# Device for determination of mass of liquefied gas

FIELD: measurement technology; high-accuracy determination of liquefied gas mass in reservoir irrespective of its phase.

SUBSTANCE: three RF sensors of different length are placed in reservoir filled with liquefied gas. Sensors are connected to secondary converter. Length of first sensor vertically placed in reservoir corresponds to height of reservoir. Length of second vertical sensor is reduced from below by value no more than 0.35 of length of first sensor. Third sensor is located in gas phase of liquefied gas and its length is no more than 0.3 of length of first sensor. Each sensor may be connected to frequency-setting circuit of respective self-excited oscillator.

EFFECT: enhanced measurement accuracy; extended field of application.

2 cl, 3 dwg

The invention relates to the field of measurement technology and can be used for high-precision determination of the mass of liquefied gas in the tank regardless of its phase state.

The known device for determining the amount (level, volume, mass) of the substance in the vessel, based on the electric - capacitive, radio wave, the principles of measuring instruments (monographs: 1) beaver G.N., Rollers A.G. Methods of level measurement. M: Engineering. 1977. S-141; 2) V.A. Viktorov, Lunkin BV, Sablukov A.S. radio-wave measurement of parameters of technological processes. M.: Nauka. 1989. P.84-117). Thus, in particular, the measurement of electrical capacitance using capacitive measurement methods, or resonant frequency of the electromagnetic oscillations of the RF or microwave resonator partially filled of controlled substances, to determine the level of the controlled fluid. Such devices are applicable in cases when the electrophysical parameters of the liquid and gas environment above it unchanged. When solving the problem of measuring the amount (mass) of liquefied gas such methods are very methodical measurement error due to variability ratio of liquid and gas phases, its arbitrary and uncontrolled changes due to temperature changes and other factors.

is the most closest to the technical essence and purpose is a capacitive device for measuring the amount (level) of the liquid, described in the patent US 3862571 and adopted as a prototype. The device prototype contains three have vertically in the tank with the liquid coaxial capacitive sensor having a different length. The degree of lling of liquid corresponds to the degree of immersion in his first sensor, and the other two sensors have a shorter bottom length compared to the length of the first sensor.

This device, however, has some significant drawbacks. The ratio of the lengths of the sensors is that it ensures the achievement of the objectives of the present invention, namely, the measurement of the level of the dielectric liquid regardless of its density. However, this solution does not allow to determine the mass of liquid in a tank, in particular, the mass of liquefied gas. In this known device, the length of the second sensor is about 0.95 length of the first level sensor, that is, the second sensor is truncated from below at length about 0.05 length of the first level sensor. The length of the third level sensor is about 0,85 length of the first sensor, the third sensor truncated from below at length about 0.15 length of the first sensor. These sensors are connected to the electronic module (bridge circuit). Schematic solution, providing the balance of the bridge circuit, allows to determine the level of liquids with different density values.

p> However, this device has a limited scope. The ratio of the lengths of these sensors and the joint transform their informative parameters implemented in this known device, do not allow to measure the mass of liquid in a tank, in particular, the mass of liquefied gas.To determine the mass of liquefied gas, which is the most objective parameter of the content of this two-phase substance in the tank, you want to make additional density measurements of the special sensor density. Because it takes place in the vessel uncontrolled transition gas depends on its temperature, composition) from a liquid phase to a gas and Vice versa, the readings of this sensor density is inaccurate; the use of two sensors density separately for liquid and gas phases significantly complicates the measurement process and the construction of the measuring device implementing this method. Since the density of vapors of liquefied gas depends on temperature, pressure and composition (in particular, the ratio of propane and butane), then measuring the mass of the vapor phase may pay an additional truncation error (3-7%). Added to this is also the error due to the variation in pressure when pumping gas. Thus, for high-precision measurement of the mass of liquefied gas neo what should be the measurement channel pair and correction of errors due to changes in the density of steam. Next, note that the liquefied gas is boiling, resulting in lost the "liquid mirror". Therefore, various known measuring device (a radio wave, ultrasonic, capacitive, which allows to determine only the level or interface cannot provide high accuracy measurements. They do not provide stable and reliable determination of the actual value of the quantity (mass) of liquefied natural gas. Besides having a place boiling liquefied gas change as the level and density of gas. Intensive boiling (increase by 5-10%) occurs at the end of the process of filling the tank with liquefied gas, the adjustment pressure vapor phase; it lasts a few minutes. More low boil (increase by 1-3%) was observed after an intense boiling as fading process, and also when selecting a pair of the compressor, when mixing liquefied gases of different composition or different temperatures and can take in this case a few hours.

