Abstract
At present, real-time online measurement of fluid density is of great significance to improve the automation level of petrochemical and food industries. The tuning fork density sensor is widely used because of its characteristics of real-time online measurement, high measurement accuracy, simple structure, and convenient use. The traditional tuning fork density sensor in the market has the disadvantage of low resolution and being susceptible to liquid viscosity, which makes the sensor’s measurement accuracy low and not suitable for the measurement of high-viscosity liquid density. The measurement resolution and antiviscosity interference capability of the tuning fork density sensor are two major indexes to measure the measurement performance of the sensor, among the antiviscosity interference capability refers to the degree to which the measurement results of the sensor are affected by viscosity properties. However, the structural design of the tuning fork density sensor results in the conflict between the measurement resolution and the antiviscosity interference capability of the sensor, and the improvement of one performance is bound to affect the performance of the other. Aiming at the problem of how to balance the measuring performance of the tuning fork sensor, a density calculation model based on viscosity compensation is proposed in this paper. By studying the working principle and structure design of the tuning fork, the vibration characteristics of tuning fork in liquid with different viscosities and densities are modelled and simulated. From the results of simulation analysis, the better set of dimensions with balanced measuring performance is selected. Not only does the structure of the tuning fork have the characteristics of high resonance frequency, but also the measured results are less affected by the viscosity of the liquid. To solve the problem that density measurement is still affected by high-viscosity liquid after tuning fork dimension optimization, in this paper, the partial least square model is used to fit the experimental data of the frequency-density characteristics; then, the density calculation model based on the viscosity compensation is obtained by combining the frequency-viscosity characteristic experiment. Finally, through the performance test experiment comparing with the traditional tuning fork density sensor, the measurement resolution of the improved tuning fork density sensor is as high as 0.0001 g/cm3; within the viscosity range of 180 MPa·s, the accuracy reached ±0.001 g/cm3, and within 480 MPa·s, the measurement accuracy reached ±0.002 g/cm3. When the liquid viscosity reaches more than 10 MPa·s, the improved tuning fork density sensor has better overall measurement performance than the traditional tuning fork density sensor, and both of its measurement resolution and antiviscosity interference capability have been greatly improved.
Highlights
In the process of chemical production, the determination of liquid density can be used to approximate the quality and chemical composition of the fluid. e accuracy and stability of the measurement directly affect the quality of the product, and the real-time measurement even endangers the stability and safety of the process equipment. erefore, the density sensor is widely used in chemical production plant, which is of great significance to chemical production
When the measured medium flows through the tube, the natural oscillation frequency of the elastic oscillator will change with the density of the measured medium, and the measurement results of this method are accurate and repeatable, but it is expensive to add the control and temperature automatic cleaning system. e float detection method [5] based on Archimedes principle, the float displacement, and buoyancy changes immersed in the measured liquid are converted into a variety of electrical or mechanical detection signals to measure the liquid density
The timeliness of the measurement results is poor, which is affected by temperature and vibration. e basic principle of the static pressure method for density detection [6] is that the static pressure of the liquid column to be measured at a certain height is proportional to its density, and it can indirectly measure the measured medium and be applied to liquids with large viscosity
Summary
In the process of chemical production, the determination of liquid density can be used to approximate the quality and chemical composition of the fluid. e accuracy and stability of the measurement directly affect the quality of the product, and the real-time measurement even endangers the stability and safety of the process equipment. erefore, the density sensor is widely used in chemical production plant, which is of great significance to chemical production. E traditional tuning fork density sensor in the market has the disadvantages of low measurement resolution, and the measurement result is affected by the liquid viscosity, so the sensor has low measurement accuracy and large measurement error in the liquid with high viscosity, which is difficult to meet the measurement standard. Combined with the above scholars’ research foundation and unsolved problems, this paper aims at the defects of the existing tuning fork density sensor in the market, which have low resolution and high accuracy and are affected by the liquid viscosity. Compared with the traditional tuning fork on market density sensor improves the resolution of frequency measurement and makes the density measurement accuracy of high viscosity liquid higher. E improved sensor solves the problem of low resolution of the traditional tuning fork density sensor and large measurement error in high viscosity liquid Compared with the traditional tuning fork on market density sensor improves the resolution of frequency measurement and makes the density measurement accuracy of high viscosity liquid higher. e improved sensor solves the problem of low resolution of the traditional tuning fork density sensor and large measurement error in high viscosity liquid
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