CN110132364A - Vortex street cross correlation flowmeter based on Miniature Transient pressure sensor - Google Patents

Vortex street cross correlation flowmeter based on Miniature Transient pressure sensor Download PDF

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CN110132364A
CN110132364A CN201910356127.XA CN201910356127A CN110132364A CN 110132364 A CN110132364 A CN 110132364A CN 201910356127 A CN201910356127 A CN 201910356127A CN 110132364 A CN110132364 A CN 110132364A
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pressure
transient
guiding pipe
vortex
miniature
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CN110132364B (en
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王超
张琳
丁红兵
李金霞
李潇亮
孙宏军
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Tianjin University
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Tianjin University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01F1/05—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
    • G01F1/20—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 detection of dynamic effects of the flow
    • G01F1/32—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 detection of dynamic effects of the flow using swirl flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01F1/05—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
    • G01F1/20—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 detection of dynamic effects of the flow
    • G01F1/32—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 detection of dynamic effects of the flow using swirl flowmeters
    • G01F1/325—Means for detecting quantities used as proxy variables for swirl

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

The present invention relates to a kind of vortex street cross correlation flowmeters based on Miniature Transient pressure sensor, using Miniature Transient sensor as measuring cell, transient pressure sensor includes probe and pick-up amplifier, wherein probe includes sensing element and pressure guiding pipe, sensing element is located at impulse pipe end, and pressure guiding pipe is connected with measurement pipeline；Of length no more than pipe thickness of pressure guiding pipe and as small as possible, impulse pipe diameter are consistent with probe impulse bore dia, guarantee that pressure guiding pipe chamber is sufficiently small with this；The acquisition that whirlpool causes surge pressure signal, wavelength of the two sensors distance l less than a vortex signal are carried out using two identical transient pressure sensors；The vortex signal acquired at two transient pressure sensors is handled using cross-correlation method, obtains vortex street convection velocity, it is in a linear relationship between convection velocity and speed of incoming flow, speed of incoming flow is obtained after demarcating, and then obtain average flow rate measured value.

