Fuel systems of gas turbine engines of aircraft, and associated methods are provided. The fuel systems and methods can permit reverse purging of one or more fuel manifolds of a gas turbine engine to prevent coking in some modes of operation. A fuel system includes first and second fuel manifolds fluidly connectable to a combustor of the gas turbine engine. A valve is operatively disposed between the second fuel manifold and a fuel supply line for controlling fuel supply to the second fuel manifold. A reservoir includes a movable piston disposed therein and dividing the reservoir into a first chamber and a second chamber. The first chamber is fluidly connectable to the fuel supply line or to a fuel purge line via the valve. The second chamber is in fluid communication with the second fuel manifold to receive residual fuel from the second fuel manifold.

Fuel systems of gas turbine engines of aircraft, and associated methods are provided. The fuel systems and methods can permit reverse purging of one or more fuel manifolds of a gas turbine engine to prevent coking in some modes of operation. A fuel system includes first and second fuel manifolds fluidly connectable to a combustor of the gas turbine engine. A valve is operatively disposed between the second fuel manifold and a fuel supply line for controlling fuel supply to the second fuel manifold. A reservoir includes a movable piston disposed therein and dividing the reservoir into a first chamber and a second chamber. The first chamber is fluidly connectable to the fuel supply line or to a fuel purge line via the valve. The second chamber is in fluid communication with the second fuel manifold to receive residual fuel from the second fuel manifold.

A flow metering system includes a pump configured to urge a fluid flow from a fluid source, and a recirculation line located at the pump. A pressure regulating valve is located along the recirculating line. One or more fluid delivery lines extend downstream of the pump to deliver the fluid flow to one or more fluid consumers. A flow control valve is located along each fluid delivery line of the one or more fluid delivery lines. A system controller is operably connected to the pressure regulating valve and the one or more flow control valves. The system controller is configured to maintain a selected delta pressure and a selected flow rate of the fluid flow by operation of the pressure regulating valve and the one or more flow control valves.

A flow metering system includes a pump configured to urge a fluid flow from a fluid source, and a recirculation line located at the pump. A pressure regulating valve is located along the recirculating line. One or more fluid delivery lines extend downstream of the pump to deliver the fluid flow to one or more fluid consumers. A flow control valve is located along each fluid delivery line of the one or more fluid delivery lines. A system controller is operably connected to the pressure regulating valve and the one or more flow control valves. The system controller is configured to maintain a selected delta pressure and a selected flow rate of the fluid flow by operation of the pressure regulating valve and the one or more flow control valves.

A system includes a recirculation conduit that recirculates working fluid and a permanent magnet generator module in communication with the recirculation conduit. The working fluid from the recirculation conduit drives the permanent magnet generator module.

A system includes a recirculation conduit that recirculates working fluid and a permanent magnet generator module in communication with the recirculation conduit. The working fluid from the recirculation conduit drives the permanent magnet generator module.

A system comprises a variable displacement pump, a metering valve, a bypass line, a pressure regulating valve, a position sensor, and a control system. At least one fuel nozzle can be in fluid communication with the output line downstream of the metering valve, wherein the variable displacement pump is configured to supply fuel to the at least one fuel nozzle. The metering valve can be disposed in the output line for controlling outlet flow from the variable displacement pump. The system can also include an actuator line parallel to the variable displacement pump and connected to the output line to provide actuation pressure from pump output of the variable displacement pump.

A system comprises a variable displacement pump, a metering valve, a bypass line, a pressure regulating valve, a position sensor, and a control system. At least one fuel nozzle can be in fluid communication with the output line downstream of the metering valve, wherein the variable displacement pump is configured to supply fuel to the at least one fuel nozzle. The metering valve can be disposed in the output line for controlling outlet flow from the variable displacement pump. The system can also include an actuator line parallel to the variable displacement pump and connected to the output line to provide actuation pressure from pump output of the variable displacement pump.

A system comprises a variable displacement pump, a metering valve, a bypass line, a pressure regulating valve, a position sensor, and a control system. At least one fuel nozzle can be in fluid communication with the output line downstream of the metering valve, wherein the variable displacement pump is configured to supply fuel to the at least one fuel nozzle. The metering valve can be disposed in the output line for controlling outlet flow from the variable displacement pump. The system can also include an actuator line parallel to the variable displacement pump and connected to the output line to provide actuation pressure from pump output of the variable displacement pump.

A method includes combusting a fuel and an oxidant in a combustor of an exhaust gas recirculation (EGR) gas turbine system that produces electrical power and provides a portion of the electrical power to an electrical grid. The method further includes controlling, via one or more processors, one or more parameters of the EGR gas turbine system to decrease the portion of the electrical power provided to the electrical grid in response to an over-frequency event associated with the electrical grid, wherein controlling the one or more parameters comprises decreasing a flow rate of fuel to the combustor in response to the over-frequency event.