SU1744593A1 - Vibration-plate viscosimeter - Google Patents

Abstract

Use: for determining the viscosity of chemical solutions and petroleum products. SUMMARY OF THE INVENTION: The vibration viscometer comprises a housing. In the case through the system of elastic elements attached rod. The rod is mechanically connected to the plate. Strings are used as elastic elements. The strings are placed between permanent magnets. 3 il.

Description

The invention relates to the field of viscometry and can be used in various fields of technology and production for determining the viscosity of chemical solutions, petroleum products, alcohols and other low viscosity liquids.

Capillary type viscometers are known, the principle of operation of which is based on determining the time of flow of a known amount of liquid through narrow capillary tubes.

The disadvantages of capillary viscometers are the relatively low monitoring performance, the inability to organize continuous measurements.

The closest to the invention according to the technical essence and the achieved result is a vibration viscometer based on measuring the maximum amplitude of oscillations of a test object immersed in the test liquid (thin plate).

The known device contains a thin plate immersed in the liquid under study, a tube attached to it, a housing, a system of linear elastic elements in the form of tensioned strings rigidly connected to the tube and the walls of the housing, an exciter with protective screens and a vibration meter. When a viscometer is in operation, its oscillating system is tuned (for example, by measuring the frequency of the vibration exciter) to the mode with the maximum amplitude of oscillation of the plate immersed in the test liquid, and the viscosity is determined from the measured maximum amplitude.

A disadvantage of the known viscometer is the low sensitivity of the measurements.

The purpose of the invention is to increase the sensitivity of measurements.

The goal is achieved by the fact that the vibration viscometer includes a housing in which a rod is located,

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A system of elastic elements, made in the form of tensioned strings, rigidly connected to the core and the walls of the case, an exciter with protective shields and a vibration meter between the strings. In this case, the viscometer additionally contains permanent magnets installed inside the housing; moreover, the magnets are arranged so that the lines of force of the magnetic field formed by them are parallel to the axis of the rod, and the strings are made of magnetic material and placed between the magnets.

FIG. 1 is a schematic diagram of a vibration viscometer; in fig. 2 - amplitude-frequency characteristics (AFC) of the movements of the sensitive element (plate) of the viscometer in the resonant frequency range (curve a corresponds to the prototype device, curve b-object of the invention); in fig. 3 - viscosity c of the test liquid (benzene) as a function of the maximum amplitude of oscillations of the Womax of the sensitive element (curve a is the device prototype, curve b is the object of the invention).

Vibration viscometer (Fig. 1) contains a plate 1, immersed in the vessel 2 with the test liquid 3, and the rod 4 attached to the plate (thin-walled tube). On the rod 4 there are holes 5 and 6 through which the strings 7 are passed, made of magnetic material and playing the role of an elastic system of the device. The strings 7 are rigidly attached to the rod 4 and the walls of the case 8, tensioned (using special screws not shown in the diagram) and placed in magnetic fields formed by permanent magnets 9. To excite forced oscillations (in the direction of the x axis) rod 4 and a plate 1 rigidly connected with it is intended to be an exciter comprising oppositely connected windings of electromagnets 10, 11, diodes 12, 13 and voltage generator 14, and a non-contact vibration meter 15 for recording vibration parameters. To protect against interference, the exciter is equipped with protective screens 16.

Vibration viscometer works as follows

When conducting vibration control, the plate 1 of the viscometer is lowered into the vessel 2 with the liquid 3 under examination, after which, using a vibration exciter, vertically directed oscillations of the suspension part of the device are excited. The strings 7, located in the fields of permanent magnets 9, are affected by electromagnetic attraction forces directed toward the displacement of the strings and contributing to a decrease (as the displacement increases) of the ecBivalent elastic restoring force of the system. As a result, the elastic characteristic of the viscometer is transformed into a non-linear soft, due to which the vibrations arising in the system also become non-linear.

