RU2597682C1 - Method of measuring amount and quality of fuel in the tank with three-layer mixture "air-fuel-water" and device for its implementation - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: use: for determination of the amount of fuel and its quality in the tanks of vehicles. Essence of the invention is in that the method of measuring amount and quality of fuel in the tank with three-layer mixture "air-fuel-water", according to which in the resonator placed in the tank electromagnetic oscillations are excited on three natural frequencies, they are measured, and by them are detected the parameters of the controlled medium-position of two interface borders and fuel dielectric permeability, by these parameters the amount of fuel and its quality is determined, lower part of the resonator is submerged into a self-contained canister completely filled with water, and its remaining part is submerged into controlled mixture for the tank completely refuelled with a fuel on three measured natural frequency of resonator the total amount of water in the tank and container and dielectric permeability of fuel are determined, their values are stored in archive, following the fuel consumption depending on its amount the parameters of three-layer mixture are determined in three modes, with a large amount of fuel - by three measured natural frequency of resonator, with an average amount - by two of the measured free frequency and an archive value of the total amount of water in the tank and in the container, with a small amount of fuel - by one measured frequency and the archive values of the total amount of water and fuel dielectric permeability.

EFFECT: provision of possibility of high accuracy of determining amount of fuel in three-layer medium and its quality.

2 cl, 3 dwg

Description

The invention relates to electrical measurement methods and is intended to determine the amount of fuel and its quality in the tanks of vehicles and stationary installations, in which during operation a three-layer mixture of "air (gas) - fuel - water" is formed. The amount of fuel is determined by the difference between the measured values of the gas – fuel interface and the fuel – water interface, and the quality of the fuel is estimated by measuring its dielectric constant. It is also applicable for measuring the amount of substances obtained as a result of the separation of liquid mixtures in technological plants of food production.

A device is widely used for land vehicles in which the amount of fuel is determined by the position of the float in the volume of the tank (Khasanov M. M. A light-guide float-free non-contact liquid level meter with a digital output of the results. RU 2359237, C1, 06/20/2009). This device has a low measurement accuracy, and the presence of moving parts leads to its low reliability.

In aviation, mainly capacitive level sensors are used. With careful monitoring of the quality of the fuel and in the presence of additional temperature and pressure sensors, they provide high accuracy of measurement (Grishov A.P., Lutsky A.S., Spivak V.B. Electrical capacitive fuel meter. RU 2014573, C1, 06.15.1994). However, the appearance of a layer of water in the tank leads, in fact, to a complete loss of information content of the sensor. Therefore, the device is supplemented with a float sensor.

Closest to the technical nature of the proposed invention is the method described in (Lunkin BV "Multichannel sensor parameters of layered media with one sensing element. Automation and telemechanics. 2012, No. 10, p. 127-141) - prototype. According to the prototype method in the resonator, which is a sensitive element of the sensor, electromagnetic waves are excited at three natural frequencies. The values of the parameters are determined from these measured frequencies by solving a system of equations composed of their dependences on the parameters of the controlled medium. The disadvantage of this method is that in order to obtain an acceptable measurement accuracy, especially in the region of small values of the amount of fuel, a high accuracy in determining the natural frequencies is required, which is difficult in practice. This raises the problem of choosing the initial parameter values when solving the above system of equations to obtain unique solutions even with high accuracy in determining the natural frequencies.

A device is known (Lunkin B.V., Azmaiparashvili A.A. A device for measuring the mass of liquefied gas in a closed tank. RU 2427805, C1, 08.27.2011) - prototype. The prototype device that implements this method includes an electromagnetic oscillation frequency synthesizer, an exciting resonator that is located in a tank with a controlled environment, a detector, an analog-to-digital converter, a microprocessor that generates a voltage for tuning the synthesizer frequency and implements an algorithm for determining parameters from three measured natural frequencies. The disadvantage of this device is that the configuration of the sensitive element and the algorithm for converting the natural frequencies do not provide the necessary accuracy; it does not even exclude the possibility of loss of primary information.

