U.S. patent application number 09/818310 was filed with the patent office on 2001-10-04 for cooling air arrangement for a heat exchanger of an aircraft air conditioning unit.
Invention is credited to Buchholz, Uwe Albert, Kelnhofer, Juergen.
Application Number | 20010025506 09/818310 |
Document ID | / |
Family ID | 7636808 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025506 |
Kind Code |
A1 |
Buchholz, Uwe Albert ; et
al. |
October 4, 2001 |
Cooling air arrangement for a heat exchanger of an aircraft air
conditioning unit
Abstract
A cooling air arrangement for an aircraft air conditioning unit
includes an air inlet, a heat exchanger, an outlet plenum, first
and second air outlet channels branching from the plenum, and a fan
arranged in the first outlet channel. During flight of the
aircraft, external ram air driven into the air inlet flows
primarily through the second outlet channel. During ground
operation, the fan primarily sucks cooling air through the first
outlet channel, which merges back into the second outlet channel at
an air mixing junction that functions as an injector nozzle and a
non-return flap valve. The first outlet channel is provided in a
spiral housing of the fan, or in a smooth curved duct. The air
inlet and outlet of the cooling air arrangement, and the air outlet
of the air cycle machine, are oriented in the same direction, e.g.
the flight forward direction.
Inventors: |
Buchholz, Uwe Albert;
(Bliedersdorf, DE) ; Kelnhofer, Juergen; (Jork,
DE) |
Correspondence
Address: |
FASSE PATENT ATTORNEYS, P.A.
P.O. BOX 726
HAMPDEN
ME
04444-0726
US
|
Family ID: |
7636808 |
Appl. No.: |
09/818310 |
Filed: |
March 27, 2001 |
Current U.S.
Class: |
62/401 ;
62/87 |
Current CPC
Class: |
B64D 13/08 20130101;
B64D 13/00 20130101 |
Class at
Publication: |
62/401 ;
62/87 |
International
Class: |
F25D 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2000 |
DE |
100 15 570.7 |
Claims
What is claimed is:
1. A cooling air arrangement for a heat exchanger of an air
conditioning unit of an aircraft, comprising: an air inlet channel;
an air outlet channel system including an outlet plenum, a first
outlet channel, a second outlet channel, a unified outlet channel,
and an air mixing junction, wherein said first and second outlet
channels are both connected at least indirectly to and communicate
with said outlet plenum and are both connected flow-parallel with
each other, wherein a downstream end of said first outlet channel
is connected to said second outlet channel at said air mixing
junction, and wherein said unified outlet channel is connected to
and extends downstream from said air mixing junction; a fan unit
including a rotatable drive shaft and a fan mounted on said drive
shaft for rotation therewith, wherein said fan is arranged in said
first outlet channel and said drive shaft extends outwardly out of
said first outlet channel, and wherein said fan is located on a fan
plane that extends perpendicularly relative to an axis of said
drive shaft; and a heat exchanger having first and second heat
exchange passages that are in heat exchange relation with each
other, wherein said heat exchanger is interposed between said air
inlet channel and said outlet plenum to establish flow
communication from said air inlet channel through said second heat
exchange passage to said outlet plenum; wherein said unified outlet
channel leads to and terminates at an exhaust air outlet; and
wherein said unified outlet channel extends from said air mixing
junction downstream toward said exhaust air outlet, on the same
side of said fan plane as said drive shaft extending outwardly out
of said first outlet channel.
2. The cooling air arrangement according to claim 1, wherein an
upstream end of said second outlet channel is connected directly to
or integrated into said outlet plenum, said outlet plenum is
connected directly to said heat exchanger, an upstream end of said
first outlet channel is connected directly to said second outlet
channel so that said first outlet channel is branched off from said
second outlet channel, said unified outlet channel is an extension
of said second outlet channel, and said first outlet channel is
rejoined back into said second outlet channel by said air mixing
junction which is integrated into said second outlet channel.
3. The cooling air arrangement according to claim 1, wherein said
unified outlet channel extends downstream from said air mixing
junction in a direction that is not more than 30.degree. divergent
from parallel with said axis of said drive shaft.
4. The cooling air arrangement according to claim 1, wherein said
fan is a suction fan that is configured and adapted to move air
through said first outlet channel across said fan plane in a
direction toward said drive shaft.
5. The cooling air arrangement according to claim 1, wherein said
first outlet channel extends from said fan to said air mixing
junction along a path that is not linearly and not coaxially
aligned with said axis of said drive shaft.
6. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises an air guide device that is
configured, arranged and adapted to direct air radially from said
fan toward said air mixing junction.
7. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises an air guide device that is
configured, arranged and adapted to direct air diagonally from said
fan toward said air mixing junction.
8. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises an air guide device that is
configured, arranged and adapted to direct air axially from said
fan toward said air mixing junction.
9. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises an air guide device that is
configured, arranged and adapted to direct air circumferentially
from said fan toward said air mixing junction.
10. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises a spiral housing with a spiral air
path therein.
11. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises a curved air duct.
12. The cooling air arrangement according to claim 1, wherein said
curved air duct has a cross-sectional area that tapers toward said
downstream end of said first outlet channel.
13. The cooling air arrangement according to claim 1, wherein said
first outlet channel comprises a plate diffuser interposed in an
air flow path through said first outlet channel.
14. The cooling air arrangement according to claim 1, further
comprising an air cycle machine including at least one of a
compressor and a turbine mounted on said drive shaft for rotation
therewith in a machine housing, wherein said air cycle machine
includes a process air inlet connected to said first heat exchange
passage and a process air outlet.
15. The cooling air arrangement according to claim 14, wherein said
unified outlet channel extending downstream from said air mixing
junction is directed toward and extends along an outside of said
machine housing of said air cycle machine.
16. The cooling air arrangement according to claim 15, wherein said
unified outlet channel extends below said machine housing of said
air cycle machine.
17. The cooling air arrangement according to claim 1, wherein said
air inlet channel, said heat exchanger, and said air outlet channel
system have an overall U-shaped configuration.
18. The cooling air arrangement according to claim 1, wherein said
air inlet channel, said heat exchanger, and said air outlet channel
system have an overall J-shaped configuration.
19. The cooling air arrangement according to claim 1, wherein said
air mixing junction comprises an injector flap that protrudes from
said downstream end of said first outlet channel into a flow
cross-section of said second channel thereby reducing a dimensional
size of said flow cross-section, and that extends toward said
unified outlet channel.
20. The cooling air arrangement according to claim 19, wherein said
injector flap is curved as it protrudes from said downstream end of
said first outlet channel and extends toward said unified outlet
channel.
21. The cooling air arrangement according to claim 19, wherein said
injector flap is flat and planar as it protrudes from said
downstream end of said first outlet channel and extends toward said
unified outlet channel.
22. The cooling air arrangement according to claim 19, wherein said
injector flap is a rigid fixed flap.
23. The cooling air arrangement according to claim 19, wherein said
injector flap is pivotally mounted relative to said first and
second outlet channels.
24. The cooling air arrangement according to claim 23, wherein said
injector flap is configured and arranged to be pivotal to a first
position in which it closes said flow cross-section of said second
outlet channel.
25. The cooling air arrangement according to claim 24, wherein said
injector flap is configured and arranged to be pivotal to a second
position in which it closes said downstream end of said first
outlet channel.
26. The cooling air arrangement according to claim 23, further
comprising an actuator connected to said injector flap and adapted
to pivotally move said injector flap.
27. The cooling air arrangement according to claim 19, wherein said
injector flap is fixedly mounted and is flexibly deflectable.
28. The cooling air arrangement according to claim 1, wherein said
air mixing junction comprises an air injector nozzle.
29. The cooling air arrangement according to claim 1, wherein said
air mixing junction comprises a non-return one-way flap valve.
Description
PRIORITY CLAIM
[0001] This application is based on and claims the priority under
35 U.S.C. .sctn.119 of German Patent Application 100 15 570.7,
filed on Mar. 29, 2000, the entire disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to an arrangement for directing both
ram air as well as fan-driven air through a heat exchanger that is
used for cooling hot compressed air for an air conditioning unit of
a passenger transport aircraft.
BACKGROUND INFORMATION
[0003] Modern passenger transport aircraft are typically equipped
with air conditioning units, namely so-called air conditioning
packs or air generation units. Hot, highly compressed engine bleed
air is conveyed to the air conditioning units through suitable
conduits or ducts, and in the air conditioning units is then
subjected to a combined thermodynamic process generally including
cooling by heat transfer through a heat exchanger, followed by
compression, further intermediate cooling in a heat exchanger, and
finally expansion through a turbine, to ultimately provide air
conditioning air at an appropriate pressure and temperature to be
introduced into the pressurized cabin of the aircraft.
[0004] During this process, which is carried out in an air cycle
machine of the air conditioning unit, a substantial proportion of
the total heat energy is given off or rejected by heat exchange
through one or more air-to-air heat exchangers. Namely, the hot
compressed engine bleed air is conveyed through a first heat
exchange channel of a heat exchanger core, while a cooling air flow
is conveyed through a second heat exchange channel of a heat
exchanger core. The first and second heat exchange channels do not
allow air flow or air exchange therebetween, but are in a thermal
transfer relationship, e.g. thermally conducting, with each other.
