Gas flow calibration device of differential pressure type flowmeter

Abstract

The utility model relates to a gas flow calibration device of a differential pressure type flowmeter. The gas flow calibration device comprises a fan; a vibration isolation plate; the rectifying assembly is connected with the fan through a pipeline and is configured to change the direction of fluid output by the fan to form laminar flow; the contraction section is connected with the rectifying assembly through a pipeline and comprises a connecting end and an output end, the connecting end is connected with the rectifying assembly, and the diameter from the connecting end to the output end is gradually reduced; the measuring section comprises a measuring channel connected with the flow regulating valve, a pressure detecting piece, a temperature detecting piece and a flow velocity meter, the pressure detecting piece and the temperature detecting piece are arranged on the measuring channel, and the flow velocity meter is configured to be capable of measuring the flow velocity of airflow in each position in the measuring channel; the differential pressure type flow meter is connected with the measuring channel, the measuring point of the flow meter is located between the temperature detecting piece and the differential pressure type flow meter, the calibration device is simple in structure and high in calibration precision, and especially for a large-caliber flow meter, the larger the caliber is, the smaller the influence of a corresponding boundary layer is, and the higher the precision is.

Description

TECHNICAL FIELD

[0001] The utility model relates to flow measurement technical field, concretely relates to a gas flow calibration device of differential pressure flowmeter. BACKGROUND

[0002] Differential pressure flowmeter has the characteristics of high measurement accuracy, stable performance and wide application range, and is widely used in petroleum and natural gas industry, chemical industry, electric power industry, metallurgical industry, water treatment industry, pharmaceutical industry and the like.

[0003] Differential pressure flowmeter is based on Bernoulli equation and flow continuity equation, when the measured medium flows through the differential pressure component, differential pressure is generated on both sides thereof, and the flow of fluid is determined by measuring the differential pressure according to the relationship between differential pressure and flow.

[0004] The measurement accuracy of differential pressure flowmeter is very important, and most of the gas flow devices on the market, such as soap film type gas flow device, bell jar type gas flow device, pVTt method gas flow device and weighing method gas flow device, can only calibrate small-bore differential pressure flowmeters, and due to the mismatch between the measurement principle and the characteristics of the equipment and the measurement requirements of large-bore high flow, it is difficult to realize high-precision, high-efficiency and high-stability flow measurement in actual industrial environment.

[0005] Therefore, it is necessary to improve the prior art to overcome the defects in the prior art. CONTENT OF THE UTILITY MODEL

[0006] Therefore, the present application provides a gas flow calibration device for differential pressure flowmeter to solve at least one problem in the background art, which comprises:

[0007] A fan;

[0008] A vibration isolation plate for isolating the vibration generated by the fan;

[0009] A rectifying assembly connected to the fan through a pipeline and configured to change the direction of the fluid output by the fan to form laminar flow;

[0010] A contraction section connected to the rectifying assembly through a pipeline, comprising a connection end and an output end, the connection end is connected to the rectifying assembly, and the diameter of the connection end to the output end gradually decreases;

[0011] A flow regulating valve configured to change the flow of fluid through the pipeline;

[0012] a measuring section comprising a measuring channel connected with the flow regulating valve, a pressure detecting member and a temperature detecting member arranged on the measuring channel, and a flow rate meter configured to measure flow rates of gas flow at various positions in the measuring channel;

[0013] a differential pressure flow meter connected with the measuring channel, and a measuring point of the flow rate meter is located between the temperature detecting member and the differential pressure flow meter.

[0014] Optionally, the differential pressure flow meter gas flow calibration device as described above, the pipeline comprises a front straight pipe section connected with the contraction section and the front end of the measuring section, and the length of the front straight pipe section is at least 10 times of the cross-sectional diameter of the measuring channel.

