CN107817026B - High-resolution differential pressure type flow sensor based on synchronous resonance and detection method - Google Patents
High-resolution differential pressure type flow sensor based on synchronous resonance and detection method Download PDFInfo
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
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- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
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Abstract
The invention provides a high-resolution differential pressure type flow sensor based on synchronous resonance and a detection method thereof, belonging to differential pressure type flow sensors. One end of the inner flow passage of the base is connected with the pressure guiding flow passage in a sealing way, the other end of the inner flow passage of the base is connected with the compression cavity of the supporting part in a sealing way, the separation film is positioned between the base and the supporting part, the supporting part is connected with two pairs of synchronous resonance cantilever beams, one end of the inner flow passage of the supporting part is connected with the compression cavity, the other end of the inner flow passage of the supporting part is connected with the detection Liang Naliu passage, the detection Liang Naliu passage is connected with the sensitive cavity, the upper surface of the detection beam substrate is provided with a piezoelectric excitation sheet, the upper surface of the vibration pickup beam substrate is provided with a piezoelectric vibration pickup sheet, and the two pairs of synchronous resonance cantilever beams form a differential structure. The invention has novel structure, is matched with the throttling device to convert the change of water pressure into the change of the density of the closed gas, and utilizes the synchronous resonance cantilever structure to realize high-resolution measurement of the pressure difference of the fluid so as to obtain the flow of the fluid to be measured.
Description
Technical Field
The invention belongs to differential pressure type flow sensors, and particularly relates to a high-resolution differential pressure type flow sensor based on synchronous resonance and a detection method thereof.
Background
In recent years, as a main tool for detecting fluid flow, a flow sensor is widely applied to various fields such as energy transportation, medical diagnosis, biochemical experiments, aerospace, public safety and the like. The differential pressure type flowmeter has the most applied orifice plate type structure, firm structure, stable and reliable performance, long service life and wide application range, and no flowmeter of any type can be compared with the differential pressure type flowmeter.
There are many mechanisms currently available for exploring and designing the structure and signal transmission of sensors to obtain high resolution flow sensors. As early as the 17 th century, toli laid the theoretical foundation of differential pressure flow meters, and since then, the prototypes of many types of meters for 18, 19 th century flow measurement, such as pitot tubes, venturi tubes, volumes, turbines, and target flow meters, began to develop. The university of greenwich proposes a new method based on wavelet transformation for evaluating the blockage of sensing lines in DP flow sensors, thereby improving the resolution of flow detection; the Chinese academy of metering and testing engineering provides a novel differential pressure type flow sensor composed of double cones, and compared with the traditional differential pressure flow meter, the flow sensor has the advantages of small pressure loss and more stable flowing state, thereby improving the measurement accuracy. However, the current flow sensor has smaller measuring range, and when the flow is less than 1/3 of the full measuring range, the pressure difference formed by throttling is smaller, so that the measuring error is larger.
Disclosure of Invention
The invention provides a high-resolution differential pressure type flow sensor and a detection method based on synchronous resonance.
The technical scheme adopted by the invention is as follows: the separation membrane is positioned between the base and the supporting part, the flow channel in the base and the compression cavity of the supporting part are positioned at two sides of the separation membrane, one ends of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are respectively connected with the supporting part, the other ends of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are respectively connected with the sensitive cavity, 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 and the second pair of synchronous resonance cantilever beams form a differential structure, wherein the first pair of synchronous resonance cantilever beams are: the detection beam is connected with the vibration pickup beam through the coupling beam, one end of the detection Liang Naliu channel is connected with the inner flow channel of the supporting part, the other end of the detection Liang Naliu channel is connected with the sensitive cavity, the inner flow channel of the supporting part is also connected with the compression cavity of the supporting part, and the compression cavity of the supporting part, the inner flow channel of the detection beam and the sensitive cavity are filled with gas.
The vibration pickup beam comprises a vibration pickup beam substrate, and a lower insulating layer I, a piezoelectric vibration pickup sheet and an upper insulating layer I are sequentially arranged on the upper surface of the vibration pickup beam substrate.
The detection beam comprises a detection beam substrate, wherein a second lower insulating layer, a piezoelectric excitation sheet and a second upper insulating layer are sequentially arranged on the upper surface of the detection beam substrate, and a detection beam inner runner is arranged in the detection beam substrate.
