JP2520188Y2 - Fluidic flow meter - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention ejects a gas flowing into a gas inlet from a jet nozzle toward a target located in a central portion downstream of the jet nozzle through a gas inlet chamber formed adjacent to the gas inlet. The present invention relates to a fluidic flow meter that has a fluidic oscillator that generates fluid vibration having a frequency proportional to a flow rate, and detects the fluid vibration to measure a gas flow rate, for example.

[0002]

2. Description of the Related Art Conventionally, a fluidic oscillator having a structure shown in FIG. 7 has been generally used as a fluidic oscillator of this type. FIG. 7 shows a state in which the lid of the fluidic oscillator is removed for easy understanding. On the case body 1 of the oscillator, a gas inlet 1a to which a gas inflow pipe is connected and a gas outlet 1b to which a gas outflow pipe is connected are formed so as to be connected in the middle of the gas pipe.

The case body 1 also has a gas inflow chamber 1c formed adjacent to the gas inflow port 1a and a gas outflow port 1b.
A gas outflow chamber 1d formed adjacent to the gas outflow chamber 1d is formed between the gas inflow chamber 1c and the gas outflow chamber 1d. A jet nozzle 1e for jetting to 1d is formed. A target 1f is provided in the gas outflow chamber 1d so as to be located at the center downstream of the ejection nozzle 1e.

In the above structure, the gas flowing from the gas pipe into the gas inlet 1a as shown by the arrow is the gas inflow chamber 1
It is ejected from the ejection nozzle 1e to the gas outflow chamber 1d through c. The gas ejected from the ejection nozzle 1e becomes a flow along the target 1f due to the Coanda effect. The pressure due to this flow is transmitted to the portion of the jet nozzle 1e to switch the flow. This switching occurs alternately and causes fluid vibration having a frequency proportional to the flow rate. This fluid vibration is detected by an arbitrary sensor and converted into an electric signal, so that the flow rate can be calculated by processing the electric signal. Further, since this fluidic oscillator is small and has no moving parts, it is extremely effective in obtaining a flowmeter having excellent durability.

[0005]

By the way, the fluidic oscillator is constructed on the premise of a two-dimensional flow field,
It is desirable that the jet flow be a perfect two-dimensional flow in order to fully exhibit its performance. However, in reality, the flow passing through the pipe is slow in the outer portion near the wall and fast in the central portion due to the wall effect, so that the gas inflow chamber 1
There was a problem that the flow flowing into c became an unstable three-dimensional flow.

Therefore, this gas flow flows into the gas inflow chamber 1c in a turbulent state and reaches the target 1f through the ejection nozzle 1e while being turbulent, so that a fluidic oscillation assuming a two-dimensional flow field is generated. Has an unstable and irregular effect, and has a problem in obtaining desired performance as a flowmeter.

Therefore, in view of the above-mentioned conventional problems, it is an object of the present invention to provide a fluidic flowmeter in which the linearity of the relationship between the flow rate and the vibration frequency is improved.

[0008]

In order to solve the above-mentioned problems, the fluidic flow meter constructed according to the present invention ejects the gas flow introduced into the gas inlet through the gas inlet chamber formed adjacent to the gas inlet. Equipped with a fluidic oscillator that ejects fluid from a nozzle toward a target located in the center downstream of the nozzle to generate fluid vibration with a frequency proportional to the flow rate, and measures the fluid flow by detecting this fluid vibration. In the flowmeter, a pair of voids that are open to the gas inflow chamber are formed in the midstream portion of the gas flow in the gas inflow chamber by wall surfaces at positions facing each other on a line orthogonal to the gas flow, and the voids are formed. The downstream side of the opening edge of is projected into the gas inflow chamber more than the upstream side, and a part of the gas flow in the gas flow chamber is cut out so as to be guided into the void, by a vortex generated in the void. It is characterized in that so as to stabilize the flow of the gas flowing into the ejection nozzle through the serial gas inlet chamber.

