CN106404084A - Method for measuring gas flow rate - Google Patents
Method for measuring gas flow rate Download PDFInfo
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- CN106404084A CN106404084A CN201510486278.9A CN201510486278A CN106404084A CN 106404084 A CN106404084 A CN 106404084A CN 201510486278 A CN201510486278 A CN 201510486278A CN 106404084 A CN106404084 A CN 106404084A
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Abstract
The invention discloses a method for measuring a gas flow rate. The method comprises the steps that ultrasonic wave transceiving devices of an ultrasonic wave flowmeter are arranged around a gas pipeline, ultrasonic waves passing through a gas are sent by the ultrasonic wave transceiving devices, and echo signals are collected; two sampling points are selected from sampling data of the echo signals, wherein the moment of an intersection point of a connected line of the two sampling points and a reference level line is recorded as T3, the cycle of the ultrasonic wave echo signals is T, the moment for ultrasonic wave sending is recorded as T0, the starting moment of the echo signals is recorded as T1, and the quantity of cycles of the echo signals between T1 and T3 is n; a computation formula of transmission time t of ultrasonic waves is t=T3-T0-n*T; and the gas flow rate is computed according to the transmission time. The method for measuring the gas flow rate disclosed by the invention has the advantages that measurement accuracy is high; the gas flow rate is measured accurately; and a gas company can conduct real-time monitoring of pipe network states, carry out remote management of gas conveying and distribution, and make a timely response to abnormal states.
Description
Technical field
The present invention relates to measuring instrument technical field is and in particular to a kind of method of measurement gas flow.
Background technology
Due to the attention rate more and more higher to environment for the people, natural gas is as the green energy resource of clean environment firendly
Obtain more and more widely paying close attention to and applying, Gas Industry all will obtain within the following some time
Fast-developing.In order to adapt to the growth requirement of Gas Industry, particularly gas company is to natural gas meter
Amount and the growth requirement of pipe network transmission ＆ distribution management, under its development of informationization technology, metering accurately,
Working stability, and have the intelligent flow meter systems of remote management capability initially enter gas metering and
In transmission ＆ distribution management.
At present, domestic application is mainly Roots's table and whirlpool in the effusion meter of gas metering and transmission ＆ distribution management
Wheel table, both measuring instruments belong to mechanical type measuring instrument it is difficult to break away from mechanical type instrument intrinsic
Weakness, for example, high to the prescription of natural gas, easily block, safeguard frequently and maintenance cost
Higher, simultaneously with the increase in natural gas transportation line portals footpath, the volume of two kinds of mechanical type measuring instruments,
Weight and price can significantly rise, and these weakness seriously constrain gas metering and pipe network transmission ＆ distribution pipe
Reason develops towards the direction of " accurate, stable, intelligent, efficient ".
In order to overcome the shortcoming of mechanical type measuring instrument, in prior art, occur in that ultrasonic flowmeter,
Carry out the detection of gas flow using ultrasonic signal, such as Authorization Notice No. is CN102914334B
Patent of invention document disclose a kind of plug-in type ultrasonic gas flowmeter, including use when insertion treat
Survey the transducer fixed mount in gas piping, transducer fixed mount is installed with for measuring ultrasound wave
The ultrasound wave of adverse current time when following current time during downstream propagation and adverse current are propagated under test gas
Transducer group, also include when using being arranged under test gas pipeline with described ultrasonic transducer group phase
It is connected at corresponding pipeline section and with this pipeline section and supply the quiet of the under test gas free diffusing in this pipeline section
Fast container, arranges the ultrasound wave for measuring ultrasonic propagation velocity in quiet speed pipe on quiet speed container
Transducer.
But in this patent of invention document, quiet speed pipe needs to insert in gas piping and carries out gas flow
Measurement, quiet speed pipe itself can cause disturbance to gas flowing, thus causing the error of flow measurement.
