CN107064295B - A kind of methane gas concentration measurement system and method - Google Patents
A kind of methane gas concentration measurement system and method Download PDFInfo
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- CN107064295B CN107064295B CN201710026720.9A CN201710026720A CN107064295B CN 107064295 B CN107064295 B CN 107064295B CN 201710026720 A CN201710026720 A CN 201710026720A CN 107064295 B CN107064295 B CN 107064295B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
- G01N29/036—Analysing fluids by measuring frequency or resonance of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2291/02—Indexing codes associated with the analysed material
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- G01N2291/02809—Concentration of a compound, e.g. measured by a surface mass change
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Abstract
The present invention provides a kind of methane gas concentration measurement system and methods, it is related to methane gas concentration measurement technical field, one sampling ball with Double Opening of installation in detection pipeline, after methane gas to be measured is passed through sampling ball, the percentage composition that methane gas can be calculated by measuring resonance frequency, not only structure is simple, it is novel in design reasonable, it is convenient to realize, and it can effectively improve the reliability of methane gas concentration measurement, other gas concentration measurements are also suitable for simultaneously, practical, application value is high.
Description
Technical field
The present invention relates to methane gas concentration measurement technical field, in particular to a kind of methane gas concentration measurement system and
Method.
Background technique
Gas is gas common in coal mining, drastically influences the safety in production of coal mine.For how accurate measurements
Gas density is a critical issue of pre- anti-gas explosion technology.Currently, the common gas management sensor of underground coal mine is big
Mostly using being catalysis sensing element, detectable concentration range is smaller, and measurement result stability is poor.Therefore, scientific research personnel is to this
Expand a large amount of new researchs.For example, document is " based on Infrared spectra adsorption principle in volume 2006 the 31st of " coal journal "
The experiment of infrared gas senor " in have developed the infrared gas senor based on Infrared spectra adsorption principle." Northcentral University is learned
Report (natural science edition) " 2008 in volume 29, document " measures skill based on the gas density of spectral absorption and harmonic detecting
Art " in propose the coal mine gas monitoring method of a kind of gas features spectral absorption characteristics and second-harmonic detection principle." piezoelectricity
With acousto-optic " the 4th phases in 2010 " research of the novel gas sensor based on acoustic resonant cavity " text in, propose one
Gas sensor of the kind based on acoustic resonant cavity, the offset for passing through the resonance frequency of piezoelectric resonator chamber detect mixed gas
The content of middle methane gas.
But the generally existing problem that structure is complicated, Measurement reliability is not high of current measuring technique.
Summary of the invention
The embodiment of the invention provides a kind of methane gas concentration measurement system and methods, deposit in the prior art to solve
The problem of.
The both ends of a kind of methane gas concentration measurement system, including detection pipeline, the detection pipeline are respectively arrival end
And outlet end, there are two interface, respectively first entrance interface and second entrance interface, the outlet ends for the arrival end tool
There are two interfaces, respectively first outlet interface and second outlet interface for tool；Pass through pipeline on the first entrance interface and enter
Mouth valve connection, the first outlet interface are connect with outlet valve by pipeline, are fixedly installed with inside the detection pipeline
Double Opening samples ball, and the Double Opening sampling ball is hollow structure, and there are two sample through-hole for surface tool；
The second entrance interface is equipped with first wave conduit, and loudspeaker is mounted on the end of the first wave conduit, institute
State the output end connection of the input terminal and function generator of loudspeaker, the input terminal of the function generator and the USB of computer
Interface connection；
Second waveguide pipe is installed on the second outlet interface, microphone is mounted on the end of the second waveguide pipe,
The output end of the microphone and the input terminal of data collector connect, the output end of the data collector and the computer
Another USB interface connection；
The computer includes that module and data processing module occur for sinusoidal waveform；
Module occurs for the sinusoidal waveform for generating scan frequency point command frame, then will scan frequency by USB interface
Rate point command frame is transferred to the function generator, and the function generator extracts in frame after receiving scan frequency point command frame
Frequency data, generate sine wave signal with the frequency data, which drives the loudspeaker sounding；
