Inner cone type differential pressure flowmeter based on multi-parameter compensation

Abstract

The utility model relates to an inner cone type differential pressure flowmeter based on multi-parameter compensation. The flow meter aims to solve the technical problem that an existing flow meter is greatly influenced by fluid parameters. According to the technical scheme, the device comprises a constant flow unit, a testing module, a transmitter module and a data processing module, a temperature measuring element and an inner cone throttler are arranged on the upstream inner wall and the downstream inner wall of a measuring pipeline in the fluid direction, the transmitter module comprises a temperature transmitter, a pressure transmitter and a differential pressure transmitter, the temperature transmitter is electrically connected with the temperature measuring element, and the pressure transmitter is electrically connected with the differential pressure transmitter. The pressure transmitter is electrically connected with a pipeline, the differential pressure transmitter is electrically connected with the head end and the tail end of the inner cone throttler, the data processing module comprises an adder, a multiplier and a squarer, the temperature transmitter, the constant current unit and the pressure transmitter are connected with the adder, the adder and the differential pressure transmitter are connected with the multiplier, the multiplier is connected with the squarer, and the squarer is connected with the output unit. Errors caused by changes of fluid physical property parameters can be eliminated to the maximum extent through measured values, and the measuring precision is greatly improved.

Description

Technical Field

[0001] This utility model belongs to the field of fluid measurement equipment technology, specifically relating to an internal cone differential pressure flow meter based on multi-parameter compensation. Background Technology

[0002] In production processes such as thermal, chemical, and petrochemical industries, especially in large power plants, the control of flow rate and related process quantities depends on flow measurement. Currently, the most widely used flow meters are differential pressure flow meters, which have the advantages of simple structure and convenient use. However, after long-term field research, it has been found that the measurement accuracy of existing differential pressure flow meters is often affected by sensor errors and changes in fluid physical parameters. Utility Model Content

[0003] The purpose of this invention is to solve the above-mentioned technical problems and provide an internal cone differential pressure flow meter based on multi-parameter compensation.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0005] An internal cone differential pressure flow meter based on multi-parameter compensation includes an initial value setting module, a testing module, a transmitter module, and a data processing module.

[0006] The test module includes a temperature sensing element and an inner conical throttle. The temperature sensing element is located on the inner wall of the upstream section of the measuring pipe in the direction of medium flow. The inner conical throttle is coaxially fixed in the downstream section of the measuring pipe in the direction of medium flow, and its inner conical head faces away from the direction of fluid flow.

[0007] The transmitter module includes a temperature transmitter, a pressure transmitter, and a differential pressure transmitter. The temperature transmitter is electrically connected to the temperature sensing element. The pressure transmitter is electrically connected to the inner wall of the pipe between the temperature sensing element and the inner conical throttle. The differential pressure transmitter is electrically connected to the pressure taps on the inner wall of the measuring pipe at both ends of the inner conical throttle.

[0008] The data processing module includes an adder, a multiplier, and a square root extractor. The outputs of the temperature transmitter, the initial value setting module, and the pressure transmitter are all connected to the input of the adder. The outputs of the adder and the differential pressure transmitter are connected to the input of the multiplier. The output of the multiplier is connected to the input of the square root extractor. The output of the square root extractor is connected to the input of the output unit.

[0009] Furthermore, one side of the inner conical throttle is a cone, the bottom surface of the cone is an arc surface, and the cone angle α of the cone is 45-60°.

[0010] Furthermore, the distance from the upstream pressure tapping point of the differential pressure transmitter to the maximum cross-section of the inner conical throttle body is the inner diameter D of the measuring pipe, and the distance from the downstream pressure tapping point to the maximum cross-section of the inner conical throttle body is half the inner diameter D / 2 of the measuring pipe.

[0011] Furthermore, the maximum cross-sectional diameter d of the cone of the inner conical throttle is 0.6-0.8D.

[0012] Furthermore, the total length of the inner conical throttle is 3 to 5 times the inner diameter D of the measuring pipe.

[0013] Furthermore, the length of the straight pipe section upstream of the inner conical throttle is 5-10 times the inner diameter D of the measuring pipe, and the length of the straight pipe section downstream is ≥ 10 times the inner diameter D of the measuring pipe.

