CN107817026B - High-resolution differential pressure type flow sensor based on synchronous resonance and detection method - Google Patents

Abstract

The invention provides a high-resolution differential pressure flow sensor and a detection method based on synchronous resonance, which belong to a differential pressure flow sensor. One end of the flow channel in the base is sealingly connected to the pressure-inducing flow channel, and the other end is sealingly connected to the compression chamber of the support part. The separation membrane is located between the base and the support part. The support part is connected to two pairs of synchronous resonance cantilever beams. One end of the flow channel in the support part is connected to the compression chamber. The cavity is connected, and the other end is connected to the flow channel in the detection beam, and the flow channel in the detection beam is connected to the sensitive cavity. The upper surface of the detection beam base is provided with a piezoelectric excitation piece, and the upper surface of the base of the pickup beam is provided with a piezoelectric vibration pickup piece. , two pairs of synchronous resonance cantilever beams form a differential structure. The invention has a novel structure and is used in conjunction with a throttling device to convert changes in water pressure into changes in closed gas density. It uses a synchronous resonance cantilever beam structure to achieve high-resolution measurement of fluid pressure difference, thereby obtaining the flow rate of the measured fluid. .

Description

High-resolution differential pressure flow sensor and detection method based on synchronous resonance

Technical field

The invention belongs to a differential pressure flow sensor, and in particular relates to a high-resolution differential pressure flow sensor based on synchronous resonance and a detection method thereof.

Background technique

In recent years, flow sensors, as the main tool for detecting fluid flow, have been widely used in various fields such as energy transportation, medical diagnosis, biochemical experiments, aerospace, and public safety. The most commonly used differential pressure flow meter is the orifice plate structure. It has a solid structure, stable and reliable performance, long service life, and a wide range of applications. So far, no flow meter can compare with it.

At present, many institutions have explored and designed the structure and signal transmission of sensors to obtain high-resolution flow sensors. As early as the 17th century, Torricelli laid the theoretical foundation for differential pressure flow meters. Since then, the prototypes of many types of flow measurement instruments began to take shape in the 18th and 19th centuries, such as pitot tubes, venturi tubes, volumetric, turbine and Target flow meter, etc. The University of Greenwich in the UK has proposed a new method based on wavelet transform to evaluate the obstruction of the sensing line in the DP flow sensor, thereby improving the resolution of flow detection; the School of Measurement and Testing Engineering of China Metrology Institute has proposed a method based on The new type of differential pressure flow sensor composed of double cones has smaller pressure loss and more stable flow state than the traditional differential pressure flow meter, thereby improving measurement accuracy. However, current flow sensors have relatively small ranges, and when the flow rate is less than 1/3 of the full scale, the pressure difference caused by throttling is small, resulting in large measurement errors.

Contents of the invention

The present invention provides a high-resolution differential pressure flow sensor and detection method based on synchronous resonance. By converting changes in pressure into changes in gas density, thereby causing changes in mass, the synchronous resonance cantilever beam structure is then used to achieve weak detection of mass. Detection of changes, thereby improving sensor resolution.

The technical solution adopted by the present invention is: the separation membrane is located between the base and the support part, the flow channel in the base and the compression cavity of the support part are located on both sides of the separation membrane, one end of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are respectively The first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams have the same structure, and the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams form a difference The first pair of synchronous resonance cantilever beam structures is a dynamic structure, in which the detection beam is connected to the pickup beam through a coupling beam. One end of the internal flow channel of the detection beam is connected to the internal flow channel of the support part, and the other end is connected to the sensitive cavity. The internal flow channel of the support part is It is also connected to the compression chamber of the support part. The compression chamber of the support part, the inner flow channel of the support part, the inner flow channel of the detection beam and the sensitive cavity are filled with gas.

The vibration-picking beam includes a vibration-picking beam base, and a lower insulation layer, a piezoelectric vibration-picking piece, and an upper insulation layer are arranged on the upper surface of the vibration-picking beam base in sequence.

The detection beam includes a detection beam base. The upper surface of the detection beam base is provided with a second lower insulation layer, a piezoelectric excitation piece, and a second upper insulation layer in sequence. There is a detection beam internal flow channel in the detection beam base.

The flow channel in the detection beam is a multi-channel capillary parallel channel structure.

