RU215504U1 - Device for determining the viscosity of a liquid - Google Patents

Abstract

The utility model relates to measuring technology and can be used to determine the dynamic viscosity of a liquid. The technical result of the proposed solution is to increase the accuracy of determining the viscosity of the liquid. The technical result is achieved by the fact that the probe for interaction with the investigated liquid are elements in the form of sectors of a thin-walled cylindrical shell. The probe drive is built on the basis of an oscillatory rotational link inertial body (balance) - elastic suspension. A system for excitation of self-oscillations of the magnetoelectric type with two coils is provided, due to which the transverse force is excluded. A procedure for metrological certification of the installation has been developed. The principle of measuring dynamic viscosity is based on energy relationships. The work of viscous friction forces in the investigated liquid is revealed, according to which the dynamic viscosity is determined. The mathematical substantiation of the measurement principle is given. 6 ill.

Description

The utility model relates to measuring technology and can be used in devices for measuring the dynamic viscosity of liquids.

A certain systematization of methods and means for measuring the viscosity of liquids is given in the monograph - Measurements of mass, density and viscosity / Under. ed. Yu.V. Tarbeeva-M.: publishing house of standards, 1988. - 176 p. The book contains the calculation ratios that are necessary when designing measuring installations.

Capillary methods are used. In a device for measuring the viscosity and density of a liquid (patent RU 147292 U1, published on November 10, 2014), the capillary is used in the oscillation mode. Fluid flow probing by pulses of ultrasonic vibrations is used (patent RU 2112231 C1, publ. 27.05.1998). Since the theory of the interaction of a ball with a liquid is well developed, ball methods are widely used. According to the method for measuring the characteristics of liquid media, namely the volumetric flow rate and viscosity, and the device for its implementation (patent RU 2379632 C1, publ. 20.01.2010), a ball is used in an annular flow. The measurement of viscosity in a liquid flow is used in the method for determining the viscosity of a liquid according to patent RU 2051372 C1, publ. 12/27/1995. In this embodiment, the ball is fixed at the end of the elastic lever. It is possible to form a ball in the form of a gas bubble (patent RU 2390757 C1, publ. 27.05.2010). The most promising is the self-oscillating movement of the ball (patent RU 2373516 C2, publ. 20.11.2009).

Known devices for measuring the viscosity of liquids have a common drawback - they are usually structurally and technologically complex, which implies high labor costs both at the production stage and during operation.

As a prototype, a device for determining the viscosity of a liquid according to patent RU 2263892 C2 IPC G01N 11/10, publ. 10.11.2005 Bull. No. 31. In the description of the invention to the patent, the design of the device is shown schematically. There is a container 3 for the investigated liquid, with which the probe (working fluid) can interact 11. The drive for moving the probe is of a potential type - the acceleration of the consolidated fall is used. The probe drive includes a rod 13 and a screen 12. The drive is controlled by means of an electromagnet 14. The recorder of the probe movement parameters is represented by LEDs 9,10. A heating system for the test liquid is provided. The output information parameter is the probe movement time on the base section. The properties of the liquid are judged by calibration graphs.

The prototype device has the same disadvantages as analogues.

The technical result of the proposed solution is to simplify the design and technological complexity of the device for determining the viscosity of a liquid.

Tasks are solved:

1. Development of the design of a device for determining the viscosity of a liquid, providing low labor costs at the stages of manufacture and operation.

2. The design of the installation should be simple and technologically advanced.

3. Justification of the adopted technical solutions.

The specified technical result is achieved by the fact that in the installation for determining the viscosity of a liquid containing a container for the investigated liquid, a probe interacting with the measured liquid, a probe movement drive and a probe movement parameter recorder, the probe is made in the form of thin-walled sectors of a cylindrical shape, the probe movement drive is made in in the form of a rotational oscillatory link, a balance-elastic suspension with a magnetoelectric system for excitation of self-oscillations, containing a circuit for generating drive pulses, while the probe is fixed coaxially on the balance in its lower part.

