Steady-flow pressure-resistant high-sensitivity differential pressure flowmeter

Abstract

The present invention provides a steady-flow pressure-resistant high-sensitivity differential pressure flowmeter, comprising: a base. A sensing assembly is provided outside the base. A throttling assembly is provided in the base. The throttling assembly and the sensing assembly are communicated by means of a measurement channel to introduce a fluid in the base into the measurement channel for flow metering. The present invention aims to solve the problem that existing flowmeters during operation can only perform unidirectional measurement and cannot achieve bidirectional measurement when a fluid direction or a high / low pressure in a flow channel changes, and the problem that existing flow meters cannot accurately meter the flow in the presence of fluid fluctuations (when the fluid direction in a pipe changes).

Description

A steady flow pressure-resistant high-sensitivity differential pressure flowmeter TECHNICAL FIELD

[0001] The present application relates to the technical field of differential pressure flowmeters, in particular to a steady flow pressure-resistant high-sensitivity differential pressure flowmeter. BACKGROUND

[0002] A differential pressure flowmeter is an instrument for measuring flow rate, which measures the pressure difference generated when fluid flows through a throttling device to realize flow rate measurement.

[0003] The throttling structure is a key component of the differential pressure flowmeter, and the throttling assembly generates a pressure difference before and after the throttling assembly due to the throttling effect. The conventional differential pressure flowmeter can only measure flow rate in one direction when in use. When the gas pressure in the pipeline changes or the fluid direction changes, such as jet flow or vortex flow, the existing flowmeter cannot accurately measure the flow rate, thereby affecting the accuracy of the pipeline flow monitoring data. SUMMARY

[0004] The present application provides a steady flow pressure-resistant high-sensitivity differential pressure flowmeter to solve the problem that the existing flowmeter can only measure flow rate in one direction when the fluid direction and the pressure in the flow passage change, and the problem that the existing flowmeter cannot accurately measure the flow rate when the fluid fluctuates (the fluid direction in the pipeline changes).

[0005] The present application provides a steady flow pressure-resistant high-sensitivity differential pressure flowmeter, which comprises a base, a sensing assembly arranged outside the base, a throttling assembly arranged in the base, and a measurement passage connecting the throttling assembly and the sensing assembly and used to introduce fluid in the base into the measurement passage for flow rate measurement.

[0006] Preferably, the pressure balance assembly comprises a pressure balance cover arranged outside the sensing assembly and used to close the sensing assembly and the measurement passage.

[0007] Preferably, a control board is arranged above the sensing assembly, and the control board is arranged above the sensor assembly by a support or is mounted on the inner top surface of the outer cover by a support.

[0008] The control board is electrically connected to the sensing assembly and an external connector by wires, the outer cover is arranged outside the control board, and the external connector is mounted on one side of the outer cover and is electrically connected to the external connector.

[0009] Preferably, the sensing assembly comprises:

[0010] A pressure sensor is arranged on the inner side wall of the pressure balance assembly and has one or more, the pressure sensor is connected to the control panel through the wire penetrating the pressure balance assembly;

[0011] A temperature and humidity sensor is arranged on the inner side wall of the pressure balance assembly and has one or more, the temperature and humidity sensor is connected to the control panel through the wire penetrating the pressure balance cover;

[0012] A differential pressure sensor is arranged on the inner side wall of the pressure balance assembly and has one or more, the differential pressure sensor is connected to the control panel through the wire penetrating the pressure balance assembly; wherein the differential pressure sensor is located at the inlet and / or outlet of the measuring channel.

[0013] Preferably, the rectifying assembly is arranged in the fluid channel in the base and includes one or more groups, the rectifying assembly is used for rectifying the fluid in the fluid channel.

[0014] Preferably, the rectifying assembly is formed by the baffle, the fixing piece, and the mesh plate connected in sequence; or the rectifying assembly is formed by the baffle, the fixing piece, the mesh plate, the fixing piece, and the mesh plate connected in sequence.

[0015] Preferably, the baffle is uniformly provided with a plurality of small holes, each of the small holes is used for splitting the inflow / outflow fluid and introducing the fluid into the fixing piece, and the fixing piece is used for introducing the fluid into the measuring channel after the fluid is secondarily rectified by the mesh plate.

[0016] Preferably, the rectifying assembly is installed at the inflow / outflow port of the base through the end cover with a channel; the end cover is connected to the pipe joint away from the base, and the pipe joint is used for connecting the straight pipe.

[0017] The measuring channel is formed by a member with a structure on the inner wall of the base; the measuring channel is a structure, the upper part of the structure is used for connecting the differential pressure sensor, and the lower part of the structure is respectively provided with the port P1 and the port P2 at both ends, the port P1 and the port P2 are located at both ends of the throttling assembly and are respectively used for introducing the fluid for throttling the throttling assembly into the measuring channel for measurement by the sensing assembly.

