U.S. patent number 3,697,020 [Application Number 05/072,091] was granted by the patent office on 1972-10-10 for vertical lift machine.
This patent grant is currently assigned to Chandler Evans Inc.. Invention is credited to Raymond V. Thompson.
United States Patent |
3,697,020 |
Thompson |
October 10, 1972 |
VERTICAL LIFT MACHINE
Abstract
A maneuverable lifting body wherein pressurized gas is
discharged at supersonic velocity over the surface of at least
three downwardly sloping lifting surfaces, the supersonically
flowing gas separating and thereafter reattaching to the surface to
provide a low pressure region intermediate the points of separation
and reattachment. The low pressure region created on the upper
surface, in cooperation with atmospheric pressure on the bottom of
the body, results in vertical lifting forces which add to the
vertical component of the momentum forces of the gas. Attitude
control and maneuverability are accomplished by selectively venting
ambient air into the low pressure regions whereby the low pressure
region may be selectively destroyed with resultant force
unbalance.
Inventors: |
Thompson; Raymond V. (Simsbury,
CT) |
Assignee: |
Chandler Evans Inc. (West
Hartford, CT)
|
Family
ID: |
22105507 |
Appl.
No.: |
05/072,091 |
Filed: |
September 14, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
836393 |
Jun 25, 1969 |
3592413 |
|
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Current U.S.
Class: |
244/12.2;
244/23C; 244/207 |
Current CPC
Class: |
B64C
39/064 (20130101); B64C 39/001 (20130101) |
Current International
Class: |
B64C
39/00 (20060101); B64c 029/00 () |
Field of
Search: |
;244/12C,23C,42CC |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buchler; Milton
Assistant Examiner: Sotelo; Jesus D.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
836,393 filed June 25, 1969, now U.S. Pat. No. 3,592,413 issued
July 13, 1971.
Claims
What is claimed is:
1. A lifting device for generating vertical lift, the lifting
device including:
a body component;
a plurality of lift elements extending generally radially from and
being circumferentially spaced apart about said body component,
each of said lift elements having a lift surface;
nozzle means associated with each of said lift elements for
delivering a gas stream at supersonic velocity to each of said lift
surfaces, each lift surface being positioned with respect to its
associated nozzle means to create a subambient pressure region at
each of said lift surfaces by separating and reattachment of said
gas stream with respect to each lift surface; and
control means connected to each of said lift elements for
selectively destroying the subambient pressure at the lift
surface.
2. A lifting device as in claim 1 wherein:
said body component is a generally annular member; and wherein
said plurality of lift elements includes at least three lift
elements equally spaced apart about said member.
3. A lifting device as in claim 1 wherein said nozzle means
includes:
a convergent-divergent nozzle connected to one end of each of said
lift elements.
4. A lifting device as in claim 1 wherein:
said body component is a generally annular member; and wherein
said plurality of lift elements includes four lift elements equally
spaced about said member in a cruciform array.
5. A lifting device as in claim 1 wherein each of said lift
surfaces includes:
a first portion extending from said nozzle means; and
a second portion extending from said first portion and inclined
with respect to said first portion at an included angle of less
than 180.degree..
6. A lifting device as in claim 1 wherein each of said lift
elements includes:
a pair of side walls bounding said lift surface; and
a housing for said nozzle means.
7. A lifting device as in claim 1 wherein said control means
includes:
valve means connected to deliver gas at higher than sub-ambient
pressure to said subambient pressure region.
8. A lifting device as in claim 1 wherein said control means
includes:
valve means connected to vent ambient air to said subambient
pressure region.
9. A lifting device as in claim 8 including:
means for delivering a flow of pressurized gas to said nozzle means
at a critical pressure ratio with respect to ambient pressure.
10. A lifting device as in claim 1 including:
gas turbine engine means for delivering a gas flow to said nozzle
means at a critical pressure ratio.
11. A lifting device as in claim 10 wherein:
said gas turbine means is a fan engine; and including
means for bleeding air from the fan of said engine to said
nozzles.
12. A lifting device as in claim 10 including:
second nozzle means for delivering exhaust gas from said engine to
flow along the upper surface of said body component between said
lift elements to create lift.