The proposed device for determining the mass of liquefied gas is free from the above disadvantages. It provides precision definition: the mass of liquefied gas in real conditions of its storage capacity, regardless of its phase composition and the ratio of liquid and gas phases, the presence of boiling; the mass of steam (above the liquid); density of si the military gas; density of steam; the level of liquefied gas; the volume of liquefied gas.

The aim of the invention is the expansion of the scope.

The goal in the proposed device for determining the mass of liquefied gas contained in the vessel, containing three have in it the RF sensor of different lengths connected to the secondary of the Converter is achieved by the fact that it is the length of the first sensor is placed vertically in the tank corresponds to the vessel height and the length of the second sensor, also have vertically in the tank, is reduced below a value of not more than 0.35 length of the first sensor and the third sensor located in the gas phase LPG, has a length of not more than 0.3 length of the first sensor.

In this device, each sensor may be included in customizados circuit corresponding oscillator included in the secondary of the Converter.

A distinctive signs, according to the authors, are: the choice of the length of the second level sensor is reduced below a value of not more than 0.35 length of the first level sensor; the choice of the length of the third sensor, radio frequency sensor, the gas density is not more than 0.3 length of the first level sensor.

The set of distinctive features of the proposed device makes it a new property: the possibility of the distribution of the real mass quantity of liquefied gas in the tank regardless of its phase state. This property provides a positive effect, formulated in the objectives of the proposals.

Figure 1 shows a diagram of the proposed device. Figure 2 - graphs of the equivalent electrical capacitance sensors level. Figure 3 - measuring channel containing the oscillator with included sensor.

Here we have introduced the following notation: 1 - first level sensor; 2 - second level sensor; 3 - sensor gas density; 4 - secondary Converter; 5 - capacity; 6 is a controlled substance; 7 - oscillator; 8 - inductance; 9 and 10 - the inner and outer conductors of the coaxial lines, respectively; 11 and 12 - dielectric bearings (bushings).

The device operates as follows.

In this device produce a measurement of any informative parameter of each of the radio-frequency sensors, included in its composition. These RF sensors operating in the frequency range within typically 0-100 MHz, include capacitive sensors, sensors based on segments of homogeneous or heterogeneous long lines; the latter is the propagation of electromagnetic waves THAT - or quasi-FACT-type (Viktorov, V.A., Lunkin BV, Sablukov A.S. high-Frequency method for measuring non-electrical quantities. M.: "Nauka". 1980. 280 C.).

So, when you implement this device applies is of capacitive sensors as measured informative parameter of each sensor may be the resonant frequency of the electromagnetic oscillations f_{
p}oscillating circuit (resonator), containing a capacitive sensor as a frequency control element. When implementing this based devices with the use of long line segments as informative parameter can also be used resonant frequency of electromagnetic oscillations f_{p}this section of the line, which is the resonator with fluctuations of THE type. In addition, the possible measurement and other informative parameters, in particular in the segment of long lines - measurement of phase shift ϕtransmitted and reflected from the end of a segment of a long line of electromagnetic waves of a fixed frequency, and other

Without loss of generality, to simplify the consideration of the essence of the present device will conduct further description with regard to its implementation using capacitive sensors. In this case, it is possible representation of such sensors in the form of an equivalent electric capacitance. The resulting conclusions are fully apply to the sales of this device based on the lengths of the long lines. In the latter case, the informative parameters used here radiowave sensor (resonant frequency f_{p}the phase shift ϕ and others) depending on the determined physical parameters are described in more complicated expressions, which, however, does not change on usaamah conclusions.

