Device and method for accurately measuring the liquid level in a nuclear reactor T-tube two-phase entrainment experiment

Abstract

The invention discloses a device and method for accurately measuring the liquid level in a tube of a nuclear reactor T-tube two-phase entrainment experiment. The device comprises a T-tube structure, the T-tube structure comprises a connected horizontal main pipe and a vertical branch pipe, the vertical branch pipe is located in the middle of the horizontal main pipe; flanges are welded at both ends of the horizontal main pipe and the outlet of the vertical branch pipe of the T-tube structure; upper pressure measuring holes and lower pressure measuring holes are respectively opened at both ends of the horizontal main pipe; the two upper pressure measuring holes are respectively connected to the lower inlet of the corresponding steam-water separation device through their own upper pressure-leading pipes, and the upper outlet of each steam-water separation device is connected to the corresponding low-pressure end of the differential pressure transmitter; the two lower pressure measuring holes are respectively connected to the high-pressure end of the corresponding differential pressure transmitter through their own lower pressure-leading pipes; the accurate liquid level in the horizontal main pipe can be indirectly measured by collecting the readings of the two differential pressure transmitters and taking the average value. The invention has a simple structure, is easy to process and install, and improves the accuracy of the liquid level measurement value in the horizontal tube in the T-tube two-phase entrainment experiment.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear reactor thermal hydraulic experimental devices, and in particular relates to a precise measuring device for the liquid level in a tube suitable for a nuclear reactor T-tube two-phase entrainment experiment. Background Art

[0002] For passive nuclear power plants, pressure relief is required after a loss of coolant accident to meet the requirements of gravity water injection. After the automatic pressure relief valve is opened, steam entrains a large number of droplets into the containment through the T-shaped structure formed by the automatic pressure relief pipeline and the heat pipe. When the flow rate of the automatic pressure relief system is greater than the injection flow rate, the core liquid level decreases; when the flow rate of the automatic pressure relief system is less than the injection flow rate, the core liquid level increases. In the short term, the discharge entrainment after the automatic pressure relief valve is opened has a significant impact on the core liquid level after the loss of coolant accident. If the liquid level is lower than the core height, it may cause oxidation and expansion of the fuel rods, and even serious accidents such as core exposure or melting; in the long term, natural circulation is achieved through the steam discharge of the automatic pressure relief valve (condensed and refluxed to the pit in the containment through the PCS) and the injection of pit water. At the same time, in this process, the boron migration balance is achieved through the droplet entrainment of the steam discharged by the automatic pressure relief valve. Therefore, it is of great significance to carry out the two-phase entrainment experiment of the nuclear reactor T-tube to study the effect of automatic pressure relief entrainment on the loss of coolant accident.

[0003] The liquid level in the T-tube horizontal main pipe is an important factor affecting the gas-liquid two-phase entrainment phenomenon. The liquid level will affect the entrainment amount, that is, the rate of change of the core liquid level. Therefore, accurate measurement of the liquid level in the tube is very important for the study of entrainment phenomenon.

[0004] For example, in the published paper on the liquid level measurement of the T-tube experimental section in the double-end air inlet T-tube entrainment experiment, the liquid levels before and after the ADS-4 branch pipe are directly measured using a differential pressure transmitter. However, due to the existence of the entrainment phenomenon, some liquid droplets will be entrained into the low-pressure end pressure pipe, causing measurement errors and failing to meet the requirements for accurate liquid level measurement in the horizontal pipe. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a precise measurement device for the liquid level in a tube suitable for a two-phase entrainment experiment in a T-tube of a nuclear reactor, which can meet the requirements for precise measurement of the liquid level in a horizontal tube during the gas-liquid two-phase entrainment process, thereby providing a more reliable tool for predicting the entrainment phenomenon in the automatic pressure relief process under a loss of coolant accident, thereby improving the safety of nuclear power plants.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A device for accurately measuring the liquid level in a T-tube of a nuclear reactor for a two-phase entrainment experiment comprises a T-tube structure 1, wherein the T-tube structure 1 comprises a horizontal main pipe 11 and a vertical branch pipe 12 connected to each other, wherein the vertical branch pipe 12 is located in the middle of the horizontal main pipe 11; flanges 2 are welded at both ends of the horizontal main pipe 11 and the outlet of the vertical branch pipe 12 of the T-tube structure 1; an upper pressure measuring hole 61 and a lower pressure measuring hole 62 are respectively opened at both ends of the horizontal main pipe; the two upper pressure measuring holes 61 are respectively connected to the lower inlet of the corresponding steam-water separation device 4 through their own upper pressure-conducting pipes 51, and the upper outlet of each steam-water separation device 4 is connected to the corresponding low-pressure end of a differential pressure transmitter 3; the two lower pressure measuring holes 62 are respectively connected to the high-pressure end of the corresponding differential pressure transmitter 3 through their own lower pressure-conducting pipes 52; the accurate liquid level in the horizontal main pipe 11 can be indirectly measured by collecting the readings of the two differential pressure transmitters 3 and taking the average value.