The technical result of the measurement method and the device that implements it is to ensure high accuracy in determining the amount of fuel in a three-layer medium (with an error not exceeding a few fractions of a percent) from the measured natural frequencies with practicable accuracy (the relative error does not exceed 10 ^-4 ) and assessment of fuel quality by measuring its dielectric constant.

The technical result is achieved by the fact that in the proposed method for measuring the quantity and quality of fuel in a tank with a three-layer mixture of “air - fuel - water”, according to which electromagnetic oscillations are excited in the tank placed in the tank at three natural frequencies, they are measured and they are used to judge the parameters controlled environment - the position of two interfaces and the dielectric constant of the fuel, these parameters determine the amount of fuel and its quality, the lower part of the resonator is immersed in an autonomous container, completely filled with water, and the rest of it is immersed in a controlled mixture, for a tank completely filled with fuel, the total amount of water in the tank and container and the dielectric constant of the fuel are determined from the three measured natural frequencies of the resonator, their values are recorded in the archive, depending on fuel consumption the parameters of a three-layer mixture are determined in three modes, for a large amount of fuel - for the three measured natural frequencies of the resonator, for an average quantity - for two of the measured x natural frequencies and the archive value of the total amount of water in the tank and container, with a small amount of fuel - according to one of the measured frequencies and the archive values of the total amount of water and dielectric constant of the fuel.

The technical result is achieved by the fact that the device for implementing the proposed method contains a frequency synthesizer of electromagnetic waves, a resonator located in a tank with a controlled mixture, a detector, an analog-to-digital converter, a microcontroller that generates a voltage for tuning the frequency of the synthesizer and implements a measurement algorithm, the resonator is made in a W-shaped conductor in a metal pipe in a dielectric sheath, the lower part of which is isolated from a controlled mixture of meta a faceplate placed on the outer surface of this shell.

In FIG. Figure 1 shows the error plots for different amounts of fuel and water.

In FIG. 2 - dependence of the measurement error on the amount of fuel.

In FIG. 3 is a sketch of the distribution of the conductor of the sensing element.

The essence of the proposed method is as follows. A three-layer medium is typical of mixtures in fuel tanks and storage tanks for oil and oil products. For definiteness, we consider a model of a layered medium with the following permittivities: the lower layer is water with ε ₁ = 3.5, the middle layer is fuel with ε ₂ = 1.6-1.8, and the upper layer is air with ε ₃ = 1 (taking into account that as a sensitive element, a segment of a long line coated with a shell is used). The dielectric constants of air and water do not really change, and the dielectric constant of a fuel is a variable and depends on temperature, grade, the presence of impurities, etc.

The parameters of the controlled medium — the position X ₁ of the water – fuel interface, X ₂ —fuel – air, and the dielectric constant ε _{2 of the} fuel can be determined from the values of the three eigenfrequencies of electromagnetic waves excited in the resonator located in the tank. The quantity of fuel is determined from the difference in the values of X ₂ and X ₁ and the fuel quality is estimated from its dielectric constant ε ₂ .

For a resonator in the form of a long line formed by a conductor distributed in a metal tube according to a W-shaped law and excited by lower types of vibrations at the first, second, and fourth eigenfrequencies, the dependences of these frequencies on the controlled parameters have the following form (the dependences of the first and third frequencies coincide) :

,

- собственные частоты порожнего и заполненного резонатора,

, l - длина распределенного отрезка длинной линии.The parameters are found from the solution of the system of equations formed by these dependencies with known (measured) values of natural frequencies. In the equations

,

- natural frequencies of the empty and filled resonator,

, l is the length of the distributed segment of the long line.

When solving the system of equations (1) by the iteration method, the true values of the parameters can not be found for any initial parameter assignments (NZP). As a result of the convergence of iterations, such parameter values can be obtained that do not correspond to the true ones, and when they are substituted into the equations of the system, at least one of the frequencies obtained in this case does not coincide with the measured one. Moreover, when choosing arbitrary NZP, along with true solutions, there may be solutions that do not have physical meaning, or iterative methods cannot find any solutions. There is a problem of choosing the initial values of the parameters.