13. A lifting device as in claim 1 wherein said body component
includes:
a load compartment.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the creation of lifting forces.
More specifically, the present invention is directed to vertical
lift machines involving boundary layer separation-reattachment
control. Accordingly, the general objects of the present invention
are to provide novel and improved methods and apparatus of such
character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is
particularly well suited for application to self-lifting bodies,
such bodies sometimes being referred to as "hovercraft." It is to
be noted that the "hovercraft" must be distinguished from the
ground effect machine (GEM) or air cushion vehicle which creates
and rides upon an air cushion established by drawing in atmospheric
air and directing it downwardly beneath the vehicle. The
"hovercraft," the most common example of which may be considered to
be the helicopter, is not constrained to operation within a few
feet of a surface as is the GEM but rather creates its own lift in
somewhat the same manner as a conventional aircraft.
Prior art operational "hovercraft" have been characterized by a
rotating airfoil or propeller which has generated the lifting
forces in a conventional manner. The complexities of such rotating
blade mechanisms, particularly in the helicopter environment where
blade pitch must be constantly changing, are well known and will
not be discussed herein. In addition to those vehicles which employ
a rotating, generally horizontally mounted propeller mechanism, a
number of self-lifting bodies have been proposed wherein air would
be discharged outwardly in all directions from a region
approximating the center of the vehicle over an immobile airfoil
structure so as to generate vertical lift. In the latter type
apparatus it was generally proposed to blow air over both upper and
lower airfoil surfaces, lift being provided in the conventional
aerodynamic manner.
The previously proposed lifting bodies of the immobile air-foil
type have not been the subject of development due to the obvious
inefficiencies in their design. That is, if reduced to practice,
prior art designs would inherently provide exceedingly limited lift
and thus little or no load carrying capacity. Perhaps more
importantly, no practical manner of maneuvering such vehicles has
been proposed. The lack of maneuverability, with the exception of
relatively expensive helicopter type vehicles, has also
characterized the rotating propeller type lifting bodies. Lack of
maneuverability is, of course, a serious disadvantage in cases
where the device is to be used as an observation platform during
military activities or for manned transportation. Previous attempts
at using comparatively inexpensive, camera bearing lifting bodies
in the field have met with failure since the devices could only be
positioned vertically above and connected to the launch site and
would thereby reveal the position of the crew.
SUMMARY OF THE INVENTION
The present invention overcomes the above-discussed and other
disadvantages of the prior art and, in so doing, provides a novel
and improved maneuverable vertical lift machine. In accomplishing
the foregoing, the present invention generates vertical lift by
creating a pressure differential across a plurality of outwardly
and downwardly flaring lift or expansion surfaces. Three or more
equally spaced lift machines are used, and the lift surfaces would
typically be four in number in a cruciform configuration.
Subatmospheric pressure is created at the upper side of the lift
surfaces through the use of supersonic flow streams discharging
from convergent-divergent nozzles at the entrance to each lift
surface. The supersonic flow separates and thereafter reattaches to
the lift surfaces to provide low pressure regions on the upper side
of each of the lift surfaces intermediate the points of separation
and reattachment. Atmospheric pressure acts on the underside of the
lift surfaces thereby providing the requisite pressure
differential. The vertical lifting forces resulting from this
pressure differential and the vertical component of the momentum
forces of the supersonic gas stream combine to provide the vertical
lift.
The invention presented in this application is further
characterized by vent ports which control the introduction of
ambient air into the low pressure regions on the lift surfaces to
deflect the supersonic stream away from the upper side of the lift
surfaces whereby the low pressure region is destroyed. A force
unbalance then results whereby pitch and roll attitude control and
directional maneuverability can be realized. A balancing of the
horizontal components of the forces on the lift surfaces produces a
hovering state whereas the force unbalance caused by the venting of
a low pressure area on a lift surface to ambient results in
selected attitude control or maneuverability. Maneuverability
and/or attitude control may also be realized by varying the volume
or pressure of the supersonic gas stream flowing over one or more
of the lift surfaces.
