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technical article
Gas vortex flowmeter with good medium adaptability
2012-2-9 10:35:12

主要用于工业管道中蒸汽介质流体的流量测量,蒸汽涡街流量计特点是压力损失小,量程范围大,精度高,在测量工况体积流量时几乎 The DEC-LU series gas vortex flowmeter is mainly used for the flow measurement of steam medium fluid in industrial pipelines. The characteristics of the steam vortex flowmeter are small pressure loss, large range and high accuracy.

Not affected by fluid density, pressure, temperature, viscosity and other parameters. No moving mechanical parts, so high reliability and low maintenance. Instrument parameters can be stable for a long time. When a triangular cylindrical vortex generator is set in a steam fluid,

Regular vortices are alternately generated on both sides of the vortex generator. This vortex is called a Carmen vortex. As shown in the figure on the right, the vortex rows are arranged asymmetrically downstream of the vortex generator.


Suppose the frequency of vortex occurrence is f, the average flow velocity of the measured medium is, the width of the front surface of the vortex generator is d, and the diameter of the surface body is D, then the following relationship can be obtained:


f = SrU1 / d = SrU / md (1)


Where U1 is the average flow velocity on both sides of the vortex generator, m / s;


Sr-Strauhal number;


m-the ratio of the arcuate area on both sides of the vortex generator to the cross-sectional area of the pipe


The volume flow qv in the pipeline is


qv = πD2U / 4 = πD2mdf / 4Sr (2)


K = f / qv = [πD2md / 4Sr] -1 (3)


In the formula, K is the meter coefficient of the flow meter, and the number of pulses / m3 (P / m3).


K is related not only to the geometry of the vortex generator and the pipeline, but also to the Strouhal number. Strouhal number is a dimensionless parameter, which is related to the shape of the vortex generator and Reynolds number. Figure 2 shows a cylindrical vortex generator

Diagram of the relationship between Strouhal number and pipeline Reynolds number. In the range of ReD = 2 × 104 ~ 7 × 106, Sr can be regarded as a constant, which is the normal working range of the meter. When measuring the gas flow, the VSF flow calculation formula is (4)


Figure 2 Relationship between Strauhal number and Reynolds number


Where qVn and qV are the volume flow under standard conditions (0oC or 20oC, 101.325kPa) and working conditions, m3 / h;


Pn, P-absolute pressures under standard conditions and working conditions, Pa;


Tn, T-the thermodynamic temperature under standard conditions and working conditions, K;


Zn, Z-the gas compression coefficients under standard conditions and working conditions, respectively.


It can be seen from the above formula that the pulse frequency signal output by VSF is not affected by the fluid physical properties and composition changes, that is, the meter coefficient is only related to the shape and size of the vortex generator and the pipeline within a certain Reynolds number range. But as a flow meter

In mass balance and energy measurement, it is necessary to detect the mass flow. At this time, the output signal of the flow meter should monitor the volume flow and fluid density at the same time. The physical properties and components of the fluid have a direct impact on the flow measurement.


Gas vortex flowmeter is a new type of flowmeter for measuring fluid flow in closed pipes based on the Carmen vortex principle. Because of its good media adaptability, it can directly measure steam, air, gas,

Water and liquid working volume flow, equipped with temperature and pressure sensors can measure standard volume flow and mass flow. It is an ideal substitute for throttling flow meters.


的耐高温及抗振动性能,我公司新近开发出了SKLUG改进型涡街流量传感器,因其独特的结构和选材使该传感器可在高温(350℃)、 In order to improve the high temperature resistance and vibration resistance of gas vortex flowmeters , our company has recently developed an improved SKLUG vortex flow sensor. Due to its unique structure and selection of materials, the sensor can be used at high temperatures (350 ° C),

Use under severe working conditions with strong vibration (≤1g).


In practical applications, the maximum flow rate is often much lower than the upper limit value of the meter. As the load changes, the minimum flow rate is often lower than the lower limit value of the meter. The meter is not working in its optimal working section. A question,

Usually reduce the diameter at the measurement to increase the flow rate at the measurement, and choose a smaller diameter instrument to facilitate the measurement of the instrument, but this method of reduction must be straightened between the reducer and the instrument with a straight pipe length of 15D or more. ,

Makes processing and installation inconvenient. The LGZ variable diameter rectifier developed by our company has a circular arc shape. It has multiple functions of rectifying, increasing the flow velocity and changing the flow velocity distribution. Its structure size is small, only 1/3 of the inner diameter of the process tube.

It is integrated with the vortex flowmeter, which not only does not need to add another straight pipe section, but also reduces the requirements for the straight pipe section of the process pipe, which is very convenient to install.


For the convenience of use, the battery-powered in-situ display type gas vortex flowmeter adopts micro power consumption high-tech. It can be operated continuously for more than one year by using lithium battery power.

Ground display instantaneous flow, cumulative flow, etc. The temperature compensation integrated vortex flowmeter also has a temperature sensor, which can directly measure the temperature of the saturated steam and calculate the pressure, thereby displaying the mass flow of the saturated steam. Temperature and pressure compensation

The compensation type has temperature and pressure sensors for gas flow measurement, which can directly measure the temperature and pressure of the gas medium, thereby displaying the standard volume flow of the gas.


The gas vortex flowmeter uses a piezoelectric stress sensor with high reliability and can work in the operating temperature range of -20 ° C to + 250 ° C. There are analog standard signals and digital pulse signal output, which is easy to match with digital systems such as computers.

