CN113933213A - Binary mixed gas mixing ratio measuring method and device based on gas substitution method - Google Patents
Binary mixed gas mixing ratio measuring method and device based on gas substitution method Download PDFInfo
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Abstract
A binary mixed gas mixing ratio measuring method and device based on a gas substitution method belong to the technical field of electric power system detection and solve the problem of how to measure the mixing ratio of binary mixed gas by using the gas substitution method; the technical scheme of the invention is based on the principle of measuring the density of the mixed insulating gas, adopts a gas substitution method to measure the gas-mixed ratio of the mixed insulating gas, can meet the gas-mixed ratio measurement of the existing binary mixed gas, can also realize full-range (0-100%), high-precision, linear, normal-pressure and pressurized measurement, can also meet the gas-mixed ratio detection of other non-insulating binary mixed gases, has wide application range, is flexible in component selection by directly using pure component gas to participate in the test, does not need to prepare standard gas, and has low test cost.
Description
Technical Field
The invention belongs to the technical field of electric power system detection, and relates to a binary mixed gas mixing ratio measuring method and device based on a gas substitution method.
Background
SF6The gas is the most excellent gas insulation medium at present, the insulation performance is about 2.5 times of the air under the same pressure, the arc extinguishing performance is 100 times of the air, and the gas is widely applied to electrical equipment of various voltage grades, so that the volume of the electrical equipment is effectively reduced, the floor area of the equipment is reduced, and the overhaul period of the equipment is prolonged.
However, SF6Also existApparent defect, SF6Is a strong greenhouse effect gas, and the equivalent greenhouse effect is CO223900 times of the total life of the product in the atmosphere, which is about 3200 years, and the environmental impact caused by the emission of the product into the atmosphere. Furthermore SF6The liquefaction temperature of the gas is higher, and once the gas is liquefied, the insulating property of the equipment is greatly reduced, thus seriously endangering the safe operation of the equipment. SF6The gas is 0.7MPa (SF in general breaker)6Pressure) of about-30 ℃ at the pressure, pure SF was obtained6The gas is not suitable for outdoor use in winter in the northeast, Xinjiang, inner Mongolia and Qinghai-Tibet plateau areas.
To cope with SF6The problem of greenhouse effect and easy liquefaction, and the widely adopted SF is adopted at present6With another gas, e.g. N2Or CF4Are mixed to form SF6/N2Or SF6/CF4Equal mixed insulating gas to replace pure SF6The application is carried out. The mixed gas can effectively reduce SF in equipment6The amount of gas used is reduced, and the SF in the equipment is reduced6The liquefaction temperature of the gas. SF6The performance of the mixed insulating gas is mainly determined by the properties of each gas and the gas mixing ratio of the gases, and the accurate measurement of the gas mixing ratio is SF6The important basis for the on-site use of mixed gases.
For the measurement of the gas-mixing ratio of the binary mixed insulating gas, there are 3 main methods at present: 1) gas chromatography. The main components in the mixed gas are separated and quantitatively measured by adopting a gas chromatography, and then the mixed gas ratio of the mixed gas is obtained by calculating according to a normalization method. 2) And (4) thermal conductivity detection. And measuring by using a sensor based on a thermal conductivity principle, and calculating a measurement result according to an external standard method to obtain the gas mixing ratio of the mixed gas. 3) Infrared spectroscopy. Using SF6The gas has characteristic absorption in infrared band, and the absorption light intensity in selected band and SF in sample gas are measured6The concentration establishes a relation, thereby obtaining the gas-mixture ratio of the mixed gas. Wherein, the chromatography has high accuracy, but the chromatograph has the defects of low analysis speed, complex operation, strict requirements on environment, power supply and carrier gas, and the like, is not suitable for field measurement,and the chromatography generally cannot realize the detection of the gas mixing ratio in the full range. The thermal conductivity detection method is only suitable for detecting the gas mixture ratio of the binary mixed insulating gas, cannot detect the gas mixture ratio of the ternary mixed insulating gas, has low detection precision, is easy to drift after being used for a long time, and needs to be calibrated regularly. The infrared spectroscopy has low detection precision and is easy to be interfered by the outside, along with the increase of service life, the performance of the instrument is reduced, the detection accuracy is reduced, and meanwhile, the instrument cannot be suitable for non-SF6Mixed gas (e.g. C)4F7N and CO2Mixed gas of (2) is detected. Document design of binary mixed gas concentration ultrasonic measuring instrument (Wangming Wei, Yaoshan, design of binary mixed gas concentration ultrasonic measuring instrument [ J]The computer measurement and control 2010,18(12):2908-2910.) discloses a new temperature measurement method which improves a calculation formula for ultrasonically detecting the gas concentration of binary mixed gas according to the theory that when ultrasonic waves are transmitted in the binary mixed gas, the sound velocity has a certain relation with the concentration and the temperature of the binary mixed gas to be detected; however, the document does not address how to determine the mixture ratio of the binary mixed gas.