The inner runner of the detection beam is of a multi-runner capillary parallel channel structure.
The sensitive cavity is of a hollow structure, and the appearance is a sphere, a cylinder, a cube or an irregular geometric body.
The gas is high-density gas which is easy to compress and has stable physicochemical properties.
A method of detecting fluid flow, comprising the steps of:
(1) The base of the device is fixedly connected with the throttling device, and the sealing connection of the pressure guiding flow passage and the base flow passage is ensured;
(2) Connecting a piezoelectric vibration excitation sheet of the flow sensor with a signal generator and connecting a piezoelectric vibration pickup sheet with a later signal processing circuit;
(3) Calibrating a sensor, introducing a fluid with fixed flow into a pipeline, applying sweep frequency excitation to a piezoelectric excitation sheet by using a signal generator when the fluid to be measured is in a turbulent state, multiplying the amplitudes of the detection beam and the vibration pickup beam under the condition that the excitation frequency is equal to the first-order natural frequency of the detection beam, generating synchronous resonance, obtaining the offset of the vibration pickup beam frequency by using the piezoelectric vibration pickup sheet and a post-processing circuit, and recording the offset of the vibration pickup beam frequency at the moment;
(4) Changing the fluid flow of the pipeline, carrying out repeated calibration, and determining the coefficient K to be calibrated of the sensor;
(5) When the fluid to be measured passes through the throttling device and is in a turbulent flow state, sweep frequency excitation is applied to the detection beam, and after synchronous resonance phenomenon occurs, the frequency offset delta omega of the two pairs of synchronous resonance cantilever beams is recorded respectively 12 、△ω 22 The measured fluid flow is:
wherein Q is the flow of the fluid to be measured, K is the calibration coefficient, beta is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression cavity, T is the Kelvin temperature of the gas in the compression cavity, R is the gas proportionality constant, ρ Fluid to be measured Omega for measured fluid density 12 For the initial natural frequency of the first pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 12 To measure the shift in resonant frequency, ω, of the first pair of synchronous resonant cantilevers Liang Shezhen 22 For the initial natural frequency of the second pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 22 To measure the shift in the resonant frequency of the second pair of synchronous resonant cantilevers Liang Shezhen.
The invention has the advantages that:
(1) By applying the ideal gas law, the pressure signal can be converted into a quality signal, the quality signal is converted into a frequency signal through a synchronous resonance cantilever beam detection structure and amplified, and the pressure can be measured through detecting the frequency offset, so that the resolution of the sensor is improved.
(2) The end of the detection beam adopts a spherical sealing cavity, so that the pressure bearing capacity is stronger, the volume is larger, the initial content of gas molecules is more, and the quality change is more sensitive, thereby improving the resolution of the sensor.
(3) The two pairs of synchronous resonance cantilever beams adopt differential structures, and the two identical and independent structures detect the pressure intensity before and after throttling at the same time, so that errors caused by environmental influence can be eliminated to a certain extent.
(4) The detected fluid is not in direct contact with the detection part of the sensor, so that the reliability of the detection of the sensor is improved.
(5) The runner that links to each other with sensitive chamber selects the multichannel micro-hole structure to use, guarantees that compressed gas reaches balanced state fast and detects the roof beam and can not make the sensitive intracavity gas volume change because of receiving the excitation effect simultaneously to the response speed of sensor and detection precision have been guaranteed.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
wherein: the device comprises a base 1, a base inner flow passage 101, a separating membrane 2, a supporting part 3, a compression cavity 301, a supporting part inner flow passage 302, a first pair of synchronous resonance cantilever beams 4, a second pair of synchronous resonance cantilever beams 5, a coupling beam structure 401, a vibration pickup beam structure 402, a detection beam structure 403, a detection Liang Naliu channel 40301, a sensitive cavity 6 and a sealing gas 7;
FIG. 2 is a cross-sectional view of a test beam of the present invention;
wherein: a supporting part 3, a supporting part inner runner 302, a detecting beam substrate inner runner 40301 and a sensitive cavity 6;
FIG. 3 is a view of a test beam structure of the present invention;
wherein: the detection beam substrate 40305, the upper insulating layer 40304, the piezoelectric excitation plate 40302 and the lower insulating layer 40303;
FIG. 4 is a vibration pickup beam structure of the present invention;
wherein: vibration pickup base 40204, upper insulating layer 40203, piezoelectric vibration pickup sheet 40201, lower insulating layer 40202;
FIG. 5 is a top view of the present invention;
FIG. 6 is a side view of the present invention;
FIG. 7 is a diagram of the operation of the present invention;
wherein: the device comprises a base 1, a base inner flow passage 101, a throttling device 8, a pressure guiding flow passage 801, a throttling orifice plate 802 and a pipeline 803;
FIG. 8 is a signal conversion principle and transmission route diagram of the present invention;
FIG. 9 is a top view of a wide range flow sensor;
fig. 10 is a bottom view of a wide range flow sensor.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments are merely for the purpose of more clearly illustrating the invention and are not intended to limit the scope of the invention.
