CN108871511B - Linkage type industrial flow accurate metering method - Google Patents
Linkage type industrial flow accurate metering method Download PDFInfo
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- CN108871511B CN108871511B CN201810695193.5A CN201810695193A CN108871511B CN 108871511 B CN108871511 B CN 108871511B CN 201810695193 A CN201810695193 A CN 201810695193A CN 108871511 B CN108871511 B CN 108871511B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
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- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C17/00—Arrangements for transmitting signals characterised by the use of a wireless electrical link
- G08C17/02—Arrangements for transmitting signals characterised by the use of a wireless electrical link using a radio link
Abstract
A linkage type industrial flow accurate metering method solves the problem that in the traditional flow measurement process, a flow meter is only an isolated device for fluid metering and does not form interconnection interaction with an upstream process and a downstream process and related metering equipment around, so that the metering accuracy of the flow meter is greatly reduced. The metering method implements process-based algorithm analysis on the existing flow metering method, so that the flow meter can be compared with the production or running condition of an upstream flow medium closest to the flow meter in the metering process, and then the flow result is calibrated through a self-calibration function in the flow meter; then, the existing flowmeter and the upstream flowmeter are communicated and interconnected, and self-correction is carried out; moreover, the situation that the straight pipe section is insufficient in the industrial field is considered in the metering process. The method can be interconnected and communicated with other upstream and downstream metering equipment, the accuracy of industrial flow metering can be improved, the upstream and downstream production processes are optimized, the production cost is reduced, and the industrial automation level is improved.
Description
Technical Field
The invention belongs to the technical field of instruments and meters, and particularly relates to a linkage type accurate industrial flow metering method which can be interconnected and communicated with other upstream and downstream metering equipment, can effectively improve the accuracy of the whole industrial flow metering, optimizes upstream and downstream production processes, reduces the production cost of enterprises, and improves the industrial automation level.
Background
At present, although various types and principles of industrial flowmeters are different, the industrial flowmeters have a common characteristic that: during the flow measurement process, data can only be read through a flowmeter which is a stand-alone device and is arranged on a pipeline, and the data is transmitted to an industrial control system through a secondary meter, a flow computer and the like. Due to the fact that the flowmeter cannot carry out large-pipe-diameter real-flow calibration and various special media and working condition calibration, errors and even deviations exist in the actual metering process of the flowmeter; further, the measurement error is further increased by the process level limitation of each manufacturer. Meanwhile, due to the fluctuation adjustment of upstream and downstream processes, the insufficient length of the on-site straight pipe section and other reasons, the working condition used by the flowmeter often changes, and further the flowmeter is not in the working condition range during the initial design in the operation process, so that the metering precision of the flowmeter is greatly reduced, the accuracy degree of the whole industrial flow metering is seriously influenced, and the development of industrial automation is not facilitated. There is a need for improvements in existing industrial flow metering methods.
Disclosure of Invention
Aiming at the problems, the invention provides the linkage type accurate industrial flow metering method which can be interconnected and communicated with other upstream and downstream metering equipment, can effectively improve the accuracy of the whole industrial flow metering, optimizes upstream and downstream production processes, reduces the production cost of enterprises and improves the industrial automation level.
The technical scheme adopted by the invention is as follows: the linkage type industrial flow accurate metering method comprises the following steps:
step one, interacting process algorithm and metering process data; the method comprises the steps of carrying out process-based algorithm analysis on the existing flow measurement method, and enabling the flow meter to be compared with the production or running condition of an upstream flow medium closest to the flow meter in the measurement process in a process of process comparison; after the process calculation and analysis are completed, the metering theoretical data of the flowmeter can be obtained;
step two, self-calibration of the linkage type metering process; after the data of the batching and metering device is obtained, the flowmeter can be compared with the existing metering data per se; then judging whether the data are consistent with theoretical metering data or not, and if the data are consistent or the error is within an allowable range, determining that the metering result is credible; if the error exceeds the allowable range, the flow meter is required to be self-calibrated in the metering process;