,

, но

, где индекс «*» относится к величинам, полученным при решении системы (1), а «М» - к измеренным.Direct calculations made it possible to compile the NZP table, in which, as a result of solving system (1), the values of the parameters were found that correspond to the true ones or do not correspond, but are in the a priori known range of parameter changes. Moreover, in the latter case, when we substitute the obtained parameters into the equations, we always have

,

but

, where the index “*” refers to the values obtained by solving system (1), and “M” refers to the measured ones.

The measurement error of the parameters is determined by the accuracy of the measurement of natural frequencies. Moreover, the accuracy of measuring the natural frequencies is determined not only by the technical capabilities of the secondary transformations, but also by the uncontrolled instability of influencing factors on the sensitive element, for example, temperature, pressure, interface fluctuations, deposition of solid particles on the surface of the sensitive element, etc. The task in this case is to search for algorithms measurements providing acceptable accuracy of parameter determination with restrictions on the accuracy of measuring natural frequencies in the entire range of variation parameters of Ia.

. Рассматривались три варианта изменения на единицу: в сторону возрастания, в сторону убывания и в разные стороны для различных частот. Для измененных таким образом значений F_i решением системы уравнений определялись параметры x₁, х₂, ε₂ и погрешности их измерения.The modeling of the error in measuring the natural frequencies obtained with high accuracy from (1) for the true parameters was carried out by changing the unit of the number in the kth decimal place of the values of F _i , which corresponds to the error in measuring the natural frequencies

. Three variants of change per unit were considered: in the direction of increase, in the direction of decrease, and in different directions for different frequencies. For the values of F _i changed in this way, the parameters x ₁ , x ₂ , ε ₂ and the errors of their measurement were determined by solving a system of equations.

от истинного количества топлива x₂-x₁ для разных значений положения границы раздела x₁ и погрешности измерения собственных частот δ_F. Существует оптимальное значение $$x_1^o$$

, при котором погрешность измерения количества топлива имеет минимальное значение; к примеру, для δ_F=10^-4 можно принять

According to the results of calculations related to the search for a solution, there is a tendency to increase the accuracy of measuring parameters with an increase in x ₁ to some limits. This is clearly confirmed by the graphs in FIG. 1a, b depending on the error $${\delta }_{x_2-x_{\mathrm{one}}}$$

from the true amount of fuel x ₂ -x ₁ for different values of the position of the interface x ₁ and the measurement error of the natural frequencies δ _F. There is an optimal value $$x_{\mathrm{one}}^o$$

at which the error in measuring the amount of fuel has a minimum value; for example, for δ _F = 10 ^-4 you can take

позволяет не только получить приемлемые точности определения параметров при более грубых измерениях собственных частот в сравнении с δ_F≤10^-6, но и существенно упростить процедуру выбора НЗП: единственное решение существует при любых НЗП, кроме может быть случая x₀₁=x₀₂=0.Optimum value $$x_{\mathrm{one}}^o$$

allows not only to obtain acceptable accuracy in determining the parameters for coarser measurements of natural frequencies in comparison with δ _F ≤10 ^-6 , but also to significantly simplify the selection of the short-circuit breaker: the only solution exists for any short-circuit breaker, except for the case x ₀₁ = x ₀₂ = 0 .

However, as can be seen from the graphs of FIG. 1a, measurements of small values of the amount of fuel are accompanied by significant errors, up to the absence of any parameter values when solving system (1).

For the indicated values of the fuel quantity, another approach to the measurement algorithm is proposed, which is determined by the specifics of the problem. It is based on the fact that in the process of fuel consumption, the amount of water in the tank practically does not change. Moreover, the algorithm associated with the excitation and rather “rough” measurement of three natural frequencies provides high accuracy (tenths of a percent) of determining the position of the water – fuel interface in a large range of changes in the amount of fuel, starting from a full tank. The obtained value of the amount of water can be stored in memory and used for further measurements. In the presence of such information, two parameters x ₂ and ε ₂ remain unknown, which can be found by solving the first two equations of system (1). These equations have the following form:

, взятого из архива, получено по измеренным (вычисленным) собственным частотам решением системы (1).where parameter value

taken from the archive, obtained by measured (calculated) natural frequencies by the solution of system (1).

