RU2614656C2 - Device for measuring the flow of liquid - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: device includes input and output channels, a cylindrical body, which is perpendicular to the axis of the input and output channels of the axis, the working and the measuring electrodes, fortified at the end of the insulating housing bushings, the flow of the formed inner side walls of the housing and the end insulating sleeve. Low-voltage power supply is connected to the working electrode. Between the measuring electrode and the ground, the metre is included. The electrodes have a disk segment shape with a turn angle of no more than 180° and mounted on the end of insulating sleeves strictly symmetrically with respect to the input and output axes of the channels with equal distance from one of the channels.

EFFECT: hypersensitivity.

5 dwg

Description

The invention relates to measuring the flow rate of fluids and is intended to measure the flow rate of highly polar dielectric fluids.

Known polarizing flowmeter containing a rectangular dielectric housing, electrodes mounted on two opposite walls of the housing, a power source and a measuring device connected between one of the electrodes and a common bus / 1 /. The flowmeter’s operating principle is based on measuring the sum of the conduction currents and polarization currents that appear due to the field of coupled charges in a moving strongly polar dielectric fluid. Polarization currents create an electric polarization field that weakens the external field created by the power source. The difference of these currents, depending on the flow rate of the measured fluid, and fixes the measuring device.

The dominant polarizing component in the flow meter / 1 / is a longitudinal one (along the axis of a rectangular dielectric casing), which is proportional to the first derivative of the measured fluid velocity along the longitudinal axis.

The disadvantage of this flow meter is its low sensitivity, due to the theoretically complete mutual compensation of the longitudinal polarization component in the interelectrode gap of the flow part. And the declared (protected) sensitivity of the flow measurement in the analogue / 1 / is due to the purely technological asymmetry of the distribution of the longitudinal velocity component along the longitudinal axis in the interelectrode gap of the flow part, and therefore there is no complete mutual compensation of the longitudinal polarization component.

Known polarizing flowmeter containing a metal cylindrical body, an input channel, the axis of which is perpendicular to the axis of the metal body, a working and measuring electrode in the form of a segment of a sphere, mounted on insulating sleeves located on the end surfaces of the body, forming a flow part with its inner side walls, a power source for supplying voltage to the working electrode and the measuring device connected between the measuring electrode and the ground / 2 /.

The dominant polarization component in the flow meter / 2 / is the transverse (perpendicular to the axis of the metal cylindrical body), which is proportional to the first derivative of the orthogonal component of the total velocity vector of the measured fluid along the longitudinal axis.

The disadvantage of this flow meter is its low sensitivity, due to the theoretically complete mutual compensation of the orthogonal polarization component in the interelectrode gap of the flow part. And the declared (protected) sensitivity of the flow measurement in the analogue / 2 / is due to the purely technological asymmetry of the distribution of the orthogonal velocity component along the orthogonal axis in the interelectrode gap of the flow part, and therefore the full mutual compensation of the orthogonal polarization component is not observed.

The prototype of the claimed invention is a device for measuring the flow rate of liquid media containing a cylindrical body, an input channel whose axis is perpendicular to the axis of the body, working and measuring electrodes mounted on insulating sleeves forming a flow part with internal side walls of the body, a low-voltage power supply for supplying voltage to the working electrode and a measuring device connected between the measuring electrode and the ground / 3 /.

The dominant polarizing component in the flow meter / 3 / is the longitudinal (along the axis of the cylindrical body), which is proportional to the first derivative of the measured fluid velocity along the longitudinal axis.

The disadvantage of this flow meter is its low sensitivity, due to the theoretically complete mutual compensation of the longitudinal polarization component in the interelectrode gap of the flow part. And the claimed (protected) sensitivity of the flow measurement in the prototype / 3 / is due to the purely technological asymmetry of the distribution of the longitudinal velocity component along the longitudinal axis in the interelectrode gap of the flow part, and therefore there is no complete mutual compensation of the longitudinal polarization component.

The technical result created by the invention is to increase the sensitivity of the flow sensor.

The specified result is achieved by the fact that in the device for measuring the flow rate containing the input and output channels, a cylindrical body, the axis of which is perpendicular to the axis of the input and output channels, working and measuring electrodes mounted on the end insulating bushings of the body, the flow part formed by the inner side walls of the body and end insulating bushings, a low-voltage power supply for supplying voltage to the working electrode, a measuring device connected between the measuring electrode and the ground second electrodes have a disk segment shape with an angle of rotation not more than 180 ° and fastened on the end of insulating sleeves strictly symmetrically with respect to the input and output axes of the channels with equal distance from one of the channels.

