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Патент USA US3062494

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Nov. 6, 1962
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T, H|MKA
3,062,484
SUPERSONIC AIR INLET CONSTRUCTION
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32
lNvEN'roR A
THEIJDDRE HIMKA
ATTORN
rates
atent
3,Ü62,484
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Patented Nov. 6, 1962
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FIG. 3 is an enlarged sectional View of the inlet of
3,062,484
FIG. 1;
FIG. 4 is a view taken along lines 4-4 of FIG. 3;
SUPERSONIC AIR INLET CONSTRUCTION
Theodore Himka, Lodi, NJ., assignor to Curtiss-Wright
FIG. 5 is a View similar to FIG. 3 but illustrating a
Corporation, a corporation of Delaware
modified construction; and
Filed Apr. 1t), 1953, Ser. No. 347,878
7 Claims. (Cl. 244-53)
FIGS. 6 and 7 are views taken along lines 6-6 and
7-7 respectively of FIG. 5.
Referring ñrst to FIGS. 1 and 2 of the drawing, an
This invention relates to fluid inlets designed for super
aircraft, which may be a missile, is indicated partly in
sonic entering flow and is particularly directed to scoop
type air inlets for aircraft designed for supersonic flight. 10 section by reference numeral 10. The power propulsion
By a “scoop-type” air inlet for an aircraft is meant an
means of the aircraft 10 is illustrated as comprising a
air inlet which projects laterally from an aircraft surface
with the entrance opening of said inlet directed forward
ly or upstream into the surrounding air flow.
an air inletdiffuser passage 14, a combustion chamber
ram jet engine having a forwardly directed air inlet 12,
sure recovery such an inlet is provided with a restricted
16 having fuel supply and burner apparatus 18 and a
rearwardly directed exhaust nozzle 20 through which the
exhaust gases discharge to provide the aircraft with for
ward propulsive thrust.
The inlet 12 is a scoop-type inlet which projects later
ally from a surface 22 of the aircraft 10. The details of
when functioning properly at supersonic flight speeds~ the
of FIGS. 3 and 4.
Jet engines for aircraft (including missiles) designed
for supersonic liight require air inlets operating at super
sonic air velocities to supply the required mass flow of air
to the engine combustion chamber. For maximum pres
15
or throat portion downstream of its leading edge and 20 the inlet are more clearly seen in the enlarged views
Y
The air inlet 12 is rectangular in cross-section and
inlet air ñow velocity upstream of the inlet throat is
its flow path is formed by a pair of opposed side walls
supersonic while downstream of said inlet throat the air
24 an inner wall 26 comprising an extension of the air
ñow velocity is subsonic. Initially, the air ñow velocity
is subsonic throughout- the inlet. 'For the inlet to start 25 craft surface 22V from whichl the inlet projects and an
outer wall _V28 opposite to the inner wall 26. As illus
after sonic flight speed is exceeded a normal or strong
trated, the outer wall 28 is contoured similar to the pro
shock wave, which divides the supersonic flow from the
iile of the nose of-a conventional supersonic nose-type
subsonic ñow, must move from the inlet entrance down
inlet comprising an annular cowl surrounding a forward
to or through the inlet throat whereby the transition from
ly projecting nose portion, the inlet throat being formed
30
supersonic flow to subsonic flow moves from the 'inlet
at 30. The portions 32 of the inner wall 26 downstream
entrance down to or beyond the inlet throat. The mass
ñow of air that will pass through the inlet throat will be
greater in the started condition so that during inlet start
ing part of the air downstream of said normal or strong
shock must spill outside the inlet.