To determine the current value of the mass of liquefied gas in the tank, the proposed device is made, in addition to the first dimension level value of the equivalent electrical capacity_{E1}sensor one of the specified types, the second measurement value of the equivalent capacitance C_{E2}another sensor. The density of the gas phase of the liquefied gas is determined by measuring its dielectric constant ε_{g}that is found by measuring the corresponding equivalent electrical capacity_{E3 effects}the third sensor located in the upper part of the tank filled with gas.

The first capacitance (capacitor) or radiofrequency (cut long lines) level sensor 1 (figure 1) provides the definition of level z liquefied gas in the whole range of its dimensions - from zero to full fill (z=l, where l is the height of the tank).

Then for the first measurement channel (sensor 1) will have the following expression for the equivalent capacitance C_{E1}:

Here ε_{W}and ε_{g}- dielectric permittivity, respectively, the liquid and gas phases of a controlled substance; (C_{0}- capacity per unit length (i.e. linear capacity).

The sensor 2 has a length that is reduced below a value of not more than 0,35l. This is the selection tool length sensor 2 due to the fact,
when a smaller value decreases the part of the working range level changes, which determine the current value of ε_{W}. For large values of the length of the sensor 2 decreases the value of l_{0}the difference between the lengths of the sensors 1 and 2, leading to the increase of error in the calculation of ε_{W}according to the procedure described below equation (3): absolute error of the measured values of tanks_{E1}and C_{E2}when divided by the small value of the product of l_{0}C_{0}(C_{0}=const) leads to a significant increase in the relative error of determination ε_{W}.

The length of the sensor 3 does not exceed 0,3l. This choice is due to the fact that when the real value of the maximum filling capacity 5 fluid it (liquid) should not reach the level at which is located the lower end of the probe 3. In practice, the maximum liquid level must not exceed the values of z_{max}=0,7-0,85 value of the measurement range. The choice of a specific maximum level values of z_{max}from this range and, therefore, the length of the sensor 3 is determined by the regulations for the safe operation of vessels.

For the second measurement channel (sensor 2) is equivalent to capacity With_{E2}the sensor can be written in the following form:

Here l_{0}the difference between the lengths of tchekov 1 and 2.

Figure 1 shows the secondary Converter 4. It is intended for excitation of electromagnetic oscillations in the sensor, determine the magnitude of his informative parameter and functional processing of signals from sensors 1, 2 and 3 to determine the required mass of liquefied gas 6 in the tank 5, the co conversion of the output signals of these sensors.

If the level z of the liquid above the lower end of the sensor 2, at each level, calculate the dielectric permittivity ε_{W}fluid according to the following formula, derived from the joint transformation of the relations (1) and (2):

This calculated value ε_{W}put in random access memory (RAM). It is part of the secondary of transformer 4.

The dielectric constant of the gas can be determined by measuring (probe 3) the equivalent capacitance C_{E3 effects}:

where- initial (when ε_{g}=1) is equivalent capacity_{E3 effects}.

From the relations (1) and (2) we obtain:

The values here ε_{W}and ε_{g}are expressed, respectively, by the formulas (3) and (4).

If the liquid level in the tank is less than the location of the lower end of the sensor 2, in which the quality measures of the value of z for this sensor is set to z,
which corresponds to the nominal value of the equivalent capacitance C_{E2}for written into the RAM (random access memory device) of the previously calculated value ε_{W}=ε_{Ls}or (in the absence of such data), it is valued at nominal temperature.

In this case, as a measure to calculate the value of ε_{W}according to (3) is the previously calculated value. If it was not (the reservoir is filled with liquefied gas for the first time), it is accepted ε_{W}=const=ε_{Ls}i.e. tabular value ε_{W}calculated for the current value of the temperature of the controlled fluid, in particular, propane-butane mixture (this dependence is known and is stored in non-volatile memory). So, for propane-butane mixture ε_{Ls}=1,7 at a temperature of t=20°C. In the formula (5) to determine the z-substituted-size ε_{Ls}.

In this case, the level of z is determined by the following formula obtained from the formula (1) and (2) when ε_{W}=ε_{Ls}- nominal value of ε_{W}substitute of RAM:

Figure 2 shows graphs of equivalent containers_{E1}(line 1) and C_{E2}(line 2) depending on the level z of the liquid. It also marked the section with a length l_{0}that reduced the n sensor 2 at the second level measurement z.
This graph also indicated by dotted lines corresponding to a certain current level value z and the corresponding equivalent capacitors C_{E1}(z) and C_{E2}(z).

