CN109405906B - Flow metering device and flow metering method - Google Patents
Flow metering device and flow metering method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
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Abstract
The invention discloses a flow metering device and a flow metering method, wherein the flow metering method comprises the following steps: (S1) setting a plurality of flow rate measurement points within the measurement pipe section; (S2) calculating a flow velocity U i at each flow velocity measurement point, and recording the coordinates P i(xpi,ypi,zpi of each flow velocity measurement point in the physical space of the measurement pipe section; (S3) assigning a respective weighting coefficient w i to the flow rate U i at each flow rate measurement point according to the coordinates P i of each flow rate measurement point, calculating a weighted average flow rate value over the entire measurement pipe section(S4) calculating the volume flow Q of the measuring tube section. The invention enlarges the measuring range in the measuring section, improves the measuring precision of the fluid flow and improves the stability of flow measurement.
Description
Technical Field
The present invention relates to the field of fluid flow metering technology, and more particularly, to a flow metering device and a flow metering method.
Background
The flow metering is one of important components of metering science and technology, and accurate and stable flow metering has close relation with national economy, national defense construction and scientific research. The water meter is used as a flow meter for measuring the volume of water flowing through a tap water pipeline, plays an important role in accounting and energy metering management, and is directly related to the benefits of water service companies and masses. The water meter types widely used at present mainly comprise mechanical water meters, ultrasonic water meters, electromagnetic water meters and the like, but the water meters have certain defects in practical use.
The mechanical water meter uses water flow to push the impeller of the water meter to rotate, and the water consumption of a user is obtained by integrating with a counter. The mechanical water meter has the advantages of mature technology, low cost, complex structure, large pressure loss and large error at a small flow rate. The movement is usually made of light plastic, and moving parts are easy to wear in the long-term use process, so that the metering accuracy is affected.
The ultrasonic water meter calculates the average flow velocity on the sound channel by utilizing the velocity difference of the sound wave propagating in the forward water flow direction and the reverse water flow direction, and obtains the surface average velocity through integration, thereby obtaining the volume flow. The ultrasonic water meter has simple structure, low pressure loss and small flow. However, the ultrasonic water meter is greatly influenced by the use environment and the installation condition, and particularly when the transverse speed or vortex flow exists in the measuring section, the speed distribution on the sound channel is distorted, and the measuring precision is influenced. In addition, the electronic control module of the ultrasonic water meter runs in a wet environment for a long time, is easy to fail, and has poor stability.
The electromagnetic water meter measures flow by utilizing Faraday electromagnetic induction law, adopts full electronic design, has no moving parts and small pressure loss, and can realize a very wide range ratio. But the electromagnetic water meter has larger exciting current, poorer battery endurance, slower flow change response, weaker environmental adaptability and easiness in electromagnetic interference when in operation. Electromagnetic water meters have not been widely accepted in the market due to the relatively high technical content and relatively complex process.
In view of the foregoing, there is a need in the art for a new flow metering device that overcomes the above-mentioned problems.
Disclosure of Invention
An object of the present invention is to provide a flow rate measuring device and a flow rate measuring method, which increase a measuring range in a measuring section and improve measuring accuracy.
Another object of the present invention is to provide a flow metering device and a flow metering method, which have a simple structure, strong environmental adaptability, improve the stability of flow metering, and realize accurate metering of flow in an economical and efficient manner.
According to one aspect of the present invention, there is provided a flow metering device comprising:
The three-dimensional net rack is suitable for being fixedly arranged in the measuring pipeline, is of a grid structure and is provided with a plurality of grid nodes;
A plurality of hotline probes fixedly disposed at the mesh nodes;
A heating device electrically connected to the hot wire probe, the heating device heating the hot wire probe and keeping the hot wire probe at a constant temperature; and
The processor is electrically connected with the heating device, and when fluid passes through the hot wire probe at a certain flow rate, part of heat can be taken away, so that the temperature of the hot wire probe is kept constant, the voltage output from the heating device to the hot wire probe can correspondingly change, and the processor analyzes and calculates the flow rate of the fluid passing through the three-dimensional net rack according to the corresponding relation between the output voltage of the heating device and the flow rate.
According to a preferred embodiment of the present invention, the space frame is formed by wire links, either as a structured grid or an unstructured grid.
