JPS5985960A - Wind speed calibrating apparatus - Google Patents

Abstract

PURPOSE:To change only the wind speed in an apparatus by 1.5 times to 1/10 of the wind speed in a wind tunnel, by providing a calibrating apparatus in the wind tunnel at the same time, utilizing the wind tunnel itself for a wind blowing function and a temperature function, changing the opening degrees of banes provided on the exhausting side, selecting a screen, and adjusting the resistance of air at a metal wire net. CONSTITUTION:A square tube shaped main body forming an apparatus is formed into a tubular body having a total length of about 172cm by bonding three members at flange parts and horizontally supported by legs 17 which are vertically provided at the lower surface. At the flange parts, screen attaching parts 18 and 18, to which screens 20 comprising metal wire nets with a specified mesh are detachably coupled, are provided. In upper plates 4, which are contacted with said attaching parts, slits 19 and 19 for inserting the screens are provided. Several kinds of the screens 20 are manufactured by applying the metal wire nets 21 with the specified mesh on frame plates 22. A control panel 23 is connected to a geared motor 15 and a potentiometer 16. The geared motor 15 is rotated in the forward and reverse directions by a knob 24, and the opening degrees of right and left banes 5 and 6 are changed. The opening degrees are digitally displayed on a display plate 25. Thus the wind speed in the apparatus can be changed from about 1.5 times to 1/10 of the wind speed of a wind tunnel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus suitable for use in calibrating a hot wire anemometer.

When investigating the diffusion phenomenon of pollutants in the atmosphere through wind tunnel experiments, it is necessary to reproduce the wind direction, wind speed, topography, buildings, atmospheric stability, etc. in a wind tunnel similar to the actual phenomenon.

In this case, the measurement of wind speed is the most important thing, and wind speed measurement devices include pitot tubes, hot wire anemometers, thermistor anemometers, and laser anemometers, but the most widely used one is the hot wire anemometer. It is a total.

However, in principle, this hot wire anemometer is affected by temperature changes, and its characteristics tend to change over time. It needs to be calibrated.

This calibration is usually done by installing the hot-wire anemometer to be calibrated and the reference anemometer (mainly a Pitot tube) in a wind tunnel, and changing the wind speed in about five steps to compare the wind speed and the hot-wire anemometer in each case. The relationship between the outputs is determined, but since the lower limit of this calibration range cannot be lower than the minimum wind speed of the wind tunnel, this becomes difficult if the actual wind speed to be measured is lower than the wind speed of the wind tunnel. Also, when calibrating to include the effects of temperature changes, if the wind speed is changed at a certain set temperature, the control of the wind tunnel temperature control system will be disrupted, and the automatic adjustment mechanism will return the wind tunnel to the original temperature. It is not possible to calibrate in a wind speed range that requires a long time to recover.

For this reason, special wind tunnels designed for calibration, or calibration wind tunnels, have been developed, but these are generally not accurate enough and are extremely expensive to make, and calibration wind tunnels are There are disadvantages such as the need to reset the settings in order to proceed to the main experiment after completing the test.

On the other hand, the calibration device of the present invention is installed inside a normal wind tunnel and used in combination, and the wind tunnel itself is used for the air blowing function and the temperature function. By changing the opening degree of the vane installed in the side diffusion section,
In addition, by appropriately selecting the screen attached to the main body of the device and changing the air resistance of the wire mesh, by adjusting these, the wind speed inside the device can be increased from 1.5 times to 1/10 of the wind tunnel wind speed.
It can be changed up to.

An embodiment of the present invention will be explained with reference to the drawings. As shown in Figs. 1 and 2, the whole duct is made as a rectangular cylindrical main body with a square cross section, and the front end suction side 1, which is the contraction part, is slightly trumpet-shaped. The cross section of the rear end discharge side 2, which is the diffusion part, gradually expands, and as shown in Figure 3, the left and right plates 3, 3 are cut out from the middle, and the upper and lower parts are removed. Only the plate 4.4 is used, and the upper and lower plates 4.4 are extended to the left and right to form a fish house shape, and there are 2 left and right plates between the upper and lower plates 4, 4.
The vanes 5 and 6 are fixed to the front edge, and a single shaft 7.8 is inserted into the shaft support hole 9 provided in the upper and lower plates 4 and 4, respectively, and installed. It can be tilted left and right around 7 and 8.

An auxiliary flap 10.10, which is a rectangular plate curved into an arc, is attached to the rear edge of the conovane 5, 6 at a slight distance from the vane. Silicone rubber sealing pieces 11 are attached to both side edges and the parts of the left and right plates 3, 3 in contact with the vanes 5, 6 via mounting plates.
. . . are attached to each of the upper and lower plates 4,
4 and left and right plates 3° Prevents air leakage from the parts that touch the 3. Note that 12.12 is a connecting piece for preventing the upper and lower plates 4, 4 from expanding.

These vanes 5, 6 are mutually rotated via gears 13, 13 of equal size fixed to each of the longitudinal shafts 7, 8; The end thereof is connected to a geared motor 15 via a worm gear speed reducer 14, and the size of the discharge port can be changed by rotating the geared motor 15 in forward and reverse directions. and the vane 5 through the potentiometer 16 connected to the gear 13.
The opening degree of °6 is displayed.

Now, the prismatic cylindrical main body that forms the device of the present invention has a total length of approximately 172 cm by connecting three members at each flange.
A pillar 17 formed into a cylindrical body of rn and hung vertically on the lower surface...
It is designed to be installed horizontally through... The flange portion is provided with a screen mounting portion 18.18 into which a screen 20 made of a wire mesh of a predetermined mesh shown in FIG. 19.19 is transparent.

