Disclosed is a thermoelectric generator including a heat source contact, a heat sink contact, and a plurality of co-axial fibers. Each of the co-axial fibers include a core and a cladding disposed about the core. The plurality of co-axial fibers extend from the heat source contact to the heat sink contact. Thermoelectric generators are disclosed including hollow core doped silicon carbide fibers and doubly clad PIN junction fibers. Methods for forming direct PN junctions between oppositely doped fibers are additionally disclosed.

Disclosed is a thermoelectric generator including a heat source contact, a heat sink contact, and a plurality of co-axial fibers. Each of the co-axial fibers include a core and a cladding disposed about the core. The plurality of co-axial fibers extend from the heat source contact to the heat sink contact. Thermoelectric generators are disclosed including hollow core doped silicon carbide fibers and doubly clad PIN junction fibers. Methods for forming direct PN junctions between oppositely doped fibers are additionally disclosed.

A metamaterial-based substrate (meta-substrate) for piezoelectric energy harvesters. The design of the meta-substrate combines kirigami and auxetic topologies to create a high-performance platform including preferable mechanical properties of both metamaterial morphable structures. The creative design of the meta-substrate can improve strain-induced vibration applications in structural health monitoring, internet-of-things systems, micro-electromechanical systems, wireless sensor networks, vibration energy harvesters, and other applications whose efficiency is dependent on their deformation performance. The meta-substrate energy harvesting device includes a meta-material substrate comprising an auxetic frame having two kirigami cuts and a piezoelectric element adhered to the auxetic frame by means of a thin layer of elastic glue.

An exciter drive circuit comprises a direct current (DC) link to provide a positive DC voltage to a positive voltage exciter rail and a negative DC voltage to a negative voltage exciter rail. An exciter winding includes a first exciter terminal connected to the positive voltage exciter rail and an opposing second exciter terminal connected to the negative voltage exciter rail. A flyback circuit establishes a first flyback current path that conducts the current from exciter winding in response to an inductive flyback event. A flyback fault protection circuit establishes a second flyback current path that conducts the current from exciter winding in response to the inductive flyback event and a fault present in the flyback circuit. The second flyback current path delivers the current output by the exciter winding from the negative voltage exciter rail to the positive voltage exciter rail.

An exciter drive circuit comprises a direct current (DC) link to provide a positive DC voltage to a positive voltage exciter rail and a negative DC voltage to a negative voltage exciter rail. An exciter winding includes a first exciter terminal connected to the positive voltage exciter rail and an opposing second exciter terminal connected to the negative voltage exciter rail. A flyback circuit establishes a first flyback current path that conducts the current from exciter winding in response to an inductive flyback event. A flyback fault protection circuit establishes a second flyback current path that conducts the current from exciter winding in response to the inductive flyback event and a fault present in the flyback circuit. The second flyback current path delivers the current output by the exciter winding from the negative voltage exciter rail to the positive voltage exciter rail.

An aircraft power system includes an auxiliary power unit (APU), a generator, and a constant speed drive (CSD). The APU drives an APU drive shaft at a first rotational speed during a first condition and a second rotational speed during a second condition. The generator is rotatably coupled to a generator shaft and produces an AC voltage having a target frequency in response to rotation of the generator shaft at a target rotational speed. The CSD unit receives the first rotational speed from the APU drive shaft and rotates the generator shaft at the target rotational speed based on the first rotational speed. The CSD further receives the second rotational speed from the APU drive shaft and rotates the generator shaft at the target rotational speed based on the second rotational speed.

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

A method to modify an aircraft including: disconnecting a first engine control device from command cables and transmission cables, wherein the first engine control device is in a fuselage section forward of a pressure bulkhead; replacing the engine control device with a jumper connector positioned in the fuselage section, wherein the jumper connector electrically connects the command cables to the transmission cables; installing a second engine control device in the fuselage aft of the pressure bulkhead, wherein the second engine control device is in an engine compartment of the fuselage; connecting the second engine control device to transmission cables at a location at or near the pressure bulkhead; connecting sensor cabling directly to the second engine control device, and connecting the engine control device directly to the engine.

A method and power distribution system for operating in a low power consumption mode includes a primary power distribution node defining a primary distribution switch having an output and operable in a first conducting mode and a second non-conducting mode, and wherein operating in the second non-conducting mode includes a leakage current through the power distribution switch, at least one enabled electrical load downstream of the primary power distribution node, the at least one enabled electrical load connectable to the primary power distribution node by way of the primary distribution switch, and a primary power distribution node power source configured to supply power to the output of the primary distribution switch when the primary distribution switch is operating in the second non-conducting mode.