[0015] Optionally, the differential pressure flow meter gas flow calibration device as described above, the pipeline further comprises a rear straight pipe section connected with the rear end of the measuring section, and the length of the rear straight pipe section is at least 5 times of the cross-sectional diameter of the measuring channel.

[0016] Optionally, the differential pressure flow meter gas flow calibration device as described above, the flow rate meter comprises a detection sensor, and the allowable error of the detection sensor to the measuring point is ±1.0 mm.

[0017] Optionally, the differential pressure flow meter gas flow calibration device as described above, the ratio of the projection area of the flow rate meter on the cross section of the measuring channel to the cross-sectional area of the measuring channel is less than or equal to 1 / 5 of the absolute value of the allowable error.

[0018] Optionally, the differential pressure flow meter gas flow calibration device as described above, the axis of the pipeline is located on a first plane parallel to the horizontal plane, and a pressure tapping hole is arranged on the pipeline, and the axis of the pressure tapping hole is perpendicular to the first plane.

[0019] Optionally, the differential pressure flow meter gas flow calibration device as described above, the pressure measuring member is installed on the pipeline through the pressure tapping hole, and the diameter of the pressure tapping hole is less than or equal to 4.0 mm.

[0020] Optionally, the differential pressure flow meter gas flow calibration device as described above, the rectifying assembly comprises a rectifier connected with the fan, a honeycomb connected with the rectifier, and a mesh member connected with the honeycomb and the contraction section.

[0021] Optionally, the differential pressure flow meter gas flow calibration device as described above, the calibration device further comprises a silencer arranged on one side of the vibration isolation plate.

[0022] Compared with the prior art, the application has the beneficial effects that: by being provided with the fan, the vibration isolation plate, the flow regulating valve, the flowmeter, the flow regulating assembly, the contraction section, the flow regulating valve and the measuring section, the vibration plate and the muffler can reduce the influence on the measurement of the pressure, the temperature and the flow rate of the measuring section, the flow regulating assembly can change the direction of the fluid output from the fan into regular, smooth and uniform laminar flow to reduce the influence of turbulence and vortex on the measurement accuracy of the measuring section, the airflow after passing through the contraction section forms accelerated airflow which further reduces the turbulence entering the measuring section, the flow rate in the measuring section is measured by the flowmeter, and the working condition flow rate at the position can be obtained by measuring the cross-sectional area of the measuring channel of the measuring section, according to the pressure and the temperature measured by the pressure detection piece and the temperature detection piece, the working condition flow rate is converted to obtain the standard flow rate value of the measuring section, and the standard flow rate value is compared with the flow rate value of the differential pressure flowmeter to complete the calibration of the differential pressure flowmeter, the calibration device has simple structure and high calibration accuracy, and especially for large-diameter flowmeters, the larger the diameter, the smaller the influence of the boundary layer, and the higher the accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic view of a gas flow calibration device of a differential pressure flowmeter shown in the embodiment.

[0024] BRIEF DESCRIPTION OF DRAWINGS: fan 1, vibration isolation plate 2, muffler 3, flow regulating assembly 4, honeycomb 5, grid piece 6, contraction section 7, connecting end 71, output end 72, flow regulating valve 8, measuring section 9, pressure detection piece 91, temperature detection piece 92, flowmeter 93, differential pressure flowmeter 10, front straight pipe section A, rear straight pipe section B. DETAILED DESCRIPTION

[0025] The exemplary embodiments disclosed in the application will be described in more detail below. In the following description, a large number of specific details are given in order to provide a more thorough understanding of the application. However, it is obvious to those skilled in the art that the application can be implemented without one or more of these details. In other examples, in order to avoid obscuring the application, some technical features known in the art are not described; that is, not all features of the actual embodiments are described here, and well-known functions and structures are not described in detail.

[0026] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application. Similarly, a second element, component, region, layer or section discussed below could be termed a first element, component, region, layer or section without departing from the teachings of the present application.

