JP6112302B2 - Wind tunnel experiment equipment - Google Patents

Description

The present invention relates to a wind tunnel experimental apparatus for measuring aerodynamic characteristics and generated noise of automobiles, airplanes, trains, and the like, and more particularly, air outlets supplied by a blower in a free jet state in which a vortex flow is generated in the vicinity. The present invention relates to a wind tunnel experimental apparatus for sucking air blown from an outlet from a suction port facing a jet outlet in a measurement chamber as it is ejected from an open type measurement chamber and passed through the measurement chamber.

  Conventionally, in this type of wind tunnel experimental apparatus, as can be seen in Patent Document 1, the air passage wall of the portion located in the measurement chamber of the suction air passage that follows the air collecting port called the collector portion is formed of a breathable material. Or, as can be seen in Patent Document 2, a short-circuit opening is formed in the air passage wall of the suction air passage so that a part of the air flowing into the suction air passage through the air collecting port is short-circuited to the measurement chamber through the duct. Alternatively, as can be seen in Patent Document 3, the pressure in the measurement chamber is formed by forming an opening for sound pressure transmission on the air passage wall where the sound pressure peak occurs in the suction air passage that follows the air collection port. The thing which suppressed the pulsation is proposed.

That is, in the wind tunnel experimental devices shown in these Patent Documents 1 to 3, pressure pulsation is generated by the vortex accompanying the free jet of the air jetted from the jet outlet colliding with the air collecting port portion, and the generated pressure pulsation is generated by the air pulsation. A feedback phenomenon that induces a new vortex flow by propagating upstream in the flow direction and reaching the jet outlet causes a pressure pulsation with a specific frequency in the measurement chamber. It was proposed based on the consideration that the pressure pulsation in the measurement chamber is amplified by the air path resonance phenomenon caused by the coincidence with the natural frequency of the suction air path that follows. By providing a road wall, a short-circuit opening or a sound pressure transmission opening, the above-described air path resonance phenomenon is avoided, thereby suppressing pressure pulsation in the measurement chamber.

JP-A-11-64156 JP 2008-76304 A JP 2010-175422 A

  However, in the wind tunnel experiment device, in order to obtain an accurate and highly accurate measurement result in the wind tunnel experiment, the turbulence degree I of the blown air expressed by the following equation 1 (that is, the pressure in the measurement chamber in the conventional device) Although it is required to reduce as much as possible the degree of variation in the wind speed of the ejected air that accompanies pulsation, in the conventional apparatus as described above that suppresses pressure pulsation in the measurement chamber by avoiding the wind path resonance phenomenon, However, it is still difficult to reliably and effectively suppress the wind speed fluctuations of the air jetted out, and there is room for further improvement in reducing the turbulence degree I.

I = u ′ × 100 / Uav (Equation 1)
Where I: degree of turbulence [%]
u ′: root mean square of wind speed fluctuation [km / h]
Uav: Average wind speed [km / h]

In view of this situation, the main problem of the present invention is to adopt a rational fluctuation suppression configuration based on a new research result on the wind speed fluctuation of the jet air ejected in the state of a free jet, and from the jet nozzle to the measurement chamber. It is in the point which suppresses the wind speed fluctuation | variation of the air ejected in the state of a free jet reliably and effectively.

The first characteristic configuration of the present invention relates to a wind tunnel experiment device,
As the air supplied by the blower is ejected from the ejection port to the open measurement chamber in a free jet state where vortex flow is generated in the vicinity and passed through the measurement chamber, the ejection air from the ejection port is In the measurement chamber, a wind tunnel experimental device for sucking into the suction air passage through the air collecting port facing the jet port,
For air flow stabilization and eddy current suppression that provides resistance to the free jet of the jet air from the jet port that flows into the air collecting port, and is located on the downstream side in the air flow direction from the installation part of the test object in the measurement chamber provided breathable resistor,
As this air-permeable resistor, there is provided a rod-like juxtaposed row in which a plurality of rod-like bodies in a posture orthogonal or oblique to the air flow direction are arranged in parallel at intervals in the opening surface direction of the air collecting port. is there.

According to the study by the present inventor, it is considered that the increase in the turbulence degree of the ejected air ejected from the ejection port in a free jet state is caused by the following generation principles (a) to (c).

(A) Generation of vortex As shown schematically in FIG. 7, vortex T is generated in the vicinity of the jet air flow A jetted from the outlet 3 to the open type measurement chamber 1 in a free jet state, and the generated vortex T Develops with the air flow A toward the air collecting port 4.