The data processing module is used to send acquisition to the data collector by the USB interface of the computer and open
Dynamic frame, the data collector receive and carry out data acquisition with default sample frequency after acquisition starting frame；The data are adopted
The data of acquisition are transferred to the data processing module of the computer by storage by USB interface, and the data processing module will
Collected data are saved；The data processing module successively recalls the corresponding acquisition data of scan frequency point, and from adopting
The corresponding maximum value of each Frequency point is found out in collection data, then finds out minimum value in these maximum values, the minimum value institute
Corresponding scan frequency point is resonance frequency fr, bring resonance frequency into gas density in formula calculating under test gas；
Specifically, the calculating process of the data processing module are as follows:
The effective volume V of the Double Opening sampling ball internal cavity is the body that inner ball volume subtracts two sampling through-holes
Product:
Wherein, RiThe inside radius of ball is sampled for the Double Opening, a is the radius of the sampling through-hole；
According to Principles of Acoustics, the acoustic capacitance of the methane gas in the Double Opening sampling ball spherical cavity is CA, then have:
Consider that the sampling through-hole both ends amendment situation, the effective length of the sampling through-hole are equal are as follows:
Wherein, RoThe outer radius of ball is sampled for the Double Opening；
The phonoreception of the sampling through-hole are as follows:
Wherein, ρ is the density of methane gas to be measured；
The phonoreception of two sampling through-holes is considered as situation in parallel, then total phonoreception are as follows:
According to resonance circuit rule, the resonance frequency of the Double Opening sampling ball are as follows:
Wherein, c is spread speed of the sound in methane gas to be measured；
The velocity of sound in methane gas to be measured meets:
Wherein, p is gas pressure intensity, and γ is the specific heat ratio of methane gas to be measured, then:
γ=(1-x) γk+xγw (8)
Wherein, x is the percentage composition of methane gas to be measured, γkFor the specific heat ratio of air, γwFor the specific heat of methane gas
Hold ratio；
The density of methane gas to be measured:
ρ=(1-x) ρk+xρw (9)
Wherein, ρkFor the density of air, ρwFor the density of methane gas；
It brings formula (7), formula (8) and formula (9) into formula (6), can obtain
In situation known to other parameters, by measuring resonance frequency fr, can be obtained described pair by formula (10) and open
Hole samples the percentage composition of methane gas to be measured in ball.
Preferably, the Double Opening sampling ball is fixedly mounted in the detection pipeline using hot melt adhesive.
Preferably, completely permutation is installed on the end face of the second outlet interface, is installed on the completely permutation
There is the second waveguide pipe.
Preferably, module occurs for the sinusoidal waveform according to stepping change scan frequency point, the frequency to be scanned for completing setting
The sinusoidal waveform occurs module and stops sounding command frame to function generator transmission after rate range, to control the loudspeaking
Device stops sounding.
Preferably, after the frequency range that module scans complete setting occurs for the sinusoidal waveform, by the data processing
Module is sent to the data collector stops acquisition instructions frame, after the data collector receives the stopping acquisition instructions frame
Stop data acquisition.
The present invention also provides a kind of methane gas concentration measurement methods, comprising:
Inlet valve and outlet valve are opened simultaneously, enters methane gas to be measured in Double Opening sampling ball, sampling is completed
Inlet valve and outlet valve are closed afterwards, wherein the inlet valve and outlet valve are separately mounted to the first of detection pipeline
In ingress interface and first outlet interface, the detection pipeline also has a second entrance interface and second outlet interface, and described
First wave conduit is installed, the first wave guide pipe end is equipped with loudspeaker, the input of the loudspeaker in two ingress interfaces
The output end connection of and function generator is held, the input terminal of the function generator is connect by USB interface with computer；It is described
Second waveguide pipe is installed on second outlet interface, the second waveguide pipe end is equipped with microphone, the microphone it is defeated
The output end of the connection of the input terminal of outlet and data collector, the data collector is connected by USB interface and the computer
It connects, the computer includes that module and data processing module occur for sinusoidal waveform；
The sinusoidal waveform occurs module and generates scan frequency point command frame, then passes through USB interface for scan frequency point
Command frame is transferred to the function generator, and the function generator receives the frequency extracted after scan frequency point command frame in frame
Rate data generate sine wave signal with the frequency data, which drives the loudspeaker sounding；
