A fuel injector for an aero-mechanical injection system for injecting an air/fuel mixture into a turbomachine combustion chamber, the injector comprising a main tubular structure of axis XX′ opening out at a downstream end for delivering the air/fuel mixture, a tubular fuel duct that is disposed inside the main structure and that opens out into the main structure via a fuel atomizer plug so as to introduce fuel into the main structure at a pressure PC into the main structure, at least one air feed channel that opens out into the main structure so as to introduce air at a pressure PA therein, and means for injecting into the fuel duct a gas at a pressure PG that is greater than PA and greater than or equal to PC so as to create effervescence in the fuel on being introduced into the main structure.