阅读说明：本技术 微流速测量装置及具有该装置的热工水力学实验台和方法 (Micro-flow velocity measuring device, thermal hydraulic experiment table with same and method ) 是由 傅晟威 陈少庆 陈玉清 于 2020-12-08 设计创作，主要内容包括：本发明公开了一种微流速测量装置及具有该装置的热工水力学实验台和方法,属于计量设备领域。本发明通过设置文丘里测流管和转子流速测量装置,可通过文丘里喉管段放大原始的微流速,进而通过转子流速测量装置的转速来反应管内的流速。本发明中的转子流速测量装置通过特殊的调节气腔结构,使得在流速测量过程中通过改变调节气腔的体积调整其浮力,即可使其整体悬浮在待测流体中,使第二套管与中心轴之间理想状态下能无接触的相对转动,尽可能减少摩擦力。由此,本发明的微流速测量装置可以适用于微流速的测定。另外,本发明还提供了一种热工水力学实验台,能够实现自然循环且内部流速可以准确得到调整,以适合于此类设备在不同流速下的试验。(The invention discloses a micro-flow measuring device, a thermal hydraulic experiment table with the device and a method, and belongs to the field of metering equipment. The invention can amplify the original micro flow rate through the Venturi throat section by arranging the Venturi flow measuring tube and the rotor flow rate measuring device, and further reflects the flow rate in the tube through the rotating speed of the rotor flow rate measuring device. The rotor flow velocity measuring device provided by the invention has the advantages that through the special structure of the adjusting air cavity, the buoyancy of the adjusting air cavity is adjusted by changing the volume of the adjusting air cavity in the flow velocity measuring process, so that the whole body of the adjusting air cavity can be suspended in the fluid to be measured, the second sleeve pipe and the central shaft can rotate relatively in a non-contact manner in an ideal state, and the friction force is reduced as much as possible. Therefore, the micro flow rate measuring device of the present invention can be applied to measurement of micro flow rate. In addition, the invention also provides a thermal hydraulic experiment table, which can realize natural circulation and accurately adjust the internal flow rate so as to be suitable for the experiment of the equipment at different flow rates.)

1. A micro-flow speed measuring device is characterized by comprising a Venturi flow measuring pipe and a rotor flow speed measuring device (8);

the Venturi flow measuring tube is formed by sequentially connecting an inlet section (1), a reducing section (2), a throat section (3), a gradually expanding section (4) and an outlet section (5), a concave shell (7) is arranged on the side part of the throat section (3), the inner cavity of the concave shell (7) is used as a flow measuring cavity (9), and the opening of the concave shell (7) is communicated with the throat section (3); the flow measuring cavity (9) is provided with at least one exhaust valve (6);

the rotor flow velocity measuring device (8) comprises a first sleeve (89), a second sleeve (85) and a rotating speed measuring device, the second sleeve (85) is coaxially arranged inside the first sleeve (89), the central shaft (83) penetrates through the second sleeve (85), a gap is reserved between the outer wall of the central shaft (83) and the inner wall of the second sleeve (85), and the rotor flow velocity measuring device (8) is integrally erected in the flow measuring cavity (9) through the central shaft (83); a plurality of impeller blades (82) are fixed around the outer wall of the first sleeve (89), part of the impeller blades (82) extend into the throat section (3), the rest impeller blades (82) are positioned in the flow measuring cavity (9), and the impeller blades (82) extending into the throat section (3) push the first sleeve (89) and the second sleeve (85) to integrally rotate under the pushing of fluid in the throat section (3); the inner wall of the first sleeve (89) is provided with continuous internal threads (86), the outer wall of the second sleeve (85) is provided with continuous external threads (84), two ends of a cavity clamped between the first sleeve (89) and the second sleeve (85) are respectively provided with a sealing end toothed ring (88), the outer annular wall and the inner annular wall of each sealing end toothed ring (88) respectively form threaded fit with the internal threads (86) and the external threads (84), and the first sleeve (89), the second sleeve (85) and the two sealing end toothed rings (88) jointly form a closed adjusting air cavity (87) with changeable volume; in the process of measuring the flow rate, the buoyancy of the adjusting air cavity (87) is adjusted by changing the volume of the adjusting air cavity, so that the second sleeve (85) and the central shaft (83) can rotate relatively without contact; the rotational speed measuring device is used for measuring the rotational speed of the second sleeve (85) for converting the rotational speed into a flow rate.

