Technical Field
[0001] The present invention relates generally to supersonic nozzles and is particularly
directed to attenuating the noise emitted by supersonic nozzles during operation.
The invention will be specifically disclosed in connection with a supersonic nozzle
having an exit to throat ratio within a specified range, internal features of the
supersonic passageway, and external configurations of the nozzle body which tend to
reduce the noise emitted therefrom.
BACKGROUND OF THE INVENTION
[0002] Supersonic nozzles are well known in the art. Conventional converging-diverging nozzles
include a converging section, a throat, and a diverging section. If sufficient pressure
is applied to a converging-diverging nozzle, air velocity of the throat will become
sonic, and then increase as the air expands at the diverging section to produce a
supersonic outlet velocity. The exact exit velocity depends on air pressure, size,
and other details of the nozzle design. A nozzle of this type is disclosed in U.S.
Patent No. 4184638.
[0003] Nozzles may be used for a variety of purposes. They may be operated automatically
while located a distance from the operator and other people. Other nozzles may be
hand held by an operator who directs the exiting flow in order to achieve a particular
purpose. One specific use of such nozzles is in combination with a particle blast
cleaning apparatus such as that disclosed in U.S. Patent No. 4,744,181. Such nozzles
are typically of the type hand held by an operator, who directs the flow, which is
a mixture of transport gas flowing at a supersonic velocity and carbon dioxide pellets
carried along by the transport gas. The flow is directed onto an object to be cleaned
by particle blast or cryogenic particle blast cleaning methods.
[0004] A major problem with the use of supersonic nozzles is the decibel level of the noise
emitted by the nozzle during operation. Such noise becomes a critical factor in the
acceptability and use of a particular nozzle design when people are required to be
nearby. Furthermore, when such nozzles are used in an enclosed area, such as a factory,
the reflective surfaces of the area can tend to increase the decibel level experienced
at particular locations.
[0005] A sound pressure level of 120 dB on the A scale (dBA) has been determined by OSHA
to be the threshold level of pain for a human being. However, in occupational situations,
OSHA limits the exposure level of a person to such noises to less than 90 dBA for
an eight hour time period. Industry and military standards establish this level at
85 dBA.
[0006] Typical prior art nozzles, as used for particle blast cleaning apparatuses, have
been measured to emit noise as high as 130 dBA at the operator's position. In particular,
the nozzle disclosed by U.S. Patent No. 4,038,786 has been documented to emit noise
in the range of 127 dBA. Since the dB scale is logarithymic, a change of three decibels
represents a doubling of the sound pressure level. Thus, the difference between the
OSHA 120 dBA threshold level of pain and the 127 dBA of the typical prior art nozzle,
represents over a fourfold increase in the sound pressure level. When compared to
the 90 dBA OSHA limit, this difference is an increase of over 4,000 times the sound
pressure level of 90 dBA. When compared to the 85 dBA standard of industry and the
military, the 127 dBA level of the typical prior art nozzle has a sound pressure level
more than 16,000 times this standard.
[0007] As is obvious, the sound emitted by supersonic nozzles must be reduced to as low
a level as possible to permit safe continuous operation. While ear protection is available,
such protective devices attenuate the noise only in the range of 20 to 25 dBA. This
would result in a sound pressure level of the typical 127 dBA prior art nozzle of
as low as a 102 dBA at the operator's position. While this would drastically reduce
the sound pressure level experienced by the operator, it would still remain above
the OSHA, industry, and military limits for eight hours of exposure. Furthermore,
in a factory situation, it is unrealistic to require workers in nearby areas who are
not involved with the supersonic nozzle use to wear such ear protection. The ultimate
goal and solution is to use a supersonic nozzle which has a sound pressure level low
enough that an operator wearing approved ear protection devices is subjected to less
than 85 dBA. Such a nozzle would have to have a sound pressure level of less than
115 dBA at the operator position. The 115 dBA level would also be acceptable to workers
without ear protection devices who are more than 15 feet from the operating nozzle.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is a primary object of the present invention to provide a supersonic
nozzle which, during operation, emits noise having a sound pressure level of less
than 115 dBA at the operator's position.
[0009] It is another object of the present invention to provide a supersonic nozzle wherein
the shock waves accompanying such supersonic flow are formed within the supersonic
passageway of the nozzle prior to the exit of the passageway.
[0010] It is yet another object of the present invention to provide a supersonic nozzle
which prevents the coalescing of the shock waves generated by the supersonic flow.
[0011] Yet another object of the present invention is to provide a supersonic nozzle which
may be used in the presence of nearby workers who do not have to wear ear protection
devices to meet the OSHA, industry, and military standards for sound pressure level
exposure.
[0012] Additional objects, advantages, and other novel features of the invention will be
set forth in part in the description that follows and in part will become apparent
to those skilled in the art upon examination of the following or may be learned with
the practice of the invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and combinations particularly
pointed out in the appended claims.
[0013] To achieve the foregoing and other objects, and in accordance with the purposes of
the present invention as described herein, an improved supersonic nozzle is provided
which has a passageway formed in a nozzle body which has an inlet, a throat, and an
exit. The exit area to throat area ratio is in the range of 2.5 to 6.0 whereby the
static pressure of the supersonic flow at the exit is less than the static ambient
pressure.
[0014] In accordance with a first aspect of the invention, there is provided a sound attenuating
supersonic nozzle connectable to a flow of compressible fluid, comprising:
(a) a nozzle body having an exterior surface; and
(b) a supersonic passageway having an interior wall, said supersonic passageway formed
in said nozzle body and having an inlet, a throat, and an exit, said supersonic passageway
also having a converging section from said inlet to said throat and a diverging section
from said throat to said exit, said supersonic passageway adapted for producing sonic
flow at said throat and supersonic flow in said diverging section, characterized by said passageway further having an exit area to throat area ratio in the range of
2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit during
operation of said nozzle is less than the static ambient pressure; and
(c) a plurality of cavities formed in said exterior surface of said nozzle body.
[0015] Preferably, said cavities are formed longitudinally in said exterior surface. A plurality
of inserts may be provided, having complimentary shapes to said longitudinal cavities,
said inserts being disposed in said cavities.
[0016] In accordance with a second aspect of the invention, there is provided a sound attenuating
supersonic nozzle connectable to a flow of compressible fluid, comprising:
(a) a nozzle body having an exterior surface; and
(b) a supersonic passageway having an interior wall, said supersonic passageway formed
in said nozzle body and having an inlet, a throat, and an exit, said supersonic passageway
also having a converging section from said inlet to said throat and a diverging section
from said throat to said exit, said supersonic passageway adapted for producing sonic
flow at said throat and supersonic flow in said diverging section, characterized by said passageway further having an exit area to throat area ratio in the range of
2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit during
operation of said nozzle is less than the static ambient pressure; and
(c) a shield disposed about said exterior surface of said nozzle body and extending
in the direction of flow beyond said exit;
(d) an exit opening formed by said shield, said exit opening being aligned with said
exit of said supersonic passageway, said exit opening being of a complementary shape
to said exit and having a cross sectional area at least as large as the cross sectional
area of said exit; and
(e) an exit cavity defined by said exit of said supersonic passageway, said shield
and said exit opening of said shield.
