U.S. patent application number 11/192970 was filed with the patent office on 2007-05-24 for low energy electric air cycle with portal shroud cabin air compressor.
Invention is credited to Henry M. Claeys, Katherine Clarke, David G. Elpern.
Application Number | 20070113579 11/192970 |
Document ID | / |
Family ID | 38052141 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070113579 |
Kind Code |
A1 |
Claeys; Henry M. ; et
al. |
May 24, 2007 |
Low energy electric air cycle with portal shroud cabin air
compressor
Abstract
An environmental control system for an aircraft cabin includes a
plurality of electrically-driven ported shroud cabin air
compressors, each cabin air compressor compressing ram air received
from the aircraft exterior, a heat exchange circuit comprising a
primary heat exchanger receiving airflow from at least one of the
cabin air compressors, and the secondary heat exchanger supplying
airflow to the aircraft cabin, and an air cycle machine comprising
a compressor adapted to receive airflow from the primary heat
exchanger and supply compressed air to the secondary heat
exchanger. The environmental control system may further comprise an
air recirculation system, having an aft recirculation fan adapted
to receive a portion of recirculation air from the aircraft cabin,
and a recirculation heat exchanger, disposed in the heat exchange
circuit in series with the primary and secondary heat exchangers,
and adapted to receive airflow from the aft recirculation fan.
Inventors: |
Claeys; Henry M.; (Lomita,
CA) ; Clarke; Katherine; (Hermosa Beach, CA) ;
Elpern; David G.; (Los Angeles, CA) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Family ID: |
38052141 |
Appl. No.: |
11/192970 |
Filed: |
July 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60604610 |
Aug 25, 2004 |
|
|
|
Current U.S.
Class: |
62/401 ;
62/402 |
Current CPC
Class: |
B64D 2013/0644 20130101;
B64D 2013/064 20130101; Y02T 50/50 20130101; Y02T 50/40 20130101;
B64D 2013/0618 20130101; F25B 9/004 20130101; B64D 13/06 20130101;
B64D 13/02 20130101 |
Class at
Publication: |
062/401 ;
062/402 |
International
Class: |
F25D 9/00 20060101
F25D009/00 |
Claims
1. An environmental control system for an aircraft cabin,
comprising: a plurality of electrically-driven cabin air
compressors, each cabin air compressor compressing ram air received
from the aircraft exterior; a heat exchange circuit comprising a
primary heat exchanger and a secondary heat exchanger in series,
the primary heat exchanger adapted to receive airflow from at least
one of the cabin air compressors, and the secondary heat exchanger
adapted to supply airflow to the aircraft cabin; and an air cycle
machine comprising a compressor, adapted to receive airflow from
the primary heat exchanger and supply compressed air to the
secondary heat exchanger, wherein at least one of the cabin
compressors comprises: a housing having an air inlet, and an air
outlet in communication with the primary heat exchanger, the air
inlet defining an outer circular wall, an inner circular shroud
wall having at least one port extending therethrough, a central
channel, and an annular channel disposed concentrically around the
central channel and in communication with the central channel by
way of the at least one port extending through the inner circular
shroud wall, and a compressor wheel having a plurality of vanes,
the wheel being interposed between the inlet and the outlet, and
disposed in the central channel.
2. The environmental control system according to claim 1, wherein
the air cycle machine compressor further comprises: a shaft that is
rotatably coupled to the air cycle machine compressor; and a
turbine that is rotatably coupled to the shaft, the turbine being
adapted to receive airflow from the secondary heat exchanger and
supply airflow to the aircraft cabin.
3. The environmental control system according to claim 2, further
comprising: a reheater disposed upstream with respect to the
turbine and adapted to receive airflow from the secondary heat
exchanger; a condenser disposed upstream with respect to the
turbine, and adapted to receive reheated air from the reheater; and
a water extractor disposed upstream with respect to the turbine,
and adapted to receive condensed air from the condenser and to
supply airflow to the turbine.
4. The environmental control system according to claim 3, wherein
the reheater is further adapted to receive airflow from the water
extractor and to supply airflow to the turbine.
5. The environmental control system according to claim 3, wherein
the condenser is further adapted to receive airflow from the
turbine and to supply airflow to the aircraft cabin.