2. The micro-flow measuring device according to claim 1, wherein the rotation speed measuring device comprises an optical signal transmitter (11), an optical signal receiver (12) and a signal analyzer (13), the concave casing (7) is provided with a transparent window (10), the impeller blade (82) is provided with an optical signal reflector (81), the optical signal transmitter (11) and the optical signal receiver (12) are arranged outside the concave casing (7) in pair, the optical signal transmitter (11) transmits an optical signal to the impeller blade (82) through the transparent window (10) and is reflected to the optical signal receiver (12) by the optical signal reflector (81), and the signal analyzer (13) is used for processing and counting the electrical signal of the optical signal receiver (12) and converting the electrical signal into the rotation speed of the second casing (85); when each impeller blade (82) rotates to the optical path reflection position of the optical signal transmitter (11) and the optical signal receiver (12), the optical signal receiver (12) generates a count.

3. The microflow rate measuring apparatus according to claim 2, wherein said signal analyzer (13) is connected to a flow rate display (14), and said flow rate display (14) converts the current rotation speed of the second casing (85) into the flow rate of said inlet section (1) according to the mapping relationship between the rotation speed of the second casing (85) and the flow rate in the pipe, and displays the converted current rotation speed on the display screen.

4. The micro flow rate measurement device according to claim 1, wherein the inner wall of the concave housing (7) is a smooth spherical surface.

5. The microfluidic flow rate measurement device according to claim 1, wherein the outer and inner annular walls of the end-capped toothed ring (88) are provided with sealing rings (90), and a water-tight seal is maintained with the internal threads (86) and the external threads (84) by the sealing rings (90).

6. Micro flow rate measuring device according to claim 1, wherein the differently oriented sides of the concave housing (7) are provided with vent valves (6).

7. The microflow measurement apparatus according to claim 1, wherein a plurality of support rods (91) are provided between the first casing (89) and the second casing (85) for reinforcing fixation to maintain the coaxial arrangement.

8. The microfluidic flow rate measurement device according to claim 1, wherein the first sleeve (89) is made of a transparent material, and a scale is axially marked on the tube.

9. A thermal hydraulic experiment table is characterized by comprising a circulating pipeline (A), a cooler (B), a heater (C), a micro-flow measuring device (D) according to any one of claims 1 to 8 and a bracket (E); the circulating pipeline (A) is a rectangular loop and can be rotatably erected on the bracket (E) through pipe sections on two sides, and an included angle between a plane where the circulating pipeline (A) is located and a horizontal plane changes in the rotating process; the top of the circulating pipeline (A) is provided with an exhaust port, a cooler (B) for cooling fluid in the pipe is arranged on a pipe section on one side of the circulating pipeline (A), a heater (C) for heating fluid in the pipe is arranged on a pipe section on the other side of the circulating pipeline (A), and the height of the cooler (B) is higher than that of the heater (C).

10. A micro flow rate measuring method using the micro flow rate measuring device according to any one of claims 1 to 8, comprising the steps of:

s1: the rotor flow velocity measuring device (8) is detached from the Venturi flow measuring pipe independently, the central shaft (83) is detached, and the whole body is immersed in debugging fluid; the debugging fluid is the same as the type of the fluid in the pipeline to be tested;

s2: two end-sealed toothed rings (88) clamped between a first sleeve (89) and a second sleeve (85) are adjusted to change the volume of the adjusting air cavity (87), so that the rotor flow velocity measuring device (8) with the central shaft (83) removed can be suspended in the debugging fluid by means of self buoyancy; then, the micro-flow speed measuring device is assembled again with the position of the end-sealing toothed ring (88) unchanged, and debugging is completed;

s3: installing and debugging the micro-flow speed measuring device, and respectively connecting an inlet section (1) and an outlet section (5) of a Venturi flow measuring pipe of the micro-flow speed measuring device into a pipeline to be measured;

s4: when the flow velocity is measured, fluid in a pipeline to be measured sequentially enters an inlet section (1), a reducing section (2), a throat section (3), a gradually expanding section (4) and an outlet section (5), and the flow velocity is amplified in the throat section (3) according to the area proportion of a cross section; the fluid flowing through the throat section (3) pushes impeller blades (82) extending into the throat section (3) so as to drive the first sleeve (89) and the second sleeve (85) to synchronously rotate around a central shaft (83), and the rotating speed of the second sleeve (85) is measured by the rotating speed measuring device;

s5: converting the real-time rotating speed of the second casing pipe (85) into the real-time flow rate of the fluid in the throat section (3) according to the mapping relation between the pre-measured rotating speed of the second casing pipe (85) and the flow rate of the fluid in the throat section (3);

s6: and according to the real-time flow velocity of the fluid in the throat pipe section (3), converting the real-time flow velocity of the fluid in the pipeline to be measured according to the ratio of the cross-sectional areas of the throat pipe section (3) and the pipeline to be measured.