[0014] Furthermore, the surface roughness Ra of the inner conical throttle is ≤0.8μm.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1. The measurement values ​​of this utility model can eliminate errors caused by changes in fluid physical parameters to the greatest extent, and the measurement accuracy is greatly improved;

[0017] 2. This utility model uses an inner conical throttling device, which has a stable flow effect, a large flow ratio, is not easy to accumulate dirt, and is suitable for measuring dirty media that are prone to crystallization.

[0018] 3. This utility model has low permanent pressure loss, high accuracy, and low maintenance, and can also measure gases and general liquids;

[0019] 4. This utility model can obtain parameters such as fluid density, pressure, and flow rate, thereby optimizing and improving the process environment, enhancing measurement accuracy and operational safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of this utility model;

[0021] Figure 2 The simulation results of the fluid velocity for the present invention are shown in the cloud diagram when the cone angle α is 45° and β = 0.6.

[0022] Figure 3 The simulation results of fluid pressure for this utility model are shown in the cloud diagram when the cone angle α is 45° and β = 0.6.

[0023] Figure 4 The graph shows the simulation results of fluid pressure when the cone angle α is 45° and β = 0.6.

[0024] In the diagram: 1-Temperature sensing element; 2-Temperature transmitter; 3-Initial value setting module; 4-Pressure transmitter; 5-Inner conical throttle; 6-Differential pressure transmitter; 7-Adder; 8-Multiplier; 9-Square root extractor; 10-Output unit; 11-Measuring pipeline.

[0025] A - Temperature correction factor, B - Pressure correction factor, D - Inner diameter of the measuring pipe, d - Maximum cross-sectional diameter of the cone of the inner conical throttle. Detailed Implementation

[0026] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0027] like Figure 1 As shown, an internal cone differential pressure flow meter based on multi-parameter compensation includes an initial value setting module 3, a testing module, a transmitter module, and a data processing module.

[0028] The test module includes a temperature sensing element 1 and an inner conical throttle 5. The temperature sensing element 1 is disposed on the inner wall of the upstream section of the measuring pipe 11 in the direction of medium flow. One side of the inner conical throttle 5 is a cone with a cone angle α of 45°, a maximum cross-sectional diameter d of 0.6D, a bottom arc surface, a total length of 4 times the inner diameter D of the measuring pipe 11, and a surface roughness Ra of 0.8μm. It is coaxially fixed in the downstream section of the measuring pipe 11 in the direction of medium flow, with the head of its inner cone facing away from the direction of fluid flow. The length of the straight pipe section of the measuring pipe 11 upstream of the inner conical throttle 5 is 5 times the inner diameter D of the measuring pipe 11, and the length of the straight pipe section downstream of the inner conical throttle 5 is 10 times the inner diameter D of the measuring pipe 11.

[0029] The transmitter module includes a temperature transmitter 2, a pressure transmitter 4, and a differential pressure transmitter 6. The temperature transmitter 2 is electrically connected to the temperature sensing element 1. The pressure transmitter 4 is electrically connected to the inner wall of the pipe between the temperature sensing element 1 and the inner conical throttle 5. The distance from the upstream pressure tap of the differential pressure transmitter 6 to the maximum cross-section of the cone of the inner conical throttle 5 is the inner diameter D of the measuring pipe 11, and the distance from the downstream pressure tap of the differential pressure transmitter 6 to the maximum cross-section of the cone of the inner conical throttle 5 is half the inner diameter D / 2 of the measuring pipe 11.

[0030] The data processing module includes an adder 7, a multiplier 8, and a square root extractor 9. The outputs of the temperature transmitter 2, the initial value setting module 3, and the pressure transmitter 4 are all connected to the input of the adder 7. The outputs of the adder 7 and the differential pressure transmitter 6 are connected to the input of the multiplier 8. The output of the multiplier 8 is connected to the input of the square root extractor 9. The output of the square root extractor 9 is connected to the input of the output unit 10.

[0031] The initial value setting module 3 is determined based on the rated temperature of the fluid to be measured in the operating system, and its output should be consistent with the output type of the temperature sensor module in module 1.

[0032] The cone angle α of the inner conical throttle 5 can also be any value between 45° and 60°.

[0033] The maximum cross-sectional diameter d of the cone of the inner conical throttle 5 can also be any value between 0.6 and 0.8D.

[0034] The total length of the inner conical throttle 5 can also be any value between (3~5)D, within which the pressure drop and space limitation can be balanced.

