Coriolis mass flow meter

Overview and purpose-----------------------------------------◆◆

Coriolis mass flow meter is a direct mass flow meter made by utilizing the principle of Coriolis force proportional to mass flow while fluid is in a rotating system while moving linearly. The Focmass series mass flowmeter was independently developed by our company. It has high measurement accuracy and can simultaneously measure flow, temperature, density, and calculate the composition (concentration) of two-component medium. And the measurement accuracy is not affected by medium pressure, temperature, viscosity, etc., which is of great significance in trade measurement and quantitative control. This product is widely used in scientific research, petroleum, chemical industry, metallurgy, pharmaceuticals, power plants, water supply and drainage, papermaking, food, energy, oil storage, mineral development, municipal, textile printing and dyeing and environmental protection, etc.  

working principle-------------------------------------------------◆◆

1. Working principle

As shown in the figure below, when a particle of mass M moves at a velocity V in a pipe that rotates with an angular velocity ω about the Z-axis, the particle is subjected to two components of acceleration and its force.

①: Normal acceleration (centripetal force acceleration) α_r, its magnitude is equal to ω²r, and the direction is towards the Z axis;

②: Tangential acceleration (Coriolis acceleration) α_t, its magnitude is equal to 2ωV, and the direction is perpendicular to α_r.

Due to the composite motion, the Coriolis force acts in the direction of αt of the particle, and according to Newton's second law Fc=2ωVM, the pipe acts on the particle with an opposite force -Fc= -2ωVM.

    When a fluid of density ρ flows at a constant velocity V in a rotating pipe, any pipe of length Δx will experience a tangential Coriolis force of ΔFc.

ΔF_c=2ωvρSΔx  (1)

In the formula, S——the inner flow cross-sectional area of the pipeline, since the flow rate of the mass flowmeter is Q_m, that is, Q_m=ρVS, so

    ΔF_c=2ωQ_mΔx  (2)

Therefore, the mass flow can be measured by directly or indirectly measuring the Coriolis force generated by the fluid flowing in the rotating pipe, which is the basic principle of the Coriolis mass flowmeter.

However, it is difficult to measure the Coriolis force through rotational motion. At present, the products are replaced by the Coriolis force generated by the vibration of the pipeline. That is, the measuring tube fixed by the shunt pipes at both ends, is driven by the resonance or near-resonance frequency of the tube at the midpoint, making the two halves before and after the midpoint of the measuring tube are deflected in opposite directions, and the amount of deflection is detected by the electromagnetic principle to obtain the mass flow.

The fluid density affects the vibration frequency of the measuring tube, and the density has a fixed relationship with the frequency, so the mass flow meter can also measure the fluid density.

Structural components-------------------------------------------◆◆

Coriolis mass flowmeter is composed of flow sensor and converter. It is mainly composed of a fixed structure composed of a shunt pipe, a measuring pipe and a connecting pipe, a driving element in the measuring pipe driving system, a detection element for detecting the deflection of the measuring pipe, and a temperature measuring element for correcting the Young's modulus of the measuring pipe material. The converter is mainly composed of the drive signal generation unit, signal detection and signal processing unit of the drive excitation system; it also has functions such as configuration setting, engineering unit conversion, signal display and communication with the host computer.

1. Converter 2. Connecting tube 3. Shunt tube 4. Detection element 5. Measuring tube 6. Driving element

Product features-------------------------------------------------◆◆

Technical parameters---------------------------------------------◆◆