[0017] Preferably, said exit opening is at least 25% larger than said exit of said supersonic
passageway.
[0018] The nozzle may also comprise first means for allowing auxiliary air flow into said
exit cavity, said first means including means for allowing said auxiliary air flow
to exit through said exit opening of said shield. Preferably, said first means comprises
a gill cavity formed between said exterior surface and said shield, said gill cavity
communicating with the ambient environment at one end and with said exit cavity at
the other end.
[0019] In a preferred embodiment, said exit opening has a perimeter and further comprises
a gill angle formed between said exterior surface and said perimeter, said gill angle
being at least 60°. The shield may so be constructed as not directly to contact any
portion of said exterior surface. Preferably, spacers are disposed between said shield
and said exterior surface of said nozzle body.
[0020] According to a third aspect of the present invention, there is provided a sound attenuating
supersonic nozzle connectable to a flow of compressible fluid, comprising:
(a) a nozzle body having an exterior surface; and
(b) a supersonic passageway having an interior wall, said supersonic passageway formed
in said nozzle body and having an inlet, a throat, and an exit, said supersonic passageway
also having a converging section from said inlet to said throat and a diverging section
from said throat to said exit, said supersonic passageway adapted for producing sonic
flow at said throat and supersonic flow in said diverging section, characterized by said passageway further having an exit area to throat area ratio in the range of
2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit during
operation of said nozzle is less than the static ambient pressure; and
(c) a plurality of longitudinal grooves formed in said interior wall adjacent said
exit thereby preventing the coalescing of shock waves created by the supersonic flow
during operation of said nozzle in said supersonic passageway.
[0021] Preferably, said longitudinal grooves extend from said exit inwardly toward said
throat to the point in said diverging section at which the static pressure of the
supersonic flow during operation of said nozzle is equal to the static ambient pressure.
The depth of said grooves is preferably in the range of 127 µm to 381 µm, and the
distance between said grooves is preferably in the range of 762 µm to 1270 µm.
[0022] In preferred embodiments, the supersonic passageway has an elongated rectangular
cross sectional shape formed by two sets of opposing surfaces, said longitudinal grooves
being formed in one set of said opposing surfaces.
[0023] Still other objects of the present invention will become apparent to those skilled
in this art from the following description wherein there is shown and described preferred
embodiments of this invention, simply by way of illustration, of the best modes contemplated
for carrying out the invention. As will be realized, the invention is capable of other
different embodiments, and that several details are capable of modification in various,
obvious aspects all without departing from the invention. Accordingly, the drawings
and descriptions will be regarded as illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The accompanying drawings incorporated in and forming a part of the specification
illustrate several aspects of the present invention, and together with the descriptions
serve to explain the principles of the invention. In the drawings:
Figure 1 is a perspective view of a first embodiment of the supersonic nozzle.
Figure 2 is an end view along line A of figure 1 showing the exit of the supersonic
nozzle.
Figure 3 is a cross sectional view taken along line 3-3 of figure 2 showing the supersonic
passageway and its profile, as well as longitudinal ribs formed adjacent the exit
of the supersonic passageway.
Figure 4 is a cross sectional view of the throat of the supersonic passageway taken
along lines 3-3 of figure 3, showing in phantom lines the mating portion of the nozzle
body.
Figure 5 is a perspective view of a second embodiment of the supersonic nozzle having
longitudinal inserts disposed in longitudinal cavities formed in the exterior surface
of the nozzle body.
Figure 6 is a perspective view of a third embodiment of the supersonic nozzle having
a shield disposed about the exterior surface of the nozzle body.
Figure 7 is an exploded perspective view of the supersonic nozzle and shield of figure
6.
Figure 8 is a side elevational view of a portion of the shield of figure 6.
Figure 9 is an end elevational view of the shield of figure 8.
Figure 10 is a top view of a portion of the shield of figure 6.
Figure 11 is a side elevational view with the shield shown in partial cross section
showing the nozzle and shield assembly of figure 6.
Figure 12 is an end view of the nozzle of figure 6 in partial cross section showing
the exit opening and the nozzle exit.
Figure 13 is a perspective view showing a fourth embodiment of the supersonic nozzle.
Figure 14 is a perspective view of a fifth embodiment showing a supersonic nozzle
having a circular exit.
[0025] Reference will now be made in detail to the present preferred embodiments of the
invention, an example of which is illustrated in the accompanying drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Referring now to the figures, figure 1 shows a supersonic nozzle generally designated
by the numeral 1 constructed in accordance with the present invention. Nozzle body
2 is shown as being formed of an upper section 3 and a lower section 4, held together
by a plurality of fasteners, such as bolts 5. Referring briefly to figure 3, the supersonic
passageway 6 is formed symmetrically in upper section 3 and lower section 4, and is
shown as a profile, having an inlet 7, a throat 8, and an exit 9. Returning to figure
1, nozzle inlet 10 is shown connected to nozzle body 2 by bolts 11. A passageway (not
shown) is formed through the interior of nozzle inlet 10 which communicates with inlet
7 at one end, and is connectable to receive a flow of compressible fluid at the other
end 12. A pair of spaced grooves 13, 14 are formed about the circumference of nozzle
inlet 10 near end 12.
[0027] Referring to figure 2, which is an end view of nozzle 1, the exterior surface 15
of nozzle body 2 can be seen as being continuous in nature. Passageway 6 and exit
9 are shown as having an elongate rectangular cross sectional shape. In principle,
as depicted here, an elongate rectangle has a dimension in one direction which is
substantially larger than the dimension in the other direction. The rectangle is formed
by an interior wall 16 of supersonic passageway 6. While supersonic passageway 6 is
shown as an elongate rectangle in cross section, as will be described later, it may
also be circular in cross section. With either shape, an elongate rectangle or a circle,
supersonic passageway 6 is considered to have one interior wall 16, although as shown
in figure 2 with the elongate rectangular cross sectional shape, there are four distinct
surfaces, 16A, 16B, 16C, and 16D. As shown, the rectangular cross section can be considered
to be constructed of two sets of opposing surfaces 16A-16C, and 16B-16D.
[0028] Formed in one set of opposing surfaces, 16B and 16D of interior wall 16, are a plurality
of grooves 17. Grooves 17 are shown adjacent exit 9 in figure 3, as actually starting
at exit 9. In practice, grooves 17 may actually extend from exit 9, or be formed a
short distance upstream of exit 9. Grooves 17 extend inwardly from exit 9 toward throat
8 along a length of supersonic passageway 6, to point 18. As shown, grooves 17 are
formed as a series of recesses 17A and ridges 17B, along interior walls 16B and 16D.
