Patent Description:
Modern "more-electric aircraft/engine" (MEA/MEE) architectures need advanced hybrid electric propulsion and electric power generation capabilities to meet the ever-increasing on-board electric power demand.

During an emergency event (e.g., main/auxiliary power-loss), a ram air turbine (RAT) can be deployed into a free airstream below an aircraft's fuselage. The RAT generates power from the airstream by ram pressure recovery due to the forward speed of the aircraft. The power generated by the RAT can be used to generate electricity to support vital on-board systems, such as flight controls, hydraulics, flight-critical instrumentation, communications, etc. Some RATs produce only hydraulic power but most modern RATs are coupled to an efficient compact electric generator. The power output of a typical RAT is about <NUM> kW. Increased power output is possible with larger RAT blades diameter, increased number of blades, optimized blades airfoils cross-sections, etc..

Due to the intermittent use of a RAT, such as during rare events like emergency power-loss, and a desire to optimize the RAT's size and weight envelope, the RAT may not be optimized for modern and future MEA electric power on-board needs during an emergency.

Systems of the prior art are disclosed by <CIT> and <CIT>.

According to an aspect of the disclosure, an electricity generation and hybrid-electric propulsion system of an aircraft is provided as defined by claim <NUM>.

In embodiments, the RAT device is deployed during a power-loss event to be operable as the RAT.

In embodiments, the RAT device is deployed during take-off or an engine power-loss event to be operable as a forward thrust generating propulsor.

In embodiments, the RAT device is deployed during landing to be operable as a braking thrust generating propulsor.

In embodiments, the system is provided as an auxiliary power unit in a tail end of the fuselage.

In embodiments, the system further includes an alternating current AC/AC converter electrically interposed between the motor-generator and the electric generator and a converter, a battery and an inverter in parallel with the AC/AC converter and electrically interposed between the motor-generator and the electric generator.

In embodiments, the RAT device includes first and second RAT devices at starboard and port sides of the fuselage, respectively, first and second retracting pylons by which the first and second RAT devices are selectively deployable, respectively, from respective stowed positions and first and second power cables by which the hybrid-electric power generation system is electrically connected to the first and second RAT devices, respectively.

In embodiments, each of the first and second RAT devices includes a propfan having blades with swept profiles.

In embodiments, each of the first and second RAT devices is operable in a forward rotational direction to generate forward propulsor thrust.

In embodiments, each of the first and second RAT devices is operable in a reverse pitch angle to generate braking propulsor thrust.

According to an aspect of the disclosure, a method of operating an electricity generation and propulsion system of an aircraft is provided as defined by claim <NUM>.

In embodiments, the RAT device includes first and second RAT devices at starboard and port sides of the aircraft, respectively.

In embodiments, the method further includes stowing the RAT device in an aircraft fuselage and deploying the RAT device from the aircraft fuselage to an exterior of the aircraft fuselage.

In embodiments, the result of the determining is affirmative in an event the current condition of the aircraft is a power-loss event and the result of the judging is that the operating includes operating the RAT device as the RAT, upon deployment, during the power-loss event.

In embodiments, the result of the determining is affirmative in an event the current flight regime of the aircraft is take-off or in an event the current condition of the aircraft is an engine power-loss event and the result of the judging is that the operating includes operating the RAT device as a forward thrust generating propulsor, upon deployment, during the take-off or the engine power-loss event.

In embodiments, the result of the determining is affirmative in an event the current flight regime of the aircraft is landing and the result of the judging is that the operating includes operating the RAT device as a braking thrust generating propulsor, upon deployment, during the landing.

According to an aspect of the disclosure, an aircraft is provided as defined by claim <NUM>.

In embodiments, the RAT devices are each operable as a RAT when deployed into an airstream that drives rotations of the RAT from which the hybrid-electric power generation system generates electricity and the RAT devices are each operable as a forward thrust generating propulsor when deployed during take-off or during an engine power-loss event and driven by the hybrid-electric power generation system.

As will be described below, a RAT is provided for use with a modern MEE/MEA aircraft and is optimized by being integrated into an on-board hybrid-electric propulsion system.

