JPH0148975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a viscosity measuring device used for measuring the viscosity of a solution.

[Prior Art] Conventionally, typical devices for measuring the viscosity of a solution include a rotating cylinder type device using a torque detector and a capillary type device using a differential pressure detector. For example, the widely used capillary type detects the differential pressure that occurs before and after the capillary when a Newtonian fluid passes through the capillary, and calculates that value based on a predetermined relational expression. This is to find the viscosity value.

By the way, when measuring the viscosity of a solution, it is sometimes required to be able to accurately handle a wide range of viscosities. However, all of the conventional methods described above have a limited range of applicability to the viscosity of the solution, and their use is limited to the following measurement conditions, making them difficult to use.

(1) The measurement range is approximately 1:10.

The reason is that in the rotating cylindrical type,
For torque detectors and capillary type differential pressure detectors, the accuracy of the differential pressure detector is about ±0.5% of the full scale, so the error in the measured value is ±0.5% below 1/10 of the full scale.
This is because it becomes more than 5%. Furthermore, in the case of a capillary type pump, the quantitative performance of the gear pump is important, and the fact that the volumetric efficiency of the gear pump decreases as the viscosity decreases is one of the factors that determines the lower limit of the measurement range.

(2) Cannot be used for slurry solutions.

The gap between the inner and outer cylinders in a rotating cylinder type and the diameter of the capillary in a capillary type are usually 2.
Since the diameter is approximately 4 mm, there is a risk that clogging may occur with a slurry solution. Additionally, if a separate filter is installed for this purpose, this filter will have to be frequently cleaned or replaced.

(3) The temperature of the solution must be approximately constant.

Since the influence of temperature is an extremely important point in viscosity measurement, conventional methods have been to place the device in a constant temperature bath, or to measure the solution temperature and correct it using an electronic circuit. However, in cases where the temperature of the solution changes over a wide range and it is not allowed to arbitrarily change the temperature of the solution to be measured, conventional methods may not be able to cope with the situation.

As a means to address these shortcomings,
Patent Application No. 58-31259 has been proposed. The content of the invention of this application is to provide a bypass flow path in the thin tube section and control the flow rate in the thin tube section by controlling this bypass flow path by the differential pressure in the thin tube section, and to detect and measure the temperature of the solution to be measured. This is to correct the viscosity value.

However, in the above-mentioned invention, the solution to be measured may temporarily accumulate in the bypass flow path, and depending on the process, changes in physical properties during this time may become a problem, and this has been improved. Therefore, a more reliable viscosity measuring device was required.

[Summary of the invention] This invention was made in view of the above circumstances.
It is an object of the present invention to provide a highly accurate viscosity measuring device that eliminates solution stagnation and also improves the viscosity calculation means.

The features of this invention are as follows.

That is, instead of the bypass channel, a variable speed electric motor is used to drive at a variable speed a pump that pressurizes the solution to be measured flowing through the channel, which is a thin tube section.

Furthermore, in general, the differential pressure that occurs at both ends of the thin tube section
Pd [Kg/cm ² ] is tube radius R [cm], tube length L
[cm], viscosity V [poise], density D [gr/cm ³ ], and solution flow rate Q [cm ³ /sec], Pd={8QV(L+nR)/πR ₄ +mDQ ₂ /π ² R ⁴ } ×10 ^-3 /
g...(1) (where n and m are coefficients, and g is 980 cm/sec ² ). Here, the second term in the above equation represents the pressure loss based on the change in the kinetic energy of the solution, and when the flow rate Q is small, it is sufficiently smaller than the first term, so it is best to ignore it. This is a conventional wisdom, and the above-mentioned inventions are treated in the same way. However, when the flow rate Q is set small, measurement errors in the differential pressure Pd and viscosity V become large and cannot be ignored, so in this invention, the second term, the kinetic energy correction term, is also measured and calculated. This ensures high accuracy and a wide measurement range.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

1 to 3 show the main body of an example of the viscosity measuring device according to the present invention.

In the figure, 1 is an upper measurement chamber, 2 is a lower measurement chamber, 3 is an inlet pipe for supplying the solution M to be measured to the upper measurement chamber 1, and 4 is a liquid pump. A rotating shaft 5 of the liquid pump 4 is connected to an output shaft 6 of a variable speed electric motor 10 with a reduction gear. 7 is the above upper measurement chamber 1
This is a flow path that connects the lower measuring chamber 2 and the lower measurement chamber 2, and constitutes a thin tube part of a so-called thin tube type. Reference numeral 8 denotes an electromagnetic flowmeter provided in the flow path 7, which measures the flow rate of the solution M to be measured flowing through the flow path 7. The inside of the conduit in this electromagnetic flowmeter 8 is a simple straight pipe, and its inner wall is smoothed. This allows the flowing solution M to be measured to flow through the thin tube portion without impairing laminar flow conditions. 11 is a solution outlet pipe connected to the lower measurement chamber 2.