[0027] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and / or

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] For a thorough understanding of the present application, reference should be made to the following detailed description together with the accompanying drawings wherein:

[0030] Reference will be made to Figure 1As shown, the gas flow calibration device of the differential pressure flowmeter 10 shown in a preferred embodiment of the present application comprises a fan 1, a vibration isolation plate 2, a silencer 3, a rectifier assembly connected to the fan 1 through a pipeline, a contraction section 7 connected to the rectifier assembly through a pipeline, a flow regulating valve 8 and a measuring section 9 arranged on one side of the contraction section 7, and a differential pressure flowmeter 10. Among them, the fan 1 drives the impeller to rotate by the motor to apply force to the air, so that the air obtains kinetic energy, thereby generating directional airflow flow in the entire calibration device, the vibration isolation plate 2 is used to prevent the vibration generated by the fan 1 from being transmitted to the measuring section 9, avoiding displacement or deformation of the measuring section 9 due to vibration, thereby improving the measurement accuracy of the single flow measurement, the silencer 3 uses glass fiber, mineral wool and other sound-absorbing materials to absorb sound waves, and converts noise into heat energy, thereby achieving the purpose of reducing noise, the rectifier assembly is configured to change the direction of the fluid output by the fan 1 to form a laminar flow or a nearly laminar flow state, the contraction section 7 is used to accelerate the airflow output from the rectifier assembly, the flow regulating valve 8 is configured to be able to change the flow of the fluid through the pipeline, the measuring section 9 can measure the airflow flow and cross-sectional area at this point, thereby obtaining the standard airflow flow through calculation, the airflow flowing out of the measuring section 9 flows through the differential pressure flowmeter 10, and the two flow values are compared, thereby realizing the calibration of the differential pressure flowmeter 10. In this embodiment, through the above design and layout, the influence of the boundary layer can be reduced, the accuracy of the flow measurement can be improved, and an effective method for calibrating large-diameter differential pressure flowmeters 10 is provided.

[0031] Specifically, the rectifier assembly comprises a rectifier 4 connected to the fan 1, a honeycomb device 5 connected to the rectifier 4, and a mesh piece 6 connecting the honeycomb device 5 and the contraction section 7. Among them, the rectifier 4 can change the irregular airflow output by the fan 1 into regular, smooth and uniform straight airflow, the honeycomb device 5 is internally provided with a plurality of regularly arranged honeycomb flow channels, thereby separating the turbulent and irregular airflow into a plurality of airflow, and guiding the plurality of airflow to flow along the honeycomb flow channel, reducing the vortex and turbulence phenomenon in the airflow, and making the gas flow closer to the laminar flow state, and the mesh piece 6 can separate the airflow flowing out of the honeycomb device 5 into a plurality of small airflow, so that the energy of the airflow can be dispersed, avoiding the airflow concentrated in some areas to form high-speed impact or strong vortex, thereby reducing the overall turbulence degree of the airflow, and providing more stable airflow conditions for the subsequent measurement of the flow rate of the measuring section 9.

[0032] In the embodiment, the contraction section 7 comprises a connection end 71 connected with the grid member 6 of the rectifying assembly and an output end 72, and the diameter of the connection end 71 gradually decreases to the output end 72, so that the airflow can be accelerated when passing through the contraction section 7, and the turbulence degree is greatly reduced to several per thousand, so that the influence of the turbulence degree on the speed measurement can be ignored, and the boundary layer is relatively thinned and the main flow area is increased, thereby reducing the error caused by the difficulty in accurately measuring the boundary layer and further improving the measurement accuracy.

[0033] The measurement section 9 comprises a measurement channel connected with the flow regulating valve 8, a pressure detection member 91 and a temperature detection member 92 arranged on the measurement channel, and a flow rate meter 93 configured to measure the flow rate of the airflow at each position in the measurement channel. The pressure detection member 91 is used to detect the pressure of the measurement channel, the temperature detection member 92 is used to detect the temperature in the measurement channel, and the measurement point of the flow rate meter 93 is located between the temperature detection member 92 and the differential pressure flow meter 10.