As shown in FIG. 4, several types of screens 20 are made by covering a frame plate 22 with a wire mesh 21 of a predetermined mesh size.

Furthermore, in FIG. 1, reference numeral 23 denotes an operation panel, which is connected to the geared motor 15 and the potentiometer 16 through conductive wires, and which rotates the geared motor 15 in forward and reverse directions using a knob 24' to rotate the left and right vanes 5°6. The opening degree is changed and the opening degree is digitally displayed on the display board 25.

The present invention uses the above-mentioned structure by appropriately changing the opening degree of the vanes 5 and 6 and the mesh of the screen 20. Next, a method of using the same will be explained.

[Preparation for Calibration] In Fig. 1, the side plates 3, 3 and the top plate 4 at the center of the measuring section can be removed by a width of about 20 crn. From this part, you will find the Pitot tube and platinum resistance thermometer for standard wind speed measurement, and the anemometer to be calibrated (hot wire wind speed). There is a hole for the cable to pass through.

[Calibration]

(1) Set the wind tunnel wind speed to the wind speed used in this experiment.

(2) Set the airflow temperature below the lowest temperature to be measured in this experiment. In the example of FIG. 6, it is 20C.

(3) The maximum wind speed inside the calibration device that should be measured in this experiment,
Change it in about 5 steps within the range that covers the lowest. The wind speed can be controlled either by using a mesh or by changing the opening degree of the vanes.

In the example shown in FIG. 6, five types of meshes are used to change the wind speed. The relationship between the output of the anemometer and the wind speed measured by the Pitot tube at each wind speed is illustrated as 20 in Figure 6.
It will look like a straight line at 21C.

(4) Change the airflow temperature in the wind tunnel and repeat without step (3). The airflow temperature setting in the wind tunnel is changed in about 5 steps within the range that covers the maximum and minimum temperatures to be measured in this experiment.

It is set in 5 levels: 40, 50, and 60C+.

(5) FIG. 6 illustrates the relationship between the wind speed and anemometer output obtained under each temperature condition using the airflow temperature as a parameter. When actually measuring wind speed, first measure the temperature, then find the relationship between the wind speed and anemometer output at that temperature by interpolation from Figure 6, and then find the wind speed that corresponds to the anemometer output. Become.

(6) In reality, the anemometer is attached to a sensor moving device called a traverse device along with a platinum resistance thermometer and a pitot tube, and moved outside the wind tunnel by remote control. After completing the calibration, the anemometer and the platinum resistance thermometer are moved outside the calibration device using a traverse device, and after being set at the desired measurement position, measurements are started. Move the calibration device outside the wind tunnel or to a location that does not interfere with this experiment.

The relationship between the opening degree of the vane and the wind speed inside the device is shown by the curve in Figure 5.
1 (wind tunnel wind speed 1.92 m/s).

By adjusting the opening degree of this vane, the wind speed inside the device can be changed from approximately 1.5 times the wind tunnel wind speed to 1/10. Also, the wind speed obtained by changing the resistance of the wire mesh is not included in Table 1.

Table 1 Types of wire mesh and wind speed at measuring point (wind tunnel wind speed 21r11/S) According to Table 1, the wind tunnel wind speed can be varied from 1.5 times to 115 times by changing the resistance of the wire mesh.

Next, the wind speed inside the device is 1 of the external wind speed (U out ).
．． Table 2 shows the wind speed distribution in each state showing 5 times, 0.5 times, and 0.25 times.

According to Table 2, the variation in the wind speed inside the device is suppressed to approximately ±2 inches or less for all wind speeds, and it can be said that the uniformity of the internal wind speed is also a satisfactory performance.

In Table 2, Z is the distance in the vertical direction from the center coordinates (0, 0) of the longitudinal section of the measuring section (plane perpendicular to the wind speed direction), and Y is the distance in the horizontal direction. The position of the measurement unit is expressed by coordinates (x, y). The relationship between wind speed and vane opening force is as follows.

Uout 1.923-Ul, 5
2.954 25UO,s 1.
575 10U0.26 o, 500
Table 3-2 (Uniformity of wind speed in the measuring section) FIG. 6 shows an example of calibration of a hot wire anemometer using the device of the present invention. This figure shows that the anemometer's characteristics change significantly with changes in temperature. In addition, in Fig. 6, the horizontal axis V "is the square root of the wind speed ((rrfs)"
), and the vertical axis E2 is the anemometer output squared ((v
ott): indicates l.

[Brief explanation of drawings]

Figure 1 is a side view, Figure 2 is a rear view, Figure 3 is an exploded perspective view of the vane, Figure 4 is a slope view of the screen,
Figure 5 is a graph showing the relationship between vane opening and wind speed.
The figure is a graph showing a calibration example. 1...Suction side, 2...Discharge side, 3...
...Left and right boards, 4...Top and bottom boards, 5, 6...
... Vane, 7, 8 ... Vertical axis, 13 ...
...Gear, 15...Gard motor, 16...
...Potential, 18...Screen mounting part, 20...Screen, 23...
Operation board. Representative Patent Attorney Toshiaki Ikeura Figure 5 Vane opening θ0 u

Claims (1)

[Claims] (1) It is a rectangular cylindrical main body with both ends expanded to be installed horizontally in the existing wind tunnel. The left and right vanes are formed to tilt relative to each other via a vertical axis connected to the drive mechanism, and this drive mechanism is connected to a separate operation panel to display the opening degree of the left and right vanes. A wind speed calibration device comprising a screen mounting part in which a screen made of a wire mesh of a predetermined mesh is inserted and erected at a suitable location near the end.