CN108801378B - Civil ultrasonic gas meter and flow detection method of integrated transducer - Google Patents
Civil ultrasonic gas meter and flow detection method of integrated transducer Download PDFInfo
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- CN108801378B CN108801378B CN201810575787.2A CN201810575787A CN108801378B CN 108801378 B CN108801378 B CN 108801378B CN 201810575787 A CN201810575787 A CN 201810575787A CN 108801378 B CN108801378 B CN 108801378B
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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
- G01F1/66—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 measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
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- G—PHYSICS
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
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Abstract
The invention discloses a civil ultrasonic gas meter and a flow detection method of an integrated transducer. The gas meter is composed of data processing and control communication, time measurement, ultrasonic transmitting/receiving switching, ultrasonic excitation, ultrasonic receiving and transducer integrated structural units. The integrated structure of the n-shaped measuring tube integrated transducer overcomes the defects of short ultrasonic propagation path and installation angle theta not equal to 900A defect; the ultrasonic wave propagation speed is corrected according to the measured temperature, and the time receiving window is compressed, so that the anti-interference capacity and the precision of the ultrasonic flowmeter are improved; the acoustic impedance of the acoustic matching layer material is between the piezoelectric ceramic and the gas medium, and the thickness of the matching layer is 1/4 of the ultrasonic wave wavelength, so that the ultrasonic wave refraction propagation attenuation on different medium interfaces is reduced, and the precision of the ultrasonic flowmeter is improved; the time difference data is beneficial to eliminating the influence of complexity and changeability of a gas flow field on the precision by means of a data cleaning technology.
Description
Technical Field
The invention belongs to the technical field of gas flow detection; in particular to a civil ultrasonic gas meter with an integrated structure of an n-shaped measuring tube and an integrated transducer and a flow detection method.
Background
In 2020, the conservative estimate of energy demand in China is 50 hundred million tons of standard coal. Satisfying the above requirements, the energy supply side will face a great pressure whether increasing domestic energy supply or utilizing foreign resources. The pollution generated by the coal serving as a main energy structure in China far exceeds the environmental capacity, and the environmental bearing capacity faces severe challenges; therefore, adjusting the dominant unreasonable energy structure of coal is not slow. The method of replacing coal with gas is a powerful measure for remedying environmental pollution under the prior art.
Natural gas is a major concern as a clean energy source, and the consumption is continuously increasing. In 2001, the domestic consumption of natural gas is only 274 hundred million m3(ii) a In 2012, the pressure increased to 1471 hundred million m3The number of grade cities using natural gas is > 210, and 2 hundred million Chinese people receive . By 12 months in 2012, the quantity of the civil gas meters is more than 2075 thousands; the output of the gas meter is 1000 thousands/year, and the gas meter is exported 250 thousands/year; the domestic civil gas meter enterprises are about 100 families, and the leading product is the membrane gas meter. The membrane type gas meter has a history of hundreds of years, and the membrane type gas meter architecture invented by James and Bogdas in the United kingdom in 1833 continues to the present; the mechanical membrane type gas meter is simple in principle, low in price (90-140 yuan), and 1.5-grade in precision; however, the price of the digital membrane gas meter is several times that of the base meter, and the price is very high (450-550 yuan).
The ultrasonic gas flowmeter has high precision, small pressure loss, simple and convenient operation and maintenance and high reliability without moving parts; a third gas legal measuring instrument which endows trade settlement qualification is formed after the orifice plate flowmeter and the turbine flowmeter; for example, 13 sets of ultrasonic natural gas flow meters are arranged on the longest global China West gas east delivery pipeline. Nowadays, ultrasonic flow meter manufacturers in developed countries occupy the leading technical position, and famous enterprises include us Controlotron, germany Krohne, british Daniel, netherlands Instromet and the like. The standards followed by the industry are: in 1998, ISO published ISO/TR12765 "measuring fluid flow in closed pipes with ultrasonic flow meters by time-propagation method"; the national standard GB/T18604-2001 uses a gas ultrasonic flowmeter to measure the natural gas flow, and the industry standard domestic ultrasonic gas meter 2012 and 2016T-JB. The history of ultrasonic flow measurement in developed countries is long, which can be traced back to 1931 o.rutten german patent; the domestic ultrasonic gas meters in the countries are put into operation in batches for many years, and get unusual achievement. The research of the ultrasonic flowmeter in China starts in sixty years, the precision and the reliability of the domestic ultrasonic flowmeter and PK in developed countries have certain differences, and the imported ultrasonic flowmeter fills the domestic market. Although units such as Zhejiang Wexing instrument system integration limited successively release ultrasonic gas meters, type approval certificates are also obtained; unfortunately, the market acceptance is limited, and commercialization of the product has a long path to go.
