Refrigeration – Air compressor – cooler and expander type
Reexamination Certificate
2001-03-27
2002-08-20
Doerrler, William C. (Department: 3744)
Refrigeration
Air compressor, cooler and expander type
C062S413000, C062S414000
Reexamination Certificate
active
06434968
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §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
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
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.
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.
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.
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.
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
′.
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.
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
′.
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
Buchholz Uwe Albert
Kelnhofer Juergen
Airbus Deutschland GmbH
Doerrler William C.
Fasse W. F.
Fasse W. G.
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