CN106404084B - A method of measurement gas flow - Google Patents
A method of measurement gas flow Download PDFInfo
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- CN106404084B CN106404084B CN201510486278.9A CN201510486278A CN106404084B CN 106404084 B CN106404084 B CN 106404084B CN 201510486278 A CN201510486278 A CN 201510486278A CN 106404084 B CN106404084 B CN 106404084B
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Abstract
The invention discloses a kind of methods for measuring gas flow, comprising the following steps: around the ultrasonic receiving device of gas pipeline arrangement ultrasonic flowmeter, the ultrasonic wave of gas is transmitted through using ultrasonic receiving device, and acquire echo-signal；Two sampled points are chosen in the sampled data of echo-signal, the line of two sampled points and the intersection point moment of reference level line are denoted as T3, the period of ultrasonic echo signal is T, and ultrasonic wave is denoted as T at the time of transmission0, the initial time of echo-signal is T1, T1With T3Between echo-signal number of cycles be n；The transmission time t calculation formula of ultrasonic wave is as follows: t=T3‑T0-n·T；Gas flow is calculated using transmission time.The method that the present invention measures gas flow, measuring accuracy is high, measurement gas flow is accurate, and gas company can be made to monitor pipe network state in real time, remotely managed gas transmission and distribution, timely responded to abnormality.
Description
Technical field
The present invention relates to measuring instrument technical fields, and in particular to a method of measurement gas flow.
Background technique
Since attention rate of the people to environment is higher and higher, natural gas has obtained more next as the green energy resource of clean and environmental protection
More extensive concern and application, Gas Industry will be all rapidly developed within the following some time.In order to adapt to natural gas
The growth requirement of industry, especially gas company are to the growth requirement of gas metering and pipe network transmission & distribution management, in information-based skill
Under the development of art, accurate, the operation is stable is measured, and the intelligent flow meter systems with remote management capability initially enter day
In right gas metering and transmission & distribution management.
Currently, domestic application is mainly Roots's table and turbine table in the flowmeter of gas metering and transmission & distribution management, this two
Kind measuring instrument belongs to mechanical measuring instrument, it is difficult to the intrinsic weakness of mechanical instrument is got rid of, for example, to the matter of natural gas
Amount requires high, is easy to block, and maintenance is frequently and maintenance cost is higher, while with the increase of natural gas transportation line portals diameter, and two
Volume, weight and the price of kind mechanical measuring instrument can significantly rise, these weakness seriously constrain gas metering and
The direction of the management of pipe network transmission & distribution towards " accurate, stable, intelligent, efficient " is developed.
, there is ultrasonic flowmeter in the prior art in the shortcomings that in order to overcome mechanical measuring instrument, utilizes ultrasonic wave
Signal carries out the detection of gas flow, such as the patent of invention document that Authorization Notice No. is CN102914334B discloses a kind of insert
Enter formula ultrasonic gas flowmeter, the energy converter fixed frame being inserted under test gas pipeline when including using is fixed in energy converter
Be installed on frame for measure fair current time of the ultrasonic wave under test gas when downstream propagation and adverse current propagate when adverse current when
Between ultrasonic transducer group, further include using when be arranged in the corresponding with the ultrasonic transducer group of under test gas pipeline
Pipeline section at and be connected and supply the quiet fast container of the under test gas free diffusing in the pipeline section with the pipeline section, in quiet fast container
Upper arrangement in quiet fast pipe for measuring the ultrasonic transducer of ultrasonic propagation velocity.
But in the patent of invention document, quiet speed pipe needs to be inserted into gas piping the measurement for carrying out gas flow, quiet speed
Pipe itself, which can flow gas, to be caused to disturb, so as to cause the error of flow measurement.
In order to meet the growth requirement of gas metering and pipe network transmission & distribution management, it is desirable to provide a kind of intelligentized gas stream
Measuring method, to realize the precise measurement to gas discharge.