Disclosure of Invention
The invention aims to solve the technical problem of how to measure the gas-mixing ratio of the binary mixed gas by adopting a gas substitution method.
The invention solves the technical problems through the following technical scheme:
a binary mixed gas mixing ratio measuring method based on a gas substitution method is applied to a mixed gas ratio measuring device, and the mixed gas ratio measuring device comprises: the device comprises a U-shaped oscillation tube (1), a magnet (2), an electronic excitation oscillator (3), a frequency counter (4), a pressure sensor (5), a first temperature sensor (6), a second temperature sensor (7), a third temperature sensor (8), a temperature control heat preservation layer (9), a three-way valve (10) and an air outlet valve (11); a magnet (2) is fixed at the bottom of the U-shaped oscillating pipe (1), and the upper parts of two vertical pipes of the U-shaped oscillating pipe (1) are respectively provided with a frequency counter (4); the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the first port of the three-way valve (10) through a pipeline, the second port and the third port of the three-way valve (10) are respectively connected with the outside through pipelines, and the pressure sensor (5) is hermetically connected on the pipeline between the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) and the first port of the three-way valve (10); the pipe orifice of the right vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the air inlet end of an air outlet valve (11) through a pipeline, and the air outlet end of the air outlet valve (11) is hermetically connected with an exhaust pipeline; the first temperature sensor (6) is arranged between the left vertical pipe and the right vertical pipe of the U-shaped oscillating pipe (1); the electronic excitation oscillator (3) is arranged below the fixed magnet (2); u type oscillating pipe (1), magnet (2), electron excitation oscillator (3), frequency counter (4), pressure sensor (5), first temperature sensor (6), gas outlet valve (11) all install in accuse temperature heat preservation (9), second temperature sensor (7) install on accuse temperature heat preservation (9) outer wall, third temperature sensor (8) install on accuse temperature heat preservation (9) inner wall.
The gas-mixing ratio measuring method comprises the following steps:
s1, calibrating the gas-mixing ratio measuring device;
s2, filling the U-shaped oscillating tube (1) with pressure P0The binary mixed gas to be measured records the oscillation period T observed when the mixed gas is in the U-shaped oscillation tube (1) at the moment0And measuring the density of the binary mixed gas as rho under the standard state0Establishing a density ρ0A relationship with the first elemental gas volume, the density at standard condition, and the second elemental gas volume, the density at standard condition;
s3, continuously filling the binary mixed gas to be measured into the U-shaped oscillation tube (1) until the pressure is P1So that P is1＝2P0Recording the oscillation period T observed when the mixed gas exists in the U-shaped oscillation tube (1) at the moment1And measuring the density of the gas in the U-shaped oscillation tube (1) under the standard state as rho1Establishing a density ρ1A relationship with the first elemental gas volume, the density at standard condition, and the second elemental gas volume, the density at standard condition;
s4, releasing the binary mixed gas in the U-shaped oscillation tube (1) to the pressure P0Then, pure first element gas is filled into the U-shaped oscillation tube (1) until the pressure is P1Instead, record this timeThe oscillation period T observed when mixed gas exists in the U-shaped oscillation tube (1)2And measuring the density of the gas in the U-shaped oscillation tube (1) under the standard state as rho2Establishing a density ρ2A relationship with the first elemental gas volume, the density at standard condition, and the second elemental gas volume, the density at standard condition;
and S5, calculating to obtain the volume of the second binary gas by comparing the density change of the gas in the U-shaped oscillating tube (1) before and after replacement and combining the densities of the first unitary gas and the second binary gas in the standard state, thereby obtaining the gas mixing ratio of the binary mixed gas.
The technical scheme of the invention is based on the principle of measuring the density of the mixed insulating gas, adopts a gas substitution method to measure the gas-mixed ratio of the mixed insulating gas, can meet the gas-mixed ratio measurement of the existing binary mixed gas, can also realize full-range (0-100%), high-precision, linear, normal-pressure and pressurized measurement, can also meet the gas-mixed ratio detection of other non-insulating binary mixed gases, has wide application range, is flexible in component selection by directly using pure component gas to participate in the test, does not need to prepare standard gas, and has low test cost.
