Schematic diagram of vortex flowmeter| Maanshan ultrasonic flowmeter manufacturer

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1. Working principle of vortex flowmeter

Under specific flow conditions, a portion of the fluid kinetic energy is converted into fluid vibration, and its vibration frequency has a certain proportional relationship with the flow rate (flow rate). A flowmeter that works based on this principle is called a fluid vibration flowmeter. At present, there are three types of fluid vibration flow meters: vortex street flow meters, vortex precession flow meters, and jet flow meters. Vortex flow juice (hereinafter referred to as VSF) is equipped with a vortex generator (blocking fluid) in the fluid, which alternately generates regular vortices from both sides of the vortex generator. This type of vortex is called a Karman vortex street, as shown in Figure 1. The vortices are arranged asymmetrically downstream of the vortex generator. Assuming the frequency of vortex occurrence is f, the average velocity of the measured medium flow is U, the width of the vortex generator face is d, and the diameter of the body is D. According to the principle of Karman vortex street, there is the following relationship: f=SrU1/d=SrU/md

(1), where U1- the average velocity on both sides of the vortex generator, m/s； Sr Strouhal number; The ratio of the arch area on both sides of the m - vortex generator to the cross-sectional area of the pipeline is shown in Figure 1. The volumetric flow rate qv in the Karman vortex street pipeline is qv=π D2U/4=π D2mdf/4Sr (2) K=f/qv=[π D2md/4Sr] -1 (3). The instrument coefficient of the K-flowmeter is the number of pulses per cubic meter (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 dimensionle

ss 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 (4). In Figure 2, the relationship curve between Strouhal number and Reynolds number, where qVn and qV - are the volumetric flow rates under standard conditions (0oC or 20oC, 101.325kPa) and operating conditions, respectively, m3/h； Pn, P - are the absolute pressures under standard and operating conditions, Pa; Tn, T - are the thermodynamic temperatures under standard and operating conditions, K; Zn, Z - are the gas compression coefficients under standard and operating 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, it is necessary to detect mass flow rate in material balance and coarse bucket tank energy measurement. 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.

2. Why is temperature and pressure compensation necessary when measuring gases with a vortex flowmeter?

When measuring gases with a vortex flowmeter, temperature and pr

Schematic diagram of vortex flowmeter

1. Working principle of vortex flowmeter

2. Why is temperature and pressure compensation necessary when measuring gases with a vortex flowmeter?

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