Inerting system, aircraft and method for inerting fuel cell system by means of inerting system

Abstract

The invention relates to an inerting system, an aircraft and a method for inerting a fuel cell system by means of an inerting system. More specifically, the present invention relates to an improved inerting system that injects inert gas around a fuel cell in a distributed manner to ensure correct dissipation of flammable agent that may occur around the fuel cell.

Description

Technical Field

[0001] The present invention relates to an inerting system for an aircraft and a method for inerting a fuel cell system. More specifically, the present invention relates to an improved inerting system that injects an inert gas around a fuel cell in a distributed manner to ensure the proper dissipation of flammable agents that may be present around the fuel cell. Background Art

[0002] It is known to those skilled in the art that an explosive or flammable gas environment on an aircraft, such as a fuel tank or a fuel cell, is inerted by providing an inert gas, such as nitrogen, inside the enclosure that houses the hydrogen-based system. Hydrogen is a gas with a very high permeability. This makes it challenging to contain hydrogen inside an enclosure. This inerting is performed to avoid the risk of explosion or combustion occurring inside the enclosure that houses the fuel cell. Nitrogen is typically used as the inert gas, and the inert gas is provided by a nitrogen cylinder or a nitrogen generation system. The nitrogen is circulated inside the fuel cell enclosure at a nominal rate that is determined based on the worst-case scenario (i.e., with the maximum nominal leakage). This parameter setting is to ensure that the volume concentration limit of the flammable mixture of hydrogen and oxygen is never reached in this gas environment. The gas mixture or fluid mixture inside the fuel tank or the fuel cell enclosure is then discharged to the outside of the aircraft. The concentrations of hydrogen and oxygen in this gas environment are kept many times below the required safety policy limits.

[0003] The injection of the inert gas is currently performed as a general injection of the inert gas inside the enclosure of the fuel cell. This enclosure can be defined as a "container" or a "housing". The term "injector" is used to define the inlet of the inert gas, such as nitrogen, into the volume to be inerted. This injection generally takes into account the general location and the ability to supply different flow rates as required. The amount of the inert gas injected is calculated to be able to dissipate a certain amount of nominal leakage that may occur in such a volume.

[0004] A common method of integrating a fuel cell inside an enclosure is to vertically arrange such fuel cells side by side inside the enclosure in a direction parallel to the longitudinal direction of the aircraft when the enclosure is on the aircraft. In this case, the inert gas flow is injected from the lower part of the enclosure, i.e., below the fuel cell, and an outlet is provided above the fuel cell. Compared with other configurations of the fuel cell inside the enclosure, this configuration results in a lower risk of local hydrogen accumulation around the fuel cell. However, this solution cannot be used for fuel cells that are horizontally arranged one above the other inside the enclosure.

[0005] The present invention attempts to solve the above and other problems by improving the inerting of the fuel cell enclosure through the distributed injection of an inert gas. Summary of the Invention

[0006] The present invention provides an inerting system according to the first aspect, an aircraft according to the second aspect, and a method for inerting a fuel cell system according to the third aspect. In other aspects of the present invention, preferred embodiments of the present invention are defined.

[0007] In a first aspect of the invention, the present invention provides an inerting system adapted to inert a fuel cell system for an aircraft, the fuel cell system including a group of fuel cells that are stacked adjacent to each other along a longitudinal direction X-X' and having a free space between consecutive fuel cells; the inerting system includes:

[0008] A housing adapted to accommodate the group of fuel cells such that there is also a free space between each fuel cell and the housing, the housing including a bottom, a top, and a plurality of side walls extending along the longitudinal direction X-X' between the bottom and the top, the housing further including a first outlet configured to connect the interior of the housing to the exterior of the aircraft;

[0009] An inert gas supply device configured to supply an inert gas;

[0010] A fluid injection device that is in fluid communication with the inert gas supply device through an inlet channel and is configured to inject at least a portion of a fluid containing the inert gas into the housing; and

[0011] A fluid regulating device configured to regulate the flow rate of the inert gas;

[0012] wherein,

[0013] The first outlet of the housing is arranged above the stack of fuel cells along the longitudinal direction X-X'; and

[0014] The fluid injection device includes:

[0015] A main channel connected to the inlet channel, and

[0016] At least two distribution channels connected to the main channel and distributed at different heights along the longitudinal direction X-X'; and

[0017] Each distribution channel includes a plurality of injectors longitudinally distributed along the distribution channel and configured to inject the fluid towards the free space between two fuel cells or the free space between a fuel cell and the housing.

[0018] The present inerting system is configured to inert any enclosure in the aircraft that has a relatively small free volume and needs to be inerted, and in particular to inert the fuel cell system of the aircraft, where the fuel is hydrogen. For the present invention, the fuel cell system includes a stack of fuel cells adjacent to each other along a longitudinal direction X-X', with a free space between each two fuel cells, i.e., the fuel cells are horizontally arranged and stacked one above the other along the longitudinal direction X-X', and there is a free space between each two consecutive fuel cells.

[0019] The longitudinal direction X-X' is the stacking direction of the fuel cells inside the housing. When the present inerting system is located on the aircraft, the longitudinal direction X-X' is substantially parallel to the vertical direction of the aircraft. This vertical direction of the aircraft is orthogonal to the horizontal plane containing the longitudinal direction of the aircraft. According to this longitudinal direction or stacking direction of the fuel cells, the housing includes a bottom or lower surface, a top or upper surface, and a plurality of lateral walls or side surfaces enclosing such lower and upper surfaces. For the present invention, relative terms such as "upper, lower, lateral, above, etc." are referred to with respect to the longitudinal direction X-X' or stacking direction of the fuel cells.

[0020] The inerting system includes a housing that houses or encloses the fuel cell system or at least the fuel cell stack. The housing means an enclosure that houses the fuel cell system or at least the fuel cell stack. This housing is used to prevent potential hydrogen leakage so that potential hydrogen leakage does not spread outside the housing. The housing includes a bottom, a top, and a plurality of lateral walls, where each lateral wall extends from the bottom to the top along the longitudinal direction X-X'. That is, the bottom is connected to the top by the lateral walls.

[0021] The fuel cell stack is arranged inside the housing such that there is a free space between each fuel cell and any one of the bottom, top, and lateral walls of the housing. In this sense, there is a free space inside the housing, between the fuel cells, and between the fuel cells and the surfaces of the housing, i.e., there is a free space between each fuel cell and any one of the following: the bottom, top, and lateral walls of the housing.

[0022] In an embodiment, the fuel cell system includes a peripheral system partially arranged inside the housing and separated from the fuel cells. There is also a free space around the peripheral system. The peripheral system is understood to be a system for regulating the hydrogen flow and air flow before they are injected into their reaction sites in the fuel cells.

[0023] The housing includes a first outlet configured to connect the interior of the housing to the exterior of the aircraft. Specifically, the first outlet is understood as a ventilation line for removing the fluid inside the housing, and this ventilation line is connected to the exterior of the aircraft. Additionally, the first outlet of the housing is arranged above the stack of fuel cells according to the longitudinal direction X-X', that is, the first outlet is remote from the stack of fuel cells. In this sense, the distance of the first outlet from the bottom of the housing is greater than the distance between the bottom and the last fuel cell in the stack that is farthest from the bottom. In an embodiment, the stack of fuel cells is arranged inside the housing closer to the bottom of the housing. In an embodiment, the first outlet is located at the top of the housing by virtue of the fact that hydrogen is a lighter gas and will tend to naturally reach the top of the housing.

[0024] In the fluid contained inside the housing, the oxygen concentration and the hydrogen concentration shall not be higher than the limits defined for safety reasons. Specifically, oxygen shall not exceed a volume concentration of 4%, and hydrogen shall not exceed a volume concentration of 4%.

[0025] An air supply pipe and a hydrogen supply pipe are arranged inside the housing in which the fuel cell is installed. The joints between these pipes may also have a nominal leakage rate, and the inerting system is sized taking into account the worst-case scenario of the nominal leakage rate. The connections of these hydrogen supply pipes to the fuel cell are the main sources of leakage.

[0026] To inert the interior of the housing, the inerting system includes supply means for supplying an inert gas to the system and fluid injection means for distributing the fluid to the interior of the housing. Additionally, the inerting system includes an inlet passage through which a fluid connection is maintained between the inert gas supply means and the fluid injection means. The fluid distributed to the interior of the housing mainly includes an inert gas. In an embodiment, the inert gas is nitrogen. In an embodiment, the inert gas is pure nitrogen. In an embodiment, the inert gas is a combination of pure nitrogen and a recirculation fluid from the housing. The meaning of "recirculation fluid" is defined hereinafter with respect to the fluid recirculation system. Furthermore, the fluid located inside the housing is understood as a gaseous fluid, such as a pure gas or a gas mixture.

