JP2004053325A - Capacitive liquid density meter - Google Patents

Abstract

An insulating liquid is provided in a pipe through which an insulating liquid flows. Even when the flow rate of the insulating liquid is high and the Re value is large, cavitation between electrode plates is suppressed, and the density of the insulating liquid can be measured with high accuracy. Provide capacitance type liquid density meter.
A positive electrode plate (2) and a negative electrode plate (3) of a capacitor section (1) have a streamlined cross section in one plane parallel to a streamline of an insulating liquid. The curvature of the cross section on the side of the insulating liquid inlet (front edge 21 side) is smaller than the curvature of the cross section on the side of the insulating liquid outlet (rear edge 22 side). By streamlining the cross section of the electrode plate, the insulating liquid does not peel off on the surfaces of the electrode plates 2 and 3, cavitation is suppressed, and the capacitance between the electrode plates accurately corresponds to the density of the insulating liquid. By measuring the capacitance between the plates, the density of the insulating liquid is measured with high accuracy.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a capacitance type liquid density meter, and more particularly to a capacitance type liquid density meter for measuring the density of a flowing insulating liquid.
[0002]
[Prior art]
FIG. 2 is a conceptual diagram showing a configuration of a capacitance type liquid density meter installed in a pipe of an insulating liquid such as LNG and LPG. This figure shows a state where the pipe 16 is cut on a plane perpendicular to the axis of the pipe 16. In this drawing, the pipe 16 and the through flange 15 appear in a cross section, but hatching indicating the cross section is omitted. If hatching is applied to the cross section, the lead line of the code and the hatching are complicated, and the drawing becomes difficult to read. Therefore, in order to avoid such complication, the hatching of the cross section is omitted in FIG. 5 (b) and FIG. In the cross-sectional view of FIG. 1B, hatching of the cross-section is omitted for the same reason.).
[0003]
As shown in FIG. 2, the capacitance type liquid density meter is configured such that the capacitor unit 1 inserted and installed in the pipe 16, the temperature sensor 6, and the measurement values obtained by the capacitor unit 1 and the temperature sensor 6 are externally provided. And an electric wire 7 for extraction. These electric wires 7 are taken out as electric wires 8 through the through flange 15 and the hermetic connector 9, and the capacitance of the capacitor section 1 and the temperature detected by the temperature sensor 6 are used as signals for liquid density measurement. Notify the processing unit. The capacitor unit 1 includes conductor plates 10 and 11 housed in a housing made of an insulating material, and a plurality of electrode plates extending in a comb shape from the conductor plates 10 and 11. The holding body 12 is holding means for holding the capacitor portion 1 with the through flange 15 as a fulcrum, in a manner in which the capacitor portion 1 is hung.
[0004]
The density measurement target is an insulating liquid such as LNG and LPG. The insulating liquid flows in the pipe 16 in the pipe axis direction, and a part of the liquid passes through the electrode gap of the capacitor unit 1. The dielectric constant between the electrodes of the capacitor 1 corresponds to the density of the insulating liquid passing through the electrode gap of the capacitor unit 1 when the temperature is constant. Further, the dielectric constant between the electrodes corresponds to the capacitance of the capacitor 1. Thus, when the temperature of the insulating liquid is constant, the capacitance of the capacitor 1 uniquely corresponds to the density of the insulating liquid. Can obtain the density of the insulating liquid from the known relationship between the density of the insulating liquid and the capacitance. Since the relationship between the density of the insulating liquid and the capacitance is based on the temperature of the insulating liquid as a parameter, the signal processing unit uses the temperature of the insulating liquid detected by the temperature sensor 6 to determine the capacitance of the capacitor 1. The density of the insulating liquid is corrected based on the above, and the accurate density of the insulating liquid is calculated.
