Device for producing water on board of an airplane

A device for producing water on board an aircraft includes at least one high temperature fuel cell entirely or partially integrated into a combustion chamber arrangement of a gas turbine aircraft engine. The combination of at least one fuel cell and a gas turbine engine is adapted to operate exclusively with hydrogen and atmospheric oxygen, and is embodied in an aircraft propulsion engine and/or an auxiliary power unit used for producing compressed air for a cabin and a power supply of the aircraft. The at least one high temperature fuel cell is fed with pure hydrogen on an anode side and with air on a cathode side. The combustion chambers of the turbine engine are fed with an air-hydrogen mixture, whereby at least the hydrogen supply can be regulated or completely shut off.

FIELD OF THE INVENTION

The invention relates to an apparatus for producing water on board of an aircraft while using one or more fuel cells, wherein a partial or complete integration of a water production unit in the form of one or more high temperature fuel cells into an aircraft engine is provided in such a manner that the combustion chambers of the aircraft engine are replaced completely or partially by the high temperature fuel cells and thus either supplementing or completely replacing the process that takes place in the conventional type combustion chambers.

BACKGROUND INFORMATION

European Patent Publication EP 957,026 A2 discloses an energy supply unit on board of an aircraft for substituting a main propulsion plant, an auxiliary power unit, a ram air turbine or a nickel cadmium (NiCd) battery. A fuel cell serves for producing d.c. current whereby exhaust air of the aircraft air-conditioning plant or external air of the aircraft are used as air supply for the fuel cell. Water is recovered from the fuel cell exhaust air for the water supply of the aircraft. Subsequently the fuel cell exhaust air is discharged to the aircraft surroundings. This also applies to the hydrogen emanating from the fuel cell. A water production is performed by a condenser arranged in the aircraft outlet.

European Patent Publication EP 967,676 A1 describes a jet engine having fuel cells integrated into the combustion chambers, wherein the fuel cells are arranged on the combustion chambers, contrary to the teaching of the new main claim as seen from the enclosure, wherein the combustion chambers are partially or completely replaced by the high temperature fuel cell or cells. In the prior, known propulsion plant the process of the propulsion plant is merely used for the operation of the fuel cell.

SUMMARY OF THE INVENTION

Thus, it is the object of the invention to provide an apparatus of the type mentioned above in which a fuel cells gas turbine combination is provided for the exclusive operation with hydrogen and air oxygen, as a propulsion plant and/or as auxiliary power unit for the water and pressurized air supply of the cabin and for current generation.

This object has been achieved according to the invention in that the high temperature fuel cells are constructed as the type: solid oxide fuel cell (SOFC) or molten carbonate fuel cell (MCFC), or are of a type comparable in power and temperature level; that pure hydrogen is supplied to the anode side of said high temperature fuel cells, that air is supplied to the cathode side of the high temperature fuel cells, that a mixture of hydrogen and air is supplied to the combustion chambers, that at least the hydrogen supply is constructed for a closed loop control or can be shut off completely, and that a single stage or multistage turbine is connected downstream of the anode side of the high temperature fuel cell, said turbine converting the thermal energy of the anode exhaust gas into rotation energy.

Embodiments of the invention are described in the dependent claims2to24.

It is provided to thereby replace at least one, preferably however, several combustion chambers by one or more high temperature fuel cells. In distinction to the mentioned subject matter at least one or more combustion chambers are retained for combusting a hydrogen water mixture. The combustion chambers and the high temperature fuel cells are preferably arranged in alternating succession as a ring shape around the shaft or shafts of the gas turbine.

The combustion chambers serve for starting the gas turbine and the high temperature fuel cells and for temporarily increasing the air throughput of the gas turbine e.g. for the start of an aircraft. During continuous operation, exclusively the thermal energy of the high temperature fuel cell is used for generating the air throughput. The water generation takes place at the anode side i.e. at the hydrogen side of the high temperature fuel cell. This so called anode exhaust gas consists of 100% water steam (superheated steam) when the supplied hydrogen is completely transformed. This superheated steam is fed through a turbine where the steam is cooled by expansion whereby thermal energy is converted into rotation energy of the turbine shaft. This rotational energy is used in a compressor for generating the pre-pressure that is required at the hydrogen side for the high temperature fuel cell.

The water vapor is eventually condensed out in a further process stage to obtain pure H2O, that is, distilled water. This water is supplied to the different consumers or to a salination unit to produce drinking water. Gray water becoming available is collected in a collecting container in the same way as the water proportion discharged when dehydrating black water. The water quantities are evaporated in an evaporator operated by the heat available from the water condensation process and supplied together with the steam proportion from the anode exhaust gas of the high temperature fuel cell, not needed for water generation, to the second turbine stage of the gas turbine. On the air side a so-called fan sucks-in external air and/or cabin exhaust air. During normal operation this fan is driven by the second turbine stage, during starting by an electric motor. The air passing through the fan is first compressed by a compressor arranged downstream, and is then further compressed in a further compressor for the combustion chambers and for the air side of the high temperature fuel cell. The thermal energy introduced through the combustion chambers or the high temperature fuel cell first drives the first turbine stage and, following the above described introduction of gray water into the hot exhaust air flow, the second turbine stage. The number of the compressor and turbine stages, as well as the number of the combustion chambers and of the high temperature fuel cells can be varied as desired depending on the requirements with regard to different types.

