At present, the elbow flowmeter produced by many manufacturers of elbow flowmeters is a 90-degree elbow with a standard geometry, and the construction party installing the throttling element often directly installs the elbow directly in a suitable space, but The effect of flow measurement is not very satisfactory.

After investigation and analysis by the project team, fluids have two kinds of operation modes inside the elbow: one is the free swirling theory and the other is the forced swirling theory. When the liquid enters the bend, it is forced to do a similar circular motion. This "forced" is the forced swirl theory.

In order to understand the distribution of speed and pressure inside the elbow under forced swirling, the project team checked the data and consulted the experts. Finally, it was learned that the fluid appeared near the inside of the elbow and the outside of the elbow before entering the elbow. Subtle changes in the velocity and pressure of the fluid appear as the pressure gradually changes into an elbow and the exponential change in pressure occurs. The flow velocity near the inside of the elbow gradually increases, and the pressure increases exponentially.

The velocity near the outside of the elbow gradually decreases, and the pressure also decreases exponentially; when the fluid enters the 45-degree section of the elbow, the velocity of the fluid near the inside is the largest, and the pressure at this time is also the largest, and the fluid on the outside is the largest. The speed is at a minimum, and the pressure at that time is also minimal; when crossing the 45 degree section, the change is reversed before the section; when the fluid flows out of the bend, the speed gradient will continue for a period of time before the speed and pressure will return to enter. Steady state before bending.

After rigorous analysis, it is concluded that the fluid has no change in speed and pressure beyond the 5 times the diameter of the elbow before it enters the elbow, and that there is a change within 5 times the diameter; the 2 times the diameter of the elbow where the fluid flows out of the elbow In addition, the fluid velocity and pressure returned to the physical state prior to entering the bend 5 times the diameter of the elbow, and the variation in the diameter of the 2 bend was significant.

Therefore, the diameter of the elbow is D, so the throttling element of the practical elbow flowmeter should be: a 90-degree elbow with a standard geometry, an elbow inlet must have a 5D straight pipe section, and the elbow outlet must have 2D straight There is a pressure hole in the pipe section, on the inside and outside of the 45 degree section.

The design diagram of the elbow flowmeter and the parameters of the flow system are passed to the manufacturer of the elbow flowmeter for manufacturing, and then the installation of the flowmeter is supervised by the installation department. The R/D ratio is preferably 0.95 to 1.95.

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