CN115993306A - Method and device suitable for simultaneous measurement of viscosity and density of fluid - Google Patents
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Abstract
The invention discloses a method and a device suitable for simultaneously measuring viscosity and density of fluid. According to a physical model of a vibrating tuning fork immersed in fluid, a set of viscosity and density measurement equations based on the double tuning forks are established; compared with the prior empirical correlation type, the density measurement type has practical physical significance without influencing the measurement precision, wherein each parameter in the formula is determined by the structure, the size and the material of the tuning fork, and the density measurement type has reference function for the design and the shape selection of the tuning fork. Based on the method, the device for simultaneously measuring the viscosity and the density of the fluid has the advantages of small volume, convenient operation, wide application field and the like, and can be used for measuring the viscosity and the density of the high-temperature high-pressure fluid.
Description
Technical Field
The invention relates to the technical field of fluid thermophysical property measurement, in particular to a method and a device for simultaneously measuring fluid viscosity and density.
Background
Viscosity and density are the fundamental thermophysical properties of a fluid. In scientific research, viscosity and density are data bases for researching subjects such as thermodynamics, heat transfer science, hydrodynamics and the like, developing and utilizing new energy, designing new materials and other professional fields; in engineering design and industrial production, accurate viscosity and density data are important basis for chemical equipment design, production flow control, equipment safety detection and product quality assessment, and have wide application in the fields of petrochemical industry, biological medicine, energy environmental protection, national defense construction and the like. Thus, the viscosity and density of the fluid are indispensable thermophysical parameters.
At present, few researches on a device for simultaneously measuring the viscosity and the density of fluid are reported. Chinese patent CN 112748046a provides a pipeline system integrating a capillary viscometer and a vibrating tube densimeter, and uses two measuring instruments to measure the viscosity and density of fluid respectively, so that the measuring accuracy is high, but the system is complex, the volume is large, and the overall cost is high. US 2003041653A discloses a method for simultaneously measuring the viscosity and density of a fluid by using a piezoelectric quartz tuning fork, wherein the viscosity and density information is extracted from the resonance frequency, impedance, quality factor and other electrical parameters of the tuning fork in the fluid, but the electrical signals are affected by factors such as an electrode arrangement scheme, impurities in the fluid environment and the like, so that the electrical signals are often difficult to accurately and stably measure, and popularization and application of the electrical signals are greatly hindered, for example, when the viscosity of lubricating oil of large-scale mechanical equipment is measured, the impedance deviation caused by metal abrasive dust in the oil often causes larger measurement error; similar problems exist with an MEMS density sensor based on in-plane resonance as disclosed in chinese patent CN107601424 a. In chinese patent CN114594021a (application No. 202210225611.0), an asymmetric two-piezoelectric tuning fork type viscosity sensor is disclosed, and the viscosity and density of the fluid can be obtained by measuring the resonance frequency of each of the two tuning forks in the fluid, so that the measurement of electrical characteristic parameters is avoided, and higher precision is provided; the sensor measures density through a given empirical correlation formula, and coefficients are required to be calibrated through experiments, however, the use of the formula has certain requirements on parameters such as the structure, the size, the materials and the like of the tuning fork, and reasonable and effective guidance cannot be provided for the design of the parameters.
Disclosure of Invention
The invention aims to provide a method suitable for simultaneously measuring the viscosity and the density of fluid, and compared with the prior empirical correlation method, the method has the advantages that each parameter in the established measurement equation is related to the physical parameters such as the structure, the size, the material and the like of a tuning fork without influencing the measurement precision, and has reference value for the design of the tuning fork.
The invention also aims to provide a device for simultaneously measuring the viscosity and the density of the fluid based on the method, which has the advantages of small volume, convenient operation, wide application scene and the like, and can be used for measuring the viscosity and the density of the high-temperature high-pressure fluid.
