery phase involves rapid changes, requiring detailed capture; therefore, a rate of 5-10 times the bandwidth of the differential pressure transmitter is typically used.

[0055] Waveform characteristics include, but are not limited to, any one of the following: recovery time constant, half-life, average recovery rate, time series vector, and geometric area;

[0056] Methods for extracting waveform features used to quantify the dynamic velocity of the recovery process in the recovered waveform include:

[0057] When the waveform characteristic is a recovery time constant, it can be calculated using the following method:

[0058] When the output current is detected to drop from above the recovery threshold and then fall below the recovery threshold for N consecutive sampling points, the moment when it first falls below the recovery threshold is marked as the recovery start time. Starting from the recovery start time, a recovery observation window is initiated, and within this window, sliding detection is performed using a sliding statistical window. Starting from time τ, a cyclic judgment is performed. When the cyclic judgment is satisfied for M consecutive sliding statistical windows, the recovery process is considered complete. The start time of the first sliding statistical window among these M consecutive sliding statistical windows is taken as the recovery completion time, and the average value of all output currents within these M consecutive sliding statistical windows is taken as the final stable output current after recovery. If the cyclic judgment is not met within the repeated observation window, the start time of the last sliding statistical window is forcibly taken as the recovery completion time, and the average value of the output current of the last sliding statistical window is taken as the final stable output current after recovery. Simultaneously, it is marked as not fully converged. The time τ is obtained by calculating the sum of the recovery start time and the recovery observation window duration, and then calculating the difference between the sum of the times and the sliding statistical window duration. The recovery threshold can be set according to the saturation threshold, such as setting it to 92%-97% of the saturation threshold to form a detection hysteresis. N is used to confirm that the trend of the output current being lower than the recovery threshold is not a noise spike. The value of N must be able to cover the shortest possible interference pulse, generally set to 3-5. The recovery observation window is determined by obtaining the overload recovery time from the differential pressure transmitter's product manual, specifically the technical parameters section. This is the time required for the output to recover to the specified accuracy range from applying a certain percentage, such as 150% overload pressure. The overload recovery time is used as the reference recovery time, and the recovery observation window is set according to this reference recovery time, such as setting it to 2-3 times the reference recovery time. The duration of the sliding statistical window is much longer than the signal's inherent fluctuation period to smooth out random noise, but shorter than the recovery process. It can be set to 2-10 seconds based on experience; it can also be adjusted according to the actual fluctuation of the differential pressure transmitter's output signal. M is used to provide redundant judgment for state switching and improve noise immunity; it can be set to 2-5 based on experience.

[0059] The cyclic judgment includes: taking the output current sequence with a sliding statistical window length prior to the current moment, calculating the mean and standard deviation of the output current sequence, calculating the ratio of the standard deviation to the mean, and obtaining the coefficient of variation. When the coefficient of variation is less than a preset stability threshold, the cyclic judgment is satisfied. The stability threshold is set based on historical data statistics. For example, during normal production after the device is installed, i.e., during the period ensuring no saturation events, the coefficient of variation of the output current is recorded for more than 24 hours. All collected coefficients of variation are statistically analyzed to calculate their probability distribution, find the maximum value or 99.9th percentile of the probability distribution, and set the threshold based on the maximum value or 99.9th percentile of the probability distribution.

[0060] Calculate the difference between the output current at the start of recovery and the final stable output current after recovery to obtain the recovery current difference. Calculate the ratio of the recovery current difference to the mathematical constant e to obtain the current decay value. Calculate the sum of the current decay value and the final stable output current after recovery to obtain the target current value. Calculate the time difference between the moment when the recovery waveform first crosses the target current value and the moment when recovery begins to obtain the recovery time constant.

[0061] When the waveform characteristic is half-life, it can be calculated as follows: calculate half of the recovery current difference and the sum of the final stable output current after recovery to obtain the midpoint current value; calculate the time difference between the moment when the waveform signal first reaches the midpoint current value and the moment when recovery begins to obtain the half-life.

