A fluid flow meter with cavity grid structure

Abstract

The present invention discloses a fluid flow meter with a cavity grid structure, which utilizes the self-excited oscillation phenomenon of the grid and the cavity flow field to generate vortices, and installs a grid cavity structure on the pipeline to measure the fluid flow rate. The flow meter has a simple structure, and by integrating the vortex generator and the pipeline, the flow process is made smoother, the flow resistance is effectively reduced, and the pressure loss is reduced, thereby effectively avoiding the problems of pressure loss and high manufacturing cost of the Karman vortex air flow meter. A grid and a cavity structure are installed on the pipeline as a vortex generator, and the total length of the grid, the aspect ratio of the grid, and the aspect ratio of the cavity are determined according to the thickness of the pipeline to obtain the corresponding Strouhal number, and then the incoming flow velocity is iterated in the ECU to continuously approach the accurate incoming flow velocity until the incoming flow velocity error is less than 5%, thereby realizing the measurement of the fluid flow rate.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid flowmeters, and in particular to a fluid flowmeter with a cavity grid structure. Background Art

[0002] The existing Karman vortex air flow meter is a device that uses the Karman vortex theory to measure the air flow. There is a streamlined or triangular vortex generator in the inlet duct of the flow meter. When a uniform airflow flows through the vortex generator, the air flow is disturbed, and a Karman vortex is generated in the airflow downstream. A large number of experiments have shown that within a certain range of Reynolds number Re, the Strouhal number St is a constant, so the frequency of vortex generation is proportional to the air flow rate. Therefore, by measuring the vortex generation frequency, the fluid flow rate can be calculated, and then the flow rate can be calculated according to Q=S×v (S is the area of ​​the fluid channel). However, since there is a vortex generator in the inlet duct of this type of air flow meter, there are problems such as limiting the flow channel and causing pressure loss, which affects the intake process of the engine. In addition, this type of flow meter is not suitable for the measurement of high viscosity, low flow rate, and small flow rate. It is easily affected by noise, which will affect the accurate measurement of the flow rate. Summary of the invention

[0003] The object of the present invention is to provide a fluid flow meter with a cavity grid structure in order to solve the above-mentioned problem.

[0004] In order to solve the above problems, the present invention provides a technical solution: a fluid flow meter with a cavity grid structure, comprising a pipeline, a fluid flow meter inlet, a fluid flow meter outlet, a rectifier, a grid, a cavity, a pressure sensor, a flange and bolts; the left end of the pipeline is fixedly connected with the fluid flow meter inlet; the right end of the pipeline is fixedly connected with the fluid flow meter outlet; the rectifier is connected to the fluid flow meter inlet; flanges are fixedly connected on the outer surfaces of the fluid flow meter inlet and the fluid flow meter outlet; a plurality of bolts are provided on the flange; the cavity is located on one side of the pipeline; the cavity is connected to the pipeline, and the grid is arranged at the connection between the cavity and the pipeline; the cavity is connected with the pressure sensor; the grid and the cavity constitute a vortex generator.

[0005] Preferably, the flange connection standard is GB / T9119-2000.

[0006] Preferably, the pressure sensor is a piezoresistive pressure sensor.

[0007] Preferably, the aspect ratio of the grille is 1, and the aspect ratio of the cavity is 1.67.

[0008] Preferably, the rectifier adopts a fixed installation mode.

[0009] Beneficial effects of the present invention: The present invention utilizes the self-excited oscillation phenomenon of the grid and cavity flow field to generate vortices, and adds a grid cavity structure to the pipeline to measure the fluid flow rate. The structure is simple, and the vortex generator and the pipeline are integrated, which can effectively reduce resistance and pressure loss, making the flow process smoother, thereby effectively avoiding the pressure loss and high manufacturing cost problems generated in the Karman vortex air flow meter. A grid and a cavity structure are added to the pipeline as a vortex generator, and the total length of the grid, the aspect ratio of the grid, and the aspect ratio of the cavity are determined according to the thickness of the pipeline to obtain the corresponding Strouhal number, and then the incoming flow velocity is iterated in the ECU to continuously approach the accurate incoming flow velocity until the incoming flow velocity error is less than 5%, thereby realizing the measurement of the fluid flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the present invention.

