AIR HUMIDIFICATION DEVICE, METHOD FOR OPERATING AN AIR HUMIDIFICATION DEVICE AND SYSTEM COMPRISING AT LEAST ONE AIR HUMIDIFICATION DEVICE

Description

[0001] The present invention relates to an air humidification device according to the features of the preamble of claim 1, a method for operating an air humidification device according to the features of the preamble of claim 6 and a system according to the features of the preamble of claim 7.

[0002] Some devices require air with a predetermined humidity level. Passive and active humidification systems are used to provide the air or an air stream with the required humidity. This is necessary, for example, for fuel cells with a polymer electrolyte membrane (PEM). Individual fuel cells can be arranged as segments in so-called fuel cell stacks. The individual fuel cell segments have their own polymer electrolyte membranes. To enable efficient operation of the fuel cells, the polymer electrolyte membranes must be humidified using cathode air in which water droplets have been evaporated. The evaporation in the stack contributes to cooling.On the other hand, it is necessary to prevent water accumulation in the fuel cell's flow field, the so-called flow profile, caused by the droplets in the cathode air. A side effect of humidification is that the evaporation of the moisture in the fuel cells cools the fuel cells. To both prevent water accumulation in the fuel cell and enable cooling of the fuel cells by the droplets, the droplets must not exceed a certain size. To provide such small droplets, dual-component atomizing nozzles are typically used in humidification devices.

[0003] However, for the aviation sector, particularly in the area of ​​primary propulsion, the known solutions and approaches for humidifying fuel cells are not feasible or have significant disadvantages. The passive humidifiers known from the automotive sector do not allow for targeted control of the relative humidity of the cathode air. In addition, they are too heavy and bulky for application in the aviation sector. They also do not contribute to cooling the fuel cell stack. To operate a dual-fluid atomizing nozzle, which is typically used to deliver fine droplets, compressed air must be provided at a pressure level significantly higher than the pressure level of the cathode air itself in order to enable atomization of the water required for humidification. The complexity is increased by the low ambient air pressure in the aviation sector.The ambient air to be humidified in the aviation sector is also significantly drier and larger volumes of air must be humidified.

[0004] Another application for air humidification devices in aviation is in aircraft turbines operated as so-called water-enhanced turbofans (WET). In this case, humidified air from a water recovery system is fed into a turbine's combustion chamber to, among other things, enable a more uniform temperature distribution during combustion in the combustion chamber. This makes it possible to reduce the formation of nitrogen oxides.

[0005] US 9385380 B2 discloses a method and system for humidification management in fuel cells. The method provides for supplying air to a cathode inlet stream of a fuel cell. It provides for detecting a fuel cell parameter related to the humidity of the cathode inlet stream. It provides for selectively operating the fuel cell either in an active humidification mode or in a deactive humidification mode based on the fuel cell parameter. In the active humidification mode, water is added to the cathode inlet stream. In the deactive humidification mode, water is not added to the cathode inlet stream.

[0006] US 5432020 A describes a device for providing conditioned process gas for the operation of air-breathing fuel cell systems. To operate the fuel cell systems, a process gas must be provided with a specified temperature and humidity. For this purpose, a metered amount of fine water droplets is sprayed into a gas supply line, thereby humidifying the process air.

[0007] CN 206163612 U discloses a humidification device for a proton exchange membrane of a fuel cell.

[0008] CN 111640968 A discloses a combination humidifier and humidification system for fuel cells. The invention comprises a membrane humidifier and a combination humidifier. The humidification system is configured to discharge a gas in a saturated state at an outlet of the humidification system.

[0009] US 6835477 B1 discloses a fuel cell stack of polymer membrane fuel cells in which the removal of heat generated by the generation of electrical energy and the humidification of the ion exchange membranes used as electrolytes are achieved by the direct injection of a water stream originating from a single hydraulic circuit.

