JPH09269334A - Measuring apparatus for gentle wind speed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which, when the flow velocity of a very small wind, a gas or the like flowing inside a conduit is measured, the flow velocity can be measured with good accuracy even under a very small flow velocity condition and which is excellent in portability and simplicity. SOLUTION: An upper column 2 is fixed to the upper part of a horizontal shaft 3 which is arranged at right angles to the flow direction of a gas, an upper-part plate 1 is attached to its end part in such a way that the thickness direction of the plate is directed to the flow of the gas, a lower column 4 is fixed to the lower part of the shaft 3, and a lower-part plate 5 whose thickness direction is directed at right angles to the flow of the gas is attached to its end part in such a way that the drag of the flow becomes maximum. Then, the weight of the lower-part plate 5 is constituted so as to be a little heavier than the weight of the upper-part plate 1, and the length of the upper-part column 2 is formed to be identical to that of the lower-part column 4. When the shaft 3 is turned, the angle od rotation of the shaft is detected by a potentiometer 7 which is installed at the end of the shaft, and a flow velocity is found according to the relationship between a precertified flow velocity and the angle of rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring the flow velocity of a gas such as a minute wind or gas flowing in a pipe.

[0002]

2. Description of the Related Art Conventionally, a Pitot tube or a hot wire anemometer has been mainly used as a simple device for measuring the flow velocity of gas flowing in a pipe. Further, ultrasonic velocity meters and laser velocity meters are also used for velocity measurement. (For example, as an example,
See 2-192260. )

The principle of measuring the flow velocity of a gas using a Pitot tube is to obtain the dynamic pressure from the difference between the total pressure of the fluid and the static pressure, and then to obtain the flow velocity. When the flow of gas hits the energized wire, the wire is cooled and the electrical resistance changes.

Further, the ultrasonic velocimeter and the laser velocimeter are large-scaled devices, have a difficulty in portability and handling, and are less utilized.

[0005]

By the way, in the gas flow velocity measuring device using the Pitot tube among the conventional techniques as described above, the dynamic pressure is very small when a minute flow velocity of 0.1 m / s or less is measured. However, the value becomes less than the error of the measuring instrument, which causes a problem that the Pitot tube cannot be used.

Also in the case of a measuring device using a hot-wire anemometer, the amount of heat dissipated by a fluid becomes extremely small under a very small flow rate, and therefore the linearity between the voltage and the flow rate cannot be maintained.
There is a problem that it is difficult to measure the flow velocity accurately.

The present invention solves each of the problems of the conventional device described above and enables measurement of the flow velocity even under a minute flow velocity condition.
Moreover, it is an object of the present invention to provide a new flow velocity measuring device which is excellent in portability and convenience.

[0008]

As a structure for achieving the above-mentioned object, a fine wind velocity measuring device of the present invention comprises upper struts of equal length above and below a shaft which is orthogonal to the flow of gas and arranged horizontally. And the lower stanchions are integrally erected vertically in the direction perpendicular to the axis. At the upper end of the upper stanchions, the wind direction is reduced by directing the plate thickness direction to the gas flow so that the drag force of the flow is minimized. Attached to the lower strut, and at the lower end of the lower strut, a flat plate whose thickness direction is oriented at right angles to the flow of gas so that the drag force of the flow is maximized is attached. Is configured to be slightly heavier than the weight of the flat plate attached to the upper column side, and a potentiometer for detecting a rotation angle of the shaft is further provided at one end of the horizontally arranged shaft.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of an example of the slight air velocity measuring device of the present invention, FIG. 2 is a front view of the same device, FIG. 3 is a conceptual diagram showing the balance of moments applied to each component of the device, and FIG. 4 is the entire device. It is a perspective view.

In these drawings, 1 is an upper plate, 2 is an upper column, 3 is a horizontal axis, which is perpendicular to the upper side of a horizontal axis 3 arranged orthogonally to the gas flow direction shown by the arrow in FIG. The upper strut 2 is vertically fixed in the direction, and the upper plate 1 attached to the tip of the upper strut 2 is arranged with the thickness direction of the plate oriented with respect to the gas flow as shown in FIG. It is set up.

Thus, the drag force of the flow is minimized.

Reference numeral 4 denotes a lower column vertically erected and fixed toward the lower side of the horizontal shaft 3. At the lower end thereof, as shown in FIG. 4, the plate thickness direction is set so as to maximize the drag force of the flow. A lower plate 5 oriented perpendicular to the flow is attached.

Then, the length L _u3 of the upper support 2 from the shaft 3
The length L ₁₃ of the lower support column 4 from the shaft 3 is equal to the length.

It should be noted that d ₁ is the thickness of the lower plate 5, d ₂ is the thickness of the upper plate 1, L _u2 is the lateral width of the upper plate 1, L _u1 is the height of the same plate, and L _l2 is the lower plate 5. The width, L ₁₁ indicates the height of the plate.

The weight of the lower plate 5 attached to the tip of the lower support column 4 is set to be slightly heavier than the weight of the upper plate 1 attached to the upper part of the upper support column 2.

Reference numeral 6 denotes a support member disposed near both sides of the horizontal shaft 3, and the support member 6 supports the horizontal shaft 3 axially.

