Patent Description:
In the context of aviation, modules may be defined as airborne equipment anchored to a dedicated point on the aircraft's structure. Mainly used in the military field, they can provide different functions such as extension of the fuel capacity or weapons and external sensors carriage. On the Clip-Air project, presented by the École Polytechnique Fédérale de Lausanne in June <NUM>, modules could even represent independent cabins to transport passengers.

It is further known from the prior art to provide "electro-propulsive modules" distributed along a wingspan of an aircraft wing wherein the propulsion modules are embedded within the wing structure and only a hydrogen storage is removable. It is also known from the prior art to have propulsion modules wherein a wing structure is built around the modules with merged fairings.

<CIT> discloses a pod for moving a vehicle and also provides a network of interchangeable pods. The pod includes an energy storage and powering machine and a nacelle. The nacelle includes an enclosure for surrounding the energy storage and powering machine and a joining structure for attaching the enclosure to the vehicle. The energy storage and the powering machine include a power generation module, a propulsion module, and an electronics module. The propulsion module includes an electric motor with a propeller module. The electronics module is provided for activating the power generation module to provide electrical energy to the electric motor, wherein the electric motor actuates the propeller module for moving the vehicle.

It is the object of the present invention to at least partially overcome the problems associated with the prior art. It is a particular object of the present invention to provide a hydrogen-fuelled, electrically driven aircraft of the above-described type exhibiting an improved operational safety.

The object is achieved by the subject-matter of the independent claims. Advantageous embodiments can be found, e.g., in the dependent claims and/or in the description.

The object is achieved by an aircraft propulsion module, comprising at least.

In general, the removable propulsion module provides an independent, autonomous, and removable part ("module") for thrust generation which, in principle, can be adapted on any aircraft. In particular, the propulsion module is not embedded in the wing or the fuselage of the aircraft but can be added to the aircraft structure, e.g., a wing, by means of a simple fastening interface. In particular, the removable propulsion module comprises all means for aircraft propulsion and only needs to be mechanically attached to the aircraft (e.g., by at least one fastening means) and, potentially, can be brought in data communication with the aircraft (e.g., by being equipped with a wired and/or a wireless communication interface) to receive data for its operation and potentially to feedback status data like a fuel level, possible defects, etc..

The hydrogen storage system may be adapted to store gaseous, liquid and/or solid hydrogen. The hydrogen storage system may comprise at least one hydrogen storage unit for physically storing hydrogen, e.g., a hydrogen tank for storing gaseous and/or liquid hydrogen, a dedicated material (e.g., metal hydride, porous carbon, etc.) for chemical or physical solid hydrogen storage, etc. The hydrogen storage system may further comprise a housing for the at least one hydrogen storage unit. The hydrogen storage system may further comprise or be connected to at least one piping network dedicated to supply the at least one electrochemical converter with hydrogen coming from the hydrogen storage unit and/or at least one piping network which allows for external hydrogen refuelling on ground without having to dismount it from the propulsion module (also called "pod") using the dedicated piping network.

In an embodiment, the electrochemical converter comprises at least one fuel cell.

The electric motor is supplied with electric energy from the electrochemical converter. In an embodiment, the electric motor is connected to and thus drives at least one propeller or at least one ducted fan, or even other propulsion means.

It is an embodiment that the propulsion module comprises at least one further means ("electric load") using or storing the electric energy generated by the electrochemical converter. Such an electric load may, for example, include at least one further electric motor (e.g., for moving retractable vortex generators), at least one electric actuator of the separation means (which may also be an electric motor), at least one electric or electronic control means, at least one voltage / current converter, at least one valve, at least one electric switch and/or at least one lamp, etc. It is an embodiment that at least one voltage / current converter is a DC/DC converter, an AC/DC converter, and/or a DC/AC converter. The at least one electric or electronic control means may comprise or be at least one control unit adapted to control operation of at least one of the components of the propulsion module, especially an energy, power, and/or torque management unit, etc. The at least one electric or electronic control means may comprise a microcontroller, ASIC, FPGA, and/or a data communication interface, e.g., an ethernet interface, etc..

