Fluid viscosity detection device and test method based on suspension type vibrating diaphragm damping characteristics

Abstract

The invention relates to the technical field of fluid viscosity testing, and discloses a fluid viscosity detection device and method based on suspension type vibrating diaphragm damping characteristics, and the fluid viscosity detection device comprises a light source, a viscosity detection unit, a demodulation module, a display unit and a test system; the demodulation module comprises a diode laser 104, a DFB laser 103, an optical fiber coupler 105, an optical fiber circulator 106, a computer, a function generator 102, a spectrum analyzer 107 and a suspension diaphragm optical fiber F-P viscosity sensor 108. The suspension type vibrating diaphragm and the cantilever beam structure are selected, so that the diaphragm is easier to start vibration and has the damping characteristic, when the diaphragm freely vibrates in liquid, due to the action of viscous damping, the amplitude of the diaphragm is attenuated, energy lost due to the viscous damping is supplemented, the attenuation rate of the amplitude of the diaphragm is related to the density and the viscosity of the liquid, and the damping effect of the diaphragm is improved. The attenuation rate of the amplitude of the diaphragm is fitted, the viscosity of the liquid can be calculated according to a certain relation, and a formula for calculating the viscosity of the fluid is obtained by establishing the relation between the viscosity of the liquid and the damping factor.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid viscosity testing, and in particular to a fluid viscosity detection device and a testing method based on the damping characteristics of a suspended diaphragm. Background Art

[0002] Viscosity is an important indicator of the physical properties of liquids. It can be characterized by the ratio of shear force to shear rate, and refers to the friction between molecules when the liquid flows. Viscosity itself is an important indicator of many chemical products. Improving the accuracy of viscosity measurement can reduce costs in the production process and create greater economic and social value. It is of great significance in the fields of medicine, petrochemicals, metallurgy, food, etc.

[0003] The mainstream viscometers in the market are designed based on the traditional viscosity measurement method and the improved methods. Traditional viscosity measurement methods include capillary method, rotation method, vibration method and falling body method. The traditional measurement methods are very mature and basically have established clear mathematical models, but most of them have disadvantages such as long measurement time and relatively complex structure. With the rapid development of science and technology, viscosity measurement technology has also achieved rapid development. After the unremitting efforts of scholars at home and abroad, many new viscosity measurement technologies have been developed. Such as ultrasonic, light scattering, electromagnetic tomography, micro-electromechanical system and other measurement methods. However, most of these have strict requirements on working conditions and working environment, and cannot be applied to field testing. In order to improve production efficiency and product quality, a test method for fluid viscosity based on the suspended diaphragm damping characteristic is proposed to solve the problem of liquid viscosity measurement. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a fluid viscosity detection device and a test method based on the damping characteristics of a suspended diaphragm, which solves the problem that the prior art cannot be applied to on-site testing.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a fluid viscosity detection device based on the damping characteristics of a suspended diaphragm, comprising a light source, a viscosity detection unit, a demodulation module, a display unit and a test system;

[0006] The demodulation module includes: a diode laser, a DFB laser, a fiber coupler, a fiber circulator, a computer, a function generator, a spectrum analyzer and a suspended diaphragm fiber FP viscosity sensor;

[0007] The computer is connected to the function generator through a communication cable, the function generator is connected to the diode laser through a communication cable, the diode laser is connected to the port 1 of the optical fiber circulator through an optical fiber jumper, the port 2 of the optical fiber circulator is connected to the port 2 of the optical fiber coupler through an optical fiber jumper, the port 3 of the optical fiber circulator is connected to the suspended diaphragm optical fiber FP viscosity sensor through an optical fiber jumper, the port 1 of the optical fiber coupler is connected to the DFB laser through an optical fiber jumper, the port 3 of the optical fiber coupler is connected to the spectrum analyzer through an optical fiber jumper, the diode laser provides light pressure to drive the sensor diaphragm to resonate, and the DFB laser light source performs reflection detection.