As shown in fig. 1, includes: the base 1, the separating membrane 2, the supporting part 3, the first pair of synchronous resonance cantilever beams 4, the second pair of synchronous resonance cantilever beams 5, the sensitive cavity 6 and the sealing gas 7,
the separation membrane 2 is located between the base 1 and the supporting part 3, the base inner runner 101 and the supporting part compression cavity 301 are located at two sides of the separation membrane 2, one ends of the first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 are respectively connected with the supporting part 3, the other ends of the first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 are respectively connected with the sensitive cavity 6, the structures of the first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 are the same, and the first pair of synchronous resonance cantilever beams 4 and the second pair of synchronous resonance cantilever beams 5 form a differential structure, wherein the structures of the first pair of synchronous resonance cantilever beams 4 are: the detection beam 403 is connected with the vibration pickup beam 402 through the coupling beam 401, one end of the detection Liang Naliu channel 40301 is connected with the supporting portion inner channel 302, the other end of the detection Liang Naliu channel 40301 is connected with the sensitive cavity 6, the supporting portion inner channel 302 is also connected with the supporting portion compression cavity 301, and the supporting portion compression cavity 301, the supporting portion inner channel 302, the detection Liang Naliu channel 40301 and the sensitive cavity 6 are filled with the gas 7.
The vibration pickup beam 402 includes a vibration pickup beam substrate 40204, and a first lower insulating layer 40202, a piezoelectric vibration pickup sheet 40201 and a first upper insulating layer 40203 are sequentially disposed on an upper surface of the vibration pickup beam substrate 40204.
The detection beam 403 includes a detection beam substrate 40305, a second lower insulating layer 40303, a piezoelectric excitation plate 40302, and a second upper insulating layer 40304 are sequentially disposed on the upper surface of the detection beam substrate 40305, and a detection Liang Naliu channel 40301 is disposed in the detection beam substrate 40305.
The detection Liang Naliu channel 40301 is a multi-channel capillary parallel channel structure.
The sensitive cavity 6 is of a hollow structure, and the appearance is a sphere, a cylinder, a cube or an irregular geometric body.
The gas 7 is high-density easily-compressed gas with stable physicochemical properties.
The method for detecting the fluid flow comprises the following steps:
(1) The base of the device is fixedly connected with the throttling device, and the sealing connection of the pressure guiding flow passage and the base flow passage is ensured;
(2) Connecting a piezoelectric vibration excitation sheet of the flow sensor with a signal generator and connecting a piezoelectric vibration pickup sheet with a later signal processing circuit;
(3) Calibrating a sensor, introducing a fluid with fixed flow into a pipeline, applying sweep frequency excitation to a piezoelectric excitation sheet by using a signal generator when the fluid to be measured is in a turbulent state, multiplying the amplitudes of the detection beam and the vibration pickup beam under the condition that the excitation frequency is equal to the first-order natural frequency of the detection beam, generating synchronous resonance, obtaining the offset of the vibration pickup beam frequency by using the piezoelectric vibration pickup sheet and a post-processing circuit, and recording the offset of the vibration pickup beam frequency at the moment;
(4) Changing the fluid flow of the pipeline, carrying out repeated calibration, and determining the coefficient K to be calibrated of the sensor;
(5) When the fluid to be measured passes through the throttling device and is in a turbulent flow state, sweep frequency excitation is applied to the detection beam, and after synchronous resonance phenomenon occurs, the frequency offset delta omega of the two pairs of synchronous resonance cantilever beams is recorded respectively 12 、△ω 22 The measured fluid flow is:
wherein Q is the flow of the fluid to be measured, K is the calibration coefficient, beta is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression cavity, T is the Kelvin temperature of the gas in the compression cavity, R is the gas proportionality constant, ρ Fluid to be measured Omega for measured fluid density 12 For the initial natural frequency of the first pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 12 To measure the shift in resonant frequency, ω, of the first pair of synchronous resonant cantilevers Liang Shezhen 22 For the initial natural frequency of the second pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 22 To measure the shift in the resonant frequency of the second pair of synchronous resonant cantilevers Liang Shezhen.