The present invention is further characterized by contouring of the
upper side of the lift surfaces to promote at least two separations
and reattachments of the flow stream whereby two low pressure
regions are established to substantially augment the total
available lift force.
The present invention is further characterized by an upper cap
assembly into which pressurized fluid is discharged by the
propulsion source, the propulsion source typically comprising a gas
turbine engine mounted vertically with its discharge nozzle facing
into the cap. The cap may be mounted from the conical plate by
means which permit tilting of the cap. In the preferred embodiment
the cap and plate cooperate to define the nozzle which creates the
supersonic flow. Maneuverability of the vehicle may be achieved by
tilting the cap so as to choke the flow at one side of the body.
Alternatively, maneuverability may be achieved by release of some
of the gas from the cap into a stagnation chamber, the chamber
having a horizontally oriented and steerable discharge nozzle.
BRIEF DESCRIPTION OF THE DRAWING
The present invention may be better understood and its numerous
objects and advantages will become apparent to those skilled in the
art by reference to the accompanying drawing wherein like reference
numerals refer to like elements in the various figures and in
which:
FIG. 1 comprises an isometric view of a first embodiment of a
lifting body in accordance with U.S. Pat. application Ser. No.
836,393 of which the present application is a continuation in
part.
FIG. 2 is a cross-sectional, side elevation view of a second
embodiment of U.S. Pat. application Ser. No. 836,393 of which the
present application is a continuation in part.
FIG. 3 is an enlarged, cross-sectional view of a portion of the
embodiments of FIGS. 1 and 2.
FIG. 4 is an isometric view of the lifting body of the present
invention.
FIG. 5 is a top plan view of the lifting body of FIG. 4.
FIG. 6 is a schematic representation of the lifting body of the
present invention.
FIG. 7 is a schematic representation of an optimized lifting
surface configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the interest of presenting the background leading to the present
invention, the description in U.S. Pat. application Ser. No.
836,393 is substantially repeated herein with respect to FIGS.
1-3.
With reference now to FIG. 1, a perspective view of a first
embodiment of that earlier application may be seen. The embodiment
of FIG. 1 is possessed of a generally conical shape and the upper
surface of the load carrying portion of the vehicle is defined by a
conical metal plate indicated generally at 10. The vehicle body
defined in part by plate 10 has an opening at its upper or smaller
diameter end. Air under pressure is discharged vertically upwards
about the axis of the vehicle through this opening.
Mounted from the vehicle and above the smaller diameter end of
plate 10 is a cap assembly indicated generally at 12. Cap assembly
12 is, as may best be seen from FIG. 3, hollow and has a riser
portion 14 into which the pressurized fluid from the propulsion
source is discharged. The cap assembly 12 also has, about the lower
periphery of riser portion 14, an outwardly extending flange 16.
The bottom surface of flange 16 and the upper or smaller diameter
end of the conical plate 10 cooperate to define an annular
convergent-divergent nozzle 18 through which pressurized gases
discharged into cap 12 will escape. Fluid flowing through nozzle 18
will, as a result of the pressure within cap 14 and the nozzle
design, be discharged down over the exterior of plate 10 at
supersonic velocity.
As may be seen from a consideration of the embodiment of FIG. 2,
the vehicle may be provided with a load space 20 which is defined
in part by the inner surface of conical plate 10 and by a base
plate 22. In a typical operational configuration, where the lifting
body would be employed as a remotely controlled and unmanned
observation platform, electronics including maneuvering control
servo systems, controllable television cameras and transreceivers
would be mounted in load space 20. Additional load space may be
provided on top of cap 12 and cameras may be located in or on such
additional space.
Also mounted within the lifting body and coaxial with conical plate
10 will, as can also be seen from FIG. 2, be a propulsion source
24. Propulsion source 24 will comprise a gas turbine engine
installed vertically with its discharge nozzle 26 facing the
interior of cap assembly 12. The combustion products discharged
under pressure to nozzle 26 will be directed into cap 12 and will
flow outwardly from the cap through the nozzle 18 as shown
diagrammatically in FIG. 3.
