JP5360835B2 - Jet noise prevention method and jet nozzle - Google Patents

Description

  The present invention relates to a jet noise prevention method and a jet nozzle, and more particularly to a jet noise prevention method and a jet nozzle that can reduce the amount of gas consumed to inject an air flow into a jet.

  Jet noise is generated by the formation of a vortex between the jet jet and the outside air due to the friction between the high-speed jet jet discharged from the jet engine and the outside air. It is known that the power of jet noise is proportional to the eighth power of the jet jet velocity.

  Methods for reducing jet noise include a method in which the jet jet is rapidly mixed with the outside air to reduce the speed of the jet jet, a method in which small pieces called tabs are inserted into the jet jet, and an air flow toward the jet jet. The method of controlling the vortex between the jet jet and the outside air by jetting has been mainly studied.

  In recent years, it has been found that the method of injecting an air stream toward a jet jet is effective not only for a subsonic jet jet but also for a supersonic jet jet. 707 (issued in July 2005), JSME Proceedings (Part B), Volume 73, 726 (issued in February 2007)).

  However, if it is attempted to reduce jet noise simply by continuously injecting airflow toward the jet, it may require as much as 4% of the main jet to reduce the total sound pressure level by 2.4 dB. all right.

  If the method of injecting an air stream toward a jet jet is to be applied to a practical jet engine, the air source of the air stream needs to be obtained from the air extracted from the compressor of the jet engine, but if the air extracted from the compressor becomes excessive, There is a problem that a drop in engine thrust cannot be ignored.

  Therefore, it is required to effectively reduce jet noise with an air flow having as small a flow rate as possible.

  The present invention has been made to solve the above-mentioned problems, and can effectively reduce noise of jets such as jet jets as well as conventional ones, and is also consumed for injecting air currents into jets. An object of the present invention is to provide a jet noise prevention method and a jet nozzle that can reduce the amount of air that is generated.

The invention according to claim 1 is formed in the wall surface of the nozzle or the vicinity of the end of the wall surface from which the jet to be reduced in noise is injected, and the dimension in the direction along the jet is a dimension in the direction perpendicular to the powder particles. More specifically, the present invention relates to a jet noise reduction method in which an airflow is jetted from an opening formed in a shape that is larger in size and extends along the direction of the powder particles .

According to a second aspect of the present invention, in the ejection layer distance reducing method according to the first aspect, the opening is an opening of a supersonic nozzle opened near a wall surface or an end of the wall surface of the nozzle, and the supersonic nozzle The present invention relates to a jet noise reduction method in which an air flow is jetted from an opening of the jet toward the jet.

A third aspect of the present invention relates to the jet noise reduction method according to the first or second aspect , wherein the airflow is jetted intermittently.

According to a fourth aspect of the present invention, in the jet noise reduction method according to any one of the first to third aspects, the jet is a subsonic jet, and the airflow is a subsonic jet injected with the subsonic jet. The present invention relates to what is jetted toward the subsonic jet near the outlet in the wall surface of the sonic nozzle or in the vicinity of the outlet behind the outlet of the subsonic nozzle.

According to a fifth aspect of the present invention, in the jet noise reduction method according to any one of the first to third aspects, the jet is a supersonic jet, and the airflow is a supersonic jet from which the supersonic jet is injected. The present invention relates to what is injected downstream of the throat portion of the sonic nozzle.

According to a sixth aspect of the present invention, in the jet noise reduction method according to the fifth aspect , the supersonic nozzle has a rectangular cross section, and the opening through which the air current is injected is a wall surface of the supersonic nozzle, or a wall surface. It relates to what is formed near the end.

Invention of Claim 7 is a jet nozzle from which a jet is ejected, Comprising: The dimension of the direction along the said powder grain which injects an airflow toward the said jet, rather than the dimension of the direction orthogonal to the said jet The present invention relates to a jet nozzle in which an opening formed in a shape that is large and spreads along the direction of the particle is formed on a wall surface or in the vicinity of an end of the wall surface.

The invention according to claim 8 relates to the jet nozzle according to claim 7 , wherein the airflow is intermittently injected from the opening.

Invention of Claim 9 is a supersonic nozzle which has a throat part whose cross-sectional area is smaller than the back and front in the jet nozzle of Claim 7 or 8 , and the said opening part is downstream from the said throat part. Related to what is formed.

A tenth aspect of the present invention relates to the jet nozzle according to the ninth aspect , wherein the jet nozzle has a rectangular cross section, and the opening is formed in the vicinity of a wall surface or a wall surface end.