The principle of ultrasonic flow measurement is as follows: when the ultrasonic wave propagates in the fluid, the ultrasonic wave signal is modulated by the fluid; therefore, the flow velocity and flow rate of the fluid can be extracted by detecting the modulated ultrasonic signal. The ultrasonic flow measurement methods include a propagation velocity difference method (time difference, phase difference, and frequency difference), a beam offset method, a doppler method, a correlation method, a spatial filtering method, a noise method, and the like; of which the time difference method is most commonly applied. The ultrasonic flowmeter transducer is classified according to the installation mode and is divided into an external clamping type, an insertion type and a pipe section type. The clip-on ultrasonic flowmeter is further classified into V, Z, N, W method and the like according to the probe attachment method and the ultrasonic propagation path. The time difference ultrasonic fluid flow velocity of the external clamping type V method is calculated according to the following formula
In the formula: t 1-forward flow propagation time, t 2-reverse flow propagation time; d- -tube wall diameter; theta-the angle between the ultrasonic propagation path and the pipe wall. On the basis of the domestic existing research results and process conditions, the problems of poor precision and difficulty in writing by a civil ultrasonic flowmeter are overcome through the improved design of the ultrasonic flowmeter; the method analyzes the source of errors of the civil ultrasonic flowmeter one by one from the formula cut-in of the flow rate of the ultrasonic fluid with the V-method time difference and provides a corresponding solution. Without loss of generality, the discussion is based on the typical working condition of the commercial ultrasonic flowmeter in XX.
The pipe diameter d of the household gas conveying pipe is 30mm, and the gas flow of a user is 0.025-4 m3Reynolds number 66.153-10584.531
The diameter d of the household gas pipe is 30mm, and the propagation path of the ultrasonic wave is very short; the air propagation speed c of the ultrasonic wave in the standard state is 331.4 m/s; obviously, too short a propagation path penalizes the measurement accuracy of the flow. If a section of n-shaped measuring tube with long L > D is inserted into the gas delivery pipe, and transducers are arranged at two ends of the horizontal section of the measuring tube; when the flow measurement is carried out, the L of the horizontal section of the measuring tube is equivalent to the diameter D of the tube, and the inherent defect of very short propagation path is expected to be solved.
The measurement accuracy of the external clip V, Z, N, W method is related to the transducer mounting angle θ (ultrasonic incident angle), and considering that refraction occurs at the pipe wall and fluid interface when ultrasonic is incident, θ error will cause double measurement error. If the transducers are arranged at the two ends of the horizontal section of the n-shaped measuring tube, the mounting process is simple when theta is equal to 90 degrees, the precision is ensured, and the 90-degree incidence has no refraction phenomenon; therefore, the integrated structure of the n-shaped measuring tube integrated transducer is beneficial to eliminating double measuring errors generated by the error of the installation angle theta.
The ultrasonic waves are severely attenuated and distorted when propagating in the fuel gas, and larger ultrasonic wave transmitting power is necessary, so that an ultrasonic wave receiving end can be interfered by a transmitting end and an external noise environment; usually, the ultrasonic receiving end introduces a time receiving window technology to shield interference, namely the time t of the ultrasonic transmitting end signal reaching the receiving end0And when the power is 0.6-1.5 times of the power, the receiving circuit is switched on and off. In view of the fact that the ultrasonic propagation speed is related to the temperature, the real-time temperature is collected to correct the ultrasonic propagation speed U, and the U is calculated according to the following formula
U＝U0×【1+T/273】0.5＝331.4×【1+T/273】0.5(2)
The existing mainstream is [ 0.6t ]0，1.5t0Time receive window can be compressed to [0.8t ]0，1.2t0And the anti-interference capability and the accuracy of the ultrasonic flowmeter are improved.
Acoustic impedance mismatching between the ultrasonic transducer and the gas, selecting an acoustic matching layer material with acoustic impedance between the piezoelectric ceramic and the gas medium, and taking the ultrasonic wave wavelength 1/4 as the matching layer thickness; in the integrated structure of the n-shaped measuring tube integrated transducer, the transducer belongs to a plug-in mounting side, so that the defect of external clamping type ultrasonic signal attenuation is overcome, and short plates which are inconvenient to plug-in mount and large in workload are supplemented to a certain extent; the accuracy of the ultrasonic flowmeter is improved.
The study shows that the actual time t to receive the monopulse ultrasonic wave is t ═ tTrue+ε+ζ+ω，tTrueTheoretical time from transmission to reception, epsilon circuit delay time, zeta counter time error, omega random noise error (satisfying normal distribution); from the view point of mathematical statistics, the multi-pulse measurement method can reduce epsilon, zeta and omega to tTrueThe influence further improves the precision of the ultrasonic flowmeter.
The summary of the more representative intellectual property achievements of the civil ultrasonic gas meter is as follows:
the invention discloses an ultrasonic gas meter mixed signal processing circuit (ZL201410140147.0), and provides an ultrasonic gas meter mixed signal processing circuit which adjusts the peak value of an ultrasonic signal in real time through an automatic gain fuzzy control circuit.
