Abstrict A system and method for providing an air curtain for impeding the
entry of dust, dirt, debris, smoke, insects and other airborne particulate
matter into an interior area of an aircraft without the need for
disposing heavy, bulky and high power consuming blower assemblies
above the opening in the aircraft. The invention comprises a pair
of air intake ducts each having a fan disposed therein. The fans
draw an ambient airflow into the air intake ducts. Pressurized air
from a power unit associated with the aircraft, such as an engine
or auxiliary power unit, is injected into the air intake ducts.
This has the effect of significantly accelerating the airflow in
the air intake ducts to a velocity suitable for forming an air curtain.
The air intake ducts are coupled to a manifold having a length sufficient
to substantially span the opening of an aircraft at which the air
curtain is formed. An air dispenser associated with the manifold
directs the airflow out of the manifold in a narrow, width-wise
pattern to form an air curtain. In preferred embodiments the manifold
can be rotated in accordance with the position of a loading ramp
of the aircraft such that the angle of impingement of the air curtain
relative to the ramp can be precisely controlled. A flow control
system also enables the pressurized airflow injected into each air
intake duct to be varied in accordance with the distance of the
ramp surface from the air dispenser.
Claims What is claimed is:
1. A pressurized airflow generating system adapted for use with
an aircraft to provide an air curtain adjacent a portion of said
aircraft, and wherein said aircraft includes a power unit for generating
a pressurized airflow, said system comprising: at least one air
intake duct operably associated with said aircraft to enable an
ambient airflow to be drawn into said air intake duct; an intake
fan operably associated with said air intake duct for drawing said
ambient airflow into said air intake duct and creating an intake
airflow having a first velocity within said air intake duct; a manifold
having an inlet and an outlet, said inlet being operably associated
with said air intake duct to receive said ambient airflow drawn
into said air intake duct; a conduit having a first end in flow
communication with said power unit for receiving said pressurized
airflow, and a second end; an injection nozzle in flow communication
with said second end of said conduit for injecting said pressurized
airflow into said air intake duct in the same direction as said
intake airflow; and said pressurized airflow operating to accelerate
said intake airflow to produce a high pressure airflow having a
second velocity greater than said first velocity through said outlet
of said manifold to thereby form said air curtain.
2. The system of claim 1, further comprising an air dispenser disposed
at said outlet of said manifold for directing said high pressure
airflow through said outlet into a narrow, width-wise airstream,
thereby forming said air curtain.
3. The system of claim 2, wherein said manifold is disposed for
rotatable movement about an axis extending longitudinally along
and parallel to said manifold.
4. The system of claim 1, wherein said manifold is disposed for
rotatable movement about an axis extending longitudinally along
and parallel to said manifold; and wherein said system further comprises
a mechanism for rotating said manifold to a desired angular position
relative to a vertical axis, to thereby direct said air curtain
at a desired angle relative to said vertical axis.
5. The system of claim 4, wherein said mechanism comprises an electric
stepper motor.
6. The system of claim 4, further comprising a position controller
operably associated with said mechanism for controlling said mechanism
in accordance with a position of a moveable portion of said aircraft
which said air curtain impinges, to thereby control an angular position
of said manifold relative to said moveable portion of said aircraft.
7. The system of claim 1, further comprising a flow control valve
disposed in said conduit to control said pressurized airflow therethrough;
and a flow controller operably associated with said flow control
valve for controlling said flow control valve, to thereby control
a rate of flow of said pressurized airflow through said conduit
to said injection nozzle.
8. The system of claim 1, further comprising: an air dispenser
disposed at said outlet of said manifold for directing said high
pressure airflow in a narrow, width-wise airstream to thereby form
said air curtain; said manifold being disposed for rotational movement
about an axis extending longitudinally along said manifold; a motor
for rotating said manifold; and a position controller for controlling
said motor to thereby control said position of said manifold to
maintain said air curtain in accordance with a desired angular position.
9. The system of claim 4, further comprising: an optical sensor
disposed adjacent said manifold for optically monitoring an angular
position of said manifold; and a position controller responsive
to an output of said optical sensor for controlling said mechanism
for rotating said manifold to thereby position said manifold at
a desired angular position.
