With the development of science and technology, industrial production on the accuracy of flow measurement requirements are increasingly high, especially gas and gas-liquid two-phase flow mass flow measurement, has become a cutting-edge problem.
Thermal mass flowmeters can be used to measure the flow of single-component gases, but there are currently no mature flowmeters available for measuring the mass of gases with variable components. The vortex gas mass flowmeter is developed based on an in-depth study of the Karman vortex street principle. The core of the flowmeter is the sensor and the dual-channel signal detection circuit. Vortex is a flow phenomenon. A vortex generator is inserted perpendicular to the flow direction of the fluid in a pipe filled with fluid. When the flow of the fluid increases to a certain extent, a series of vortices will be formed on the downstream side of the vortex generator, and the vortices generated on both sides of the vortex generator appear alternately in a periodic manner.
When the generated stable vortex array satisfies the formula h=1.3b (h is the distance between the two vortex arrays), the frequency f of vortex generation and the flow velocity of the measured fluid have the following relationship: f=St*v1/b(1)where: v is the average flow velocity on both sides of the vortex generator; b is the maximum width of the frontal surface of the vortex generator; St is the Strouhal number (dimensionless, after the shape of the vortex generator is determined, it is a constant within a certain Reynolds number range). At this time, the volume flow rate qv of the fluid flowing through the pipeline and the vortex generator is: qv=A1*b/St*f(2)where: A1 is the flow cross-sectional area on both sides of the pipeline vortex generator. The current vortex flowmeter uses the above principle to measure the flow.
Along with the generation of vortex, a circulating flow is generated around the vortex generator. When the vortex separates on one side of the generator, the magnitude of the lateral lift FLf on the generator is: FLf = ± CLf × 0.5pv12So (3) where CLf is the lateral lift coefficient; p is the density of the measured fluid; So is the projected area of the vortex generator in the flow direction. Dividing equation (3) by equation (1) can eliminate a common variable p1 and obtain the mass flow rate qm: FLf/bSoCLf/2St*pv1=Kpv1=Kqm According to equation (4), when the instrument coefficient K is a constant, the quotient of FLf and f represents the mass flow rate qm of the measured fluid. After the geometric shape of the vortex generator is determined, b, So, and CLf are all constants. When the flow rate of the measured fluid reaches a certain level, St is also a constant, so K is a constant.
This is the measurement principle of the vortex mass flowmeter. Detailed experimental data show that CLf is a function of the Reynolds number Re and the shape of the vortex generator, as shown in Figure 2. When the shape of the vortex generator is trapezoidal, rectangular, and triangular, the lateral lift coefficient is 0.92, 0.62, and 0.80, respectively. In summary, if the measurement of f and FLf is achieved and the division operation is performed, the mass flow can be measured.
The above is the "Vortex Gas Mass Flow Meter Measurement Principle" shared by the vortex gas mass flow meter manufacturer. Thank you for watching. If you have any questions, you can consult online or leave us a message. We will answer you wholeheartedly.
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