Question 1

S-shaped measuring tube

Accepted Answer

As shown in the figure, the measurement system of the S-shaped measuring tube mass flowmeter consists of two parallel S-shaped measuring tubes, a driver and a sensor. The two ends of the tube are fixed, and the center of the tube is equipped with a driver to make the tube vibrate.

Sensors are installed at the symmetrical positions of the measuring tubes. The relative displacement between the vibrating tubes is measured at these two points. The mass flow is proportional to the phase difference of the oscillation frequencies measured at these two points.

Question 2

U-shaped measuring tube

Accepted Answer

The U-shaped tube has two structures of single and double measuring tubes.

The electromagnetic drive system drives the U-shaped measuring tube to vibrate at a fixed frequency. When the fluid is forced to accept the vertical movement of the tube, the tube moves upward during the first half of the vibration cycle, and the fluid in the measuring tube generates a downward pressure force before the driving point, which hinders the upward movement of the tube. An upward force is generated after the actuation point, accelerating the upward movement of the tube. The combination of these two forces twists the measuring tube. During the other half cycle of the vibration, the direction of the twist is reversed.

The degree of distortion of the measuring tube is directly proportional to the mass flow rate of the fluid flowing through the measuring tube. Install electromagnetic inductors on the measuring tubes on both sides of the driving point. To measure the phase difference of its movement, this phase difference is directly proportional to the mass flow through it.

In the double U-shaped measuring tube structure, the two measuring tubes vibrate in opposite directions. Make the measuring tube twisted out of phase by 180 degrees. as the picture shows. Compared with the single-measurement tube type, the detection signal of the double-tube type is amplified, and the flow capacity is also improved.

Question 3

Double J-tube

Accepted Answer

The two J-shaped pipes are centered on the pipe and distributed symmetrically. A driver mounted on the J-shaped section causes the tube to vibrate at a certain fixed frequency.

When the fluid in the measuring tube flows at a certain speed, the fluid in the measuring tube produces a Coriolis force effect due to the existence of vibration. This Coriolis force acts on the measuring tube, but the direction of the Coriolis force generated on the upper and lower tubes is different. The straight pipe part of the pipe produces different additional motion, that is, produces a phase difference of relative displacement.

In a double J-tube measurement system, the two tubes vibrate in opposite directions at the same time. The phase difference of the relative displacement between the upper and lower two straight pipes is increased. When the fluid is not flowing, the phase difference of the displacement signals measured by the sensors A and B is zero.

When the fluid in the measuring tube flows, the influence of the reaction force generated by the Coriolis force on the measuring tube in a certain direction that drives its vibration. When the pipe 1 separates and the pipe 2 approaches, the upper part of the pipe 1 moves faster and the lower part slows down, while the upper part of the pipe 2 speeds up and the lower part slows down in the opposite direction. As a result, there is a phase difference between the signals measured by the upper and lower mounted sensors. The magnitude of this signal directly reflects mass flow.

Question 4

B-tube

Accepted Answer

B-tube The Coriolis Mass Flowmeter flow measurement system consists of two B-tubes parallel to each other. The measured fluid is evenly sent into two B-shaped measuring tubes through the flow divider. The drive unit is mounted centrally between the two tubes. The measuring tube is driven to vibrate at a stable harmonic frequency. During the outward movement of the measuring tube, the straight tube parts are pushed away from each other. Under the action of the driver, the loops L1' and L1'' are close to each other, and the loops L2' and L2'' are also close to each other. Since each loop is fixed at one end to the meter body, rotational motion is restrained at the end regions and thus concentrated near the nodes.

However, the fluid in the circuit slows down when the circuits L1 ′ and L1 ″ approach each other under the action of the Coriolis force. And the two loops at the other end L2' and L2'' approach each other and the speed increases.

The opposite happens when the measuring tube is moved inwards. The straight pipe sections approach each other under the action of the driving force, while the two loops on the two cross-sections move away from each other. The Coriolis force generated by the fluid in the pipeline is superimposed on this basic motion, which will speed up the separation speed of the two circuits of L1' and L1'', and reduce the separation speed of the two circuits of L2' and L2''.

