JPS62233721A - Measuring method for flow rate - Google Patents

Abstract

PURPOSE:To accurately measure flow rate without being influenced by a kind of liquid, a change of viscosity, etc., by pouring gas into a liquid duct with closed cross-sectional structure and forming bubbles to contact totally with an inwall of the duct and measuring the moving speed of the bubbles at a downstream area. CONSTITUTION:A bubble moving speed computer 18 receives passing signals of the bubbles 15 at the 1st measuring point O1 by a phototube bubble measuring sensor 16 and the 2nd measuring point O2 by a phototube 17 bubble measuring sensor and the passing time TL between both the points O1 and O2 is measured by counting a clock pulse in the course of the time, for instance, by a counter. Then, the speed of the bubbles 15, namely, the average flow velocity L/TL of a fluid in the duct 10 is calculated from the distance L being known and the liquid flow rate Q is calculated from the result and the known cross section of the duct 10 as well and the result is transmitted to a flow rate indicator 19. The flow rate indicator 19 receives the signal and displays the instantaneous flow rate, the integrate flow rate or both of them, etc., as necessary.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for measuring the flow rate of a liquid.

[Prior art]

Various methods are known for measuring the flow rate of a liquid flowing through a closed cross-section channel such as a pipe, and are appropriately selected depending on the properties of the liquid, the measurement purpose, the measurement conditions, and the like. For example, the method using a volumetric flowmeter, which directly measures the volume of liquid passing within a certain period of time, has relatively good accuracy and is not affected by the viscosity or density of the fluid, so it is A rotor-type flowmeter is a specific example of a rotor-type flowmeter, in which two elliptical gears A and B are fitted in a sealed outer box 1 so as to be rotatable by fluid. The space (measuring chamber) 3 between the gear and the outer box is filled with the fluid flowing in from the inlet 2, and a fixed volume of fluid is sent to the outlet 4 for each rotation, and the amount of fluid that has passed is determined based on the number of rotations of the gear. This is to find the volume.

However, this type of flowmeter consists of gears with complex shapes, so when measuring multiple types of fluid,
It is unsuitable for liquids where the previous liquid remains and easily mixes with the subsequent liquid, and therefore contains solids that may interfere with the meshing of gears, or liquids such as paints where colors must not mix. It is.

Therefore, in order to measure the flow rate of liquids containing solids, instead of directly determining the volume of the fluid, the flow rate of the fluid is measured, and the volume of the fluid is indirectly determined from that value and the cross-sectional area of the flow path. The desired method has been adopted. Flow rate measurement means using such an indirect method・)-1, Yl+ Example 1! rp
The ultrasonic flow meter shown in Figure 55 is used. Plane Jf in Figure 4
In the l flow, the float 5, which has a higher specific gravity than the fluid, is placed -
It is placed inside a transparent tapered tube 6 whose diameter increases toward the opposite direction. When the liquid 7 flows from the bottom to the top inside the tapered tube 6, the float 5 is pushed up by the flow.
As the gap between the outer diameter of the float 5 and the inner diameter of the tapered tube 6 (i.e., the throttle area) increases as you move upward, the float pushing force (i.e., the differential pressure generated by the throttle) becomes smaller, and it is balanced at a position according to the flow rate. Then the float stops rising. By reading the position of the float, the flow velocity and thus the flow rate can be determined. Figure 5(a) shows the principle of the propagation time difference method in an ultrasonic flowmeter.
'ff-Ultrasonic transmitters TI, T in the tract 8 or on the outer wall of the tube
2 and reception fiR,, R2 are installed, and the ultrasonic wave is transmitted at a flow rate V
This method calculates the fluid flow velocity V from the difference Δt between the time t1 required for a sound wave to propagate along the flow and the time t2 required for the sound wave to propagate against the flow.

That is, if the sound velocity of the current wave of Mi is now C, the time difference Δt of propagation through the distance between the instruments can be regarded as C; shiV, so ΔL = L 2 - t + = 2LV/C2...
・(1), and if the time difference Δt is measured, L and C
The flow velocity V can be determined by knowing (time difference method)
.

Note that if one phase φ=ωt is used instead of the time difference Δt.