The advantages of the apparatus according to the invention reside in the following:a) flexibility with regard to short duration power demands,b) high integration of the individual process steps,c) high purity of the generated water,d) high system efficiency ande) a weight reduction.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT OF THE INVENTION

The drawing illustrates an example embodiment according to the invention.

The single FIGURE shows a water generation system including a tank for liquid hydrogen.

Thus, a use in a so-called “cryoplane” is particularly advantageous. As can be seen in the drawing, a high temperature fuel cell7replaces partially a combustion chamber7A of an aircraft propulsion plant2. Pure hydrogen is supplied to the anode side and air is supplied to the cathode side of the high temperature fuel cell7, while a mixture of hydrogen and air is supplied to the combustion chamber7A, whereby at least the hydrogen supply is constructed to be controllable in closed loop fashion or to be completely shut-off. A single stage or multistage turbine16is connected downstream to the anode side of the high temperature fuel cell7. The turbine16converts the thermal energy of the anode exhaust gas35into rotation energy. Fuel cells of the type solid oxide fuel cell (SOFC) or molten carbonate fuel cell (MCFC) or of a type comparable with regard to power and temperature may be used.

A condensation process18is connected downstream of the high temperature fuel cell7. The process18condenses water out of a portion of the anode exhaust gas35of the fuel cell7. Further, the high temperature fuel cell7may be pressurized on both sides, on the one hand, on the air or oxygen side and on the fuel or hydrogen side, on the other hand, whereby equal or even unequal pressures are permissible on the anode side and on the cathode side. Using liquid or gaseous hydrogen is possible. Liquid hydrogen1can be evaporated prior to entering the high temperature fuel cell7or the combustion chamber7A, whereby the evaporator17may be operated with the process heat of the anode exhaust gas condenser18. A special embodiment of the apparatus according to the invention is characterized in that the evaporator17is arranged in a ring shape around the condenser18or circularly inside the condenser18whereby the evaporator is constructed as a pipe bundle heat exchanger. In this case also at least a portion of the condensation process18can be operated with cooling air19.

It is possible to collect used water as well as not needed condensate in a container32. The air20that was heated in the condensation process18is advantageously used for evaporating the gray water in a separate container33into which the gray water is fed by a pump45, whereby a filter is provided for retaining solid and suspended materials. Water having a distilled quality is taken from the condensation process18via a drinking water tank22, and is distributed in such a manner that galleys23, hand wash basins24and the showers25receive drinking water that has been generated by adding a dose of salt in a salination unit43, while toilets27and the air humidification26are supplied with distilled water. The turbine stages8,9can drive the compressor stages5,6as well as the fan11, whereby the compressor stages5,6pressurize the air side of the high temperature fuel cell7and of the combustion chamber7A. The air throughput3of the fan11can be used either for propulsion in an engine or in an APU for pressurizing the compressed air systems and/or of the air conditioning. For this purpose respectively one fan11is coupled with a first compressor stage5and a second turbine stage9, and a second compressor stage6and a first turbine stage8, that that run on coaxial shafts one within the other and at different revolutions per minute. The number of coaxial shafts running one within the other is constructed as desired.

The waste water is collected in a collection tank28, which has a separator/blower29connected to an outlet thereof, and the waste water is then completely or partially dehydrated in a dehydration unit30connected to an outlet of the tank28through a pump44. The water proportion thus gained is fed to the gray water collection tank32from which it is pumped by a pump45to the gray water evaporator33. Waste water is discharged at31from the tank28. It is of special advantage:that the apparatus can also be operated without dispensing water to a water system,that the combustion chambers and the high temperature fuel cells can be operated separately and in any desired combination with one another; andthat in a separate operation of combustion chambers or high temperature fuel cells7individual combustion chambers or high temperature fuel cells can be switched off.

Further as shown in the single drawing figure, the inventive apparatus may additionally have the following features. The high temperature fuel cell7can provide a direct current output4. An output of the gray water evaporator33can provide a gray water injection10into the low pressure turbine stage9. Air21can also be output from the gray water evaporator33. The turbine16can drive a hydrogen compressor13that provides a flow of compressed hydrogen15to the fuel cell7, and can be coupled via a belt drive37with a starter12that is coupled to the fan11for starting the propulsion plant2. Hydrogen14can be provided to the hydrogen compressor13from the hydrogen evaporator17. Water steam34from the turbine16can be fed to the condenser18and the gray water evaporator33. Exhaust air or steam36can be emitted from the low pressure turbine stage9.