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Viscosity coefficient measurement method based on photoacoustic effect

A technology of viscosity coefficient and measurement method, applied in the field of physical measurement, which can solve the problems of difficulty in judging the whereabouts of the center line of a small glass tube, low accuracy, and poor repeatability of falling ball measurement time.

Inactive Publication Date: 2011-07-20
SOUTH CHINA NORMAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There are three problems in the traditional measurement method: 1. Using a stopwatch to time manually, the accuracy is low
2. It is difficult to judge whether the ball falls along the centerline of the glass tube, which is precisely a source of experimental error
3. Poor repeatability of falling ball measurement time

Method used

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  • Viscosity coefficient measurement method based on photoacoustic effect
  • Viscosity coefficient measurement method based on photoacoustic effect
  • Viscosity coefficient measurement method based on photoacoustic effect

Examples

Experimental program
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Effect test

Embodiment 1

[0050] Embodiment 1. Measuring the time-domain photoacoustic signal of glycerol aqueous solutions with different viscosity coefficients:

[0051] (1) Different viscosity coefficients ξ n The liquid samples are placed in the container respectively, and the pulsed laser is focused and irradiated on the liquid sample to excite the photoacoustic signal;

[0052] (2) Using the acquisition system to record the photoacoustic signal P(t) of the liquid sample. Plotting thermoacoustic signals with Origin figure 2 (a), and calculate the thermoacoustic conversion efficiency by known parameters.

[0053] It can be seen from the figure that with the increase of the viscosity coefficient, the amplitude of the liquid thermoacoustic signal decreases, which is consistent with the change law of equation (10). Due to the effect of heat dissipation caused by viscosity, the conversion efficiency of thermoacoustic signal is significantly reduced.

Embodiment 2

[0054] Embodiment 2, measuring the frequency-domain photoacoustic signal of glycerol aqueous solution with different viscosity coefficients:

[0055] (1) Different viscosity coefficients ξ n The liquid samples are placed in the container respectively, and the pulsed laser is focused and irradiated on the liquid sample to excite the photoacoustic signal;

[0056] (2) Using the acquisition system to record the photoacoustic signal P(t) of the liquid sample. Use the acquisition system to record the photoacoustic signal of the liquid sample and use Matlab to perform Fourier transform on the recorded photoacoustic signal to obtain the spectrum of the liquid thermoacoustic signal with different viscosity coefficients figure 2 (b).

[0057] It can be seen from the figure that with the increase of the viscosity coefficient, the main frequency and bandwidth of the liquid thermoacoustic signal decrease, which is consistent with the change law of equation (10).

Embodiment 3

[0058] Embodiment 3, obtain the viscosity coefficient of glycerol aqueous solution with different viscosity coefficients by thermoacoustic signal frequency shift calculation:

[0059] (1) The known viscosity coefficient ξ 1 The glycerol aqueous solution is placed in a container, and the pulsed laser (continuously modulated laser) is focused and irradiated on the glycerol aqueous solution to excite the photoacoustic signal;

[0060] (2) Use the acquisition system to record the photoacoustic signal P(t) of the liquid sample, and use Matlab to perform Fourier transform on the recorded photoacoustic signal;

[0061] (3) Extract the main frequency or bandwidth ω of the photoacoustic signal 1 , according to k 1 = ω 1 / c s1 Get the wavelength k 1 ; The photoacoustic pressure function P(t) is obtained by ultrasonic transducer detection, according to the main frequency of the photoacoustic signal in the following photoacoustic signal frequency domain expression equation The rela...

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Abstract

The invention discloses a viscosity coefficient measurement method based on photoacoustic effect, which comprises the following steps: placing a liquid sample with a known viscosity coefficient in a container, and irradiating pulse laser after being focused on the liquid sample to arouse a photoacoustic signal; collecting the photoacoustic signal of the liquid sample, and extracting the basic frequency of the photoacoustic signal; obtaining a photoacoustic pressure function P(t) through detection with an ultrasonic transducer; obtaining a constant alpha according to the expression equation ofthe frequency domain of the photoacoustic signal; arranging liquid to be tested in the container, irradiating pulse laser after being focused on the liquid to be tested to arouse a photoacoustic signal; receiving a photoacoustic signal of the liquid to be tested with an ultrasonic detector, and collecting data after amplifying the photoacoustic signal with a signal amplifier; processing the recorded photoacoustic signal with Matlab, carrying out Fourier transformation for the recorded photoacoustic signal, and extracting the basic frequency of the photoacoustic signal; and obtaining the viscosity coefficient Xin of the liquid to be tested according to Xin = lvnpncsn. The method has the advantages of high speed, high precision, no destruction, high online measurement capability and high practicality.

Description

technical field [0001] The invention belongs to the technical field of physical measurement, in particular to a method for measuring viscosity coefficient based on photoacoustic effect. Background technique [0002] The viscosity coefficient is an important physical quantity that expresses the properties of the fluid. The viscosity coefficient of the liquid is also called the internal friction coefficient. In engineering technology, production technology and medicine, it is of great significance to measure the viscosity coefficient of the liquid. For example, to study the energy loss of water, oil and other fluids during long-distance transport, to reduce the resistance of moving objects in liquids in the shipbuilding industry, to obtain valuable diagnoses by measuring the viscosity of blood in medicine, etc. These are all related to the measurement The viscosity coefficient of the liquid is related. [0003] The Stokes method is the basic method for determining the viscosi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N11/00
Inventor 娄存广邢达
Owner SOUTH CHINA NORMAL UNIVERSITY
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