U.S. patent application number 09/739640 was filed with the patent office on 2001-06-21 for device for discharging hot air for a jet engine air inlet cowl, with a deicing circuit.
Invention is credited to Porte, Alain, Viala, Stephane.
Application Number | 20010003897 09/739640 |
Document ID | / |
Family ID | 9553553 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010003897 |
Kind Code |
A1 |
Porte, Alain ; et
al. |
June 21, 2001 |
Device for discharging hot air for a jet engine air inlet cowl,
with a deicing circuit
Abstract
Device for discharging hot air for a jet engine air inlet cowl,
with a deicing circuit. The air inlet cowl (9) for a jet engine,
the leading edge (16) of which is hollow and swept with a flow of
deicing hot air (17), comprises orifices for discharging the hot
air flow to the outside of said leading edge (16), which form an
arrangement (18) such that at least two pressurized hot air jets
passing through two adjacent orifices have, downstream of a
calibration piece (23) in which said orifices are made, different
inclinations with respect to said calibration piece.
Inventors: |
Porte, Alain; (Allee de
Belle-Ile, FR) ; Viala, Stephane; (Hameau Lacour,
FR) |
Correspondence
Address: |
STEVENS, DAVIS, MILLER & MOSHER, L.L.P.
Suite 850
1615 L. Street, N.W.
Washington
DC
20036
US
|
Family ID: |
9553553 |
Appl. No.: |
09/739640 |
Filed: |
December 20, 2000 |
Current U.S.
Class: |
60/39.093 ;
137/15.1 |
Current CPC
Class: |
F02C 7/047 20130101;
B64D 15/04 20130101; Y10T 137/0536 20150401; B64D 2033/0233
20130101; Y02T 50/60 20130101; B64D 33/02 20130101; Y02T 50/672
20130101 |
Class at
Publication: |
60/39.093 ;
137/15.1 |
International
Class: |
F02C 007/047 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 1999 |
FR |
99 16155 |
Claims
1. An air inlet cowl for a jet engine, particularly for an
aircraft, said air inlet cowl being equipped, at the front, with
means for deicing its leading edge and for this purpose comprising:
a hollow leading edge delimiting an internal peripheral chamber
which is closed by an internal partition, said internal partition
being equipped with a trough-shaped duct directed toward the rear
of said leading edge and open toward the periphery of said air
inlet cowl; a pipe which can be connected, at its rear end which is
the opposite end to said leading edge, to a pressurized hot air
circuit and, at its front end toward said leading edge, to an
injector injecting said pressurized hot air into said internal
chamber; and a calibration piece made of a material resistant to
high temperatures and forming part of the external surface of said
cowl, to the rear of said leading edge, said piece closing off said
trough-shaped duct and being pierced with at least two orifices to
place said internal chamber in communication with the outside, said
orifices being distributed at least roughly parallel to said
leading edge and serving to calibrate the flow of pressurized hot
air ejected by said trough-shaped duct, while deflecting away from
said cowl the pressurized hot air jets resulting from the passage
of said flow of hot air through said orifices, wherein said
orifices form an arrangement such that at least two pressurized hot
air jets passing through two adjacent orifices have, downstream of
said calibration piece, different inclinations with respect to said
calibration piece, and wherein said piece extends longitudinally in
said external surface of said cowl, toward the rear thereof, to act
as thermal protection for said cowl with respect to said hot air
jets passing through said orifices.
2. The air inlet cowl as claimed in claim 1, wherein said orifices
form an arrangement such that at least one pressurized hot air jet
passing through an orifice of said calibration piece is absorbed,
downstream of this piece, by at least one pressurized hot air jet
passing through an orifice occupying an adjacent position in said
calibration piece.
3. The air inlet cowl as claimed in claim 1, in which said orifices
have an oblong shape and are oriented at least approximately
longitudinally with respect to said cowl, wherein the area of each
orifice depends on the position of this orifice in said
arrangement, this area varying according to how laterally
positioned said orifice is.