As a further improvement of the technical scheme of the invention, the method for calibrating the gas-mixture ratio measuring device comprises the following steps: firstly, connecting an air inlet pipeline of a U-shaped oscillation pipe (1) with clean air, and opening an air inlet valve (10) and an air outlet valve (11) to ensure that the air keeps a stable flow rate to wash the U-shaped oscillation pipe (1) and the corresponding pipeline; then closing the air inlet valve (10) and the air outlet valve (11), keeping the temperature of the measuring device constant through the temperature control insulating layer (9), controlling the air outlet valve (11), balancing the air pressure in the U-shaped oscillating tube (1) with the atmospheric pressure, and recording the reading P of the pressure sensor (5) at the moment; starting the measuring device and recording the stable oscillation period TAAnd the temperature t of the U-shaped oscillation tube (1)A(ii) a After the air calibration is finished, pure water is replaced for calibration, the U-shaped oscillation pipe (1) is flushed by the pure water, then the U-shaped oscillation pipe (1) is filled with the pure water, no bubbles exist in the water in the pipe, the temperature of the measuring device and the pure water in the pipe is stabilized through the temperature control heat preservation layer (9), the measuring device is started, and the stable oscillation period T is recordedwAnd the temperature t of the U-shaped oscillation tube (1)w(ii) a And finally, calculating a constant F of the U-shaped oscillation tube (1) according to the recorded data.
As a further improvement of the technical solution of the present invention, a calculation formula of the constant F of the measuring apparatus is:
wherein F represents a constant of the U-shaped oscillation tube (1); rhowThe density of water at the test temperature is expressed in g/cm3；ρAThe density of air at the test temperature is expressed in g/cm3；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1); t isAThe unit is s, which represents the oscillation period observed when air is filled in the U-shaped oscillation tube (1).
As a further improvement of the technical scheme of the invention, the density rho0Density rho1Density rho2The calculation formula is as follows:
where ρ iswThe density of water at the test temperature is expressed in g/cm3；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1).
As a further improvement of the technical scheme of the invention, the density rho is established0The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
ρ0V0＝V1ρ11+V2ρ12 (3)
wherein, V1The volume of the first element gas in the mixed gas is referred to as the volume hereinafter, and the second element gas and the third element gas have the same principle; v2Volume of the second component gas, p11Is the density of the first component gas in the standard state, p12Is a second element in a standard stateThe density of the gas.
As a further improvement of the technical scheme of the invention, the density rho is established1The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
ρ1V0＝2V1ρ11+2V2ρ12 (4)。
as a further improvement of the technical scheme of the invention, the density rho is established2The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
as a further improvement of the technical scheme of the invention, the method for obtaining the gas mixture ratio of the binary mixed gas by calculating the volume of the second binary gas comprises the following steps:
from equation (5) to equation (4):
namely obtain V2And then:
V1＝V0-V2 (7)
the binary gas-to-gas ratio can be calculated by carrying out formula (8):
as a further improvement of the technical scheme of the invention, the binary mixed gas is as follows: SF6/N2Or SF6/CF4Or C4F7N/CO2。
The device of the binary mixed gas mixing ratio measuring method based on the gas substitution method comprises the following steps: the device comprises a U-shaped oscillation tube (1), a magnet (2), an electronic excitation oscillator (3), a frequency counter (4), a pressure sensor (5), a first temperature sensor (6), a second temperature sensor (7), a third temperature sensor (8), a temperature control heat preservation layer (9), a three-way valve (10) and an air outlet valve (11); a magnet (2) is fixed at the bottom of the U-shaped oscillating pipe (1), and the upper parts of two vertical pipes of the U-shaped oscillating pipe (1) are respectively provided with a frequency counter (4); the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the first port of the three-way valve (10) through a pipeline, the second port and the third port of the three-way valve (10) are respectively connected with the outside through pipelines, and the pressure sensor (5) is hermetically connected on the pipeline between the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) and the first port of the three-way valve (10); the pipe orifice of the right vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the air inlet end of an air outlet valve (11) through a pipeline, and the air outlet end of the air outlet valve (11) is hermetically connected with an exhaust pipeline; the first temperature sensor (6) is arranged between the left vertical pipe and the right vertical pipe of the U-shaped oscillating pipe (1); the electronic excitation oscillator (3) is arranged below the fixed magnet (2); u type oscillating pipe (1), magnet (2), electron excitation oscillator (3), frequency counter (4), pressure sensor (5), first temperature sensor (6), gas outlet valve (11) all install in accuse temperature heat preservation (9), second temperature sensor (7) install on accuse temperature heat preservation (9) outer wall, third temperature sensor (8) install on accuse temperature heat preservation (9) inner wall.