Preferably, the diameter of the wires constituting the three-dimensional net frame is 10 micrometers to 100 micrometers.
Preferably, the three-dimensional net frame is composed of one or a combination of tetrahedron units, pentahedron units, hexahedron units and heptahedron units.
Preferably, the hot wire probe is a platinum wire or a tungsten wire.
Preferably, the length of the hot wire probe is 0.4-0.6 mm, and the diameter is 9-11 microns.
Preferably, the hot wire probe is connected to the heating device through a wire, and the hot wire probe and the wire are hermetically fixed on the three-dimensional net frame through a quartz coating so as to maintain insulation and stability.
According to another aspect of the present invention, the present invention further provides a flow metering method, which includes the steps of:
(S1) setting a plurality of flow rate measurement points within the measurement pipe section;
(S2) calculating a flow velocity U i at each flow velocity measurement point, and recording the coordinates P i(xpi,ypi,zpi of each flow velocity measurement point in the physical space of the measurement pipe section;
(S3) assigning a respective weighting coefficient w i to the flow rate U i at each flow rate measurement point according to the coordinates P i of each flow rate measurement point, calculating a weighted average flow rate value over the entire measurement pipe section
Wherein w i is a weighting coefficient, U i is the actual measurement flow velocity of each flow velocity measurement point, and n is the number of flow velocity measurement points;
(S4) calculating the volumetric flow rate Q of the measurement spool piece:
Wherein S is the area of the cross section of the measured pipe section.
According to a preferred embodiment of the present invention, in the step (S2), the flow rate U i at each flow rate measurement point is measured as follows:
(S21) fixedly disposing a three-dimensional net frame having a plurality of mesh nodes within the measuring pipe section, with the mesh nodes as flow rate measuring points, fixedly disposing a hot wire probe at each mesh node of the three-dimensional net frame;
(S22) heating the hot wire probe using the heating device output voltage E so that the hot wire probe maintains a constant temperature in the fluid;
(S23) establishing a relation between the output voltage E and the flow rate U at each flow rate measurement point, and calculating the flow rate U at each flow rate measurement point:
E2＝A+B·Um
Wherein E is the output voltage of the heating device, U is the flow rate at each flow rate measuring point, A, B and m are calibration constants, and the calibration is carried out in a measuring pipe section with known flow rate.
Preferably, the electrical signal output by the heating means is amplified and compensated before the relation between the output voltage E and the flow rate U at each flow rate measurement point is established, thereby improving the accuracy of the data.
According to a preferred embodiment of the present invention, the weighting factor w i of the flow rate U i at each flow rate measurement point is calculated by:
(S31) assuming that there is a set of flow measurement points x 0,x1,x2……xn ε [ a, b ], and establishing a Gaussian integral Under the condition that the number of the integral points is given, solving the coordinates and the corresponding coefficient w i of a group of nodes to enable the product formula to reach algebraic accuracy of 2n-1, wherein the Gaussian node is the root of n-degree orthogonal polynomials of 0;
When the coordinate positions of the flow velocity measurement points are consistent with gaussian nodes, a method for solving a linear equation set is adopted to calculate a weighting coefficient w i of each node, f (x) =1, x, &..:
…
Solving the linear equation set to obtain a weighting coefficient w i;
When the coordinate positions of the respective flow velocity measurement points do not coincide with the gaussian node, the weighting coefficient w i is corrected using the following formula:
Wherein z i is the distance between the flow velocity measuring point and the center of the cross section of the measuring pipe section N is the number of flow velocity measurement points, D is the diameter of the cross section of the measured pipe section (if the cross section of the pipe section is square, the diameter is high); k is a coefficient related to the section shape of the measuring tube section, the circular section takes k=0.5, and the square section takes k=0.6; l i is Lagrangian polynomial
(S32) takingWherein w xi is the weighting coefficient of the flow velocity measurement point in the x-axis direction, w yi is the weighting coefficient of the flow velocity measurement point in the y-axis direction, and since the gaussian value integration in the above step (S31) is the integration for the single direction of the x-axis or the y-axis, according to the arrangement position of the flow velocity measurement point in the present invention, the flow velocity measurement point data is integrated in the x-axis and the y-axis directions to obtain the area integration, and therefore the weighting coefficient of the flow velocity of each flow velocity measurement point depends on the position of the flow velocity measurement point in the x-axis and the y-axis directions;
In the x-axis direction, z xi is the distance from the flow velocity measurement point to the center of the cross section of the measurement pipe section in the x-axis direction, and the distance is as follows:
Wherein R is the radius of the cross section of the measuring pipe section, U xi is the velocity of the flow at the flow velocity measuring point in the x-axis direction, and n is the number of the flow velocity measuring points;
In the y-axis direction, z yi is the distance from the flow velocity measurement point to the center of the cross section of the measurement pipe section in the y-axis direction, and the distance is as follows:
Wherein R is the radius of the cross section of the measuring pipe section, U yi is the velocity of the flow at the flow velocity measuring point in the y-axis direction, and n is the number of the flow velocity measuring points;
thus, the volumetric flow rate Q of the measurement spool is calculated:
preferably, when setting up three-dimensional rack, will be provided with the one side of hot wire probe towards the side that faces water to avoid three-dimensional rack self to cause the interference to the fluid, influence the precision of velocity of flow measurement.
