WO2015029196A1

WO2015029196A1 - Method and device for finding shear rate of fluid by vibration-type viscometer

Info

Publication number: WO2015029196A1
Application number: PCT/JP2013/073202
Authority: WO
Inventors: 直人出雲; 菅野　将弘
Original assignee: 株式会社エー・アンド・デイ
Priority date: 2013-08-29
Filing date: 2013-08-29
Publication date: 2015-03-05

Abstract

Provided is a method for using a vibration-type viscometer to determine the shear rate applied to a fluid. Focusing on the continuous sinusoidal reciprocating motion of an oscillator (1) of a tuning fork vibration-type viscometer, the present invention expresses as a sine curve the shear rate that acts on a fluid (9) when the oscillator (1) moves in a reciprocating manner around a fluid-contacting surface center (1o) thereof in a direction parallel to a fluid-contacting surface (1a), and having captured the shear rate as the root mean square (D'=D₀/√2) of the shear rate, can determine the shear rate and quantitatively manage the shear rate even using the vibration-type viscometer.

Description

Method and apparatus for determining fluid shear rate in vibratory viscometer

The present invention relates to a method and apparatus for determining a shear rate applied to a fluid in a vibratory viscometer.

As shown in FIG. 5, the viscosity η, which is an important element for evaluating the physical properties of the fluid, is obtained by arranging two parallel flat plates P and Q in the x direction in a fluid space by orthogonal coordinates. A unit area on a plane parallel to the flow direction between the flat plates PQ generated due to the difference between the shear rate D, which is a speed gradient when the flat plate Q is moved at a constant speed in the x direction, and P is fixed. It is known that it is expressed by the equation (1) using a shear stress S that is a frictional force acting on a hit.

Here, especially in a non-Newtonian fluid, the behavior of the fluid changes when the shear rate D is changed. Therefore, the measurement of the shear rate is indispensable in designing the physical properties of the fluid. The value you want to get.

On the other hand, a vibratory viscometer is used as one of the devices for evaluating the physical properties of the fluid. Among them, the tuning fork vibration type viscometer immerses two vibrators in a fluid, resonates like a tuning fork, and drives a pair of vibrators by electromagnetic force generated by a combination of a magnetic circuit and an electromagnetic coil. The viscosity is measured by utilizing the fact that there is a correlation between the driving current and the sample viscosity (Patent Document 1). A rotational vibration (or torsional vibration) viscometer measures or constants the torque required to resonate one vibrator immersed in a fluid in the rotational direction and maintain a constant amplitude. The viscosity of the fluid sample liquid is measured by measuring the amplitude while maintaining the torque (Non-Patent Document 1).

Japanese Patent Laid-Open No. 5-149861

However, in a vibratory viscometer, the vibrator reciprocates in the fluid, so the shear rate changes with time, and the shear rate applied to the fluid remains constant with time. Therefore, the vibration type is recognized as a measurement method and apparatus that cannot determine the shear rate.

In order to solve the problems of the prior art, the present invention proposes a method for determining the shear rate applied to a fluid in a vibratory viscometer, and provides a vibratory viscometer that can determine the shear rate. is there.

Means for Solving the Invention

In order to achieve the above object, in the method for determining the shear rate generated in the fluid in the present invention, a pair of thin vibrators immersed in the fluid are vibrated by an electromagnetic drive unit having a coil, and the vibrator The shear rate generated in the fluid is obtained in a tuning-fork vibration viscometer that measures the viscosity of the fluid by passing a drive current through the coil so that the amplitude of the fluid becomes a set amplitude value. a method, a shear rate D which acts on the fluid when the vibrator vibrates the wetted surface parallel direction about its wetted surface center, a sine curve, 1 / √ maximum shear rate D ₀ 2 is obtained as the effective value D ′ of the shear rate, and the effective value D ′ of the shear rate is handled as the shear rate acting on the fluid at that time.

In the tuning fork vibration type viscometer according to the present invention, a pair of thin vibrators immersed in a fluid is vibrated by an electromagnetic drive unit provided with a coil, and the amplitude of the vibrator becomes a set amplitude value. A tuning fork vibratory viscometer that measures the viscosity of a fluid by passing a drive current through a coil and measuring the drive current, and the vibrator vibrates in a direction parallel to the liquid contact surface around the liquid contact surface center. The shear rate D sometimes acting on the fluid is a sine curve, and 1 / √2 of the maximum shear rate D ₀ is obtained as the effective value D ′ of the shear rate, and the effective value D ′ of the shear rate is then calculated as the fluid. It is characterized by comprising a shearing speed determining means that handles the shearing speed acting on the

Further, in the method for obtaining the shear rate generated in the fluid according to the present invention, it is necessary to drive one resonator immersed in the fluid to resonate in the rotational direction and maintain a constant amplitude. In a rotational vibration viscometer that measures the viscosity of a fluid by measuring the torque or maintaining a constant torque and measuring the amplitude, the shear speed generated in the fluid is obtained, and the vibrator has a rotational axis The shear rate D acting on the fluid when rotating and oscillating periodically at the center is a sine curve, and 1 / √2 of the maximum shear rate D ₀ is obtained as the effective value D ′ of the shear rate, and the effective value of the shear rate is obtained. D ′ is treated as the shear rate acting on the fluid at that time.