The sensitive cavity is a hollow structure with a shape of sphere, cylinder, cube or irregular geometry.

The gas is high-density, easily compressible and has stable physical and chemical properties.

A method for detecting fluid flow, including the following steps:

(1) Securely connect the base of the device to the throttling device, and ensure the sealing connection between the pressure flow channel and the base flow channel;

(2) Connect the piezoelectric excitation piece of the flow sensor to the signal generator, and connect the piezoelectric vibration pickup piece to the post-signal processing circuit;

(3) Calibrate the sensor and pass a fixed flow rate of fluid into the pipeline. When the measured fluid is in a turbulent state, use a signal generator to apply sweep frequency excitation to the piezoelectric excitation piece. When the excitation frequency is equal to the detection beam At the first-order natural frequency, the amplitudes of the detection beam and the pickup beam are doubled, and synchronous resonance occurs. The offset of the pickup beam frequency can be obtained through the piezoelectric pickup piece and post-processing circuit. At this time, the frequency of the pickup beam is recorded. Offset;

(4) Change the fluid flow in the pipeline, perform repeated calibration, and determine the coefficient K of the sensor to be calibrated;

(5) When the measured fluid passes through the throttling device and is in a turbulent state, apply sweep frequency excitation to the detection beam. After synchronous resonance occurs, record the frequency offsets △ω ₁₂ and △ of the two pairs of synchronous resonance cantilever beams. ω ₂₂ , then the measured fluid flow rate is:

Among them, Q is the measured fluid flow rate, K is the calibration coefficient, β is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression chamber, T is the Kelvin temperature of the gas in the compression chamber, R is the gas proportionality constant, ρ _{The measured fluid} is the density of the measured fluid, ω ₁₂ is the initial natural frequency of the first pair of synchronous resonance cantilever beams, and △ω ₁₂ is the offset of the resonant frequency of the first pair of synchronous resonance cantilever beams during the measurement process. , ω ₂₂ is the initial natural frequency of the second pair of synchronous resonant cantilever beam pickup beams, and Δω ₂₂ is the offset of the resonant frequency of the second pair of synchronous resonant cantilever beam pick-up beams during the measurement process.

The advantages of the present invention are:

(1) Applying the ideal gas law, the pressure signal can be converted into a mass signal, and the synchronous resonance cantilever beam detection structure can be used to convert it into a frequency signal and amplify it. The pressure can be measured by detecting the frequency offset, thus Improve sensor resolution.

(2) The end of the detection beam adopts a spherical sealed cavity, which has stronger pressure-bearing capacity and larger volume. The initial content of gas molecules is more, and the mass change is more sensitive, thereby improving the resolution of the sensor.

(3) Two pairs of synchronous resonance cantilever beams adopt a differential structure. Two identical and independent structures detect the pressure before and after throttling at the same time, which can eliminate errors caused by environmental influences to a certain extent.

(4) There is no direct contact between the measured fluid and the sensor detection part, which improves the reliability of sensor detection.

(5) The flow channel connected to the sensitive cavity adopts a multi-channel micro-through hole structure to ensure that the compressed gas quickly reaches an equilibrium state and the detection beam will not change the gas volume in the sensitive cavity due to excitation, thereby ensuring The response speed of the sensor and its detection accuracy.

Description of the drawings

Figure 1 is a schematic structural diagram of the present invention;

Among them: base 1, base inner flow channel 101, separation membrane 2, support part 3, compression chamber 301, support part inner flow channel 302, first pair of synchronous resonance cantilever beams 4, second pair of synchronous resonance cantilever beams 5, coupling beam structure 401, pickup beam structure 402, detection beam structure 403, detection beam internal flow channel 40301, sensitive cavity 6, sealing gas 7;

Figure 2 is a cross-sectional view of the detection beam of the present invention;

Among them: support part 3, support part inner flow channel 302, detection beam base inner flow channel 40301, sensitive cavity 6;

Figure 3 is the detection beam structure of the present invention;

Among them: detection beam base 40305, upper insulation layer 40304, piezoelectric excitation piece 40302, lower insulation layer 40303;

Figure 4 is the vibration pickup beam structure of the present invention;

Among them: the vibration pickup beam base 40204, the upper insulation layer 40203, the piezoelectric vibration pickup piece 40201, and the lower insulation layer 40202;

Figure 5 is a top view of the present invention;

Figure 6 is a side view of the present invention;

Figure 7 is a working state diagram of the present invention;

Among them: base 1, base inner flow channel 101, throttling device 8, pressure flow channel 801, throttle orifice plate 802, pipe 803;

Figure 8 is a signal conversion principle and transmission route diagram of the present invention;

Figure 9 is a top view of the wide range flow sensor;

Figure 10 is a bottom view of the wide range flow sensor.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments are only intended to illustrate the present invention more clearly and are not intended to limit the scope of the present invention.