от количества топлива для этого случая показана на фиг. 2 (график 2). Из сравнения графика 2 с графиком 1, изображающим ту же погрешность в случае измерения параметров по трем собственным частотам, отметим, что точность определения количества топлива по формуле (2) в два раза выше, чем по формуле (1) в диапазоне (x₂-x₁)<0,2.Measurement Error $${\delta }_{x_2-x_{\mathrm{one}}}$$

of the amount of fuel for this case is shown in FIG. 2 (chart 2). From a comparison of graph 2 with graph 1, which depicts the same error in the case of measuring parameters at three natural frequencies, we note that the accuracy of determining the amount of fuel by formula (2) is two times higher than by formula (1) in the range (x ₂ - x ₁ ) <0.2.

. Причем для этого можно использовать значения, полученные при решении системы уравнений (1) при большом количестве топлива. Используя архивные данные по диэлектрической проницаемости топлива

и положения границы раздела «вода - топливо»

задача измерения сводится к нахождению единственного оставшегося неизвестного параметра - положения границы раздела «топливо - воздух», из соотношения, полученного из первого уравнения системы (1) в виде:As can be seen from FIG. 2 (graph 2), for (x ₂ -x ₁ ) <0.02, the error in determining the amount of fuel increases sharply until there is no solution to the system of equations (2). In order to obtain acceptable measurement accuracy in the vicinity of these fuel quantity values, it is proposed to additionally generate an archive of dielectric constant values

. And for this, you can use the values obtained when solving the system of equations (1) with a large amount of fuel. Using archived dielectric constant data

and the provisions of the water-fuel interface

the measurement task is reduced to finding the only remaining unknown parameter - the position of the "fuel - air" interface, from the ratio obtained from the first equation of system (1) in the form:

диэлектрической проницаемости

не должна превышать 7,5%, а погрешность

измерения положения границы раздела

- быть не более 0,1-0,2%. Эти показатели достижимы при решении уравнений (1) в пределах изменения количества топлива 0,2<(x₂-x₁)<0,5. При снижении требований к точности измерения количества топлива (прямая 3 на фиг. 2) естественно снижаются требования к точности значений архивных параметров, и вместе с этим существует возможность их измерения при меньшем количестве топлива.Note that to obtain high accuracy in measuring the parameter x ₂ with a small amount of fuel, restrictions on the measurement errors of the parameters recorded in the archive are necessary. The calculations show that to obtain measurements of the amount of fuel with an error of not more than 0.5% (line 3 in Fig. 2), the measurement error

dielectric constant

should not exceed 7.5%, and the error

measuring the position of the interface

- be no more than 0.1-0.2%. These indicators are achievable when solving equations (1) within the limits of changing the amount of fuel 0.2 <(x ₂ -x ₁ ) <0.5. When reducing the requirements for the accuracy of measuring the amount of fuel (line 3 in Fig. 2), the requirements for the accuracy of the values of the archive parameters naturally decrease, and at the same time there is the possibility of measuring them with a smaller amount of fuel.

Thus, the proposed method for measuring the parameters of a three-layer mixture — the position of two interfaces between the layers and the dielectric constant of the middle layer, which determine the quantity and quality of fuel in the tank, is reduced to measuring three natural frequencies excited in a W-shaped electromagnetic resonator. The resonator is placed in the upper part of the fuel tank, and the bottom in an autonomous container, completely filled with water. Pre-measure the frequency for an empty tank and container. Then, for the tank and container completely refueled with fuel, the total amount of water in the tank and container is determined from the system of equations (1) using the three measured natural frequencies of the resonator, and the dielectric constant of the fuel and their values are recorded in the archive. As fuel is consumed, depending on its quantity, the parameters of the three-layer mixture are determined in three modes. With a large amount of fuel - according to the three measured natural frequencies of the resonator, solving the system of equations (1). With an average amount of fuel - according to two of the measured natural frequencies and the archive value of the total amount of water in the tank and container, solving the system of equations (2). With a small amount of fuel - according to one of the measured frequencies and archival values of the total amount of water and the dielectric constant of the fuel. As a result, it is possible to obtain high accuracy in measuring the amount of fuel (error not more than 0.5%) in the entire range of its change - from an empty tank to a completely filled three-layer mixture, and dielectric constant (error not more than 5%) for large quantities of fuel.