With reference to <FIG> and <FIG>, an aircraft <NUM> is provided. The aircraft <NUM> includes on-wing engine assemblies <NUM>. Each of the on-wing engine assemblies <NUM> can have, but are not required to have, an absence of thrust-reversers that would normally be present to facilitate a reduction in aircraft <NUM> velocity during landing. In addition, the aircraft <NUM> includes a fuselage <NUM>, a hybrid-electric power generation system <NUM> (see <FIG>) that is operably disposed in a tail end <NUM> of the fuselage <NUM> and ram air turbine (RAT) devices <NUM>. The RAT devices <NUM> are each coupled with the hybrid-electric power generation system <NUM>, and which are each stowable in the fuselage <NUM> and deployable to an exterior of the fuselage <NUM>. The RAT devices <NUM> are each operable in multiple modes given a current flight regime and a current condition of the aircraft <NUM>.

For example, in a case in which the on-wing engine assemblies <NUM> have an absence of thrust-reversers or insufficient thrust-reversion (i.e., the on-wing engine assemblies <NUM> lack thrust-reversers entirely or the on-wing engine assemblies <NUM> have thrust-reversers that are inoperative or insufficient to reduce a velocity of the aircraft <NUM> alone), each of the RAT devices <NUM> can be operated as a braking thrust generating propulsor when deployed during a landing of the aircraft <NUM> and when driven by the hybrid-electric power generation system <NUM> to reduce a velocity of the aircraft <NUM>. Actually, each of the RAT devices <NUM> can be operated as the braking thrust generating propulsor when deployed during the landing of the aircraft <NUM> and when driven by the hybrid-electric power generation system <NUM> to reduce a velocity of the aircraft <NUM> whether the on-wing engine assemblies <NUM> have the absence of thrust-reversers or not. In the latter case, each of the RAT devices <NUM> can be operated as the braking thrust generating propulsor when deployed during the landing of the aircraft <NUM> in order to supplement or provide redundancy for the thrust-reversers of the on-wing engine assemblies <NUM>.

In addition, the RAT devices <NUM> are each operable as a RAT when deployed into an airstream that drives rotations of the RAT from which the hybrid-electric power generation system <NUM> generates electricity. Also, the RAT devices <NUM> are each operable as a forward thrust generating propulsor when deployed during take-off or during an engine power-loss event and driven by the hybrid-electric power generation system <NUM>. In these or other cases, the RAT devices <NUM> are capable of electrically modulating propulsor blade angles to optimally absorb energy from a free air stream to in turn drive rotations of the RAT from which the hybrid-electric power generation system <NUM> generates electricity. The RAT devices <NUM> can also electrically modulate propulsor blade angles to optimally create thrust when being operable as a propulsor when deployed and driven by the hybrid-electric power generation system <NUM>. The RAT devices <NUM> are also capable of electrically modulating the propulsor blades in a reverse pitch direction to generate braking propulsor thrust.

With continued reference to <FIG> and with additional reference to <FIG>, an electricity generation and propulsion system <NUM> of an aircraft, such as the aircraft <NUM>, is provided. The electricity generation and propulsion system <NUM> includes a fuselage <NUM>, a hybrid-electric power generation system <NUM> that is operably disposed in a tail end <NUM> of the fuselage <NUM> and a RAT device <NUM>. The hybrid-electric power generation system <NUM> can be provided as an auxiliary power unit (APU) in the tail end <NUM> of the fuselage <NUM>. The RAT device <NUM> is coupled with (i.e., electrically connected with) the hybrid-electric power generation system <NUM>. The RAT device <NUM> is stowable in the fuselage <NUM> and is selectively deployable to an exterior of the fuselage <NUM>.

In an exemplary case, such as when there is a power-loss event on the aircraft <NUM>, the RAT device <NUM> can be operable as a RAT by being selectively deployed into an airstream so that the airstream drives rotations of the RAT from which the hybrid-electric power generation system <NUM> generates electricity. In another exemplary case, such as during take-off of the aircraft <NUM> or during an engine power-loss event, the RAT device <NUM> can be operable as a forward thrust generating propulsor by being selectively deployed and while being driven in a forward rotational direction by the hybrid-electric power generation system <NUM>. In yet another exemplary case, such as during landing of the aircraft <NUM>, the RAT device <NUM> can be operable as a braking thrust generating propulsor by being selectively deployed with propulsor blades in a reverse pitch direction to thereby generate braking thrust while being driven by the hybrid-electric power generation system <NUM>.