As shown in Figure 1, it includes: base 1, separation film 2, support part 3, first pair of synchronous resonance cantilever beams 4, second pair of synchronous resonance cantilever beams 5, sensitive cavity 6 and sealing gas 7,

The separation membrane 2 is located between the base 1 and the support part 3. The flow channel 101 in the base and the compression chamber 301 of the support part are located on both sides of the separation membrane 2. One end of the first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 are respectively The first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 have the same structure, and the first pair of synchronous resonance cantilever beams 4 are synchronous with the second pair. The resonant cantilever beams 5 form a differential structure, in which the structure of the first pair of synchronous resonant cantilever beams 4 is: the detection beam 403 is connected to the pickup beam 402 through the coupling beam 401, and one end of the detection beam inner flow channel 40301 is connected to the support part inner flow channel 302. The other end is connected to the sensitive chamber 6. The support inner flow channel 302 is also connected to the support compression chamber 301. The support compression chamber 301, the support inner flow channel 302, the detection beam inner flow channel 40301 and the sensitive cavity 6 are filled with gas 7.

The vibration-picking beam 402 includes a vibration-picking beam base 40204. The upper surface of the vibration-picking beam base 40204 is sequentially provided with a lower insulation layer 40202, a piezoelectric vibration-picking piece 40201, and an upper insulation layer 40203.

The detection beam 403 includes a detection beam base 40305. The upper surface of the detection beam base 40305 is sequentially provided with a lower insulation layer 40303, a piezoelectric excitation piece 40302, and an upper insulation layer 40304. The detection beam base 40305 contains a detection beam inner layer. Runner 40301.

The flow channel 40301 in the detection beam is a multi-channel capillary parallel channel structure.

The sensitive cavity 6 is a hollow structure with a shape of sphere, cylinder, cube or irregular geometry.

The gas 7 is a gas with high density, easy compression and stable physical and chemical properties.

The detection method of fluid flow is carried out as follows:

(1) Securely connect the base of the device to the throttling device, and ensure the sealing connection between the pressure flow channel and the base flow channel;

(2) Connect the piezoelectric excitation piece of the flow sensor to the signal generator, and connect the piezoelectric vibration pickup piece to the post-signal processing circuit;

(3) Calibrate the sensor and pass a fixed flow rate of fluid into the pipeline. When the measured fluid is in a turbulent state, use a signal generator to apply sweep frequency excitation to the piezoelectric excitation piece. When the excitation frequency is equal to the detection beam At the first-order natural frequency, the amplitudes of the detection beam and the pickup beam are doubled, and synchronous resonance occurs. The offset of the pickup beam frequency can be obtained through the piezoelectric pickup piece and post-processing circuit. At this time, the frequency of the pickup beam is recorded. Offset;

(4) Change the fluid flow in the pipeline, perform repeated calibration, and determine the coefficient K of the sensor to be calibrated;

(5) When the measured fluid passes through the throttling device and is in a turbulent state, apply sweep frequency excitation to the detection beam. After synchronous resonance occurs, record the frequency offsets △ω ₁₂ and △ of the two pairs of synchronous resonance cantilever beams. ω ₂₂ , then the measured fluid flow rate is:

Among them, Q is the measured fluid flow rate, K is the calibration coefficient, β is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression chamber, T is the Kelvin temperature of the gas in the compression chamber, R is the gas proportionality constant, ρ _{The measured fluid} is the density of the measured fluid, ω ₁₂ is the initial natural frequency of the first pair of synchronous resonance cantilever beams, and △ω ₁₂ is the offset of the resonant frequency of the first pair of synchronous resonance cantilever beams during the measurement process. , ω ₂₂ is the initial natural frequency of the second pair of synchronous resonant cantilever beam pickup beams, and Δω ₂₂ is the offset of the resonant frequency of the second pair of synchronous resonant cantilever beam pick-up beams during the measurement process.

