CN112557696B - A kind of pneumatic piston type micro flow rate measuring device and method thereof - Google Patents

Abstract

The invention discloses a pneumatic piston type micro flow rate measuring device and a method thereof, belonging to the field of measuring equipment. The rotor flow rate measuring device in the present invention adopts the structure of the adjusting air cavity driven by air pressure, so that the buoyancy can be adjusted by changing the volume of the adjusting air cavity during the flow rate measurement process, so that the whole can be suspended in the fluid to be measured, so that the second Ideally, the casing and the central shaft can rotate relative to each other without contact, reducing friction as much as possible. Moreover, the present invention can amplify the original micro-flow velocity through the Venturi throat section, and then reflect the flow velocity in the tube through the rotational speed of the rotor flow velocity measuring device. Therefore, the microflow rate measuring device of the present invention can be applied to the measurement of the microflow rate. Since the volume of the adjustable air cavity in the present invention can be controlled by the suction device connected to the central shaft, the overall buoyancy of the device can be adjusted in real time without disassembling the device, so as to adapt to different fluid environments and have greater flexibility.

Description

A kind of pneumatic piston type micro flow rate measuring device and method thereof

technical field

The invention belongs to the field of measuring equipment, and in particular relates to a pneumatic piston type micro-flow velocity measuring device and a method thereof.

Background technique

A flow meter is a device used to measure the flow rate of fluids. Generally speaking, flow meters are divided into rotor flow meters, Venturi flow meters, electromagnetic flow meters, and ultrasonic Doppler flow meters.

Among them, the core component of the rotor-type flow meter is the impeller, which is usually used in high flow velocity and rivers. The propeller-type flowmeter, the rotary-cup flowmeter and the rotary-vane flowmeter are all rotor-type flowmeters, and the working principle is basically the same. However, such devices are generally not suitable for the measurement of medium and low flow rates due to the large frictional force at the rotating shaft.

In addition, Venturi flowmeter, electromagnetic flowmeter and ultrasonic Doppler flowmeter are more accurate for the measurement of medium and high flow velocity, but the measurement of low flow velocity is still a big difficulty for the current flow velocity measurement instruments. The existing flow meter generally has the problem that the minimum range is too high, and cannot be used to measure the flow rate that is too small, that is, the micro flow rate. Therefore, how to realize the measurement of micro-flow rate is a technical problem that needs to be solved urgently.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the defect that the measurement of micro-flow rate is difficult in the prior art, and to provide a pneumatic piston type micro-flow rate measuring device and a method thereof.

The concrete technical scheme adopted in the present invention is as follows:

In a first aspect, the present invention provides a pneumatic piston type micro-flow velocity measuring device, which comprises a Venturi flow measuring tube and a rotor flow velocity measuring device;

The Venturi flow measuring tube is formed by connecting the inlet section, the tapered section, the throat section, the gradually expanding section and the outlet section in sequence, and the side of the throat section is provided with a concave shell, and the concave shell is provided with a concave shell. The inner cavity is used as a flow measuring cavity, and the opening of the concave shell is connected to the throat section; the flow measuring cavity is provided with at least one exhaust valve;

The rotor flow velocity measuring device includes a first sleeve, a second sleeve, a synchronous movement control device and a rotational speed measuring device, the second sleeve is coaxially arranged inside the first sleeve and the two are kept relative to each other by a number of support rods. Fixed, the central shaft penetrates the second casing and a gap is reserved between the outer wall of the central shaft and the inner wall of the second casing, the rotor flow rate measuring device is integrally erected in the flow measuring cavity through the central shaft; surrounds the outer wall of the first casing A number of impeller blades are fixed, and some of the impeller blades extend into the throat section, the remaining impeller blades are located in the flow measuring cavity, and the impeller blades that extend into the throat section are pushed by the fluid in the throat section to push the first casing and The second sleeve rotates as a whole; the inner wall of the first sleeve and the outer wall of the second sleeve are both smooth surfaces, and an end-sealing annular plate is respectively provided at both ends of the cavity sandwiched between the first sleeve and the second sleeve , and the outer ring wall and inner ring wall of each end-sealing annular plate respectively form a sliding seal pair with the inner wall of the first casing and the outer wall of the second casing; the first casing, the second casing and the two end-sealing annular plates share the same A closed and adjustable air cavity is formed; the synchronous movement control device is used to maintain the synchronism during the movement of the two end-capped annular plates;

The central shaft is a hollow shaft with one end closed and the other open open, and its inner cavity is used as a first air channel; the middle of the hollow shaft has an opening section, and the shaft sidewalls within the range of the opening section are spaced apart along the way with several The air holes are arranged in a circumferential direction, a second air hole is opened in the support rod, and the inlet of the second air hole is opened on the inner wall of the second sleeve and is located in the axial interval of the opening section, and the second air hole The outlet of the channel communicates with the regulating air cavity;

During the flow rate measurement process, by pumping or blowing the first air channel, the volume of the air cavity is adjusted and its buoyancy is adjusted through the air path formed by the opening section and the second air channel, so that the second sleeve and the center The shafts can rotate relative to each other without contact; the rotational speed measuring device is used to measure the rotational speed of the second casing, so as to convert the rotational speed into a flow rate.

