CN112557696B - Pneumatic piston type micro-flow speed measuring device and method thereof - Google Patents
Pneumatic piston type micro-flow speed measuring device and method thereof Download PDFInfo
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- CN112557696B CN112557696B CN202011443975.3A CN202011443975A CN112557696B CN 112557696 B CN112557696 B CN 112557696B CN 202011443975 A CN202011443975 A CN 202011443975A CN 112557696 B CN112557696 B CN 112557696B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/14—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring differences of pressure in the fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/02—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring forces exerted by the fluid on solid bodies, e.g. anemometer
- G01P5/06—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring forces exerted by the fluid on solid bodies, e.g. anemometer using rotation of vanes
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Abstract
The invention discloses a pneumatic piston type micro-flow speed measuring device and a method thereof, belonging to the field of measuring equipment. The rotor flow velocity measuring device provided by the invention has the advantages that the buoyancy of the rotor flow velocity measuring device is adjusted by changing the volume of the adjusting air cavity in the flow velocity measuring process through the adjusting air cavity structure driven by air pressure, so that the whole rotor flow velocity measuring device can be suspended in the fluid to be measured, the second sleeve pipe and the central shaft can rotate in a non-contact manner in an ideal state, and the friction force is reduced as much as possible. In addition, the invention can amplify the original micro flow rate through the Venturi throat section, and further reflect the flow rate in the pipe through the rotating speed of the rotor flow rate measuring device. Therefore, the micro flow rate measuring device of the present invention can be applied to measurement of micro flow rate. Because the volume of the adjusting air cavity can be controlled by the suction device connected to the central shaft, the integral buoyancy of the adjusting air cavity can be adjusted in real time without disassembling the device, so that the adjusting air cavity can adapt to different fluid environments, and has higher flexibility.
Description
Technical Field
The invention belongs to the field of measuring equipment, and particularly relates to a pneumatic piston type micro-flow speed measuring device and a method thereof.
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 them, the core component of the rotor type flow meter is an impeller, which is generally 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 or 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 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 difficult micro-flow speed measurement in the prior art and provides a pneumatic piston type micro-flow speed measurement device and a method thereof.
The invention adopts the following specific technical scheme:
in a first aspect, the invention provides a pneumatic piston type micro-flow velocity measuring device, which comprises a Venturi flow tube and a rotor flow velocity 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, a synchronous movement control device and a rotating speed measuring device, the second sleeve is coaxially arranged in the first sleeve, the second sleeve and the first sleeve are kept relatively fixed through a plurality of support rods, 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 and the outer wall of the second sleeve are smooth surfaces, two end-sealed annular plates are arranged at two ends of a cavity clamped between the first sleeve and the second sleeve respectively, and the outer annular wall and the inner annular wall of each end-sealed annular plate and the inner wall of the first sleeve and the outer wall of the second sleeve form a sliding sealing pair respectively; the first sleeve, the second sleeve and the two end-sealed annular plates form a closed adjusting air cavity with changeable volume; the synchronous movement control device is used for keeping the synchronism of the two end-sealing annular plates in the moving process;
the central shaft is a hollow shaft with one end closed and the other end opened, and an inner cavity of the hollow shaft is used as a first air duct; 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 support rod is internally provided with a second air hole channel, the inlet of the second air hole channel is arranged on the inner wall of the second sleeve and is positioned in the axial interval of the opening section, and the outlet of the second air hole channel is communicated with the regulating air cavity;
in the flow velocity measurement process, the first air pore channel is pumped or blown, and the volume of the adjusting air cavity is changed through the air path formed by the open hole section and the second air pore channel to adjust the buoyancy 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 synchronous movement control device comprises two racks and a gear, the two racks are respectively fixed on the two end-sealing annular plates, and the sawtooth parameters on the racks are completely the same; the gear is clamped between the sawtooth sides of the two racks and is meshed with the sawtooth sides of the two racks, and a rotating shaft of the gear is fixed on the supporting rod.