The invention is realized by the following technical scheme:
a method for simultaneous measurement of fluid viscosity and density, comprising the steps of:
1) In vacuum, the inverse piezoelectric effect of the piezoelectric material is used to drive the double tuning fork structure to vibrate, and the piezoelectric effect of the other piezoelectric body in each tuning fork is used to detect the resonance frequency f of the tuning fork 1,vac 、f 2,vac ；
2) Under the condition of constant temperature and constant pressure, the double tuning forks are immersed in a plurality of fluids with known viscosity eta and density rho in sequence, the tuning forks are driven to vibrate in the fluids, and the resonant frequencies f of the two tuning forks are measured respectively 1,liq 、f 2,liq ；
3) From the measurement dataset (eta, rho, f 1,liq ,f 2,liq ) And combining the calibrated constants f 1,vac 、f 2,vac At f 1,liq Is an independent variable, and ρ is an independent variable according to the formula
Fitting to obtain a calibration coefficient B 1 The method comprises the steps of carrying out a first treatment on the surface of the At f 2,liq And ρ is an independent variable and η is an independent variable according to the formula +.>
Fitting to obtain a calibration coefficient A 2 、B 2 ，
4) When unknown fluid is measured, the double tuning forks are immersed in the fluid to be measured, and the resonance frequency f of the double tuning forks is measured 1,liq And f 2,liq The viscosity and density values of the fluid can be found by substituting the following equation:
in the formula, subscripts 1,2 correspond to the density-sensitive tuning fork and the viscosity-sensitive tuning fork, respectively, of the dual tuning forks.
Calibration coefficient A i 、B i (i=1, 2) is the viscosity-sensitive characteristic parameter of each tuning fork, and can be expressed by the following formula
Estimation is carried out and used as a reference value of experimental calibration, wherein ρ is as follows m The material density of the tuning fork is that w and t are the width and thickness of the tuning fork arms; conversely, the material and the size parameters can be set correspondingly according to the formula according to the requirement when the tuning fork is designed.
The applicability of the two equations in the measurement equation set is different, so that the subscripts 1 and 2 are adopted for distinguishing: wherein the density measurement equation is applied to a density sensitive tuning fork, corresponding to parameter subscript 1, i.e. a change in fluid density will cause the tuning fork to resonate at frequency f 1,liq Obvious changes; the viscosity measurement equation is suitable for a tuning fork sensitive to viscosity, and the corresponding parameter subscript 2, namely the change of the density and viscosity of the fluid, can cause the tuning fork resonant frequency f 2,liq Obvious variations.
An apparatus adapted for simultaneous measurement of fluid viscosity and density, comprising: the device comprises an experiment body, a double tuning fork structure body, a signal generation and detection unit and a temperature and pressure control system, wherein the experiment body is a sealed metal container, and fluid to be detected can be filled in the experiment body; the double tuning fork structure body consists of a density sensitive tuning fork and an adhesive density sensitive tuning fork which are fixed on the same end face of the same base together, the base is fixed at an opening of one side of the experiment body through threads or a flange plate, and the tuning fork body faces the inside of the container; the signal generating and detecting unit body is an integrated circuit embedded in the tuning fork base and used for providing sweep frequency excitation signals for the two tuning forks and acquiring the resonance frequency of each tuning fork in the fluid to be detected; the temperature and pressure control system consists of a metal heating rod, a pump and a built-in temperature and pressure sensor.
The heating rod of the temperature and pressure control system is circumferentially arranged in the shell of the experiment body and used for controlling the temperature of fluid in the container, and the pump is externally arranged on the body and is communicated with the inside of the experiment body through a pipeline and used for controlling the pressure of the fluid in the container.
The signal generating and detecting unit body is connected to the electrode of the piezoelectric material in each tuning fork body through an insulated wire.
The experimental body is not limited to metal, and can be glass, ceramic or plastic; nor is it limited to a closed structure, but may be an open container.
The dual tuning fork structure is not limited to work in the experimental body, and is assembled in various containers by means of threads, flanges or fixed in various open fluid environments by means of clamps.
The two tuning forks are arranged in such a way that the centers of the bottom ends of the two tuning forks coincide with the center of the base and do not interfere with each other; meanwhile, two electrodes on the piezoelectric material of the double tuning forks are connected with the signal generating and detecting unit in parallel through wires and are mutually independent, and due to the differences in material, size and the like, the resonance frequencies of the two electrodes are different by more than ten times, the two electrodes are not interfered with each other, and the measurement is not influenced.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the method for simultaneously measuring the viscosity and the density of the fluid, a set of viscosity and density measurement equations are established according to the interaction relation between the vibration tuning fork immersed in the fluid and the fluid. Compared with the commonly adopted experience correlation type for density measurement in the existing scheme, the density measurement equation deduced by the method is concise in form and equivalent to the original precision, and each undetermined parameter is determined by the physical property of the tuning fork, so that the method has a guiding effect on the related parameter design of the tuning fork type viscosity/densimeter.