[0027] Specifically, the fluid injection means includes a main passage and at least two distribution passages. The main passage is connected to the inlet passage. The distribution passages are connected to the main passage and are arranged in a distributed manner one above the other according to the longitudinal direction X-X'. The term "distributed" does not necessarily mean a uniform distribution. According to the present invention, each distribution passage is located at a different height along the longitudinal direction X-X'.

[0028] Each distribution channel includes a plurality of injectors longitudinally distributed along the distribution channel, such that rows of injectors are distributed at different heights along the longitudinal direction X-X'. These injectors are configured to inject fluid into the free space between two fuel cells or into the free space between a fuel cell and the housing.

[0029] The injectors are arranged in different rows such that the injectors of one distribution channel are arranged along a row. In an embodiment, a row of injectors is arranged in a region within the housing that includes any free space within the free space.

[0030] Furthermore, the inerting system includes means for conditioning the fluid flowing through the inerting system, in particular for conditioning a fluid that at least partially contains an inert gas.

[0031] Thus, the inerting system is arranged to inert the volume surrounding the fuel cell in a distributed manner to prevent local accumulation of hydrogen and / or oxygen, which otherwise might create a flammable fluid in that volume.

[0032] Advantageously, the present inerting system is provided with a specific and improved fluid injection device for injecting an inert gas into the housing in a distributed manner such that the inert gas flows around the fuel cell in a way that ensures proper dilution of possible flammable agents. This fluid injection device is capable of injecting the inert gas towards the free spaces already mentioned above to have a good drag force on the fluid around the fuel cell. That is, the inert gas is not directly conveyed towards the outlet of the housing, but rather provides a circulation of the inerting fluid within the housing, which allows minimizing the non-ventilated volume within the housing and thereby minimizing the local accumulation of flammable gases. Turbulence can also be generated inside the housing to increase the dilution of potential local accumulations of flammable gases, thus creating a very homogeneous mixture throughout the entire housing volume.

[0033] In addition, this fluid injection device allows the uniform injection of an inert gas inside the housing that is sufficient to drag the fluid towards the vicinity of an interface where a leak of flammable fluid might occur. The injected inert gas flow has sufficient velocity around the surface where a leak might occur.

[0034] In an embodiment, the outlet of the injector inside the housing is arranged at a distance from the lower surface of the fuel cell, which distance is preferably higher than 10 mm and lower than half of the distance between the lower surface of the top fuel cell and the top surface of the lower fuel cell.

[0035] In an embodiment, the fluid injection device is located outside the housing such that the injector of each distribution channel passes through the housing for injecting fluid into the interior of the housing, and each injector is an inlet leading to the interior of the housing. In this embodiment, the main channel and the distribution channels are located outside the housing, while the injector or at least a part of the injector is located inside the housing. In an embodiment, the injector passes through at least one of the lateral walls of the housing.

[0036] In an embodiment, the fluid injection device is located inside the housing such that the inlet channel passes through the housing. In this embodiment, the main channel and the distribution channels are located inside the housing together with the injector. In an embodiment, the inlet channel passes through at least one of the lateral walls of the housing.

[0037] In an embodiment, the fluid injection device is built into the housing.

[0038] In an embodiment, the main channel is partially arranged parallel to the longitudinal direction X-X'. In an embodiment, the distribution channels are arranged perpendicular to the longitudinal direction X-X'.

[0039] In an embodiment,

[0040] the fluid injection device further includes an additional distribution channel that is connected to the main channel and includes a plurality of additional injectors arranged along the additional distribution channel, and

[0041] the additional injectors are configured to inject fluid from the bottom of the housing to the top of the housing into the interior of the housing according to the longitudinal direction X-X'.

[0042] Specifically, the additional injectors inject fluid from the bottom of the housing along the free space between the stack of fuel cells and one of the lateral walls of the housing according to the longitudinal direction X-X'.

[0043] Advantageously, the additional distribution channel enables the fluid to be discharged more quickly, thereby preventing the accumulation of flammable gases that may leak inside the housing.

[0044] In an embodiment, the distribution channels are arranged on the same side of the stack of fuel cells. In this embodiment, the injector is configured to inject fluid from one lateral wall of the housing towards the opposite lateral wall of the housing in the same first direction. In this sense, the fluid is injected only from one lateral wall of the housing, that is to say, the fluid is injected from the side of the stack of fuel cells with respect to the longitudinal direction X-X'. The term "side" will be understood as the space next to each of the faces of the stack of fuel cells with respect to the faces of the stack, that is to say, the side faces of the stack of fuel cells are the regions immediately adjacent to the stack. If the fluid injection device is located inside the housing, both the distribution channels and their corresponding injectors are positioned on the same side of the stack of fuel cells, that is, between the stack of fuel cells and at least one of the lateral walls of the housing. On the other hand, if the fluid injection device is located outside the housing, the distribution channels are positioned beyond one of the lateral walls of the housing, and the corresponding injectors are located between these distribution channels and the said lateral wall of the housing. In any of these embodiments, the fluid is injected from the same side of the stack of fuel cells.

[0045] In an embodiment, at least:

[0046] a first distribution channel and a corresponding injector are arranged on a first side of the stack of fuel cells such that the injector is configured to inject fluid in a first direction through a first free space between two fuel cells or between a fuel cell and the housing, and

[0047] a second distribution channel and a corresponding injector are arranged on a second side of the stack of fuel cells different from the first side such that the injector is configured to inject fluid in a second direction different from the first direction through a second free space continuous with the first free space.

[0048] In other words, the distribution channels are arranged alternately between two different sides of the stack of fuel cells such that for each free space, the fluid is injected from a different side of the stack of fuel cells. According to the longitudinal direction X-X', there is a first row of injectors for injecting fluid in a first direction into a first free space inside the housing. A second row of injectors is for injecting fluid in a second direction into a second free space continuous with the first free space, and so on, such that the injection alternates from at least two sides of the stack of fuel cells. The first injection direction is different from the second injection direction. In this embodiment, for the same free space, there are not two rows of injectors on the same side of the stack of fuel cells for injecting fluid into each free space, but rather the injection alternates from each side of the stack for each free space.

[0049] In the present embodiment, for each free space between fuel cells and between the fuel cells and the housing, there is a row of injectors located on either side of the stack of fuel cells, injecting fluid from either one of the two lateral walls of the housing. According to the longitudinal direction X-X', for the first free space, such as the free space between the bottom of the housing and the first fuel cell, the first row of injectors is located on the first side of the stack of fuel cells for injecting fluid from the first side of the stack in a first direction. For the second free space contiguous to the first free space, such as the free space between the first fuel cell and the second fuel cell, the second row of injectors is located on the second side of the stack of fuel cells for injecting fluid from the second side in a different second direction. The second side is different from the first side, and the second direction is different from the first direction. For the third free space contiguous to the second free space, such as the free space between the second fuel cell and the third fuel cell, the third row of injectors is located on the first side of the stack of fuel cells for injecting fluid from the first side according to the first direction. For each additional fuel cell in the stack, this will continue in a similar manner, that is, alternating which side of the stack the fluid is injected from.

[0050] By the configuration of the above embodiment in which the rows of injectors alternate in height (according to the longitudinal direction X-X'), a wavy or serpentine fluid flow around the fuel cells inside the housing is achieved. Thus, it is ensured that all or almost all of the fluid in the fluid around the fuel cells is cleared.

[0051] In an embodiment, the first side of the stacked fuel cells is opposite to the second side. In an embodiment, the first direction is opposite to the second direction. In an embodiment, the first lateral wall of the housing is opposite to the second lateral wall.

[0052] In an embodiment, the distribution channels and the corresponding injectors are arranged on two different sides of the stack of fuel cells, and for each free space, such that each free space can be injected with fluid from either side of the stack of fuel cells. For each free space between two fuel cells or between a fuel cell and the housing, the fluid injection device is configured to selectively actuate only the injectors located on one of the respective sides of the stack of fuel cells.

[0053] In this embodiment, although there are injectors on both sides of the stack of fuel cells, the fluid injection device allows selective injection of fluid only from one side of the stack of fuel cells. This means that the fluid injection device selects for each free space whether to actuate the injectors on one side or the other side of the stack of fuel cells.

