RU2559840C1 - Microwave technique for determining precipitated moisture in liquid hydrocarbons - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: technique envisages filling of cylindrical cavity resonator with longitudinal axis perpendicular to horizon with the tested liquid, removal of the liquid upon expiry of time t≥10s from the resonator cavity with remaining moisture at the lower end wall, excitation of electromagnetic oscillation of H₀₁₁ type and evaluation of Q-factor of cylindrical cavity resonator for volume concentration of precipitated moisture, at that Q-factor is measured in conditions of excited electromagnetic oscillation of the resonator by a hollow dielectric rod placed on the resonator axis. Thickness of its walls is Δ≥0.5mm and ratio of diameter of the hollow dielectric rod d_d the resonator diameter d_OP is selected on condition that it is equal or more than 0.1.

EFFECT: increasing sensitivity of the technique at simultaneous simplification of the device hardware.

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Description

The present invention relates to methods for determining moisture. It can find application in the petrochemical industry, and in particular for express quality control of aviation kerosene in an aerodrome.

The known conductometric method for determining humidity (see Zhukov Yu.P., Kulakov MV High-frequency electrodeless conductometry. - M .: Energy, 1968. P.104). In the range of volumetric humidity 0-2%, measurement is almost impossible, since the values of the resistance of the materials become greater than the input resistance of the measuring devices.

A known resonator method for determining humidity (see Berliner MA, Measurement of humidity. - M .: Energy, 1973). The studied liquid is placed in a cuvette located in the cavity of a cylindrical volume resonator (RR). The cuvette is made in the form of a cylinder or disk and is installed along or perpendicular to the longitudinal axis of the cavity resonator. The oscillation of the electromagnetic field (EMF) type H ₀₁₁ . The output value of the primary measuring transducer (PIP) is the change in the Q factor of the resonator ΔQ = Q ₀ -Q (Q - loaded; Q ₀ - unloaded Q factor of the resonator), caused by the introduction of the investigated material with unknown humidity. The disadvantage of this method is the low accuracy of determining the moisture content in the form of sediment due to the influence of soluble moisture contained in the studied hydrocarbon and which depends on temperature, pressure and type of hydrocarbon.

The prototype adopted a method for determining the microwave method for determining precipitated moisture in liquid hydrocarbons (RF Patent No. 2451929, MKL ⁶ G01N 22/04. Microwave method for determining precipitated moisture in liquid hydrocarbons / Suslin MA, Shatalov A.L. (RF ) - No.2010147251 / 09; declared on 11/18/10., Published on 05/27/12 Bull No. 15). In this method, the investigated liquid hydrocarbon is placed in a cavity of a cylindrical volume resonator with a longitudinal axis perpendicular to the horizon, an electromagnetic field of type H _{011 is} excited, a change in the quality factor of a cylindrical volume resonator with oscillation H ₀₁₁ , which is caused by the introduction of the material to be studied, is further excited by an electromagnetic field of type E ₀₁₀ measured change in the Q of the cylindrical cavity resonator with oscillation E _010, which is caused by administration of the test material, the cylindrical esky first cavity is completely filled with the test liquid, after a certain settling time - about ten seconds, the liquid is drained so that sucks moisture remained on the bottom end wall of the cavity. The change in the quality factor of a cylindrical volume resonator with a fluctuation of E ₀₁₀ judges the volume concentration of precipitated moisture in the range up to 0.4%, and the change in the quality factor of a cylindrical volume resonator with a fluctuation of H ₀₁₁ is in the range of 0.4-2%.

The disadvantage of the prototype is the lack of sensitivity to determine precipitated moisture. To implement the proposed method using two spatial modes of a cylindrical volume resonator, a microwave generator is necessary simultaneously with a wide (for exciting H ₀₁₁ and E ₀₁₀ oscillations) and precision frequency tuning (for measuring the quality factor of a loaded oscillatory system over the passband). Such a generator is complicated in execution and configuration, which greatly complicates the technical implementation of the device.

The technical result of the invention is to increase the sensitivity of determining the volumetric concentration of precipitated moisture in liquid hydrocarbons and simplifying the device that implements the method.

This technical result is achieved by the fact that in the known method for determining the volumetric concentration of precipitated moisture in liquid hydrocarbons, which consists in completely filling a cylindrical volume resonator with a longitudinal axis perpendicular to the horizon of the liquid under investigation, removing liquid from the cavity of the resonator after a time t≥10 sec, leaving moisture on the bottom end wall, the excitation of electromagnetic oscillations of H ₀₁₁ and evaluation of a change in the Q volume concentration of the cylindrical cavity sazhdennoy moisture, the quality factor measurements are carried out under conditions of disturbance of the electromagnetic field of the resonator hollow dielectric rod disposed in a resonator axis, the wall thickness Δ≥0,5 mm and the ratio of the diameter of the hollow rod of the insulator to the diameter d _∂ resonator d _OP selected from conditions

In FIG. 1 shows the appearance of the internal volume of the resonator with a dielectric hollow rod on the axis, FIG. 2 - the results of numerical simulation of the electric field of electromagnetic waves H ₀₁₁ empty resonator; in FIG. 3 - the results of numerical simulation of the transformation of the electric field of the electromagnetic wave H _{011 of a} resonator with a dielectric hollow rod; in FIG. 4 - the results of experimental studies.