Description

Vortex street cross correlation flowmeter based on Miniature Transient pressure sensor
Technical field
The present invention, which relates to, belongs to field of flow measurement, is related to a kind of vortex street cross correlation flowmeter.
Background technique
Karman vortex street is phenomenon important in hydrodynamics, and when fluid flows through bluff body, bluff body two sides replace at frequency f Vortex Shedding occurs, and forms vortex street in wake flow, the measurement of flow can be realized by measuring vortex-shedding frequency.Vortex street is wide It is general to be present in the industrial circles such as chemical industry, space flight, petroleum, the accurate measurement of vortex street flow field flow is realized, for industrial Process control and production safety important in inhibiting.
The method measured for fluid flow in vortex street flow field is many kinds of, such as conducting probe, optical fiber probe, piezoelectricity Sensor etc..Probe class sensor, method is simple, it is cheap but due to its invade flow field measure, stream field generate disturbance Its measurement accuracy substantially reduces, and is gradually substituted in recent years.Piezoelectric transducer also belongs to intrusive measurement, and supports Anti-vibration interference signal ability is poor, so that flux of vortex street measurement has distortion；Signal is only obtained in signal acquisition Frequency information, to true flow field fluctuation information almost without embodiment, and in vortex field phenomena such as Vortex Shedding, diverging, separation The dynamic fluctuation of pressure in flow field will all be caused, the variation of internal flow conditions plays important work for improving measurement accuracy With.In addition, current measurement means are frequently present of the lesser problem of range ratio in small-bore vortex street flow field survey, cause to measure Precision is lower, and measurement range is relatively narrow, and practical value reduces.
Summary of the invention
The object of the present invention is to provide a kind of vortex street cross correlation flowmeter based on Miniature Transient pressure sensor, Ke Yishi Small-bore wide range measure under the conditions of existing High Speed Flow Field.Technical solution is as follows:
A kind of vortex street cross correlation flowmeter based on Miniature Transient pressure sensor, using Miniature Transient sensor as measurement Element, transient pressure sensor includes probe and pick-up amplifier, wherein probe includes sensing element and pressure guiding pipe, sensing element Positioned at impulse pipe end, pressure guiding pipe is connected with measurement pipeline；Of length no more than pipe thickness of pressure guiding pipe and as small as possible, impulse Pipe diameter is consistent with probe impulse bore dia, guarantees that pressure guiding pipe chamber is sufficiently small with this；Using two identical transient state pressures Force snesor carries out the acquisition that whirlpool causes surge pressure signal, and two sensors distance l pacifies respectively less than the wavelength of a vortex signal At the 0.2D and 1.0D apart from bluff body fluoran stream surface, wherein D is internal diameter of the pipeline, and it is preferable that signal quality is fixed in radial position 45 ° of oblique upper position；The vortex signal acquired at two transient pressure sensors is handled using cross-correlation method, is obtained Vortex street convection velocity, it is in a linear relationship between convection velocity and speed of incoming flow, speed of incoming flow is obtained after demarcating, and then put down Equal flow measurements.
The measurement range of usual DN15 piezoelectric vortex flowmeter is 13~25m3/ h, range ratio 2:1.Of the invention has Benefit as a result, by design the transient pressure sensor with miniature impulse system, improve small-bore high-speed gas phase medium The easy problem of dtmf distortion DTMF of pressure in measurement, it is ensured that transient pressure measurement accuracy and cross-correlation calculation precision.Based on Miniature Transient pressure Linear measurement range can be expanded to 8~25m by the vortex street cross correlation flowmeter of force snesor3/ h, while guaranteeing that measurement is uncertain Degree effectively reduces measurement lower limit, improves range ratio within ± 2%.Meanwhile transient pressure sensor bulk is small, and Flush-mounted in experiment measuring section tube wall, avoids intrusive detection device and disturbing influence is caused for flow field and has good antivibration Performance ensure that measurement result authenticity.
Detailed description of the invention
Fig. 1 transient pressure sensor structure
Wherein: 1- probe, 1-a pressure guiding pipe, 1-b sensing element；The front end 2- lead；3- pick-up amplifier；The rear end 4- lead
Its miniature impulse system of Fig. 2 transient pressure sensor
Wherein: 5- measures pipeline；6- washer；7-M5 screw thread；8- nut
The installation site of Fig. 3 transient pressure sensor
Wherein: 9- bluff body
Vortex street convection velocity and convection coefficient calibration result in Fig. 4 single phase gas medium
(experiment condition: pressure 300kPa in pipeline；Medium is air, and range of flow is 8~25m3/h。)
Vortex street convection velocity and convection coefficient calibration result under Fig. 5 moist conditions
(experiment condition: pipeline pressure 300kPa, gas phase media are air, flow 17m3/h；Liquid phase medium is water, stream Amount range is 1.64~5.10mL/s, and liquid phase loading capacity is 0~0.35)
Specific embodiment
The present invention provides one kind flux of vortex street measuring device suitable for small-bore pipeline.The device can meet high frequency, height Whole frequency range measurement in fast gas phase vortex street flow field, and expand flux of vortex street characteristic curve range.The specific present invention passes through Following device and technical method are realized:
A kind of small-bore wide-range vortex street cross correlation flowmeter based on Miniature Transient pressure sensor is suitable for high velocity stream The flow measurement of field condition lower small mouth diameter pipeline is carried out using Miniature Transient sensor as measuring cell based on Cross-Correlation Theory Tachometric survey.Transient pressure sensor mainly includes probe 1, front end lead 2, pick-up amplifier 3, rear end lead 4.Wherein pop one's head in It include sensing element 1-a and pressure guiding pipe 1-b in 1, sensing element 1-a is located at the end pressure guiding pipe 1-b, and pressure guiding pipe 1-b passes through nut 8 It is connected with measurement pipeline 5, pick-up amplifier 3 is accessed by front end lead 2 afterwards, exports signal through rear end lead 4.
For the frequency response for ensuring transient pressure sensor, transient pressure measurement under the conditions of small-bore high gas velocity is improved Precision, it is preferred that