[0029] Referring again to figure 3, supersonic passageway 6 is shown having a converging
section 19 from inlet 7 to throat 8. A diverging section 19A is shown from throat
8 to exit 9. Figure 4 shows a cross section taken through throat 8, showing the rectangular
shape thereof, and also indicating that throat 8 has the smallest cross sectional
area of any location in supersonic passageway 6.
[0030] In operation, end 12 of nozzle inlet 10 is connected to flexible hose (not shown)
which delivers a continuous flow of a compressible fluid. As is well understood in
the art, compressible fluids are gases and may be accelerated to supersonic flow through
a converging-diverging nozzle. Grooves 13 and 14 are adapted to be received by a quick
disconnect mechanism (not shown) attached to the hose delivering the flow of compressible
fluid. In the present embodiment of the invention, air flows through the circular
cross section at end 12 of nozzle inlet 10. The interior cavity (not shown) of nozzle
inlet 10 changes from a circular cross section to a rectangular cross section along
the length of nozzle inlet 10 to where it is delivered into inlet 7 of supersonic
passageway 6. The air flows through converging section 19 where it is accelerated
to sonic flow at throat 8. Flowing downstream from throat 8, the sonic flow, following
well known laws of physics, is accelerated to a supersonic velocity as it flows through
diverging section 19A and leaves the nozzle 1 through exit 9.
[0031] In a supersonic nozzle which maximizes the flow momentum, the static pressure of
the flow at the exit will be equal to 0 psig, or stated another way, will be equal
to the static ambient pressure. A nozzle which has a lower static pressure at exit
9 is referred to as an overexpanded - underdeveloped nozzle. In such an overexpanded
nozzle, the static pressure of the flow reaches 0 psig at a point upstream of the
exit. This reduces the efficiency of the nozzle in terms of maximizing the momentum
of the flow exiting the nozzle.
[0032] Shock waves form in such supersonic flow as present here at the point at which the
static pressure of the flow is equal to 0 psig. In the case of a nozzle having greater
than 0 psig static pressure at the exit, shock waves are formed externally at the
exit, and travel from the supersonic passageway. It is these shock waves which produce
the high sound pressure level of a supersonic nozzle while it is operating.
[0033] The present embodiment of the invention lowers the noise generated by the supersonic
nozzle 1 by overexpanding the nozzle. Thus, as shown in figure 3, the flow through
the supersonic nozzle 1 reaches 0 psig static pressure at location 18. It is at this
point in supersonic passageway 6 that shock waves form. The shock waves are attenuated
as they travel from location 19 through exit 9 and out to the ambient environment.
Thus, the noise level is reduced by this design.
[0034] The point at which 0 psig static pressure is achieved in supersonic flow is determined
by the exit to throat ratio, which is the ratio of the cross sectional area of exit
9 to the cross sectional area of throat 8. In isentropic flow (no losses), the ratio
of 2.77 theoretically achieves 0 psig static pressure at the exit. Because ideal flow
(no losses) is impossible to achieve, the actual ratio which produces 0 psig static
pressure is in fact less than 2.77. Empirically, it has been determined that an exit
area to throat area ratio of 2.48 will produce a static pressure of 0 psig at the
exit. Thus, in order to cause the generation of shock waves to occur inside of supersonic
passageway 6, an exit area to throat area ratio of greater than 2.5 is necessary.
The inventors have determined that, as a practical matter, an exit area to throat
area ratio of greater than 6.0 is impractical due to boundary layer separation turbulence
and the potential of stalling the nozzle.
[0035] While maintaining the generation of shock waves within supersonic passageway 6 attenuates
some of the noise of the operation of supersonic nozzle 1, another embodiment of the
present invention also includes grooves 17 formed in the exterior wall 16 of supersonic
passageway 6 as described above. The location of these grooves 17 near exit 9 of supersonic
passageway 6, assists in preventing the shock waves from coalescing with one another
and thereby enhancing and re-enforcing themselves. Grooves 17 are shown as extending
upstream from exit 9 to the point along the length of supersonic passageway 6 at which
0 psig static pressure occurs in the flow. If grooves 17 were to extend beyond this
point, there would be some loss in efficiency of the nozzle without any corresponding
gain in sound attenuation. This is because the shock waves are not formed upstream
of location 18, and, therefore, any portion of grooves 17 extending beyond location
18 will not be functional with respect to preventing the coalescing of shock waves.
[0036] As shown in figure 2, grooves 17 are formed in interior wall 16, and in particular,
on one set of opposing surfaces 16B, 16D. This embodiment operates efficiently when
the distance between the grooves 17 from ridge to ridge 17B is 762µm to 1270µm (.030
inches to .050 inches). It is particularly efficient when this distance is 762µm (.030
inches). Too great of a distance will reduce the efficiency of the grooves 17 in preventing
the coalescing of shock waves.
[0037] The depth of grooves 17 from ridge 17B to recess 17A is in the range of 127µm to
381µm (.005 inches to .015 inches). If the grooves 17 are too shallow, the grooves
17 are ineffective in preventing the coalescing of shock waves. If the grooves 17
are too deep, they reduce the efficiency of the nozzle.
[0038] Referring now to figure 5, supersonic nozzle 1 is shown having a plurality of inserts
20 complementary in shape to and disposed in longitudinal cavities 20A formed in exterior
surface 15. As indicated, in the present embodiment, inserts 20 are disposed on opposite
exterior surfaces 15B and 15D. Inserts 20 and cavities 20A are shown as running the
length of nozzle body 2, terminating at end 21 of nozzle body 2. Inserts 20 may be
flush with exterior surface 15 as shown or may terminate above or below exterior surface
15. Inserts 20 may be a single piece per cavity 20A or may be layered of several inserts
20 in one cavity 20A.
[0039] While nozzle body 2 may be formed of any suitable material, in the present embodiment
it is formed of aluminum. Inserts 20 are preferably of a similar material, having
a greater density than the material which forms nozzle body 2. In the present embodiment,
inserts 20 are made of lead.
[0040] Noise generated by the operation of supersonic nozzle 1 may also travel through nozzle
body 2, being absorbed and then re-emitted from the nozzle. By disposing inserts 20
in cavities 20A on exterior surface 15 of nozzle body 2, the ability of nozzle body
2 to transmit the noise is reduced. By forming discontinuous shapes, i.e. cavities
20A, in exterior surface 15, resonance in surface 15 is prevented at certain frequencies.
Inserts 20 formed of lead, absorb some of the energy of the transmitted sound due
to the density of the lead, and thereby reduces the transmission of sound from the
surface of the lead.