A positive effect in the implementation of the proposed technical solution will increase the sensitivity of the flow sensor.

The proposed device for measuring flow is shown in FIG. 1 a, 1 b.

A flow measuring device comprises a housing 1, a working electrode 2, a measuring electrode 3, input 4 and output 5 channels, end insulating sleeves of the housing 6 and 7, a flowing part 8. The flowing part 8 is formed by the inner side walls of the housing 1 and the end insulating sleeves of the housing 6 and 7 with electrodes 3 and 4 attached to them.

A circuit for connecting a flow measuring device is shown in FIG. 2.

A voltage of 20-60 V is supplied to the working electrode 2 from the source 9. The measuring device 10, which is a milliammeter connected to the measuring electrode 3, is grounded.

The static characteristic of the flow meter is shown in FIG. 3.

The operation of the device for measuring flow is as follows. The working fluid flow is supplied to the device through the input channel 4, the axis of which is perpendicular to the axis of the cylindrical body 1. Next, the flow enters the flow part 8 of the device. The flow part 8 is formed by the surfaces of the working 2 and measuring 3 electrodes, which are mounted on the end insulating sleeves 6 and 7 and the inner walls of the housing 1. From the control voltage source 9, a voltage of about 60 V is applied to the working electrode 2. Under the action of an external electric field, a dielectric strongly polar liquid polarized, the dielectric molecules will be oriented along the field lines of force, while creating an internal electric field that is opposite to the external field and weakens him.

Analysis of the hydrodynamics and electrostatics of the prototype / 3 / shows that the device is based on measuring the current, the continuous density of which can be represented in the form (Fig. 4a, b, c):

,

,

where j _z is the projection of the density vector of the total current in the interelectrode gap of the flowing part on the vertical axis z, A / m ² ;

ρ _e - volumetric charge density, which creates a conduction current between the electrodes, C / m ³ ;

b is the coefficient of mobility of charges in the medium, m / Vs;

E _z is the electric field along the z axis in the continuum of the interelectrode gap, V / m;

V _y - projection of the velocity vector of the measured medium on the y axis, m / s;

; E_z - напряженность электрического поля в континууме межэлектродного промежутка, В/м).P _z are the projections of the polarization vector of the electric field in the continuum of the interelectrode gap on the z axis, C / m ² (recall that P _z = χε ₀ E _z , where - χ is the dielectric susceptibility of the dielectric, 1; ε ₀ is the electric constant,

; E _z is the electric field strength in the continuum of the interelectrode gap, V / m).

Let us analyze (1).

, где d - расстояние между электродами, м), тем больше ток проводимости, который в «чистом» виде измеряется между электродами при отсутствии расхода измеряемой жидкости.1) The component ρ _e bE _z is the basis of the conduction current between the electrodes. It is the greater, the greater ρ _e (contamination of the liquid) and E _z (voltage between the electrodes

, where d is the distance between the electrodes, m), the greater the conductivity current, which in a "pure" form is measured between the electrodes in the absence of flow of the measured liquid.

. Первый сомножитель компонента скорости V_y является в проточной части доминирующим, однако второй сомножитель по всей проточной части практически равен нулю, поскольку напряженность электростатического поля E_z по всей проточной части при плоскопараллельных электродах постоянна (E_z = const).2) Component

. The first factor of the velocity component V _y is dominant in the flow part, however, the second factor over the entire flow part is practically zero, since the electrostatic field strength E _{z is} constant over the entire flow part at plane-parallel electrodes (E _z = const).

. На Фиг.4 б приведено континуальное распределение компоненты скорости V_y по каждой точке проточной части межэлектродного промежутка. Первая частная производная этой скорости по координате y (вдоль оси входного и выходного каналов)

также приведена на Фиг.4 б. Из графика распределения сомножителя

по всей проточной части межэлектродного промежутка следует, что наблюдается полная взаимокомпенсация продольной поляризационной компоненты в межэлектродном промежутке проточной части. Т.е. в прототипе /3/ наблюдаемая экспериментально поляризационная компонента полного тока обусловлена чисто технологической несимметрией распределения продольной компоненты скорости вдоль продольной оси у в межэлектродном промежутке проточной части. Именно поэтому, в частности, ток в измерительной цепи с возрастанием расхода уменьшается.3) Component

. Figure 4 b shows the continuous distribution of the velocity component V _y at each point of the flowing part of the interelectrode gap. The first partial derivative of this velocity with respect to the y coordinate (along the axis of the input and output channels)

also shown in Fig.4 b. From the distribution chart of the factor

over the entire flow part of the interelectrode gap it follows that there is complete mutual compensation of the longitudinal polarization component in the interelectrode gap of the flow part. Those. in the prototype / 3 / the experimentally observed polarization component of the total current is due to purely technological asymmetry in the distribution of the longitudinal velocity component along the longitudinal axis y in the interelectrode gap of the flow part. That is why, in particular, the current in the measuring circuit decreases with increasing flow rate.