[0054] In an embodiment, each injector includes an injection channel and a nozzle. The nozzle is oriented towards and opens into the interior of the housing. The injection channel is connected to the distribution channel and the nozzle.

[0055] In an embodiment, the nozzle includes a nozzle opening for the outlet of the injector fluid, wherein the cross-sectional area of the nozzle opening is larger than the cross-sectional area of the injection channel.

[0056] The above-mentioned difference in cross-section between the injection channel and the nozzle opening allows the fluid diffusion to be uniform and have a velocity sufficient to purge the fluid inside the housing.

[0057] In an embodiment, each distribution channel and its corresponding injector are included in an enclosed structure, which includes a common outlet opening into the housing and a common space located upstream of the common outlet, and wherein the nozzle opening of each injector opens into the common space. Advantageously, this configuration allows it to be manufactured as a one-piece for ease of assembly into the system.

[0058] In an embodiment, the inerting system includes:

[0059] a sensing device configured to measure the oxygen concentration and the hydrogen concentration of the fluid located inside the housing; and

[0060] a control device in data communication with the sensing device and configured to independently control at least the fluid regulating device based on the oxygen concentration and the hydrogen concentration inside the housing.

[0061] The sensing device measures the oxygen concentration and the hydrogen concentration of the fluid contained in the housing in which the fuel cell is disposed. These oxygen concentration and hydrogen concentration refer to the volume concentration inside the housing and are expressed as a percentage.

[0062] The control device is connected to the sensing device such that, based on the data regarding the oxygen concentration and the hydrogen concentration provided by the sensing device, the control device controls at least the fluid regulating device as needed. That is, if the oxygen concentration condition and / or the hydrogen concentration condition is higher than a first preset threshold, a portion of the fluid in the housing is discharged by pumping it out of the housing and an inert gas or a pure inert gas is supplied through the inert gas supply device. Thus, at least when the oxygen concentration and / or the hydrogen concentration of the fluid in the housing is higher than the first preset threshold, the control device actuates at least the fluid regulating device. Specifically, the term "actuate" is understood to cause a portion of the fluid located inside the housing to recirculate towards the inlet channel.

[0063] According to the hydrogen concentration and / or the oxygen concentration, the fluid injection device injects a greater or lesser mass flow rate into the housing. If only the hydrogen concentration or the oxygen concentration inside the housing is higher than the corresponding first preset threshold, more inert gas or pure inert gas needs to be injected.

[0064] Thus, the inerting system is thus arranged to inert the volume surrounding the fuel cell in a controlled manner to prevent fires or the generation of flammable fluids in undesired areas of the volume inside the enclosure.

[0065] These first thresholds are based on a safety policy.

[0066] By means of the sensing means and the control means, the inerting system advantageously allows the measurement and monitoring of both the hydrogen concentration and the oxygen concentration inside the enclosure at any time and is able to prevent fires inside the enclosure.

[0067] In an embodiment, the inerting system includes a fluid regulation system configured to recirculate a portion of the fluid located inside the enclosure to the inlet passage for supplying the recirculated fluid mixed with an inert gas to the interior of the enclosure through a fluid injection device; wherein the control means is further configured to:

[0068] independently control the fluid recirculation system based on the oxygen concentration and the hydrogen concentration measured by the sensing means; and

[0069] initiate the recirculation in the fluid recirculation system only when the oxygen concentration and / or the hydrogen concentration of the fluid located inside the enclosure is / are respectively below a second preset threshold.

[0070] The fluid recirculation system partially recirculates the fluid located inside the enclosure through the inerting system. A portion of the fluid located in the enclosure is recirculated to the inlet passage to be supplied back into the enclosure through the fluid injection device, but mixed with an inert gas or pure inert gas so that the interior of the enclosure remains inert.

[0071] In an embodiment, the control means is configured to independently control at least the fluid regulation means and the fluid recirculation system based on the oxygen concentration and the hydrogen concentration inside the enclosure. Thus, the control means is configured to initiate the recirculation in the fluid recirculation system only when the oxygen concentration and / or the hydrogen concentration of the fluid located inside the enclosure is / are respectively below a second preset threshold.

[0072] Therefore, based on the data regarding oxygen concentration and hydrogen concentration provided by the sensing device, the control device controls the fluid regulating device and the fluid recirculation system separately as needed. That is to say, if the oxygen concentration condition and / or hydrogen concentration condition are appropriate, a portion of the fluid in the enclosure is recirculated by withdrawing it from the enclosure and reinjecting the portion of the fluid mixed with pure inert gas or inert gas supplied by the inert gas supply device. When the oxygen concentration and / or hydrogen concentration are respectively lower than the second preset threshold, they are considered suitable for allowing a portion of the fluid contained in the enclosure to be recirculated. Therefore, the control device only initiates recirculation when the oxygen concentration and / or hydrogen concentration of the fluid in the enclosure are lower than such a second preset threshold.

[0073] According to the hydrogen concentration and / or oxygen concentration, the fluid recirculation system recirculates a greater or lesser mass flow of the fluid from the enclosure. If the hydrogen concentration and oxygen concentration of the fluid to be recirculated are lower than the second preset threshold, a greater mass flow of the fluid from the enclosure is recirculated, and less pure inert gas or inert gas is required. However, if only the hydrogen concentration or oxygen concentration of the fluid to be recirculated is lower than the corresponding second preset threshold, less fluid from the enclosure is recirculated, and more inert gas or pure inert gas is required.

[0074] These second preset thresholds are based on safety policies such that if the oxygen concentration and / or hydrogen concentration are far enough from the limits considered by the safety policy, the gas located inside the enclosure will be partially recirculated.

[0075] In an embodiment where the inerting system includes a fluid recirculation system, advantageously, this inerting system requires less installation space in the aircraft because it reduces the amount of inert gas or pure inert gas required for inerting by providing the possibility of partially recirculating the fluid located inside the enclosure. Additionally, this reduction in the inert gas supply device (bottle or generation system) in turn reduces the weight of the aircraft.

[0076] Furthermore, this inerting system allows for a greater mass flow into the enclosure and a lower mass flow from the inert gas supply device due to the recirculation of the fluid located inside the enclosure. This allows for limiting the local accumulation of oxygen and / or hydrogen by increasing the flow rate of the inerted gas circulating in the enclosure. It also allows for obtaining a more turbulent flow, thereby also increasing the uniformity of the mixing of the inert gas (nitrogen), oxygen, and hydrogen. This homogenization advantageously prevents instantaneous points that could lead to a large concentration of a locally flammable mixture inside the enclosure.

[0077] In addition, due to the higher mass flow rate entering the enclosure through the fluid injection device, the flow velocity through the enclosure is greater, and then the arrival time of the inerted fluid containing oxygen or hydrogen at a hazardous concentration flowing through the enclosure will be detected more quickly because it will reach the sensing device more quickly. Therefore, the present inerting system provides a rapid detection of oxygen concentration values and hydrogen concentration values that can indicate risks inside the enclosure. For example, if a mixture of oxygen and hydrogen with a sufficient volume concentration of these gases appears in the fluid of the enclosure, there is a higher risk of fire. To this end, the present invention allows action to be taken before reaching one of the first preset threshold or the second preset threshold of the oxygen concentration and the hydrogen concentration locally.

[0078] In addition, the present inerting system advantageously has the ability to adjust and change the mass flow rate from the inert gas supply device as needed based on the information provided by the sensing device to the control device. The fluid regulating device controls to allow continuous purging of the fluid inside the enclosure.

[0079] In an embodiment, the fluid regulating device includes:

[0080] An inlet valve configured to regulate the supply of at least the inert gas from the inert gas supply device towards the fluid injection device; and

[0081] A first outlet valve configured to regulate the outlet flow of the fluid located inside the enclosure through the first outlet.

[0082] In another embodiment, the fluid regulating device includes an inlet orifice having a predetermined diameter that always allows the same flow rate to pass through.

[0083] The first outlet valve regulates the discharge of the fluid located inside the enclosure through the first outlet of the enclosure. The first outlet valve has a minimum orifice that allows flow through to discharge the enclosure even in its tightest position.

[0084] In an embodiment, the control device is further configured to control the regulation of at least the first outlet valve based on the measured oxygen concentration and hydrogen concentration.

[0085] In an embodiment, the control device is further configured to control the regulation of the inlet valve.