The following further describes the effects of the invention by analyzing the structural characteristics and the detection method principle of the invention.
The base inner flow channel 101 and the compression chamber 301 can be integrally formed by assembling the base 1 and the supporting part 3, so that smooth connection between the base inner flow channel 101 and the compression chamber 301 is ensured. The smooth connection of the base inner flow channel 101 and the compression cavity 301 prevents the separation membrane 2 from generating external force due to asymmetric structure when the separation membrane 2 is acted by fluid, and the separation membrane 2 is only acted by the fluid and the sealing gas 7, thereby ensuring the accuracy of fluid flow detection.
The compression cavity 301 is connected with the sensitive cavity 6 through the supporting part inner flow passage 302 and the detection Liang Naliu passage 40301, so that the physical properties of the gas 7 in the sealing cavity formed by the compression cavity 301, the supporting part inner flow passage 302, the detection Liang Naliu passage 40301 and the sensitive cavity 6 are the same everywhere.
Further, detection Liang Naliu channel 40301 improves the rapidity of the system response while ensuring the system stability. When the measured fluid acts on the separation membrane 2 through the base inner flow channel 101, the sealing gas 7 flows to the sensitive cavity 6 through the support inner flow channel 302 and the detection Liang Naliu flow channel 40301 due to uneven pressure, wherein the multi-flow channel structure 40301 can enable the system to reach a stable state quickly, the response speed of the system is improved, when the piezoelectric excitation sheet 40302 is excited by the sweep frequency to generate resonance, the backflow phenomenon of the sealing gas 7 in the sensitive cavity 6 is avoided due to the fact that the pressure drop of the capillary channel 40301 is large, and the stability of the system during detection of the sensor can be improved.
The insulating layers are arranged on the upper layer and the lower layer of the piezoelectric vibration excitation sheet 40302 and the piezoelectric vibration pickup sheet 40201, so that the influence caused by environmental factors can be reduced, and the application range of the flow sensor is enlarged.
The sensitive cavity 6 is of a spherical hollow structure, the wall thickness value of the sensitive cavity depends on the material characteristics and the maximum static pressure of the measured flow, and compared with other sealed cavities, the spherical sensitive cavity 6 is larger in volume and larger in ultimate bearing capacity. However, other shapes of sensing cavities (e.g., cylinders, cubes, irregular geometries, etc.) may be used in addition to spherical sensing cavities; in this embodiment, a spherical sensitive cavity 6 with larger unit mass and volume and larger bearing is selected for detection.
The high-density and easily-compressed gas can improve the resolution of the sensor, and when the external force causes the pressure change of the sealing gas 7, the high-density and easily-compressed gas has more obvious density change, and the stability of the sensor operation is ensured due to stable physicochemical properties.
When the mass of the sensitive cavity is changed, the resonance frequency of the detection beam is shifted, the resonance frequency shift is amplified through the synchronous resonance structure, and the resonance frequency change of the detection beam is delta omega 1 The resonance frequency variation of the vibration pickup beam is delta omega 2 Then there is Deltaomega 2 ＝β△ω 1 Beta is the frequency amplification of the synchronous resonant cantilever.
As shown in fig. 8, the flow sensor is matched with a throttling device, the base 1 is fixedly connected with the throttling device 8, and the pressure guiding flow passage 801 is hermetically connected with the base inner flow passage 101.
When fluid flows through the orifice plate 802, the hydrostatic pressure of the front and back of the orifice plate 802 changes, the front and back of the orifice plate 802 acts on the separation membrane 2 through the pressure guiding flow channel 801 and the base inner flow channel 101, and the hydrostatic pressure of the front and back of the orifice plate 802 is equal to the pressure acting on the separation membrane.