Preferably, the rotation speed measuring device comprises an optical signal emitter, an optical signal receiver, a signal analyzer and a flow speed display, 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 pairs, the optical signal emitter emits optical signals to the impeller blade through the transparent window and the optical signals are reflected to the optical signal receiver by the optical signal reflector, and the signal analyzer is used for processing and counting the electrical signals of the optical signal receiver and converting the electrical signals 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 one-time counting; 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 synchronous movement control device is composed of a plurality of synchronous movement control devices, all the synchronous movement control devices and all the support rods are symmetrically arranged around the central shaft, and the whole rotor flow velocity measuring device does not have eccentricity when rotating.
Preferably, the inlet aperture of the second pore channel is larger than the aperture of the pore.
Preferably, the side surfaces of the concave shell in different directions are provided with exhaust valves, and 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 annular plate are both provided with sealing rings, and the sealing rings are kept watertight with the inner wall of the first sleeve and the outer wall of the second sleeve.
Preferably, the number of the support rods is 4, the support rods are all positioned on a mirror symmetry plane of the adjusting air cavity perpendicular to the axial direction and are uniformly arranged along the annular direction of the second sleeve at equal angles; each support rod is provided with the second air duct.
Preferably, the open end of the first air duct is connected to a suction device for sucking or blowing air.
In a second aspect, the present invention provides a micro-flow rate measuring method using the pneumatic piston type micro-flow rate measuring device according to any one of the first aspect, including the following steps:
s1: respectively connecting an inlet section and an outlet section of a venturi flow measuring pipe in the pneumatic piston type micro-flow rate measuring device into a pipeline to be measured, so that the interior of a concave shell is filled with fluid in the pipe;
s2: keeping the regulating air cavity at the minimum volume in advance, and then slowly blowing air into the first air duct through a suction device until the regulating air cavity is at the maximum volume; in the process of the volume change of the adjusting air cavity, keeping the flow rate in the pipeline to be measured constant, and acquiring the maximum value of the rotation speed of the second sleeve measured by the rotation 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 to enable the rotation speed of the second sleeve measured by the rotation speed measuring device to reach the maximum rotation speed of the second sleeve, removing the suction device and plugging the open end of the first air duct;
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 pipe section according to the mapping relation between the rotating speed of the second sleeve and the flow rate of the fluid in the throat pipe section, which is measured in advance;
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 air pressure-driven adjusting air cavity structure, the buoyancy force 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 can be suspended in the fluid to be measured, the second sleeve pipe and the central shaft can rotate 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 the measurement of micro flow rate.
The volume of the adjusting air cavity can be controlled by the suction device connected to the central shaft, so that the integral buoyancy of the adjusting air cavity can be adjusted in real time without disassembling the device, the adjusting air cavity is convenient to adapt to different fluid environments, and the adjusting air cavity has greater flexibility.
Drawings
FIG. 1 is a schematic diagram of a pneumatic piston type micro-flow rate measuring device;
FIG. 2 is a cross-sectional view of the position of a support rod of the rotor flow rate measuring device;
FIG. 3 is an enlarged view of the position I in 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 sectional view showing the position of a synchronous movement control means of the rotor flow rate measuring means;
fig. 6 is a schematic view of the assembly of the pumping device on the micro flow rate measuring device.
The reference numbers in the figures are: the device comprises an inlet section 1, a tapered section 2, a throat section 3, a tapered 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 instrument 14, a rack 15, a gear 16, a suction device 17, an optical signal reflector 81, an impeller blade 82, a central shaft 83, a second air duct 84, a second sleeve 85, a first air duct 86, a regulating air cavity 87, an end-sealing annular plate 88, a first sleeve 89, a sealing ring 90 and a support rod 91.