[0018] Preferably, when the flow direction state of the fluid Q in the fluid channel of the base through the throttling assembly is static, the pressure in the flow channel is port P1 = port P2;

[0019] When the flow direction of the fluid Q in the fluid channel of the base through the throttling assembly is from the port P1 to the port P2, the pressure in the flow channel is port P1 > port P2;

[0020] When the flow direction of the fluid Q in the fluid channel of the base via the throttling assembly is from port P2 to port P1, the pressure in the measurement channel is port P1<port P2.

[0021] Preferably, the measurement channel is provided with a pressure balance opening for introducing the fluid in the flow channel into the pressure balance assembly.

[0022] When the external of the differential pressure sensor bears air pressure P0, the pressure difference between port P1 and the external of the differential pressure sensor is (P1-P0)·S, and the pressure difference between port P2 and the external of the differential pressure sensor is (P2-P0)·S.

[0023] When the external of the differential pressure sensor bears air pressure P1, the pressure difference between port P1 and the external of the differential pressure sensor is 0, and the pressure difference between port P2 and the external of the differential pressure sensor is (P2-P1)·S.

[0024] Wherein, S is the internal force area of the structure shell of the differential pressure sensor.

[0025] Preferably, the throttling assembly comprises a low-pressure throttling assembly and a high-pressure throttling assembly, and the throttling channel of the low-pressure throttling assembly is less than that of the high-pressure throttling assembly.

[0026] Preferably, the temperature and air pressure of the fluid to be measured in the measurement channel are corrected.

[0027] Step 1, use formula (1) to obtain the gas mass flow in the measurement channel:

[0028] Wherein, C is the discharge coefficient; β is the diameter ratio of the opening area diameter of the throttling assembly (7) to the pipe cross-sectional area diameter; A0 is the opening area of the throttling assembly; Δp is the static pressure difference (Pa) of the throttling assembly; ε is the expansibility coefficient; ρ1 is the gas density before the throttling assembly; wherein, ρ, Δp are all measured values; ε is a statistical quantity;

[0029] Step 2, obtain the gas density in the flow channel, and correct it by using formula (2) and its temperature and air pressure:

[0030] Wherein, ρ n is the gas density under standard state; P n is the gas pressure under standard state; T n is the gas thermodynamic temperature under standard state; P is the actual air pressure; T is the actual thermodynamic temperature.

[0031] Step 3, use formula (3) to calculate and obtain the corrected gas flow:

[0032] Wherein, Δp is the static pressure difference of the throttling assembly; Pin P is the pressure in the pipe; P is the actual ambient atmospheric pressure; T is the actual gas thermodynamic temperature; k is the flow coefficient.

[0033] Preferably, the density of the mixed gas is calculated according to the content of each gas component; wherein the mixed gas is dry air added with oxygen, carbon dioxide and water vapor.

[0034] Wherein, Δp is the static pressure difference at the pressure taking position of the throttling assembly; P in P is the pressure in the pipe; P is the actual ambient atmospheric pressure; T is the actual thermodynamic temperature; φ is the actual relative humidity; G is the actual carbon dioxide concentration; FIO2 is the actual oxygen concentration; F(T) is the air saturated water vapor percentage; k is the flow coefficient.

[0035] The working principle and beneficial effects of the present application are as follows:

[0036] The present application provides a kind of steady flow pressure-resistant high sensitivity differential pressure flowmeter, comprising: base, the base is provided with sensing assembly outside;Throttling assembly is arranged in the base, and the throttling assembly and sensing assembly are communicated by measurement channel, and for the fluid in base is introduced into measurement channel and carries out flow measurement.

[0037] Specifically, the throttling assembly is the key component of the differential pressure flowmeter, and the throttashing of the throttling member causes the pressure difference between the front and rear ends of the throttling assembly. The throttling member of the traditional differential pressure flowmeter has a structure of orifice plate, venturi tube, nozzle, etc. After nearly a hundred years of research, a large amount of experience data has been accumulated, and standardization has been realized, but they all have their own shortcomings, such as small range, complex processing, poor repeatability, easy to be blocked, etc. The throttling assembly in the present application has the advantages of good repeatability, stable measurement, high precision, simple structure, high reliability and no movable parts. Through the technical scheme provided by the present application, the problem that the flowmeter can only measure in one direction when the fluid direction changes in the pipeline can be solved. In addition, the current flowmeter cannot accurately measure the flow when there is fluid fluctuation (the fluid direction changes in the pipeline).

[0038] Other features and advantages of the present application will be described in the following specification, and some of them will become apparent from the specification, or will be understood by those skilled in the art. The purpose and other advantages of the present application can be achieved and obtained by the structure specifically pointed out in the written specification and the accompanying drawings.

