JPH0452897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an airflow passage inserted in a direction transverse to an electrically heated heating wire in a thermoelectric anemometer that measures local velocity in an airflow.

Conventionally, this type of thermoelectric anemometer was developed in Japanese Patent Application Laid-open No.
As shown in Publication No. 79258, a high-temperature contact for measuring wind speed has an electrically heated heating wire stretched vertically on top of the base and has the same temperature as the heating wire, which is cooled according to the speed of the airflow. and a thermocouple with a low-temperature contact on the base for wind temperature correction that has the same temperature as the airflow,
A gate-shaped hood that covers the hot and cold contacts of the thermocouple and the heating wire is attached to the base, forming an air flow passageway with a rectangular cross-section that is inserted in the front-rear direction across the heating wire.

With this conventional product, it is possible to accurately measure the wind speed even when the direction of the airflow is deflected from the insertion direction of the rectangular cross-sectional airflow passage to the vertical direction along the heating wire or the horizontal direction perpendicular to the heating wire. I can do it.

However, the allowable deflection angle of airflow with small measurement error is about 35 to 40 degrees in the vertical direction and 25 degrees in the horizontal direction.
The temperature is around 30 degrees, so it is still not wide enough.

In addition, when the direction of the airflow is deflected diagonally from the insertion direction of the airflow passageway with a rectangular cross section in a diagonal direction midway between the vertical and horizontal directions, the airflow flowing into the airflow passageway with a rectangular crosssection will flow into the corner of the entrance of the passageway. The airflow is disturbed and the cooling of the heating wire by the airflow is promoted.
It is not possible to accurately measure the wind speed, and the permissible angle of deflection of the airflow in an oblique direction with a small measurement error is narrow.

An object of the present invention is to solve the conventional problems as described above.

The present invention comprises a thermocouple in which a heating wire that is electrically heated is stretched, and a high temperature contact that has the same temperature as the heating wire that is cooled according to the speed of the airflow, and a low temperature contact that has the same temperature as the airflow. However, in an electrothermal anemometer in which a hood is provided to cover the hot and cold contacts of the thermocouple and the heating wire, and an airflow passage is formed that extends in a direction transverse to the heating wire, the cross-sectional shape of the airflow passage is formed into a circular shape. This is an air flow passage structure for an electrothermal anemometer, characterized in that an introduction part having a circular cross section that becomes larger as it approaches the inlet is formed on the inlet side of the air flow passage.

In the present invention, the permissible deflection angle of the airflow in the vertical direction, the horizontal direction, or the diagonal direction with small measurement error is wide.

Next, examples of the present invention will be described.

First Example (See Figures 1 to 4) The thermoelectric anemometer with the air flow passage structure of this example is as follows:
As shown in Fig. 1, a phosphor bronze straight columnar column 3 and an inverted L-shaped column 4 are protruded from the center and leeward end of the tip surface 2 of an insulating square rod-shaped base 1, respectively. A heating wire 5 made of nichrome wire is connected between the tip of the protruding inverted L-shaped column 4 and the tip of the straight columnar column 3 located directly below, and the heating wire 5 to be electrically heated is made perpendicular to the tip surface 2 of the base. The first and second columns 6 and 7 of alumel are respectively protruded from the intermediate position of both columns 3 and 4 on the basic tip surface 2 and at the windward end, and one end is placed in the center of the heating wire 5. The other end of the first thermocouple wire 9 made of alumel, to which 8 was connected, is connected to the tip of the first support 6, and one end 10 of the first thermocouple wire 9 is connected to a position close to the heating wire connection end 8 of chlormel. The other end of the second thermocouple wire 11 is connected to the tip of the second support column 7.

Therefore, the first thermocouple wire 9 of Amel, the first support 6, the second support 7 and the second thermocouple wire 11 of Chromel constitute a thermocouple, and the heating wire is cooled according to the speed of the airflow. The thermocouples 6, 7, at the connection point 10 of the first and second thermocouple wires 9, 11 have the same temperature as the center of the thermocouples 5,
Connection point 1 between the second thermocouple wire 11 and the second pillar 7, which is used as a high temperature contact for measuring wind speed, and has the same temperature as the airflow.
2 serves as a low temperature contact point for correcting the wind temperature of the thermocouples 6, 7, 9, and 11. In addition, a power source for heating the heating wire 5 is connected between the ends of both the heating wire supports 3 and 4,
A thermocouple 6,
Wind speed indicators measuring the thermoelectromotive force of Nos. 7, 9, and 11 are connected.

At the tip of the base 1, as shown in FIGS. 1 and 2, each strut 3, 4, 6, 7
and a cylindrical hood 13 covering the heating wire 5 and each thermocouple wire 9, 11 is attached to form an airflow passage 14 with a circular cross section inserted in a direction perpendicular to the heating wire 5,
On the inlet side of the airflow passage 14, an introduction part 16 is formed which has a circular cross section in the shape of a morning glory or a bell mouth and whose diameter increases as it approaches the inlet 15.