Supersonic scoop-type inlets have been provided with
swept-back side plates to permit spillage of air down-_
stream of the normal or strong shock wave which moves
of the throat 30 preferably is contoured similar to the
inner surface of the cowl in said conventional supersonic
nose-type inlet. Each side plate 24 is cut or swept back
from the leading edge of the outer wall 28 along a line
34 terminating at the inlet throat 30. At the designed
-flight speed of the aircraft 10 the line 34 coincides with
an oblique shock wave within the inlet extending from
the leading edge of the outer inlet wall 28. This swept
down the inlet during starting of the inlet. This swept
back side plate construction provides a triangular air 4.0 back construction of each side plate 24 provides a triangu
lar-shaped opening 36 in said side plate tapering down
spillage opening in each side plate, each said opening
having a maximum height at the inlet entrance. With
such a scoop-type inlet construction it has been found that
although the inlet may have sufficient spillage area down
stream of the normal or strong wave to permit said shock
wave to start moving down the inlet, said shock wave may
reach a point where the inlet no longer has sufficient
spillage area downstream of said shock wave. This is
particularly so in the case of an inlet having low aspect
stream and terminating at the inlet throat 30.
The inlet 12, as so far described, is conventional. Dur
ing starting of the inlet 12 a portion of the air downstream
of the normal or strong shock wave entering the inlet
spills out laterally through the side plate openings 36 to
permit said shock wave to move down toward the inlet
throat 30. If the spillage openings 36 are suiiiciently large
said shock wave will move down to or through the inlet
ratio (ratio of inlet height to width) and/ or having high 50 throat whereupon the inlet is fully started. It has been
found however that unless the aspect ratio (ratio of inlet
contraction ratio (ratio of inlet height at entrance to
height to width) of the inlet is sufîiciently large, as the
inlet height at throat).
shock wave moves down the inlet a critical point is
An object of the present invention comprises the pro
reached where the side wall openings 36 no longer provide
vision of a modiñed scoop-type inlet having swept-back
side plates and having increased spillage area without 55 sufficient spillage area downstream of said shock wave.
any substantial accompanying increase in the external l When such is the case the inlet does not fully start in that
the normal shock wave does not move all the way down
aerodynamic drag of the inlet and so that the inlet will
to or through the inlet throat 30 as is required for opti
have eii‘icient compression and will readily start not
mum or design operation. As a result, the mass ilow o-f
withstanding a low aspect ratio and/or a high contrac
tion ratio. In accordance with the present invention the 60 air flowing through the inlet throat and the total pressure
recovery are less than would be the case had the inlet
inlet door is constructed to provide for air spillage there
through. More specifically at least the portion of the
inlet iloor adjacent to and upstream of the inlet throat is
fully started.
'If the side plates are further cut back or are slotted
downstream of the oblique shock wave 34 to increase the
perforated for air spillage therethrough in addition to
the air spillage provided by the swept-back inlet side 65 spillage openings 36 then, because of the higher pres
plates.
sures downstream of said oblique shock wave 34, there
Other objects of the invention will become apparent
upon reading the annexed detailed description in con
nection with the drawing in which:
would be continual leakage through said increased spillage
a scoop-type air inlet embodying the invention;
aerodynamic drag of the inlet.
area after the inlet had started. This air spillage after
the inlet has started results in a corresponding loss in air
FIG. l is a schematic view of a ram jet engine having 70 ñow through the inlet throat and increases the external
FIG. 2 is a view taken along lines 2--2 of FIG.' l;
.
In accordance with the present invention, the spillage
3,062,484
à
4
area of the inlet is increased by providing air spillage
tional perforations may be provided in the surface of
perforations 4G through the inlet floor or inner wall 25.
The entire inner Wall '26 of the inlet may be so perforated
communicating with the chamber 54. A passage 56 leads
or, as illustrated, the perforations 40 preferably are con
from the chamber 54 to a rearwardly directed nozzle 58.