In order to meet the growth requirement of gas metering and the management of pipe network transmission ＆ distribution, it is desirable to provide a kind of intelligence
The gas flow measurement method changed, to realize the accurate measurement to gas discharge.
Content of the invention
The invention provides a kind of method of measurement gas flow, it is capable of accurate to gas flow
Measurement, and monitor in real time can be carried out to pipe network state, the exception of natural gas transmission and distribution is rung in time
Should.
A kind of method of measurement gas flow, comprises the following steps：
(1) arrange the ultrasonic receiving device of ultrasonic flowmeter around gas pipeline, using ultrasonic
Ripple R-T unit is transmitted through the ultrasound wave of gas, and gathers echo-signal；
(2) two sampled points, the line of two sampled points are chosen in the sampled data of echo-signal
It is designated as T with the intersection point moment of reference level line3, the cycle of ultrasonic echo signal is T, and ultrasound wave is sent out
The moment sent is designated as T0, the initial time of echo-signal is T1, T1With T3Between echo-signal cycle
Number is n；The transmission time t computing formula of ultrasound wave is as follows：
T=T3-T0-n·T
The selection range of two sampled points is：After triggering ripple, first positive amplitude is more than VHH-VbAnd
Negative sense amplitude is more than Vb-VLLWave band trailing edge；
In two sampled points, one of sampling optimization is in [VHL, VHH] in the range of, another sampling
Point is located at [VLL, VLH] in the range of；
VHL、VHH、VLL、VLHDetermine according to sample frequency, determine that principle is：Sample every time inevitable
There is sampling optimization in selected level range, and fall into the sampled point in selected level range
Number is few as much as possible；
(3) calculate gas flow using the transmission time that step (2) obtains.
The present invention provide gas flow measurement method be particularly suited for natural gas, be also applied for natural
The measurement of the similar gas of gas property, for example, at least one in methane, ethane, propane, butane.
Using ultrasonic flowmeter gas flow is measured it is critical that Accurate Determining ultrasound wave
Transmission time in gas, the echo-signal being received due to ultrasonic probe, ultrasonic receiver generally by weak to
By force, then progressively decay, therefore, determine that the moment receiving ultrasound wave becomes true in echo-signal
Determine the key of transmission time.The determination method of the ultrasonic transmission time that the present invention provides, can be accurate
And reliably obtain ultrasound wave transmission time, thus obtaining accurate gas flow.
In echo-signal, due to the restriction of sample frequency, the intersection point of echo-signal and reference level line
Moment is difficult to accurately obtain, the present invention by the use of two sampled point lines and reference level line intersection point as
Echo-signal and the intersection point moment of reference level line, method is simple, and ensure that necessary calculating essence
Degree.
Preferably, on the premise of sample frequency determines, [VHL, VHH] and [VLL, VLH] model
Enclose little as much as possible.To make the sampled point in respective range few as much as possible, improving and calculating really
Qualitative.If [VHL, VHH] or [VHL, VHH] in exist multiple meet require sampled points, select lean on most
The sampled point of nearly respective range intermediate value.
VHHAnd VLLSelection mode be：When gas flow reaches the ultrasonic flow rate measuring journey upper limit,
Deduct certain allowance using the maximum amplitude of corresponding ultrasound wave to obtain.
Select [VHL, VHH] and [VLL, VLH] purpose be, make two sampled point lines and benchmark
The intersection point moment of level line can approach the intersection point moment of echo-signal and reference level line, can reach
To on the premise of this purpose, determine V according to sample frequencyHL、VHH、VLL、VLH.
If preferably, can not find in the sampled data of echo-signal meeting the sampled point requiring,
Automatically adjust gain, meet, to obtain, the sampled point requiring.
In extreme circumstances, for example when ultrasound probe damages, it is possible that adjust increase anyway
Yidu can not obtain meet require sampled point situation, through after a while attempt after, if begin
Eventually can not obtain meet require sampled point, can to probe whether be normally carried out judge if it is decided that
Probe is abnormal, then carry out abnormal log and store and report to the police.