The dimensions of each part are based on the length of the airflow passage 14.
11.5 mm, its diameter is 6 mm, the length of the introduction part 16 is 5.5 mm, the diameter of the inlet 15 is 15 mm, the height of the inverted L-shaped support 4 for the heating wire is 5 mm, and the heating wire The depth of No. 5 is 9.1 mm from entrance No. 15.

Experiment on the allowable deflection angle of airflow Using the thermoelectric anemometer of this example and the conventional thermoelectric anemometer with an airflow passage with a rectangular cross section described above,
The direction of the airflow maintained at a constant speed of about 10m/sec,
It is held parallel to the plane containing each support 3, 4, 6, 7 and the heating wire 5, and the direction of the airflow before entering the airflow path 14 is perpendicular to the heating wire 5. The deflection angle θ, which is shifted in the vertical direction, was set to each value, and the velocity of the airflow was measured for each value. Figure 3 shows the measurement results, with the vertical axis representing the measured wind speed V and the horizontal axis representing the deflection angle θ. Each is indicated by a dashed line.

As is clear from the diagram in Figure 3, the permissible vertical deflection angle of the airflow with small measurement error is about 35 to 40 degrees for the conventional product, while it is about 70 degrees for the invented product. Yes, inventions are more widespread.

In addition, the direction of the airflow maintained at a constant speed of about 10 m/sec is kept parallel to a plane perpendicular to the heating wire 5, and the direction of the airflow before entering the airflow passage 14 is changed from the direction of the airflow passage 14 to the heating wire 5. The deflection angle α shifted in orthogonal lateral directions was set to each value, and the airflow velocity was measured for each value. Figure 4 shows
The measurement results are shown in the same manner as in FIG.

As is clear from the diagram in Figure 4, the permissible horizontal deflection angle of the airflow is 25 to 25 in the conventional product.
Although it is about 30 degrees, the invention product has a temperature of 60 to 30 degrees.
It is about 80 degrees, and the invented product is wider.

In addition, in the electrothermal anemometer of this example, since the cross-sectional shape of the introduction part 16 of the airflow passage is circular, unlike in conventional products which are rectangular, the airflow flowing into the introduction part 16 of the airflow passage is disturbed. Since there are no corners, the wind speed can be accurately measured even when the airflow is deflected diagonally between the vertical and horizontal directions, and the allowable angle of deflection of the airflow in the diagonal direction is wide.

Second embodiment (see Figures 5, 3, and 4) The thermoelectric anemometer with the air flow passage structure of this example is as follows:
As shown in FIG. 5, an introduction part 16 with a circular cross section provided on the inlet 15 side of the airflow passage 14 is formed into a conical cylinder shape or a tapered hole shape with an opening angle of 60 degrees. Other points are the same as those in the previous example, so the same reference numerals are given to FIG. 5 and the explanation will be omitted.

For the thermoelectric anemometer of this example, experiments were conducted on the allowable deflection angle of the airflow in the same manner as in the previous example, and the measurement results shown in FIGS. 3 and 4 by the dashed line with half-black circles were obtained.

As is clear from the diagrams in FIGS. 3 and 4, the permissible angle of vertical or lateral deflection of the air flow in the thermoelectric anemometer of this example is as wide as in the previous example. Also, the allowable angle of deflection of the airflow in the diagonal direction is also wide as in the previous example.

In the thermoelectric anemometers of the above embodiments, if an airflow resistor such as a grid or net is installed at the outlet of the airflow passage, if there is an object that disturbs the airflow near the outlet of the airflow passage, the airflow turbulence does not spread into the airflow path, allowing accurate measurement of wind speed.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinal side view of the air flow passage structure of a thermoelectric anemometer according to the first embodiment of the present invention, and FIG. 2 is a front view of the same air flow passage structure. Figure 3 is a diagram showing the relationship between the measured wind speed V and the deflection angle θ in the vertical direction of the airflow in the invention and the conventional product, and Figure 4 is a diagram showing the relationship between the measured wind speed V and the horizontal direction of the airflow in the invention and the conventional product. FIG. 3 is a diagram showing the relationship of the deflection angle α to FIG. 5 is a partially vertical side view of the airflow passage structure of the thermoelectric anemometer according to the second embodiment of the present invention. 5: Heating wire, 6, 7, 9, 11: Thermocouple, 1
0: High temperature contact, 12: Low temperature contact, 13: Hood,
14: Airflow passage, 15: Inlet, 16: Introduction section.

Claims (1)

[Claims] 1. A thermoelectric device in which a heating wire that is electrically heated is stretched, and a high temperature contact that has the same temperature as the heating wire and a low temperature contact that has the same temperature as the air flow is provided. In an electrothermal anemometer in which a hood is provided to cover the high-temperature and low-temperature contacts of the thermocouples and the heating wire, and an airflow passage is formed that extends in a direction transverse to the heating wire, the cross-sectional shape of the airflow passageway is circular. An air flow passage structure for an electrothermal anemometer, characterized in that an introduction part having a circular cross section that becomes larger in diameter as it approaches the inlet is formed on the inlet side of the air flow passage.