[0039] The technical solutions of the present application will be further described in detail below by means of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0040] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and are meant to explain the present application but are not intended to limit the application. In the drawings:

[0041] Fig. 1 is a schematic diagram of the structure of the present application;

[0042] Fig. 2 is a schematic diagram of the gas flow of the present application;

[0043] Fig. 3 is a schematic diagram of the gas flow of the present application;

[0044] Fig. 4 is a schematic diagram of the gas flow of the present application;

[0045] Fig. 5 is a schematic diagram of the structure of the present application without a pressure balance assembly;

[0046] Fig. 6 is a schematic diagram of the structure of the present application with a pressure balance assembly;

[0047] Fig. 7 is a schematic diagram of the structure of the present application at A;

[0048] Fig. 8 is a schematic diagram of the structure of the rectifier assembly of the present application;

[0049] Fig. 9 is a schematic diagram of the structure of the cross section of the rectifier assembly of the present application;

[0050] Fig. 10 is a schematic diagram of the structure of the throttle assembly of the present application;

[0051] Fig. 11 is a schematic diagram of the structure of the throttle assembly of the present application;

[0052] Fig. 12 is a schematic diagram of the structure of the differential pressure sensor installation position of the present application;

[0053] Fig. 13 is a schematic diagram of the structure of the flowmeter sample disassembly of the present application;

[0054] Fig. 14 is a schematic diagram of the structure of the flowmeter sample of the present application;

[0055] Fig. 15 is the flow measurement deviation rate of the present application under open pressure conditions;

[0056] Fig. 16 is the flow measurement deviation rate of the present application under 100 KPa pressure conditions;

[0057] Fig. 17 is the flow measurement deviation rate of the present application under 200 KPa pressure conditions;

[0058] Fig. 18 is the flow measurement deviation rate of the present application under 300 KPa pressure conditions;

[0059] Fig. 19 is the flow measurement deviation rate of the present application under 400 KPa pressure conditions;

[0060] Figure 20 is the flow measurement deviation rate of the present application under the condition of 500KPa pressure;

[0061] Figure 21 is the flow measurement deviation rate of the present application under the condition of 600KPa pressure;

[0062] Figure 22 is the flow measurement deviation rate of the present application under the condition of 750KPa pressure;

[0063] Figure 23 is the flow measurement deviation rate curve comparison of the present application in the pressure range of 0-750KPa;

[0064] Figure 24 is the full-scale deviation rate curve comparison of the flow meter measurement of the present application in the pressure range of 0-750KPa;

[0065] Wherein, 1 - rectifier assembly, 2 - base, 3 - pressure sensor, 4 - temperature and humidity sensor, 5 - differential pressure sensor, 6 - pressure balance cover, 7 - throttling assembly, 8 - control board, 9 - cover, 10 - external connector, 11 - end cap, 12 - pipe joint, 13 - pressure balance opening, 101 - baffle, 102 - fixing piece, 103 - mesh plate. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings, it should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0067] According to Figure 1, the embodiment of the present application provides a steady flow pressure-resistant high-sensitivity differential pressure type flow meter, comprising: a base 2, the base 2 is provided with a sensing assembly outside; the base 2 is provided with a throttling assembly 7 inside, the throttling assembly 7 and the sensing assembly are communicated through a measurement channel, and are used to introduce the fluid in the base 2 into the measurement channel for flow metering.

[0068] The throttling assembly is a key component of the differential pressure type flow meter, and the throttling of the throttling member causes the pressure difference between the front and rear ends of the throttling assembly. The throttling member of the traditional differential pressure type flow meter has a structure of orifice plate, venturi tube, nozzle, etc. After nearly a hundred years of research, a large amount of experience data has been accumulated, and standardization has been achieved, but all have their own shortcomings, such as small range, complex processing, poor repeatability, easy to be blocked, etc. The throttling assembly in the present application has the advantages of good repeatability, stable measurement, high precision, simple structure, high reliability, no movable parts, etc. Through the technical scheme provided by the present application, the problem that when the fluid direction changes, the flow meter can only measure in one direction and cannot measure in both directions can be solved. In addition, the current flow meter cannot accurately measure the flow when there is fluid fluctuation (the fluid direction in the pipeline changes).

[0069] The flow meter is used for measuring gas flow, comprising a throttling device and a rectifying device, a pressure balance cavity is built-in, a sensor measurement influence factor is introduced for the measured value of a sensing assembly, compensation correction is realized on the result to improve the measurement accuracy.

[0070] In one embodiment, according to figures 1, 6, 7, the pressure balance assembly comprises a pressure balance cover 6, which covers the outside of the sensing assembly and is used for closing the sensing assembly and the measurement flow channel and forming a pressure balance cavity.

[0071] The measurement channel is formed by a member with a cross-section of The measurement channel is formed by a member with a cross-section of The upper part of the structure is used for connecting a differential pressure sensor 5, and the lower part of the structure is respectively provided with a port P1 and a port P2, which are located at the two ends of the throttling assembly 7 and are respectively used for introducing the fluid throttled by the throttling assembly 7 into the measurement channel for measurement by the sensing assembly.

[0072] The measurement channel is provided with a pressure balance opening 13, which is used for introducing the pressure in the pipeline into the pressure balance cover to realize pressure balance and measurement purposes; the pressure balance opening 13 can be at any one of the port P1 and the port P2.

[0073] Further, as shown in figures 2-4, when the flow direction state of the fluid Q in the fluid channel of the base 2 via the throttling assembly 7 is static, the pressure in the flow channel is port P1 = port P2;

[0074] When the flow direction of the fluid Q in the fluid channel of the base 2 via the throttling assembly 7 is from the port P1 to the port P2, the pressure in the flow channel is port P1 > port P2;

[0075] When the flow direction state of the fluid Q in the fluid channel of the base 2 via the throttling assembly 7 is from the port P2 to the port P1, the pressure in the measurement channel is port P1 < port P2.