step three, upstream and downstream communication and linkage type correction algorithm; the method comprises the following steps that the existing flowmeter and an upstream flowmeter are communicated and interconnected in a wireless communication protocol-based mode, a wireless transmitting and receiving module is additionally arranged inside the communicated flowmeters, and a self-correcting algorithm is implanted into a chip layer of the flowmeters; in the linkage type flow metering process, the sum of the precision lower limit calculation values of the downstream flow meter is not greater than the self-calibrated output value of the main network flow meter; the sum of the numerical values of the accuracy upper limit calculation is not less than the self-calibrated output value of the main network flow meter; namely: the self-calibrated output value of the flowmeter is between the upper limit and the lower limit of a downstream flowmeter; if the correction result can not meet the requirement, repeating the correction algorithm again after waiting for the instantaneous flow change of the flowmeter until the requirement is met; if one of the flowmeters still does not meet the requirement after being corrected for many times, the flowmeter sends out an alarm signal to prompt that the flowmeter fails or does not meet the field metering requirement;
fourthly, metering and correcting the working conditions of the upstream and downstream straight pipe sections; according to the industrial field condition that the length of the upstream and downstream straight pipe sections is insufficient, working condition measurement correction is carried out; the meter coefficient under the working condition is used as the measuring basis of the industrial field, so that the reliability of flow measurement is greatly improved; working condition metering correction of the upstream and downstream straight pipe sections is mainly characterized in that the problem of meter coefficients of a flowmeter is solved, so that metering is more accurate and credible; the flow calculation formula of the flowmeter is as follows:
in the formula: q. q.smMass flow of fluid in pipe
C-the corresponding outflow coefficient of the throttling device, is related to the structural parameter operating parameter
d-orifice diameter corresponding to the throttle device
β -ratio of throttling device opening to upstream conduit internal diameter
Delta P-differential pressure value generated when fluid flows through a throttling device
Rho-density of fluid as it flows through a restriction
D-inner diameter of pipe through which fluid flows
In the above equation, the density of the fluid flowing in the pipe at a given temperature and pressure is known, and once the geometry of the restriction is determined, the pipe internal diameter D, the ratio β of the restriction opening to the upstream pipe internal diameter are determined, the variables are the differential pressure Δ P, the outflow coefficient C, and the expansion coefficient ε, and the above equation is further rewritten as:
k-instrument coefficient of the throttling device under the working condition, wherein the expression is as follows:
in the metering process, the flow is calculated by adopting the on-site straight pipe section data and the meter coefficient obtained under the working condition, so that the metering precision is further improved.
In the first step, two methods for acquiring data of each batching and metering device by the flowmeter are provided:
(1) each ingredient metering device is provided with a wireless transmitting and receiving module, and a flowmeter is provided with a wireless transmitting and receiving module; the flowmeter can respectively obtain metering data from each ingredient metering device through a wireless module; so as to meet the use requirements of industrial fields with small change period of various ingredients;
(2) the wireless module is not arranged in each ingredient metering device, and the metering data of each ingredient device is manually input in the virtual wireless transmitting device; then, sending the data to the flowmeter through the virtual wireless transmitting equipment; so as to adapt to the use requirement of an industrial field with large ingredient change period or basically unchanged ingredients.
In the second step, the algorithm for self-calibration of the flow meter in the metering process is as follows:
simultaneously, the requirements are satisfied:
in the formula: q1Theoretical metering data by process algorithms
Q10Instantaneous flow of the flowmeter when not self-calibrated
Q11Upper limit of accuracy of the flowmeter when not self-calibrated
Q12-lower limit of accuracy flow calculation for a flow meter when not self-calibrated
Q13-flow value of flowmeter output after self-calibration
Y-value of process error set in flowmeter, can be set
S1-a value of the metering accuracy class of the flowmeter, which can be entered
If the self-calibration result can not meet the requirement on the set numerical value of the process error, the self-calibration algorithm is continuously repeated after the instantaneous flow of the flowmeter is changed until the requirement is met; if the requirements can not be met after the self-calibration algorithm is performed for multiple times, the flowmeter sends out an alarm signal to prompt that the flowmeter is in failure or the performance of the flowmeter does not reach the standard.
Before the linkage type correction algorithm is implemented, anti-interference processing between upstream and downstream communication is required; in order to reduce the influence of electromagnetic interference on a metering device in the wireless communication process to the maximum extent, an electromagnetic interference detection algorithm is built in the metering device, namely: after the flowmeter transmits data in a frequency band 1 in a wireless communication mode, if return data is detected within set time, the frequency band 1 is adopted as the working frequency band of the flowmeter; if the time for detecting the returned data in the frequency band 1 does not meet the set requirement, the flowmeter transmits the data in the frequency band 2 in a wireless communication mode, and if the data signals are returned in the set time, the frequency band 2 is adopted as the working frequency band of the flowmeter; if the time for detecting the returned data in the frequency band 2 does not meet the requirement, the flowmeter transmits the data in the frequency band 3 in a wireless communication mode, and the data is returned in a set time range, and the frequency band 3 is used as the working frequency band of the flowmeter; otherwise, repeating the above process, and continuing to judge the next frequency band until the requirement is met.