2. The device for simultaneously measuring the viscosity and the density of the fluid can be fixed in various fluid environments in various modes, the miniaturization of the device and the diversification of the types of the measured fluid are realized, and the device has the characteristics of small volume, convenient operation and wide application field, and can be suitable for measuring the viscosity and the density of the high-temperature high-pressure fluid.
Drawings
FIG. 1 is a schematic diagram of a physical model of a vibrating single tuning fork immersed in a fluid;
FIG. 2 is a schematic diagram showing the derivation of the method for simultaneously measuring the viscosity and the density of a fluid according to the present invention;
FIG. 3 is an image of a function g (f) in an embodiment of the invention;
FIG. 4 is a schematic diagram showing the overall structure of the device for simultaneously measuring the viscosity and the density of the fluid according to the present invention;
FIG. 5 is a basic workflow diagram of a simultaneous fluid viscosity and density measurement apparatus of the present invention;
FIG. 6 is a graph showing the comparison of the effects of fitting experimental values using different correlations in an embodiment of the invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
A method for simultaneous measurement of fluid viscosity and density, the principle deduction comprising the steps of:
s0: consider a single-fork structure immersed in a fluid, which is caused to vibrate by the inverse piezoelectric effect. Based on analysis of an interaction model between the fluid and the tuning fork, the resonance frequency of the tuning fork in the fluid has the following basic mathematical relationship with the viscosity and density of the fluid:
wherein ρ is m Is the material density of tuning fork, unit kg·m -3 The method comprises the steps of carrying out a first treatment on the surface of the w and t are the width and thickness of the tuning fork arms, respectively, in m; η and ρ are the dynamic viscosity and density of the fluid, respectively, in Pa.s, kg.m -3 ；f vac 、f liq The values of the resonant frequencies of the tuning fork in vacuum and fluid, respectively, are in Hz.
Defining a constant
The tuning fork is an adhesive density sensitive characteristic parameter for representing the influence degree of the viscosity and density of the fluid on the resonance frequency of the tuning fork, is related to the structure, the size and the density of the tuning fork, can be estimated according to a formula, and can be calibrated through experiments.
S1: the formula (1) is arranged into a direct expression of viscosity:
from equation (2), it can be seen that for an unknown fluid, except for measuring the tuning fork resonant frequency f in the fluid liq It is also necessary to know the density ρ of the fluid to calculate the viscosity η. For this purpose, it is considered to add a tuning fork separately to measure the density of the fluid on the basis of a single tuning fork.
S2: to derive a measurement expression of density, equation (1) may be formulated as a unitary quadratic equation as follows:
using the root equation, we can obtain:
due to the force of the fluid on the tuning fork, the resonance frequency of the tuning fork in the fluid is always smaller than that of the tuning fork in the same vibration mode in vacuum, namely f liq <f vac The method comprises the steps of carrying out a first treatment on the surface of the And each physical quantity in the formula is a positive value, and takes a positive solution:
further, consider the ratio of the two root entries in the molecule of formula (4), and substituting the expression of A, B to obtain:
the expression on the far right side of expression (5) can be seen as the product of four terms. First item
Is a constant; second item->
Is a constant related to the material and the size of the tuning fork; the third term η is the viscosity of the fluid; fourth item->
For the resonant frequency f of the tuning fork in vacuum, fluid vac 、f liq Is an expression of (2).
Setting a function
g (f) is an independent variable of the excitation frequency f, and g (f) =0 and f=f vac Is an asymptote, at (0, f vac ) Positive functions that monotonically increase over the interval. For the width w and thickness t of the fork arm, 10 -3 ～10 -2 Tuning forks of the order of m and with aspect ratios l/w.gtoreq.10 and common liquids (ρ=500 to 2500 kg.m -3 For η=0 to 2pa·s, g (f) ≡10 -6 ～10 -2 。
Substituting the numerical values of the physical quantities within the above ranges into formula (5), and calculating to obtain:
and
further, on the basis of satisfying the measurement accuracy requirement, the above two relatively smaller amounts can be sequentially omitted on the basis of the density expression (4), and the simplification is gradually made:
namely:
in B, f vac Are all constant coefficients related to the structure, the size and the material of the tuning fork, f liq To be measured.