The invention has the advantages that:
the technical scheme of the invention is based on the principle of measuring the density of the mixed insulating gas, adopts a gas substitution method to measure the gas-mixed ratio of the mixed insulating gas, can meet the gas-mixed ratio measurement of the existing binary mixed gas, can also realize full-range (0-100%), high-precision, linear, normal-pressure and pressurized measurement, can also meet the gas-mixed ratio detection of other non-insulating binary mixed gases, has wide application range, is flexible in component selection by directly using pure component gas to participate in the test, does not need to prepare standard gas, and has low test cost.
Drawings
FIG. 1 is a structural diagram of a binary mixed gas mixture ratio measuring device based on a gas substitution method;
FIG. 2 is a flow chart of a binary mixed gas mixture ratio measurement method based on a gas substitution method;
FIG. 3 is a schematic diagram of the measurement principle of the gas mixing ratio of the binary mixed gas in the gas substitution method.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is further described by combining the drawings and the specific embodiments in the specification:
1. structural composition of device
As shown in fig. 1, the binary mixed gas/gas ratio measuring device based on the gas substitution method includes: the device comprises a U-shaped oscillation tube (1), a magnet (2), an electronic excitation oscillator (3), a frequency counter (4), a pressure sensor (5), a first temperature sensor (6), a second temperature sensor (7), a third temperature sensor (8), a temperature control heat preservation layer (9), a three-way valve (10) and an air outlet valve (11).
The U-shaped oscillation tube (1) is made of boronized glass, the volume of the U-shaped oscillation tube is 3mL (calibrated by a water injection weighing method), a magnet (2) is fixed at the bottom of the U-shaped oscillation tube (1), and the upper parts of two vertical tubes of the U-shaped oscillation tube (1) are respectively provided with a frequency counter (4); the pipe orifice of the left side vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the first port of the three-way valve (10) through a pipeline, the second port and the third port of the three-way valve (10) are respectively connected with the outside through pipelines, the pressure sensor (5) is hermetically connected on the pipeline between the pipe orifice of the left side vertical pipe of the U-shaped oscillation pipe (1) and the first port of the three-way valve (10), and the three-way valve (10) is used for controlling different gases to enter the U-shaped oscillation pipe (1); the pressure sensor (5) is used for monitoring the pressure value of gas in the U-shaped oscillating tube (1), and the detection precision is +/-0.01 kPa; the pipe orifice of the right vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the air inlet end of an air outlet valve (11) through a pipeline, and the air outlet end of the air outlet valve (11) is hermetically connected with an exhaust pipeline; the first temperature sensor (6) is arranged between the left vertical pipe and the right vertical pipe of the U-shaped oscillating pipe (1); electronic excitation oscillator (3) install in the below that is fixed with magnet (2), U type oscillating pipe (1), magnet (2), electronic excitation oscillator (3), frequency counter (4), pressure sensor (5), first temperature sensor (6), air outlet valve (11) all install in accuse temperature heat preservation (9), second temperature sensor (7) install on accuse temperature heat preservation (9) outer wall, accuse temperature heat preservation (9) be used for carrying out temperature regulation and control to the test area, third temperature sensor (8) install on accuse temperature heat preservation (9) inner wall.
2. Principle for measuring substance density by U-shaped oscillation tube method
The U-shaped oscillation tube (1) method for measuring the density of the substance has been widely applied for many years, and has the advantages of rapidness, reliability, high accuracy, high measurement precision and the like. The principle of the oscillating tube method for detecting the density of a substance is to utilize the oscillation frequency of a U-shaped glass tube based on electromagnetic initiation, namely a magnet is fixed on the U-shaped glass measuring tube, an oscillator is excited by electrons to generate oscillation, the oscillation period of the glass tube is measured by an oscillation sensor, and each U-shaped glass tube has the characteristic frequency or oscillates according to the natural frequency. When the glass tube is filled with an object, the frequency is a function of the mass of the filling material in the tube. The frequency of the substance decreases as its mass increases, i.e. the period of oscillation T increases. During measurement, some substances are selected as standard substances, and the density value of the measured substance is calculated through the difference of the oscillation frequency between the measured substance and the standard substances after the frequency is measured.