Preferably, the flow metering method of the present invention further comprises the steps of: and (S5) measuring the volume flow Q School and school (Uj) at each corresponding flow rate through a meter calibrating table experiment as a standard quantity, establishing a functional relation between Q School and school (Uj) and Q (U j), correcting the volume flow Q obtained in the steps, and improving the accuracy of flow metering, wherein j is the number of the flow rates tested on the meter calibrating table.
The above and other objects, features, and advantages of the present invention will become further apparent from the following detailed description, the accompanying drawings, and the appended claims.
Drawings
Fig. 1 is a schematic cross-sectional structure of a three-dimensional net frame according to a preferred embodiment of the present invention;
fig. 2 is another cross-sectional structural schematic view of a three-dimensional net frame according to a preferred embodiment of the present invention;
fig. 3 is another cross-sectional structural schematic view of a three-dimensional net frame according to a preferred embodiment of the present invention;
Fig. 4 is another cross-sectional structural schematic view of a three-dimensional net frame according to a preferred embodiment of the present invention;
FIG. 5 is a schematic view of a perspective net rack in use according to a preferred embodiment of the present invention, showing the perspective net rack fixedly disposed within a measuring tube section;
FIG. 6 is another use schematic of a space frame according to a preferred embodiment of the present invention, showing the space frame fixedly disposed within a survey pipe segment;
FIG. 7 is a schematic diagram of the relationship between average velocity and velocity profile of grid nodes within a measured pipe segment;
FIG. 8 is a schematic diagram of a cross-sectional grid distribution of a three-dimensional grid within a survey pipe segment;
FIG. 9 is a schematic diagram of another cross-sectional grid distribution of a space frame within a survey pipe segment;
FIG. 10 is a schematic view of another cross-sectional grid distribution of a space frame within a survey pipe segment;
fig. 11 is a flow chart of a flow metering method according to a preferred embodiment of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and the detailed description, wherein it should be noted that, on the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.
The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be appreciated by those skilled in the art that in the present disclosure, the terms "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc. refer to an orientation or positional relationship based on that shown in the drawings, which is merely for convenience of description and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore the above terms should not be construed as limiting the present invention.
It will be understood that the terms "a" and "an" should be interpreted as referring to "at least one" or "one or more," i.e., in one embodiment, the number of elements may be one, while in another embodiment, the number of elements may be plural, and the term "a" should not be interpreted as limiting the number.
Referring to fig. 1 to 6 of the drawings, a flow metering device according to a preferred embodiment of the present invention, which is suitable for flow metering of liquids and gases, will be elucidated in the following description. The flow metering device includes a solid rack, a plurality of hot wire probes, a heating device, and a processor, wherein the solid rack is adapted to be fixedly disposed within a measurement conduit. The three-dimensional net rack is of a grid structure and is provided with a plurality of grid nodes, and the hot wire probe is fixedly arranged at the grid nodes.
The heating device is electrically connected to each hot wire probe, and the heating device heats the hot wire probe and keeps the hot wire probe constant in fluid. When fluid passes through the hot wire probe at a certain flow rate, part of heat is taken away, and in order to keep the temperature of the hot wire probe constant, the voltage output to the hot wire probe by the heating device is correspondingly changed. The processor is electrically connected with the heating device, and the processor analyzes and calculates the flow rate of the fluid passing through the three-dimensional net rack according to the corresponding relation between the output voltage of the heating device and the flow rate.