The invention discloses an ultrasonic flow gas chamber for an ultrasonic gas meter (ZL201310084985.6), and provides the ultrasonic flow gas chamber for the ultrasonic gas meter, which changes the traditional mounting modes such as V-shaped and X-shaped modes and forms a long-distance correlation measurement path.
The beneficial exploration provides that the automatic gain fuzzy control circuit adjusts the peak value of the ultrasonic signal in real time, but the mixed signal processing circuit is realized by an analog device, so that the reliability is poor, the complexity is overhigh, and the function is limited; a long-distance correlation type measurement path air chamber is provided, but the air chamber is complex in structure, influences the distribution of a gas flow field, has corresponding countermeasure defects, and easily leaves impurities in a cavity of the lower straight pipe section to influence the measurement accuracy. Therefore, the exploration has a certain reference value, but the achievement still has limitation; further innovative design is needed on the basis of the existing results.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a civil ultrasonic gas meter with an integrated transducer and a flow detection method.
The civil ultrasonic gas meter of the integrated transducer consists of a data processing and control communication unit, a time measuring unit, an ultrasonic transmitting/receiving switching unit, an ultrasonic excitation unit, an ultrasonic receiving unit and a transducer integrated structural unit, wherein the ultrasonic transmitting/receiving switching unit takes an ADG1234 chip as a core, the ultrasonic excitation unit comprises an insulated gate MOSFET and a step-up transformer, and the ultrasonic receiving unit comprises a pre-amplification module, a second-order band-pass filtering module and a threshold zero-crossing detection module; the data processing and control communication unit is connected with the time measuring unit and the ultrasonic transmitting/receiving switching unit, and the ultrasonic transmitting/receiving switching unit is connected with the time measuring unit, the ultrasonic exciting unit, the ultrasonic receiving unit and the transducer integrated structural unit;
the data processing and control communication unit controls the operation of the time measuring unit, reads a time difference measuring value output by the time measuring unit, generates gas flow through a data processing and control module of the data processing and control communication unit, and transmits the gas flow through a Bluetooth communication module of the data processing and control communication unit; the data processing and control communication unit controls the on and off of the analog switch of the ultrasonic transmitting/receiving switching unit, and a transmitting/receiving channel of the time measuring unit is respectively connected to the ultrasonic exciting unit and the ultrasonic receiving unit through the ultrasonic transmitting/receiving switching unit; the ultrasonic excitation unit and the ultrasonic receiving unit are respectively connected to the 1 st transmitting and receiving dual-purpose transducer and the 2 nd transmitting and receiving dual-purpose transducer of the transducer integrated structural unit through the ultrasonic transmitting/receiving switching unit, or the 2 nd transmitting and receiving dual-purpose transducer and the 1 st transmitting and receiving dual-purpose transducer.
The data processing and control communication unit comprises a data processing and control module taking an MSP430F135 chip as a core and a Bluetooth communication module of a BLE-CC41-A model, wherein MSP430F135 pins 32 and 33 are respectively connected with BLE-CC41-A pins 2 and 1; the data processing and control module cleans the time difference measurement value output by the time measurement unit, calculates the gas flow rate based on the cleaned time difference data, and gas flow obtained by integrating the gas flow and the flow, and transmits the gas flow and the gas flow through the Bluetooth communication module.
The time measuring unit takes a TDC _ GP21 chip as a core, pins 4, 21 and 28 of TDC _ GP21 are grounded, pins 14 and 29 are connected with Vcc, and R is230、C230、R240One end of which is connected with a pin 17,18，R230Is connected to the other end of the foot 20, 19, C230The other end of (A) is grounded, R240The other end of which is connected with the feet 24, 23; TDC _ GP21 pins 8, 9, 10, 11, 12 are connected to MSP430F135 pins 27, 28, 31, 29, 30 of the data processing and control module, respectively; r210、C210One end of which is connected with an ADG1234 pin 3, R of an ultrasonic wave transmitting/receiving switching unit210Is connected to the foot 5 at the other end, C210The other end of which is connected with a foot 30; r220、C220One end of which is connected with an ADG1234 pin 8, R of an ultrasonic wave transmitting/receiving switching unit220Is connected to the other end of the pin 6, C220The other end of which is connected with a foot 27; the foot 5 and the foot 30 of the TDC _ GP21 form an ultrasonic channel, and the foot 6 and the foot 27 of the TDC _ GP21 form another ultrasonic channel; r240The model of the fuel gas temperature acquisition device is a Pt1000 platinum thermal resistor, and the fuel gas temperature T is acquired.
