JPS5836295B2 - Flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flowmeter, and more particularly to a flowmeter that is robust and has a wide measurement flow range and has no moving parts.

Conventional flowmeters generally include (1) an orifice flowmeter, a venturi flowmeter, a flow nozzle flowmeter, etc., in which a restriction is placed in the pipe, and the flow rate is determined by the differential pressure generated by this restriction. (2) such as turbine flowmeters, which measure the flow rate based on the number of revolutions of a rotary impeller placed in a pipe; (3) fluids that move in a magnetic field, such as electromagnetic flowmeters. (4) A method that measures the flow rate by measuring the potential difference that occurs in a container, and (4) a method that measures the flow rate by flowing fluid into a container and measuring the rise in the liquid level.

In the differential pressure measuring type flowmeter (1), the relationship between the flow velocity V and the differential pressure Ap is expressed as follows.

The measurable range of ap is approximately 5 to 10% of the full scale of the transformer, taking measurement errors into account, and the error increases in flow rate ranges lower than this.

The value obtained by taking the square of the measurable range of this Jp, that is,
From the above equation, 22 to 100% becomes the measurement range of the flow rate, that is, the flow rate.

Differential pressure type flowmeters have a measurable flow rate range of 5, which is the lowest flow rate.
It's only about twice that.

Next, in the turbine flowmeter (2), since the flow rate and the rotational speed of the rotor are proportional, the flow rate measurement range is 5 to 5.
100%, and it is possible to measure up to a range of about 20 times the lowest flow rate.

However, since it has a rotating part, bearing maintenance is required and it is relatively expensive.

Since the electromagnetic flowmeter (3) has no moving parts and the output and flow rate are proportional, the measurable range of flow rate is 1 to 100%, and it is possible to measure up to about ioo times the lowest flow rate.

However, in order to measure the potential difference occurring in a fluid, it is necessary to electrically insulate between the pipe wall and the fluid to prevent current from flowing through the pipe wall.

Due to problems with the strength of this insulator, the heat resistance temperature of electromagnetic flowmeters is limited to over 100 degrees Celsius.

Furthermore, electromagnetic flowmeters are also relatively expensive instruments, just like turbine flowmeters.

The above three types of flowmeters are all for measuring the instantaneous flow rate of single-phase flow, and are used when liquid is mixed with bubbles, when the flow rate range is extremely wide, or when liquid flows intermittently. Can not.

For these purposes, the method (4) of measuring the flow rate based on the rate of rise in the liquid level in the container is suitable.

By continuously measuring the rate of rise in the liquid level and differentiating it with respect to time, you can obtain the instantaneous flow rate.By measuring the time it takes for the liquid level to rise a certain distance, you can calculate the average flow rate over that time. The flow rate can be determined.

In the latter method of calculating the average flow rate, two level gauges are placed at different heights in the container and the time interval between these two level gauges being turned on is simply measured. If the flow rate is made appropriately large so that the liquid level rise rate at the maximum flow rate does not become extremely high, the measurable range of the flow rate can be expanded virtually unlimitedly.

However, with this flow meter, when the container is full of fluid, it must be emptied with a drain, and conventionally this drain has been done using a solenoid valve attached to the bottom of the container.

That is, when a liquid level gauge or the like detects that the container is full, the solenoid valve is opened.

When the drain is finished, this valve is closed and measurement of the rate of rise in the liquid level is started again.

Fluid flows into the container even during draining, so
In order to displace fluid within the container, the drain flow rate must be greater than the inflow flow rate.

Therefore, if the measurable range of flow rate is widened, the drain flow rate must be correspondingly increased, and a large electromagnetic valve is required.

Solenoid valves require maintenance, and their large size is expensive.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to provide a flowmeter that has no moving parts and has a wide flow rate measurement range.

A feature of the present invention is that one end of a plurality of siphon tubes having different heights and inner diameters up to the U-shaped part is connected to a liquid storage tank, a liquid level gauge is provided in the liquid storage tank, and the other end of the siphon tubes with a small inner diameter is connected to a liquid storage tank. , to open into a siphon tube having a larger inner diameter.

The present invention maintains the above-mentioned (4) advantage of the flow meter that measures the rate of rise in the liquid level in the container to determine the flow rate, and
Instead of using a solenoid valve that requires maintenance as a draining means, the fluid inside the container is intermittently drained using a siphon pipe attached to the bottom of the container.

The characteristics when water is supplied at a constant flow rate Qi to a system with a siphon pipe attached to the bottom of the container will be explained using FIG.

As water is injected into the container 1 from the water supply pipe 3, water finally begins to flow down from the siphon pipe 2 as shown in FIG. 1(a).

When the water supply flow rate Qi is small, the air 5 in the downcomer pipe section 4 of the siphon pipe 2 is not removed, and water only overflows from the upper end of the siphon pipe 2 and flows down inside the downcomer pipe section 4.

In such a state, the flow rate flowing out from the siphon pipe 2 is equal to the water supply flow rate Qi, and the liquid level in the container 1 does not fall.