[0010] US 20140048615 A1 discloses a two-component nozzle for atomizing liquids, comprising a nozzle housing. The nozzle housing has at least one liquid inlet for a liquid to be atomized, a second liquid inlet for a gaseous liquid, a mixing chamber, a nozzle outlet opening, and an annular gap opening surrounding the nozzle outlet opening. Within the nozzle housing, a device for generating a liquid film to be atomized on a wall of the mixing chamber and inlet openings for injecting the gaseous liquid into the mixing chamber are provided.

[0011] US 8028934 B2 discloses a two-component atomizing nozzle designed to spray a liquid with the aid of a compressed gas. The two-component atomizing nozzle comprises a mixing chamber into which a liquid inlet and a compressed gas inlet extend. The two-component atomizing nozzle comprises an outlet located downstream of the mixing chamber. Additional annular gap atomization produces a significantly finer droplet spectrum with the same energy expenditure. Furthermore, the two-component atomizing nozzle is designed to reduce the average droplet size by twisting a core jet.

[0012] JP 4718811 B2 discloses a method for converting a liquid into fine particles and a nozzle used in the method. The method involves focusing a resulting jet stream onto a collision point to atomize droplets at the collision point. The atomized droplets are then sprayed in a circular pattern.

[0013] CN 110237953 B discloses an environmentally friendly atomizing device with a nozzle. The atomizing device is designed to mix and collide a three-phase mixed liquid several times, allowing the liquid to be sprayed to be atomized more evenly and to have finer and smaller droplet sizes.

[0014] It is an object of the invention to provide an air humidification device which enables a safe and improved humidification of an air flow with fine liquid droplets, in particular in the area of ​​primary drives in aeronautical technology.

[0015] The object is achieved according to the invention by an air humidification device according to the features of claim 1, a method for operating an air humidification device according to the features of claim 6, and a system according to the features of claim 7. Advantageous embodiments with expedient further developments of the invention are specified in the respective subclaims, wherein advantageous embodiments of each aspect of the invention are to be regarded as advantageous embodiments of the respective other aspects of the invention.

[0016] A first aspect of the invention relates to an air humidification device having a mixing chamber in which an atomizing nozzle is arranged, which is configured to dispense a liquid as a spray. In other words, the air humidification device has the mixing chamber, which has an atomizing nozzle for atomizing the liquid. The mixing chamber can be provided to provide a volume for mixing a gas with a liquid. To enable mixing of the gas with the liquid, it is provided that the atomizing nozzle atomizes the liquid so that the liquid is dispensed as droplets that form a spray. The atomizing nozzle is a single-substance atomizing nozzle. The mixing chamber is configured to mix the gas, which is guided through the mixing chamber along a main flow path, with the spray and to discharge it at an outlet opening of the mixing chamber.In other words, the mixing chamber is designed to direct the gas to be mixed along the main flow path and, after mixing the gas with the liquid, discharge it at the outlet opening of the mixing chamber. Within the mixing chamber, the gas being passed through mixes with the spray mist, so that the gas discharged at the outlet opening is mixed with the liquid.

[0017] For certain applications, it may be necessary for the mixed gas to contain only fine droplets. In other words, it may be necessary that the droplets contained in the discharged gas do not exceed a certain size. Droplets emitted by atomizing nozzles can differ in size, so that the spray mist can contain finer and coarser droplets. It may therefore be necessary to separate the coarser droplets so that only the finer droplets are emitted. To achieve this, the atomizing nozzle is provided with a swirl device designed to impart a swirl to droplets of the spray mist in order to emit the spray mist as a straight circular spray cone opening along the main flow path with a cone angle. In other words, the atomizing nozzle has the swirl device.The swirl device is designed to discharge the spray mist in such a way that the droplets of the spray mist are imparted with angular momentum. This can be achieved, for example, by discharging the droplets in a spiral pattern. Due to the imparted angular momentum and the movement of the droplets along the main flow path of the gas, the individual droplets move from the atomizing nozzle along opening spiral paths. The application of swirl to the droplets results in the individual droplets being deflected outward to varying degrees depending on their size. Due to the spiral paths of the individual droplets, the spray mist consisting of the droplets takes the form of an opening, straight spray cone.The spray cone has a cone angle, with larger droplets moving in an outer region of the spray cone and smaller droplets moving in an inner region. By creating the described spray cone, the size spectrum of the droplets is distributed from the inside outward with increasing size. This can provide a basis for separating the droplets based on their size.