The data processing module sends acquisition starting to the data collector by the USB interface of the computer
Frame, the data collector receive the acquisition starting frame after with default sample frequency carry out data acquisition；The data acquisition
The data of acquisition are transferred to the data processing module of the computer by device by USB interface, and the data processing module will be adopted
The data collected are saved；The data processing module successively recalls the corresponding acquisition data of scan frequency point, and from acquisition
The corresponding maximum value of each Frequency point is found out in data, then finds out minimum value in these maximum values, and minimum value institute is right
The scan frequency point answered is resonance frequency fr, bring resonance frequency into gas density in formula calculating under test gas；
Specifically, the calculating process of the data processing module are as follows:
The effective volume V of the Double Opening sampling ball internal cavity is the body that inner ball volume subtracts two sampling through-holes
Product:
Wherein, RiThe inside radius of ball is sampled for the Double Opening, a is the radius of the sampling through-hole；
According to Principles of Acoustics, the acoustic capacitance of the methane gas in the Double Opening sampling ball spherical cavity is CA, then have:
Consider that the sampling through-hole both ends amendment situation, the effective length of the sampling through-hole are equal are as follows:
Wherein, RoThe outer radius of ball is sampled for the Double Opening；
The phonoreception of the sampling through-hole are as follows:
Wherein, ρ is the density of methane gas to be measured；
The phonoreception of two sampling through-holes is considered as situation in parallel, then total phonoreception are as follows:
According to resonance circuit rule, the resonance frequency of the Double Opening sampling ball are as follows:
Wherein, c is spread speed of the sound in methane gas to be measured；
The velocity of sound in methane gas to be measured meets:
Wherein, p is gas pressure intensity, and γ is the specific heat ratio of methane gas to be measured, then:
γ=(1-x) γk+xγw (18)
Wherein, x is the percentage composition of methane gas to be measured, γkFor the specific heat ratio of air, γwFor the specific heat of methane gas
Hold ratio；
The density of methane gas to be measured:
ρ=(1-x) ρk+xρw (19)
Wherein, ρkFor the density of air, ρwFor the density of methane gas；
It brings formula (7), formula (8) and formula (9) into formula (6), can obtain
In situation known to other parameters, by measuring resonance frequency fr, can be obtained described pair by formula (20) and open
Hole samples the percentage composition of methane gas to be measured in ball.
Preferably, module occurs for the sinusoidal waveform according to stepping change scan frequency point, the frequency to be scanned for completing setting
The sinusoidal waveform occurs module and stops sounding command frame to function generator transmission after rate range, to control the loudspeaking
Device stops sounding.
Preferably, after the frequency range that module scans complete setting occurs for the sinusoidal waveform, by the data processing
Module is sent to the data collector stops acquisition instructions frame, after the data collector receives the stopping acquisition instructions frame
Stop data acquisition.
The beneficial effects of the present invention are: 1, present invention employs integrated design, and structure is simple, novel in design reasonable,
It is convenient to realize；
2, the present invention can effectively improve the reliability of methane gas concentration measurement；
3, the present invention is also suitable for other gas concentration measurements, practical, and application value is high.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
It obtains other drawings based on these drawings.
Fig. 1 is a kind of structure chart of methane gas concentration measurement system provided in an embodiment of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
Referring to Fig.1, the embodiment of the invention provides a kind of methane gas concentration measurement system, including detection pipeline 100, institutes
The both ends for stating detection pipeline 100 are respectively arrival end and outlet end, and there are two interfaces, respectively first entrance for the arrival end tool
Interface and second entrance interface, the outlet end also have there are two interface, respectively first outlet interface and second outlet interface.
It is connect by pipeline with inlet valve 120 on the first entrance interface, the first outlet interface passes through pipeline and outlet valve
Door 130 connects, and 100 inside of detection pipeline is fixedly installed with Double Opening sampling ball 110 using hot melt adhesive, and the Double Opening is adopted
Sample ball 110 is hollow structure, and there are two sample through-hole for surface tool.
The second entrance interface is equipped with first wave conduit 140, and loudspeaker 200 is mounted on the first wave conduit 140
End, the audio output port of the loudspeaker 200 is located inside the first wave conduit 140.The input of the loudspeaker 200
The output end connection of and function generator 300 is held, the USB of the input terminal and computer 400 of the function generator 300 is (general
Universal serial bus) interface connection.