Summary of the invention
The present invention provides a kind of methods for measuring gas flow, can be realized the precise measurement to gas flow, and energy
It is enough that pipe network state is monitored in real time, the exception of natural gas transmission and distribution is timely responded to.
A method of measurement gas flow, comprising the following steps:
(1) it around the ultrasonic receiving device of gas pipeline arrangement ultrasonic flowmeter, is sent out using ultrasonic receiving device
The ultrasonic wave across gas is sent, and acquires echo-signal；
(2) two sampled points, the line and reference level line of two sampled points are chosen in the sampled data of echo-signal
The intersection point moment be denoted as T3, the period of ultrasonic echo signal is T, and ultrasonic wave is denoted as T at the time of transmission0, the starting of echo-signal
Moment is T1, T1With T3Between echo-signal number of cycles be n；The transmission time t calculation formula of ultrasonic wave is as follows:
T=T3-T0-n·T
The selection range of two sampled points are as follows: first positive amplitude is greater than V after triggering waveHH-VbAnd negative sense amplitude is big
In Vb-VLLWave band failing edge；
In two sampled points, one of sample is in [VHL, VHH] in range, another sample is in [VLL, VLH]
In range；
VHL、VHH、VLL、VLHIt is determined according to sample frequency, determines principle are as follows: sampling necessarily has sample in selected every time
In the level range taken, and the number of sampling points fallen into selected level range is few as much as possible；
(3) gas flow is calculated using the transmission time that step (2) obtain.
Gas flow measurement method provided by the invention is particularly suitable for natural gas, is also applied for similar to natural gas property
Gas measurement, for example, at least one of methane, ethane, propane, butane.
Using ultrasonic flowmeter to gas flow measure it is critical that Accurate Determining ultrasonic wave in gas
Then transmission time gradually decays since the echo-signal that ultrasonic probe, ultrasonic receiver receives usually grows from weak to strong, therefore,
Key at the time of receiving ultrasonic wave as determining transmission time is determined in echo-signal.Ultrasonic transmission provided by the invention
The determination method of time can accurately and reliably obtain the transmission time of ultrasonic wave, to obtain accurate gas flow.
In echo-signal, due to the limitation of sample frequency, the intersection point moment of echo-signal and reference level line is difficult to standard
It really obtains, the present invention is using the intersection point of two sampled point lines and reference level line as the friendship of echo-signal and reference level line
Point moment, method is simple, and can guarantee necessary computational accuracy.
Preferably, under the premise of sample frequency determines, [VHL, VHH] and [VLL, VLH] range it is as small as possible.With
Just make the sampled point in respective range few as much as possible, improve the certainty of calculating.If [VHL, VHH] or [VHL, VHH] in exist
Multiple sampled points met the requirements select the sampled point near respective range median.
VHHAnd VLLSelection mode are as follows: when gas flow reaches the ultrasonic flow rate measuring journey upper limit, using corresponding super
The maximum amplitude of sound wave subtracts certain allowance and obtains.
Selected [VHL, VHH] and [VLL, VLH] purpose be, when making the intersection point of two sampled point lines and reference level line
The intersection point moment that can approach echo-signal Yu reference level line is carved, under the premise of can reach the purpose, according to sampling frequency
Rate determines VHL、VHH、VLL、VLH。
Preferably, automatically adjusting increasing if can not find the sampled point met the requirements in the sampled data of echo-signal
Benefit, to obtain the sampled point met the requirements.
In extreme circumstances, when such as ultrasonic probe damages, it is possible that adjusting gain anyway cannot all obtain
The case where sampled point that must be met the requirements, after attempting after a period of time, if adopting of meeting the requirements can not be obtained always
Whether sampling point can be normally carried out judgement to probe, if it is decided that probe is abnormal, then carries out abnormal log storage and alarm.
In order to guarantee the accuracy of gas flow measurement, it is preferable that acquire three groups of echo-signals when each flow measurement, often
The corresponding forward transmission time for obtaining a ultrasonic wave and gas symport of group echo-signal and a ultrasonic wave and gas are anti-
To the reverse transmission time of transmission.The transmission path of difference group echo-signal is different, each group echo-signal is calculated first
Beginning gas flow rate is weighted and averaged, and obtains average weighted gas flow rate, and then corresponding gas flow is calculated.