According to the present invention, attention is paid to the fact that the vibrator in the vibration type viscometer continuously reciprocates sinusoidally, and in the tuning fork vibration type, the vibrator is parallel to the liquid contact surface around the liquid contact center. Sine curve D = D ₀ · sin ωt where D _{0 is the} maximum shear rate, ω is the angular velocity of the vibrator, t is the time, and the shear rate is Assuming that the effective value of the shear rate is D ′ = D ₀ / √2, in the rotational vibration type, the shear rate D acting on the fluid when the vibrator periodically oscillates around the rotation axis is expressed as a sine curve D = D ₀ · sin ωt, and the shear rate is regarded as the effective value of the shear rate D '= D ₀ / √2, so the shear rate can be determined even in the vibration viscometer, and the shear rate is quantified. Can be handled.

Schematic diagram of the structure of a drive mechanism of a tuning fork vibration viscometer according to the present invention Block diagram of the control drive system of the tuning fork vibratory viscometer Diagram explaining the effective value of shear rate Graph showing effective value of shear rate Schematic diagram for deriving viscosity definition

Next, a preferred embodiment of the present invention will be described.

FIG. 1 is a configuration diagram of a tuning-fork vibration viscometer according to the present invention, and is a schematic configuration diagram of a drive mechanism unit 10 in a viscometer body. The detailed configuration of the viscometer body and the drive mechanism 10 is described in International Patent Application No. 2012/074654.

In the drive mechanism unit 10,

reference numerals

1 and 1 are a pair of thin vibrators immersed in the fluid sample liquid 9, which are formed from a thin flat plate material such as a ceramic member or a metal member, and have a circular shape at the tip. An enlarged portion is provided. This enlarged portion becomes the liquid contact surface 1 a with the sample liquid 9.

Numeral 7 is a container filled with the sample liquid 9, and numeral 3 is a temperature sensor.

Reference numerals

4 and 4 are leaf springs having the

vibrators

1 and 1 fixed at the tip, and reference numeral 8 is a central support member to which the

leaf springs

4 and 4 are fixed. The

vibrators

1 and 1 are the sample liquid in the container 7. 9 is configured to be immersed in a certain depth.

Reference numeral 2b denotes an electromagnetic coil, and reference numeral 2a denotes a neodymium magnet. The

vibrators

1 and 1 provided at the tips of the

leaf springs

4 and 4 by a moving magnet type electromagnetic drive unit 2 including the electromagnetic coil 2b and the neodymium magnet 2a. Is configured to vibrate with a set amplitude value. Reference numeral 5 denotes an eddy current loss detection non-contact type displacement sensor, which measures the amplitude values of the

vibrators

1 and 1.

Next, FIG. 2 is a block diagram of the control drive system of the tuning-fork vibration type viscometer according to the present invention.

Reference numeral 12 is a PWM modulation circuit, reference numeral 13 is a sine wave generation circuit, reference numeral 14 is a comparator, reference numeral 15 is a controller, reference numeral 16 is an I / V converter,

reference numerals

17 and 19 are A / D converters, and reference numeral 18 is An arithmetic processing unit.

A drive signal is output from the arithmetic processing unit 18 so that the

vibrators

1 and 1 immersed in the sample liquid 9 vibrate with a set amplitude value, and the drive current generated via the sine wave generation circuit 13 is generated. The electromagnetic coil 2 b of the electromagnetic drive unit 2 is energized and applied to the

leaf springs

4 and 4. As a result, the

vibrators

1 and 1 vibrate in opposite phases to form a resonance state. The amplitude values of the

vibrators

1 and 1 are detected by the displacement sensor 5, and the detected amplitude value signal is compared with the set amplitude value by the comparator 14, and the

vibrators

1 and 1 vibrate at the set amplitude value. Thus, a signal is output from the controller 15 and feedback control is performed. When the

vibrators

1 and 1 vibrate with a set amplitude value, the drive current I energized to the electromagnetic coil 2b at that time is detected. Then, this drive current I is input to the arithmetic processing unit 18 via the I / V converter 16 and the A / D converter 17, and the viscosity of the sample liquid 9 is calculated. The viscosity calculation process is described in Japanese Published Patent Publication No. 5-149861. An input signal of the temperature sensor 3 is input to the arithmetic processing unit 18 via the temperature A / D converter 19.

A PWM modulation circuit 12 is connected between the arithmetic processing unit 18 and the comparator 14, and the amplitude value input to the comparator 14 is set by performing pulse width modulation according to a command from the arithmetic processing unit 18. The amplitude value is arbitrarily changed, the amplitude of the

vibrators

1 and 1 is changed during measurement, and the shear rate generated in the sample liquid 9 is changed.

The arithmetic processing unit 18 is connected to a memory 21, a display unit 22, a key switch unit 23 (all not shown), and the user can set measurement conditions from the key switch unit 23. Examples of measurement conditions include measurement time and amplitude change settings (input of lower and upper limit values of the amplitude and determination of the amount of change in the amplitude timetable, whether to increase, decrease, or reciprocate the amplitude), etc. It is. Details of this are described in International Patent Application No. 2012/074654.

Now, the vibrator 1 periodically reciprocates around the center 1o of the liquid contact surface 1a in a direction parallel to the liquid contact surface 1a (X direction in FIG. 1). That is, the shear rate applied to the sample liquid 9 is zero when the displacement of the vibrator 1 is maximum, and the shear speed applied to the sample liquid 9 is maximum when the displacement of the vibrator 1 is zero. That is, the shear rate D applied to the sample liquid 9 by the vibration of the vibrator 1 is represented by a sine curve as shown in FIG. 3A and can be expressed by the equation (2).

Here, D _{0 is the} maximum shear rate, ω is the angular velocity of the vibrator, and t is the time.

The angular velocity ω can be transformed to ω = 2πf = 2π / T. Where f: frequency of the vibrator, T: vibration period of the vibrator.

At this time, if the resistance component in the sample solution 9 is R, the shear rate corresponds to the current, and if the thermal energy applied to the sample solution 9 per 1 s is RD ² , the result is as shown in FIG. Is given by equation (3).

When the average energy in the period T is obtained with respect to the periodically changing energy, Expression (4) is obtained.

Therefore, the relationship between the maximum value of the shear rate and the effective value D ′ of the shear rate is expressed by Equation (5).

Note that the maximum shear rate D ₀ is obtained by Expression (6).

Here, B: magnetic flux density of the coil, I ₀ : maximum current value flowing through the coil, L: coil length, α: leverage ratio of the vibrator, η: viscosity of the sample liquid, A: wetted area of the vibrator is there.

Specifically, the force F ₁ generated by the electromagnetic drive unit 2 is obtained from F ₁ = BIL. Driving force F in the wetted surface center 1o of the vibrator 1, a force F ₁ generated by the electromagnetic drive unit 2, with respect to the vertical center of the thinnest portion 4a of the leaf spring 4 as a supporting point of the vibrator 1, It is obtained by dividing by the ratio (leverage ratio) α of the distance d1 to the center in the vertical direction of the electromagnetic drive part 2 and the distance d2 to the liquid contact part center 1o of the vibrator (see FIG. 1). When the driving force F at the liquid contact surface center 1o of the vibrator 1 is divided by the liquid contact area A of the vibrator 1 (area of the liquid contact surface 1a), the shear stress S generated between the sample liquid 9 and the vibrator 1 is obtained. Can be requested. Therefore, if the viscosity η of the sample liquid 9 can be measured from the equation (1), the maximum shear rate D ₀ can be obtained from the equation (6) with the maximum current value I ₀ flowing through the coil 22. The magnetic flux density B, the coil length L, and the liquid contact area A are known values from the apparatus configuration. The maximum current value I ₀ is determined by measuring with the set amplitude. Thus, the effective value D ′ of the shear rate is calculated by the arithmetic processing unit 18 (shear rate determining means).

FIG. 4 is a graph showing the shear rate at each viscosity value as an effective value D ′ in the tuning-fork vibration viscometer according to the present invention. The horizontal axis represents the amplitude [mm] of the vibrator 1 and the vertical axis represents the viscosity value [mPa · s]. The liquid contact area A of the tuning fork vibration type viscometer used for the measurement is 0.000304 [mm], the leverage α is 3.81, the magnetic flux density B of the coil 22 is 0.308 [Web / m ² ], and the coil length L Was 4 [m]. The maximum current value I ₀ is a variable measured by the sample.