Technical Field

The invention belongs to the field of metering equipment, and particularly relates to flow velocity measuring equipment.

Background

A flow meter is a device for measuring a flow rate of a fluid, and is generally classified into a rotor type flow meter, a venturi type flow meter, an electromagnetic type flow meter, and an ultrasonic doppler flow meter.

Among the core components of the rotor type flow meter are impellers, which are commonly used in high flow velocity and river. The propeller type current meter, the cup type current meter and the vane type current meter all belong to rotor type current meters, the working principle is basically the same, the rotor is pushed to rotate by water flow power, and the current speed is calculated according to the rotating speed. However, such devices are generally not suitable for measuring medium and low flow rates due to the high friction at the rotating shaft.

In addition, the venturi velocity meter, the electromagnetic velocity meter and the ultrasonic doppler velocity meter are accurate for measuring medium and high velocity of flow, but the measurement of low velocity of flow is still a big difficulty for the current velocity measuring instrument. The problem that the lowest measuring range of the existing flow meter is too high generally exists, and the existing flow meter cannot be used for measuring too small flow rate, namely micro flow rate. Therefore, how to realize the measurement of micro flow rate is a technical problem to be solved urgently at present.

Disclosure of Invention

The invention aims to solve the defect of difficulty in micro-flow rate measurement in the prior art, and provides a micro-flow rate measuring device, a thermal hydraulic experiment table with the device and a method.

The invention adopts the following specific technical scheme:

a micro-flow speed measuring device comprises a Venturi flow measuring pipe and a rotor flow speed measuring device;

the Venturi flow measuring tube is formed by sequentially connecting an inlet section, a reducing section, a throat section, a gradually expanding section and an outlet section, a concave shell is arranged on the side part of the throat section, the inner cavity of the concave shell is used as a flow measuring cavity, and the opening of the concave shell is communicated with the throat section; the flow measuring cavity is provided with at least one exhaust valve;

the rotor flow velocity measuring device comprises a first sleeve, a second sleeve and a rotating speed measuring device, the second sleeve is coaxially arranged in the first sleeve, the central shaft penetrates through the second sleeve, a gap is reserved between the outer wall of the central shaft and the inner wall of the second sleeve, and the rotor flow velocity measuring device is integrally erected in the flow measuring cavity through the central shaft; a plurality of impeller blades are fixed around the outer wall of the first sleeve, part of the impeller blades extend into the throat section, the rest impeller blades are positioned in the flow measuring cavity, and the impeller blades extending into the throat section push the first sleeve and the second sleeve to integrally rotate under the pushing of fluid in the throat section; the inner wall of the first sleeve is provided with continuous internal threads, the outer wall of the second sleeve is provided with continuous external threads, two ends of a cavity clamped between the first sleeve and the second sleeve are respectively provided with an end-sealing toothed ring, the outer annular wall and the inner annular wall of each end-sealing toothed ring are respectively in threaded fit with the internal threads and the external threads, and the first sleeve, the second sleeve and the two end-sealing toothed rings jointly form a closed adjusting air cavity with the changeable volume; in the flow velocity measurement process, the buoyancy of the adjusting air cavity is adjusted by changing the volume of the adjusting air cavity, so that the second sleeve and the central shaft can rotate relatively without contact; the rotating speed measuring device is used for measuring the rotating speed of the second sleeve so as to convert the rotating speed into flow rate.

Preferably, the rotation speed measuring device comprises an optical signal emitter, an optical signal receiver and a signal analyzer, wherein a transparent window is formed in the concave shell, an optical signal reflector is arranged on the impeller blade, the optical signal emitter and the optical signal receiver are arranged outside the concave shell in pair, the optical signal emitter emits an optical signal to the impeller blade through the transparent window and is reflected to the optical signal receiver by the optical signal reflector, and the signal analyzer is used for processing and counting an electric signal of the optical signal receiver and converting the electric signal into the rotation speed of the second sleeve; when each impeller blade rotates to the light path reflection position of the light signal transmitter and the light signal receiver, the light signal receiver generates a count.