S3: since the viscosity measurement equation (2) and the density measurement equation (6) are different in applicability to tuning forks having different structures, sizes, materials, etc. (i.e., different in viscosity sensitivity characteristics), they are rewritten as a system of equations for tuning forks of two different characteristics:
in the formula, a density measurement equation is applied to the density sensitive tuning fork, and the corresponding parameter subscript 1, namely, the change of the fluid density causes the tuning fork resonant frequency f 1,liq Obvious changes; the viscosity measurement equation is suitable for a tuning fork sensitive to viscosity, and the corresponding parameter subscript 2, namely the change of the density and viscosity of the fluid, can cause the tuning fork resonant frequency f 2,liq Obvious variations.
The invention also provides a device suitable for simultaneously measuring the viscosity and the density of the fluid, which comprises: experiment body, two tuning fork structures, signal generation and detecting element and temperature pressure control system.
The experiment body is a sealed metal container, and the inside of the experiment body can be filled with fluid to be detected; the double tuning fork structure body consists of a density sensitive tuning fork and an adhesive density sensitive tuning fork which are fixed on the same end face of the same base together, the base is fixed at an opening of one side of the experiment body through threads or a flange, and meanwhile, the tuning fork body faces to the inside of the container; the signal generating and detecting unit body is an integrated circuit embedded in the tuning fork base and connected with electrodes of piezoelectric materials in each tuning fork body through insulated wires, and is used for providing sweep excitation signals for the tuning fork and acquiring the resonance frequency temperature of the tuning fork in fluid; the temperature and pressure control system comprises a metal heating rod, a pump, and a temperature sensor and a pressure sensor which are arranged in the metal heating rod and the pump, and is used for controlling the temperature and the pressure of the fluid to be measured.
Further, the material of the experiment body is not limited to metal, and can be glass, ceramic, plastic and the like; nor is it limited to a fully closed structure, but may be an open container.
Further, the base of the dual tuning fork structure has a circumferential threaded structure that can be threaded into other containers or secured in an open fluid environment by clamps.
Further, both tuning forks may be made of piezoelectric material and metal. The working principle is as follows: the piezoelectric material is symmetrically distributed on the two fork arms of the tuning fork. One end is driven by the inverse piezoelectric effect, the tuning fork vibrates and is influenced by the acting force of the fluid, and the other end outputs an electric signal containing the viscosity information of the fluid by the piezoelectric effect.
Furthermore, the two electrodes of the piezoelectric material of the double tuning forks are connected with the signal generating and detecting unit in parallel through wires and are mutually independent, and the resonance frequencies of the two electrodes are different by more than ten times due to the differences in the aspects of materials, sizes and the like, so that the two electrodes are not interfered with each other, and the measurement is not influenced.
Further, the density-sensitive tuning fork means that the tuning fork has a 'density-sensitive' characteristic, namely, the change of the fluid density can cause obvious change of the resonance frequency of the tuning fork, and the influence of the change of the viscosity on the resonance frequency is small and can be ignored; similarly, by a density sensitive tuning fork is meant a tuning fork that has "density sensitive" characteristics, i.e., changes in fluid density and viscosity both cause a significant change in the resonant frequency of the tuning fork.
Further, in the temperature and pressure control system, a plurality of electric heating rods are circumferentially distributed in the experimental body shell layer and used for controlling the temperature of the fluid; the pump is arranged outside the experiment body and is communicated with the inside of the experiment body through a pipeline, so as to control the pressure of the fluid in the container.