4. The air inlet cowl as claimed in claim 1, wherein the front
edges of the orifices of the arrangement are at least roughly
aligned parallel to said leading edge.
5. The air inlet cowl as claimed in claim 1, wherein each oblong
orifice is oriented at least roughly parallel to the stream lines
of the aerodynamic flow flowing over said piece.
6. The air inlet cowl as claimed in claim 1, wherein said orifices
have an at least roughly rectangular shape.
7. The air inlet cowl as claimed in claim 1, wherein said
arrangement of orifices comprises at least one large central
orifice, two small lateral orifices arranged on each side of said
central orifice and two intermediate orifices, the area and
position of which are respectively between those of said large
central orifice and those of said small lateral orifices.
8. The air inlet cowl as claimed in claim 1, wherein the number of
orifices is an odd number.
9. The air inlet cowl as claimed in claim 1, wherein said
arrangement of orifices is symmetrical.
10. The air inlet cowl as claimed in claim 1, wherein at least one
of the longitudinal edges of said calibration piece has the shape
of the stream lines of the aerodynamic flow flowing over said piece
when said aircraft is in cruising flight.
11. The air inlet cowl as claimed in claim 1, wherein said
calibration piece is an inspection hatch for said pipe.
12. The air inlet cowl as claimed in claim 1, wherein said
trough-shaped duct is peripherally in the vicinity of said
pipe.
13. The air inlet cowl as claimed in claim 1, wherein said
trough-shaped duct widens toward the periphery of said air inlet
cowl.
14. The air inlet cowl as claimed in claim 1, wherein said
trough-shaped duct forms an integral part of said internal
partition.
15. The air inlet cowl as claimed in claim 1, wherein said
trough-shaped duct consists of a piece attached to said internal
partition.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to the deicing of air inlet
cowls of jet engines, particularly aircraft engines.
[0002] It is known that, if necessary (as a preventative measure
against the formation of ice or to eliminate ice already formed),
the leading edge of the air inlet cowl of such engines is deiced by
heating it with pressurized hot air tapped from said engine and
supplied to said leading edge by a hot air circulation circuit.
[0003] To this end, an air inlet cowl such as this comprises:
[0004] a hollow leading edge delimiting an internal peripheral
chamber closed by an internal partition (or frame) and equipped
with orifices placing said internal chamber in communication with
the outside; and
[0005] a pipe which can be connected, at its rear end which is the
opposite end to said leading edge, to said hot air circulation
circuit and, at its front end toward the leading edge, to an
injector injecting said hot air into said internal chamber.
[0006] Thus, the pressurized hot air injected by said injector
sweeps through said internal peripheral chamber, heating it up, and
is discharged through said orifices.
DESCRIPTION OF THE PRIOR ART
[0007] U.S. Pat. No. 5,365,731 already discloses an air inlet cowl
of this type comprising a number of such hot air discharge orifices
made directly in the leading edge of said cowl, the rate of flow of
the deicing hot air being controlled by the cross section of said
orifices. A known air inlet cowl such as this has the major
drawbacks of weakening the leading edge of said cowl (which happens
to be the most vulnerable part of an engine nacelle, because it is
located at the front, and to be difficult to repair because of its
large size) and of substantially degrading the aerodynamic
performance of said cowl. Specifically, as far as the latter
drawback is concerned, this is because said orifices are located in
a shape of leading edge that encourages scooping--and therefore
makes the ejection of hot air difficult--this being true throughout
all the phases of flight of the aircraft when the deicing is not in
operation. In addition, the ejection orifices produce a large
ejection area, which leads to drag over a high proportion of the
leading edge, this drag being accentuated by the fact that the
surface of the nacelle immediately downstream of this
aerodynamically polluted surface, is also generally very disturbed,
which means that it generates additional drag. Furthermore, in a
known air inlet cowl such as this, it is difficult to correct the
ejection cross section during flight trials, because this section
consists of orifices made in a very large part (the leading
edge).