[0086] In an embodiment, the fluid recirculation system includes:

[0087] A recirculation channel that connects the interior of the enclosure to the inlet channel upstream of at least one inlet of the enclosure;

[0088] A compressor interposed on the recirculation channel; and

[0089] A recirculation valve, which is located on the recirculation passage between the compressor and the connection portion of the recirculation passage and the inlet passage, and is configured to regulate the flow rate of the recirculating fluid toward the inlet passage.

[0090] The recirculation passage of the fluid recirculation system connects the interior of the housing to the inlet passage to mix the recirculating fluid with the inert gas or a mixture of pure inert gas before supplying the mixture of the recirculating fluid and the inert gas or pure inert gas to the housing through the fluid injection device. The recirculation passage of the recirculation system is connected to the inlet passage in the section of the inlet passage between the inert gas supply device and the inlet of the housing, that is, upstream of the inlet of the housing.

[0091] The recirculation system further includes a compressor, which is inserted on the recirculation passage and is configured to compress the fluid from the interior of the housing to a pressure lower than the pressure of the inert gas or pure inert gas supplied to the inlet passage. The compressor ensures the pumping of the recirculating fluid through the fluid recirculation system. The supply of the recirculating fluid to the inlet passage must be at a lower pressure than the supply of the inert gas or pure inert gas to prevent the recirculating fluid from flowing back to the inert gas inlet in the inlet passage.

[0092] In addition, the fluid recirculation system includes a recirculation valve for regulating the passage of fluid from the recirculation passage to the inlet passage. Specifically, the recirculation valve is connected to the recirculation passage between the compressor and the connection portion of the recirculation passage and the inlet passage.

[0093] The opening of the recirculation valve and / or the flow rate of the fluid recirculated by the compressor depends on the measured hydrogen concentration and / or oxygen concentration.

[0094] More specifically, the inerting system further includes a mixer, which is inserted on the inlet passage between the inert fluid regulating device and at least one inlet of the housing. The mixer is connected to the recirculation passage and is configured to mix the inert gas or pure inert gas from the inert gas supply device with the recirculating fluid from the fluid recirculation system.

[0095] The mixer is understood to be an enclosure inserted on the inlet passage and in fluid communication with the inert gas supply device, the fluid recirculation system, and the interior of the housing through the fluid injection device. The mixer is the place where the recirculating fluid is mixed with the inert gas or pure inert gas before entering the interior of the housing. In an embodiment, the inlet valve regulates the passage of the inert gas or pure inert gas toward the mixer, and the recirculation valve regulates the passage of the recirculating fluid toward the mixer.

[0096] This inerting system provides a purge mode that increases the flow rate of inert gas or pure inert gas to reduce the hydrogen concentration and / or oxygen concentration below a preset flammable limit and extinguish a fire within a short period of time.

[0097] In an embodiment, the inerting system further includes a fire detection device that communicates data with a control device and is configured to detect a fire inside the enclosure. The control device is further configured to open the inlet valve and the first outlet valve at a maximum flow rate when the fire detection device detects a fire.

[0098] In another embodiment, the control device is further configured to open the inlet valve and the first outlet valve at a maximum flow rate when a high concentration of oxygen or hydrogen is detected by a sensing device, that is, when the oxygen concentration or hydrogen concentration is higher than a fourth preset threshold.

[0099] When the first outlet valve is opened at a maximum flow rate, the flammable gas is advantageously discharged from inside the enclosure. Additionally, when the inlet valve is opened at a maximum flow rate, the flammable gas is purged from the enclosure and the interior of the enclosure is quickly inerted again. Furthermore, when the first outlet valve is opened at a maximum flow rate, overpressure inside the enclosure is avoided.

[0100] Moreover, by providing this inerting system, the use of any fire extinguishing agent (such as halon) is achieved. Additionally, since the fire extinguishing agent bottle has been replaced by the fluid recirculation system necessary to inert the enclosure under any circumstances, the installation space and weight of the fire extinguishing agent bottle are also saved.

[0101] The fact that the first outlet valve has a greater outlet flow rate portion in case of failure provides an additional margin in terms of safety because the pressure is released from the enclosure faster.

[0102] Furthermore, compared to prior art solutions or nominal flow rates, that is, compared to the case where the inlet valve is not opened at its maximum flow rate, the reaction time for extinguishing a fire and re-inerting the interior of the enclosure by this inerting system is shorter. Additionally, with the new fluid injection device, the fluid can be supplied to the interior of the enclosure in a more uniform and effective manner by quickly purging the fluid around the fuel cell inside the enclosure.

[0103] More specifically, the fire detection device may include an overpressure sensor for detecting overpressure inside the enclosure. When overpressure inside the enclosure is detected, the inlet valve and the outlet valve are adjusted to release the generated overpressure.

[0104] In an embodiment, the inerting system further includes a pressure measuring device that communicates data with the control device and is configured to measure the pressure inside the enclosure, wherein the control device is configured to open the outlet valve at a flow rate higher than a preset flow rate threshold when the measured pressure exceeds a preset pressure threshold. That is, if overpressure is detected inside the enclosure, the inlet valve of the enclosure is adjusted to release the generated overpressure, and thus a greater purging of the fluid inside the enclosure is achieved. Additionally, when overpressure is detected inside the enclosure, the inlet valve can also be opened at a flow rate higher than a preset flow rate threshold to continue inerting the interior of the enclosure to the maximum. In this case, the outlet flow rate of the outlet valve is greater than the inlet flow rate of the inlet valve to prevent an increase in the pressure inside the enclosure.

[0105] In an embodiment, the sensing device includes at least a first sensor for measuring the oxygen concentration and at least a second sensor for measuring the hydrogen concentration. Advantageously, the sensing device allows the measurement of the hydrogen concentration and the oxygen concentration so that the control device can determine whether the fluid contained in the enclosure can be recycled.

[0106] In an embodiment, the sensing device is located inside the enclosure and / or in the fluid recirculation system and / or in the discharge passage connected to the first outlet of the enclosure. Arranging the sensing device in the enclosure, the fluid recirculation system, and the discharge passage allows the measurement of the oxygen and hydrogen concentrations at different points where the fluid contained in the enclosure flows in the inerting system.

[0107] In an embodiment, the sensing device is located inside the enclosure and / or is positioned upstream of the compressor in the recirculation passage of the fluid recirculation system.

[0108] In an embodiment, there are a plurality of sensing devices located inside the enclosure for the purpose of covering several areas inside the enclosure, thus avoiding local accumulation of oxygen and hydrogen.

[0109] In a second aspect of the invention, the present invention provides an aircraft that includes an inerting system according to the first aspect of the invention.

[0110] In a third aspect of the invention, the present invention provides a method for inerting a fuel cell system by an inerting system that includes a fluid injection device, wherein:

[0111] The fuel cell system is housed in an enclosure and includes a set of fuel cells that are stacked adjacent to each other along a longitudinal direction X-X', wherein there are free spaces between consecutive fuel cells and between each fuel cell and the enclosure; and

[0112] The fluid injection device includes a main channel and a plurality of distribution channels. The plurality of distribution channels are connected to the main channel and are distributed at different heights along the longitudinal direction X-X'. Each distribution channel includes a plurality of injectors. The plurality of injectors are distributed along each distribution channel and are configured to inject fluid into the free space between two fuel cells or the free space between a fuel cell and the housing.

[0113] Wherein, the method includes:

[0114] (a) Supplying an inert gas to the fluid injection device through an inert gas supply device; and

[0115] (b) Discharging a part of the fluid located inside the housing through a first outlet;

[0116] Wherein, in step (a), at least the inert gas supplied by the supply device is injected into the inside of the housing through the injector towards the free space between the fuel cells and / or the free space between the fuel cell and the housing.

[0117] The purpose of this method is to inert the fuel cell system, especially the housing enclosing a fuel cell system with hydrogen as fuel or a part of the fuel system, by injecting the inert gas in a uniform manner and removing the fluid around the fuel cell as quickly as possible. In an embodiment, the inerting system for inerting the fuel cell system or a part of the fuel cell system is according to the first inventive aspect. The fuel cell system of the aircraft is enclosed in an inerted housing to maintain the inerting of the fuel cell system.

[0118] In an embodiment, the method includes:

[0119] (c) Monitoring the oxygen concentration and hydrogen concentration inside the housing through a sensing device;

[0120] (d) Recycling a part of the fluid located inside the housing through the fluid recycling system of the inerting system when the hydrogen concentration and / or oxygen concentration of the fluid to be recycled is lower than a second preset threshold; and

[0121] (e) Injecting the recycled fluid mixed with the inert gas into the inside of the housing through the fluid injection device.