According to the first aspect of the present invention, if the flow rate of the gas ejected as an air stream is the same, the air stream enters deeper into the jet as compared with the case where the air stream is ejected from the opening of the perfect circle. A reduction effect is obtained. Accordingly, the jet noise reduction that requires less gas flow than the case where the opening is formed in a perfect circle or a shape that shrinks along the direction of the jet is required to obtain the same noise reduction effect. A method is provided. Also,

According to the invention of claim 2, since the supersonic nozzle is used as the nozzle for injecting the air current, and the air current is injected at the supersonic speed in the jet, compared with the case of injecting the air current using the subsonic nozzle. Since the air current enters deeper into the jet, a higher noise reduction effect can be obtained. Therefore, the gas flow rate required to obtain the same noise reduction effect is smaller than when the opening is a perfect circle or when the airflow is ejected from the subsonic nozzle.

According to the invention of claim 3, the jet noise that can further reduce the consumption of gas such as air injected as an air current in the jet as compared with the case of injecting the air current continuously in the invention of claim 1 or 2. A reduction method is provided.

According to invention of Claim 4, the jet noise reduction method applicable to a subsonic jet is provided.

According to invention of Claim 5, the jet noise reduction method applicable to a supersonic jet is provided.

According to invention of Claim 6, the jet noise reduction method applicable to the jet jet of a hypersonic machine is provided.

According to the seventh aspect of the present invention, an equivalent or higher jet flow can be obtained with less gas consumption compared to a shape in which the opening for jetting the airflow is formed into a perfect circle or a shape that shrinks along the direction of the jet. A jet nozzle capable of obtaining a noise reduction effect is provided.

According to the eighth aspect of the present invention, there is provided a jet nozzle capable of obtaining an equivalent or higher jet noise reduction effect with a smaller amount of gas consumption compared to that in which an air flow is continuously jetted from an opening.

According to invention of Claim 9, the jet nozzle which can reduce significantly the jet noise of a hypersonic machine is provided.

FIG. 1 is a perspective view illustrating an overall configuration of a supersonic nozzle according to the first embodiment. FIG. 2 is a perspective view illustrating an overall configuration of another example of the supersonic nozzle according to the first embodiment. FIG. 3 is a cross-sectional view showing a cross section of the supersonic nozzle shown in FIG. 2 cut along a vertical plane along the jet flow direction. FIG. 4 is a cross-sectional view showing a cross section of the supersonic nozzle shown in FIG. 2 cut along a horizontal plane along the jet jet direction. FIG. 5 is a schematic diagram illustrating an example of the shape of the opening in the supersonic nozzle according to the first embodiment. FIG. 6 is an explanatory diagram illustrating the definition of the duty ratio when airflow is intermittently ejected from the opening in the supersonic nozzle according to the first embodiment. FIG. 7 is a graph showing the relationship between the total pressure of the airflow and the sound pressure reduction amount when the opening is a circular shape or a wedge shape that expands along the jet jet in the supersonic nozzle according to the first embodiment. FIG. 8 shows the relationship between the amount of bleed air, which is the flow rate ratio between the air flow and the jet jet, and the sound pressure reduction when the opening is circular or a wedge shape that expands along the jet jet in the supersonic nozzle according to the first embodiment. It is a graph which shows. FIG. 9 shows the relationship between the jet noise frequency and the sound pressure when the opening is a wedge shape with an apex angle of 27 degrees and the total pressure of the airflow is set to 0.6 MPa in the supersonic nozzle according to the first embodiment. It is a graph. FIG. 10 is a graph showing the relationship between the bleed air% and the sound pressure reduction amount when the airflow is continuously jetted and intermittently jetted in the supersonic nozzle having a circular opening. FIG. 11 is a graph showing the relationship between the bleed air% and the sound pressure reduction amount when the airflow is continuously injected and intermittently injected in the supersonic nozzle having the wedge-shaped opening.

1. Embodiment 1

  Hereinafter, an example of a supersonic nozzle included in the jet nozzle of the present invention will be described.

  The supersonic nozzle 1 according to the first embodiment is a jet nozzle that discharges a jet jet in the direction of an arrow a as shown in FIGS. 1 to 3, has a rectangular cross section, and has a ceiling surface of a flow path. , A cowl 3 that forms the bottom surface of the flow path, and side walls 4 and 5 that couple the lamp 2 and the cowl 3.