[0076] Figures 2, 3, 4 are schematic diagrams of differential pressure measurement principles (air flow schematic diagram when air flow passes through the pressure balance assembly); based on different flow directions and different pressure states, the flow rate through the measurement channel is calculated according to the static pressure difference at the throttling assembly, the gas pressure in the pipeline, the actual ambient atmospheric pressure and the thermodynamic temperature.

[0077] According to the figures 5-7, the measuring channel is provided with a pressure balance opening 13 for introducing fluid in the flow channel into the pressure balance assembly;

[0078] When the external pressure of the differential pressure sensor 5 is P0, the pressure difference between the port P1, the port P2 and the external pressure of the differential pressure sensor 5 is (P1-P0)·S, (P2-P0)·S) respectively; wherein S is the internal force area of the differential pressure sensor structure shell;

[0079] When the external pressure of the differential pressure sensor 5 is P1, the pressure difference between the port P1, the port P2 and the external pressure of the differential pressure sensor 5 is 0, (P2-P1)·S) respectively;

[0080] Wherein S is the internal force area of the differential pressure sensor structure shell.

[0081] In this scheme, without the pressure balance cover (pressure balance assembly), the pressure of the differential pressure sensor structure shell is P0 (shown in figure 5), the pressure difference between the port P1, the port P2 and the external pressure of the differential pressure sensor 5 is (P1-P0)·S, (P2-P0)·S) respectively;

[0082] And after adding the pressure balance cover, the pressure of the differential pressure sensor structure shell is P1 (shown in figure 6), the pressure difference between the port P1, the port P2 and the external pressure of the differential pressure sensor 5 is 0, (P2-P1)·S) respectively; wherein S is the internal force area of the differential pressure sensor structure shell.

[0083] Because the values of the port P1, the port P2 are close and much larger than P0, after adding the pressure balance cover, the pressure difference between the differential pressure sensor shell and the port is significantly reduced. The pressure sensor (piezoelectric or piezoresistive differential pressure sensor) measures the pressure value by evaluating the deformation of the diaphragm caused by the pressure difference between the port P1, the port P2, but when the pressure difference between the port P1, the port P2 and the shell exceeds the standard value, it will cause additional deformation of the diaphragm, even damage, causing measurement error; therefore, by designing the pressure balance cover, it can widen the applicable pressure range of the sensor and improve the measurement accuracy.

[0084] In one embodiment, according to figures 1-7, the control board 8 is arranged above the sensor assembly, and the control board 8 is arranged above the sensor assembly by means of a support column, or is installed on the inner top surface of the outer cover 9 by means of a support column;

[0085] The control board 8 is electrically connected to the sensor assembly and the external connector 10 by wires, and the outer cover 9 is arranged outside the control board 8, and the external connector 10 is installed on one side of the outer cover 9 and is used for electrical connection with the external connector 10.

[0086] The sensing assembly comprises:

[0087] A pressure sensor 3 is arranged on the inner side wall of the pressure balance assembly and is provided with one or more pressure sensors 3 which are connected to the control panel 8 through wires penetrating the pressure balance assembly.

[0088] A temperature and humidity sensor 4 is arranged on the inner side wall of the pressure balance assembly and is provided with one or more temperature and humidity sensors 4 which are connected to the control panel 8 through wires penetrating the pressure balance assembly.

[0089] A differential pressure sensor 5 is arranged on the inner side wall of the pressure balance assembly and is provided with one or more differential pressure sensors 5 which are connected to the control panel 8 through wires penetrating the pressure balance assembly; wherein the differential pressure sensor 5 is arranged at the inlet and / or outlet of the measurement channel.

[0090] In this embodiment, the sensing assembly is used to obtain sensing data such as pressure, temperature and humidity, and differential pressure. The obtained sensing data is controlled by the control panel to realize calculation and output of flow metering data. Finally, the data is transmitted to the outside through the external connector, which is an aviation plug or terminal, a wireless transmission module, a wire, or any other means that can realize data transmission.

[0091] In one embodiment, according to FIGS. 1, 8, and 9, the rectifying assembly 1 is arranged in the fluid channel in the base 2 and comprises one or more rectifying assemblies which are used to rectify the fluid in the fluid channel.

[0092] The rectifying assembly 1 is formed by connecting the baffle 101, the fixing member 102, and the mesh plate 103 in sequence; or the rectifying assembly 1 is formed by connecting the baffle 101, the fixing member 102, the mesh plate 103, the fixing member 102, and the mesh plate 103 in sequence.

[0093] According to FIGS. 1, 8, and 9, the baffle 101 is uniformly provided with a plurality of small holes, each of which is used to divide the inflow / outflow fluid and introduce it into the fixing member 102, and the fixing member 102 further rectifies the fluid through the mesh plate 103 and then flows into the measurement channel for fluid flow metering.