Preferably, further including step (4), gained gas flow is judged with the presence or absence of exception, exception, then record if it exists
Abnormality, and alarm.
Preferably, further including step (5), according to the working temperature and pressure at measurement gas flow moment, to resulting
Gas flow is modified.
Preferably, further include step (6), using wireless communication mode by the gas flow measured, floor data and
Equipment state is sent to pipeline monitoring center.
Preferably, further including step (7), after a gas flow measurement, ultrasonic flowmeter enters suspend mode shape
State, and automatically begin to measure next time at preset time intervals afterwards.
The step of step (4)~step (7), numbers the differentiation for only doing different step, does not limit between each step
Sequence and the presence or absence of each step, for example, can directly be carried out step (7) after having carried out step (4).
The method that the present invention utilizes ultrasonic flow rate measurement amount gas flow, measuring accuracy is high, measurement gas flow is accurate
(at least up to identical precision with stem-winder), can enable gas company be monitored in real time to pipe network state, to combustion gas
Transmission & distribution are remotely managed, are timely responded to abnormality, and informationization of the gas company to gas ductwork can be effectively improved
Management level.
Detailed description of the invention
The schematic diagram that ultrasonic receiving device is arranged in the ultrasonic flowmeter of Fig. 1 a to realize the present invention；
Fig. 1 b is A in Fig. 1 a to schematic diagram；
Fig. 1 c is B in Fig. 1 b to schematic diagram；
Fig. 1 d is cuing open for the ultrasonic receiving device that ultrasonic wave propagation path passes through pipe centerline in ultrasonic flowmeter
View；
The structural schematic diagram of the ultrasonic flowmeter of Fig. 2 to realize the present invention；
The workflow schematic diagram of the ultrasonic flowmeter of Fig. 3 to realize the present invention；
Fig. 4 is the flow diagram of present invention measurement gas flow method；
Fig. 5 is original echoed signals schematic diagram；
Fig. 6 is the portion the B enlarged drawing in Fig. 5.
Specific embodiment
With reference to the accompanying drawing, the method for present invention measurement gas flow is described in detail.
The present invention is as follows using the principle of ultrasonic flow rate measurement amount gas flow:
The ultrasonic probe of the ultrasonic signal that the ultrasonic probe of air-flow upstream issues to airflow downstream receives ultrasonic wave
During signal, since gas flowing generates velocity component in the transmission direction of ultrasonic signal, ultrasonic wave can be accelerated to believe
Number transmission；The ultrasonic probe of the ultrasonic signal that the ultrasonic probe of airflow downstream issues to air-flow upstream receives ultrasonic wave
During signal, since gas flowing generates velocity component in the transmission direction of ultrasonic signal, ultrasonic wave letter can be slowed down
Number transmission, calculate gas stream using the difference of ultrasonic signal transmission time in along gas flow and inverse gas flow
Amount.
As shown in Figure 1 d, L is the linear distance of upstream and downstream ultrasonic probe in figure, and D is pipe diameter, and θ is ultrasonic wave biography
The angle in defeated path and measurement tube hub line, V are the mean flow rate of gas, t1For ultrasonic wave forward transmission time, t2For ultrasonic wave
Reverse transmission time, then have:
It 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 indicates the spread speed of ultrasonic wave；A indicates the cross-sectional area of measurement pipe.
By formula (IV) it can be seen that gas flow rate is not related with ultrasonic propagation velocity, it can thus be avoided due to temperature
The difference of the factors such as degree, pressure causes ultrasonic propagation velocity to change, and the measurement of gas flow is caused deviation occur.