[0035] The length of the straight pipe section of the measuring pipe 11 upstream of the inner conical throttle 5 can be any value between 5 and 10 times the inner diameter D of the measuring pipe 11, and the length of the straight pipe section downstream can be any value ≥ 10 times the inner diameter D of the measuring pipe 11.

[0036] The surface roughness Ra of the inner conical throttle 5 can also be any value ≤0.8μm to reduce turbulence and wear.

[0037] The simulation experiments show that the throttling phenomenon of the fluid varies significantly with different cone angles and β.

[0038] like Figure 2-4 The image shown is a simulation result of fluid pressure when the cone angle α is 45° and β = 0.6.

[0039] Simulation results show that the throttling phenomenon of the fluid is most typical when the cone angle α is 45° and β = 0.6. Figure 2 The velocity contour map reflects the fluid velocity. The decrease in the cross-sectional area at the bottom of the inner cone leads to a sharp increase in velocity, and the velocity contour map can show the high-speed region. Figure 3 The fluid static pressure cloud map shows the sudden drop and recovery of pressure, and clearly displays the pressure changes before and after the throttling area (inner cone), reflecting the sudden drop in local pressure caused by throttling and whether the downstream pressure gradually recovers. Figure 4 It is a hydrostatic diagram that reflects the acceleration and decompression phenomena during fluid flow.

[0040] As shown in Table 1-2, the differences, errors and advantages between this embodiment and the traditional orifice plate are compared. The results show that the relative error accuracy of flow measurement using the data of this embodiment can be improved by up to 3-10 times compared with the traditional orifice plate measurement and venturi tube flow measurement.

[0041] Table 1 Comparison of flow meter errors after implementation of this embodiment

[0042] Throttling type After typical error calibration Standard orifice plate ±2％～5％ Venturi tube ±0.7％～1.5％ This embodiment ±0.5％～1％

[0043] Note: The specific parameters for this embodiment are cone angle 45°, β=0.6, and Ra≤0.8μm.

[0044] Table 2 Comparison of Error Sources and Advantages of the Conical Throttling Device in this Invention

[0045]

[0046] The working principle of this utility model is as follows:

[0047] The fluid being measured enters the measuring pipe 11 and first passes through the temperature sensing element 1. The temperature value of the fluid is obtained and processed by the temperature transmitter 2 to obtain the temperature correction coefficient A, which is then transmitted to the adder 7. Then, the pressure value of the fluid is obtained by the pressure transmitter 4. The pressure correction coefficient B is obtained by the pressure transmitter 4 and transmitted to the adder 7. At the same time, the initial value setting module 3 transmits the initial value to the adder 7 according to the fluid type, operating conditions, etc. Finally, the fluid flows through the inner conical throttle 5. The differential pressure transmitter 6 detects the pressure at the pressure taps at both ends of the inner conical throttle 5 and transmits the calculated relationship between the fluid flow rate and the differential pressure to the multiplier 8.

[0048] The temperature correction coefficient A and pressure correction coefficient B, along with the initial value, are calculated by addition compensation in adder 7 and then transmitted to multiplier 8. After multiplication with the relationship between fluid flow rate and pressure difference, the product of pressure difference and fluid density is obtained. The result is then transmitted to function calculation square root unit 9 for square root calculation, and finally the mass flow rate of the fluid is obtained and displayed in real time on output unit 10.

[0049] In the inner conical throttling device 5, the presence of the inner cone causes the fluid to be throttled, resulting in a reduction in the flow area and an increase in flow velocity. According to the principle of energy conservation, the static pressure of the fluid will decrease accordingly at the location where the flow velocity increases, forming a static pressure difference before and after throttling. There is a certain mathematical relationship between this pressure difference and the flow velocity. The corresponding mass flow rate can be derived using Bernoulli's equation and the fluid continuity equation as follows:

[0050] The SI unit is kg / s

[0051] In the formula, C is the outflow coefficient; ε is the expandability coefficient; d is the diameter of the circle at the minimum annular gap under operating conditions, corresponding to the maximum cross-section of the pointed cone; and ρ is the diameter of the circle at the minimum annular gap under operating conditions. A D is the fluid density upstream of the throttle under operating conditions; D is the inner diameter of the measuring pipe under operating conditions.

[0052] β is the equivalent diameter ratio of the internal cone flowmeter.