[0122] In an embodiment, the inert gas is a pure inert gas.

[0123] Advantageously, as long as the conditions of the fluid contained in the housing permit, that is, as long as the hydrogen concentration and oxygen concentration remain below the second preset threshold, the method according to the above embodiment allows the reuse of the inert gas that has been supplied and mixed with other gases in the housing.

[0124] In an embodiment, as long as the hydrogen concentration measured by the sensing device is lower than the second hydrogen preset threshold and / or the oxygen concentration is lower than the second oxygen preset threshold, the fluid recirculation system causes the fluid to recirculate from the outer casing.

[0125] In an embodiment, the recirculation of step (d) is performed when the hydrogen concentration and the oxygen concentration of the fluid to be recirculated (inside the outer casing) are lower than the second preset threshold.

[0126] In another embodiment, the method further includes the step of monitoring the pressure inside the outer casing by a pressure measuring device that communicates data with the control device. Wherein, when the control device determines that the pressure inside the outer casing exceeds the preset pressure threshold, the control device opens the first outlet valve to discharge the pressure from the outer casing until the pressure inside the outer casing is the same as the pressure outside the aircraft. The control device determines whether there is overpressure inside the outer casing based on the pressure measured by the pressure measuring device. More specifically, when it is determined that the pressure inside the outer casing exceeds the preset pressure threshold, the control device also opens the inlet valve to supply inert gas to the inside of the outer casing. Additionally, when overpressure inside the outer casing is detected, the first outlet valve and / or the inlet valve are opened at a flow rate higher than the preset flow rate threshold. According to the normal operating mode of the inerting system, the pressure inside the outer casing is slightly higher than the outside, so as to limit the inhalation of oxygen from the surrounding air of the outer casing in case of limited leakage of the outer casing.

[0127] In an embodiment, when the hydrogen concentration inside the outer casing is higher than the third preset threshold and / or the oxygen concentration inside the outer casing is higher than the third preset threshold, the control device opens the first outlet valve at a flow rate higher than the preset flow rate threshold to discharge the fluid from the outer casing, and opens the inlet valve at a flow rate higher than the preset flow rate threshold to supply inert gas to the inside of the outer casing until the hydrogen concentration and the oxygen concentration are lower than the third preset threshold.

[0128] When the oxygen concentration or the hydrogen concentration or both are higher than the third preset threshold, the system is reconfigured to discharge the fluid contained inside the outer casing and re-inert the inside of the outer casing, but no recirculation is performed, that is, the recirculation system stops working.

[0129] In an embodiment, when the hydrogen concentration and / or the oxygen concentration inside the outer casing is higher than the fourth preset threshold, or when a fire is detected inside the outer casing, the control device opens the inlet valve and the first outlet valve at the maximum flow rate.

[0130] In an embodiment, if the hydrogen concentration and the oxygen concentration are lower than the corresponding second preset threshold, the mass flow rate of the recirculation through the compressor of the fluid recirculation system is increased, and the mass flow rate from the inert gas supply device in the inlet conduit is decreased to reduce the oxygen concentration and the hydrogen concentration inside the outer casing as needed.

[0131] In an embodiment, if the hydrogen concentration or the oxygen concentration is lower than the corresponding second preset threshold, the mass flow rate of the fluid recirculated through the compressor of the fluid recirculation system is reduced, and the mass flow rate from the inert gas supply device is increased in the inlet duct to reduce the oxygen concentration or the hydrogen concentration inside the housing as needed.

[0132] In an embodiment, the second preset threshold is consistent with the third preset threshold, such that there is a single preset threshold for setting whether the fluid located in the housing can be recirculated. That is, if the oxygen concentration and the hydrogen concentration are lower than this preset threshold, recirculation can be performed, but if the oxygen concentration and the hydrogen concentration are higher than this threshold, recirculation cannot be performed. Additionally, if only one of the oxygen concentration or the hydrogen concentration is lower than the above threshold, recirculation can be performed, although the amount of recirculated fluid is less as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0133] With reference to the drawings, these and other features and advantages of the present invention will be clearly understood in view of the detailed description of the present invention that becomes apparent from the preferred embodiments of the present invention, which are given by way of example only and are not limited thereto.

[0134] Figure 1 : This figure shows a schematic diagram of an inerting system according to an embodiment of the present invention.

[0135] Figure 2 : This figure shows a schematic diagram of an inerting system according to another embodiment of the present invention.

[0136] Figure 3 : This figure shows a schematic perspective view of a fluid injection device according to an embodiment of the present invention.

[0137] Figure 4 : This figure shows a schematic diagram of a fluid injection device according to an embodiment of the present invention.

[0138] Figure 5 : This figure shows a schematic diagram of a fluid injection device according to another embodiment of the present invention.

[0139] Figure 6 : This figure shows a schematic diagram of a fluid injection device according to another embodiment of the present invention.

[0140] Figure 7 : This figure shows a schematic diagram of a part of a fluid injection device according to an embodiment of the present invention.

[0141] Figure 8 : This figure shows a schematic diagram of a part of a fluid injection device according to another embodiment of the present invention.

[0142] Figure 9 : This figure shows a schematic view of an aircraft having an inerting system according to the present invention. Detailed Description

[0143] Figure 1 and Figure 2 shows an inerting system adapted to inert a hydrogen fuel cell system housed in a housing 2 by means of a fluid injection device 10, the inerting system being provided with different configurations in each of the Figure 1 and Figure 2 embodiments. The inerting system is configured to be installed in an aircraft 20. Specifically, Figure 9 shows an aircraft 20 adapted to include any inerting system of the inerting systems according to any of the Figure 1 and Figure 6 embodiments shown.

[0144] For Figures 1 to 6 any of the embodiments shown, there is a housing 2 internally accommodating a fuel cell system or a part of a fuel cell system. The fuel cell system includes three fuel cells 1 arranged horizontally one stacked on top of the other according to the longitudinal direction X-X'. The housing 2 (according to the longitudinal direction X-X') includes a bottom 2.3, a top 2.4, and at least a first side wall 2.5 and a second side wall 2.6, each side wall 2.5, 2.6 being in contact with both the bottom 2.3 and the top 2.4. Inside the housing 2, there is a free space between every two fuel cells 1, i.e., between two consecutive fuel cells 1, and between the fuel cell 1 closest to the bottom 2.3 of the housing 2 and the bottom 2.3 of the housing 2.

[0145] The housing 2 includes an inlet 2.2 and a first outlet 2.1 that allow fluid to flow through the housing 2. The inlet 2.2 is connected to an inlet passage 11 and the first outlet 2.1 is connected to a discharge passage 19. The inlet passage 11 is in turn connected to an inert gas supply device 4 adapted to supply nitrogen to inert the interior of the housing 2. On the other hand, the first outlet 2.1 is configured to be connected to the outside of the aircraft 20. The inlet flow rate of the fluid through the inlet 2.2 corresponds to the mass flow rate or m in entering the housing 2. The outlet flow rate of the fluid through the first outlet 2.1 corresponds to the mass or m out that leaves the aircraft 20 and does not return.

[0146] Figure 1 and Figure 2The inerting system shown also shows an inlet valve 5 of a fluid regulating device interposed in the inlet passage 11, and this inlet valve 5 is used to regulate the flow rate of nitrogen gas supplied from the inert gas supply device 4 to the inside of the housing 2 through the fluid injection device 10. That is to say, nitrogen gas is supplied to the inside of the housing 2 through the inlet passage, and the inlet flow rate of nitrogen gas to the fluid injection device 10 is regulated by the inlet valve 5. The inlet flow rate of nitrogen gas through the inlet passage 11 corresponds to the mass flow rate from the inert gas supply device 4 or m a 。

[0147] These Figure 1 and Figure 2 The inerting system also shows an outlet valve 6 interposed in the discharge passage 19, and this outlet valve 6 is used to regulate the outlet flow rate of the fluid from the inside of the housing 2 through the first outlet 2.1.