Thereby, the heat exchange core serves to transfer heat from the
hot bleed air or process air to the cooling air flow.
[0005] The second channel or cooling air channel of the heat
exchanger is connected to an air channel or conduit system which
conveys external cooling air from the external environment outside
of the aircraft into and through the heat exchanger core, and then
exhausts the now-heated cooling air back out to the external
environment. In this context, two different air flow conditions
must be taken into account. In a first condition, when the aircraft
is flying in cruise flight or during take-off and landing at a
particular air speed, an inlet channel is arranged in such a manner
so that ram air will be introduced into and flow through the heat
exchanger. Namely, the aerodynamic pressure difference between the
inlet channel and the outlet channel is used as an energy source
for driving the cooling air flow through the channel system and
through the heat exchanger core.
[0006] On the other hand, in a second air flow condition, when the
aircraft is parked or taxiing on the ground or in low speed or low
altitude flight, whereby nonetheless the air conditioning unit is
to be operated to provide air conditioning air, there is
insufficient or non-existent ram air flow to provide the required
flow rate of cooling air, so it is necessary to mechanically drive
an air flow through the heat exchanger using a turbo air machine
such as a fan or blower. This turbo air machine may be rotationally
driven by a rotating shaft that is driven from any source of
rotational power, for example the shaft of an electric motor, or
the shaft of the air cycle machine of the air conditioning unit
itself.
[0007] FIGS. 4 and 5 of the present application show two different
conventional cooling air arrangements for conveying cooling air
through a heat exchanger of an aircraft air conditioning unit.
Particularly, FIG. 4 shows the cooling air arrangement used in the
present day Boeing 747 and 777 aircraft, while FIG. 5 shows the
cooling air arrangement used in the present day Airbus A340
aircraft. Each of these prior art arrangements includes a cooling
air inlet channel 8' and a cooling air or heat exchanger outlet
plenum 4' with the heat exchanger 1' interposed therebetween, so
that the cooling air A flows from the external environment outside
of the aircraft into the inlet channel 8', through the heat
exchanger 1', and then to the outlet plenum 4', before being
ultimately exhausted back out to the external environment outside
the aircraft. Each of the arrangements further includes, as
components of or extending from the outlet plenum 4', a first
outlet channel 7' through which air can be mechanically blown
during ground operation of the aircraft, and a second outlet
channel 9' through which ram air flows during flight of the
aircraft. In this context, a turbo blower or fan 3' is driven by
the main shaft of the air cycle machine 5' of the air conditioning
unit, and is arranged at an inlet portion of the first outlet
channel 7' so as to suck air from the heat exchanger 1' and from
there through the outlet plenum 4', and finally blow this air out
through the first outlet channel 7'.
[0008] The mechanical, structural, aerodynamic, and air flow
arrangement and configuration of the several components and
particularly the outlet plenum 4', the first channel 7', the second
channel 9', and the turbo blower or fan 3' are very significant and
rather complicated to design. Namely, the design and configuration
of the arrangements must take into account the two different
operating conditions, i.e. air flow conditions, that have been
described above, as well as the altitude dependent variation of the
air density, the aerodynamic conditions and flow patterns of air
outside of the aircraft, the arrangement and orientation of the air
cycle machine 5' relative to the aircraft and relative to the heat
exchanger arrangement, and the like. For example, the shaft
orientation of the associated air cycle machine that is driving the
fan 3' necessitates an axis-parallel orientation of the heat
exchanger arrangement in order to achieve an optimal air flow of
the turbo blower or fan 3'. Mounted on the same shaft as the fan
3', the air cycle machine 5' includes one or more compressors C and
turbines T for compressing and expanding the process air, to
ultimately provide the cooled air conditioning air AC from the air
outlet 21'. Therefore, the orientation of the installed air cycle
machine 5' is specified based on other considerations, and
typically the expansion turbine T and particularly the air
conditioning air outlet 21' of the air cycle machine 5' must be
oriented lying in the flight direction, while the flow of cooling
air A being exhausted from the outlet plenum 4' must be oriented
opposite thereto, namely opposite the flight direction of the
aircraft.
[0009] Taking the above considerations into account, the prior art
arrangements of FIGS. 4 and 5 both have an overall air flow pattern
of the cooling air A substantially in an S-shape or Z-shape,
especially with regard to the fan-driven air flow during ground
operation of the aircraft. The conventional arrangements further
both use a bypass system in which ram air, to the extent that it is
available, will first bypass the first outlet channel 7' and
instead flow directly from the outlet plenum 4' out through the
second channel 9' to the exhaust outlet. In the conventional Boeing
arrangement shown in FIG. 4, this bypass arrangement is achieved
with non-return air valves or one-way check valves 2', and in the
conventional Airbus arrangement shown in FIG. 5, this bypass
arrangement is achieved with an air injector arrangement 6' as well
as non-return flaps 12'.