And step four, the instrument coefficient can be corrected according to the algorithm of linear interpolation, namely:
in the formula: delta PmaxDifferential pressure corresponding to maximum design flow
ΔPminDifferential pressure corresponding to the minimum value of the design flow
Delta P is the differential pressure value under the working condition and can be read by a field differential pressure transmitter
Kmax-maximum value of coefficient calculation of instrument
Kmin-minimum value of instrument coefficient calculation
K-Meter coefficient under operating conditions
Thereby achieving the correction of the working condition measurement under the condition of insufficient straight pipe section; the influence of the shortage of the straight pipe section on the metering can be well reduced, the metering deviation is greatly reduced, and the metering precision and the metering reliability are improved.
The invention has the beneficial effects that: the invention implements process-based algorithm analysis on the existing flow measurement method, so that the flow meter can be compared with the production or running condition of the upstream flow medium nearest to the flow meter in the measurement process, and then the flow result is calibrated through a self-calibration function in the flow meter. Then, the existing flowmeter and the upstream flowmeter are communicated and interconnected, the existing flowmeter and the upstream flowmeter are connected in a wireless communication protocol-based mode, a wireless transmitting and receiving module is additionally arranged in the intercommunicated flowmeter, and a self-correcting algorithm is implanted into a chip layer of the flowmeter. Meanwhile, the instrument coefficient can be calculated hydrodynamically according to the difference of the straight pipe sections at the upstream and the downstream in the technological process, so that the instrument coefficient under the working condition is obtained. Compared with the prior art, the linkage type accurate industrial flow metering method can avoid metering errors caused by the difference of the flow meter under the design condition and the actual working condition, and can be interconnected and communicated with other upstream and downstream metering equipment, so that the accuracy of the whole industrial flow metering is improved, the upstream and downstream production processes are optimized, the production cost of an enterprise is reduced, and the purposes of improving quality and increasing efficiency and reducing energy consumption are achieved. Furthermore, the industrial automation level is improved by improving the accuracy and the reliability of the flowmeter, and the flowmeter has great economic benefit and social benefit.
Drawings
FIG. 1 is a block flow diagram of a linked flow metering method of the present invention.
Fig. 2 is a functional schematic block diagram of a flow meter under a conventional metering method.
FIG. 3 is a schematic block diagram of the process and metering integration in a linkage type flow metering process.
FIG. 4 is a self-calibration algorithm block diagram of a coordinated flow metering process.
Fig. 5 is a schematic block diagram of upstream and downstream communication between flow meters.
Fig. 6 is a block diagram of an anti-electromagnetic interference detection algorithm for wireless communication.
Fig. 7 is a three-dimensional schematic diagram of a circulating water pipe network structure of a chemical industry enterprise.
Fig. 8 is a cloud of circulating water pipe velocity profiles of the water piping network structure of fig. 7.
Fig. 9 is a cloud of circulating water line pressure distributions for the water piping network structure of fig. 7.
Fig. 10 is a constant velocity line diagram of a longitudinal section of a circulating water pipe of the water piping network structure of fig. 7.
Fig. 11 is a line chart of a water piping line profile of the water piping network structure of fig. 7.
Detailed Description
The specific steps of the present invention are explained in detail. The linkage type industrial flow accurate metering method comprises the following steps:
step one, interacting process algorithm and metering process data. The process involved in the method of the present invention refers to a process for generating a fluid medium, wherein the fluid medium is generated by an industrial device and then transported and distributed through a main pipe network. The flow meter 1 is a flow meter arranged on a main pipe network and is used for measuring the mass or volume flow of a flowing medium produced by an industrial device. In the traditional flow metering process, data obtained by metering by the flowmeter 1 can be directly transmitted to an industrial control system DCS (distributed metering control system) or transmitted to the DCS through a secondary meter (or a flow computer); then, the DCS performs the next execution (as shown in FIG. 2).
As can be seen from fig. 2, in the conventional flow metering process, the flow meter 1 disposed on the main network is a relatively isolated device. The traditional metering process makes the accuracy and reliability of medium flow metering of a main pipe network completely depend on the performance of the flowmeter 1, if the flowmeter 1 is inaccurate in meter coefficient when leaving a factory, or the problems of corrosion, sensor deformation, sensor blockage, siltation in a pipeline and the like occur in the metering process, data can still be displayed and output, so that the metering of an industrial field is greatly influenced, a light person makes a subsequent process influenced, and a heavy person possibly causes a great safety accident.
During the metering process, data from various process steps before the media is produced by the industrial device can be transmitted to the flow meter 1. As shown in fig. 3, the metering data of the batching plant 1, the batching plant 2 and the batching plant 3 can all be acquired by the flow meter 1. Because the industrial field has complex ingredients, the ingredients adopted by different processes are different; if the ingredient is a solid material, the weight unit is measured by adopting a weighing method, and if the ingredient is a gas or liquid material, the ingredient is measured by adopting a flowmeter or a weighing device.
