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Патент USA US3027719

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April 3, 1962
RAE
R. S.
SCOOP DIFFUSER FOR USE ON RAM JETS FOR
3,027,711
SECURING ISENTROPIC COMPRESSION
OF A SUPERSONIC STREAM
Filed Feb. '7, 1950
2 Sheets-Sheet 1
FIG!
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12
,3
/
"
23
FUEL
n
_
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u
I,
"7?
24
I
FIG. 2
./|4
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FIG. 4
INVENTOR.
RANDOLPH S. RAE
BY
.
ATTORNEY
April 3, 1962
3,027,711
R. S. RAE
SCOOP DIFFUSER FOR USE ON RAM JETS FOR
SECURING ISENTROPIC COMPRESSION
Filed Feb. 7, 1950
OF A SUPERSONIC STREAM
2 Sheets-Sheet 2
F165
FIG. 6
AIR
FLOW
FIG. 7
Prandll-Meyer, Expansion over a corner.
Flow 01‘ sonjc velocity aqd parallel to the surface at m.
6
Flow at supersamc velocity and parallel to thev surface of .
I
INVENTOR.
RANDOLPH S.v RAE
BY
'
ATTORNEY
" .5 nite
States Patent O?ice
1
3,027,711
SCOOP DIFFUSER FOR USE ON RAM JETS FOR
SECURING ISENTROPIC COMPRESSION OF A
SUPERSONKI STREAM
Randolph S. Rae, Silver Spring, Md., assignor to the
United States of America as represented by the Secre
tary of the Navy
Filed Feb. 7, 1950, Ser. No. 142,727
4 Claims. (Cl. 60-356)
3,027,711
Patented Apr. 3, 1962
2
Within the scoop diffuser 11 supersonic compression
during ?ight is achieved by the reversal of the Prandtl
Meyer expansion of supersonic flow around a corner,
illustrated in FIG. 7. This is made possible by a longi
tudinally curved base surface 13 of the scoop 11. Side
plates 14 that cover only the portion of the stream within
the “Mach angle” 15, namely, the angle whose sine is the
reciprocal of the Mach number, are la?ixed to the scoop
as shown in FIG. 2. Under ‘optimum operating condi
10 tions supersonic flow exists at 16 ahead of the point of
The present invention relates in general to guided
intersection of the scoop and missile body, while behind
missiles, and more speci?cally to an improvement in air
this point, as at 17, subsonic ?ow supplies air to the com
intakes for ram- jet driven missiles, operating at super
bustor 19.
'
sonic speeds.
FIG. 7 shows the idealized isentropic ?ow conditions
The diffuser intakes of ram jet missiles ?ying at veloci 15 existing at a flow around a corner, ‘Wherea supersonic
ties that are relatively high in comparison with the velocity
flow 6 is converted into sonic ?ow a, under reversible
of sound, have generally been of the Oswati-tsch converg
conditions, without loss in either direction of conversion,
ent-divergent central duct design. A paramount objection
according to the Prandtl-Meyer expansion. The scoop
to this type of diffuser intake is its inherent high drag.
diffuser of the present invention is based on such conver
To approach isentropic compression a supersonic diffuser 20 sion, which is made possible by the curved bottom surface
must provide a converging stream in the supersonic part,
13 of the scoop.
and a divergent stream in the subsonic part of the diffuser.
‘' In the speci?c case where the supersonic velocity of the
Other objects of the present invention are to provide a
vehicle is twice that of sound, the Mach number is 2, and
ram jet intake having the full isentropic compression of
hence the sine of the Mach angle is 0.5, the reciprocal of
the supersonic stream, to provide a ram jet diffuser intake
2, which corresponds to the Mach angle ‘of 30°. The
with suitable flow characteristics at nearly isentropic pres
scoop used as an illustration in the present case is designed
sure conditions, and to [achieve the above conditions with
arbitrarily for a vehicle operating at Mach 2, and hence
out producing excessive drag.
the ,angle 15 shown in FIG. 6 is 30°.
A speci?c object of the present invention is to provide a
While speci?c details of the internal structure of the
ram jet diffuser intake positioned to occupy a minimum 30 ram jets are relatively unimportant ‘as far as the present
of space, thereby providing room in the major portion of
the missile for greater fuel supply, pay load, and instru
invention is concerned, for completeness such structure
is disclosed brie?y as follows:
Referring to FIGS. 2 to 5, it will be seen that the air
mentation.
Other objects and many of the attendant advantages of
intake passage within the ram jet increases in cross-sec
the invention will be readily understood by reference to 35 tional area from inlet region 17, where it is a relatively
the following detailed description when considered in
narrow rectangle as shown in FIG. 4, to a substantially
connection with the accompanying drawings, wherein:
FIG. 1 is an elevational view of a ram jet missile em
bodying the invention;
FIG. 2 is a fragmentary axial section of the ram jet 40
missile embodying the invention;
FIG. 3 is a transverse section of the ram jet missile
according to the present invention, in plane 3-3 of
FIG. 1;
square shape at 20, shown best in FIG. 5, thus decreasing
the air speed at 20 to approximately one-half the speed
at 17.
From region 20 to region 21 at the outlet end of the
air passage, the shape of the cross section changes from
square to circular, so that a more nearly uniform distribu
tion of the air results at the combustor 19. Fuel is sup
plied to said combustor from tank 22 through conduit
FIG. 4 is a section through the scoop, in the plane 4-4 45 23, and burning takes place beyond the vfuel discharge
of FIG. 2;
nozzles 24.