By calculating process it is found that measurement gas flow it is critical that it is accurate measurement ultrasonic wave transmission time, in order to obtain
The correct time for obtaining ultrasonic transmission, utilizes the method for ultrasonic flow rate measurement amount gas flow, comprising the following steps:
(1) it around the ultrasonic receiving device of gas pipeline arrangement ultrasonic flowmeter, is sent out using ultrasonic receiving device
The ultrasonic wave across gas is sent, and acquires echo-signal；
Ultrasonic receiving device, as shown in Fig. 1 a, 1b, 1c, supersonic flow that the present invention uses are arranged around gas pipeline
Meter includes three pairs of ultrasonic probes (i.e. ultrasonic receiving device), respectively ultrasonic probe 11 and ultrasonic probe 12, is surpassed
Sonic probe 21 and ultrasonic probe 22, ultrasonic probe 31 and ultrasonic probe 32, wherein ultrasonic probe 11 and ultrasonic wave
The ultrasonic wave propagation path of probe 12 intersects with the center line of gas pipeline, and the ultrasonic wave that remaining two pairs of ultrasonic probe is formed passes
It broadcasts path to be parallel to each other, and is symmetrically distributed in the two sides of gas pipeline center line, each pair of ultrasonic probe is formed by ultrasonic wave
The angle of the center line of propagation path and gas pipeline is 60 degree, and the distance of ultrasonic probe 21 and ultrasonic probe 31 is less than
The diameter of under test gas flow conduit, and can be according to being selected.
In Fig. 1 a, ultrasonic probe 32 and ultrasonic probe 22 are overlapped, and ultrasonic probe 31 and ultrasonic probe 21 are overlapped,
Ultrasonic probe 11 and ultrasonic probe 12 are omitted in Fig. 1 c.
A pair of of ultrasonic probe be formed by ultrasonic wave be it is a branch of, the present invention in using the central axes of the beam ultrasonic wave as phase
The ultrasonic wave propagation path answered.
Each flow measurement acquires three groups of echo-signals, and every group of echo-signal correspondence obtains a ultrasonic wave and gas is in the same direction
The forward transmission time of transmission and the reverse transmission time of a ultrasonic wave and gas reverse transfer；Difference group echo-signal
Transmission path is different, and every group of echo-signal is obtained by a pair of of ultrasonic receiving device.
(2) two sampled points, the line and reference level line of two sampled points are chosen in the sampled data of echo-signal
The intersection point moment be denoted as T3, the period of ultrasonic echo signal is T, and ultrasonic wave is denoted as T at the time of transmission0, the starting of echo-signal
Moment is T1, T1With T3Between echo-signal number of cycles be n；The transmission time t calculation formula of ultrasonic wave is as follows:
T=T3-T0-n·T
The selection range of two sampled points are as follows: first positive amplitude is greater than V after triggering waveHH-VbAnd negative sense amplitude is big
In Vb-VLLWave band failing edge；As shown in Figure 5, Figure 6；Vb in Fig. 5, Fig. 6 is benchmark level line, and reference level line is different
Be set to zero, for example, by using 1.645V level line as reference level line.
In two sampled points, one of sample is in [VHL, VHH] in range, another sample is in [VLL, VLH]
In range；
VHL、VHH、VLL、VLHIt is determined according to sample frequency, determines principle are as follows: sampling necessarily has sample in selected every time
In the level range taken, and the number of sampling points fallen into selected level range is few as much as possible.
Under the premise of sample frequency determines, [VHL, VHH] and [VLL, VLH] range it is as small as possible.If [VHL, VHH] or
[VHL, VHH] in there are multiple sampled points met the requirements, select the sampled point near respective range median.
Part A in Fig. 5 is to trigger wave, i.e. first in echo-signal wave, as shown in Figure 5, Figure 6, in the present embodiment,
S1And S2Respectively two selected sampled points, S1And S2Line and reference level line the intersection point moment be T3, echo-signal with
The intersection point moment of reference level line is T2, with T3As T2Substitution value carry out the ultrasonic transmission time determination, n 2.
