Wide-range air volume measuring device and measuring method

Abstract

According to the wide-range air volume measuring method, the measuring and calculating method is simple, the measuring air volume range is not limited, and therefore the wide-range air volume measuring device is adjustable and convenient to use. The measuring cylinder core is characterized in that wall molded lines in the circumferential direction of the measuring cylinder core are designed according to Bernoulli lemniscate lines symmetrically divided by a rectangular coordinate system, throat static pressure holes are formed in the minimum open area of an axial flow channel of the measuring cylinder core in the circumferential direction of the inner wall of the axial flow channel, throat pressure tapping holes are formed in the outer wall of the measuring cylinder core, and the throat static pressure holes are communicated with the throat static pressure holes. The throat pressure tapping hole and the throat static pressure hole are both through holes and are always kept in the same plane state or the state close to the same plane state.

Description

Technical Field

[0001] The invention relates to the technical field of air volume measurement, and in particular to a wide-range air volume measurement device and a measurement method. Background Art

[0002] Air volume measurement is mainly used to evaluate system performance, optimize system design, ensure safe production and improve energy efficiency. When the fluid enters the measuring device from the outside, the fluid will increase in velocity and decrease in static pressure when flowing through the measuring device. Based on this phenomenon, the static pressure difference between the upstream side and the throat or downstream side of the pressure transmitter is measured, and then according to the Bernoulli equation: (where P is pressure, ρ is fluid density, is the velocity of the fluid at the corresponding point, g is the acceleration due to gravity, is the height of the fluid at the corresponding point) and the flow continuity equation: (In the formula , The flow cross section of the flow tube is , The average velocity on the surface of the air flow meter can be used to calculate the air volume flowing through the measuring device: (where C is the outflow coefficient; ε is the expansion coefficient; β is the diameter ratio, , d is the throat diameter, D is the inner diameter of the pipe; π is a mathematical constant; is the density of the fluid being measured; is the pressure difference).

[0003] At present, there are three main types of commonly used air volume measuring devices: orifice plate type, nozzle type, and venturi tube type. The venturi tube is a pipe that first contracts axially and then gradually expands. It can accurately measure the fluid. The existing venturi cone flowmeter disclosed in announcement number CN106197576B mainly has an inlet straight pipe connected to a diffuser cone via a contraction cone, and upstream pressure holes are distributed on the inlet straight pipe. The upstream pressure holes are connected by a pressure equalizing ring, and an inner conical throttling piece is embedded at the outlet end of the contraction cone. A downstream pressure hole connected to the contraction cone located at the downstream surface of the inner conical throttling piece is provided. However, its measurement and calculation method is complicated, and the measurement range of air volume is limited and cannot be adjusted, so it is less convenient to use. Summary of the invention

[0004] In view of the disadvantages of the existing measuring devices, the measuring technology methods are complex, the measuring air volume range is limited, and the convenience of use is low. The present invention provides a wide-range air volume measurement method, the measurement and calculation method is relatively simple, and the measuring air volume range is not limited. To this end, the present invention also provides a wide-range air volume measurement device, which is adjustable and easy to use.

[0005] The present invention provides the following technical solutions: It includes a measuring cylinder and a measuring cylinder core, both of which are provided with axial flow channels, the inner cavity of the measuring cylinder is cylindrical, and the diameter of the measuring cylinder core first decreases and then increases along the axial direction, and is characterized in that: the measuring cylinder and the measuring cylinder core are sleeved together to form a cavity, an upstream static pressure hole is circumferentially arranged on the inner wall of the cylinder mouth at one end of the measuring cylinder, the measuring cylinder core installed in the measuring cylinder cannot block the upstream static pressure hole, and the cylinder mouths at both ends of the measuring cylinder core are both sealed, and the outer wall of the measuring cylinder is sleeved with a pressure equalizing ring. The pressure-equalizing ring is provided with an upstream pressure-taking hole, which opens on the outer circumferential surface of the pressure-equalizing ring. The upstream static pressure holes and the upstream pressure-taking hole are connected to each other through the pressure-equalizing ring. The circumferential wall profiles of the measuring cylinder core are designed according to the Bernoulli double-hedral curves symmetrically divided by a rectangular coordinate system. At the minimum flow area of ​​the axial flow channel of the measuring cylinder core, a throat static pressure hole is opened along the circumference of its inner wall. The outer wall of the measuring cylinder is provided with a throat pressure-taking hole. The throat pressure-taking hole and the throat static pressure hole are both through holes, and the two always maintain the same plane or a state close to the same plane.