Example 1
As shown in FIG. 1, a physical model of a vibrating single tuning fork immersed in a fluid is a basis and source of a simultaneous measurement method of viscosity and density of the fluid. The length, width and thickness of the tuning fork arms are l, w and t respectively, and the density and viscosity of the fluid are ρ and η respectively. Based on the interaction between the fluid and the tuning fork, the tuning fork has a resonant frequency f in the fluid liq The viscosity and density of the fluid have the following mathematical relationship:
wherein ρ is m Is the material density of tuning fork, f vac Is the resonant frequency of the tuning fork in vacuum. Constant coefficient is set
FIG. 2 is a schematic diagram showing the derivation process of the method for simultaneously measuring the viscosity and the density of the fluid. In one aspect, formula (1) can be converted to a direct expression for viscosity:
from equation (2), it can be seen that for an unknown fluid, except for measuring the tuning fork resonant frequency f in the fluid liq In addition, the density ρ of the fluid needs to be known to obtain viscosityDegree η. For this purpose, it is considered to add a tuning fork separately to measure the density of the fluid on the basis of a single tuning fork.
Thus, in another aspect, to find a direct expression for density, equation (1) is converted into the following unitary quadratic equation:
solving to obtain:
considering the ratio of two root entries in the expression molecule, substituting the expression of A, B to obtain:
the right side of equation (5) can be seen as the product of four terms. Respectively is
Constant->
The material density, the width and the thickness of the fork arms of the tuning fork are determined; fluid viscosity η; with respect to resonant frequency f of tuning fork in vacuum and fluid respectively vac 、f liq Is the value of (1): />
Setting a function
g (f) is a variable of frequency f, g (f) =0 and f=f vac Is an asymptote, at (0, f vac ) The image of a monotonically increasing positive function within the interval is shown in fig. 3. As can be seen from the figure, over a larger frequency range,g (f) are all small values.
Taking a typical density tuning fork as an example of the parameter values given in table 1, the resonance frequency values of the tuning fork in several common liquids with known viscosity and density were measured at a pressure of 0.1MPa and a temperature of 298.15K, the experimental results are shown in table 2, and the corresponding values of formula (5) were calculated.
TABLE 1
TABLE 2
Among them, there are:
and
the above two relatively small amounts are sequentially omitted from the density expression (4) in a range satisfying the measurement accuracy requirement (0.1 to 1%).
The density measurement formula can be derived:
because the viscosity and the applicability of the density measurement type to tuning forks are different, two equations are rewritten as:
in the formula, the subscript 1 corresponds to the density-sensitive tuning fork, and the subscript 2 corresponds to the viscosity-sensitive tuning fork. B (B) 1 、A 2 And B 2 Is the coefficient to be calibrated determined by tuning fork related parameters, f l,liq And f 2,liq To be measured. The viscosity and density can be calculated by measuring the resonant frequency of each tuning fork in the fluid.
Example two
Fig. 4 is a schematic structural diagram of a device for simultaneously measuring viscosity and density of fluid according to the present invention. As shown in fig. 4 (a), the whole structure mainly comprises an experiment body 1, the inside of which is filled with fluid to be tested, and a double tuning fork structure 2 is composed of two tuning forks fixed on the same base, and the base is connected with the experiment body through threads; the tuning fork base is embedded with an electronic control system 3 integrated with a signal generation and detection unit, and the experimental body is matched with a temperature and pressure control system 4. Fig. 4 (b) further shows a three-dimensional image of the dual tuning fork structure 2, the main structure of which is a density-sensitive tuning fork 201 and an adhesion-sensitive tuning fork 202 together fixed on a base 203.
Preferably, the two tuning forks may be arranged in such a way that the centers of the bottom ends of the two tuning forks coincide with the center of the base 203, or the two tuning forks are arranged in parallel, but are not limited to these arrangements.
Preferably, the double tuning fork structure is not limited to work in the experimental body, and can be assembled in other containers through threads and flanges or fixed in various fluid environments through clamps; the sensor can also be used as a sensor to be installed on an industrial site to realize on-line monitoring of the viscosity and the density of the fluid.
Fig. 5 shows a basic workflow based on the device for simultaneously measuring the viscosity and density of a fluid. Firstly, filling fluid to be tested into an experiment body to enable the fluid to be tested to fully submerge the two tuning forks, and controlling a temperature and pressure control system to enable the temperature and pressure of the fluid to reach set values and keep stable; then a signal generating unit is used for applying sweep frequency excitation signals to the tuning forks, and a signal detecting unit is used for detecting that each tuning fork is in fluidResonant frequency f of (2) 1,liq 、f 2,liq The method comprises the steps of carrying out a first treatment on the surface of the And finally, calculating the density and viscosity of the fluid to be measured according to a measurement equation set, and taking the average value of multiple measurements as a final measurement result.