Furthermore, the signal analyzer is connected with a flow rate display instrument, and the flow rate display instrument converts the current rotating speed of the second sleeve into the inlet section flow rate according to the mapping relation between the rotating speed of the second sleeve and the flow rate in the pipe and displays the inlet section flow rate on a display screen.

Preferably, the inner wall of the concave shell is a smooth spherical surface.

Preferably, the outer ring wall and the inner ring wall of the end-sealing toothed ring are provided with sealing rings, and the sealing rings, the internal threads and the external threads are kept watertight.

Preferably, the side surfaces of the concave shell, which face different directions, are provided with exhaust valves.

Preferably, a plurality of support rods are arranged between the first sleeve and the second sleeve for reinforcing fixation so as to maintain a coaxial arrangement state.

Preferably, the first sleeve is made of transparent materials, and a graduated scale is marked on the tube body along the axial direction.

In a second aspect, the invention provides a thermal hydraulic experiment table, which comprises a circulating pipeline, a cooler, a heater, a micro-flow rate measuring device according to any one of the schemes in the first aspect and a bracket; the circulating pipeline is a rectangular loop and can be rotatably erected on the bracket through the pipe sections on two sides, and an included angle between a plane where the circulating pipeline is located and a horizontal plane changes in the rotating process; the top of the circulating pipeline is provided with an exhaust port, a cooler for cooling fluid in the pipe is arranged on a pipe section on one side of the circulating pipeline, a heater for heating fluid in the pipe is arranged on a pipe section on the other side of the circulating pipeline, and the height of the cooler is higher than that of the heater.

In a third aspect, the present invention provides a micro flow rate measurement method using the micro flow rate measurement device according to any one of the first aspect, comprising the following steps:

s1: the rotor flow velocity measuring device is detached from the Venturi flow measuring tube independently, the central shaft is detached, and the whole body is immersed in debugging fluid; the debugging fluid is the same as the type of the fluid in the pipeline to be tested;

s2: adjusting two end-sealing gear rings clamped between the first sleeve and the second sleeve to change the volume of the adjusting air cavity, so that the rotor flow velocity measuring device with the central shaft removed can be suspended in the debugging fluid by means of buoyancy of the rotor flow velocity measuring device; then, the micro-flow speed measuring device is assembled again after the position of the end-sealing toothed ring is kept unchanged, and debugging is completed;

s3: installing a debugged micro-flow speed measuring device, and respectively connecting an inlet section and an outlet section of a Venturi flow measuring pipe of the micro-flow speed measuring device into a pipeline to be measured;

s4: when measuring the flow velocity, the fluid in the pipeline to be measured sequentially enters an inlet section, a reducing section, a throat section, a gradually expanding section and an outlet section, and the flow velocity is amplified in the throat section according to the area proportion of the cross section; the fluid flowing through the throat section pushes impeller blades extending into the throat section, so that the first sleeve and the second sleeve are driven to synchronously rotate around the central shaft, and the rotating speed of the second sleeve is measured by the rotating speed measuring device;

s5: converting the real-time rotating speed of the second sleeve into the real-time flow rate of the fluid in the throat section according to the mapping relation between the pre-measured rotating speed of the second sleeve and the flow rate of the fluid in the throat section;

s6: and according to the real-time flow velocity of the fluid in the throat pipe section, converting the real-time flow velocity of the fluid in the pipeline to be measured according to the ratio of the cross-sectional area of the throat pipe section to the cross-sectional area of the pipeline to be measured.

Compared with the prior art, the invention has the following beneficial effects:

the invention can amplify the original micro flow rate through the Venturi throat section by arranging the Venturi flow measuring tube and the rotor flow rate measuring device, and further reflects the flow rate in the tube through the rotating speed of the rotor flow rate measuring device. The rotor flow velocity measuring device provided by the invention has the advantages that through the special structure of the adjusting air cavity, the buoyancy of the adjusting air cavity is adjusted by changing the volume of the adjusting air cavity in the flow velocity measuring process, so that the whole body of the adjusting air cavity can be suspended in the fluid to be measured, the second sleeve pipe and the central shaft can rotate relatively in a non-contact manner in an ideal state, and the friction force is reduced as much as possible. Therefore, the micro flow rate measuring device of the present invention can be applied to measurement of micro flow rate.

In addition, the invention also provides a thermal hydraulic experiment table utilizing the micro-flow-rate measuring device, which can realize natural circulation and accurately adjust the internal flow rate so as to be suitable for performance tests of the equipment at different flow rates.