The integrated structural unit of the energy converter comprises a 1 st transmitting and receiving dual-purpose energy converter, a 2 nd transmitting and receiving dual-purpose energy converter, a 1 st gas elbow, a 2 nd gas elbow and an n-shaped measuring tube, wherein the 1 st transmitting and receiving dual-purpose energy converter consists of a 1 st energy converter piezoelectric ceramic sensor of an LHQ200-3 type and a 1 st energy converter acoustic impedance matching layer, and the 2 nd transmitting and receiving dual-purpose energy converter consists of a 2 nd energy converter piezoelectric ceramic sensor of an LHQ200-3 type and a 2 nd energy converter acoustic impedance matching layer; the 1 st transmitting and receiving transducer and the 2 nd transmitting and receiving transducer are respectively arranged at the left end and the right end of the horizontal section of the n-shaped measuring tube; the n-shaped measuring pipe is connected into the gas conveying pipe through the 1 st gas elbow pipe and the 2 nd gas elbow pipe;
the total thickness of the acoustic impedance matching layer of the 1 st transducer is a circular sheet with the ultrasonic sound wave wavelength of 1/4 lambda, and the total thickness is 0.425mm by taking the 200KHz sound wave wavelength at 25 ℃; the 1 st transducer acoustic impedance matching layer is composed of a 1 st transducer epoxy resin colloid layer and a 1 st transducer mica sheet, and the 1 st transducer epoxy resin colloid layer tightly connects the 1 st transducer piezoelectric ceramic sensor of LHQ200-3 type with the 1 st transducer mica sheet; the 1 st transmitting and receiving dual-purpose transducer is arranged in the 1 st transducer sleeve, the 1 st transducer sleeve is positioned and fixed at the air inlet end of the n-shaped measuring tube through four screws of the 1 st transducer, and the 1 st transducer sealing washer is arranged between the 1 st transducer sleeve and the n-shaped measuring tube to ensure air tightness; the 2 nd transmitting & receiving transducer is mounted in the same way as the 1 st transmitting & receiving transducer.
The flow of the gas meter flow detection method comprises the following steps:
(1) the time measuring unit (200) collects the gas temperature T;
(2) corrected ultrasonic wave propagation speed U is 331.4X (1+ T/273)0.5；
(3) The propagation time t from the ultrasonic transmitting end to the receiving end is equal to L/U, L: the span of the n-shaped measuring tube (650) in the horizontal direction;
(4) the ultrasonic excitation unit (400) emits at the 1 st emission&Ultrasonic waves are generated at the time t with the aid of a receiving dual-purpose transducer (610), and an ultrasonic receiving unit (500) receives a window [0.8t, 1.2t ] in time]Carrying out downstream sampling for 4 times in a time period; after sampling, the ultrasonic wave transmission/reception switching unit (300) switches the ultrasonic wave excitation unit (400) and the ultrasonic wave reception unit (500) and performs reverse flow sampling in the above-described manner. Thus, for each sampling period, 4 downstream propagation times t are obtainedi cisAnd 4 counter-current propagation times tinverse of iTo obtain the 4 th measurement time difference Deltat ═ tInverse direction-tCis-trans。
After the ultrasonic excitation unit (400) generates N times of excitation signals, 4N measurement time differences are obtained in total.
(5) Data cleaning: sorting 4N deltat according to size, eliminating deltat sorted in [1, N ] and [3N +1,4N ], and storing the deltat sorted between [ N +1,3N ].
(6) For each stored Δ tjCalculating the gas flow velocity Vj＝[Δτj/τj inverseⅹτj cis]ⅹ0.5L；
The average gas flow rate for N measurement cycles is:
the average gas flow of N measurement periods is as follows: qaverage＝Vaverage×SMeasuring tube，SMeasuring tubeCross section of measuring tube
The 4 gas amounts for the N measurement cycles are: vol ═ Qaverage×4N Ts。
Compared with the background technology, the invention has the following beneficial effects: the integrated structure of the n-shaped measuring tube integrated transducer has the advantages that the horizontal section length of the measuring tube is equivalent to the tube diameter, the transducer is installed at 90 degrees, and the defects that an ultrasonic wave propagation path is short and the installation angle theta is not equal to 90 degrees are overcome; the ultrasonic wave propagation speed is corrected according to the measured temperature, and the time receiving window is compressed, so that the anti-interference capacity and the precision of the ultrasonic flowmeter are improved; the acoustic impedance of the acoustic matching layer material is between the piezoelectric ceramic and the gas medium, and the thickness of the matching layer is 1/4 of the ultrasonic wave wavelength, so that the ultrasonic wave refraction propagation attenuation on different medium interfaces is reduced, and the precision of the ultrasonic flowmeter is improved; the time difference data is beneficial to eliminating the influence of complexity and changeability of a gas flow field on the precision by means of a data cleaning technology.
