JPS61292020A - Liquid flowmeter - Google Patents

Abstract

PURPOSE:To measure a fine flow rate by arraying chambers which have an orifice on a bottom wall successively to an intake so that each chamber receives only the overflow of a precedent chamber. CONSTITUTION:Liquid flowing in from the intake 1 enters the foremost chamber 2a firstly and part of it flows out of the orifice 3 of the chamber to a downstream space 5, but when the inflow is larger than the discharge from the orifice 3, the liquid level in the chamber 2a rises and the liquid overflows a weir 12a, so that the overflowing liquid flows out of the chamber 2b from its orifice 3 as well. Therefore, the liquid flows out of several orifices successively from the orifice 3 of the foremost part and the total of the discharge of the respective orifices is equal to the quantity of flow from the intake 1. Thus, the discharge from one orifice and the discharge of the smallest unit are measured, so a fine flow rate is measured by decreasing the diameter of each orifice.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a flowmeter for measuring the flow rate of liquid, and has a configuration having an orifice and a weir, and is particularly useful for measuring condensate generated in steam piping. It is something.

<Prior Art> ゛The applicant of the present invention has proposed the following as an improvement on a flowmeter having a proportional weir in which the flow rate is proportional to the water head, which has the disadvantage that the flow rate measurement accuracy deteriorates as the flow rate decreases. We proposed a flowmeter with an equal precision weir as shown in Figure 3. The flow meter has a configuration as shown in the figure, in which liquid enters the upstream space 18 of the partition wall 16 through an inlet 22, flows out into the downstream space 26 through an orifice 32 and a weir 34, and is discharged through an outlet 28. be done.

Since the relationship between the liquid level in the upstream space 18 and the flow rate passing through the orifice 32 and weir 34 is known, the liquid level in the upstream space 18 is measured to determine the flow rate.

The weir 34 shown in Fig. 4 is designed so that the ratio of increase or decrease in flow rate to the total flow rate due to a certain amount of change in the liquid level will be constant at any liquid level as long as the liquid level is within the range of the weir. It is. Because such a weir 34 is provided and the error in measuring the liquid level is almost constant at any liquid level, the flow meter has a constant flow rate measurement accuracy at any liquid level. ing.

Note that the measurement of the liquid level of the flowmeter shown in FIG. This is done by converting the displacement of the rod 54 into an electrical signal using the potentiometer 42 and extracting it. Then, the flow rate is calculated and obtained by another calculation section.

<Problems to be Solved by the Invention> In the conventional flowmeter described above, when measuring a minute flow rate where the liquid level is near the lower limit of the range of the weir 34, because the lower part of the weir 34 is narrow, Because the outflow state is not stable due to viscosity, surface tension, etc., and the water level is also not stable, there is a problem that there is a large hysteresis in the relationship between the flow rate and the liquid level, and in fact, it is impossible to measure.

A technical problem of the present invention is to obtain a flowmeter that can measure minute flow rates.

<Means for solving the problem> The means according to the present invention is such that chambers having an orifice in the bottom wall following the inlet are arranged so as to receive only the overflow of the previous chamber, and The liquid flow rate is measured by detecting how many chambers are in an overflow state using liquid level detectors installed in each chamber.

<Operation> The flow rate of each orifice can be calculated if its area, flow coefficient, gravitational acceleration, and liquid level are known. These values are values that can be known except for the liquid level in one chamber where liquid is flowing in but not overflowing, so if we ignore the amount flowing out from the orifice of that one chamber, then ,
The flow rate is obtained by summing the flow rates from the orifices of the chambers in the overflow state. The resulting flow rate value will be stepwise even if the actual flow rate change is linear. Note that as the flow rate increases, the head of the overflow section (weir) rises, but the increase in the flow rate from each orifice is determined by the number of chambers in which the overflow state occurs. That is, once the shape and dimensions of each part of the flowmeter are determined, the amount of flow from each orifice can be calculated theoretically or experimentally depending on the chamber size and whether the flow is in an overflow state. Therefore, even if the head is considered, the flow rate can be measured only by detecting which chamber the overflow state is.
Although the measured flow rate value changes stepwise with respect to changes in the actual flow rate, the diameter of the orifice is reduced to create a chamber. 5 is a downstream space, 6 is a discharge port, and 7a to 7j are liquid level detectors.

The inlet port 1 is provided at the top of one end of the elongated box-shaped main body 1o. The chambers 2a-2j are connected to the main body 1 following their inlets l.
o both side walls 10a, bottom wall 10a spanning between the lobs]
It is formed by providing the weirs 12a to 12j in the form of steps that descend one after another. Orifice 3, chamber 2
One piece is provided on each of the bottom walls 11a to 11j of a to 2j.

The second-flow space 4 is the space above each chamber 2a-2j, and the downstream space 5 is the space below the bottom walls 11a-1]j. The upstream space 4 and the downstream space 5 communicate with each other at a position beyond the weir 12j of the chamber 2j. The discharge port 6 is provided at the bottom of the main body 1o at the end opposite to the inflow port 1.

The liquid level detectors 7a to 7j may be of any type as long as they can detect when the liquid level in each chamber 2a to 2j has risen to the height of the corresponding weir 12a to 12j. For example, if the liquid to be measured is conductive If it is, it may be just an electrode;
If not, you can use a float switch etc. In this example, an electrode is provided insulated from the main body 1o, and when its lower end comes into contact with the liquid surface, the main body (made of metal) 0
The liquid level of each is detected by being electrically connected to the two.

Although not shown, each liquid level detector (electrode) 7a~
Reference numeral 7j is configured such that conductive wires are connected separately outside the main body 10 to constitute a detection circuit, and the detection results are provided to a flow rate indicator or a flow rate recorder.

This flowmeter becomes stable in a specific state when liquid flows in from the inlet 1 at a constant flow rate, and the flow rate at that time is displayed on, for example, a display. That is, the liquid flowing in from the inflow port 1 first enters the frontmost chamber 2a and a part of it flows out from the orifice 3 of that chamber to the downstream space 5, but if the amount of inflow is larger than the amount of flow out from the orifice 3, The liquid level in chamber 2a rises and the liquid begins to overflow from the weir 12a, and the overflow flows into chamber 2.
It also flows out from the orifice 3 at point b. Therefore,
Liquid begins to flow out from several orifices in sequence starting from the orifice 3 at the forefront, and the total flow rate flowing out from each orifice matches the flow rate flowing in from the inlet port 1. Assuming that the last orifice from which the liquid is flowing is in chamber 2h, the liquid level in chambers 2a to 2g is detected by the liquid level detector 7.
a to 7g, respectively, and the liquid level in chamber 2h is not detected. Through this detection, the total flow rate of the orifice 3 up to Murohana, where up to chamber 2g is in an overflow state, is known.
The value is displayed on the display. The above explanation assumes that the flow rate is constant, but even if the flow rate fluctuates, the flow rate can be measured by following the fluctuation.

In the above embodiment, each chamber is arranged in a straight line, but the arrangement may be arranged so that it moves back and forth along a straight line,
A spiral arrangement or the like may also be used.

<Effects of the Invention> According to the present invention, since the flow rate is measured using the flow rate from one orifice as the minimum unit, by reducing the diameter of the orifice, minute flow rates, such as condensate generated in steam piping, can be measured. can be measured.

However, by selecting the number of chambers equipped with orifices and liquid level detectors, it is possible to create a system with low accuracy or high accuracy.

Furthermore, since the signal from the liquid level detector is digital, the data can be digitally processed.

The flow meter of the present invention belongs to the weir type flow meter in which the liquid passes, and is thus effective for measuring condensate generated in steam piping, like the conventional weir type flow meter. That is, condensate re-evaporates when the pressure fluctuates, but because the pressure is the same before and after the point belonging to the weir type, the condensate passes through without re-evaporating, and measurement errors due to re-evaporation do not occur.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 4 is an enlarged development view showing the shape of the weir and orifice of the flowmeter shown in FIG. 3. 1... Inflow port, 2ay 2j... Chamber, 3... Orifice, 4... Upstream space, 5... Downstream space, 6...
・Discharge port, 7a-7j...Liquid level detector, 10...Main body, xla-1lj...Bottom wall, 12a-12j...
Weir (overflow section). Patent applicant Chiinirbu Co., Ltd. Agent
Tetsu Shimizu and 2 others 4th M

Claims (1)

[Claims] (1) A number of chambers are provided to sequentially receive the overflow from the front chamber following the foremost chamber that receives the entire amount of inflowing liquid from the inlet, and an orifice is provided in the bottom wall of each of the chambers. A downstream space is provided so that the liquid flowing out from the chamber and the overflow from the rearmost chamber are combined, a discharge port is provided in the downstream space, and a liquid level detection device is provided to detect whether or not there is an overflow state in each of the chambers. A liquid flow meter equipped with a device.