Drawings

FIG. 1 is a schematic view of a micro flow rate measurement device;

FIG. 2 is a schematic structural view of a rotor flow rate measuring device;

FIG. 3 is a cross-sectional view A-A of FIG. 2;

FIG. 4 is a schematic view of a micro flow rate measurement device with a data processing and display device;

FIG. 5 is a schematic structural view of a thermal hydraulic experimental bench;

fig. 6 is a schematic view of the rotation between the circulation pipe and the support.

The reference numbers in the figures are: the device comprises an inlet section 1, a reducing section 2, a throat section 3, a reducing section 4, an outlet section 5, an exhaust valve 6, a concave shell 7, a rotor flow velocity measuring device 8, a flow measuring cavity 9, a transparent window 10, an optical signal emitter 11, an optical signal receiver 12, a signal analyzer 13, a flow velocity display 14, an optical signal reflector 81, an impeller blade 82, a central shaft 83, an external thread 84, a second sleeve 85, an internal thread 86, an adjusting air cavity 87, a sealing end toothed ring 88, a first sleeve 89, a sealing ring 90, a support rod 91, a circulating pipeline A, a cooler B, a heater C and a support E.

Detailed Description

The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.

In a preferred embodiment of the present invention, as shown in fig. 1, a micro flow rate measuring device is provided, which comprises two major components, a venturi flow tube and a rotor flow rate measuring device 8. The venturi flow measuring tube is used for providing an installation site for the rotor flow velocity measuring device 8, and meanwhile, the venturi flow measuring tube can be connected with a pipeline with the flow velocity to be measured to amplify the original micro flow velocity through the venturi throat section, so that accurate measurement is facilitated. And the rotor flow rate measuring device 8 functions similarly to a component for measuring the rotational speed in a conventional rotameter, which can reflect the flow rate in the tube by its own rotational speed.

It should be noted that the micro flow rate in the present invention refers to a flow rate with a low value, but is not limited to a value below which the present invention can be used to measure a medium-high flow rate.

In a common rotameter, because of the friction force between the impeller and the rotating shaft, a large error is introduced at a micro flow rate, and when the flow rate is lower than a certain value, the impeller cannot be pushed to rotate even, so that the flow measurement fails. Therefore, in the invention, the friction force between the impeller and the rotating shaft is reduced as much as possible by the special improvement of the Venturi flow tube and the rotor flow velocity measuring device 8, thereby improving the lower limit of the measuring range. The specific structure of the venturi flow tube and rotor flow rate measuring device 8 in the present embodiment will be specifically described below.

Referring to fig. 1, the venturi flow measuring tube is formed by sequentially connecting an inlet section 1, a reducing section 2, a throat section 3, a reducing section 4 and an outlet section 5, the main structure form of the venturi flow measuring tube is similar to that of a common venturi tube, but the venturi flow measuring tube is characterized in that an additional concave shell 7 is arranged on the side portion of the throat section 3, the concave shell 7 is provided with an opening on one side only, the inner cavity of the concave shell 7 serves as a flow measuring cavity 9, and the opening of the concave shell 7 is communicated with the side direction of the throat section 3. In addition, the flow measuring cavity 9 is used as a rotating space of the impeller in the invention, so that the inner wall of the concave shell 7 should be provided with a smooth spherical surface in order to avoid generating vortex and disturbance.

When in use, the Venturi tube section is subsequently installed in a pipeline to be measured, so that the air in the Venturi tube section needs to be removed to normally work, and at least one exhaust valve 6 is arranged on the flow measuring cavity 9. However, since the fluid in the pipe to be measured is generally liquid, and the air in the flow measuring cavity 9 always gathers above the plane of the liquid, it is preferable that a plurality of exhaust valves 6 are provided, and the exhaust valves 6 are provided on the sides of the concave housing 7 facing different directions. In the present embodiment, the exhaust valves 6 are provided in three orientations. Before the flow rate in the pipe is measured normally, the exhaust valve 6 needs to be opened to exhaust the internal air, so that the fluid in the pipe fills the whole flow measurement cavity 9.

