CN104020358B - A kind of measure dielectric permittivity and the method for liquid level in LNG gas tank - Google Patents
A kind of measure dielectric permittivity and the method for liquid level in LNG gas tank Download PDFInfo
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- CN104020358B CN104020358B CN201410254083.7A CN201410254083A CN104020358B CN 104020358 B CN104020358 B CN 104020358B CN 201410254083 A CN201410254083 A CN 201410254083A CN 104020358 B CN104020358 B CN 104020358B
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Abstract
The present invention relates to a kind of measure dielectric permittivity and the method for liquid level in LNG gas tank, comprise the steps: that (1) is respectively provided with top capacity, intermediate capacitance and bottom capacitor in LNG gas tank inner upper end, middle part and lower end.(2) its capacitance in atmosphere, respectively C is measuredH1、CM1And CL1.(3) according to formulaCalculate the DIELECTRIC CONSTANT ε of liquid1.(4) according to formulaCalculate the DIELECTRIC CONSTANT ε of gas2.(5) formula is passed throughCalculate the liquid level H in LNG gas tankx.Syllogic capacitance sensor can be as checking and the instrument calibrating other sensor, and itself also can be as high-accuracy liquid level sensor simultaneously.The measurement error that the factors such as the change of temperature, pressure and magazine cause can be overcome when measuring liquid level.
Description
Technical field
This utility model relates to field of measuring technique, is specifically related to dielectric permittivity and liquid in a kind of measurement LNG gas tank
The method of position.
Background technology
Liquefied natural gas (Liquefied Natural Gas, LNG) has been widely used in automobile, and automobile LNG stores
Exist in the gas tank that insulation is adiabatic, it is necessary to be equipped with Level Detection dress instrument and show LNG liquid level in real time.Level meter generally comprises:
The liquid level sensor being installed in gas tank, the fluid level transmitter processed for collecting sensor signal and fluid level indicator.
Automobile LNG liquid level sensor is installed in the inner chamber of gas tank, is the critical component of whole detector, generally electric capacity
Formula sensor.The detection method of current most of Level meter is: it is aerial that (one) first detects capacitance type sensor
Unloaded electric capacity C0, and liquid level when being recorded as zero load；(2) record electric capacity when filling it up with LNG, be i.e. fully loaded with electric capacity C1, and be recorded as
The liquid level of full load；(3) assume that the dielectric constant of gas and liquid immobilizes, the capacitance of capacitance type sensor and liquid level
Change be linear, therefore fluid level transmitter detection sensor capacitance, according to formulaCalculate liquid level h also
Liquid level information is sent to fluid level indicator.
Above-mentioned liquid-level detecting method has a disadvantage in that other gas componant comprised of (one) liquefied natural gas can be because producing
The difference of the factors such as ground and variant, composition difference can affect the dielectric constant of LNG, thus fully loaded electric capacity there may be change,
Thus the precision of level gauging can be affected, need after each aerating fluid level transmitter is calibrated；(2) automobile liquefied natural gas
Pressure limit in gas tank is 0.4-1.5MPa, close-162 DEG C of storage temperature, and temperature can increase over time, temperature and pressure
The change of power can affect the dielectric constant of liquids and gases in gas tank.
Summary of the invention
This utility model is in order to overcome the deficiency of above technology, it is provided that in the measurement LNG gas tank that a kind of certainty of measurement is high
The method of dielectric permittivity and do not affected the method measuring liquid level by change in dielectric constant.
