JP2805176B2 - Flow velocity measurement probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an omnidirectional flow velocity measuring probe having a characteristic at the tip of the probe.

[0002]

2. Description of the Related Art FIG. 9A is a side view showing an example of a conventional omnidirectional spherical flow velocity measuring probe. As shown in the figure, the conventional flow velocity measuring probe 21 has a spherical sensor 24 attached to the tip of a probe body 22 via a support 23. As shown in the partial cross-sectional view of FIG. 9B, the spherical sensor 24 is formed by winding an ultrafine platinum wire 25 held by a glass tube fixed at the center of the inside.
The platinum wire 25 has a positive temperature characteristic, and is widely used as a temperature sensor in terms of heat resistance and stability. Coated lead wires are connected to both ends of the platinum wire 25, and are fixed at the surface of the spherical sensor 24 with an adhesive 26.

When a flow rate sensor 1 using such a platinum wire 25 constitutes, for example, a constant temperature type flow meter, a bridge circuit is formed by the platinum wire 25 and a fixed resistor. By connecting a feedback amplifier that supplies a potential difference between a pair of terminals of the bridge circuit as a feedback current, the bridge is maintained in balance. When the fluid flows around the spherical sensor 24 and the temperature of the platinum wire 25 changes, a current that compensates for the temperature change flows in the bridge circuit, and the bridge top voltage changes. Therefore, the flow velocity of the fluid can be measured based on the output of the feedback amplifier.

When the surface temperature of the spherical sensor is evenly distributed in such a flow velocity measuring probe, the sensitivity to the flow is in all three directions of the three-dimensional space centered on the platinum wire as the heating element. And become uniform. Such a characteristic is called omnidirectional omnidirectionality. Here, when the support portion of the probe is erected as shown in FIG. 10, the horizontal directivity shown in FIG. 10A is changed to the horizontal direction directivity, and the vertical direction shown in FIG. Expressed as vertical directivity.

[0005]

However, in such a flow velocity measuring probe, it is necessary to support the spherical sensor 24 and to provide a support portion 23 for penetrating the lead wire. Therefore, even if the sensor is made spherical, the directivity is not always omnidirectional, and the effect of the support portion 23 cannot be ignored. When the directivity of such a probe is analyzed, the influence of the support portion of the probe on the directivity in the horizontal direction is uniform.
As shown in (a), uniform characteristics can be obtained in almost all directions. However, assuming that the diameter of the spherical sensor 24 is D in the vertical direction and the diameter of the support portion 23 is d, if the diameter of the support portion is large, for example, as shown in FIG. A characteristic having a peak and decreasing around 0 ° is obtained. If the diameter d of the supporting portion 23 is made relatively smaller than the diameter D of the spherical sensor, the characteristics of the probe become almost ideal. However, in practice, the diameter of the supporting portion cannot be significantly reduced, so that it is difficult to obtain uniform characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem of the conventional omnidirectional probe, and has been made to improve the omnidirectionality by making the directivity in the vertical direction uniform within a predetermined range. Subject.

[0007]

According to the present invention, there is provided a spherical sensor having a support portion including a lead wire attached at one end, a heating element fixed at a center position of the spherical sensor and connected to the lead wire,
A flow rate measurement probe that conducts heat generated by energization of the heating element to the surface of the spherical sensor and measures the flow velocity by a change in the amount of heat generated by passage of the fluid, and is symmetrical with the support of the spherical sensor. A protrusion which is substantially symmetrical with the support portion is formed at the position.

[0008]

According to the probe of the present invention having such features, the support portion and the projection provided on the opposite side with respect to the center of the spherical sensor are substantially symmetric. Therefore, the influence of the support portion and the projection on the fluid becomes uniform when viewed from the horizontal plane of the spherical sensor. Therefore, a substantially uniform vertical directional characteristic can be obtained within a range of an angle which is not affected by the center of a plane horizontal to an axis passing through the support portion and the projection.

