A method for measuring dielectric constant and liquid level of medium in lng gas tank

Abstract

The invention relates to a method for measuring the dielectric constant and liquid level of a medium in an LNG gas tank, comprising the following steps: (1) setting a top capacitor, a middle capacitor and a bottom capacitor at the upper end, the middle part and the lower end of the LNG gas tank respectively. (2) Measure its capacitance value in air, respectively C H1 、C M1 and C L1 . (3) According to the formula Calculating the dielectric constant ε of a liquid 1 . (4) According to the formula Calculate the dielectric constant ε of the gas 2 . (5) by formula Calculate the liquid level height H in the LNG tank x . The three-segment capacitive sensor can be used as a tool for verifying and calibrating other sensors, and it can also be used as a high-precision liquid level sensor itself. When measuring the liquid level, it can overcome the measurement errors caused by factors such as temperature, pressure changes and magazines.

Description

technical field [0001] The utility model 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 gas tanks, and a liquid level detector must be equipped to display the LNG liquid level in real time. The liquid level detector generally includes: a liquid level sensor installed in the gas tank, a liquid level transmitter and a liquid level indicator for sensor signal acquisition and processing. [0003] The automotive LNG liquid level sensor is installed in the inner cavity of the gas 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 record ...

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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 refueling; (2) The pressure range of liquefied natural gas for automobiles in the gas 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 the liquid and gas inside the tank

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