Fuel system for starting an APU using a hybrid pump arrangement

摘要

A fuel system for an auxiliary power unit includes a mechanical fuel pump, an electric fuel pump, and a controller. The mechanical fuel pump provides fuel flow to the auxiliary power unit and has an output dependent upon an operational speed of the auxiliary power unit. The electric fuel pump provides fuel flow to the auxiliary power unit, and is located in flow series with the mechanical fuel pump. The controller causes the electric fuel pump to provide fuel flow during starting of the auxiliary power unit.

主权项

1. A fuel system for an auxiliary power unit, the fuel system comprising:
a mechanical fuel pump for providing fuel flow to the auxiliary power unit, the mechanical fuel pump having an output dependent upon an operational speed of the auxiliary power unit; an electric fuel pump for providing fuel flow to the auxiliary power unit, the electric fuel pump located upstream of the mechanical fuel pump on a common fuel supply conduit; and a controller for causing the electric fuel pump to provide fuel flow during starting of the auxiliary power unit; a bypass conduit having a first end and a second end, the first end of the bypass conduit fluidly connected to the fuel supply conduit upstream of the electric fuel pump and the second end of the bypass conduit fluidly connected to the fuel supply conduit downstream of the electric fuel pump, wherein the first and second ends of the bypass conduit are upstream from the mechanical fuel pump; a bypass check valve located on the bypass conduit, the check valve having an open configuration that allows fuel to flow from the first end of the bypass conduit to the second end of the bypass conduit and a closed configuration that prevents fuel from flowing from the second end of the bypass conduit to the first end of the bypass conduit; a relief conduit having a first end and a second end, the first end of the relief conduit fluidly connected to the fuel supply conduit downstream of the electric fuel pump and the second end of the relief conduit fluidly connected to the fuel supply conduit upstream of the electric fuel pump; and a relief check valve located on the relief conduit, the check valve having an open configuration that allows fuel to flow from the first end of the relief conduit to the second end of the relief conduit and a closed configuration that prevents fuel from flowing from the second end of the relief conduit to the first end of the relief conduit.