Preferably, the synchronous movement control device includes two racks and gears, the two racks are respectively fixed on the two end-sealing annular plates and the sawtooth parameters on the racks are exactly the same; the gears are clamped between the two racks. The toothed sides of the rack are meshed with each other, and the rotating shaft of the gear is fixed on the support rod.

Preferably, the rotational speed measuring device includes an optical signal transmitter, an optical signal receiver, a signal analyzer and a flow velocity indicator, a transparent window is provided on the concave shell, and an optical signal reflector is provided on the impeller blade , the optical signal transmitter and the optical signal receiver are placed in pairs outside the concave housing, the optical signal transmitter transmits the optical signal to the impeller sheet through the transparent window, and is reflected to the optical signal receiver by the optical signal reflector, so The signal analyzer is used to process and count the electrical signal of the optical signal receiver and convert it into the rotation speed of the second sleeve; when each impeller blade rotates to the optical path reflection position of the optical signal transmitter and the optical signal receiver, the optical signal is received. According to the mapping relationship between the rotational speed of the second casing and the flow velocity in the pipe, the flow rate display instrument converts the current rotational speed of the second casing into the flow velocity of the inlet section, and displays it on the display screen.

Preferably, there are multiple synchronous movement control devices, all synchronous movement control devices and all support rods are symmetrically arranged around the central axis, and the entire rotor flow velocity measurement device does not have eccentricity when rotating.

Preferably, the inlet diameter of the second air channel is larger than the diameter of the air hole.

Preferably, the sides of the concave casing with different orientations are provided with exhaust valves, and the inner wall of the concave casing is a smooth spherical surface.

Preferably, the outer ring wall and the surface of the inner ring wall of the end-sealing annular plate are provided with sealing rings, and the sealing rings are kept watertight with the inner wall of the first casing and the outer wall of the second casing.

Preferably, there are four support rods, all of which are located on the mirror symmetry plane of the adjusting air cavity and the axial direction perpendicular to the axial direction, and are evenly arranged at equal angles along the circumferential direction of the second sleeve; each support rod is provided with a the second air hole.

Preferably, the open end of the first air channel is connected to a suction device for inhalation or air blowing.

In a second aspect, the present invention provides a method for measuring a micro-flow rate using the pneumatic piston-type micro-flow rate measuring device described in any of the solutions of the first aspect, the steps of which are as follows:

S1: Connect the inlet section and the outlet section of the venturi flow measuring tube of the pneumatic piston type micro-velocity measuring device into the pipeline to be measured respectively, so that the inside of the concave shell is filled with the fluid in the tube;

S2: Keep the adjustment air cavity at the minimum volume in advance, and then slowly blow air into the first air channel through the suction device until the adjustment air cavity is at the maximum volume; during the volume change of the adjustment air cavity, Keep the flow velocity in the pipeline to be measured constant, and obtain the maximum rotational speed of the second casing measured by the rotational speed measuring device;

S3: Continue to keep the flow velocity in the pipeline to be measured constant, and re-adjust the volume of the adjustment air cavity, so that after the rotational speed of the second casing measured by the rotational speed measuring device reaches the maximum rotational speed of the second casing, the suction is removed device and block the open end of the first air channel;

S4: When the flow velocity is measured, the fluid in the pipeline to be measured is sequentially inlet section, tapered section, throat section, gradually expanding section and outlet section, and the flow velocity is enlarged in the throat section according to the area ratio of the cross section; the fluid flowing through the throat section Pushing the impeller blade extending into the throat section, and then driving the first casing and the second casing to rotate synchronously around the central axis, and measuring the rotational speed of the second casing by the rotational speed measuring device;

S5: convert the real-time rotational speed of the second casing into the real-time flow velocity of the fluid in the throat section according to the pre-determined mapping relationship between the rotational speed of the second casing and the fluid flow rate in the throat section;

S6: According to the real-time flow velocity of the fluid in the throat section, the real-time flow velocity of the fluid in the pipeline to be measured is obtained by conversion through the ratio of the cross-sectional area of the throat section to the pipeline to be measured.

