Four mode thermal recirculation throttle valve

A main fuel throttle valve assembly for an aircraft fuel system including a fuel storage tank and a main pump, the main fuel throttle valve assembly comprising:

• a main fuel throttle valve configured to receive fuel from the main pump and drawn from the fuel storage tank;
• a thermal recirculation throttle valve, comprising:
• a housing having a throttling valve chamber, an inlet configured to be fluidly coupled to an outlet of the main pump, a first outlet configured to be fluidly coupled to the inlet of the main pump, and a second outlet configured to be fluidly coupled to an inlet of the fuel storage tank;
• a power piston disposed within the housing for translational movement therein;
• a throttling valve mounted to the piston and configured to move therewith between:
• (i) a fuel shut-off position wherein the throttling valve substantially blocks fuel flow from the inlet to the first outlet and substantially permits fuel flow from the throttling valve chamber to the second outlet, (ii) a fully open operating position wherein the throttling valve substantially permits fuel flow from the inlet to the first outlet and substantially blocks fuel flow from the throttling valve chamber to the second outlet, (iii) a failsafe extended position wherein the throttling valve permits a predetermined flow from the inlet to the first outlet, and (iv) a failsafe retracted position wherein the throttling valve permits a predetermined restricted flow from the inlet to the first outlet;
• a first structural element within the housing and configured to engage at least one of the power piston and the throttling valve to prevent the throttling valve from extending beyond the failsafe extended position;
• and a second structural element within the housing and configured to engage at least one of the power piston and the throttling valve to prevent the throttling valve from retracting beyond the failsafe retracted position;
• wherein the fuel shut-off position resides between the fully open operating position and the failsafe extended position, and wherein the fully open operating position resides between the fuel shut-off position and the failsafe retracted position.

A fuel system for an aircraft including a plurality of gas generator nozzles, the fuel system comprising:

• a fuel storage tank;
• a main fuel throttle valve configured to be fluidly coupled to the plurality of gas generator nozzles and to supply metered fuel thereto;
• a main fuel pump fluidly coupled between the main fuel throttle valve and the fuel storage tank, the main fuel pump configured to supply the main fuel throttle valve with pressurized fuel from the fuel storage tank;
• and
• a thermal recirculation throttle valve, comprising:
• a housing having a throttling valve chamber, an inlet fluidly coupled to an outlet of the main pump, a first outlet fluidly coupled to the inlet of the main pump, and a second outlet fluidly coupled to an inlet of the fuel storage tank;
• a power piston disposed within said housing for translational movement therein;
• and
• a throttling valve mounted to the piston and configured to move therewith between:
• (i) a fuel shut-off position wherein the throttling valve substantially blocks fuel flow from the inlet to the first outlet and substantially permits fuel flow from the throttling valve chamber to the second outlet, (ii) a fully open operating position wherein the throttling valve substantially permits fuel flow from the inlet to the first outlet and substantially blocks fuel flow from the throttling valve chamber to the second outlet, (iii) a failsafe extended position wherein the throttling valve permits a predetermined flow from the inlet to the first outlet, and (iv) a failsafe retracted position wherein the throttling valve permits a predetermined flow from the inlet to the first outlet;
• wherein the fuel shut-off position and the fully open operating position reside intermediate the failsafe extended position and the failsafe retracted position;
• and wherein the thermal recirculation throttle valve further comprises means for preventing the throttling valve from extending beyond the failsafe extended position, and means for preventing the throttling valve from retracting beyond the failsafe retracted position.