The effects of the present invention will be further described below by analyzing the structural features and detection method principles of the present invention.

The base inner flow channel 101 and the compression chamber 301 can be uniformly processed after the base 1 and the support part 3 are assembled, thereby ensuring smooth connection between the base inner flow channel 101 and the compression chamber 301. The smooth connection between the flow channel 101 inside the base and the compression chamber 301 prevents the separation membrane 2 from causing external force due to structural asymmetry when acted upon by the fluid. The separation membrane 2 is only affected by the fluid and the sealing gas 7, ensuring the accuracy of fluid flow detection. Spend.

The compression chamber 301 is connected to the sensitive chamber 6 through the inner flow channel 302 of the support part and the inner flow channel 40301 of the detection beam. Therefore, the compression chamber 301, the inner flow channel 302 of the support part, the inner flow channel 40301 of the detection beam, and the inner flow channel 40301 of the detection beam form a sealed cavity gas 7. The physical properties are the same everywhere.

Furthermore, the flow channel 40301 in the detection beam improves the rapidity of system response while ensuring system stability. When the measured fluid acts on the separation membrane 2 through the inner flow channel 101 of the base, the sealing gas 7 flows to the sensitive cavity 6 through the inner flow channel 302 of the support part and the inner flow channel 40301 of the detection beam due to uneven pressure. The multi-channel structure 40301 can The system quickly reaches a stable state and improves the response speed of the system. When the piezoelectric excitation piece 40302 is excited by the frequency sweep and resonates, the large pressure drop of the capillary channel 40301 ensures that the sealed gas 7 in the sensitive cavity 6 will not occur. The backflow phenomenon can improve the stability of the system during sensor detection.

Arranging insulating layers on both the upper and lower layers of the piezoelectric excitation piece 40302 and the piezoelectric vibration pickup piece 40201 can reduce the impact of environmental factors and expand the use range of the flow sensor.

The sensitive cavity 6 is a spherical hollow structure, and its wall thickness depends on the material characteristics and the maximum static pressure of the measured flow. Compared with other shaped sealed cavities, the spherical sensitive cavity 6 has a larger volume and a limit Greater pressure-bearing capacity. However, in addition to the spherical sensitive cavity, other shapes of sensitive cavities (such as cylinders, cubes, irregular geometries, etc.) can also be used; in this embodiment, a spherical sensitive cavity 6 with a larger volume per unit mass and a larger pressure-bearing capacity is selected. detection.

Among them, high-density and easily compressible gas can improve the resolution of the sensor. When external force causes the pressure of the sealed gas 7 to change, the density change of the high-density and easily compressible gas will be more obvious. The stable physical and chemical properties ensure the stability of the sensor's operation.

When the mass of the sensitive cavity changes, the resonant frequency of the detection beam will shift. The resonance frequency shift will be amplified through the synchronous resonance structure. The change in the resonant frequency of the detection beam is △ω ₁ , and the change in the resonant frequency of the pickup beam is △ω. ₂ , then there exists △ω ₂ =β△ω ₁ , where β is the frequency amplification factor of the synchronous resonance cantilever beam.

As shown in Figure 8, the flow sensor is used in conjunction with the throttling device. The base 1 is fixedly connected to the throttling device 8, and the pressure flow channel 801 is sealingly connected to the flow channel 101 in the base.

When the fluid flows through the orifice plate 802, the hydrostatic pressure before and after the orifice plate 802 changes. The fluid before and after the orifice plate 802 acts on the separation membrane 2 through the pressure flow channel 801 and the inner flow channel 101 of the base, and the throttling orifice plate 802 acts on the separation membrane 2. The hydrostatic pressure before and after the orifice plate 802 is equal to the pressure acting on the separation membrane respectively.

This example takes the first pair of synchronous resonance cantilever beams as an example. The two pairs of synchronous resonance cantilever beams of the flow sensor work on the same principle and have the same structural parameters.