If two sampled points met the requirements in the actual operation process, can not be found in echo-signal, then automatically
Gain is adjusted until the sampled point met the requirements can be found in echo-signal, if can not find always, is determined corresponding
Ultrasonic receiving device is abnormal.
When calculating the transmission time of ultrasonic wave, it is necessary first to be adjusted to the echo-signal of ultrasonic wave, make ultrasonic wave
Triggering wave (as shown in part A in Fig. 5, first wave of the ultrasonic echo signal) amplitude of echo-signal is greater than sampling triggering electricity
Flat VTH, ultrasonic wave starts to sample after issuing a period of time, if sample circuit issues a signal to ultrasonic receiving device and starts to send
The time span of ultrasonic wave is constant, is denoted as ts, ultrasonic receiving device receives echo-signal to sample circuit receive echo letter
Number time span be constant, be denoted as tr, then when calculating transmission time, need to deduct the two times, that is, t=T3-T0-
n·T-ts-tr。
(3) gas flow rate is calculated using the transmission time that step (2) obtain, and gas flow is further calculated.
The gas travel time that difference group echo-signal obtains is weighted and averaged, and obtains average weighted time, and benefit
The calculating that gas flow is carried out with the average weighted time, obtains final gas flow.
It is abnormal to judge that gained gas flow whether there is for step (4), abnormal if it exists, then recording exceptional state, and carries out
Alarm.
Step (5) repairs resulting gas flow according to the working temperature and pressure at measurement gas flow moment
Just.
When gas flows in the duct, due to the influence of the factors such as pipe friction, the flow on cross-section of pipeline exists
Difference, after directly needing to correct by the gas flow that formula (IV) obtains, can truly reaction gas practical stream
Amount, in order to improve the precision of metering, the present invention using three pairs totally six ultrasonic receiving devices multi-point flux is sampled, so
Gas flow is calculated by average weighted method afterwards, and gas flow is modified, with the gas stream of approaching to reality
Amount.
The gas flow measured, floor data and equipment state are sent to pipe using wireless communication mode by step (6)
Road monitoring center.
Step (7), after a gas flow measurement, ultrasonic flowmeter enters dormant state, and in the predetermined time
It automatically begins to measure next time behind interval.
It include bandpass filtering, programmable-gain and signal sampling three parts function electricity in each ultrasonic receiving device
The adjustment of ultrasonic echo signal is completed on road by sampling-adjustment-sampling cyclic process, obtains capable of being correctly validated
Ultrasonic echo.
Band-pass filtering function circuit by frequency-selecting function, guarantee ultrasonic echo signal it is lossless by while, can filter
Except the clutter in echo-signal, to guarantee that the programmable gain circuit of rear class can obtain purer ultrasonic echo signal.
In addition to ultrasonic receiving device, as shown in Fig. 2, realizing ultrasonic flowmeter of the invention further include: control unit,
Power module, input module, data memory module, wireless communication module, display module, working condition acquiring module, output module.
Power module is used to provide power supply output to each power unit of ultrasonic flowmeter, and the input of power module is
The DC power supply of 4.5~16V wide-voltage range is powered to each power unit of ultrasonic flowmeter respectively using conversion circuit.Directly
Stream power input can use external power supply, can also be supplied by the battery inside ultrasonic flowmeter.
Ultrasonic flowmeter provided by the invention includes both of which, a kind of operating mode to measure when gas flow,
For another kind to stop low-power consumption mode when gasmetry, it is automatic between both of which that control unit controls ultrasonic flowmeter
Switching, automatic switching procedure can pass through program setting in advance, also can use input module manually input.
The controlled process that power module is powered to each power unit is in control unit, and control unit is according to ultrasonic flowmeter
Operating mode and low-power consumption mode difference, to power module send control signal, coordinate ultrasonic flowmeter with minimum
Power consumption is effectively run, that is, the power unit of work is needed to power, and the power unit without work stops power supply.