The end face of the second outlet interface is equipped with completely permutation, and second waveguide is equipped on completely permutation
Pipe 150, microphone 500 are mounted on the end of the second waveguide pipe 150, and the output end and data of the microphone 500 acquire
The input terminal of device 600 connects, and the output end of the data collector 600 is connect with another USB interface of the computer 400.
The computer 400 includes that module 410, data recordin module 420 and data processing module occur for sinusoidal waveform
430。
Module 410 occurs for the sinusoidal waveform for generating scan frequency point command frame, the scan frequency point command frame by
Initial order code (1BYTE) and frequency data (2BYTE) are constituted, and are then passed scan frequency point command frame by USB interface
Defeated to arrive the function generator 300, the function generator 300 receives the frequency extracted after scan frequency point command frame in frame
Data generate sine wave signal with the frequency data, which drives 200 sounding of loudspeaker；The sine wave
Shape occurs module 410 and changes scan frequency point, the sinusoidal waveform hair after the frequency range to be scanned for completing setting according to stepping
Raw module 410 is sent to the function generator 300 stops sounding command frame, and the stopping sounding command frame is by halt instruction code
(1BYTE) and halt instruction (1BYTE) are constituted, and stop sounding to control the loudspeaker 200；
The data processing module 430 is sent by the USB interface of the computer 400 to the data collector 600
Acquisition starting frame, acquisition starting frame are made of enabled instruction code (1BYTE) and enabled instruction (1BYTE)；The data are adopted
Storage 600 receive the acquisition starting frame after with default sample frequency carry out data acquisition；The data collector 600 will acquisition
Data the data processing module 430 is transferred to by USB interface in a manner of communication frame.Communication frame is by initial code
(1BYTE) and acquisition data (2BYTE) are constituted, and the data processing module 430 saves collected data；When sampling
It is 2 seconds long；Occur after the frequency range set is completed in the scanning of module 410 after the sinusoidal waveform by the data processing module 430
Sent to the data collector 600 and stop acquisition instructions frame, the stopping acquisition instructions frame by halt instruction code (1BYTE) and
Halt instruction (1BYTE) is constituted；The data collector 600 stops data acquisition after receiving the stopping acquisition instructions frame；
The data processing module 430 successively recalls the corresponding acquisition data of scan frequency point, and therefrom finds out each frequency
The corresponding maximum value of point, then finds out minimum value, the point of scan frequency corresponding to the minimum value is in these maximum values
fr, bring resonance frequency into gas density in formula calculating under test gas；
Specifically, the calculating process of the data processing module 430 are as follows:
The effective volume V of Double Opening sampling 110 internal cavity of ball is that inner ball volume subtracts two sampling through-holes
Volume:
Wherein, RiThe inside radius of ball 110 is sampled for the Double Opening, a is the radius of the sampling through-hole；
According to Principles of Acoustics, the acoustic capacitance of the methane gas in Double Opening sampling 110 spherical cavity of ball is CA, then have:
Consider that the sampling through-hole both ends amendment situation, the effective length of the sampling through-hole are equal are as follows:
Wherein, RoThe outer radius of ball 110 is sampled for the Double Opening；
The phonoreception of the sampling through-hole are as follows:
Wherein, ρ is the density of methane gas to be measured；
The phonoreception of two sampling through-holes is considered as situation in parallel, then total phonoreception are as follows:
According to resonance circuit rule, the resonance frequency of the Double Opening sampling ball 110 are as follows:
Wherein, c is spread speed of the sound in methane gas to be measured；
The velocity of sound in methane gas to be measured meets:
Wherein, p is gas pressure intensity, and γ is the specific heat ratio of methane gas to be measured, then:
γ=(1-x) γk+xγw (8)
Wherein, x is the percentage composition of methane gas to be measured, γkFor the specific heat ratio of air, γwFor the specific heat of methane gas
Hold ratio；
The density of methane gas to be measured:
ρ=(1-x) ρk+xρw (9)
Wherein, ρkFor the density of air, ρwFor the density of methane gas；
It brings formula (7), formula (8) and formula (9) into formula (6), can obtain
In situation known to other parameters, by measuring resonance frequency fr, can be obtained described pair by formula (10) and open
Hole samples the percentage composition of methane gas to be measured in ball 110.