It is an embodiment that the propulsion module further comprises at least one electric energy storage unit comprising or being, e.g., at least one rechargeable battery, and/or at least one super capacitor (e.g., a gold cap), etc. This gives the advantage that the at least one electric load of the propulsion module can be supplied with electric energy even if the electrochemical converter generates not enough power (e.g., during peak demand) or is faulty. This also enhances operational safety. In an embodiment, the electric energy storage unit is electrically connected to the electrochemical converter. This gives the advantage that the electric energy storage unit can be charged in flight if the electric power generated by the electrochemical converter is greater than the electric power used by the other components.

Operation of the propulsion module under normal conditions (i.e., without component failure) may comprise at least one operational phase out of the following group of phases:.

It is an embodiment that the propulsion module further comprises at least one cooling system. The cooling system may be an active and/or a passive cooling system (or any other form of cooling) and may, in case of an active cooling system, thus also regarded to be an electric load. The cooling system may comprise a heat exchanger.

The first part and the second part can be separated / disconnected from each other, e.g., by actuation of a separation means and/or during maintenance.

The first part comprises the power generating function(s) of the propulsion module. To this effect, the first part comprises at least the at least one electrochemical converter and the at least one electric motor. This gives the advantage that maintenance of components of the first part can be carried out separately from refilling which saves time. The first part may also comprise the electric energy storage unit and the cooling system.

The fairing of the first part gives the advantage that it reduces drag penalty, in particular if the first part is a front part located in front of a wing profile (see also below). Advantageously, the shape of the fairing of the first part is continuous with the wing profile at the contact area, i.e., there are no sharp changes at the transition between the fairing of the first part and the wing profile. Also, the fairing protects the components located in the first part from external damages. In an embodiment, a thrust vector of the propulsion module is aligned with the chord of the wing.

In an embodiment, the first part comprises a support in form of a frame, that is surrounded by the fairing. Fixed / attached to the frame is at least one of the components of the first part, e.g., the at least one electric motor, the at least one electric energy storage unit, and/or the at least one electrochemical converter. Other components of the first part like the cooling system etc. may also be attached / fixed to the frame.

The second part comprises the hydrogen storage system. To this effect, the second part may comprise at least one hydrogen storage unit in its fairing, e.g., a hydrogen tank, and optionally at least one piping network. Its fairing protects the hydrogen storage unit from external damages. The fairing may also create a mechanical link between the wing and the hydrogen storage unit without having to modify the hydrogen storage unit. This is particularly advantageous if an off-the-shelf hydrogen storage unit is used, e.g. an off-the-shelf reusable hydrogen bottle. This in particular reduces the time and tools required to change the hydrogen storage unit with a functional one and/or with a full one.

It is an embodiment that the hydrogen storage unit can be removed from its hydrogen storage unit housing during maintenance operation and be replaced by another similar hydrogen storage unit in case the initial one was malfunctioning. It is an embodiment that this replacement can be done with hydrogen storage unit in any state between full and empty.

In an embodiment, the fairing of the second part can be a hydrogen storage unit housing. This hydrogen storage unit housing may comprise two parts, namely a core and a cap. The core is preferably cylindrical (not necessarily presenting a circular cross-section), one end being open, and the other end presenting a shape matching with one of the hydrogen storage unit's extremities. This end is holed / has a hole to allow a head of the hydrogen storage unit (e.g., a bottle head) to be accessed when the hydrogen storage unit is positioned in the housing. The cap may be cylindrical, one end being open, and the other end being closed. The closed end may comprise drilled holes so that air can circulate, therefore preventing hydrogen accumulation in an enclosed environment.

The hydrogen storage unit may be slid in the core through the open end of the core until the surface of the hydrogen storage unit is in contact with the end of the housing. By now, the hydrogen storage unit's head may, e.g., be sticking out of the hydrogen storage unit housing and can be connected to at least one piping network, in particular of the first part.

When the hydrogen storage unit is inserted into the housing, the cap can be fixed on the core and holds the hydrogen storage system in place.

Alternatively, the hydrogen storage unit housing and the fairing may be two separate parts, wherein the fairing surrounds the housing, e.g., for aerodynamical reasons. In this case, the housing may be attached to the wing and holds the hydrogen storage unit as well as the fairing. Alternatively, the fairing may be attached to the wing and holds the hydrogen storage unit as well as the housing.