[0008] Preferably, the upper pressure measuring hole 61 and the lower pressure measuring hole 62 are bilaterally symmetrical about the symmetry axis of the stainless steel T-tube structure 1 , and are located at equal distances from the flanges 2 at both ends of the horizontal main pipe 11 and the vertical branch pipe 12 in the horizontal direction.

[0009] Preferably, the T-tube structure 1 and the flange 2 are made of stainless steel.

[0010] The invention discloses a measuring method of an accurate measuring device for measuring the liquid level in a T-tube of a nuclear reactor during a two-phase entrainment experiment. Before the T-tube two-phase entrainment experiment begins, the lower pressure-inducing pipe 52 is filled with liquid identical to the experimental working medium, and the upper pressure-inducing pipe 51 is filled with gas identical to the experimental working medium. During the T-tube two-phase entrainment experiment, gaseous and liquid working medium enter the horizontal main pipe 11 from both ends of the horizontal main pipe 11. Part of the liquid working medium is entrained into the vertical branch pipe 12 under the action of the gas phase lifting force, and the gas phase working medium and the entrained liquid working medium flow out of the T-tube structure 1 through the outlet of the vertical branch pipe 12. During the experiment, due to the existence of the entrainment phenomenon, part of the liquid droplets are entrained into the upper pressure-inducing pipe 51, and the liquid phase is carried by the gas phase to the steam-water separation device 4 to achieve separation of the gas phase and the liquid phase. After the experiment continues for a period of time, the valve at the bottom of the steam-water separation device 4 is opened to drain the accumulated liquid. At this time, the reading of the differential pressure transmitter is collected in real time and the average value is taken to obtain the accurate liquid level in the horizontal main pipe 11.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. The pressure measuring hole of the present invention is located in the main body of the experimental section. By measuring the upper and lower pressure differences at the same horizontal position of the T-tube to obtain the liquid level in the tube, a three-way structure can be added to the connection section between the steam-water separation device and the low-pressure end of the differential pressure transmitter. A branch pressure lead pipe is led out on the basis of the original pressure lead pipe and connected to the pressure transmitter to meet the need of measuring the pressure of the experimental section, thereby avoiding repeated drilling of holes in the experimental section, ensuring the reliability of the experimental section and improving the accuracy of the measurement data.

[0013] 2. The pressure measuring tube on the upper part of the T-tube is first connected to the low-pressure end of the differential pressure transmitter through the steam-water separation device, which can effectively remove the liquid entrained into the pressure pipe due to the entrainment effect, and can effectively improve the accuracy of liquid level measurement in the horizontal pipe.

[0014] 3. The horizontal main pipe, vertical branch pipe and flange of the T-tube structure of the present invention are all made of stainless steel and welded together. It has a simple structure and can withstand gas-liquid two-phase entrainment experiments under high temperature and high pressure.

[0015] In conclusion, the present invention has a simple structure, is easy to process and install, and can realize accurate measurement of the liquid level in the horizontal tube during the two-phase entrainment experiment of the T-tube of a nuclear reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The invention is a front view of a device for accurately measuring the liquid level in a tube suitable for a two-phase entrainment experiment in a T-tube of a nuclear reactor. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0018] See also Figure 1 As shown, the present invention discloses a precise measuring device for the liquid level in a nuclear reactor T-tube two-phase entrainment experiment, comprising a T-tube structure 1; the T-tube structure 1 comprises a horizontal main pipe 11 and a vertical branch pipe 12, and the vertical branch pipe 12 is located in the middle of the horizontal main pipe 11; flanges 2 are welded at both ends of the horizontal main pipe 11 of the T-tube structure 1 and at the outlet of the vertical branch pipe 12; the flange 2 can be fastened with a corresponding flange through a mounting hole to realize the connection between the experimental section of the T-tube structure 1 and the overall experimental loop pipeline.

[0019] Four pressure measuring holes are opened on the horizontal main pipe, including an upper pressure measuring hole 61 at the upper part and a lower pressure measuring hole 62 at the lower part at both ends of the horizontal main pipe 11. The two upper pressure measuring holes 61 and the two lower pressure measuring holes 62 are respectively symmetrical about the symmetry axis of the T-tube structure 1, and the upper and lower corresponding pressure measuring holes are in the same horizontal position; the two upper pressure measuring holes 61 are respectively connected to the corresponding lower inlet of the steam-water separation device 4 through their respective upper pressure-leading pipes 51, and the upper outlet of the steam-water separation device 4 is connected to the corresponding low-pressure end of the differential pressure transmitter 3; the two lower pressure measuring holes 62 are respectively connected to the corresponding high-pressure end of the differential pressure transmitter 3 through their respective lower pressure-leading pipes 52.

