Annular pressure device for measuring the differential pressure of liquid in a vertical circular tube at the experimental site

Abstract

The present invention discloses an annular pressure-taking device for measuring the differential pressure of liquid in a vertical circular tube at an experimental site, which belongs to the field of flow measurement; wherein a throttling device is arranged at the middle section of the vertical circular tube, and two annular pressure-taking devices are respectively vertically installed on the high-pressure section and the low-pressure section of the vertical circular tube; the annular pressure-taking device comprises a pressure-leading pipe, a pressure-equalizing ring and a measuring pipe whose axes are located in the same plane, wherein the pressure-equalizing ring is an annular pipe, four pressure-leading pipes are evenly installed inside the pressure-equalizing ring, four pressure-leading pipes are smoothly connected to the vertical circular tube to be measured through pressure-taking holes, the measuring pipe is installed outside the pressure-equalizing ring, a differential pressure transmitter is installed outside the measuring pipe, and the liquid in the vertical circular tube enters the pressure-equalizing ring through the pressure-leading pipe, and is evenly mixed inside the pressure-equalizing ring. The present invention improves the direct pressure-taking method widely used in current thermal hydraulics experiments, avoids the adverse effects of pulsating pressure, vibration, etc. on differential pressure measurement, and improves the accuracy of differential pressure measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of flow measurement, and in particular relates to an annular pressure-taking device for measuring the differential pressure of liquid in a vertical circular pipe at an experimental site. Background Art

[0002] Thermal hydraulics experimental research is an important part of fluid mechanics research in professional disciplines such as energy and power engineering, nuclear engineering and nuclear technology, and petrochemical engineering. Fluid differential pressure is a key measurement parameter in thermal hydraulics experiments. Therefore, in the experimental environment, accurate measurement of the experimental fluid differential pressure is an important guarantee for experimental accuracy and measurement reliability.

[0003] Pressure is defined as the force acting vertically on a unit area of ​​a medium, which is what is called pressure in physics; and the difference in pressure between any two points is the differential pressure. In the thermal hydraulics experimental environment, according to the principles of fluid mechanics, fluid pressure mainly consists of two parts, namely the static pressure of the fluid caused by gravity and the dynamic pressure of the flow caused by the flow of the fluid. At present, in industrial applications, the widely used pressure measurement methods mainly include liquid column pressure gauges, elastic pressure gauges, electrical pressure gauges and piston pressure gauges. Among them, liquid column pressure gauges and elastic pressure gauges are generally not used for automated differential pressure measurement at the thermal hydraulics experimental site due to their shortcomings such as inconvenient reading and inability to be remotely controlled; piston pressure gauges are mainly used as standard instruments for calibration and calibration of other pressure measurement equipment, and are not used for differential pressure measurement at the experimental site; considering that the fluid flow rate is large and the pressure is considerable in thermal hydraulics experiments, and in order to facilitate automated data acquisition, transmission and remote control, the measurement of differential pressure in the experimental environment is mostly achieved by differential pressure transmitters. The present invention is based on an industrial differential pressure transmitter as a pressure measuring device. During the installation of the differential pressure transmitter, the arrangement of pressure taking points and the pressure taking method have a significant impact on the measurement accuracy.

[0004] Domestic and foreign research on differential pressure measurement is mostly focused on the terminal development and theoretical research of measuring equipment, while research on the basic content of pressure taking methods is very lacking. Xu Sijie and others took the water level monitoring of pressure vessels after nuclear power accidents as the application background and designed a pressure vessel water level measurement system based on the principle of heat diffusion. The water level detector is inserted into the key point to be measured by immersion method, and the liquid level can be displayed through signal processing. The system has the characteristics of intuitive measurement and simple signal processing.

[0005] In order to solve the cause of the deviation in the differential pressure measurement of the left and right intake ducts of the engine, Liu Kun et al. analyzed the structure and principle of the intake duct pressure measurement system in the article "Analysis of the Cause of the Deviation in the Pressure Drop Measurement of the Left and Right Intake Ducts of the Engine", clarified the relationship and influence between the pressure measuring pipeline, test equipment and static pressure holes, and determined the cause of the deviation; reasonable layout of the pressure measuring pipeline, reasonable selection of test equipment and reasonable maintenance of the static pressure holes were adopted to reduce the measurement deviation of the left and right intake ducts; however, the measurement of the differential pressure in this scheme still adopts the traditional direct pressure measurement method.

[0006] For example, an annular orifice throttling device and a pressure-taking and sewage-discharging method thereof disclosed in China Publication No. ZL201810394606.6, by shifting and modifying the sewage-discharging pipe on the annular orifice throttling device, the pressure-leading pipe and the sewage-discharging pipe are in the same straight line, which is convenient for timely sewage discharge and dredging of the pressure-taking pipeline. This invention is mainly used for gaseous working fluids such as coal gas, with sewage discharge as the main focus.