[0008] Another source, document EP-A-0 205 283, discloses an air
inlet cowl in which said pressurized hot air supply pipe is
surrounded by an enveloping metallic structure comprising pipework,
the free end of which forms an orifice used for ejecting deicing
air to the rear of the leading edge of said cowl. This then avoids
the aforementioned drawbacks but, in this known device, the rate of
flow of hot air is controlled by the cross section of said ejection
pipework, as well as by the orientation of fins located at the free
end thereof. This results in poor control over the ejection rate
and in layers of hot air on the outside. In addition, the ejection
of the hot air is highly concentrated, which may damage nearby
structures which are sensitive to heat. In any case, a device such
as this is the source of significant thermal radiation, also with
the risk of damaging said structures. Finally, the device is
expensive because it consists of many parts which have to be
assembled using joints whose life is limited because they are
subjected to high temperatures.
[0009] Also known, for example from document GB-A2 259 679, is an
air inlet cowl in which the deicing hot air is discharged to the
outside by bent pipework passing through said internal partition to
eject the hot air at the rear of said leading edge. Here again, the
rate of flow of hot air is controlled by the cross section of the
pipework and by the orientation of fins arranged therein. This air
inlet cowl therefore again encounters the same drawbacks as those
mentioned hereinabove with regard to document EP-A-0 205 283.
[0010] Finally, document EP-A-0 536 089 discloses an air inlet cowl
in which said internal partition is equipped with a trough-shaped
duct directed toward the rear of the leading edge and open toward
the periphery of said air inlet cowl. The trough-shaped duct is
closed off by a plate pierced with a multitude of identical
rectangular orifices, whose direction is orthogonal to the leading
edge, said orifices being aligned parallel to the latter.
[0011] By virtue of this arrangement, said orifices, which serve to
discharge to the outside the pressurized hot air which has heated
up said leading edge, may be in the part of said cowl that is
located just behind said leading edge. This therefore means that
the leading edge, which is a part which is sensitive from the
aerodynamic point of view in terms of engine performance and from
the maintenance point of view because it is exposed to various
impacts, is not weakened by said orifices. However, an arrangement
such as this does not make it possible to optimize the ejection of
the deicing hot air either aerodynamically or thermally or
acoustically, particularly because:
[0012] the jets of hot air passing through said rectangular
orifices tend to group together downstream of said plate, which
gives rise to significant aerodynamic drag and detracts from the
cooling of said jets (the thermal radiation of which thus runs a
risk of burning the outer surface--generally made of composite
material--of said cowl downstream of said plate); and
[0013] the jets of hot air passing through the lateral rectangular
orifices widen laterally and burn the lateral surface, also made of
composite material, of said cowl, which surface is located
laterally to said plate.
[0014] Furthermore, such orifices give rise to aerodynamic noise,
whistling, etc.
SUMMARY OF THE INVENTION
[0015] The object of the present invention is to overcome these
drawbacks.
[0016] To this end, according to the invention, the air inlet cowl
for a jet engine, particularly for an aircraft, said air inlet cowl
being equipped, at the front, with means for deicing its leading
edge and for this purpose comprising:
[0017] a hollow leading edge delimiting an internal peripheral
chamber which is closed by an internal partition, said internal
partition being equipped with a trough-shaped duct directed toward
the rear of said leading edge and open toward the periphery of said
air inlet cowl;
[0018] a pipe which can be connected, at its rear end which is the
opposite end to said leading edge, to a pressurized hot air circuit
and, at its front end toward said leading edge, to an injector
injecting said pressurized hot air into said internal chamber;
and
[0019] a calibration piece made of a material resistant to high
temperatures and forming part of the external surface of said cowl,
to the rear of said leading edge, said piece closing off said
trough-shaped duct and being pierced with orifices to place said
internal chamber in communication with the outside, said orifices
being distributed at least roughly parallel to said leading edge
and serving to calibrate the flow of pressurized hot air ejected by
said trough-shaped duct, while deflecting away from said cowl the
pressurized hot air jets resulting from the passage of said flow of
hot air through said orifices, is noteworthy in that said orifices
form an arrangement such that at least two pressurized hot air jets
passing through two adjacent orifices have, downstream of said
calibration piece, different inclinations with respect to said
calibration piece, and in that said calibration piece extends
longitudinally in said external surface of said cowl, toward the
rear thereof, to act as thermal protection for said cowl with
respect to said hot air jets passing through said orifices.