As shown in <FIG>, the hybrid-electric power generation system <NUM> includes a first drive shaft <NUM> and a second drive shaft <NUM>, a gas turbine engine <NUM> that is disposed on the first drive shaft <NUM>, a motor-generator <NUM> that is disposed on the first drive shaft <NUM>, a power turbine <NUM> and an electric generator <NUM>.

The gas turbine engine <NUM> includes a compressor <NUM>, a combustor <NUM> and a compressor turbine <NUM>, all of which are operably disposed on the first drive shaft <NUM>. Air is compressed in the compressor <NUM> and compressed air output from the compressor <NUM> is then provided to the combustor <NUM> or bled off for pneumatic/hybrid (electro-pneumatic) systems on-board the aircraft <NUM>. Within the combustor <NUM>, the compressed air is mixed with fuel and combusted to produce high-temperature and high-pressure working fluid that is expanded in the compressor turbine <NUM> to drive the first drive shaft <NUM> and in turn to drive the compressor <NUM> and the motor-generator <NUM>. Due to the compact/lightweight design of the gas turbine engine <NUM>, very high operational rotational speeds can be obtained, which can improve operational efficiency while keeping the overall weight/size to a minimum.

In addition, by providing the motor-generator <NUM> as an assist for the compressor <NUM>, the hybrid-electric power generation system <NUM> can increase a power output when necessary. This, in turn increases the power output of the power turbine <NUM> and as a result more output power is provided to the electric generator <NUM>.

The power turbine <NUM> can be a standard wound-field synchronous generator or other generator types (e.g., induction, permanent magnet or switched-reluctance generators). The power turbine <NUM> is receptive of exhaust from the gas turbine engine <NUM>. The electric generator <NUM> is drivable by the power turbine <NUM> via the second drive shaft <NUM>.

The hybrid-electric power generation system <NUM> can further include an alternating current AC/AC converter <NUM>, which is electrically interposed between the motor-generator <NUM> and the electric generator <NUM>, and a serial formation <NUM>, which is disposed in parallel with the AC/AC converter and which is also electrically interposed between the motor-generator <NUM> and the electric generator <NUM> and includes an AC/DC converter <NUM>, a battery <NUM> and a DC/AC inverter <NUM>. The AC/AC converter <NUM> can be a solid-state power converter that effectively controls an output speed of the hybrid-electric power generation system <NUM>. The AC/AC converter <NUM> can be a variable frequency-constant frequency (VF-CF) power converter or a converter of any other suitable architecture.

The electric generator provides electric power for the RAT device <NUM> as well as electric power for other on-board needs (e.g., electric accessories, etc.). In addition, where the electric power from the electric generator <NUM> flows through the AC/AC converter <NUM> to the motor-generator <NUM>, the motor-generator <NUM> can be used as a starter (reversed electric power flow) during initial engine start. The start can also be powered by the battery <NUM> and the DC/AC inverter <NUM>. To this end, the motor-generator <NUM> can be provided as an induction and/or a permanent magnet brushless motor that can be used as an inverter-fed electric motor coupled mechanically with the first drive shaft <NUM>.

Any additional electric power generated by the electric generator <NUM>, which is not immediately needed/consumed, can be stored in the battery <NUM>.

It is to be understood that the hybrid-electric power generation system <NUM> can quickly follow load variations, in seconds instead of in minutes, because a time constant of motor torque control is a fraction of second.

As shown in <FIG>, the RAT device <NUM> includes a first RAT device <NUM> at a starboard side of the fuselage <NUM> and a second RAT device <NUM> at a port side of the fuselage <NUM>, respectively, a first retracting pylon <NUM> and a second retracting pylon <NUM> and a first power cable <NUM> and a second power cable <NUM>. The first and second RAT devices <NUM> and <NUM> are selectively deployable from respective stowed positions in the fuselage <NUM> by the first and second retracting pylons <NUM> and <NUM>, respectively. The hybrid-electric power generation system <NUM> is electrically connected to the first and second RAT devices <NUM> and <NUM> by the first and second power cables <NUM> and <NUM>, respectively. In addition, each of the first and second RAT devices <NUM> and <NUM> includes a propfan <NUM>. The propfan <NUM> has blades <NUM> with swept profiles and with adjustable pitch angles (i.e., pitch angles that produce forward thrust and pitch angles that produce reverse thrust). Each of the first and second RAT devices <NUM> and <NUM> is operable in a forward rotational direction to generate forward propulsor thrust at an optimal angle to generate forward thrust or in a reverse pitch angle generate braking propulsor thrust.