[0008] A test method for a fluid viscosity detection device based on the damping characteristics of a suspended diaphragm is applied to the fluid viscosity detection device based on the damping characteristics of a suspended diaphragm as claimed in claim 1, comprising the following steps:

[0009] Step 1: Collect the reflection spectrum data of the suspended diaphragm optical fiber FP viscosity sensing probe when it is unloaded;

[0010] Step 2: Insert the suspended diaphragm-based sensing probe into the fluid to collect reflectance spectrum data at different viscosity values;

[0011] Step 3: Demodulate the reflection spectrum using Fourier algorithm to obtain the frequency and amplitude at different viscosity values;

[0012] Step 4: Fitting the frequency and amplitude by the least square method to obtain the sensor damping factor β;

[0013] Step 5: Establish the relationship between liquid viscosity η and damping factor β to obtain viscosity;

[0014]

[0015] Where a is a constant, β represents the damping factor, β0 represents the damping factor of the sensor itself, and ρ represents the liquid density.

[0016] Preferably, the sensing probe in step 1 is a fiber FP interference structure consisting of a single-mode optical fiber and a suspended diaphragm.

[0017] Preferably, the no-load in step 1 is to obtain the sensor's own damping factor β0 by removing the vibration characteristics of the measured liquid.

[0018] Preferably, the suspended diaphragm material in step 1 is silicon nitride, with a diameter of D=2.5 mm, a thickness of d=210 nm, and four cantilevers.

[0019] Preferably, the fluid in step 2 is a Newtonian fluid.

[0020] Preferably, the spectrometer acquisition range in step 2 is 1510-1600nm, the sampling point is set to 9001, and the spectrometer resolution is 0.05nm.

[0021] Preferably, the Fourier algorithm in step 3 is a demodulation algorithm, which converts wavelength domain spectral information into frequency domain spectral information for cavity length calculation.

[0022] The invention provides a fluid viscosity detection device and a test method based on the damping characteristics of a suspended diaphragm.

[0023] It has the following beneficial effects:

[0024] 1. The present invention uses a suspended diaphragm. The structure of the cantilever beam makes it easier for the diaphragm to vibrate and has damping characteristics. When the diaphragm vibrates freely in the liquid, its amplitude will decay due to the effect of viscous damping, thereby compensating for the energy lost due to viscous damping. The decay rate of the diaphragm amplitude is related to the density and viscosity of the liquid. The viscosity of the liquid can be calculated according to a certain relationship by fitting the decay rate of the diaphragm amplitude. By establishing the relationship between the liquid viscosity and the damping factor, a formula for calculating the viscosity of the fluid is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The fluid viscosity detection device based on the damping characteristics of the suspended diaphragm of the present invention;

[0026] Figure 2 The present invention is a flow chart of a testing method of a fluid viscosity detection device based on the damping characteristics of a suspended diaphragm.

[0027] Among them, 101, host computer; 102, function generator; 103, DFB laser; 104, diode laser; 105, fiber coupler; 106, fiber circulator; 107, spectrum analyzer; 108, suspended diaphragm fiber FP viscosity sensor; 109, liquid to be tested. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example:

[0030] Please see attached Figure 1 , the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm provided by the present invention comprises a light source, a viscosity detection unit, a demodulation module, a display unit and a test system;

[0031] The demodulation module includes: a diode laser 104, a DFB laser 103, a fiber coupler 105, a fiber circulator 106, a computer, a function generator 102, a spectrum analyzer 107 and a suspended diaphragm fiber FP viscosity sensor 108;

[0032] The computer is connected to the function generator 102 through a communication cable, the function generator 102 is connected to the diode laser 104 through a communication cable, the diode laser 104 is connected to port 1 of the fiber circulator 106 through a fiber optic jumper, port 2 of the fiber circulator 106 is connected to port 2 of the fiber coupler 105 through a fiber optic jumper, port 3 of the fiber circulator 106 is connected to a suspended diaphragm fiber FP viscosity sensor 108 through a fiber optic jumper, port 1 of the fiber coupler 105 is connected to the DFB laser 103 through a fiber optic jumper, port 3 of the fiber coupler 105 is connected to the spectrum analyzer 107 through a fiber optic jumper, the diode laser 104 provides light pressure to drive the sensor diaphragm to resonate, and the DFB laser light source performs reflection detection.