[0005]
FIG. 4 is a perspective view showing the external structure of the capacitor unit 1 in the conventional capacitance type liquid density meter. FIG. 5A is a front view of the capacitor unit 1, and FIG. 5B is a sectional view taken along line BB of FIG. In the figure, 2 is a positive electrode plate, 3 is a negative electrode, 4a is an upper plate, 4b is a lower plate, and 5 is a side plate. Reference numeral 101 indicates the direction in which the insulating liquid flows. FIG. 5A is a view of the capacitor section 1 viewed from the side where the insulating liquid flows. In FIG. 5B, the positive electrode plate 2, the negative electrode plate 3, and the side plate 5 appear in a cross section. However, hatching is omitted in the cross section. The reason why the hatching is omitted in the cross section is the same as that described with reference to FIG. The positive electrode plate 2 extends in a comb shape from the conductor plate 10 in FIG. However, the positive electrode plate 2 and the conductor plate 10 are formed integrally, and the boundary between them does not appear specifically. The negative electrode plate 3 extends in a comb shape from the conductor plate 11 in FIG. However, the positive electrode plate 3 and the conductor plate 11 are formed integrally, and the boundary between them does not appear specifically.
[0006]
As is clear from FIGS. 5A and 5B, the positive electrode plate 2 is a simple rectangular plate, and the wide plane of the positive electrode plate 2 is rectangular. The negative electrode plate 3 is also a rectangular plate having exactly the same shape as the positive electrode plate 2. As described above, both the positive electrode plate 2 and the negative electrode plate 3 are formed as parallel plate electrode plates, and the insulating liquid enters inside from the inlet side of the capacitor unit 1 along the flow direction 101. And exits into the pipe 16 from the outflow side through the space between the opposite positive and negative electrode plates. Since the positive electrode plate 2 and the negative electrode plate 3 are rectangular plates, the end faces of the positive electrode plate 2 and the negative electrode plate 3 on the inflow side and the outflow side are orthogonal to the stream lines of the insulating liquid. In such a flow state of the insulating liquid, as shown in FIG. 2, the capacitance between the positive and negative electrode plates in the capacitor section 1 and the temperature of the insulating liquid by the temperature sensor 6 are measured. Is transmitted to an external signal processing unit via the lead wire 8 and processed, whereby the density of the insulating liquid is measured.
[0007]
[Problems to be solved by the invention]
In the conventional example described above with reference to FIGS. 4 and 5, both the positive and negative electrode plates arranged for measuring the capacitance in the capacitor section are each formed of a simple parallel flat plate. As described above, when both the positive and negative electrode plates are simple parallel flat plates, the Re number (Reynolds number) increases with an increase in the flow rate of the insulating liquid in the pipe, so that the insulating liquid flows in the electrode gap. Cavitation occurs due to separation from the positive and negative electrode plates and the like. When cavitation occurs in the insulating liquid between the positive and negative electrode plates, the capacitance between the positive and negative electrode plates becomes smaller than when no cavitation occurs. Then, the liquid density obtained by the operation of the signal processing unit is measured to be smaller than the actual density of the insulating liquid.
[0008]
An object of the present invention is to provide a capacitance type densitometer capable of suppressing the occurrence of cavitation in an insulating liquid flowing between electrode plates and measuring the density of the insulating liquid with high accuracy.
[0009]
[Means for Solving the Problems]
The present invention provides the following means to solve the above-mentioned problems.
[0010]
(1) A capacitor having a plurality of plate-like electrodes arranged substantially in parallel with each other, and a liquid of the insulating liquid based on the capacitance of the capacitor when the insulating liquid flows in a gap between the plurality of electrodes. In a capacitance type liquid density meter that measures density,
A capacitance-type liquid density meter, wherein one section of the plate-like electrode forms a streamline.
[0011]
(2) When a parallel plate type capacitor having at least two plate-like electrodes facing each other substantially in parallel is provided, the capacitor is immersed in an insulating liquid, and the insulating liquid flows through the electrode gap. In a capacitance type liquid density meter that measures the density of the insulating liquid based on the capacitance of the capacitor in,
A capacitance type liquid density meter, wherein a cross-sectional shape of the electrode on one surface parallel to a streamline of the insulating liquid is streamlined.