Example III
In order to improve the measurement accuracy, the device needs to be calibrated before actual measurement. The calibration process is as follows:
(1) Vacuumizing the container, controlling the temperature to a set value and keeping stable, applying a certain excitation frequency to the two tuning forks to enable the two tuning forks to be in an in-plane reverse bending resonance state, and measuring to obtain the resonance frequencies f of the density sensitive tuning forks and the viscosity sensitive tuning forks in vacuum 1,vac 、f 2,vac ；
(2) Sequentially filling a plurality of standard fluids with known viscosity eta and density rho into the experimental body to completely submerge the two tuning forks, controlling the temperature and the pressure to reach set values and keeping stable, and respectively measuring the resonant frequency f of the two tuning forks in the fluid 1,liq 、f 2,liq ；
(3) From the measured dataset (eta, rho, f 1,liq ,f 2,liq ) According to density and viscosity measurement expressions
And->
Respectively by->
And f 2,liq ρ is an independent variable, and a parameter B is obtained based on least square fitting 1 、A 2 、B 2 。
In order to verify the fitting effect of the density measurement formula to the experimental value, the invention compares the fitting effect with the following two common empirical correlation formulas:
ρ＝a 2 f 2 +a 1 f+a 0 (7a)
wherein a is i 、b i All are constant coefficients to be calibrated, i=0, 1,2.
Definition of root mean square error
As an evaluation index of the fitting effect of the measurement equation. Wherein ρ is exp For the fluid density values known in the experiments ρ cal For fluid density values calculated using the fit, N is the number of experimental points.
Under the conditions of 298.15K temperature and 0.1MPa pressure, the device is calibrated by sequentially using a plurality of fluids with known viscosity and density, and the experimental result and the fitting effect are shown in figure 6. In the figure, points are experimental data points and lines are fitted curves. The temperature is 298.15K, the pressure is 0.1MPa, and the difference of root mean square errors between the density measurement formula established by the invention and other two formulas is very small, which indicates that the fitting effect is equivalent; at the same time, the parameters to be calibrated are fewer and have physical meaning, and can be expressed according to given parameters
Therefore, the parameters such as the structure, the size, the material and the like of the tuning fork are estimated, and the design of each parameter of the tuning fork can be guided in turn.
The foregoing is illustrative of the principles and preferred embodiments of the present invention, and is not in limitation of the scope of the invention. Other specific technical solutions of the present invention can be suggested to those skilled in the art without any inventive effort, and fall within the scope of the present invention.
Claims (9)
1. A method for simultaneous measurement of fluid viscosity and density, comprising the steps of:
1) In vacuum, the dual tuning fork structure is driven to vibrate by the inverse piezoelectric effect of the piezoelectric material, and the tuning forks are usedThe piezoelectric effect of another piezoelectric body to detect the resonant frequency f of the tuning fork 1,vac 、f 2,vac ；
2) Under the condition of constant temperature and constant pressure, the double tuning forks are immersed in a plurality of fluids with known viscosity eta and density rho in sequence, the tuning forks are driven to vibrate in the fluids, and the resonant frequencies f of the two tuning forks are measured respectively 1,liq 、f 2,liq ；
3) From the measurement dataset (eta, rho, f 1,liq ,f 2,liq ) And combining the calibrated constants f 1,vac 、f 2,vac At f 1,liq Is an independent variable, and ρ is an independent variable according to the formula
Fitting to obtain a calibration coefficient B 1 The method comprises the steps of carrying out a first treatment on the surface of the At f 2,liq And ρ is an independent variable and η is an independent variable according to the formula +.>
Fitting to obtain a calibration coefficient A 2 、B 2 ，
4) When unknown fluid is measured, the double tuning forks are immersed in the fluid to be measured, and the resonance frequency f of the double tuning forks is measured 1,liq And f 2,liq The viscosity and density values of the fluid can be found by substituting the following equation:
in the formula, subscripts 1,2 correspond to the density-sensitive tuning fork and the viscosity-sensitive tuning fork, respectively, of the dual tuning forks.