10. A method for producing an air curtain adjacent a portion of
an aircraft, said method comprising the steps of: generating an
intake airflow having a first velocity within a conduit placed adjacent
an opening in said aircraft; injecting a pressurized airflow from
a power unit of said aircraft into said conduit to mix with said
intake airflow to thereby form a pressurized, high velocity airstream
having a second velocity substantially greater than said first velocity;
and directing said pressurized, high velocity airstream from said
conduit through a flow directing member over said opening in said
aircraft to form said air curtain.
11. The method of claim 10, further comprising the step of rotating
said flow directing member to thereby direct said air curtain at
a desired angle relative to a vertical axis.
12. The method of claim 11, wherein the step of rotating said flow
directing member comprises the step of using an electric motor to
rotate said conduit; and using a controller to control said electric
motor.
13. A pressurized airflow generating system adapted for use with
an aircraft to provide an air curtain adjacent a portion of said
aircraft, and wherein said aircraft includes a power unit for generating
a pressurized airflow, said system comprising: a conduit having
first and second portions, said first portion being disposed to
enable an ambient airflow to be drawn thereinto; an intake fan operably
associated with said first portion of said conduit for drawing said
ambient airflow into said first portion of said conduit and creating
an intake airflow having a first velocity within conduit; said second
portion of said conduit forming a manifold adapted to be disposed
adjacent said portion of said aircraft; an injection system adapted
to receive a pressurized airflow from said power unit and to inject
a high velocity jet stream airflow having a second velocity into
said conduit in the same direction as said intake airflow, wherein
said second velocity is substantially greater than said first velocity;
said high velocity jet stream airflow operating to accelerate said
ambient airflow to produce a high pressure airflow through an outlet
of said manifold to thereby form said air curtain; and a system
for rotationally moving said manifold portion to precisely direct
said air curtain at a desired orientation relative to said portion
of said aircraft. Description TECHNICAL FIELD
This invention relates to apparatuses and methods for forming air
curtains, and more particularly to an apparatus and method specifically
adapted for use with an aircraft to form an air curtain at a desired
area of an aircraft such as a cargo door opening.
BACKGROUND OF THE INVENTION
Background Art
Air curtains are typically used in buildings having a portion which
is open to the ambient environment, and where it is desirable to
form a barrier to prevent the entry of airborne contaminants into
the building. The air curtain is used to form a wall of air which
acts as an impediment to the entry of dust, dirt and debris, as
well as insects and other undesirable elements into the open area
of the building. The air curtain also can help to form a temperature
boundary by producing a pressure differential between the interior
of the building and the outer ambient environment.
Typically, air curtains are formed by placing a plurality of high
flow capacity blower systems alongside one another in an overhead
orientation along the full width of the opening where the air curtain
is to be formed. One such prior art blower system 200 is shown in
FIG. 7. The blower system 200 includes a duct 202 within which is
mounted a fan or blower 204. The fan or blower 204 is driven by
an electric motor (not shown) which is also disposed within the
duct 202. The blower draws air into the duct 202 and discharges
it at an outlet at a suitably high velocity to form a wall or curtain
206 of air.
Blower systems such as that shown in FIG. 7 are typically quite
large, heavy, noisy and bulky units and are entirely unsuitable
for use with commercial or military aircraft. Furthermore, such
prior art blower systems typically require a significant amount
of electrical power to operate, which further makes the integration
of such blower systems into an aircraft impossible or impractical.
Commercial and military aircraft nevertheless would significantly
benefit if a system for forming an air curtain could be installed
on the aircraft without introducing significant expense, weight,
and without requiring significant modifications to the structure
of the aircraft or significant electrical power to operate. The
use of an air curtain would be highly desirable, for example, with
cargo aircraft which have a relatively large cargo door which is
opened during loading and removal of cargo from the fuselage of
the aircraft. Since many such cargo aircraft are forced to operate
in environments where a high degree of dust, dirt, smoke and even
insects may be present, the use of an air curtain would be highly
useful for preventing the entry of such elements into the fuselage
of the aircraft during loading or unloading operations.