The design of the installation for determining the viscosity of a liquid is illustrated by drawings:

Fig. 1. General view;

Fig. 2. Axial section of the sensor;

Fig. 3. Section A-A in FIG. 2;

Fig. 4. Section B-B in Fig. 2;

Fig. 5. Scheme for calculating the pulse angle;

Fig. 6. Scheme of formation of drive pulses.

Accepted designations

1. Foundation.

2. Capacity for the investigated liquid.

3. Sensor.

4. Probe.

5. Sensor bracket.

6. Sensor fastening screws.

7. Bracket fastening screws 5.

8. Sensor body.

9. Balance - an inertial body of an oscillatory link.

10. Balance bushing.

11. Upper balance wing.

12. The lower wing of the balance.

13. Balance collet.

14. Elastic suspension.

15. Body collet.

16. Permanent magnets.

17. 18. Electric coils.

19. Bracket for the self-oscillation excitation system.

20. 21. Coil pads.

22. Cover screws.

23. Electrical connector.

24. Bracket fastening screws 19.

25. Bearing.

26. Bearing bracket.

27. Bracket screws 26.

28. Protective cover.

. Пространственное положение датчика реализуется посредством кронштейна 5. Крепление датчика осуществляется винтами 6, а крепление кронштейна - винтами 7.The mounting basis of the installation is base 1, in a small recess of which a container 2 is installed for the test liquid. The container may have a level mark. Above the tank there is a sensor 3 with a probe 4 protruding from its body. The probe has a mark (not shown in the drawing) of the immersion depth

. The spatial position of the sensor is realized by means of the bracket 5. The sensor is fixed with screws 6, and the bracket is fixed with screws 7.

The sensor is made in the form of a separate assembly unit, all its elements are mounted on a housing 8 of rectangular L-shaped shape. Probe movement drive 4 is made on the basis of a rotational oscillatory link balance-elastic suspension. Assembly unit balance (inertial body) 9 contains a central magnetic sleeve 10, to which is attached the upper magnetic wing 11 in the form of a circle, the lower magnetic wing 12 in the form of an inverted bowl and a collet clamp 13 for attaching the lower end of the elastic suspension 14. The elastic suspension is a segment round wires made of a material with low internal friction (narrow mechanical hysteresis loop). The upper end of the elastic suspension is fixed in the collet clamp 15 of the sensor housing. Collets are standard items, so FIG. 2 they are shown conditionally.

There is a magnetoelectric system for excitation of balance self-oscillations. It includes two pairs of permanent magnets with 16 axial magnetization diametrically fixed with glue on the balance wings. In general, the balance is axially balanced. Frameless flat electric coils 17, 18 are installed in the magnetic gaps of the balance. The coils have the same outer diameters. One coil is wound bifilarly (in two wires) and contains a W _u section and a W _o section, and the second coil contains only a W _and section. The coils are included in the drive pulse shaping circuit (SFIP) - fig. 6. The spatial position of the coils is provided with the help of a bracket made of insulating material 19 - see Fig. 3. This bracket, together with other elements, forms a separate assembly unit. Coils 17, 18 are placed in the bores of the end sections of the bracket and are pressed with pads 20, 21 using screws 22. The transistor VT and capacitor C SFIP are mounted on the bracket by the hinged mounting method. External electrical connection is made using connector 23. Bracket 19 is attached to sensor body 8 with screws 24.

. Кромки секторов притуплены. Зонд соединен с приводом перемещения, а именно с балансом. Учитывая форму этих элементов, зонд и нижнее крыло баланса следует выполнять в виде единой детали. К расчетным параметрам зонда относятся:When designing a probe, it is necessary to keep in mind the provision of shear stresses in the investigated liquid. In FIG. 4 shows a section of the probe. It consists of two sectors of a thin-walled cylindrical shell with a height exceeding the calculated immersion depth

. The edges of the sectors are blunted. The probe is connected to the movement drive, namely to the balance. Given the shape of these elements, the probe and the lower balance wing should be made as a single piece. The design parameters of the probe include:

R is the radius of the shell;

α - sector angle;

h is the shell thickness;

- глубина погружения;

- immersion depth;

S is the total area of interaction with the measured liquid.