[0041] An alternative embodiment to figure 5, is to form cavities 20A in exterior surface
15 of nozzle body 2 without disposing inserts in cavities 20A. As mentioned above,
such discontinuity of exterior surface 15 helps to decrease the transmission of sound
therefrom. However, also as described, the sound is reduced even further by filling
cavities 20A with inserts 20. Although longitudinal cavities and inserts are shown,
randomly sized and located cavities and inserts will also produce similar sound attenuation.
Although figure 5 shows the use of cavities 20A and inserts 20 on a nozzle having
grooves 17 in supersonic passageway 6, it should be understood that either may be
used alone or in combination.
[0042] Referring to figures 6 and 7, another embodiment is shown. Supersonic nozzle 1 has
a shield 22 disposed about a portion of exterior surface 15 of nozzle body 2. The
shield is formed of two portions, 22A, 22B, and is secured by a plurality of bolts
23 which also hold upper section 3 and lower section 4 of nozzle body 2 together.
Shield 22 is shown extending beyond exit 9 in the direction of flow. Exit opening
24 is formed at end 25 of shield 22. Exit opening 24 is defined by perimeter 26 and
is generally aligned with exit 9 as shown in figure 12. Exit opening 24 is larger
than exit 9, and as shown, is preferably at least 25% larger than exit 9.
[0043] Figure 8 shows a side elevational view of shield portion 22B. Referring also figures
9 and 10, shield 22B has sides 27A and 27B extending perpendicularly from wall 28.
Relief 29 is shown formed in wall 28, resulting in steps 30A and 30B formed adjacent
sides 27A and 27B, respectively. End 31 is formed between side 27A, wall 28, and side
27B at one end of shield 22B. A portion of perimeter 26 is formed by end 31.
[0044] Referring to figure 7, symmetrical shields 22A and 22B are assembled about nozzle
body 2, with spacers 33 located between exterior surface 15 and steps 30A and 30B,
thereby preventing any direct contact between shield 22 and nozzle body 2. The distance
between sides 27A and 27B is greater than the distance between exterior surfaces 15A
and 15C, also preventing any direct contact between shield 22 and nozzle body 2.
[0045] Referring now to figure 11, shows shield 22 in partial cross section as disposed
about nozzle body 2 of supersonic nozzle 1. Exit cavity 34 is defined by exit 9 of
supersonic passageway 6, shield 22A, 22B, and exit opening 24. Formed between shield
22 and exterior surface 15 is an air cavity or gill cavity 35 which communicates with
the ambient environment at gill opening 36 at one end, and with exit cavity 34 at
the other end. The size of gill cavity 35 is further enhanced by the spacing of shield
22A, 22B from exterior surface 15 by a plurality of spacers 33, and by relief 29 of
shield 22B and the corresponding symmetrical relief of shield 22A.
[0046] By assembling shield 22 to surround nozzle body 2 as shown in figures 6, 11, and
12, additional sound attenuation is achieved. The transmission of sound from exterior
surface 15 of nozzle body 2 is reduced due to the spacing of shield 22A, 22B from
exterior surface 15. Sound which reaches shield 22A, 22B is reflected and absorbed
by the interior surface 37A of shield 22 and only a portion of the sound is re-emitted
from the exterior surface 37 of shield 22. Furthermore, exit cavity 34 acts to attenuate
the shock waves emerging with the flow from exit 9 prior to exiting through exit opening
24.
[0047] It is important that exit opening 24 not act as the exit of supersonic nozzle 1.
To prevent this, an auxiliary air flow passes through gill cavity 35, and exits through
exit opening 24 in combination with the supersonic flow from exit 9. The supply of
auxiliary air through gill cavity 27 must be sufficient to prevent any effect of exit
cavity 34 on the actual supersonic flow at exit 9. Satisfactory auxiliary air flow
has been achieved in practice by maintaining the depth of relief 29 formed in shield
22A and 22B at .050 inches.
[0048] The auxiliary air flow mixes with the supersonic air flow while exiting through exit
opening 24. To prevent turbulence and other undesirable effects, it is best if the
mixing of the two flows occurs as tangentially as possible. To this end, it has been
determined that optimum results are obtained if the angle 38 formed between exterior
surface 15 at end 39 of nozzle body 2 and perimeter 26 be no less than 60°, although
the nozzle 1 is operable with an angle 38 of less than 60°. Angle 38 is called the
gill angle.
[0049] It is anticipated that the nozzle body will be formed of aluminum. Shield 22 may
be formed of brass or other similar material. Spacers 33 are formed of a fiber material,
having poor sound transmission properties, to reduce the transmission of sound from
exterior surface 15 through spacers 33 to shield 22. While it is anticipated that
shield 22 be used in combination with grooves 17 and a supersonic nozzle having an
exit to throat ratio in the range of 2.5 to 6.0, the shield will in fact attenuate
sound independent of the presence of grooves 17. Of course, for optimum sound attenuation,
the preferred embodiment encompasses all three of these features. Additionally, one
skilled in the art may find improvement in the sound attenuation performance of the
preferred embodiment by further disposing cavities and inserts (not shown) on exterior
surface 37 of shield 22.
[0050] Figure 12 shows an end view of the nozzle of figure 6, with shield 22 partially cut
away. As can be seen, exit opening 24 is aligned with exit 9. Gill cavity 35 extends
completely around nozzle body 2 between exterior surface 15 and interior surface 37A
of shield 22.
[0051] The inventors have determined that a nozzle according to the present invention, having
an exit to throat ratio of 2.69 in combination with grooves formed in the supersonic
passageway as described above, will produce a sound pressure level of 112 dBA at the
operator position. By adding the shield to this nozzle, further sound attenuation
is achieved and the sound pressure level at the operator's location is reduced to
as low as 104 dBA.
[0052] Figure 13 shows another embodiment of the present invention having an elongated nozzle
body 40, with shield 41 secured near the end of the nozzle body 40 as described above
in conjunction with the embodiment of figure 6.
[0053] Figure 14 shows another embodiment having a supersonic passageway with a circular
cross section in combination with grooves formed in the interior wall of the supersonic
passageway, and a shield disposed about the nozzle body, spaced therefrom.
[0054] In summary, numerous benefits have been described which result from employing the
concepts of the invention. The supersonic nozzle described herein produces highly
attenuated sound pressure levels at the operator position, which allows safer and
more convenient use thereof.
[0055] The foregoing description of preferred embodiments of the invention has been presented
for purposes of illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise formed disclosed. Obvious modifications or
variations are possible in light of the above teachings. The embodiments were chosen
and described in order to best illustrate the principles of the invention and its
practical application to thereby enable one of ordinary skill in the art to best utilize
the invention in various embodiments and with various modifications as are suited
to the particular use contemplated.