The first pair of synchronous resonance cantilever beams is taken as an example for illustration, the two pairs of synchronous resonance cantilever beams of the flow sensor have the same working principle, and all structural parameters are consistent.
The compression cavity 301, the supporting part inner flow passage 302, the detection Liang Naliu passage 40301 and the sensitive cavity 6 are closed spaces before the action, and the sealing gas 7 is filled in the closed spaces, so that the pressure delta P is a certain initial pressure delta P 0 ；
When the measured fluid acts on the separation membrane 2, the separation membrane 2 is deformed due to unbalanced force, the volume of the sealing gas 7 is also changed 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 balance state, and the hydrostatic pressure and the initial pressure of the sealing gas exist:
P 1 ＝P 0 +△P 1
wherein P is 1 To act on the hydrostatic pressure of the separation membrane, P 0 To seal the gas initial pressure, ΔP 1 Is the amount of change in seal gas pressure after the fluid is applied.
According to the ideal gas law, the pressure of the sealing gas 7 in the compression cavity is changed due to the change of the volume, so that the density of the sealing gas 7 in the sensitive cavity 6 is changed, and the change amount of the pressure and the change amount of the density of the sealing gas 7 in the compression cavity 301 are as follows:
wherein Deltaρ 1 Delta P is the variation of the gas density in the compression chamber for the first pair of synchronous resonant cantilever beams 1 The method is characterized in that the method is used for changing the pressure of gas in a compression cavity of a first pair of synchronous resonance cantilever beams after the fluid acts, M is the molar mass of the gas in the compression cavity, T is the Kelvin temperature of the gas in the compression cavity, and R is the proportionality constant of the gas.
When the sealing gas 7 is in an equilibrium state after the action, the sealing gas pressure and density in the sensitive cavity 6 are the same as those in the compression cavity 301, the sensitive cavity 6 can be regarded as a rigid structure, and the volume is not changed, so that the mass change of the sealing gas 7 in the sensitive cavity 6 and the density of the sealing gas 7 in the sensitive cavity 6 are linearly changed, the sensitive cavity 6 and the detection beam 403 are rigidly connected, and the relationship between the mass change amount and the density change amount of the sealing gas 7 in the sensitive cavity 6 is as follows:
wherein r is the radius of the sensitive cavity, deltam 1 For the mass change quantity of sealing gas in a first pair of synchronous resonance cantilever sensitive cavities after the action, deltaρ 1 The amount of variation in gas density is sealed for the first pair of synchronous resonant cantilevers.
The presence of a certain natural frequency of the detection beam 403 before the fluid is applied can be determined by experiment or calculation. In this example, as shown in fig. 8, the synchronous resonance beams connected to the front pressure guiding flow channel 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 detecting beams 403 is ω 11 The first order natural frequency of the vibration pickup beam 402 is ω 12 The ratio of the natural frequency of the detection beam 403 to the natural frequency of the vibration pickup beam 402 is 1: beta, i.e. omega 12 ＝βω 11 。
When the measured fluid acts on the separation membrane 2, the physical properties of the gas in the compression cavity 301 change, and when the sealing gas 7 in the compression cavity 301 is stable, namely, the physical properties of the sealing gas 7 are the same everywhere, the mass of the sealing gas 7 in the sensitive cavity 6 changes, and the natural frequency of the detection beam 403 changes due to the fact that the sensitive cavity 6 is fixedly connected with the detection beam 403, 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. At the first-order natural frequency of the detection beam 403, the amplitudes of the detection beam 403 and the vibration pickup beam 402 are increased, and the vibration pickup beam 402 is multiplied in frequency, that is, a synchronous resonance phenomenon occurs, and the resonance frequency ω 'of the vibration pickup beam 402 after the fluid acts' 12 Resonant frequency ω 'with detection beam 403' 11 Omega 'is still present' 12 ＝βω' 11 。
The frequency offset delta omega of the vibration pickup beam 402 can be obtained through the acquisition of the piezoelectric vibration pickup piece 40201 signals and the processing of a later-stage circuit 12 And the offset Deltaomega of the frequency of the vibration pickup beam 402 12 With the mass of sealing gas 7 in the sensitive chamber 6The variation Δm is present:
△ω 12 ＝β△ω 11
wherein Deltam 1 K for the mass change of the sealing gas in the sensitive cavity of the first pair of synchronous resonant cantilevers Liang Gulian 1 Omega is a parameter related to the material and dimensions of a synchronous resonant cantilever structure 11 For the natural frequency of the first pair of synchronous resonance cantilever beams before the action, deltaomega 11 For the offset of the natural frequency of the first pair of synchronous resonance cantilever beams after the action, delta omega 12 Is the shift in natural frequency of the beam of the first pair of synchronous resonant cantilevers Liang Shezhen after actuation.