The flowmeter 1 can obtain the data of each ingredient metering device by two methods:
(1) each ingredient metering device is provided with a wireless transmitting and receiving module, and the flowmeter 1 is provided with a wireless transmitting and receiving module; the flowmeter 1 can respectively obtain metering data from each ingredient metering device through a wireless module. The data acquisition mode is suitable for industrial fields with small change periods of various ingredients.
(2) The wireless module is not arranged in each ingredient metering device, and the metering data of each ingredient device is manually input in the virtual wireless transmitting device; the data is then sent to the flow meter 1 via the virtual wireless transmitting device. The data acquisition mode is suitable for industrial fields with large ingredient change period or basically unchanged ingredients.
After the flow meter 1 acquires the metering data of each ingredient metering device, process calculation analysis can be performed on each set of acquired data according to the process conditions on site (the process calculation analysis is derived from the chemical and physical reaction processes of the medium generating devices, and the reactions performed by different medium generating devices are different). for example, the metering data of the ingredient equipment 1 shows that the ingredient 1 has A, the ingredient 2 has B and the ingredient 3 has C, so the medium generation relationship in the industrial device is (by way of example, simple relationship), the ingredient 3 with the amount of the ingredient 1+ B and the ingredient 2+ C of the amount of the ingredient 1+ B and the amount of the ingredient 3 + D in the amount of the ingredient 3 + C in the amount of the amount A, the efficiency of the industrial device is η, and the medium from the industrial device theoretically should be η XD.
By analogy, if the metering data for ingredient 1, ingredient 2, ingredient 3 is halved and the industrial plant efficiency is unchanged, the medium coming out of the industrial plant is theoretically 0.5 × η × D.
After the process calculation and analysis are completed, the flowmeter 1 has already metering theoretical data, and the theoretical data is a basis for the next data processing and outputting.
And step two, self calibration of the linkage type metering process. After acquiring the data of the batching and metering device, the flowmeter 1 compares the data with the existing metering data per se; and then judging whether the data are consistent with theoretical metering data or not, and if the data are consistent with the theoretical metering data or the error is within an allowable range, determining that the metering result is credible. If the error is outside the allowable range, the flow meter 1 is required to self-calibrate during the metering process.
The self-calibration method comprises the steps that firstly, reference data come from theoretical data generated after process analysis of the flowmeter 1; second, self-calibration requires a basis for a determination of calibration, which results from setting an error. In general, the error requirements are different for different principle types of flow meters, but in general, the error requirements are no greater than 1.0% (coriolis mass flow meters generally require within 0.5%, standard differential pressure flow meters require within 1.0%, electromagnetic flow meters require within 0.5%, ultrasonic flow meters require within 1.0%). The specific error can be set at each industrial field according to specific requirements.
The self-calibration algorithm of the present invention is schematically illustrated in FIG. 4. Taking the flowmeter 1 as an example for explanation, in the actual measurement process, the flowmeter 1 has its own accuracy class, and the accuracy class of the flowmeter 1 is assumed to be S here. Before the calibration is not carried out, the flow of the main pipe network measured by the flowmeter 1 according to the metering principle of the flowmeter is Q10(ii) a After the accuracy grade is added, the upper limit flow of the flowmeter 1 under the working condition is Q11＝Q10×(1+S1) The lower limit flow of the flowmeter 1 under the working condition is Q12＝Q10×(1-S1). And a process error requirement is set in the self-calibration, and if the set error requirement is Y, the flowmeter 1 carries out the self-calibration according to the precision and the process error requirement thereofThe specific calibration algorithm is as follows:
simultaneously, the requirements are satisfied:
in the formula: q1Theoretical metering data by process algorithms
Q10Instantaneous flow of the flowmeter 1 when not self-calibrated
Q11Upper limit of accuracy flow calculation for a non-self-calibrated flowmeter 1
Q12Lower limit of accuracy flow calculation for a non-self-calibrated flowmeter 1
Q13Flow value output by flowmeter 1 after self-calibration
Y-Process error value set in flowmeter 1, settable
S1The value of the measurement accuracy class of the flowmeter 1 can be input
If the formula (1.2) can not be satisfied, the self-calibration algorithm is repeated after the instantaneous flow of the flowmeter 1 is changed until the requirement is satisfied. If the requirements can not be met after the self-calibration algorithm is performed for multiple times, the flowmeter 1 sends out an alarm signal to prompt that the flowmeter is in failure or the performance of the flowmeter does not reach the standard, and the flowmeter cannot be normally used for metering the flow of the main pipe network.
And step three, upstream and downstream communication and linkage type correction algorithm. The upstream and downstream in the upstream and downstream communication mentioned in the method of the present invention refer to the upstream and downstream relationship in the process production. The linkage type correction algorithm is particularly a correction algorithm between flowmeters, and does not comprise a flowmeter and a process medium generating end (a fluid generating end in a pipeline, which can be regarded as an industrial device of the figure 1 in the invention).