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

The invention can amplify the original micro-flow velocity through the venturi throat section by setting the Venturi flow measuring tube and the rotor flow velocity measuring device, and then reflect the flow velocity in the tube through the rotating speed of the rotor flow velocity measuring device. The rotor flow rate measuring device in the present invention adopts the structure of the adjusting air cavity driven by air pressure, so that the buoyancy can be adjusted by changing the volume of the adjusting air cavity during the flow rate measurement process, so that the whole can be suspended in the fluid to be measured, so that the second Ideally, the casing and the central shaft can rotate relative to each other without contact, reducing friction as much as possible. Therefore, the microflow rate measuring device of the present invention can be applied to the measurement of the microflow rate.

Since the volume of the adjustable air cavity in the present invention can be controlled by the suction device connected to the central shaft, the overall buoyancy of the device can be adjusted in real time without disassembling the device, so as to adapt to different fluid environments and have greater flexibility.

Description of drawings

Fig. 1 is the structural representation of the micro-flow measuring device of pneumatic piston type;

Fig. 2 is the sectional view of the position of the support rod of the rotor flow velocity measuring device;

Fig. 3 is an enlarged view of position I in Fig. 2;

Fig. 4 is the schematic diagram of the micro flow measuring device with data processing and display device;

5 is a sectional view of the position of the synchronous movement control device of the rotor flow velocity measuring device;

FIG. 6 is a schematic diagram of the assembly of the suction device on the micro-flow measuring device.

The reference signs in the figure are: inlet section 1, tapered section 2, throat section 3, gradually expanding section 4, outlet section 5, exhaust valve 6, concave casing 7, rotor flow velocity measuring device 8, flow measuring cavity 9 , transparent window 10, optical signal transmitter 11, optical signal receiver 12, signal analyzer 13, flow velocity indicator 14, rack 15, gear 16, suction device 17, optical signal reflector 81, impeller blade 82, center Shaft 83 , second air channel 84 , second sleeve 85 , first air channel 86 , regulating air cavity 87 , end-sealing annular plate 88 , first sleeve 89 , sealing ring 90 , support rod 91 .

Detailed ways

The present invention will be further elaborated and described below with reference to the accompanying drawings and specific embodiments. The technical features of the various embodiments of the present invention can be combined correspondingly on the premise that there is no conflict with each other.

As shown in FIG. 1 , in a preferred embodiment of the present invention, a pneumatic piston type micro-flow measuring device is provided, and its main structure includes two parts: a Venturi flow measuring tube and a rotor flow measuring device 8 . The Venturi flow measuring tube is used to provide an installation site for the rotor flow velocity measuring device 8, and at the same time, it can be connected with the pipeline of the flow velocity to be measured to amplify the original micro flow velocity through the Venturi throat section, so as to facilitate accurate measurement. The function of the rotor flow rate measuring device 8 is similar to that of the traditional rotor flowmeter for measuring the rotational speed, which can reflect the flow rate in the tube through its own rotational speed.

It should be noted that the micro flow rate in the present invention is a flow rate with a lower exponential value, but there is no limit to how much the value must be lower. In fact, the present invention can also be used to measure medium and high flow rates.

In the ordinary rotor flowmeter, due to the friction between the impeller and the rotating shaft, it will introduce a large error under the micro flow rate, and when the flow rate is lower than a certain value, the impeller cannot even be driven to rotate, resulting in the failure of flow measurement. Therefore, in the present invention, the friction force between the impeller and the rotating shaft is reduced as much as possible through the special improvement of the Venturi flow measuring tube and the rotor flow velocity measuring device 8, thereby increasing the lower limit of the measuring range. The specific structures of the Venturi flow measuring tube and the rotor flow velocity measuring device 8 in this embodiment will be described in detail below.

Referring to Figure 1, the Venturi flow measuring tube consists of an inlet section 1, a tapered section 2, a throat section 3, a gradually expanding section 4, and an outlet section 5 connected in sequence, and the main structure is similar to that of an ordinary Venturi tube. , but the feature of the present invention is that an additional concave shell 7 is provided on the side of the throat section 3, the concave shell 7 has only one side opening, and the inner cavity of the concave shell 7 is used as the flow measuring cavity 9, And the opening of the concave shell 7 communicates with the lateral direction of the throat section 3 . In addition, in the present invention, the flow measuring cavity 9 is used as the rotation space of the impeller, so in order to avoid eddy current and disturbance, the inner wall of the concave casing 7 should be set as a smooth spherical surface.