[0012]
(3) A capacitor portion including a positive and negative electrode plate and a temperature sensor are provided, and an insulating liquid is flown between the positive and negative electrode plates of the capacitor portion, and the temperature sensor is immersed in the insulating liquid. In a capacitance-type liquid density meter that measures the density of the insulating liquid based on the capacitance between the electrode plates and the temperature detected by the temperature sensor,
The two wide planes of the electrode plate are symmetrical with respect to one virtual plane, and the contour of the electrode plate in a cross section orthogonal to the virtual plane and parallel to the streamline of the insulating liquid flow is the insulating liquid. Are substantially semicircular at the inflow side end and the outflow side end, the semicircular curvature at the inflow side end is the first curvature, and the semicircular curvature at the outflow side end is the first curvature. When the curvature is 2, the first curvature is smaller than the second curvature.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described more specifically with reference to embodiments of the present invention.
[0014]
FIG. 1 is a diagram illustrating an external structure of a capacitor unit according to an embodiment of the present invention. FIG. 3 is a perspective view of the positive electrode plate 2 in the embodiment of FIG. FIG. 2 is a conceptual diagram showing a state in which the embodiment of FIG. 1 is arranged in a pipe 16 of an insulating liquid. FIG. 2 is a diagram already described with respect to the conventional capacitance type liquid density meter shown in FIGS. 4 and 5, and in terms of the form of use of the present invention in which the insulating liquid is disposed in the piping 16, the embodiment of the present invention is not shown. There is no difference between the form and the conventional capacitance type liquid density meter.
[0015]
FIG. 1A is a front view of the capacitor section 1 as viewed from the side where the insulating liquid flows (a side where the insulating liquid flows, that is, a view as viewed from the upstream side of the insulating liquid). FIG. 2B is a sectional view taken along line AA of FIG. In FIG. 1B, the positive electrode 2, the negative electrode 3, and the side plate 5 appear in a cross section, but hatching in the cross section is omitted as described above in order to avoid complicated lines. FIG. 3 is a perspective view of the positive electrode plate 2, but a perspective view of the negative electrode plate 3 appears in the same manner as FIG. As is clear from the comparison between FIG. 1A and FIG. 5A and the comparison between FIG. 1B and FIG. 5B, the embodiment of the present invention and the conventional capacitance type liquid density It differs from the meter in the cross-sectional shapes of the positive and negative electrode plates 2 and 3, and there is no difference between the structures in other respects.
[0016]
The positive electrode plate 2 is a plate-like body that is symmetrical with respect to the line BB in FIG. 1B. As shown in FIG. 1B and FIG. 3, the positive electrode plate 2 of the plate-like body passes through a line BB and is perpendicular to the upper surface of the conductor plate 10 (the upper surface in FIG. 1A). It has wide planes 2a and 2b of symmetric shape. The positive electrode plate 2 is integral with the conductor plate 10, and a boundary surface between the upper surface 23 of the positive electrode plate 2 and the conductor plate 10 does not appear as a specific surface. As is clear from FIG. 1, the positive electrode plate 2 extends in a comb shape from the conductor plate 10. The negative electrode plate 3 has the same structure as the positive electrode plate 2. The negative electrode plate 3 extends in a comb shape from the conductive plate 11, and the negative electrode plate 3 and the conductive plate 11 are integrated.
