Vortex flowmeter application
DXLU series vortex flowmeter is mainly used to measure the flow of medium fluid in industrial pipelines, such as gas, liquid, vapor and other media. It is characterized by small pressure loss, large measuring range and high accuracy. It is hardly affected by parameters such as fluid density, pressure, temperature, and viscosity when measuring working volume flow. No moving mechanical parts, so high reliability and low maintenance. Instrument parameters can be stable for a long time. The vortex flowmeter uses a piezoelectric stress sensor with high reliability, and can work in the operating temperature range of -20 ℃ ～ + 250 ℃. It has analog standard signal and digital pulse signal output. It is easy to be used with digital systems such as computers. It is a relatively advanced and ideal flow meter.
The principle of the vortex flowmeter is to set a triangular cylindrical vortex generator in the fluid, and regular vortices are alternately generated from both sides of the vortex generator. This vortex is called a Carmen vortex. As shown in the figure, the vortex is arranged downstream of the vortex generator. Asymmetrically arranged.
Suppose the frequency of vortex occurrence is f, the average flow velocity of the measured medium is
f = SrU1 / d = SrU / md (1)
Where U1--average flow velocity on both sides of the vortex generator, m / s;
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 in the pipe 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. The Strouhal number is a dimensionless parameter, which is related to the shape of the vortex generator and the Reynolds number. Figure 2 shows the relationship between the Strawhall number of the cylindrical vortex generator and the Reynolds number of the pipeline. It can be seen from the figure that 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
Figure 2 Strouhal number and Reynolds number curve qVn, qV--the volume flow under standard conditions (0oC or 20oC, 101.325kPa) and working conditions, m3 / h;
Pn, P--absolute pressure under standard conditions and working conditions, Pa;
Tn, T-the thermodynamic temperature under standard conditions and working conditions, K;
Zn, Z--respectively the gas compression coefficients under standard conditions and working conditions.
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 needs to detect the mass flow in the material balance and energy measurement, the output signal of the flow meter should monitor the volume flow and fluid density at the same time. The fluid properties and components have a direct impact on the flow measurement.
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 medium adaptability, it can directly measure the working volume flow of steam, air, gas, water, and liquid without temperature and pressure compensation. Equipped with temperature and pressure sensors, it can measure standard volume flow and mass flow, which is throttling. The ideal replacement for the flow meter.
In order to improve the high temperature resistance and vibration resistance of the vortex flowmeter, the DXLU improved vortex flow sensor. Due to its unique structure and selection of materials, the sensor can be used under severe conditions of high temperature (350 ° C) and strong vibration (≤1g). Use.
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. One problem is usually to reduce the diameter at the measurement site to increase the flow velocity at the measurement site, and choose a smaller diameter instrument to facilitate the measurement of the instrument, but this method of diameter reduction must have a straight length of 15D or more between the reducer and the instrument. Pipe sections are rectified, making processing and installation inconvenient. 涡街流量计作成一体，不仅不需要另外附加一段直管段，还可以降低对工艺管直管段的要求，安装非常方便。 The LGZ variable diameter rectifier with a circular arc shape has multiple functions of rectifying, increasing the flow rate and changing the flow rate distribution. Its small structure size is only 1/3 of the inner diameter of the process tube. It is integrated with the vortex flowmeter. In addition, the addition of a straight pipe section can also reduce the requirements for the straight pipe section of the process pipe, and the installation is very convenient.
涡街流量计 采用微功耗高新技术，采用锂电池供电可不间断运行一年以上，节省了电缆和显示仪表的采购安装费用，可就地显示瞬时流量、累积流量等。 For the convenience of use, the battery-powered local display-type vortex flowmeter uses micro-power high-tech. It can be operated continuously for more than one year using lithium battery power, which saves the procurement and installation costs of cables and display instruments. It can display instantaneous flow rates, Cumulative flow, etc. 一体型涡街流量计还带有温度传感器，可以直接测量出饱和蒸汽的温度并计算出压力，从而显示饱和蒸汽的质量流量。 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 integrated type with temperature and pressure sensors for gas flow measurement can directly measure the temperature and pressure of the gas medium, thereby displaying the standard volume flow of the gas.
◆ Measuring medium: gas, liquid, vapor ◆ caliber specifications flange-mounted caliber selection 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 See Table 2 for liquid and gas flow measurement ranges; Table 3 for vapor flow range
◆ Measurement accuracy 1.0 grade 1.5 grade ◆ 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
◆ 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
◆ Ex-grade intrinsically safe iaIIbT3-T6
Protection class IP65
产品选型 Vortex flowmeter product selection
The way to
Flow range ㎡ / h
1 ~ 10 (liquid)
25 ~ 60 (gas)
Please refer to the instruction manual for steam flow rate. Insertion vortex flowmeter is recommended for DN300
1.5 ~ 18 (liquid)
15 ~ 150 (gas)
2.2 ~ 27 (liquid)
22.6 ~ 150 (gas)
4 ~ 55 (liquid)
35 ~ 350 (gas)
9 ~ 135 (liquid)
90 ~ 900 (gas)
14 ~ 200 (liquid)
140 ~ 1400 (gas)
32 ~ 480 (liquid)
300 ~ 3000 (gas)
56 ~ 800 (liquid)
550 ~ 5500 (gas)
No temperature and pressure compensation
With temperature and pressure compensation
4-20mA output (two-wire system)
4-20mA output (three-wire system)
RS485 communication interface
Internal 3.6V power supply
DC24V power supply