[0007] In summary, in medium-low pressure and medium-low temperature thermal hydraulic experiments, the research on the pressure measurement and pressure taking methods of liquid differential pressure in vertical circular tubes is still insufficient and not targeted enough. This is mainly reflected in the following three aspects: 1) At present, the measurement of liquid differential pressure in thermal hydraulic experiments mostly adopts the traditional direct pressure taking method, which has inherent defects in measurement accuracy and there are few related experimental studies; 2) In medium-low pressure and medium-low temperature thermal hydraulic experimental environments, there are few studies on differential pressure measurement and pressure taking methods, and there are no clear design standards; 3) There are few related studies on the pressure measurement and pressure taking methods of liquid differential pressure in vertical circular tubes. At the same time, in order to make the fluid flow stable, the length of the pressure pipe should be as long as possible in the traditional direct pressure taking method, which has adverse effects on equipment installation and space utilization in narrow spaces such as laboratories.

[0008] Aiming at the shortcomings of the direct pressure-taking method currently used to measure the liquid differential pressure in a vertical circular tube in thermal hydraulics experiments, in order to accurately measure the liquid differential pressure in thermal hydraulics experiments, an annular pressure-taking device suitable for measuring the liquid differential pressure in experimental sites such as medium-low pressure and medium-low temperature thermal hydraulics experimental benches and experimental devices was designed, which has positive significance for both experimental measurement accuracy and engineering applications. Summary of the invention

[0009] In view of the problems existing in the background technology, the present invention provides an annular pressure-taking device for measuring the differential pressure of liquid in a vertical circular tube at an experimental site, characterized in that it comprises: a vertical circular tube, a throttling device and two annular pressure-taking devices, wherein the throttling device is arranged in the middle section of the vertical circular tube, and the two annular pressure-taking devices are respectively vertically installed on the high-pressure section and the low-pressure section of the vertical circular tube;

[0010] The annular pressure taking device includes a pressure-guiding pipe, a pressure-equalizing ring and a measuring pipe whose axes are located in the same plane, wherein the pressure-equalizing ring is an annular pipe, four pressure-guiding pipes are evenly installed on the inner side of the pressure-equalizing ring, the four pressure-guiding pipes are smoothly connected to the vertical circular pipe to be measured through pressure taking holes, the measuring pipe is installed on the outer side of the pressure-equalizing ring, a differential pressure transmitter is installed outside the measuring pipe, the liquid in the vertical circular pipe 1 enters the pressure-equalizing ring through the pressure-guiding pipe and is evenly mixed in the pressure-equalizing ring; the length of the pressure-guiding pipe is ≥ 10 times the diameter of the pressure taking hole.

[0011] The inner diameter of the pressure-guiding tube, the inner diameter of the pressure-equalizing ring, and the inner diameter of the measuring tube are equal to the aperture of the pressure-taking hole.

[0012] The pressure-taking hole is circular; the axis of the pressure-taking hole is perpendicular to the axis of the vertical circular tube, and the diameter of the pressure-taking hole is less than 8% of the diameter of the vertical circular tube.

[0013] The measuring tube is colinear with an axis of any one of the four pressure-inducing tubes.

[0014] The beneficial effects of the present invention are:

[0015] 1. Accurate measurement of liquid differential pressure in circular tubes at medium-low pressure, medium-low temperature thermal hydraulics experimental benches, experimental devices and other experimental sites.

[0016] 2. Effectively alleviate the adverse effects of excessively high flow velocity on differential pressure measurement when the liquid flows in a circular tube, and play a buffering role.

[0017] 3. It improves the direct pressure measurement method widely used in thermal hydraulic experiments, avoids the adverse effects of pulsating pressure, vibration, etc. on differential pressure measurement, improves the accuracy of differential pressure measurement, and ensures experimental accuracy and measurement reliability.

[0018] 4. The pressure equalizing tube allows the liquid to be evenly mixed, has a good buffering effect, and improves measurement accuracy and data stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of an embodiment of an annular pressure taking device for measuring the differential pressure of liquid in a vertical circular tube in an experimental field according to the present invention;

[0020] Figure 2 A front view of an embodiment of the present invention;

[0021] Figure 3 for Figure 2 Section view at section AA.