(B) Collision of the vortex flow with the air collection port portion The vortex flow T developed around the jet air flow A collides with the air collection port 4 portion facing the jet port 3 and the air flow is disturbed around the air collection port 4 due to this collision. 4 pressure and airflow wind speed fluctuate (this pressure fluctuation corresponds to the pressure pulsation caused by the vortex collision described in Patent Documents 1 and 3).

  FIG. 8A to FIG. 8B visualize the air flow change in the vicinity of the air collecting port 4 due to the vortex collision. In this figure, a large air flow change (air turbulence) due to the vortex collision is seen. Existence of large fluctuations in wind speed due to changes in airflow.

(C) Air velocity fluctuation of the air jetted from the jet outlet The jet air flow A from the jet outlet 3, which is a free jet, is inherently unstable. The air flow A from the outlet 3 is affected by the influence of pressure fluctuation, wind speed fluctuation, etc., and it oscillates with a peak at a specific frequency determined by the equipment conditions (particularly the dimensions and wind speed of each part of the measurement chamber). Thus, the turbulence degree I expressed by the above formula 1 increases.

  This is also recognized from the wind speed fluctuation data shown in FIG. 9 and the Fourier analysis result of the same wind speed fluctuation data shown in FIG.

  In order to oscillate the air flow A, the pressure fluctuation around the air collecting port 4 propagates to the upstream side in the air flow direction, and the downstream end of the suction air passage following the air collecting port 4 is passed through a blower. In the case of a recirculation device connected to the jet outlet 3, pressure fluctuations and turbulence in the air flow around the air collecting port 4 reach the jet outlet 3 through the suction air passage (circulation air passage) on the downstream side in the air flow direction. In addition, there is an influence that the amount of air blown out from the outlet 3 also changes due to fluctuations in the amount of air drawn into the air intake passage due to fluctuations in the pressure and wind speed around the air collecting port 4 and turbulence of the airflow. Conceivable.

In other words, the ejected air flow ejected from the ejection port to the open type measurement chamber is unstable as a free jet, and eddy currents are likely to occur around the ejected air flow that is a free jet. However, according to the study by the inventor, the development from the spout that flows into the air collecting port is caused by the fact that it develops greatly as it progresses toward the air collecting port. If resistance is given to the free jet of ejected air by a breathable resistor, turbulence of the air flow and fluctuations in pressure and wind speed due to vortex impingement on the resistor are avoided by the breathability of the resistor. In addition, it was found that the air flow that is a free jet can be stabilized by restraining the air flow by providing resistance, and the generation and development of vortex around the jet air can be effectively suppressed, further Was, it was also found that already may expect the effect of eliminating or attenuating the vortex in the generated developmental stage.

  FIG. 11A to FIG. 11B show the change in the airflow in the vicinity of the air collecting port 4 when the air-permeable resistor X is provided, and the previous case when there is no air-permeable resistor X is shown. As can be seen from the comparison with FIG. 8, in FIG. 11, the change of the airflow (airflow turbulence) is effectively mitigated by stabilizing the airflow and suppressing the eddy current by the air-permeable resistor X. It can be seen that the wind speed fluctuation is effectively suppressed.

Therefore, according to the first characteristic configuration in which the air-flow resistance for imparting resistance to the free jet flow of the jet air from the jet port flowing into the air collecting port and for suppressing the vortex flow is provided , the jet air that is the free jet flow flow and to suppress the generation development of a vortex around the injected air flow while stabilizing, root cause itself turbulence degree rise can be effectively suppressed, thereby, the resonance of the suction air passage Compared with the above-mentioned conventional device that avoids (air path resonance phenomenon) and suppresses only the amplification of pressure pulsation due to the air path resonance phenomenon, the fluctuation of the wind speed of the air jetted from the jet port to the measurement chamber in a free jet state Can be more reliably and effectively suppressed, the degree of turbulence of the jet air can be reliably and effectively reduced, and the accuracy and measurement accuracy of the wind tunnel experiment can be further enhanced.

  FIG. 12 shows the degree of turbulence I in the case where the air-permeable resistor is not provided and in the case where the aperture ratio of the air-permeable resistor is changed. In this figure, the turbulence is effective by providing the air-permeable resistor. It can be seen that the effect of reducing the degree of turbulence is greater as the aperture ratio of the air-permeable resistor is smaller (that is, the greater the applied resistance).

  FIG. 13 shows the Fourier analysis results of the wind speed fluctuation data in the case where the air-permeable resistor is not provided and in the case where the aperture ratio of the air-permeable resistor is changed. It can be seen that the fluctuation in the wind speed having a peak in frequency is effectively suppressed (especially the peak is suppressed), and the fluctuation in the wind speed having a peak in a specific frequency (especially the peak) as the aperture ratio of the air-permeable resistor is smaller It can be seen that the inhibitory effect on is high.