[0017]
As is clear from FIGS. 1A and 1B and FIG. 3, both the positive electrode plate 2 and the negative electrode plate 3 in the embodiment of the present invention are not simple parallel flat plates, and the cross-sectional shape along the line AA is It is streamlined. The curvature of the cross-sectional shape on the side of the insulating liquid inlet (the cross-sectional shape taken along line AA of the front edge 21 in FIG. 3) is determined by the cross-sectional shape on the side of the insulating liquid outlet (A of the rear edge 22 in FIG. 3). -A line cross section). By making the cross-sectional shape of the positive and negative electrode plates streamlined, the occurrence of cavitation between the positive and negative electrode plates is suppressed even when the Re value of the insulating liquid is large. Since the occurrence of cavitation between the positive and negative electrode plates is suppressed, the capacitance of the capacitor unit 1 accurately corresponds to the density of the insulating liquid regardless of the magnitude of the Re value of the insulating liquid. The accuracy of the calculated density of the insulating liquid is significantly improved. The signal processing unit corrects the density of the insulating liquid obtained from the capacity of the capacitor unit 1 based on the temperature of the insulating liquid detected by the temperature sensor 6, and calculates the density of the insulating liquid with higher accuracy.
[0018]
【The invention's effect】
As described above in detail with reference to the embodiment, according to the present invention, the cross-sectional shape of the positive and negative electrode plates in one plane parallel to the streamline of the insulating liquid is streamlined. Even if the flow rate of the insulating liquid is high and the Re value is large, peeling of the insulating liquid hardly occurs on the electrode plate surface, cavitation on the electrode plate surface is suppressed, and the capacity between the positive and negative electrode plates is It is possible to provide a capacitance type densitometer capable of responding to the density with high precision and measuring the density of the insulating liquid with high precision by measuring the capacitance.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of a capacitor unit according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram showing an arrangement state of a capacitance type liquid density meter in a pipe.
FIG. 3 is a perspective view showing a positive electrode 2 in the embodiment of FIG.
FIG. 4 is a perspective view showing an appearance of a conventional capacitance type density meter.
FIG. 5 is a diagram showing a structure of a capacitor unit in a conventional capacitance type density meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Capacitor part 2 Positive electrode plate 2a, 2b Wide plane of positive electrode plate 3 Negative electrode plate 4a Upper plate 4b Lower plate 5 Side plate 6 Temperature sensor 7 Electric wire 8 Leader wire 9 Hermetic connector 10, 11 Conductor plate 12 Holder 15 Through flange 16 Piping 21 Front edge of positive electrode plate 22 Rear edge of positive electrode plate 23 Upper surface of positive electrode plate 24 Lower surface of positive electrode plate

Claims (3)

A capacitor having a plurality of plate-like electrodes arranged substantially parallel to each other is provided, and the liquid density of the insulating liquid is measured based on the capacitance of the capacitor when the insulating liquid flows in the gap between the plurality of electrodes. In the capacitance type liquid density meter,
A capacitance-type liquid density meter, wherein one section of the plate-like electrode forms a streamline. A parallel plate type capacitor having at least two plate-like electrodes facing each other substantially parallel to each other, the capacitor being immersed in an insulating liquid, and flowing when the insulating liquid flows through the electrode gap. In a capacitance-type liquid density meter that measures the density of the insulating liquid based on the capacitance of,
A capacitance type liquid density meter, wherein a cross-sectional shape of the electrode on one surface parallel to a streamline of the insulating liquid is streamlined. A capacitor portion composed of opposing positive and negative electrode plates and a temperature sensor; an insulating liquid flowing between the positive and negative electrode plates of the capacitor portion; the temperature sensor being immersed in the insulating liquid; In a capacitance liquid density meter that measures the density of the insulating liquid based on the capacitance between the plates and the temperature detected by the temperature sensor,
The two wide planes of the electrode plate are symmetrical with respect to one virtual plane, and the contour of the electrode plate in a cross section orthogonal to the virtual plane and parallel to the streamline of the insulating liquid flow is the insulating liquid. Are substantially semicircular at the inflow side end and the outflow side end, the semicircular curvature at the inflow side end is the first curvature, and the semicircular curvature at the outflow side end is the first curvature. When the curvature is 2, the first curvature is smaller than the second curvature.

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