JPH04104030A - Double nozzle for wind tunnel - Google Patents

Abstract

PURPOSE:To obtain a low-noise secondary air stream with a compact apparatus by providing a first nozzle for blowing a main air stream, providing a second nozzle for blowing the secondary air stream around the first nozzle, and providing hole parts for the secondary stream in a wind tunnel duct at the upstream side. CONSTITUTION:Double nozzle 10 for a wind tunnel comprise a first nozzle 12 for blowing a main air stream M and a slit shaped second nozzle 14 which is provided around the first nozzle 12. Opening parts 18 for taking air for a secondary air streams S are provided at the wind tunnel duct 16 on the upstream side of the nozzle 12. The opening parts are communicated to the nozzle 14 through a flow path 20. A pressure P16 at the inside of the duct 16 at the upstream side of the nozzle 12 is higher than a pressure P12 at the blowing-out part. Therefore, the air for the secondary air stream can be readily taken. Thus, it is not necessary to provide a blower and the like separately. The sound of the air for the secondary stream S is already silenced in the duct 16. Therefore, it is not necessary to otherwise provide a muffler device. Thus, the low-noise secondary air stream can be obtained with the compact apparatus.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used in a wind tunnel device that blows airflow to a measuring section, and includes a first nozzle that blows out a main airflow, and a structure around the first nozzle. Regarding a wind tunnel double nozzle having a second nozzle in the form of a slit which blows out a secondary airflow having a flow velocity lower than that of the main airflow, the wind tunnel double nozzle is particularly suitable for use in high-speed wind tunnels and reduces jet noise when airflow is generated. This relates to a double nozzle for use.

[Prior Art] When high-speed airflow is used in a semi-open wind tunnel that has a measurement unit in the open space between the nozzle and the bell mouth, or in a wind tunnel that blows air directly into the open space, problems occur in the measurement unit. The main component of the noise generated is the jet noise from the nozzle.

It is well known to those skilled in the art that this jet noise is reduced by creating a coaxial double air stream using a dual nozzle as shown in FIG. In FIG. 4, the double nozzle, which is generally designated by the reference numeral 1, includes a first nozzle 2 that blows out the main airflow, and a slit-shaped second nozzle 3 formed around the first nozzle 2. The second nozzle 3 is configured to blow out a secondary airflow whose flow velocity is slower than that of the main airflow.

This secondary airflow is blown out to the outer periphery of the main airflow.
It is blowing out from nozzle 3. Conventionally, a main airflow blower (not shown) is used as an airflow generation source for the subairflow.
Separately, a small blower (not shown) was used.

[Problems to be Solved by the Invention] However, with the conventional double nozzle, in order to reduce the noise of the secondary airflow, a noise reduction device separate from the noise reduction device of the wind tunnel body is required, and the secondary airflow is A device and channel for collecting the water will also be required. Therefore, there is a problem in that the configuration becomes extremely complicated and manufacturing costs and maintenance costs increase.

In addition, since the wind tunnel was designed to have a wind tunnel that was slightly smaller than the wind tunnel itself, creating a double airflow, there was a problem in that extra space, volume, and control equipment were required.

The present invention was proposed in view of the problems of the prior art described above, and aims to provide a double nozzle for wind tunnels that can reduce noise generated from high-speed airflow and does not have a complicated configuration. It is said that

[Means for Solving the Problems] The dual nozzle for wind tunnel of the present invention is used in a wind tunnel device of the type that blows airflow to a measuring section, and includes a first nozzle that blows out the main airflow, and a double nozzle of the first nozzle that blows out the main airflow. In a wind tunnel double nozzle having a slit-shaped second nozzle around which blows out a secondary airflow having a flow velocity slower than the main airflow, an opening for taking out air for the secondary airflow into a wind tunnel duct on the upstream side of the first nozzle. A flow path is formed that communicates the opening with the slit-shaped second nozzle.

Further, - the double nozzle for a wind tunnel of the present invention is provided with means near the opening for controlling the area of the opening to adjust the flow rate of the secondary airflow from the wind tunnel duct.

Further, in the double nozzle for a wind tunnel of the present invention, a flow rate regulating valve is provided in the middle of the flow path that communicates the opening and the slit-shaped second nozzle.

Note that it is preferable that the flow velocity of the secondary airflow be approximately 50% of the flow velocity of the main airflow.

[Function] According to the double nozzle for wind tunnel of the present invention having the above-described configuration, the opening for taking out the air for the secondary airflow is provided in the wind tunnel duct on the upstream side of the first nozzle. Here, since the pressure inside the wind tunnel on the upstream side of the first nozzle provided with the opening is higher than the pressure at the outlet of the first nozzle, air for the secondary airflow is taken out from the opening. This is done very easily. Therefore, there is no need to use a blower separate from the main airflow blower. Since the air for the secondary airflow has already been muffled in the wind tunnel main body and is a quiet airflow, it is not necessary to separately provide a muffling device for the secondary airflow.

In addition, the area of the opening for taking out the air for the secondary airflow can be optimally set and the area can be variably controlled, or the flow rate can be controlled with a valve added to the flow path that communicates the opening and the second nozzle. By doing this, it is possible to easily create a secondary airflow with an optimal blowing flow velocity.

As a result of these effects, a noise prevention effect can be obtained with a device that is more compact than the conventional double nozzle, and a low-noise secondary airflow can be obtained.