The pre-action compression chamber 301, the inner flow channel 302 of the support part, the inner flow channel 40301 of the detection beam, and the sensitive chamber 6 are closed spaces filled with sealing gas 7 and have a certain initial pressure △P ₀ ;

When the measured fluid acts on the separation membrane 2, the separation membrane 2 deforms due to unbalanced force, and the volume of the sealing gas 7 also changes, until the pressure of the sealing gas 7 is equal to the hydrostatic pressure acting on the separation membrane 2, The separation membrane 2 reaches a dynamic equilibrium state, and the hydrostatic pressure and the initial pressure of the sealing gas exist:

P ₁ =P ₀ +△P ₁

Among them, P ₁ is the hydrostatic pressure acting on the separation membrane, P ₀ is the initial pressure of the sealing gas, and ΔP ₁ is the change in sealing gas pressure after the action of the fluid.

According to the ideal gas law, the volume change of the sealed gas 7 in the compression chamber causes the pressure of the sealed gas 7 to change, causing the density of the sealed gas 7 in the sensitive chamber 6 to change. The change amount and density change amount of the pressure of the sealed gas 7 in the compression chamber 301 should satisfy :

Among them, △ρ ₁ is the change in gas density in the compression chamber of the first pair of synchronous resonance cantilever beams, △P ₁ is the change in gas pressure in the compression chamber of the first pair of synchronous resonance cantilever beams after the action of fluid, and M is the change in the compression chamber The molar mass of the gas, T is the Kelvin temperature of the gas in the compression chamber, and R is the gas proportionality constant.

When the sealing gas 7 is in a balanced state after the action, the pressure and density of the sealing gas in the sensitive chamber 6 and the sealing gas in the compression chamber 301 are the same. The sensitive chamber 6 can be considered as a rigid structure, and the volume does not change. Therefore, the sealing gas in the sensitive chamber 6 The mass change of 7 changes linearly with the density of the sealed gas 7 in the sensitive chamber 6. The sensitive chamber 6 and the detection beam 403 are rigidly connected. The relationship between the mass change and the density change of the sealed gas 7 in the sensitive chamber 6 is:

Among them, r is the radius of the sensitive cavity, △m ₁ is the mass change of the sealing gas in the sensitive cavity of the first pair of synchronous resonance cantilever beams after the action, and △ρ ₁ is the change of the sealing gas density of the first pair of synchronous resonance cantilever beams.

Before the fluid acts, the detection beam 403 has a certain natural frequency, which can be determined through experiments or calculations. In this example, as shown in Figure 8, the synchronous resonance beams connected to the pressure flow channel in front of the orifice plate 802 are the first pair of cantilever beams 4, and the first-order natural frequency of the first pair of synchronous resonance detection beams 403 is ω ₁₁ , the first-order natural frequency of the pickup beam 402 is ω ₁₂ , then the ratio of the natural frequency of the detection beam 403 to the natural frequency of the pickup beam 402 is 1:β, that is, ω ₁₂ =βω ₁₁ .

When the measured fluid acts on the separation membrane 2, the physical properties of the gas in the compression chamber 301 change. When the sealed gas 7 in the compression chamber 301 becomes stable, that is, the physical properties of the sealed gas 7 are the same everywhere, and the mass of the sealed gas 7 in the sensitive chamber 6 Changes occur. Since the sensitive cavity 6 is fixedly connected to the detection beam 403, the natural frequency of the detection beam 403 changes. Frequency sweep excitation is applied to the piezoelectric excitation piece 40302 of the detection beam 403, and the detection beam 403 is deformed due to the excitation. Under the first-order natural frequency of the detection beam 403, the amplitudes of the detection beam 403 and the pickup beam 402 increase, and the frequency of the pickup beam 402 doubles, that is, a synchronous resonance phenomenon occurs. The resonant frequency ω' of the pickup beam 402 after the action of the fluid ₁₂ and the resonant frequency ω' ₁₁ of the detection beam 403 still exist ω' ₁₂ =βω' ₁₁ .

Through the collection of the signal of the piezoelectric vibration pickup piece 40201 and the processing of the later circuit, the frequency offset Δω ₁₂ of the vibration pickup beam 402 can be obtained, and the frequency offset Δω ₁₂ of the vibration pickup beam 402 is consistent with the sealing gas in the sensitive cavity 6 7The change in mass Δm exists:

△ω ₁₂ =β△ω ₁₁

Among them, △m ₁ is the mass change of the sealing gas in the sensitive cavity fixedly connected to the first pair of synchronous resonance cantilever beams, K ₁ is the parameter related to the material and size of the synchronous resonance cantilever beam structure, and ω ₁₁ is the first For the natural frequency of the synchronous resonance cantilever beam detection beam, △ω ₁₁ is the offset of the natural frequency of the first pair of synchronous resonance cantilever beam detection beams after the action, △ω ₁₂ is the natural frequency of the first pair of synchronous resonance cantilever beam pickup beams after the action Frequency offset.