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 pneumatic piston type micro flow rate measuring device is provided, and its main components include 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 rotor flowmeter, because friction force exists between an impeller and a rotating shaft, a large error is introduced under a micro-flow speed, and when the flow speed 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 connecting an inlet section 1, a reducing section 2, a throat section 3, a gradually expanding section 4 and an outlet section 5 in sequence, the main structural 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 is used 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 accuracy of measurement of micro flow velocity. 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 lengths of the first sleeve 89 and the second sleeve are basically the same, and the two ends of the first sleeve are respectively aligned. 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 (preferably not larger than 2-5 mm) 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 reducing the friction force between the central shaft 83 and the second sleeve 85 is provided. In addition, a plurality of support rods 91 are arranged between the first sleeve 89 and the second sleeve 85 for reinforcing fixation, so that the two sleeves are always in a coaxial arrangement state without deviation. In this embodiment, in order to ensure that the overall balance does not generate eccentricity, 4 support rods 91 are disposed in the annular cavity, and the 4 support rods 91 are all located on the mirror symmetry plane inside the adjusting air cavity 87 and axially perpendicular to the central shaft 83 and are uniformly arranged at equal angles of 90 ° in the annular direction of the second sleeve 85, so as to maintain the overall balance.
The rotor flow rate measuring device 8 is integrally erected in the flow measuring chamber 9 through a central shaft 83, and the rotation power thereof is provided by the impeller blades 82. A plurality of impeller blades 82 are fixed around the outer wall of the first sleeve 89, and a total of 8 impeller blades are arranged in the embodiment 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 arranged on the surface of the central shaft 83 to rotate, so that large friction force is generated between the inner wall and the central shaft, which is not beneficial to the measurement of micro flow rate, and therefore, the self gravity of the rotor flow rate measuring device 8 is expected to be counteracted through buoyancy by adjusting the buoyancy of the second sleeve, so that the rotor flow rate 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 to fig. 2, in this embodiment, the inner wall of the first sleeve 89 is a smooth surface, the outer wall of the second sleeve 85 is also a smooth surface, and two end-sealing annular plates 88 are respectively disposed at two ends of the cavity clamped between the first sleeve 89 and the second sleeve 85. The end-capped annular plate 88 is an annular plate having a smooth outer circumferential wall or outer circumference and a smooth inner circumferential wall or inner circumference. Thus, each of the end-capping annular plates 88, in the assembled state, has its outer and inner annular walls constituting sliding sealing pairs with the inner wall of the first sleeve 89 and the outer wall of the second sleeve 85, respectively, and both end-capping annular plates 88 are movable in the axial direction of the central shaft 83 while 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 relative movement in synchronization as much as possible to compress or expand the internal gas, so that the first sleeve 89, the second sleeve 85 and the two end-capped annular plates 88 together form a closed regulating gas chamber 87 with changeable volume. 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.
In this arrangement, since the pressure of the fluid in the tube is generally constant, adjustment of the volume in the air chamber 87 is achieved by a change in the internal air pressure. However, the first sleeve 89, the second sleeve 85 and the two end-capped annular plates 88 which form the air conditioning chamber 87 are continuously rotated, and the air pipes arranged on the upper parts of the first sleeve, the second sleeve and the end-capped annular plates 88 can cause the twisting of the air pipes in the rotating process to be incapable of realizing corresponding functions. Thus, in the present invention, inflation or aspiration is achieved through a central shaft 83 that is stationary throughout the device. Referring to fig. 2 and 3, the central shaft 83 is a hollow shaft with one end closed and the other end open, and the inner cavity of the central shaft 83 is used as a first air duct 86, and the open end of the hollow shaft extends out of the entire rotor flow rate measuring device 8 so as to be connected with external air charging equipment. The middle part position of center pin 83 has one section trompil section, and the center pin 83 axle lateral wall of trompil section within range has seted up a plurality of circles and has encircled to the gas pocket of arranging, and each circle gas pocket is arranged along the hoop of axle is equidistant, and the round gas pocket is total 4 in this embodiment. In addition, each support rod 91 is provided with a second air duct 84, an inlet of the second air duct 84 is arranged on the inner wall of the second sleeve 85, and viewed along the axial direction, the inlet is located in the axial interval of the perforated section on the central shaft 83, i.e. the air outlet range, and an outlet of the second air duct 84 is communicated with the air conditioning chamber 87. The interval between two adjacent circles of air holes is the same, in this embodiment, a total of 5 circles of air holes are arranged along the axial direction of the central shaft 83, and the inlet of the second air hole passage 84 is opposite to the middle circle of air holes.
