SU868474A1 - Device for determining dynamic viscosity of liquid and gel-like products - Google Patents

Description

(54) DEVICE FOR DETERMINING DYNAMIC VISCOSITY OF LIQUID AND GEL PRODUCT

one

The invention relates to a technique for determining the physicomechanical characteristics of liquid and gel products by measuring the parameters of free vibrations (logarithmic decrement, frequency) of a combined oscillatory system and can be applied in the chemical, petrochemical, automotive, engineering and other industries for scientific research, laboratory express control and as a calibration tool for the production of industrial viscometers.

A device for measuring the viscosity and elastic characteristics of liquid media is known, comprising an elastic element, an inertial part, a thin-plate sensitive element, electromechanical and stimulating transducers, an information processing unit.

Determination of dynamic viscosity and dynamic shear modulus is carried out by measuring the logarithmic decrement and frequency of the oscillatory system, which is brought out of equilibrium with the help of an exciter converter, and then performs free circuits converted by an electromechanical converter into electrical ones processed by information processing unit 1.

The drawback of the device is that the measurement accuracy is not high enough due to the occurrence in the medium of various types of waves besides shear waves.

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It is also known to have a device for determining the dynamic viscosity and shear modulus in liquid media by measuring the logarithmic decrement and frequency of an oscillatory system performing torsional vibrations. The device contains an elastic element, an inertial part, a sensitive element.

20 in the form of a body of rotation (disk, cylinder, ball, cone, etc.), exciting and electromechanical transducers, information processing unitpp. The device works as described above.

In the case of the implementation of torsional oscillations of bodies of rotation in a controlled medium, only shear waves appear, therefore the error

30 due to the occurrence in the environment

waves other than shear, in this device is missing 3.

The disadvantage of this device is a sharp increase in the error in the case of measurements in gel products, which is associated with large recovery times (relaxation) of such media after immersing any rotation body into them.

The closest in technical essence to the present invention is a device for determining the viscosity and elasticity of liquid and gel products by measuring oscillation parameters (logarithmic decrement, frequency) of an oscillatory system that performs free torsional vibrations.

The device contains an elastic element (torsion), an inertial disk, a sensitive element, including movable and stationary cylinders, electromechanical and exciting transducers and an information processing unit. The controlled medium is pumped through a special dispenser into the gap between the coaxially arranged cylinders 4.

The disadvantages of the known device are the dependence of the measurement error: on the dosing accuracy, as well as the low express speed of measurements associated with the use of a special dosing device requiring washing and reloading, and the need to disassemble, assemble and adjust the oscillating system after each filling of the sensitive element . In addition, frequent assembly, disassembly and adjustment of the oscillatory system increases the magnitude {of the subjective error in the measurements.

The purpose of the invention is to improve the accuracy and speed of measurements.

The goal is achieved by the fact that in a device for determining the dynamic viscosity of liquid and gel products containing an oscillatory system consisting of an elastic element connected to each other, an inertial disk and a sensing element including moving and stationary parts, the movable part of the sensitive element is made the form of a double cylinder, the submerged part of which is made hollow and rigidly connected to the non-immersed part of it, the strips being the continuation of the submerged part.

FIG. 1 is a simplified illustration of the structure of a device measuring transducer; in fig. 2 diagram of the sensitive element.

The measuring transducer consists of an elastic element 1 in the form of a tube torsion, the upper end fixed in a fixed support 2, and the lower end in a movable support 3 of the inertia disk 4. A rod 5 is attached to the lower plane of the inertial disk, the axis of which is on the same axis with the elastic element 1 The sensing element of the converter contained a movable part in the form of a hollow thin-walled cylinder b of radius RJ rigidly connected to a non-submerged part 7 of it by two strips 8 that are extensions of the body of a hollow cylinder 6, and a stationary part in the form of a hollow torus formed by coaxially arranged cylinders 9 and 10 with an outer radius RY and inner R. The measured medium is deformed into the gap R2 - R and Rj - H, i.e. between coaxially arranged cylinders 9 and 10. The wall of the hollow torus is the upper wall of a liquid thermostat (not shown). The thermostat moves in the vertical direction and is fixed by an abutment (not shown), THAT allows the immersion depth of the cylinder 6 to be kept constant.

The outer cylinder 9 of the fixed part is provided with a flange 11, the upper plane of which corresponds to the level of the filled liquid (height h).

The device works as follows.

The stationary part, consisting of cylinders 9 and 10, is lowered to a previously lower position, after which a controlled medium is placed into the cavity between these cylinders with a filling level slightly higher than the level corresponding to the upper plane of the flange 11. Then, using a special scraper, the plane of which is superimposed on the annular plane of the flange 11, remove the excess medium so that its level coincides with the annular plane of this flange. The moving part is raised until it stops. In this case, the hollow cylinder b is completely immersed in the controlled medium, and the strips 8 are submerged half its length. After removing the additional torque set for a short time by means of an exciter converter (not shown), the oscillatory system elastic element 1 — inertial disk 4 — the hollow cylinder b performs free oscillations, which are converted by using an electromechanical converter (not shown) electrical oscillations whose parameters (logarithmic decrement and frequency) are measured by an information processing unit (not shown).

