Pitot tube velocity meter or flowmeter being free from influence of flow velocity in non-measuring direction

Abstract

The invention discloses a pitot tube velocity meter or flowmeter being free from the influence of the flow velocity in the non-measuring direction. The pitot tube velocity meter or flowmeter comprises a head part and a supporting rod. The supporting rod is used for supporting the head part, the head part comprises an expansion section and a contraction section, the position with the maximum sectional area of the expansion section is close to the position with the maximum sectional area of the contraction section, and the expansion section and the contraction section on the head part are provided with two or more holes. With respect to the pitot tube velocity meter or flowmeter, after fluid flows around the surface, variations of the pressure values on the pitot hole and the static hole along with cross flow can be partially or wholly offset, and influence of cross flow on flow velocity / flow measurement can be reduced or eliminated.

Description

technical field [0001] The invention relates to a flow meter or a flow meter, in particular to a pitot tube flow meter or a flow meter which is not affected by the flow velocity in a non-measurement direction. Background technique [0002] The Pitot tube is a traditional differential pressure flow rate measuring instrument. The conventional Pitot tube has two pressure measurement holes, one of which faces the direction of incoming flow, and measures the total pressure p of the fluid. t , the other hole is at a 90-degree angle to the incoming flow direction or against the incoming flow direction to measure the static pressure p of the fluid s . Common Pitot tube flowmeters for measuring two pressure values ​​include L-type Pitot tube and S-type Pitot tube, such as figure 1 As shown, the total pressure hole of the L-shaped pitot tube faces the direction of the flow velocity to be measured at the front end of the pitot tube, and the static pressure hole is composed of several...

AI Technical Summary

Problems solved by technology

However, in reality, the Pitot tube cannot identify the flow velocity direction, or the Pitot tube that can identify the direction cannot rotate the Pitot tube to the same working condition (toward the flow velocity direction) as the calibration due to the site conditions and the limitations of the Pitot tube structure, so the flow cannot be realized. Accurate measurement of channel flow

For example, the S-type Pitot tube is usually used as a measurement tool for flue gas flow in the flue, such as Figure 4 As shown, when measuring the flow velocity at a certain point in the flue, you can find the plane where the flow velocity direction is by changing the twist angle (yaw angle) of the pitot tube, but since the S-type pitot tube cannot recognize the deflection angle (pitch angle), it cannot Change the deflection angle, so the direction of the flow velocity cannot be determined, and the uncertainty of the point velocity measurement introduced by this can be as high as tens of percent

[0010] Therefore, the traditional pitot tube has many problems such as the inability to distinguish the direction of the flow velocity, the pressure difference value of the pitot tube is related to the flow velocity in the direction and the flow velocity of the lateral flow, and the lateral flow will introduce measurement uncertainty when measuring the flow channel flow.

Images