The U-shaped oscillation tube (1) needs to measure an instrument constant F before the test is carried out, and generally at least two standard substances are adopted for measurement, and the density interval of the two standard substances is required to cover the density range of a test sample. For SF6The gas, whose density is generally 6.16kg/m at 20 ℃3Therefore, air and pure water can be selected as standard substances, and the instrument can be calculated according to the density measurement result of the standard substances by the U-shaped oscillation tube (1)Constant F of (d):
wherein F represents the instrument constant of the U-shaped oscillation tube (1) tester; rhowThe density of water at the test temperature is expressed in g/cm3(at 20 ℃ C.). sup.w＝0.9982g/cm3)；ρAThe density of air at the test temperature is expressed in g/cm3(at 20 ℃ C.). sup.A＝0.00120g/cm3)；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1); t isAThe unit is s, which represents the oscillation period observed when air is filled in the U-shaped oscillation tube (1).
Therefore, the binary mixed gas is detected by the U-shaped oscillation tube (1), and the oscillation period T of the mixed gas is measuredMixing ofThe density rho of the mixed gas can be obtainedMixing of：
Wherein: rhoMixing ofDenotes the density of the mixture in g/cm at the test temperature3；ρwThe density of water at the test temperature is expressed in g/cm3；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1); t isMixing ofThe unit is s, which represents the oscillation period observed when the mixed gas is present in the U-shaped oscillation tube (1).
3. Measuring the gas-to-liquid ratio of binary gas
3.1 principle
SF at normal temperature and pressure6The mixed gas can be treated as an ideal gas. For a binary mixed gas, when the mixing ratio of the two gases is determined, the density of the mixed gas at a specific temperature and pressure is also determined. The invention adopts a gas substitution method for measurement, namely, high-purity component gas is used for substituting part of mixed insulating gas to be measured, and then the density change of the gas before and after substitution is compared, so that the invention uses the meterAnd calculating the gas mixing ratio of the mixed insulating gas to be measured. The binary mixed gas is as follows: SF6/N2Or SF6/CF4Or C4F7N/CO2。
As shown in FIG. 2, with SF6/N2For example, the first component gas is SF6The second component gas is N2：
a. Firstly, the U-shaped oscillation tube (1) is filled with gas with pressure P0Measured as rho, the density of the mixed insulating gas to be measured at 20 DEG C0；
b. Continuously filling the mixed insulating gas to be detected into the U-shaped oscillation tube (1) until the pressure is P1So that P is1＝2P0And the density of the gas in the U-shaped tube at 20 ℃ is measured as rho1；
c. Releasing the gas in the U-shaped oscillation tube (1) to the pressure P0(or the U-shaped oscillating tube (1) is refilled with the gas with the pressure P0Mixed insulating gas to be measured), and then high-purity SF is continuously filled into the U-shaped oscillation tube (1)6Gas to pressure P1The density of the gas in the U-shaped oscillation tube (1) at 20 ℃ is measured as rho2；
d. SF at 20 ℃ and a gas pressure which is not too high (several atmospheres)6The gas can be treated and calculated as an ideal gas, with the ratio of the pressures of the gases being equal to the ratio of the volumes.
As shown in FIG. 3, the above operation corresponds to setting the pressure to P1Using high-purity SF with the same volume as half of gas in the sample to be detected6Gas substitution, practically equivalent to half of N in the mixed insulating gas to be measured2With equal volume of SF6Instead of this. By comparing the change in gas density before and after substitution, SF is combined6Density and N of2Can be established with N2Correspondence between volumes, thereby realizing N2And (3) accurately measuring the volume to obtain the gas mixing ratio of the binary mixed gas.