[0148] In these Figure 1 and Figure 2 The fluid injection device 10 shown is located inside the housing 2 and includes a main passage 7 connected to the inlet passage 11 and three distribution passages 8 connected to the main passage 7. The main passage 7 is a connecting pipe or a distribution pipe. In these figures, the inlet passage 11 passes through the housing 2 to connect to the main passage 7 of the fluid injection device 10. The distribution passages 8.1, 8.2, 8.3 are horizontally arranged and perpendicular to the longitudinal direction X-X', and each distribution passage is distributed at different heights along the longitudinal direction X-X'. Each distribution passage 8.1, 8.2, 8.3 includes a plurality of injectors 9 configured to inject the fluid from the inlet passage 11 into the inside of the housing 2. Specifically, the injectors 9 are arranged inside the housing 2 at the following heights according to the longitudinal direction X-X': this height coincides with the area included in the free space. More specifically, there is a first row of injectors 9 for injecting the fluid towards the free space between the first fuel cell 1.1 and the bottom 2.3 of the housing 2. The second row of injectors 9 is used to inject the fluid towards the free space between the first fuel cell 1.1 and the second fuel cell 1.2. Finally, there is a third row of injectors 9 for injecting the fluid towards the free space between the second fuel cell 1.2 and the third fuel cell 1.3 of the stack of fuel cells 1.

[0149] Figure 1 and Figure 2 The inerting system also shows a sensing device 12 for measuring the oxygen concentration and hydrogen concentration inside the housing 2. The sensing device 12 includes a first sensor 12.1 for measuring the oxygen concentration and a second sensor 12.2 for measuring the hydrogen concentration. According to Figure 1 ,the first sensor 12.1 and the second sensor 12.2 are located on the housing 2 and on the discharge passage 19. In contrast, in Figure 2In [the figure], the first sensor 12.1 and the second sensor 12.2 are located on the housing 2 and on the recirculation duct 18.

[0150] In addition, the inerting system further includes a control device 13 for independently controlling at least the inlet valve 5 and the outlet valve 6. The control device 13 communicates data with the sensing device 12 to determine the oxygen concentration and the hydrogen concentration inside the housing 2.

[0151] According to Figure 2 an embodiment of [the figure], the inerting system further includes a fluid recirculation system S for recirculating a part of the fluid contained in the housing 2. Such recirculation includes recirculating the fluid from inside the housing 2 to the inlet passage 11 and recirculating it back into the housing 2 together with the nitrogen gas supplied by the inert gas supply device 4. The inerting system also shows a mixer 15 interposed on the inlet passage 11. Specifically, the mixer 11 is arranged between the inlet valve 1.1 and the inlet 2.2 of the housing 2.

[0152] The fluid recirculation system S includes a recirculation duct 18 connecting the inside of the housing 2 to the mixer 11. The recirculation duct 18 is arranged between the discharge passage 19 and the mixer 11. The fluid recirculation system S further includes a compressor 16, which is interposed on the recirculation duct 18, and the compressor 16 is configured to pump the fluid from inside the housing 2 and to adjust the pressure of the recirculating fluid to adjust the pressure of the recirculating fluid to be lower than the pressure of the supplied nitrogen gas. The inlet flow rate of the recirculation flow through the outlet recirculation duct 18 corresponds to the mass flow rate or m of the recirculating fluid through the compressor 16 c .

[0153] The fluid recirculation system S further includes a recirculation valve 17 arranged between the compressor 16 and the connection of the recirculation duct 18 and the mixer 11. The regulating valve 17 is provided for regulating the inlet of the recirculating fluid towards the recirculation duct 18.

[0154] Figure 2 The control device 13 shown in [the figure] also independently controls the compressor 16 and the recirculation valve 17. In addition, the control device 13 communicates data with the sensing device 12 to determine the oxygen concentration and the hydrogen concentration inside the housing 2 and whether the fluid recirculation system S can be actuated. That is, the fluid can be recirculated only when the control device 13 determines that the oxygen concentration and / or the hydrogen concentration is respectively lower than a second preset threshold. The fluid recirculates from inside the housing 2 towards the inlet passage 11 to be supplied back into the inside of the housing 2, but mixed with the nitrogen gas supplied by the inert gas supply device 4.

[0155] Figure 3 The inerting system is shown, such as in Figure 1The fluid injection device 10 of the inerting system shown, that is, where the fluid injection device 10 is located inside the housing 2. In this embodiment, the fluid injection device 10 includes a main channel 7 and three distribution channels 8.1, 8.2, 8.3, and the three distribution channels 8.1, 8.2, 8.3 have their respective multiple injectors 9. In the embodiment of this figure, the regulating device is a restricting device 21 understood as a bypass of the discharge channel 19, and this restricting device 21 is responsible for regulating the discharge of the fluid from the housing 2. The discharge channel 19 includes a channel loop 19.1, and this channel loop 19.1 starts at a point of the discharge channel 19 between the restricting device 21 and the first outlet 2.1 of the housing and ends at a point of the discharge channel 19 between the restricting device 21 and the outside of the aircraft 20. In this case, the safety valve 6 is located on the channel loop 19.1 of the discharge channel 19. Therefore, in the event of a failure of the safety valve 6, it is ensured that the restricting device 21 always remains operative. In the case of a sudden release of hydrogen, air or even nitrogen inside the housing 2 and the safety valve 6 not working, the restricting device 21 will always remain pressure - releasing and will avoid a continuous pressure increase in the housing, and this continuous pressure increase may cause other failures.

[0156] Figure 4 An embodiment of the inerting system is shown, where the fluid injection device 10 is located outside the housing 2 except for the injectors 9, and the injectors 9 pass through the second lateral wall 2.6 of the housing 2 in this case. In this embodiment, the main channel 7 and the distribution channels 8.1, 8.2, 8.3 are located outside the housing 2. Specifically, there are three rows of injectors 9, and each row corresponds to one of the distribution channels 8.1, 8.2, 8.3. According to the longitudinal direction X - X’, there is a first row of injectors 9 for injecting fluid into the free space between the first fuel cell 1.1 and the bottom 2.3 of the housing 2. The second row of injectors 9 is for injecting fluid into the free space between the first fuel cell 1.1 and the second fuel cell 1.2. The third row of injectors 9 is for injecting fluid into the free space between the second fuel cell 1.2 and the third fuel cell 1.3 of the stack of fuel cells 1. All these injectors 9 inject the fluid in the same direction, thus purging the fluid around the fuel cells.

[0157] Figure 4The embodiment further shows that the fuel cell system includes a Balance of Plant (BoP) system disposed inside the housing 2 and separated from the fuel cell 1. There is also free space around the BoP system. The BoP is a component of valves, pipes, and actuators, and there is space between different components. The fluid injected through the injector 9 also causes the removal of the fluid around the BoP system, causing the fluid to flow towards the first outlet 2.1 inside the housing 2, as indicated by the arrow. In practice, it has been observed that hydrogen accumulation may occur near the lower surface of the fuel cell 1. These accumulations can be reduced by injecting fluid into the free space between the fuel cells 1 and the free space between the fuel cell 1 and the bottom 2.3 of the housing 2, pushing these accumulations towards the first outlet 2.1. In this Figure 4 , oxygen particles and hydrogen particles have been represented as O2 and H2, respectively. The embodiment of this figure also shows that the discharge channel 19 protrudes into the housing 2 such that the first outlet 2.1 of the housing 2 is disposed at the end of the discharge channel 19 inside the housing 2. The arrangement of the last-mentioned oxygen particles, hydrogen particles, and a part of the discharge channel 19 inside the housing 2 is also shown for the Figure 5 embodiment to be explained below.

[0158] Figure 5 An embodiment of the inerting system is shown, where the fluid injection device 10 is also located outside the housing 2 in addition to the injector 9, and the injector 9 passes through the first side wall 2.5 and the second side wall 2.6 of the housing 2. In this embodiment, the main channel 7 and the distribution channels 8.1, 8.2, 8.3 are located outside the housing 2. There are three rows of injectors 9, each row corresponding to the distribution channels 8.1, 8.2, 8.3. According to the longitudinal direction X-X' of the fuel cell 1, there is a first row of injectors 9 disposed on the first side of the stack of fuel cells 1 for injecting fluid in a first direction towards the free space between the first fuel cell 1.1 and the bottom 2.3 of the housing 2. The second row of injectors 9 is disposed on the second side of the stack of fuel cells 1 opposite to the first side for injecting fluid in a second direction opposite to the first direction towards the free space between the first fuel cell 1.1 and the second fuel cell 1.2. Finally, there is a third row of injectors 9 disposed on the first side of the stack of fuel cells 1 for injecting fluid in the same first direction towards the free space between the second fuel cell 1.2 and the third fuel cell 1.3 of the stack of fuel cells 1. Each row of injectors 9 is located at a different height from the bottom 2.3 of the housing and alternates between the two opposite sides of the stack of fuel cells 1.