Given that R>>h

The sensor provides for the blocking of pendulum oscillations of the balance, respectively of the probe, possible due to external disturbances. A bushing (bearing) 25 is installed in the lower part of the elastic suspension. The bushing is a standard and widely used in instrumentation support made of artificial minerals (ruby, leucosapphire) with an olive hole. The sleeve is pressed into the hole of the bracket 26, which is attached to the body 8 of the sensor with screws 27.

After mounting the functional elements of the sensor, a protective casing 28 is installed from a U-shaped sheet material. For reasons of clarity, in Fig. 3 it is shown conditionally by a dotted line.

The calculated stationary amplitude of self-oscillations of the balance, therefore, of the probe, is realized by the power supply level E of the drive pulse shaping circuit (SFIP) - FIG. 6. When the balance moves in the direction ω (Fig. 5) within the pulse angle λ, an EMF is induced in the coil windings 17, 18.

Release winding emf W _o in vector form

- магнитная индукция в зазоре;where

- magnetic induction in the gap;

- направление витка;

- the direction of the coil;

- линейная скорость.

- linear speed.

витка и ЭДС меняет знак. Для транзистора VT принятий проводимости (n-р-n) положительная полуволна ЭДС открывает транзистор и по обмоткам импульса W_u1 и W_u2 проходит импульс тока, обеспечивающий подкачку энергии к колебательному звену. Катушки включены последовательно (фиг. 6), токи в них равны, следовательно, образуется пара сил, что исключает появление поперечной (маятниковой) силы. Возможный диапазон амплитуд φ автоколебанийThe ends of the winding W _o are connected so that e _o is positive within λ. After passing through the equilibrium position, the direction changes

turn and the EMF changes sign. For a transistor VT of accepting conductivity (n-p-n), a positive half-wave of the EMF opens the transistor and a current pulse passes through the pulse windings W _u1 and W _u2 , which provides energy pumping to the oscillatory link. The coils are connected in series (Fig. 6), the currents in them are equal, therefore, a pair of forces is formed, which eliminates the appearance of a transverse (pendulum) force. Possible range of amplitudes φ of self-oscillations

For definiteness, we take the value of the stationary amplitude φ _st =1 rad.

Let us explain the principle of revealing the required parameter (dynamic viscosity of a liquid). Consider the properties of the system.

The first parameter of the oscillatory link is the natural frequency f

where T is the period of oscillation;

ω - cyclic frequency,

here D is the torsional rigidity of the suspension;

J - moment of inertia of the balance.

The energy properties of the vibrational link are characterized by the value of the quality factor Q

where

- vibrational energy at amplitude φ;

E _sweat is the energy loss in one period T.

Instead of the quality factor, the value of the integral friction coefficient h _u is used

The values \u200b\u200bof h _u or Q are determined experimentally (Sharygin L.N., Sorokin A.A. Self-oscillating systems in measurement and control tools: study guide. - Vladimir: ed. Atlas, 2016. - 205 pp. ISBN 978-5- 903087-53-2). To do this, get the run-out function φ=f(t). With regard to the installation under consideration, the EMF pulses e _{o of the} winding W _o SFIP are recorded with the power supply turned off E. It follows from formula (2) that the peak value e _o is proportional to the amplitude φ

because the

V _max \u003d ωφr _b ,

where r _b is the interaxial displacement of the magnets 16. The value of the coefficient K - formula (9) - is found at φ=φ _st .

Formula (9) shows that during the operation of the installation, when establishing the desired value of the amplitude of self-oscillations of the balance φ _st , the maximum value of the release EMF e _o should be measured. Since the positive half-wave e _o is somewhat reduced by the base current of the transistor VT, it is preferable to use a negative half-wave.