This utility model overcomes its technical problem be the technical scheme is that
In this measurement LNG gas tank, dielectric permittivity and the method for liquid level, comprise the steps:
A) it is respectively provided with top capacity, intermediate capacitance and bottom in LNG gas tank inner upper end, middle part and lower end
Electric capacity, described top capacity, intermediate capacitance and bottom capacitor be inner tube, outer tube for circle, and radius just as coaxial electrical
Holding, the inner tube radius of described top capacity, intermediate capacitance and bottom capacitor is r, and outer tubing radius is R；
B) top capacity, intermediate capacitance and bottom capacitor measure its capacitance in atmosphere, respectively C respectivelyH1、CM1
And CL1, capacitance CH1、CM1And CL1Transmitted to signal by output cable I, output cable II and output cable III respectively
Processing unit；
C) liquefied natural gas is injected in LNG gas tank, and when liquefied natural gas liquid level is higher than bottom capacitor, bottom capacitor
The capacitance measured is CL2, and transmitted to signal processing unit by output cable III, signal processing unit is according to formulaCalculate the DIELECTRIC CONSTANT ε of LNG in LNG gas tank1, H in formula1For bottom capacitor
Highly, ε0Dielectric constant for air；
D) when the liquefied natural gas liquid level in LNG gas tank is less than top capacity bottom, top capacity is in gas,
The capacitance that top capacity is measured is CH 2, and transmitted to signal processing unit by output cable I, signal processing unit according to
FormulaCalculate the DIELECTRIC CONSTANT ε of gas in LNG gas tank2, H in formula2For top electricity
The height held, ε0Dielectric constant for air；
E) when the liquid level of liquefied natural gas is less than top capacity and is higher than bottom capacitor, calculate according to signal processing unit
The liquid obtained and the DIELECTRIC CONSTANT ε of gas1And ε2And pass through formulaCalculate
Draw the liquid level H in LNG gas tankx, H in formulaMHeight for intermediate capacitance.
In order to ensure measuring the dielectric constant arriving liquid, the height H of bottom capacitor1Less than (H1+HM+H2) × 10%.
In order to ensure measuring the dielectric constant arriving gas, the height H of top capacity2Less than (H1+HM+H2) × 10%.
For simple in construction, convenient installation, keep coaxial when above-mentioned top capacity, intermediate capacitance and bottom capacitor are installed
And on same vertical line.
The beneficial effects of the utility model are: the dielectric constant that top capacity and bottom capacitor record is real-time, permissible
The dielectric constant of reference is provided for conventional capacitive formula liquidometer.This method can also measure the liquid level of LNG in real time, owing to recording in real time
Dielectric constant the most accurate, changed by temperature and pressure and affected.Liquid level is measured also than other condenser type by this method
Liquidometer is the most accurate, syllogic capacitance sensor therein can as checking and calibrate the instrument of other sensor, simultaneously its
Itself also can be as high-accuracy liquid level sensor.The factors such as the change of temperature, pressure and magazine can be overcome when measuring liquid level to cause
Measurement error.
Accompanying drawing explanation
Fig. 1 is the capacitance sensor mounting structure schematic diagram of the present invention；
In figure, 1. output cable I 2. top capacity 3.LNG gas tank 4. intermediate capacitance 5. bottom capacitor 6. exports electricity
Cable II 7. output cable III 8. signal processing unit.
Detailed description of the invention
1 pair of this utility model is described further below in conjunction with the accompanying drawings.