[0011] Figure 2 It is a structural schematic diagram of the grid of the present invention.

[0012] 1-pipeline; 2-fluid flow meter inlet; 3-fluid flow meter outlet; 4-rectifier; 5-grid; 6-cavity; 7-pressure sensor; 8-flange; 9-bolt. DETAILED DESCRIPTION

[0013] like Figure 1 and Figure 2 As shown, this specific embodiment adopts the following technical scheme: a fluid flow meter with a cavity grid structure, including a pipeline 1, a fluid flow meter inlet 2, a fluid flow meter outlet 3, a rectifier 4, a grid 5, a cavity 6, a pressure sensor 7, a flange 8 and a bolt 9; the left end of the pipeline 1 is fixedly connected with the fluid flow meter inlet 2; the right end of the pipeline 1 is fixedly connected with the fluid flow meter outlet 3; the fluid flow meter inlet 2 is connected with a rectifier 4, and the rectifier 4 is installed at the inlet. The rectifier 4 can make the air velocity flowing through uniform, and the airflow state changes from turbulent flow to flat flow, so that the back end can measure more accurate results. The rectifier 4 needs to be cleaned and maintained regularly. At the same time, Compared with other resistance elements, the pressure loss coefficient generated by the rectifier 4 is smaller, and the pressure loss caused to the entire intake system is small and can be ignored. The installation mode of the rectifier 4 currently used is fixed. In order to achieve a better rectification effect, the distance between the rectifier 4 and the vortex generator is at least 4D of the straight pipe distance; a flange 8 is fixedly connected to the outer surface of the fluid flow meter inlet 2 and the fluid flow meter outlet 3; a plurality of bolts 9 are provided on the flange 8; the cavity 6 is located on one side of the pipeline 1; the cavity 6 is connected to the pipeline 1, and the grille 5 is arranged at the connection between the cavity 6 and the pipeline 1; a pressure sensor 7 is connected to the cavity 6; the grille 5 and the cavity 6 constitute a vortex generator.

[0014] The connection standard of the flange 8 is GB / T9119-2000; the pressure sensor 7 is a piezoresistive pressure sensor, which has a very thin silicon wafer, which is thicker around and thinner in the middle. This thin silicon wafer is its main component. There is a layer of silicon dioxide film on the upper and lower sides of the silicon wafer, and there are 4 sensor resistors around the silicon wafer, connected to form a bridge circuit. When the pressure changes, the silicon wafer will deform, causing the change of the resistance value of the sensor resistor, the balance state of the bridge is destroyed, and a potential difference is generated. After processing, the voltage signal is transmitted to the electronic control unit. The electronic control unit performs Fourier transform on the input voltage signal, performs spectrum analysis to obtain a vortex frequency signal, and can measure the air flow according to the frequency. The pressure sensor of the present invention is connected by bolts, which is easy to replace; the aspect ratio of the grid 5 is 1, and the aspect ratio of the cavity 6 is 1.67. The fluid flow meter based on the self-oscillation of the grid and cavity flow field will only be affected by the self-oscillation of the grid and cavity flow field when the cavity length is very small (DL / L<1.5, DL is the cavity length, L is the grid length). As the cavity height gradually increases, the self-oscillation of the flow field becomes easy to be excited. When the cavity size is large enough (DH / L>5, DH is the cavity length, L is the grid length), the cavity wall will not affect the self-oscillation process; the rectifier 4 adopts a fixed installation mode.

[0015] The present invention Figure 1 and Figure 2 The specific dimensions are shown in the table below:

[0016]

[0017]

[0018] The use state of the present invention is as follows: when the fluid flows through the rectifier 4, passes through the grille 5 and the cavity 6 structure, due to the large difference in flow velocity inside and outside the grille 5 and the cavity 6, under the action of the shear layer, vortices moving downstream will gradually form, and these vortices are equivalent to a disturbance, which is called a shear layer disturbance; when the vortex hits the back of the grille 5 and the cavity 6, a feedback disturbance propagating forward will be formed, and under the coupling action of these two disturbances, a self-excited oscillation phenomenon of the flow field will be formed, and new vortices will be continuously generated. When the air in the pipeline 1 flows through the grille 5 and the cavity 6 structure, the pressure in the flow field oscillates periodically, and a pressure sensor 7 is installed in the middle position of the rear wall of the cavity. Its sensing resistor will generate a corresponding charge signal and transmit the signal to the electronic control unit, thereby realizing the measurement of the fluid flow rate.

