A ram air turbine system includes a ram air turbine and an actuator to move the ram air turbine between a stowed position and a deployed position. The actuator is in fluid communication with an aircraft hydraulic system configured to return the ram air turbine to the stowed position from the deployed position during operation of the aircraft utilizing hydraulic fluid pressure from the aircraft hydraulic system. A method of operating a ram air turbine system includes slowing or stopping rotation of the ram air turbine during flight of the aircraft, directing hydraulic fluid pressure from an aircraft hydraulic system to a ram air turbine actuator to urge movement of the actuator from a deployed position to a stowed position and urging movement of the ram air turbine from a deployed position to a stowed position via movement of the actuator from the deployed position to the stowed position.

A method of tracking variable states of a gas turbine engine in transient conditions includes obtaining input data representative of rotor velocity and pressure ratio; calculating a reference transient scheduled trajectory based on the input data; calculating a speed reference transient scheduled trajectory based on the input data; calculating a feedforward variable based on the reference transient scheduled trajectory; obtaining a feedback control variable; and determining a control variable based on a combination of the feedforward variable and the feedback control variable.

A propulsion system includes at least two propulsors. The at least two propulsors each include a fan and a controller having one or more processors configured to implement controller logic. The controller logic includes a phase angle control scheme and a speed control scheme. In implementing the controller logic, the one or more processors are configured to: determine an actual pairwise phase difference between a pair of propulsors of the at least two propulsors; generate a reference phase angle for the pair of propulsors; compare the actual pairwise phase difference to the reference phase angle to generate a phase error; provide the phase error to a phase controller module to generate an output based on the phase error; and adjust a speed of at least one propulsor of the at least two propulsors based on the output to drive the phase error towards zero.

A propulsion system includes at least two propulsors. The at least two propulsors each comprising a fan having a plurality of fan blades. A controller includes memory and one or more processors. The memory stores instructions that when executed by the one or more processors cause the system to perform the following: determine a pairwise phase difference between one propulsor of the at least two propulsors and another propulsor of the at least two propulsors; generate a reference phase angle; determine a target phase shift for each propulsor of the at least two propulsors; and adjust a speed of each propulsor of the at least two propulsors based on the target phase shift until the pairwise phase difference is equal to the reference phase angle.

A fuel system includes: a constant-volume pump and a centrifugal pump increasing the pressure of fuel to be supplied to an engine for aviation and discharging the fuel; an operation controller configured to select in accordance with the operation state of the engine, one of a constant-volume pump-using mode of increasing the pressure of fuel using the constant-volume pump and a centrifugal pump-using mode of increasing it using the centrifugal pump; and a speed changer connecting the engine and the centrifugal pump, changing the rotational speed of rotational power output from the engine and transmitting the rotational power to the centrifugal pump, and being capable of adjusting the speed-changing ratio of the rotational speed.

An engine fuel control system includes a fuel metering valve that controls the flow of fuel between supply and delivery lines which delivers fuel to engine burners. The fuel control system includes a fixed displacement main pump which receives fuel from a low pressure source and delivers the fuel at a first high pressure to the supply line, an augmenter pump which receives fuel from the low pressure source and delivers the fuel at a second high pressure to one or more fuel-pressure operated auxiliary engine devices, and a start valve which is actuated at low engine speeds to open a flow path which diverts fuel delivered by the augmenter pump away from the auxiliary engine devices to the supply line to augment the fuel delivered thereto by the main pump, the start valve being actuated at higher engine speeds to shut the flow path.

A propulsion system includes at least two propulsors. The at least two propulsors each include a fan and a controller having one or more processors configured to implement controller logic. The controller logic includes a phase angle control scheme and a speed control scheme. In implementing the controller logic, the one or more processors are configured to: determine an actual pairwise phase difference between a pair of propulsors of the at least two propulsors; generate a reference phase angle for the pair of propulsors; compare the actual pairwise phase difference to the reference phase angle to generate a phase error; provide the phase error to a phase controller module to generate an output based on the phase error; and adjust a speed of at least one propulsor of the at least two propulsors based on the output to drive the phase error towards zero.

The invention relates to respirator technology. in particular to an atmospheric pressure compensation control system for a powered air-purifying respirator and a method. The atmospheric pressure compensation control system comprises a main unit and a battery pack, wherein a waterproof breathable membrane is installed over a through hole formed in an outer shell of the main unit or the battery pack; A collection module inside the main unit or battery pack detects atmospheric pressure in real time, while the chamber contains conversion, comparison, and control modules. The conversion module converts atmospheric pressure into an electrical signal, which is then processed by the comparison module to calculate and compare the pressure difference with a standard. The control module adjusts the fan speed in real time based on the pressure difference to maintain a constant internal-external pressure differential, ensuring stable airflow and the normal operation of the respirator.

A propulsion system includes at least two propulsors. The at least two propulsors each include a fan and a controller having one or more processors configured to implement controller logic. The controller logic includes a phase angle control scheme and a speed control scheme. In implementing the controller logic, the one or more processors are configured to: determine an actual pairwise phase difference between a pair of propulsors of the at least two propulsors; generate a reference phase angle for the pair of propulsors; compare the actual pairwise phase difference to the reference phase angle to generate a phase error; provide the phase error to a phase controller module to generate an output based on the phase error; and adjust a speed of at least one propulsor of the at least two propulsors based on the output to drive the phase error towards zero.

A pumping system includes a plurality of interconnected integrated motor/pump modules (IMPs) submerged in a process liquid, such as liquid hydrogen (LH2), within a container, the IMPs being separately controlled by adjustable speed drives (ASDs). The rotation speeds of the IMP impellers are controlled such that the NPSH_A for each IMP remains above a minimum, critical suction head NPSH_c of the IMP, while the outlet pressure and flow of the last IMP is maintained at a specified level unless its NPSH_A falls substantially to its NPSH_c, or until the container is substantially empty. The IMPs can be identical, initially operating at the same speeds, or the first IMP can be an inducer IMP having a reduced NPSH_c. The IMPs can comprise permanent magnets or induction coils attached to their impellers that pass in proximate radial or axial alignment with stator coils. The ASDs can be variable frequency drives (VFDs).