SU892214A1 - Method of measuring medium mass consumption - Google Patents

Description

The invention relates to a measurement technique and can be used, in particular, to determine the mass flow rate of a medium. The known method of measuring the mass flow rate of pressure drop across the septum (the diaphragm installed in the pipeline through which the measured flow flows and density is also required to measure 1) The need to measure the density of the medium complicates the method of determining the flow rate and reduces its accuracy, and The fact that the flow rate is measured by creating an additional flow of matter in the form of a jet, in the direction perpendicular to the measured flow, crossing a part of the section of the measured flow, and determining the pressure drop at points located against the jet outflow hole in the zone of action - this jet 2. The disadvantage of this method is the limited range of measured flow rates. , by the pressure differential, it is possible to determine only the speed of the measured flow, or the mass flow rate at a known and constant density of the substance of the flow. In order to measure the mass flow rate at a variable density, as in flowmeters with a diaphragm, it is necessary to measure the density additionally. There is also known a method for measuring the mass flow rate by pressure differential occurring in a pipeline in the cylinder area, rotating the centrifugal fluid at a constant speed, partially blocking the measured flow — and creating an additional flow as part of the measured flow — rotates together with the cylinder. The pressure drop by this method is directly related to the mass flow rate and, therefore, no additional density measurement is required. Perexp pressure, moreover, is directly proportional to mass flow; consequently, there are no limitations to the measurement range that diaphragm meters have in place, due to the quadratic relationship between the flow rate and the difference in the DSS. However, accurate flow measurement using this method is limited

very low cost. In addition, the accuracy of flow measurement significantly depends on the flow structure. The flow structure is influenced by the accuracy of the measurement due to the location of the pressure selection points in the zone of interaction between the measured and secondary flows. A change in the structure of the measured flow can lead to changes or fluctuations in the differential at the same flow rate. This creates an additional measurement error.

The purpose of the invention is to expand the range of measurable flow rates and increase the accuracy of measurements.

The goal is achieved by the fact that the measured flow is crossed by the additional one and the latter is removed from the zone of their intersection, and the pressure drop is measured between the points of the measured flow located before and after its crossing by the additional flow, and the parameters of the additional flow are determined from the conditions:

} --iy

V;

and c.

"

BUT

ON

de N and N.

the transverse dimensions, respectively, of the measured and additional flows in the plane of intersection of the directions of the flows in the zone of this intersection,

B, and B are the transverse dimensions of the measuring tube and additional flows in the intersection zone, in the direction perpendicular to said plane;

Bw average additional flow rate in the same plane in the intersection flow area

 The average velocity of the measured flow in the same zone with the maximum measurable flow rate.

The drawing shows a diagram of the device that implements the proposed method.

The device comprises a pipeline 1, a pump 2 placed in an additional pipeline 3 connected at right angles to the pipeline 1. The pump 2 is mounted on the shaft of the electric motor 4 and has a constant volumetric capacity. Differential pressure gauge 5 is connected to the pipeline 1 in front of and behind the pipeline 3.

. An embodiment of the method may be a device in which a pump with a molopast impeller is used in the viesto of the pump, installed in such a way that its axis of rotation is located outside the measured flow.

The method is implemented as follows.

The measured flow passes through pipeline 1. An additional constant speed flow is provided by pump 2, which is driven at a constant speed from a synchronous motor 4. The additional flow created by pump 2 crosses the measured one.

Differential pressure gauge 5 measures the pressure drop in the pipeline 1 before and after the intersection of the flows.

The flow circulates in the closed pipeline 3, the transverse dimension of which In, determining the size of the additional flow, is equal to or greater than the size of the Vi measured flow. Under this condition, the additional flow completely crosses the measured flow.

The pressure drop arises due to the resistance to movement of the measured flow created by the additional flow crossing it. This resistance is caused by the inertia of the particles of the additional flow that moves past the parts of the measured flow. At the same time, between the parts of the measured flow there are constantly parts of the additional flow that do not have speed in the direction of movement of the measured flow, acquiring movement in this direction only between the specified parts of the measured flow. Such movement is ensured by the fact that parts of the additional flow, after intersection with the measured flow, are withdrawn from the zone of their interaction during the circulation of the additional flow in the pipeline 3.

The pressure drop versus mass flow rate is determined as follows.

Any elementary cross-section S in the additional stream, having dckUn. Equal to the size Nd of the additional stream in the plane of intersection of the directions of the streams, the passage through the measured stream, is affected by the pressure differential l before the intersection of streams and behind it. At the end of the movement in the measured flow, the length of this elementary cross section, which is under the influence of such a pressure differential, becomes equal to y due to the displacement of this cross section under the action of the differential and its position from the measured flow. At the same time, a part of the section with the length Uv U-UO actually enters the pipeline 1 after the additional flow. From these parts of the additional flow, the measured flow is added.

Claims (3)

1. Tsaytlin V.G. A technique for measuring flow and quantity of liquids, gas and vapors. M., 1968, p. 27-40. 2. Kremlevsky P.P. Flow meters and quantity counters. L., 1975, with. 645-646, fig. 340. 3. The patent of Germany No. 1046350, cl. 42e, 23/20, 1959 (prototype). A: ±