In an embodiment, the first part comprises a frame to which the at least one electrochemical converter, the at least one electric motor and the second part, in particular its hydrogen storage housing, are attached.

In an embodiment, the hydrogen storage housing comprises a core and a cap, one end of the core being an open end for inserting the hydrogen storage unit and the other end comprising a hole allowing a head of the hydrogen storage unit to be accessed.

In an embodiment, the cap comprises holes, e.g., drilled holes, to prevent hydrogen accumulation.

In an embodiment, the hydrogen storage housing is adapted to attach the aircraft propulsion module to a wing of an aircraft.

In an embodiment, the hydrogen storage housing is the fairing of the second part.

In an embodiment, the hydrogen storage system comprises at least one piping network adapted to refill the hydrogen storage unit when the hydrogen storage unit is positioned in the hydrogen storage housing.

Regarding the link between the hydrogen storage unit housing or fairing and the wing, a rail may be fixed on the outer side of the storage system's fairing, parallel to the axis of revolution of the cylinder, it presents one or several side rods. A part with respective tracks carved in it may be mounted on the wing. When needed, the hydrogen storage unit housing rail can be slid in the track to fix the hydrogen storage unit housing to the wing. The rail may have a specific shape such that the hydrogen storage unit housing cannot drop due to gravity. Movements may be limited by locks or track ends. For example, one of the following alternative lock systems may be used:.

The first part and second part are connected via at least one fluid connection line (e.g., a feeding pipe / tube for flowing hydrogen fluid from the second part to the first part). Electric connection lines may be connected to different electronics of the first and/or second part of the module, e.g., for monitoring purposes. Mechanical connection lines may be mechanically connected to certain components and may, e.g., be thin metal wires, plastic cables etc. In the following, fluid connection lines (e.g., for supplying hydrogen), electric connection lines (e.g., for supplying voltage, sending electrical signals, and/or data communication) and mechanical connection lines (e.g., of a components separation means) may collectively called connection lines or "channels".

If the electric motor for generating thrust is connected to a front-side propeller, the first part may be a front part and the second part is a rear part positioned aft of the front part. This enables a particularly compact design.

It is an embodiment that the first part is attached to the second part and/or to the wing. It is an embodiment that the second part is attached to the first part and/or to the wing. If the second part is attached to the wing, it may be positioned underneath the wing profile. It is an embodiment that the first part is only attached to the second part, and the second part is attached to the wing. It is an embodiment that, in this case, the first / front part can be separately dismounted while keeping the second / rear part on the aircraft. It is an embodiment that, in order to dismount the second part of the aircraft, the first part has to be taken out too. It is an embodiment that the hydrogen storage unit can be dismounted from the second part without having to dismount the first part nor the rear part fairing / housing from the wing.

The above-described features and advantages of the invention as well as their kind of implementation will now be schematically described in more detail by at least one embodiment in the context of one or more figures.

<FIG> shows a cross-sectional side view of one possible embodiment of the propulsion module <NUM>, <NUM>.

To reduce costs and maintenance procedures, the propulsion module <NUM>, <NUM> is divided in several parts.

A first part <NUM>, presenting the power generating part, is attached to a wing (profile) W of an aircraft A to align the thrust vector with the chord of the wing W. It comprises a frame <NUM> surrounded by a fairing <NUM> to reduce drag penalty. Fixed / attached to the frame <NUM> are at least a propulsive device <NUM> (for example, without loss of generality, a motor / engine / fan), a battery <NUM>, an electrochemical converter in form of a fuel cell <NUM>, and a cooling system <NUM>. Other components may also be fixed to the frame.

A second part <NUM>, which may be placed underneath the wing W, as shown, hosts a hydrogen storage system <NUM> in a fairing <NUM>. This fairing <NUM> protects the hydrogen storage system <NUM> from external damages. It also creates a link between the wing W and the storage system <NUM> without having to modify the storage system <NUM>. This is particularly advantageous if the storage system <NUM> uses an off-the-shelf, reusable hydrogen storage unit <NUM>, e.g., a hydrogen bottle.