12 and 13 are diaphragm type pressure detectors, which are installed in the upper measurement chamber 1 and the lower measurement chamber 2, respectively, and the detected pressures of both pressure detectors 12 and 13 are transmitted via capillaries 14 and 14 to a differential pressure transmitter. 15. The differential pressure transmitter 15, together with the pressure detectors 12, 13, etc., constitutes a differential pressure measuring means 16 that measures the differential pressure generated between the upstream side and the downstream side of the flow path 7 and outputs an electric signal. Along with the above-mentioned electromagnetic flowmeter 8, etc., the support column 1 shown in
7, for example by U-shaped bolts 18,19.

Reference numerals 20 and 21 designate temperature detectors, for example, resistance temperature detectors such as platinum resistors, which are attached to the upper measurement chamber 1 and the lower measurement chamber 2, respectively, and are used to detect the temperature that flows into the flow path 7 together with the temperature detectors described later. It constitutes a solution temperature detection means 22 that measures the temperature of the measurement solution M. In addition, upper and lower measurement chambers 1,
2. The electromagnetic flowmeter 8 and the like are insulated from the outside air by a heat insulating material (not shown).

Next, the circuit of the device of this invention will be explained with reference to FIG.

In FIG. 4, 23 is the variable speed electric motor 10.
For example, a frequency converter (commonly known as a VVVF inverter),
24 is a distributor connected to the differential pressure transmitter 15, 25 is a flow rate converter connected to the electromagnetic flowmeter 8, 26 is a temperature converter connected to the temperature detectors 20 and 21, and 27 is a device to be measured. It is a manual setting device for setting the specific parameters of the solution M,
The distributor 24, the flow rate converter 25,
The temperature converter 26 and the manual setting device 27 convert their respective signals into standard voltage signals and input them to the control circuit 28.

The control circuit 28 includes, for example, an analog input 4
It has a microprocessor with two analog output points and two analog output points, and its configuration is as follows. That is, 29 is a parameter setting device for setting the differential pressure, and 30 is a subtracter 3 connected to the parameter setting device 29 and the distributor 24.
1 is an amplifier connected to the subtracter 30, 40 is a parameter setter for setting the flow rate, 41 is a subtracter connected to the parameter setter 40 and the flow rate converter 25, and 42 is connected to the subtracter 41. An amplifier 43 is a multiplier that calculates the product of the outputs of the amplifiers 31 and 42, and the output of the multiplier 43 is configured to be input to the variable speed motor drive means 23 via the limiter 32. 44 is a computing unit that computes the correction amount of kinetic energy for the differential pressure based on the signal from the flow rate converter 25, and 45 subtracts the output signal of the computing unit 44 from the differential pressure signal sent from the distributor 24. It is a subtractor. 33 is a divider to which the output of the subtracter 45 and the output of the flow rate converter 25 are applied.

34 is an arithmetic circuit which receives the output from the temperature converter 26 and the output from the manual setting device 27 and calculates a value related to the reference temperature for viscosity conversion. 35 is an exponential relation calculator connected to the calculation circuit 34; 36 is a multiplier for obtaining a viscosity value converted to a reference temperature from the output of the divider 33 and the output from the index relation calculator 35; 37 is a correction parameter A setting device 38 is a multiplier connected to the parameter setting device 37 and the multiplier 36. 39 is a recorder for recording the output from the control circuit 28.

Next, the operation of the above configuration will be explained.

The solution M to be measured supplied to the inlet pipe 3 is pressurized by the liquid feed pump 4, and is discharged from the outlet pipe 11 to the outside of the system via the upper measurement chamber 1, the flow path 7, and the lower measurement chamber 2. .

In this state, both pressure detectors 12 and 13 detect the pressure at each part, and based on these outputs, the differential pressure transmitter 15 measures the differential pressure and outputs it to the distributor 24. Further, the electromagnetic flowmeter 8 measures the flow path of the flow path 7 and outputs the measurement output to the flow rate converter 25 . on the other hand,
For example, the temperature detectors 20 and 21 have a combined resistance value.
It is set as 100Ω, and thereby the average value of the temperatures measured by both temperature detectors 20 and 21 is measured. In this case, since the upper and lower measurement chambers 1 and 2 and the flow path 7 are cut off from the outside air, the measured temperature is considered to be representative of the solution temperature in the flow path 7, and the temperature is converted. It is output to the device 26. Further, the manual setting device 27 is used to set the unique value of the solution, which will be described later.