[0034] In the embodiment, the flow rate meter 93 comprises a detection sensor, and the allowable error of the detection sensor to the measurement point is ±1.0 mm. It can be understood that a plurality of measurement points are arranged in the measurement channel of the measurement section 9, and when measuring each specific measurement point, the positional error between the point reached by the detection sensor and the target measurement point is ±1.0 mm, so as to ensure the measurement accuracy.

[0035] In the embodiment, the ratio of the projection area of the flow rate meter 93 on the cross section of the measurement channel to the cross-sectional area of the measurement channel is less than or equal to 1 / 5 of the absolute value of the allowable error, and the forward projection of the detection sensor is perpendicular to the axial flow rate and the maximum angle of deviation is ±3°, which should be ensured when moving in the flow field that the incident direction does not change. The advantage of such arrangement is that it helps to reduce the interference of the flow rate meter 93 itself on the airflow, and ensures the authenticity of the fluid flow state.

[0036] It is worth noting that in the embodiment, the pipeline comprises a front straight pipe section A connecting the contraction section 7 and the front end of the measurement section 9, and the length of the front straight pipe section A is at least 10 times the diameter of the cross section of the measurement channel, so as to ensure that the airflow has enough distance to develop into a stable flow state before entering the measurement section 9, so that the flow rate distribution of the fluid is more uniform, and the measurement accuracy of the measurement section 9 is ensured.

[0037] Further, the pipeline further comprises a rear straight pipe section B connected to the rear end of the measuring section 9, the length of the rear straight pipe section B is at least 5 times of the diameter of the cross section of the measuring channel, so that the gas flow through the measuring section 9 has enough distance to maintain the stable state of the fluid, thereby ensuring the stable gas flow through the differential pressure flowmeter 10, reducing the error of the differential pressure flowmeter 10, and thereby realizing the accurate calibration of the differential pressure flowmeter 10. It should be noted that the length shown in the figure, i.e. the proportion of each section, is not the actual value of the calibration device, but is only used as a reference for the connection relationship between the components of the calibration device.

[0038] As described above, the axis of the pipeline is located on a first plane parallel to the horizontal plane, and a pressure tapping hole is formed in the pipeline, and the axis of the pressure tapping hole is perpendicular to the first plane. Specifically, the pressure measuring member is installed on the pipeline through the pressure tapping hole, and the diameter of the pressure tapping hole is less than or equal to 4.0 mm, thereby facilitating accurate measurement of the fluid pressure, avoiding fluid disturbance and measurement error caused by the pressure tapping hole being too large, and thereby improving the accuracy and reliability of pressure measurement.

[0039] As described above, the calibration process of the gas flow calibration device for a differential pressure flowmeter according to the present embodiment is as follows:

[0040] (1) Pre-calibration work: measure the diameters of n (n≥4) approximately equiangularly distributed cross sections of the measuring channel in the measuring section, take the average value, and calculate the cross-sectional area A of the measuring channel in the measuring section.

[0041] (2) Start the calibration device: turn on the power supply to make the calibration device run, open the flow regulating valve, and make the gas flow from the fan pass through the vibration isolation plate, the silencer, the rectifier, the honeycomb, the grid member, the contraction section, the flow regulating valve, the measuring section and the differential pressure flowmeter in turn, and run for a period of time until the gas flow is stable.

[0042] (3) Flow rate distribution detection: adjust the flow rate to the maximum value Q max using the flow rate meter to measure the flow rates of the test points at n (n≥2) approximately equiangularly distributed diameters, and measure at least 7 points (including the flow rate at the center of the measuring channel) on each diameter, and then adjust the flow rate to the intermediate value 0.5Q max and the minimum value Q min , and repeat the above steps.