Still another important use for an air curtain would be in preventing
the entry of chemical and biological warfare (CBW) airborne contaminants
into a cargo bay or other interior area of an aircraft, such as
during loading and unloading of a cargo compartment of the aircraft.
Such a system would also help to reduce the in-flight CBW decontamination
time by air purging that is presently required with military aircraft.
Accordingly, it would be highly desirable to provide an air curtain
adapted specifically for use with an aircraft to provide a relatively
narrow, width-wise wall of air which acts as a boundary to impede
the entry of dust, dirt, smoke, insects or other airborne contaminants
into an interior area of an aircraft while the interior area is
exposed to the ambient environment. It would further be highly desirable
to provide an air curtain adapted specifically for use with an aircraft
which can be cost effectively installed on the aircraft and which
does not require a plurality of heavy, high power consuming and
bulky electric blower devices to be mounted within the aircraft.
Still further, it would be highly desirable to provide a system
for forming an air curtain which is specifically adapted for use
with an aircraft to provide a wall of air at a cargo door opening
area of the aircraft to prevent the entry of dust, dirt, debris,
smoke, insects and other airborne particulate matter into the fuselage
of the aircraft, and where the angular orientation of the air curtain
can be controllably adjusted for maximum effectiveness in forming
a barrier to the entry of foreign, airborne particulate matter into
the fuselage of the aircraft.
SUMMARY OF THE INVENTION
The above and other objects are provided by an apparatus and method
for forming an air curtain in accordance with preferred embodiments
of the present invention. The apparatus of the present invention
is specifically adapted for use with an aircraft, although it will
be appreciated that the system and method of the present invention
will find utility in a variety of other applications, such as with
transport vehicles and ground facilities, where it is impossible
or undesirable to mount a plurality of heavy, bulky, high power
consuming prior art blower devices in an overhead orientation to
form an air curtain.
The apparatus and method of the present invention comprises at
least one air intake duct which is disposed adjacent a portion of
the aircraft, such as adjacent a cargo doorway formed in the fuselage
of the aircraft. The air intake duct includes a fan for drawing
ambient air into the duct. Preferably, a filter is also included
at the intake side of the air intake duct to filter out dust, dirt,
insects and other airborne contaminants. The air intake duct is
coupled to a manifold which is disposed in an overhead fashion across
the opening where it is desired to form an air curtain. A power
unit of the aircraft is coupled via a suitable conduit to the air
intake duct and includes an injector nozzle for injecting a pressurized
airflow supplied by the power unit directly into the air intake
duct. The pressurized airflow operates to significantly accelerate
the ambient airflow delivered by the fan to produce a high pressure
airflow which is directed into the manifold.
The manifold includes an outlet through which the high pressure
airflow is directed to form the air curtain. In one preferred embodiment
an air dispenser is secured to the outlet of the manifold. The air
dispenser directs the high pressure airflow passing through the
outlet of the manifold into a narrow, width-wise air stream which
forms the air curtain.
The apparatus and method of the present invention thus entirely
eliminates the need for overhead mounting of a plurality of large,
heavy, bulky and power consuming electric blowers across the full
width of the opening where the air curtain is to be formed. This
significantly eases integration and implementation of the present
invention into existing aircraft with a minimal degree of modifications
needed to the fuselage of the aircraft.
In another preferred embodiment the manifold is mounted for rotational
movement about an axis extending longitudinally along the manifold.
A mechanism is included for rotating the manifold in a controlled
fashion. In one preferred form this mechanism comprises an electric
stepper motor. A position control system may also be included for
monitoring the angular position of the manifold and controlling
the stepper motor such that the manifold is rotated as needed to
maintain a desired angular orientation. The ability to modify the
angular orientation is desirable in those applications where, for
example, the floor of the structure at which the air curtain is
being directed is movable, such as when the floor comprises a loading
ramp of a cargo aircraft. In such applications it is highly desirable
to be able to vary the angular direction of the air curtain in accordance
with the angle of the loading ramp to maintain optimum effectiveness
of the air curtain in forming a barrier to the entry of airborne
dust and dirt particulates, insects, etc.