  The ramp 2 projects downstream from the outlet of the supersonic nozzle 1 along the jet jet a. Then, on the upstream side of the outlet of the supersonic nozzle 1, the height of the lower surface is low, and the throat portion 6 is formed between the flat cowl 3. Therefore, the cross-sectional area of the supersonic nozzle 1 is smaller in the throat portion 6 than before and after.

  The side walls 4 and 5 have a flat plate shape, and are formed with wedge-shaped openings 7 (7a) that expand along the jet jet direction a. The opening 7 may be provided only in the side walls 4 and 5 as shown in FIG. 1, or provided in the lamp 2 as shown by reference numeral 7b in addition to the side walls 4 and 5 as shown in FIGS. Alternatively, it may be provided on the cowl 3 as indicated by reference numeral 7c. However, in the case where the opening 7 is provided on any of the side walls 4 and 5, the lamp 2, and the cowl 3, the position where the opening 7 is provided is on the downstream side of the throat portion 6. Further, as indicated by reference numeral 7 d in FIGS. 2 and 3, it may be provided in the vicinity of the side walls 4 and 5 on the downstream side of the injection port of the supersonic nozzle 1. Here, in the present specification, “the wall surface of the nozzle or the vicinity of the end of the wall surface” refers to the side walls 4 and 5 of the supersonic nozzle 1, the ramp 2 and the cowl 3, as indicated by reference numerals 7a, 7b and 7c. This means that it includes both the position that penetrates the wall surface and the vicinity of the wall surface on the outside of the injection port of the supersonic nozzle 1, the side end of the lamp 2, and the outside of the downstream end, as indicated by reference numeral 7d.

  An air flow is ejected from the opening 7 toward the jet jet a as indicated by an arrow b. The angle φ formed by the air flow b and the jet jet a is most preferably 90 degrees as shown in FIG. 4, but is not limited thereto.

  As long as the shape of the opening 7 is smaller than the circular opening having the same cross-sectional area, the projected area projected in the direction along the jet jet a is (a) in FIGS. It is not limited to the wedge shape expanding along the jet jet flow a as shown in FIG. Specifically, a rhombus which is long in the direction of the jet jet a as shown in FIG. 5B, a wedge shape whose trailing edge is rounded as shown in FIG. 5B, and FIG. An oval shape that is long in the direction of the jet jet a as shown, an ellipse whose major axis is the same as the direction of the jet jet a as shown in FIG. 5E, and a jet jet a as shown in FIG. There is a shape such as a long slit in the direction. In addition, it can be paraphrased that these openings 7 have a dimension in the direction along the jet jet a that is larger than a dimension in a direction perpendicular to the jet jet a.

  When the opening 7 has a wedge shape or a diamond shape as shown in FIGS. 5A to 5C, the apex angle θ on the upstream side with respect to the jet jet a is less than 90 degrees, preferably 5 It is -60 degrees, Most preferably, it is 10-30 degrees.

  The gas ejected as the air flow b is normally air, but may be a gas other than air, such as nitrogen gas, carbon dioxide gas, or combustion gas. The air flow b may be continuously injected from the opening 7, but if it is intermittently injected, the amount of gas consumption can be further reduced. The frequency of injecting the air flow b is preferably 10 times / second or more, but there is almost no difference in the jet noise reduction effect obtained even if it exceeds 100 times / second. As shown in FIG. 6, the duty ratio is the jetting time of the air flow b in one cycle, but is preferably in the range of 0.1 to 0.9, and particularly preferably in the range of 0.3 to 0.8. When the duty ratio is less than 0.1, the effect of suppressing the formation of vortices between the jet jet a and the outside air is not sufficiently obtained, and therefore a sufficient jet noise reduction effect may not be obtained. When the ratio exceeds 0.9, there is almost no difference from the continuous injection, so there is almost no effect of reducing gas consumption.

(1) Examples 1 and 2 and Reference Examples 1 to 4

  A wedge-shaped (Examples 1 and 2) or circular (Reference Examples 1 to 4) opening 7 is formed on the side walls 4 and 5 of the supersonic nozzle 1 of the form shown in FIG. The air flow b was jetted in the orthogonal direction. The width of the flow path of the supersonic nozzle 1 was 20 mm, and the height H of the throat portion 6 was 2.8 mm. The upstream side of the throat portion 6 was a straight channel having a height of 7.5 mm. The height of the outlet was 5.9 mm.