It should be noted that, before the implementation of the linkage type correction algorithm, an anti-interference process between the upstream and downstream communications is required. The traditional measuring instrument to DCS system generally adopts a wired communication mode, so that the interference of the periphery is small. After the upstream and downstream communication adopts a wireless communication mode, the interference from the surroundings is greater, and the main interference is electromagnetic interference. Therefore, in order to reduce the influence of electromagnetic interference on the metering instrument in the wireless communication process to the maximum extent, an electromagnetic interference detection algorithm is built in the metering instrument. The logic diagram of the algorithm is shown in fig. 6 (taking the flow meter 1 as an example for explanation): after the flowmeter 1 transmits data in the frequency band 1 in a wireless communication mode, if return data is detected within set time (the set time can be modified in a program according to different industrial fields), the frequency band 1 is adopted as a working frequency band of the flowmeter 1, and the communication flow is shown as a time sequence 1; if the time for detecting the returned data by the frequency band 1 does not meet the set requirement, the flowmeter 1 transmits the data in the frequency band 2 in a wireless communication mode, if the data signals are returned within the set time, the frequency band 2 is adopted as the working frequency band of the flowmeter 1, and the communication process is shown as a time sequence 2; if the time for detecting the returned data in the frequency band 2 does not meet the requirement, the flowmeter 1 transmits the data in the frequency band 3 in a wireless communication mode, and the data is returned in a set time range, and the frequency band 3 is used as the working frequency band of the flowmeter 1. Otherwise, repeating the above process, and continuing to judge the next frequency band until the requirement is met. And if the flowmeter 1 can complete one of the time sequence processes, the anti-electromagnetic interference capability of the communication process is considered to reach the standard.
As can be seen from the schematic diagram of upstream and downstream communication between flowmeters shown in fig. 5 (also taking the flowmeter 1 as an example for the description of upstream and downstream communication), the flowmeter 1 outputs a wireless flow value Q after self-calibration of its upstream process13. The flowmeter 2 is installed to the branch pipe network 1 that user 1 corresponds, and the flow data of flowmeter 2 can be transmitted to adjacent three flowmeters through wireless module, promptly: the flow meters 1, 3 and 4 can all receive the flow value of the flow meter 2; the flow meter 4 is arranged on the branch pipe network 2, and the flow data of the flow meter 4 can be transmitted to the flow meter 1, the flow meter 2 and the flow meter 3 through the wireless module; the flow data of the flowmeter 3 installed in the branch pipe network 3 can be obtained by a wireless moduleTo flow meter 1, flow meter 2 and flow meter 4. The upstream and downstream communication is the basis of a correction algorithm in linkage type metering, and an information isolated island mode of the traditional flow metering process is broken through.
The flow output value of the flow meter 1 after self calibration is Q13The value is acquiescent to be accurate flow measurement data of the main network; and based on the correction algorithm, developing a linkage type correction algorithm among the flowmeter 2, the flowmeter 3 and the flowmeter 4.
The upper accuracy limit of the flowmeter 2 is calculated by the following numerical values: q21＝Q2×(1+S2) (ii) a The lower accuracy limit calculation value of the flowmeter 2 is as follows: q22＝Q2×(1-S2). Wherein Q is2For the flow meter 2 flow measurement before correction, S2Is the accuracy class of the flow meter 2.
The upper limit of accuracy of the flowmeter 3 is calculated by the following numerical values: q31＝Q3×(1+S3) (ii) a The lower accuracy limit calculation value of the flowmeter 3 is as follows: q32＝Q3×(1-S3). Wherein Q is3For the flow metering value before correction of the flowmeter 3, S3The accuracy class of the flowmeter 3.
The upper accuracy limit of the flowmeter 4 is calculated by the following numerical values: q41＝Q4×(1+S4) (ii) a The lower accuracy limit of the flowmeter 4 is calculated by the following numerical values: q42＝Q4×(1-S4). Wherein Q is4For the flow metering value before correction of the flow meter 4, S4The accuracy class of the flow meter 4.
The correction algorithm needs to satisfy the following conditions:
Q22+Q32+Q42≤Q13≤Q21+Q31+Q41(1.3)
Q31+Q41≤Q13-Q22(1.4)
Q41≤Q13-Q22-Q32(1.5)
formulas (1.3) to (1.5) show that in the linkage type flow metering process, the sum of the accuracy lower limit calculation values of the downstream flowmeter 2, the flowmeter 3 and the flowmeter 4 cannot be greater than the self-calibrated output value of the main pipe network flowmeter 1; the sum of the numerical values calculated by the upper precision limit cannot be smaller than the self-calibrated output value of the main pipe network flowmeter 1; namely: the self-calibrated output value of the flowmeter 1 is between the upper and lower limits of three flowmeters downstream.