In the preferred embodiment described above, the position control
system is also responsive to the position of the manifold and the
position of the loading ramp of a cargo aircraft which the air curtain
impinges. The position control system allows the manifold to be
rotated closely in accordance with the angular position of the ramp
to thus maintain the air curtain at a desired angular orientation
for maximum effectiveness.
In the preferred embodiment described above a flow control system
is also incorporated for controlling the flow of pressurized air
into the air intake duct. This enables the force of the air discharged
from the manifold to be varied in accordance with a changing height
of a floor which the air curtain impinges. Thus, the pressure of
the air stream forming the air curtain can be varied in accordance
with the distance of the manifold from a floor member such as a
loading ramp.
The apparatus and method of the present invention thus forms a
low cost, easy to install means for forming an air curtain specifically
adapted for use with an aircraft. Advantageously, the system of
the present invention makes use of a pressurized airflow provided
by a power unit of the aircraft, such as an engine or an auxiliary
power unit, to accelerate the ambient airflow within the air intake
duct to produce a pressurized airflow within the manifold which
is of suitable velocity to form an air curtain.
BRIEF DESCRIPTION OF THE DRAWINGS
The various advantages of the present invention will become apparent
to one skilled in the art by reading the following specification
and subjoined claims and by referencing the following drawings in
which:
FIG. 1 is a rear view of an aircraft illustrating a preferred embodiment
of the present invention disposed in an overhead fashion over a
cargo door opening in the fuselage of the aircraft, and directing
an air curtain down against a loading ramp extending from the cargo
opening;
FIG. 2 is a simplified perspective schematic drawing of a preferred
embodiment of the present invention disposed above the loading ramp
of FIG. 1;
FIG. 3 is a view from beneath the apparatus of the present invention
illustrating the openings in the air dispenser;
FIG. 4 is a simplified schematic representation of the invention
from the side of the aircraft of FIG. 1, illustrating the apparatus
directing an air curtain against the loading ramp shown in FIG.
1 when the loading ramp is in two different positions;
FIG. 5 is a simplified schematic view of the present invention
further illustrating the ability of the apparatus to draw in ambient
air into the air intake duct;
FIG. 6 is a simplified side view of the air intake duct and a portion
of the manifold for helping to illustrate the changing flow of velocity
of the air stream flowing through the air duct and into the manifold
as a result of the pressurized airflow injected into the air intake
duct; and
FIG. 7 is a perspective view of a typical prior art blower assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, there is shown a system 10 for forming an
air curtain across an opening 12 in a fuselage 14 of an aircraft
16. In this example, the opening 12 forms a cargo door opening,
but it will be appreciated immediately that the system 10 could
be used to form an air curtain at virtually any other location on
the aircraft where it is desired to impede the entry of dust, dirt,
smoke, chemical and biological warfare elements, insects and other
airborne contaminants into the aircraft 16. The air curtain is designated
by arrows 18 and extends preferably the entire, or substantially
the entire, width of the cargo door opening 12. The force of the
air curtain 18 is sufficient to form a barrier against the entry
of airborne particulates down to a loading ramp 20 of the aircraft
16.
Referring to FIG. 2, the system 10 is shown in greater detail.
The system 10 includes at least one, and preferably a pair, of air
intake ducts 22 disposed adjacent opposite width-wise ends of the
cargo door opening 12. Each air intake duct 22 includes a fan assembly
24 disposed therein for drawing ambient air into its associated
air intake duct 22. Preferably, a filter element 26 is disposed
at the opening 28 of each air intake duct 22 to filter undesirable
airborne particulates and prevent same from being drawn into the
air intake ducts 22. The fan assemblies 24 may vary significantly
in capacity depending upon the overall dimensions of the air curtain
that needs to be formed. However, in one preferred embodiment each
fan assembly 24 comprises a two horsepower axial fan assembly capable
of producing an airflow of about 4,000 CFM (about 112 cubic meters
per minute).
Each air intake duct 22 includes an outlet end 30 which is coupled
to an associated inlet 34 formed at opposite longitudinal ends of
an elongated, tubular manifold 32. The manifold 32 has a pair of
narrow, elongated outlets 36 which are in airflow communication
with an air dispenser member 38. The manifold may be made from lightweight
sheet metal, aluminum or possibly even PVC tubing.