3.2 operational procedure of the apparatus
1) Device calibration
Is arranged atThe calibration is needed when the device is used for the first time. And calibrating the U-shaped oscillating tube (1) by adopting air and water as standard substances. Firstly, clean air is introduced into the U-shaped oscillating pipe (1) through the three-way valve (10), and the reading of the pressure sensor (5) is recorded, namely PAir conditionerThe temperature is controlled through a temperature control heat preservation layer (9), the three temperature sensors including a first temperature sensor (6), a second temperature sensor (7) and a third temperature sensor (8) are read, after the air and the U-shaped oscillation tube (1) reach the set temperature and are stable, an electronic excitation oscillator (3) is started to measure, and the oscillation period T is recorded through a frequency counter (4) and the first temperature sensor (6)AAnd the temperature t of the U-tubeA. After the air measurement is finished, water is injected into the U-shaped oscillating pipe (1) through the three-way valve (10), no air bubbles exist in the water in the pipe, the temperature is controlled through the temperature control heat preservation layer (9), and after the temperature of the water and the temperature of the U-shaped oscillating pipe (1) reach the set temperature and are stable, the oscillation period T is recorded through the frequency counter (4) and the first temperature sensor (6)wAnd the temperature t of the U-shaped oscillation tube (1)w. The instrument constant F of the device is calculated according to equation (1).
2) Sample detection
The method comprises the steps of connecting a sample to be detected to a mixed insulating gas interface to be detected of a three-way valve (10), purging a U-shaped oscillation pipe (1) for 3-5 min by using sample gas, stopping gas inflow, closing the three-way valve (10), and adjusting a gas outlet valve (11) to enable the gas pressure in the U-shaped oscillation pipe (1) to be 0.1MPa when the reading of a pressure sensor (5) is 0.1 MPa. Opening the temperature control insulating layer (9) to enable the temperature of the U-shaped oscillation tube (1) to be 20 +/-0.01 ℃ (measuring through the first temperature sensor (6)), opening the electronic excitation oscillator (3) to start measuring, and recording the oscillation period T through the frequency counter (4) and the first temperature sensor (6)MeasuringAnd the temperature t of the U-shaped oscillation tube (1)MeasuringThe density of the sample mixed gas is measured as ρ according to the formula (2)0。
Continuously filling the mixed insulating gas to be detected into the U-shaped oscillating pipe (1) through the three-way valve (10) until the reading of the pressure sensor (5) is P1Let P stand1＝2P0According to the above steps, the density of the gas in the U-shaped oscillation tube (1) at 20 ℃ is measured as rho1。
3) PureSF6Gas replacement
The gas pressure in the U-shaped oscillating pipe (1) is P by opening a gas outlet valve (11)1The reading of the pressure release of the mixed insulating gas to be measured to the pressure sensor (5) is P0(or the mixed insulating gas to be measured in the U-shaped oscillation tube (1) can be completely emptied and then refilled with the pressure P0The mixed insulating gas to be measured), the gas outlet valve (11) is closed. High-purity SF is introduced into the U-shaped oscillating pipe (1) through a three-way valve (10)6Gas to pressure sensor (5) reading P0Closing the three-way valve (10), enabling the temperature of the U-shaped oscillation pipe (1) to be 20 +/-0.01 ℃ (measuring through the first temperature sensor (6)) through the temperature control heat preservation layer (9), opening the electronic excitation oscillator (3) to start measuring, and recording the oscillation period T through the frequency counter (4) and the first temperature sensor (6)MeasuringAnd the temperature t of the U-shaped oscillation tube (1)MeasuringThe density of the gas in the U-shaped oscillation tube (1) at this time is measured as rho according to the formula (2)2. After the test is finished, the gas outlet valve (11) is opened to release the pressure in the U-shaped oscillating pipe (1), and the three-way valve (10) is opened to use high-purity SF6And fully washing the U-shaped oscillating tube (1) and the corresponding pipeline, and closing the instrument.