[0019] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0020] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0021] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

[0022] The control method of the present invention is to control by manually starting and closing the switch. The wiring diagram of the power element and the provision of power supply are common knowledge in the field, and the present invention is mainly used to protect mechanical devices, so the present invention will no longer explain the control method and wiring layout in detail.

Claims

1. A fluid flow meter with a cavity grid structure, characterized in that: It comprises a pipeline (1), a fluid flow meter inlet (2), a fluid flow meter outlet (3), a rectifier (4), a grid (5), a cavity (6), a pressure sensor (7), a flange (8) and bolts (9); The left end of the pipeline (1) is fixedly connected to an inlet (2) of a fluid flow meter; The right end of the pipeline (1) is fixedly connected to a fluid flow meter outlet (3); The fluid flow meter inlet (2) is connected to a rectifier (4); Flanges (8) are fixedly connected on the outer surfaces of the fluid flow meter inlet (2) and the fluid flow meter outlet (3); The flange (8) is provided with a plurality of bolts (9); The cavity (6) is located on one side of the pipe (1); The cavity (6) is in communication with the pipeline (1), and the grille (5) is arranged at the connection between the cavity (6) and the pipeline (1); The cavity (6) is connected to a pressure sensor (7); The grille (5) and the cavity (6) constitute a vortex generating body; The connection standard of the flange (8) is GB / T9119-2000; The pressure sensor (7) is a piezoresistive pressure sensor; it has a very thin silicon chip, which is thicker around the edges and thinner in the middle. A layer of silicon dioxide film is respectively provided on the upper and lower surfaces of the silicon chip, and four sensing resistors are provided around the silicon chip, connected to form a bridge circuit. When the pressure changes, the silicon chip will deform, causing the resistance value of the sensing resistor to change, the balance state of the bridge will be destroyed, and a potential difference will be generated. After processing, the voltage signal is transmitted to the electronic control unit; the electronic control unit performs Fourier transform on the input voltage signal, performs spectrum analysis to obtain a vortex frequency signal, and can measure the air flow according to the frequency; The aspect ratio of the grille (5) is 1, and the aspect ratio of the cavity (6) is 1.67; The rectifier (4) adopts a fixed installation mode; The distance between the rectifier (4) and the vortex generator is at least 4D of the straight tube distance; The fluid flow meter has the following dimensional parameters: the inlet diameter D is 70 mm, the cavity length DL is 99 mm, and the cavity width DH is 59.4 mm; the length L of the grid plate is 14.2 mm, the thickness H of the grid ribs is 0.635 mm, the width W is 0.408 mm, and the rib spacing G is 0.635 mm; the distance between the inlet and the grid and cavity structure is 300 mm on the left side (LL) and 200 mm on the right side (LR); the bolt specification used is M12×50, the flange thickness DN is 10 mm, and the thickness d of the flow meter pipe is 4.5 mm; The working method of the fluid flow meter comprises the following steps: When the fluid flows through the rectifier (4) and passes through the grid (5) and cavity (6) structures, due to the large difference in flow velocity inside and outside the grid (5) and cavity (6), under the action of the shear layer, vortices moving downstream will gradually form. These vortices are equivalent to a disturbance, which is called a shear layer disturbance. When the vortex hits the back of the grid (5) and cavity (6), a feedback disturbance propagating forward will be formed. Under the coupling action of these two disturbances, a self-excited oscillation phenomenon of the flow field will be formed, and new vortices will be continuously generated. When the air in the pipeline (1) flows through the grid (5) and cavity (6) structures, the pressure in the flow field will oscillate periodically. A pressure sensor (7) is installed in the middle position of the rear wall of the cavity. Its sensing resistor will generate a corresponding charge signal and transmit the signal to the electronic control unit, thereby realizing the measurement of the fluid flow rate.

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