Therefore, at such a low flow rate, water in the container 1 cannot be drained using the drain method using the siphon pipe 2.

When the water supply flow rate Qi from the water supply pipe 3 is increased beyond a certain critical flow rate Qi, the air 5 in the downcomer pipe section 4 of the siphon pipe 2 becomes
It is carried away by the flowing water and removed, resulting in a state as shown in FIG. 1(b), and finally the inside of the downcomer pipe section 4 of the siphon pipe 2 is filled with water.

In this state, the water in the container 1 is drained by the siphon pipe 2 in a so-called siphon action.

The drain flow rate Qd by the siphon pipe 2 at this time is the water supply flow rate Qi (the above-mentioned Q
Equal to i.

), experiments have shown that it is about 10 times as large.

That is, when the water supply flow rate Qi is larger than Qi and smaller than Qd, the liquid level in the container 1 rises to near the upper end of the siphon pipe 2, and the drain from the siphon pipe 2 causes the siphon pipe 2<! :Repeat descending as shown in Figure 1 (Q) until reaching the connection with container 1.

By measuring the rising speed of the liquid level at this time, the average flow rate of the water supply can be determined.

If the water supply flow rate Qi exceeds the drain flow rate Qd by the siphon pipe 2, the liquid level in the container 1 will continue to rise despite the draining by the siphon pipe 2, so it cannot be used as a flow meter.

In summary, the flow measurement range of a flowmeter using a device combining a container 1 and a siphon tube 2 as shown in FIG. 1 is about 10 times the range between Qi and Qd.

This drain method using the siphon tube 2 has no moving parts and has a simple configuration with only piping, so it has good environmental resistance and economical efficiency, but the flow rate measurement range is 10.
It is about twice as narrow.

In order to expand this, the method of the present invention described below uses a plurality of siphon tubes with different diameters and is capable of operating between Qi of the thinnest siphon tube and Qd of the thickest siphon tube. .

FIG. 2 shows an embodiment of the present invention.

In this example, the left ascending pipe sections of a plurality of siphon pipes 2A, 2B and 2C with different diameters are connected to the container 1 via the header 6, and the descending pipe section 4 of the two siphon pipes and 2B is connected to the container 1 via the header 6.
The lower ends of A and 4B are opened into ejectors 7A and 7B provided in downcomer pipe sections 4B and 4C, respectively.

The inner diameter of the siphon tubes 4A, 4B, and 4C increases in this order.

Also, U-shaped portions 1 4 of each siphon tube 2A, 2B and 2B
The height of A, 14B and 14C increases as the inner diameter of the siphon tube increases.

Two liquid level measuring electrodes 8A and 8B are inserted into the container 1 via insulations 9A and 9B.

When the lower ends of electrodes 8A and 8B come into contact with the liquid due to a rise in the liquid level in container 1, changes in the electrical conductivity between electrodes 8A and 8B and container 1 are detected, and the liquid level is adjusted to It is possible to measure whether it is below or above the bottom edge of the .

These two electrodes 8A and 8B, that is, the lower end portions of the liquid level gauge, are respectively arranged above the upper surface of the header 6 and below the U-shaped portion 14A of the two narrowest siphon tubes.

A water supply pipe 3 and an air vent 10 are provided in the upper part of the container 1.

A fluid whose flow rate is to be measured flows into the container 1 from the water supply pipe 3, and air in the container 1 flows in and out from the air vent 10 as the liquid level in the container 1 rises and falls.

This air vent 10 is generally connected to the upper part of a drain tank 13, as shown in FIG. 3, so that the pressures inside the siphon pipe 2 and the container 1 are equalized.

A cylinder 11 having a hole 15 in the upper side is installed in the container 1 so as to surround the electrodes 8A and 8B of the liquid level gauge.

The cylinder 11 prevents the effects of ripples on the liquid surface caused by water flowing into the container 1 from the water supply pipe 3 from reaching the electrodes 8A and 8B.

Next, the operating principle of this embodiment will be explained using FIGS. 4 to 9.

When water is supplied into the container 1 from the water supply pipe 3 as shown in FIG. 4, the liquid level in the container 1 gradually rises to the state shown in FIG. 5.

The rising rate of the liquid level in this state is measured using two level gauges 8A and 8B, and the average flow rate of the water supply is determined.

When water flows further into the container 1 than in the state shown in FIG. 5, water begins to overflow from the two narrowest siphon pipes on the left end.

At this time, if the water supply flow rate Qi is greater than the siphon starting flow rate Qi of the two siphon tubes, all the air in the two siphon tubes will be removed, and the two siphon tubes will be filled with water as shown in Figure 6. , water in the container 1 begins to drain due to siphon action.

At this time, the lower end of the descending pipe section 4A of the two siphon tubes opens into the ejector 7A provided in the descending pipe section 4B of the adjacent siphon tube 2B, which has a larger inner diameter, so that the air inside the siphon tube 2B is removed. It is sucked out by the action of the ejector 7A.