Control unit is the core of ultrasonic flowmeter data processing and each composition partial function control, using list
Piece machine (STM32 microprocessor) and FPGA complete the function of control unit jointly to be controlled when ultrasonic flowmeter works using FPGA
The ultrasonic signal of ultrasonic receiving device processed is received and dispatched and carries out time calculating, after FPGA calculates the time, acquisition
Time Transmission to single-chip microcontroller, single-chip microcontroller completes the calculating of flow according to the time.
Single-chip microcontroller carries out the calculating and volume amendment of gas flow in addition to the time inputted according to FPGA, is also counted
According to storage management, the information exchange of data and remaining equipment control, the function of controlling display module shows, the finger of input module
Enable input, the switching of mode, the acquisition of floor data and signal output.
Programmable-gain functional circuit in ultrasonic receiving device and led between control unit by SPI interface
Letter carries out amplitude adjustment to echo-signal according to the instruction of control unit, and sample circuit samples ultrasonic echo signal,
And give the data after sampling to control unit by SPI interface, control unit judges whether to need according to the sampling of sample circuit
Ultrasonic echo signal is adjusted.
Control unit is communicated by RS485 interface with host computer, when enabling an administrator to system through host computer
Between, the parameters such as mode, operational process parameter, volume correction chart be issued to control unit, can also be by querying command to control
Unit obtains the status informations such as current temperature, pressure, flow, the ultrasonic velocity of system, and suspend mode/call out can also be issued to system
Wake up etc. control commands realize system between operating mode and low-power consumption mode switching (system suspend mode corresponds to low-power consumption mode,
Wake up corresponding operating mode).
Data memory module includes ferroelectric memory and SPI flash storage two parts, is connect with control unit by SPI
Mouth is communicated, the storage for system parameter, various list items, system mode and continuous data.
Wireless communication module uses GPRS module, is communicated by UART interface with control unit, and in control unit
Control under the information exchange of equipment and pressure management area center is realized by public cordless communication network, complete continuous data
The reception of the control instruction at upload and pressure management area center.
Input module realizes contactless keypress function using Hall sensor, for inputting various instructions, for example, system
Sleeping/waking, menu control and information inquiry etc. functions.
Display module uses OLED module, is communicated by SPI interface with control unit, current for display system
The metrical informations such as temperature, pressure, flow, ultrasonic velocity, wherein flow includes present flow rate, integrated flow, timing flow, work
The multiple types such as condition flow, mark condition flow.
Output module is communicated by I/O mouthfuls of number and SPI interface with control unit, in the control of control unit
Under, export digital pulse signal and 4~20mA electric current ring signal, wherein digital pulse signal is with low and high level output abnormality
The status signals such as alarm, 4~20mA electric current ring signal characterize specific system mode by output quantization electric current.
Working condition acquiring module includes temperature collecting module and pressure acquisition module, and wherein temperature collecting module is connect by simulation
Mouth is communicated with control unit, and control unit is searched the temperature in data memory module according to the temperature data that sampling obtains and turned
Table is changed, can learn working site temperature to realize the amendment of the data such as gas flow.
Pressure acquisition module is communicated by analog interface with control unit, the pressure that control unit is obtained according to sampling
Pressure conversion table in data search data memory module can learn working site pressure to realize the data such as gas flow
Amendment.
As shown in figure 3, ultrasonic flowmeter in use, first with control unit and power module completion system it is upper
Electricity and initialization, the power up of system are as follows: power module is first to the minimum system that can guarantee that control unit works normally
It is powered on, after the minimum system of control unit works normally, control unit controls power module and carries out to remaining power unit
It powers on.
After system completion powers on, under the control of the control unit, communication and status is carried out to each functional module of system automatically
Detection, after the completion of detection, if system mode is normal, opening corresponding timing routine, (time of timing routine is set with effective
For the purpose of reducing system power dissipation, when the length of timing time has to be larger than needed for the primary complete measurement flow of system completion
Between) enter idle state, corresponding interrupt instruction is waited, if system mode is abnormal, under the control of the control unit, by exporting
Module exports digital pulse signal and 4~20mA electric current ring signal, carries out abnormal alarm.