In order to ensure the accuracy of gas flow measurement it is preferable that gathering three groups during each flow measurement
Echo-signal, every group of echo-signal correspondence obtains the forward transmission of a ultrasound wave and gas symport
Time, and the reverse transmission time of a ultrasound wave and gas reverse transfer.Different group echo-signals
Transmission path is different, is weighted averagely to each group echo-signal calculated initial gas flow velocity,
Obtain average weighted gas flow rate, and then be calculated corresponding gas flow.
Preferably, also including step (4), judge that gained gas flow whether there is abnormal, if depositing
In exception, then recording exceptional state, and reported to the police.
Preferably, also including step (5), according to working temperature and the pressure in measurement gas flow moment
Power, is modified to the gas flow of gained.
Preferably, also including step (6), using wireless communication mode by the gas flow recording,
Floor data and equipment state send to pipeline monitoring center.
Preferably, also including step (7), after one time gas flow measurement finishes, ultrasonic flow
Meter enters resting state, and automatically begins to afterwards at preset time intervals measure next time.
The number of steps of described step (4)～step (7) only does the differentiation of different step, not
Limit the presence or absence of order and each step between each step, for example, after having carried out step (4),
Step (7) can directly be carried out.
The method that the present invention utilizes ultrasonic flow rate measurement amount gas flow, measuring accuracy is high, measurement gas
Body flow accurately (at least up to stem-winder identical precision), can enable gas company to pipe
Net state carries out monitor in real time, gas transmission and distribution is carried out with remote management, abnormality is rung in time
Should, the information system management level to gas ductwork for the gas company can be effectively improved.
Brief description
Fig. 1 a is the schematic diagram of ultrasonic receiving device arrangement in the ultrasonic flowmeter realize the present invention；
Fig. 1 b is for the A in Fig. 1 a to schematic diagram；
Fig. 1 c is for the B in Fig. 1 b to schematic diagram；
Fig. 1 d is that in ultrasonic flowmeter, ultrasonic wave propagation path passes through the ultrasound wave of pipe centerline to receive
The sectional view of transmitting apparatus；
Fig. 2 is the structural representation of the ultrasonic flowmeter realizing the present invention；
Fig. 3 is the workflow schematic diagram of the ultrasonic flowmeter realizing the present invention；
Fig. 4 measures the schematic flow sheet of gas flow method for the present invention；
Fig. 5 is original echoed signals schematic diagram；
Fig. 6 is the B portion enlarged drawing in Fig. 5.
Specific embodiment
Below in conjunction with the accompanying drawings, the method measuring gas flow to the present invention is described in detail.
The present invention utilizes the principle of ultrasonic flow rate measurement amount gas flow as follows：
The ultrasonic signal that the ultrasound probe of air-flow upstream sends is to the ultrasound probe of airflow downstream
During received ultrasonic signal, because gas flowing produces in the transmission direction of ultrasonic signal
Velocity component, can accelerate the transmission of ultrasonic signal；It is ultrasonic that the ultrasound probe of airflow downstream sends
Ripple signal to during the ultrasound probe received ultrasonic signal of air-flow upstream, due to gas flowing
The transmission direction of ultrasonic signal produces velocity component, the transmission of ultrasonic signal can be slowed down, profit
With ultrasonic signal, in pleasant direction of flow and inverse gas flow, the difference of transmission time calculates gas
Body flow.
As shown in Figure 1 d, in figure L is the air line distance of upstream and downstream ultrasound probe, and D is pipe diameter,
θ is ultrasonic transmission path and the angle measuring tube hub line, and V is the mean flow rate of gas, t1It is super
Sound wave forward transmission time, t2For the reverse transmission time of ultrasound wave, then have：
Can be obtained by formula I and formula II：
Due to flow=flow velocity * cross-sectional area, the expression formula by flow relocity calculation flow is as follows：
Wherein, C represents the spread speed of ultrasound wave；A represents the cross-sectional area measuring pipe.