3.3, calculation Process
The U-shaped oscillating tube (1) is filled with gas with pressure P0Assuming that SF in the mixed insulating gas to be measured in the U-shaped oscillation tube (1) at the moment6Volume occupied by gas is VsF6，N2Volume occupied by gas is VN2And the density of the mixed insulating gas to be measured is measured as rho0And then:
ρ0V0＝VSF6ρSF6+VN2ρN2 (3)
continuously filling the mixed insulating gas to be detected into the U-shaped pipe until the pressure is P1(P1＝2P0) The density of the gas at this time was measured as ρ1。
ρ1V0＝2VSF6ρSF6+2VN2ρN2 (4)
Mixing the insulating gas to be measured in the U-shaped oscillation tube (1)Pressure drop to P0Then filled with pure SF6Gas to P1At this time, the density of the gas in the U-shaped oscillation tube (1) is measured as rho2：
Subtracting equation (4) from equation (5):
namely obtain VN2And then:
VSF6＝V0-VN2 (7)
the binary gas-to-gas ratio can be calculated by carrying out formula (8):
the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The binary mixed gas mixing ratio measuring method based on the gas substitution method is characterized by being applied to a mixed gas ratio measuring device, and the mixed gas ratio measuring device comprises: the device comprises a U-shaped oscillation tube (1), a magnet (2), an electronic excitation oscillator (3), a frequency counter (4), a pressure sensor (5), a first temperature sensor (6), a second temperature sensor (7), a third temperature sensor (8), a temperature control heat preservation layer (9), a three-way valve (10) and an air outlet valve (11); a magnet (2) is fixed at the bottom of the U-shaped oscillating pipe (1), and the upper parts of two vertical pipes of the U-shaped oscillating pipe (1) are respectively provided with a frequency counter (4); the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the first port of the three-way valve (10) through a pipeline, the second port and the third port of the three-way valve (10) are respectively connected with the outside through pipelines, and the pressure sensor (5) is hermetically connected on the pipeline between the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) and the first port of the three-way valve (10); the pipe orifice of the right vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the air inlet end of an air outlet valve (11) through a pipeline, and the air outlet end of the air outlet valve (11) is hermetically connected with an exhaust pipeline; the first temperature sensor (6) is arranged between the left vertical pipe and the right vertical pipe of the U-shaped oscillating pipe (1); the electronic excitation oscillator (3) is arranged below the fixed magnet (2); the U-shaped oscillation tube (1), the magnet (2), the electronic excitation oscillator (3), the frequency counter (4), the pressure sensor (5), the first temperature sensor (6) and the gas outlet valve (11) are all arranged in the temperature control heat preservation layer (9), the second temperature sensor (7) is arranged on the outer wall of the temperature control heat preservation layer (9), and the third temperature sensor (8) is arranged on the inner wall of the temperature control heat preservation layer (9);
the gas-mixing ratio measuring method comprises the following steps:
s1, calibrating the gas-mixing ratio measuring device;
s2, filling the U-shaped oscillating tube (1) with pressure P0The binary mixed gas to be measured records the oscillation period T observed when the mixed gas is in the U-shaped oscillation tube (1) at the moment0And measuring the density of the binary mixed gas as rho under the standard state0Establishing a density ρ0A relationship with the first elemental gas volume, the density at standard condition, and the second elemental gas volume, the density at standard condition;
s3, continuously filling the binary mixed gas to be measured into the U-shaped oscillation tube (1) until the pressure is P1So that P is1＝2P0Recording the oscillation period T observed when the mixed gas exists in the U-shaped oscillation tube (1) at the moment1And measuring the density of the gas in the U-shaped oscillation tube (1) under the standard state as rho1Establishing a density ρ1With the volume of the first component gas, the density in the standard state, the volume of the second component gas and the density in the standard stateThe relationship of degrees;
s4, releasing the binary mixed gas in the U-shaped oscillation tube (1) to the pressure P0Then, pure first element gas is filled into the U-shaped oscillation tube (1) until the pressure is P1Instead, the oscillation period T observed when the mixed gas exists in the U-shaped oscillation tube (1) is recorded2And measuring the density of the gas in the U-shaped oscillation tube (1) under the standard state as rho2Establishing a density ρ2A relationship with the first elemental gas volume, the density at standard condition, and the second elemental gas volume, the density at standard condition;
and S5, calculating to obtain the volume of the second binary gas by comparing the density change of the gas in the U-shaped oscillating tube (1) before and after replacement and combining the densities of the first unitary gas and the second binary gas in the standard state, thereby obtaining the gas mixing ratio of the binary mixed gas.
2. The binary mixed gas mixing ratio measuring method based on the gas substitution method as claimed in claim 1, wherein the method for calibrating the mixing ratio measuring device is as follows: firstly, connecting an air inlet pipeline of a U-shaped oscillation pipe (1) with clean air, and opening an air inlet valve (10) and an air outlet valve (11) to ensure that the air keeps a stable flow rate to wash the U-shaped oscillation pipe (1) and the corresponding pipeline; then closing the air inlet valve (10) and the air outlet valve (11), keeping the temperature of the measuring device constant through the temperature control insulating layer (9), controlling the air outlet valve (11), balancing the air pressure in the U-shaped oscillating tube (1) with the atmospheric pressure, and recording the reading P of the pressure sensor (5) at the moment; starting the measuring device and recording the stable oscillation period TAAnd the temperature t of the U-shaped oscillation tube (1)A(ii) a After the air calibration is finished, pure water is replaced for calibration, the U-shaped oscillation pipe (1) is flushed by the pure water, then the U-shaped oscillation pipe (1) is filled with the pure water, no bubbles exist in the water in the pipe, the temperature of the measuring device and the pure water in the pipe is stabilized through the temperature control heat preservation layer (9), the measuring device is started, and the stable oscillation period T is recordedwAnd the temperature t of the U-shaped oscillation tube (1)w(ii) a And finally, calculating a constant F of the U-shaped oscillation tube (1) according to the recorded data.