[0033] In order to verify its feasibility, it is necessary to conduct experimental research on it. The experimental system consists of a viscosity sensor, a laser light source, a data acquisition device, a constant temperature water bath heating device and an oil cup; the function generator 102 is connected to the diode laser 104 through a communication cable to control the modulation frequency of the 808nm diode laser; the light of the DFB laser resonates in the fiber Fabry-Perot cavity and reflects interference fringes for measuring vibration; the 3 ports of the fiber circulator are connected to the spectrum analyzer through a fiber jumper to obtain the reflection spectrum under different viscosity values.

[0034] like Figure 2 The test method of the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm shown is applied to the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm of claim 1, comprising the following steps:

[0035] Step 1: Collect the reflection spectrum data of the suspended diaphragm optical fiber FP viscosity sensing probe when it is unloaded;

[0036] Step 2: Insert the suspended diaphragm-based sensing probe into the fluid to collect reflectance spectrum data at different viscosity values;

[0037] Step 3: Demodulate the reflection spectrum using Fourier algorithm to obtain the frequency and amplitude at different viscosity values;

[0038] Step 4: Fit the frequency and amplitude by the least square method to obtain the sensor damping factor β;

[0039] Step 5: Establish the relationship between liquid viscosity η and damping factor β to obtain viscosity;

[0040]

[0041] Where a is a constant, β represents the damping factor, β0 represents the damping factor of the sensor itself, and ρ represents the liquid density.

[0042] (1) inserting a fiber optic sensing probe based on a suspended diaphragm into the fluid and controlling its insertion depth so that it is a certain distance from the bottom of the cup;

[0043] (2) Turn on the diode laser light source to start oscillation, and transmit it to the sensitive diaphragm of the Fabry-Perot sensor through the optical fiber, so that the sensitive diaphragm begins to vibrate under forced vibration. The movement of the sensitive diaphragm of the Fabry-Perot probe in the measured liquid can be regarded as simple harmonic vibration, and the viscosity probe of the Fabry-Perot sensor can be regarded as an ideal spring oscillator model. Under the combined effect of the sensor's own elastic force and viscous resistance, its forced vibration equation is:

[0044]

[0045] Where m is the mass of the probe, x is the vibration displacement of the probe, t is the vibration time of the probe, γ is the damping coefficient, k is the stiffness coefficient of the probe, H is the maximum value of the driving force, ω is the angular frequency of the driving force, and the damping factor of the probe motion is β, the natural angular frequency is ω0, and We can get:

[0046]

[0047] The steady-state solution of the equation is:

[0048]

[0049] Where: A represents the amplitude of the probe's forced vibration in a stable state, represents the phase difference between the forced vibration and the driving force in the steady state, where the amplitude A is:

[0050]

[0051] When the sensitive diaphragm moves in the liquid to be tested, it is subjected to the viscous shear force, and the vibration characteristics change. When ω0=ω, that is, when the driving force angular frequency is equal to the natural frequency of the system, the vibration amplitude of the probe reaches the maximum, and resonance occurs, so that the entire system can obtain energy to the maximum extent. By collecting experimental data within a certain range around the resonance frequency, the change characteristics of the vibration characteristics of the probe are obtained, combined with the relationship between ω0 and the resonance frequency f0:

[0052] ω0=2πf0 (5)

[0053] Applying the formula for least squares fitting, the damping factor β of the entire system motion can be obtained. The damping factor of the system includes two parts: the damping factor of the sensor itself and the damping factor of the liquid. The damping factor of the sensor itself can be obtained by measuring the vibration characteristics of the system when it is unloaded (static). Set it as β0, set S as the area of ​​the sensitive diaphragm, η as the dynamic viscosity of the measured liquid, and ρ as the density of the measured liquid, then:

[0054]

[0055] Where: k1 is a fixed coefficient, which is only related to the mass of the spring oscillator. The expression of liquid viscosity η is inversely deduced as:

[0056]

[0057] make have to:

[0058]

[0059] Where: k1, s, f0, ρ are all constants. According to the damping factors β and β0 obtained by measurement fitting, the viscosity value of the measured liquid can be calculated to achieve viscosity measurement.