[0020] Thus, said orifices allow control over the rate of ejection
and, also, make it possible to obtain favorable heat exchange
between the ejected hot air and the external ambient air while at
the same time controlling the spread of the hot air jet in order to
keep it away from the temperature-sensitive structures of the
nacelle. This then avoids the drawbacks of the orifices of the
known deicing devices which:
[0021] when they are in the form of a circular orifice, excessively
concentrate the ejection cross section and afford a small area for
heat exchange between the jet of deicing air and the ambient
external air, the energy of said jet being too great which means
that it risks reaching the temperature-sensitive structures and
damaging them; and
[0022] when they are spread, as a multitude of orifices, give rise
to acoustic emissions, aerodynamic drag prejudicial to aircraft
performance, even when the deicing circuit is not in operation, and
the risk of burning the cowl around said orifices.
[0023] It will in fact be noted that, by virtue of the differences
in inclination of said hot air jets with respect to said
calibration piece, the fresh aerodynamic flow can very easily
penetrate between these jets, cooling them efficiently and
avoiding, or at the very least reducing, the generation of
parasitic drag and acoustic noise.
[0024] It will also be noted that, by virtue of the invention, the
longitudinal extension of said calibration piece can be chosen so
that the heating of the external surface of the cowl, downstream of
said piece as a result of the thermal radiation of said hot air
jets, remains below a given temperature threshold capable of
avoiding thermal damage to said surface.
[0025] In one particular embodiment, said orifices form an
arrangement such that, in addition, at least one pressurized hot
air jet passing through an orifice (lateral or otherwise) of said
calibration piece is absorbed, downstream of this piece, by at
least one pressurized hot air jet passing through an orifice
occupying an adjacent position, for example a less lateral
position, in said calibration piece.
[0026] Furthermore, in an advantageous embodiment, in which said
orifices have an oblong shape and are oriented at least
approximately longitudinally, that is to say from the front of the
cowl to the rear, the area of each orifice depends on the position
of this orifice in said arrangement, this area varying according to
how laterally positioned said orifice is. As a preference, the area
is all the smaller the more lateral the position of the orifice,
and all the greater the more central the position of said orifice,
although the reverse is, however, equally possible.
[0027] By virtue of this arrangement, the energy of a hot air jet
is all the greater the greater the area of the corresponding
orifice, so that:
[0028] the inclination of a hot air jet with respect to said
calibration piece depends on the area of the orifice through which
said jet passes, a jet corresponding to an orifice of larger area
being kept further away from the surface of the cowl than a jet
corresponding to an orifice of smaller area; and
[0029] the air jets of lower energy, particularly the lateral hot
air jets, can be absorbed by the jets of higher energy.
[0030] The front edges of said orifices of the arrangement may be
at least roughly aligned parallel to said leading edge and said
orifices may have an at least roughly rectangular shape.
[0031] Furthermore, to optimize the penetration of the aerodynamic
flow between said jets and therefore optimize the heat exchange
between said flow and these jets, it is advantageous for each
oblong orifice to be oriented at least roughly parallel to the
stream lines of said aerodynamic flow flowing over said calibration
piece, for example when the aircraft is in cruising flight.
[0032] In one particularly simple and effective embodiment of the
cowl according to the present invention, said arrangement of
orifices comprises at least one large central orifice, two small
lateral orifices arranged on each side of said central orifice and
two intermediate orifices, the area and position of which are
respectively between those of said large central orifice and those
of said small lateral orifices.