Note that the secondary airflow having a flow velocity of approximately 50% of the main flow velocity is
It is already obvious that blowing from the second nozzle on the outer periphery of the nozzle is effective in reducing jet noise, and the present invention utilizes this fact to reduce jet noise.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings. In addition, in FIGS. 1 to 3, the same members are given the same reference numerals and repeated explanations will be omitted.

FIG. 1 shows a chest 1 embodiment of the present invention, and a double nozzle for wind tunnel, which is designated as a whole by the reference numeral 10, includes a first nozzle (main nozzle) 12 that blows out a main air flow M, and a periphery of the nozzle 12. A slit-shaped second nozzle 14 (secondary airflow nozzle) provided in the airflow chamber 14 includes a slit-shaped second nozzle 14 (secondary airflow nozzle) provided in the airflow. Then, the secondary airflow S blows out from the second nozzle 14 in such a manner as to surround the main airflow M. The external appearance of this wind tunnel double nozzle 10 is the same as the double nozzle 1 shown in FIG. 4.

The wind tunnel duct 16 on the upstream side (the U side) of the main nozzle 12 is provided with an opening 18 for taking out air for the secondary airflow S, and the opening 18 and the secondary airflow nozzle 14 are connected to the flow path 2.
They are connected by 0.

Here, the opening 18 may be formed in an annular shape, or an appropriate number of holes may be formed in the circumferential direction. And opening 1
The cross-sectional area of No. 8 is set to an optimum value for allocating air for the auxiliary airflow S in consideration of various conditions.

A blower or the like is not provided in the open section 18, the flow path 20, and the auxiliary air flow nozzle 14. The pressure P 16 inside the wind tunnel duct 16 on the upstream side of the main nozzle 12 is
The pressure is higher than the pressure P12 at the blowout location. Therefore, air for the auxiliary airflow can be taken into the flow path 20 from the opening 18 very easily. Therefore, there is no need to separately provide a blower or the like.

In addition, the air for the auxiliary airflow S has already been muffled in the wind tunnel duct 16 and is a quiet airflow. Therefore, there is no need to separately provide a muffling device for the side airflow S.

FIG. 2 shows a second embodiment of the invention.

The double nozzle for wind temperature, which is generally designated by the reference numeral 30, has approximately the same structure as the double nozzle 10 for wind tunnel shown in FIG. It has a variable structure nearby.

That is, the opening 18 is provided with a closing member 32 and a control device 34 for actuating it. This control device 34
In response to an output signal from a sensor (not shown) or a scanning signal from an operation panel (not shown), the closing member 32 is operated to close the opening so that the opening area of the opening 18 becomes the optimum value at that time. 18 (part of) is blocked. In other words, the opening area of the opening 18 is varied by the closing member operated by the control device 34, and the amount of air flowing into the flow path 20 from the opening 18 is also varied accordingly.

FIG. 3 shows a third embodiment of the present invention, in which a double nozzle for wind tunnels, designated as a whole by reference numeral 40, has a flow control valve 42 installed in the middle of the flow path 20, and the valve is controlled by a control device. 4
4 controls its opening degree. When it is desired to reduce the flow rate of the auxiliary airflow S, the valve 42 reduces its opening in response to a command from the control device 44, and on the other hand, when it is desired to increase the flow rate of the auxiliary airflow S, the opening of the valve 42 is increased. do.

Other configurations and operations are the same as those in the first embodiment.

[Effects of invention The effects of the present invention are listed below.

(1) Jet noise can be effectively reduced.

(2) There is no need to provide a blower for the auxiliary airflow separately from a blower for the main airflow.

(3) It is not necessary to separately provide a silencer for the side airflow.

(4) It is possible to easily create a secondary airflow with an optimal blowout flow rate.

(5) A noise prevention effect can be obtained with a device that is more compact than the conventional double nozzle, and a low-noise secondary airflow can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional side view showing a first embodiment of the invention, FIG. 2 is a sectional side view showing a second embodiment of the invention, and FIG. 3 is a sectional side view showing a third embodiment of the invention. , FIG. 4 is a perspective view showing the appearance of the double nozzle. 1.12. First nozzle (main nozzle) 2.14.
...Second nozzle 14 (secondary airflow nozzle) 10.30.
40...Double nozzle for wind tunnel 16...Wind tunnel duct 18...Opening part 20...Flow path (secondary airflow guiding conduit) M...Main airflow S...Secondary airflow 1st round纂3＠＠211 41st!1

Claims (3)

[Claims] (1) Used in a wind tunnel device that blows out airflow to a measurement section, it includes a first nozzle that blows out the main airflow, and a slit-shaped nozzle that blows out a secondary airflow that has a flow rate slower than the main airflow around the first nozzle. In the wind tunnel dual nozzle having a second nozzle, an opening for taking out air for a secondary airflow is provided in the wind tunnel duct upstream of the first nozzle, and the opening and the slit-shaped second nozzle are connected to each other. A double nozzle for wind tunnels, characterized in that a flow path is formed to communicate with the wind tunnel. (2) The double nozzle for a wind tunnel according to claim 1, further comprising means for controlling the area of the opening and adjusting the flow rate of the sub-air flow from the wind tunnel duct near the opening. (3) The double nozzle for a wind tunnel according to claim 1, further comprising a flow rate regulating valve provided in the middle of the flow path that communicates the opening and the slit-shaped second nozzle.