[0018] To carry out the separation, it is provided that the mixing chamber has a separation device designed to capture droplets of the spray cone that move from the atomizing nozzle along a hollow cone having a predetermined internal angle. In other words, it is provided that the separation device is designed to capture the droplets located in the outer region of the spray cone. Consequently, larger droplets are separated by the separation device. Due to the described size distribution, the larger droplets move along the hollow cone emanating from the atomizing nozzle. The hollow cone has the predetermined internal angle that separates the droplets to be separated from the droplets to be forwarded.The separation device is designed to collect the captured droplets and discharge the liquid recovered through the collection of the droplets at a separation outlet of the separation device. Droplets moving within the hollow cone are guided by the separation device to the outlet opening of the mixing chamber. The use of the separation device results in the advantage that the gas discharged from the outlet opening of the mixing chamber contains only the finer droplets because the larger droplets have been filtered out. The advantage of the invention lies in the fact that air can be humidified with fine droplets without having to use a dual-fluid nozzle.The disadvantage of using the single-component nozzle, that there is no additional, variable control parameter and therefore it may be necessary to accept that larger droplets are released into the gas, is compensated for by the fact that the larger droplets are filtered out of the gas by the separation device.

[0019] The invention also includes optional developments which result in further advantages.

[0020] A further development of the invention provides that the separation device has a coaxial tube. In other words, the separation device comprises the coaxial tube, which has an outer tube which has an inner tube inside it. The outer tube of the coaxial tube is provided to collect the larger droplets which move along the hollow cone. The inner tube is provided to guide the finer droplets which move within the hollow cone to the outlet opening of the mixing chamber. The coaxial tube can be arranged centered opposite the atomizing nozzle so that the spray circular cone is aligned along the main flow path towards the coaxial tube. A base surface of a cone which has the inner angle can coincide with an opening of the inner tube.The finer droplets are thus guided from the atomizing nozzle along the main flow path into the inner tube, through which they are directed to the outlet opening. An annular base surface of the hollow circular cone can coincide with an inlet surface of the outer tube, so that the coarser droplets are guided into the outer tube. This prevents these droplets from being directed to the outlet opening.

[0021] A further development of the invention provides that the separation device has a separation opening circumferentially enclosed by a diaphragm, wherein the diaphragm is designed to collect the droplets moving along the hollow cone. The separation opening is designed to guide the droplets moving within the hollow cone to the outlet opening of the mixing chamber. In other words, the separation device has the separation opening, which can be, for example, a round opening that can be enclosed on the outside by a diaphragm. The diaphragm can be an annular surface that is intended to collect the droplets of the hollow cone. The separation opening can be an inlet of a pipe that can be connected to the outlet opening of the mixing chamber. The main flow path through the mixing chamber can run through the separation opening.

[0022] A further development of the invention provides that the air humidification device has a recovery device configured to feed the recovered liquid from the separation device to the atomizing nozzle. In other words, the liquid collected by the droplets in the separation device is fed to the atomizing nozzle by the recovery device so that the liquid can be discharged again through the atomizing nozzle. This results in the advantage that the liquid consumption by the air humidification device can be reduced, thereby reducing the amount of liquid to be provided by a liquid reservoir. The recovery device can, for example, have a membrane or a condenser for collecting the liquid.

[0023] A further development of the invention provides that the air humidification device has a control device configured to adjust the amount of liquid to be discharged through the atomizing nozzle in order to regulate a predetermined mixing ratio between the gas and the liquid at the outlet opening of the mixing chamber. In other words, the air humidification device is configured to regulate a predetermined mixing ratio between the gas and the liquid at the outlet opening of the mixing chamber. For this purpose, the air humidification device has the control device, which selects the amount of liquid discharged through the atomizing nozzle in a certain time window such that the mixture discharged at the outlet opening of the mixing chamber has the predetermined mixing ratio.In order to provide a mixing ratio of the introduced and discharged gas to the control device, sensor data can be received by sensors of an installation location in which the air humidification device is arranged.