For LPG the most appropriate parameter to determine its reserves in the tank is its mass. For nonpolar substances, including liquefied petroleum gas (LPG), is just the ratio of the Clausius - Mosotti describing the functional relationship between the density of matter (liquid, gas) and dielectric constant (Skanavi GI Physics of dielectrics (the region of weak fields). M. - L., Gill. 1949).

where ε - permittivity substance, μ - its molecular weight, ρ - density of matter, α - polarizability of molecules, N is the Avogadro's number.

From (7) it follows that

where A=4πNα/3μ - constant for each compound value.

Therefore,

Then, knowing the density of the liquid and gas phases of a substance can help determine the appropriate mass values:

It is known that mixtures of gases, mixtures of liquefied gases, in particular, propane-butane mixtures, spravedlivo with high accuracy the following relationship (Rudakov GY and other "Dielectric permeability of gas condensate and its fractions". Scientific and technical. the overview. Series: the Processing of gas and gas condensate. M: Negatron. 1973):

Here ρ_{cm}and ε_{cm}the density and dielectric constant of the mixture; n_{i}the number of molecules of the ith species per unit volume, α_{i}the polarizability of molecules of the ith species, μ_{i}- molecular weight molecules of the ith species.

For each mixture the value of the

is constant.

From relations (13) and (14) imply the following formula for mixtures of substances:

This ratio is fairly high accuracy for any phase state of a mixture of substances, including liquefied gases. Therefore, in this case on the basis of (15) can be found, as in (11) and (12), the mass of liquid, gaseous phase of the mixture and the total mass M=M_{W}+M_{g}.

When carrying out measurements using capacitive sensors or sensors in the form of segments of long lines are often used scheme in which such sensors are customizability elements of the oscillating circuit. For circuits with capacitive sensors, the resonant frequency f_{p}capacitive sensor

where L is the inductance connected to the sensor with e vigalantee capacity With_{
e}. For circuits with RF sensors on the basis of long segments of lines based on the designated level describes the exact transcendental equations implicitly or explicitly, close relationships, which, however, accurate enough for the task solution process measurements (see, for example, the monograph: V.A. Viktorov, Lunkin BV, Sablukov A.S. radio-wave measurement of parameters of technological processes. M.: Nauka. 1989. 280 C.).

Figure 3 shows a diagram of the measuring channel, containing each of the sensors 1, 2 or 3, included as a frequency control element in the composition of the oscillator 7. Here the oscillatory circuit formed by the combination of the capacitor (when implementing a device with a capacitive sensor) with the corresponding sensor 1, 2 or 3 the value of the equivalent capacitance and connected inductance 8. Hard mutual arrangement of conductors 9 and 10 sensors is provided with a dielectric, such as Teflon, bushings 11 and 12 (they are really over 0.7 m along the length of the sensors). Figure 3 shows only two such bushings. They have a through hole for the free flow of liquid.

The output signal of the oscillator 7 (frequency up to ten megahertz) is divided to 1-2 kHz, convenient for transmission over the communication line. Unit 7 included in wtorek the CSO Converter 4.
In it coming from the sensors 1, 2 and 3, the signals undergo joint functional processing according to the above ratios. Indicator contained in unit 4, shows the current values of the mass of liquefied gas 6 in the tank, including separately the liquid mass M_{W}gas M_{g}phases and the total mass M

Thus, the proposed device provides a high-precision determination of the actual values of the mass of liquefied gas in the tank regardless of its phase state and the ratio of the component that is in a liquid or gas phase, from having a boiling liquefied gas.

1. Device for determining the mass of liquefied gas contained in the vessel, containing three have in it the RF sensor of different lengths connected to the secondary of the Converter, characterized in that the length of the first sensor placed vertically in the tank corresponds to the vessel height and the length of the second sensor, also have vertically in the tank, is reduced below a value of not more than 0.35 length of the first sensor and the third sensor located in the gas phase LPG, has a length of not more than 0.3 length of the first sensor.

2. The device according to claim 1, characterized in that each sensor included in customizados circuit of the corresponding oscillator, part of the secondary transformed is the Converter.