When in use, the venturi section is subsequently installed in the pipeline to be measured, so the air inside it needs to be exhausted to work properly, so in the present invention, at least one exhaust valve 6 is provided on the flow measuring chamber 9 . However, since the fluid in the pipeline to be measured is generally liquid, and the air in the flow-measuring chamber 9 will always gather above the liquid level, it is better to set multiple exhaust valves 6, and the concave shell 7 faces different sides. Both are provided with an exhaust valve 6 . In this embodiment, the exhaust valves 6 are provided in three directions. Before measuring the flow velocity in the pipe normally, it is necessary to open the exhaust valve 6 to discharge the internal air, so that the fluid in the pipe fills the entire flow measuring cavity 9 .

Referring to FIGS. 2 and 3 , the rotor flow velocity measuring device 8 in this embodiment is specially designed to reduce the rotational frictional force, so as to improve its measurement accuracy for micro flow velocity. The rotor flow velocity measuring device 8 includes a first sleeve 89, a second sleeve 85, a synchronous movement control device and a rotational speed measuring device. The second sleeve 85 is coaxially arranged inside the first sleeve 89, and the lengths of the two are basically the same. , the ends of which are aligned. The inner diameter of the first sleeve 89 is larger than the outer diameter of the second sleeve 85, and there is an annular cavity therebetween. Both ends of the central shaft 83 are fixed on the concave housing 7 through bearings, the central shaft 83 penetrates 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 the outer wall of the central shaft 83 is connected to the inner diameter of the second sleeve 85. A gap (preferably no larger than 2-5 mm) may be reserved between the inner walls of the second sleeve 85, so as to provide a possibility for the subsequent reduction of the frictional force between the two. In addition, there are several support rods 91 between the first sleeve 89 and the second sleeve 85 for reinforced fixing, so as to keep the two sleeves in a coaxial arrangement state without deviation. In this embodiment, in order to ensure that the overall balance does not produce eccentricity, a total of four support rods 91 are arranged in the annular cavity, and the four support rods 91 are all located inside the adjustment air cavity 87 and the mirror symmetry plane perpendicular to the axial direction of the central axis 83 , the second sleeve 85 is evenly arranged at an equal angle of 90° along the circumferential direction of the second sleeve 85, so as to maintain the overall balance.

The rotor flow velocity measuring device 8 is integrally erected in the flow measuring cavity 9 through the central shaft 83 , and its rotational power is provided by the impeller blade 82 . A plurality of impeller blades 82 are fixed around the outer wall of the first sleeve 89 , a total of 8 blades are provided in this embodiment, and they are evenly arranged in the same direction along the circumferential direction. Among the 8 impeller blades 82, some of the impeller blades 82 protrude into the throat section 3 through the opening of the flow measuring cavity 9, and the remaining impeller blades 82 are located in the flow measuring cavity 9, so the impeller blades 82 extending into the throat section 3 can be The first sleeve 89 and the second sleeve 85 are pushed by the fluid in the throat section 3 to rotate around the central axis 83 as a whole.

When only gravity acts, the inner wall of the second sleeve 85 will be integrally mounted on the surface of the central shaft 83 for rotation, so a large frictional force will be generated between the two, which is not conducive to the measurement of micro-flow velocity. To adjust the buoyancy, it is expected that the self-gravity of the rotor flow rate measuring device 8 can be offset by the buoyancy, so that the rotor flow rate measuring device 8 can be suspended in the fluid. Since a gap may remain 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 the fluid, the friction between the two can be reduced to a minimum. However, due to the different densities of different fluids, the buoyancy of the same device will also be different, so in the present invention, a cavity with a variable volume is required to realize the buoyancy adjustment, so as to adapt to different fluid types. 2 , in this embodiment, the inner wall of the first sleeve 89 has a smooth surface, and the outer wall of the second sleeve 85 also has a smooth surface, and the first sleeve 89 and the second sleeve 85 are sandwiched between An end-sealing annular plate 88 is respectively set at both ends of the cavity. The end-capped annular plate 88 is an annular plate body whose outer annular wall, ie, the outer circumference, has a smooth surface, and the inner annular wall, ie, the inner circumference, also has a smooth surface. Therefore, in the assembled state of each end-sealing annular plate 88, its outer and inner annular walls form a sliding sealing pair with the inner wall of the first sleeve 89 and the outer wall of the second sleeve 85 respectively, and the two end-sealing annular plates 88 can be moved along the axial direction of the central axis 83 under the condition of abutting against the inner wall of the first sleeve 89 and the outer wall of the second sleeve 85 . The two end-capped annular plates 88 should keep moving relative to each other as far as possible to compress or expand the internal gas, so the first sleeve 89, the second sleeve 85 and the two end-capped annular plates 88 together form a closed and changeable volume Size adjustment air chamber 87. According to the calculation formula of buoyancy, it can be known that adjusting the change of the volume of the air cavity 87 will directly affect the size of its buoyancy. Therefore, the present invention adjusts the buoyancy of the air cavity 87 by changing the volume of the air cavity 87 during the flow rate measurement, so that the whole can be suspended in the fluid to be measured, so that the second sleeve 85 and the central axis 83 can ideally be free from The relative rotation of the contacts minimizes friction.