6. The environmental control system according to claim 1, further
comprising: an air recirculation system, comprising: a forward
recirculation fan adapted to supply a portion of recirculation air
from the aircraft cabin to the airflow supplied from the secondary
heat exchanger to the aircraft cabin.
7. The environmental control system according to claim 1, further
comprising: an air recirculation system, comprising: an aft
recirculation fan adapted to receive a portion of recirculation air
from the aircraft cabin; a recirculation heat exchanger, disposed
in the heat exchange circuit in series with the primary and
secondary heat exchangers, and adapted to receive airflow from the
aft recirculation fan.
8. The environmental control system according to claim 7, wherein
the recirculation heat exchanger is further adapted to supply
airflow from the aft recirculation fan to the to the airflow
supplied from the secondary heat exchanger to the aircraft
cabin.
9. The environmental control system according to claim 1, wherein
the heat exchange circuit has ambient ram air passing therethrough,
which cools air in at least the primary and secondary heat
exchangers.
10. The environmental control system according to claim 1, wherein
the heat exchange circuit receives external air drawn during
aircraft flight.
11. The environmental control system according to claim 1, wherein
the heat exchange circuit is driven by an electric fan disposed
downstream from the primary and secondary heat exchangers.
12. The environmental control system according to claim 1,
comprising two pairs of the cabin air compressors, and a pair of
the air cycle machines, each pair of cabin air compressors
providing airflow to one air cycle machine.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/604,610 filed Aug. 25, 2004.
TECHNICAL FIELD
[0002] The present invention relates to environmental control
systems for various aircrafts. More particularly, the present
invention relates to electrically-driven air cycle systems that
regulate the temperature of at least the aircraft fuselage.
BACKGROUND
[0003] Passenger aircrafts are typically equipped with an
environmental control system, including an air cycle conditioning
system for cooling the aircrew cabins, and other aircraft locations
and components. One class of air cycle conditioning systems that
are widely used in aircraft to provide cooled air takes advantage
of a supply of pressurized air that is bled from an aircraft
engine, known as bleed air. Other electrically-driven environmental
control systems generally operate by receiving fresh ram air from
inlets that are located in at least one favorable position near the
aircraft's forward belly fairing leading edge. The fresh ram air is
supplied to at least one electric motor-driven air compressor that
raises the air pressure to, for example, the desired air pressure
for the aircrew cabins. From the at least one air compressor, the
air is supplied to an ozone converter. Because air compression
creates heat, the air is then supplied to an air conditioning pack
in which the air is cooled and then transported to the aircraft
fuselage. At least one recirculation system is also provided to
recycle air from the fuselage back to the at least one air
compressor. The recirculation system may be used at both high and
low altitudes, but is particularly useful when the aircraft is
flying at high altitudes where the pressure for the ram air is
relatively low.
[0004] The numerous applications and components in a typical
environmental control system, including the ram air cycle, the
recirculation cycle, heat exchangers, condensers, reheaters, water
extractors, and an air cycle machine, can require large amounts of
energy to operate. Further, the large number of components in a
typical environmental control system tends to be heavy and complex.
Hence, there is a continuing need for simplification of
environmental control systems for various aircrafts, including a
reduction in the number of components, programming, and circuitry.
There is also a need for environmental control systems that can be
operated with minimized power consumption and weight.
BRIEF SUMMARY
[0005] The present invention provides an environmental control
system for an aircraft cabin. The environmental control system
comprises a plurality of electrically-driven cabin air compressors,
each cabin air compressor compressing ram air received from the
aircraft exterior; a heat exchange circuit comprising a primary
heat exchanger and a secondary heat exchanger in series, the
primary heat exchanger adapted to receive airflow from at least one
of the cabin air compressors, and the secondary heat exchanger
adapted to supply airflow to the aircraft cabin; and an air cycle
machine comprising a compressor, adapted to receive airflow from
the primary heat exchanger and supply compressed air to the
secondary heat exchanger. At least one of the cabin air compressors
comprises a housing having an air inlet, and an air outlet in
communication with the primary heat exchanger, the air inlet
defining an outer circular wall, an inner circular shroud wall
having at least one port extending therethrough, a central channel,
and an annular channel disposed concentrically around the central
channel and in communication with the central channel by way of the
at least one port extending through the inner circular shroud wall.
The air cycle machine compressor further comprises a compressor
wheel having a plurality of vanes, the wheel being interposed
between the inlet and the outlet, and disposed in the central
channel.