2. A method for simultaneous measurement of fluid viscosity and density according to claim 1, wherein the calibration factor a i 、B i (i=1, 2) is the viscosity-sensitive characteristic parameter of each tuning fork, and can be expressed by the following formula
Estimation is carried out and used as a reference value of experimental calibration, wherein ρ is as follows m The material density of the tuning fork is that w and t are the width and thickness of the tuning fork arms; conversely, the material and the size parameters can be set correspondingly according to the formula according to the requirement when the tuning fork is designed.
3. A method for simultaneous measurement of fluid viscosity and density according to claim 1, wherein the applicability of the two equations in the system of measurement equations is different, so that the subscripts 1,2 are used to distinguish: wherein the density measurement equation is applied to a density sensitive tuning fork, corresponding to parameter subscript 1, i.e. a change in fluid density will cause the tuning fork to resonate at frequency f 1,liq Obvious changes; the viscosity measurement equation is suitable for a tuning fork sensitive to viscosity, and the corresponding parameter subscript 2, namely the change of the density and viscosity of the fluid, can cause the tuning fork resonant frequency f 2,liq Obvious variations.
4. An apparatus for simultaneous measurement of fluid viscosity and density, comprising: the device comprises an experiment body, a double tuning fork structure body, a signal generation and detection unit and a temperature and pressure control system, wherein the experiment body is a sealed metal container, and fluid to be detected can be filled in the experiment body; the double tuning fork structure body consists of a density sensitive tuning fork and an adhesive density sensitive tuning fork which are fixed on the same end face of the same base together, the base is fixed at an opening of one side of the experiment body through threads or a flange plate, and the tuning fork body faces the inside of the container; the signal generating and detecting unit body is an integrated circuit embedded in the tuning fork base and used for providing sweep frequency excitation signals for the two tuning forks and acquiring the resonance frequency of each tuning fork in the fluid to be detected; the temperature and pressure control system consists of a metal heating rod, a pump and a built-in temperature and pressure sensor.
5. The device for simultaneous measurement of viscosity and density of fluid according to claim 4, wherein the heating rod of the temperature and pressure control system is circumferentially arranged in the housing of the experimental body for controlling the temperature of the fluid in the container, and the pump is externally arranged on the body and is communicated with the inside of the experimental body through a pipeline for controlling the pressure of the fluid in the container.
6. The device of claim 4, wherein the signal generating and detecting unit body is connected to the electrode of the piezoelectric material in each tuning fork body by an insulated wire.
7. The device for simultaneously measuring viscosity and density of fluid according to claim 4, wherein the experimental body is not limited to metal, and can be glass, ceramic or plastic; nor is it limited to a closed structure, but may be an open container.
8. The device for simultaneous measurement of fluid viscosity and density according to claim 4, wherein the double tuning fork structure is not limited to work in an experimental body, and is assembled in various containers by means of threads, flanges or is fixed in various open fluid environments by means of clamps.
9. The device for simultaneously measuring viscosity and density of fluid according to claim 4, wherein the two tuning forks are arranged in such a way that the centers of the bottom ends of the two tuning forks coincide with the center of the base and do not interfere with each other; meanwhile, two electrodes on the piezoelectric material of the double tuning forks are connected with the signal generating and detecting unit in parallel through wires and are mutually independent, and due to the differences in material, size and the like, the resonance frequencies of the two electrodes are different by more than ten times, the two electrodes are not interfered with each other, and the measurement is not influenced.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211610001.9A CN115993306A (en) | 2022-12-14 | 2022-12-14 | Method and device suitable for simultaneous measurement of viscosity and density of fluid |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211610001.9A CN115993306A (en) | 2022-12-14 | 2022-12-14 | Method and device suitable for simultaneous measurement of viscosity and density of fluid |
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| CN115993306A true CN115993306A (en) | 2023-04-21 |
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| CN202211610001.9A Pending CN115993306A (en) | 2022-12-14 | 2022-12-14 | Method and device suitable for simultaneous measurement of viscosity and density of fluid |
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| CN (1) | CN115993306A (en) |
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