Preferably, the hot wire probe is provided at each of the grid nodes to cover the full measurement range within the measurement pipe segment.
Specifically, the three-dimensional net frame is formed by linking metal wires with certain strength according to a certain rule, and is provided with a plurality of grid nodes. As shown in fig. 1 to 4, the grid nodes may be arranged in a structured grid or an unstructured grid used in hydrodynamics. As will be readily understood by those skilled in the art, the structured grid is composed of hexahedral units, the adjacencies between grid nodes are orderly and regular, and the iterative computation efficiency is high; the unstructured grid consists of tetrahedrons, triangular prisms or pyramid units, the adjacent relation among grid nodes is unordered and irregular, each grid node can have different adjacent grid numbers, and the adaptability to the shape of the pipe section is strong. The arrangement mode and the density of the grid nodes can be realized through grid division software and verified through CFD simulation.
Fig. 1 to 4 show schematic cross-sectional views of three-dimensional net racks in different grid node arrangements. The cross section referred to in the present invention is the cross section of the measuring tube section, that is, the cross section referred to in the present invention is the cross section perpendicular to the flow direction of the measuring tube section. Fig. 1 shows a full tetrahedral mesh (single face is a triangle), fig. 2 shows a full hexahedral mesh (single face is a quadrangle), fig. 3 shows a full hexahedral "o" mesh, and fig. 4 shows a tetrahedral hybrid mesh.
Preferably, the wires constituting the space frame have a diameter of 10 to 100 micrometers to reduce the influence of the space frame itself on the fluid. It will be readily understood by those skilled in the art that in other possible preferred embodiments of the space frame of the present invention, the space frame may be formed of other materials having a certain strength, for example, but not limited to, carbon fiber materials, etc.
The hot wire probe is connected to the heating device through a wire, and metal wires between grid nodes are used for fixing the wire. Preferably, the hot wire probe and the wire are hermetically fixed to the space frame by a quartz coating to maintain insulation and stability.
Preferably, the hot wire probe is a platinum wire or a tungsten wire, has higher sensitivity, and can realize accurate measurement under the condition of smaller flow. It will be readily appreciated by those skilled in the art that the type of hot wire probe is not limited in the flow metering device of the present invention, and in other possible embodiments of the present invention, the hot wire probe may be implemented to be made of other metals having good thermal conductivity, such as, but not limited to, copper, aluminum, sodium, etc.
Preferably, the length of the hot wire probe is 0.4-0.6 mm, and the diameter is 9-11 microns.
As shown in fig. 5 and 6, the space frame is fixedly arranged in the measuring tube section in a use state, and the measuring tube section is suitable for circulating gas or liquid. And each grid node of the three-dimensional grid frame is provided with a hot wire probe, so that a micro-detection probe beam covering a section of flow space is formed, and the surface flow parameters of the measured pipe sections are obtained by fusing the flow parameters (speed and space position) and the numerical algorithm of each grid node, so that the volume flow is obtained, and the accurate metering of liquid and gas is realized.
Compared with an ultrasonic water meter, the flow metering device disclosed by the invention has the advantages that through grid point distribution, the total measuring point can cover all the measuring range of the measuring pipe section, the error generated by obtaining the surface speed through the linear speed integration of a limited sound channel is avoided, and the metering precision is improved. In addition, the grid distribution points can realize real-time detection of radial and axial space velocity distribution of the measuring pipe section and cover a certain measuring length, so that transverse velocity and vortex flow existing in a flow field can be captured in real time, and accurate measurement of flow can be realized even if a flow blocking piece exists at the front end of the measuring pipe section.
In addition, the hot wire probes with a large number are respectively arranged at each grid node, so that the flow metering device can still work normally and maintain certain metering accuracy under the condition that an individual hot wire probe fails, and the stability of flow metering is improved. The flow metering device provided by the invention has the advantages of simple structure and stronger environmental adaptability, and realizes accurate metering of flow in an economic and effective mode.
