CN201060094Y - Low frequency oscillations inhibition structure used for opening reversed flow type pneumatic-acoustics wind tunnel - Google Patents

Abstract

The utility model discloses a low-frequency pulsation suppression structure for an open return-flow type aero-acoustic wind tunnel, the wind tunnel comprises a regulating test chamber and a return-flow channel which is composed of a diffusion section, a first corner, a first transition section, a second corner, a blower and an inlet and an outlet sections thereof, a third and a forth corners, a second transition section and a contraction section. A pulsation absorbing chamber is arranged above the return-flow channel which is composed of the diffusion section, the first corner, the first transition section and the second corner, and at least one vent is arranged between the pulsation absorbing chamber and the return-flow channel. The structure of the pulsation absorbing chamber is added above the return-flow channel in the utility model from studying the induction factors that generate low frequency pulsation phenomena in the regulating test chamber, sound resonance mode in the channel is altered, and then the low-frequency pulsation is reduced. The test measuring environment of the flow field and the acoustic field of a test section is improved.

Description

Be used for open closed formula pneumatic-the low frequency structure for restraining flutter of acoustic wind tunnel

Technical field

The utility model relates to a kind of open closed formula pneumatic-acoustic wind tunnel particularly relates to the low frequency structure for restraining flutter of this wind-tunnel.

Background technology

Highway, high-speed rail transportation speed of development make rapid progress, and except that automobile, other high-speed rail transportation instrument (as bullet train, magnetic suspension train etc.) also continues to bring out.Like this, lightweight car that the design air kinematic behavior is good and high-speed rail transportation rolling stock, improve the aerodynamic stability of rapid, improve their dynamic property and the inner flowing characteristic of economy and pilothouse, improve the usefulness of engine, brake system, reduce the primary study exploitation content that aerodynamic noise becomes this class automobile and high-speed rail transportation instrument.Vehicle complete vehicle wind tunnel test equipment plays irreplaceable effect in these research work.But still there are many technological difficulties in automobile wind tunnel design and the construction, wherein, low frequency flutter problem directly has influence on the flow quality of test section, influence pneumatic and acoustics (in the acoustic wind tunnel) performance measurement of testpieces, the experimental ability of wind-tunnel is restricted, always be the world-famous puzzle of open closed-circuit wind tunnel research field, also do not have effective solution up to now.

Since the seventies in last century, people recognize that gradually ubiquity low frequency flutter phenomenon in the automobile wind tunnel, promptly in full-scale wind tunnel, several tangible resonance peaks appear in the interior meeting of frequency range that is lower than 20Hz in the acoustic pressure frequency spectrum, and the frequency that these peak values occur is relevant with wind speed, the wind speed that peak-peak occurs also is uncertain, the size of its peak value is difficult to prediction especially, thereby the research that how to reduce low frequency flutter amplitude also becomes one of essential scientific research project gradually in the design process of automobile wind tunnel.External wind-tunnel construction experiences shows, if can not effectively suppress low frequency flutter phenomenon, brings not only can for relevant wind tunnel experiment and seriously influence, even might destroy the structure of wind-tunnel itself.Because people are not very clear producing such flutter mechanism, thereby control method miscellaneous appearred, yet different control methods stresses results for different wind-tunnel and also is not quite similar, and simultaneously its relative merits is arranged respectively also, but that ubiquitous problem has is following several:

Caused the increase of high band noise when 1) suppressing low frequency flutter amplitude;

Caused when 2) improving the acoustics field that the flow field axial pressure distribution is inhomogeneous, caused the reduction of flow field quality and wind-tunnel efficient.

So, also need the novel control device of continuous pilot development to suppress low frequency flutter amplitude at present, also to avoid or reduce above-mentioned negative effect as far as possible simultaneously, could in automobile wind tunnel, obtain good experimental situation like this.

