JPS6166929A - Solid-vapor two-phase flow meter - Google Patents

Abstract

PURPOSE:To reduced variation in the dielectric constant of the section in piping and measure a flow rate with high precision by providing a cylindrical electrode outside the piping and further arranging cylindrical electrodes at both sides of the cylindrical electrode, and covering those electrode with an electromagnetic shield plate. CONSTITUTION:The 1st, the 2nd, and the 3rd cylindrical electrodes 11, 12, and 13 are provided at the periphery of the piping 1. Further, those electrodes 11-13 are covered and shielded with the electromagnetic shield plate 14. When a high frequency voltage is applied to the 1st electrode 11, a current flows through the 2nd electrode 12 and the 3rd electrode 13. This current fluctuates with the concentration of the solid component in the piping 1 and a speed computing element 25 calculates the flow rate from the time delay at a detection part. The output when no fluid flows is found by a detector amplifying 27 and the measured detected value is corrected to calculated the flow rate in the solid component in a solid-vapor two-phase flow. For the purpose, the electromagnetic shield plate is provided to eliminate the influence of variation in the dielectric constant of the section in the piping, so the flow rate is measured with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to gas (e.g. air) and solid (e.g. pulverized coal)
The present invention relates to a solid-gas two-phase flow meter that measures the concentration and flow velocity of solid components in a so-called solid-gas two-phase flow that flows in a mixed manner, and calculates the flow rate from the measured values.

(Prior Art) As one of the means for measuring the solid components in a solid-gas two-phase flow, a capacitive flow method as described in Japanese Patent Application Laid-Open No. 198-190'i'19 is used. There is a countermeasure.

FIG. 8 shows one embodiment of this. As shown in the figure, a counter electrode 2 made of a metal plate is placed on the outer periphery of a pipe 1 made of an insulator.
-1 and 2-2, and furthermore, a second counter electrode 3-1.3-2 and a third counter electrode 4-1.4-2 having a similar structure are provided at a certain distance in the fluid flow direction. Electronic circuit for measuring the capacitance between the respective opposing electrodes 5.6
．． 7, the output of the second electronic circuit 6 and the output of the third electronic circuit 7) are connected to the speed calculator 8, and the output of the first electronic circuit J' circuit S) and the speed The output of the arithmetic unit 8 is connected to a multiplier.

The capacitance of the first counter electrode 2-1, 2-2 is measured by the electronic circuit 5, and the capacitance when no fluid is flowing is +7. ．． (Due to the space between the pipe wall and electrodes)
are arranged to cancel, so that the output of the electronic circuit 5 will be indicative of the solids concentration within the plumber. Also, the second
counter electrode 3-1.3-2 and third counter electrode 4-1
．． The change in the capacitance 111 of 4-2 is caused by the change in the capacitance 111 of
Then, the velocity calculator 8 uses the correlation method to measure the time IHH1y, T+rt, 7ti, the distance between the poles T-t(7), the distance between the poles, and the i;'l calculation of 1. Therefore, the 111 force indicates the velocity of the solid-gas two-phase flow.

The multiplier 9 outputs a flow rate signal obtained by multiplying the output 4''rz; of the electronic circuit 5 indicating the concentration and the velocity operation p2 indicating the flow rate by 8 (INJ).

However, in the case of the flow rate d1 of such a system, the following problem occurs. That is, since it is difficult to create a uniform electric field over the entire cross-section of the pipe, the detection sensitivity differs depending on the location of the cross-section of the pipe. For this reason, when a concentration distribution occurs in the flow, especially in inclined piping, accurate flow rate measurement becomes impossible.

FIG. 9 shows an example of the sensitivity distribution of the electrode section in the conventional flow meter J1.
A thin rod (several mm in diameter) of glass was inserted to investigate the change in indication.The sensitivity in the center is shown as r11 vs. value when it is 1.0, but it is 20% in the periphery. There are varying degrees of severity.

(Problems to be Solved by the Invention) The present invention solves the problems of the conventional capacitance-solid/gas-solid two-phase flowmeter as described above, and solves the problems of the conventional capacitance type solid-gas flowmeter. Qi 2 Phase Ryuharu,? The purpose is to provide 1.