[0060] (3) Turn on the DFB laser for reflection detection and use an oscilloscope to record the vibration characteristics of the Fabry-Perot probe, namely the amplitude and frequency.

[0061] (4) After obtaining the above experimental data, the amplitude and frequency are nonlinearly fitted using formula (4) to obtain the corresponding damping factors β and β0.

[0062] (5) Substitute the damping factor obtained by fitting into formula (8) to obtain the liquid viscosity value.

[0063] The method for measuring liquid viscosity achieved through the above steps has a wide range of application scenarios.

[0064] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fluid viscosity detection device based on the damping characteristics of a suspended diaphragm, comprising a light source, a viscosity detection unit, a demodulation module, a display unit and a test system, characterized in that: The demodulation module comprises: a diode laser (104), a DFB laser (103), an optical fiber coupler (105), an optical fiber circulator (106), a computer, a function generator (102), an optical spectrum analyzer (107) and a suspended diaphragm optical fiber FP viscosity sensor (108); The computer is connected to a function generator (102) via a communication cable, the function generator (102) is connected to a diode laser (104) via a communication cable, the diode laser (104) is connected to a port 1 of a fiber circulator (106) via a fiber jumper, the port 2 of the fiber circulator (106) is connected to a port 2 of a fiber coupler (105) via a fiber jumper, the port 3 of the fiber circulator (106) is connected to a suspended diaphragm fiber FP viscosity sensor (108) via a fiber jumper, the port 1 of the fiber coupler (105) is connected to a DFB laser (103) via a fiber jumper, the port 3 of the fiber coupler (105) is connected to a spectrum analyzer (107) via a fiber jumper, the diode laser (104) provides light pressure to drive the sensor diaphragm to resonate, and the DFB laser light source performs reflection detection.

2. A test method for a fluid viscosity detection device based on the damping characteristics of a suspended diaphragm, characterized in that: The fluid viscosity detection device based on the damping characteristics of the suspended diaphragm as described in claim 1 comprises the following steps: Step 1: Collect the reflection spectrum data of the suspended diaphragm optical fiber FP viscosity sensing probe when it is unloaded; Step 2: Insert the suspended diaphragm-based sensing probe into the fluid to collect reflectance spectrum data at different viscosity values; Step 3: Demodulate the reflection spectrum using Fourier algorithm to obtain the frequency and amplitude at different viscosity values; Step 4: Fitting the frequency and amplitude by the least square method to obtain the sensor damping factor β; Step 5: Establish the relationship between liquid viscosity η and damping factor β to obtain viscosity; Where a is a constant, β represents the damping factor, β0 represents the damping factor of the sensor itself, and ρ represents the liquid density.

3. The testing method of the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2 is characterized in that: The sensing probe in step 1 is a fiber FP interference structure composed of a single-mode optical fiber and a suspended diaphragm.

4. The testing method of the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2 is characterized in that: The no-load in step 1 is to remove the vibration characteristics of the measured liquid to obtain the sensor's own damping factor β0.

5. The testing method of the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2, characterized in that: The suspension diaphragm material in step 1 is silicon nitride, with a diameter of D=2.5 mm, a thickness of d=210 nm, and 4 cantilevers.

6. The testing method of the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2 is characterized in that: The fluid in step 2 is a Newtonian fluid.

7. The method for testing the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2, characterized in that: The spectrometer acquisition range in step 2 is 1510-1600nm, the sampling point is set to 9001, and the spectrometer resolution is 0.05nm.

8. The method for testing the fluid viscosity detection device based on the damping characteristics of the suspended diaphragm according to claim 2, characterized in that: The Fourier algorithm in step 3 is a demodulation algorithm, which converts wavelength domain spectral information into frequency domain spectral information for cavity length calculation.

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