The feature of the present invention is that the flow rate of the flow path 7 is controlled by the differential pressure signal sent to the distributor 24, and this point will be described in detail. That is, when the differential pressure signal converted into a standard voltage signal (1 to 5 V) by the distributor 24 is input to the control circuit 28, this differential pressure signal is combined with the value set by the parameter setting device 29 and the subtracter. It is compared with 30. The deviation value between the two above is amplified by an amplifier 31. On the other hand, the flow rate in the flow path 7 detected by the electromagnetic flowmeter 8 is converted into a standard voltage signal (1 to 5 V) by the flow rate converter 25.
When inputted to the control circuit 28 as a flow rate signal,
This flow rate signal is compared with the value set by the parameter setting device 40 by a subtracter 41, and the deviation value between the two is amplified by an amplifier 42. Both outputs of the amplifier 31 and the amplifier 42 are normalized to a value between 0 and 1, and after being multiplied by the multiplier 43, the outputs are output from the limiter 3.
2, the voltage is set within the standard voltage range and output to the variable speed motor drive means 23. Variable speed electric drive means 23
For example, if it is a VVVF inverter,
The output frequency is increased or decreased to drive the variable speed electric motor 10 to control the flow rate of the pump. That is, by this, the flow rate of the solution M to be measured flowing through the flow path 7 is controlled until the above-mentioned two deviation values become close to zero.

If we were to show the function of the above control system using concrete numerical values, let us assume that the measurement range of the viscometer is 10 to 1000 poise.
When the viscosity of the solution M to be measured is 10 to 100 poise, the variable speed motor 10 is controlled by the variable speed motor driving means 23 to control the solution M to be measured, which is pressurized and supplied by the liquid feed pump 4, to the parameter setting device 40. A set amount (6944 cm ³ /sec) flows through the channel 7. In this case, the differential pressure generated between the upper measurement chamber 1 and the lower measurement chamber 2,
In other words, the differential pressure based on the measured value from the differential pressure transmitter 15 is in direct proportion to the measured viscosity, and 100 poise
The differential pressure at a viscosity of is 1Kg/cm ² . Since the setting value of the parameter setting device 29 is 1Kg/cm ² ,
When the viscosity exceeds 100 poise, the rotation of the electric motor 10 begins to decrease, and the fluid flowing into the flow path 7 decreases, so that the differential pressure is controlled so as not to exceed 1 Kg/cm ² . The higher the viscosity, the lower the rotation speed of the variable speed electric motor 10. For example, if the viscosity is
At 1000 poise, it is about 1/10 of the maximum rotation speed. On the other hand, the flow rate through channel 7 is 6944 cm ³ /sec when the viscosity is 100 poise or less;
If it exceeds , the viscosity decreases in inverse proportion to the viscosity.
At 1000poise, it is 694cm ³ /sec.

On the other hand, the output of the flow rate converter 25 has a kinetic energy correction term calculated by the calculation unit 44, and the differential pressure from the distributor 24 is subtracted by the subtractor 45 by the calculated value. The error term due to energy is removed, and this value is further applied to the multiplier 33 together with the flow rate value which is the output from the flow rate converter 25, and the differential pressure value is divided by the flow rate value to obtain Pd/ Q=8QV(L+nR)/πR ⁴ ×10 ^-3 /g (2), and a value directly proportional to the viscosity V is obtained.

On the other hand, temperature correction is performed as follows.

The change in viscosity of a viscous fluid due to temperature is unique to each substance, but when expressed mathematically, the following equation holds true for many substances.

Vs=Vt・EXP(A)...(3) A=B(T-Ts)/(273+T)(273+Ts)...
(4) Here, Vs...mucosal value at temperature Ts℃ (poise) Vt...viscosity value (poise) at temperature T℃ B...value unique to each substance (-) The arithmetic circuit 34 is connected to the temperature converter mentioned above When the measured temperature from 26 is T, the setting value of manual setting device 27 is B, and the reference temperature for converting viscosity is Ts, the above formula (4)
Calculate the value of A. The reference temperature Ts is defined in the program. Thus, the exponential function calculator 35 receives the calculation result A from the calculation circuit 34 and calculates EXP(A) in the above equation (3).

The multiplier 36 multiplies the viscosity value at the temperature T obtained by the divider 33 by the calculation result of the exponential function calculator 35. This provides the viscosity value converted to the reference temperature, that is, Vs in the above equation (3).