Drawings
FIG. 1 is a schematic block diagram of a civil ultrasonic gas meter with an integrated transducer;
FIG. 2 is a circuit diagram of a data processing and control communication unit;
FIG. 3 is a circuit diagram of a time measurement unit;
FIG. 4(a) is a block diagram of a transducer-integrated structural unit;
FIG. 4(b) is a block diagram of the acoustic impedance matching layer of the transducer;
FIG. 4(c) is an assembly view of the transducer on an n-tube;
fig. 5 is a flow chart of flow detection of the integrated transducer ultrasonic gas meter.
Detailed Description
As shown in fig. 1 and 4, the civil ultrasonic gas meter with an integrated transducer is composed of a data processing and control communication unit 100, a time measuring unit 200, an ultrasonic transmitting/receiving switching unit 300, an ultrasonic exciting unit 400, an ultrasonic receiving unit 500 and a transducer integrated structural unit 600, wherein the ultrasonic transmitting/receiving switching unit 300 takes an ADG1234 chip as a core, the ultrasonic exciting unit 400 comprises an insulated gate MOSFET and a step-up transformer, and the ultrasonic receiving unit 500 comprises a pre-amplification module, a second-order band-pass filtering module and a threshold zero-crossing detection module; the data processing and control communication unit 100 is connected with the time measuring unit 200 and the ultrasonic wave transmitting/receiving switching unit 300, and the ultrasonic wave transmitting/receiving switching unit 300 is connected with the time measuring unit 200, the ultrasonic wave exciting unit 400, the ultrasonic wave receiving unit 500 and the transducer integrated structure unit 600;
the data processing and control communication unit 100 controls the operation of the time measuring unit 200, reads the time difference measurement value output by the time measuring unit 200, generates gas flow through a data processing and control module of the data processing and control communication unit 100, and uploads the gas flow through a Bluetooth communication module of the data processing and control communication unit 100; the data processing and control communication unit 100 controls the ultrasonic transmitting/receiving switching unit 300 to open and close the analog switch, and the transmitting/receiving channel of the time measuring unit 200 is respectively connected to the ultrasonic exciting unit 400 and the ultrasonic receiving unit 500 through the ultrasonic transmitting/receiving switching unit 300; the ultrasonic excitation unit 400 and the ultrasonic receiving unit 500 are respectively connected to the 1 st transmitting & receiving dual-purpose transducer and the 2 nd transmitting & receiving dual-purpose transducer, or the 2 nd transmitting & receiving dual-purpose transducer and the 1 st transmitting & receiving dual-purpose transducer of the transducer integrated structural unit 600 through the ultrasonic transmitting/receiving switching unit 300.
Description 1: the ultrasonic transmitting/receiving switching unit is used for performing transmitting/receiving switching of two ultrasonic channels of the time measuring unit and performing transmitting/receiving switching of a No. 1 transmitting/receiving dual-purpose transducer and a No. 2 transmitting/receiving dual-purpose transducer of the transducer integrated structural unit; the ultrasonic excitation unit amplifies and shapes the ultrasonic signal provided by the time measuring unit and drives the transmitting transducer to transmit ultrasonic waves; the ultrasonic receiving unit amplifies and conditions the ultrasonic signals received by the receiving transducer, and carries out threshold zero-crossing processing on the conditioning signals.
As shown in fig. 2, the data processing and control communication unit 100 comprises a data processing and control module 110 with MSP430F135 chip as core, a bluetooth communication module 120 of type BLE-CC41-a, with MSP430F135 pins 32, 33 connected to BLE-CC41-a pins 2, 1, respectively; the data processing and control module 110 cleans the time difference measurement value output by the time measurement unit 200, calculates the gas flow rate based on the cleaned time difference data, and calculates the gas flow rate and the gas quantity obtained by integrating the gas flow rate and the gas quantity, and uploads the gas flow rate and the gas quantity through the bluetooth communication module 120.
As shown in FIG. 3, the time measurement unit 200 uses a TDC _ GP21 chip as a core, TDC _ GP21 pins 4, 21 and 28 are grounded, pins 14 and 29 are connected to Vcc, and R is connected to Vcc230、C230、R240Is connected to the legs 17, 18, R230Is connected to the other end of the foot 20, 19, C230The other end of (A) is grounded, R240The other end of which is connected with the feet 24, 23; TDC _ GP21 pins 8, 9, 10, 11, 12 are connected to MSP430F135 pins 27, 28, 31, 29, 30 of data processing and control module 110, respectively; r210、C210One end of which is connected with an ADG1234 pin 3, R of an ultrasonic wave transmission/reception switching unit (300)210Is connected to the foot 5 at the other end, C210The other end of which is connected with a foot 30; r220、C220One end of which is connected to an ADG1234 pin 8, R of the ultrasonic transmission/reception switching unit 300220Is connected to the other end of the pin 6, C220The other end of which is connected with a foot 27; the foot 5 and the foot 30 of the TDC _ GP21 form an ultrasonic channel, and the foot 6 and the foot 27 of the TDC _ GP21 form another ultrasonic channel; r240The model of the fuel gas temperature acquisition device is a Pt1000 platinum thermal resistor, and the fuel gas temperature T is acquired.