[0043] (4) Flow field stability detection: adjust the flow rate to the maximum value Q max using the flow rate meter to measure the change of the flow rate within a specified time, calculate the stability, and check whether it is within the specified range. Then adjust the flow rate to the intermediate value 0.5Q max and the minimum value Q min , and repeat the above steps.

[0044] (5) Start calibration: make the flow reach the maximum value Q through the flow regulating valve max , the flowmeter starts to measure point by point from the tube wall of the measuring channel closest to the measuring section along the radius to the center of the measuring channel, a total of three position points are measured, and the average value is taken as the current flow rate V1, and the standard working condition flow rate q1= V1×A is calculated. According to the pressure and temperature measured by the pressure detection member and the temperature detection member at the measuring section, the standard working condition flow rate is converted to obtain the standard standard condition flow rate q s1 at the measuring section, and the display value q m1 of the differential pressure flowmeter is recorded. The indication error of the flow point is calculated:

[0045] ;

[0046] The flow point is measured repeatedly for 3 times, the calculated indication error is averaged, and then the average indication error is used to correct the flow point of the differential pressure flowmeter.

[0047] (6) Make the flow reach 0.75Q max , 0.5Q max , 0.25Q max and Q min in turn through the flow regulating valve, repeat step (5), and correct each flow point of the differential pressure flowmeter respectively, so as to complete the calibration of the differential pressure flowmeter.

[0048] The above is only one specific embodiment of the present application, and any improvement made on the basis of the concept of the present application is considered to be within the protection scope of the present application.

Claims

1. A gas flow calibration device for a differential pressure flow meter, characterized in that, include: Fan; Vibration isolation plates are used to isolate the vibrations generated by the fan. A rectifier assembly, connected to the fan via a pipeline, is configured to change the direction of the fluid output by the fan to form laminar flow; The contraction section is connected to the rectifier assembly via a pipeline, and includes a connection end and an output end. The connection end is connected to the rectifier assembly, and the diameter gradually decreases from the connection end to the output end. A flow regulating valve is configured to change the flow rate of fluid passing through the pipeline; The measurement section includes a measurement channel connected to the flow regulating valve, a pressure detection element and a temperature detection element disposed on the measurement channel, and a flow meter, the flow meter being configured to measure the flow velocity of the airflow at various points within the measurement channel; A differential pressure flow meter is connected to the measurement channel, and the measurement point of the flow meter is located between the temperature detection element and the differential pressure flow meter.

2. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The pipeline includes a front straight pipe section connecting the contraction section and the front end of the measurement section, the length of which is at least 10 times the cross-sectional diameter of the measurement channel.

3. The gas flow calibration device for a differential pressure flowmeter according to claim 2, characterized in that, The pipeline also includes a rear straight pipe section connecting the rear end of the measuring section, the length of which is at least 5 times the cross-sectional diameter of the measuring channel.

4. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The flow meter includes a detection sensor, and the permissible error from the detection sensor to the measurement point is ±1.0 mm.

5. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The ratio of the projected area of ​​the flowmeter on the cross-section of the measuring channel to the cross-sectional area of ​​the measuring channel is less than or equal to 1 / 5 of the absolute value of the allowable error.

6. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The axis of the pipeline is located on a first plane parallel to the horizontal plane, and a pressure tapping hole is provided on the pipeline, the axis of which is perpendicular to the first plane.

7. The gas flow calibration device for a differential pressure flow meter according to claim 6, characterized in that, The pressure sensing element is installed on the pipeline through the pressure tapping hole, and the diameter of the pressure tapping hole is less than or equal to 4.0 mm.

8. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The rectifier assembly includes a rectifier connected to the wind turbine, a honeycomb unit connected to the rectifier, and a mesh element connecting the honeycomb unit to the contraction section.

9. The gas flow calibration device for a differential pressure flowmeter according to claim 1, characterized in that, The calibration device also includes a silencer disposed on one side of the vibration isolation plate.

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