The fuel and air supply system of the present invention provides fuel from a fuel pump (42) at a first pressure upstream of a pressure reducer (46), fuel being provided directly to the fuel injector (10) at a reduced pressure on the downstream side of the pressure reducer (46). A bypass line (34) in communication with the fuel line (44) upstream of the pressure reducer (46) provides fuel to an air reservoir (50) at the first pressure. The air reservoir (50) lies in communication with a porous member(s) (30) in the fuel injector (10) in an air inlet (32) to a fuel volume (24) within the injector (10). Upon flow of fuel into the air reservoir (50) and closure of normally open fuel and air valves (58,60) in the reservoir (50), air at the first pressure is supplied the porous member(s) (30), creating a pressure differential across the member(s) (30), causing air to flow through the porous member(s) (30) to form air bubbles in the fuel volume (24) for two-phase flow through the fuel injector orifice (28). The air flows for a predetermined time until the reservoir (50) fills with fuel which precludes further air flow into the injector (10). Upon shutdown of the engine, the valves (58,60) in the air reservoir (50) open, draining the fuel from the air reservoir (50) and enabling air at atmospheric pressure to enter the reservoir (50), returning the system for reuse upon engine startup.

A fuel injection system having a fuel injector (22) disposed in a first bore (38) formed in the wall of an air intake passage of an engine.

A porous tubular element (32) having a mixture passage (44) open at both its ends is received in a second bore (36) in close contact with the fuel injector (22). An air passage (34) is provided for introducing air into the mixture passage (44) through fine passages formed in the wall of the porous tubular element (32). This air will atomize the fuel (F) adhering to the inner surface of the mixture passage (44) into fine particles (B) in order to form a homogeneous mixture.

A needle is forced to open an injection hole by reducing a pressure of fuel in an injection control chamber to thereby inject fuel stored in a fuel storage, while the needle is forced to close the injection hole by increasing the pressure of fuel in the injection control chamber to thereby terminate injection of fuel from the injection hole. In a valve-closing stroke of the needle to close the injection hole, fuel pressure is supplied from a common accumulator to the fuel storage and the injection control chamber in such a manner that the pressure to supply fuel to the fuel storage is lower than that to supply fuel to the injection control chamber. In this way, a force acting on the needle toward the injection hole side can be increased in the valve-closing stroke, to thereby accelerate a valve-closing speed of the needle.

A fuel injector for an engine includes a fuel volume (24) having an air inlet port (30) having a porous membrane (38). The membrane (38) is permeable to air and impermeable to fuel whereby air inlet to the fuel volume (24) forms a two-phase air bubble/fuel dispersion within the fuel volume (24). Upon actuation of the needle valve (18) of the injector, this two-phase air bubble/fuel dispersion flows through the orifice (28) into the engine whereby improved atomization, burn and fuel economy with resultant reduction in emissions are provided.

A supply system (1), for supplying an internal combustion engine (3) with air and fuel, is provided with a first fuel supply circuit (18), having at least one electro-injector (17) controlled by an electronic unit (16), an intake conduit (5) conveying combustion air, a throttle valve (10) in the intake conduit (5), and a second fuel supply circuit (20), activated in the event of failure and having a nozzle (25) that atomizes fuel due to a depression in the intake conduit (5); a fuel flow rate adjusting valve (27) varies the flow rate exiting from the nozzle (25), under the operation of a mechanical transmission (28), according to the operation of the throttle valve (10).