In the embodiment of FIG. 1, in the interest of maneuverability,
the cap 12 is provided with a rotatable upper section 30. Cap
section 30 defines, in its interior, a stagnation chamber which may
be placed into communication with the interior of the lower cap
section via suitable valving. The stagnation chamber has a
discharge nozzle 34 which may be aimed by rotating cap section 30
by means not shown. Accordingly, horizontal maneuvering thrust may
be generated by placing the stagnation chamber into communication
with the interior of the lower cap section whereby engine exhaust
gas will be discharged through nozzle 34 and the cap rotated so as
to point the nozzle 34 in the desired direction.
Alternately, or in addition to the employment of a rotatable cap
section and associated structure as above described, the
maneuvering control of FIG. 2 may be utilized. In the FIG. 2 scheme
the cap 12 is mounted from plate 10 by a plurality of linkage
mechanisms, such as the double pivot linkage 36. Accordingly, the
cap 12 may be tilted to any desired angle relative to a vertical
axis through the vehicle to thereby unbalance the horizontal
momentum component of the gases exhausting through nozzle 18. The
means for moving linkages 36 have been omitted from the drawing in
the interest of clarity.
Operation of the lifting body may be best understood by
consideration of FIG. 3 which shows a cross section of the
discharge nozzle 18. In FIG. 3, P.sub.s represents the supply
pressure in cap assembly 12 of a gas being admitted to
three-dimensional convergent-divergent nozzle 18. The dimensions of
the upper end of the conical plate 10 and the lower surface of
flange 16, the plate and flange cooperating to define nozzle 18,
are chosen so that assymetric separation of the supersonic gas jet
discharging from nozzle 18 will occur along line A--A' at the
downstream end of the nozzle. The effect of the flat annular plate
10 attached to the convergent-divergent nozzle 18 is to promote a
process of turbulent mixing between the separating jet boundary and
the ambient gas trapped adjacent to the plate thereby resulting in
a low pressure region. Restated, gas discharged from nozzle 18
flows at supersonic velocity over the surface of plate 10 and, in
the manner known in the art, separates from the plate at point A
and thereafter reattaches to the plate at point B a substantial
distance downstream from point A. Ambient gas trapped between the
points of separation and reattachment will be mixed with and
entrained in the supersonic stream thereby creating a near vacuum
on the surface of the plate between points A and B. Obviously, the
combined effect of the low pressure region acting on the upper
surface of plate 10 and atmospheric pressure acting on the bottom
of the vehicle (plate 22) will create a lifting force. This lifting
force, when combined with the vertical component of the momentum of
the gases being discharged from nozzle 18, will create sufficient
lift whereby the vehicle will rise vertically.
Referring again to FIG. 2 it is to be noted that conical plate 10
may be provided with a vertically movable, outboard section 40.
Downward movement of annular section 40 out of the usual plane of
plate 10 will increase the length of the vortex between points A
and B by moving the reattachment point of the supersonic gas stream
downstream. Increasing vortex length will enhance lift by enlarging
the area of the near vacuum region created above the surface of
plate 10.
Considering again FIG. 3, tests have shown that angle .theta.
defined by the divergent portion of nozzle 18 should be in the
range of 30.degree.-50.degree.. This design parameter can, however,
be satisfied by making angle .alpha. as great as 90.degree.. When
angle .alpha. is 90.degree., flange 16 obviously flares outwardly
and upwardly and there will be no vertical momentum component to be
added to the lift generated by the created pressure
differential.
Referring now to FIGS. 4-7, the embodiment of the present invention
is shown. The lifting device, which is indicated generally at 110,
has a lower body component in the form of a skirt 112 and an upper
body component in the form of a shroud 114. Skirt 112 is a
generally annular element and it may be approximately hemispherical
as shown or frusto-conical. Of course, it might also be formed from
a number of flat tapered segments joined together. Shroud 114 is
generally cylindrical. Four lift elements 116a, 116b, 116c, and
116d are mounted between cylindrical shroud 114 and skirt 112 and
are spaced equi-distant about skirt 112 to take on a generally
cruciform shape as best seen in FIG. 5. Each of these lifting
elements has a pair of side walls 118 and 120, a lift surface 122
contained between the side walls, and an upper housing 124 which
defines a nozzle 126 therein communicating with the interior of
shroud 114. The nozzles 126 are two-dimensional
convergent-divergent nozzles (as indicated generally in FIG. 7),
and they extend between the respective side walls 118 and 120 of
each lift element.