[0020] As a preferred embodiment of the present invention, the upper pressure measuring hole 61 and the lower pressure measuring hole 62 are symmetrical about the axis of symmetry of the stainless steel T-tube structure 1, and are located at equal distances from the flanges 2 at both ends of the horizontal main pipe 11 and the vertical branch pipe 12 in the horizontal direction, so that the average liquid level in the horizontal main pipe 11 can be calculated based on the liquid levels on both sides of the horizontal pipe 11.

[0021] As a preferred embodiment of the present invention, the T-tube structure 1 and the flange 2 are made of stainless steel, which is easy to process and install, and can withstand experimental conditions simulating the high temperature and high pressure environment in a nuclear reactor, thereby ensuring the reliability of the experimental section structure.

[0022] Before the T-tube two-phase entrainment experiment begins, the lower pressure-inducing pipe 52 should be filled with the same liquid as the experimental working medium, and the upper pressure-inducing pipe 51 should be filled with the same gas as the experimental working medium; during the T-tube two-phase entrainment experiment, the gas phase and liquid phase working medium can enter the horizontal main pipe 11 from both ends of the horizontal main pipe 11; part of the liquid phase working medium is entrained into the vertical branch pipe 12 under the action of the gas phase lifting force, and the gas phase working medium and the entrained liquid phase working medium flow out of the T-tube structure 1 through the outlet of the vertical branch pipe 12; during the experiment, due to the existence of the entrainment phenomenon, some droplets will The liquid phase is entrained into the upper pressure-introducing pipe 51, and the liquid phase is carried by the gas phase to the steam-water separation device 4 to realize the separation of the gas phase and the liquid phase. After the experiment lasts for a period of time, the valve at the bottom of the steam-water separation device 4 can be opened to drain the accumulated liquid. At this time, the readings of the two differential pressure transmitters, namely the pressures P1 and P2, are collected in real time. The precise liquid level data h1 and h2 on both sides of the horizontal main pipe 11 can be obtained through the formula P=ρgh. The average value of the liquid level data h1 and h2 on both sides can be used to obtain the precise liquid level data h in the horizontal main pipe 11, wherein ρ is the density of the liquid working fluid.

[0023] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. An accurate measuring device for the liquid level in a T-tube of a nuclear reactor for two-phase entrainment experiment, characterized in that: The invention comprises a T-tube structure (1), wherein the T-tube structure (1) comprises a horizontal main pipe (11) and a vertical branch pipe (12) connected to each other, wherein the vertical branch pipe (12) is located in the middle of the horizontal main pipe (11); flanges (2) are welded at both ends of the horizontal main pipe (11) and the outlet of the vertical branch pipe (12) of the T-tube structure (1); an upper pressure measuring hole (61) and a lower pressure measuring hole (62) are respectively opened at both ends of the horizontal main pipe; the two upper pressure measuring holes (61) are respectively connected to the lower inlet of the corresponding steam-water separation device (4) through their own upper pressure-conducting pipes (51), and the upper outlet of each steam-water separation device (4) is connected to the low-pressure end of the corresponding differential pressure transmitter (3); the two lower pressure measuring holes (62) are respectively connected to the high-pressure end of the corresponding differential pressure transmitter (3) through their own lower pressure-conducting pipes (52); the accurate liquid level in the horizontal main pipe (11) can be indirectly measured by collecting the readings of the two differential pressure transmitters (3) and taking the average value; Before the T-tube two-phase entrainment experiment begins, the lower pressure-inducing pipe (52) is filled with a liquid identical to the experimental working medium, and the upper pressure-inducing pipe (51) is filled with a gas identical to the experimental working medium. During the T-tube two-phase entrainment experiment, the gas phase and liquid phase working medium enter the horizontal main pipe (11) from both ends of the horizontal main pipe (11). Part of the liquid phase working medium is entrained into the vertical branch pipe (12) under the action of the gas phase lifting force, and the gas phase working medium and the entrained liquid phase working medium flow out of the T-tube structure (1) through the outlet of the vertical branch pipe (12). During the experiment, due to the existence of the entrainment phenomenon, part of the liquid droplets are entrained into the upper pressure-inducing pipe (51), and the liquid phase is carried by the gas phase to the steam-water separation device (4) to achieve separation of the gas phase and the liquid phase. After the experiment continues for a period of time, the valve at the bottom of the steam-water separation device (4) is opened to drain the accumulated liquid. At this time, the reading of the differential pressure transmitter is collected in real time and the average value is taken to obtain the accurate liquid level in the horizontal main pipe (11).

2. The device for accurately measuring the liquid level in a T-tube of a nuclear reactor for two-phase entrainment experiment according to claim 1, characterized in that: The upper pressure measuring hole (61) and the lower pressure measuring hole (62) are symmetrical about the symmetry axis of the stainless steel T-shaped pipe structure (1), and are located at positions equidistant from the flanges (2) at both ends of the horizontal main pipe (11) and the vertical branch pipe (12) in the horizontal direction.

3. The device for accurately measuring the liquid level in a T-tube of a nuclear reactor for two-phase entrainment experiment according to claim 1, characterized in that: The T-shaped pipe structure (1) and the flange (2) are made of stainless steel.

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