The second pair of synchronous resonance cantilever beam structures is used to detect the static pressure of the measured fluid after throttling. Similarly, when the fluid flowing through the throttling orifice plate acts on the separation membrane of the second pair of synchronous resonance cantilever beams, it can pass through the second pair of synchronous resonance cantilever beams. For the synchronous resonance cantilever beam, the offset of the natural frequency of the pickup beam is measured, and the hydrostatic pressure P ₂ after throttling is obtained.

The measured fluid pressure difference before and after throttling is:

△P _throttling =P ₁ -P ₂

Among them, △P _throttling is the pressure difference between the fluid before and after throttling when the measured fluid passes through the throttling device, P ₁ is the hydrostatic pressure before throttling, and P ₂ is the hydrostatic pressure after throttling.

The flow sensor adopts a differential structure. The differential structure means that the structural parameters of the first pair of synchronous resonance cantilever beam structures 4 and the second pair of synchronous resonance cantilever beam structures 5 are consistent. When used, the pressure before and after throttling is measured at the same time. Detection can eliminate errors caused by environmental influences to a certain extent.

When the measured fluid flows through the throttling device 8, there is a certain relationship between the measured fluid flow rate and the fluid pressure difference before and after throttling. The measured fluid flow rate can be calculated by the fluid pressure difference before and after throttling:

Among them, Q is the flow rate of the measured fluid, △P _throttling is the fluid pressure difference before and after throttling, ρ _{the measured fluid} is the density of the measured fluid, and K ₂ is a constant, which depends on the structure of the throttling device and the properties of the measured fluid.

In this example, the initial parameters of the two pairs of synchronous resonant cantilever beams are completely consistent, so the measured fluid flow can be measured through the offset of the natural frequencies of the two pairs of synchronous resonant cantilever beams. The offset of the measured fluid flow and the natural frequency of the pickup beam Shift exists:

Among them, Q is the measured fluid flow rate, β is the frequency amplification factor of the synchronous resonance cantilever beam, K is the calibration coefficient, M is the molar mass of the gas in the compression chamber, T is the Kelvin temperature of the gas in the compression chamber, R is the gas proportionality constant, ρ _{The measured fluid} is the measured fluid density, ω ₁₂ is the initial natural frequency of the first pair of synchronous resonance cantilever beam pickup beams, Δω ₁₂ is the offset of the resonant frequency of the first pair of synchronous resonance cantilever beam pickup beams during the measurement process, ω ₂₂ is the initial natural frequency of the second pair of synchronous resonance cantilever beam pickup beams, and Δω ₂₂ is the offset of the resonance frequency of the second pair of synchronous resonance cantilever beam pickup beams during the measurement process.

This invention takes advantage of the high sensitivity of the synchronous resonance cantilever beam to change the offset of the cantilever beam frequency caused by the mass change from Δω to βΔω, thereby improving the resolution of hydrostatic pressure detection. It combines the differential structure and the sealing The variable initial gas pressure in the compression chamber can improve detection accuracy and detection range.

In addition, as shown in Figures 9 and 10, multiple pairs of synchronous resonance cantilever beams are used in parallel to increase the range of the flow sensor.

The volume of the compression chamber 301 is determined by the design parameters. When the fluid interacts with the separation membrane 2, the separation membrane 2 is deformed due to the action of the fluid, thereby changing the gas pressure. The change in the pressure of the sealing gas 7 depends on the degree of deformation of the separation membrane 2. , the degree of deformation of the separation membrane 2 depends on the initial pressure of the sealing gas 7 and the volume of the compression chamber 301 .

When the initial pressure of the sealed gas is changed, the measurement of fluid flow in different ranges can be achieved. Gases with different initial pressures are filled into different pairs of synchronous resonance cantilever beams. Connecting them in parallel can increase the range of the sensor.