The lifting device of the present invention is powered by a
turbofan type gas turbine engine which is located within shroud 114
and which delivers a supersonic gas stream to flow along the lift
surfaces 122 of lift elements 116 whereby lift is created by
separation and reattachment of the supersonic stream as will be
more fully discussed hereinafter. The portions of skirt 112 between
adjacent lift elements may also be employed to create additional
lift by flowing either supersonic or subsonic gas streams along
their upper surfaces. The air entering shroud 114 to flow through
the gas turbine engine is indicated by the arrows 127, and the
supersonic air or gas streams flowing over lift surfaces 122 and
skirt 112 are indicated by the arrows 130 and 132, respectively.
The gas flowing over skirt 112 is delivered from the interior of
shroud 114 via a nozzle segment 134 which communicates with the
interior of shroud 114 to deliver a stream of gas to the surface of
skirt segment 112. There would be a similar nozzle 134
communicating with each of the skirt segments between the adjacent
lift elements.
Referring now to FIG. 6, a schematic representation is shown of the
device of the present invention. The turbofan gas turbine engine is
of well known typical construction having a fan and compressor unit
136, a burner section 138, and a turbine 140. Compressed air is
bled from the fan and is delivered through the convergent-divergent
nozzles 126 and flows along lift surfaces 122. As will be described
in more detail with respect to FIG. 7, the supersonic gas streams
separate and reattach to lift surfaces 122 thus generaling
localized low pressure areas on the lifting surfaces 122 whereby a
vertical lifting force results from the differential between those
low pressure areas and the ambient pressure on corresponding areas
on the bottom of the lifting device. The turbine discharge gases,
or at least parts thereof, may also be passed through nozzles 134
to flow over the segments of skirt 112 in supersonic streams
whereby lift is also generated. If the turbine discharge gas is to
be passed over the skirts segments in a subsonic stream (which will
create a slightly subambient pressure on the upper surface of skirt
112 with resultant lift) nozzle 134 will be convergent; if the
turbine discharge gas is to be passed over the skirt segments at
supersonic speed, the nozzles 134 will be convergent-divergent, a
significantly subambient pressure will exist on the upper surface
of skirt 112 resulting from separation and reattachment of the gas
stream to generate lift as discussed in parent application Ser. No.
836,393.
Referring now to FIG. 7, an enlarged cross-sectional profile of one
nozzle 126 and lift surface 122 is shown. The gas stream 130
passing through nozzle 126 is at a super-critical pressure ratio;
that is, the ratio P.sub.0 /P.sub.a (where P.sub.0 is the
compressive fan bleed pressure upstream of the throat of nozzle 126
and P.sub.a is atmospheric pressure) is greater than 3, and
preferably about 10. After passing through the two-dimensional
convergent-divergent nozzle 126, the gas expands freely and tends
to separate from the walls of the duct. The upper divergent surface
of nozzle 126 is physically restricted to a length equal to or
slightly less than that corresponding to the point of free
separation, S.sub.1, of the immediate boundary layer. The pressure
at this point is subambient, and consequently the local free
boundary of the jet is acted upon by a transverse pressure gradient
which deflects the fluid stream to flow along surface 122, the
upper boundary of the stream being indicated at 136. The action of
deflecting the fluid jet to flow along surface 122 produces a
curved shock 137 extending from the free separation point S.sub.1
to a point R.sub.1 on surface 122.