It doesn't matter with ultrasonic propagation velocity gas flow rate can be seen by formula IV, therefore, can
To avoid causing ultrasonic propagation velocity to change due to the difference of the factors such as temperature, pressure, and lead to gas
Deviation in flowmeter body amount.
From calculating process, measure gas flow it is critical that accurately measuring the transmission of ultrasound wave
Time, in order to obtain the correct time of ultrasonic transmission, using ultrasonic flow rate measurement amount gas flow
Method, comprise the following steps：
(1) arrange the ultrasonic receiving device of ultrasonic flowmeter around gas pipeline, using ultrasonic
Ripple R-T unit is transmitted through the ultrasound wave of gas, and gathers echo-signal；
Arrange ultrasonic receiving device around gas pipeline, as shown in Fig. 1 a, 1b, 1c, the present invention adopts
Ultrasonic flowmeter includes three pairs of ultrasound probes (i.e. ultrasonic receiving device), respectively super
Sonic probe 11 and ultrasound probe 12, ultrasound probe 21 and ultrasound probe 22, ultrasound probe
31 and ultrasound probe 32, the wherein ultrasonic wave propagation path of ultrasound probe 11 and ultrasound probe 12
Intersect with the centrage of gas pipeline, the ultrasonic wave propagation path phase that remaining two pairs of ultrasound probe is formed
Mutually parallel, and it is symmetrically distributed in the both sides of gas pipeline centrage, each pair ultrasound probe is formed
The angle of the centrage of ultrasonic wave propagation path and gas pipeline is 60 degree, ultrasound probe 21 and super
The distance of sonic probe 31 is less than the diameter of under test gas flow conduit, and can be selected according to needs
Select.
In Fig. 1 a, ultrasound probe 32 and ultrasound probe 22 overlap, ultrasound probe 31 and ultrasound wave
Probe 21 coincidence, omits ultrasound probe 11 and ultrasound probe 12 in Fig. 1 c.
The ultrasound wave that a pair of ultrasound probe is formed is a branch of, with this bundle ultrasound wave in the present invention
Axis is as corresponding ultrasonic wave propagation path.
Flow measurement gathers three groups of echo-signals every time, and every group of echo-signal correspondence obtains a ultrasound wave
With the forward transmission time of gas symport, and the reverse biography of ultrasound wave and gas reverse transfer
The defeated time；The transmission path of different group echo-signals is different, and every group of echo-signal is received by a pair of ultrasound wave
Transmitting apparatus obtain.
(2) two sampled points, the line of two sampled points are chosen in the sampled data of echo-signal
It is designated as T with the intersection point moment of reference level line3, the cycle of ultrasonic echo signal is T, and ultrasound wave is sent out
The moment sent is designated as T0, the initial time of echo-signal is T1, T1With T3Between echo-signal cycle
Number is n；The transmission time t computing formula of ultrasound wave is as follows：
T=T3-T0-n·T
The selection range of two sampled points is：After triggering ripple, first positive amplitude is more than VHH-VbAnd
Negative sense amplitude is more than Vb-VLLWave band trailing edge；As shown in Figure 5, Figure 6；Vb in Fig. 5, Fig. 6
On the basis of level line, reference level line differs and is set to zero, for example with 1.645V level line as base
Quasi- level line.
In two sampled points, one of sampling optimization is in [VHL, VHH] in the range of, another sampling
Point is located at [VLL, VLH] in the range of；
VHL、VHH、VLL、VLHDetermine according to sample frequency, determine that principle is：Sample every time inevitable
There is sampling optimization in selected level range, and fall into the sampled point in selected level range
Number is few as much as possible.
On the premise of sample frequency determines, [VHL, VHH] and [VLL, VLH] scope as much as possible
Little.If [VHL, VHH] or [VHL, VHH] in exist multiple meet require sampled points, select near
The sampled point of respective range intermediate value.