In the proposed technical solution, this disadvantage is fundamentally eliminated (Fig. 4, c): the electrodes are in the form of a disk segment with a rotation angle of not more than 180 ° and are mounted on the end insulating bushings strictly symmetrically with respect to the axis of the input and output channels with an equal distance from one of the channels. Thus, when the device is used, one of two mutually compensating polarization components is used, which is fixed by electrodes - half disks (in particular, sectors 2 + 3 in Fig. 4 c). It is this fact that is the reason for the increased sensitivity of flow measurement in the claimed technical device compared with the prototype / 3 /.

In FIG. 3 shows the static characteristics of devices for measuring flow (curve 1 for the prototype / 3 /, curve 2 for the claimed technical solution).

Experimental conditions: medium to be measured - drinking tap water at a temperature of 20 ° C; voltage at the working electrode 60 V; distance between electrodes 5 mm; electrode diameter 30 mm; The electrode material is aluminum.

From the above static characteristics, it can be seen that for a given device geometry, the working metrological range of flow measurement is the range 0-15 cm ³ / s, where there is a linearity of static characteristics with maximum sensitivity (slope). The decrease in sensitivity with an increase in flow rate of more than 15 cm ³ / s is most likely due to the appearance of a transitional regime in the flow part: from laminar to turbulent with the appearance of vortices, which, as is known, reduce the polarization effects in strongly polar dielectric liquids (water ε = 81, glycerol ε = 43, alcohol ε = 26).

The graph of the static characteristics of the prototype / 3 / (curve 1, Fig. 4 b) is higher than that of the claimed technical solution (curve 2, Fig. 4 b), which is explained by a decrease of exactly 2 times the area of each of the electrodes in the claimed technical solution.

On the metrologically sound range of flow measurement (0-15 cm ³ / s), the sensitivity (slope) of the static characteristics of the prototype / 3 / (curve 1, Fig. 4 b) is 6.66 mA / (cm ³ / s), sensitivity (slope ) the static characteristics of the claimed technical solution (curve 2, Fig. 4 b) is 8.33 mA / (cm ³ / s).

If we take the metrologically effective range of flow measurement (0-5 cm ³ / s), the sensitivity (steepness) of the static characteristics of the prototype / 3 / (curve 1, Fig. 4 b) is 10.0 mA / (cm ³ / s), the sensitivity (steepness) of the static characteristic of the claimed technical solution (curve 2, Fig. 4 b) is 20 mA / (cm ³ / s).

Thus, the technical and economic advantages of the proposed technical solution over the prototype / 3 / are obvious.

The claimed technical solution can be implemented by adding sectors 4 + 5 (Fig. 5 a). The sensitivity of the flow measurement will remain the same as in the case of adding sectors 2 + 3 (Fig. 5 b), as described above.

Information sources

1. A.S. USSR 1553830 - analogue.

2. RF patent 2130590 - analogue.

3. RF patent 2148798 - prototype.

Claims (1)

A device for measuring the flow rate, comprising input and output channels, a cylindrical body, the axis of which is perpendicular to the axis of the input and output channels, working and measuring electrodes mounted on the end insulating sleeves of the body, a flow part formed by the inner side walls of the body and end insulating sleeves, a low voltage source power supply voltage for the working electrode, a measuring device connected between the measuring electrode and the ground, characterized in that the electrodes have му му сегмента сегмента сегмента сегмента сегмента сегмента сегмента сегмента сегмента му сегмента му му сегмента му му му му му му му му му му му му му му му му му му му му му му му му му му му му муму му муму му муму му му муму му муму му муму му му му муму му му муму му му муму му му муму му муму му муму му муму му муму му муму му муму му му му му му му му му the disk segment angle to be 180 ° and mounted on the end insulating bushings symmetrically with respect to the axis of the input and output channels with equal distance from one of the channels.

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