[0009]

FIG. 1A is an external view showing the shape of a flow velocity measuring probe according to an embodiment of the present invention, and FIG. 1B is an enlarged sectional view of a spherical portion thereof. As shown in these figures, the flow velocity measuring probe 1 according to the present embodiment has a connector portion 3 at a lower end of a probe body 2 and a support portion 4 at a tip. The support portion 4 is a cylindrical member, through which a thin covered lead wire passes. A spherical sensor 5 is attached to one end of the support 4. At the other end of the spherical sensor 5, a cylindrical projection 6 having the same diameter as the support 4 is formed. Here, the internal structure of the spherical sensor 5 is similar to the above-described conventional example, and a heating element is formed by winding a fine platinum wire 12 around a glass tube 11 or a ceramic tube in a coil shape. Then, both ends of the platinum wire 12 are connected to the covered lead wires 13a and 13b. These platinum wires 12 and lead wires 13 a are insulated from the spherical sensor 5. The spherical sensor 5 is formed of a metal having a high thermal conductivity such as aluminum.

In this embodiment, the diameter of the spherical sensor 5 is D, the diameters of the support 4 and the protrusion 6 are d, and the length of the protrusion 6 is L. The reason why the projections 6 are provided here is to make them vertically symmetric with respect to the spherical sensor 5 to improve the vertical directivity.

Next, the diameter D of the spherical sensor 5 is set to 3.
FIGS. 2 (a), 2 (b) and 2 (b) show vertical directional characteristics of a first probe having a diameter of 2 mmφ, a diameter d of the support 4 and the protrusion 6 of 0.7 mmφ, and a length L of the protrusion 6 of 7 mmφ. 3
(A) and (b) show. FIGS. 2 (a) and 2 (b) show the vertical directional characteristics of the probe at a wind speed of 5 m / s and 10 m / s, respectively. FIGS. 3 (a) and 3 (b) show the wind speed of the probe of 15 m / s. And the vertical directional characteristics for a wind speed of 20 m / s. As is clear from the figure, the change in wind speed within the range of 45 to 135 ° in the vertical direction is within ± 4% around 100%, and good characteristics are obtained.

FIGS. 4 (a) and 4 (b) and FIGS.
(B) shows wind speeds of 5 m / s, 10 m / s, 15 m / s, and 20 m / s for the second probes, each having a length L of 5 mm and other shapes identical to those of the first probe.
This shows the vertical directional characteristics up to this point. In this case, since the length L of the protrusion 6 is shorter than that of the first probe,
Even in the range of 45 to 135 °, unevenness is slightly observed in the characteristics. However, this probe is also sufficiently improved as compared with the conventional example.

In order to improve the responsiveness of the flow velocity measurement, it is preferable to reduce the heat capacity of the spherical sensor 5, that is, to reduce its diameter as much as possible. Therefore, the diameter D of the spherical sensor is 2.5 mmφ, and the diameter of the platinum heating element is 0.6 mmφ.
× 1.0 mm, the diameter d of the support 4 and the protrusion 6 is 0.5 mmφ
6 (a), (b), and FIG. 7 show the vertical directivity characteristics of the third probe in which the length L of the protrusion is 5 mm.
(A) and (b) show. FIGS. 6 (a) and 6 (b) show the vertical directional characteristics of the probe at wind speeds of 5 m / s and 10 m / s, respectively, and FIGS. 7 (b) and 7 (b) show the wind speed of the probe at 15 m / s. 5 shows vertical directional characteristics for s and a wind speed of 20 m / s. As is clear from these figures, the change in wind speed within the range of 45 ° to 135 ° in the vertical direction is within ± 2% around 100%, and good characteristics are obtained.

Similarly, the diameter D of the spherical sensor 5 is set to 2.
FIGS. 8A and 8B show the characteristics of the fourth probe in which the diameter d of the support portion 4 and the projection 6 is 0.5 mmφ, the length L of the projection 6 is short and 3 mm. FIG. 8 (a),
(B) shows the characteristics of 5 m / s and 20 m / s, respectively. In this case, almost good characteristics can be obtained in the range of 45 to 130 °, but the characteristics are deteriorated when the wind speed is high.

Further, the diameter D of the spherical sensor 5 is set to 2.5 mmφ,
A fifth probe was prototyped in which the diameter d of the support 4 and the protrusion 6 was 0.7 mmφ, and the length L of the protrusion 6 was 5 mm as in the case described above. In this case, since the diameters of the support portion 4 and the protrusion 6 were too large, the characteristic was obtained in which the dip was large and fluctuated to the + side.

