SU443286A1 - Device for measuring the density of dielectric particles in two-phase flows - Google Patents

Description

The invention relates to the field of measuring the density of granular dielectric materials in apparatus with dispersed systems.

A device is known for counting the number of particles in two-phase flows by the number of pulses appearing on a sensor — an annular electrode as particles pass through it — containing three or more current pulse sensors, pulse counting circuits, and a secondary device.

Measurement accuracy is provided by duplicating measurement channels and determining the average value of all samples. However, since the sensors of the known device are located in the same plane, neither the total number of particles at the location of the sensors for flows having different directions of movement of the particles and, thus, nor the density of the material in these flows can be accurately determined.

In order to improve the measurement accuracy, the sensors are installed in three mutually perpendicular planes.

FIG. 1-2 shows the scheme of the proposed device.

A sensor is used, made in the form of three annular electrodes 1,2,3 located in three mutually perpendicular planes. This makes it possible to take into account the willow tea in the volume occupied by the sensor and having any heating motion.

Ring made of foil with a thickness of 0.15 mm and a width of 0.7 mm. An insulating lacquer film with a thickness of 0.1-0.2 mm is applied on the foil and then an aquadag coating that serves as a screen. The screen eliminates the influence on the ring electrode of both external electric fields and contact electrification. The shielding also excludes borrowing (the effect of charges induced by

on the ring electrodes at the moment of particle passage through one of the electrodes. The screen determines the so-called effective electrode height, numerically equal to the segment of the particle trajectory at which it induces a charge on the ring. The effective sensor height determines the pulse width on the oscilloscope screen, which determines the particle velocity. The values of the velocities of 1 particles allow to go from registering the number of particles to calculating the density of the material in the stream.

The measuring part of the device includes a pulse count measurement circuit and a secondary device. On is. Figure 2 shows a schematic diagram of one of the circuit channels from pulse count measurements. The ring electrode is connected to the gate of the field effect transistor 5 of the type KP-102. A field-effect transistor 5 is connected to a shoulder of a DC bridge consisting of a resist 1; a voltage of 6.7.8 and fed from a constant voltage source 9. A resistance 10 is connected to the bridge diagonal. The signal is transmitted through a type II amplifier. The U4-1 is fed to an EO-7 instrument oscilloscope 12.

Before the measurement, all bridges are balanced by the booster resistance at resistance 8. As a charged particle passes through the ring electrode 4, a charge is induced on the latter, affecting the current in the source-drain circuit of the field-effect transistor. The balance of the bridge is disturbed and a voltage pulse occurs on the resistance 10, which is detected by the secondary device 12.

The concentration of MX particles passing through the ring electrode in the direction of the X axis can be calculated by the formula:

"NX -

(I) Wrx-Sp

where NX is the number of pulses on the oscillogram per unit of time;

Wf-x - average particle velocity

in the direction of the X axis; Sp is the cross-sectional area of the frame. The velocity of the particles W is determined by the time of flight of the particle of the effective height of the ring electrode. The time of flight is inversely proportional to the pulse width on the waveform. Concentration of mate

The rial at the location of the sensor will be:

П П П + П + П2, (2)

where Pu and HZ, are the concentration of particles in the directions y, z.

In order to account for particles hitting the edge of the frame, a coefficient is introduced to:

(3)

.

bf

So is the area of the circle, which is visible in the cross section of the ring electrode; 5 „- midsection section of a spherical particle. There is no useful signal in this case. Actual particle concentration at the measurement site:

 .

m

Datzhk device has a small size 2, Lx2, Lx2,5mmU, which introduces insignificant distortions in the hydrodynamics of the layer and improves the measurement accuracy.

SUBJECT OF INVENTION

A device for measuring the density of dielectric particles in two-phase flows, comprising current pulse sensors made in the form of an annular electrode, a pulse count measurement circuit, and a secondary device, characterized in that the sensors are installed in three mutually perpendicular planes to improve measurement accuracy.