[0024] A second aspect of the invention relates to a method for operating an air humidification device having a mixing chamber in which an atomizing nozzle is arranged. Gas is passed through the mixing chamber along a main flow path. A liquid is discharged as a spray through the atomizing nozzle. The gas in the mixing chamber is mixed with the spray and discharged through an outlet opening of the mixing chamber. It is provided that droplets of the spray are subjected to a swirl by a swirl device of the atomizing nozzle. Due to the swirl of the droplets, the spray is discharged through the atomizing nozzle as a straight circular spray cone opening along the main flow path with a cone angle.Droplets of the circular spray cone, which move from the atomizing nozzle along a hollow cone with a predetermined internal angle, are collected by a separating device in the mixing chamber. Liquid recovered by collecting the droplets is discharged by the separating device at a separation outlet of the separating device. Droplets moving within the hollow cone are guided by the separating device to the outlet opening of the mixing chamber. Further features and their advantages can be found in the descriptions of the first aspect of the invention.

[0025] A third aspect of the invention relates to a system comprising air humidification devices and a fuel cell stack. The fuel cell stack comprises a plurality of fuel cells as segments. The system comprises a cathode air supply device configured to introduce cathode air, which is to be mixed with water, into the air humidification devices. The air humidification devices are connected to a respective one of the fuel cells at their respective outlet openings, in particular outlet openings of a respective mixing chamber of the air humidification devices. In other words, each of the fuel cell stack segments is assigned its own air humidification device. The mixtures output by the air humidification devices are thus each supplied to only one of the fuel cell segments.This has the advantage of allowing individual control of the humidification devices in order to individually regulate the air humidity in the fuel cells.

[0026] A further development of the invention provides that the system is configured as an aviation primary propulsion system. In other words, the system is intended for powering an aircraft.

[0027] Further features and their advantages can be found in the descriptions of the first and second aspects of the invention.

[0028] Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments are to be regarded as encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced by separate combinations of features from the explained embodiments. Embodiments and combinations of features are also to be regarded as disclosed that therefore do not have all the features of an originally formulated independent claim.Furthermore, embodiments and combinations of features are to be considered disclosed, in particular by the embodiments presented above, which go beyond or deviate from the combinations of features presented in the claims. This shows: . Fig. 1 a schematic representation of an air humidification device according to the invention; Fig. 2 a schematic representation of a possible embodiment of the system according to the invention, which has several of the air humidification devices; and Fig. 3 another schematic representation of the Fig. 2 shown system.