  Then, air was jetted as a jet jet a from the nozzle inlet toward the outlet under the condition that the total pressure at the nozzle inlet was 0.27 MPa (a) and the static pressure at the nozzle outlet was atmospheric pressure. The sound pressure of the jet jet a was measured with a microphone (Bruel & Kjaer, Model 4939) at a point 120 mm behind the outlet of the supersonic nozzle 1 and a distance from the jet jet a of 130 mm.

  In Example 1, the apex angle θ on the upstream side of the opening 7 was 14 degrees, and the height w on the downstream side was 0.475 mm. Therefore, w / H is 0.19. In Example 2, the apex angle θ on the upstream side of the opening 7 was 27 degrees, and the height w on the downstream side was 0.575 mm. Therefore, w / H is 0.23.

  On the other hand, in Reference Examples 1 to 4, the diameter d of the opening 7 is 0.3 mm (Reference Example 1), 0.5 mm (Reference Example 2), 0.8 mm (Reference Example 3), 1.0 mm (Reference Example). 4). Therefore, d / H is 0.11, 0.18, 0.29, and 0.36, respectively. About the total pressure of the air flow b in the opening part 7, it set to the range of 0.2 MPa (a) to 0.6 MPa (a) in any of Example 1, 2 and Reference Examples 1-4. In addition, since airflow injection total pressure is described by the absolute pressure, in the case of 0.1 MPa (a), airflow is not injected. The results are shown in FIG.

  As shown in FIG. 7, when the opening 7 is circular, when the diameter is 0.3 mm (d / H = 0.11) and 0.5 mm (d / H = 0.18), the opening 7 Even in the case where the total pressure at 0.6 MPa was 0.6 MPa, the jet noise reduction effect was small, about 0.2 to 0.8 dB. When the diameter is 0.5 mm (d / H = 0.29) and 1.0 mm (d / H = 0.36), the jet noise is sufficiently reduced to 3 to 4 dB (total pressure = 0.6 MPa) for the first time. The effect was obtained.

  On the other hand, in Examples 1 and 2, w / H corresponding to d / H in Reference Examples 1 to 4 is 0.19 to 0.23, which is smaller than d / H in Reference Examples 3 and 4. Regardless, a jet noise reduction effect equivalent to that of Reference Examples 3 and 4 was obtained at about 3 dB at a total pressure of 0.6 MPa.

  Further, as shown in FIG. 8, the extraction%, which is the ratio between the flow rate of the air flow b and the flow rate of the jet jet a required to obtain the jet noise reduction effect of about 3 dB, is 2.5 in the first and second embodiments. It was 4% or more in Reference Examples 3 and 4 while it was ˜3%.

  From this, it can be seen that if the opening 7 is wedge-shaped, the same jet noise reduction effect can be obtained with a smaller gas flow rate than in the case of the round shape.

  When the air flow b is injected from the opening 7 under the condition of the total pressure of 0.6 MPa (a) using the jet nozzle of Example 1, the sound pressure level particularly in a high frequency region of 10 kHz or higher is obtained as shown in FIG. It turns out that it is low. The human audible frequency is said to be 20 Hz to 20 kHz, but in the examples, measurement was performed up to a frequency higher than the human audible frequency. Since the size of the nozzle of the jet jet used in the example is as small as 1/100 of the actual jet engine, the noise frequency measured in the example is about 100 times the noise frequency that would be measured in the actual jet engine. It is considered to be. That is, 10 kHz in FIG. 9 corresponds to about 100 Hz in an actual jet engine.

(2) Examples 5 to 7, Reference Example 5

  When the supersonic nozzle 1 having a circular shape with an opening 7 having a diameter of 0.8 mm is used and continuous injection is performed from the opening 7 (Reference Example 5), the injection is performed at a frequency of 10 times / second (Example 5). For the case of injection at a frequency of 50 times / second (Example 6) and the case of injection at a frequency of 100 times / second (Example 7), the relationship between the extraction% and the sound pressure reduction amount (dB) was obtained. . The duty ratio (DR) was set at three points of 0.3, 0.5, and 0.8, and the total pressure of the air flow b was 0.6 MPa (a). The results are shown in FIG.

  As shown in FIG. 10, when the bleed% is 1.66% and 2%, only the sound pressure reduction amount of 0.4 dB and 1 dB can be obtained in the case of continuous injection, whereas in the case of intermittent injection. The sound pressure reduction amount of 2 to 2.5 dB was obtained. When the frequency of intermittent injection was 10 times / second (f = 10 Hz) and 50 times / second (f = 50 Hz), the latter had a larger sound pressure reduction amount than the former. On the other hand, there was almost no difference in the amount of decrease in sound pressure when the frequency of intermittent injection was 50 times / second (f = 50 Hz) and 100 times / second (f = 100 Hz).

