Method for measuring dielectric constant and liquid level of medium in LNG tank

Abstract

The invention relates to a method for measuring the dielectric constant and the liquid level of a medium in an LNG tank. The method for measuring the dielectric constant and the liquid level of the medium in the LNG tank comprises the step that a top capacitor, a middle capacitor and a bottom capacitor are arranged at the upper end, in the middle and at the lower end of the interior of the LNG tank respectively, (2) the capacitance CH1 of the top capacitor, the capacitance CM1 of the middle capacitor and the capacitance CL1 of the bottom capacitor are measured respectively in the air, (3) the dielectric constant epsilon 1 of liquid is calculated according to a formula (please see the specifications for the formula), (4) the dielectric constant epsilon 2 of the liquid is obtained through calculation according to a formula ((please see the specifications for the formula), and (5) the level Hx of the liquid in the LNG tank is obtained through calculation according to a formula (please see the specifications for the formula). According to the method for measuring the dielectric constant and the liquid level of the medium in the LNG tank, a three-section capacitor sensor can serve as tools for verifying and calibrating other tools and can also serve as high-precision liquid level sensors; when the liquid level is measured, measurement errors caused by factors such as temperature change, pressure change and impurities can be avoided.

Description

technical field [0001] The invention relates to the technical field of measurement, in particular to a method for measuring the dielectric constant and liquid level of a medium in an LNG gas tank. Background technique [0002] Liquefied Natural Gas (LNG) has been widely used in automobiles. LNG for automobiles is stored in thermally insulated storage tanks, and a liquid level detector must be equipped to display the LNG liquid level in real time. A liquid level detector generally includes: a liquid level sensor installed in a storage tank, a liquid level transmitter and a liquid level indicator for collecting and processing sensor signals. [0003] The automotive LNG liquid level sensor is installed in the inner cavity of the storage tank and is a key component of the entire detector, generally a capacitive sensor. At present, the detection methods of most liquid level detectors are: (1) First detect the no-load capacitance C of the capacitive sensor in the air 0 , and rec...

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Problems solved by technology

[0004] The above-mentioned liquid level detection method has the following disadvantages: (1) The other gas components contained in the liquefied natural gas will vary due to factors such as the place of origin, and the different components will affect the dielectric constant of LNG, so the full-load capacitance may change, so It will affect the accuracy of liquid level measurement, and the liquid level transmitter needs to be calibrated after each filling; (2) The pressure range of LNG for automobiles in the storage tank is 0.4-1.5MPa, and the storage temperature is close to -162°C. Will increase over time, changes in temperature and pressure will affect the dielectric constant of liquids and gases in the tank

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