1. A sound attenuating supersonic nozzle (1) connectable to a flow of compressible fluid,
comprising:
(a) a nozzle body (2) having an exterior surface (15); and
(b) a supersonic passageway (6) having an interior wall (16), said supersonic passageway
(6) formed in said nozzle body (2) and having an inlet (7), a throat (8), and an exit
(9), said supersonic passageway (6) also having a converging section (19) from said
inlet (7) to said throat (8) and a diverging section (19a) from said throat (8) to
said exit (9), said supersonic passageway (6) adapted for producing sonic flow at
said throat (8) and supersonic flow in said diverging section (19a), characterized by said passageway (6) further having an exit area to throat area ratio in the range
of 2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit (9)
during operation of said nozzle (1) is less than the static ambient pressure; and
(c) a plurality of cavities (20a) formed in said exterior surface (15) of said nozzle
body (2).
2. A nozzle (1) as claimed in claim 1 wherein said cavities (20a) are formed longitudinally
in said exterior surface (15).
3. A nozzle (1) as claimed in claim 2 further comprising a plurality of inserts (20),
said inserts (20) having complementary shapes to said longitudinal cavities (20a),
said inserts (20) being disposed in said cavities (20a).
4. A sound attenuating supersonic nozzle (1) connectable to a flow of compressible fluid,
comprising:
(a) a nozzle body (2) having an exterior surface (15); and
(b) a supersonic passageway (6) having an interior wall (16), said supersonic passageway
(6) formed in said nozzle body (2) and having an inlet (7), a throat (8), and an exit
(9), said supersonic passageway (6) also having a converging section (19) from said
inlet (7) to said throat (8) and a diverging section (19a) from said throat (8) to
said exit (9), said supersonic passageway (6) adapted for producing sonic flow at
said throat (8) and supersonic flow in said diverging section (19a), characterized by said passageway (6) further having an exit area to throat area ratio in the range
of 2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit (9)
during operation of said nozzle (1) is less than the static ambient pressure; and
(c) a shield (22) disposed about said exterior surface (15) of said nozzle body (2)
and extending in the direction of flow beyond said exit (9);
(d) an exit opening (24) formed by said shield (22), said exit opening (24) being
aligned with said exit (9) of said supersonic passageway (6), said exit opening (24)
being of a complementary shape to said exit (9) and having a cross sectional area
at least as large as the cross sectional area of said exit (9); and
(e) an exit cavity (34) defined by said exit (9) of said supersonic passageway (6),
said shield (22) and said exit opening (24) of said shield (22).
5. A nozzle (1) as claimed in claim 4 wherein said exit opening (24) is at least 25%
larger than said exit (9) of said supersonic passageway (6).
6. A nozzle (1) as claimed in claim 4 or 5 further comprising first means (35) for allowing
auxiliary air flow into said exit cavity (34), said first means (35) including means
for allowing said auxiliary air flow to exit through said exit opening (24) of said
shield (22).
7. A nozzle (1) as claimed in claim 6 wherein said first means (35) comprises a gill
cavity (35) formed between said exterior surface (15) and said shield (22), said gill
cavity (35) communicating with the ambient environment at one end and with said exit
cavity (34) at the other end.
8. A nozzle (1) as claimed in claim 7 wherein said exit opening (24) has a perimeter
(26) and further comprises a gill angle (38) formed between said exterior surface
(15) and said perimeter (26), said gill angle (38) being at least 60°.
9. A nozzle (1) as claimed in any one of claims 4-8 wherein said shield (22) does not
directly contact any portion of said exterior surface (15).
10. A nozzle (1) as claimed in claim 9 wherein spacers (33) are disposed between said
shield (22) and said exterior surface (15) of said nozzle body (2).
11. A sound attenuating supersonic nozzle (1) connectable to a flow of compressible fluid,
comprising:
(a) a nozzle body (2) having an exterior surface (15); and
(b) a supersonic passageway (6) having an interior wall (16), said supersonic passageway
(6) formed in said nozzle body (2) and having an inlet (7), a throat (8), and an exit
(9), said supersonic passageway (6) also having a converging section (19) from said
inlet (7) to said throat (8) and a diverging section (19a) from said throat (8) to
said exit (9), said supersonic passageway (6) adapted for producing sonic flow at
said throat (8) and supersonic flow in said diverging section (19a), characterized by said passageway (6) further having an exit area to throat area ratio in the range
of 2.5 to 6.0, whereby the static pressure of the supersonic flow at said exit (9)
during operation of said nozzle (1) is less than the static ambient pressure; and
(c) a plurality of longitudinal grooves (17) formed in said interior wall adjacent
said exit (9) thereby preventing the coalescing of shock waves created by the supersonic
flow during operation of said nozzle (1) in said supersonic passageway (6).
12. A nozzle (1) as claimed in any one of claims 1-10 further comprising a plurality of
longitudinal grooves (17) formed in said internal wall adjacent said exit (9) thereby
preventing the coalescing of shock waves created by the supersonic flow during operation
of said nozzle (1) in said supersonic passageway (6).
13. A nozzle (1) as claimed in claim 11 or claim 12 wherein said longitudinal grooves
(17) extend from said exit (9) inwardly toward said throat (8) to the point in said
diverging section (19a) at which the static pressure of the supersonic flow during
operation of said nozzle (1) is equal to the static ambient pressure.
14. A nozzle (1) as claimed in any one of claims 11-13 or claim 13 wherein the depth of
said grooves (17) is in the range of 127 µm to 381 µm (.005 inches to .015 inches).
15. A nozzle (1) as claimed in any one of claims 11-14 wherein the distance between said
grooves (17) is in the range of 762 µm to 1270 µm (.030 inches to .050 inches).
16. A nozzle (1) as claimed in any one of claims 11-15 wherein said supersonic passageway
(6) has an elongate rectangular cross sectional shape formed by two sets of opposing
surfaces (16a,16b,16c,16d), said longitudinal grooves (17) being formed in one set
of said opposing surfaces.
17. A nozzle (1) as claimed in any preceding claim further comprising:
(a) a nozzle inlet connected to said nozzle body (2); and
(b) an inlet passageway formed in said nozzle inlet, said inlet passageway adapted
to receive the flow of compressible fluid and to deliver the flow of compressible
fluid to said inlet (7) of said supersonic passageway (6), said inlet passageway having
an inlet of circular cross section and an outlet of rectangular cross section.
18. A nozzle (1) as claimed in claim 17 wherein said nozzle inlet is adapted to be used
with a quick disconnect mechanism.
19. A nozzle (1) as claimed in claim 3 wherein said inserts (20) do not extend beyond
said exterior surface (15).
20. A nozzle (1) as claimed in claim 3 or 19 wherein said inserts (20) are formed of a
material which is different than the material from which said exterior surface (15)
of said nozzle body (2) is formed.
21. A nozzle (1) as claimed in claim 3, 19 or 20 wherein said inserts (20) are formed
of a material which is denser than the material from which said exterior surface (15)
of said nozzle body (2) is formed.