For the equipment of external power supply, system in an idle state, can enter dormant state to reduce system power dissipation,
Dormant state can not be entered to guarantee the response speed of system；For battery powered low power consuming devices, the idle shape
State is the low power consumpting state of suspend mode, reduces system power dissipation in the case where guaranteeing measuring accuracy.
When needed, system manager can be corresponding to control unit publication by the host computer being connected with control unit
Instruction, is issued or is modified to system time, operating mode, operational process parameter, various amendment list items etc.；System manager
Can also be by host computer using status informations such as temperature, pressure, the flows of querying command acquisition system, it can also be by stopping
Dormancy/wake up instruction control system carries out the switching of working condition.
When exhausting a time-count cycle of timing routine, system can generate corresponding Interruption to open a metering
Process and a metering cycle, in each measurement flow, on the one hand control unit is believed according to the echo of ultrasonic receiving device
The calculating for number completing transmission time, on the other hand carries out AD sampling by temperature-measuring module and pressure measuring module, and inquire
Corresponding transformation table entries to be in data memory module to obtain the work informations such as working site temperature, pressure, then control unit root
Data processing is carried out according to parameters such as the time of acquisition, temperature and pressures, to complete the metering and amendment of gas flow；Had
After the continuous data of effect, the storage of data is completed as required, terminates this measurement flow.
In each measurement flow, control unit controls ultrasonic receiving device and carries out ultrasonic wave according to required order
Transmitting and reception, as shown in figure 4, firstly, control unit is complete according to that can be obtained in measurement flow with most fast speed
Effective time data needed for portion are principle, choose the transmitting that ultrasonic receiving device carries out ultrasonic wave, and corresponding ultrasonic wave is received
Transmitting apparatus carries out the reception of echo-signal, after echo signal reception, controls sampling circuit samples by control unit, and sampling
To echo-signal according to rule choose two sampled points, utilize the intersection point moment of two sampled point lines and reference level line
The transmission time of ultrasonic wave is calculated, ultrasonic receiving device informs control unit read access time data by interrupt signal, obtains
Once effectively time data and after recording data in memory module, this precise time measurement procedure terminates.
After the completion of each measurement flow, control unit is according to system Current Temperatures, pressure, gas flow and ultrasonic acoustic
The metrical informations such as speed, judgement are that no there are abnormal conditions for gas distributing system；If system mode is normal, working-flow enters
Next stage；Abnormal conditions if it exists then carry out abnormality mark storage, and can export digital pulse signal and 4- by output module
20mA electric current ring signal carries out abnormal alarm；Wherein, digital pulse signal is with the states letter such as low and high level transmission abnormality alarm
Number, 4-20mA electric current ring signal characterizes specific system mode by output quantization electric current can also for the equipment of external power supply
Long-range abnormal alarm is carried out with module by wireless communication.
If system uses external power supply, as needed, module and administrative center can establish in real time by wireless communication
Wireless communication connection, to complete the real-time upload of continuous data and system mode etc..
System in the process of running, can be by the suspend mode of the cooperation carry out system of input module and display module/call out
The functions such as awake, menu control, continuous data and state information searching.
When ultrasonic flowmeter is without gasmetry, system enters idle state.
Above embodiment is the preferable embodiment of the present invention, but embodiments of the present invention are not by the embodiment
Limitation, other any modifications made by without departing from the spirit and principles of the present invention substitution, combination, cut,
It should be equivalent substitute mode, be included within the scope of the present invention.
