Device and method for measuring void fraction of in-tube cryogenic fluid

Abstract

The invention discloses a device and a method for measuring a void fraction of in-tube cryogenic fluid. The device comprises a measuring zone tube shell, a capacitance acquisition circuit board, a connecting pipeline, a conductive pin, a polytetrafluoroethylene insulation sleeve, an electrode plate and a sealing copper ring. According to the device, by utilizing the characteristic that the polytetrafluoroethylene shrinks at a low temperature, the connecting pipeline is shrunk and locked at the low temperature, and seal is enhanced. Meanwhile, aiming at the characteristic that the liquid gas dielectric constants of the cryogenic fluid are close, the measuring zone tube shell serves as a skeleton of the measuring section and is grounded to serve as a shielding case. The electrical capacitance tomography device for cryogenic fluid has the characteristics that the device is simple in structure, can be rapidly detached, and can be conveniently connected with other pipelines of the system; the device can be applied to a wider range from a room temperature to a cryogenic temperature, and the measurement accuracy is not influenced due to repeated great temperature cycling; and the device is excellent in stray capacitance resistance and excellent in electromagnetic shielding effect. According to the measuring method disclosed by the invention, the measured capacitance value is associated with the void fraction by utilizing a support vector regression manner, and the obtained fitting result is high in accuracy.

Description

technical field [0001] The invention relates to low-temperature refrigeration engineering technology, the field of fluid flow process monitoring and sensor science and technology, in particular to a device and method for measuring the void ratio of low-temperature fluid in a tube. 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] Different from room temperature fluids, the gas-liquid dielectric constant has a large difference. The liquid-gas dielectric constant ratio of low-temperature 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 a better imaging effect, it is necessary to Build a good electromagnetic shielding structure. In additi...

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Problems solved by technology

[0004] A Chinese patent for a low-temperature capacitive void rate measurement device (201610332690.X) discloses a device that uses a two-electrode capacitive sensor to correlate the capacitance measurement with the low-temperature fluid in the tube. The device uses a two-electrode structure, and in The correlation method is a simple one-to-one correspondence between the capacitance value and the cavitation rate. It is more sensitive to changes in the flow pattern, and it is difficult to obtain good results under complex flow patterns. This patent has both the device structure and the correlation mechanism of the measurement data. It is very different from this patent

[0005] Chinese Patent A Capacitance Tomography Device for Cryogenic Fluid Tube Flow (201711264162.6) discloses a capacitive tomography device applied to two-phase flow of cryogenic fluid. The electrode sheet and the test circuit are connected softly, and the shielding cover is not used as a device. A part of the pipe body, while using the inversion algorithm of electrical capacitance tomography as the solution method, has a large difference from this application in terms of device structure and processing algorithm

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 It involves the specific structural design of the capacitance tomography sensor for the measurement of cryogenic fluid two-phase flow, and its solution algorithm is also very different from this patent

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