(Means/effects for solving the problems) The present invention provides a method for controlling the solid gas two-phase flow flowing inside the piping, based on the change in the capacitance nt between the electrodes installed outside the piping, which is an electrical insulator. A method of measuring the flow f, f of solid components [in the previous 81, a cylindrical first electrode provided so as to surround the pipe,
Cylindrical second and third electrodes are provided at intervals on both sides of the first electrode in the axial direction; an electromagnetic shielding plate provided, a means for applying an alternating current voltage to the first electrode, and an electrostatic capacity between the first electrode and the second electrode and between the first electrode and the third electrode. By using an electrode with such a structure, the sensitivity distribution in the cross section of the pipe can be made almost uniform, so it is possible to carry out regular measurements even when the concentration in the cross section is not uniform. becomes possible.

The present invention will be explained in detail below based on illustrated embodiments.

FIG. 1 181 is a block diagram of an embodiment of the solid-gas two-phase flow meter according to the present invention, and FIG.
FIG.

First, second and third cylindrical electrodes 11.1 are placed around the pipe l.
2 and 13 are provided, and each electrode is covered with a shielding plate 14 made of a conductor for electromagnetically shielding each other.

Several 10 electrodes are connected to the first electrode 11 placed in the center from the power source 20.
A high frequency voltage of KHz is applied. The second electrode 12 on the upstream side and the third electrode 13 on the downstream side are provided with an amplifier 21.2.
2. Connect the speed calculator 25 via band pass filters 23 and 24.

In addition, the amplifier 21 connected to the second electrode 12 has
Another bandpass filter 26 and detection amplifier 27 are connected. Furthermore, the output of the speed calculator 25 and the output of the detection amplifier 27 are connected to a multiplier 28.

The operation of the flowmeter of this embodiment is as follows.

Due to the alternating voltage applied to the central first electrode 11, a current flows through the second and third electrodes 12.13 on either side thereof, and this current is amplified by the amplifier 21.22. This current is determined by the applied frequency, voltage, electrode size, dielectric constant of the piping material, etc., as well as the solid air 2 flowing through the piping.
It is determined by the amount of solids in the phase flow, but since everything else other than the amount of solids can be considered constant, it can be considered that the magnitude of the current is determined by the amount of solids.

In general, the concentration of solids (particularly fine powder) in a solid-gas two-phase flow has irregular shading (fluctuations), and therefore the flowing current also has fluctuations.

Here, the high frequency voltage applied from the power supply 20 to the first all poles 11 has a frequency of several tens of KHz (for example, 40 KHz), and the fluctuation of the solid-gas two-phase flow has a frequency of several tens of NHz. The current flowing to the third electrode 12.13 is in the form of several tens of K and lHz modulated at several tens of Hz. Therefore, band pass filter 2
3.24, only the fluctuation component can be extracted.

Fluctuations in the solid-gas two-phase flow hardly change over a very short distance, so the fluctuations in the output detected by the second electrode 12 and the fluctuations in the output detected by the third electrode 13 By knowing this delay time T, the flow velocity of the solid-gas two-phase flow can be determined.

In this embodiment, the output detected by the second electrode 12 and the output detected by the third electrode 13 are led to the speed calculator 25, and the time at which the cross-correlation becomes maximum is determined. Since the effective distance between the second electrode 12 and the third electrode 13 is determined by the structure and size of the electrodes, the flow rate can also be determined by L/T.

Further, since the magnitude of the current flowing through the second electrode 12 or the third electrode 13 changes depending on the concentration of solid in the solid-gas two-phase flow, the concentration of the solid can be determined from this output.

In this embodiment, the solid concentration is detected by using the output of the second electrode and removing the fluctuation component by the band pass filter 26, and then extracting only the DC component by the detection amplifier 27.

Note that in the detection amplifier 27, a value corresponding to the output when no fluid is flowing is canceled out. Then, the multiplier 28 multiplies the solid concentration, which is the output of the detection amplifier 27, by the velocity, which is the output of the velocity calculator 25, to obtain the flow rate of the solid component in the solid gas two-phase flow.