In the first characteristic configuration, since the air-permeable resistor for stabilizing the airflow and suppressing the eddy current is disposed on the downstream side in the air flow direction from the installation portion of the experimental product in the measurement chamber, it passes through the installation portion of the experimental product. There is no direct influence of the airflow resistance for stabilizing the air flow and suppressing the vortex flow on the air flow from the jet outlet.

Further, in the implementation of the first characteristic configuration, the air-permeable resistor for stabilizing the airflow and suppressing the eddy current is disposed in a state of covering the entire opening area of the air collecting port in a front view with respect to the air collecting port, or with respect to the air collecting port. Any of the installation forms arranged so as to cover only a part of the opening area of the air collecting opening (for example, the central part and the outer peripheral edge part) in the front view may be adopted.

In the first characteristic configuration described above , a plurality of rod-like bodies in a posture orthogonal or oblique to the air flow direction are arranged in parallel in the opening direction of the air collecting port as the air-permeable resistor. since Ru provided like body juxtaposed columns can be obtained the following effects.

In other words, by applying resistance by individual rod-shaped bodies, the air jets are uniformly restrained against the free jet of the air jetted from the jet port flowing into the air collecting port and uniformly applied over the entire arrangement range of the rod-shaped body juxtaposed rows. Accordingly, it is possible to reliably and effectively reduce the degree of turbulence of the ejected air ejected from the ejection port to the measurement chamber in a free jet state .

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The second feature configuration of the present invention specifies a configuration suitable for the implementation of the first feature configuration .
A plurality of the breathable resistors are arranged at intervals in the air flow direction.

According to the second characteristic configuration, by providing resistance by each of the plurality of air-permeable resistors, it is possible to more effectively provide resistance to the free jet of the jet air from the jet port flowing into the air collecting port, Thereby, the turbulence degree of the jet air which jets from a jet nozzle to a measurement chamber can be reduced more reliably and effectively.

The third feature configuration of the present invention specifies a configuration suitable for the implementation of the first or second feature configuration .
The suction pressure is positioned at a short-circuit opening for short-circuiting a part of the air flowing into the suction air passage through the air collecting port to the measurement chamber, or at a position where a sound pressure peak is generated in the suction air passage. The sound pressure transmitting opening that transmits the outside of the passage is formed in the air passage wall of the suction air passage on the downstream side in the air flow direction from the air-permeable resistor.

According to the third characteristic configuration, the air jetted from the jet outlet is provided by providing resistance to the free jet of the jet air flowing from the jet outlet flowing into the air collecting port by the air-permeable resistor for stabilizing the airflow and suppressing the vortex flow. If there is still some wind speed fluctuation or pressure pulsation of the ejected air even in a state where the wind speed fluctuation is effectively suppressed, the remaining wind speed fluctuation or pressure pulsation is reduced by the above-mentioned short-circuit opening or sound pressure transmission opening. By avoiding the path resonance, the degree of turbulence of the ejected air ejected from the ejection port to the measurement chamber can be further reliably and effectively reduced as a whole.

Plan view showing the overall configuration of the wind tunnel test equipment Front view (a) and side view (b) of a breathable resistor comprising juxtaposed rod-shaped bodies Front view of a breathable resistor made of a net-like body showing a reference example (a) Front view (a) and partial perspective view (b) of breathable resistor made of honeycomb structure showing reference example Front view (a), (b), (c) showing examples of arrangement of air-permeable resistors Side view showing an example of arrangement of breathable resistors Schematic diagram explaining the vortex generation mode Side views (a) and (b) showing airflow changes in the vicinity of the air collecting port Graph showing wind speed fluctuation data Graph showing the results of Fourier analysis Side views (a) and (b) showing changes in airflow in the vicinity of the air collecting port in the presence of a breathable resistor Graph showing turbulence degree comparison results Graph showing comparison results of Fourier analysis

FIG. 1 shows the overall configuration of a wind tunnel experimental apparatus for measuring aerodynamic characteristics and generated noise of automobiles, airplanes, trains, and the like. In this wind tunnel experimental apparatus, an open type measurement chamber 1 is provided. Injecting the air A from the jet outlet 3 through which the air A is jetted in the state of a free jet at a set wind speed and the jet air A from the jet outlet 3 that has passed through the experimental installation section 2 toward the experimental installation section 2 in the room A wind collecting port 4 is provided.

