Pentagonal velocity-averaging tube

Abstract

A pentagonal velocity-averaging tube flowmeter test rod is suitable for the field of a flow measuring instrument. The shape of the cross section of the test rod is an axisymmetric pentagon in the flow direction of fluid. An inflow angle is arranged at a water meeting side. Furthermore the angle-of-attack and two flow meeting edges which form the angle-of-attack constitute a high-pressure chamber of which the cross section is triangular. Flow opposing edges at two sides and the flow opposing bottom edges of the pentagon form a quadrangular low-pressure chamber. High-pressure sampling holes are distributed at the angle-of-attack. Low-pressure sampling holes are next to a connection portions between the flow opposing edges and a middle baffle plate. The flow meeting edges are linear. The value range of the angle-of-attack is 0-180 DEG. The distances between the low-pressure sampling holes and a wake zone is changed through increasing the length of a wake edge, thereby reducing an influence of a wake-zone whirlpool to the low-pressure sampling holes, and realizing a more stable flow coefficient. The shape of each pressure sampling hole has an elongated groove shape. A pressure sampling area increase, a relatively small effect to an output pressure difference and a relatively good anti-blockage performance are realized. The pentagonal velocity-averaging tube flowmeter test rod has advantages of simple structure, greatly reduced requirement for a producing process, and greatly reduced production cost.

Description

Technical field [0001] The invention belongs to the field of flow measuring instruments, in particular to a uniform velocity tube flowmeter. Background technique [0002] The averaging tube flowmeter is a differential pressure flowmeter with simple structure, low price and low energy consumption. It occupies an important position in flowmeters and is used in petrochemical, electric power, metallurgy, air conditioning and many other fields at home and abroad. . The averaging tube flowmeter is developed and evolved based on the principle of Pitot tube velocity measurement. The Pitot tube can only measure the flow velocity of a single point, while the averaging tube measures the flow velocity of multiple points on the pipeline section to obtain the average flow velocity of the pipeline section. The section of the uniform velocity tube is divided into front and rear chambers, the front chamber communicates with the high-pressure pressure-taking hole, and the rear chamber commun...

AI Technical Summary

Problems solved by technology

Although the average velocity tube with a circular cross-section is simple in structure and easy to process, its separation point changes with the flow velocity, causing a measurement error of about 10% in the average velocity tube

The separation point of the diamond-shaped equalizing tube is fixed to eliminate the measurement error caused by the change of the separation point. However, since the low-pressure pressure tapping hole is set in the wake area, it is difficult to grasp the change law of the vortex in the wake area, so that the pressure change in the wake area is also difficult. Irregularity, so that the flow coefficient of the equalizing tube is still not stable enough

The bullet-shaped cross-section equalizing tube has a fixed separation point, and the low-pressure pressure-taking hole is set before the separation point, so that the low-pressure hole is less affected by the vortex in the wake area, so the flow coefficient is more stable, and more importantly, its high-pressure pressure-taking The hole and the low-pressure pressure-taking hole are on the same streamline, and the mathematical model of the flow coefficient can be established, but its biggest disadvantage is still the low output pressure difference, especially under the condition of low Reynolds number.

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