Refrigeration – Air compressor – cooler and expander type – Motor-type expander
Reexamination Certificate
2002-07-02
2003-12-02
Bennett, Henry (Department: 3744)
Refrigeration
Air compressor, cooler and expander type
Motor-type expander
C062S087000
Reexamination Certificate
active
06655168
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an air conditioner that controls the internal temperature, oxygen partial pressure and pressure of aircraft, including fixed-wing aircraft and rotating-wing aircraft and that supplies air of reduced oxygen concentration to the fuel system.
DESCRIPTION OF THE RELATED ART
As air conditioners in aircraft, conventionally air cycle cooling devices are chiefly employed in which temperature-adjusted and pressure-adjusted cooled air is obtained by using a radial compressor to perform adiabatic compression of extracted air compressed in a compression section of an engine after subjecting the air to heat exchanging with external air for cooling, and by using an expansion turbine to perform adiabatic expansion of the air after subjecting the adiabatic compressed air to heat exchanging with external air for cooling.
Some military aircraft are provided with an OBIGGS (on board inert gas generation system) whereby nitrogen gas or air of elevated nitrogen concentration is injected into the fuel tank in order to prevent explosion in the event of the fuel tank being hit during a mission. Also, accident investigations of civil aircraft in recent years have revealed occurrences of fire when sparks generated from on-board wiring etc have ignited a mixture of air and fuel vapor accumulated in the space within fuel tanks. In order to prevent such fires, adoption of the above OBIGGS in civil aircraft is being studied.
This OBIGGS comprises an air separation section having a function of separating air constituents. In one type of air separation section, a selectively permeable membrane is employed whose permeability for nitrogen is higher than its permeability for oxygen. Nitrogen-enriched gas is generated by introducing air extracted from the engine to this selectively permeable membrane.
In the conventional aircraft air conditioner shown in
FIG. 14
, air extracted from engine
101
is cooled by a heat exchanger called a pre-cooler
102
before being practically adiabatically compressed by a radial compressor
103
; the air which has thereby been raised in temperature is cooled by a heat exchanger called a main cooler
104
and practically adiabatically expanded by expansion turbine
105
. Cooled air is thereby obtained. In this pre-cooler
102
and main cooler
104
, cooling is performed by external air passing through ram air flow path
109
. The expansion work of this expansion turbine
105
is utilized as compressive power by being transmitted to compressor
103
through shaft
106
. It should be noted that when the aircraft is on the ground or in low-level flight, the external air temperature is high and the moisture content of the air is high, so when expansion takes place in expansion turbine
105
, moisture in the air condenses and a mist of water droplets is formed. A water separator
107
is therefore arranged downstream of expansion turbine
105
to capture the moisture. Cabin cooling is performed by supplying the cooled air that has passed through this water separator
107
to the interior of cabin
108
, including the cockpit space of the aircraft. If the engine is stopped while the aircraft is on the ground, it is arranged to be possible to supply extracted air from a high-pressure air supply unit such as an auxiliary engine called an auxiliary power unit, instead of engine
101
, to the air conditioner.
In order to perform cabin heating at high altitude etc, a bypass air flow path
111
is provided to feed air extracted from engine
101
into cabin
108
; this bypass air flow path
111
is opened/closed by means of a hot-air modulating valve
112
. Some of the extracted air is fed to a mixing duct
113
arranged downstream of water separator
107
instead of being cooled by the air cycle cooling device constituted by compressor
103
and expansion turbine
105
, by opening this hot-air modulating valve
112
. In this mixing duct
113
, extracted air cooled by the air cycle cooling device and extracted air that has not been cooled are mixed. Air of a suitable temperature is thus obtained by adjusting the degree of opening of hot-air modulating valve
112
. Cabin heating can be performed by supplying this air of suitable temperature into cabin
108
. When cruising at high altitude, the ram air flow path
109
is throttled, so the air extracted from engine
101
is kept in a moderately high temperature since it is not excessively cooled in pre-cooler
102
or main cooler
104
. The air within this cabin
108
is discharged directly into the space
114
outside the fuselage through pressure reducing valve
110
in an amount corresponding to the difference obtained by subtracting the amount of leakage from the fuselage from the amount supplied by the air conditioner.
The conventional OBIGGS is provided with an air separation section
116
independent of the air cycle cooling device constituted by the compressor
103
and the expansion turbine
105
. Specifically, a branch air flow path
111
a
is provided so that the extracted air passing through the pre-cooler
102
is branched before being fed into the air cycle cooling device, and an air separating section
116
is provided in this branch air flow path
111
a
. This air separating section
116
is constituted by covering a selectively permeable membrane
116
a
comprising a large number of hollow fibers with a housing
116
b
. The permeability for nitrogen (N
2
) and carbon dioxide (CO
2
) in the air of this selectively permeable membrane
116
a
is made higher than its permeability for oxygen (O
2
). The extracted air of engine
101
is separated into nitrogen-enriched gas passing through this selectively permeable membrane
116
a
and the remainder, oxygen-concentrated air. The nitrogen separating ability of this selectively permeable membrane
116
a
varies in accordance with the extracted air pressure. The nitrogen-enriched gas is supplied into a fuel peripheral region
115
such as the interior of the fuel tank or fuel pipe setting region, and the remainder of the gas that is supplied to the region
115
more than needed is discharged to the space
114
outside the fuselage through a discharge flow path. The oxygen-concentrated air that has not permeated through the selectively permeable membrane
116
a
is discharged into the space
114
outside the fuselage from a pressure reducing valve
110
a.
The conventional air separating section
116
is provided independently of the air cycle cooling device constituting the air conditioner. The air of raised oxygen concentration obtained by separating the nitrogen by means of the air separating section
116
is therefore wasted without being effectively utilized. Furthermore, if both the air cycle cooling device and air separating section
116
are employed in parallel, the engine load is increased due to increase in the amount of air extracted from the engine.
Since the engine output is throttled during the descent of the aircraft, the pressure of extracted air from the engine is lowered. When this extracted air pressure drops, the nitrogen separating ability of the selectively permeable membrane
116
a
drops. Furthermore, fuel is consumed and the empty volume within the fuel tank becomes large when the aircraft descends after cruising, in which a large amount of nitrogen enriched gas becomes necessary. As a result, supply of the nitrogen-enriched gas required becomes insufficient.
Furthermore, the air supplied into the cabin
108
by the conventional air conditioner is discharged to outside the fuselage. That is, since the internal pressure of the cabin
108
is higher than the pressure outside the fuselage at high altitudes, the air having this pressure difference is wasted without being effectively utilized.
An object of the present invention is to provide an aircraft air conditioner capable of solving these problems.
SUMMARY OF THE INVENTION
An aircraft air conditioner according to the present invention wherein air extracted from an engine is cooled by a cooling device and fed into the cabin of the aircraft, comprising: an ai
Mitani Hisashi
Saito Hidefumi
Armstrong Westerman & Hattori, LLP.
Bennett Henry
Drake Malik N.
Shimadzu Corporation
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