The second pair of synchronous resonance cantilever structures are used for detecting the static pressure of the fluid to be detected after throttling, and similarly, when the fluid flowing through the throttling orifice plate acts on the separation membranes of the second pair of synchronous resonance cantilever structures, the deflection of the natural frequency of the vibration pickup beam can be detected through the second pair of synchronous resonance cantilever structures, so that the static pressure P of the fluid after throttling is obtained 2 。
The measured fluid pressure difference before and after throttling is as follows:
△P throttling ＝P 1 -P 2
Wherein DeltaP Throttling To throttle the pressure difference of the fluid before and after the fluid to be measured passes through the throttling device, P 1 To hydrostatic pressure before throttling, P 2 Is the post-throttling hydrostatic pressure.
The flow sensor adopts a differential structure, the differential structure refers to that the first pair of synchronous resonance cantilever structures 4 and the second pair of synchronous resonance cantilever structures 5 have identical structural parameters, and the pressure intensity before and after throttling is detected during use, so that errors caused by environmental influence can be eliminated to a certain extent.
When the measured fluid flows through the throttling device 8, a certain relationship exists between the measured fluid flow and the fluid pressure difference before and after throttling, and the measured fluid flow can be obtained through the fluid pressure difference before and after throttling:
wherein Q is the flow of the fluid to be measured, deltaP Throttling To throttle the front-to-back fluid pressure difference ρ Fluid to be measured To be measured for fluid density, K 2 Is constant and depends on the structure of the restriction and the nature of the fluid being measured.
In this example, the parameters of the two pairs of synchronous resonant cantilevers Liang Chushi are completely consistent, so that the measured fluid flow can be measured by the offset of the natural frequencies of the two pairs of synchronous resonant cantilevers, and the offset of the measured fluid flow and the natural frequencies of the vibration picking beams exists:
wherein Q is the flow of the fluid to be measured, beta 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 cavity, T is the Kelvin temperature of the gas in the compression cavity, R is the gas proportionality constant, and ρ Fluid to be measured Omega for measured fluid density 12 For the initial natural frequency of the first pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 12 To measure the shift in resonant frequency, ω, of the first pair of synchronous resonant cantilevers Liang Shezhen 22 For the initial natural frequency of the second pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 22 To measure the shift in the resonant frequency of the second pair of synchronous resonant cantilevers Liang Shezhen.
The invention utilizes the advantage of high sensitivity of the synchronous resonance cantilever beam, changes the offset of the cantilever beam frequency caused by the mass change from delta omega to beta delta omega, improves the resolution of hydrostatic pressure detection, combines the characteristic of variable initial gas pressure of a differential structure and a closed compression cavity, and can improve the detection precision and the detection range.
In addition, as shown in fig. 9 and 10, the measuring range of the flow sensor can be increased by using a plurality of pairs of synchronous resonance cantilevers in parallel.
The volume of the compression chamber 301 is determined by design parameters, when the fluid acts on the separation membrane 2, the separation membrane 2 deforms due to the action of the fluid to change the gas pressure, the variation of the pressure of the sealing gas 7 depends on the deformation degree of the separation membrane 2, and the deformation degree 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 different ranges of fluid flow can be realized, the gas with different initial pressures is filled into different pairs of synchronous resonance cantilever beams, and the gas with different initial pressures is connected in parallel, so that the measuring range of the sensor can be improved.