On the run-out function in the vicinity of the stationary amplitude φ _st , take two values φ ₁ > φ _st and φ _N <φ _st and calculate the quality factor

where N is the number of periods T during the movement from the amplitude φ ₁ to the amplitude φ _N .

In accordance with formula (6), the loss energy E _sweat for one period T of oscillations will be

During this time, energy was transferred from the energy source E of the excitation system

where I _cf is the average source current E.

Taking into account that in the initial position the transistor VT is in the cutoff mode due to zero bias, then at large values of the current transfer coefficient β of the transistor, the shape of the current pulses is close to rectangular, then

where I _t is the amplitude of the current in the pulse;

t _u - pulse duration.

равенIn accordance with formulas (11), (12), the efficiency

equals

достаточно при нахождении энергии потерь E_пот в процессе эксплуатации установки измерить среднее значение потребляемого тока I_ср From formulas (13), (14) it follows that after certifying the value of the efficiency coefficient

it is sufficient to measure the average value of the consumed current I _cf when finding the energy losses E _sweat during the operation of the installation

, K, φ_ст,

, Q⁰,

,

. Параметрам, которые изменяются при измерении вязкости жидкости, присвоен верхний индекс 0. В спецификацию установки входят: измеритель среднего значения импульсного тока, источник регулируемого постоянного электропитания, измеритель ЭДС.Based on the results of metrological certification, the main parameters of the installation are fixed - J, D, ω, T,

, K, φ _st ,

, Q ⁰ ,

,

. The parameters that change when measuring the viscosity of a liquid are assigned the superscript 0. The installation specification includes: a meter for the average value of the pulsed current, a regulated DC power supply, an EMF meter.

Use the setup as follows:

зонда 4.1. Fill container 2 with the test liquid, maintaining the immersion level

probe 4.

2. By adjusting the power supply level E, the value of the stationary amplitude of self-oscillations φ _st of the balance is set. The control is carried out according to the value of e _o (negative half-wave).

3. Measure the average value of the current I _cf.

вычисляют E_пот, h_u и находят величины их увеличения4. By difference

calculate E _sweat , h _u and find the magnitude of their increase

равна работе сил вязкого трения в исследуемой жидкости.Energy

is equal to the work of viscous friction forces in the investigated fluid.

5. Accept the fluid model and find the dynamic viscosity η. In the monograph cited on p. 1 of this description - see p. 163 - for a Newtonian liquid with an oscillatory method of measurement, an expression was obtained for finding the dynamic viscosity η

where ρ is the density of the liquid;

S - probe area - see formula (1).

Thus, the proposed installation for determining the viscosity of a liquid due to the block design is structurally simple and high-tech, which implies low labor costs during development in production. The procedure for revealing the parameters of viscous friction of the studied liquid does not require high qualification of the operator.

A device for determining the viscosity of a liquid, containing a base on which a container for the test liquid is installed, a probe interacting with the test liquid, a drive for moving the probe and a recorder for the parameters of the movement of the probe, is characterized in that the probe is made in the form of thin-walled sectors of a cylindrical shape, the drive for moving the probe is made in the form of a rotational oscillatory link, a balance-elastic suspension with a magnetoelectric system for excitation of self-oscillations, containing a circuit for generating drive pulses, while the probe is fixed coaxially on the balance in its lower part, and the recorder of the movement parameters of the probe is made in the form of a power supply parameters meter for the drive pulse formation circuit.

Claims (1)

A device for determining viscosity, comprising a base on which a container for the test liquid is installed, a probe interacting with the test liquid, a drive for moving the probe and a recorder of probe pressure parameters, characterized in that the probe is made in the form of thin-walled sectors of a cylindrical shape, the drive for moving the probe is made in in the form of a rotational oscillatory link, a balance-elastic suspension with a magnetoelectric system for excitation of self-oscillations, containing a circuit for generating drive pulses, while the probe is fixed coaxially on the balance in its lower part.

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