[0006] According to one embodiment, the environmental control
system further comprises an air recirculation system, having an aft
recirculation fan adapted to receive a portion of recirculation air
from the aircraft cabin, and a recirculation heat exchanger,
disposed in the heat exchange circuit in series with the primary
and secondary heat exchangers, and adapted to receive airflow from
the aft recirculation fan.
[0007] Other independent features and advantages of the preferred
environmental control system will become apparent from the
following detailed description, taken in conjunction with the
accompanying drawings which illustrate, by way of example, the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a flow chart illustrating the top-level
architecture of an environmental control system for an aircraft in
which the present invention may be incorporated;
[0009] FIG. 2 is a flow chart illustrating an air cycle pack for an
aircraft according to an embodiment of the present invention;
[0010] FIG. 3 is a graph illustrating operational relationships
between corrected compressor flow and a compressor pressure ratio
in prior art air cycle systems and vapor cycle systems for an
aircraft; and
[0011] FIG. 4 is a cross sectional elevation view of a ported
shroud air compressor that is incorporated in the air cycle pack of
FIG. 2 according to an embodiment of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0012] The following detailed description of the invention is
merely exemplary in nature and is not intended to limit the
invention or the application and uses of the invention.
Furthermore, there is no intention to be bound by any theory
presented in the preceding background of the invention or the
following detailed description of the invention.
[0013] Turning now to the figures, FIG. 1 is a flow chart
illustrating the top-level architecture of an exemplary
environmental control system 100 for an aircrew cabin or other area
in an aircraft fuselage 30. The illustrated system 100 includes
four electrically-driven cabin air compressors 10a-10d, each
receiving fresh ram air from inlets that are located in at least
one favorable position near the aircraft's forward belly fairing
leading edge. Although there are four compressors 10a-10d in the
illustrated embodiment, a system that incorporates fewer
compressors may still be used without departing from the scope of
the present invention. However, the four-compressor configuration
has inherent advantages of maintaining symmetrical loading of the
left and right-side electric power buses, and providing redundancy
in the case of minor environmental control system failures.
[0014] The air compressors 10a-10d raise the ram air pressure to a
level that is slightly above the desired aircraft cabin pressure.
The compressed air then passes through check valves 12a-12d, and
through one of two ozone converters 14a, 14b. If air conditioning
is not necessary, bypass valves 15a, 15b are opened and the
compressed air is supplied directly to the aircraft fuselage 30
from the ozone converters 14a , 14b . Since some air temperature
control is typically required, the air is normally supplied to one
of two air conditioning packs 20a , 20b , which then transfer the
air to an air distribution system 26 that delivers the air about
the aircraft fuselage 30.
[0015] The air conditioning packs 20a, 20b may receive about 50%
fresh air from the cabin air compressors 10a-10d, and about 50%
recirculation air from the aircraft fuselage 30, although these
percentages vary according to a range of factors including the
aircraft velocity and altitude. Air that is recirculated to the air
conditioning packs 20a, 20b from the aircraft fuselage 30 passes
through valves 22a, 22b and regulators 24a, 24b. The environmental
control system 100 thus uses a relatively cool air supply compared
to the conventional system in which a supply of hot pressurized air
is bled from an aircraft engine, known as bleed air. In fact, the
environmental control system 100 of the present invention entirely
eliminates the conventional engine air bleed system.
[0016] Turning now to FIG. 2, details pertaining to an air
conditioning pack 20 are illustrated, it being understood that the
illustrated air conditioning pack 20 may represent either of the
air conditioning packs 20a, 20b depicted in FIG. 1. The air
conditioning pack includes the components to the right of the ozone
converter 14a, and to the left of the vertical discontinuous line
58 in FIG. 2, the components and flow paths to the right of the
discontinuous line 58 being directed into or disposed inside the
aircraft fuselage.
[0017] As previously mentioned, the air conditioning pack 20
receives two air sources, namely, fresh ram air and recirculation
air. First, fresh ram air is supplied to the air conditioning pack
20 from the compressors 10a, 10b powered by motors 11a, 11b. The
ozone converter 14a removes all or most of the ozone from the
compressed ram air, specifically at high altitudes where ozone is
included in the air at relatively high concentrations.