[0006] It is further characterized by: The cylinder wall of the measuring cylinder is provided with a positioning hole, near the throat pressure taking hole, and the outer wall of the measuring cylinder core is installed with a positioning tube, the position of the positioning tube corresponds to the positioning hole of the measuring cylinder; The measuring cylinder core is sealed and connected to the measuring cylinder body via a positioning tube; A method for measuring air volume with a wide range measuring device, characterized in that it comprises the following steps: (1) First, place the measuring cylinder with the measuring cylinder core assembled into the optimal position for the air volume to be measured, and connect the upstream pressure hole and throat pressure hole of the measuring cylinder to the pressure measuring device respectively; (2) When the fluid enters the measuring cylinder from the inlet, the pressure at the upstream static pressure hole of the measuring cylinder is The upstream static pressure hole is connected to the upstream pressure hole through the pressure equalizing ring, so the pressure of the upstream pressure hole and the upstream static pressure hole are the same. , which is finally measured by the pressure measuring transmitter; (3) The fluid then passes through the measuring tube core. The change in the flow cross-sectional area will cause a change in the static pressure. At this time, the static pressure of the static pressure hole at the throat of the measuring tube core is There is a cavity between the measuring cylinder core and the measuring cylinder body to connect the throat static pressure hole and the throat pressure hole, so the pressure of the throat static pressure hole and the throat pressure hole are the same. , which can be directly measured by the pressure measurement transmitter; (4) According to Bernoulli's double twisted line polar coordinate formula: ; Among them, r represents the distance from the point on the curve to the origin of the coordinate system, and a is a constant that determines the size and shape of the curve. It represents the angle from the polar axis to the point in counterclockwise direction. At the minimum flow area of ​​the axial flow channel of the measuring tube core, this is the maximum value of the distance from the point on the double twist line to the horizontal axis of the rectangular coordinate system. According to the formula, this value can be deduced as , so the diameter of the minimum flow area of ​​the axial flow channel of the measuring tube core is , where D is the diameter of the measuring cylinder; (5) Combined with the traditional flow calculation formula, the flow settlement formula of this device can be derived as follows: ; Where C is the outflow coefficient, ε is the expansion coefficient, D is the diameter of the measuring cylinder, and a is a constant. , is the pressure value of the upstream pressure-taking hole, The pressure value of the throat pressure hole; is the density of the fluid being measured; Substituting the corresponding values ​​into the formula, the fluid air volume can be calculated. The value of .

[0007] In the above technical solution, the technical effects and advantages provided by the present invention are: The wall profile of the measuring cylinder core is designed according to the Bernoulli lemniscate after symmetrical division of the rectangular coordinate system. The diameter of the minimum flow area of ​​the axial flow channel of the measuring cylinder core can be calculated by a formula. It is not necessary to measure and calculate the diameter of the minimum flow area of ​​itself like conventional measuring devices. It is only necessary to use a pressure measuring device to detect the pressure of the upstream static pressure hole and the throat pressure hole, and substitute it into the derived formula of the device to calculate the fluid air volume. The measurement is simple and convenient. The measuring cylinder core installed in the measuring cylinder is replaceable. The measuring cylinder core is sealed and connected to the measuring cylinder through the positioning tube, which is easy to disassemble. The measuring range can be changed by simply replacing the measuring cylinder core with a different wall profile, which greatly increases the convenience of using the measuring device. The pressure equalizing ring ensures that the pressure of the upstream static pressure hole and the upstream pressure taking hole are the same, and the cavity between the measuring cylinder and the measuring cylinder core keeps the throat pressure taking hole and the throat static pressure hole the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the core structure of the present invention; Figure 3 It is a relationship diagram between the tube core structure and the double twisted wire of the present invention.