1. Schalldämpfende Überschalldüse (1), die mit einer Strömung kompressiblen Fluids verbunden
ist, umfassend:
a) ein Düsengehäuse (2) mit einer Außenfläche (15); und
b) einen Überschalldurchgang (6) mit einer Innenwandung (16), wobei dieser Überschalldurchgang
(6) in diesem Düsenkörper (2) ausgebildet ist und über einen Einlaß (7), einen Hals
(8) und einen Auslaß (9) verfügt, wobei dieser Überschalldurchgang (6) auch einen
konvergierenden Abschnitt (19) von diesem Einlaß (7) zu diesem Hals (8) und einen
divergierenden Abschnitt (19a) von diesem Hals (8) zu diesem Auslaß (9) aufweist,
wobei dieser Überschalldurchgang (6) so ausgelegt ist, daß er Schallströmung an diesem
Hals (8) und Überschallströmung in diesem divergierenden Abschnitt (19a) erzeugt dadurch gekennzeichnet, daß dieser Durchgang (6) weiterhin ein Verhältnis von Austrittsfläche zu Halsfläche
im Bereich von 2,5 bis 6,0 hat, wobei der statische Druck der Überschallströmung an
diesem Austritt (9) während des Betriebes dieser Düse (1) geringer als der statische
Umgebungsdruck ist; und
c) eine Vielzahl von Ausnehmungen (20a) in dieser Außenfläche (15) dieses Düsenkörpers
(2) ausgebildet sind.
2. Eine Düse (1) nach Anspruch 1, wobei diese Ausnehmungen (20a) in Längsrichtung in
dieser Außenfläche (15) geformt sind.
3. Eine Düse nach Anspruch 2, die weiterhin eine Vielzahl von Einsätzen (20) umfaßt,
wobei diese Einsätze (20) Formen komplementär zu diesen Längsausnehmungen (20a) haben,
wobei diese Einsätze (20) in diesen Ausnehmungen (20a) angeordnet sind.
4. Eine schalldämpfende Überschalldüse (1), die mit einer Strömung kompressiblen Fluids
verbindbar ist, umfassend:
a) einen Düsenkörper (2) mit einer Außenfläche (15); und
b) einen Überschalldurchgang (6) mit einer Innenwandung (16), wobei dieser Überschalldurchgang
(6) in diesem Düsenkörper (2) ausgebildet ist und über einen Einlaß (7), einen Hals
(8) und einen Austritt (9) verfügt, wobei dieser Überschalldurchgang (6) auch einen
konvergierenden Abschnitt (19) von diesem Eintritt (7) zu diesem Hals (8) sowie einen
divergierenden Abschnitt (19a) von diesem Hals (8) zu diesem Austritt (9) hat, wobei
dieser Überschalldurchgang (6) so ausgelegt ist, daß er Schallströmung an diesem Hals
(8) und Überschallströmung in diesem divergierenden Abschnitt (19a) erzeugt, dadurch gekennzeichnet, daß dieser Durchgang (6) weiterhin ein Verhältnis von Austrittsfläche zu Halsfläche
im Bereich von 2,5 bis 6,0 hat, wobei der statische Druck der Überschallströmung an
diesem Austritt (9) während des Betriebs dieser Düse (1) geringer als der statische
Umgebungsdruck ist; und
c) einen Schirm (22), der um diese Außenfläche (15) dieses Düsengehäuses (2) angeordnet
ist und in Strömungsrichtung über diesen Austritt (9) hinaus sich erstreckt;
d) eine durch diesen Schirm (23) gebildete Austrittsöffnung (24), wobei diese Austrittsöffnung
(24) ausgerichtet bezüglich dieses Austritts (9) dieses Überschalldurchgangs (6) ist,
wobei diese Austrittsöffnung (24) in der Gestalt komplementär zu diesem Austritt (9)
ist und über eine Querschnittsfläche verfügt, die wenigstens so groß wie die Querschnittsfläche
dieses Austritts (9) ist; und
e) einen Austrittshohlraum (34), der definiert wird durch diesen Austritt (9) dieses
Überschalldurchgangs (6), diesen Schirm (22) und diese Austrittsöffnung (24) dieses
Schirms (22).
5. Eine Düse (1) nach Anspruch 4, wobei diese Austrittsöffnung (24) wenigstens 25% größer
als dieser Austritt (9) dieses Überschalldurchgangs (6) ist.
6. Eine Düse (1) nach Anspruch 4 oder 5, die weiterhin erste Mittel (35) umfaßt, die
eine Hilfsluftströmung in diese Austrittsausnehmung (34) ermöglicht, wobei diese ersten
Mittel (35) Mittel umfassen, um diese Hilfsluftströmung durch diese Austrittsöffnung
(24) dieses Schildes (22) austreten zu lassen.
7. Eine Düse (1) nach Anspruch 6, wobei dieses erste Mittel (35) eine Rippenausnehmung
(35) umfaßt, die zwischen dieser Außenfläche (15) und diesem Schild (22) ausgebildet
ist, wobei diese Rippenausnehmung (35) mit der Umgebung an einem Ende und mit der
Austrittsausnehmung (34) am anderen Ende in Verbindung steht.
8. Eine Düse (1) nach Anspruch 7, wobei diese Austrittsöffnung (24) einen Umfang (26)
hat und weiterhin einen Rippenwinkel (38) aufweist, der zwischen dieser Außenfläche
(15) und diesem Umfang (26) gebildet ist, wobei dieser Rippenwinkel (38) wenigstens
60° beträgt.
9. Eine Düse (1) nach einem der Ansprüche 4 bis 8, wobei dieser Schirm (22) nicht direkt
irgendeinen Teil dieser Außenfläche (15) kontaktiert.
10. Eine Düse nach Anspruch 9, wobei Distanzstücke (33) zwischen diesem Schirm (22) und
dieser Außenfläche (15) dieses Düsenkörpers (2) angeordnet sind.
11. Eine schalldämpfende Überschalldüse (1), die mit einer Strömung kompressiblen Fluids
verbindbar ist, umfassend:
a) ein Düsengehäuse (2) mit einer Außenfläche (15); und
b) einen Überschalldurchgang (6) mit einer Innenwand (16), wobei dieser Überschalldurchgang
(6) in diesem Düsenkörper (2) gebildet ist und über einen Einlaß (7), einen Hals (8)
und einen Austritt (9) verfügt, wobei dieser Überschalldurchgang (6) auch einen konvergierenden
Abschnitt (19) von diesem Einlaß (7) zu diesem Hals sowie einen divergierenden Abschnitt
(19a) von diesem Hals (8) zu diesem Austritt (9) aufweist, wobei dieser Überschalldurchgang
(6) so ausgelegt ist, daß er Schallströmung an diesem Hals (8) und Überschallströmung
in diesem divergierenden Abschnitt (19a) erzeugt,
dadurch gekennzeichnet, daß dieser Durchgang (6) weiterhin ein Verhältnis von Austrittsfläche zu Halsfläche
im Bereich von 2,5 bis 6,0 aufweist, wobei der statische Druck dieser Überschallströmung
an diesem Austritt (9) während des Betriebs dieser Düse (1) geringer als der statische
Umgebungsdruck ist; und
c) eine Vielzahl von Längsnuten (17), die in dieser Innenwand benachbart diesem Austritt
(9) gebildet sind, wodurch das Koaleszieren von Stoßwellen verhindert wird, die durch
die Überschallströmung während des Betriebs dieser Düse (1) in diesem Überschalldurchgang
(6) erzeugt wurden.
