SU1004763A1 - Machine and device for measuring consumption - Google Patents

Description

The invention relates to instrumentation, and more specifically to methods for measuring flow and devices for its implementation.

There is a known method for measuring the flow rate, which is called the square-speed, based on the measurement of the cross-sectional area of the flow and the local velocity in one or several characteristic points of the flow-section 1.

A disadvantage of the known method of measuring the flow rate is its low accuracy and sensitivity to the shape of the velocity profile. The more complex the flow velocity profile and the fewer points in the flow section at which the local velocity changes, the lower the flow measurement accuracy.

A device for carrying out a known method for measuring flow is a pipeline with local velocity meters installed therein.

A disadvantage of the known condition is the low accuracy of flow measurement when changing the flow rate profile.

As a measurer of the local flow rate can be drawn

famous electromagnetic meter. This meter has a round body and a cylindrical shape, inside which is located an electromagnet, and two electrodes are installed diametrically opposite to each other on the outer surface. The speed meter is located in the pipeline.

- in such a way that the flow flows

10 along the generatrix of the cylindrical surface of its body. Application of this speed meter c. A flowmeter that implements the Area-speed method also allows you to measure only flows with a normalized turbulent velocity profile. The flow meter is sensitive to flow rate to the same extent as the flow meter, in which

20, some other device has been applied. O for measuring the flow rate: 2 The aim of the invention is to improve the accuracy of the flow measurement.

This goal is achieved by additionally measuring the gradients of the flow velocity at the sites where the local velocity is measured. According to the velocity gradients of the flow and the coordinates of the measurement points, the result of the measurement is corrected. The method of measuring the flow rate can be implemented using devices having a pipeline with at least one electromagnetic flow velocity meter installed in it, which is made in the form of a cylindrical flow body located parallel to the axis of the pipeline and having two measuring electrodes on the surface the body is wrapped around a magnetic system, and the local electromagnetic velocity meter is equipped with two additional electrodes located on the outer surface of the body around the body ohm distance from the measuring electrodes according sectional perimeter, passing through the line connecting the electrodes, perpendicular to the axis of the meter, and the meter is the velocity in the conduit so that the line connecting the electrodes, located along the radius of the pipe. FIG. Figure 1 shows the noTQKa velocity profile in a pipe with a circular cross section of the channel; in fig. 2 is a flow meter that implements the proposed flow measurement method. At the cross-sectional point of channel 1 (Fig. 1), the local CKO velocity of flow V and the velocity gradient dv / dn are measured along the coordinate-n, directed normally, to this current line. The normal line in this case coincides with the line radius of the pipeline. To improve measurement accuracy, m velocity meters and the corresponding number of velocity gradient meters can be installed. The flow rate is calculated by the formula (fQ (1) where S is the cross-sectional area of the channel, H, "average flow rate calculated over one or more (ha) measured by the local velocity, as is done using the known method area-speed H --T m- (1) cf. WiVi correction for the effect of the shape of the forward velocity file, calculated by the formula “-1 |.„ Ь,

where a is a constant coefficient determined by the coordinates of the i-th measurement point. The Q factor may also depend on the velocity gradient of 5

where, measuring potentials

Claims (2)

J „electrodes; V, V - local velocities near the electrodes. The i-th point, however, this dependence is weakly expressed and in many cases it can be neglected to measure consumption. - velocity gradient in the i-th point along the coordinate directed normally to the streamline. The Q factor is determined either calculatedly or experimentally, by pouring the instrument on a flow meter installation. In the pipeline (Fig. 21, an electromagnetic flowmeter 2 of the flow network 2 with a cylindrical body around is placed. The speed meter has a core 3 with two poles and an excitation winding 4 fed from an alternating current source 5. The outer surface of the coating speed meter layer 6. On the outside the surfaces are two measuring electrodes 7 and two additional electrodes 8 that are in contact with the measured liquid. Additional electrodes 8 are interconnected by a conductor and grounded. Speed meter 2 is located in t in such a way that the line connecting the measuring electrodes 7 coincides with the direction of the radius of the pipeline 1. The measuring electrodes 9 are connected to the measuring electrodes, the flow meter works as follows: As the flow moves along the pipeline 1, the conductive liquid intersects the magnetic field lines generated by the magnetic a velocity meter system. An electric field is generated around the velocity meter, the intensity of which is proportional to the magnetic field induction and the flow velocity. In this case, the potentials of the electric field on the contact surface of the measuring electrodes 7 are proportional to the values of the local flow velocities near each electrode. The potentials on the contact surface of the additional electrodes are the same, since these electrodes are closed by a conductor. Additional electrodes are located along the magnetic neutral line 10 of the velocity meter, therefore the potential at these electrodes is equal to the potential of the fluid remote from the magnetic field, i.e. to zero. The signal of the algebraic sum of potentials between measuring electrodes is proportional to the sum of local velocities near measuring electrodes 4.4. (4) ... The signal of algebraic potential difference between measuring electrodes is proportional to the difference in local flow velocities near the measuring electrodes or to the speed of the tube along the radius of the pipeline. li 4W-.grma ,, (5) where 2R is the distance between the measuring electrodes, R is the radius of the velocity meter. Using the measuring device b, the signals taken from the electrodes are processed and converted into an output signal proportional to the flow rate of the pipeline 1. The presence of additional electrodes that are grounded allows the measuring circuit to be balanced and thereby reduce the effect of various kinds of interference with the result flow measurement. . This is especially important when measuring the algebraic difference of the potential of the F – F I proportional to the flow velocity gradient, since it has a significantly lower level than the algebraic sum of the potentials f – i – f proportional to the local flow rate. Claim 1. Method for measuring flow in a pipeline by measuring local flow rates at at least one point of the channel cross section, characterized in that, in order to improve measurement accuracy, flow velocity gradients are measured at the local speed measurement sites and correct the measurement result. 2. An apparatus for carrying out the method of. Section 1, a pipeline with an installed, at least one, electromagnetic electromagnetic velocity meter, which is made in the form of a cylindrical body of flow, located parallel to the axis of the pipeline and having two measuring electrodes on the surface, inside the body of flow, a magnetic system, It is different that the local electromagnetic velocity meter has two additional electrodes located on the outer surface of the body, which is flowed at an equal distance from the measuring electrodes around the perimeter. at the section passing through the lines connecting the electrodes, perpendicular to the axis of the velocity meter, both additional electrodes connected by a conductor, and the velocity meter itself is located in the pipeline so that the lines connected to the copper measuring electrodes are located along the pipeline radius. Sources of information taken into account in the examination 1.Katys GP Systems for automatic control of speed and expense fields. M., Science, 1965, p. 464. 2.Velt ID, Krylova G.I., Leg Bedev S.MG Optimization of parameters of an electromagnetic flow velocity meter. Sat materials for UE Tallinn meeting on electromagnetic flowmeters and electrical fluid conductors, vol. one; Ed. Estonian Republican Board NTO Priborprom, 1976, p. 57-67. g orrtjf-