Referring to fig. 2 and 3, the rotor flow velocity measuring device 8 in the present embodiment is specially designed to reduce the rotational friction force, so as to improve the measurement accuracy for micro flow velocity. The rotor flow velocity measuring device 8 includes a first sleeve 89, a second sleeve 85, and a rotation speed measuring device, wherein the second sleeve 85 is coaxially disposed inside the first sleeve 89, and has substantially the same length, and the two ends are aligned with each other. The first sleeve 89 has an inner diameter greater than the outer diameter of the second sleeve 85 with an annular cavity therebetween. The two ends of the central shaft 83 are fixed on the concave shell 7 through bearings, the central shaft 83 penetrates through the second sleeve 85, and the outer diameter of the central shaft 83 is slightly smaller than the inner diameter of the second sleeve 85, so that a gap can be reserved between the outer wall of the central shaft 83 and the inner wall of the second sleeve 85, and the possibility of subsequently reducing the friction force between the two parts is provided. The rotor flow velocity measuring device 8 is integrally erected in the flow measurement chamber 9 through a central shaft 83. A plurality of impeller blades 82, 8 in total in this embodiment, are fixed around the outer wall of the first sleeve 89 and are uniformly arranged in the same direction along the circumferential direction. Of the 8-blade impeller blades 82, some of the blades 82 extend into the throat section 3 through the opening of the flow measurement chamber 9, while the remaining blades 82 are located in the flow measurement chamber 9, so that the blades 82 extending into the throat section 3 can push the first sleeve 89 and the second sleeve 85 to rotate integrally about the central shaft 83 under the pushing of fluid in the throat section 3.

When only gravity acts, the inner wall of the second sleeve 85 is integrally carried on the surface of the central shaft 83 to rotate, so that a large friction force is generated between the two, which is not beneficial to the measurement of micro flow velocity, therefore, the self gravity of the rotor flow velocity measuring device 8 is expected to be counteracted through buoyancy by carrying out buoyancy adjustment on the sleeve, so that the rotor flow velocity measuring device 8 can be suspended in the fluid. And because a gap can be reserved between the outer wall of the central shaft 83 and the inner wall of the second sleeve 85, when the rotor flow velocity measuring device 8 can be suspended in fluid, the friction force between the two can be reduced to the lowest. However, since the buoyancy of the same device is different due to the different densities of different fluids, the buoyancy adjustment of the device needs to be realized by a cavity with variable volume so as to adapt to different fluid types. Referring specifically to fig. 3, in the present embodiment, a continuous internal thread 86 is tapped on the inner wall of the first sleeve 89, a continuous external thread 84 is tapped on the outer wall of the second sleeve 85, and two end-capped toothed rings 88 are respectively disposed at two ends of the cavity clamped between the first sleeve 89 and the second sleeve 85. The end-capping toothed ring 88 is an annular plate having an outer circumferential wall provided with a thread matching the internal thread 86 of the first sleeve 89, and an inner circumferential wall provided with a thread matching the external thread 84 of the second sleeve 85. Thus, each end stop ring gear 88 is in assembled condition with its outer and inner annular walls in threaded engagement with the internal and external threads 86, 84, respectively, and is movable axially of the central shaft 83 by rotation of the end stop ring gear 88. The two end-stop toothed rings 88 can be moved synchronously relative to each other to compress or expand the gas inside, so that the first casing 89, the second casing 85 and the two end-stop toothed rings 88 together form a closed and variable-volume adjustment gas chamber 87. According to the buoyancy calculation formula, the change of the volume of the adjusting air cavity 87 directly affects the buoyancy thereof. Therefore, in the flow velocity measurement process, the buoyancy of the adjustment air chamber 87 is adjusted by changing the volume thereof, so that the whole body can be suspended in the fluid to be measured, the second sleeve 85 and the central shaft 83 can rotate relatively without contact in an ideal state, and the friction force is reduced as much as possible.

Based on the above structure, the amplification and measurement of the minute flow rate can be realized, but the measurement is not a direct flow rate signal, but the rotation speed of the second sleeve 85 is measured by a rotation speed measuring device, and then the rotation speed is converted into the flow rate. The specific form of the rotating speed measuring device can be similar to that of a traditional rotameter, and the same mapping conversion of the rotating speed and the flow rate can also refer to the practice of the traditional rotameter.