  From this, even if the opening 7 is circular, it is possible to reduce the bleed% required to achieve the same jet noise reduction effect as in the case of continuous injection by intermittently injecting the air flow b. I understand. Moreover, although the injection frequency of the airflow b is preferably 10 times / second or more, it can be seen that the jet noise reduction effect is hardly improved even if the air frequency b exceeds 100 times / second. It can also be seen that the duty ratio is preferably in the range of 0.3 to 0.8.

(3) Examples 8 to 10, Reference Example 6

  When supersonic nozzle 1 used in Example 2 is used and continuous injection is performed from opening 7 having apex angle θ of 27 degrees (Reference Example 6), when injection is performed at a frequency of 10 times / second (Example 8), For the case of injection at a frequency of 50 times / second (Example 9) and the case of injection at a frequency of 100 times / second (Example 10), the relationship between the extraction% and the sound pressure reduction amount (dB) was obtained. . The duty ratio (DR) was set at three points of 0.3, 0.5, and 0.8, and the total pressure of the air flow b was 0.6 MPa (a). The results are shown in FIG.

  As shown in FIG. 11, even in the case of continuous injection, a sufficient sound pressure reduction amount of 2.5 dB was obtained with 3% and a bleed air% less than 4% of Reference Example 5, but in the case of intermittent injection, When the injection frequency was 50 Hz and 100 Hz, a sound pressure reduction amount almost equivalent to that in the case of continuous injection was obtained with a bleed rate of 1.5% at most. From this, even if the opening 7 has a wedge shape that expands along the direction of the jet jet, it is possible to further reduce the extraction% required to inject the air b by intermittently injecting the air b. I know I can do it.

  In these examples, it was found that the frequency of intermittent injection is 10 to 100 times / second, but the suitable frequency of intermittent injection varies depending on the size of the jet nozzle such as a supersonic nozzle. It is considered that the present invention is not limited to the range of 10 to 100 times / second.

  In addition to subsonic or supersonic jet jets, the present invention can be used to reduce noise caused by friction between the jet and surrounding air, such as wind tunnel exhaust noise.

Explanation of symbols

1 Supersonic Nozzle 2 Lamp 3 Cowl 4 Side Wall 5 Side Wall 6 Throat 7 Opening

Claims (10)

The nozzle is formed on the wall surface or near the end of the wall surface of the nozzle where the jet to reduce noise is injected, and the dimension along the jet is larger than the dimension perpendicular to the jet and in the direction of the jet. A jet noise reduction method for jetting an air flow from an opening formed in a shape that extends along the jet toward the jet. The opening is an opening of a supersonic nozzle which opens in the vicinity of a wall or wall end of the nozzle, the jet noise of claim 1, airflow toward the jet from the opening of the supersonic nozzle is injected Reduction method. The jet noise reduction method according to claim 2 , wherein the airflow is jetted intermittently. The jet is a subsonic jet, and the airflow is directed toward the subsonic jet near the outlet of the wall of the subsonic nozzle to which the subsonic jet is injected, or near the outlet behind the outlet of the subsonic nozzle. jet noise reduction method according to any one of claim 1 to 3 to be injected. The jet noise according to any one of claims 1 to 3 , wherein the jet is a supersonic jet, and the airflow is jetted downstream of a throat portion of a supersonic nozzle through which the supersonic jet is jetted. Reduction method. The jet noise reduction method according to claim 5 , wherein the supersonic nozzle has a rectangular cross section, and an opening through which the airflow is injected is formed on a wall surface of the supersonic nozzle or in the vicinity of an end of the wall surface. A jet nozzle from which a jet is ejected, wherein an airflow is ejected toward the jet, a dimension in a direction along the jet is larger than a dimension in a direction perpendicular to the jet, and along the direction of the jet The jet nozzle in which the opening part formed in the shape which expands was formed in the wall surface or the wall surface edge part vicinity. The jet nozzle according to claim 7 , wherein the air stream is intermittently ejected from the opening. The jet nozzle according to claim 7 or 8 , wherein the jet nozzle is a supersonic nozzle having a throat portion whose cross-sectional area is smaller than that of the upstream side and the downstream side, and the opening is formed on the downstream side of the throat portion. The jet nozzle according to claim 9, wherein the jet nozzle has a rectangular cross section, and the opening is formed near a wall surface or an end of the wall surface.

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