An aircraft propulsion system comprises a gas turbine engine arranged to provide propulsive thrust and a fuel cell system having an air input port, the aircraft propulsion system being configured such that air from a compressor of the gas turbine engine is provided to the air input port during operation of the aircraft propulsion system. The fuel cell system is able to provide appreciable electrical power at altitude without the need for a dedicated compressor.

A electrical power system comprises: an electrical machine operable to output AC; a DC electrical network; a power electronics converter connected between the AC output of the electrical machine and the DC electrical network and including a plurality of transistors and associated diodes connected in parallel with the transistors; and a controller configured to control switching of the transistors of the converter so that, during normal operation of the electrical power system, the converter rectifies the AC output of the electrical machine to supply the DC electrical network with DC electrical power. The controller is further configured, responsive to a determination to the effect there is a fault in the DC electrical network, to control a voltage source, to inject a voltage to bias the diodes of the converter, and to control the switching of the transistors to control a level of current supplied to the faulted DC electrical network.

A electrical power system comprises: an electrical machine operable to output AC; a DC electrical network; a power electronics converter connected between the AC output of the electrical machine and the DC electrical network and including a plurality of transistors and associated diodes connected in parallel with the transistors; and a controller configured to control switching of the transistors of the converter so that, during normal operation of the electrical power system, the converter rectifies the AC output of the electrical machine to supply the DC electrical network with DC electrical power. The controller is further configured, responsive to a determination to the effect there is a fault in the DC electrical network, to control a voltage source, to inject a voltage to bias the diodes of the converter, and to control the switching of the transistors to control a level of current supplied to the faulted DC electrical network.

An electrical power system includes: an electrical machine to output AC; DC electrical network; power electronics converter connected between the AC output of the electrical machine and the DC electrical network and having a phase leg having first and second branches respectively having first and second bi-directional MOSFETs; and controller controlling switching of the first and second bi-directional MOSFETs of each phase leg of the converter so that current is commutated between the phase leg first and second branches rectifying the AC input to DC to supply the DC electrical network with DC electrical power. The controller is responsive to a determination to the effect that there is a fault in the DC electrical network, to control the switching of each phase leg first and second bi-directional MOSFETs to switch the converter into a crow-bar configuration in which electrical machine current does not flow to the DC network.

An electrical power system includes: an electrical machine to output AC; DC electrical network; power electronics converter connected between the AC output of the electrical machine and the DC electrical network and having a phase leg having first and second branches respectively having first and second bi-directional MOSFETs; and controller controlling switching of the first and second bi-directional MOSFETs of each phase leg of the converter so that current is commutated between the phase leg first and second branches rectifying the AC input to DC to supply the DC electrical network with DC electrical power. The controller is responsive to a determination to the effect that there is a fault in the DC electrical network, to control the switching of each phase leg first and second bi-directional MOSFETs to switch the converter into a crow-bar configuration in which electrical machine current does not flow to the DC network.

Systems and methods to increase intake air flow to a gas turbine engine of a hydraulic fracturing unit when positioned in an enclosure may include providing an intake expansion assembly to enhance intake air flow to the gas turbine engine. The intake expansion assembly may include an intake expansion wall defining a plurality of intake ports positioned to supply intake air to the gas turbine engine. The intake expansion assembly also may include one or more actuators connected to a main housing of the enclosure and the intake expansion assembly. The one or more actuators may be positioned to cause the intake expansion wall to move relative to the main housing between a first position preventing air flow through the plurality of intake ports and a second position providing air flow through the plurality of intake ports to an interior of the enclosure.

An assembly is provided for a turbine engine. This turbine engine assembly includes a rotating structure, a stationary structure and an electric machine. The rotating structure is configured to rotate about a rotational axis. The stationary structure circumscribes the rotating structure. The electric machine includes a rotor and a stator. The rotor circumscribes the rotating structure and is coupled to the rotating structure through a spline connection. The stator is connected to the stationary structure.

An assembly is provided for a turbine engine. This turbine engine assembly includes a rotating structure, a stationary structure and an electric machine. The rotating structure is configured to rotate about a rotational axis. The stationary structure circumscribes the rotating structure. The electric machine includes a rotor and a stator. The rotor circumscribes the rotating structure and is coupled to the rotating structure through a spline connection. The stator is connected to the stationary structure.

A hybrid hydrogen-electric and hydrogen turbine engine and system is disclosed. The hydrogen-electric system has an air inlet, a hydrogen fuel source, a fuel cell stack, and a motor assembly disposed in electrical communication with the fuel cell stack. The hydrogen turbine system has an air intake in fluid communication with the air inlet of the hydrogen-electric system, a combustion chamber in fluid communication with the air intake and the hydrogen fuel source of the hydrogen-electric system, the combustion chamber configured to mix air received from the air intake with hydrogen received from the hydrogen fuel source, and a turbine driven by energy received from the combustion chamber. The hydrogen-electric system and the hydrogen turbine system cooperate with one another to generate the output power of the hybrid hydrogen engine system.

A hybrid hydrogen-electric and hydrogen turbine engine and system is disclosed. The hydrogen-electric system has an air inlet, a hydrogen fuel source, a fuel cell stack, and a motor assembly disposed in electrical communication with the fuel cell stack. The hydrogen turbine system has an air intake in fluid communication with the air inlet of the hydrogen-electric system, a combustion chamber in fluid communication with the air intake and the hydrogen fuel source of the hydrogen-electric system, the combustion chamber configured to mix air received from the air intake with hydrogen received from the hydrogen fuel source, and a turbine driven by energy received from the combustion chamber. The hydrogen-electric system and the hydrogen turbine system cooperate with one another to generate the output power of the hybrid hydrogen engine system.