From the above experimental results, the following conclusions were drawn as requirements necessary for a probe having favorable characteristics. (1) Assuming that the diameter D of the spherical sensor 4 and the diameters of the support 4 and the protrusion 6 are d, the ratio (D / d) is 4 or more. The value is 4.57 for the first and second probes, and 5 for the third and fourth probes. (2) The ratio (L / D) of the length L of the projection to the diameter D of the spherical sensor 5 is 2 or more. The value is 2.18 for the first probe and 2 for the third probe. Second
This ratio was 1.54 for the probe No. 1 and 1.2 for the fourth probe, and good characteristics were not obtained.

The above examples are merely examples, and it goes without saying that probes of other various sizes can be arbitrarily selected. In this embodiment, the spherical sensor is an aluminum sphere, but it is needless to say that another metal body having a high thermal conductivity can be used. Further, the heating element is not limited to platinum, but may be made of various materials that generate heat when energized, for example, a tungsten wire.

[0018]

As described in detail above, according to the present invention, the projection is formed at a position symmetrical to the support of the spherical sensor. The vertical directional characteristics are greatly improved with respect to the wind speed in the vertical direction by the protrusions. Therefore, it is possible to obtain uniform vertical directional characteristics within a specific range centered on a plane horizontal to an axis passing through them.

[Brief description of the drawings]

FIG. 1A is a side view showing an overall configuration of a flow velocity measuring probe according to an embodiment of the present invention, and FIG. 1B is a partial sectional view showing a spherical sensor portion thereof.

2 (a) and 2 (b) show the wind speed of the first probe 5m /
6 is a graph showing vertical directivity characteristics of s and 10 m / s.

FIGS. 3A and 3B are wind speeds of the first probe of 15 m;
5 is a graph showing vertical directional characteristics at 20 m / s and 20 m / s.

4 (a) and 4 (b) show the wind speed of the second probe 5m /
6 is a graph showing vertical directivity characteristics of s and 10 m / s.

FIGS. 5A and 5B are wind speeds of a second probe of 15 m;
5 is a graph showing vertical directional characteristics at 20 m / s and 20 m / s.

6 (a) and 6 (b) show the wind speed of the third probe 5m /
6 is a graph showing vertical directivity characteristics of s and 10 m / s.

FIGS. 7A and 7B are wind speeds of a third probe of 15 m;
5 is a graph showing vertical directional characteristics at 20 m / s and 20 m / s.

8 (a) and (b) show the wind speed of the fourth probe 5m /
5 is a graph showing vertical directional characteristics at s and 20 m / s.

FIG. 9A is a side view showing an overall configuration of a conventional flow velocity measuring probe, and FIG. 9B is a partial cross-sectional view showing a spherical sensor portion thereof.

FIG. 10A is a perspective view illustrating the horizontal directivity of a conventional flow velocity measuring probe, and FIG. 10B is a side view illustrating the vertical directivity of the probe.

11A is a graph illustrating an example of the vertical directionality of a conventional flow velocity measurement probe, and FIG. 11B is a graph illustrating an example of the vertical directionality.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow velocity measurement probe 2 Probe body 3 Connector 4 Support part 5 Spherical sensor 6 Projection part 12 Platinum wire

Claims (3)

(57) [Claims] 1. A spherical sensor having a support portion including a lead wire attached to one end thereof; and a heating element fixed to a center position of the spherical sensor and connected to the lead wire. A flow rate measuring probe that conducts heat generated by energization to the surface of the spherical sensor and measures a flow rate by a change in a calorific value caused by passage of a fluid, wherein the support section is located at a position symmetrical to the support section of the spherical sensor. A flow velocity measurement probe characterized in that a projection which is substantially symmetrical with the probe is formed. 2. The flow velocity according to claim 1, wherein the ratio (D / d) is 4 or more, where D is the diameter of the spherical sensor, and d is the diameter of the support and the protrusion. Measuring probe. 3. The flow velocity measurement according to claim 1, wherein the ratio (L / D) is 2 or more, where D is the diameter of the spherical sensor and L is the length of the projection. probe.