  The jet outlet 3 and the air collecting port 4 are communicated with each other through the circulating air passage 5 outside the measurement chamber 1, and air A is supplied to the jet outlet 3 in the middle of the circulating air passage 5 to supply air A. Is provided with a blower 6 for ejecting the air from the jet outlet 3.

That is, this wind tunnel experimental device uses the portion between the blower 6 and the air collecting port 4 in the circulating air passage 5 as the suction air passage 5B, and the portion between the blower 6 and the outlet 3 in the circulating air passage 5. supply air path in the 5A, ejecting air a sucked into the suction air passage 5B through wind collecting port 4 by the operation of the blower 6 in the form of a free jet in the measuring chamber 1 of open type from jetting port 3 through supply air path 5A circumfluence This is a wind tunnel experimental device of the type

  Both the jet port 3 and the air collecting port 4 are rectangular openings in front view, and the vicinity of the jet port 3 in the supply air passage 5A (that is, the vicinity of the outlet of the supply air passage 5A) is downstream in the air flow direction. The air passage cross-sectional area is gradually reduced toward the side, and the compressed air portion 5a that reaches the outlet 3 is formed.

  On the other hand, the air collecting port 4 is provided with a trumpet-shaped air collecting portion 4a that expands toward the measurement chamber 1, and a portion in the vicinity of the air collecting port 4 in the suction air passage 5B (that is, a portion near the inlet of the suction air passage 5B). Is a wind expansion portion 5b in which the air passage cross-sectional area gradually increases toward the downstream side in the air flow direction.

  The air collecting port 4 provided with the trumpet-shaped air collecting unit 4a and the jet port 3 are opposed to each other with the experimental product installation unit 2 sandwiched between the air collecting port 4 and the ejection port 3 that protrude into the measurement chamber 1. .

In this type of wind tunnel experimental apparatus, as schematically shown in FIG. 7, a vortex flow T is generated and developed around a jet air flow A jetted from the jet nozzle 3 to the open type measurement chamber 1 in a free jet state. The developed vortex S collides with the air collecting port 4 (specifically, the trumpet air collecting portion 4a or the air channel wall of the suction air channel 5B in the vicinity of the air collecting port 4). The pressure and wind speed around the turbulent air collection port 4 fluctuate.

  The air flow A from the outlet 3 which is an unstable free jet is affected by the turbulence, pressure fluctuations, and wind speed fluctuations around the air collecting port 4 due to the vortex collision. It swings in a state having a peak at a specific frequency determined by the dimensions of each part of the measurement chamber and the wind speed), and this causes the turbulence degree I of the ejected air A expressed by the following equation 1 to rise and There was a problem that performance was limited to a low level.

I = u ′ × 100 / Uav (Equation 1)
I: Turbulence degree [%]
u ′: root mean square of wind speed fluctuation [km / h]
Uav: Average wind speed [km / h]

On the other hand, in the wind tunnel experimental device of this example, as shown in FIGS. 1 and 2, the air ejected from the ejection port 3 flowing into the air collection port 4 on the downstream side in the air flow direction from the installation portion 2 of the experimental product. A breathable resistor X for airflow stabilization and eddy current suppression that imparts resistance to the free jet of A is installed in a state that extends over the entire opening area of the air collecting port 4 in a front view with respect to the air collecting port 4. By restricting the free jet of the jet air A from the jet port 3 by applying resistance by the air-permeable resistor X, the jet air flow A from the jet port 3 is stabilized and the periphery of the jet air flow A is This suppresses the generation and development of eddy currents, effectively suppresses the root cause of the increase in turbulence, and also hopes to have the effect of extinguishing or attenuating eddy currents T that have already occurred and are in the developmental stage. by Zhou of a free jet from the spout 3 In are as effectively reducing the turbulence degree I of injected air A to be ejected.

Specifically, a plurality of rod-like bodies 7a in a horizontal posture perpendicular to the air flow direction are arranged in parallel in the up-down direction at equal intervals at a position in front of the air collecting port 4. The juxtaposed row 7 is formed, and this rod-like body juxtaposed row 7 is used as the air-permeable resistor X for stabilizing the airflow and suppressing the eddy current.

[Another embodiment]
Next, other embodiments of the present invention will be listed.

In the above-described embodiment, the rod-like juxtaposed row 7 composed of the rod-like bodies 7a in the horizontal posture is the air-permeable resistor X for stabilizing the airflow and suppressing the eddy current. Instead, the rod-like body in the vertical posture is used in the horizontal direction. Alternatively, the rod-like juxtaposed rows arranged in parallel to each other may be used as the air-permeable resistor X for airflow stabilization and eddy current suppression .