[0010] In view of the above, the air inlet channel 8' in the prior
art arrangements generally faces forward in the flight direction,
while the exhaust air outlet 20' generally faces rearwardly or
downstream relative to the flight direction, as shown in FIGS. 4
and 5. If the conventionally known installation orientation of the
equipment is changed, then it may become necessary to achieve a
common orientation of the expansion turbine outlet 21', the heat
exchanger inlet 8', and the outlet plenum exhaust outlet 20' all
facing in the same direction, e.g. in the flight direction. Any
attempt to achieve such a configuration or orientation using the
cooling air arrangements according to conventional FIGS. 4 and 5
would be impossible or suffer considerable aerodynamic
disadvantages, or would simply not be able to achieve acceptable
operating characteristics.
[0011] Namely, additional air channels as well as air flow
redirecting elbows or channel curve members, as well as additional
valves or air flaps would have to be provided in the arrangement.
This would lead to a disadvantageous increase of the installation
size and weight of the overall arrangement, as well as requiring
additional maintenance efforts. Also, the aerodynamic efficiency of
the cooling air channel directing air through the heat exchanger
would be reduced due to the extra air channel components and
deflections, and heat exchange energy would thereby be lost. It
would also be necessary to increase the size of the various air
channel components to try to compensate for such a loss of
aerodynamic efficiency, which in turn would result in a greater
installation space requirement as well as an increased total weight
in the aircraft.
SUMMARY OF THE INVENTION
[0012] In view of the above, it is an object of the invention to
provide a cooling air arrangement for a heat exchanger of an
aircraft air conditioning unit with an integrated turbo blower or
fan, which achieves a very compact arrangement with an efficient
air flow and low flow energy losses, especially for an orientation
and arrangement of the components in which the air inlets and air
outlet directions face generally in the same direction, and
particularly the flight direction of the aircraft. The invention
further aims to avoid or overcome the disadvantages of the prior
art, and to achieve additional advantages, as apparent from the
present specification.
[0013] The above objects have been achieved according to the
invention in a cooling air arrangement for an aircraft air
conditioning unit, comprising a cooling air inlet channel and a
cooling air outlet plenum that are each connected to the external
environment outside of the aircraft, and a heat exchanger with
second heat exchange passages interposed between the cooling air
inlet channel and the cooling air outlet plenum and with first heat
exchange passages interposed between a source of hot compressed air
such as engine bleed air and the process air inlet of an air cycle
machine of the air conditioning unit. According to the invention,
the cooling air outlet plenum is divided into or connected to a
first outlet channel and a second outlet channel, which will
respectively convey the cooling air to the cooling air exhaust
outlet dependent on the operating conditions. The second channel
extends from the outlet plenum, or substantially forms the outlet
plenum, and is connected directly to the outlet side of the heat
exchanger. The first channel is branched off of this portion of the
second channel in the area of the cooling air plenum, and an outlet
end of the first channel then leads back into an air mixing
junction or portion of the second channel.
[0014] A turbo blower or fan is installed in the inlet area of the
first channel, so as to suck cooling air through the heat exchanger
during ground operation of the aircraft. On the other hand, during
normal flight of the aircraft, ram air is directly driven through
the second channel by the pressure difference between the cooling
air inlet and the cooling air exhaust outlet. The first channel is
particularly provided as a channel in an air guide device which may
have an axial, diagonal or radial configuration. For example, the
air guide device may comprise a pipe section, a spiral housing, or
a plate diffuser respectively defining the first air channel. An
air injector or particularly an air injector flap may be arranged
between or adjoining the first channel and the second channel in
the area of the air mixing junction where the two air channels
rejoin each other. This injection flap carries out the function of
an injector nozzle or a non-return flap valve depending on the
particular operating conditions, so as to allow a proper and
compatible air flow of ram air through the second outlet channel
and fan-driven air through the first outlet channel.
[0015] According to a further detailed feature of the invention,
the overall air flow pattern of cooling air through the inventive
cooling arrangement is generally a U-shape, namely entering the
cooling air inlet from the forward flight direction, then
deflecting by substantially a half-turn (e.g. at least 150.degree.)
through the heat exchanger, to then be ultimately discharged
through the cooling air exhaust outlet channel in a generally
flight forward direction, possibly with further deflection. Thus,
the air flow deflection of the entire cooling arrangement is, for
example, at least 135.degree.. The cooling air inlet and the
cooling air exhaust outlet channel extending from the present
arrangement preferably both are oriented generally toward the
forward flight direction, as is the air conditioning air outlet of
the air cycle machine of the air conditioning unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order that the invention may be clearly understood, it
will now be described in connection with example embodiments, with
reference to the accompanying drawings, wherein:
[0017] FIG. 1 is a schematic side view of a first embodiment of a
cooling air arrangement for a heat exchanger of an aircraft air
conditioning unit according to the invention;
[0018] FIG. 1A is a schematic sectional view of a portion of the
arrangement of FIG. 1, taken along the section line IA-IA;
[0019] FIG. 2 is a schematic top view of the arrangement of FIG.
1;
[0020] FIG. 2A is a schematic sectional view of a portion of the
arrangement of FIG. 2, taken along the section line IIA-IIA;
[0021] FIG. 3 is a schematic side view of a simplified embodiment
of a cooling air arrangement according to the invention;
[0022] FIG. 4 is a schematic top view of a conventional cooling air
arrangement as installed in present day Boeing 777/747 aircraft;
and
[0023] FIG. 5 is a schematic top view of a conventional cooling air
arrangement as installed in present day Airbus A340 aircraft.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE
BEST MODE OF THE INVENTION
[0024] The conventional arrangements according to FIGS. 4 and 5
will not be described further here, because they have been
adequately discussed in the above Background Information section of
this specification. Moreover, a person of ordinary skill in the art
will be familiar with and have additional information available
regarding these prior art configurations as shown in FIGS. 4 and
5.
[0025] FIG. 1 shows a schematic side view of a first example
embodiment of a cooling air arrangement for a heat exchanger of an
aircraft air conditioning unit according to the invention. FIG. 2
shows a schematic top view of the same arrangement. The arrangement
primarily comprises a cooling air inlet channel 8, a heat exchanger
1 primarily including a heat exchanger core, and an air outlet
channel system including a heat exchanger plenum or cooling air
outlet plenum 4, and a two-part divided outlet air channel
including a first outlet channel 7 and a second outlet channel 9.
An air-sucking turbo blower or fan 3 is integrated into the first
outlet channel 7.
[0026] The heat exchanger 1 includes first heat exchange passages
that receive hot compressed air, e.g. engine bleed air, from a hot
air supply channel 15. The heat exchanger 1 further includes second
heat exchange passages that are in a heat exchange relation with
the first heat exchange passages. Cooling air A from the external
environment immediately outside of the aircraft flows into the air
inlet channel 8, through the second heat exchange passages of the
heat exchanger 1, and then into the outlet plenum 4, and further
through either one or both of the outlet channels 7 and 9, to be
finally exhausted through the exhaust air outlet 20 back to the
external environment outside of the aircraft. Note that reference
number 20 does not label the actual outlet end that opens to the
exterior environment, but rather labels the exhaust air duct or
channel which is shown broken off and which ultimately leads to the
exhaust outlet itself. During the air flow process, heat is given
off from the hot bleed air in the first heat exchange passages to
the cooling air in the second heat exchange passages of the heat
exchanger 1, whereby the hot bleed air is cooled and provided at a
cooled process air outlet 15A. On the other hand, the cooling air A
becomes heated as it passes through the heat exchanger 1.
[0027] As has been generally discussed above, the flow of cooling
air A proceeds differently under different operating conditions.
During normal forward flight of the aircraft, the cooling air is
effectively pressed into the cooling air inlet channel 8 as ram
air. For this purpose, the inlet end of the cooling air channel 8
is located at a relatively high pressure area of the outside of the
aircraft fuselage, and particularly includes a forward facing air
intake that stagnates the oncoming flow of air and causes a ram
effect. On the other hand, the cooling air exhaust outlet 20 is
located at a relatively lower pressure area of the outside of the
aircraft fuselage, so that the pressure difference between the
inlet and the outlet drives the flow of cooling air A through the
inlet channel 8, the heat exchanger 1, the outlet plenum 4, and at
least the second air outlet channel 9, which can thus also be
designated as a ram air outlet channel 9.
[0028] On the other hand, when the aircraft is on the ground,
either parked or taxiing, or in slow or low altitude flight
conditions in which there is insufficient ram cooling air, but in
which the air conditioning unit is operating and requires cooling
air for the heat exchanger 1, the turbo blower or fan 3 operates to
actively suck the cooling air A into the air inlet channel 8,
through the heat exchanger 1, and then through the first outlet
channel 7 equipped with the blower or fan 3. Thus, the first air
channel can be designated as a fan-driven air channel 7.
[0029] Particularly according to the present embodiment of the
invention, the second outlet channel 9 is connected directly to
and/or extends from the outlet plenum 4. Another way of considering
this is that a plenum portion 91 of the second outlet channel 9
forms the outlet plenum 4. FIG. 2 also illustrates the length L and
the width B of the air outlet plenum 4, especially formed by the
plenum portion 91 of the second air outlet channel 9, and generally
including the entire portion of the second air outlet channel 9
upstream of a constricted or reduced cross-sectional area of the
throat thereof in the air mixing junction 10. The first outlet
channel 7 branches off from the second outlet channel 9, for
example from the plenum portion 91 thereof. The flow of cooling air
A will be divided and apportioned between the first outlet channel
7 and the second outlet channel 9, depending on the operating
condition as described above. Thereby, a respective portion of the
total cooling air flow can flow through each of the two channels 7
and 9, or the entire cooling air flow under any particular
condition may flow through a single operative one of the two
channels 7 and 9. The details of this divided air flow will be
described further below.
[0030] A downstream end of the first air channel 71 is connected or
merged back into the second air channel 9 at an air mixing junction
10. In this context, the first channel 7 reduces the enclosed
cross-section of the second channel 9 by its own cross-sectional
area at this mixing junction 10, as shown in FIG. 1A. The blower or
fan 3 is installed in the first outlet channel 7 between its inlet
junction with the second outlet channel 9, and the air mixing
junction 10. With this arrangement, the two channels are connected
flow-parallel with each other, i.e. not strictly mechanically
parallel but establishing a parallel (rather than series) flow of
air respectively therethrough. Also in this context, the second ram
air outlet channel 9 can be regarded as the primary or principle
channel, while the first outlet channel 7 forms a partial loop that
branches off from and then rejoins the second channel 9.
[0031] Downstream from the air mixing junction 10, an outlet
portion of the second channel 9, which may be referred to as a
unified outlet channel since the two separate first and second
channels have been rejoined or unified therein by the air mixing
junction, extends substantially straight relative to the second
channel portion leading into the air mixing junction. A lateral
deflection of this unified outlet channel, as shown in the top view
of FIG. 2, may be necessary for the unified outlet channel to clear
around the air cycle machine 5, for example. Generally, if one
defines a fan plane as extending through the fan 3 perpendicularly
to the axis of the fan shaft 13, then the unified outlet channel
extends from the air mixing junction 10 downstream toward the
exhaust air outlet 20 on the same side of the fan plane as the fan
shaft 13 extends from the fan 3 outwardly out of the first outlet
channel toward the air cycle machine 5. More particularly, the
unified outlet channel extends in a direction that is generally
aligned with the axis of the shaft 13 of the fan 3, e.g. no more
than 300 divergent from parallel to the axis of the fan shaft.
[0032] In the forward flight operating condition, the cooling air
is driven through the air channel arrangement by a ram effect, as
described above. In this situation, the cooling air A that has
passed through the heat exchanger 1 and thereby becomes heated, is
then further driven through the outlet plenum 4 and primarily
through the second outlet channel 9. However, a rather small
portion of the cooling air A may also be driven through the first
outlet channel 7 and flow past the blower or fan 3, which in effect
is just idling with the air flowing therethrough in this condition.
At the air mixing junction 10, these two partial air flows will be
reunited and mixed together. The proportionally substantially
smaller air flow through the first outlet channel 7 is driven by
the relatively higher pressure at the inlet end of the first outlet
channel 7 in comparison to the relatively lower pressure created at
the mixing air junction 10, due to the effect of the reduced
cross-sectional area of the second outlet channel 9 and the
resulting acceleration of the air flow therethrough. Thus, the air
mixing junction 10 has the effect of an injector nozzle or a jet
pump in this manner (see FIG. 1A).
[0033] The air flow situation is different when the aircraft is on
the ground or at a low flight altitude, i.e. when there is no ram
air or insufficient ram air being forced into the inlet channel 8.
Under such operating conditions, the turbo blower or fan 3 must be
operated to actively draw air through the heat exchanger 1. To
achieve this, the blower or fan 3 is preferably mounted on an end
of the rotating drive shaft 13 of the air cycle machine 5 of the
air conditioning unit of the aircraft. This air cycle machine 5
includes, e.g., at least one compressor and at least one turbine
mounted on the same rotating drive shaft 13 with the blower or fan
3. Throughout this specification, the term "fan" will be used
generally to refer to any type of rotating air-moving device, such
as radial, axial, or diagonal flow fans, blowers, ventilators, and
the like. In any event, whenever the air cycle machine 5 is
operating, the fan 3 will also be rotating with the shaft 13,
unless a de-coupling clutch is provided, which is an option.
[0034] Whenever there is an insufficient ram air flow, the fan 3
will actively move a sufficient quantity of cooling air through the
heat exchanger 1 and through the first air outlet channel 7 to the
air mixing junction 10. As this air is forcefully driven from the
first outlet channel 7 into the air mixing junction 10, where it
merges into the second air outlet channel 9, the air mixing
junction 10 achieves an air injector nozzle or jet pump effect,
which draws an additional quantity of cooling air through the
second outlet channel 9, by a suction effect created by the
positively driven air flow through the mixing junction 10 (see FIG.
1A).
[0035] Under both operating conditions, the two air flows
respectively flowing through the first outlet channel 7 and the
second outlet channel 9 are reunited at the air mixing junction 10,
to then flow together through the unified outlet portion of the
second outlet channel 9 leading to the cooling air exhaust outlet
20. With regard to FIGS. 1 and 2, it is noted that the united or
combined outlet portion of the second outlet channel 9 extends in a
generally flight-forward direction of the aircraft toward and along
the side of the air cycle machine 5 of the air conditioning unit.
This is also the direction in which the air conditioning air AC is
output by the air cycle machine 5 at its air conditioning air
outlet 21. This is further the direction in which the air inlet
channel 8 extends from the heat exchanger 1, so that the overall
air channel arrangement has a U-shape or a J-shape, or the shape of
a smoking pipe. Generally, it is seen that the cooling air flow is
directed through a nearly 1800 direction reversal or deflection as
it flows through the heat exchanger 1. In the illustrated
embodiment of FIG. 2, the ultimate flow deflection between the
inlet and outlet is about 135.degree., but the flow deflection
through the heat exchanger is about 160.degree..
[0036] As can be understood especially from FIGS. 1, 2 and 2A, the
first air outlet channel 7 in the present example embodiment is
preferably embodied in an air guide device 71, which, for example,
comprises a spiral housing, or a spiral-wound pipe with a spiral or
circumferential curvature of the first air outlet channel 7 defined
in this air guide device 71. Alternatively, the air guide device 71
may comprise a plate diffuser through which the cooling air is
directed. Conveniently, the air guide device 71 may be a spiral
housing of the fan 3 or directly connected to the fan 3, for
example the housing of a radial or centrifugal blower. Such an
arrangement provides a compact structure while providing efficient
use and redirection of the fan output air flow, and allows the
first air channel 7 to be branched off from and then rejoined into
the second air channel 9, while maintaining a substantially
straight continuous air flow path in the second air channel 9.
[0037] Now referring again more particularly to FIGS. 1A and 2A,
special details of the air mixing junction 10 or in general the
junction area at which the first air outlet channel 7 rejoins into
the second air outlet channel 9, will be described. As can be seen,
the air mixing junction 10 is connected to the outlet side of the
air guide device 71, and merges into the second air outlet channel
9. Thereby, a cross-sectional area of the second outlet channel 9
is reduced, as mentioned, to form a throat area, which is
preferably bounded by a deflectable or pivotable injector flap 11
as shown in FIG. 1A. For example, this flap 11 is pivoted along a
hinge pin 11A. This injector flap 11 forms the constricted throat
of the second air outlet channel 9, to create the injector nozzle
or jet pump effect that has been described above.
[0038] The pivotal position or the flexible deflected position of
the injector flap 11 will vary dependent on the aerodynamic flow
conditions within the air mixing junction 10. Namely, the air
injector flap 11 will take up the appropriate position at any time
for achieving the optimum cooling air flow, while balancing the air
flow between the first outlet channel 7 and the second outlet
channel 9 in the different operating conditions, as has been
described above. It is alternatively possible to provide a fixed
rigid injector flap 11, which has a constant fixed position. Also,
the injector flap 11 preferably has a curved contour as shown in
FIG. 1A, but may alternatively have a straight or flat planar
contour. Particularly, the curvature of the injector flap 11 is a
generally parabolic curvature that extends from the outlet of the
first air outlet channel 7 and curves in the flow direction of the
air toward the cooling air exhaust outlet 20, so as to deflect the
air flow from the first outlet channel 7 in the appropriate
direction.
[0039] The preferably flexibly deflectable or pivotable injector
flap 11 serves the functions both of an injector nozzle and a
non-return one-way flap valve. Namely, when the injector flap 11 is
in an intermediate position as shown in FIG. 1A, thereby allowing
an open flow passage from both the first outlet channel 7 and the
second outlet channel 9 through the air mixing junction 10, while
creating a reduced cross-sectional throat of the second outlet
channel 9, this injector flap 11 forms the above described air
injector nozzle or jet pump. This effect is also achieved with a
fixed or stationary ejector flap 11. This applies to both the ram
air condition during flight, and the fan-driven air flow condition
during ground operation, but with respectively opposite suction
effect, i.e. a reversal of which air flow is the driving air flow
and which air flow is the driven air flow, as described above.
[0040] On the other hand, if the air flow provided through either
the first outlet channel 7 or the second outlet channel 9 is so
strong that it causes the pivotable or deflectable air injector
flap 11 to tilt or pivot entirely toward the respective opposite
air outlet channel, thereby closing off this other outlet channel,
then the flap 11 functions as a non-return flap valve. For example,
when the fan 3 is driving a substantial air flow through the first
air outlet channel 7, then the injector flap 11 will close the
throat of the second air outlet channel 9, thereby acting as a
non-return valve and preventing an unintended back flow circulation
of fan-driven air in a reverse direction through the second air
outlet channel 9 back into the inlet of the first air outlet
channel 7. Alternatively, during ram air conditions, if a
sufficient ram air flow is flowing through the second air outlet
channel 9, then the flap 11 will tilt upwardly to close off the
first air outlet channel 7, and thereby provide a greater flow
cross-section through the throat of the second air outlet channel
9, and bypassing the flow resistance of the idling fan 3 in this
condition. Thereby, the flow resistance overall is reduced.
[0041] The flap 11 may be spring-biased or gravitationally-biased
in any manner to achieve the desired operation thereof. As a
further option according to the invention, the position of the air
injector flap 11 may be actively driven by any suitable actuator,
so that the air injector flap 11 can be positively set to any
desired position that is appropriate for the respective prevailing
operating condition. In addition to or instead of the injector flap
11, a non-return flap valve can be arranged in the second channel 9
or in the first channel 7 above the air mixing junction 10, for
example especially to prevent an unintended back flow of air in an
arrangement with a fixed injector flap 11.
[0042] FIG. 3 is a schematic side view of a simplified further
embodiment of the cooling air arrangement according to the
invention. Components generally corresponding to those of the above
described embodiment are labeled with the same reference numbers as
above. A redundant description will not be provided here. The
principle difference of this embodiment relative to the embodiment
of FIGS. 1, 1A, 2 and 2A, is a simplification or difference of the
air guide device 71 providing or defining the first air outlet
channel 7. In this embodiment, rather than the above described
spiral configuration of the air guide device 71, the present air
guide device 71A is simply a smoothly contoured duct member in
which the fan 3 is arranged.
[0043] The plenum portion 91 of second air outlet channel 9, or the
outlet plenum 4, is configured and split in a Y-shape, whereby the
inlet end of the first air outlet channel 7 is joined onto one of
the two split arms of the Y-shape, and the fan 3 is arranged in the
vicinity of this inlet end of the second air outlet channel 7. From
there, the first air outlet channel 7 slopes at an angle downwardly
and in the flow direction of air through the second channel 9, i.e.
toward the left in FIG. 3, while also tapering to a reduced
cross-sectional area at the air mixing junction 10, at which the
first air outlet channel 7 is reunited into the second air outlet
channel 9. Thereby, the air injection flap 11 separates the reduced
cross-sectional area of the first air channel 7 from the reduced
cross-sectional area of the second air channel 9. The functioning
of the present embodiment of the cooling air arrangement
corresponds to the above described functioning of the first
embodiment of the inventive cooling air arrangement.
[0044] The inventive cooling air arrangement achieves an
advantageous combination and orientation of the air cycle machine 5
(for example referring to the orientation of the expansion turbine
outlet 21 providing the air conditioning air AC), the heat
exchanger 1, the air inlet 8, and the outlet plenum 4.
Particularly, the inventive arrangement allows the air inlet of the
cooling arrangement, the air outlet of the cooling arrangement, and
the air outlet of the air cycle machine to be oriented all
generally in the same direction, e.g. the flight forward direction
of the aircraft. This allows convenient and compact installation in
aircraft in which the prior art arrangements would not have been
suitable or would have required significant additional air ducting
or the like to redirect the air flow into a different direction.
These advantages of the invention are achieved without impairing
the aerodynamic characteristics, but rather achieving an improved
air flow with reduced air flow resistance in comparison to the
prior art. This is true for all of the different operating
conditions as described above. This is also achieved with a
relatively low total structural weight and compact structural size
of the arrangement installed in an aircraft.
[0045] Although the invention has been described with reference to
specific example embodiments, it will be appreciated that it is
intended to cover all modifications and equivalents within the
scope of the appended claims. It should also be understood that the
present disclosure includes all possible combinations of any
individual features recited in any of the appended claims.
Throughout this specification, the terms "downstream" and
"upstream" refer to the portions or locations of the components
with reference to the normal air flow direction through the
respective components.
* * * * *