fined to that portion of said wall immediately upstream
the wall 28a at or downstream of the throat 30a and
With this added structure of FIGS. 5-7, the relatively
of the inlet throat where the side wall spillage areas 36
are not suñìcient to permit further downstream starting
slow moving boundary layer of air flowing over the inlet
surface of the wall 23a is removed upstream of the throat
movement of the inlet normal shock wave toward the in
30a by the perforations 5'2, said boundary layer bleeding
let throat 30. A plenum chamber 42 is provided on the
through the perforations 52 into the chamber 54 and
other side of the inlet Wall 26 whereby the perforations l0 discharging from said chamber through the passage 56
49 provide communication between the air inlet and said
and nozzle 5S into the surrounding atmosphere. The re
chamber. The chamber 42 is ducted'by a passage 44 to
quired amount of flow through the perforations 52 for
free stream flow of the surrounding atmosphere at some
removing said boundary layer is small compared to the
point on the aircraft body spaced from the inlet 12. The
flow required through the perforations 40a during inlet
passage 44 should terminate at a point on the surface of
starting. Hence the flow area required of the perforations
the aircraft body 10 where the pressure is sufficiently low
52 is much less than that required of the perforations
to permit air spillage flow therethrough from the perfora
40a. As in the case of the inlet 12, after the inlet 12a
tions 40 during inlet starting. Preferably, the discharge
has started there may also be a small leakage flow through
end of the passage 44 is disposed at a point where said
the perforations 40a which will tend to remove the
spillage flow would be helpful aerodynamically for ex
boundary layer of air iiowing along the surface 26a.
ample in maintaining boundary layer flow over the ad
If the flow of the surrounding air stream over the dis
jacent surface portion of the aircraft or in minimizing the
charge end of the passage 44a acts as an educer to draw
external drag attributable to the air pressure forces acting
air therethrough or if said passage .discharges into a low
on the aircraft. In order to assist spillage flow through
pressure region there will also be a small leakage air
the perforations 40, the discharge passage 44 may, as il 25 flow through the perforations 40a after the inlet has
lustrated, terminate in an ejector nozzle 46 projecting
started. A small amount of such flow is desirable after
from the aircraft 10 and directed downstream relative to
the inlet has started because it tends to remove the
the surrounding air flow thereover. With this latter ar
boundary layer of slow moving air along the inlet surface
rangement the ejector action of the surrounding free
26a. If desired the magnitude of this small leakage air
stream air flowing over the nozzle 46 helps to draw 30 flow through the perforations 40a after the inlet has
spillage air through the perforations 40.
started may be controlled by a suitable valve as for
After the inlet has fully started, the normal shock wave
is disposed at or downstream of the throat 30 of the inlet
example by an external flap at the discharge end of the
passage 44a. At this point it should be noted that after
the inlet has started any leakage ñow through the per
forations 40a is much smaller than the leakage flow
so that free stream pressure exits in the inlet 12 upstream
of said throat and upstream of the oblique shock wave
34. Accordingly after the inlet has started fully there
will be little or no leakage through the perforations itil.
In FIGS. 1-4 no attempt has been made to remove the
through said perforations during inlet starting because
the pressure in the inlet at said perforations drops to that
of the surrounding free stream after the inlet has started.
boundary layer of relatively slow moving air entering the
The inlet floor 26a is illustrated as being rectangular
inlet 12 adjacent to the aircraft surface 22 or to other 40 with its leading edge disposed upstream to the same extent
wise provide means to insure substantially uniform air
as the leading edge of the outer Wall 28. Actually how
velocity across the entrance to the inlet 12. FIGS. 5-7
ever the inlet floor 26 may have other configurations.
illustrate a modification in which a boundaryv layer re
For example the inlet floor 26a may have a spike-type
moval scoop has been added to the inlet. Except for the
shape so that its profile coincides with that of the bound
addition of said scoop the inlet of FIGS. 5~7 is identical
ary layer removal spike 50.
with that of FIGS. l-4 and like parts have been indicated
In each of the modifications described, the percent
by like reference numerals but with a subscript a added
open area provided by the perforations 40 or 40a and
thereto.
the minimum distance to which they extend upstream
In FIGS. 5-7 the inlet inner wall or floor 26a is spaced
of the inlet throat depends on the inlet aspect ratio,
from the adjacent surface 22a of the aircraft 10a. Be
the inlet contraction ratio and the flight speed for which
tween the inlet iloor 26a and the aircraft 10a there is
the aircraft is designed. Thus more spillage area is re
provided afspike-type scoop 50 for taking the boundary
quired for an inlet of lower aspect ratio, higher contrac
layer of air flowing over the aircraft surface 22a and de~
tion ratio and/or higher fright speed. If desired the per
fleeting said air laterally from the scoop 12a. Also, as
forations may extend over the entire ñoor area 26 in
illustrated, the perforations 40a extend through the inlet 55 FIGS. l1-4 or over the entire portion of the floor area
iloor 26a and through the spike of the scoop 50 to the
26a in FIGS. 5-7 included Within the profìfe of the bound
plenum chamber 42a. Therefore the perforations 40a
ary layer removal spike Si). Preferably, however, the
are confined to the dimensions of the scoop 50.