Part A in Fig. 5 is triggering ripple, i.e. first in echo-signal ripple, as shown in Figure 5, Figure 6,
In the present embodiment, S1And S2It is respectively two sampled points selected, S1And S2Line and reference level line
The intersection point moment be T3, echo-signal is T with the intersection point moment of reference level line2, with T3As T2's
Substitution value carries out the determination of ultrasonic transmission time, and n is 2.
If find in actual mechanical process it is impossible in echo-signal meeting two samplings requiring
Point, then automatically adjust gain until can find in echo-signal and meet the sampled point requiring, if
All the time can not find, then judge that corresponding ultrasonic receiving device is abnormal.
When calculating the transmission time of ultrasound wave it is necessary first to adjust to the echo-signal of ultrasound wave
Whole, make ultrasonic echo signal triggering ripple (as shown in part A in Fig. 5, ultrasonic echo signal
First ripple) amplitude be more than sampling triggering level VTH, ultrasound wave send a period of time after start sample,
If sample circuit issue a signal to ultrasonic receiving device start send ultrasound wave time span be normal
Amount, is designated as ts, ultrasonic receiving device receive echo-signal to sample circuit receive echo-signal when
Between length be constant, be designated as tr, then when calculating transmission time, need this two time deductions,
That is, t=T3-T0-n·T-ts-tr.
(3) calculate gas flow rate using the transmission time that step (2) obtains, and calculate further
To gas flow.
The gas travel time that different group echo-signals obtain is weighted averagely, obtaining average weighted
Time, and carry out the calculating of gas flow using this average weighted time, obtain final gas stream
Amount.
Step (4), judging that gained gas flow whether there is abnormal, if existing abnormal, recording different
Often state, and reported to the police.
Step (5), according to working temperature and the pressure in measurement gas flow moment, the gas to gained
Flow is modified.
When gas flows in the duct, due to the impact of the factors such as pipe friction, on cross-section of pipeline
Flow have differences, directly pass through after the gas flow that public formula IV obtains needs to revise,
It is capable of the actual flow of truly reacting gas, in order to improve the precision of metering, it is three right that the present invention adopts
Totally six ultrasonic receiving devices are sampled to multi-point flux, then by average weighted method meter
Calculation obtains gas flow, and gas flow is modified, with the gas flow of approaching to reality.
Step (6), using wireless communication mode by the gas flow recording, floor data and equipment
State sends to pipeline monitoring center.
Step (7), after one time gas flow measurement finishes, ultrasonic flowmeter enters resting state,
And automatically begin to afterwards measure at preset time intervals next time.
Each ultrasonic receiving device includes bandpass filtering, programmable-gain and signal sampling three
Divide functional circuit, the adjustment of ultrasonic echo signal completed by the cyclic process of sampling-adjustment-sampling,
Obtain the ultrasonic echo that can be correctly validated.
Band-pass filtering function circuit passes through frequency-selecting function, passes through ensureing that ultrasonic echo signal is lossless
Meanwhile, the clutter in echo-signal can be filtered, be obtained in that with the programmable gain circuit ensureing rear class
Purer ultrasonic echo signal.
Except ultrasonic receiving device, as shown in Fig. 2 the ultrasonic flowmeter realizing the present invention also wraps
Include：Control unit, power module, input module, data memory module, wireless communication module, aobvious
Show module, working condition acquiring module, output module.
Power module is used for providing power supply output, power supply mould to each power unit of ultrasonic flowmeter
The input of block is the DC source of 4.5～16V wide-voltage range, using change-over circuit respectively to ultrasound wave
The each power unit of effusion meter is powered.DC supply input can be using external power supply it is also possible to by ultrasonic
Battery supply within low.