By properly installing the sensor between the two circuits on the end face. These movements induced by the Coriolis force can be used to accurately determine the mass flow rate of fluids.

Question 5

Single Straight Pipe

Accepted Answer

The measurement system of this single straight tube mass flowmeter consists of a straight tube with fixed ends (flanges) and a vibration driver on it.

When the fluid in the tube does not flow, the driver makes the tube vibrate, and the fluid in the tube does not generate Coriolis force. Points A and B are subjected to equal force and change at the same rate.

When the fluid in the measuring tube flows in the tube at the velocity V, it is affected by the vibration force at point C (the vibration force at this time is upward). When the fluid particle moves from point A to point C, it is accelerated, and the particle produces a reaction force F1, which slows down the upward movement of the pipe. And between point C and point B, the fluid particle is decelerated. Accelerates the upward motion of the pipe. As a result, these two opposing forces on either side of point C cause a deformation of the tube. The phase difference of this deformation is proportional to the mass flow rate of the fluid flowing through the measuring tube.

Question 6

Double Straight Tube

Accepted Answer

Compared with the single straight tube, the double straight tube shape can reduce the pressure loss and increase the signal of the sensor. The actual structure is shown in the figure. The driver is placed in the center, and the two photoelectric sensors are only symmetrical to the two sides of the center. The measuring tube is less affected by the axial force.

When the fluid is not flowing, the photoelectric sensor is subjected to the same phase of the displacement generated by the tube. Coriolis forces are generated when a fluid medium flows through two vibrating measuring tubes.

This force causes opposite displacements on either side of the vibration point of the measuring tube. The fluid medium in the measuring tube before the vibration point attenuates the vibration of the tube, that is, the displacement speed of the tube slows down. The fluid medium in the test tube after the vibration point strengthens the vibration, that is, the displacement speed of the tube is accelerated.

Through the photoelectric sensor, the phase difference between the two ends is measured. This phase difference is proportional to the mass flow in the measuring tube when the oscillation frequency is constant.

Question 7

Ω-shaped measuring tube

Accepted Answer

The structure of the Ω-shaped measuring tube Coriolis Mass Flowmeter is shown in the figure. The driver is placed in the middle of the straight pipe section. When the fluid in the pipe flows at a certain speed, the pipes are separated or approached due to the vibration of the driver.

As the tubes separate, Coriolis forces generated in the fluid ahead of the vibration point oppose the vibrating force, slowing the tubes down. After the vibration point, the Coriolis force generated by the fluid in the pipe is in the same direction as the vibration, which accelerates the movement speed of the pipe.

When the driver brings the tubes closer together, the opposite effect occurs. The phase difference of the two tube word movements can be measured by the sensors at A and B. From this, the mass flow rate of the fluid flowing through the measuring tube can be obtained.

Question 8

Double ring measuring tube

Accepted Answer

The double annular measuring tube Coriolis Mass Flowmeter consists of a pair of parallel helical tubes with a short straight tube.

In the middle position D of the pipe is equipped with a driver. The two measuring tubes are subjected to periodic opposite vibrations. Two sensors are arranged at the two ends of the elliptical spiral tube, equidistant from the middle point D. Measure the relative velocity of motion between the pipes at these two points. The phase difference between these two relative speeds is proportional to the mass flow rate of the fluid flowing through the measuring tube.

When the fluid in the measuring tube does not flow, the deformation of the tube caused by the vibration force is the same on both sides of the middle point. At the two measuring points at the sensor, the phase difference of the measured vibration displacement is zero. When the fluid flows in the measuring tube, before the point of maximum amplitude, the fluid particle produces an effect opposite to the vibration direction due to the Coriolis force. force. After this point, however, a force acting in the same direction as the vibration is produced.

Since the force on the two measuring tubes at the same moment is equal in size and opposite in direction, it is reflected that the moving speed of the tubes at the measuring points at the two sensors is increased or decreased, and the phase difference between these two points can be measured to obtain a pass Measure the mass flow rate of the tube fluid.

Month: September 2023

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