[0094] In this scheme, the thickness of the baffle 101 is about D / 8, the baffle 101 is uniformly provided with a plurality of small holes which are regular hexagons or circles outwardly pulled, the diameter of the inscribed circle of the small hole is not greater than 0.06D, and the sum of the hole areas is greater than 30% of the cross-sectional area of the pipeline.

[0095] The mesh plate 103 is made of steel mesh material and is made of stainless steel, the mesh hole diameter of the mesh plate is not greater than 0.01D, and the wire diameter is about 0.004D.

[0096] In the scheme, the stable flow state is the basis for accurate measurement. The function of the straightening structure is to reduce the vortex of the airflow, and to make the axial velocity of the points at different positions on the cross section of the pipeline consistent before the airflow passes through the throttling element.

[0097] Further, the straightening assembly 1 is installed on the inflow / outflow port of the base 2 through an end cover 11 with a channel; the end cover 11 is connected to a pipe joint 12 away from the base 2, and the pipe joint 12 is used to connect a straight pipe.

[0098] Due to the existence of vortex and cross-sectional flow velocity unevenness, in order to ensure measurement accuracy, the existing technical flowmeter usually needs to maintain a straight pipe section of 8-10 times the pipe diameter length at the inlet end; in the present application, the straightening structure is integrated at both ends of the throttling element, which can reduce the length of the straight pipe section, adapt to more specifications of pipe diameters, and support bidirectional measurement. It has better installability and solves the problem of industrial integration. In some precision environments, the straight pipe can also be replaced by a compressed volume elbow; the outermost hard porous baffle in the straightening structure provides protection for the internal weak components, improving the reliability of the product itself.

[0099] In one embodiment, when the pipeline is deformed, the flow will also change; when there is no record of pipeline replacement or maintenance, the flowmeter provided by the present application is installed on the pipeline, and when the flowmeter is working, the input flow and output flow are calibrated to v1 and v2 after installation calibration. Under the same working conditions, if the flowmeter value is greater than the first preset value, it means that the pipeline may be deformed;

[0100] Further, the present application also includes: verifying the deformation, the pipeline is provided with a vibration sensor, when the vibration sensor receives a vibration signal sufficient to cause the pipeline to be deformed, it is recorded as a pipeline deformation mark, and an alarm signal is sent for the user to verify. If the pipeline is deformed, the deformed pipeline is repaired to ensure the accuracy of the input and output flow.

[0101] The pipeline is provided with a photoelectric sensor, when the vibration sensor receives a vibration signal sufficient to cause the pipeline to be deformed, there will be one or more violent vibrations (damage), and one-time violent damage may not cause the pipeline to be deformed, such as falling. At this time, by installing a micro photoelectric sensor in the pipeline, the photoelectric sensor is used to monitor the inner wall of the pipeline, and the data collected by the photoelectric sensor is used to further verify whether the pipeline is deformed, to further ensure that the flowmeter value caused by the deformation of the pipeline is not accurate.

[0102] In the scheme, the data of the vibration sensor can be: when there is abnormal data, the calibrated flow of the photoelectric sensor and the input and output is checked, and when the checking result is within the second preset range, no abnormal alarm is needed.

[0103] The judgment of the photoelectric sensor can be: when there is data anomaly, directly alarming; when the data is not abnormal, but the calibration flow range value of the input and output is abnormal, then the data of the photoelectric sensor is used for secondary verification.

[0104] In the above case, when the pipeline leaks, the flow metering will also deviate, so when the vibration sensor and the photoelectric sensor do not have data anomalies, but the calibration flow range value of the input and output is abnormal, it is considered that the pipeline leaks, at this time, the verification instruction is issued, reminding the user to verify the leakage point, thereby improving the metering accuracy, and at the same time, in the metering process, the purpose of troubleshooting or alarming can also be achieved, based on the detection condition, the control board can perform multiple metering data verification, and then the verification result is used to correct or alarm.

[0105] When correcting, if there is no fault and no pressure difference change caused by deformation, at this time, the data before and after t time (the before and after data are: t+1 time, t-1 time) is compared, if the data of t-1 time and t+1 time are consistent, it is considered that the data of t time is drift data, which is recorded as invalid, and the average value of t-1 and t+1 is recorded as the data of t time, thereby making up the error drift data. However, when a time is concentrated, there are multiple: there is no fault, and there is no pressure difference change, and the data before and after t time are all in the normal range; then it is considered that the sensor assembly may have a fault, the control board generates a sensor assembly fault code and reports it.

[0106] The rectifying assembly 1 in the application not only can realize the rectification of the fluid, but also can realize the filtration of the fluid, reduce or reduce the impurities such as debris and lint in the fluid, which may damage or affect the core components of the flow meter, can ensure the cleanliness of the throttling assembly 7 and the measurement channel, and improve the service life of the flow meter.

[0107] In one embodiment, according to FIGS. 10 and 11, the throttling assembly 7 includes a low-pressure throttling assembly 7 and a high-pressure throttling assembly 7, and the throttling channel of the low-pressure throttling assembly 7 is less than that of the high-pressure throttling assembly 7.