And the realization sequence of the correction algorithm is carried out according to the sequence of the branch pipe networks adjacent to the main pipe network. The three correction algorithm conditions described above are present in flow meter 2, flow meter 3 and flow meter 4. And if the correction algorithm is not satisfied, repeating the correction algorithm again after waiting for the instantaneous flow change of the flowmeter until the requirement is satisfied. And if one of the flowmeters is corrected for a plurality of times and does not meet the requirement, the flowmeter sends out an alarm signal to prompt that the flowmeter is in failure or does not meet the field metering requirement.
And step four, metering and correcting the working conditions of the upstream and downstream straight pipe sections. It can be understood that, in terms of the actual operation flow, step four should be performed synchronously with step three; for ease of understanding, step four is listed. In the traditional metering process, the provided metering instrument coefficients are all instrument coefficients obtained under an ideal state, and the real situation of an industrial field cannot be reflected, particularly the industrial field with insufficient lengths of upstream and downstream straight pipe sections. The invention carries out working condition metering correction aiming at the industrial field condition that the lengths of the upstream and downstream straight pipe sections are insufficient, and takes the meter coefficient under the working condition as the metering basis of the industrial field, thereby greatly improving the reliability of flow metering.
In order to describe the working condition metering correction of the upstream and downstream straight pipe sections in more detail, taking the flowmeter 1 as an example, the flowmeter 1 is assumed to be a differential pressure type throttling device; for incompressible fluid, the flow calculation formula of the differential pressure type flow meter is as follows:
in the formula: q. q.smMass flow of fluid in pipe
C-the corresponding outflow coefficient of the throttling device, is related to the structural parameter operating parameter
d-orifice diameter corresponding to the throttle device
β -ratio of throttling device opening to upstream conduit internal diameter
Delta P-differential pressure value generated when fluid flows through a throttling device
Rho-density of fluid as it flows through a restriction
Considering the compressibility of the fluid, the flow calculation formula of the differential pressure type flowmeter is shown as the formula (1.7):
wherein epsilon is the expansion coefficient of the fluid, and the general thermodynamic equation of isentropic expansion is taken as the basis.
Under the traditional condition, two variables of the efflux coefficient and the expansibility coefficient are respectively taken as the key points of the research. The medium expansion coefficient can be calculated by a formula, the outflow coefficient can be obtained by experiments, but the experimental conditions are all carried out in a fully developed flow field in a circular pipe with a sufficient straight pipe section. This also results in inaccurate final flow metering results when field conditions fail to meet straight pipe section requirements in an experimental environment.
The working condition metering correction of the upstream and downstream straight pipe sections provided by the method is mainly used for solving the problem of meter coefficients of the flowmeter, so that the metering is more accurate and credible. Taking a differential pressure type flowmeter as an example, the following formula can be obtained by rewriting the formula (1.7):
wherein D is the inner diameter of the pipe through which the fluid flows.
In the above equation, the density of the fluid flowing in the pipe is known at a given temperature and pressure, and once the geometry of the restriction is determined, the pipe internal diameter D, the ratio β of the restriction opening to the upstream pipe internal diameter are determined, the variables being the differential pressure Δ P, the outflow coefficient C, and the expansion coefficient ∈.
Further rewriting the formula (1.8) gives the formula (1.9):
k-instrument coefficient of the throttling device under the working condition, wherein the expression is as follows:
the influence of the upstream and downstream straight pipe sections needs to be analyzed by combining the resistance structures of the front part and the rear part of the upstream and downstream straight pipe sections. Through the analysis of the upstream and downstream straight pipe sections, the influence of the upstream and downstream straight pipe sections on the flow can be integrated into an instrument coefficient K. The coefficient reflects the real instrument coefficient under the condition of working condition, and the data of differential pressure can be obtained by extracting the result of fluid analysis. This establishes a true functional relationship between flow and differential pressure under operating conditions. It should be noted that computational fluid dynamics cannot be performed completely online at present, so that fluid dynamics analysis under the condition of insufficient straight pipe sections needs to be performed in advance before the flow meter is installed for correcting the straight pipe sections, and the database is implanted into a correction algorithm aiming at the defects of the straight pipe sections at the upstream and the downstream in advance.
The working condition measurement correction process of the upstream and downstream straight pipe sections is explained below by taking the circulating water measurement of a certain chemical enterprise site as an example. The total length of the straight pipe section in the metering process of circulating water of a chemical industry enterprise is 3.2D, the upstream structure of the straight pipe section is a butterfly valve, the downstream structure is a single elbow, the length of the upstream straight pipe section is 2.1D, the length of the downstream straight pipe section is 1.1D, and the structure is shown in FIG. 7. If the calculation is directly carried out according to the formula (1.6), the outflow coefficient in the formula can be adopted only if the straight pipe section meets the requirements of upstream 10D and downstream 5D; however, the industry cannot meet the straight pipe section requirements, and if the formula (1.6) is continuously adopted, a significant metering deviation is generated.