Since the central shaft 83 and the inner wall of the second sleeve 85 should not contact during rotation to reduce friction, they cannot be directly connected in butt joint as other air passages. However, the present invention creates a larger air outlet range by providing multiple circles of air holes, which can avoid the problem that the inlet of the second air duct 84 can not be aligned with the air holes. Moreover, since the distance between the central shaft 83 and the inner wall of the second sleeve 85 is small, the on-way resistance is large, and the first air duct 86, the plurality of circles of air holes, the inlet of the second air duct 84 and the second air duct 84 actually form an air path, when the air suction or air blowing operation is performed on the open end of the first air duct 86, the air pressure change thereof can be sensitively reflected to the adjustment air chamber 87. In addition, in order to reduce the flow resistance of the air passage itself, it is preferable that the inlet aperture of the second air duct 84 is larger than the aperture of the air hole. Therefore, in the using process, aiming at fluids with different densities, the volume of the fluids can be changed by adjusting the pressure of the adjusting air cavity 87, so that the whole device is suspended in the fluid to be measured, and the second sleeve 85 is kept to rotate without contact with the central shaft 83.
In addition, since the adjustment air chamber 87 drives the two side end-capped annular plates 88 to move by changing the internal air pressure, the friction between the end-capped annular plates 88 and the surfaces of the first and second sleeves 89, 85 is not excessively large. Under the condition that the water pressure in the pipe is not high, the situation that fluid enters the regulating air cavity 87 generally does not occur due to the surface tension of water, and the end-sealing annular plate 88 is kept in contact with the surfaces of the first sleeve 89 and the second sleeve 85 without arranging additional sealing parts. However, in the case where there is a high-pressure fluid in the pipe or the volume of the gas in the adjustment air chamber 87 needs to be changed frequently, there is still a possibility that the fluid enters the adjustment air chamber 87. Therefore, in another embodiment, it is contemplated that the sealing rings 90 are disposed on both the outer and inner annular walls of the closed end annular plate 88, and the sealing rings 90 are sealed against the surfaces of the first and second sleeves 89, 85. Of course, the material of the sealing ring 90 should be selected to have a low friction, which would make it difficult to slide.
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 rotating speed and flow rate mapping conversion can also be carried out by referring to 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 apparatus includes an optical signal transmitter 11, an optical signal receiver 12, a signal analyzer 13, and a flow rate display 14, wherein a transparent window 10 is opened on the concave housing 7, so that an optical signal can pass through the transparent window 10. The impeller blade 82 is provided with an optical signal reflector 81, and the optical signal reflector 81 is a light reflecting 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 addition, the flow rate display instrument 14 may be continuously connected after the signal analyzer 13, the flow rate display instrument 14 pre-stores the mapping relationship between the rotational speed of the second sleeve 85 and the flow rate in the pipe, which is calibrated through a test, 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 carried out according to the ratio of the pipe section cross sections of the inlet section 1 and the pipeline to be measured based on the principle that the flow rates of the inlet section and the pipeline to be measured are equal.
In addition, during the adjustment of the adjustment air chamber 87, the adjustment amount of the end-sealing annular plates 88 on both sides should be ensured to be the same as much as possible to avoid the imbalance phenomenon. Because the two end-sealed annular plates 88 of the invention move automatically by depending on the internal air pressure, the friction force of the movement is different inevitably due to processing factors and the like, so that the movement of the two sides is asynchronous, the integral rotation is unbalanced, and the friction force at the central shaft is increased. Therefore, in the present invention, it is necessary to provide a synchronous movement control device to keep the synchronism of the movement of the two end closing ring plates 88, that is, the movement amount of both sides is completely the same. The balance of the device is adjusted in advance when the device leaves a factory, and the balance of the device can still be ensured under the control of the synchronous movement control device in the subsequent use process, so that the eccentric moment is prevented from occurring.