Along the direction of following current, open closed formula low-speed wind tunnel is made up of blower fan, blower fan diffuser, the 3rd turning, heat interchanger, the 4th turning, honeycomb, damping screen, contraction section, spout, jet segment, collection mouth, diffuser, first turning, first transition section, second turning and blower fan wind inlet section successively.Fig. 1, Fig. 2 and Fig. 3 show one section reflux line between chamber and blower fan wind inlet section, wherein spout 1, jet segment 2 and collection mouth 3 all are contained in wind-tunnel in chamber 8, and diffuser 4, first turning 5, first transition section 6 and second turning 7 have constituted the reflux line of wind-tunnel.

The utility model content

The low frequency structure for restraining flutter of the technical problems to be solved in the utility model provides a kind of open closed formula pneumatic-acoustic wind tunnel, it can not only effectively suppress the low frequency flutter phenomenon that exists in the wind-tunnel, also can improve the axial pressure gradient in flow field in the wind-tunnel simultaneously.

In order to solve the problems of the technologies described above, the utility model adopts following technical scheme: a kind of be used for open closed formula pneumatic-the low frequency structure for restraining flutter of acoustic wind tunnel, described wind-tunnel comprises stays the chamber and by diffuser, first turning, first transition section, second turning, blower fan and advance the reflux line that wind outlet section, third and fourth turning, second transition section, contraction section constitute, the top of the described reflux line that is made of diffuser, first turning, first transition section and second turning is provided with the absorbing chamber, is provided with an air vent between described absorbing chamber and the reflux line at least.

Preferably, described air vent is between diffuser and absorbing chamber.

Preferably, described air vent is between second turning and absorbing chamber.

The utility model is stayed the inducement of indoor generation low frequency flutter phenomenon from research, above reflux line, increase the absorbing cavity configuration, and perforate between reflux line and absorbing chamber, thereby absorbed the low frequency flutter energy of some frequency range, also changed ducted resonance acoustic mode attitude, and then reduced the low frequency flutter, improve the experimental measurement environment of test section flow field and sound field.

Description of drawings

Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.

Fig. 1 is the vertical view (analysing and observe) of original construction of wind tunnel.

Fig. 2 is the front view of original construction of wind tunnel.

Fig. 3 is the right view of original construction of wind tunnel.

Fig. 4 adopts the vertical view (analysing and observe) of construction of wind tunnel behind the absorbing chamber for the utility model.

Fig. 5 adopts the front view of construction of wind tunnel behind the absorbing chamber for the utility model.

Fig. 6 adopts the right view of construction of wind tunnel behind the absorbing chamber for the utility model.

The situation of change of the different wind speed downforce in standard measuring point place ripple factor when Fig. 7 is original structure.

Fig. 8 is the pressure fluctuation coefficient figure after the employing structure of the present utility model.

Fig. 9 is the pressure fluctuation coefficient figure after the employing another kind of structure of the present utility model.

Number in the figure: 1 is spout, and 2 is jet segment, and 3 for collecting mouth, and 4 is diffuser, 5 is first turning, and 6 is first transition section, and 7 is second turning, and 8 for staying the chamber, 9 is the air vent between diffuser and the absorbing chamber, and 10 is the air vent between second turning and the absorbing chamber, and 11 are the absorbing chamber.

Embodiment

A kind of open closed formula that the utility model is suitable for is pneumatic-and acoustic wind tunnel is made up of blower fan, blower fan diffuser, the 3rd turning, heat interchanger, the 4th turning, honeycomb, damping screen, contraction section, spout, jet segment, collection mouth, diffuser, first turning, first transition section, second turning and blower fan wind inlet section.Fig. 4, Fig. 5 and Fig. 6 show wherein a part, spout 1 wherein, jet segment 2, collect mouthfuls 3 and are positioned in the chamber 8, and diffuser 4, first turning 5, first transition section 6 and second turning 7 have constituted the partial reflux pipeline of wind-tunnel.The utility model is provided with absorbing chamber 11 above reflux line, be used to suppress the low frequency flutter, offered an air vent 9 that is connected with absorbing chamber 11 at the top of diffuser 4, offered an air vent 10 that is connected with absorbing chamber 11 at the top at second turning 7, air vent 9 and air vent 10 can open and close separately.