The data recordin module 420 saves the gas percentage composition data of measurement.
Based on identical inventive concept, the present invention also provides a kind of methane gas concentration measurement method, the realities of this method
The implementation that can refer to above system is applied, overlaps will not be repeated:
First step opens simultaneously inlet valve and outlet valve, enters methane gas to be measured in Double Opening sampling ball,
Inlet valve and outlet valve are closed after the completion of sampling；
Second step, the sinusoidal waveform of computer occur module and generate scan frequency point command frame, and will by USB interface
Scan frequency point command frame is transferred to function generator, and function generator extracts frequency after receiving the scan frequency point command frame
Data generate sine wave signal, the sine wave signal drive the speaker sounding with the frequency data；
Third step, data processing module send acquisition starting frame, number to data collector by the USB interface of computer
It is received according to collector and data acquisition is carried out with default sample frequency after acquiring starting frame, data collector leads to the data of acquisition
The data processing module that USB interface is transferred to computer is crossed, the data processing module saves collected data；
Four steps, sinusoidal waveform occur module and change scan frequency point according to stepping, recycle second and third step, scan
After the frequency range for completing setting, is sent from data processing module to data collector and stop acquisition instructions frame, data collector
Stop data acquisition after receiving the stopping acquisition instructions frame；Module occurs for sinusoidal waveform to function generator transmission stopping simultaneously
Sounding command frame stops sounding to control loudspeaker；
5th step, data processing module successively recalls the corresponding acquisition data of scan frequency point, and therefrom finds out each frequency
The corresponding maximum value of rate point, then finds out minimum value in these maximum values, the point of scan frequency corresponding to the minimum value, will
Resonance frequency brings formula (10) into and then calculates the gas percentage composition under test gas；
6th step, data recordin module save the gas percentage composition data of measurement.
It should be understood by those skilled in the art that, the embodiment of the present invention can provide as method, system or computer program
Product.Therefore, complete hardware embodiment, complete software embodiment or reality combining software and hardware aspects can be used in the present invention
Apply the form of example.Moreover, it wherein includes the computer of computer usable program code that the present invention, which can be used in one or more,
The computer program implemented in usable storage medium (including but not limited to magnetic disk storage, CD-ROM, optical memory etc.) produces
The form of product.
The present invention be referring to according to the method for the embodiment of the present invention, the process of equipment (system) and computer program product
Figure and/or block diagram describe.It should be understood that every one stream in flowchart and/or the block diagram can be realized by computer program instructions
The combination of process and/or box in journey and/or box and flowchart and/or the block diagram.It can provide these computer programs
Instruct the processor of general purpose computer, special purpose computer, Embedded Processor or other programmable data processing devices to produce
A raw machine, so that being generated by the instruction that computer or the processor of other programmable data processing devices execute for real
The device for the function of being specified in present one or more flows of the flowchart and/or one or more blocks of the block diagram.
These computer program instructions, which may also be stored in, is able to guide computer or other programmable data processing devices with spy
Determine in the computer-readable memory that mode works, so that it includes referring to that instruction stored in the computer readable memory, which generates,
Enable the manufacture of device, the command device realize in one box of one or more flows of the flowchart and/or block diagram or
The function of being specified in multiple boxes.
These computer program instructions also can be loaded onto a computer or other programmable data processing device, so that counting
Series of operation steps are executed on calculation machine or other programmable devices to generate computer implemented processing, thus in computer or
The instruction executed on other programmable devices is provided for realizing in one or more flows of the flowchart and/or block diagram one
The step of function of being specified in a box or multiple boxes.
Although preferred embodiments of the present invention have been described, it is created once a person skilled in the art knows basic
Property concept, then additional changes and modifications may be made to these embodiments.So it includes excellent that the following claims are intended to be interpreted as
It selects embodiment and falls into all change and modification of the scope of the invention.
Obviously, various changes and modifications can be made to the invention without departing from essence of the invention by those skilled in the art
Mind and range.In this way, if these modifications and changes of the present invention belongs to the range of the claims in the present invention and its equivalent technologies
Within, then the present invention is also intended to include these modifications and variations.