The ultrasonic flowmeter that the present invention provides comprises both of which, during a kind of gas flow for measurement
Mode of operation, low-power consumption mode during another kind of gasmetry for stopping, control unit controls ultrasound wave
Effusion meter automatically switches between both of which, and automatic switching procedure can pass through program setting in advance,
Can also be manually entered using input module.
, in control unit, control unit is according to super for the controlled process that power module is powered to each power unit
The mode of operation of acoustic wave flow meter and the difference of low-power consumption mode, send control signal to power module,
Coordinate ultrasonic flowmeter effectively to run with minimum power consumption, that is, need the power unit of work to power,
Power unit without work is stopped power supply.
Control unit is the core that ultrasonic flowmeter data processing and each composition partial function control
Part, completes the function of control unit jointly using single-chip microcomputer (STM32 microprocessor) and FPGA,
During ultrasonic flowmeter work, control the ultrasonic signal transmitting-receiving of ultrasonic receiving device using FPGA
And carry out Time Calculation, after FPGA calculates the time, the Time Transmission obtaining to single-chip microcomputer,
Single-chip microcomputer completes the calculating of flow according to this time.
Single-chip microcomputer carries out the calculating of gas flow and volume is repaiied except the time being inputted according to FPGA
Just, the information exchange also carrying out storage management, data and remaining equipment of data controls, and controls display
The function of module shows, the switching of the instruction input of input module, pattern, floor data collection with
And signal output.
Connect by SPI between programmable-gain functional circuit in ultrasonic receiving device and control unit
Mouth is communicated, and line amplitude adjustment, sample circuit pair are entered in the instruction according to control unit to echo-signal
Ultrasonic echo signal is sampled, and the data after sampling is delivered to control unit by SPI interface,
Control unit judges whether to need ultrasonic echo signal is adjusted according to the sampling of sample circuit.
Control unit is communicated with host computer by RS485 interface, enables an administrator to by upper
The parameters such as system time, pattern, running parameter, volume correction chart are issued to control unit by machine,
The current temperature of system, pressure, flow, ultrasonic can also be obtained to control unit by querying command
The status informations such as wave sound speed, can also issue the control commands such as sleeping/waking to system and realize system in work
(system dormancy corresponds to low-power consumption mode, wakes up corresponding work for switching between operation mode and low-power consumption mode
Operation mode).
Data memory module includes ferroelectric memory and SPI flash storage two parts, with control unit
Communicated by SPI interface, for systematic parameter, various list item, system mode and stoichiometric number
According to storage.
Wireless communication module adopts GPRS module, is communicated with control unit by UART interface,
And realized in equipment and pressure management area by public cordless communication network under the control of the control unit
The information exchange of the heart, completes the upload of continuous data, and the connecing of the control instruction at pressure management area center
Receive.
Input module realizes contactless keypress function using Hall element, for inputting various fingers
Order, for example, the sleeping/waking of system, the function such as menu control and information inquiry.
Display module adopts OLED module, is communicated with control unit by SPI interface, for showing
Show the metrical informations such as the current temperature of system, pressure, flow, ultrasonic velocity, wherein flow includes
The polytypes such as present flow rate, integrated flow, timing flow, operating mode flow, mark condition flow.
Output module is communicated with control unit by digital I/O mouth and SPI interface, single controlling
Under the control of unit, export digital pulse signal and 4～20mA electric current ring signal, wherein, digital arteries and veins
Rush signal with status signals such as low and high level output abnormality warnings, 4～20mA electric current ring signal passes through defeated
Output galvanic current characterizes specific system mode.
Working condition acquiring module includes temperature collect module and pressure acquisition module, wherein temperature collect module
Communicated with control unit by analog interface, control unit is looked into according to the temperature data that sampling obtains
Look for the temperature transition table in data memory module, working site temperature can be learnt to realize gas flow
Correction etc. data.
Pressure acquisition module is communicated with control unit by analog interface, and control unit is according to sampling
Pressure conversion table in the pressure data searching data memory module obtaining, can learn that working site is pressed
Power is to realize the correction of the data such as gas flow.