Phase difference Δφ=φl-φ2=2ωLV/C2...
...(2) Then, the flow velocity V can be found by measuring Δφ (phase difference method). Also, if the frequencies whose periods are the above times tl and t2 are fl and f2, respectively, then the frequency difference, af= f+ −
f2=2V/L・Old・−(3), and it is also possible to obtain the flow velocity V without being affected by fluctuations in the sound velocity C (frequency method).

ff15 Figure (b) shows the principle of the Doppler method in an ultrasonic flowmeter, in which a sound wave transmitter T and a receiver aR are installed at symmetrical positions in the pipe, and the transmitter T transmits Jfl at a frequency ft.
'+°? When a wave is sent out, a frequency fr given by the following equation is obtained at the receiving mR due to the Doppler effect.

fr=2Vcosθft 7 c =---(4) Therefore, by measuring the Doppler frequency fr, the flow velocity V at the center of the pipe can be determined by constricting the sound ray as sharply as possible.

[Problem that the invention seeks to solve]

However, conventional liquid flow rate measuring methods such as those in which the flow rate is determined by measuring the flow velocity in two series have the following problems.

(b): The method using an area flowmeter shown in Figure 54 is as follows:
Since the flow rate is measured based on the resistance force exerted on the float 5 by the liquid flowing in the tapered tube 6, measurement errors due to changes in the viscosity of the liquid are large.

(b) The method using an ultrasonic flowmeter shown in FIG.
If the flow velocity distribution in the pipe changes due to changes in viscosity or flow velocity, measurement errors will increase.

Other flow rate measurement methods, such as a method using an electromagnetic flowmeter, can be applied to fluids containing solids, but are generally expensive and cannot be used for non-conductive liquids.

This invention was made by focusing on these conventional problems, and it is possible to accurately measure the flow rate without being affected by the presence or absence of solids in the fluid, changes in viscosity, or fluctuations in the flow velocity distribution. , it can also respond quickly to changes in the type of liquid. The purpose is to provide a simple flow rate measurement method.

[Means for solving problems]

The present invention achieves the above object by injecting gas into a liquid channel having a closed cross-section structure to form all kinds of bubbles on the inner wall of the channel,
This flow measurement method is characterized by measuring the attribute velocity of the bubbles in the downstream region.

[Effect]

In the method for measuring the flow rate of a liquid according to the present invention, bubbles injected into a flow path are pushed by Pi while in contact with the inner wall of the moat, and flow through the pipe at an average velocity of the fluid. Therefore, it is sufficient to measure the traveling speed of the bubbles using a known measuring means that can be selected depending on the situation, minimizing the effects of fluctuations such as the presence of solids, changes in viscosity, and flow velocity distribution. It can also respond quickly to changes in species.

〔Example〕

The present invention will be explained below based on the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In addition,
In this example, a case will be described in which the fluid to be measured is a silver metallic color pIi paint for automobiles.

In the figure, lO is a pipe as a liquid flow path with a closed cross-section structure, and an air injection port 1 for injecting air into this pipe.
1. It is best to install the tube IO horizontally, at least in the flow rate measurement area described later, to prevent the influence of buoyancy.In addition, the material of the tube IO is, in this example, a transparent glass tube. But in general.

In order to make it easier for the bubbles to come into contact with the entire circumference of the inner wall of ``rFlO, it is preferable to use a material with a large contact angle with the liquid.For example, materials made of silicone resin or Teflon resin, or materials coated with such resins are suitable.

Reference numeral 12 denotes an air injector connected to the air inlet 11, which includes a solenoid valve that opens and closes a thread path connected to an air source 14 via an air pipe 13, a variable throttle that adjusts the air flow rate from an air discharge nozzle, etc. (not shown) is built-in. Reference numeral 15 represents a bubble formed in the tube 10 by this air injection 4ai12, which is in contact with the entire inner wall of the tube 10 (total contact state). 16 and 17 are two sets of photocells consisting of receiving stage light devices. They are installed at predetermined intervals so that the passage of the bubbles 15 through the glass tube IO can be detected. -h
The area between the locations is the flow rate measurement area.

18 is a bubble traveling speed calculator, and the first
Measurement point 01 and photoelectric 'F? 17 at the second side fixed point 02, and for example, by counting the clock pulses during that time with a counter, both points 0
In addition to measuring the transit time TL between 1 and 02, since the distance is known, the speed of the bubble 15, that is, the pipe lO
It has a function of calculating the average flow velocity V=L/TL of the internal fluid, calculating the fluid flow rate Q from the result and the known cross-sectional area of the pipe 10, and transmitting the result to the flow rate display 19. The flow rate display 4i119 receives the signal and displays instantaneous flow rate, cumulative flow rate, or both as necessary.

It is meant to show.

Reference numeral 20 denotes a controller that controls the operations of the air injector 12 and the bubble traveling speed calculator 18 in a correlated manner.

For example, a start switch (not shown) is provided to manually command the start of measurement, and when the start switch is turned on, an air injection signal is sent to the air injection device 12 for a predetermined time that can be set in advance by a timer, and the air injection device 12 is A calculation command signal is sent to the travel speed calculation fi18.

Next, the effect will be explained.

When measuring the flow rate of fluid flowing through the pipe 10, the controller 20
Turn on the start switch provided. As a result, air is injected under control a20. In response to this, the air injection 4112 opens the built-in air injection passage opening/closing solenoid valve, and passes the air injection port 11 through the air injection port 11 at a pre-adjusted air flow rate via a variable throttle. Inject air into the IO. As a result, bubbles 15 are formed, but it is necessary that the bubbles 15 are all present on the inner circumferential wall of the pipe IO (so that the flow velocity of the bubbles can be detected as the average flow velocity of the fluid). It is important to adjust the air injection time and air flow rate. In addition, as already mentioned, it is better to consider the influence of the contact angle of the liquid on the inner wall of the tube 10.At the same time as the air injection time elapses, the control
0 outputs a calculation command signal to the bubble traveling speed calculator 18.

The bubbles 15 move from left to right in the figure along with the flow of the liquid, passing through the first measurement point 01 and then the second measurement point 02.

The phototubes 16 and 17 at each measurement point Or, 0.2 transmit a pulse signal of a change in light transmittance due to passage of the bubble 15 to the bubble traveling speed calculator 18. The calculation Ja18 is performed based on a calculation command signal from the controller 20, and the fluid flow rate Q is calculated from the calculation result and the flow path cross-sectional area of the pipe IO given in advance.
t- is calculated, and the calculated data is transmitted to the flow rate display device 19 to display a meteor.

FIG. 2 shows another embodiment.

In this embodiment, as means for detecting the bubbles 15 at the m I J1 fixed point 01 and the second JIl fixed point 02, the already-mentioned known ultrasonic sensor (sonic wave transmitter/receiver) T, instead of the phototube, is used.
This embodiment differs from the first embodiment in that R is used.

This is effective when the tube 10 may be opaque and the liquid to be measured is transparent and the bubbles 15 are difficult to detect with a phototube. Further, even when the viscosity of the liquid is high and therefore a film of opaque liquid is interposed between the inner wall of the tube 10 and the bubble 15, there is an advantage that the passage of @15 can be reliably detected. According to each of the above embodiments, not only is it possible to accurately measure the flow rate regardless of the type of liquid, changes in viscosity, and fluctuations in flow velocity distribution, but also there is no mixing of fluids separated by bubbles, for example in automobiles. It can also be installed after the color change mechanism of an automatic top coating machine to handle multiple colors with a single flowmeter. Furthermore, since the configuration of the equipment used is simple and compact, the scope of application is widened.

〔Effect of the invention〕

As explained above, according to the present invention.

Gas is injected into a liquid channel with a closed cross-section structure to form all kinds of bubbles on the inner wall of the channel, and the flow rate is determined by measuring the velocity of the bubbles, resulting in the following effects. .

(a) Accurate flow rate measurement is possible regardless of the type of liquid or changes in viscosity.

(b) Even if the flow velocity distribution in the pipe changes due to changes in the viscosity or flow velocity of the liquid, the average flow velocity can always be measured, and stable measurement values with small measurement errors can be obtained.

(c) The sensor will not be damaged even in the case of paint such as metallic paint containing slurry-like solids.

[Brief explanation of drawings]

F! The Sf diagram is a schematic diagram explaining the principle of one embodiment of the flow rate measuring method according to the present invention, FIG. 2 is a schematic diagram showing another embodiment, and FIGS. 3 to 5 are various conventional flow rate measuring methods. With a schematic diagram explaining the principle of. Figures 3 (a) and (b) are based on a rotor type flowmeter, Figure 4 is an area type flowmeter, and Figure 5 (a)
Figure 5(b) is based on the message time difference method in an ultrasonic flowmeter, and Fig. 5(b) is also based on the Doppler method in an ultrasonic flowmeter. liquid flow path)i
t...... Air inlet 12... Air injector 14... Air source 15... Foam 16 .17...Phototube T, R...Ultrasonic transmitter/receiver 18...Bubble attribute speed calculator 19...
. . . Flow rate indicator 20 . Figure 1 Figure 2 Figure 3 Figure 5 (a) Figure 4 (b)

Claims (1)

[Claims] A flow rate measurement method characterized by injecting gas into a liquid flow channel with a closed cross-section structure to form bubbles that are in full contact with the inner wall of the flow channel, and measuring the traveling speed of the bubbles in the downstream region.