The synchronous movement control device can be implemented by any existing device, and in a preferred embodiment, the specific implementation form thereof can be seen in fig. 5, which is another schematic sectional position diagram with the support rod 91 staggered. The synchronous movement control device comprises two racks 15 and a gear 16, wherein the two racks 15 are respectively fixed on two end-sealing annular plates 88, and the sawtooth parameters on the two racks 15 are completely the same. The gear 16 is clamped between the sawtooth sides of the two racks 15 and is engaged with the sawtooth sides, and the rotating shaft of the gear 16 is fixed on the supporting rod 91. When one rack 15 moves, the other rack 15 can be controlled to move synchronously through the gear 16, thereby ensuring synchronism.
Because the synchronous movement control device is additionally arranged, the overall stress is unbalanced, the synchronous movement control devices can be arranged in a plurality of numbers, all the synchronous movement control devices and all the support rods 91 are symmetrically arranged around the central shaft 83, and the whole rotor flow velocity measuring device 8 is ensured not to have eccentricity when rotating. In this embodiment, 4 synchronous movement control devices are provided, and 1 is provided on each support rod 91.
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.
In addition, the open end of the first air duct 86 may be detachably connected to any suction device 17 for suction or blowing. Since the volume of the adjustment air chamber 87 in the device is generally small, a plunger type air pump can be used for control, either manually or automatically, as shown in fig. 6.
The invention also provides a micro flow rate measuring method based on the pneumatic piston type micro flow rate measuring device, which comprises the following steps:
s1: the inlet section 1 and the outlet section 5 of the Venturi flow tube in the pneumatic piston type micro-flow velocity measuring device are respectively connected into a pipeline to be measured, and the pipeline connection can be realized by arranging flange plates. The interior of the concave housing 7 is filled with the fluid in the pipe by opening the exhaust valve 6 to exhaust the internal gas.
S2: it should be noted that the air blowing process should be as slow as possible by sucking air by the suction device 17, keeping the damper air chamber 87 at the minimum volume in advance, and then slowly blowing air into the first air duct 86 by the suction device 17 until the damper air chamber 87 is at the maximum volume. In the air blowing process, the volume change of the adjusting air cavity 87 gradually changes from minimum to maximum, in the process, the flow speed in the pipeline to be measured needs to be kept constant, so the rotation speed change of the second sleeve 85 in the process can be measured by a rotation speed measuring device, and the maximum value of the rotation speed of the second sleeve 85 is determined from the rotation speed change curve. Since the rotation speed of the second sleeve 85 is necessarily the maximum when the second sleeve 85 rotates relative to the central shaft 83 without contact, it can be determined that the volume of the conditioned air chamber 87 corresponding to the rotation speed is the optimal volume for suspending the whole device.
S3: and continuously keeping the flow rate in the pipeline to be measured to be constant and consistent with the flow rate in the step S2, and readjusting the volume of the adjusting air cavity 87 to ensure that the rotating speed of the second sleeve 85 measured by the rotating speed measuring device reaches the determined maximum rotating speed of the second sleeve 85, then removing the suction device 17 and plugging the open end of the first air duct 86.
Of course, in the actual use process, the whole process of changing the volume of the air conditioning chamber 87 from the minimum volume to the maximum volume in step S2 may not be completed, and the peak position may be determined as long as the rotation speed of the second sleeve 85 decreases in the changing process.
S4: when the debugging is completed, the real flow velocity measurement can be carried out. 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 the throat section 3 pushes the 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 the central shaft 83, and the rotating speed of the second sleeve 85 is measured by a rotating speed measuring device;
s5: converting the real-time rotating speed of the second sleeve 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 sleeve 85 and the flow rate of the fluid in the throat section 3;
s6: according to the real-time flow velocity of the fluid in the throat section 3, the real-time flow velocity of the fluid in the pipeline to be measured can be converted through the ratio of the cross-sectional area of the throat section 3 to the cross-sectional area of the pipeline to be measured.
It can be seen that even if the density of the target fluid changes due to temperature changes or changes of the fluid medium itself, the present invention can realize the in-situ optimal volume calibration joint by changing the volume of the adjustment air chamber by the external air pump, so that the second sleeve 85 and the central shaft 83 can rotate relatively without contact without disassembling the whole device. Therefore, the pneumatic adjustment mode of the invention has higher flexibility.
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 solutions obtained by means of equivalent substitution or equivalent transformation all 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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