A system has first and second fuel stores for first and second fuels, an engine, a fuel distribution system, first and second flow rates of the fuel contributing to a total flow rate of fuel; and a controller for controlling the relative fractions of the total flow rate of fuel to the engine according to the required power output of the engine such that the relative fraction of the total flow rate of fuel to the engine represented by the second flow rate increases with increasing required power output of the engine. The fuels are selected such that using only the second fuel results in a lower engine temperature than using only the first fuel, for the same mechanical power and/or the second fuel has a lower specific energy than the first and/or the second fuel produces more water during combustion than the first fuel per unit of fuel energy.

A system comprises first and second first fuel stores, an engine arranged to produce mechanical power, a fuel distribution system arranged to deliver fuel from the first and second fuel stores to the engine, the first fuel delivered at a first mass flow rate, the second fuel delivered at a second mass flow rate, the first and second mass flow rates contributing to a total mass flow rate of fuel to the engine, and a control system arranged to increase the relative fraction of the total mass flow rate of fuel represented by the second mass flow rate during a period of acceleration of the engine, in order to control a surge margin of the engine. The second fuel is selected to have a higher specific energy than the first fuel and to release a greater mass of water per unit mass of fuel than the first fuel.

An engine system comprises a first fuel store, a second fuel store, an engine arranged to produce mechanical power by combustion or oxidation of a fuel in an engine, a fuel distribution system arranged to deliver fuel from the first and second fuel stores to the engine, the first fuel delivered at a first mass flow rate, the second fuel delivered at a second mass flow rate, the first and second mass flow rates contributing to a total mass flow rate of fuel to the engine; and a control system arranged to control the relative fractions of the total mass flow rate of fuel to the engine represented by the first mass flow rate and the second mass flow rate, based on an engine temperature.

A continuous variable trim compressor includes: a plurality of rotary vanes provided in a passage of air flowing toward a compressor wheel; and a rotating device configured to rotate the plurality of rotary vanes simultaneously, wherein as the plurality of rotary vanes is rotated simultaneously by the rotating device, a cross-sectional area of the passage of air flowing toward the compressor wheel is variable.

A compressor surge control system includes a rotor system with at least one compressor section and at least one turbine section operably coupled to a shaft. The compressor surge control system also includes one or more rotor system sensors configured to collect a plurality of sensor data from the rotor system, an electric motor operably coupled to the rotor system, and a controller. The controller is operable to monitor the one or more rotor system sensors while the rotor system is rotating. The controller determines whether the plurality of sensor data from the one or more rotor system sensors is indicative of an early-stage compressor surge oscillation. A surge control torque is determined to diminish the early-stage compressor surge oscillation of the rotor system. The electric motor is commanded to apply the surge control torque to the rotor system.

A system and method for diagnosing load compressor health state for an auxiliary power unit that includes a power compressor, a combustor, a power turbine, and a load compressor is provided. The auxiliary power unit is operated and bleed air is discharged from the load compressor at a bleed air pressure. Using a pressure sensor, the bleed air pressure discharged from the load compressor is sensed and supplied to a processor. In the processor, power compressor health state is diagnosed based solely on the sensed bleed air pressure.

A gas turbine engine comprising at least one radially extending bleed passage in fluid communication with at least one generally circumferentially extending plenum. A plenum has an upstream end in fluid communication with a bleed passage and an outlet for releasing air from the plenum. A plenum further comprises a downstream surface defining a downstream closed end of the plenum and the downstream surface of one or more plenum is/are provided with an outwardly extending projection extending into the plenum.

In a gas turbine engine of the type having a high-pressure (HP) spool and a low-pressure (LP) spool, methods of increasing surge margin and compression efficiency at a given thrust are provided. One method increases compression efficiency and comprises transferring mechanical power from the HP spool to the LP spool to reduce a corrected speed of a HP compressor therein and raise a working line of a LP compressor therein. Another method increases surge margin and comprises transferring mechanical power from the LP spool to the HP spool to increase a corrected speed of a HP compressor therein and lower a working line of a LP compressor therein.

A coolant system includes a multistage compressor having a plurality of surge detection sensors. A condenser is connected to an outlet of the multistage compressor. An economizer is connected to an outlet of the condenser and has a gaseous coolant outlet and a liquid coolant outlet. The liquid coolant outlet is connected to a cooler and the gaseous coolant outlet is connected to a second or later stage of the multistage compressor via a controllable valve. A controller is communicatively coupled to the surge detection sensors and the controllable valve. The controller includes a non-transitory medium storing instructions for causing the controller to detect an occurrence of a surge and restricting a flow through the controllable valve until the surge has ceased.

A computer implemented method for the prediction of the surge point of a compressor includes: generating a plurality of meshes: a compressor inlet mesh, at least a compressor rotor stage mesh, and a compressor outlet mesh, representing a plurality of exit guide vanes and an exit nozzle and extending up to a final nozzle exit area; assembling the plurality of meshes to obtain the CFD domain; specifying boundary conditions of the computational domain; specifying atmospheric pressure conditions at the final nozzle exit area; computing compressor inlet mass flow rate and compressor pressure ratio; checking if the numerical stability limit is not reached, as a result of the numerical stability limit not being reached: decreasing dimensions of the final nozzle exit area; generating again the compressor outlet mesh; repeating the steps of specifying atmospheric pressure at the final nozzle exit area, the step of computing, and the step of checking.