Description 2: correcting the ultrasonic wave propagation speed U-U according to the gas temperature T0×【1+T/273】0.5＝331.4×【1+T/273】0.5(ii) a Compress the time receive window to [0.8t ]0，1.2t0】，t0Theoretical time of an ultrasonic signal from a transmitting end to a receiving end; the TDC _ GP21 enables the ultrasonic receiving signal in the time receiving window, and improves the anti-interference capability and precision of the ultrasonic flowmeter.
As shown in fig. 4(a), 4(b), and 4(c), the integrated structural unit 600 of transducers includes a 1 st transmitting & receiving dual-purpose transducer 610, a 2 nd transmitting & receiving dual-purpose transducer 620, a 1 st gas elbow 630, a 2 nd gas elbow 640, and an n-shaped measuring tube 650, wherein the 1 st transmitting & receiving dual-purpose transducer 610 is composed of a 1 st transducer piezoelectric ceramic sensor 611 and a 1 st transducer acoustic impedance matching layer 612 of LHQ200-3 type, and the 2 nd transmitting & receiving dual-purpose transducer 620 is composed of a 2 nd transducer piezoelectric ceramic sensor 621 and a 2 nd transducer acoustic impedance matching layer 622 of LHQ200-3 type; the 1 st transmitting & receiving transducer 610 and the 2 nd transmitting & receiving transducer 620 are respectively arranged at the left end and the right end of the horizontal section of the n-shaped measuring tube 650; the n-shaped measuring pipe 650 is connected to the gas conveying pipe through a 1 st gas elbow 630 and a 2 nd gas elbow 640;
the total thickness of the acoustic impedance matching layer 612 of the 1 st transducer is a circular sheet with the ultrasonic sound wave wavelength of 1/4 lambda, and the total thickness is 0.425mm by taking the sound wave wavelength of 200KHz at 25 ℃; the 1 st transducer acoustic impedance matching layer 612 is composed of a 1 st transducer epoxy resin colloid layer 613 and a 1 st transducer mica sheet 614, and the 1 st transducer epoxy resin colloid layer 613 tightly connects the 1 st transducer piezoelectric ceramic sensor 611 of LHQ200-3 type with the 1 st transducer mica sheet 614; the 1 st transmitting & receiving transducer 610 is installed in the 1 st transducer sleeve 615, the 1 st transducer sleeve 615 is positioned and fixed at the air inlet end of the n-shaped measuring tube 650 through the 1 st transducer four screws 616, and the 1 st transducer sealing washer 617 is placed between the 1 st transducer sleeve 615 and the n-shaped measuring tube 650 to ensure air tightness; the 2 nd transmit & receive transducer 620 is mounted in the same manner as the 1 st transmit & receive transducer 610.
As shown in fig. 5, 4(a) and 3, the detection method of the device includes:
1. the time measuring unit 200 collects the gas temperature T
2. Correcting the ultrasonic propagation velocity U-U0×【1+T/273】0.5＝331.4×【1+T/273】0.5
3. The propagation time t from the ultrasonic transmitting end to the receiving end is L/U L: n-shaped length of measuring tube
Get the "time receive Window" [0.8t, 1.2t ] -TDC _ GP21 Transmit & receive Enable time
4. Time measurement unit i belongs to [1, 4N ] and N positive integer Ts time measurement period
One/another ultrasonic channel transmits/receives downstream signals, get ti cis
The other ultrasonic channel transmits/receives a reverse flow signal to obtaintinverse of i
Obtaining the time difference Deltat of the ith measurementi＝tinverse of i-ti cis
5. Data cleansing
ΔtiSorting by size Δ τjCleaning and removing large difference delta taujj∈[1,N]And [3N +1,4N]
Storing near time difference data delta tauj，j∈[N+1,3N]
Based on a similar Δ τjCalculating the gas flow velocity Vj＝[Δτj/τj inverseⅹτj cis]ⅹ0.5L
Calculating average gas flow rate of 4N measuring period
Calculating average gas flow Q of 4N measuring periodaverage＝Vaverage×SMeasuring tube，SMeasuring tubeCross section of measuring tube
Calculating the gas quantity Vol ═ Q of 4N measuring periodaverage×4N Ts。
The specific process is as follows:
(1) the time measuring unit 200 collects the gas temperature T;
(2) corrected ultrasonic wave propagation speed U is 331.4X (1+ T/273)0.5；
(3) The propagation time t from the ultrasonic transmitting end to the receiving end is equal to L/U, L: the span of the n-shaped probe 650 in the horizontal direction;
(4) the ultrasonic excitation unit 400 emits at the 1 st position&With the aid of the receiving dual-purpose transducer 610, ultrasonic waves are generated at time t, and the ultrasonic receiving unit 500 receives the window [0.8t, 1.2t ] in time]Carrying out downstream sampling for 4 times in a time period; the ultrasonic wave transmission/reception switching unit 300 switches the ultrasonic wave excitation unit 400 and the ultrasonic wave reception unit 500, and performs the inverse flow sampling in the above-described manner. Thus, for each sampling period, 4 downstream propagation times t are obtainedi cisAnd 4 counter-current propagation times tinverse of iTo obtain the 4 th measurement time difference Deltat ═ tInverse direction-tCis-trans。
After the ultrasonic excitation unit 400 generates the excitation signals N times, 4N measurement time differences are obtained in total.