[0022] Among them: 1-vertical circular tube, 2-annular pressure taking device, 3-throttling device, 201-pressure guiding tube, 202-pressure equalizing ring, 203-measuring tube, 204-pressure taking hole. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1 The embodiment of the present invention shown is used to measure the liquid differential pressure (pressure difference) between two points in a vertical circular tube 1, so the annular pressure-taking device 2 is divided into two parts, namely, a high-pressure section pressure-taking device and a low-pressure section pressure-taking device, according to the liquid flow direction; the embodiment comprises: a vertical circular tube 1, a throttling device 3 and two annular pressure-taking devices 2, and the middle section of the vertical circular tube 1 is provided with a throttling device 3; due to the existence of the throttling device 3, there is a differential pressure in the flowing liquid in the vertical circular tube 1, and the downstream direction of the vertical circular tube 1 is a low-pressure section;

[0025] The two annular pressure-taking devices 2, the high-pressure section pressure-taking device and the low-pressure section pressure-taking device, are respectively installed vertically on the high-pressure section and the low-pressure section of the vertical circular tube 1; in order to make the pressure-taking point accurately reflect the liquid pressure and to avoid the pressure loss caused by the local resistance, the distance between the high-pressure section pressure-taking device and the throttling device 3 should be as large as possible, i.e., 10D (D is the inner diameter of the vertical circular tube 1); the distance between the low-pressure section pressure-taking device and the throttling device 3 should be as large as 5D; in addition, according to the principles of fluid mechanics, the following principles should be followed when installing the annular pressure-taking device 2:

[0026] In this embodiment, the throttling device 3 is a stainless steel metal sheet in the shape of a tangent circle, and the throttling device 3 is installed between the flanges of the plurality of vertical circular tubes 1 through the flanges provided on the outside;

[0027] In this embodiment, the inner diameter of the vertical circular tube 1 is 123 mm;

[0028] In this embodiment, the distance between the high-pressure section pressure taking device and the throttling device 3 is 1403 mm, and the distance between the low-pressure section pressure taking device and the throttling device 3 is 630 mm;

[0029] 1) The annular pressure taking device 2 should be installed in the pipe section where the liquid flows in a straight line, and should not be installed in places where vortices may occur, such as elbows and tees, to avoid local pressure loss;

[0030] 2) The annular pressure taking device 2 needs to be perpendicular to the liquid flow direction in the vertical circular tube 1;

[0031] 3) It is necessary to ensure that the liquid entering the pressure taking device is a single-phase medium without gas mixture, and an exhaust port needs to be reserved. In this annular pressure taking device 2, the exhaust hole of the differential pressure transmitter is used for exhaust;

[0032] 4) In order to prevent ice from forming on the outside of the pipe wall of the annular pressure taking device 2 under cold conditions, an insulation layer is required to be used during the experiment to avoid large temperature changes.

[0033] like Figure 2As shown, the annular pressure-taking device 2 includes a pressure-taking tube 201, a pressure-equalizing ring 202 and a measuring tube 203, the axes of which are located in the same plane, wherein the pressure-equalizing ring 202 is an annular tube, four pressure-taking tubes 201 are evenly installed on the inner side of the pressure-equalizing ring 202, and the four pressure-taking tubes 201 are smoothly connected to the vertical circular tube 1 to be measured through the pressure-taking holes 204, and the measuring tube 203 is installed on the outer side of the pressure-equalizing ring 202, and the axis of the measuring tube 203 is collinear with any one of the diameters of the pressure-equalizing ring 202, and the outer end of the measuring tube 203 is connected to the high-pressure end or the low-pressure end corresponding to the differential pressure transmitter through a metal hose, and the differential pressure transmitter is connected to the high-pressure end or the low-pressure end corresponding to the differential pressure transmitter. The measured liquid is drawn out during the measurement; the liquid in the vertical circular tube 1 enters the pressure equalizing ring 202 through the pressure-guiding tube 201 and is evenly mixed in the pressure equalizing ring 202, thereby avoiding the adverse effects of flow-induced vibration and pulsating pressure on the differential pressure measurement and playing a buffering role; the liquid mixed by the pressure equalizing ring 202 is finally connected to the high and low pressure receiving ends of the differential pressure transmitter through the measuring tube 203 to complete the differential pressure measurement; the inner and outer diameters of the pressure-guiding tube 201, the pressure equalizing ring 202 and the measuring tube 203 are equal, and the inner diameters are equal to the aperture of the pressure-taking hole 204, and the length of the pressure-guiding tube 201 is ≥ 10 times the diameter of the pressure-taking hole 204;

[0034] The pressure-taking hole 204 is circular; the axis of the pressure-taking hole 204 is perpendicular to the axis of the vertical circular tube 1; to ensure that the liquid is fully mixed in the pressure-equalizing ring 202, the pressure-leading pipe 201 is directly connected to the vertical circular tube 1 to be measured; at the same time, since the pressure-leading pipe 201 is directly connected to the vertical circular tube 1 to be measured, and because the flow velocity in the circular tube is relatively high, the diameter of the pressure-taking hole 204 is less than 0.08D under the condition of ensuring the drilling accuracy and smooth flow of the liquid, to avoid interference with the flow of the liquid in the circular tube, and the inner diameter of the pressure-equalizing ring 202 is adjusted according to the diameter of the circular tube to be measured;

[0035] Since the liquid flowing from the pressure-inducing pipe 201 has been mixed evenly in the pressure-equalizing ring, in this embodiment, the measuring pipe 203 is arranged in line with (directly facing) any axis of the four pressure-inducing pipes 201 without affecting the measurement result.