As shown in figure 3, when ultrasonic flowmeter uses, first with control unit and power module
The upper electricity of completion system and initialization, the power up of system is：Power module is first to ensure that
The minimum system of control unit normal work carries out upper electricity, the minimum system normal work of control unit
Afterwards, control unit controls power module to carry out upper electricity to remaining power unit.
After system completes electricity, under the control of the control unit, to system, each functional module is carried out automatically
Communication and state-detection, after the completion of detection, if system mode is normal, open corresponding timing routine
(time of timing routine sets for the purpose of effective reduction system power dissipation, and the length of timing time is necessary
Complete once the time needed for complete measurement flow more than system) enter idle condition, wait corresponding
Interrupt instruction, if system mode is abnormal, under the control of the control unit, exported by output module
Digital pulse signal and 4～20mA electric current ring signal, carry out abnormal alarm.
For the equipment of externally fed, system in an idle state, can enter resting state to reduce
System power dissipation is not it is also possible to enter resting state to ensure the response speed of system；Battery is powered
Low power consuming devices, described idle condition is the low power consumpting state of dormancy, ensureing measuring accuracy
In the case of reduce system power dissipation.
When needed, system manager can be by the host computer that is connected with control unit to control unit
Issue corresponding instruction, to system time, mode of operation, running parameter, various correction list item
Etc. being issued or changed；System manager can also use querying command to obtain system by host computer
Temperature, pressure, the status information such as flow, can also be carried out by sleeping/waking command control system
The switching of working condition.
When exhausting a time-count cycle of timing routine, system can produce corresponding Interruption to hold
Open a measurement flow and a metering cycle, in each measurement flow, control unit one side according to
Complete the calculating of transmission time according to the echo-signal of ultrasonic receiving device, on the other hand surveyed by temperature
Amount module and pressure measuring module carry out AD sampling, and inquire about in data memory module and change accordingly
List item to obtain the work informations such as working site temperature, pressure, then control unit according to obtain when
Between, the parameter such as temperature and pressure carry out data processing, to complete metering and the correction of gas flow；
After obtaining effective continuous data, complete the storage of data on request, terminate this measurement flow.
In each measurement flow, control unit controls ultrasonic receiving device according to required order
Carry out transmitting and the reception of ultrasound wave, as shown in figure 4, first, control unit is according to a metering stream
All required effective time data can be obtained as principle with speed the fastest in journey, choose ultrasound wave
R-T unit carries out the transmitting of ultrasound wave, and corresponding ultrasonic receiving device carries out connecing of echo-signal
Receive, after echo signal reception, sampling circuit samples are controlled by control unit, and in returning that sampling obtains
Two sampled points are chosen according to rule, using two sampled point lines and reference level line in ripple signal
The intersection point moment calculates the transmission time of ultrasound wave, and ultrasonic receiving device informs control by interrupt signal
Unit read access time data, obtains once time data recording data in memory module effectively
Afterwards, this precise time measurement procedure terminates.
Every time after the completion of measurement flow, control unit is according to system Current Temperatures, pressure, gas flow
And the metrical information such as ultrasonic velocity, judgement is that gas distributing system is no has abnormal conditions；If system
State is normal, then working-flow enters next stage；If there are abnormal conditions, carry out abnormal mark
Will stores, and can export digital pulse signal and 4-20mA electric current ring signal by output module, enters
Row abnormal alarm；Wherein, digital pulse signal with low and high level transmission abnormality report to the police etc. status signal,
4-20mA electric current ring signal characterizes specific system mode by output quantization electric current, supplies for outside
The equipment of electricity is it is also possible to carry out long-range abnormal alarm by wireless communication module.
If system adopts externally fed, as needed, wireless communication module and administrative center can be passed through
Set up real-time wireless communication connection, to complete the real-time upload of continuous data and system mode etc..