Therefore, the descending pipe portion 4B of the siphon pipe 2B is also filled with water as shown in FIG. 7, and the water in the container 1 begins to be drained by the two siphon pipes 2 and 2B.

As shown in FIG. 7, the drain water flowing through the siphon pipes 2 and 2B is removed by the action of the ejector 7B, which removes the air in the thickest siphon pipe 2C at the right end.

Finally, as shown in Fig. 8, three siphon pipes 2A
, 2B and 2C, the water in the container 1 will be drained.

Therefore, if the water supply amount Qi from the water supply pipe 3 is smaller than the drain flow rate Qd of the siphon pipe 2C, the water level in the container 1 will decrease.

When the liquid level drops to the height of the header 6, the air in the container 1 flows into the header 6 and further flows into each siphon pipe 2A, 2B.
and 2C, and the drain action by siphon action is stopped as shown in FIG.

After this, the state returns to the state shown in FIG. 4, and the liquid level in the container 1 rises and falls repeatedly.

In summary, if the device of this embodiment is used, it is possible to measure the flow rate if the water supply flow rate Qi is between the siphon start flow rate Qi of the two siphon tubes and the drain flow rate Qd of the siphon tube 2C. I understand.

It has been found that the ratio of the inner diameters of the siphon tubes 2A, 2B and 2C can be determined experimentally as follows based on the performance limits of the ejectors 7A and 7B.

(Qd of 2 siphon tubes) = (Qi of siphon tube 2B
) (Qd of siphon tube 2B) - (Qi of siphon tube 2C
C From this, if the ratio of the inner diameters of each siphon tube 2A, 2B and 2C is increased, the ejectors 7A and 7B will no longer be able to discharge the air in the adjacent siphon tube.

Furthermore, if the ratio of the inner diameters is decreased, the number of siphon tubes required to obtain the required flow rate measurement range will increase, which is undesirable.

Here, for one siphon tube, as mentioned above, Q
d: 10Qi, so using the relationship just described, in the device shown in Figure 2, (Qd of the siphon tube 2C with the largest inner diameter) is 1000X (Qi of the two siphon tubes with the smallest inner diameter), and the flow rate is The measurable range is as wide as about 1000 times the minimum measured flow rate.

If the principle of the present invention is applied to increase the number of siphon tubes,
In principle, the flow rate measurement range can be expanded infinitely, but the time required for flow rate measurement increases accordingly, so in practice, it is appropriate to set the range to about 1000 times that of this embodiment.

In this embodiment, a plurality of siphon pipes 2A, 2B and 2C are connected to the container 1 via the header 6, but as shown in FIG.
You can get exactly the same effect even if you attach it to

Further, the liquid level gauge installed in the container 1 is not limited to the conductivity type shown in the embodiment shown in FIG. 2, but any type can be used as long as it is capable of measuring the liquid level in the container 1.

Furthermore, the air vent 10 attached to the upper part of the container 1 is not particularly necessary if the fluid discharged from the drain pipe 12 of the flowmeter of the present invention is released into the atmosphere. It would be good if it was provided.

According to the present invention, the liquid in the container can be automatically drained without moving parts by using the siphon pipe drain system consisting of only a simple piping structure, so the flow rate measurement range is about 1000 times wider, and maintenance becomes unnecessary.

[Brief explanation of the drawing]

Figure 1 shows the principle of the present invention, (a), (b)
) and (c) are explanatory diagrams showing the flow of water flowing out of the container, FIG. 2 is a longitudinal cross-sectional view of a flowmeter that is a preferred embodiment of the present invention, and FIG. 3 is an embodiment shown in FIG. 2. 4 to 9 show the operating state of the embodiment shown in FIG. 2, and FIG. 4 is an explanatory diagram showing the state of water supply into the container.
Fig. 5 is an explanatory diagram showing the state in which water is accumulated in the container, Fig. 6 is an explanatory diagram showing the state in which the siphon pipe with the minimum inner diameter is in operation, and Fig. 7 is an explanatory diagram showing the state in which the siphon pipe with the minimum inner diameter is operating. An explanatory diagram showing the state in which the pipes are in operation. Figure 8 is an explanatory diagram showing the state in which all siphon pipes are in operation, including the siphon pipe with the largest inner diameter. Figure 9 is an explanatory diagram showing the state in which the water in the container is drained. An explanatory diagram showing the state, FIG. 10 is a structural diagram of another embodiment of the present invention. 1... Container, 2A, 2B, 2C... Siphon tube, 7A, 7B... Ejector, 8A, 8
B...Liquid level gauge, 1 4A, 14B, 1 4C.
...U-shaped part.

Claims (1)

[Claims] 1 Consisting of a liquid storage tank, a plurality of siphon pipes with different inner diameters and heights up to the U-shaped part, one end of which is connected to the liquid storage tank, and a liquid level gauge provided in the liquid storage tank, and which have a small inner diameter. A flowmeter in which the other end of the siphon tube opens into a siphon tube with a larger inner diameter.