[0036] In this embodiment, the differential pressure transmitter used is Rosemount's 3051DP4A22A1AB4M5HR5K8 differential pressure transmitter, where the range is 248.6 to 710 kPa and the operating temperature is -50 to 250 ° C. The high and low pressure ends of this differential pressure transmitter are connected to the metal hose through threads, and the exhaust operation is completed through its built-in exhaust knob;

[0037] In this embodiment, the smooth connection is smooth welding, that is, the welding part near the pressure-taking hole 204 has no obvious chamfers, grooves, burrs, etc., so as to avoid pressure loss caused by additional resistance;

[0038] In this embodiment, the outer diameter of the pressure equalizing ring 202 is 173.50 mm;

[0039] In this embodiment, the length of the pressure-guiding tube 201 is 100 mm. Please see Table 1 for other main parameters of the annular pressure-taking device 2.

[0040] Table 1 Main parameters of annular pressure taking device 2

[0041]

[0042] The specific installation workflow of this embodiment is as follows:

[0043] 1) The annular pressure-taking device 2 is manufactured according to Table 1, and then installed on the vertical circular pipe 1, and divided into a high-pressure section pressure-taking device and a low-pressure section pressure-taking device according to the specific position;

[0044] 2) Connect the measuring tubes 203 in the high-pressure section pressure taking device and the low-pressure section pressure taking device to the high-pressure and low-pressure ends of the differential pressure transmitter respectively;

[0045] 3) Wait until the experimental liquid medium fills the entire circular pipe to be measured and the annular pressure taking device 2;

[0046] 4) Exhaust air through the reserved exhaust hole of the differential pressure transmitter to ensure that the liquid entering the annular pressure taking device 2 is single-phase liquid to prevent gas blockage;

[0047] 5) Complete differential pressure measurement during the experiment.

Claims

1. An annular pressure-taking device for measuring the differential pressure of liquid in a vertical circular tube at an experimental site, characterized in that: include: A vertical circular tube (1), a throttling device (3) and two annular pressure-taking devices (2), wherein the throttling device (3) is arranged in the middle section of the vertical circular tube (1), and the two annular pressure-taking devices (2) are respectively vertically installed on the high-pressure section and the low-pressure section of the vertical circular tube (1); The annular pressure-taking device (2) comprises a pressure-guiding pipe (201), a pressure-equalizing ring (202) and a measuring pipe (203) whose axes are located in the same plane, wherein the pressure-equalizing ring (202) is an annular pipe, four pressure-guiding pipes (201) are evenly installed on the inner side of the pressure-equalizing ring (202), the four pressure-guiding pipes (201) are smoothly connected to a vertical circular pipe (1) to be measured through a pressure-taking hole (204), the measuring pipe (203) is installed on the outer side of the pressure-equalizing ring (202), a differential pressure transmitter is installed outside the measuring pipe (203), and the liquid in the vertical circular pipe (1) enters the pressure-equalizing ring (202) through the pressure-guiding pipe (201) and is evenly mixed in the pressure-equalizing ring (202); The inner diameters of the pressure-guiding tube (201), the inner diameters of the pressure-equalizing ring (202), and the inner diameters of the measuring tube (203) are equal to the aperture of the pressure-taking hole (204); the length of the pressure-guiding tube (201) is ≥ 10 times the diameter of the pressure-taking hole (204); and the adverse effects of flow-induced vibration and pulsating pressure on differential pressure measurement are avoided; The pressure-taking hole (204) is circular; the axis of the pressure-taking hole (204) is perpendicular to the axis of the vertical circular tube (1); and the diameter of the pressure-taking hole is less than 8% of the diameter of the vertical circular tube (1); The measuring tube (203) is colinear with an axis of any one of the four pressure-inducing tubes (201); The distance between the high-pressure section pressure-taking device and the throttling device (3) is more than 10D, and the distance between the low-pressure section pressure-taking device and the throttling device 3 is more than 5D, wherein D is the inner diameter of the vertical circular tube (1).

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