perforations 40 or 40a extend upstream from the inlet
The inlet outer wall 28 (FIG. l) is of considerable
throat only so far as to provide the extra air spillage
length so that a region of relatively slow moving air 60 necessary for inlet starting in order to minimize any air
(boundary layer) builds up along the surface of this wall.
spillage therethrough after the inlet has started. In actual
This boundary layer, which gradually thickens as the ñow
inlets which were successfully tested the inlet floor per
progresses downstream along the wall, tends to cause flow
forations provided the inlet ñoor with an open area equal
‘detachment from the surface due to the adverse pressure
to at least 50% of the floor area bounded by said per
gradient through the strong shock waves at the inlet 65 forations.
region of the subsonic diffuser, that is in the region of the
While I have described my invention in detail in its
inlet throat. Any such flow detachment will tend to
present preferred embodiment, it will 'be obvious to those
cause a loss in the overall pressure recovery of the inlet.
skilled in the art, after understanding my invention, that
various changes -and modifications may be made therein
this latter boundary layer along the surface of the wall 70 without departing from the spirit or scope thereof. I
28a. For this purpose the surface of the wall 28a has
aim in the appended claims -to cover all such modifica
been provided with a plurality of perforations 52 pref
tions.
erably immediately upstream of the inlet throat 30a and
I claim as my invention:
communicating with a chamber 54 within the inlet wall
1. In combination with a body member of an aircraft
28a. In addition or in lieu of the perforations 52 addi 75 designed for supersonic flight; a scoop-type air inlet pro
The modification of 5-7 discloses means for removing
3,062,484
5
jecting laterally from said body member with the wall
of said inlet having a pair o-f opposed side portions and
opposed inner and outer portions defining the iiow path
of said inlet and with said inlet having a throat portion
disposed downstream o-f its leading edge, each side portion
of said inlet wall being cut back from the leading edge
of said outer portion of said inlet wall to provide a tri
angular air spillage opening in said side portion -tapering
6
of said inlet with said inlet having a throat portion dis
posed downstream `of its leading edge, each said side por
tion of the inlet wall being cut back from the leading edge
of said outer portion of the inlet w-all to provide a tri
angular air spillage opening in said side portion taper
ing toward and terminating substantially at the inlet
throat such that said side portion islcut back along a line
which, at a particular flight speed, substantially coin
cides with the oblique shock wave extending from said
toward and terminating substantially at said inlet throat
portion, and said inner portion of the inlet wall having 10 leading edge into said inlet, said inner portion of the
inlet wall having a plurality of perforations therethrough
openings therethrough upstream of said throat portion to
upstream of said throat portion; means providing a cham
provide air spillage from said inlet through said latter
ber within said aircraft body member communicating
open-ings during inlet starting.
with said inlet through said perforations; and passage
2. In combination with a body member of an aircraft
means
providing communication between said chamber
designed for supersonic fright; a scoop-type air inlet prom
and the surrounding atmosphere for air spillage flow,
jecting laterally from said -body member with the wall of
during inlet starting, from said inlet through said perfora
said inlet having a pair of opposed side portions and
tions,
cham-ber and passage means into the surrounding
opposed inner and outer portions defining the íiow path
atmosphere.
of said inlet with said inlet having a throat portion dis
6. In combination with a body member of an air
posed downstream of its leading edge, each side portion 20 craft
designed for supersonic flight; a scoop-type air inlet
of said inlet wall being cut back from the leading edge of
projecting
laterally from said body member with the wall
said outer portion of the inlet wall to provide a triangular
of said inlet having a pair of opposed side portions and
air spillage opening in said side portion tapering toward
opposed inner and outer portions defining the ñow path
and terminating substantially at said inlet throat portion,
of
said inlet with said inlet having a throat portion dis
25
and said inner portion of the inlet wall having a plurality
posed
downstream of its leading edge, each side portion
of perforations therethrough upstream of said throat por
tion; and means providing a chamber with said aircraft
bdoy member communicating with said inlet through said
perfor-ations for air spillage therein during inlet starting.