System, during running, can carry out system by the cooperation of input module and display module
Sleeping/waking, menu control, the function such as continuous data and state information searching.
When ultrasonic flowmeter does not carry out gasmetry, system enters idle condition.
Above-mentioned embodiment is the present invention preferably embodiment, but embodiments of the present invention are not subject to
The restriction of described embodiment, others are any to be made under the spirit without departing from the present invention with principle
Modification, replacement, combination, cutting, all should be equivalent substitute mode, be included in the present invention's
Within protection domain.
Claims (10)
1. a kind of method of measurement gas flow is it is characterised in that comprise the following steps：
(1) arrange the ultrasonic receiving device of ultrasonic flowmeter around gas pipeline, using ultrasonic
Ripple R-T unit is transmitted through the ultrasound wave of gas, and gathers echo-signal；
(2) two sampled points, the line of two sampled points are chosen in the sampled data of echo-signal
It is designated as T with the intersection point moment of reference level line3, the cycle of ultrasonic echo signal is T, and ultrasound wave is sent out
The moment sent is designated as T0, the initial time of echo-signal is T1, T1With T3Between echo-signal cycle
Number is n；The transmission time t computing formula of ultrasound wave is as follows：
T=T3-T0-n·T
The selection range of two sampled points is：After triggering ripple, first positive amplitude is more than VHH-VbAnd
Negative sense amplitude is more than Vb-VLLWave band trailing edge；
In two sampled points, one of sampling optimization is in [VHL, VHH] in the range of, another sampling
Point is located at [VLL, VLH] in the range of；
VHL、VHH、VLL、VLHDetermine according to sample frequency, determine that principle is：Sample every time inevitable
There is sampling optimization in selected level range, and fall into the sampled point in selected level range
Number is few as much as possible；
(3) calculate gas flow using the transmission time that step (2) obtains.
2. the method for measurement gas flow as claimed in claim 1 is it is characterised in that sampling frequently
On the premise of rate determines, [VHL, VHH] and [VLL, VLH] scope little as much as possible.
If 3. the method for measurement gas flow as claimed in claim 2 is it is characterised in that [VHL,
VHH] or [VHL, VHH] in exist multiple meet require sampled points, select near in respective range
Between value sampled point.
If 4. the method for measurement gas flow as claimed in claim 3 is it is characterised in that in echo
Can not find in the sampled data of signal and meet the sampled point requiring, then automatically adjust gain, full to obtain
The sampled point that foot requires.
5. the method for measurement gas flow as claimed in claim 1 is it is characterised in that each flow
Three groups of echo-signals are gathered, every group of echo-signal correspondence obtains a ultrasound wave with gas in the same direction during metering
The forward transmission time of transmission, and the reverse transmission time of a ultrasound wave and gas reverse transfer.
6. the method for measurement gas flow as claimed in claim 5 is it is characterised in that difference is organized back
The transmission path of ripple signal is different, each group echo-signal calculated initial gas flow velocity is carried out add
Weight average, obtains average weighted gas flow rate, and then is calculated corresponding gas flow.
7. the method for measurement gas flow as claimed in claim 1 is it is characterised in that also include walking
Suddenly (4), judge that gained gas flow whether there is abnormal, if there is abnormal, recording exceptional state,
And reported to the police.
8. the method for measurement gas flow as claimed in claim 7 is it is characterised in that also include walking
Suddenly (5), according to working temperature and the pressure in measurement gas flow moment, the gas flow of gained is entered
Row is revised.
9. the method for measurement gas flow as claimed in claim 8 is it is characterised in that also include walking
Suddenly (6), using wireless communication mode, the gas flow recording, floor data and equipment state are sent out
Deliver to pipeline monitoring center.
10. the method for measurement gas flow as claimed in claim 9 is it is characterised in that also include
Step (7), after one time gas flow measurement finishes, ultrasonic flowmeter enters resting state, and
Automatically begin to after predetermined time interval measure next time.
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