[0159] By Figure 5The configuration of the fluid injection device 10 shown, as indicated by the arrows, enables a wave flow or a serpentine flow around the fuel cell 1 through the free space, which clears the fluid inside the housing 2 towards the first outlet 2.1.

[0160] Figure 5 Also shown is that the fluid injection device 10 includes an additional distribution channel 8', which is connected to the main channel 7 and includes a plurality of additional injectors 9'. The additional distribution channel 8' is arranged above the bottom 2.3 of the housing 2 according to the longitudinal direction X-X', and the corresponding injectors 9' of the additional distribution channel 8' pass through the bottom 2.3. In this case, the additional injectors 9' inject the fluid in the direction from the bottom 2.3 to the top 2.4 of the housing 2 and inject through the free space provided between the stack of the fuel cell 1 and the second side wall 2.6 of the housing 2.

[0161] Figure 6 An embodiment of the inerting system is shown, in which the fluid injection device 10 is also located outside the housing 2 in addition to the injectors 9, and the injectors 9 pass through both the first side wall 2.5 and the second side wall 2.6 of the housing 2. In this embodiment, the main channel 7 (not shown) and the distribution channels 8.1, 8.2, 8.3 are located outside the housing 2. There are three rows of injectors 9, each row corresponding to the distribution channels 8.1, 8.2, 8.3, and for the same free space, there are two rows of distribution channels 8.1, 8.2, 8.3 that are aligned with each other. According to the longitudinal direction X-X', there is a first row of injectors 9 arranged on the first side of the stack of the fuel cell 1 and the second side opposite to the first side. The injectors 9 located on the first side can inject the fluid into the free space between the first fuel cell 1.1 and the bottom 2.3 of the housing 2 according to the first direction. The injectors 9 located on the second side can inject the fluid into the free space between the first fuel cell 1.1 and the bottom of the housing 2 according to the second direction opposite to the first direction. This is also the same for the next two rows of injectors 9 in the free space between the first fuel cell 1.1 and the second fuel cell 1.2 and between the second fuel cell 1.2 and the third fuel cell 1.3.

[0162] For Figure 6 the embodiment, the fluid can be injected into the same free space from either the first side wall 2.5 or the second side wall 2.6 of the housing 2 as needed. In this case, the control device 13 is also configured to actuate the fluid injection device 10 such that the fluid injection device 10 selectively enables the regulating devices of each distribution channel 8.1, 8.2, 8.3.

[0163] Figure 6 Also from Figure 4Different perspectives show the balance of plant (BoP) system located behind the fuel cell 1.

[0164] For Figures 3 to 6 an embodiment, the inlet of the housing 2 corresponds to the injector 9.

[0165] Figure 7 The distribution channel 8.1 with multiple injectors 9 is shown. Each injector 9 includes an injection channel 9.1 and a nozzle 9.2. The injection channel 9.1 connects the distribution channel 8.1 with the nozzle 9.2, and the nozzle 9.2 includes a nozzle opening 9.2.1 for fluid outlet. Specifically, the cross-sectional area of the nozzle opening 9.2.1 is larger than the cross-sectional area of the injection channel 9.1 of the injector 9. This configuration is the same for all injectors 9. Additionally, the nozzle 9.2 includes an intermediate plate 9.2.2 that helps with the diffusion of the fluid.

[0166] Figure 8 An embodiment is shown in which the distribution channel 8.1 and its corresponding injectors 9 are included in a closed structure 14. The closed structure 14 includes a common outlet 14.1 that opens towards the housing 2 and a common space 14.2 located upstream of the common outlet 14.1. Additionally, the nozzle opening 9.2.1 of each injector 9 opens towards the common space 14.2.

[0167] Method for inerting a fuel cell system of an aircraft

[0168] The present invention also provides a method for inerting the fuel cell system of an aircraft 20 by means of an inerting system. An example of a method for inerting the housing 2 of the fuel cell 1 in the aircraft 20 is explained below, where the inerting is performed by any of the inerting systems described above with respect to Figure 1 and Figure 6 the inerting system.

[0169] The method includes a first step (a) of supplying nitrogen to the fluid injection device 10 by means of an inert gas supply device 4. The control device 13 controls the operation of an inlet valve 5 for regulating the flow rate of the nitrogen supplied towards the fluid injection device 10 through the inlet channel 11, that is, for regulating m a If it is the first time to generate an inert fluid in the housing 2, the inlet valve 5 will be opened to its maximum flow rate to allow for rapid inerting of the housing 2, and in this case, m a is the same as m in

[0170] Specifically, in this step (a), the nitrogen supplied by the supply device 4 is injected into the interior of the housing 2 towards the free space between the fuel cells 1 and the free space between the bottom 2.3 of the housing 2 and the fuel cells 1. This fluid injection is performed by the fluid injection device 10.​

[0171] During the inerting process, there must not only be a fluid inlet but also a fluid outlet inside the housing 2, such that there is a continuous fluid flow through the housing 2. To this end, the method includes the step (b) of discharging a part of the fluid contained inside the housing 2 through the first outlet 2.1 of the housing 2. The control device 13 also controls the operation of the outlet valve 6 for regulating the outlet flow rate from the housing 2, that is, for regulating m out The control device 13 controls the operation of both the inlet valve 5 and the outlet valve 6 such that there is always fluid flowing through the housing 2, thereby maintaining m a equal to m out in balance.

[0172] In an embodiment of the inerting system as shown in Figure 2 and during inerting, the method also monitors the oxygen concentration and the hydrogen concentration inside the housing 2 according to step (c). This monitoring is performed by means of a sensing device 12 that continuously measures these concentrations.

[0173] Based on the data measured by the sensing device 12, the control device 13 determines whether a part of the fluid contained in the housing 2 can be recycled through the fluid recycling system S. That is, according to step (d) of the method, if the control device 13 determines that the oxygen concentration and / or the hydrogen concentration of the fluid inside the housing 2 is lower than a second preset threshold, the control device 13 controls the recycling of a part of the fluid located inside the housing 2. That is, the recycling system S starts to operate.

[0174] While inerting is being performed, if the control device 13 determines that fluid recycling can be performed, the compressor 16 is operated to pump the fluid from the inside of the housing 2, that is, to pump m c , along the recycling conduit 18. Then the recycling valve 17 is controlled to regulate the passage of the recycled fluid to the mixer 15. During fluid recycling, the inlet valve 5 is controlled to reduce m a , for the purpose of compensating for some of the nitrogen in the nitrogen that is not supplied by the recycled fluid. In the case of recycling, m a +m c is equal to m in .

[0175] In this inerting method, there is also a step of monitoring the pressure inside the housing 2 by a pressure measuring device (not shown), and the pressure measuring device communicates data with the control device 13. If the control device 13 determines based on the data (measured pressure) provided by the pressure measuring device that the pressure inside the housing 2 exceeds a preset pressure threshold, the first outlet valve 6 is opened at a flow rate higher than a preset flow rate threshold to discharge the pressure from the housing 2. At the same time, the inlet valve 5 can also be opened at a flow rate higher than a preset flow rate threshold to supply nitrogen to the fluid injection device 10, so as to inject the fluid into the housing 2 until the pressure in the housing 2 reaches the same pressure as the pressure outside the aircraft 20. The preset pressure threshold and the preset flow rate threshold can vary according to the configuration of the housing and the fuel cell system.

[0176] In addition, if the control device 13 determines that the hydrogen concentration and / or oxygen concentration inside the housing 2 exceeds a third preset threshold, both the inlet valve 5 and the first outlet valve 6 are opened at a flow rate higher than a preset flow rate threshold. This is to quickly purge the fluid contained in the housing 2 until the hydrogen concentration and oxygen concentration in the housing 2 reach below a second preset threshold. In an example, the third preset threshold is a hydrogen volume concentration of 0.75% and an oxygen volume concentration of 2%.

[0177] In addition, the method includes the following steps: extinguishing a fire inside the housing 2 when a fire detection device of the inerting system detects a fire inside the housing 2. For example, to initiate a fire, there must be an air supply leak inside the housing 2, an overpressure inside the housing 2, and a small amount of hydrogen leak. All of these can trigger a fire, thereby locally consuming a part of the oxygen located inside the housing 2. Although the hydrogen fuel cell 1 is turned off at the moment of fire occurrence, there is always residual hydrogen in the pipeline of the fuel cell 1.

