Fuel system and engine head assembly having double-walled fuel connector for cooling fuel return

A fuel system comprising:

• a fuel injector including an injector housing defining a longitudinal axis and including a nozzle case having a cooling fuel outlet, an injector body threaded engaged with the nozzle case and including a fuel inlet and a connector seat extending circumferentially around the fuel inlet, and a stack including a tip piece having a plurality of spray orifices and an orifice piece clamped between the injector body and the tip piece and having an injection control valve seat;
• an injection control valve assembly including a control valve movable to open and close the control valve seat;
• a direct-operated nozzle check movable to open and close the plurality of spray orifices;
• a high-pressure fuel inlet path extends, between the fuel inlet and the plurality of spray orifices, through the injector body;
• and
• a low-pressure cooling fuel outlet path extends, between the injection control valve seat and the cooling fuel outlet, through a first clearance defined between the injector body and the orifice piece and a second clearance defined between the stack and the nozzle case.

A method of operating a fuel system comprising:

• feeding a fuel through a fuel supply passage in a fuel connector to a fuel injector;
• opening a control valve seat for an injection control valve to expel fuel through the control valve seat from a check control chamber for a nozzle check in the fuel injector;
• conveying the fuel expelled through the control valve seat to a fuel outlet formed in a nozzle case of the fuel injector;
• dissipating heat of the fuel injector to the expelled fuel conveyed to the fuel outlet;
• limiting a temperature difference between material of the fuel injector at a first location and material of the fuel injector at a second location based on the dissipating heat of the fuel injector;
• and
• conveying the expelled fuel to a fuel return passage formed at least in part by the fuel connector.