[0009]

In the above structure, a pair of cavities are formed in the middle portion of the gas flow in the gas inflow chamber by opening to the gas inflow chamber at the wall surfaces at positions facing each other on a line orthogonal to the gas flow,
The downstream side of the opening edge of the void is projected into the gas inflow chamber more than the upstream side so that a part of the gas flow in the gas flow chamber is cut off and introduced into the void, and the gas inflows by the vortex generated in the void. Since the flow of the gas flowing into the ejection nozzle through the chamber is stabilized, when the gas flows into the gas inflow chamber, a part of the flow near the wall becomes a vortex, and this vortex causes the wall effect. The flow near the delayed wall surface is accelerated to make the gas flow two-dimensional. As a result, the unstable three-dimensional flow does not reach the target through the jet nozzle, and the unstable fluidization due to the fluidic oscillation assuming the two-dimensional flow field
There will be no irregular effects.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of an oscillator used in a fluidic flow meter according to the present invention, FIG. 1 is a top view with a lid removed, and FIG. 2 is a sectional view taken along line AA in FIG. The inside 2 is a lid. In these figures, the same parts as those described above with reference to FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the gas inflow chamber 11c is formed so as to have a wall surface which is a smooth curved surface continuous from the gas inflow port 1a toward the inlet of the ejection nozzle 1e. In the midstream portion of the gas flow in the gas inflow chamber 11c, there is formed a pair of voids 1g that are open to the gas inflow chamber 11c on the wall surfaces at positions facing each other on a line orthogonal to the gas flow. The opening edge 112c of the void 1g has a shape in which the downstream side projects into the gas inflow chamber 11c more than the upstream side, so that a part of the gas flow in the gas inflow chamber 11c is cut off and introduced into the void 1g. It has become.

With the above structure, when the disturbed gas flow from the gas pipe flows into the gas inflow chamber 11c, a part of the gas flow near the wall surface is taken into the void 1g by the opening edge 112c. As a result, a vortex is generated in the void 1g. The vortex comes into contact with the gas flow close to the wall surface at the opening of the vacant space 1g, and accelerates the flow near the wall surface, which is delayed by the wall effect of the gas pipe or the like, to bring the flow closer to the central portion. As a result, the stabilized gas flow reaches the target 1f through the ejection nozzle 1e.

FIG. 3 shows the relationship between the flow rate and the vibration frequency which are not in the proportional relationship of the fluidic flowmeter in which the void 1g is not formed. By forming the void 1g, FIG.
As shown in, the linearity is improved. 5 and 6 show the flow velocity of the gas flowing in the nozzle of the fluidic flowmeter with and without the formation of the void 1g × nozzle width / Reynolds number and vibration frequency represented by kinematic viscosity × The relationship with the Strouhal number represented by the nozzle width / flow velocity is shown. As is clear from FIG.
By forming the vacant space 1g, the Strouhal number can be kept constant over a wide range of Reynolds numbers.

[0014]

As described above, according to the present invention, the three-dimensional gas flow is generated by accelerating the outer flow causing the instability by the vortex generated in the void of the gas inflow chamber. Is stabilized, and the unstable three-dimensional flow does not reach the target through the jet nozzle, resulting in instability due to fluidic oscillation assuming a two-dimensional flow field.
Since there is no irregular influence, a fluidic flowmeter with improved linearity of the relation between flow rate and vibration frequency is obtained.

[Brief description of drawings]

FIG. 1 is a top view showing an embodiment of a fluidic flow meter according to the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a graph showing a flow rate-vibration frequency characteristic of a fluidic flow meter in which no void is formed.

FIG. 4 is a graph showing a flow rate-vibration frequency characteristic of the fluidic flow meter according to the present invention.

FIG. 5 is a graph showing a Reynolds number-Strouhal number curve of a fluidic flowmeter in which no void is formed.

FIG. 6 is a graph showing a Reynolds number-Strouhal number curve of a fluidic flow meter according to the present invention.

FIG. 7 is a top view showing an example of a conventional fluidic flow meter.

[Explanation of symbols]

 1a Gas inlet (gas inlet) 1e Jet nozzle 1f Target 11c Gas inflow chamber (gas inflow chamber) 1g Vacancy

Claims (1)

(57) [Scope of utility model registration request] 1. A frequency proportional to a flow rate of a gas flowing into a gas inlet is jetted from a jet nozzle toward a target located in a central portion downstream of the jet nozzle through a gas inlet chamber formed adjacent to the gas inlet. In a fluidic flowmeter that has a fluidic oscillator that generates a fluid vibration with, and measures the flow rate by detecting this fluid vibration, in a midstream part of the gas flow in the gas inflow chamber, on a line orthogonal to the gas flow. A pair of cavities that open to the gas inflow chamber are formed on the wall surfaces at positions facing each other, and the downstream side of the opening edge of the cavities projects into the gas inflow chamber more than the upstream side, and A part of the gas flow is cut out and introduced into the void, and the vortex generated in the void stabilizes the flow of the gas flowing into the ejection nozzle through the gas inflow chamber. Fluidic flowmeter according to claim.