JP2559174B2 - Fluid viscosity measuring device and fluid force detecting device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fluid viscosity measuring device.

[0002]

2. Description of the Related Art Conventionally, several methods have been devised and put to practical use for measuring the viscosity of a fluid, and typical examples thereof are a capillary tube type, a rotary type, a falling body type, a vibration type, and a hot wire type. Etc. The measurement principles and problems are as follows.

Capillary type: The gravity flow type measurement method represented by the Ostwald viscometer is not suitable for a high viscosity fluid, and since the shear rate cannot be changed, the flow characteristics of a non-Newtonian fluid cannot be measured. Moreover, there is a problem that it cannot be used as an online viscometer.

The method of forcibly flowing a fluid through a thin tube and determining the viscosity from the flow rate and the differential pressure at that time enables accurate viscosity measurement, but depending on the nature of the fluid, blockage in the differential pressure measuring tube may occur. It may happen that the differential pressure cannot be measured accurately,
In particular, in the measurement of suspension, there is a problem that accurate viscosity measurement cannot be performed unless the diameter and length of the thin tube are large.

Rotation method: A method in which a rotating body such as a cylinder is rotated in the liquid to be measured, and the viscosity is obtained from the shear stress applied to the rotating body at that time, depending on the shape of the rotating body and the method of measuring the stress. Has been devised. Although it is small and simple, it requires careful handling in order to avoid overloading the rotating torque measuring section, and its absolute viscosity measurement accuracy is inferior to that of the capillary type. In particular, when measuring a suspension, a portion with a low solid content concentration (concentration polarization) is generated near the surface of the rotating body, which causes a measurement error.

Falling body type: A method of obtaining the viscosity from the falling velocity when a ball or a cylinder falls in a liquid to be measured,
Although the measurement is simple, it can measure only the viscosity at a limited shear stress, and is not suitable for measuring the flow characteristics of a non-Newtonian fluid.

Vibration type: A microvibration body is put in the liquid to be measured,
It is a method that calculates viscosity from the phase difference of the vibration wave, and is a simple method for measuring uniform material on solution, but for measuring suspension, for example, where concentration polarization occurs near the vibrating body, Measurement errors such as underestimation are unavoidable.

Hot wire method: When the hot wire is immersed in the liquid to be measured, the viscosity of the liquid is estimated because the convection strength and temperature gradient of the liquid near the hot wire depend on the physical properties of the liquid including the viscosity. The relative change in viscosity can be measured, but it is not suitable for measuring absolute viscosity.

As described above, each of the known viscosity measuring methods has advantages and disadvantages, and there is an inconvenience in that the measuring method must be selected depending on the properties of the liquid to be measured and the measuring purpose. Further, when particularly strict sanitary properties are required from the viewpoints of hygiene and quality control such as food materials, the structure of the measuring device must be simple and robust in addition to the measurement accuracy. In addition, it is difficult to measure the viscosity and flow characteristics of fluids having various properties with high accuracy over a wide range of shear stress and shear rate by the conventional techniques.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide an apparatus capable of performing proper viscosity measurement.

That is, in the device according to the present invention, an inner tube having a circular cross section, an outer tube having a circular cross section and having a diameter larger than that of the inner tube, and an inner tube arranged concentrically in the outer tube and moved in the axial direction. A means for supporting as much as possible, a fluid inlet for introducing the fluid to be measured between the inner pipe and the outer pipe, and an annular flow path formed between the inner pipe and the outer pipe in the axial direction. A fluid outlet for discharging the measured fluid to the outside, a detecting means for detecting an axial force exerted on the outer peripheral surface of the inner pipe by the measured fluid passing through the annular flow path, and the detecting means. Means for calculating the viscosity of the fluid to be measured based on the value of the axial force detected by.

The above device according to the present invention is based on the following principle.

That is, the viscosity μ (Pa.Pa.s) is formed in the annular flow path formed between the outer pipe and the inner pipe having concentric circular cross sections.
When flowing a fluid of s), the following relational expression is theoretically established between the force Fi (N) acting on the inner peripheral surface of the length L (m) and the flow rate Q (m ³ / s). .