In this device, since the pressure of the fluid in the tube is generally constant, the volume in the air chamber 87 is adjusted by changing the internal air pressure. However, the first sleeve 89 , the second sleeve 85 and the two end-sealing annular plates 88 that constitute the regulating air cavity 87 are constantly rotating, and arranging the trachea on the upper part of the trachea will cause the trachea to be twisted during the rotation process and cannot complete the corresponding functions. . Therefore, in the present invention, the inflation or degassing is realized through the fixed central shaft 83 in the whole device. 2 and 3, the central shaft 83 is a hollow shaft with one end closed and the other open open, the inner cavity of the central shaft 83 serves as the first air channel 86, and its open end extends out of the entire rotor flow velocity measuring device 8, so as to facilitate Connect an external inflatable device. The central position of the central shaft 83 has an opening section, and the shaft side wall of the central shaft 83 within the range of the opening section is provided with several rings of air holes arranged in the circumferential direction. In the example, there are 4 air holes in a circle. In addition, each support rod 91 is provided with a second air hole 84, and the inlet of the second air hole 84 is opened on the inner wall of the second sleeve 85, and viewed in the axial direction, the inlet is opened on the central axis 83. The axial interval of the hole segment is in the air outlet range, and the outlet of the second air hole channel 84 communicates with the regulating air cavity 87 . The intervals of two adjacent circles of air holes are the same. In this embodiment, a total of 5 circles of air holes are arranged along the axial direction of the central axis 83 , and the entrance of the second air hole channel 84 is facing the middle circle of air holes.

Since the central shaft 83 and the inner wall of the second sleeve 85 in the present invention should not be in contact with each other during the rotation process to reduce friction, they cannot be directly connected to each other like other air paths. However, in the present invention, a larger air outlet range is created by arranging multiple circles of air holes, which can avoid the problem that the inlet of the second air hole channel 84 cannot be aligned with the air holes. Moreover, since the distance between the central axis 83 and the inner wall of the second sleeve 85 is very small, the resistance along the way is relatively large. The air hole 84 actually constitutes an air path, and when the open end of the first air hole 86 is pumped or blown, the air pressure change can be sensitively reflected to the regulating air cavity 87 . In addition, in order to reduce the airflow resistance of the gas path itself, it is preferable to make the inlet aperture of the second air hole 84 larger than the aperture of the air hole. Therefore, during use, for fluids of different densities, the volume of the air cavity 87 can be changed by adjusting the pressure of the air cavity 87, so that the whole device is suspended in the fluid to be measured, and the second sleeve 85 and the central shaft 83 are kept free from each other. Contact rotation.

In addition, since the adjusting air chamber 87 drives the movement of the end-sealing annular plates 88 on both sides through the change of the internal air pressure, the frictional force between the end-sealing annular plates 88 and the surfaces of the first sleeve 89 and the second sleeve 85 is not suitable. is too big. When the water pressure in the pipe is not high, due to the surface tension of the water, the fluid generally does not enter the regulating air cavity 87 , and the sealing ring plate 88 and the surfaces of the first sleeve 89 and the second sleeve 85 are kept between A snug contact is sufficient, no additional seals are required. However, in the case of high-pressure fluid in the pipe or the need to frequently change the gas volume in the adjustment air chamber 87 , there is still a possibility that the fluid enters the adjustment air chamber 87 . Therefore, in another embodiment, it can be considered that a sealing ring 90 is provided on the surface of the outer ring wall and the inner ring wall of the end sealing ring plate 88 , and the sealing ring 90 and the surfaces of the first sleeve 89 and the second sleeve 85 pass through the sealing ring 90 . Keep a watertight seal. Of course, the material of the sealing ring 90 should be a material with less friction, otherwise it will be difficult to slide.

Based on the above structure, the amplification and measurement of the fine flow rate can be realized, but it is not a direct flow rate signal, but needs to measure the rotation speed of the second sleeve 85 through a rotation speed measuring device, and then convert the rotation speed into a flow rate. The specific form of the rotational speed measuring device can be similar to that of the traditional rotameter, and the same mapping conversion between the rotational speed and the flow velocity can also refer to the practice of the traditional rotameter.