[0108] The throttling effect of the throttling assembly causes the pressure difference between the front and rear ends of the throttling assembly. The throttling member of the traditional differential pressure flow meter has a structure of a hole plate, a Venturi tube, a nozzle, etc. After nearly a hundred years of research, a large amount of experience data has been accumulated, and standardization has been realized, but all have their own shortcomings, such as small range, complex processing, poor repeatability, easy to be blocked, etc. The throttling assembly in the application has the advantages of good repeatability, stable measurement, high precision, simple structure, high reliability, no movable parts, etc.

[0109] In one embodiment, the present application also includes the following technical solutions: temperature and air pressure correction is performed on the measured fluid in the measuring channel:

[0110] Step 1, the gas mass flow in the measuring channel is obtained by using formula 1:

[0111] Wherein, C is the discharge coefficient; β is the diameter ratio of the diameter of the opening area of the throttling component 7 to the diameter of the pipe cross-sectional area; Δp is the static pressure difference Pa at the pressure tapping of the throttling component 7; ε is the expandability coefficient; ρ1 is the gas density before the throttling component 7; wherein, ρ, Δp are all measured values; ε is a statistical quantity;

[0112] Further, A1 is the diameter of the pipe cross-sectional area; A0 is the diameter of the opening area of the throttling component 7;

[0113] Step 2, the gas density in the flow channel is obtained, and formula 2 is used to correct the temperature and air pressure:

[0114] Wherein, ρ n is the gas density under standard conditions (the air density under standard atmospheric pressure at 0℃ is 1.293kg / m3); P n is the gas pressure under standard conditions (101325Pa); T n is the gas thermodynamic temperature under standard conditions (0℃, 273.15K); P is the actual gas pressure; T is the actual thermodynamic temperature;

[0115] Step 3, the corrected gas flow is calculated and obtained by using formula 3:

[0116] Wherein, Δp is the static pressure difference at the pressure tapping of the throttling component 7; P in is the gas pressure in the pipe; P is the actual ambient atmospheric pressure; T is the actual gas thermodynamic temperature; k is the flow coefficient.

[0117] Specifically, the derivation process of formula 3 is: the temperature and air pressure correction formula in formula 2 is substituted into formula 1, and the corrected gas flow formula is obtained; formula 2 is substituted into formula 1 as: After simplification, formula 3 is Q ATP1 is the gas flow.

[0118] Step 4, the density of the mixed gas is calculated according to the content of each gas component; wherein the mixed gas is dry air added with oxygen, carbon dioxide and water vapor;

[0119] Wherein, Δp is the static pressure difference at the pressure tapping of the throttling component 7; P inP is the pressure inside the tube; P is the actual atmospheric pressure; T is the actual thermodynamic temperature; φ is the actual relative humidity; G is the actual carbon dioxide concentration; FIO2 is the actual oxygen concentration; F(T) is the percentage of saturated water vapor in air; k is the flow coefficient.

[0120] When several known gases are mixed, the density of the mixed gas can be calculated according to the content of each gas component.

[0121] Taking the medical use scenario as an example, the mixed gas is dry air added with oxygen, carbon dioxide and water vapor:

[0122] Since the density of a gas is proportional to its relative molecular mass at the same temperature and pressure, the densities of various gases have the following relationship:

[0123] wherein, ρO2 is the density of oxygen, M Air is the relative molecular mass, ρN2 is the density of nitrogen, M Ar is the density of argon gas, ρCO2 is the density of carbon dioxide gas;

[0124] The percentage of saturated water vapor in air at temperature T is f(T) (273.15K≤T≤373.15K); according to statistical data, it is fitted as: f(T) = 0.00000072300413880654T 3 - 0.000595041483584363T 2 +0.163867651715586T-15.0930949796368

[0125] If the oxygen concentration is FIO2 and the relative humidity is φ, the mixed gas can be assumed to be composed of dry air, incremental water vapor, incremental pure oxygen and incremental carbon dioxide; wherein the proportion of water vapor is φF(T), and the proportion of carbon dioxide is G.

[0126] Let the proportion of incremental pure oxygen be x, then the proportion of dry air is: 1-x-G-φF(T), and the value of oxygen concentration FIO2 is: (incremental pure oxygen + O2 in dry air) / total volume.

[0127] Then: FIO2 = x + (1-x-G-φF(T)) ×0.20948 Formula (5) FIO2 = 0.79052x + 0.20948 × (1-G-φF(T)) Formula (6)

[0128] We have:

[0129] Then, ρ = [0.9721 + 0.133164FIO2 + 0.5483G - 0.3497φF(T)]ρ g Equation (7)

[0130] Substitute equation (7) into equation (2), then,

[0131] Substitute equation (8) into equation 1 and equation (3), then,

[0132] Simplify equation (9) to obtain equation (4). The flow equation can be obtained by measuring the value of k using the coefficient detection method.