[0033] It will be noted that the number of orifices depends on the
dimensions of the calibration piece. Specifically, the shorter this
piece, the greater the efficiency of the heat exchanger (consisting
of the orifices) will have to be. It may therefore be necessary to
vary the number of orifices in order to obtain the desired effect.
Conversely, the longer the calibration piece, the more the number
of orifices can be reduced, the quality of the heat exchanger being
less of an important issue here.
[0034] Of course, in the context of the present invention, the
total number of orifices may be even or odd. However, as a
preference, said number of orifices is an odd number. This in
particular makes it possible to improve the efficiency because the
lateral jets then, through a lift effect, play a part in lifting
the central jet.
[0035] Moreover and advantageously, said arrangement of orifices is
symmetrical, preferably with respect to a longitudinal plane which,
in the case of an odd number of orifices, passes through the
central orifice and, in the case of an even number, passes mid-way
between the two central orifices.
[0036] In order to optimize the thermal protection afforded by said
calibration piece while at the same time minimizing its mass, it is
advantageous for at least one of the longitudinal edges of said
calibration piece to have the shape of the stream lines of the
aerodynamic flow flowing over said calibration piece when the
aircraft is in cruising flight.
[0037] As a preference, said trough-shaped duct is peripherally in
the vicinity of said pressurized hot air supply pipe. Thus, said
hot air sweeps through the entire circumference of said leading
edge and very uniform distribution of said hot air inside the
latter, and therefore very good deicing performance, are
obtained.
[0038] Said calibration piece may in addition form the inspection
hatch for said hot air supply pipe. Benefit can therefore be
derived from the presence, compulsory for access to the deicing air
pipework, of a dismantleable and high-temperature-resistant panel
located immediately behind said ejection orifices. As mentioned
above, such a hatch may extend longitudinally in the external
surface of the cowl over sufficient length to protect the entire
part of that surface which may be subjected to the action of the
flow of hot air ejected by said orifices. In addition, by providing
several dismantleable panels equipped with different ejection
orifice arrangements, one panel can easily be replaced with another
to test various ejection orifice arrangements.
[0039] Furthermore, it is advantageous for said trough-shaped duct
to widen toward the external periphery of said cowl. It may thus
have an aerodynamic shape that encourages the ejection of air.
[0040] Said trough-shaped duct may form an integral part of said
internal partition and, for example, be formed by pressing the
latter. It may also constitute a piece attached to said internal
partition, in a recess thereof.
[0041] It can thus be seen that the leading edge of the cowl
according to the present invention is homogeneous over all
360.degree. of its circumference, without protrusions or vent
orifices, thus preserving its aerodynamic and mechanical strength
qualities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The figures of the appended drawing make it easy to
understand how the invention may be realized. In these figures,
identical references denote similar elements.
[0043] FIG. 1 shows, in exploded perspective, one example of an
aircraft jet engine and its various cowlings.
[0044] FIGS. 2 and 3 are views in partial perspective from the
front, with cutaway, of two embodiments of the air inlet cowl
according to the present invention.
[0045] FIG. 4 is a face-on view illustrating one advantageous
embodiment of the arrangement of ejection orifices according to the
present invention.
[0046] FIG. 5 illustrates, in an enlarged and schematic partial
perspective view, the action of the arrangement of ejection
orifices according to the present invention.
[0047] FIG. 6 illustrates, in a view similar to FIG. 5, an
alternative form of action of the arrangement of ejection orifices
according to the present invention.
[0048] FIG. 7 is a perspective view from the front, with cutaway,
of one embodiment of the air inlet cowl according to the present
invention.
[0049] FIG. 8 is a diagrammatic and partial half section of the
front part of an air inlet cowl according to the present
invention.
[0050] FIG. 9 shows, in a partial plan view of FIG. 8, an
alternative form of the arrangement of ejection orifices according
to the invention.
[0051] FIG. 10 is a perspective view from the front, with cutaway,
of an alternative form of the air inlet cowl according to the
present invention, corresponding to FIGS. 8 and 9.