Both parts <NUM> and <NUM> are connected at least via a connection line in form of a feeding channel <NUM> exchanging hydrogen fluid between the first part <NUM> and the second part <NUM>. At least one channel may be connected to different elements of the first part <NUM> and/or second part <NUM> of the module, e.g., for monitoring purposes.

Operation of the module <NUM>, <NUM> may comprise at least one out of the group comprising the following five phases:.

The connection between the first part <NUM> of the propulsion module <NUM>, <NUM> and the wing should be as compact as possible to reduce the frontal area of the module and thus the drag penalty. In one embodiment, notches may be provided in the wing W to access a wing spar, which makes attachment easier. This embeds the module <NUM>, <NUM> in the wing W, therefore reducing the frontal area.

When the module <NUM>, <NUM> generates thrust for the aircraft A, the fastening system should be able to withstand and transfer important loads to the structure. Offsets of the centre of gravity and thrust vectors create torques that should be reacted to as well.

This attachment system should be suitable for every spanwise position, accommodating chord and thickness variations as well as twists and dihedral angles.

As shown in <FIG>, the hydrogen storage system <NUM> may comprise a hydrogen storage unit housing <NUM> for accommodating the hydrogen storage unit <NUM>. The hydrogen storage unit housing <NUM> comprises two parts, namely a core <NUM> and a cap <NUM>. The core <NUM> is cylindrical (not necessarily presenting a circular cross-section), one end <NUM> being open and the other end <NUM> presenting a shape matching with the hydrogen storage unit's extremities. The end <NUM> is holed to allow a head <NUM> of the hydrogen storage unit <NUM> (e.g., a bottle head) to be accessed when the hydrogen storage unit <NUM> is positioned in the housing <NUM>.

The cap <NUM> is cylindrical, one end <NUM> being open and the other end <NUM> being closed. The end closed end <NUM> comprises holes <NUM> so that air can circulate preventing hydrogen accumulation in an enclosed environment.

To store the hydrogen storage unit <NUM> in the housing <NUM>, it is slid into the core <NUM> through the open end <NUM> with its <NUM> first until the surface of the hydrogen storage unit <NUM> comes in contact with the end <NUM> of the core <NUM>. By now, the hydrogen storage unit's head <NUM> is sticking out of the core <NUM> and can be connected to supplying and feeding piping network <NUM>. Then, the cap <NUM> can be fixed to the core <NUM> at its open end <NUM>, e.g., by screwing it on, and holds the hydrogen storage unit <NUM> in place.

The hydrogen storage unit housing <NUM>, in particular its core <NUM>, comprises an attachment means, e.g., a rail <NUM>, to create a link with the wing W (see also <FIG>). The rail <NUM> is fixed on the outer side of the core <NUM>, parallel to the axis of revolution of the cylindrical core <NUM>, comprising one or more laterally protruding rode ("side rods") <NUM>. A component <NUM> with at least one track <NUM> carved in it is mounted on the wing W. When needed, the hydrogen storage unit housing rail <NUM> can be slid in the track <NUM> to fix the core <NUM> of hydrogen storage unit housing <NUM> to the wing W. The rail <NUM> has a specific shape so that the hydrogen storage unit housing <NUM> cannot drop due to gravity. Movements are limited by locks and/or track ends. For example, one of the following alternative lock systems may be used:.

Claim 1:
An aircraft propulsion module (<NUM>, <NUM>) comprising
- a hydrogen storage system (<NUM>),
- at least one electrochemical converter (<NUM>) connected to the hydrogen storage system, wherein the at least one electrochemical converter is adapted to convert hydrogen supplied from the hydrogen storage system into electric energy, and
- at least one electric motor (<NUM>) electrically connected to the at least one electrochemical converter, wherein the electric motor is adapted to generate thrust;
wherein
- the propulsion module comprises a first part (<NUM>) and a second part (<NUM>), each of which comprise a respective fairing (<NUM>, <NUM>);
- the first part and the second part are separable from each other;
- the first part comprises the at least one electrochemical converter and the at least one electric motor; and
- the second part comprises a hydrogen storage housing (<NUM>, <NUM>) of the hydrogen storage system for storing a reusable hydrogen storage unit (<NUM>).