[0018] The compressed ram air passes through a primary heat
exchanger 32 that is disposed in a ram air heat exchanger circuit
56. The ram air heat exchanger circuit 56 has ambient ram air
passing therethrough, which cools compressed air in the primary
heat exchanger 32, a secondary heat exchanger 34, and an air
recirculation heat exchanger 36 that are located in the circuit 56.
The ram air heat exchanger circuit 56 receives air drawn through a
ram scoop during aircraft flight, and is driven by an electric fan
54 when the aircraft is stationary. In the preferred embodiment
illustrated in FIG. 2, the electric fan 54 is disposed downstream
of the heat exchangers 32, 34, 36 so the heat from the fan 54 is
directed overboard rather than into the heat exchangers 32, 34, 36.
A portion of the air entering the ram air heat exchanger circuit 56
is diverted upstream of the primary heat exchanger for use as trim
air by the cabin temperature control system. Because the ambient
ram air in the circuit 56 is cooler than the air passing through
the heat exchangers 32, 34, 36, the ambient ram air serves as a
heat sink before the air is expelled using the electric fan 54.
[0019] After the compressed ram air passes through the primary heat
exchanger 32, the air is supplied to a bootstrap air cycle machine,
referring specifically to a compressor 40 and turbine 42 that
either share the same rotating axis or are otherwise powered and
rotated together. The compressor 40 further pressurizes and heats
the ram air. The compressed air is then supplied to the secondary
heat exchanger 34, causing the compressed air to cool. During
normal operation, an altitude valve 60 is closed, causing the air
to pass through a re-heater 44 and a condenser 46, and then through
a water extractor 48, which substantially dries the air. From the
water extractor 48, the air is again heated in the re-heater 44,
and then the hot and dry air is supplied to the turbine 42. The
turbine 42 forwards the air to the condenser 46, which cools the
air further and supplies the air to the aircrew cabins in the
aircraft fuselage 30. At high altitudes, the altitude valve 60, and
also a compressor bypass check valve 62, is opened, causing air
from the secondary and primary heat exchangers 34, 32,
respectively, to bypass the bootstrap air cycle machine and revert
to the ram air heat exchanger circuit 56 for cooling. This bypass
mode of operation minimizes the supply pressure to the air
conditioning pack 20 and reduces the required input power to the
cabin air compressors 10a-10d. At low elevations, a recirculation
heat exchanger bypass valve 64 is opened, allowing the
recirculation air from an aft recirculation fan 52 to bypass the
recirculation heat exchanger 36.
[0020] A forward recirculation fan 50 mixes some recirculation air
from the aircraft fuselage 30 into the fresh air supplied from the
air conditioning pack 20 before the fresh air reaches the aircrew
cabins. However, a majority of the recirculation air is transferred
back to the air conditioning pack 20 using the aft recirculation
fan 52, which supplies the recirculation air to the recirculation
heat exchanger 36 for cooling. The cooled recirculation air leaves
the recirculation heat exchanger 36 and is then mixed with the
fresh air being supplied to the aircraft fuselage 30. Thus, the air
conditioning pack 20 delivers a dry, subfreezing supply of air to
the air distribution system 26 with a significant portion of the
ventilation air entering the aircrew cabins being recirculation
air.
[0021] In the embodiment illustrated in FIG. 2, the recirculation
heat exchanger 36 is located with the primary and secondary heat
exchangers 32, 34 in the ram air heat exchanger circuit 56.
Additional heat exchangers may also be located in a series
arrangement with the primary, secondary, and recirculation heat
exchangers 32, 34, 36. For example, motor cooling heat exchangers
for the cabin air compressor motors may be located in the ram air
heat exchanger circuit 56. Also, a power electronics chiller, which
is a liquid-to-air heat exchanger, can be located in the ram air
heat exchanger. In an alternate embodiment, the motor cooling heat
exchangers and the power electronics chiller are disposed in series
in a separate, parallel ram circuit that is powered by a separate
electric fan.
[0022] In a preferred environmental control system 100, the
compressors 10a-10d are ported shroud compressors. One example of a
suitable ported shroud compressor is illustrated in FIG. 4,
although various other designs may also be incorporated. The
compressor 10 includes a housing 162 with an outer wall 164
defining an inlet 166. The inlet 166 includes an outer portion 167
and an inner portion 168. The compressor housing 162 also defines
an outlet 186. Within the outer wall 164 is a shroud 170 that is
defined by an inner compressor wall 172 having an inner surface 174
and an outer surface 176. In one embodiment, the outer wall 164
defined by the housing 162 is circular, and the shroud is defined
by the circular inner compressor wall 172 concentric to the outer
wall 164.