3. The method for measuring the mixture ratio of a binary mixed gas based on a gas substitution method as claimed in claim 2, wherein the constant F of the measuring device is calculated by the formula:
wherein F represents a constant of the U-shaped oscillation tube (1); rhowThe density of water at the test temperature is expressed in g/cm3；ρAThe density of air at the test temperature is expressed in g/cm3；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1); t isAThe unit is s, which represents the oscillation period observed when air is filled in the U-shaped oscillation tube (1).
4. The method for measuring the mixing ratio of binary mixed gas based on gas substitution method as claimed in claim 3, wherein the density p is0Density rho1Density rho2The calculation formula is as follows:
where ρ iswThe density of water at the test temperature is expressed in g/cm3；TwThe unit is s, which represents the oscillation period observed when water is in the U-shaped oscillation tube (1).
5. The method for measuring the mixing ratio of binary mixed gas based on gas substitution method as claimed in claim 4, wherein the density p is established0The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
ρ0V0＝V1ρ11+V2ρ12 (3)
wherein, V1Volume of first elementary gas, V2Is a secondVolume of elementary gas, p11Is the density of the first component gas in the standard state, p12Is the density of the second component gas in the standard state.
6. The method for measuring the mixing ratio of binary mixed gas based on gas substitution method as claimed in claim 5, wherein the density p is established1The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
ρ1V0＝2V1ρ11+2V2ρ12 (4)。
7. the method for measuring the mixing ratio of binary mixed gas based on gas substitution method as claimed in claim 6, wherein the density p is established2The relationship with the first elemental gas volume, the density under standard conditions, and the second elemental gas volume, the density under standard conditions is as follows:
8. the method for measuring the gas mixture ratio of the binary mixed gas based on the gas substitution method as claimed in claim 7, wherein the method for calculating the volume of the second binary gas to obtain the gas mixture ratio of the binary mixed gas is as follows:
from equation (5) to equation (4):
namely obtain V2And then:
V1＝V0-V2 (7)
the binary gas-to-gas ratio can be calculated by carrying out formula (8):
9. the method for measuring the gas mixture ratio of a binary mixed gas based on a gas substitution method according to any one of claims 1-8, wherein the binary mixed gas is: SF6/N2Or SF6/CF4Or C4F7N/CO2。
10. The device of the binary mixed gas mixing ratio measuring method based on the gas substitution method is characterized by comprising the following steps: the device comprises a U-shaped oscillation tube (1), a magnet (2), an electronic excitation oscillator (3), a frequency counter (4), a pressure sensor (5), a first temperature sensor (6), a second temperature sensor (7), a third temperature sensor (8), a temperature control heat preservation layer (9), a three-way valve (10) and an air outlet valve (11); a magnet (2) is fixed at the bottom of the U-shaped oscillating pipe (1), and the upper parts of two vertical pipes of the U-shaped oscillating pipe (1) are respectively provided with a frequency counter (4); the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the first port of the three-way valve (10) through a pipeline, the second port and the third port of the three-way valve (10) are respectively connected with the outside through pipelines, and the pressure sensor (5) is hermetically connected on the pipeline between the pipe orifice of the left vertical pipe of the U-shaped oscillation pipe (1) and the first port of the three-way valve (10); the pipe orifice of the right vertical pipe of the U-shaped oscillation pipe (1) is hermetically connected with the air inlet end of an air outlet valve (11) through a pipeline, and the air outlet end of the air outlet valve (11) is hermetically connected with an exhaust pipeline; the first temperature sensor (6) is arranged between the left vertical pipe and the right vertical pipe of the U-shaped oscillating pipe (1); the electronic excitation oscillator (3) is arranged below the fixed magnet (2); u type oscillating pipe (1), magnet (2), electron excitation oscillator (3), frequency counter (4), pressure sensor (5), first temperature sensor (6), gas outlet valve (11) all install in accuse temperature heat preservation (9), second temperature sensor (7) install on accuse temperature heat preservation (9) outer wall, third temperature sensor (8) install on accuse temperature heat preservation (9) inner wall.
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