An important advantage of the present invention is the use of a
pressurized airflow from a component of the aircraft 16. This airflow
may comprise a bleed airflow from the engine of the aircraft 16
or a pressurized airflow from a power unit or an auxiliary power
unit (APU) of the aircraft 16. This pressurized airflow is supplied
from one of these components of the aircraft 16 through a suitably
small diameter conduit 40. Conduit 40 branches such that portions
42 thereof extend to each air intake duct 22. Alternatively, it
will be appreciated that a second airflow conduit 40' could be incorporated
and coupled to the aircraft's power unit so that no branching of
the pressurized airflow is required at a point near the air intake
ducts 22.
At the end of each portion 42 of conduit 40 an injector nozzle
42a is disposed. The injector nozzle 42a is positioned inside of
its associated air intake duct 22 and functions to inject the pressurized
airflow from its associated conduit 42 into the air intake duct
22 in a direction in accordance with that of the ambient airflow
drawn in by its associated fan assembly 24. As will be explained
further, this pressurized airflow injected into each air intake
duct 22 serves to significantly accelerate the airflow generated
by the fan assemblies 24 to a velocity suitable to form the air
curtain 18.
Referring further to FIG. 2, in a preferred embodiment the manifold
32 is mounted to suitable structure for allowing rotation thereof
about a limited arc. Rotational movement is imparted to the manifold
32 by coupling it to an output shaft 44b of a motor 44. It will
be appreciated that other mechanisms for imparting rotational movement
to the manifold 32 could be employed, but in the preferred embodiments
the motor 44 comprises an electric stepper motor. The stepper motor
44 is controlled by control signals supplied on line 44a from a
position controller 46 operating in connection with an optical sensor
48. The optical sensor 48 receives optical signals from an optical
transmitter 48a which is driven by the position controller 46. The
optical transmitter 48a is preferably secured to a portion of the
aircraft 16 closely adjacent the manifold 32 such that there is
little or no risk of objects passing between the small distance
separating the optical sensor 48 from the optical transmitter 48a,
which might potentially interfere with the monitoring of the manifold
32 position.
The optical sensor 48 is used to monitor the angular position of
the manifold 32 and to provide output signals related thereto via
suitable conductors 50 to the position controller 46. The position
controller 46 also receives output signals via one or more conductors
52 which are coupled to a ramp positioning sensor array 54. The
ramp positioning sensor array 54 preferably comprises a plurality
of optical receiving elements 54a spaced apart along one edge of
the ramp 20. These optical receiving elements 54a detect the presence
of an optical signal 55 transmitted from a second optical transmitting
element 57 fixedly secured to the air dispenser 38. The angular
position of the ramp 20 affects where the optical signal 55 impinges
the sensor array 54. This in turn affects the output of the sensor
array 54, which produces an output signal indicative of which one
of the sensors thereof are receiving the optical signal 55. Thus,
this enables the position controller 46 to monitor the angular position
of the ramp 20 relative to the manifold 32 position. The output
from the ramp positioning sensor array 54 is also used by the position
controller 46 to determine the approximate distance from the upper
surface 20a of the ramp 20 to the lower edge 38a of the air dispenser
38. The sensor array 54 could be formed by a wide variety of photoelectric
devices such as phototransistors or photodiodes, or possibly even
infrared devices.
With further reference to FIG. 2, an airflow controller system
56 receives control signals via one or more conductors 58 from an
output 58a of the position controller 46. These control signals
control at least one flow control valve 60 in accordance with the
sensed distance of the upper surface 20a of the ramp 20 from the
lower edge 38a of the air dispenser 38. Thus, when the ramp 20 is
lowered, thereby increasing this distance, the flow control system
56 is informed of this condition by the position controller 46 and
it transmits control signals to valve 60 to open this valve to permit
a greater amount of pressurized airflow to be injected into the
air intake ducts 22. If a second airflow conduit 40' is incorporated,
then preferably a second valve 60 is also included and controlled
by the flow control system 56.
