A fuel control system for a gas turbine engine includes a fuel metering valve, a pressure raising and shut-off valve (PRSOV), and a shutoff effector including a first stage unit that is electrically powered and a second stage unit that is controlled by the first stage unit. The second stage unit actuates a valve member of the PRSOV between an open position that allows supply of a fuel to burners of the gas turbine engine and a closed position that prevents supply of the fuel to the burners. Upon loss of electrical power to the first stage unit during operation of the gas turbine engine, the first stage unit is configured to: control the second stage unit to actuate the valve member of the PRSOV to the closed position after a predetermined time duration; or retain the valve member of the PRSOV in the open position.

A fuel pump system can include a motor and a pump connected to the motor. The pump can be configured to receive an inlet flow from an inlet line, to pressurize the inlet flow, and to output a pressurized flow to an output line for an engine. The system can include a bypass line disposed between the outlet line and the inlet line, and a bypass valve disposed on the bypass line and configured to allow pressurized flow to flow to the inlet line in an open state, and to prevent pressurized flow from flowing to the inlet line in a closed state. The bypass valve can be configured to allow pressurized flow to flow to the inlet line to circulate flow and to maintain a constant pressure on the output line.

A fluid delivery system can include a main pump disposed in a primary fluid line configured to receive a low pressure fluid on a low pressure side and output a high pressure fluid on a high pressure side to provide flow from the fluid source to a fluid destination via the primary fluid line. An interconnected valve system can be disposed in the primary fluid line configured to control flow through the primary fluid line.

In accordance with at least one aspect of this disclosure, a pump selector system can include a primary pump fluidly connected to provide a primary flow to a fluid destination, a secondary pump fluidly connected to provide a secondary flow to the fluid destination, and a selector valve disposed downstream of the primary pump and the secondary pump. The selector valve can be configured to toggle between a first position configured to allow flow from the primary pump to flow to the fluid destination and to block flow from the secondary pump to the fluid destination, and a second position configured to allow flow from the secondary pump to flow to the fluid destination and to block flow from the primary pump to the fluid destination.

In accordance with at least one aspect of this disclosure, a pump selector system can include a primary pump fluidly connected to provide a primary flow to a fluid destination, a secondary pump fluidly connected to provide a secondary flow to the fluid destination, and a selector valve disposed downstream of the primary pump and the secondary pump. The selector valve can be configured to toggle between a first position configured to allow flow from the primary pump to flow to the fluid destination and to block flow from the secondary pump to the fluid destination, and a second position configured to allow flow from the secondary pump to flow to the fluid destination and to block flow from the primary pump to the fluid destination.

A controller for a gas turbine is arranged to supply a load L. The gas turbine includes a fuel supply arranged to supply fuel at a fuel flow rate FF to a combustor, wherein the fuel supply includes a first fuel supply and a second fuel supply. The controller is arranged to determine one or more ratios R of one or more combustor operating parameters COP respectively at the load L to respective reference combustor operating parameters COPR at a reference load LR. The controller is further arranged to control a proportion P of the fuel flow rate FF supplied via the first fuel supply based, at least in part, on the determined one or more ratios R. A gas turbine with the controller and a method controls the gas turbine.

Systems and methods for operating systems are provided. For example, a system comprises a coolant flowpath having a coolant flowing therethrough, a cooling system for cooling the coolant disposed along the coolant flowpath, a fuel flowpath having a fuel flowing therethrough, a heat exchanger fluidly connected to the coolant flowpath and the fuel flowpath for heat transfer between the coolant and the fuel to cool the fuel, and a fuel tank for accumulating the cooled fuel. The fuel is in thermal communication with a first thermal load to cool the load. An exemplary method comprises flowing a heat exchange fluid along a flowpath; flowing a fuel along a fuel flowpath including a fuel tank; passing both the heat exchange fluid and fuel through a heat exchanger to cool the fuel; and controlling the fuel flow from the heat exchanger to the fuel tank for accumulation of the cooled fuel.

Systems and methods for operating systems are provided. For example, a system comprises a coolant flowpath having a coolant flowing therethrough, a cooling system for cooling the coolant disposed along the coolant flowpath, a fuel flowpath having a fuel flowing therethrough, a heat exchanger fluidly connected to the coolant flowpath and the fuel flowpath for heat transfer between the coolant and the fuel to cool the fuel, and a fuel tank for accumulating the cooled fuel. The fuel is in thermal communication with a first thermal load to cool the load. An exemplary method comprises flowing a heat exchange fluid along a flowpath; flowing a fuel along a fuel flowpath including a fuel tank; passing both the heat exchange fluid and fuel through a heat exchanger to cool the fuel; and controlling the fuel flow from the heat exchanger to the fuel tank for accumulation of the cooled fuel.

A method and system for fuel nozzle cleaning during engine operation is provided. The steps or operations include operating the compressor section to provide the flow of oxidizer to the combustion chamber, operating the fuel system at a first fuel flow condition, in which the first fuel flow condition provides a fuel-oxidizer ratio at the combustion chamber, operating the fuel system at a second fuel flow condition, in which the second fuel flow condition provides the fuel-oxidizer ratio at the combustion chamber equal at the first fuel flow condition and the second fuel flow condition, and operating the fuel system at a third fuel flow condition after operating the fuel system at the second fuel flow condition.

A system for monitoring fuel additives on board a vehicle includes a fuel line carrying fuel from a fuel source to an engine; a fuel additive sensor configured to measure concentration of additives in fuel at a point along the fuel line; a fuel additive dispenser connected in parallel to the fuel line; at least one flow control device for controlling an amount of flow from the fuel line into the fuel additive dispenser; and a controller configured to receive input from the fuel additive sensor and to control the flow control device to adjust the amount of the flow from the fuel line into the fuel additive dispenser.