High temperature vortex flowmeter

High temperatureVortex FlowmeterBased on the principle of Karman vortex street measurement, it is mainly used to measure the flow rate of gases, liquids, vapors and other fluids in industrial pipelines. The characteristics of vortex street flowmeter are low pressure loss, large range, and no movable mechanical parts, so it has high reliability and low maintenance. It can work in the temperature range of -20 ℃ to+350 ℃ and is widely used.

Working principle of high-temperature vortex flowmeter:

If a non streamlined vortex generator (fluid barrier) is set up in the fluid, two regular vortices are alternately generated from both sides of the vortex generator. This type of vortex is called a Karman vortex street, as shown in the figure.

Specification parameters of high-temperature vortex flowmeter:

Calculation formula for high-temperature vortex flowmeter:

The vortex column is arranged asymmetrically downstream of the vortex generator. Assuming the frequency of vortex occurrence is f, the average velocity of the measured medium flow is V, the width of the upstream face of the vortex generator is d, and the diameter of the body is D. According to the principle of Karman vortex street, the following relationship is obtained:

F=StV/d

In the formula:

Frequency of Karman vortex generated on one side of the f-body

St Strouhal number (dimensionless number)

The average flow velocity of V-fluid

The width of the vortex generator

From this, it can be seen that the instantaneous flow rate can be calculated by measuring the separation frequency of the Karman vortex street.

Measurement range of high-temperature vortex flowmeter:

Characteristics of high-temperature vortex flowmeter:

1. Small pressure loss, large range, high accuracy, and almost unaffected by fluid density, pressure, temperature, viscosity, and other parameters when measuring volumetric flow rate under working conditions.

2. No movable mechanical parts, therefore high reliability and low maintenance. The instrument parameters can remain stable for a long time.

3. This instrument uses piezoelectric stress sensors with high reliability and can operate within a temperature range of -25 ℃ to+320 ℃.

4. There are analog standard signals and digital pulse signal outputs, which are easy to use in conjunction with digital systems such as computers.

Precautions for installation of high-temperature vortex flowmeter:

1. Vortex flowmeter can be installed indoors or outdoors. If installed in underground wells, there is a possibility of flooding, and submersible sensors should be selected. Sensors can be installed horizontally, vertically, or obliquely on pipelines, but when measuring liquids and gases, attention should be paid to the installation position to prevent interference from bubbles and droplets, as shown in Figure 1.

2. The vortex flowmeter must ensure that the upstream and downstream straight pipe sections have the necessary length, as shown in Figure 2. There are differences in data among various sources, which may be due to the lack of standardization of vortex generators, and the impact of differences in shape and size remains to be verified; The experimental research on the necessary length of straight pipe sections for various types of flow blocking components is still insufficient, that is, it is not yet mature. Compared with throttling differential pressure flow meters, this work is still in its initial stage.

3. The connection between the sensor and the pipeline is shown in Figure 3. Pay attention to the following issues when connecting with pipelines.

1) The inner diameter D of the upstream and downstream piping is the same as the inner diameter D 'of the sensor, and the difference satisfies the following condition: 0.95D ≤ D' ≤ 1.1D.

2) The piping should be concentric with the sensor, and the coaxiality should not be less than 0.05D '

3) The sealing gasket cannot protrude into the pipeline, and its inner diameter can be 1-2mm larger than the inner diameter of the sensor

4) If a cut-off inspection and cleaning of the sensor is required, a bypass pipeline should be installed as shown in Figure 4.

5) The impact of small source vibrations on vortex flowmeters should be addressed as a prominent issue during on-site installation of vortex flowmeters. Firstly, when selecting the installation location for sensors, try to avoid vibration sources as much as possible. Secondly, elastic hose connection can be considered in China. Thirdly, installing pipeline supports is an effective method of vibration reduction.

4. Electrical installation should pay attention to using shielded cables or low-noise cables to connect sensors and converters, and the distance should exceed the specifications in the user manual. When wiring, it should be kept away from high-power power lines and protected with separate metal sleeves as much as possible. The principle of "one point grounding" should be followed, and the grounding resistance should be less than 10 Ω. Both integral and separated types should be grounded on the sensor side, and the grounding point of the converter housing should be "same ground" as the sensor.