By the way, the overall accuracy of the viscosity measuring device is confirmed by actually measuring it using a standard liquid (for example, silicone oil) whose viscosity value and temperature characteristics are well known. The output of multiplier 36 is multiplied by multiplier 38 for final correction. The output of this multiplier 36 is recorded by a recorder 39 as the output of the control circuit 28.

Next, the effects confirmed when the viscosity of the solution M to be measured was measured under specific conditions using the apparatus of the present invention will be described.

The viscosity value to be measured is 10 to 1000 poise, and the solution temperature is 120 to 30°C, and both the viscosity and temperature change from moment to moment. The solution M discharged from the viscosity measuring device must be returned to the original tank, and in order to prevent a chemical reaction from occurring in the solution, rapid temperature changes cannot be applied to the solution in the viscosity measuring device. The solution M to be measured contains 20 mm of solid matter, so in order to avoid clogging the tube, it is necessary to make the diameter of the tube considerably larger, as well as to compensate for the drop in differential pressure caused by increasing the diameter of the tube. Therefore, the flow rate Q is required to be increased to a certain extent.In addition, as explained in the prior art, in the case where a control valve bypass passage is provided, in order to prevent the slurry solution from accumulating in the bypass passage, It was found that the regulating valve bypass method was not suitable.

When the viscosity measuring device of the present invention was used under the above conditions, the viscosity measurement range covered the above-mentioned necessary range. Also, the differential pressure at a viscosity of 10 poise is 0.084 according to the first term of the theoretical formula.
0.0116 Kg/cm ² is generated due to the second term of kinetic energy with respect to Kg/cm ² . Therefore, if the kinetic energy is not corrected, a measurement error of approximately 14% will occur, but by employing the kinetic energy correction of the present invention, this error could be eliminated. .

Furthermore, regarding temperature correction, conversion could be performed with high accuracy over the entire temperature range.

The part of this device with the narrowest pipe diameter is the part of the electromagnetic flowmeter 8, but since its inner diameter was set to 75 mm in the example, the phenomenon of solid matter clogging therein was completely eliminated. Also, regarding pump 4,
Gear pumps are suitable for general use, but when there is solid matter mixed in as shown in the example,
By using a slurry pump, there was no practical problem at all.

[Effects of the Invention] As described above, according to the present invention, the flow rate in the flow path can be increased or decreased by changing the rotation speed of the pump, so the flow rate and differential pressure can be easily controlled. This makes it possible to measure viscosity under measurement conditions that could not be handled using the control valve bypass method.In addition, by adding a kinetic energy correction circuit, measurement performance is dramatically expanded, making it easier to use. We can provide a good viscosity measuring device.

[Brief explanation of drawings]

1 to 3 are a front view, a top view, and a side view showing the main body of an example of the viscosity measuring device according to the present invention, and FIG. 4 is the overall circuit configuration of the viscosity measuring device according to the same embodiment. It is a diagram. 1... Upper measurement chamber, 2... Lower measurement chamber, 3...
Pump, 4... Variable speed electric motor, 7... Channel (thin tube part), 8... Electromagnetic flow meter, 10... Variable speed electric motor,
16... differential pressure measuring means, 22... temperature detecting means,
23... Variable speed motor drive means, 27... Parameter setting means, 28... Control circuit, 39... Recording means, M... Solution to be measured.

Claims (1)

[Claims] 1. A channel formed between the upper measurement chamber to which the solution to be measured is supplied under pressure to the lower measurement chamber to form a thin tube section, and a channel connected to the upper measurement chamber to supply the solution to be measured. A pump that performs the above pressurization,
a variable speed electric motor that drives the pump at variable speed;
an electromagnetic flowmeter provided in the flow path; a differential pressure measuring means for measuring a differential pressure generated between the upstream side and the downstream side when the solution to be measured flows in the flow path; a solution temperature detection means for measuring the temperature of the solution to be measured, a parameter setting means for setting a parameter specific to the solution to be measured, and a differential pressure from the differential pressure measuring means and an electromagnetic flowmeter. In response to the flow rate signal, the variable speed motor is controlled so that the differential pressure and flow rate approximate the set values, and the capillary flow rate from the electromagnetic flowmeter and the kinetic energy of the solution to be measured determined from this capillary flow rate are controlled. ,
A control circuit that calculates and outputs a viscosity value converted to a specified temperature from each measured value of the capillary differential pressure from the differential pressure measuring means and the solution temperature from the solution temperature detecting means and the parameter value of the parameter setting means; A viscosity measuring device comprising a recording means for recording output from a circuit.