Referring to fig. 7 to 11 of the drawings, a flow metering method according to a preferred embodiment of the present invention will be elucidated in the following description. The flow metering method comprises the following steps:
(S1) setting a plurality of flow rate measurement points within the measurement pipe section;
(S2) calculating a flow velocity U i at each flow velocity measurement point, and recording the coordinates P i(xpi,ypi,zpi of each flow velocity measurement point in the physical space of the measurement pipe section;
(S3) assigning a respective weighting coefficient w i to the flow rate U i at each flow rate measurement point according to the coordinates P i of each flow rate measurement point, calculating a weighted average flow rate value over the entire measurement pipe section
Wherein w i is a weighting coefficient, U i is the actual measurement flow velocity of each flow velocity measurement point, and n is the number of flow velocity measurement points;
(S4) calculating the volumetric flow rate Q of the measurement spool piece:
Wherein S is the area of the cross section of the measured pipe section.
In the preferred embodiment, a space rectangular coordinate system is established with the center of the cross section of the measuring tube section as the origin, and the coordinates Pi (xpi, ypi, zpi) of each flow velocity measuring point in the physical space of the measuring tube section are recorded.
Specifically, in the step (S2), the flow rate U i at each flow rate measurement point is measured as follows:
(S21) fixedly disposing a three-dimensional net frame having a plurality of mesh nodes within the measuring pipe section, with the mesh nodes as flow rate measuring points, fixedly disposing a hot wire probe at each mesh node of the three-dimensional net frame;
(S22) heating the hot wire probe by using the output voltage E of the heating device so that the hot wire probe maintains a constant temperature in the fluid, and taking away part of heat when the fluid passes through the hot wire probe at a certain speed U, so that the hot wire probe maintains a constant temperature, and the output voltage E of the heating device changes accordingly;
(S23) establishing a relation between the output voltage E and the flow rate U at each flow rate measurement point, and calculating the flow rate U at each flow rate measurement point:
E2＝A+B·Um
wherein E is the output voltage of the heating device, U is the flow rate at each flow rate measurement point, A, B and m are calibration constants, and the calibration can be performed in a measurement pipe section with a known flow rate.
Preferably, the electrical signal output by the heating means is amplified and compensated before the relation between the output voltage E and the flow rate U at each flow rate measurement point is established, thereby improving the accuracy of the data.
It is worth mentioning that the hot wire probe should be set up in the meeting water survey of three-dimensional rack in order to reduce the influence of three-dimensional rack self to rivers. In addition, a certain distance should be kept between different grid nodes to reduce interference of water flow disturbance caused by an upstream grid node to measurement of a downstream grid node hot wire probe, and meanwhile, a certain grid node density should be ensured to improve measurement accuracy.
In the pipeline flow, the flow velocity at the pipeline wall surface is consistent with the pipeline speed according to the non-slip wall surface theory, namely zero, because of the resistance of the pipeline wall surface. In the laminar flow state, the velocity profile of the pipe wall is the profile line as shown in fig. 7. If the velocity measured at the flow velocity measurement point as shown in fig. 8 represents the average velocity of a quadrilateral, then the sum of a finite number of average velocities in the x-axis direction can be taken to represent the face velocity of the measurement plane, i.e. the area between the profile line and the x-axis is represented by the area of a number of rectangles. But this algorithm ignores the non-linear variation of the velocity gradient in the pipeline and therefore causes some error. In order to ensure accuracy, a certain weighting coefficient w i needs to be assigned to the actual measurement speed of each flow velocity measurement point according to the coordinate position of the flow velocity measurement point.
Further, the weighting coefficient w i of the flow rate U i at each flow rate measurement point is obtained by a gaussian numerical integration method, and specifically includes the following steps:
(S31) assuming that there is a set of flow measurement points x 0,x1,x2……xn ε [ a, b ], and establishing a Gaussian integral Under the condition that the number of the integral points is given, the coordinates and the corresponding coefficients w i of a group of nodes can be solved to enable the product formula to reach algebraic accuracy of 2n-1, wherein the Gaussian node is the root of an n-degree orthogonal polynomial of 0;
when the coordinate positions of the flow rate measurement points are consistent with the gaussian node, calculating a weighting coefficient w i of each flow rate measurement point by adopting a method of solving a linear equation set, and respectively taking f (x) =1, x.