Claims (10)
1. a kind of method for measuring gas flow, which comprises the following steps:
(1) it around the ultrasonic receiving device of gas pipeline arrangement ultrasonic flowmeter, is worn using ultrasonic receiving device transmission
The ultrasonic wave of gas is crossed, and acquires echo-signal；
(2) two sampled points, the friendship of the line and reference level line of two sampled points are chosen in the sampled data of echo-signal
Point moment is denoted as T3, the period of ultrasonic echo signal is T, and ultrasonic wave is denoted as T at the time of transmission0, the initial time of echo-signal
For T1, T1With T3Between echo-signal number of cycles be n；The transmission time t calculation formula of ultrasonic wave is as follows:
T=T3-T0-n·T
The selection range of two sampled points are as follows: first positive amplitude is greater than V after triggering waveHH-VbAnd negative sense amplitude is greater than Vb-
VLLWave band failing edge；VbFor benchmark level line；
In two sampled points, one of sample is in [VHL, VHH] in range, another sample is in [VLL, VLH] range
It is interior；
VHL、VHH、VLL、VLHIt is determined according to sample frequency, determines principle are as follows: sampling necessarily has sample in selected every time
In level range, and the number of sampling points fallen into selected level range is few as much as possible；VHHAnd VLLSelection mode
Are as follows: when gas flow reaches the ultrasonic flow rate measuring journey upper limit, subtracted using the maximum amplitude of corresponding ultrasonic wave certain
Allowance obtains；
(3) gas flow is calculated using the transmission time that step (2) obtain.
2. the method for measurement gas flow as described in claim 1, which is characterized in that under the premise of sample frequency determines,
[VHL, VHH] and [VLL, VLH] range it is as small as possible.
3. the method for measurement gas flow as claimed in claim 2, which is characterized in that if [VHL, VHH] or [VLL, VLH] in deposit
In multiple sampled points met the requirements, the sampled point near respective range median is selected.
4. the method for measurement gas flow as claimed in claim 3, which is characterized in that if in the sampled data of echo-signal
It can not find the sampled point met the requirements, then automatically adjust gain, to obtain the sampled point met the requirements.
5. the method for measurement gas flow as described in claim 1, which is characterized in that acquire three groups when each flow measurement and return
Wave signal, every group of echo-signal correspondence obtain the forward transmission time and a ultrasound of a ultrasonic wave and gas symport
The reverse transmission time of wave and gas reverse transfer.
6. the method for measurement gas flow as claimed in claim 5, which is characterized in that the transmission path of difference group echo-signal
Difference is weighted and averaged the initial gas flow velocity that each group echo-signal is calculated, obtains average weighted gas flow rate,
And then corresponding gas flow is calculated.
7. the method for measurement gas flow as described in claim 1, which is characterized in that further include step (4), judge to be brought about the desired sensation
Body flow whether there is exception, abnormal if it exists, then recording exceptional state, and alarm.
8. the method for measurement gas flow as claimed in claim 7, which is characterized in that further include step (5), according to measurement gas
The working temperature and pressure at body flow moment, are modified resulting gas flow.
9. the method for measurement gas flow as claimed in claim 8, which is characterized in that further include step (6), utilize channel radio
The gas flow measured, floor data and equipment state are sent to pipeline monitoring center by news mode.
10. the method for measurement gas flow as claimed in claim 9, which is characterized in that further include step (7), a gas
After flow measurement, ultrasonic flowmeter enters dormant state, and automatically begins to measure next time at preset time intervals afterwards.
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| JP3698667B2 (en) * | 2001-10-31 | 2005-09-21 | 東京計装株式会社 | Ultrasonic flow meter by propagation time difference method |
| CA2557432C (en) * | 2004-02-26 | 2012-09-04 | Fuji Electric Systems Co., Ltd. | Ultrasonic flowmeter and ultrasonic flow rate measurement method |
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| CN1202248A (en) * | 1995-09-25 | 1998-12-16 | 施蓝姆伯格工业公司 | Method for acoustically measuring fluid flow rate |
| CN1864047A (en) * | 2003-09-08 | 2006-11-15 | 丹尼尔工业公司 | Self-tuning ultrasonic meter |
| CN101813515A (en) * | 2010-04-30 | 2010-08-25 | 重庆理工大学 | Method and device for precisely measuring ultrasonic wave transmission time |
| CN102297712A (en) * | 2011-07-12 | 2011-12-28 | 北京理工大学 | Method for measuring propagation time of ultrasonic echo |
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