In order to further facilitate understanding, the present invention provides an implementation form of a rotational speed measuring device, which can realize non-contact rotational speed measurement, and further avoid the increase of friction force caused by direct measurement of the central shaft. Referring to FIG. 4 , the rotational speed measuring device includes an optical signal transmitter 11, an optical signal receiver 12, a signal analyzer 13 and a flow velocity indicator 14, wherein a transparent window 10 is opened on the concave shell 7, so that the optical signal can be through the transparent window 10 . The impeller blade 82 is provided with an optical signal reflector 81, and in this embodiment, the optical signal reflector 81 is a reflective sheet. The optical signal transmitter 11 and the optical signal receiver 12 are placed in pairs outside the concave housing 7. The optical signal transmitter 11 transmits an optical signal to the impeller blade 82 through the transparent window 10, and is reflected by the optical signal reflector 81 to receive the optical signal. In the device 12, the optical signal receiver 12 can sense the reflected optical signal, and then convert it into an electrical signal.

The signal analyzer 13 is used to process and count the electrical signals of the optical signal receiver 12 . Each impeller blade 82 has an optical signal reflector 81, so when the optical signal transmitter 11 and the optical signal receiver 12 are rotated to the optical path reflection position, the optical 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 equipment components can be realized by using existing equipment, and no special design is required. In addition, within a fixed period of time, after the number of counts of the optical signal is obtained, it can be converted into the rotational speed of the second sleeve 85, and thus can be further converted into a corresponding flow rate or flow rate.

In addition, after the signal analyzer 13 can continue to connect the flow rate indicator 14, the flow rate indicator 14 pre-stores the mapping relationship between the rotational speed of the second sleeve 85 and the flow velocity in the pipe calibrated by the test, and then according to the second sleeve The mapping relationship between the rotational speed of 85 and the flow velocity in the tube is converted into the current real-time rotational speed of the second casing 85 into the flow velocity of the inlet section 1, and displayed on the display screen. If the cross section of the inlet section 1 is consistent with the pipeline to be tested, then the flow velocity of the inlet section 1 is equivalent to the flow velocity of the pipeline to be tested, but if the two are inconsistent, then it is necessary to base on the principle of equal flow, according to the two The ratio of the cross-sectional area of the pipe section is converted.

In addition, in the process of adjusting the air cavity 87, it should be ensured that the adjustment amounts of the end-sealing annular plates 88 on both sides are the same, so as to avoid unbalanced phenomenon. Since the two end-sealing annular plates 88 of the present invention move by themselves depending on the internal air pressure, the frictional force of their movement is inevitably different due to processing factors and other reasons, which in turn causes the two sides to move out of synchronization, resulting in an overall rotational imbalance, and further Increase friction with the central axis. Therefore, in the present invention, it is necessary to provide a synchronous movement control device to maintain the synchronism during the movement of the two end-capped annular plates 88 , that is, the movement amounts on both sides are exactly the same. Its balance is pre-adjusted before leaving the factory, and its balance can still be guaranteed under the control of the synchronous movement control device during subsequent use to prevent eccentric moment.

The synchronous movement control device can be implemented by any existing equipment. In a preferred embodiment, the specific implementation form can be seen in FIG. The synchronous movement control device includes two racks 15 and gears 16 , the two racks 15 are respectively fixed on the two end-sealing annular plates 88 and the sawtooth parameters on the two racks 15 are identical. The gear 16 is clamped between the serrated sides of the two racks 15 and meshes with each other. The rotation shaft of the gear 16 is fixed on the support rod 91 . When one rack 15 moves, the other rack 15 can be controlled to move synchronously through the gear 16, thereby ensuring synchronization.

Since the addition of the synchronous movement control device may cause the overall force to be unbalanced, multiple synchronous movement control devices can be installed. All synchronous movement control devices and all support rods 91 are symmetrically arranged around the central axis 83 to ensure the flow rate measurement of the entire rotor. There is no eccentricity when the device 8 rotates. In this embodiment, a total of four synchronous movement control devices are provided, and one is provided on each support rod 91 .

In addition, in the present invention, the material used in the micro flow rate measuring device should not be made of heavy materials such as metal, preferably plexiglass, polymer plastic and other materials, so that the overall specific gravity of the rest of the components except the adjustment air cavity 87 is greater than that of the environment. The specific gravity of the fluid should not be too large, so that it can be suspended in the fluid by changing the volume of the gas in the adjusting air cavity 87 .

In addition, the open end of the first air hole 86 can be detachably connected to any suction device 17 for inhalation or air blowing. Since the volume of the regulating air cavity 87 in the device is generally small, as shown in FIG. 6 , a plunger-type air pump can be used for control, both manual and automatic.

Based on the above-mentioned pneumatic piston type micro-flow rate measuring device, the present invention also provides a micro-flow rate measurement method, the steps of which are as follows:

S1: Connect the inlet section 1 and the outlet section 5 of the venturi flow measuring tube of the pneumatic piston type micro-velocity measuring device of the present invention respectively into the pipeline to be measured, and the connection of the pipeline can be realized by setting a flange plate. By opening the exhaust valve 6 to discharge the internal gas, the inside of the concave casing 7 is filled with the fluid in the pipe.