[0053] In this formula, β and d are constants as measurable and calculable data, D is the inner diameter of the measuring pipe under operating conditions, d is the diameter of the circle at the maximum cross-section of the inner cone under operating conditions, and the discharge coefficient C can also be regarded as a constant within a certain range. Therefore, the parameters in the formula other than density and pressure difference can be simplified to k, and the flow rate at this time can be obtained, which is determined by density and pressure difference. When the pressure or temperature of the fluid changes, the density of the fluid will change. If the flow velocity does not change, the differential pressure remains unchanged. The optimal value of the fluid density can be obtained based on the change of fluid pressure or temperature, so that the compensation of temperature and pressure for fluid density can be realized.

[0054] Research shows that changes in temperature or pressure affect fluid density.

[0055] ρ = -0.0055t 2 +0.028t+999.99;

[0056] Fluid density is an important property of fluids, and the relationship between density and temperature is interdependent. When the temperature rises, the molecular motion speed of the fluid increases, the intermolecular distance increases, resulting in a decrease in the number of molecules per unit volume, that is, a decrease in fluid density. The relationship between fluid density and temperature is as follows:

[0057]

[0058] ρ is the working density of the fluid; ρ0 is the fluid density at the reference temperature; β is the coefficient of thermal expansion of the fluid; T is the working temperature of the fluid; T0 is the reference temperature of the fluid.

[0059] The relationship between density and pressure is more complex. In the case of an ideal gas, density can be obtained using the equation of state PV=nRT, where P is the fluid pressure and V is the fluid volume. For non-ideal gases or other fluids, the relationship between density and pressure is more complex, exhibiting complex nonlinear characteristics.

Claims

1. A multi-parameter compensation based internal cone differential pressure flow meter, characterized in that, The application relates to a temperature and pressure transmitter, which comprises an initial value setting module (3), a test module, a transmitter module and a data processing module. The test module comprises a temperature measuring element (1) and an inner conical throttler (5), the temperature measuring element (1) is arranged on the inner wall of the upstream section of the measuring pipeline (11) in the medium flow direction, and the inner conical throttler (5) is coaxially arranged in the downstream section of the measuring pipeline (11) in the medium flow direction, and the head of the inner conical body faces away from the fluid flow direction. The transmitter module comprises a temperature transmitter (2), a pressure transmitter (4) and a differential pressure transmitter (6), the temperature transmitter (2) is electrically connected with the temperature measuring element (1), the pressure transmitter (4) is electrically connected with the inner wall of the pipeline between the temperature measuring element (1) and the inner conical throttler (5), and the differential pressure transmitter (6) is electrically connected with the pressure points on the inner wall of the measuring pipeline (11) at the two ends of the inner conical throttler (5) respectively. The side of the inner conical throttler (5) is a conical body, the bottom surface of the conical body is a circular arc surface, the conical angle of the conical body is 45-60 degrees, the distance from the pressure point upstream of the differential pressure transmitter (6) to the maximum cross section of the conical body of the inner conical throttler (5) is the inner diameter D of the measuring pipeline (11), and the distance from the pressure point downstream to the maximum cross section of the conical body of the inner conical throttler (5) is half of the inner diameter D / 2 of the measuring pipeline (11). The data processing module comprises an adder (7), a multiplier (8) and a square root generator (9), the output ends of the temperature transmitter (2), the initial value setting module (3) and the pressure transmitter (4) are connected with the input end of the adder (7), the output end of the adder (7) is connected with the input end of the multiplier (8), the output end of the multiplier (8) is connected with the input end of the square root generator (9), and the output end of the square root generator (9) is connected with the input end of an output unit (10).

2. A multi-parameter compensated internal cone differential pressure flow meter as claimed in claim 1, wherein, The maximum cross section diameter d of the conical body of the inner conical throttler (5) is (0.6-0.8)D.

3. A multi-parameter compensated internal cone differential pressure flow meter as claimed in claim 1, wherein, The total length of the inner conical throttler (5) is 3-5 times of the inner diameter D of the measuring pipeline (11).

4. A multi-parameter compensated internal cone differential pressure flow meter as claimed in claim 1, wherein, The length of the straight pipeline section of the measuring pipeline (11) upstream of the inner conical throttler (5) is 5-10 times of the inner diameter D of the measuring pipeline (11), and the length of the straight pipeline section downstream is greater than 10 times of the inner diameter D of the measuring pipeline (11).

5. A multi-parameter compensated, internal-cone differential pressure flow meter according to claim 1, wherein, The surface roughness Ra of the inner conical throttler (5) is less than or equal to 0.8 microns.

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