As shown in Figure 1, when a mass point with a mass of m moves at a speed υ in a pipe rotating at an angular velocity ω on the p axis, the mass point is subjected to the acceleration and force of two components.
a. Normal acceleration is the centripetal force acceleration αr, its magnitude is equal to ω2r, and the direction is toward the P axis;
b. Tangential acceleration αt is Coriolis acceleration, its magnitude is equal to 2ωυ, and the direction is perpendicular to αr. Due to the compound motion, Coriolis Fc=2ωυm acts in the αt direction of the particle, and the pipe exerts a reverse force on the particle -Fc= -2ωυm.
When a fluid with a density of ρ flows at a constant speed υ in a rotating pipe, any pipe with a length of Δx will be subjected to a tangential Coriolis force of ΔFc.
In the formula-the internal cross-sectional area of the pipeline. Since the mass flow rate is δm, δm=ρυA, so
Therefore, the mass flow can be measured by directly or indirectly measuring the Coriolis force generated by the fluid flowing in the rotating pipe. This is the basic principle of the Coriolis mass flowmeter.
However, it is difficult to generate Coriolis force by rotating motion. At present, products are all produced by pipe vibration, that is, a thin-walled measuring tube fixed at both ends is excited by the resonance of the measuring tube at the midpoint or a frequency close to resonance. , The fluid flowing in the tube generates Coriolis force, which makes the two halves before and after the midpoint of the measuring tube bend in opposite directions. Electromagnetic methods are used to detect the amount of deflection to obtain the mass flow rate. Because the fluid density will affect the vibration frequency of the measuring tube, and the density has a fixed relationship with the frequency, the mass flowmeter can also measure the fluid density.
1. A multi-variable digital processing system is adopted. Strengthen signal filtering, greatly improve the sensitivity and accuracy of signal measurement, speed up the response time of the system, and make the measurement more reliable;
2. The adoption of multi-variable digital processing system makes the system composition more flexible and convenient. In many occasions, multi-variable digital processing system modules and sensors can form a complete flow measurement system without the need to configure a flow converter. For example, CNG, LNG dispenser system, quantitative control system, flow or density single parameter measurement system, etc.;
3. The measurement accuracy is high, the general mass flow measurement accuracy can reach 0.1%-0.2%, the density measurement resolution can reach 0.002-0.02g/cm^3; the temperature measurement error is less than 0.5 degrees;
4. The density and temperature measurement functions are realized, and the medium concentration measurement function can be derived (two-component medium);
Liquid mass flow meter reference range table
|model||Diameter (mm)||Recommended flow range (kg/h)||Maximum flow range (kg/ h)|
General technical parameters of liquid mass flow meters
●Flow measurement accuracy
|●Density measurement range||:||0< ρ < 5g/ cm3|
|●Density measurement |
|●Temperature measurement range||:||-200~350℃|
|●Temperature measurement accuracy||:||±1℃|
|●Measured medium temperature||:||-50℃ ~200℃|
|●Applicable ambient temperature||:||-40℃ ~80℃|
|●Material quality||:||Wetted part 316L shell 304|
|●Work pressure||:||Conventional 4MPa, high pressure can be customized|
|●output signal||:||4-20mA DC current signal, 0-10KHz frequency pulse signal、|
|Pulse equivalent signal, RS485 communication signal|
|●Explosion-proof grade||:||Exd(ib) II CT6|
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