In this measurement LNG gas tank, dielectric permittivity and the method for liquid level, comprise the steps:
(1) be respectively provided with in LNG gas tank 3 inner upper end, middle part and lower end top capacity 2, intermediate capacitance 4 and
Bottom capacitor 5, described top capacity 2, intermediate capacitance 4 and bottom capacitor 5 are inner tube, outer tube is circle, and radius is identical
Coaxial capacitance, the inner tube radius of described top capacity 2, intermediate capacitance 4 and bottom capacitor 5 is r, and outer tubing radius is R.(2)
Top capacity 2, intermediate capacitance 4 and bottom capacitor 5 measure its capacitance in atmosphere, respectively C respectivelyH1、CM1And CL1,
Capacitance CH1、CM1And CL1Transmitted to signal processing by output cable I 1, output cable II 6 and output cable III 7 respectively
Unit 8.(3) liquefied natural gas is injected in LNG gas tank 3, and when liquefied natural gas liquid level is higher than bottom capacitor 5, bottom electricity
The capacitance holding 5 measurements is CL2, and transmitted to signal processing unit 8 by output cable III 7, signal processing unit 8 is according to public affairs
FormulaCalculate the DIELECTRIC CONSTANT ε of LNG in LNG gas tank 31, H in formula1For bottom electricity
Hold the height of 5, ε0Dielectric constant for air.(4) when the liquefied natural gas liquid level in LNG gas tank 3 less than top capacity 2 under
During end, top capacity 2 is in gas, and the capacitance that top capacity 2 is measured is CH2, and by output cable I 1 transmission to letter
Number processing unit 8, signal processing unit 8 is according to formulaCalculate gas in LNG gas tank 3
The DIELECTRIC CONSTANT ε of body2, H in formula2For the height of top capacity 2, ε0Dielectric constant for air.(5) when the liquid of liquefied natural gas
When position is less than top capacity 2 and higher than bottom capacitor 5, according to the calculated liquid of signal processing unit 8 and the dielectric of gas
Constant ε1And ε2And pass through formulaCalculate the liquid level in LNG gas tank 3 high
Degree Hx, H in formulaMHeight for intermediate capacitance 4.In LNG gas tank 3, the usual excursion of temperature and pressure is relatively big, and natural gas liquids
And the dielectric constant of gas affected by temperature and pressure be change, therefore by arrange three capacitance level transducers
The dielectric constant of liquids and gases in gas tank can be apparent from.Top capacity 2 in this method and bottom capacitor 5 record
Dielectric constant is real-time, can be the dielectric constant of conventional capacitive formula liquidometer offer reference.Due to the dielectric recorded in real time
Constant is the most accurate, and it is also more accurate than other capacitance level gauge that this method measures liquid level, syllogic electric capacity therein
Sensor can be as checking and the instrument calibrating other sensor, and itself also can be as high-accuracy liquid level sensor simultaneously.Survey
The measurement error that the factors such as the change of temperature, pressure and magazine cause can be overcome during amount liquid level.
The height H of bottom capacitor 51Less than (H1+HM+H2) × 10%, therefore bottom capacitor 5 ensures the shortest length,
Can guarantee that natural gas liquids liquid level still can be measured time low in LNG gas tank 3 as far as possible.
The height H of top capacity 22Less than (H1+HM+H2) × 10%, natural in LNG gas tank 3 can being guaranteed as far as possible
Gas gas can be measured.
Top capacity 2, intermediate capacitance 4 and bottom capacitor 5 can keep coaxial and on same vertical line when installing, so
Arrangement is simple, low cost, easily install, and signal processing unit is simple.
Claims (4)
1. measure dielectric permittivity and the method for liquid level in LNG gas tank for one kind, it is characterised in that: comprise the steps:
A) be respectively provided with in LNG gas tank (3) inner upper end, middle part and lower end top capacity (2), intermediate capacitance (4) with
And bottom capacitor (5), described top capacity (2), intermediate capacitance (4) and bottom capacitor (5) are inner tube, outer tube is circle,
And the coaxial capacitance that radius is identical, the inner tube radius of described top capacity (2), intermediate capacitance (4) and bottom capacitor (5) is r,
Outer tubing radius is R；
B) top capacity (2), intermediate capacitance (4) and bottom capacitor (5) measure its capacitance in atmosphere respectively, are respectively
CH1、CM1And CL1, capacitance CH1、CM1And CL1Respectively by output cable I (1), output cable II (6) and output cable
III (7) transmits to signal processing unit (8)；
C) liquefied natural gas is injected in LNG gas tank (3), and when liquefied natural gas liquid level is higher than bottom capacitor (5), bottom electricity
Holding the capacitance (5) measured is CL2, and transmitted to signal processing unit (8), signal processing unit by output cable III (7)
(8) according to formulaCalculate the DIELECTRIC CONSTANT ε of LNG in LNG gas tank (3)1, H in formula1
For the height of bottom capacitor (5), ε0Dielectric constant for air；
D) when the liquefied natural gas liquid level in LNG gas tank (3) is less than top capacity (2) bottom, top capacity (2) is in gas
In body, the capacitance that top capacity (2) is measured is CH2, and transmitted to signal processing unit (8), signal by output cable I (1)
Processing unit (8) is according to formulaCalculate the dielectric constant of LNG gas tank (3) interior gas
ε2, H in formula2For the height of top capacity (2), ε0Dielectric constant for air；
E) when the liquid level of liquefied natural gas is less than top capacity (2) and is higher than bottom capacitor (5), according to signal processing unit
(8) calculated liquid and the DIELECTRIC CONSTANT ε of gas1And ε2And pass through formulaMeter
Calculation draws the liquid level H in LNG gas tank (3)x, H in formulaMFor the height of intermediate capacitance (4), CM2It is filled with LNG gas for natural gas
The measured value of the intermediate capacitance (4) measured after tank (3).
