Capacitive tomography sensor applied to two-phase flow phase distribution measurement of low-temperature fluid

Abstract

The invention discloses a capacitive tomography sensor applied to the two-phase flow phase distribution measurement of a low-temperature fluid. The device comprises a vacuum insulating pipeline, electrode sheets, a capacitance collection circuit board, a shielding cover, an insulating adhesive layer and a metal flange. According to the device, a vacuum jacket structure is adopted as a sensor measuring section; the electrode sheets are attached onto the outer side of the vacuum jacket; the good heat insulation performance of a low-temperature fluid flowing pipeline is kept, meanwhile, the circuit board can work at a safe temperature; and the low-temperature failure of a measuring circuit is avoided. The capacitive tomography device for the low-temperature fluid can be integrally disassembled and assembled as a modular structure and can be adapted to different measurement pipelines; the capacitive tomography device can be used for a relatively wide temperature section range from room temperature to cryogenic temperature; and a plurality of times of large-range temperature circulation does not influence measurement precision. The capacitive tomography sensor has the advantages of goodanti-stray capacitance capability and good electromagnetic shielding effect.

Description

technical field [0001] The invention relates to the fields of low-temperature refrigeration engineering technology, fluid flow process monitoring and sensor science and technology, in particular to an electric capacitance tomography sensor applied to the measurement of two-phase flow phase distribution of low-temperature fluid. Background technique [0002] Two-phase flow in pipes often occurs in fluid-related industries such as chemical industry and air separation, and involves design optimization and operation safety. Therefore, the detection of two-phase distribution is of great significance. [0003] For the measurement of fluids using capacitance tomography sensors, different from the measurement environment of room temperature fluids, three major problems need to be faced in the measurement of low temperature fluids: one is that the safe working temperature range of the measurement circuit will be exceeded in the deep low temperature environment , so that the measureme...

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Problems solved by technology

[0003] For the measurement of fluids using capacitance tomography sensors, different from the measurement environment of room temperature fluids, three major problems need to be faced in the measurement of low temperature fluids: one is that the safe working temperature range of the measurement circuit will be exceeded in the deep low temperature environment , so that the measurement fails and effective data cannot be obtained; the second is the influence of the temperature of the electrode sheet on the measured value of the capacitance. When the electrode sheet is directly in contact with the low-temperature fluid pipeline, due to the different flow conditions of the low-temperature fluid, there will be different heat transfer effects , resulting in a large change in the temperature of the electrode sheet, which in turn causes a deviation in the measurement capacitance; the third is the problem of heat leakage in the low-temperature fluid pipeline. When the room temperature end is connected to the instrument, the heat will be input into the low-temperature fluid pipeline through the transmission line, resulting in heat leakage. At the same time, if the pole piece is installed in a built-in arrangement attached to the inner wall of the pipeline, there will still be a problem of low-temperature fluid leakage; the fourth is that it is different from room temperature. There is a large difference in the dielectric constant of fluid gas and liquid. The liquid-gas dielectric constant ratio of cryogenic fluids such as liquid oxygen and liquid nitrogen is generally less than 1.5. The imaging results are extremely sensitive to measurement noise. In order to ensure better imaging results, it is necessary to construct a good Electromagnetic shielding structure

[0005] A Chinese patent for a low-temperature capacitive void rate measurement device (201610332690.X) discloses a device that uses a bipolar capacitive sensor to correlate the capacitance measurement with the low-temperature fluid in the tube. The device adopts a bipolar structure, and The correlation method is a simple one-to-one correspondence between the capacitance value and the cavitation rate. It is more sensitive to the change of the flow pattern, and it is difficult to obtain good results under the complex flow pattern, and it cannot measure the phase distribution. The patent is in the structure of the device All have very big difference with the present invention on the association mechanism of above and measurement data

The document "Preliminaryevaluation of cryogenic two-phase flow imaging using electrical capacitance tomography" (Cryogenics, 2017, 86) theoretically verified the electrical capacitance tomography technology applied to cryogenic fluid measurement, and found that the results of the numerical experiments were better, but the article did not Involves specific structural design of electrical capacitance tomography sensor for cryogenic fluid two-phase flow measurement

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