(1) pressure guiding pipe 1-b its length L is no more than pipe thickness and as small as possible until close to 0, and diameter d draws with probe Pressure bore dia is consistent, and guarantees that its sufficiently small volume of pressure guiding pipe 1-b chamber is negligible with this.
(2) sensing element 1-a selects polysilicon, and small volume is approximately 0.
(3) two identical transient pressure sensors As are used1、B1The acquisition of progress whirlpool cause surge pressure signal, two Sensor distance l less than the wavelength of a vortex signal, be respectively arranged in apart from bluff body 0.2D and 1.0D (wherein D be pipeline in Diameter) at, radial position is installed on 45 ° of preferable oblique upper of signal quality position.
(4) by A1、B1Place's strongest vortex signal of correlation is handled using cross-correlation method, obtains vortex street to flow velocity Degree, it is in a linear relationship between convection velocity and speed of incoming flow, speed of incoming flow is obtained after disposably demarcating, and then obtain mean flow Measurement.
It is had the following characteristics that compared with existing measuring technique using flux of vortex street measuring device of the invention
(1) it by the transient pressure sensor with miniature impulse system of design, improves small-bore high-speed gas phase and is situated between The easy problem of dtmf distortion DTMF of pressure in matter measurement, it is ensured that transient pressure measurement accuracy and cross-correlation calculation precision.
(2) usually the measurement range of the small-bore piezoelectric vortex flowmeter of DN15 is 13~25m3/ h, range ratio 2:1. Linear measurement range can be expanded to 8~25m by the vortex street cross correlation flowmeter based on Miniature Transient pressure sensor3/ h, simultaneously Guarantee that uncertainty of measurement within ± 2%, effectively reduces measurement lower limit, improves range ratio.
(3) it ensures the frequency response of transient pressure sensor, improves transient pressure under the conditions of small-bore high gas velocity Measurement accuracy is, it can be achieved that pressure measurement errors ensure that transient pressure measurement standard less than 10% within the scope of 760~2230Hz of frequency True property.Measuring pressure of sensor range is 100~400kPa (absolute pressure), accuracy 0.25%FS, resolution ratio 0.02%.
(4) simultaneously, transient pressure sensor bulk is small, and flush-mounted in experiment measuring section tube wall, avoids intrusive inspection It surveys device to cause disturbing influence for flow field and have good resistance to shock, ensure that measurement result authenticity.
In order to further appreciate that feature of the invention, technological means and specific purposes achieved, function, tie below Closing attached drawing, detailed description of the preferred embodiments.
Vortex street cross correlation flowmeter of the invention by with lower sensor (Fig. 1 is shown in structural representation) and measurement method realization, The polysilicon that transient pressure sensor sensing element selects volume very small, in the DN15 developmental tube that pipe thickness is 8.5mm Duan Zhong designs pressure guiding pipe (see Fig. 2) length L=8.5mm, impulse pipe diameter d=1.5mm, flush-mounted in experiment measuring section tube wall, no Invade flow field.Transient pressure sensors A1、B1It is respectively arranged in apart from sounding body 0.2D and 1.0D (wherein D is internal diameter of the pipeline) tiltedly At 45 ° of top, specific installation site is as shown in Figure 3.
Measurement method is as follows, and fluid average flow rate Q is represented by
Wherein, fluid speed of incoming flow vlIt can be obtained by vortex convection speed.In certain speed range, convection velocity vcWith speed Spend vlRatio be a constant k, i.e.,
Wherein, k is convection coefficient.Average convection velocities can be estimated as follows
Wherein, spacing of the l between two sensors, τ0When being traveled to needed for downstream sensor for whirlpool as upstream sensor Between, referred to as transition time.Based on Cross-Correlation Theory, transition time τ0Equal to upstream and downstream Pressure Fluctuation Signal maximum cross-correlation coefficient Corresponding delay time, wherein A1、B1Related coefficient is between place's signal
Real system is usually digital display circuit, and related coefficient discrete expression is
N is sampled point, and τ is delay time, fsFor sample frequency.
To guarantee convection velocity vcEstimated accuracy need to accurately obtain transition time τ0, then sensing system should have sufficiently high Sample frequency and the time of integration, wherein sample frequency fsIt needs to meet
vcmaxFor maximum convection velocity, δ is maximum relative error.
Time of integration T needs to meet
T≥10τ0max\*MERGEFORMAT (7)
To further illustrate, experimental verification has been carried out.Pipeline pressure is 300kPa in experiment, and test medium is air, stream Amount range is 8~25m3/h。
According to above content, to obtain vortex street convection velocity in correlation speed measurement, it is necessary first to determine sample frequency fsAnd product T between timesharing.When maximum vortex street convection velocity is according to vcmax=37.7m/s (flow 20m3/ h conversion), time measurement is maximum opposite Error takes δ=± 5%, when sensor spacing l is 0.8D=0.012m, obtains f by formula 6s=30.7kHz, it is final to determine sampling frequency Rate is 60kHz；Minimum vortex street convection velocity is according to vcmin(flow is according to 10m by=14.1m/s3/ h conversion), getted over by 7 maximum of formula Time is 7.07 × 10-4S, therefore the time of integration should be greater than being equal to 7.07 × 10-3S, i.e. integral points are at least 700, finally really Fixed experiment integral points are 800.To guarantee result accuracy, finally using the average value of 500 calculated result as related coefficient.
The experimental results showed that vortex street cross correlation flowmeter of the present invention is 8~25m in gas phase flow rate3Within the scope of/h, gas is obtained K=0.866 in phase vortex street field, uncertainty is ± 2%, as a result such as Fig. 4.
Furthermore by experimental verification, the present invention is equally applicable in gas-liquid mist flow vertically downward.Experimental channel pressure 300kPa, gas phase media are air, flow 17m3/ h, liquid phase medium are water, and range of flow is 1.64~5.10mL/s, liquid phase Loading capacity is 0~0.35.The experimental results showed that k=0.6, uncertainty is ± 5%, as a result such as Fig. 5.
The present invention improves volatile in small-bore high-speed gas phase pressure medium measurement by design micro pressure sensor True problem, it is ensured that transient pressure measurement accuracy and cross-correlation calculation precision.Measurement lower limit is effectively reduced, range ratio is mentioned Height arrives 3:1, in 8~25m3Gas phase flow rate measurement accuracy ± 2%, k=0.866 is realized within the scope of/h, improves flow measurement The scope of application.