The same factors which caused the separation of the supersonic air
stream from the upper surface of nozzle 126 are also experienced by
the stream expanding along wall 122 thus resulting in separation at
point S.sub.2 to create a localized entrainment 138 of air at an
extremely low pressure. The low pressure on lifting surface 122 in
the projected area of entrainment 138 is very much lower than
ambient. This low pressure area assists in maintaining alignment of
the air stream with surface 122 and it also provides a substantial
vertical pressure gradient with respect to the ambient pressure
acting on the bottom of the lifting device whereby vertical lift is
created. Thus, the supersonic gas stream flowing along surface 122
separates at point S.sub.2 and reattaches at point R.sub.1 creating
between those two points an area of localized very low pressure,
even approaching a vacuum, whereby a vertical force imbalance
exists as a result of the pressure differential between the low
pressure on surface 122 and ambient pressure acting on the rear of
the surface 122 so that vertical lift is created. Of course, it
will be understood that the profile depicted in FIG. 7 extends
across the width of each of the lift elements 116 so that, for
example, the separation point S.sub.2 and the reattachment point
R.sub.1 are actually lines extending the full width of the lift
elements, and the pressure differential exists across the width of
the lift elements between walls 118 and 120.
Lift surface 122 extends in a straight line or plane from the mouth
140 of nozzle 126 to reattachment point R.sub.1. If this straight
plane were continued at this point, the air stream would remain
attached to the surface and no further lift would be generated.
However, in accordance with the present invention, lift surface 122
is contoured to bend or incline downward at point R.sub.1 so that
the included angle between segment 122a and segment 122b is less
than 180.degree.. This contouring results in a further expansion
and/or a second separation of the gas stream at point R.sub.1 with
reattachment at point R.sub.2 thereby resulting in a second low
pressure entrainment 142 and a reflected shock 144. This second low
pressure entrainment 142 results, similarly, in an extremely low
pressure area at the projected upper surface of lift surface 122
and a resultant upward force from the pressure differential between
this second low pressure area and ambient air on the bottom of the
lift device thereby substantially augmenting the vertical lift.
Attitude control and maneuverability of the lift device of the
present invention are readily accomplished by a pneumatic switching
technique. Each of the lift devices is provided with an ambient
vent port 146 which is in direct communication with entrainment
area 138 at one end and is normally closed, such as via a valve
148, at the other end. Valve 148 is connected to atmosphere, and
when valve 148 is opened the ambient air, which is at a
substantially higher pressure than the greatly reduced pressure in
entrained volume 138, flows into entrained volume 138 whereby the
low pressure is destroyed and the stream separates from surface
122. This destruction of the low pressure entrainment and
separation of the stream from lift surface 122 terminates the lift
force on that particular surface 122 and causes generation of a
lateral steering thrust component. Accordingly, it can readily be
seen that a force imbalance is then created with regard to the
remaining three lift elements with a resultant change in attitude
or direction of the lift device. Closing of the valve 148 cuts off
the flow of ambient air and allows the supersonic stream to return
to surface 122 for recreation of the low pressure volume 138. As
can be readily understood, the vent valves 148 can be opened or
closed in any desired sequence or combination to produce desired
attitude control and maneuverability of the lift device.
It is contemplated that a load compartment, either for cargo or
passengers would be mounted under skirt 112 (as indicated in FIG.
6), which compartment could be of any desired shape depending upon
the intended use for the lift vehicle. The ease with which attitude
control and maneuverability can be achieved in the present
invention through the use of programmed vent valves results in an
extremely compact vehicle which does not have any need for main
rotor and tail systems traditionally present in vertical lift
devices. The vehicle is, accordingly, readily concealed when not in
use and easy to transport if it is desired to move it over ground.
Furthermore, since most, if not all of the fan air and turbine
exhaust gases are directed outwardly rather than straight down
toward the ground, ground erosion effects and injection of dirt
laden air into the engine, both of which are problems with
traditional vertical lift devices, are substantially eliminated.
Accordingly, the lift device of the present invention can be
readily used from unprepared landing sites thereby further
enhancing its utility.
It will also be readily understood by those skilled in the art that
while four lift elements 116 in a generally cruciform array have
been shown as the preferred arrangement, any number from three or
more, preferably equally spaced around the vehicle, can be used
with comparable results.
While a preferred embodiment has been shown and described, various
modifications and substitutions may be made thereto without
departing from the spirit and scope of the present invention.
Accordingly, it is to be understood that the present invention has
been described by way of illustration and not limitation.
* * * * *