Ecology valve and system in an aircraft engine fuel system

An ecology system for a fuel system of an aircraft engine, the ecology system adapted to supply pressurized fuel to a fuel manifold during engine operation and suction fuel from the fuel manifold at engine shut off, the ecology system comprising:

• an inlet for receiving pressurized fuel;
• an outlet for communicating pressurized fuel received at the inlet to the fuel manifold;
• a mode switching valve movable between open and closed positions, the mode switching valve allowing fuel flow between the inlet and the outlet in the open position and blocking fuel flow between the inlet and the outlet in the closed position;
• an ecology valve having a piston slidable in a piston chamber, the piston dividing piston chamber into a sump chamber and an actuation chamber, the piston sliding between shut-off and run positions in which the sump chamber is maximized and minimized, respectively, the ecology valve having a spring biasing the piston to the shut-off position;
• and
• a drain passageway between the sump chamber and the actuation chamber, the mode switching valve blocking the drain passageway when in the open position and opening the drain passageway thereby fluidically connecting the sump chamber and the actuation chamber when in the closed position.

A method for ecologically regulating fuel flow in a fuel system of an aircraft engine, the fuel system comprising a fuel pump adapted to pressurize fuel from a fuel supply, a plurality of nozzles arranged in a combustion chamber, a fuel metering unit adapted to control the flow of fuel from the fuel pump to the fuel nozzles, and a fuel manifold adapted to communicate the flow of fuel to the fuel nozzles, the method comprising:

• providing an ecology valve fluidically connected to the fuel manifold, the ecology valve having a piston chamber, a piston slidable in the piston chamber dividing piston chamber into a sump chamber and an actuation chamber;
• actuating the piston with working fuel and thereby return fuel contained in the sump chamber to the fuel manifold;
• suctioning sufficient fuel from the fuel manifold into the sump chamber upon engine shut-down to prevent coking of the nozzles;
• and
• draining the working fuel into the sump chamber of the ecology valve upon engine shut-down.

A fuel system for ecologically regulating fuel flow in an aircraft engine, the fuel system comprising a fuel pump adapted to pressurize fuel from a fuel supply, a plurality of nozzles arranged in a combustion chamber, a fuel metering unit adapted to control the flow of fuel from the fuel pump to the fuel nozzles, and a fuel manifold adapted to communicate the flow of fuel to the fuel nozzles, the method comprising:

• means for providing an ecology valve fluidically connected to the fuel manifold, the ecology valve having a piston chamber, a piston slidable in the piston chamber dividing piston chamber into a sump chamber and an actuation chamber;
• means for actuating the piston with working fuel and thereby return fuel contained in the sump chamber to the fuel manifold;
• means for suctioning sufficient fuel from the fuel manifold into the sump chamber upon engine shut-down to prevent coking of the nozzles;
• and
• means for draining the working fluid into the sump chamber of the ecology valve upon engine shut-down.