Claims (1)

1. a kind of vortex street cross correlation flowmeter based on Miniature Transient pressure sensor, using Miniature Transient sensor as measurement member Part, transient pressure sensor includes probe and pick-up amplifier, wherein probe includes sensing element and pressure guiding pipe, sensing element position In impulse pipe end, pressure guiding pipe is connected with measurement pipeline；Of length no more than pipe thickness of pressure guiding pipe and as small as possible, pressure guiding pipe Diameter is consistent with probe impulse bore dia, guarantees that pressure guiding pipe chamber is sufficiently small with this；Using two identical transient pressures Sensor carries out the acquisition that whirlpool causes surge pressure signal, and two sensors distance l is installed respectively less than the wavelength of a vortex signal At the 0.2D and 1.0D apart from bluff body fluoran stream surface, wherein D is internal diameter of the pipeline, and it is preferably oblique that signal quality is fixed in radial position 45 ° of top position；The vortex signal acquired at two transient pressure sensors is handled using cross-correlation method, obtains whirlpool Street convection velocity, it is in a linear relationship between convection velocity and speed of incoming flow, speed of incoming flow is obtained after demarcating, and then be averaged Flow measurements.
CN201910356127.XA 2019-04-29 2019-04-29 Vortex street cross-correlation flowmeter based on miniature transient pressure sensor Active CN110132364B (en)

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CN111649789A (en) * 2020-04-16 2020-09-11 天津大学 Wet air flow measuring method integrating vortex street frequency and convection characteristic

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CN111649789A (en) * 2020-04-16 2020-09-11 天津大学 Wet air flow measuring method integrating vortex street frequency and convection characteristic

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