When the upper surface 20a of the ramp 20 is at a higher elevation,
an airflow of lesser velocity out of the air dispenser 38 is required
to form the air curtain 18 down to the upper surface 20a of the
ramp 20. The flow control system 56 senses this to close valve(s)
60 slightly to reduce the pressurized airflow into the air intake
ducts 22. In this manner the velocity of the airflow exiting the
air dispenser 38 can be controlled both in angular orientation and
in terms of magnitude to form an air curtain having a desired airflow
velocity and desired angular position. This allows the air curtain
to be positioned as needed for maximum effectiveness in impeding
the entry of dust, dirt, smoke, insects and other airborne particulates,
regardless of the position at which the ramp 20 needs to be maintained
at during loading or unloading of the aircraft 16.
Referring to FIG. 3, the system 10 can be seen form a view underneath
the manifold 32 with a portion of the air intake ducts 22 and manifold
32 broken away for illustrative purposes. The manifold 32 includes
a center divider 32a which serves to separate the interior of the
manifold 32 into independent, elongated channels 32b and 32c. Accordingly,
the high pressure airflow supplied from the left most one of the
air intake ducts 22 is used to supply channel 32b while the high
pressure airflow from the right side air intake duct 22 supplies
channel 32c of the manifold 32.
It will be appreciated that the width of the manifold 32 and air
dispenser 38 can vary significantly, but in one preferred embodiment
suitable for use with a large cargo aircraft the length of the manifold
32 will need to be on the order of about 17 feet (5.185 meters)
in order to produce an air curtain having a width of about 18 feet
(5.49 meters) at the upper surface 20a of the ramp 20. For smaller
openings of the aircraft, a shorter manifold 32 may suffice. In
general, however, the overall length of the manifold 32 will preferably
be just slighter shorter than the maximum width of the air curtain
that needs to be produced. With the preferred embodiments described
herein, the two horsepower axial fans 24 are sufficient to produce
an ambient airflow which can be used to form an air curtain having
a maximum width of about 18 feet (5.49 meters) over a distance of
about 11 ft-13 ft (3.35 m-3.97 m) from the air dispenser 38.
Referring now to FIG. 4, the manifold 32 is shown in two different
positions. It will be appreciated that the air curtain 18 is preferably
angled slightly outwardly of the opening with which it is associated.
It is believed that in most instances angling the air curtain 18
slightly outwardly away from the opening will further help to repel
airborne contaminants than if the air curtain 18 were to be directed
along a perfectly vertical axis.
With further reference to FIG. 4, the air dispenser 38 is shown
in dashed lines indicating that the manifold 32 has been rotated
by the stepper motor 44 (FIG. 2) when the ramp 20 has been lowered.
It will be appreciated that when the ramp 20 is in the lower position
shown by the dashed lines, that a greater airflow velocity will
need to be provided to extend the air curtain 18 down to the upper
surface 20a of the ramp 20. Accordingly, when the ramp 20 is in
the position shown indicated by dashed lines in FIG. 4, the flow
control system 56 and position control system 46 sense this position
of the ramp 20 and open the flow control valve(s) 60 such that the
airflow to each injector 42a is increased, which in turn causes
a greater degree of acceleration of the airflow through each air
intake duct 22 into the manifold 32.
Referring to FIG. 5, it can be seen that the system 10 of the present
invention can also be used in systems where a door 62 needs to be
opened up to a position adjacent the inlet 28 of the air intake
and the ramp 20 extends down to a ground surface.