[0133] In the present application, Figs. 13-14 are actual sample diagrams, and the flow is tested based on the structural technical scheme and flow calculation scheme proposed in the present application. Figs. 1 and 12 are structural principle diagrams, Figs. 2-7 are measurement principle illustrations, according to Figs. 15-24, the present application performs multiple measurements under 0-750 Kpa environment, and compares the corrected and uncorrected flow measurement results based on the measurement results, wherein the flow measurement formula is calculated using equation (4), wherein the value of k is 3.58 and 3.5757, and the test conditions are: no condensate water air, ambient temperature 22℃; measurement pipe diameter: 8mm before and after;

[0134] According to the 8 groups of flow test data under the conditions of output opening 0 KPa, 100 KPa, 200 KPa, 300 KPa, 400 KPa, 500 KPa, 600 KPa, and 750 KPa internal pressure, it can be seen that the test results of the industrial flowmeter against the TSI gas flow analyzer are as follows:

[0135] 1. Under the condition of output opening pressure, in the range of 27-445 L / min, the flow measurement deviation rate is <±2% of the actual measurement value.

[0136] 2. Under the condition of 100 KPa pressure, in the range of 38-244 L / min, the flow measurement deviation rate is <±1.5% of the actual measurement value.

[0137] 3. Under the condition of 200 KPa pressure, in the range of 35-367 L / min, the flow measurement deviation rate is <±3% of the actual measurement value.

[0138] 4. Under the condition of 300 KPa pressure, in the range of 30-438 L / min, the flow measurement deviation rate is <±5% of the actual measurement value.

[0139] 5. Under the condition of 400 KPa pressure, in the range of 34-391 L / min, the flow measurement deviation rate is <±3% of the actual measurement value.

[0140] 6. Under the condition of 500KPa pressure, the flow measurement deviation rate is <±5% of the actual measured value in the range of 24-380L / min.

[0141] 7. Under the condition of 600KPa pressure, the flow measurement deviation rate is <±4% of the actual measured value in the range of 17-324L / min.

[0142] 8. Under the condition of 750KPa pressure, the flow measurement deviation rate is <±5% of the actual measured value in the range of 22-258L / min.

[0143] In summary, in the pressure range of 0-750KPa, the flow measurement deviation rate is <±5% of the actual measured value in the range of 32-244L / min.

[0144] In summary, the application can have the following technical effects:

[0145] Through the structural design of the differential pressure flowmeter, the flow measurement range is increased, and the measurement stability and accuracy are improved. The problems existing in the differential pressure flowmeter under different pressures can be solved, and stable and accurate measurement can be realized under the condition of-0.1MPa to 1Mpa.

[0146] In the application, the rectifier assembly 1 solves the problems of inaccurate measurement and limited measurement caused by gas source interference of the general differential pressure flowmeter, solves the data stability and consistency problems of piezoelectric and piezoresistive differential pressure sensors under large pressure variation, and improves the measurement accuracy. The pressure sensor is built-in, and negative pressure flow measurement can be realized, so that the bidirectional measurement function (forward and reverse) is realized. Through the design of the rectifier assembly 1, the problem of gas flow state stability is solved, and compared with the existing structure, the rectifier assembly 1 does not need a long straight pipe section, and can be compatible with smaller pipe diameter piping. It has better installability and solves the problem of industrial integration.

[0147] The pressure balance assembly (pressure balance cover 6) can well solve the problems of high sensitivity positive and negative pressure and bidirectional flow measurement, and can measure small flow (0.2L / min) and large flow (>3000L / min) with low pressure loss. The pressure balance structure enables the flowmeter to stably and accurately measure fluid in different pressure environments, and has obvious advantages in similar products around the world.

[0148] The flow correction scheme of the application considers the influencing factors of fluid flow measurement, including internal and external pressure, pressure difference, temperature, humidity and gas composition. It is suitable for all differential pressure flowmeters.

[0149] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A steady flow pressure resistant high sensitive differential pressure flow meter, characterized in that, The application relates to a differential pressure sensor, which comprises the following components: a base (2) provided with a sensing assembly outside; a throttling assembly (7) arranged in the base (2) and connected with the sensing assembly through a measuring channel, and used for guiding fluid in the base (2) into the measuring channel for flow measurement; a pressure balance assembly comprising a pressure balance cover (6) arranged outside the sensing assembly and used for sealing the sensing assembly and the measuring channel; The measurement channel has a cross section of The components of the modular structure are formed in the inner wall of the base (2); the measuring channel is a structure, the upper part of the structure is used for connecting a differential pressure sensor (5), and the lower part of the structure is provided with a port P1 and a port P2 at two ends respectively, the port P1 and the port P2 are arranged at two ends of the throttling assembly (7) and are used for guiding fluid throttled by the throttling assembly (7) into the measuring channel for measurement by the sensing assembly; the measuring channel is provided with a pressure balance opening used for guiding fluid in the measuring channel into the pressure balance assembly; when the external air pressure of the differential pressure sensor (5) is P0, the pressure difference between the port P1 and the external pressure of the differential pressure sensor (5) is (P1-P0)S, and the pressure difference between the port P2 and the external pressure of the differential pressure sensor (5) is (P2-P0)S; when the external air pressure of the differential pressure sensor (5) is P1, the pressure difference between the port P1 and the external pressure of the differential pressure sensor (5) is 0, and the pressure difference between the port P2 and the external pressure of the differential pressure sensor (5) is (P2-P1)S; wherein S is the internal force area of the structure shell of the differential pressure sensor.

2. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 1, wherein, a control board (8) arranged above the sensing assembly, the control board (8) is arranged above the sensing assembly by a support or is arranged on the inner top surface of an outer cover (9) by a support; the control board (8) is electrically connected with the sensing assembly and an external connector (10) by wires, the outer cover (9) is arranged outside the control board (8), and the external connector (10) is arranged on one side of the outer cover (9) and is used for electrical connection with the external connector (10).

3. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 1, wherein, the sensing assembly comprises: a pressure sensor (3) arranged on the inner side wall of the pressure balance assembly and provided with one or more, the pressure sensor (3) is connected with the control board (8) by wires penetrating through the pressure balance assembly; a temperature and humidity sensor (4) arranged on the inner side wall of the pressure balance assembly and provided with one or more, the temperature and humidity sensor (4) is connected with the control board (8) by wires penetrating through the pressure balance assembly; a differential pressure sensor (5) arranged on the inner side wall of the pressure balance assembly and provided with one or more, the differential pressure sensor (5) is connected with the control board (8) by wires penetrating through the pressure balance assembly; wherein the differential pressure sensor (5) is arranged at the inlet and / or outlet of the measuring channel.

4. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 1, wherein, a rectifying assembly (1) arranged in the fluid channel in the base (2) and comprising one or more groups, the rectifying assembly is used for rectifying fluid in the fluid channel.

5. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 4, wherein, the rectifying assembly (1) is formed by sequentially connecting a baffle (101), a fixing piece (102) and a mesh plate (103); or the rectifying assembly (1) is formed by sequentially connecting a baffle (101), a fixing piece (102), a mesh plate (103), a fixing piece (102) and a mesh plate (103).

6. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 5, wherein, The baffle (101) is uniformly distributed with a plurality of small holes, each of which is used to shunt the inflow / outflow fluid, and a fixing member (102) is introduced, which further flows into the measuring channel after the fluid is secondary rectified by the mesh plate (103) for fluid flow measurement.

7. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 4, wherein, The rectifying assembly (1) is installed at the inflow / outflow port of the base (2) through the end cover (11) with a channel; the end cover (11) is connected with the pipe joint (12) at the end away from the base (2), and the pipe joint (12) is used to connect the straight pipe.

8. The steady flow pressure-resistant high-sensitivity differential pressure flowmeter of claim 1, wherein, When the flow direction of the fluid Q in the fluid channel of the base (2) through the throttling assembly (7) is static, the pressure in the flow channel is port P1 = port P2; When the flow direction of the fluid Q in the fluid channel of the base (2) through the throttling assembly (7) is from port P1 to port P2, the pressure in the flow channel is port P1 > port P2; When the flow direction of the fluid Q in the fluid channel of the base (2) through the throttling assembly (7) is from port P2 to port P1, the pressure in the measuring channel is port P1 < port P2.

9. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 1, wherein, The throttling assembly (7) includes a low-pressure throttling assembly (7) and a high-pressure throttling assembly (7), and the throttling channel of the low-pressure throttling assembly (7) is less than that of the high-pressure throttling assembly (7).

10. A steady flow pressure resistant high sensitivity differential pressure flow meter as claimed in claim 1, wherein, The temperature and air pressure of the fluid to be measured in the measuring channel are corrected: Step 1, obtain the mass flow rate of the gas in the measurement channel using equation (1): Wherein, C is the outflow coefficient; β is the diameter ratio of the opening area diameter of the throttling assembly (7) to the pipe cross-sectional area diameter; Δp is the static pressure difference (Pa) of the throttling assembly (7); ε is the expansibility coefficient; ρ1 is the gas density before the throttling assembly (7); wherein, ρ, Δp are all measured values; ε is a statistical quantity; Step 2, the gas density in the flow channel is obtained, and formula (2) is used and corrected for temperature and gas pressure: wherein p n is the density of the gas at standard conditions; P n is the pressure of the gas at standard conditions; T n is the thermodynamic temperature of the gas at standard conditions; P is the actual pressure; T is the actual thermodynamic temperature; Step 3, the corrected gas flow is calculated and obtained using equation (3): where Δp is the static pressure difference at the throttle assembly (7) pressure taps; P in P is the actual ambient atmospheric pressure; T is the actual gas thermodynamic temperature; k is the flow coefficient.

11. A current stabilized, pressure resistant, high sensitivity differential pressure flow meter as defined in claim 10 wherein, The density of the mixed gas is calculated according to the content of each gas component; wherein the mixed gas is dry air added with oxygen, carbon dioxide and water vapor; where Δp is the static pressure difference at the throttle assembly (7) pressure taps; P in P is the actual ambient atmospheric pressure; T is the actual thermodynamic temperature; φ is the actual relative humidity; G is the actual carbon dioxide concentration; FIO2 is the actual oxygen concentration; F(T) is the air saturation vapor percentage; k is the flow coefficient.

Images