…
Solving the linear equation set to obtain a weighting coefficient w i;
When the coordinate positions of the respective flow velocity measurement points do not coincide with the gaussian node, the weighting coefficient w i is corrected using the following formula:
Wherein z i is the distance between the flow velocity measuring point and the center of the cross section of the measuring pipe section N is the number of flow velocity measurement points, D is the diameter of the cross section of the measured pipe section (if the cross section of the pipe section is square, the diameter is high); k is a coefficient related to the section shape of the measuring tube section, the circular section takes k=0.5, and the square section takes k=0.6; l i is Lagrangian polynomial
(S32) takingWherein w xi is a coefficient of the flow rate measurement point in the x-axis direction, w yi is a coefficient of the flow rate measurement point in the y-axis direction, and since the gaussian value integration in the above step (S31) is an integration for a single direction of the x-axis or the y-axis, according to the arrangement position of the flow rate measurement point in the present invention, the flow rate measurement point data is integrated in the x-axis and the y-axis directions to obtain the area integration, and thus the weighting coefficient of the flow rate of each flow rate measurement point depends on the position of the flow rate measurement point in the x-axis and the y-axis directions;
As shown in fig. 9, in the x-axis direction, z xi is the distance between the flow velocity measurement point and the center of the cross section of the measurement pipe section in the x-axis direction, and includes:
Wherein R is the radius of the cross section of the measuring pipe section, U xi is the velocity of the flow at the flow velocity measuring point in the x-axis direction, and n is the number of the flow velocity measuring points;
As shown in fig. 10, in the y-axis direction, z yi is the distance between the flow velocity measurement point and the center of the cross section of the measurement pipe section in the y-axis direction, and includes:
Wherein R is the radius of the cross section of the measuring pipe section, U yi is the velocity of the flow at the flow velocity measuring point in the y-axis direction, and n is the number of the flow velocity measuring points;
thus, the volumetric flow rate Q of the measurement spool is calculated:
Preferably, the flow metering method of the present invention further comprises the steps of: and (S5) measuring the volume flow Q School and school (Uj) at each corresponding flow rate through a meter calibrating table experiment as a standard quantity, establishing a functional relation between Q School and school (Uj) and Q (U j), correcting the volume flow Q obtained in the steps, and improving the accuracy of flow metering, wherein j is the number of the flow rates tested on the meter calibrating table.
The meter calibrating table is a device for checking the flow accuracy of a flow metering device such as a water meter. In this embodiment, a static capacity method is adopted, and the medium discharged from the pressure stabilizing container passes through the test tube section, and the flow metering device enters the working volume device. And comparing the flow metering device with the indicating value of the working gauge to determine the error of the flow metering device.
After a sufficient amount of [ Q School and school (Uj),Q(Uj) ] data is obtained, the flow rate characteristics are computer corrected to obtain a functional relationship of Q School and school (Uj and Q (U j), thereby correcting the flow rate values obtained in the above steps (S1) to (S4). The computer correction of the flow characteristic can digitally correct the part with out-of-tolerance indication value in the flow characteristic curve, so that the flow characteristic curve meets the standard requirement in the measuring range, and the ideal state is achieved, namely, the error curve is flat and is close to the zero error position.
Specifically, by comparing the flow meter measurement data (input amount) with the data (standard amount) measured by the calibration table, the flow meter value in the measurement range is made equal to or close to the standard amount by setting a method such as piecewise coefficient correction or fitting straight line correction. The specific correction function form is to determine a single correction coefficient or a piecewise correction coefficient or polynomial fitting curve correction according to the presentation trend of the two groups of data Q School and school (Uj) and Q (U j).
According to the flow metering method, according to the weighted average method of the flow velocity measuring point positions, the surface speed of the measuring section is represented by the limited flow velocity measuring point speeds through weighted summation, so that the volume flow is obtained through calculation, the measuring range is wide, and the measuring precision is high.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are by way of example only and are not limiting. The objects of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been shown and described in the examples and embodiments of the invention may be modified or practiced without departing from the principles described.