The functional diagram of the proposed device is similar to the circuit described in the prototype. They differ in sensitive elements and measurement algorithms implemented in the microcontroller.

In this circuit, in the resonator, which is the sensitive element of the sensor, electromagnetic oscillations are excited from the block of the high-frequency generator with a tunable frequency. The continuous signal received at the resonator output is detected and converted into a digital binary code. The generator unit includes a frequency synthesizer controlled by a step-like sawtooth voltage, three frequency filters that transmit signals in accordance with the range of natural frequencies, and a selector that separates these signals in time. The signal from the resonator after detection and analog-to-digital conversion is fed to the input of the microcontroller, in which three natural frequencies of the resonator are measured. The correspondence of the synthesizer frequencies to the natural frequencies is established by the maximum voltage of the signal received at the detector output.

The microcontroller’s memory contains the values of the previously measured three frequencies corresponding to the natural frequencies of the resonator in the empty tank and other values, in accordance with the proposed method. The microcontroller also contains algorithms for determining the parameters of a three-layer mixture from measured natural frequencies, based on the solution of systems of equations (1) - (3).

In FIG. Figure 3 shows a sketch of an electromagnetic resonator used as a sensitive element. In accordance with the proposed method, the device should contain an autonomous container filled with water, in which the resonator is immersed in its lower part. Such a technical embodiment of the sensing element is cumbersome and impractical. A resonator in the form of a conductor in a dielectric sheath, W-shapedly distributed in a metal cylinder, was chosen as a sensitive element. In it, coating the outer surface of the dielectric shell with a metal screen simulates the constant filling of the sensing element with water over the length of this coating. This allows you to make the design of the sensitive element compact. In FIG. 3 marked: 4 - metal wall of the upper part of the SE; 5 - its lower part, located at the level of the bottom of the tank; 6 - trace lines of the conductor in the upper part of the SE; 7 - distributed conductor in the lower part, simulating the immersion of the SE in water; 8-11 - junction points of conductors; 12 and 13 - generator for exciting electromagnetic waves and a detector. The conductor along the entire length is in the dielectric sheath, while in the lower part of the CE it is additionally equipped with a metal screen.

и слой воды, содержащейся в топливном баке.For such a sensitive element, of course, the eigenfrequency dependences are described by the system of equations (1), only in them it should be borne in mind that parameter x ₁ includes a value simulating a water layer with a thickness $$x_{\mathrm{one}}^o$$

and a layer of water contained in the fuel tank.

Claims (2)

1. A method of measuring the quantity and quality of fuel in a tank with a three-layer mixture of “air - fuel - water”, according to which electromagnetic oscillations are excited in the tank placed in the tank at three natural frequencies, measure them and judge the parameters of the controlled environment — the position of two boundaries section and dielectric constant of fuel, these parameters determine the amount of fuel and its quality, characterized in that the lower part of the resonator is immersed in an autonomous container completely filled with water, and the rest of it immersed in a controlled mixture, for a tank completely filled with fuel, the total amount of water in the tank and container and the dielectric constant of the fuel are determined from the three measured natural frequencies of the resonator, their values are recorded in the archive, as the fuel is consumed, depending on its quantity, the parameters of the three-layer mixture are determined in three modes, with a large amount of fuel - according to the three measured natural frequencies of the resonator, with an average quantity - according to two of the measured natural frequencies and the archive symbol the total amount of water in the tank and container, with a small amount of fuel - according to one of the measured frequencies and the archive values of the total amount of water and dielectric constant of the fuel. 2. A device for measuring the quantity and quality of fuel in a tank with a three-layer mixture of “air - fuel - water” containing an electromagnetic frequency synthesizer, a resonator located in a tank with a controlled environment, a detector, an analog-to-digital converter, a microprocessor that generates voltage for tuning the frequency of the synthesizer and implementing a measurement algorithm, characterized in that the resonator is made in the form of a conductor W-shapedly distributed in a metal pipe in a dielectric sheath, the lower part of which is insulated is isolated from the controlled mixture by a metal screen placed on the outer surface of this shell.

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