JP2870370B2 - Void fraction measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a volume ratio of a gas mixed in a gas-liquid two-phase flow.

[0002]

2. Description of the Related Art A flowmeter of a volumetric type has a good measurement accuracy and is stable over a wide flow rate range, and is therefore widely used in a liquid supply device of a gas station or the like. However, even in this type of flow meter, when air as a compressed fluid is mixed as bubbles in a liquid,
Since a large error occurs, a pretreatment device for separating the mixed air is indispensable.

[0003] As a means for separating bubbles for this purpose, there are generally a method utilizing the buoyancy of bubbles and a method utilizing centrifugal force. However, it is necessary to apply a centrifugal force even when the liquid is not supplied, which increases the power cost and has a problem that the separation effect is poor in a low flow velocity region.

On the other hand, it has been practically used to measure the difference in the dielectric constant between a liquid and a gas as the difference in capacitance and to correct the measured value of the liquid supply amount based on the difference. Since the dielectric constant of gasoline and gas oil as liquids is only about twice that of air, a counter electrode type dielectric constant measuring device with a relatively small electrode surface can measure the void fraction with high accuracy. In addition to the difficulty, there is a problem that errors due to the liquid type, temperature, and the like cannot be sufficiently corrected.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem.
It is an object of the present invention to provide a new apparatus capable of quickly and accurately measuring the ratio of a gas contained in a gas-liquid two-phase flow without separating the gas.

[0006]

That is, according to the present invention, a void ratio measuring device for achieving such a problem is provided so that a part of the liquid supply passage surrounds the liquid supply passage.
Measurement of capacitance value of cylindrical gas-liquid two-phase flow
Electrode and a reference electrode for measuring the capacitance value of the liquid
The measurement electrode is located inside and the reference electrode is located outside
In such a manner as to be arranged in multiple concentric circles .

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a void fraction measuring device according to an embodiment of the present invention, and FIG. 3 shows an example of a lubricating device to which the device is applied.

In the figure, a main body 1 of a void fraction measuring device indicated by a reference numeral 1 has an oil supply pump 11 and a flow meter 13 in a liquid supply line 10 with an inflow port 2 down and an outflow port 3 up. It is located between them.

The apparatus main body 1 is provided with an oil supply pipe so that a gas-liquid two-phase flow can flow vertically upward from an inlet at a lower end to an outlet 3 at an upper end, and pressure loss can be ignored. The reference electrode 7 is configured as a cylindrical body having a size not to be smaller than the flow path cross-sectional area of the passage 10, and a plurality of cylindrical measurement electrodes 4 位置 are positioned inside the cylindrical body. Are located on the outside, so that the axes of the main body 1 are common to each other, and a gap of approximately 1/100 or less of the cross-sectional area of the flow path of the main body 1 is provided. It is fixed integrally.

The inner surface of the plurality of measurement electrodes 4 # for measuring the capacitance of the gas-liquid two-phase flow is activated to prevent air bubbles from adhering thereto. A length equal to or greater than a value obtained by multiplying the maximum flow rate and the measurement interval time so that measurement can be performed for all the liquids in the electrode,
For example, the maximum flow rate is 3 m / sec, and the measurement interval is 30 ms.
In the case of ec, the length L of the electrode 4 is set to 9 cm or more.

On the other hand, a cylindrical comparative reference electrode 7 which is located outside these and measures the capacitance of only the liquid.
The gap δ between the measuring electrodes 4 ‥‥ is set so that the inner electrode of the main body 1 is in contact with the innermost measuring electrode 4 and about 1/100 of the total inflowing liquid flows into the outermost measuring electrode 4. Is attached to the outside of the outermost measurement electrode 4 with a gap of about の.

The surface of the comparative reference electrode 7 is
In the same manner as described above, a treatment for increasing the hydrophilicity is performed so that air bubbles do not adhere, and the opening is 10 to 100 μm, preferably 20 to 100 μm on the outer circumferential surface on the entrance side of the outermost measurement electrode 4, that is, the lower circumferential surface. Plural mesh filters 5 made of polyester monofilament subjected to hydrophilic treatment of 60 μm
‥‥ is provided so as to cover the liquid passage hole 6, and is configured to prevent air from flowing between the outermost measurement electrode 4 and the comparison reference electrode 7.

When the mesh filter 5 is provided at the lower end of the outermost measurement electrode 4 to prevent the inflow of air bubbles, the liquid pressure is 0.3 to 1.3 kg.
In the range of / cm ² , even if a liquid having a bubble mixing rate of 30% is supplied, as shown in FIG. 4, the effect on the comparative reference electrode 7 is practically negligible, ie, 0.8. % Or less.

The measuring electrode 4 and the comparative reference electrode 7 are
It is connected to the void ratio calculation means 21 through the lead wire 8 and calculates the void ratio, that is, the total, from the capacitance value of the liquid containing bubbles detected under substantially the same temperature condition and the capacitance value of only the liquid. It is configured to calculate the ratio of the volume occupied by the gas phase in the channel volume.

On the other hand, the actual liquid integrating means 22 in FIG.
A circuit means for calculating the actual supply liquid amount and displaying and controlling the output based on the output. The actual liquid supply amount is calculated based on a pulse signal proportional to the flow rate from the flow meter 13 and an output signal from the void ratio calculation means 21. The integrated value is displayed on the display means 25, and this signal is output to an external device such as a POS to store the supplied liquid amount and the price corresponding to the supplied liquid amount, and input from the ten key 23 or the like. A match signal between the set value signal and the integrated value signal is output to the motor control means 24, and the refueling pump 12 is stopped by the output signal and the automatic refueling stop signal from the refueling nozzle 15.

