1、 Measurement principle of ZY-LU steam vortex flowmeter:

When a triangular cylindrical vortex generator is set up in the fluid, regular vortices are alternately generated from both sides of the vortex generator, which are called Karman vortices. As shown in the figure on the right, 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 face of the vortex generator is d, and the diameter of the body is D, the following relationship can be obtained:

（1）f=SrU1/d=SrU/md

In the formula, U1 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

(2)qv=πD2U/4=πD2mdf/4Sr

(3)K=f/qv=[πD2md/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. Figure 2 shows the relationship between the Strouhal number of a cylindrical vortex generator and the Reynolds number of a pipeline. As shown in the figure, Sr can be regarded as a constant within the range of ReD=2 × 104 to 7 × 106, 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 positive 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.

A vortex flowmeter is a flowmeter that measures fluid flow in a closed pipeline based on the Karman vortex principle. Due to its excellent medium adaptability, it can directly measure the volumetric flow rate of steam, air, gas, water, and liquid without temperature and pressure compensation. Equipped with temperature and pressure sensors, it can measure standard volumetric flow rate and mass flow rate, making it an ideal alternative to throttling flow meters.

In practical applications, the flow rate is often much lower than the upper limit value of the instrument. With changes in load, the minimum flow rate often falls below the lower limit value of the instrument. The instrument does not work in its working section. To solve this problem, it is usually used to reduce the diameter at the measuring point to increase the flow velocity at the measuring point, and smaller diameter instruments are selected to facilitate the measurement of the instrument. However, this variable diameter method has a straight pipe section with a length of more than 15D between the variable diameter tube and the instrument for rectification, which makes processing and installation inconvenient. The LGZ variable diameter rectifier with a curved longitudinal section has multiple functions such as rectification, increasing flow velocity, and changing flow velocity distribution. Its structural size is small, only one-third of the inner diameter of the process pipe, integrated with the vortex flowmeter. It not only does not require an additional straight pipe section, but also reduces the requirements for the straight pipe section of the process pipe, making installation very convenient.

For the convenience of use, the battery powered local display vortex flowmeter adopts low-power high-tech. It can operate continuously for more than a year with lithium battery power supply, saving the procurement and installation costs of cables and display instruments. It can display instantaneous flow, cumulative flow, etc. on site. The temperature compensated integrated vortex flowmeter also comes with a temperature sensor, which can directly measure the temperature of saturated steam and calculate the pressure, thereby displaying the mass flow rate of saturated steam. The temperature pressure compensation integrated type is equipped with temperature and pressure sensors, which can directly measure the temperature and pressure of the gas medium for gas flow measurement, thereby displaying the standard volume flow rate of the gas.

2、 Technical parameters of steam vortex flowmeter:

1. Measurement medium: gas, liquid, vapor;

2. The caliber specification for flange card mounted calibers is 25, 32, 50, 80, and 100;

3. Flange connection type with a diameter of 100, 150, 200;

4. Flow measurement range Normal measurement flow velocity range Reynolds number 1.5 × 104~4 × 106; Gas velocity of 5-50m/s; Liquid 0.5-7m/s;

The normal measurement range for liquid and gas flow is shown in Table 2; The steam flow range is shown in Table 3
5. Measurement accuracy of 1.0 level and 1.5 level;

6. Temperature of the tested medium: normal temperature -25 ℃ to 100 ℃;

7. High temperature -25 ℃~150 ℃ -25 ℃~250 ℃;

8. Output signal pulse voltage output signal high level 8-10V low level 0.7-1.3V;

9. The pulse duty cycle is about 50%, and the transmission distance is 100m;

10. Pulse current remote transmission signal 4-20 mA, transmission distance of 1000m;

11. Instrument operating environment temperature: -25 ℃~+55 ℃ humidity: 5-90% RH50 ℃;

12. Material: stainless steel, aluminum alloy;

13. Power supply DC24V or lithium battery 3.6V;

14. Explosion proof grade intrinsic safety type iaIIbT3-T6;

15. Protection level IP65.

3、 Flow Range Table of Steam Vortex Flow Meter:

Table 1: Liquids and Gases (Unit: m³/h):

orifice （DN）

L （mm）

H （mm）

10

66

360

15

66

360

20

66

360

25

66

360

32

66

365

40

80

370

50

80

375

65

93

383

80

100

390

100

125

400

125

145

470

150

165

500

200

196

580

250

235

650

300

255

700

5 Installation diagram of vortex flowmeter:

precautions

legend

1. Installation of expansion pipe: For small caliber large flow, expansion installation is required, while ensuring that the front straight pipe section of the flowmeter is ≥ 15D and the rear straight pipe section is ≥ 5D

2. Installation of shrink tubing: For large caliber and small flow, shrink fit installation should be carried out while ensuring that the front straight pipe section of the flowmeter is ≥ 15D and the rear straight pipe section is ≥ 5D

3. Installation of bent pipes: If the front end of the flowmeter has a 90 ° elbow or T-shaped joint, it is necessary to ensure that the front straight pipe section of the flowmeter is ≥ 15D and the rear straight pipe section is ≥ 5D

4. Installation of two bent pipes on the same plane If there are two 90 ° elbows at the front end of the flowmeter, it is necessary to ensure that the front straight pipe section of the flowmeter is ≥ 20D and the rear straight pipe section is ≥ 5D

5. Installation of two curved pipes in different planes If there are two 90 ° elbows at the front end of the flowmeter, it is necessary to ensure that the front straight pipe section of the flowmeter is ≥ 25D and the rear straight pipe section is ≥ 5D

6. Installation of regulating valve If regulating valves need to be installed before and after the flowmeter, it is necessary to ensure that the front straight pipe section of the flowmeter is ≥ 25D and the rear straight pipe section is ≥ 5D

lsixVortex flowmeter selection table:

ZY-LU

Intelligent vortex flowmeter

caliber （mm）

10

DN10

20

DN20

…

…

1500

DN1500

Installation method

B

wafer type

L

Flange connection type

C

plug-in

Compensation method

not have

No compensation

BC

temperature and pressure compensation

W

Single temperature compensation

Y

Single pressure compensation

Measurement medium

Y

liquid

Q

gas

Z

steam

temperature range

T1

Room temperature type (below 120 ℃)

T2

High temperature type (below 250 ℃)

pressure rating

P1

Normal pressure~1.6MPa

P2

2.5MPa

P3

4.0MPa

BODY MATERIAL

A

carbon steel

B

304 stainless steel

C

316 stainless steel

Power supply mode

D

Two wire system DC24V 4-20mA

H

Two wire DC24V 4-20mA+HART protocol

C

On Battery

Additional Options

R

RS485 MODBUS communication protocol

M

pulse output

B

Explosion proof (ExII CT6)