12. Eine Düse nach einem der Ansprüche 1 bis 10, die weiterhin eine Vielzahl von Längsnuten
(17) umfaßt, die in dieser Innenwand benachbart diesem Austritt (9) ausgebildet sind,
wodurch das Koaleszieren von Schallwellen verhindert wird, die durch die Überschallströmung
während des Betriebs der Düse (1) in diesem Überschalldurchgang (6) erzeugt wurden.
13. Eine Düse (1) nach einem der Ansprüche 11 oder 12, wobei diese Längsnuten (17) sich
von diesem Austritt (9) nach innen gegen diesen Hals (8) bis zu der Stelle in diesem
divergierenden Abschnitt (19a) erstrecken, an dem der statische Druck der Überschallströmung
während des Betriebs der Düse (1) gleich dem statischen Umgebungsdruck ist.
14. Eine Düse (1) nach einem der Ansprüche 11 bis 13 oder 13, wobei die Tiefe dieser Nuten
(17) im Bereich von 127 µm bis 381 µm (0,05 englische Zoll bis 0,15 englische Zoll)
beträgt.
15. Eine Düse (1) nach einem der Ansprüche 11 bis 14, wobei der Abstand zwischen den Nuten
(17) sich im Bereich von 762 µm bis 1270 µm (0,030 englische Zoll bis 0,050 englische
Zoll) beträgt.
16. Eine Düse (1) nach einem der Ansprüche 11 bis 15, wobei dieser Überschalldurchgang
(6) eine längliche rechtwinklige Querschnittsgestalt hat, die durch zwei Gruppen von
sich gegenüberstehenden Flächen (16a, 16b, 16c, 16d) gebildet sind, wobei diese Längsnuten
(17) in einer Gruppe dieser sich gegenüberstehenden Flächen ausgebildet sind.
17. Eine Düse (1) nach einem der vorhergehenden Ansprüche weiterhin umfassend:
a) einen mit diesem Düsengehäuse (2) verbundenen Düseneinlaß; und
b) einen Einlaßdurchgang in diesem Düseneinlaß, wobei der Einlaßdurchgang so ausgelegt
ist, daß er die Strömung kompressiblen Fluids aufnimmt und diese Strömung kompressiblen
Fluids an diesen Einlaß (7) dieses Überschalldurchgangs (6) liefert, wobei der Einlaßdurchgang
einen Einlaß kreisförmigen Querschnitts sowie einen Auslaß rechtwinkligen Querschnitts
aufweist.
18. Eine Düse (1) nach Anspruch 17, wobei dieser Düseneinlaß so ausgelegt ist, daß er
sich mit einem Schnellkupplungsmechanismus verbinden läßt.
19. Eine Düse nach Anspruch 3, wobei diese Einsätze (20) sich nicht über diese Außenfläche
(15) hinaus erstrecken.
20. Eine Düse (1) nach Anspruch 3 oder 19, wobei diese Einsätze (20) aus einem Material
gebildet sind, das unterschiedlich zu dem Material ist, aus dem diese Außenfläche
(15) dieses Düsenkörpers (2) gebildet ist.
21. Eine Düse (1) nach Anspruch 3, 19 oder 20, wobei diese Einsätze (20) aus einem Material
gebildet sind, das dichter als das Material ist, aus dem diese Außenfläche (15) dieses
Düsenkörpers (2) gebildet ist.
1. Tuyère supersonique (1) atténuant le bruit, pouvant être raccordée à un écoulement
d'un fluide compressible, comprenant:
(a) un corps de tuyère (2) possédant une surface extérieure (15); et
(b) un passage supersonique (6) possédant une paroi intérieure (16), ledit passage
supersonique (6) étant formé dans ledit corps de tuyère (2) et possédant une entrée
(7), un rétrécissement (8) et une sortie (9), ledit passage supersonique (6) possédant
également une section convergente (19) s'étendant de ladite entrée (7) audit rétrécissement
(8) et une section divergente (19a) s'étendant dudit rétrécissement (8) à ladite sortie
(9), ledit passage supersonique (6) étant adapté pour produire un écoulement sonique
au niveau dudit rétrécissement (8) et un écoulement supersonique dans ladite section
divergente (19a),
caractérisé en ce que ledit passage (6) possède en outre un rapport de la surface
de sortie à la surface du rétrécissement compris dans la plage de 2,5 à 6,0 , ce qui
a pour effet que la pression statique de l'écoulement supersonique au niveau de ladite
sortie (9) pendant le fonctionnement de ladite tuyère (1) est inférieure à la pression
ambiante statique; et
(c) une pluralité de cavités (20a) formées dans ladite surface extérieure (15) dudit
corps de tuyère (2).
2. Tuyère (1) selon la revendication 1, dans laquelle lesdites cavités (20a) sont formées
dans la direction longitudinale dans ladite surface extérieure (15).
3. Tuyère (1) selon la revendication 2, comprenant en outre une pluralité d'inserts (20),
lesdits inserts (20) possédant des formes complémentaires desdites cavités longitudinales
(20a), lesdits inserts (20) étant disposés dans lesdites cavités (20a).
4. Tuyère supersonique (1) atténuant le bruit, pouvant être raccordée à un écoulement
de fluide compressible,
(a) un corps de tuyère (2) possédant une surface extérieure (15); et
(b) un passage supersonique (6) possédant une paroi intérieure (16), ledit passage
supersonique (6) étant formé dans ledit corps de tuyère (2) et possédant une entrée
(7), un rétrécissement (8) et une sortie (9), ledit passage supersonique (6) possédant
également une section convergente (19) s'étendant de ladite entrée (7) audit rétrécissement
(8) et une section divergente (19a) s'étendant dudit rétrécissement (8) à ladite sortie
(9), ledit passage supersonique (6) étant adapté pour produire un écoulement sonique
au niveau dudit rétrécissement (8) et un écoulement supersonique dans ladite section
divergente (19a),
caractérisé en ce que ledit passage comporte en outre un rapport de la surface
de sortie à la surface du rétrécissement compris dans la plage de 2,5 à 6,0, ce qui
a pour effet que la pression statique de l'écoulement supersonique au niveau de ladite
sortie (9) pendant le fonctionnement de ladite tuyère (1) est inférieure à la pression
ambiante statique; et
(c) un blindage (22) disposé autour de ladite surface extérieure (15) dudit corps
de tuyère (2) et s'étendant dans la direction d'écoulement au-delà de ladite sortie
(9);
(d) une ouverture de sortie (24) formée par ledit blindage (22), ladite ouverture
de sortie (24) étant alignée avec ladite sortie (9) dudit passage supersonique (6),
ladite ouverture de sortie (24) ayant une forme complémentaire de ladite sortie (9)
et possédant une surface en coupe transversale au moins aussi grande que la surface
en coupe transversale de ladite sortie (9); et
(e) une cavité de sortie (34) définie par ladite sortie (9) dudit passage supersonique
(6), ledit blindage (22) et ladite ouverture de sortie (24) dudit blindage (22).