Claims (5)
1. A method of metering a flow, comprising the steps of:
s1, setting a plurality of flow velocity measurement points in a measurement pipe section;
S2, measuring and calculating the flow velocity U i at each flow velocity measuring point, and recording the coordinate P i(xpi,ypi,zpi of each flow velocity measuring point in the physical space of the measuring pipe section;
S3, according to the coordinates Pi of each flow velocity measuring point, a respective weighting coefficient w i is given to the flow velocity U i at each flow velocity measuring point, and a weighted average flow velocity value in the whole measuring pipe section is calculated ，
Wherein n is the number of flow velocity measurement points;
s4, calculating the volume flow Q of the measured pipe section:
，
s is the area of the cross section of the measured pipe section;
The weighting factor w i for the flow rate U i at each flow rate measurement point is calculated by:
S31 assume that there is a set of flow measurement points x 0,x1,x2......xn ε [ a, b ], and a Gaussian integral is established Under the condition that the number of the integral points is given, solving the coordinates and the corresponding coefficient w i of a group of nodes so that the Gaussian integral formula reaches algebraic accuracy of 2n-1, wherein the Gaussian nodes are roots of n-degree orthogonal polynomials of 0;
when the coordinate positions of the flow rate measurement points are consistent with the gaussian node, calculating a weighting coefficient w i of each flow rate measurement point by adopting a method of solving a linear equation set, and respectively taking f (x) =1, x.
…
，
Solving the linear equation set to obtain a weighting coefficient w i;
When the coordinate positions of the respective flow velocity measurement points do not coincide with the gaussian node, the weighting coefficient w i is corrected using the following formula:
，
Wherein z i is the distance of the flow velocity measurement point from the center of the cross section of the measurement pipe section, i=1..N, N is the number of flow velocity measurement points, D is the diameter of the cross section of the measured pipe section, and if the cross section of the pipe section is square, the measured pipe section is high; k is a coefficient related to the section shape of the measuring tube section, the circular section takes k=0.5, and the square section takes k=0.6; l i is Lagrangian polynomial
S32 takingWherein w xi is the weighting coefficient of the flow velocity measurement point in the x-axis direction, and w yi is the weighting coefficient of the flow velocity measurement point in the y-axis direction;
In the x-axis direction, z xi is the distance from the flow velocity measurement point to the center of the cross section of the measurement pipe section in the x-axis direction, and the distance is as follows:
，
Wherein R is the radius of the cross section of the measuring pipe section, uxi is the component speed of the flow velocity at the flow velocity measuring point in the x-axis direction; in the y-axis direction, z yi is the distance from the flow velocity measurement point to the center of the cross section of the measurement pipe section in the y-axis direction, and the distance is as follows:
，
wherein Uyi is the component speed of the flow velocity in the y-axis direction at the flow velocity measurement point;
thus, the volumetric flow rate Q of the spool piece is measured:
2. The flow metering method according to claim 1, wherein in said step S2, the flow rate Ui at each flow rate measurement point is measured as follows:
S21, fixedly arranging a three-dimensional net rack with a plurality of grid nodes in a measuring pipe section, taking the grid nodes as flow velocity measuring points, and fixedly arranging a hot wire probe at each grid node of the three-dimensional net rack;
S22, heating the hot wire probe by utilizing the output voltage E of the heating device, so that the hot wire probe keeps constant temperature in fluid;
S23, establishing a relation between the output voltage E and the flow rate U at each flow rate measurement point, and calculating the flow rate U at each flow rate measurement point:
E2＝A+B·Um，
Wherein E is the output voltage of the heating device, U is the flow rate at each flow rate measuring point, A, B and m are calibration constants, and the calibration is carried out in a measuring pipe section with known flow rate.
3. A flow metering method as claimed in claim 2 wherein the electrical signal output by the heating means is compensated for amplification before the output voltage E is related to the flow rate U at each flow rate measurement point.
4. The flow rate measurement method according to claim 2, wherein when the space frame is provided, a side on which the hot wire probe is provided is directed in a direction of an incoming path of the fluid.
5. The flow metering method of claim 1, further comprising the step of: s5, measuring the volume flow Q School and school (Uj) at each corresponding flow rate through a meter calibrating table experiment as a standard quantity, establishing a functional relation between Q School and school (Uj) and Q (U j), correcting the volume flow Q obtained in the steps S1 to S4, and improving the accuracy of flow metering, wherein j is the number of the flow rates tested on the meter calibrating table.
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| CN112698052B (en) * | 2021-01-07 | 2023-05-16 | 深圳云顶智慧科技有限公司 | Working method, controller and system of flow velocity metering device |
| CN115638848A (en) * | 2022-10-13 | 2023-01-24 | 江苏福吉特管业有限公司 | Gas-liquid two-phase rotational flow metering device and method |
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