Figure 2 shows an example of the sensitivity distribution of the electrode section in the flowmeter of this embodiment.Similar to the case of Figure 9, a thin dielectric glass rod is inserted into the detection section of the flowmeter, and the The change in sensitivity is shown as a relative value when the sensitivity in the center is set to 1.0, but the overall sensitivity difference is less than 1%.
It can be seen that this is greatly improved compared to the conventional flowmeter shown in FIG.

By the way, in a solid-gas two-phase flow, when the pipe is not installed, the flow may be separated into a slow flow with high concentration in the lower part of the pipe and a fast flow with low concentration in the upper part of the pipe, as shown in FIG. In this case, even the flowmeter of the embodiment shown in FIG. 1 cannot measure the correct flow rate. In the case of such a flow, there is no problem because the solid concentration is measured as the average value at the pipe cross section S, but the flow velocity component with the largest fluctuation is detected, and the correct representative value of the flow velocity distribution is detected. Not done.

FIG. 4 is a block diagram of the @2 embodiment of the present invention applied to such a case. The second electrode on the upstream side and the third electrode on the downstream side are each divided into four in the circumferential direction.
As electrodes (12-a, 12-b, 12-c, 1
2-d) As the third electrode (13-a, 13-b,
13-c, 13-d), and as in the case of the first embodiment shown in FIG.
A high frequency voltage of several tens of KHz is applied from the second and third
Each divided electrode (12-a to 12-d,
13-a to 13-d), amplifiers (21-a to 2l
-d22-a to 22-a) and bandpass filters (
23-a to 23-d, 24-a to 24-d, 2
6-a-26-a), and also a speed calculator (25-
a ~ 25-a) Detection amplifier (27-a ~ 27-d)
Multipliers (2B-a to 2B-d) are provided, and the electrodes (12-a and 13) are connected in the same manner as in the first embodiment.
-a) (12-b and 13-b) (12-C and 12-c
) Four sets of flow rate measuring circuits (only one set is shown in the figure) are constructed between the four sets of electrodes (12-d and 13-d).

Each electrode divided in the circumferential direction detects the concentration and flow velocity of each divided part of the pipe cross section, and as a result, the flow rate corresponding to each part is determined. The values obtained by each set of flow rate measurement circuits are input to the adder 30, and the flow rate corresponding to the entire cross section of the pipe is determined.

The third embodiment shown in FIG. 5 is a modification of the signal processing circuit of the second embodiment shown in FIG. By providing switches 31 and 32, the flow rate measurement circuit can be
The adder 33 adds the four flow rate values obtained each time the switch is made into a set.
to calculate the total flow rate of the pipe cross section.

In addition, in the second and third embodiments, each electrode divided in the circumferential direction does not measure the piping cross section by accurately dividing it into four equal parts, so the sum of the four flow rates is the correct total flow rate. In such cases, it is best to calibrate using the correct flow rate measured by another method, such as the heavy duty method.

FIG. 6 shows a fourth embodiment, and the structure of the electrodes is the same as that shown in FIGS. 4 and 5 above.

The circuit for concentration measurement consists of four electrodes (13-a to 13-1).
-a) (only two sets are shown), and the circuit for measuring the flow velocity consists of four electrodes (12-a to 12-a).
A changeover switch 37 that switches each input from 12-d)
Only one is provided through the.

In this example, four downstream electrodes (13-a to
13-d), each amplifier (21-a to 2l-4)
is connected, and a bandpass filter (26-
a to 26-d) to detection amplifiers (27-a to 27-
d) is connected.

The outputs of these detection amplifiers (2'i'-a to 2'7-d) indicate the concentrations of the cross sections corresponding to the respective electrodes (13-a to 13-d). By calculating the average of each output of the detection amplifier 1] (2'i'-a to 27-d) using the average calculator 34, the average concentration in the cross section of one tube can be obtained.

The sequence circuit 35 includes detection amplifiers (27-a to 27-
Determine which of the outputs in a) has the largest signal, and switch to detect the flow velocity at the electrode part corresponding to the largest signal, that is, the part with the highest solids concentration within the pipe cross section. Activate switches 36,37.