**Same patents:**

FIELD: measurement technology; high-accuracy determination of liquefied gas mass in reservoir irrespective of its phase.

SUBSTANCE: three RF sensors of different length are placed in reservoir filled with liquefied gas. Sensors are connected to secondary converter. Length of first sensor vertically placed in reservoir corresponds to height of reservoir. Length of second vertical sensor is reduced from below by value no more than 0.35 of length of first sensor. Third sensor is located in gas phase of liquefied gas and its length is no more than 0.3 of length of first sensor. Each sensor may be connected to frequency-setting circuit of respective self-excited oscillator.

EFFECT: enhanced measurement accuracy; extended field of application.

2 cl, 3 dwg

FIELD: measuring engineering.

SUBSTANCE: water level alarm comprises the section of coaxial long line provided with inner conductor projecting beyond its end. The section is connected with the high-frequency generator and recorder. The generator is made of a self-excited oscillator. The section is connected to the frequency generating circuit of the self-excited oscillator. The recorder is made of a frequency meter. The projecting part of the inner conductor is made of two members of the same length, but different diameters. The diameter of the end part exceeds that of the other part of the projecting part of the inner conductor by a factor of ten. The projecting part of the conductor can be covered with a dielectric shell.

EFFECT: enhanced sensitivity.

1 cl, 5 dwg

FIELD: measuring equipment engineering.

SUBSTANCE: device has excitation winding, fed by alternating current and measuring winding, connected to alternating voltage meter. Both windings are enveloped by protective cover, placed in controlled electric-conductive environment. To provide for high sensitivity to level of environment and decrease of temperature error from influence of construction materials, conductors of measuring winding are distanced from excitation winding conductors for distance, equal to one to ten sums of thickness of protective cover and radius of excitation winding cable cover. Also provided are different variants of constructions of level meters both with solenoid and frame windings.

EFFECT: higher precision.

7 cl, 5 dwg

FIELD: measurement technology.

SUBSTANCE: first measurement of level of liquid is performed from value of measured electric capacitance C1 of first radio-frequency detector. Density of gaseous phase is determined on the base of value of electric capacitance C3 of corresponding radio-frequency detector. Simultaneously the second measurement is performed of level of liquid in reduced or increased range of change on the base of measured value of electric capacitance C2 of corresponding radio-frequency detector. Then functional conversion of measured electric capacitances C1, C2 and C3 is performed and dielectric permeability of liquid and gaseous phases is measured.

EFFECT: improved precision of measurement; widened functional capabilities.

2 dwg

FIELD: electric engineering equipment.

SUBSTANCE: device can be used for measuring electric parameters of two-terminal devices used as physical process detectors (temperature, pressure, level of loose and liquid matters and et cetera) at transportation vehicles and in systems for measuring level of filling of rocket-space equipment. Device for measuring level of dielectric matter has first and second measuring inputs, sinusoidal voltage source, equivalent circuit preset unit, standard which has first output connected with first input of switching unit, current-to-voltage converter, scaling amplifier and analog-to-digital converter. Switching unit is made to be multi-channel one, which has first measuring, input with second output of standard and with output of sinusoidal voltage generator. Control input of the latter is connected with first output of frequency-control unit. Measuring inputs starting from second to (n+1) are connected with corresponding inputs of switching unit which has output connected with first outputs of electric capacity and active resistance calculators through current-to-voltage converter, scale amplifier and analog-to-digital converter all connected in series. It is also connected with first input of measurement control input which has outputs connected with control inputs of switching unit, of scale amplifier and analog-to-digital converter as well as with first input of frequency control unit and with second inputs of electric capacity and active resistance calculators. Control input of measurement control unit is connected with control output of mode control unit which has outputs connected with second input of frequency control unit, with equivalent circuit setting unit, with first input of electric capacitance total increment calculator, with first input of level calculator, with first input of electric capacitance current increment calculator and with input switching control unit. Output of the latter is connected with second control input of switch unit. Output electric capacitance calculator is connected with second input of calculator of current increment in electric capacitance. Output of the latter is connected with second input of level calculator. Third and fourth inputs of electric capacitance and active resistance calculators are connected with output equivalent circuit preset unit and with second output of frequency control unit. Output of calculator of current increment in electric capacitance is connected with third input of level calculator. Output of the latter as well as outputs of active resistance calculator and switch control unit have to be outputs of the device.