[0052] FIGS. 11 and 12 show, in views similar to FIGS. 4 and 9, two
other alternative forms of the arrangement of ejection orifices
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] The bypass engine 1 depicted diagrammatically in FIG. 1
comprises, in a known way, a central hot air generator 2, a fan 3
and compressor stages 4, and is equipped with an attachment 5 for
suspending from a support stub (not depicted). Associated with and
fixed to the engine 1 are a jet pipe assembly 6, two lateral cowls
7 and 8 and an air inlet cowl 9.
[0054] As illustrated diagrammatically in FIG. 1, the air inlet
cowl 9 comprises an internal pipe 10 equipped, at its rear end
facing toward the engine 1, with a coupling 11 and, at its front
end, housed in the hollow leading edge 16 of said air inlet cowl,
with an injector 12. Moreover, arranged on one compressor stage of
the engine 1 is a pressurized hot air inlet 13 which is connected
to a pipe 14 equipped, facing the coupling 11 of the pipe 10, with
a complementary coupling 15.
[0055] Thus, when the complementary couplings 11 and 15 are coupled
together, hot air (for example at a temperature of 400.degree. C.)
tapped at 13 from the engine 1 is conveyed through the pipes 14 and
10 as far as the injector 12. The latter can therefore blow this
pressurized hot air (dotted arrows 17) into the leading edge 16 to
deice it. An arrangement 18 of oblong orifices is provided,
according to the present invention, in the outer surface 9E of the
cowl 9 to discharge to the open air (arrows 19) the hot air which
has circulated inside the leading edge 16 (now, for example, at a
temperature of 200.degree. C.).
[0056] As shown in detail and on a larger scale in FIGS. 2, 3, 5, 7
and 8, the hollow leading edge 16 is closed at the rear by an
internal partition 20 so that an annular peripheral chamber 21 is
formed inside said leading edge 16. The injector 12 injects
pressurized hot air into the chamber 21 and the arrangement of
oblong orifices 18 places said chamber 21 in communication with the
outside.
[0057] The internal partition 20 is equipped with a trough-shaped
duct 22 directed and widening toward the rear of said leading edge
16, that is to say on the side of the actual cowl 9 proper, and
open toward the periphery of said air inlet cowl 9. The duct 22 may
be produced by indenting said internal partition 20, for example by
pressing, or may alternatively consist of a part attached to said
partition 20.
[0058] The arrangement of oblong orifices 18 is made in a
calibration piece 23 forming part of the outer surface 9E of the
cowl 9, behind the leading edge 16, and faces the duct 22 limiting
and calibrating the cross section thereof.
[0059] Thus, the hot air which has heated up the leading edge 16 is
conveyed by the duct 22 to the arrangement of orifices 18 which
discharges it toward the outside, controlling its rate of flow.
[0060] FIGS. 2 and 3 show that the injector 12 may be of any kind:
for example, it comprises multiple nozzles (FIG. 2) or consists of
a pierced annulus (FIG. 3). They also show, as do FIGS. 4 and 5,
that the duct 22 is peripherally near the pipe 10. Thus, although
the calibration piece 23 can be specially designed to close off the
duct 22 (see FIGS. 2 and 3), it may advantageously constitute the
hatch made in the cowl 9 for inspecting the pipe 10, as shown in
FIGS. 7 and 10. In both instances, the piece 23 is made of a fire
and heat resistant material, for example a metallic material. The
piece 23 may extend over the entire length of the cowl 9. FIGS. 7
and 10 show the flange 24 capable of collaborating with the front
flange 25 of the engine, to attach said air inlet cowl 9 to this
engine.
[0061] In the example depicted in FIGS. 1 to 7, the arrangement 18
comprises five orifices 18.1 to 18.5, in the form of rectangular
slits, the front edges of which are aligned parallel to the leading
edge 16 (see, in particular, FIG. 4 and the corresponding FIG. 7).