Referring now to FIG. 6, a portion of the air intake duct 22 and
a portion of the manifold 32 are shown. The continuity, momentum
and energy of the airflow produced in the air intake duct 22 can
be represented by the following equations 64-68 applied for points
"1", "2" and "3" in the drawing of
FIG. 6:
The above equations 64-68 can be applied for a typical air curtain
configuration of 18 foot (5.49 meters) width produced with the assistance
of a typical aircraft auxiliary power unit: p.sub.1 =14.7 psia;
T.sub.1 =70.degree. F.; Q.sub.1 =4,000 cfm (112 cubic meters per
minute); A.sub.1 =A.sub.2 =38.48 in.sup.2 (248.27 cm.sup.2) (Manifold
32 duct diameter: D.sub.1 =D.sub.2 =7 in) (17.78 cm); A.sub.3 =270
in.sup.2 (1742.04 cm.sup.2) (Air Dispenser 38 area: 2.5 inch width
by 108 inch length) where P.sub.1 is the atmospheric pressure at
sea level where T.sub.1 is the temperature of the ambient airflow
in the intake duct 22; where Q.sub.1 is the airflow velocity generated
by the fan assemblies 24; where T.sub.01 is the total temperature
of the airflow in the intake duct 22; where T.sub.02 is the total
temperature of the airflow in the manifold duct 32. V.sub.1 =Q.sub.1
/A.sub.1 =249.5 ft/s, W.sub.1 =p.sub.1 V.sub.1 A.sub.1 =5.0 lb/s
p.sub.On =40 psia, T.sub.On =200.degree. F., W.sub.n =0.63 lb/s
(choked injector nozzle 42a flow at nozzle diameter D.sub.n =1 inch)
(2.54 cm), V.sub.n =49.02(0.8333T.sub.On).sup.0.5 =1,150 ft/s (flow
velocity out of each injector nozzle 42a) (350 meters/sec) where
P.sub.On is the total pressure of airflow in the injector nozzle
42a; and where T.sub.On is the total temperature of airflow in the
injector nozzle 42a.
Using the above equations, the flow conditions after flow injection
are approximately: V.sub.2 =296.3 ft/s (in Manifold 32) V.sub.3
=42.23 ft/s=2,533 ft/min (772.57 meters/min) (through Dispenser
38 exit) T.sub.03 =85.degree. F. where: V.sub.2 represents the velocity
of the airflow within the manifold 32; V.sub.3 represents the velocity
of the airflow exiting the air dispenser 38; and T.sub.03 represents
the total temperature of the airflow exiting the air dispenser 38.
The above calculations demonstrate the velocity boost effect that
the pressurized airflow from the aircraft's power unit has on the
ambient airflow drawn into the air intake ducts 22 by the fan assemblies
24. The system 10 of the present invention thus provides a suitably
high velocity airflow out of the air dispenser 38 for forming an
air curtain without the need for mounting heavy, high power consuming
and bulky blower combinations directly above the cargo opening 12
of the aircraft 16.
While the system 10 of the present invention provides an effective
air curtain for preventing dust, dirt, debris, smoke, odors, insects
and other undesirable airborne particulates from entering the fuselage
of the aircraft 16, the system 10 is just as readily usable for
filtering the air within the fuselage of the aircraft and/or reducing
the in-flight chemical, biological warfare (CBW) decontamination
time by air purging.
The following chart summarizes the advantages of the system 10
relative to a system using conventional blower assemblies for an
air curtain having a width of about 17 feet (5.185 meters).
Weight Volume Power Technology (lb) (cu. ft) (hp) Remarks Conventional
540 21.1 7.5 5 .times. 1.75 hp fans System 10 75 7.5 4 2 .times.
2.0 hp fans
It will also be appreciated that while the system 10 of the present
invention is shown as being disposed in an overhead orientation
relative to the cargo door opening 12, that horizontally directed
air curtains could just as easily be formed at the cargo opening
12. This could readily be accomplished by disposing a pair of manifold
sections on opposite sides of the opening 12 and directing a pair
of horizontally disposed airflows to form a pair of air curtains
directed towards each other and slightly outwardly of the opening
12.
It will also be appreciated that the system 10 and method of the
present invention could be used with little or no modifications
in more conventional applications such as with buildings, where
an opening of the building, such as a loading/unloading dock, would
need to be covered by an air curtain. The system 10 and method of
the present invention is ideal for those applications where space
or cost would otherwise prohibit the implementation of a plurality
of large, heavy, high power consuming blower assemblies in an overhead
arrangement.
Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the present invention can
be implemented in a variety of forms. Therefore, while this invention
has been described in connection with particular examples thereof,
the true scope of the invention should not be so limited since other
modifications will become apparent to the skilled practitioner upon
a study of the drawings, specification and following claims. |