Claims (7)
1. a kind of methane gas concentration measurement system, which is characterized in that including detecting pipeline, the both ends difference of the detection pipeline
For arrival end and outlet end, there are two interfaces, respectively first entrance interface and second entrance interface for the arrival end tool, described
Outlet end also has there are two interface, respectively first outlet interface and second outlet interface；Pass through on the first entrance interface
Pipeline is connect with inlet valve, and the first outlet interface is connect by pipeline with outlet valve, is made inside the detection pipeline
It is fixedly installed with Double Opening sampling ball with hot melt adhesive, the Double Opening sampling ball is hollow structure, and there are two samplings for surface tool
Through-hole；
The second entrance interface is equipped with first wave conduit, and loudspeaker is mounted on the end of the first wave conduit, described to raise
The output end of the input terminal and function generator of sound device connects, the input terminal of the function generator and the USB interface of computer
Connection；
Second waveguide pipe is installed, microphone is mounted on the end of the second waveguide pipe, described on the second outlet interface
The output end of microphone and the input terminal of data collector connect, and the output end of the data collector is another with the computer
The connection of one USB interface；
The computer includes that module and data processing module occur for sinusoidal waveform；
Module occurs for the sinusoidal waveform for generating scan frequency point command frame, then passes through USB interface for scan frequency point
Command frame is transferred to the function generator, and the function generator receives the frequency extracted after scan frequency point command frame in frame
Rate data generate sine wave signal with the frequency data, which drives the loudspeaker sounding；
The data processing module is used to send acquisition starting to the data collector by the USB interface of the computer
Frame, the data collector receive the acquisition starting frame after with default sample frequency carry out data acquisition；The data acquisition
The data of acquisition are transferred to the data processing module of the computer by device by USB interface, and the data processing module will be adopted
The data collected are saved；The data processing module successively recalls the corresponding acquisition data of scan frequency point, and from acquisition
The corresponding maximum value of each Frequency point is found out in data, then finds out minimum value in these maximum values, and minimum value institute is right
The scan frequency point answered is resonance frequency fr, bring resonance frequency into gas density in formula calculating under test gas；
Specifically, the calculating process of the data processing module are as follows:
The effective volume V of the Double Opening sampling ball internal cavity is the volume that inner ball volume subtracts two sampling through-holes:
Wherein, RiThe inside radius of ball is sampled for the Double Opening, a is the radius of the sampling through-hole；
According to Principles of Acoustics, the acoustic capacitance of the methane gas in the Double Opening sampling ball spherical cavity is CA, then have:
Consider that the sampling through-hole both ends amendment situation, the effective length of the sampling through-hole are equal are as follows:
Wherein, RoThe outer radius of ball is sampled for the Double Opening；
The phonoreception of the sampling through-hole are as follows:
Wherein, ρ is the density of methane gas to be measured；
The phonoreception of two sampling through-holes is considered as situation in parallel, then total phonoreception are as follows:
According to resonance circuit rule, the resonance frequency of the Double Opening sampling ball are as follows:
Wherein, c is spread speed of the sound in methane gas to be measured；
The velocity of sound in methane gas to be measured meets:
Wherein, p is gas pressure intensity, and γ is the specific heat ratio of methane gas to be measured, then:
γ=(1-x) γk+xγw (8)
Wherein, x is the percentage composition of methane gas to be measured, γkFor the specific heat ratio of air, γwFor the specific heat capacity of methane gas
Than；
The density of methane gas to be measured:
ρ=(1-x) ρk+xρw (9)
Wherein, ρkFor the density of air, ρwFor the density of methane gas；
It brings formula (7), formula (8) and formula (9) into formula (6), can obtain
In situation known to other parameters, by measuring resonance frequency fr, the Double Opening can be obtained by formula (10) and sample
The percentage composition of methane gas to be measured in ball.
2. the system as claimed in claim 1, which is characterized in that be equipped with exact matching on the end face of the second outlet interface
Layer, the second waveguide pipe is installed on the completely permutation.
3. the system as claimed in claim 1, which is characterized in that the sinusoidal waveform occurs module and changes scanning frequency according to stepping
Rate point, module occur for the sinusoidal waveform send to the function generator to stop hair after the frequency range to be scanned for completing setting
Vocal command frame stops sounding to control the loudspeaker.
4. system as claimed in claim 3, which is characterized in that the frequency that module scans complete setting occurs to the sinusoidal waveform
After rate range, is sent from the data processing module to the data collector and stop acquisition instructions frame, the data collector
Stop data acquisition after receiving the stopping acquisition instructions frame.