Claims (7)
1. A high-resolution differential pressure type flow sensor based on synchronous resonance is characterized in that: the separation membrane is positioned between the base and the supporting part, the flow channel in the base and the compression cavity of the supporting part are positioned at two sides of the separation membrane, one ends of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are respectively connected with the supporting part, the other ends of the first pair of synchronous resonance cantilever beams and the second pair of synchronous resonance cantilever beams are respectively connected with the sensitive cavity, 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 and the second pair of synchronous resonance cantilever beams form a differential structure, wherein the first pair of synchronous resonance cantilever beams are: the detection beam is connected with the vibration pickup beam through the coupling beam, one end of the detection Liang Naliu channel is connected with the inner flow channel of the supporting part, the other end of the detection Liang Naliu channel is connected with the sensitive cavity, the inner flow channel of the supporting part is also connected with the compression cavity of the supporting part, and the compression cavity of the supporting part, the inner flow channel of the detection beam and the sensitive cavity are filled with gas.
2. The high-resolution differential pressure type flow sensor based on synchronous resonance according to claim 1, wherein: the vibration pickup beam comprises a vibration pickup beam substrate, and a lower insulating layer I, a piezoelectric vibration pickup sheet and an upper insulating layer I are sequentially arranged on the upper surface of the vibration pickup beam substrate.
3. The high-resolution differential pressure type flow sensor based on synchronous resonance according to claim 1, wherein: the detection beam comprises a detection beam substrate, wherein a second lower insulating layer, a piezoelectric excitation sheet and a second upper insulating layer are sequentially arranged on the upper surface of the detection beam substrate, and a detection beam inner runner is arranged in the detection beam substrate.
4. A high resolution differential pressure type flow sensor based on synchronous resonance according to claim 3, wherein: the inner runner of the detection beam is of a multi-runner capillary parallel channel structure.
5. The high-resolution differential pressure type flow sensor based on synchronous resonance according to claim 1, wherein: the sensitive cavity is of a hollow structure, and the appearance is a sphere, a cylinder, a cube or an irregular geometric body.
6. The high-resolution differential pressure type flow sensor based on synchronous resonance according to claim 1, wherein: the gas is high-density gas which is easy to compress and has stable physicochemical properties.
7. A method for detecting a fluid flow rate using a synchronous resonance-based high-resolution differential pressure type flow sensor according to claim 1, characterized by: comprises the following steps:
(1) Fixedly connecting the base with the throttling device, and ensuring that the pressure guiding flow channel is in sealing connection with the base flow channel;
(2) Connecting a piezoelectric vibration excitation sheet of the flow sensor with a signal generator and connecting a piezoelectric vibration pickup sheet with a later signal processing circuit;
(3) Calibrating a sensor, introducing a fluid with fixed flow into a pipeline, applying sweep frequency excitation to a piezoelectric excitation sheet by using a signal generator when the fluid to be measured is in a turbulent state, multiplying the amplitudes of the detection beam and the vibration pickup beam under the condition that the excitation frequency is equal to the first-order natural frequency of the detection beam, generating synchronous resonance, obtaining the offset of the vibration pickup beam frequency by using the piezoelectric vibration pickup sheet and a post-processing circuit, and recording the offset of the vibration pickup beam frequency at the moment;
(4) Changing the fluid flow of the pipeline, carrying out repeated calibration, and determining the coefficient K to be calibrated of the sensor;
(5) When the fluid to be measured passes through the throttling device and is in a turbulent flow state, sweep frequency excitation is applied to the detection beam, and after synchronous resonance phenomenon occurs, the frequency offset delta omega of the two pairs of synchronous resonance cantilever beams is recorded respectively 12 、△ω 22 The measured fluid flow is:
wherein Q is the flow of the fluid to be measured, K is the calibration coefficient, beta is the frequency amplification factor of the synchronous resonance cantilever beam, M is the molar mass of the gas in the compression cavity, T is the Kelvin temperature of the gas in the compression cavity, R is the gas proportionality constant, ρ Fluid to be measured Omega for measured fluid density 12 For the initial natural frequency of the first pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 12 To measure the shift in resonant frequency, ω, of the first pair of synchronous resonant cantilevers Liang Shezhen 22 For the initial natural frequency of the second pair of synchronous resonant cantilevers Liang Shezhen beams, Δω 22 To measure the shift in the resonant frequency of the second pair of synchronous resonant cantilevers Liang Shezhen.
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| CN112546368B (en) * | 2020-11-30 | 2022-12-23 | 深圳市科曼医疗设备有限公司 | Differential pressure type flow sensor and breathing machine |
| CN113340986B (en) * | 2021-06-16 | 2024-05-03 | 吉林大学 | High-resolution sensor and method for collaborative regulation and control of parameter excitation and synchronous resonance |
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