With reference to <FIG>, a method of operating an electricity generation and propulsion system of an aircraft, such as the aircraft <NUM>, is provided. As shown in <FIG>, the method includes initially stowing a RAT device in an aircraft fuselage (<NUM>). The method also includes ascertaining a current flight regime and a current condition of the aircraft (<NUM>), determining whether to deploy a RAT device from the aircraft fuselage to an exterior of the aircraft fuselage in accordance with at least one of the current flight regime and the current condition of the aircraft (<NUM>) and deploying the RAT device from the aircraft fuselage to the exterior of the aircraft fuselage based on a result of the determining (<NUM>). In addition, the method includes judging whether to operate the RAT device, upon deployment, as one of a RAT and a propulsor in accordance with at least one of the current flight regime and the current condition of the aircraft (<NUM>) and then operating the RAT device as the one of the RAT and the propulsor based on a result of the judging (<NUM>).

In accordance with embodiments, the result of the determining of operation <NUM> can be affirmative to deploy in an event the current condition of the aircraft is a power-loss event and the result of the judging of operation <NUM> is that the operating of operation <NUM> includes operating the RAT device as the RAT, upon deployment, during the power-loss event. Likewise, the result of the determining of operation <NUM> can be affirmative to deploy in an event the current flight regime of the aircraft is take-off or an engine power-loss event and the result of the judging of operation <NUM> is that the operating of operation <NUM> includes operating the RAT device as a forward thrust generating propulsor, upon deployment, during the take-off or during the engine power-loss event. Similarly, the result of the determining of operation <NUM> can be affirmative in an event the current flight regime of the aircraft is landing and the result of the judging of operation <NUM> is that the operating of operation <NUM> includes operating the RAT device as a braking thrust generating propulsor, upon deployment, during the landing.

Technical effects and benefits of the present disclosure are the provision of an electric-hybrid propeller fan that is stowable in an aircraft and has the following capabilities and advantages: a capability to augment thrust power during critical flight phases (e.g., takeoff/climb, etc.); a capability for independent operation of the electric propfans using electrical power from the electric generator; the provision of electric fans providing thrust reverse; the provision of a high fan bypass ratio with smaller gas turbine cores required for cruise sizing; a capability to "freewheel" the electric propfans in a "RAT"-style mode to help turn electric motor and provide electric power; a compact EM-driven contra-rotating PM motor-driven rotary propulsion system and a capability to achieve fast response to sudden fluctuations (fast transients) in load. In addition, at high ambient temperature conditions, an output of a gas turbine engine tends to decrease, but the electric motor can increase the rotation speed and compensate for the power drop. The RAT has a lower weight and smaller volume envelope (minimum number of parts) compared to using an additional battery or a separate flywheel. A high power-density electric motor can provide high propulsive force/torque (through reduction gearboxes). The electric-hybrid propeller fan is compatible with advanced modern MEA/MEE/Hybrid architectures and with clean technologies applications for advanced aircraft systems.

Claim 1:
An electricity generation and hybrid-electric propulsion system of an aircraft, comprising:
a fuselage (<NUM>);
a hybrid-electric power generation system (<NUM>) operably disposed in the fuselage; and
a ram air turbine, RAT, device (<NUM>), which is coupled with the hybrid-electric power generation system, and which is stowable in the fuselage and deployable to an exterior of the fuselage,
the RAT device being operable as a RAT when deployed into an airstream that drives rotations of the RAT from which the hybrid-electric power generation system generates electricity, and
the RAT device being operable as a propulsor when deployed and driven by the hybrid-electric power generation system; and characterised in that:
the hybrid-electric power generation system comprises:
first and second drive shafts (<NUM>, <NUM>);
a gas turbine engine (<NUM>) disposed on the first drive shaft;
a motor-generator (<NUM>) disposed on the first drive shaft for electrically coupling the RAT device and the hybrid-electric power generation system;
a power turbine (<NUM>), which is receptive of exhaust from the gas turbine engine; and
an electric generator (<NUM>), which is drivable by the power turbine via the second drive shaft.