(5) Data cleaning: sorting 4N deltat according to size, eliminating deltat sorted in [1, N ] and [3N +1,4N ], and storing the deltat sorted between [ N +1,3N ].
(6) For each stored Δ tjCalculating the gas flow velocity Vj＝[Δtj/tj inverseⅹtj cis]ⅹ0.5L；
The average gas flow rate for N measurement cycles is:
the average gas flow of N measurement periods is as follows: qaverage＝Vaverage×SMeasuring tube，SMeasuring tubeCross section of measuring tube
The 4 gas amounts for the N measurement cycles are: vol ═ Qaverage×4N Ts。
Claims (1)
1. The flow detection method of the civil ultrasonic gas meter with the integrated transducer is characterized in that the civil ultrasonic gas meter consists of a data processing and control communication unit (100), a time measuring unit (200), an ultrasonic transmitting/receiving switching unit (300), an ultrasonic exciting unit (400), an ultrasonic receiving unit (500) and a transducer integrated structure unit (600), wherein the ultrasonic transmitting/receiving switching unit (300) takes an ADG1234 chip as a core, the ultrasonic exciting unit (400) comprises an insulated gate type MOSFET and a step-up transformer, and the ultrasonic receiving unit (500) comprises a pre-amplification module, a second-order band-pass filtering module and a threshold zero-crossing detection module; the data processing and control communication unit (100) is connected with the time measuring unit (200) and the ultrasonic transmitting/receiving switching unit (300), and the ultrasonic transmitting/receiving switching unit (300) is connected with the time measuring unit (200), the ultrasonic exciting unit (400), the ultrasonic receiving unit (500) and the transducer integrated structural unit (600);
the data processing and control communication unit (100) controls the operation of the time measuring unit (200), reads a time difference measured value output by the time measuring unit (200), generates gas flow through a data processing and control module of the data processing and control communication unit (100), and uploads the gas flow through a Bluetooth communication module of the data processing and control communication unit (100); the data processing and control communication unit (100) controls the opening and closing of an analog switch of the ultrasonic transmitting/receiving switching unit (300), and a transmitting/receiving channel of the time measuring unit (200) is respectively connected to the ultrasonic exciting unit (400) and the ultrasonic receiving unit (500) through the ultrasonic transmitting/receiving switching unit (300); the ultrasonic excitation unit (400) and the ultrasonic receiving unit (500) are respectively connected to the 1 st transmitting and receiving dual-purpose transducer and the 2 nd transmitting and receiving dual-purpose transducer of the transducer integrated structural unit (600) through the ultrasonic transmitting/receiving switching unit (300), or the 2 nd transmitting and receiving dual-purpose transducer and the 1 st transmitting and receiving dual-purpose transducer;
the integrated structural unit (600) of the energy converter comprises a 1 st transmitting & receiving dual-purpose energy converter (610), a 2 nd transmitting & receiving dual-purpose energy converter (620), a 1 st gas elbow (630), a 2 nd gas elbow (640) and an n-shaped measuring pipe (650); in the n-shaped measuring pipe (650), the length L of a horizontal pipe in the horizontal direction is greater than the diameter D, and the length H of a vertical pipe in the vertical direction is greater than the diameter D; the 1 st transmitting and receiving dual-purpose transducer (610) consists of a 1 st transducer piezoelectric ceramic sensor (611) of an LHQ200-3 type and a 1 st transducer acoustic impedance matching layer (612), and the 2 nd transmitting and receiving dual-purpose transducer (620) consists of a 2 nd transducer piezoelectric ceramic sensor (621) of an LHQ200-3 type and a 2 nd transducer acoustic impedance matching layer (622); the 1 st transmitting and receiving dual-purpose transducer (610) and the 2 nd transmitting and receiving dual-purpose transducer (620) are respectively arranged at the left end and the right end of the upper horizontal section of the n-shaped measuring tube (650); two ends of the n-shaped measuring pipe (650) are respectively connected to the gas conveying pipe through a 1 st gas elbow (630) and a 2 nd gas elbow (640);