The essence of the microwave method for determining precipitated moisture in liquid hydrocarbons is the disturbance (placing inside the resonator) of the electromagnetic field of the cylindrical volume resonator (COR) by a hollow dielectric rod located on the axis. The presence of a perturbing dielectric hollow rod leads to the transformation of the fundamental vibration H ₀₁₁ . In the middle of the length of the pipeline and at the end walls, a field concentration is observed, which significantly increases the sensitivity to the moisture content on this wall. Let us explain this by the results of numerical modeling and experiment.

The electric field of the spatial oscillation H _{011 of an} unperturbed resonator (see Korbansky, I.N. Theory of an electromagnetic field. - M .: VVIA named after prof. N.E. Zhukovsky, 1964. - 356 p.) Is a closed concentric circle, the field maximum in the middle of the length and radius, the electric field is zero on the axis and at the end walls. The numerical analysis of the electric field of the spatial oscillation H _{011 of the} electromagnetic field by the finite element method in the COMSOL Multiphysics system shows the same results: the field is maximum (red in Fig. 2) in the middle of the length and radius and is equal to zero on the axis and at the end walls (blue color). Therefore, the sensitivity to the content of the medium with losses on the end wall is low. In the prototype, the loaded figure of merit is reduced by an order of magnitude with respect to the empty resonator at about 2% of the volume fraction of moisture.

The introduction of a dielectric hollow rod located along the axis into the resonator makes it possible to increase the sensitivity to the content on the end wall of moisture. In FIG. 1 shows such a system. The wall thickness of the rod is 1 mm, the diameter is 25 mm. Material - plastic with a relative dielectric constant of 5.3. In FIG. Figure 3 presents the results of modeling the EM field by the finite element method in the COMSOL Multiphysics system. The presence of a perturbing dielectric pipeline leads to field transformation. In the middle of the length of the pipeline and at the end walls, a field concentration is observed. In this case, the resonant frequency with respect to the resonant frequency of the fundamental oscillation H ₀₁₁ equal to

, изменяется примерно на 10 МГц. При этом добротность вырастает примерно на 30%.where a is the radius; l is the length of the resonator, for the oscillation H ₀₁₁ characteristic number $$x_{\mathrm{one}}^0=\mathrm{3,832}$$

, changes by about 10 MHz. At the same time, the quality factor increases by about 30%.

Such a transformation is observed when the diameter of the hollow rod of the dielectric d _∂ to the diameter of the resonator d _OP

and wall thickness greater than 0.5 mm.

Two maxima of the electric field along the radius on the end wall significantly increase the sensitivity to the moisture content on this wall.

In this case, as in the prototype, a cylindrical volume resonator with a longitudinal axis perpendicular to the horizon is completely filled with the investigated liquid. After some time of sedimentation (for aviation kerosene this time does not exceed ten seconds), the liquid begins to drain so that the sediment in the form of moisture remains on the lower end wall of the resonator. The presence of a thin layer practically does not change the resonant frequency of oscillations (the frequency remains within the confinement band of an unloaded system), and the quality factor (due to a change in the effective conductivity of the lower wall) varies significantly.

In FIG. Figure 4 shows the experimental values of the loaded figure of merit of a resonator with a dielectric hollow core on the axis of the volumetric concentration of moisture in the sediment% V. The volumetric moisture concentration in the sediment% V was calculated as the ratio of the effective moisture height l _eff to the cavity height l _OP

The concentration of the field at the end walls of the resonator increases the sensitivity of the moisture content in the sediment: the loaded Q factor decreases by an order of magnitude with respect to the empty resonator at about 0.25% volume fraction of moisture. Which is significantly higher than for the oscillation H _{011 of the} empty resonator, and two times higher than for the oscillation of E ₀₁₀ (results of the prototype). This is explained by the presence of two maximum electric fields along the radius on the end wall in the transformed field against one for the oscillation E ₀₁₀ .

The implementation of the device is similar to the prototype. Only the use in the measurement circuit of two resonators (empty and with a pipeline) and one microwave generator with a small frequency tuning range (tens of MHz versus GHz units in a single resonator circuit, as in the prototype) will allow for higher sensitivity to the moisture content in the sediment and at the same time Simplify the hardware implementation of the device.

Claims (1)

The method for determining the volumetric concentration of precipitated moisture in liquid hydrocarbons, which consists in completely filling a cylindrical volumetric resonator with a longitudinal axis perpendicular to the horizon, the liquid being studied, removing the liquid from the cavity after t≥10 sec, leaving moisture on the lower end wall, and exciting electromagnetic oscillations of the type H ₀₁₁ for changing and evaluating the quality factor of the cylindrical cavity resonator volume concentration of moisture deposited, characterized in that the measurement of Q n oestriasis in a perturbation of the electromagnetic field of the resonator hollow dielectric rod disposed in a resonator axis, the wall thickness Δ≥0,5 mm and the ratio of the diameter of the hollow rod of the insulator to the diameter d _∂ resonator d _OP is selected from the condition

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