[0062] When the waveform characteristic is the average recovery rate, it can be calculated as follows: calculate the time difference between the recovery completion time and the recovery start time to obtain the recovery duration, and calculate the ratio of the recovery current difference to the recovery duration to obtain the average recovery rate.

[0063] When the waveform characteristics are time series vectors, the following method can be used to calculate: calculate the time t10, t30, t50, t70 required for the signal to recover to 90%, 70%, 50%, and 30% of the difference from the steady-state value, respectively, that is, the time required to recover 10%, 30%, 50%, and 70%.

[0064] When the waveform characteristic is a geometric area, it can be calculated as follows: calculate the absolute value of the difference between the recovered waveform and the final stable output current after recovery, and numerically integrate the absolute value of the difference within the recovery observation window to obtain the geometric area.

[0065] The above steps extract waveform features, such as the recovery time constant and half-life, which quantify the dynamics of the recovery process, transforming the severity of the damage into a clear and calculable number. These waveform features are essentially the external manifestations of the changes in the physical state of the transmitter sensing unit after being subjected to an overload impact. Extracting these features captures and quantifies the unique physical fingerprint of this saturation event. A causal relationship, determined by hardware physical characteristics, exists between the physical fingerprint and the permanent offset caused by the saturation impact event. This physical fingerprint also provides an accurate reference for subsequent steps to query a preset fingerprint table to determine the specific compensation amount.

[0066] Based on the permanent offset corresponding to the waveform characteristics queried from the preset fingerprint table, the output current is converted into an engineering differential pressure value. The engineering differential pressure value is then compensated based on the permanent offset to obtain a corrected differential pressure value. This step enables the system to proactively mitigate the long-term negative effects of saturation shocks without sacrificing measurement resolution and accuracy in the low-flow range. It directly breaks the causal chain between transient saturation events and persistent measurement errors, transforming the differential pressure measurement system from a static, vulnerable device into an intelligent system with self-sensing, self-diagnostic, and self-calibration capabilities.

[0067] Methods for obtaining a preset fingerprint table include:

[0068] Install the differential pressure transmitter to be calibrated on the standard pressure calibration device, connect the power supply and signal output of the differential pressure transmitter to be calibrated to the data logger, and set the sampling frequency of the data logger according to the preset sampling rate. It needs to be higher than the preset sampling rate to capture more detailed recovery dynamics and provide high-fidelity data for analysis.

[0069] A preset reference differential pressure value is applied to the differential pressure transmitter to be calibrated. After the output current of the transmitter stabilizes, the current is recorded as the standard output current. The transmitter is considered stable when the rate of change of its output current is below a threshold value. The preset reference differential pressure value is set according to the transmitter's range, typically selecting points such as 20%, 50%, and 80% of the range. The rate of change threshold is set based on the transmitter's static accuracy specifications and is typically set to 0.01% per second of the full-scale output change rate.

[0070] While maintaining the preset reference differential pressure value, apply an impact pressure P to the differential pressure transmitter to be calibrated for a duration of t1. Remove the impact pressure P, restoring the transmitter to the state where only the preset reference differential pressure value exists. Sample the output current from before the application of the impact pressure P to obtain the waveform of the entire process. The sampling duration is the preset maximum duration. The amplitude of P is set according to the upper limit of the differential pressure transmitter's range and needs to be much higher than the upper limit to ensure that the differential pressure transmitter experiences deep saturation, simulating the worst-case scenario. It can be set to 120%-150% of the full scale. t1 should simulate the possible impact duration in the field and needs to be longer than the response time of the differential pressure transmitter, but short enough not to cause permanent damage. Specifically, consult the differential pressure transmitter's product manual to obtain its step response time. t1 can be set according to the step response time of the differential pressure transmitter, such as setting it to 1 to 2 times the step response time of the differential pressure transmitter. This ensures that the impact time is sufficient to cover the main response process of the transmitter to the step input. The maximum duration can be set according to the actual recovery time and t1, such as setting it to the superposition of 1.5-2.0 times the actual recovery time and t1. The actual recovery time can be determined through pre-experimentation, such as selecting a commonly used combination of impact parameters and reference differential pressure, applying the impact and recording it. During the recording process, the time elapsed from the end of the impact to the system determining that the recovery is complete is the actual recovery time.

[0071] For the recovery phase of the entire waveform, i.e., from the start of recovery to the completion of recovery, all waveform features used to quantitatively describe the dynamic velocity of the recovery process of the recovered waveform are extracted. All waveform features include, but are not limited to, recovery time constant, half-life, average recovery rate, time series vector, and geometric area.

[0072] Take the output current at the moment of recovery completion as the steady-state value, calculate the difference between the steady-state value and the standard output current, and obtain the permanent offset;

[0073] By changing the impact parameters and preset baseline differential pressure values, the corresponding permanent offsets are recalculated, resulting in R sets of data pairs. R is set based on the number of sets using the impact parameters and preset baseline differential pressure values, and should not be less than the number of full-factor experimental sets where the impact parameters and preset baseline differential pressure values ​​are used as independent variables. Each data pair consists of all waveform features and their corresponding permanent offsets; the same recovered waveform corresponds to one set of waveform features and one permanent offset. Each data pair is obtained by averaging E sets of data. In E sets, each set of data is measured using the same impact parameters and preset baseline differential pressure values. E is used to reduce random errors and improve the reliability of single-point data. According to statistical principles, 3-5 repetitions can effectively estimate the mean error. A two-dimensional lookup table is constructed, using each waveform feature as the query index and the corresponding permanent offset as the query result. The two-dimensional lookup tables corresponding to all waveform features are then summarized to obtain a preset fingerprint table. The impact parameters include impact pressure and duration.

[0074] The above steps involve offline calibration, actively applying simulated saturation shocks of varying intensities, and simultaneously recording the recovered waveform characteristics and the measured permanent offset, thus establishing a definite mapping relationship between the two. This transforms the hidden hardware offset into a known quantity that can be precisely queried through quantifiable signal characteristics that can be detected online, thereby providing a fundamental basis for eliminating the offset.

[0075] Methods for converting output current into engineering differential pressure values ​​include:

[0076] Acquire the first count value when the input current is at the lower limit of the current range, and the second count value when the input current is at the upper limit of the current range. Calculate the real-time difference between the output current and the first count value, and calculate the first count difference between the second count value and the first count value. Calculate the ratio of the real-time difference to the first count difference to obtain the first ratio. Calculate the first range difference between the upper and lower limits of the current range. Calculate the product of the first ratio and the first range difference to obtain the first product. Calculate the sum of the first product and the lower limit of the current range to obtain the current engineering value, i.e., the current engineering value. ,in, For output current; This is the first count value; This is the second count value; This is the upper limit of the current range of the differential pressure transmitter; This is the lower limit of the current range of the differential pressure transmitter.

[0077] Calculate the engineering difference between the current engineering value and the lower limit of the differential pressure transmitter's output current range. Calculate the second count difference between the upper and lower limits of the differential pressure transmitter's current range. Calculate the ratio of the engineering difference to the second count difference to obtain the second ratio. Calculate the second range difference between the upper and lower limits of the differential pressure transmitter's differential pressure range. Calculate the product of the second ratio and the second range difference to obtain the second product. Calculate the sum of the second product and the lower limit of the differential pressure transmitter's differential pressure range to obtain the engineering differential pressure value, i.e., the engineering differential pressure value. ,in, This refers to the current engineering value; This is the upper limit of the differential pressure range of the differential pressure transmitter; This is the lower limit of the differential pressure range of the differential pressure transmitter. The above steps restore the output current to the engineering differential pressure value without distortion, ensuring the accuracy of the signal basis for subsequent processing.

[0078] For example, the initial conditions are set as follows:

[0079] Differential pressure transmitter current range: , ;

[0080] Differential pressure transmitter differential pressure range: , ;

[0081] Current range corresponding count value: ,correspond , ,correspond ;

[0082] Actual output current count value: ;

[0083] The derivation process and reasoning are as follows: The differential pressure transmitter adopts a linear calibration design for current and differential pressure, and the current and differential pressure have a linear correspondence. Therefore, the derivation is performed using the linear interpolation method:

[0084] First, convert the count value to an engineering current value: by using the relative proportion of the count value, convert it to the actual value within the current range; then convert the current to an engineering differential pressure value: similarly, by using the relative proportion of the current, convert it to the actual value within the differential pressure range.

[0085] Interrelationship between formulas: The current engineering value formula is an intermediate calculation step, and its result is the input parameter of the engineering differential pressure value formula; the two formulas share the linear interpolation logic of the relative proportion of the range.

[0086] Boundary conditions must satisfy the constraints of an effective algorithm: Must meet Otherwise, it is determined that the signal is out of range;

[0087] like ,Pick ,like ,Pick ;

[0088] Unit consistency constraint: The unit of differential pressure range must be consistent with the output unit;

[0089] Substitute parameters for calculation: ; ;

[0090] like Then take ,have to ; .

[0091] Methods for obtaining the corrected differential pressure value include:

[0092] The product of the permanent offset and the disturbance attenuation function is calculated to obtain the disturbance amount. The difference between the engineering differential pressure value and the disturbance amount is calculated to obtain the corrected differential pressure value. ,in, This is a permanent offset; This is the disturbance decay function. The disturbance decay function is a time function with the compensation start time as the origin. It can preferably be an exponential decay function or a linear decay function, where the compensation start time corresponds to the recovery completion time. The exponential decay function can be calculated as follows: calculate the time difference between the current time and the compensation start time, then calculate the negative of the ratio of the time difference to the decay time constant to obtain the time exponent, and finally calculate the time exponent power of the mathematical constant e to obtain the exponential decay function. ,in, To compensate for the start time; The decay time constant, The linear decay function can be calculated as follows: Calculate the time difference between the current time and the compensation start time, then calculate the ratio of the time difference to the total decay time, calculate the difference between the value 1 and the time ratio to obtain the time difference, and take the maximum value between the time difference and the value 0 as the linear decay function. ,in, This refers to the total decay time. The total decay time can be set based on empirical values ​​from industrial processes, such as 5 minutes. Five minutes is both long enough to avoid significant disturbances to most fast loops such as pressure and flow rates caused by compensation actions, and short enough to complete the correction of measurement deviations within a reasonable time window. In practice, it can be adjusted according to actual conditions. The decay time constant is set based on the total decay time, generally set to 1 / 3 to 1 / 5 of the total decay time.

[0093] For example, the initial conditions are set as follows:

[0094] Permanent offset: ;

[0095] Disturbance decay function: exponential decay function, decay time constant ;

[0096] Compensation start time: ;

[0097] Compensation real-time time: ;

[0098] Engineering differential pressure value: ;

[0099] Derivation process and reasoning: Transmitters subjected to saturation shocks will experience permanent offsets, which need to be eliminated through dynamic attenuation compensation;

[0100] Disturbance amount: Represents the offset that needs to be compensated. It is calculated using the permanent offset and the disturbance attenuation function, which simulates the offset recovery process.

[0101] Corrected differential pressure value: Subtract the disturbance from the engineering differential pressure value to obtain the accurate differential pressure after eliminating the offset.

[0102] Interrelationship between formulas: The disturbance formula is an intermediate calculation step, and its result is the input parameter of the correction differential pressure formula; together, they achieve the offset compensation function.

[0103] Boundary conditions: Disturbance attenuation function Must meet: Otherwise, truncate;

[0104] like ,Pick ;

[0105] Perturbation attenuation function selection: exponential attenuation is suitable for slowly recovering offsets, while linear attenuation is suitable for rapidly recovering offsets;

[0106] Substitute parameters for calculation: ;

[0107] like , That is, calculation When the value is less than 0, take .

[0108] Based on the permanent offset obtained from the preset fingerprint table, the differential pressure value is compensated by subtraction, directly correcting the system error introduced by hardware offset. The introduction of the disturbance attenuation function ensures that the compensation is applied smoothly and gradually, avoiding secondary interference to the process control system caused by sudden correction.

[0109] Based on the corrected differential pressure value, combined with the fluid density and device parameters, the gas phase mass flow rate and liquid phase mass flow rate are calculated and then transmitted to the display output module for display. Among them, the fluid density includes the gas phase density and the liquid phase density; the device parameters include the throat area of ​​the venturi tube and the flow coefficient of the venturi tube.

[0110] Reference Figure 2 Methods for calculating gas phase mass flow rate and liquid phase mass flow rate include:

[0111] Calculate the product of the numerical value 2, the initial density, and the corrected differential pressure to obtain the third product. Calculate the square root of the third product, the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube, to obtain the initial total mass flow rate, i.e., the initial total mass flow rate. ;in, The initial density is taken as the liquid phase density; To correct the differential pressure value; This represents the area of ​​the throat of the Venturi tube. The flow coefficient of the venturi tube is obtained by directly reading the throat area and flow coefficient of the venturi tube from the memory.

[0112] Calculate the product of the corrected differential pressure and the gas density to obtain the fourth product. Calculate the product of the square root of the fourth product and the instrument coefficient to obtain the apparent gas flow rate, i.e., the apparent gas flow rate. ;in, The density of the gas; The instrument coefficient is obtained through single-phase gas calibration. It can be obtained by fitting a single-phase gas flow through a standard device based on the actual measured apparent gas flow rate.

[0113] Calculate the ratio of the apparent gas flow rate to the initial total mass flow rate to obtain the flow rate ratio. Then, calculate the product of the flow rate ratio and the correction factor to obtain the gas phase mass content, i.e., the gas phase mass content. ;in, The correction coefficient is determined through the two-phase flow calibration of the device; it can be obtained by averaging or fitting multiple sets of data under known actual gas phase mass content conditions; it is equivalent to localizing the theoretical model with experimental data, which improves the accuracy and reliability of the simplified model in practical applications, so that the calculation based on the correction differential pressure value can remain accurate even when the gas-liquid ratio changes.

[0114] Calculate the ratio of gas phase mass fraction to gas density to obtain the third ratio. Calculate the difference between the value 1 and the gas phase mass fraction, and calculate the ratio of this difference to the liquid phase density to obtain the fourth ratio. Calculate the sum of the ratios of the third and fourth ratios, and then calculate the ratio of the value 1 to the sum of the ratios to obtain the true mixed density, i.e., the true mixed density. ,in; The density of the liquid phase;

[0115] Calculate the product of numerical value 2, the actual mixed density, and the corrected differential pressure to obtain the fifth product. Calculate the quadratic root of the fifth product, the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube, and obtain the total mass flow rate. ;

[0116] The gas phase mass flow rate is obtained by multiplying the gas phase mass content by the total mass flow rate. ;

[0117] Calculate the difference between the total mass flow rate and the gas phase mass flow rate to obtain the liquid phase mass flow rate, i.e., the liquid phase mass flow rate. .

[0118] For example, the initial conditions are set as follows:

[0119] Corrected differential pressure value: ;

[0120] Venturi tube parameters: ; ;

[0121] Fluid density: ; ;

[0122] coefficient: ; ;

[0123] Derivation process and rationale: For gas-liquid two-phase flow, the approach is to first assume a single phase and then correct for a two-phase flow, including:

[0124] Initial total mass flow rate: Assuming a completely liquid phase, the reference value is calculated using the single-phase Venturi tube flow rate formula;

[0125] Apparent flow rate in the gas phase: reflects the degree of contribution from the gas phase;

[0126] Gas phase mass content: Determines the proportion of the gas phase in the total mass flow rate;

[0127] Mixed density: The actual density considering the superposition of gas and liquid volumes;

[0128] Actual total mass flow rate: Substitute the mixed density into the single-phase Venturi tube flow rate formula to obtain the actual flow rate;

[0129] Gas-liquid flow rate: obtained by multiplying the total mass flow rate by the gas phase mass content and the remaining proportion.

[0130] Interrelationships between formulas: The formulas are progressively ordered as initial total mass flow rate, apparent gas flow rate, gas mass content, mixing density, actual total mass flow rate, and gas-liquid flow rate. The result of the previous formula is the input of the next formula, and together they achieve two-phase flow separation.

[0131] Boundary conditions must satisfy: Effective algorithm constraint: Gas phase mass content Must meet: Otherwise, cut off, that is, if Then let ;like Then let ;

[0132] like or If so, it is determined to be a single-phase flow, and no two-phase calculation is required;

[0133] Unit consistency: Differential pressure needs to be converted to Pa, and area is... The final unit of flow rate is ;

[0134] Substitute parameters to calculate: Initial total mass flow rate: ;

[0135] Apparent flow rate in the gas phase: ;

[0136] Gas phase mass content: ,Pick ;

[0137] Mixed density: ;

[0138] Actual total mass flow rate: ;

[0139] Gas-liquid flow rate: ; .

[0140] The above steps, by calculating the two-phase flow rate based on the corrected differential pressure value, ensure that all subsequent complex flow rate conversions do not inherit or amplify the initial measurement errors caused by saturation impact. While the calculation model itself may be complex, if there are undetected fixed biases in the input signal, the output result will continuously deviate, regardless of the model's accuracy. By using the corrected signal, these steps fundamentally cut off the path of hardware offset transmission to flow rate readings, directly resolving the problem of consistently high or low flow rate readings. Furthermore, the above steps replace the traditional method's requirement for online iterative simultaneous solution of multiple complex equations with a sequential calculation of estimation followed by correction. This design significantly reduces the demands on the processor's real-time computing power, making it possible to stably and quickly complete high-precision two-phase flow calculations in embedded modules, thus enhancing the overall engineering feasibility of the solution.

[0141] Example 2:

[0142] Please see Figure 3 As shown, this embodiment provides a differential pressure transmitter and differential pressure flow meter gas-liquid two-phase flow device, including:

[0143] A differential pressure flow meter 1 is installed on a gas-liquid two-phase flow pipeline, and a differential pressure transmitter 2 is connected to the pressure tap of the differential pressure flow meter. Specifically, the differential pressure flow meter 1 includes a differential pressure sensor 6, a data acquisition and analysis module 3, a display and output module 4, and a venturi tube 5. The upstream and downstream pressure taps of the venturi tube 5 are connected to the differential pressure transmitter 2 through pressure guide pipes, and the signal output terminal of the differential pressure transmitter 2 is connected to the signal input terminal of the data acquisition and analysis module 3. The data acquisition and analysis module 3 is connected to the display and output module 4.

[0144] When the gas-liquid two-phase fluid flows through the differential pressure flowmeter 1, a differential pressure signal is generated before and after the throat. The differential pressure signal is transmitted to the differential pressure transmitter 2 through the pressure guide tube. The differential pressure transmitter 2 converts the differential pressure signal into a standard electrical signal within the output current range of the differential pressure transmitter and outputs it to the acquisition and analysis module 3. The acquisition and analysis module 3 filters and amplifies the received electrical signal and then performs A / D conversion to convert the analog signal into an output current value.

[0145] Example 3:

[0146] Please see Figure 4 As shown, this embodiment provides a gas-liquid two-phase flow calculation system using a differential pressure transmitter and a differential pressure flow meter, including:

[0147] Status marking module: A differential pressure flow meter is installed on the gas-liquid two-phase flow pipeline, and a differential pressure transmitter is connected to the pressure tap of the differential pressure flow meter; the acquisition and analysis module in the differential pressure flow meter acquires the real-time output current of the differential pressure transmitter, performs statistical analysis, and marks the saturation risk status based on the analysis results;

[0148] Waveform analysis module: When the saturation risk state is detected to change from 1 back to 0, the output current within the sampling time is recorded at a preset sampling rate to obtain the recovery waveform. Based on the statistical analysis of the recovery waveform, waveform characteristics used to quantitatively describe the dynamic speed of the recovery process are calculated.

[0149] Differential pressure compensation module: Based on the permanent offset corresponding to the waveform characteristics queried by the preset fingerprint table, the output current is converted into an engineering differential pressure value, and the engineering differential pressure value is compensated based on the permanent offset to obtain the corrected differential pressure value;

[0150] Flow calculation module: Based on the correction differential pressure value, combined with fluid density and device parameters, calculates the gas phase mass flow rate and liquid phase mass flow rate.

