Vortex Flowmeter_Anhui Honglin Instrument Cable Co., Ltd.

Vortex Flowmeter

Vortex flowmeter is mainly used for the flow measurement of industrial pipeline medium fluid, such a…

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Description

application
Vortex flowmeter is mainly used for the flow measurement of industrial pipeline medium fluid, such as gas, liquid, steam and other media. It is characterized by small pressure loss, large measuring range and high precision. It is hardly affected by the parameters such as fluid density, pressure, temperature and viscosity when measuring the volume flow. There is no movable mechanical parts, so the reliability is high and the maintenance is small. The instrument parameters can be stable for a long time. The vortex flowmeter adopts piezoelectric stress sensor with high reliability, which can work in the temperature range of - 20 ℃ to + 250 ℃. It has analog standard signal and digital pulse signal output. It is easy to use with computer and other digital systems. It is an advanced and ideal flow meter.
principle
If the triangular cylinder vortex generator is set in the fluid, regular vortices will be generated alternately from both sides of the vortex generator. This kind of vortex is called Carmen vortex. As shown in Fig. 1, the vortex array is asymmetrically arranged downstream of the vortex generator.

涡街流量计漩涡形成示意图

Suppose that the frequency of the vortex is f, the average velocity of the measured medium is, the width of the upstream surface of the vortex generator is D, and the path of the body is D, the following formula can be obtained:

　f=SrV1/d=SrV/md 　　　　　　　　　　　　　　　　　　　　（1）
Where V1 is the average velocity on both sides of vortex generator, M / S;
SR -- Strouhal number;
M -- the ratio of the arcuate area on both sides of the vortex generator to the cross-sectional area of the pipeline

The volume flow rate in the pipeline QV is
　　　　　　　　　　　　 qv=πD2V/4=πD2mdf/4Sr 　　　　　　　　　　　　　　　　(2)
　　　　　　　　　　　　 K=f/qv=[πD2md/4Sr]-1 　　　　　　　　　　　　　　　　 (3)
Where k is the instrument coefficient of flowmeter, pulse number / m3 (P / m3).
K is not only related to the geometry of vortex generator and pipe, but also to Strouhal number. Strouhal number is a dimensionless parameter, which is related to the shape of vortex generator and Reynolds number,

涡街流量计斯特罗哈数与雷诺数的关系
Fig. 2 shows the relationship between the Strouhal number of the cylindrical vortex generator and the Reynolds number of the pipe. As can be seen from the figure, in red = 2 × 104~7 × In the range of 106, SR can be regarded as a constant, which is the normal operating range of the instrument. When measuring the gas flow rate, the flow calculation formula of VSF is (4)
Fig. 2 relation curve between Strouhal number and Reynolds number
Where qvn, QV -- volume flow under standard conditions (0oC or 20oC, 101.325kpa) and working conditions, m3 / h
PN, P -- respectively the pressure of ￥ under standard state and working condition, PA;
TN, T -- thermodynamic temperature under standard state and working condition respectively, K;
Zn, Z -- compression coefficient of gas under standard state and working condition respectively.
It can be seen from the above formula that the pulse frequency signal output by VSF is not affected by the change of fluid physical properties and components, that is, the instrument coefficient is related to the shape and size of vortex generator and pipe in a certain range of Reynolds number. However, as a flowmeter, it needs to detect mass flow in material balance and energy measurement. At this time, the output signal of flowmeter should monitor the volume flow rate and fluid density at the same time. The physical properties and components of fluid have a direct impact on the flow measurement.
Vortex flowmeter is a new type of flowmeter which is based on the principle of Karman vortex to measure the fluid flow in a closed pipe. Because of its good medium adaptability, it can directly measure the volume flow of steam, air, gas, water and liquid without temperature and pressure compensation. Equipped with temperature and pressure sensors, it can measure the volume flow and mass flow under standard conditions. It is an ideal substitute for throttling flowmeter.
In order to improve the high temperature resistance and vibration resistance performance of vortex flowmeter, our company has recently developed an improved sklu vortex flow sensor. Because of its special structure and material selection, the sensor can be used in the harsh working conditions of high temperature (350 ℃) and strong vibration (≤ 1g).
In practical application, the high flow rate is often much lower than the upper limit value of the instrument. With the change of load, the small flow rate is often lower than the lower limit value of the instrument. The instrument does not work in its good working section. In order to solve this problem, it is usually adopted to reduce the diameter at the measuring point to increase the flow rate at the measuring point, and select the instrument which is more than ≡ to facilitate the measurement of the instrument, However, in this way, there must be a straight pipe section with a length of more than 15d between the reducer and the instrument for rectification, which makes the processing and installation inconvenient. The LGZ variable diameter rectifier with arc profile developed by our company has multiple functions of rectifying, increasing flow rate and changing velocity distribution. Its structure size is small, * * is 1 / 3 of the inner diameter of process pipe. It is integrated with vortex flowmeter. It does not need to add another straight pipe section. It can also reduce the requirements for straight pipe section of process pipe and is very convenient for installation.
In order to use conveniently, the battery powered local display vortex flowmeter adopts micro power consumption high-tech. lithium battery power supply can operate continuously for more than one year, saving the purchase and installation costs of cables and display instruments, and can display instantaneous flow and cumulative flow on site. The integrated vortex flowmeter with temperature compensation also has a temperature sensor, which can directly measure the temperature of saturated steam and calculate the pressure, so as to display the mass flow rate of saturated steam. The temperature and pressure compensation system is equipped with temperature and pressure sensors for gas flow measurement. It can directly measure the temperature and pressure of gas medium and display the volume flow of gas under standard condition.
Measuring medium: gas, liquid and vapor
Select 25,32,50,80100 for flange clamping type
The diameter of flange connection is 100150200
Flow measurement range normal measurement flow rate range Reynolds number 1.5 × 104~4 × 106； The gas is 5-50m / s; Liquid 0.5 ~ 7m / S
The normal flow measurement range of liquid and gas is shown in Table 2; See Table 3 for steam flow range
The measurement accuracy is 1.0 and 1.5
Temperature of measured medium: 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
The duty cycle of pulse is about 50%, and the transmission distance is 100m
The long-distance transmission signal of pulse current is 4-20 mA, and the transmission distance is 1000m
Environment temperature: - 25 ℃～ + 55 ℃, humidity: 5 ～ 90% Rh50 ℃
Material: stainless steel, aluminum alloy
Power supply DC24 V or lithium battery 3.6 V
Explosion proof intrinsically safe iaiibt3-t6

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