5. Tuyère (1) selon la revendication 4, dans laquelle ladite ouverture de sortie (24)
est au moins 25% plus étendue que ladite sortie (9) dudit passage supersonique (6).
6. Tuyère (1) selon la revendication 4 ou 5, comprenant en outre des premiers moyens
(35) pour permettre l'introduction d'un écoulement d'air auxiliaire dans ladite seconde
cavité de sortie (34); lesdits premiers moyens (35) comprenant des moyens pour permettre
audit écoulement d'air auxiliaire de sortie par ladite ouverture de sortie (24) dudit
blindage (22).
7. Tuyère (1) selon la revendication 6, dans laquelle lesdits premiers moyens (35) comprennent
une cavité d'aération (35) formée entre ladite surface (15) et ledit blindage (22),
ladite cavité d'aération (35) communiquant, à une extrémité, avec l'environnement
ambiant et, à l'autre extrémité, avec ladite cavité de sortie (34).
8. Tuyère (1) selon la revendication 7, dans laquelle ladite ouverture de sortie (24)
possède un pourtour (26) et comporte en outre un angle d'aération (38) formé entre
ladite surface extérieure (15) et ledit pourtour (26), ledit angle d'aération (38)
étant égal au moins à 60°.
9. Tuyère (1) selon l'une quelconque des revendications 4-8, dans laquelle ledit blindage
(22) ne vient pas en contact direct avec une partie quelconque de ladite surface extérieure
(15).
10. Tuyère (1) selon la revendication 9, dans laquelle des entretoises (33) sont disposées
entre ledit blindage (22) et ladite surface extérieure (15) dudit corps de tuyère
(2).
11. Tuyère supersonique (1) atténuant le bruit, pouvant être raccordée à un écoulement
de fluide compressible, comprenant:
(a) un corps de buse (2) possédant une surface extérieure (15); et
(b) un passage supersonique (6) possédant une paroi intérieure (16), ledit passage
supersonique (6) étant formé dans ledit corps de tuyère (2) et possédant une entrée
(7), un rétrécissement (8) et une sortie (9), ledit passage supersonique (6) possédant
également une section convergente (19) s'étendant de ladite entrée (7) audit rétrécissement
(8) et une section divergente (19a) s'étendant dudit rétrécissement (8) à ladite sortie
(9), ledit passage supersonique (6) étant adapté pour produire un écoulement sonique
au niveau dudit rétrécissement (8) et un écoulement supersonique dans ladite section
divergente (19a),
caractérisé en ce que ledit passage (6) possède en outre un rapport de la surface
de sortie à la surface du rétrécissement compris dans la plage de 2,5 à 6,0, ce qui
a pour effet que la pression statique de l'écoulement supersonique au niveau de ladite
sortie (9) pendant le fonctionnement de ladite tuyère (1) est inférieure à la pression
ambiante statique; et
(c) une pluralité de rainures longitudinales (17) ménagées dans ladite paroi intérieure
adjacente à ladite sortie (9), ce qui empêche la coalescence des ondes de choc créées
par l'écoulement supersonique pendant le fonctionnement de ladite tuyère (1) dans
ledit passage supersonique (6).
12. Tuyère (1) selon l'une des revendications 1-10, comprenant en outre une pluralité
de rainures longitudinales (17) ménagées dans ladite paroi interne adjacente à ladite
sortie (9), de manière à empêcher la coalescence des ondes de choc créées par l'écoulement
supersonique pendant le fonctionnement de ladite tuyère (1) dans ledit passage supersonique
(6).
13. Tuyère (1) selon la revendication 11 ou 12, dans laquelle lesdites rainures longitudinales
(17) s'étendent à partir de ladite sortie (9) vers l'intérieur en direction dudit
rétrécissement (8) jusqu'au point situé dans ladite section divergente (19a) et où
la pression statique de l'écoulement supersonique pendant le fonctionnement de ladite
tuyère (1) est égale à la pression statique ambiante.
14. Tuyère (1) selon l'une quelconque des revendications 11-13 ou selon la revendication
13, dans laquelle la profondeur desdites rainures (17) dans la plage de 127 µm à 381
µm (0,005 pouce à 0,015 pouce).
15. Tuyère (1) selon l'une quelconque des revendications 11-14, dans laquelle la distance
entre lesdites rainures (17) se situer dans la plage de 762 µm à 1270 µm (0,030 pouce
à 0,050 pouce).
16. Tuyère (1) selon l'une quelconque des revendications 11-15, dans laquelle ledit passage
supersonique (6) possède une forme en coupe transversale rectangulaire formée de deux
ensembles de deux surfaces opposées (16a, 16b, 16c, 16d), lesdites rainures longitudinales
(17) étant formées dans un ensemble desdites surfaces opposées.
17. Tuyère (1) selon l'une quelconque des revendications précédentes, comprenant en outre:
(a) une entrée de tuyère raccordée audit corps de tuyère (2); et
(b) un passage d'entrée ménagé dans ladite entrée de tuyère, ledit passage d'entrée
étant adapté pour recevoir l'écoulement du fluide compressible et à envoyer l'écoulement
du fluide compressible à ladite entrée (7) dudit passage supersonique (6), ledit passage
d'entrée possédant une entrée ayant une section transversale circulaire, et une sortie
possédant une section transversale rectangulaire.
18. Tuyère (1) selon la revendication 17, dans laquelle ladite entrée de tuyère est adaptée
pour être utilisée avec un mécanisme de déconnexion rapide.
19. Tuyère (1) selon la revendication 3, dans laquelle lesdits inserts (20) ne s'étendent
pas au-delà de ladite surface extérieure (15).
20. Tuyère (1) selon la revendication 3 ou 19, dans laquelle lesdits inserts (20) sont
réalisés en un matériau, qui diffère du matériau dont est constituée ladite surface
extérieure (15) dudit corps de tuyère (2).
21. Tuyère (1) selon la revendication 3, 19 ou 20, dans laquelle lesdits inserts (20)
sont réalisés en un matériau qui est plus dense que le matériau dont est constituée
ladite surface extérieure (15) dudit corps de tuyère (2).