Due to the fact that in each measurement the strictly constant filling level between the cylinders 9 and 10 is difficult to maintain, the overall lateral surface of the strips 8 is chosen to be much smaller, the total lateral surface of the immersed cylinder 6. Therefore, the error is measured the smaller, the smaller the maximum ratio differences in the loading area of the strips to the total immersed area for any quantities of loading. The value of said ratio is determined as follows. The value of dynamic viscosity for a sensitive element (fig. Is defined by the expression J.2V.I 1 where A is the logarithmic decrement of the oscillating system; I is the moment of inertia of the oscillating system; T |, is the oscillation period of the oscillatory system with the measured medium; b is a form factor. Logarithmic (1), we have en i - e, v 24tnx + e, n -tvibtvi.ci) We define the relative measurement error of the dynamic viscosity: "..- IfMYI - / /. For determination (i, it is necessary to evaluate each term of the right part of expression (3). Magnitude X is determined by the measurement error of the logarithmic decrement by the electronic circuit and can be taken into account. The error L | / 1 is small and can be eliminated by introducing corrections. The maximum error value measuring the period of oscillations by time electronic time meter gauges is 0.03% and can also be taken into account. To estimate the magnitude of K, it is necessary to determine the expression for the form fact sensitive element of this devices. As is known, when a liquid medium is deformed in a narrow gap between coaxial cylinders, the form factor is determined by

WT

where b is the length of the cylinders;

Rgj is the radius of the inner cylinder;

Rgc is the radius of the outer cylinder. Since in the proposed device the liquid is deformed between two

 -2tsl t2eMnivtn) V-2En1t-2eM6-tni,

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Errors

dp

 also

w can Syt be accounted for

Claims (4)

those. cf .., (,,) where LA / A is an error. cylinders with radii R and R ,, then the form factor is determined by the expression -. R R-R, After the transformations, we have (RV-HV Value 4lLRj in expression (6) defines the common lateral surface of the immersed cylinder 6 (assuming an extremely thin wall), i.e. S 4. Take, r) - b, (1J Then AB-A5. J. 1 Differentiating expression (7) and substituting the values for the radii of the cylinders, taking into account the tolerances in their manufacture, determine L. b | b. This value is 0.05% and can also be The error L5 / 5 is nothing but the ratio of the difference in the area of the immersion of the strips to the total immersed area, if the measured medium is filled in between the cylinders. GDSs relative measurement error of viscosity change is determined 1Only dipping cylinder space 6, by varying the floating conductive liquid level, i.e. rf ,, - f, 0), where l / A-recorded error. , From expression (9) it is clear that it is advisable to choose as miniature as the technical implementation of the moving part allows, but in all cases they do not need more than the required magnitude of the relative error of measuring the dynamic viscosity. In the case of cylinder 6 immersion in an inorganic medium, dynamic viscosity is limited by the expression A-KHo-V / I / -U f, -ici.ea.2 Find the relative error in viscosity measurement, logarithm expression (10): From expression (11) it can be seen that, in the case of an unlimited medium, it is necessary to choose two times smaller than the required relative error-measurement of the dynamic viscosity. Those. The choice of a ratio two times smaller than the relative error in measuring viscosity is valid in the case of the use of measuring transducers of any structures. The use of the proposed sensor in the device not only improves the accuracy, but also the rapidity of the measurements, since no adjustment of the recording converter is required after each filling. Repeated measurements are carried out as follows. A thermostat with a fixed part inserted into it (cylinders 9 and 10) is lowered to its lowest position. The stationary part is removed from the thermostat, and in its place a similar part is placed with a new controlled medium. Then the thermostat is raised to the upper extreme position until it stops, after which the device is ready for repeated measurements. The expressiveness of the measurements in the proposed device is much higher also because it does not require the use of special metering devices that require a long run after each measurement. Apparatus of the Invention A device for determining the dynamic viscosity of liquid and gel products containing an oscillatory system consisting of an elastic element connected to each other, an inertial disk and a sensitive element including moving and stationary parts, in order to improve the accuracy and express measurement, the movable part of the sensing element is made in the form of a double cylinder, the loading part of which is made hollow and rigidly connected to the non-loaded part of the rag E, is a continuation-expandable mounting part. Sources of information taken into account in the examination 1. Vibration viscometer. Sat scientific papers ed. Corr. USSR Academy of Sciences Kutateladze. Novosibirsk, 1976, p. 153-156. 2. Patent. Japan No. 15276/72, 113 (c), 1967. 3. Grechishin V.A. The state and tendencies of the development of oscillatory methods and means for determining the rheological characteristics of polymers during their production. 4. Research physical properties. Ser. Systems and means of automation of chemical production. M., 1976, p. 39-42 (PROTOTYPE,); at w //. eleven.