A potentiometer 7 is attached to one end of a horizontally arranged shaft 3, and the potentiometer detects the rotational angle of the shaft.

Next, the operation of the above device will be described.
When a flow such as wind or gas exists in the pipeline, moments about the axis 3 are generated on the upper and lower flat plates 1 and 5 due to the force of gravity and the drag force of the flow.

Since the flow drag acts more strongly on the lower flat plate 5, a moment for rotating the shaft 3 is generated by the drag.

On the other hand, since the weight of the lower flat plate 5 is extremely slight but heavier than that of the upper flat plate 1, strong gravity acts on the lower flat plate 5 to generate a moment that hinders the rotation of the shaft 3.

Therefore, since the shaft 3 rotates so that the above two moments are balanced, this rotation angle is derived by the potentiometer 7 provided at the shaft end, and the flow velocity is obtained in accordance with the relation between the flow velocity and the rotation angle which has been verified in advance. It is a thing.

FIG. 3 is an explanatory view showing the balance of the moments about the axes applied to the respective members, and the operation of the present invention will be described in more detail with reference to the drawing.

In FIG. 3, G _l is the gravity applied to the lower plate 5, m _Gl is its moment, D _l is the flow drag force applied to the lower plate 5, m _Dl is its moment, and G _u is the upper plate 1.
Gravity, m _Gu is the moment, D _u is the upper plate 1
The flow drag force, m _Du, is the moment.

If the clockwise moment is positive, the positive and negative moments are equal, so the positive moment, that is, (m _Gl
+ M _Du ) and the negative moment (m _Dl + m _Gu ) are equal, the moment around the axis is m _Gl −m _Dl −m _Gu + m _Du = 0
Becomes

Here, the thickness of the upper plate 1 and the lower plate 5,
If d ₂ and d ₁ are sufficiently small compared to other dimensions,

[0026]

[Equation 1]

It can be assumed that

Therefore, the moment is (m _Gl −m _Gu ) −m _Dl
= 0.

Here, the moment is calculated using the dimensions of each member defined in FIGS. 1 and 2 as follows.

[0030]

[Equation 2]

[0031]

(Equation 3)

[0032]

(Equation 4)

Here, P ₁ is the density of the lower member, g is the acceleration of gravity, P ₂ is the density of the upper member, P _a is the density of the fluid, u is the flow velocity, and C _d is the resistance coefficient.

As an example, the lengths of the columns 2 and 4 are 10
cm, the lower plate 5 and the upper plate 1 were made of cedar (density = 0.40 g / cm ³ ) and their respective dimensions were L _l1
= 10.05 cm (the lower member is made slightly heavier) L _l2 = L _u1
= L _u2 = 10 cm and d ₁ = d ₂ = 0.1 cm,
The inclination θ of this measuring instrument is 1 in the air flow of 0.1 m / s
It becomes 3.6 °.

However, since the moment due to the drag force of the upper plate is ignored in the above calculation, the inclination θ is 13.6.
It is considered that the upper and lower members are 100 times different in thickness in the direction toward the wind, so the moment due to the drag force of the upper member is sufficiently small. The device sufficiently performs its function even at a low wind speed of 0.1 m / s.

When aluminum is used as a member,
The dimensions of the respective parts _{L l1 = 10.02cm, L l2 =} L u1 = L u3
= 10 cm and d ₁ = d ₂ = 0.05 cm, θ becomes 10.2 degrees, and this also sufficiently exhibits its function.

[0037]

As described above, the slight air velocity measuring device of the present invention has the following effects. (1) Since the difference in the drag force of the flow applied to the flat plates set above and below the measuring instrument and the minute difference in weight between the upper and lower flat plates are used,
It is possible to measure with a certain degree of accuracy even at a slight wind speed of about 0.1 m / s.

(2) Since the device has a very simple structure, it is excellent in portability and convenience, and it is difficult to install it with a conventional laser velocimeter or ultrasonic velocimeter (for example, in the field of a power plant). It is possible to measure the flow even in the pipe).

[Brief description of drawings]

FIG. 1 is a side view of an example of a slight air velocity measuring device of the present invention.

FIG. 2 is a front view of the same device.

FIG. 3 is a conceptual diagram showing a state of balance of moments applied to each member in the same apparatus.

FIG. 4 is an overall perspective view of the same device.

[Explanation of symbols]

 1 Upper plate 2 Upper strut 3 Shaft 4 Lower strut 5 Lower plate 6 Supporting material 7 Potentiometer

Claims (1)

[Claims] 1. An upper strut and a lower strut of equal length are vertically provided integrally with each other vertically above and below a shaft which is orthogonal to the flow of gas and is horizontally arranged. At the upper end of the plate, a flat plate with a reduced wind-receiving area with the thickness direction of the plate facing the gas flow is installed to minimize the flow drag force.
Further, a flat plate whose thickness direction is perpendicular to the gas flow is attached to the lower end of the lower strut to maximize the flow drag force, and the weight of the lower strut side flat plate is set to the upper strut side. A slight wind velocity measuring device characterized in that it is constructed to be slightly heavier than the weight of the attached flat plate, and further provided with a potentiometer for detecting the rotation angle of the shaft at one end of the horizontally arranged shaft.