The HY-LUGB vortex street heat transfer oil flowmeter measures the volumetric flow rate, standard condition volumetric flow rate, or mass flow rate of gases, vapors, or liquids based on the Karman vortex street principle. And it can be used as a flow transmitter in applications and automation control systems. The instrument adopts advanced differential technology, combined with isolation, shielding, filtering and other measures, to overcome the problems of poor seismic resistance and small signal disorder of similar products. It also adopts special sensor packaging technology and protective measures to ensure the reliability of the product. There are two forms of products: basic type and composite type. The basic type measures a single flow signal, while the composite type can uniformly measure temperature, pressure, and flow. Each form has a whole or separate structure to suit different installation environments.

The HY-LUGB vortex street heat transfer oil flowmeter is equipped with a triangular cylindrical vortex generator in the fluid, which alternately generates regular vortices from both sides of the vortex generator. This type of vortex is called a Karman vortex, as shown in Figure 1. The vortex columns are asymmetrically arranged downstream of the vortex generator.

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

F=SrV1/d=SrV/md

In the formula, V1 represents the average velocity on both sides of the vortex generator, m/s；

Sr Strouhal number;

M - The ratio of the bow shaped area on both sides of the vortex generator to the cross-sectional area of the pipeline

The volumetric flow rate qv inside the pipeline is

Qv=π D2V/4=π D2mdf/4Sr

K=f/qv=[π D2md/4Sr] -1

In the formula, K represents the instrument coefficient of the flowmeter, with pulse count in m3 (P/m3).

K is not only related to the geometric dimensions of the vortex generator and pipeline, but also to the Strouhal number. The Strouhal number is a dimensionless parameter that is related to the shape of the vortex generator and the Reynolds number,

The relationship between Strouhal number and Reynolds number of vortex flowmeter

Within the range of ReD=2 × 104 to 7 × 106, Sr can be regarded as a constant, which is the normal operating range of the instrument. When measuring gas flow rate, the flow calculation formula for VSF is

In the equation, qVn and qV - represent the volumetric flow rates under standard conditions (0oC or 20oC, 101.325kPa) and operating conditions, respectively, m3/h；

Pn and P - are the absolute pressures under standard and operating conditions, respectively, Pa；

Tn and T - are the thermodynamic temperatures under standard and operating conditions, respectively, K；

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

As can be seen from the above equation, the pulse frequency signal output by VSF is not affected by fluid properties and composition changes, that is, the instrument coefficient is only related to the shape and size of the vortex generator and pipeline within a certain Reynolds number range. However, as a flowmeter in material balance and energy measurement, it is necessary to detect mass flow rate. At this time, the output signal of the flowmeter should simultaneously monitor volume flow rate and fluid density. Fluid properties and components still have a direct impact on flow measurement.

1. No movable parts, long-term stability, simple structure for easy installation and maintenance

2. The sensor output is a pulse frequency, which is linear with the actual flow rate of the measured fluid. There is no zero drift, and the performance is very stable. There are various structural forms, including pipeline insertion flow sensors

3. High precision, typically with a measurement accuracy of ± 1% for liquids; The measurement accuracy of gas is ± 1.5%

4. The measurement range is wide, reaching up to 1:20 within the Reynolds number range of 2 × 10 ⁴~7 × 10 ⁶

5. Low pressure loss (about 1/4~1/2 of orifice flowmeter), belonging to energy-saving flow meters

6. The installation method is flexible, and it can be installed horizontally, vertically, and at different angles according to the different process pipelines on site

7. Adopting anti-interference circuit and anti vibration sensing head, it has certain anti environmental vibration performance

8. Using ultra-low power single-chip microcomputer technology, one 3V10AH lithium battery can be used for more than 5 years

9. Correction of instrument coefficient nonlinearity by software to improve measurement accuracy

10. Using EEPROM for power down protection of accumulated traffic, with a protection time greater than 10 years