As a reference example , instead of the rod-like juxtaposed row 7 or together with the rod-like juxtaposed row 7, a mesh-like body 8 as shown in FIG. 3 or a honeycomb structure 9 as shown in FIG. 4 is used for airflow stabilization and eddy current suppression. It is also possible to install as a breathable resistor X. In addition, air flow stabilization and vortex flow of porous plate bodies such as punching plates, lattice bodies such as vertical and horizontal lattice bodies and jungle gym bodies, and filter bodies, etc. It is also conceivable to use it as a breathable resistor X for suppression .

As shown in FIG. 5 (a), the rod-like juxtaposed row as the air-permeable resistor X for stabilizing the airflow and suppressing the eddy current covers the entire opening area of the air collecting port 4 in a front view with respect to the air collecting port 4. As shown in FIG. 5 (b), the arrangement is not limited to the arrangement, and it is arranged so as to cover only the outer peripheral edge of the opening area of the air collection port 4 in a front view with respect to the air collection port 4, or as shown in FIG. Furthermore, it arrange | positions in the state which covers only the center part of the opening area of the air collection opening 4 in the front view with respect to the air collection opening 4, for example, arrange | positions in the state which covers only a part of opening area of the air collection opening 4 in the front view with respect to the air collection opening 4. You may do it.

Moreover, if the installation location in the air flow direction of the juxtaposed rod-shaped body as the air-permeable resistor X for airflow stabilization and vortex suppression is downstream in the air flow direction from the installation portion 2 of the test object, FIG. What is necessary is just to determine suitably in the range from the near part of the air collection port 4 to the innermost part of the air collection port 4 (namely, the location which entered the suction air path 5B) as shown.

  As indicated by a broken line in FIG. 6, a short-circuit opening 10 for leading a part of the air A flowing into the suction air passage 5 </ b> B through the air collecting port 4 to the measurement chamber 1 through a duct (not shown), or the suction air The sound pressure transmitting opening 11 that is located at the sound pressure peak occurrence position of the path 5B and transmits the sound pressure to the outside of the suction air path 5B is located downstream of the breathable resistor X in the air flow direction of the suction air path 5B. You may form in an air channel wall.

In this way, resistance is imparted to the free jet flow of the jet air A from the jet port 3 flowing into the air collecting port 4 by the breathable resistor X for stabilizing the airflow and suppressing the vortex flow . In the case where the wind speed fluctuation and pressure pulsation of the jet air A still remain to some extent even in the state where the wind speed fluctuation of the jet air A is effectively suppressed, the remaining wind speed fluctuation and pressure pulsation are represented by the short-circuit opening 10 or the sound pressure. This can be suppressed by avoiding wind path resonance by the transmission opening 11.

  The present invention is not limited to the circulating wind tunnel experimental device, and may be applied to a transient wind tunnel experimental device that does not return the air A flowing into the suction air passage 5B to the jet outlet 3.

  The wind tunnel experiment apparatus according to the present invention can be used for various wind tunnel experiments.

6 Air blower A Blowing air 3 Spout 1 Measurement chamber 4 Ventilation port 5B Suction air passage 2 Test material installation part X Breathable resistor 7 for air flow stabilization and eddy current control 7a Rod body 7 Parallel arrangement of rod bodies 10 Short circuit opening 11 Sound Pressure transmission opening

Claims (3)

As the air supplied by the blower is ejected from the ejection port to the open measurement chamber in a free jet state where vortex flow is generated in the vicinity and passed through the measurement chamber, the ejection air from the ejection port is In the measurement chamber, a wind tunnel experimental device for sucking into the suction air passage through the air collecting port facing the jet port,
For air flow stabilization and eddy current suppression that provides resistance to the free jet of the jet air from the jet port that flows into the air collecting port, and is located on the downstream side in the air flow direction from the installation part of the test object in the measurement chamber provided breathable resistor,
A wind tunnel experiment in which a plurality of rod-like body juxtaposed rows arranged in a parallel state at intervals in the opening surface direction of the air collecting port are arranged as this air-permeable resistor in a posture orthogonal or oblique to the air flow direction. apparatus. The wind tunnel experimental device according to claim 1, wherein a plurality of the breathable resistors are arranged at intervals in the air flow direction . The suction pressure is positioned at a short-circuit opening for short-circuiting a part of the air flowing into the suction air passage through the air collecting port to the measurement chamber, or at a position where a sound pressure peak is generated in the suction air passage. The wind tunnel experimental device according to claim 1 or 2 , wherein an opening for transmitting sound pressure to be transmitted to the outside of the passage is formed on an air passage wall of the suction air passage at a downstream side of the air-permeable resistor in the air flow direction. .