For example, if the solid concentration at the gold electrode (13-a) is the highest, the changeover switch 36
Only the output of electrode (12-a) is connected to the bandpass filter 27, and the selector switch 37 connects the output of electrode (12-a)
Only the output of is connected to a bandpass filter 24 via an amplifier 22 and guided to a speed calculator 25.

Therefore, in this case, the output of the speed meter 25 will indicate the flow velocity at the region with the highest concentration within the pipe cross section.

In this case, the flow rate obtained by the multiplier 28 will not be the correct sum of the parts of the pipe cross section, but if there is a significant difference in the solids concentration in each part, there will be a large error in practical terms even if the flow rate is calculated from the flow velocity of the part with the highest concentration. It is not.

In addition, in the above explanation, the second and third electrodes are arranged in four directions in the circumferential direction.
Although an example of division has been described, it goes without saying that other division numbers may be used depending on the pipe diameter, flow conditions, etc. In addition, in the above examples, the concentration was determined only by the upstream electrode or the downstream electrode, but the concentration may be determined by both the upstream electrode and the downstream electrode and the average value thereof may be used. .

In the above embodiments, all the electrodes were provided around the pipes, but in such a structure, the magnitude of the current flowing through the electrodes is affected by the capacitance formed by the pipes. The capacitance caused by piping is determined by the shape and dimensions of the piping and the dielectric constant of the insulator that makes up the piping, but the dielectric constant of the insulator often changes depending on the temperature. Therefore, when the temperature of the fluid flowing through the flowmeter changes or the temperature around the flowmeter changes, the reading on the flowmeter changes.

Figure 9 shows an example of an electrode structure to alleviate such problems.
1.12.13 is provided, and its inner surface is further coated with an insulating film 15. In the case of such a structure, the magnitude of the current flowing between the electrodes is affected by the change in the dielectric constant of the insulating film 15. The magnitude of temperature change can be greatly reduced. Note that this insulating film is for preventing the electrodes from being shorted together by the fluid, and the fluid is an insulator J4. ! , it can be omitted in some cases.

(Effects of the Invention) As explained in the examples, the present invention applies an alternating voltage using a cylindrical electrode provided to surround the piping in a capacitance 112 solid gas two-phase flow meter. By detecting the electrostatic capacitance between cylindrical electrodes and adjacent cylindrical electrodes, the flow rate of solid components in the solid-gas two-phase flow flowing inside the pipe is measured. Even if the concentration distribution of components is uneven, the flow rate can be accurately measured, and since it is not affected by dielectric constant changes due to concentration changes in the piping itself, it has the excellent effect of high accuracy in flow measurement. .

[Brief explanation of drawings]

FIG. 1 1al is a detailed explanatory diagram of the present invention, (bl is (al
FIG. 2 is a sensitivity distribution diagram of the cross section of the piping of the present invention, FIG. 3 is a schematic diagram showing concentration bias in the piping of the present invention, FIGS. 4, 5, and 6 7 are detailed explanatory diagrams of the present invention, FIG. 8 is an explanatory diagram of a conventional device, and FIG. 9 is a sensitivity distribution diagram of a cross section of a pipe in a conventional example.

Claims (1)

[Claims] 1. A method for measuring the flow rate of a solid component in a solid-gas two-phase flow flowing inside an electrically insulating pipe based on changes in capacitance between electrodes installed outside the pipe. In the flowmeter of
A cylindrical first electrode provided so as to surround the flow path, cylindrical second and third electrodes provided at intervals on both sides of the first electrode in the axial direction, and the first electrode. , an electromagnetic shielding plate provided outside the second and third electrodes so as to surround each electrode, means for applying an alternating current voltage to the first electrode, the first electrode, and the second electrode. A solid-gas two-phase flowmeter comprising: means for detecting capacitance between the first electrode and the third electrode. 2. The solid-gas two-phase flowmeter according to claim 1, wherein the second and third electrodes are divided into a plurality of electrodes in the circumferential direction.