S2: pump air through the suction device 17, keep the adjustment air cavity 87 at the minimum volume in advance, and then slowly blow air into the first air channel 86 through the suction device 17 until the adjustment air cavity 87 is at the maximum volume. The aeration process should be as slow as possible. During the blowing process, the volume change of the adjusting air cavity 87 will gradually change from the smallest to the largest. During this process, the flow velocity in the pipeline to be measured needs to be kept constant. Therefore, it can be measured by the rotational speed measuring device that the second sleeve 85 is in this air. The rotational speed changes during the process, and the maximum rotational speed of the second sleeve 85 is determined from the rotational speed change curve. Since the second sleeve 85 and the central shaft 83 rotate relative to each other without contact, the rotation speed of the second sleeve 85 must be the largest. Therefore, it can be determined that the volume of the adjustment air cavity 87 corresponding to the rotation speed is the best for suspending the device as a whole. volume.

S3: Continue to keep the flow velocity in the pipeline to be measured consistent with the flow velocity in S2, and re-adjust the volume of the air cavity 87 so that the rotational speed of the second casing 85 measured by the rotational speed measuring device reaches the maximum rotational speed of the second casing 85 determined above. After the test, the suction device 17 is removed and the open end of the first air hole 86 is blocked.

Of course, in the actual use process, it is not necessary to complete the whole process of adjusting the volume of the air cavity 87 from the smallest to the largest in step S2, as long as the rotation speed of the second sleeve 85 decreases during the change process, its peak position can be determined.

S4: When the above debugging is completed, the real flow rate measurement can be performed. When the flow velocity is measured, the fluid in the pipeline to be measured is sequentially inlet section 1, tapered section 2, throat section 3, gradually expanding section 4 and outlet section 5, and the flow velocity is enlarged in the throat section 3 according to the area ratio of the cross section; The fluid in the pipe section 3 pushes the impeller blade 82 extending into the throat section 3, and then drives the first casing 89 and the second casing 85 to rotate synchronously around the central axis 83, and the rotational speed of the second casing 85 is measured by the rotational speed measuring device. ;

S5: Convert the real-time rotational speed of the second casing 85 to the real-time flow velocity of the fluid in the throat section 3 according to the pre-measured mapping relationship between the rotational speed of the second casing 85 and the fluid flow velocity in the throat section 3;

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

It can be seen that even if the density of the target fluid changes due to changes in temperature or the fluid medium itself, the present invention can also adjust the volume of the air cavity by changing the external air pump to achieve the optimal volume calibration section in situ, so that the second set of Contactless relative rotation between the tube 85 and the central shaft 83 requires no disassembly of the entire device. Therefore, the pneumatic adjustment method of the present invention has higher flexibility.

The above-mentioned embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. Various changes and modifications can also be made by those of ordinary skill in the relevant technical field without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (10)

1. A micro-flow velocity measuring device of a pneumatic piston type is characterized by comprising a Venturi flow measuring pipe and a rotor flow velocity 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 an 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), a synchronous movement control device and a rotating speed measuring device, wherein the second sleeve (85) is coaxially arranged inside the first sleeve (89), the second sleeve and the first sleeve are kept relatively fixed through a plurality of supporting rods (91), a 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) and the outer wall of the second sleeve (85) are smooth surfaces, two end-sealed annular plates (88) are respectively arranged at two ends of a cavity clamped between the first sleeve (89) and the second sleeve (85), and the outer annular wall and the inner annular wall of each end-sealed annular plate (88) respectively form a sliding sealing pair with the inner wall of the first sleeve (89) and the outer wall of the second sleeve (85); the first sleeve (89), the second sleeve (85) and the two end-sealed annular plates (88) jointly form a closed adjusting air cavity (87) with changeable volume; the synchronous movement control device is used for keeping synchronism during the movement of the two end-sealing annular plates (88);

the central shaft (83) is a hollow shaft with one end closed and the other end opened, and the inner cavity of the hollow shaft is used as a first air duct (86); the middle part of the hollow shaft is provided with an opening section, the side wall of the shaft in the range of the opening section is provided with a plurality of circles of air holes which are arranged in the circumferential direction at intervals along the way, the supporting rod (91) is provided with a second air hole channel (84), the inlet of the second air hole channel (84) is arranged on the inner wall of the second sleeve (85) and is positioned in the axial interval of the opening section, and the outlet of the second air hole channel (84) is communicated with the adjusting air cavity (87);

in the flow rate measuring process, the first air duct (86) is pumped or blown, and the volume of the adjusting air cavity (87) is changed through the air path formed by the open hole section and the second air duct (84) to adjust the buoyancy 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 rate measuring device of the pneumatic piston type according to claim 1, wherein the synchronous movement control device comprises two racks (15) and a gear (16), the two racks (15) are respectively fixed on the two end-capped annular plates (88), and sawtooth parameters on the racks (15) are identical; the gear (16) is clamped between the sawtooth sides of the two racks (15) and is meshed with the sawtooth sides, and a rotating shaft of the gear (16) is fixed on the supporting rod (91).