[0029] FIG. 1 a schematic representation of an air humidification device 1 according to the invention, which is arranged in a system 2. The air humidification device 1 can be provided to mix a liquid 25 with a gas 26. The liquid 25 can be water, for example, which is provided to be mixed with air in order to ensure a predetermined air humidity of the gas 26. The air humidification device 1 can be integrated into the system 2 via an inlet pipe 3 and an outlet pipe 4. The air humidification device 1 can have a mixing chamber 5, which can be configured to enable mixing of the liquid 25 with the gas 26. The mixing chamber 5 can have an inlet opening 6, to which the inlet pipe 3 can be connected. The mixing chamber 5 can have an outlet opening 7, to which the outlet pipe 4 of the system 2 can be connected.The gas 26 to be mixed can be provided through the inlet pipe 3, which can be introduced into the mixing chamber 5 through the inlet opening 6 and discharged at the outlet opening 7 of the mixing chamber 5, wherein the gas 26 can be guided along a main flow path 8. The main flow path 8 can, for example, be caused by providing an overpressure at the inlet pipe 3. To enable mixing of the introduced gas 26 in the mixing chamber 5, an atomizing nozzle 9 can be arranged in the mixing chamber 5. The atomizing nozzle 9 can be configured to emit a spray 10 which can comprise droplets 11 of the liquid 25 to be mixed. The liquid 25 can, for example, be supplied to the atomizing nozzle 9 via a supply line. The atomizing nozzle 9 is, in particular, a single-substance atomizing nozzle.The atomizing nozzle 9 can have a swirl device that can be configured to impart a swirl to the droplets 11 to be dispensed, so that the discharged spray 10 has the shape of a circular spray cone. The circular spray cone 12 can be created by the droplets 11 moving in a spiral direction due to an applied swirl and the gas 26 moving along the main flow path 8. Droplets 11 with a greater mass move along an edge of the circular spray cone 12, while droplets 11 with a lower mass can move closer to the center of the circular spray cone 12. The circular spray cone 12 can have a specific cone angle 13 depending on the speed of the gas 26 flowing through along the main flow path 8 and the applied swirl of the droplets 11. The atomizing nozzle 9 can be aligned along the main flow path 8 in the direction of the outlet opening 7.The outlet opening 7 can have a round shape with a predetermined radius. The cone angle 13 of the spray circle cone 12 can be such that only a portion of the droplets 11 are delivered to the outlet opening 7. Droplets 11 with a greater mass can be directed to an area outside the outlet opening 7. This results in the spray circle cone 12 being divided into an inner cone and a hollow cone 14, wherein the inner cone can have an inner angle 15. Droplets 11 moving within the inner cone are directed to the outlet opening 7, while droplets 11 moving along the hollow cone 14 are not directed to the outlet opening 7.In order to be able to collect the droplets 11 of the hollow cone 14, the air humidification device 1 can have a separation device 16, which can be configured to collect the droplets 11 of the hollow cone and to guide the inner droplets 11 to the outlet opening 7. For this purpose, the separation device 16 can have a separation opening 17 to collect the droplets 11 flowing within the inner angle 15. The separation device 16 can be configured, for example, as a coaxial tube, wherein an outer tube 18, which can be provided for receiving the outer droplets 11 of the hollow cone 14, can have an inner tube 19 inside it, which is intended to guide the droplets 11 moving within the inner angle 15 to the outlet opening 7.The separation device 16 can have a separation outlet 20, which can be configured to discharge the liquid 25 collected by the collected droplets 11 in the separation device 16. In an alternative embodiment of the air humidification device 1, the separation device 16 can have a diaphragm through which the outer droplets 11 can be collected. The diaphragm can be configured to circumferentially enclose the separation opening 17. The air humidification device 1 can have a recovery device 21, which can be configured to feed the recovered liquid 25 from the separation device 16 to the atomization nozzle 9. The recovery device 21 can, for example, have a condenser or a pump.By providing the recovery device 21, for example, the amount of liquid to be stored in a reservoir can be reduced. The air humidification device 1 can have a control device 22, which can be configured to determine the amount of liquid to be discharged through the atomizing nozzle 9 in order to regulate a predetermined mixing ratio between the gas 26 and the liquid 25 at the outlet opening 7 of the mixing chamber 5.The control device 22 can, for example, comprise a microprocessor or a microcontroller and be configured to detect the mixing ratio between the gas 26 and the liquid 25 and, depending on a predetermined mixing ratio between the gas 26 and the liquid 25, to control the atomizing nozzle 9 in order to adjust the amount of liquid to be dispensed through the atomizing nozzle 9 such that the predetermined mixing ratio between the gas 26 and the liquid 25 can be achieved.

[0030] FIG. 2 shows a schematic representation of a possible embodiment of the system 2, which has several of the air humidification devices 1. For operation of the system 2, it may be necessary for a predetermined mixing ratio between the liquid 25 and the gas 26 to be humidified. For example, it can be provided that the gas 26 to be humidified can be provided by a pump or a compressor. The gas 26 can be air, for example. The gas 26 can be provided at a predetermined pressure so that it can flow along the inlet pipe 3 and through the mixing chamber 5 of the air humidification device 1 along the main flow path 8.It can be provided that the gas 26 is passed through several of the air humidification devices 1, wherein the air humidification devices 1 can be provided to mix the gas 26 with the liquid 25 to a respective mixing ratio, wherein the mixing ratio to be regulated can differ between the individual air humidification devices 1.