[0014]

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overall outline of a viscosity measuring device 10 according to an embodiment of the present invention, and FIG. 2 shows a fluid force measuring device 24 which is a main part of the device.

As shown in the figure, the viscosity measuring apparatus 10 includes an inner tube 12 having a circular cross section set vertically, an outer tube 14 having a circular cross section and having a diameter larger and larger than that of the inner tube 12, and a fluid to be measured. A fluid inlet 18 provided at the lower end of the outer pipe for introducing into the annular flow passage 16 formed between the pipe and the inside of the outer pipe, and the fluid to be measured passed through the annular flow passage 16 in the axial direction to the outside. A fluid outlet 20 provided at the upper end of the outer tube for discharging
And the inner pipe 1 by the fluid to be measured which is passed through the annular flow path.
2 is a fluid force detecting device 24 including a detecting means 22 for detecting an axial force applied to the outer peripheral surface of the outer peripheral surface, that is, "shear stress", and based on the value of the axial force detected by the detecting device. And a computer 26 for calculating the viscosity of the fluid to be measured. The fluid to be measured is supplied from the fluid tank 30 through the fluid inlet 18 to the annular flow path 16 by the pump 28, and the fluid outlet 20 is supplied. It is designed to be returned to the fluid tank 30 via the. In the illustrated embodiment, the outer tube 14
A constant temperature water jacket 32 is attached around the
The jacket is supplied with constant temperature water from a constant temperature water tank 33 set around the fluid tank 30 via an inlet at the lower end of the jacket and discharged from an outlet 34 at the upper end of the jacket. ing.

The fluid force measuring device 24 has a base 36 at the lower end of the outer pipe 14, and a cylindrical inner pipe support member 38 is set on the base so that the fluid is not measured. 2, the inner pipe 12 is placed on the inner pipe support member 38 as shown in FIG. The inner tube 12 is a hollow member whose both ends are closed, and when a fluid is supplied into the fluid force measuring device, the inner tube supporting member 3
It is designed to rise from 8.

The detecting means 22 is fixed to the upper end of the outer pipe 14 inside the outer pipe 14, and is supported above the inner pipe 12 by a support pipe 40 axially aligned with the inner pipe and a mounting member 42. And a pressure sensitive element 44 fixed to the lower end of the tube.
The mounting member 42 has an upper recess 46 for accommodating the pressure sensitive element 44.
And a lower recess 50 for loosely accommodating the upper protrusion 48 formed in the central portion of the upper end wall of the inner pipe 12, and the partition wall 52 between these recesses has a protrusion 52 of the inner pipe. A force transmission pin 54 extending from 48 to a position close to the pressure sensitive element 44.
A through hole 56 is provided for passing through.

A guide pin 60 extending downward is provided at the center of the lower end wall of the inner pipe 12, and a guide hole 6 for loosely receiving the guide pin is provided at the center of the upper end surface of the inner pipe support member 38.
2 is formed. These guide pins 60 and guide holes 62
In combination with the protrusion 48 at the upper end of the inner pipe and the lower recess 50, guides the inner pipe axially when it is moved upward by the fluid.

In measuring the viscosity, the fluid is stored in the tank 30.
The fluid inlet 18, the annular flow path 16, the fluid outlet 20, and the tank 30 are continuously circulated in this order.

As described above, when the fluid is filled in the annular passage, the inner tube 12 floats upward due to its buoyancy.
The upper end of the force transmission pin 54 contacts the pressure sensitive element 44. Further, when the fluid is circulated as described above, the shear stress of the fluid that is passed through the annular flow passage 16 acts on the outer peripheral surface of the inner pipe 12 and applies an upward axial force to the inner pipe. Therefore, the force transmission member 54 transmits the axial force to the pressure sensitive element 44.
The axial force detected by the pressure sensitive element is transmitted to the computer 26, and the viscosity of the fluid is calculated.

[0022]

[0023] Where L is the axial length of the outer surface of the inner tube, Fi is the axial force acting on the outer surface, Q is the flow rate, R is the inner radius of the outer tube, a
Is the ratio of the outer radius of the inner tube to R, and the viscosity μ of the fluid can be obtained if Fi and other parameters such as Q are known.

In order to make an accurate measurement, the annular channel 16
It is necessary to make the fluid flow uniformly in the inside, and for that,
The distance from the fluid inlet 18 to the lower end of the inner pipe 12 is about several times to 100 times the width of the annular flow path (that is, the difference between the inner peripheral surface radius of the outer pipe and the outer peripheral surface radius of the inner pipe) depending on the property of the fluid. is necessary.

In addition to the shear stress Fi acting on the outer peripheral surface of the inner pipe, the force actually detected by the pressure sensitive element 44 is the static pressure P of the fluid to be measured which directly acts on the pressure sensitive element and the inner pipe 12. Since the difference ΔF in static pressure acting on the cross section between the upper end and the lower end is included, it is necessary to correct these values. The value of P is measured for each flow rate, and the value of ΔF is theoretically obtained by the following equation.

[0026]

[0027]

The apparatus according to the present invention has the above-mentioned structure and operation, and therefore has a problem in the above-mentioned conventional measuring method, that is, since the fluid velocity cannot be changed, the flow characteristics of the non-Newtonian fluid are It is possible to solve the problems that measurement cannot be performed, accurate measurement cannot be performed due to clogging of fluid, absolute viscosity cannot be measured, and proper measurement can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a viscosity measuring device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a fluid force measuring device which is a main part of the device.

[Explanation of symbols]

12 --- inner tube, 14 --- outer tube, 16 --- annular flow path, 18 --- fluid inlet, 20 --- fluid outlet, 22-
--- Force detecting means, 26 --- Data processing means.

Claims (4)

(57) [Claims] 1. An inner tube having a circular cross section , both ends of which are closed, an outer tube having a circular cross section and having a diameter larger than that of the inner tube, and an inner tube which is concentrically arranged in the outer tube and is movable in an axial direction. Means for supporting the fluid to be measured, a fluid inlet for introducing the fluid to be measured into an annular flow path formed between the inner tube and the outer tube, and the fluid to be measured passed through the annular flow path in the axial direction. A fluid outlet for discharging the fluid to the outside, a detection means for detecting an axial force exerted on the outer peripheral surface of the inner pipe by the fluid to be measured that is passed through the annular flow path, and the axis detected by the detection means. And a data processing unit for calculating the viscosity of the fluid to be measured based on the value of the directional force. 2. An inner tube having a circular cross section , both ends of which are closed, an outer tube having a circular cross section and having a diameter larger than that of the inner tube, and an inner tube which is concentrically arranged in the outer tube and is movable in an axial direction. Means for supporting the fluid to be measured, a fluid inlet for introducing the fluid to be measured into an annular flow path formed between the inner tube and the outer tube, and the fluid to be measured passed through the annular flow path in the axial direction. And a detection means for detecting an axial force exerted on the outer peripheral surface of the inner pipe by the fluid to be measured which is passed through the annular flow path. Detection device. 3. The axial direction is set to be vertical, and the fluid inlet and the fluid outlet are provided at the lower end and the upper end of the outer tube, respectively, so that the fluid to be measured flows from the lower end to the upper end. The measuring means is a pressure sensitive element set at a position above the inner tube, and the upper end of the inner tube is provided with a pressure sensitive element when the inner tube receives the axial force and is displaced upward. 3. The fluid force detection device according to claim 2, further comprising a transmission member that abuts and transmits the axial force. 4. The inner pipe is shorter than the outer pipe, both ends of the inner pipe are set inward of both ends of the outer pipe in the axial direction, the fluid inlet is formed at one end of the outer pipe, and 4. The fluid force detecting device according to claim 2, wherein the distance to one end of the pipe is about several times to about 100 times the width of the annular flow path formed between the inner pipe and the outer pipe.