The orifices 18.1 to 18.5 are mutually parallel and parallel to the
longitudinal axis of the cowl 9 (not depicted). The arrangement 18
comprises small lateral orifices 18.1 and 18.5, a large central
orifice 18.3 and two intermediate orifices 18.2 and 18.4 which are
placed respectively between said large central orifice 18.3 and
said small lateral orifices 18.1 and 18.5, and the area of which is
between those of said small orifices 18.1 and 18.5 and of the large
central orifice 18.3.
[0062] Thus, as illustrated by FIG. 5:
[0063] the central hot air jet 19.3 passing through the large
central orifice 18.3 has a great deal of energy and is kept a great
distance away from the piece 23;
[0064] the intermediate hot air jets 19.2 and 19.4, passing
respectively through the intermediate orifices 18.2 and 18.4 have
less energy than the hot air jet 19.3 and are also less far away
from the piece 23 than the latter jet; and
[0065] the lateral hot air jets 19.1 and 19.5, passing respectively
through said lateral orifices 18.1 and 18.5, have little energy and
are far less far away from the piece 23.
[0066] Moreover, the particular embodiment depicted in FIG. 6
differs from the aforementioned one in FIG. 5 in that some of the
pressurized hot air jets, in this particular instance the lateral
air jets 19.1 and 19.5, passing through orifices 18.1 and 18.5 of
said calibration piece 23, are absorbed, downstream of this piece,
by at least one pressurized hot air jet 19.2 and 19.4 passing
through an orifice 18.2 and 18.4 occupying an adjacent position, in
this particular instance a less lateral position, in said
calibration piece 23. This is achieved by tailoring the areas of
said orifices 18.1 to 18.5.
[0067] In the embodiments of FIGS. 1 to 7, the orifices 18.1 to
18.5 and the lateral edges 23.1 and 23.2 of the piece 23 are
longitudinal, that is to say extend from the front to the rear,
parallel to the longitudinal axis of the cowl 9.
[0068] By contrast, in the embodiments of FIGS. 8, 9 and 10, the
orifices 18.1 to 18.5 and at least the lateral edge 23.1 of the
piece 23 are respectively oriented and/or shaped at least roughly
parallel to the stream lines 26 of the aerodynamic flow flowing
over said piece 23, for example when the aircraft comprising the
engine 1 is in cruising flight.
[0069] Of course, the number of orifices depends on the dimensions
of the calibration piece 23. Specifically, the shorter this piece,
the greater the efficiency of the heat exchanger (consisting of the
orifices) will have to be. It may therefore be necessary to vary
the number of orifices in order to obtain the desired effect.
Conversely, the longer the calibration piece 23, the more the
number of orifices may be reduced, the quality of the heat
exchanger being less of an important issue in this case. Thus, at
the minimum, it may be possible to provide two orifices of
different areas, the maximum number of orifices being governed by
the calibration piece 23.
[0070] In addition, in the context of the present invention, the
number of orifices may be an even number (FIG. 12) or an odd number
(FIG. 11 for example). However, an odd number of orifices is more
favorable, because simulation shows that the lateral jets then
contribute, through a lift effect, to lifting the central jet.
[0071] Furthermore, and as a preference, although not exclusively,
said arrangement 18 of orifices is symmetric with respect to a
longitudinal plane, namely:
[0072] a plane passing through the mid-point of the central orifice
18.3, in the case of an odd number of orifices 18.1 to 18.5, as
illustrated by a straight line D1 representing this plane in FIG.
11; and
[0073] a plane passing through the mid-point of the two central
orifices 18.8 and 18.9, in the case of an even number of orifices
18.6 to 18.11, as illustrated by a straight line D2 representing
this plane in FIG. 12.
[0074] It will also be noted that the variation in area of the
orifices may either decrease toward the lateral orifices, as
depicted, for example, in FIGS. 4, 9 and 12, or increase toward
said lateral orifices, as depicted, for example, in FIG. 11.
[0075] In the latter instance, the geometry of the calibration
piece 23 will need to be adapted to suit.
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