[0009] Description of reference numerals: 1. Measuring cylinder; 11. Upstream static pressure hole; 12. Upstream pressure taking hole; 13. Throat pressure taking hole; 14. Positioning hole; 2. Measuring cylinder core; 21. Throat static pressure hole; 22. Positioning tube; 3. Equalizing pressure ring. DETAILED DESCRIPTION

[0010] The present invention provides Figure 1 A wide-range air volume measuring device is shown, which comprises a measuring cylinder 1 and a measuring cylinder core 2. An axial flow channel is arranged in the measuring cylinder 1 and the measuring cylinder core 2. The inner cavity of the measuring cylinder 1 is cylindrical. The diameter of the measuring cylinder core 2 decreases first and then increases along the axial direction. The measuring cylinder 1 and the measuring cylinder core 2 are fitted together to form a cavity. The measuring cylinder core 2 installed in the measuring cylinder 1 cannot block the upstream static pressure hole 11, and the ends of the measuring cylinder core 2 are sealed. The circumferential wall profile of the measuring cylinder core 2 is designed according to the Bernoulli lemniscate after being symmetrically divided by a rectangular coordinate system (see Figure 3 ),See Figure 2 At the minimum flow area of ​​the axial flow channel of the measuring cylinder core 2, a throat static pressure hole 21 is opened along the circumference of the inner wall thereof, and a throat pressure taking hole 13 is provided on the outer wall of the measuring cylinder body 1. The throat pressure taking hole 13 and the throat static pressure hole 21 always maintain the same plane or a state close to the same plane; An upstream static pressure hole 11 is provided at the inner wall of one end of the measuring cylinder 1 along the circumferential direction, and a pressure equalizing ring 3 is sleeved on the outer wall of the measuring cylinder 1; The pressure equalizing ring 3 is provided with an upstream pressure taking hole 12. Figure 1 As shown, the upstream pressure-taking hole 12 opens on the outer peripheral surface of the pressure-equalizing ring 3, and the upstream static pressure holes 11 and the upstream pressure-taking holes 12 are connected and communicated with each other through the pressure-equalizing ring 3; A positioning hole 14 is provided on the wall of the measuring cylinder 1 , and a positioning tube 22 is installed on the outer wall of the measuring cylinder core 2 near the throat pressure hole 13 . The position of the positioning tube 22 corresponds to the positioning hole 14 of the measuring cylinder 1 .

[0011] The following describes the measurement method of the wide-range air volume measurement device in the present invention in conjunction with the accompanying drawings, which includes the following steps: (1) First, place the measuring cylinder 1 with the measuring cylinder core 2 assembled into the optimal position for the air volume to be measured, and connect the upstream pressure hole 12 and the throat pressure hole 13 of the measuring cylinder to the pressure measuring device respectively; (2) When the fluid enters from the inlet of the measuring cylinder 1, the pressure of the upstream static pressure hole 11 of the measuring cylinder 1 is The upstream static pressure hole 11 is connected to the upstream pressure hole through the pressure equalizing ring, so the pressure of the upstream pressure hole 12 and the upstream static pressure hole 11 are the same. , which is finally measured by the pressure measuring transmitter; (3) The fluid then passes through the measuring cylinder core 2. The change in the flow cross-sectional area will cause a change in the static pressure. At this time, the static pressure of the throat static pressure hole 21 of the measuring cylinder core is There is a cavity between the measuring cylinder core 2 and the measuring cylinder body 1 to connect the throat static pressure hole 21 and the throat pressure hole 13, so the pressure of the throat static pressure hole 21 and the throat pressure hole 13 are the same. , which can be directly measured by the pressure measurement transmitter; (4) According to Bernoulli's double twisted line polar coordinate formula: ; Among them, r represents the distance from the point on the curve to the origin of the coordinate system, and a is a constant that determines the size and shape of the curve. It represents the angle from the polar axis to the point in counterclockwise direction. At the minimum flow area of ​​the axial flow channel of the measuring tube core, this is the maximum value of the distance from the point on the double twist line to the horizontal axis of the rectangular coordinate system. According to the formula, this value can be deduced as , so the diameter of the minimum flow area of ​​the axial flow channel of the measuring tube core 1 is , where D is the diameter of the measuring cylinder; (5) Combined with the traditional flow calculation formula, the flow settlement formula of this device can be derived as: Where C is the outflow coefficient, ε is the expansion coefficient, D is the diameter of the measuring cylinder, and a is a constant. , is the pressure value of the upstream pressure tapping hole, The pressure value of the throat pressure hole; is the density of the fluid being measured; Substituting the corresponding values ​​into the formula, the fluid air volume can be calculated. The value of .