The open closed formula that the utility model is suitable for is pneumatic-and acoustic wind tunnel absorbing cavity configuration, can suppress the low frequency flutter, improve acoustic enviroment in the chamber and flow field quality.For the inhibition effect that low frequency flutter amplitude produces, can pass through calculating pressure ripple factor Cp, peak weighs, and computing method are as follows:

$\mathrm{Cp},\mathrm{peak}=\frac{{\tilde{p}}_{\max }}{p_{\mathrm{dyn}}}=\frac{10^{(\frac{L_{p,\mathrm{<figure-callout\; id="20"\; label="peak"\; filenames="Y20072014403100091.png,Y20072014403100092.png"\; state="\{\{state\}\}">peak</figure-callout>}}}{20}+1g{p}_0)}}{p_{\mathrm{dyn}}}$

Cp, peak---pressure fluctuation coefficient in peak value place under a certain frequency band;

---maximum fluctuation pressure value;

p _Dyn---the measuring point dynamic pressure;

P ₀---reference pressure (20 μ Pa)

Lp, peak---peak value place sound pressure level under a certain frequency band.

Compare experiment with original structure and structure of the present utility model, by draw pressure fluctuation coefficient figure as can be seen the utility model structure in the effect that suppresses aspect the low frequency flutter.

Fig. 7 is the pressure fluctuation coefficient figure of original structure, Fig. 8 is under the situation of opening the air vent 9 between diffuser 4 and the absorbing chamber 11, pressure fluctuation coefficient figure of the present utility model, Fig. 9 is under the situation of opening the air vent 10 between second turning 7 and the absorbing chamber 11, pressure fluctuation coefficient figure of the present utility model.3 curves among each figure are corresponding to three different frequency bands.

Generally, low frequency flutter amplitude is along with the increase of wind speed constantly increases, as shown in Figure 7.Comparison diagram 8 and Fig. 7, the low frequency flutter maximum amplitude that can see the 3rd frequency band have dropped near 0.3% from 0.63%, have decreased by 52.4%.

Under the situation of opening the air vent 10 between second turning 7 and the absorbing chamber 11, comparison diagram 9 and Fig. 7 as can be seen, the low frequency flutter maximum amplitude of first frequency section has dropped near 0.74% from 1.2%, the range of decrease is near 38%.

Change the area of air vent 9 and air vent 10, the 11 pairs of low frequency flutters in absorbing chamber can produce different inhibition effects again.The position of air vent and the inhibition effect that area all can influence the low frequency flutter between this explanation absorbing chamber and the reflux line.From result of experiment, the utility model has been obtained good effect, the maximum range of decrease of low frequency flutter amplitude of place, axis in chamber standard measuring point can reach 52.4%, the flutter peak value that occurs at different wind speed sections particularly, can connect the absorbing chamber by different holes and different perforated areas controls, these all help carrying out in the wind-tunnel aerodynamics and noise analysis experiment, thereby obtain believable experimental data.

Claims (3)

1. One kind be used for open closed formula pneumatic-the low frequency structure for restraining flutter of acoustic wind tunnel, described wind-tunnel comprises stays chamber (8) and by diffuser (4), first turning (5), first transition section (6), second turning (7), blower fan and advance the reflux line that wind outlet section, third and fourth turning, second transition section, contraction section constitute, it is characterized in that: the top of the described reflux line that is made of diffuser, first turning, first transition section and second turning is provided with absorbing chamber (11), at least be provided with an air vent (9,10) between described absorbing chamber (11) and the reflux line.
2. 2. according to claim 1 be used for open closed formula pneumatic-the low frequency structure for restraining flutter of acoustic wind tunnel, it is characterized in that: described air vent (9) is positioned between diffuser (4) and absorbing chamber (11).
3. 3. according to claim 1 be used for open closed formula pneumatic-the low frequency structure for restraining flutter of acoustic wind tunnel, it is characterized in that: described air vent (10) is positioned between second turning (7) and absorbing chamber (11).

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