3. The micro-flow rate measurement device of a pneumatic piston type according to claim 1, the rotating speed measuring device comprises an optical signal transmitter (11), an optical signal receiver (12), a signal analyzer (13) and a flow rate display instrument (14), a transparent window (10) is arranged on the concave shell (7), an optical signal reflector (81) is arranged on the impeller blade (82), the optical signal transmitter (11) and the optical signal receiver (12) are arranged outside the concave shell (7) in pairs, the optical signal transmitter (11) transmits optical signals to the impeller blades (82) through the transparent window (10), and reflected by the optical signal reflector (81) into the optical signal receiver (12), the signal analyzer (13) is used for processing and counting the electric signals of the optical signal receiver (12) and converting the electric signals into the rotating speed of the second sleeve (85); when each impeller blade (82) rotates to the light path reflection position of the light signal transmitter (11) and the light signal receiver (12), the light signal receiver (12) generates a count; and the flow rate display instrument (14) converts the current rotating speed of the second sleeve (85) into the flow rate of the inlet section (1) according to the mapping relation between the rotating speed of the second sleeve (85) and the flow rate in the pipe, and displays the flow rate on a display screen.

4. The aerodynamic-piston type micro flow rate measurement device according to claim 1, wherein the plurality of synchronous motion control devices are provided, all of the synchronous motion control devices and all of the support bars (91) are symmetrically arranged around the central axis (83), and the entire rotor flow rate measurement device (8) rotates without eccentricity.

5. The micro flow rate measurement device of an air piston type according to claim 1, wherein the inlet aperture of the second air hole passage (84) is larger than the aperture of the air hole.

6. The micro flow rate measuring device of the pneumatic piston type according to claim 1, wherein the different facing sides of the concave housing (7) are provided with vent valves (6), and the inner wall of the concave housing (7) is a smooth spherical surface.

7. The micro flow rate measurement device of the pneumatic piston type according to claim 1, wherein the outer and inner annular walls of the closed end annular plate (88) are provided with sealing rings (90), and the sealing rings (90) are kept water-tight and airtight with the inner wall of the first casing (89) and the outer wall of the second casing (85).

8. The aerodynamic piston type micro-flow velocity measurement device according to claim 1, wherein 4 support rods (91) are provided, are all positioned on a mirror symmetry plane of the adjusting air cavity (87) perpendicular to the axial direction, and are uniformly arranged along the circumferential direction of the second sleeve (85) at equal angles; the second air duct (84) is arranged in each supporting rod (91).

9. Pneumatic piston type micro flow rate measurement device according to claim 1, characterized in that the open end of the first air duct (86) is connected to a suction device (17) for suction or blowing.

10. A micro-flow measurement method using the pneumatic piston type micro-flow measurement device according to any one of claims 1 to 9, comprising the steps of:

s1: respectively connecting an inlet section (1) and an outlet section (5) of a venturi flow measuring tube in the pneumatic piston type micro-flow rate measuring device into a pipeline to be measured, so that the interior of a concave shell (7) is filled with fluid in the tube;

s2: keeping the regulating air cavity (87) at the minimum volume in advance, and then slowly blowing air into the first air duct (86) through a suction device (17) until the regulating air cavity (87) is at the maximum volume; in the volume change process of the adjusting air cavity (87), keeping the flow rate in the pipeline to be measured constant, and acquiring the maximum value of the rotating speed of the second sleeve (85) measured by the rotating speed measuring device;

s3: continuously keeping the flow rate in the pipeline to be measured constant, and readjusting the volume of the adjusting air cavity (87) to ensure that the suction device (17) is removed and the opening end of the first air duct (86) is blocked after the rotating speed of the second sleeve (85) measured by the rotating speed measuring device reaches the maximum rotating speed of the second sleeve (85);

s4: when the flow velocity is measured, fluid in the pipeline to be measured sequentially passes through 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 the throat section (3) pushes impeller blades (82) extending into the throat section (3) to further drive a first sleeve (89) and a second sleeve (85) to synchronously rotate around a central shaft (83), and the rotating speed of the second sleeve (85) is measured through 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.

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