Sample liquid 9 was 45 ml each of ion-exchanged water and a standard solution for viscosity calibration (JS20, JS200, JS2000, JS14000) defined in JIS Z8809 (under constant conditions at 25 ° C.). The measurement conditions were as follows: each fluid, measurement time 11 minutes, amplitude lower limit value 0.2 mm, upper limit value 1.2 mm, amplitude timetable change Δ0.2 mm / min, amplitude decreased and then reciprocated. Moreover, since the viscosity (25 [° C.]) of each fluid is known (conforms to JIS Z8803), measurement was performed by inputting a value. The value of the effective value D ′ [1 / s] of the shear rate obtained as a result is shown in a white frame. FIG. 4 shows that even if the same amplitude is applied, the shear rate (effective value D ′) varies depending on the viscosity value.

As described above, according to the present invention, paying attention to the fact that the vibrator 1 in the tuning fork vibration type viscometer reciprocally moves in a sinusoidal manner, the vibrator 1 is in contact with the liquid contact surface centering on the liquid contact surface center 1o. The shear velocity D acting on the fluid (sample liquid 9) when reciprocating in the direction parallel to 1a is expressed as a sine curve, and effective value D ′ = D ₀ / √2: In the tuning fork vibration type viscometer, the shear rate can be determined, and the shear rate can be handled quantitatively.

The present invention can be applied not only to a tuning fork vibration type viscometer but also to a rotational vibration type viscometer.

A rotational vibration (or torsional vibration) viscometer resonates a cylindrical vibrator immersed in a fluid in the direction of rotation, and generates the torque necessary for the vibrator to maintain a constant amplitude. This is a device that measures the viscosity of a fluid sample liquid by measuring or maintaining a constant torque and measuring the amplitude. In this vibratory viscometer, the vibrator rotates and vibrates periodically around the rotation axis. (The node is reciprocally oscillated periodically in a clockwise / counterclockwise direction). That is, since the shear rate applied to the sample liquid by the rotational vibration of the vibrator of the rotational vibration type viscometer can be expressed by a sinusoidal equation (2) as in the tuning fork vibration type viscometer, the expressions (3) to (4) Therefore, also in the rotational vibration viscometer, the shear rate can be expressed by an effective value by the equation (5).

DESCRIPTION OF SYMBOLS 1 Vibrator 1a Liquid contact part 1o Liquid contact part center 2 Electromagnetic drive part 2a Neodymium magnet 2b Electromagnetic coil 3 Temperature sensor 4 Leaf spring 4a Thinnest part 5 Displacement sensor 7 Container 8 Center support member (plate spring fixation)
9 Sample solution 10 Drive mechanism

Claims

A pair of thin vibrators immersed in a fluid is vibrated by an electromagnetic drive unit having a coil, and a drive current is passed through the coils so that the amplitude of the vibrator becomes a set amplitude value. In a tuning fork vibration type viscometer that measures the viscosity of a fluid by measuring a shear rate generated in the fluid,
The shear rate D which acts on the fluid when the vibrator vibrates the wetted surface parallel direction about its wetted surface center, a sine curve, a 1 / √2 of the maximum shear rate D 0 of the shear rate A method for obtaining a shear rate generated in a fluid, characterized in that it is obtained as an effective value D ′, and the effective value D ′ of the shear rate is treated as a shear rate acting on the fluid at that time.
A pair of thin vibrators immersed in a fluid is vibrated by an electromagnetic drive unit having a coil, and a drive current is passed through the coils so that the amplitude of the vibrator becomes a set amplitude value. A tuning fork vibratory viscometer that measures the viscosity of a fluid by measuring
The shear rate D which acts on the fluid when the vibrator vibrates the wetted surface parallel direction about its wetted surface center, a sine curve, a 1 / √2 of the maximum shear rate D 0 of the shear rate A tuning fork vibratory viscometer characterized by comprising a shear rate determining means that obtains the effective value D 'as an effective value D' and handles the effective value D 'of the shear rate as a shear rate acting on the fluid at that time.
A single vibrator immersed in a fluid is driven to resonate in the rotational direction, and the torque required for the vibrator to maintain a constant amplitude is measured or the amplitude is measured while maintaining a constant torque. In a rotational vibration viscometer for measuring the viscosity of a body, a method for obtaining a shear rate generated in a fluid,
The shear rate D acting on the fluid when the vibrator periodically oscillates around the rotation axis is defined as a sine curve, and 1 / √2 of the maximum shear rate D 0 is obtained as the effective value D ′ of the shear rate. A method for determining a shear rate generated in a fluid, wherein the effective value D ′ of the shear rate is treated as a shear rate acting on the fluid at that time.