the 1 st transducer acoustic impedance matching layer (612) is a circular thin sheet with the total thickness of 1/4 lambda of ultrasonic sound wave, and the total thickness is 0.425mm based on 200KHz sound wave at 25 ℃; the 1 st transducer acoustic impedance matching layer (612) is composed of a 1 st transducer epoxy resin colloid layer (613) and a 1 st transducer mica sheet (614), and the 1 st transducer epoxy resin colloid layer (613) tightly connects the 1 st transducer piezoelectric ceramic sensor (611) of LHQ200-3 type with the 1 st transducer mica sheet (614); the 1 st transmitting and receiving dual-purpose transducer (610) is installed in a 1 st transducer sleeve (615), the 1 st transducer sleeve (615) is fixedly positioned at the air inlet end of the n-shaped measuring tube (650) through a 1 st transducer four-screw (616), and a 1 st transducer sealing gasket (617) is placed between the 1 st transducer sleeve (615) and the n-shaped measuring tube (650) to ensure air tightness; the 2 nd transmitting & receiving transducer (620) is installed in the same way as the 1 st transmitting & receiving transducer (610);
the data processing and control communication unit (100) comprises a data processing and control module (110) taking an MSP430F135 chip as a core and a Bluetooth communication module (120) with a BLE-CC41-A model, wherein MSP430F135 pins 32 and 33 are respectively connected with BLE-CC41-A pins 2 and 1; the data processing and control module (110) is used for obtaining a gas flow rate and a gas quantity obtained by integrating the gas flow and the flow based on time difference measured values output by the cleaning time measuring unit (200) and uploading the gas flow and the gas quantity through the Bluetooth communication module (120);
the time measuring unit (200) takes a TDC _ GP21 chip as a core, pins 4, 21 and 28 of TDC _ GP21 are grounded, pins 14 and 29 are connected with Vcc, and pins 17 and 18 are connected with a resistor R230Capacitor C230Resistance R240，R230Is connected to the other end of the foot 20, 19, C230The other end of (A) is grounded, R240The other end of which is connected with the feet 24, 23; TDC _ GP21 pins 8, 9, 10, 11, 12 are connected to MSP430F135 pins 27, 28, 31, 29, 30, respectively, of the data processing and control module (110);
ADG1234 pin 3 connection resistor R of ultrasonic wave transmitting/receiving switching unit (300)210Capacitor C210，R210Is connected to TDC _ GP21 pin 5, C210Is connected with a TDC _ GP21 pin 30; ADG1234 pin 8 of ultrasonic wave transmission/reception switching unit (300) is connected with R220、C220，R220Is connected to TDC _ GP21 pin 6, C220The other end of which is connected with a TDC _ GP21 pin 27; the foot 5 and the foot 30 of the TDC _ GP21 form an ultrasonic channel, and the foot 6 and the foot 27 of the TDC _ GP21 form another ultrasonic channel; r240The model of the gas sensor is Pt1000 platinum thermal resistor, the gas temperature T is collected, and the ultrasonic wave transmission is correctedA speed U;
the detection method comprises the following steps:
(1) the time measuring unit (200) collects the gas temperature T;
(2) corrected ultrasonic propagation velocity U ═ 331.4 × (1+ T/273)0.5；
(3) The propagation time t from the ultrasonic transmitting end to the receiving end is equal to L/U, L: the span of the n-shaped measuring tube (650) in the horizontal direction;
(4) the ultrasonic excitation unit (400) emits at the 1 st emission&Ultrasonic waves are generated at the time t with the aid of a receiving dual-purpose transducer (610), and an ultrasonic receiving unit (500) receives a window [0.8t, 1.2t ] in time]Carrying out downstream sampling for 4 times in a time period; an ultrasonic wave transmitting/receiving switching unit (300) switches an ultrasonic wave excitation unit (400) and an ultrasonic wave receiving unit (500) and performs countercurrent sampling according to the method; thus, for each sampling period, 4 downstream propagation times t are obtainedi cisAnd 4 counter-current propagation times tinverse of iTo obtain the 4 th measurement time difference Deltat ═ tInverse direction-tCis-trans；
After the ultrasonic excitation unit (400) generates N times of excitation signals, 4N measurement time differences are obtained;
(5) data cleaning: sorting 4N deltat according to size, eliminating the deltat sorted in [1, N ] and [3N +1,4N ], and storing the deltat sorted between [ N +1,3N ];
(6) for each stored Δ tjCalculating the gas flow velocity Vj＝[Δtj/tj inverse×tj cis]×0.5L；
The average gas flow rate for N measurement cycles is:
the average gas flow of N measurement periods is as follows: qaverage＝Vaverage×SMeasuring tube，SMeasuring tubeMeasuring the section of the pipe;
the gas amount of N measurement periods is: vol ═ QaverageX 4N Ts, Ts measures the time period.
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