Claims (7)

1. A high-resolution differential pressure flow sensor based on synchronous resonance, characterized in that: the separation membrane is located between the base and the support part, the flow channel in the base and the compression cavity of the support part are located on both sides of the separation membrane, and the first pair of synchronous resonance One end of the cantilever beam and the second pair of synchronous resonance cantilever beams are connected to the support part and the other end is connected to the sensitive cavity respectively. The structures of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are the same, and the first pair of synchronous resonance cantilever beams are synchronous. The resonant cantilever beam and the second pair of synchronous resonant cantilever beams form a differential structure. The structure of the first pair of synchronous resonant cantilever beams is: the detection beam is connected to the pickup beam through the coupling beam, and one end of the inner flow channel of the detection beam is connected to the inner flow channel of the support part. , the other end is connected to the sensitive cavity, and the inner flow channel of the support part is also connected to the compression cavity of the support part. The support part compression cavity, the inner flow channel of the support part, the inner flow channel of the detection beam and the sensitive cavity are filled with gas. 2. A high-resolution differential pressure flow sensor based on synchronous resonance according to claim 1, characterized in that: the vibration-picking beam includes a vibration-picking beam base, and the upper surface of the vibration-picking beam base is arranged in sequence. Lower insulation layer 1, piezoelectric vibration pickup piece and upper insulation layer 1. 3. A high-resolution differential pressure flow sensor based on synchronous resonance according to claim 1, characterized in that: the detection beam includes a detection beam base, and the upper surface of the detection beam base is sequentially provided with an insulating layer. 2. The piezoelectric excitation piece, the upper insulation layer 2, and the detection beam inner flow channel in the base of the detection beam. 4. A high-resolution differential pressure flow sensor based on synchronous resonance according to claim 3, characterized in that: the flow channel in the detection beam is a multi-channel capillary parallel channel structure. 5. A high-resolution differential pressure flow sensor based on synchronous resonance according to claim 1, characterized in that: the sensitive cavity is a hollow structure and the shape is a sphere, a cylinder, a cube or an irregular geometry. 6. A high-resolution differential pressure flow sensor based on synchronous resonance according to claim 1, characterized in that the gas is a gas with high density, easy compression and stable physical and chemical properties. 7. The detection method of fluid flow using the high-resolution differential pressure flow sensor based on synchronous resonance as claimed in claim 1, characterized in that: it includes the following steps: (1) Securely connect the base to the throttling device, and ensure the sealing connection between the pressure flow channel and the base flow channel; (2) Connect the piezoelectric excitation piece of the flow sensor to the signal generator, and connect the piezoelectric vibration pickup piece to the post-signal processing circuit; (3) Calibrate the sensor and pass a fixed flow rate of fluid into the pipeline. When the measured fluid is in a turbulent state, use a signal generator to apply sweep frequency excitation to the piezoelectric excitation piece. When the excitation frequency is equal to the detection beam At the first-order natural frequency, the amplitudes of the detection beam and the pickup beam are doubled, and synchronous resonance occurs. The offset of the pickup beam frequency can be obtained through the piezoelectric pickup piece and post-processing circuit. At this time, the frequency of the pickup beam is recorded. Offset; (4) Change the fluid flow in the pipeline, perform repeated calibration, and determine the coefficient K of the sensor to be calibrated; (5) When the measured fluid passes through the throttling device and is in a turbulent state, apply sweep frequency excitation to the detection beam. After synchronous resonance occurs, record the frequency offsets △ω ₁₂ and △ of the two pairs of synchronous resonance cantilever beams. ω ₂₂ , then the measured fluid flow rate is: Among them, Q is the measured fluid flow rate, K is the calibration coefficient, β is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression chamber, T is the Kelvin temperature of the gas in the compression chamber, R is the gas proportionality constant, ρ _{The measured fluid} is the density of the measured fluid, ω ₁₂ is the initial natural frequency of the first pair of synchronous resonance cantilever beams, and △ω ₁₂ is the offset of the resonant frequency of the first pair of synchronous resonance cantilever beams during the measurement process. , ω ₂₂ is the initial natural frequency of the second pair of synchronous resonant cantilever beam pickup beams, and Δω ₂₂ is the offset of the resonant frequency of the second pair of synchronous resonant cantilever beam pick-up beams during the measurement process.