FIG. 5 is 'a transverse section in the plane 5-5 of
Pressure increases, due to instability within the com
FIG. 2, showing diffuser details;
bustor, in the speci?c example, will cause shock waves at
FIG. 6 is a diagrammatic section, illustrating the char
a greater angle than 30° to be generated temporarily
acteristics of a scoop diffuser embodying the present in 50 forward of the diffuser throat, as indicated in dash-dot
vention; and
lines at 18 in FIG. 6. However, as this large-angle shock
FIG. 7 is a diagram illustrating the “Prandtl-Meyer”
wave moves forward, air spills or escapes laterally over
theory of expansion of supersonic ?ow around a corner.
the side plates 14, thereby re-establishing the supersonic
Referring to the drawing and particularly to FIG. 1,
flow regime in the throat area as soon as such spillage
there is shown a ram jet missile 10 embodying near its 55 causes the pressure in the subsonic part of the di?user to
rear end the “scoop diffuser” or air chute 11 which con
fall below the maximum steady state value. This is an
stitutes the present invention. This scoop diffuser 11 is
located on the under side of the missile forward of the
important feature of the scoop diffuser, in that provision
for excess diffuser pressure leakage thus becomes a func~
tion of the pressure involved, and hence serves to stabilize
as shown, and leaves unobstructed the entire forward 60 the diffuser pressures. The scoop diffuser is thus an ideal
diffuser in that no air ?ow is needlessly lost after the
portion 12 of the missile for space for fuel, pay load and
combustion chamber, cooperates therewith, substantially
shock has passed to the diffuser throat.
Obviously many modi?cations and variations of the
the ram jet, where under ordinary ?ight conditions the 65 present invention are possible in the light of the above
teachings. It is therefore to be understood that within
missile will have a positive angle of attack, resulting in a
the scope of the appended claims, the invention may be
thin boundary layer at the junction of the scoop and
practiced otherwise than as speci?cally described.
missile body, and thereby minimizing detrimental aero
What is claimed is:
dynamic interference. “Mach number” limitations on the
1. In a ram jet device for use at supersonic speeds, a
design e?iciency of the scoop diffuser are eliminated, since 70 diffuser chute of rectangular, four-walled construction ex
the angle at which the ?ow enters the body has no narrow
tending from the interior of the device to the exterior
limits.
through a rectangular aperture in the wall of the device,
instrumentation.
The scoop dilfuser 11 is positioned on the underside of
3,027,711
a
the chute having two opposite, normally vertical walls
chute having two opposite, transverse walls situated gen
and two opposite, transverse walls situated generally one
above the other, the upper transverse wall residing only
within the device and extending to a forward transverse
edge of said aperture, the lower transverse wall extending
outwardly and forwardly of the aperture and ending in a
transverse leading edge substantially forward of the aper
erally one above the other, the upper transverse wall re
siding only within the device and extending inwardly from
a forward, transverse edge of said aperture at an obtuse
angle to the adjacent portion of the wall of the device, the
lower transverse wall extending outwardly and forwardly
and terminating in a transverse leading edge forwardly
of the aperture, the lower transverse Wall curving smooth~
ture, the vertical walls having leading edges that extend
ly from said leading edge to a substantial distance within
from their respective ends of the leading edge of the lower
wall to the respective ends of the forward transverse edge 10 the device whereby Prandtl-Meyer ?ow takes place in the
chute.
.
of the aperture.
2. In a device for use at supersonic speeds, an air-intake
4. An air intake device for use with a supersonic ram
jet vehicle having a combustor, said device comprising a
scoop communicating with said combustor through an
in the wall of the device, the chute having two opposite, 15 aperture in the wall of said vehicle and extending outward
ly from said aperture to an opening for receiving air,
normally vertical walls and two opposite, transverse walls
said scoop having an end edge located forward of said
situated generally one, above the other, the upper trans
chute of four-walled construction extending from the in
terior of the device to the exterior through an aperture
verse wall residing only within the device and extending
inwardly from a forward, transverse edge of said aper
ture, the lower transverse wall extending outwardly and
forwardly of the device and terminating in a transverse
leading edge situated forwardly of the aperture, the verti
cal walls having leading edges that extend from the lead
aperture and straight side edges extending forwardly from
the forwardmost end of said ‘aperture at an acute angle to
the wall of said vehicle and intersecting with said end
edge.
References Cited in the ?le of this patent
ing edge of the lower wall to the respective ends of the
forward transverse edge of the aperture, the leading edges 25
‘of the vertical walls being inclined at an angle to the di
rection of the neighboring portion of the wall of the de
UNITED STATES P TENTS
D. 143,822
D. 155,404
1,069,694
vice, said angle being approximately complementary to
2,352,790
the Mach angle at the air speed for which the device is
30 2,439,273
intended.
2,474,143
' 3. In a device for use at supersonic speeds, an air-intake
chute extending from the interior of the device to the ex
terior through an aperture in the wall of the device, the
Johnson ______________ __ Feb. 12, 1946
Ebel et a1 ______________ __ Oct. 4,
Hayot _______________ __ Aug. 12,
Jordan _____________ __l___ July 4,
Silvester ______________ __ Apr. 6,
Forsyth ______________ __ June 21,
1949
1913
1944
1948
1949
2,503,973
Smith ________________ __ Apr. 11, 1950
2,632,295
Price ________________ __ Mar. 24, 1953
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