Next, the operation of the apparatus configured as described above will be described. Now, when the refueling nozzle 15 removed from the nozzle hook (not shown) is inserted into the refueling port of the automobile and the lever is pulled to operate the refueling pump 11 to start refueling, the air sucked from the outside together with the gasoline and light oil is sucked. In air as bubbles.

When the gas-liquid two-phase flow containing bubbles flows into the void fraction measuring device main body 1, a part thereof, that is, the gas-liquid two-phase flow of approximately 99/100 in total becomes a multi-cylindrical structure. Flows into the gap between the measuring electrodes 4 #, and
The gas-liquid two-phase flow of 0 flows out between the measurement electrode 4 and the comparison reference electrode 7 after the bubbles are removed by the mesh filter 5 provided on the outermost measurement electrode 4. ‥
And the comparison reference electrode 7 detect the capacitance value of the liquid containing bubbles and the capacitance value of only the liquid. Further, these detection data are sent to the void ratio calculating means 21 to calculate the void ratio at each time of the liquid temperature.

Here, the measured capacitance value of the measuring electrode 4 in perfect air is CA, the measured capacitance value in perfect liquid is CL, the measured capacitance value in a gas-liquid two-phase flow is CM,
The measured capacitance value of the comparative reference electrode 7 in perfect air is BA, the measured capacitance value in perfect liquid is BL, the measured capacitance value in a gas-liquid two-phase flow is BM, and the comparative reference electrode 7 is
The correction multiple of the measured value of G is G, the void fraction is α, and the actual liquid fraction is β
(Α + β = 1), CL> CA BL> BA
Therefore, if G is set so that CL−CA = (BL−BA) G, β = 1−α = (CM−CA) / (CL−CA) = (CM−CA) / (BL−BA) ) G ‥‥ (1).

Since the comparison reference electrode 7 is configured so that no air bubble enters, it can be considered that BL = BM. Therefore, the expression (1) is expressed as follows: β = 1−α = (CM−CA) / (BM-BA) G ‥‥ (2), CA, BA, and G are adjusted and fixed at the time of initial calibration, and the measurement circuit error disappears by subtraction of the numerator and denominator of the two equations. When the BM is in the same temperature environment, the change can be offset, the change in the dielectric constant due to the pressure of air can be ignored, and the dielectric constant due to the dissolution of air in the liquid can be ignored. α can be calculated from the value CM of the measurement electrode 4 and the value BM of the comparison reference electrode 7.

The void ratio α calculated in this way is:
Next, the measured liquid amount output from the void ratio calculating unit 21 to the actual liquid calculating unit 22 is corrected by the void ratio, and the actual liquid integrated amount is displayed on the display unit 25, while the keyboard 23 is used. The input set amount is compared with the actual liquid integrated amount, and a reconciliation signal is output with a coincidence signal.
Stop 2

Although the present invention has been described above with reference to a device applied to a fueling device such as a gas station, the void ratio measuring device according to the present invention also includes a control device for measuring the mixing ratio of methanol and gasoline. The present invention can be applied to a device, a flow measurement device with a contamination monitoring function, a flow measurement control device used in other chemical plants and the like, and further a measurement device of a mixed state of a mixer of a liquid, a granular material, or the like.

[0022]

As described above, according to the present invention, a part of the liquid supply passage is formed into a cylindrical shape so as to surround the liquid supply passage.
A measuring electrode for measuring the capacitance value of the formed gas-liquid two-phase flow,
A reference electrode for measuring the capacitance value of the liquid
So that the measurement electrode is on the inside and the reference electrode is on the outside
Because they are arranged concentrically, under almost the same temperature conditions
Capable of measuring capacitance between gas-liquid two-phase flow and liquid
Then, to further simplify this kind of void fraction measurement device,
At the same time, the measurement accuracy can be further improved.

[0023] Furthermore, the measurement electrode on the inside, by which is arranged to compare reference electrode to the outside, by using the property of easily bubbles gather in the center, a liquid containing no gas-liquid two-phase flow and the bubble <br /> and separation can be more efficient to perform the.

[Brief description of the drawings]

FIG. 1 is a side view showing a cross section of an apparatus according to an embodiment of the present invention.

2 (a) and 2 (b) are lines AA and B in FIG. 1, respectively.
It is sectional drawing of the -B line.

FIG. 3 is a configuration diagram showing an example of an oil supply device provided with the above device.

FIG. 4 is a diagram showing a relationship between a mixed air amount and a void ratio during a constant liquid flow rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Void fraction measuring device main body 4 Measurement electrode 5 Mesh filter 6 Liquid passage hole 7 Reference electrode 10 Oil supply pipe 11 Oil supply pump 13 Flowmeter 15 Oil supply nozzle

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 27/00-27/24

Claims (2)

(57) [Claims] 1. A measuring electrode for measuring a capacitance value of a gas-liquid two-phase flow formed in a part of a liquid supply passage so as to surround the liquid supply passage, and a capacitance value of a liquid. And a comparison reference electrode for measuring the void ratio is arranged in multiple concentric circles such that the measurement electrode is located inside and the comparison reference electrode is located outside. 2. The void ratio measuring device according to claim 1, wherein a mesh filter for preventing air bubbles from being inserted is disposed at a start end of the flow path in contact with the comparison reference electrode.