[0031] FIG. 3 shows another schematic representation of system 2 from Fig. 2The system 2 can, for example, be provided to humidify air for operating a fuel cell stack 23, which can have multiple fuel cells 24. The gas 26 can, for example, be air, which can be fed into the fuel cells 24 as cathode air to humidify a separating membrane of a cathode. To enable operation of the individual fuel cells 24, it may be necessary to humidify the membranes of the fuel cells 24 with fine droplets 11. The membranes can, in particular, be polymer electrolyte membranes. To ensure uniform humidification of the membrane, it may be necessary for the droplets 11 supplied to the air by the air humidification device 1 not to exceed a certain size.This enables cooling of the fuel cells 24 by evaporation and prevents the accumulation of water in the fuel cell 24, particularly in a flow profile of the fuel cells 24. The current humidity level of the respective membranes may differ between the individual fuel cells 24. For this reason, it may be advantageous if each of the fuel cells 24 is assigned a respective air humidification device 1. This provides the advantage that the air humidity can be individually regulated for the respective fuel cells 24.

[0032] System 2 can, for example, be configured as an aviation primary propulsion system and be provided for humidifying the cathode air for fuel cells 24 used to drive an electric motor of an aircraft. Another possible embodiment of system 2 can, for example, be provided for humidifying a turbine combustion chamber to enable uniform temperature distribution or to minimize the formation of undesirable gas components in the combustion chamber.

[0033] Passive humidifiers are well known from the automotive sector. These do not allow for targeted control of the relative humidity of the cathode air, are heavy and bulky, and do not contribute to cooling a cell stack. Active humidification systems have already been investigated using dual-fluid atomizing nozzles. These require an additional compressed air level, significantly above that of the cathode air itself, to achieve the atomizing effect. Generating this compressed air level is complex, especially at low ambient air pressure, such as that found in aircraft at cruising altitude.

[0034] The polymer electrolyte membrane (PEM) of each fuel cell segment must be individually humidified without causing water to accumulate in the flow field. A relative humidity of 100% must be set at the outlet of a fuel cell stack.

[0035] The humidification system must be suitable for an aviation primary engine. Unlike automotive applications, the ambient air in the aviation sector contains less water and the air volumes to be humidified are larger.

[0036] The plan is to use active humidification for each fuel cell stack segment, using a single-component atomizing nozzle that injects an individually defined amount of water into the cathode air of the stack segment. The atomizing nozzle creates a swirl in the spray cone, causing the larger water droplets to migrate outward. These droplets are separated by a type of aperture or a stepped tube, and only the inner part of the spray cone, containing the fine water droplets, is directed further into the stack segment. The separated water can be recirculated for further discharge through the atomizing nozzle.

[0037] The energy consumption, weight, and installation space required for the water pump of a single-fluid nozzle are significantly smaller than those of an additional compressor stage for a dual-fluid nozzle. The less fine atomization of the single-fluid nozzle is compensated for by the separation of the coarser portion of the droplet spectrum. The fine water droplets contribute to cooling through their evaporation in the stack. Passive humidifiers used in the automotive sector are too large and heavy for an aircraft primary propulsion system and cannot guarantee the required 100% relative humidity at the stack outlet under the given conditions. List of reference symbols:

[0038] 1 Humidification device 2 System 3 Inlet pipe 4 Outlet pipe 5 Mixing chamber 6 Inlet opening 7 Outlet opening 8 Main flow path 9 Atomizing nozzle 10 Spray 11 Droplets 12 Spray cone 13 Cone angle 14 Hollow cone 15 Inner angle 16 Separation device 17 Separation opening 18 Inner pipe 19 Outer pipe 20 Separation outlet 21 Recovery device 22 Control device 23 Fuel cell stack 24 Fuel cell 25 Liquid 26 Gas