EFFECT: improved precision of measurement; improved manufacturability; improved efficiency of measurement.

6 dwg

FIELD: electric measurement engineering.

SUBSTANCE: method can be used for measurement of electrical parameters of two-terminal networks used as detectors of physical processes (temperature, pressure, level of liquid and loose maters et cetera) at industrial installations, transportation vehicles and in systems for measuring level of setting-up of rocket-space equipment. Sinusoidal voltage is formed in capacitive level gauge and complex current is measured which passes through dry capacitive level gauge as well as through filled-in capacitive level gauge. Equivalent circuit of capacitive level gauge is specified which circuit consists of electric capacitance and active resistance. Sinusoidal voltage is formed in capacitive detector at two frequencies. After it complex current is measured through dry level detector and through reference detector for any of those frequencies. Results of measurement are registered, electric capacitance of capacitive level gauge is measured and registered and increment in electric capacitance of capacitive level gauge is measured and registered when submerging gauge into dielectric matter completely. Subsequent measurement and registration of complex current is carried out through capacitive level gauge filled with dielectric matter and through reference gauge for any of mentioned frequencies. For any periodical measurement the electric capacitance of capacitive level gauge is measured and registered. Relative filling of capacitive level gauge with dielectric matter is measured as difference of values of electric capacitance of dry capacitive level gauge and electric capacitance of filled-up capacitive level gauge related to increment in electric capacitance of capacitive level gauge submerged into liquid totally.

EFFECT: improved precision of measurement; improved adaptability to manufacture.

2 dwg

FIELD: measuring equipment engineering, possible use for measuring level of liquid products, in particular, oil and oil products in railroad cisterns.

SUBSTANCE: level meter for measuring level of liquid contains bar with single capacity level indicators, positioned along its length, bar is made in form of hollow elongated construction, inside the construction a pair of electronic boards is positioned in form of rods, mounted in parallel to one another and at fixed distance from each other, forming single capacity level indicators on opposite planes facing each other, by means of electrodes on one electronic board and common electrode on the other board. When measuring level of liquid, serial scanning of indicators is performed in pairs of following indicator with previous one and on basis of received scanning results, level of liquid is calculated.

EFFECT: increased manufacturability, reliability and precision when measuring level of liquid product.

2 cl, 2 dwg

FIELD: measuring level of melt metals, possibly in systems for controlling manufacturing processes in metallurgical industry, for example in apparatuses for thermal-magnetic reduction of titanium.

SUBSTANCE: device includes exciting windings and metal level pickups in the form of induction turns, computing unit. Said windings and level pickups are placed in pairs around vessel with melt metal. Computing unit is connected with level pickups. It provides possibility for scanning pickups, digitizing voltage values of pickups, approximating pickups readings of designed curve found according to decision of simulation task, calculating derivative of said curve and determining metal level according maximum value of derivative. Excitement windings of device are connected in series and they form electromagnet.

EFFECT: enhanced accuracy, lowered labor consumption of measuring process.

2 cl, 3 dwg

FIELD: measuring technique.

SUBSTANCE: fuel level meter comprises elongated capacitive sensor connected in the frequency-generating circuits of functional and base self excited oscillators. The main and additional counters generate the position code of the fuel level from the output frequencies of the self-excited oscillators. The level is indicated by the linear or pointer indicator provided with a converter of position code into the current of supplied to the pointer indicator.

EFFECT: reduced power consumption and enhanced reliability.

2 cl, 2 dwg

FIELD: measuring equipment engineering.

SUBSTANCE: holding system for measuring device for controlling and/or determining level of environment in reservoir, containing at least one body (13) and at least one elongated block (1). In accordance to invention, body (13) of device includes at least one incision ring (4), which is cut into external layer of elongated block (1) oriented from end process with possible connection of elongated block (1) to body (13) of device electrically, with resistance to compression and stretching.

EFFECT: creation of holding system, by means of which holding block may be fastened on or in a body of device.

8 cl, 3 dwg