In order to further facilitate understanding, the invention provides a realization form of the rotating speed measuring device, which can realize non-contact rotating speed measurement and further avoid friction force increase caused by direct measurement of the central shaft. Referring to fig. 4, the rotation speed measuring device includes an optical signal transmitter 11, an optical signal receiver 12 and a signal analyzer 13, wherein a transparent window 10 is opened on the concave casing 7, so that the optical signal can pass through the transparent window 10. The impeller blades 82 are provided with an optical signal reflector 81, and the optical signal reflector 81 is a reflective blade in this embodiment. The optical signal transmitter 11 and the optical signal receiver 12 are arranged outside the concave casing 7 in pairs, the optical signal transmitter 11 transmits optical signals to the impeller blades 82 through the transparent window 10 and reflects the optical signals to the optical signal receiver 12 through the optical signal reflector 81, and the optical signal receiver 12 can sense the reflected optical signals and further convert the reflected optical signals into electrical signals.

The signal analyzer 13 is used for processing and counting the electrical signals of the optical signal receiver 12. Each impeller blade 82 has a light signal reflector 81 thereon, so that when rotated to a light path reflecting position of the light signal emitter 11 and the light signal receiver 12, the light signal receiver 12 can generate a count. In this embodiment, the optical signal transmitter 11, the optical signal receiver 12 and the signal analyzer 13 constitute a reflective photoelectric sensor, and such devices can be implemented by using existing devices without special design. In addition, after the number of times of counting the optical signal is obtained within a fixed time, the number of times of counting the optical signal is converted into the rotation speed of the second sleeve 85, so that the rotation speed can be further converted into a corresponding flow speed or flow.

In another embodiment, the flow rate display 14 may be connected after the signal analyzer 13, the flow rate display 14 stores a mapping relationship between the rotational speed of the second sleeve 85 and the flow rate in the pipe, which is calibrated by a test, in advance, and then converts the current real-time rotational speed of the second sleeve 85 into the flow rate of the inlet section 1 according to the mapping relationship between the rotational speed of the second sleeve 85 and the flow rate in the pipe, and displays the flow rate on the display screen. If the cross section of the inlet section 1 is consistent with the pipeline to be measured, the flow speed of the inlet section 1 is equivalent to the flow speed of the pipeline to be measured, but if the cross section of the inlet section 1 is inconsistent with the flow speed of the pipeline to be measured, the conversion is required to be carried out according to the ratio of the pipe section cross sections of the inlet section and the pipeline to be measured on the basis of the principle that the flow rates of the inlet section.

In addition, although the end-capping ring gear 88 is threadedly engaged with the first and second casings 89, 85, fluid entry into the conditioned air chamber 87 generally does not occur under normal water pressure due to surface tension of water, but there is still a possibility of fluid entry into the conditioned air chamber 87 under high pressure or frequent changes in the volume of gas in the conditioned air chamber 87. Thus, in another embodiment, it is contemplated that a seal 90 may be provided on both the outer and inner annular walls of the end stop ring gear 88, with the seal 90 maintaining a fluid-tight seal with the internal and external threads 86, 84. Of course, the surface of the sealing ring 90 also needs to be provided with corresponding threads for matching.

In addition, although two end-capped gear rings 88 can play a certain role in fixing the first sleeve 89 and the second sleeve 85, it is preferable to add a plurality of support rods 91 between the first sleeve 89 and the second sleeve 85 for strengthening the fixing so as to keep the two sleeves in a coaxial arrangement.

In addition, during the adjustment of the adjustment air cavity 87, the adjustment amount of the end-capping gear rings 88 on both sides should be ensured to be the same as much as possible to avoid the imbalance phenomenon. Therefore, in another embodiment, the first sleeve 89 is preferably made of transparent material such as plexiglass, and the body thereof is marked with a scale along the axial direction for alignment during adjustment.

In addition, in the present invention, the material used in the micro flow rate measuring device is preferably not heavy material such as metal, preferably organic glass, polymer plastic, etc., so that the total specific gravity of the rest of the components except the air adjusting chamber 87 is larger than that of the environmental fluid, but not too large, so that the air volume in the air adjusting chamber 87 can be changed to suspend the air in the fluid.

Based on the micro-flow-rate measuring device, the invention also provides a micro-flow-rate measuring method, which comprises the following steps:

s1: the rotor flow rate measurement device 8 is detached from the venturi flow tube alone, the central shaft 83 in the second sleeve 85 is removed, and the whole is immersed in the conditioning fluid. It should be noted that the conditioning fluid should be the same type as the fluid inside the pipe to be tested, and both are water in this embodiment.

S2: two end-capped toothed rings 88 clamped between the first sleeve 89 and the second sleeve 85 are adjusted to change the volume of the adjusting air cavity 87 therein, so that the rotor flow velocity measuring device 8 with the central shaft 83 removed can be suspended in the debugging fluid by means of self-buoyancy. When the position of the probe is not changed after being hovered for 1 minute, the probe can be regarded as successful in debugging. And then the micro-flow speed measuring device is assembled again by keeping the position of the end-sealing toothed ring 88 unchanged, and debugging is completed.