of said inlet wall being cut back from the leading edge
of said outer portion of the inlet wall to provide a tri
angular air spillage opening in said side portion tapering
toward and terminating substantially at said inlet throat
3. In combination with a body member of an aircraft 30 portion and the leading edge of the inner portion of the
designed yfor supersonic liight; a scoop-type air inlet pro
jecting laterally from said body member with the wall
of said inlet having a pair of opposed side portions #and
opposed inner and outer portions defining the flo-w path
inlet wall being spaced from the adjacent surface of the
of perforations therethrough upstream of said throat por
tion, said perforations providing said inner portion with
forations for air spillage therein during inlet starting.
aircraft body member from which the inlet projects; an
air deliection scoop member disposed between said inner
portion and said aircraft body member surface for re
of said inlet with said inlet having a throat portion dis~ 35 moving the boundary layer of air flowing over said air
posed downstream of its leading edge, each side portion
craft body member surface toward the air inlet; said in
of said inlet wall being cut back from the leading edge of
ner portion and said deflection scoop member having per
said outer portion of the inlet wall to provide a triangular
forations therethrough, said perforations being confined
air spillage opening in said side portion tapering toward
Within the profile of said air deñection scoop member; and
40
and terminating substantially at said inlet throat portion,
means providing a chamber within said aircraft body
and said inner portion of the inlet wall having a plurality
member communicating with said inlet through said per
7. In combination with a body member of an air
craft designed for supersonic flight; a scoop-type air inlet
45
area of said portion Ábounded by said perforations; and
projecting laterally from said body member with the
means providing a chamber with said aircraft body mem
wall of said inlet having a pair of opposed side portions
an open area equal to at least iifty percent of the wall
lber communicating with said inlet through said perfora
tions for `air spillage therein during inlet starting.
and opposed inner and outer portions deiining the flow
path of said inlet with said inlet having a throat portion
4. In combination with a body member of an aircraft
disposed downstream of its leading edge, each side por
designed for supersonic flight; a scoop-type air inlet pro- 50 tion of said inlet Wall being cut back from the leading
jecting laterally from said body member with the wall
edge of said outer portion of the inlet wall to provide a
of said inlet having a pair of opposed side portions and
triangular air spillage opening in said side portion taper
opposed inner and outer portions defining the flow path
ing toward and terminating substantially at said inlet
of said inlet with said inlet having a throat portion dis
throat portion, and said inner portion of the inlet Wall
55
posed downstream of its leading edge, each said side por
having air flow openings upstream of said inlet throat and
tion of the inlet Wall being cut back from the leading edge
said outer portion having air flow openings in the region
of said outer portion of the inlet wall to provide »a tri
angular air spillage opening in said side portion tapering
of said inlet throat.
‘
toward and terminating substantially at the inlet throat
References Cited in the iile of this patent
portion such that said side portion is cut back along a 60
UNITED STATES PATENTS
line which, at a particular iiight speed, substantially c0
incides with the oblique shock wave extending from said
2,480,036
Lloyd _______________ __ Aug. 23, 1949
leading edge into said inlet, and said inner portion of the
2,573,834
Davidson ____________ __ Nov. 6, 1951
inlet wall having openings therethrough to provide air
Leduc ______________ __ Mar. 18, 1952
spillage from said inlet through said openings during in- 65 2,589,994
2,631,425
Nordfors ____________ __ Mar. 17, 1953
let starting.
5. In combination With a body member of an aircraft
FOREIGN PATENTS
designed for supersonic flight; a scoop-type air inlet pro
579,758
Great Britain _________ __ Aug. 14, 1946
jecting laterally from said body member with the wall of
50,033
France ______________ __ Nov. 10, 1939’
said inlet having a pair of opposed side portions and 70
_opposed inner and outer portions defining the ñow path
(Addition to Pat, 779,655)
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