Claims

1. A wide-range air volume measurement device, comprising a measuring cylinder and a measuring cylinder core, wherein both the measuring cylinder and the measuring cylinder core are provided with an axial flow channel, the inner cavity of the measuring cylinder is cylindrical, and the diameter of the measuring cylinder core first decreases and then increases along the axial direction, characterized in that: The measuring cylinder body and the measuring cylinder core are sleeved to form a cavity therebetween. An upstream static pressure hole is circumferentially arranged on the inner wall of the cylinder mouth at one end of the measuring cylinder body. The measuring cylinder core installed in the measuring cylinder body cannot block the upstream static pressure hole, and both ends of the cylinder mouth of the measuring cylinder core are sealed. A pressure-equalizing ring is sleeved on the outer wall of the measuring cylinder body. The pressure-equalizing ring is provided with an upstream pressure-taking hole. The upstream pressure-taking hole opens on the outer circumferential surface of the pressure-equalizing ring. The upstream static pressure holes and the upstream pressure-taking hole are connected and communicated with each other through the pressure-equalizing ring. The circumferential wall profiles of the measuring cylinder core are designed according to the Bernoulli double-negative curves symmetrically divided by a rectangular coordinate system. A throat static pressure hole is opened along the circumferential direction of its inner wall at the minimum flow area of ​​the axial flow channel of the measuring cylinder core. A throat pressure-taking hole is provided on the outer wall of the measuring cylinder body. The throat pressure-taking hole and the throat static pressure hole are both through holes, and the two always maintain the same plane or a state close to the same plane.

2. A wide range air volume measuring device according to claim 1, characterized in that: The cylinder wall of the measuring cylinder is provided with a positioning hole, close to the throat pressure taking hole, and the outer wall of the measuring cylinder core is installed with a positioning tube, the position of the positioning tube corresponds to the positioning hole of the measuring cylinder.

3. A wide range air volume measuring device according to claim 1 or 2, characterized in that: The measuring cylinder core is sealed and connected to the measuring cylinder body through a positioning tube.

4. A measurement method for a wide range air volume measurement device, characterized in that: It includes the following steps: (1) First, place the measuring cylinder with the measuring cylinder core assembled into the optimal position for the air volume to be measured, and connect the upstream pressure hole and throat pressure hole of the measuring cylinder to the pressure measuring device respectively; (2) When the fluid enters the measuring cylinder from the inlet, the pressure at the upstream static pressure hole of the measuring cylinder is The upstream static pressure hole is connected to the upstream pressure hole through the pressure equalizing ring, so the pressure of the upstream pressure hole and the upstream static pressure hole are the same. , which is finally measured by the pressure measuring transmitter; (3) The fluid then passes through the measuring tube core. The change in the flow cross-sectional area will cause a change in the static pressure. At this time, the static pressure of the static pressure hole at the throat of the measuring tube core is There is a cavity between the measuring cylinder core and the measuring cylinder body to connect the throat static pressure hole and the throat pressure hole, so the pressure of the throat static pressure hole and the throat pressure hole are the same. , which can be directly measured by the pressure measurement transmitter; (4) According to Bernoulli's double twisted line polar coordinate formula: ; Among them, r represents the distance from the point on the curve to the origin of the coordinate system, and a is a constant that determines the size and shape of the curve. It represents the angle from the polar axis to the point in counterclockwise direction. At the minimum flow area of ​​the axial flow channel of the measuring tube core, this is the maximum value of the distance from the point on the double twist line to the X axis of the rectangular coordinate system. According to the formula, this value can be deduced as , so the diameter of the minimum flow area of ​​the axial flow channel of the measuring tube core is , where D is the diameter of the measuring cylinder; (5) Combined with the traditional flow calculation formula, the flow settlement formula of this device can be derived as follows: ; Where C is the outflow coefficient, ε is the expansion coefficient, D is the diameter of the measuring cylinder, and a is a constant. , is the pressure value of the upstream pressure-taking hole, The pressure value of the throat pressure hole; is the density of the fluid being measured; Substituting the corresponding values ​​into the formula, the fluid air volume can be calculated. The value of .

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