[0178] To extinguish the fire in the housing 2, both the inlet valve 5 and the first outlet valve 6 are opened at the maximum flow rate to quickly discharge the affected fluid inside the housing 2 and generate a new inerted fluid. Specifically, the first outlet valve 6 is first opened to flush oxygen and / or hydrogen, but the pressure in the housing 2 increases due to the fire. Then, the inlet valve 5 is fully opened to smother the fire, aiming to obtain a lower oxygen concentration and hydrogen concentration inside the housing 2. In an embodiment, when the inerting system is operated to have extinguished the fire inside the housing 2 as described above, the oxygen concentration drops below 4%. Therefore, when the volume concentration of oxygen is below 4%, a fire cannot occur stably inside the housing 2. In an embodiment, according to the safety policy restrictions for fire extinguishing, the flammability limit for the hydrogen concentration is 4%, and the flammability limit for the oxygen concentration is 4%.

[0179] The mass flow rate of nitrogen can be increased as required. This mass flow rate of nitrogen is related to the free volume of the enclosure and the time required to re-inert the enclosure in the event of a malfunction or fire inside the enclosure.

Claims

1. An inerting system, the inerting system being adapted to inert a fuel cell system of an aircraft (20), the fuel cell system comprising a set of fuel cells (1), the fuel cells (1) being stacked adjacent to each other along a longitudinal direction X-X' and having a free space between consecutive fuel cells (1); The inerting system comprises: a housing (2) adapted to receive the set of fuel cells (1) such that there is also free space between each fuel cell (1) and the housing (2), the housing (2) including a bottom (2.3), a top (2.4) and a plurality of lateral walls (2.5, 2.6) extending between the bottom (2.3) and the top (2.4) along the longitudinal direction X-X', the housing further including a first outlet (2.1) configured to connect the interior of the housing (2) to the exterior of the aircraft (20); an inert gas supply device (4) configured to supply inert gas; a fluid injection device (10) fluidly connected to the inert gas supply device (4) via an inlet channel (11) and configured to inject a fluid containing at least a portion of inert gas into the housing (2); and a fluid regulating device configured to regulate the flow rate of the fluid containing at least a portion of inert gas; wherein, the first outlet (2.1) of the housing (2) is arranged above the stack of fuel cells (1) along the longitudinal direction X-X'; and the fluid injection device (10) includes: a main channel (7) connected to the inlet channel (11), and at least two distribution channels (8.1, 8.2, 8.3) connected to the main channel (7) and distributed at different heights along the longitudinal direction X-X'; and each distribution channel (8.1, 8.2, 8.3) includes a plurality of injectors (9) distributed along the distribution channel (8.1, 8.2, 8.3) and configured to inject fluid into the free space between two fuel cells (1) or into the free space between a fuel cell (1) and the housing (2).

2. The inerting system according to the preceding claim, wherein, The fluid injection device (10) is located outside the housing (2) such that the injectors (9) of each distribution channel (8.1, 8.2, 8.3) pass through the housing (2) for injecting fluid into the interior of the housing (2).

3. The inerting system according to claim 1, wherein, The fluid injection device (10) is located inside the housing (2) such that the inlet channel (11) passes through the housing (2) to the fluid injection device.

4. The inerting system according to any one of the preceding claims, wherein, the fluid injection device (10) further includes an additional distribution channel (8') connected to the main channel (7) and including a plurality of additional injectors (9') arranged along the additional distribution channel (8'), and the additional injectors (9') are configured to inject fluid from the bottom (2.3) of the housing (2) towards the top (2.4) of the housing (2) into the interior of the housing (2) along the longitudinal direction X-X'.

5. The inerting system according to any one of the preceding claims, wherein, the distribution channels (8, 8.1, 8.2, 8.3) are arranged on the same side of the stack of the fuel cell (1), and the injector (9) is configured to inject fluid from one side wall (2.5) of the housing (2) towards the opposite side wall (2.6) of the housing (2) in the same first direction.

6. The inerting system according to any one of claims 1 to 4, wherein, At least, the first distribution channels (8.1, 8.2, 8.3) and the corresponding injectors (9) are arranged on a first side of the stack of the fuel cell (1) such that the injector (9) is configured to inject fluid in a first direction through a first free space between two fuel cells (1) or between the fuel cell (1) and the housing (2), and the second distribution channels (8.1, 8.2, 8.3) and the corresponding injectors (9) are arranged on a second side of the stack of the fuel cell (1) different from the first side such that the injector (9) is configured to inject fluid in a second direction different from the first direction through a second free space continuous with the first free space.

7. The inerting system according to any one of the preceding claims, wherein, Each injector (9) includes an injection channel (9.1) and a nozzle (9.2), the nozzle (9.2) being oriented towards the interior of the housing (2) and opening into the interior of the housing (2), wherein the injection channel (9.1) is connected to the distribution channels (8.1, 8.2, 8.3) and the nozzle (9.2).

8. The inerting system according to the preceding claim, wherein, Each distribution channel (8.1, 8.2, 8.3) and its corresponding injector (9) are included in an enclosed structure (14), the enclosed structure (14) including a common outlet (14.1) opening into the housing (2) and a common space (14.2) located upstream of the common outlet (14.1), and wherein the nozzle opening (9.2.1) of each injector (9) opens into the common space (14.2).

9. The inerting system according to any one of the preceding claims, further comprising: a sensing device (12) configured to measure the oxygen concentration and hydrogen concentration of the fluid located inside the housing (2); and a control device (13) in data communication with the sensing device (12) and configured to independently control at least the fluid regulating device based on the oxygen concentration and hydrogen concentration inside the housing (2).

10. The inerting system according to the preceding claim further comprises a fluid regulation system (S), the fluid regulation system (S) being configured to recirculate a portion of the fluid located inside the housing (2) to the inlet channel (11) for supplying the recirculated fluid mixed with the inert gas to the inside of the housing (2) through the fluid injection device (10); wherein, The control device (13) is further configured to: independently control the fluid recirculation system (S) based on the oxygen concentration and hydrogen concentration measured by the sensing device (12); and initiate recirculation in the fluid recirculation system (S) when the oxygen concentration and / or hydrogen concentration of the fluid located inside the housing (2) is respectively lower than a first preset threshold.

11. The inerting system according to any one of the preceding claims, wherein, The fluid regulating device includes: an inlet valve (5) configured to regulate the supply of at least inert gas from the inert gas supply device (4) towards the fluid injection device (10); and A first outlet valve (6), the first outlet valve (6) being configured to regulate the outlet flow of fluid located inside the housing (2) through the first outlet (2.1).

12. An aircraft (20), the aircraft (20) comprising an inerting system according to any one of the preceding claims.

13. A method for inerting a fuel cell system by means of an inerting system, the inerting system comprising a fluid injection device (10), wherein:[[]] The fuel cell system is housed in a housing (2) and comprises a set of fuel cells (1), the fuel cells (1) being stacked adjacent to each other along a longitudinal direction X-X', and having free spaces between consecutive fuel cells (1) and between each fuel cell (1) and the housing (2); and The fluid injection device (10) comprises a main channel (7) and a plurality of distribution channels (8.1, 8.2, 8.3), the plurality of distribution channels (8.1, 8.2, 8.3) being connected to the main channel (7) and distributed at different heights along the longitudinal direction X-X', each distribution channel (8.1, 8.2, 8.3) comprising a plurality of injectors (9), the plurality of injectors (9) being distributed along each distribution channel (8.1, 8.2, 8.3) and being configured to inject fluid into the free space between two fuel cells (1) or into the free space between the fuel cell (1) and the housing (2); wherein the method comprises: (a) Supplying an inert gas to the fluid injection device (10) by means of an inert gas supply device (4); and (b) Discharging a part of the fluid located inside the housing (2) through the first outlet (2.1); wherein, in step (a), at least the inert gas supplied by the supply device (4) is injected into the interior of the housing (2) through the injectors (9) towards the free space between the fuel cells (1) and / or the free space between the fuel cell (1) and the housing (2).

14. The method according to the preceding claim, further comprising: (c) Monitoring the oxygen concentration and the hydrogen concentration inside the housing (2) by means of a sensing device (12); (d) Recycling a part of the fluid located inside the housing (2) by means of a fluid recycling system (S) of the inerting system when the hydrogen concentration and / or the oxygen concentration of the fluid to be recycled is lower than a second preset threshold; and Injecting the recycled fluid mixed with pure inert gas into the interior of the housing (2) through the fluid injection device (10).

Images