Claims

1. Air humidification apparatus (1), comprising a mixing chamber (5) in which an atomizing nozzle (9) designed to dispense a liquid (25) as a spray mist (10) is arranged, - the mixing chamber (5) being designed to mix a gas (26), conveyed along a main flow path (8) through the mixing chamber (5), with the spray mist (10) and to discharge it at an outlet opening (7) of the mixing chamber (5), and - the atomizing nozzle (9) comprising a swirl device which is designed to impart a swirl to droplets (11) of the spray mist (10) in order to dispense the spray mist (10) as a straight spray circular cone (12) opening along the main flow path (8) at a cone angle (13), characterized in that the mixing chamber (5) comprises a separating device (16) which is designed to - collect droplets (11) of the spray circular cone (12) which move from the atomizing nozzle (9) along a hollow cone (14) having a predetermined internal angle (15), - dispense a liquid (25) recovered by collecting the droplets (11) at a separation outlet of the separating device (16), and - supply droplets (11) moving within the hollow cone (14) to the outlet opening (7) of the mixing chamber (5).

2. Air humidification apparatus (1) according to claim 1, characterized in that the separating device (16) comprises a coaxial tube, an outer tube (19) of the coaxial tube being designed to collect the droplets (11) moving along the hollow cone (14), and an inner tube (18) of the coaxial tube being designed to supply the droplets (11) moving within the hollow cone (14) to the outlet opening (7) of the mixing chamber (5).

3. Air humidification apparatus (1) according to claim 1, characterized in that the separating device (16) comprises a separation opening (17) which is circumferentially surrounded by a baffle, - the baffle being designed to collect the droplets (11) moving along the hollow cone (14), and - the separation opening (17) being designed to supply the droplets (11) moving within the hollow cone (14) to the outlet opening (7) of the mixing chamber (5).

4. Air humidification apparatus (1) according to any of claims 1 to 3, characterized in that the air humidification apparatus (1) comprises a recovery device (21) which is designed to supply the recovered liquid (25) from the separating device (16) to the atomizing nozzle (9).

5. Air humidification apparatus (1) according to any of the preceding claims, characterized in that the air humidification apparatus comprises a control device (22) which is designed to adjust the amount of liquid to be dispensed through the atomizing nozzle (9) in order to regulate a predetermined mixing ratio between the gas (26) and the liquid (25) at the outlet opening (7) of the mixing chamber (5).

6. Method for operating an air humidification apparatus (1) comprising a mixing chamber (5) in which an atomizing nozzle (9) is arranged, - gas (26) being conveyed along a main flow path (8) through the mixing chamber (5), - a liquid (25) being dispensed as a spray mist (10) by the atomizing nozzle (9), and - the gas (26) being mixed with the spray mist (10) in the mixing chamber (5) and discharged at an outlet opening (7) of the mixing chamber (5), characterized in that - a swirl is imparted to droplets (11) of the spray mist (10) by a swirl device of the atomizing nozzle (9), - due to the swirl of the droplets (11), the spray mist (10) is dispensed as a straight spray circular cone (12) opening along the main flow path (8) at a cone angle (13) by the atomizing nozzle (9), - droplets (11) of the spray circular cone (12) which move from the atomizing nozzle (9) along a hollow cone (14) having a predetermined internal angle (15) are collected by a separating device (16) of the mixing chamber (5), - a liquid (25) recovered by collecting the droplets (11) is dispensed by the separating device (16) at a separation outlet (20) of the separating device (16), and - droplets (11) moving within the hollow cone (14) are supplied by the separating device (16) to the outlet opening (7) of the mixing chamber (5).

7. System (2) comprising air humidification apparatuses (1) according to any of claims 1 to 5 and a fuel cell stack (23), - the fuel cell stack (23) comprising fuel cells (24), - the system (2) comprising a cathode air supply apparatus which is designed to introduce cathode air to be mixed with water into the air humidification apparatuses (1), characterized in that - the air humidification apparatuses (1) are each connected to a particular fuel cell (24) at their respective outlet openings (7), in particular outlet openings (7) of a particular mixing chamber (5) of the air humidification apparatuses (1).

8. System (2) according to claim 7, characterized in that the system (2) is designed as an aviation primary drive.