Therefore, in order to improve the accuracy of the metering, a computational fluid analysis method is adopted to perform flow field analysis on the pipe network of the circulating water in advance, and the analysis results are shown in fig. 8-11 (fig. 8 is a speed distribution cloud graph of the circulating water pipeline, fig. 9 is a pressure distribution cloud graph of the circulating water pipeline, fig. 10 is a longitudinal section constant velocity line graph of the circulating water pipeline, and fig. 11 is a longitudinal section isobaric line graph of the circulating water pipeline). It can be known from the figures that the serious shortage of the straight pipe section causes the obvious change of the downstream flow field after the fluid passes through the flowmeter, and further influences the change of the downstream pressure, so that the differential pressure value at the position and the differential pressure value in an ideal state generate large change. According to the formula (1.9), when the differential pressure changes, the meter coefficient changes in order to ensure that the flow rate does not change.
The results of comparing the differential pressure change and the instrument coefficient change under the working conditions with those under the ideal conditions are shown in table 1. The ideal state instrument coefficient can be corrected through the table 1. Furthermore, as can be seen from table 1, if the meter coefficient under the operating condition is not corrected, the metering result is reduced by more than 5% compared with the actual flow rate in the pipeline.
TABLE 1 comparison table of working condition measurement and ideal measurement data
The working condition instrument coefficient K in the table 1 is adopted to participate in the flow calculation formula (1.9), so that the influence of the shortage of the straight pipe section on the measurement can be well reduced, the measurement deviation is greatly reduced, and the measurement precision and the reliability are improved. If the flow in actual operation is within a certain range in table 1, the meter coefficient can be corrected according to the algorithm of linear interpolation:
in the formula: delta PmaxDifferential pressure corresponding to maximum design flow
ΔPminDifferential pressure corresponding to the minimum value of the design flow
Delta P is the differential pressure value under the working condition and can be read by a field differential pressure transmitter
Kmax-maximum value of coefficient calculation of instrument
Kmin-minimum value of instrument coefficient calculation
K-Meter coefficient under operating conditions
Thereby achieving the correction of the working condition measurement under the condition of insufficient straight pipe section. The correction algorithm is put into each flow calculation method through a program, and can be executed when the straight pipe section does not meet the requirement.
Claims (4)
1. A linkage type industrial flow accurate metering method is characterized in that: the method comprises the following steps:
step one, interacting process algorithm and metering process data; the method comprises the steps of carrying out process-based algorithm analysis on the existing flow measurement method, and enabling the flow meter to be compared with the production or running condition of an upstream flow medium closest to the flow meter in the measurement process in a process of process comparison; after the process calculation and analysis are completed, the metering theoretical data of the flowmeter can be obtained;
step two, self-calibration of the linkage type metering process; after the data of the batching and metering device is obtained, the flowmeter can be compared with the existing metering data per se; then judging whether the data are consistent with theoretical metering data or not, and if the data are consistent or the error is within an allowable range, determining that the metering result is credible; if the error exceeds the allowable range, the flow meter is required to be self-calibrated in the metering process;
the algorithm for self calibration of the flowmeter in the metering process is as follows:
simultaneously, the requirements are satisfied:
in the formula: q1Theoretical metering data by process algorithms
Q10Instantaneous flow of the flowmeter when not self-calibrated
Q11Non-self-calibrated flow meterUpper limit of accuracy of (2)
Q12-lower limit of accuracy flow calculation for a flow meter when not self-calibrated
Q13-flow value of flowmeter output after self-calibration
Y-value of process error set in flowmeter, can be set
S1-a value of the metering accuracy class of the flowmeter, which can be entered
If the self-calibration result can not meet the requirement on the set numerical value of the process error, the self-calibration algorithm is continuously repeated after the instantaneous flow of the flowmeter is changed until the requirement is met; if the requirements can not be met after the self-calibration algorithm is performed for multiple times, the flowmeter sends out an alarm signal to prompt that the flowmeter is in failure or the performance of the flowmeter does not reach the standard;
step three, upstream and downstream communication and linkage type correction algorithm; the method comprises the following steps that the existing flowmeter and an upstream flowmeter are communicated and interconnected in a wireless communication protocol-based mode, a wireless transmitting and receiving module is additionally arranged inside the communicated flowmeters, and a self-correcting algorithm is implanted into a chip layer of the flowmeters; in the linkage type flow metering process, the sum of the precision lower limit calculation values of the downstream flow meter is not greater than the self-calibrated output value of the main network flow meter; the sum of the numerical values of the accuracy upper limit calculation is not less than the self-calibrated output value of the main network flow meter; namely: the self-calibrated output value of the flowmeter is between the upper limit and the lower limit of a downstream flowmeter; if the correction result can not meet the requirement, repeating the correction algorithm again after waiting for the instantaneous flow change of the flowmeter until the requirement is met; if one of the flowmeters still does not meet the requirement after being corrected for many times, the flowmeter sends out an alarm signal to prompt that the flowmeter fails or does not meet the field metering requirement;
fourthly, metering and correcting the working conditions of the upstream and downstream straight pipe sections; according to the industrial field condition that the length of the upstream and downstream straight pipe sections is insufficient, working condition measurement correction is carried out; the meter coefficient under the working condition is used as the measuring basis of the industrial field, so that the reliability of flow measurement is greatly improved; working condition metering correction of the upstream and downstream straight pipe sections is mainly characterized in that the problem of meter coefficients of a flowmeter is solved, so that metering is more accurate and credible; the flow calculation formula of the flowmeter is as follows:
in the formula: q. q.smMass flow of fluid in pipe
C-the corresponding outflow coefficient of the throttling device, is related to the structural parameter operating parameter
d-orifice diameter corresponding to the throttle device
β -ratio of throttling device opening to upstream conduit internal diameter
Delta P-differential pressure value generated when fluid flows through a throttling device
Rho-density of fluid as it flows through a restriction
D-inner diameter of pipe through which fluid flows
In the above equation, the density of the fluid flowing in the pipe at a given temperature and pressure is known, and once the geometry of the restriction is determined, the pipe internal diameter D, the ratio β of the restriction opening to the upstream pipe internal diameter are determined, the variables are the differential pressure Δ P, the outflow coefficient C, and the expansion coefficient ε, and the above equation is further rewritten as:
k-instrument coefficient of the throttling device under the working condition, wherein the expression is as follows:
in the metering process, the flow is calculated by adopting the on-site straight pipe section data and the meter coefficient obtained under the working condition, so that the metering precision is further improved.
2. The linkage type industrial flow accurate metering method according to claim 1, characterized in that: in the first step, two methods for acquiring data of each batching and metering device by the flowmeter are provided:
(1) each ingredient metering device is provided with a wireless transmitting and receiving module, and a flowmeter is provided with a wireless transmitting and receiving module; the flowmeter can respectively obtain metering data from each ingredient metering device through a wireless module; so as to meet the use requirements of industrial fields with small change period of various ingredients;
(2) the wireless module is not arranged in each ingredient metering device, and the metering data of each ingredient device is manually input in the virtual wireless transmitting device; then, sending the data to the flowmeter through the virtual wireless transmitting equipment; so as to adapt to the use requirement of an industrial field with large ingredient change period or basically unchanged ingredients.
3. The linkage type industrial flow accurate metering method according to claim 1, characterized in that: before the linkage type correction algorithm is implemented, anti-interference processing between upstream and downstream communication is required; in order to reduce the influence of electromagnetic interference on a metering device in the wireless communication process to the maximum extent, an electromagnetic interference detection algorithm is built in the metering device, namely: after the flowmeter transmits data in a frequency band 1 in a wireless communication mode, if return data is detected within set time, the frequency band 1 is adopted as the working frequency band of the flowmeter; if the time for detecting the returned data in the frequency band 1 does not meet the set requirement, the flowmeter transmits the data in the frequency band 2 in a wireless communication mode, and if the data signals are returned in the set time, the frequency band 2 is adopted as the working frequency band of the flowmeter; if the time for detecting the returned data in the frequency band 2 does not meet the requirement, the flowmeter transmits the data in the frequency band 3 in a wireless communication mode, and the data is returned in a set time range, and the frequency band 3 is used as the working frequency band of the flowmeter; otherwise, repeating the above process, and continuing to judge the next frequency band until the requirement is met.
4. The linkage type industrial flow accurate metering method according to claim 1, characterized in that: and step four, the instrument coefficient can be corrected according to the algorithm of linear interpolation, namely:
in the formula: delta PmaxDifferential pressure corresponding to maximum design flow
ΔPminDifferential pressure corresponding to the minimum value of the design flow
Delta P is the differential pressure value under the working condition and can be read by a field differential pressure transmitter
Kmax-maximum value of coefficient calculation of instrument
Kmin-minimum value of instrument coefficient calculation
K-Meter coefficient under operating conditions
Thereby achieving the correction of the working condition measurement under the condition of insufficient straight pipe section; the influence of the shortage of the straight pipe section on the metering can be well reduced, the metering deviation is greatly reduced, and the metering precision and the metering reliability are improved.
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