Fuel pump systems for turbomachines

A fuel system for a turbomachine engine, comprising:

• a mechanically driven primary pump configured to be driven by an input shaft connected to the turbomachine engine;
• a boost pump driven by an electric motor configured to supply pressurized fuel to the primary pump via a boost branch;
• a bypass valve that includes a three-way valve disposed in a downstream branch downstream of the primary pump and the boost pump, and
• a flow system configured to allow the boost pump to also directly provide pressurized fuel to one or more fuel metering valves and/or one or more fuel nozzles through a bypass branch to the downstream branch, such that when the bypass valve is in a bypass position, flow from the primary pump does not flow to the downstream branch, and the bypass valve allows communication between an output of the primary pump and the boost branch, wherein the electric motor is controlled by a controller, wherein the controller is operatively connected to a speed sensor that senses the speed of the input shaft, and the controller controls the electric motor at least in part as a function of the input shaft speed.

A method of providing fuel to a turbomachine engine, comprising:

• pumping fuel with a primary pump mechanically driven by an input shaft of the turbomachine engine;
• pumping fuel with a boost pump driven by an electric motor;
• supplying pressurized fuel from the boost pump to the primary pump via a boost branch;
• moving a bypass valve to a bypass position, wherein the bypass valve is or includes a three-way valve disposed in a downstream branch downstream of the primary pump and the boost pump;
• supplying pressurized fuel from the boost pump directly to one or more fuel metering valves and/or one or more fuel nozzles through a bypass branch from the boost branch to the downstream branch such that when the bypass valve is in a bypass position, flow from the primary pump does not flow to the downstream branch, and the bypass valve allows communication between an output of the primary pump and the boost branch;
• and
• controlling the electric motor with a controller at least in part as a function of a speed of the input shaft, wherein the controller is operatively connected to a speed sensor that senses the speed of the input shaft.