[0151] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0152] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flowmeter, characterized in that... include: A differential pressure flow meter is installed on a gas-liquid two-phase flow pipeline, and a differential pressure transmitter is connected to the pressure tap of the differential pressure flow meter; the acquisition and analysis module in the differential pressure flow meter acquires the real-time output current of the differential pressure transmitter and performs statistical analysis, and marks the saturation risk state according to the analysis results; the differential pressure flow meter is a Venturi tube type differential pressure flow meter. Calculate the rate of change of the real-time output current. When the real-time output current exceeds the saturation threshold and the rate of change exceeds the positive threshold, or when the real-time output current exceeds the saturation threshold for more than W sampling periods, the saturation risk state is marked as 1. When the saturation risk state is 1, continuous monitoring is performed. If the real-time output current does not exceed the saturation threshold and the rate of change is lower than the negative threshold, and this is maintained for a preset period of time, the saturation risk state is reset to 0. When the saturation risk state is detected to change from 1 back to 0, the output current within the sampling time is recorded at a preset sampling rate to obtain the recovery waveform. Based on the statistical analysis of the recovery waveform, the waveform characteristics used to quantitatively describe the dynamic speed of the recovery process are calculated. Based on the permanent offset corresponding to the waveform characteristics queried from the preset fingerprint table, the output current is converted into an engineering differential pressure value. The engineering differential pressure value is compensated based on the permanent offset to obtain the corrected differential pressure value. The product of the permanent offset and the disturbance attenuation function is calculated to obtain the disturbance amount. The difference between the engineering differential pressure value and the disturbance amount is calculated to obtain the corrected differential pressure value. Based on the corrected differential pressure value, combined with the fluid density and device parameters, the gas phase mass flow rate and liquid phase mass flow rate are calculated.

2. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flowmeter according to claim 1, characterized in that, Methods for obtaining a preset fingerprint table include: Install the differential pressure transmitter to be calibrated on the standard pressure calibration device, and connect the power supply and signal output of the differential pressure transmitter to be calibrated to the data logger. Apply a preset reference differential pressure value to the differential pressure transmitter to be calibrated. After the output current of the differential pressure transmitter to be calibrated stabilizes, record the output current at this time as the standard output current. While maintaining the preset reference differential pressure value, an impact pressure P is applied to the differential pressure transmitter to be calibrated for a duration of t1; the output current is sampled from before the application of the impact pressure P to obtain the waveform of the entire process; the sampling duration is maintained for the preset maximum duration. Statistical analysis was performed on the recovery phase of the entire waveform to extract waveform features from the recovery phase. Take the output current at the moment of recovery completion as the steady-state value, calculate the difference between the steady-state value and the standard output current, and obtain the permanent offset; Change the impact parameters and preset baseline differential pressure value, recalculate the corresponding permanent offset, and obtain R sets of data pairs; where the impact parameters include impact pressure and duration; the data pairs are waveform features and corresponding permanent offsets; construct a two-dimensional lookup table with each waveform feature as the query index and the corresponding permanent offset as the query result, summarize the two-dimensional lookup tables corresponding to all waveform features, and obtain the preset fingerprint table.

3. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flow meter according to claim 2, characterized in that, When the rate of change of the output current of the differential pressure transmitter to be calibrated is lower than the rate of change threshold, the output current of the differential pressure transmitter to be calibrated is determined to be stable.

4. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flow meter according to claim 1, characterized in that, Methods for obtaining gas phase mass flow rate and liquid phase mass flow rate include: Calculate the product of the corrected differential pressure and the gas density to obtain the fourth product. Calculate the product of the second root of the fourth product and the instrument coefficient to obtain the apparent gas flow rate. Calculate the ratio of apparent gas flow rate to initial total mass flow rate to obtain the flow rate ratio. Calculate the product of the flow rate ratio and the correction factor to obtain the gas mass content. Calculate the ratio of gas phase mass content to gas density to obtain the third ratio. Calculate the difference between value 1 and gas phase mass content. Calculate the ratio of the difference to liquid phase density to obtain the fourth ratio. Calculate the sum of the ratios of the third and fourth ratios. Then calculate the ratio of value 1 to the sum of the ratios to obtain the true mixed density. Calculate the product of numerical value 2, the actual mixing density and the corrected differential pressure value to obtain the fifth product. Calculate the quadratic root of the fifth product and the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube to obtain the total mass flow rate. Calculate the product of the gas phase mass content and the total mass flow rate to obtain the gas phase mass flow rate; Calculate the difference between the total mass flow rate and the gas phase mass flow rate to obtain the liquid phase mass flow rate.

5. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flow meter according to claim 4, characterized in that, Methods for obtaining the initial total mass flow rate include: Calculate the product of numerical value 2, initial density and corrected differential pressure to obtain the third product. Calculate the quadratic root of the third product and the product of the throat area of ​​the Venturi tube and the flow coefficient of the Venturi tube to obtain the initial total mass flow rate.

6. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flow meter according to claim 1, characterized in that, Methods for calculating the rate of change of real-time output current include: Calculate the arithmetic mean of the real-time output current corresponding to the first Q sampling points to obtain the average current value; obtain the average current value corresponding to the Q sampling points in the previous sampling period, calculate the current difference between the average current value and the average current value in the previous sampling period, calculate the ratio of the current difference to the sampling period to obtain the rate of change.

7. The method for calculating the gas-liquid two-phase flow rate using a differential pressure transmitter and differential pressure flowmeter according to claim 1, characterized in that, Methods for converting output current into engineering differential pressure values ​​include: Obtain the first count value when the input current is at the lower limit of the current range, and the second count value when the input current is at the upper limit of the current range. Calculate the real-time difference between the output current and the first count value, and calculate the first count difference between the second count value and the first count value. Calculate the ratio of the real-time difference to the first count difference to obtain the first ratio. Calculate the first range difference between the upper limit of the current range and the lower limit of the current range. Calculate the product of the first ratio and the first range difference to obtain the first product. Calculate the sum of the first product and the lower limit of the current range to obtain the current engineering value. Calculate the engineering difference between the current engineering value and the lower limit of the differential pressure transmitter output current range; calculate the second count difference between the upper limit of the differential pressure transmitter current range and the lower limit of the differential pressure transmitter current range; calculate the ratio of the engineering difference to the second count difference to obtain the second ratio; calculate the second range difference between the upper limit of the differential pressure range and the lower limit of the differential pressure range of the differential pressure transmitter; calculate the product of the second ratio and the second range difference to obtain the second product; calculate the sum of the second product and the lower limit of the differential pressure range of the differential pressure transmitter to obtain the engineering differential pressure value.

8. A gas-liquid two-phase flow calculation system using a differential pressure transmitter and differential pressure flowmeter, implementing the gas-liquid two-phase flow calculation method using a differential pressure transmitter and differential pressure flowmeter as described in any one of claims 1-7, characterized in that... include: Status marking module: A differential pressure flow meter is installed on the gas-liquid two-phase flow pipeline, and a differential pressure transmitter is connected to the pressure tap of the differential pressure flow meter; the acquisition and analysis module in the differential pressure flow meter acquires the real-time output current of the differential pressure transmitter, performs statistical analysis, and marks the saturation risk status based on the analysis results; Waveform analysis module: When the saturation risk state is detected to change from 1 back to 0, the output current within the sampling time is recorded at a preset sampling rate to obtain the recovery waveform. Based on the statistical analysis of the recovery waveform, waveform characteristics used to quantitatively describe the dynamic speed of the recovery process are calculated. Differential pressure compensation module: Based on the permanent offset corresponding to the waveform characteristics queried by the preset fingerprint table, the output current is converted into an engineering differential pressure value, and the engineering differential pressure value is compensated based on the permanent offset to obtain the corrected differential pressure value; Flow calculation module: Based on the correction differential pressure value, combined with fluid density and device parameters, calculates the gas phase mass flow rate and liquid phase mass flow rate.

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