[0023] A compressor wheel 180 is rotatably mounted within the
shroud 170. In one embodiment, the compressor wheel 180 includes a
plurality of vanes or blades 182. The compressor wheel 180 is
located so the shroud inner surface 174 is adjacent to the
compressor wheel blades 182. The wheel 180 is coupled to a shaft
184. As the compressor wheel turns, air is drawn into the
compressor 10 through the inlet 166, through the blades or vanes
182 of the compressor wheel 180, and then forced out through the
outlet 186.
[0024] The shroud inner wall 172 defines a central channel 188. An
annular channel 190 is defined between the outer surface 176 of the
shroud inner wall 172 and an inner surface of the housing wall 164.
The central channel 188 and the annular channel 190 form the inlet
inner portion 168. At least one port 192 extends through the shroud
inner wall 172, allowing communication between the annular channel
190 and the compressor wheel blades or vanes 182. In one
embodiment, the at least one port 192 comprises a series of
apertures through the shroud inner wall 172. However, slots or
other methods of allowing flow through the shroud inner wall 172
may also be incorporated.
[0025] Ram air enters the ported shroud compressor 10 through the
inlet outer portion 167. The air then passes through the central
channel 188, into the compressor wheel 180, and is forced to the
outlet 186. A surge condition may exist at low altitudes, in which
the volume of air entering the compressor exceeds the compressor
requirements. In order to avoid a surge condition, air also bleeds
from the compressor wheel 180 through the at least one port 192 and
flows through the annular channel 190 back to the inlet outer
portion 167 where the air re-enters the central channel 188. This
bypass action allows the compressor to reach an equilibrium
state.
[0026] A choke condition may exist at high elevations, in which the
compressor's requirements exceed the volume of air entering the
compressor. In order to avoid a choke condition, air enters the
compressor 10 through the inlet outer portion 167, where a portion
passes through the central channel 188 and into the compressor
wheel 180, and another portion bleeds through the annular channel
190 and directly into the compressor wheel blades or vanes 182
through the at least one port 192, with both portions then forced
to the outlet 186. This inward flow bypass action allows greater
airflow into the compressor wheel 180.
[0027] Referring to the graph of FIG. 3, the data represented by
line 80 denote an operation range in which conditions are optimal,
meaning that the compressor 10 is neither at risk of a choke
condition or a surge condition. The data represent a relationship
between a compressor pressure ratio, with values for such on the
Y-axis, and a corrected flow per compressor, with values for such
on the X-axis. If the compressor pressure ratio for a given flow
rate is to the left of line 80, there is a risk of a surge
condition since the air exceeds the requirements of the compressor
10. As seen by the data set for a conventional air conditioning
pack that includes electric compressors, the data set represented
by line 90, at a high altitude of 43 kft the conventional air
conditioning pack operates well within optimal range. However, for
low aircraft velocities at which the airflow per compressor
approaches 1 lb/s, there is a risk of a surge condition.
[0028] Some conventional ways to correct this condition include
turning off one or more of the compressors 10a-10d at low velocity
or when the aircraft is not moving, thereby increasing the airflow
per compressor and shifting the line 80 to the right. However,
automating a power shut-off requires additional programming and
circuitry, and can consequently be inefficient in terms of cost and
complexity. Other conventional ways to correct this condition
include installing a more complex variable diffuser compressor as
part of the bootstrap air cycle machine. However, a variable
diffuser compressor is costly as it requires its own actuation
mechanism, and includes a large number of moving components that
introduce the possibility for compressor leakage and increased
maintenance.
[0029] Utilizing the ported shroud air compressor 10 to receive the
ram air for the environmental control system 100 overcomes the
problems of operating with a risk of a surge or choke condition by
enabling operation within at least a 10% to 15% margin between line
80 and line 90 in FIG. 3 by effectively shifting the line 80 to the
left in the low pressure, low flow region.
[0030] Thus, the previously-described environmental control system
100 provides a low energy consumption cycle that minimizes the
expenditure of power and reduces the weight of the overall system.
While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt to a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *