JPH0814958A - Whistle-type flowmeter - Google Patents

Abstract

PURPOSE:To provide a whistle-type flowmeter in which a linear proportionality range for the flow rate of a flowing fluid and for the oscillating frequency of a whistle sound is expanded as far as possible and which can measure a flow rate in a wide range from a low-flow-rate region up to a high-flow-rate region. CONSTITUTION:A whistle-type flowmeter is provided with a sound-generating unit 10, which is provided with a mouthpiece if into which a fluid flows, with an acoustic hole 1b through which a jet stream from the mouthpiece is passed and with a cavity by which the jeat stream gives a fluid sediment a rotating and vibrating motion, with a sound-collecting means 2 which collects a sound generated by the sound-generating unit 10, with a filter means 3 which makes the fundamental-frequency component of the generated sound by the sound- generating unit 10 out of an output-signal frequency component pass from the sound-collecting means, with a frequency detection means 5 which detects the frequency of the fundamental frequency component and with an arithmetic means 6 which operates the flow rate of the fluid on the basis of the frequency of the fundamental frequency component by means of a relational expression between a predetermined flow rate and a predetermined frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a whistle type flow meter for measuring the flow rate of a fluid such as a gas or a liquid by modifying a whistle structure of a physical education whistle type.

[0002]

2. Description of the Related Art Conventionally, many flowmeters for measuring the flow rate of gas or liquid are known, and they are classified according to the principle, structure or use. For example, a volumetric flowmeter such as a turbine flowmeter incorporates a movable part such as a rotor and a piston, and a fixed volume of fluid is discharged in one cycle of the movable part from a measurement space formed by the movable part and a case. The flow rate can be known by counting the number of cycles of the movable part. On the other hand, when an electromagnetic flowmeter applies a magnetic field at right angles to the flow direction of a conductive fluid, an electrode placed at a position orthogonal to both the flow direction of the fluid and the magnetic field is proportional to the flow velocity and the strength of the magnetic field. Since electric power is generated, if the strength of the magnetic field is kept constant, an electromotive force proportional to the flow velocity is obtained, and since this flow velocity is proportional to the flow rate,
The flow rate can be measured. As described above, there are an acoustic flowmeter (including an ultrasonic flowmeter), a heat flowmeter, and a throttle flowmeter using an orifice as a type of flowmeter having no movable part in the flow path. However, since the positive displacement flowmeter has a movable portion, flow resistance of the fluid is generated, there is a limit to downsizing, and it is difficult to deal with a failure.
Other flow meters also have their own drawbacks.

[0003]

In the whistle of the physical education whistle type, the flow rate is proportional to the sound emission frequency in the low flow rate range.
By utilizing this phenomenon, a small and highly reliable whistle type flow meter of physical education, which has a simple structure with no moving parts and can measure the flow rate of even non-conductive fluid, will be developed. Became.

FIG. 10 is a block diagram of a conventional whistle type flow meter.

This whistle type flow meter measures the flow rate of gas. A sounding unit 1 having a whistle structure is connected in the middle of the gas pipelines 10a and 10b, and when gas is flowing through the gas pipelines. A microphone 2 for collecting the sound emitted by the sound generation unit 1 is attached to a part of the signal, and a component outside the measurement target range included in a signal output from the microphone 2 is removed through a high cut filter 3, and the signal is subjected to hysteresis (see FIG. 5). The waveform is shaped by comparing with a constant value by the comparator 4 to which the waveform (b) shown by the broken line is applied, and the pulse signal output from the comparator 4 is counted by the counter / timer 5 to obtain the frequency. Based on this, the flow rate is calculated from the predetermined relational expression in the flow rate calculation statement 6, and the gas flow rate of the calculation result is displayed on the display unit 7.

FIG. 9 is a perspective view showing a schematic structure of a sounding unit used in a conventional whistle type flow meter of a physical education whistle type.

The sounding unit 1 of FIG. 9 is a whistle of a physical education whistle type, and has side walls 1e on both sides (see FIG. 5).
Are omitted. The sounding unit 1 includes a horizontally long inlet 1a for introducing gas flowing in from the gas pipeline 10a, a mouthpiece 1f including a gas flow path continuous to the inlet 1a, and an outlet for discharging gas to the gas pipeline 10a, that is, an acoustic hole 1.
b, a cavity 1c, and an edge 1d, which is a resin-made molded product, the inlet 1a and the cavity 1c communicate with each other, and the edge 1d is inclined to the acoustic hole 1b in a direction counter to the gas inflow direction. Is formed. Cavity 1
A hole is made in the outer wall 1e of c, and the microphone 2 is airtightly attached thereto.

FIG. 4 is a dimensional diagram of a physical education whistle type whistle used in the experiment.

The whistle type flow meter of the physical education whistle type as shown in FIG. 4 has three pronunciation phenomena of Helmholtz resonance, edge tone and cavity tone. Therefore, the phenomenon that the loudest sound is emitted for a certain flow rate is detected as the whistle sound. In this conventional whistle type flow meter, the relationship between the flow rate and the frequency of sound changes at a certain flow rate because the main sounding phenomenon is different between the high flow rate side and the low flow rate side on both sides of this boundary point. The frequency of whistle noise is linearly proportional to the flow rate in the range of 200 L / H to 700 L / H, and 800 L / H
When the above is applied, the increase rate of the whistle sound transmission frequency becomes gentle, and becomes substantially constant at higher flow rates. The former low whistle sound frequency is linearly proportional to the flow rate. Therefore, when trying to widen the measurement range of this flow meter, the linear range is expanded by enlarging the main body of the flow meter, or another oscillating element corresponding to the flow rate is incorporated by incorporating a small ball into the flow meter. You will have to add it. Increasing the size of the main body is against the miniaturization of the flowmeter, and incorporating the small sphere is contrary to not having a movable part in the flow path of the flowmeter, and incorporating the small sphere. It is necessary to properly use the two types of calculation methods, that is, the case where it is performed and the case where it is not built-in, depending on the conditional branch. In addition, both methods result in some deterioration of the signal-to-noise ratio in the original measurement range.

The present invention has been made in view of the above points, and has a small and simple structure, does not have a small ball inside, and expands the linear proportional range of the flow rate of flowing fluid and the transmission frequency of whistle noise as much as possible. It is an object of the present invention to provide a whistle type flow meter capable of measuring a wide range of flow rate from a low flow rate range to a high flow rate range.

[0011]

In order to achieve the above object, the present invention has a mouthpiece into which a fluid flows, an acoustic hole through which a jet stream from the mouthpiece passes, and a cavity in which the jet stream imparts rotational oscillating motion to a fluid stagnation. And a sound collecting unit that collects sounds generated by the sound generating unit, and a filter that passes the fundamental frequency component of the sound generated by the sound generating unit among the output signal frequency components from the sound collecting unit. Means, frequency detecting means for detecting the frequency of the fundamental frequency component, and computing means for computing the flow rate of the fluid based on the frequency of the fundamental frequency component from a predetermined relational expression between the flow rate and the frequency. Characterize.

Further, according to the present invention, the sounding unit is housed in a box in a hermetically sealed manner, the mouthpiece of the sounding unit projects from the box, and a fluid outlet for discharging the sounding unit is provided on the outer wall of the box. Is characterized by.

The present invention is also characterized in that a fluid inflow conduit is connected to the mouthpiece of the sounding unit, and the measured fluid that has passed through the acoustic hole is discharged into the atmosphere.

[0014]

According to the present invention, the edge tone is suppressed by removing the edges from the conventional whistle type flow meter of the physical education whistle type, and the generation of the Helmholtz resonance sound is suppressed by expanding the acoustic hole. The cavity tone that is not affected becomes remarkable, and the flow rate range in which the flow rate and the frequency of the cavity tone are proportional is three times or more than the range in which the edge tone of the conventional whistle is observed, so that a wide range of flow rate can be measured. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 5 is an exploded view of the basic elements of the physical education whistle type whistle used in the experiment. FIG. 8 is a conceptual diagram of simple vibration of fluid stagnation in a cross section orthogonal to a surface formed by the acoustic holes.

The frequency of the sound generated when the whistle is blown lightly seems to be proportional to the blowing amount. The inventor of the present invention searches for a new frequency output type flow meter in consideration of this fact and separates and extracts from the whistle elements that generate only a sound having a frequency linearly proportional to the flow rate. Whole whistle, (b) edge element,
(C) It was decomposed into a shape having a basic element of the cavity element (see FIG. 5), and the role of each element played in the generation of sound was examined by an experiment. As a result, it was discovered that the shape having the cavity element (c) exhibits the most excellent characteristics as a flow meter in terms of rangeability, stability, and linearity. This is because the component of the motion of the fluid stagnation in the cavity, which is orthogonal to the surface formed by the acoustic holes, is due to the simple oscillation principle of simple oscillation (see Fig. 8) due to the restoring force of the jet flow distorted by the stagnation air. it is conceivable that.

As shown in the center view of FIG. 8, when the jet from the mouthpiece passes through the upper part of the acoustic hole, this fluid comes into contact with the cylindrical fluid stagnation in the cavity and gives it a rotational movement. As shown in the upper diagram of FIG. 8, when the fluid stagnation moves upward, the streamline of the fluid passing through the upper portion of the acoustic hole is deformed upward. At this time, the vertical component of the dynamic pressure of the flow acts as a restoring force that pushes down the mass. As shown in the lower diagram of FIG. 8, when the mass is pushed down into the cavity, the streamline is also drawn downwards due to the principle of continuity. The deformed streamline tries to pull up the mass by a force proportional to the displacement of the mass. In this way, the three states of FIG. 8 are repeated.

FIG. 3 is a graph showing the characteristics of the sound based on the cavity element of the physical education whistle type whistle investigated this time.

In the graph of FIG. 3, the horizontal axis represents the frequency of sound (unit:
Hertz), and the vertical axis indicates gas flow rate (unit: liter / hour) and microphone output voltage (unit: decibel volt)
Indicates. From this graph, it can be seen that the rotational vibration sound of the fluid stagnation based on the cavity element, that is, the cavity tone, has a frequency linearly proportional to the flow rate in a wide range of the flow rate of 400 to 2000 liters / hour. Also, from the frequency distribution of the output voltage of the condenser microphone used for sound detection in this experiment, it is found that the cavity tone does not contain harmonic components and has a single peak frequency characteristic. These characteristics are favorable characteristics for the flow meter.

The present invention adopts this cavity tone characteristic in a flow meter. In other words, the present invention suppresses the sound as a normal whistle, that is, the Helmholtz resonance sound and the edge tone by adopting the structure in which the edge is deleted from the conventional physical education whistle type whistle, and the oscillation frequency of the cavity tone is reduced. It is a flow meter to measure.

FIG. 1 is a block diagram of a whistle type flow meter of the present invention. FIG. 2 is a diagram showing a schematic configuration of a sounding unit used in the whistle type flow meter of the present invention. FIG. 6 is a graph showing the relationship between each sounding phenomenon and the generated frequency when the strength of blowing the gas into the whistle alone is changed in three stages. FIG. 7 is a graph showing the characteristics of the main generated sound of the whistle.

As shown in FIG. 6, the whistle of the physical education whistle type is (A) Helmholtz resonance, (B) edge tone,
(C) It has three pronunciation phenomena of cavity tone. Therefore, the phenomenon that the loudest sound is emitted for a certain flow rate is detected as the whistle sound. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents microphone output voltage.

As described above, in the conventional whistle type flowmeter, the relationship between the flow rate and the sound frequency changes at a certain flow rate, and the main sounding phenomenon on both sides of this boundary point is the high flow rate side (A). This is because it is different from the low flow rate side (B) (see FIGS. 6 and 7). In view of this, in the present invention, as shown in FIG. 2, the conventional edge element is removed at a position where the inflowing gas blows directly above it, and the acoustic hole is enlarged so that the effect of the cavity 1c becomes remarkable.

The embodiment of the present invention in FIG. 1 is described as measuring the gas flow rate in various fluids. The main part is a sounding unit 10 having a whistle structure. A cubic box 11 is connected in the middle of the gas pipelines 10a and 10b, and the sounding unit 10 is housed in the box 11 in a sealed state. The mouthpiece 1f of the sound producing unit 10 projects from the front wall of the box 11, and the gas pipeline 10a is connected to this front wall. The gas pipeline 10a is connected to, for example, a rear end (outlet end) of a chimney, an exhaust pipe, or the like. Therefore, the box 11 is not necessary when measuring the exhaust volume at the smoke outlet. That is, the box 11 does not necessarily have to be attached. Further, an outlet for the gas emitted from the sounding unit 10 is provided on the upper wall of the box 11, and the gas pipeline 10b is provided at this outlet.
Is connected. However, when the box 11 is not attached, the gas pipeline 10b is directly connected to the atmosphere without being connected.

The sounding unit 10 shown in FIG. 2 is shown with the side walls 1e (shown in FIG. 1) on both sides omitted for clarity. This pronunciation unit 10
As described above, the gymnastics whistle-type whistle (see FIG. 9) is modified as described above so that the cavity tone appears remarkably over the entire measurement range. It is a resin molded product composed of three elements, 1b and a cavity 1c. The mouthpiece 1f includes a gas inlet 1a for allowing gas to flow in from the gas pipe 10a, and a gas passage continuous with the gas inlet 1a having a horizontally long rectangular cross section. The jet from the mouthpiece 1f passes through the upper portion of the acoustic hole 1b in the direction of arrow A. The acoustic hole 1b is formed on an extension of the gas flow path of the mouthpiece 1f. The cavity 1c is a cylindrical body having substantially the same width as the gas flow path of the mouthpiece 1f, and is continuous with the lower side of the acoustic hole 1b. The jet flowing from the acoustic hole 1b imparts a rotational movement in the direction of arrow B to the fluid stagnation inside the cavity 1c. As can be seen from FIG. 2, there is no conventional edge.
The fluid obtained by rotating the fluid stagnation of the cavity 1c is discharged from the acoustic hole 1b into the box 11 in the direction of arrow C.

A hole is formed in the side wall 1e of the sound producing unit 10, and the microphone 2 is hermetically connected to the hole. The microphone 2 is connected to a high cut filter 3, a comparator 4, a counter / timer 5, a flow rate calculator 6 outside the side wall 10c of the box 11, and further connected to a display 7.

Gas is emitted from the gas line 10a into the sound generation unit 1
0, flows through the sounding unit 10, and passes through the gas pipeline 10
The microphone 2 collects the sound emitted by the sound generation unit 10 when the sound is emitted from b. A comparator 4 in which a component outside the measurement target range included in the signal output from the microphone 2 is removed through the high-cut filter 3 and the signal is subjected to hysteresis (shown by a broken line in the waveform (b) shown in FIG. 1) is applied. The pulse signal output from the comparator 4 is shaped by comparing with a fixed value by the counter / timer 5
The frequency is calculated by counting with, the flow rate is calculated from the predetermined relational expression in the flow rate calculation record 6 based on this frequency, and the gas flow rate of the calculation result is displayed on the display unit 7.

[0029]

As described above, the whistle type flow meter of the present invention has a sound generating unit as a main constituent element, which includes a mouthpiece into which a fluid flows, an acoustic hole for discharging the fluid, and a cavity in which the fluid stagnates. Since the oscillation frequency of the sound due to the vibration of stagnant air, which is proportional to the flow rate in the cavity, is used for measuring the flow rate, the linear proportional range between the flow rate of the fluid passing through this whistle type flow meter and the sound transmission frequency is conventionally The flow rate can be measured over a wide range by expanding the flow rate by 3 times or more, and there is no movable part in the flow path, so that a very small size and simple structure can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a whistle type flow meter of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a sounding unit used in the whistle type flow meter of the present invention.

FIG. 3 is a graph showing characteristics of cavity tones based on cavity elements.

FIG. 4 is a dimensional diagram of a physical education whistle type whistle used in an experiment.

FIG. 5 is an exploded view of basic elements of a physical education whistle type whistle used in an experiment.

FIG. 6 is a graph showing the relationship between each sounding phenomenon and the generated frequency when the strength of blowing the gas into the whistle alone is changed in three stages.

FIG. 7 is a graph showing characteristics of a main generated sound of a whistle.

FIG. 8 is a conceptual diagram of simple vibration of fluid stagnation in a cross section orthogonal to a surface formed by an acoustic hole.

FIG. 9 is a perspective view showing a schematic configuration of a sounding unit used in a conventional whistle type flow meter of a physical education whistle type.

FIG. 10 is a block diagram of a conventional whistle type flow meter.

[Explanation of symbols]

 1a Gas inlet 1b Acoustic hole 1c Cavity 1e Side wall 1f Mouthpiece 2 Microphone 3 High-cut filter 4 Comparator 5 Counter / timer 6 Flow rate calculation record 7 Indicator 10 Sounding unit 10a Gas line 10b Gas line 10c Side wall 11 Box

Claims (7)

[Claims] 1. A sounding unit provided with a mouthpiece into which a fluid flows, an acoustic hole through which a jet flow from the mouthpiece passes, and a cavity for giving a rotational oscillating motion to the fluid stagnation, and the sounding unit is generated by the sounding unit. Sound collecting means for collecting a sound, filter means for passing a fundamental frequency component of a sound generated by the sounding unit among frequency components of an output signal from the sound collecting means, and frequency detection for detecting a frequency of the fundamental frequency component A whistle type flow meter, comprising: a means for calculating the flow rate of the fluid based on the frequency of the fundamental frequency component from a predetermined relational expression between the flow rate and the frequency. 2. The sounding unit is hermetically housed in a box, a mouthpiece of the sounding unit protruding from the box is connected to a fluid inflow conduit, and a metered fluid is placed on an outer wall of the box. The whistle type flow meter according to claim 1, wherein a pipe line for discharging is attached. 3. The whistle type flow meter according to claim 1, wherein a fluid inflow conduit is connected to the mouthpiece of the sounding unit to discharge the measured fluid that has passed through the acoustic hole into the atmosphere. . 4. The whistle type flow meter according to claim 1, wherein the sound collecting means is attached in the vicinity of the cylindrical cavity. 5. The whistle type flow meter according to claim 1, wherein the sound collecting means is attached to the box without impairing airtightness. 6. The whistle type flow meter according to claim 1, wherein the frequency detecting means is a counter / timer for converting the output signal from the sound collecting means within a predetermined time into pulses and counting. 7. The whistle type flow meter according to claim 1, wherein the frequency detecting means is a peak detector.