The higher sensitivity of the object of the invention is confirmed by the results of experimental studies in a laboratory setup made in

according to the circuit diagram of the device shown in FIG. 1. Benzene was used as the test liquid, the viscosity of which was varied by changing the temperature

test mode. The temperature of the test benzene was stabilized at a given level (with an accuracy of ± 0.05 ° C) by placing it in a double-wall glass vessel 2 (not shown in the diagram

shown), between which the circulating fluid from a thermostat type U-8. The main part of the rod 4 was made of a non-magnetic material, and its middle section (shaded in the diagram) is made of magnetic

alloy alnico. The oscillations of the plate 1 and the rod 4 bonded to it on the strings 7 were excited using an electromagnetic vibration exciter controlled by the generator 14. Due to the presence of diodes 12 and

13, a sinusoidal electric current generated by the generator 14, one half of the period passed through the winding 10, the other half of the period through the winding 11. On the magnetic section of the rod 4 at

This force acted, causing our rod to alternately retract into the winding 10, then into the winding 11. As a result, vertical oscillations of the rod 4 were excited and rigidly connected with

He plate 1, which were recorded with a contactless meter 15 vibrations.

FIG. 2 shows experimentally obtained (at Po / ka 0.005, rj 0.8 mPa s and t0 20 ° С, where Ro is the amplitude of the test harmonic effect, k is the equivalent stiffness coefficient of the elastic part of the viscometer) of the frequency response of the sensitive element of the viscometer in the main resonance zone with harmonic

5 of the type of exposure P0sin with t (curve and corresponds to the device of the prototype, curve b - the object of the invention). With this axis, the dimensionless amplitudes Yo х0 / a and frequency v (V / oscillations

(x0 is the half-range of oscillations of the sensitive element of the viscometer, and is the gap between the string and the permanent magnets, (Do is the frequency of free oscillations of the system, u is the frequency of external harmonic action.

A comparative analysis of the given frequency response allows us to establish the following. In the prototype device, the elastic characteristic is linear, so the corresponding frequency response (curve a) has a sharp resonance peak characteristic of linear systems. The informative parameter used to determine the viscosity i is the maximum amplitude of the Usomax oscillation, which corresponds to point C on the frequency response.

After the introduction of permanent magnets into the viscometer design, the elastic equivalent of the suspension becomes non-linear soft, which is reflected in the frequency response (curve b) accordingly. The zone of oscillation ambiguity appears, within which the system has two stable modes of motion: the resonant one (section AV AFC) and the nonresonant section (section А В1 AFC). In this case, the highest sensitivity of the control is achieved when using the amplitude of oscillations at the resonance point B of the frequency response as the informative sign (the maximum amplitude of the UvOmax).

According to the test results, calibration curves (Fig. 3) were obtained that establish the relationship of the maximum amplitude of Vomass oscillations with the viscosity g) of the test liquid (curve a corresponds to the prototype device, curve b to the object of the invention). As the analysis of the calibration curves and the corresponding calculations show, a relative change in viscosity q by one conditional unit corresponds to a change in the informative attribute Uvomax by one unit in the prototype device and by 1.6-1.8 units in the object of the invention. In practice, this is equivalent to the measurement sensitivity increased 1.6-1.8 times when using the object of the invention to determine the viscosity of the test liquid.

Thus, the main technical and economic advantage of the invention is a higher measurement sensitivity, which ultimately allows to determine the viscosity of the test liquid with increased accuracy.

Claims (1)

Vibration viscometer, comprising a housing in which a rod rigidly connected to a plate-like sensing element is located, a system of elastic elements made up in tensioned strings rigidly connected to the rod and the walls of the housing, an exciter with protective screens placed between the strings, and a meter vibration, characterized in that, in order to increase the measurement sensitivity, the viscometer further comprises permanent magnets installed inside the housing, so that the lines of force of the magnetic field formed by them are parallel to the axis of the rod, and the strings are made of magnetic material and placed between the magnets. ge O5 you y h-y W. 0.3 0.2 0.7 OMG 0,60,7,07,2 9 Ve then tlh .0 w / 70c 7.0 0.5 FIG. 2