5. a kind of methane gas concentration measurement method characterized by comprising
Inlet valve and outlet valve are opened simultaneously, enters methane gas to be measured in Double Opening sampling ball, is closed after the completion of sampling
Close inlet valve and outlet valve, wherein the inlet valve and outlet valve are separately mounted to detect the first entrance of pipeline
On interface and first outlet interface, the detection pipeline also has second entrance interface and second outlet interface, and described second enters
First wave conduit is installed on mouthful interface, the first wave guide pipe end is equipped with loudspeaker, the input terminal of the loudspeaker with
The output end of function generator connects, and the input terminal of the function generator is connect by USB interface with computer；Described second
Second waveguide pipe is installed, the second waveguide pipe end is equipped with microphone, the output end of the microphone on discharge coupling
It is connect with the input terminal of data collector, the output end of the data collector is connect by USB interface with the computer, institute
Stating computer includes that module and data processing module occur for sinusoidal waveform；
The sinusoidal waveform occurs module and generates scan frequency point command frame, is then instructed scan frequency point by USB interface
Frame is transferred to the function generator, and the function generator receives the frequency number extracted after scan frequency point command frame in frame
According to frequency data generation sine wave signal, which drives the loudspeaker sounding；
The data processing module sends acquisition starting frame, institute to the data collector by the USB interface of the computer
State data collector receive the acquisition starting frame after with default sample frequency carry out data acquisition；The data collector will be adopted
The data of collection are transferred to the data processing module of the computer by USB interface, and the data processing module will be collected
Data are saved；The data processing module successively recalls the corresponding acquisition data of scan frequency point, and from acquisition data
The corresponding maximum value of each Frequency point is found out, then finds out minimum value in these maximum values, is swept corresponding to the minimum value
Retouching Frequency point is resonance frequency fr, bring resonance frequency into gas density in formula calculating under test gas；
Specifically, the calculating process of the data processing module are as follows:
The effective volume V of the Double Opening sampling ball internal cavity is the volume that inner ball volume subtracts two sampling through-holes:
Wherein, RiThe inside radius of ball is sampled for the Double Opening, a is the radius of the sampling through-hole；
According to Principles of Acoustics, the acoustic capacitance of the methane gas in the Double Opening sampling ball spherical cavity is CA, then have:
Consider that the sampling through-hole both ends amendment situation, the effective length of the sampling through-hole are equal are as follows:
Wherein, RoThe outer radius of ball is sampled for the Double Opening；
The phonoreception of the sampling through-hole are as follows:
Wherein, ρ is the density of methane gas to be measured；
The phonoreception of two sampling through-holes is considered as situation in parallel, then total phonoreception are as follows:
According to resonance circuit rule, the resonance frequency of the Double Opening sampling ball are as follows:
Wherein, c is spread speed of the sound in methane gas to be measured；
The velocity of sound in methane gas to be measured meets:
Wherein, p is gas pressure intensity, and γ is the specific heat ratio of methane gas to be measured, then:
γ=(1-x) γk+xγw (18)
Wherein, x is the percentage composition of methane gas to be measured, γkFor the specific heat ratio of air, γwFor the specific heat capacity of methane gas
Than；
The density of methane gas to be measured:
ρ=(1-x) ρk+xρw (19)
Wherein, ρkFor the density of air, ρwFor the density of methane gas；
It brings formula (7), formula (8) and formula (9) into formula (6), can obtain
In situation known to other parameters, by measuring resonance frequency fr, the Double Opening can be obtained by formula (20) and sample
The percentage composition of methane gas to be measured in ball.
6. method as claimed in claim 5, which is characterized in that the sinusoidal waveform occurs module and changes scanning frequency according to stepping
Rate point, module occur for the sinusoidal waveform send to the function generator to stop hair after the frequency range to be scanned for completing setting
Vocal command frame stops sounding to control the loudspeaker.
7. method as claimed in claim 5, which is characterized in that the frequency that module scans complete setting occurs to the sinusoidal waveform
After rate range, is sent from the data processing module to the data collector and stop acquisition instructions frame, the data collector
Stop data acquisition after receiving the stopping acquisition instructions frame.
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