Is a relatively advanced and ideal flow meter.


Measurement medium: gas, liquid, vapor


◆ Caliber specifications: Flange-mounted flange diameter: 25, 32, 50, 80, 100


◆ Flange connection caliber selection: 100, 150, 200


◆ Flow measurement range Normal measurement flow range Reynolds number 1.5 × 104 ~ 4 × 106; gas 5 ~ 50m / s; liquid 0.5 ~ 7m / s


Normal measurement flow range Liquid and gas flow measurement range; Vapor flow range


◆ Measurement accuracy 1.0 grade 1.5 grade


◆ Measured medium temperature: normal temperature -25 ℃ ~ 100 ℃


◆ High temperature-25 ℃ ~ 150 ℃ -25 ℃ ~ 250 ℃


◆ Output signal pulse voltage output signal high level 8 ~ 10V low level 0.7 ~ 1.3V


◆ Pulse duty is about 50%, transmission distance is 100m


◆ Pulse current remote transmission signal 4 ~ 20 mA, transmission distance is 1000m


◆ Using ambient temperature of the meter: -25 ℃ ~ + 55 ℃ Humidity: 5 ~ 90% RH50 ℃


◆ Material stainless steel, aluminum alloy


◆ Power DC24V or lithium battery 3.6V


◆ Explosion-proof grade intrinsically safe iaIIbT3-T6 protection grade IP65

Common faults and causes of gas vortex flowmeters

The gas vortex flowmeter uses a triangular cylindrical vortex generator in the fluid, and regularly generates vortices alternately from both sides of the vortex generator. This vortex is called a Carmen vortex (similar to the floating of the flag behind the flagpole)

The frequency of this vortex is proportional to the flow velocity.


Gas vortex flowmeters are mainly used to measure the flow of medium fluids in industrial pipelines, such as gases, liquids, vapors and other media. At present, there are many domestic manufacturers of vortex flowmeters, and the quality of their products is also uneven.

There are also many problems in the use process, which cause a lot of inconvenience to the user. Here are some of the main problems and causes of vortex flowmeters for users' reference.

First, the common problems of gas vortex flowmeters are:


1. Always without instructions;


2. The instructions are not allowed for a long time;


3. The instruction does not return to zero;


4. Indication of large-scale fluctuations, unable to read;


5. The indication is okay when the flow is large, and the indication is not accurate when the flow is small;


6, no indication at small flows;


7. Indication change cannot keep up when the flow changes;


8. The K factor of the instrument cannot be determined, and the data are inconsistent in many places.

2. Summarize the main causes of these problems, mainly related to the following aspects:


1. Problems occurred during selection.


The lower measurement limit of this main gas vortex flowmeter is determined. Some vortex sensors have a large selection on the caliber selection or after design selection due to process conditions changes. The actual selection should be as small as possible

In order to improve the measurement accuracy, for example, a vortex street pipeline is designed for several devices. Because the process part of the equipment is sometimes not used, the current actual use flow is reduced, and the actual use causes the original design selection port.

If the diameter is too large, it is equivalent to increasing the lower limit of the measurable flow rate. The indication cannot be guaranteed when the flow rate of the process pipeline is small. It can also be used when the flow rate is large, because it is sometimes too difficult to rebuild. Changes in process conditions are only temporary.

Can be combined with parameter re-tuning to improve the indication accuracy.


2. A problem occurred during installation.


The main reason is that the length of the straight pipe section in front of the sensor is not enough, which affects the measurement accuracy. For example, the installation point is too close to the pump, regulating valve and other equipment, which may cause vibration to affect the measurement during work, or there may be other vibration, high frequency and high pressure near the installation.

The equipment affects the normal operation of the flow meter.


3. Problems with instrument settings.


Due to the wrong parameter setting, the meter indication is incorrect. Mainly check the meter coefficient, set pressure (temperature) and actual working pressure (temperature).


4. Problems with signal line connection.


Some circuits look good on the surface of the circuit. Carefully check that some connectors are actually loose and cause the circuit to be interrupted. Although some connectors are tightly connected, the screws are fastened to the wire cover due to the problem of the auxiliary line, which also makes the circuit Break.


5. The connection between the secondary instrument and the subsequent instrument. The mA output circuit of the secondary instrument was interrupted due to a problem with the subsequent instrument or the maintenance of the subsequent instrument. For this type of secondary instrument, especially for the latter instrument,

For continuous recorders, if the recorder is damaged for a long time and cannot be repaired, be sure to pay attention to shorting the output of the secondary meter.


6, the use of environmental issues.

Especially the sensor part installed in the ground well, due to the high ambient humidity, which caused the circuit board to be damp. Through corresponding technical reform measures, some sensors with high ambient humidity were re-separated from the probe part and the conversion part.

The processing was changed to a separate sensor, so the working environment was improved, and this part of the instrument was running well a few days ago.


7, due to the on-site adjustment is not good, or due to the actual situation after the adjustment.


Due to poor on-site vibration and noise balance adjustment and sensitivity adjustment. Or because of changes in the on-site conditions after running for a period of time after adjustment, causing indication problems. 都有灵敏度 General gas vortex flowmeters have sensitivity

And the adjustment of the trigger level can be adjusted appropriately at the scene.


8. The last thing to pay attention to is the conversion of flow units.


Such situations are also more common on the site. Pay special attention to the conversion of mass and volume, volume standard flow and working flow.