Dielectric permittivity and the method for liquid level in measurement LNG gas tank the most according to claim 1, it is characterised in that: the end
The height H of portion's electric capacity (5)1Less than (H1+HM+H2) × 10%.
Dielectric permittivity and the method for liquid level in measurement LNG gas tank the most according to claim 1, it is characterised in that: top
The height H of portion's electric capacity (2)2Less than (H1+HM+H2) × 10%.
4., according to dielectric permittivity and the method for liquid level in the measurement LNG gas tank described in claim 1 or 2 or 3, its feature exists
In: keep when described top capacity (2), intermediate capacitance (4) and bottom capacitor (5) are installed coaxially and on same vertical line.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104457908A (en) * | 2014-12-10 | 2015-03-25 | 华帝股份有限公司 | Novel liquid level measuring device |
| CN105136245A (en) * | 2015-09-21 | 2015-12-09 | 中国石油大学(华东) | Triangular capacitive sensor and liquid level measuring system |
| CN105091979A (en) * | 2015-09-21 | 2015-11-25 | 中国石油大学(华东) | Method for conducting liquid level measuring through triangular capacitance-type sensor |
| CN105136246B (en) * | 2015-10-26 | 2018-03-09 | 中国石油大学(华东) | Plate capacitor formula sensor and liquid level measuring system |
| CN106771046A (en) * | 2016-12-08 | 2017-05-31 | 北京航天试验技术研究所 | LNG quality device for fast detecting |
| DE102017223855A1 (en) * | 2017-12-28 | 2019-07-04 | Kautex Textron Gmbh & Co. Kg | Operating fluid tank with integrated system for the detection of the filling level |
| CN111060181A (en) * | 2019-12-23 | 2020-04-24 | 航天科技控股集团股份有限公司 | Liquid level measuring device based on capacitive sensor |
| CN113091818A (en) * | 2021-04-06 | 2021-07-09 | 宁夏弘茂特种设备检验检测有限公司 | LNG raffinate recovery unit |
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| CN86210228U (en) * | 1986-12-13 | 1987-12-05 | 李煜辉 | Automatic water level monitor |
| EP1677084A1 (en) * | 2004-12-22 | 2006-07-05 | Roxer Industries S.A. | LIquid level sensor and method of estimation |
| DE102008003802A1 (en) * | 2008-01-10 | 2009-07-16 | Robert Bosch Gmbh | Capacitive level sensor and method for estimating a level |
| CN102997974B (en) * | 2012-12-24 | 2014-12-10 | 电子科技大学 | Adaptive capacitance liquid level meter |
| CN203376025U (en) * | 2013-05-31 | 2014-01-01 | 永康市兰雪龙智能科技有限公司 | LNG gas cylinder double-cable double-capacitor self-adaption sensor |
| CN203310480U (en) * | 2013-06-06 | 2013-11-27 | 成都中阳实业公司 | Two-line three-capacitor sensor liquid level meter |
| CN103528642B (en) * | 2013-10-07 | 2016-09-07 | 北京航天试验技术研究所 | The capacitance level gauge of a kind of real-time correction dielectric constant and level measuring method thereof |
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