S3: and installing and debugging the micro-flow speed measuring device, and respectively connecting the inlet section 1 and the outlet section 5 of the Venturi flow measuring tube into the pipeline to be measured. The connection of the pipes can be realized by arranging a flange.

S4: when measuring the flow velocity, the fluid in the pipeline to be measured sequentially enters the inlet section 1, the reducing section 2, the throat section 3, the gradually expanding section 4 and the outlet section 5, and the flow velocity is amplified in the throat section 3 according to the area proportion of the cross section; the fluid flowing through throat section 3 pushes against impeller blades 82 extending into throat section 3, which in turn drives first sleeve 89 and second sleeve 85 to rotate synchronously about central axis 83, and the rotational speed of second sleeve 85 is measured by the rotational speed measuring means described above.

S5: the real-time rotational speed of the second sleeve 85 is converted to the real-time flow rate of the fluid in the throat section 3 according to a predetermined mapping relationship between the rotational speed of the second sleeve 85 and the flow rate of the fluid in the throat section 3.

S6: and according to the real-time flow velocity of the fluid in the throat section 3, converting the real-time flow velocity of the fluid in the pipeline to be measured according to the ratio of the cross-sectional area of the throat section 3 to the cross-sectional area of the pipeline to be measured.

The micro-flow measuring device can be suitable for various flow speed/flow measuring environments, and is applied to a scene with strong demand on micro-flow measurement to show the use method of the micro-flow measuring device.

Referring to fig. 5, in an embodiment, a thermal hydraulic experimental bench is provided, which includes a circulation pipeline a, a cooler B, a heater C, a micro flow rate measuring device D shown in fig. 4, and a support E. The circulating pipeline A is a rectangular loop and consists of a top pipe section, a bottom pipe section and two side pipe sections, and a round chamfer is arranged at the turning position of the circulating pipeline A. An exhaust port is formed in the top of the circulating pipeline A, a cooler B for cooling fluid in the pipe is arranged on a pipe section on one side of the circulating pipeline A, a heater C for heating fluid in the pipe is arranged on a pipe section on the other side of the circulating pipeline A, and the height of the cooler B is higher than that of the heater C. In this embodiment, the cooler B is a box body having heat exchange tubes, a water inlet and a water outlet, the fluid in the circulation pipeline a is introduced into the bundled heat exchange tubes, and cooling water enters from the water inlet and is discharged from the water outlet, thereby cooling the fluid inside the heat exchange tubes to increase the density thereof. The heater C is a box with a plurality of heating rods, and is installed on the circulating pipeline to heat the fluid in the pipe, so that the density of the fluid is reduced.

The thermodynamic experiment table is a natural circulation device, and natural circulation is formed by overcoming local resistance, frictional resistance and the like of a pipeline along the way by using driving pressure generated by density difference and high-low potential difference between cold fluid and hot fluid without depending on an external power source in a closed loop. The natural circulation has important application in the nuclear industry, not only can be used as an important cooling means after a reactor accident happens, but also can be used as a main circulation cooling mode of a pressurized water reactor, reduces the dependence of a system on an external power supply, and improves the inherent safety of the reactor. The circulating pipeline of the device is provided with a heater C and a cooler B, so that the device is actually provided with a heating section and a cooling section. The heating section is arranged at a low position, the cooling section is arranged at a high position, and the temperature of the fluid in the cooler is lower than that of the fluid in the heating section, so that a density difference is formed between the fluid at the high position and the fluid at the low position, and the density difference drives the fluid to flow under the action of gravity. However, the natural circulation driven by the density difference has low flow rate, and the common Doppler flowmeter, the Venturi flowmeter and the rotameter cannot accurately measure the flow rate, but the micro-flow rate measuring device provided by the invention can well measure the micro-flow rate, so that a basis is provided for parameter control of the platform.

In addition, referring to fig. 6, the circulation pipeline a is rotatably mounted on the bracket E through pipe sections on both sides, and the rotation position is realized through a horizontal rotating shaft and a bearing. The included angle between the plane of the circulating pipeline A and the horizontal plane changes in the rotating process. Through the change of this angle, can adjust the size of density difference, and then the velocity of flow of control inside fluid.

The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.