Exhaust gas recirculation system having flow control valve combined with supersonic nozzle

In an internal combustion engine, an exhaust gas recirculation system comprising:

• means defining a fluid flow channel connecting an exhaust passage of the engine to an induction passage of the engine to recirculate a portion of the exhaust gas therethrough;
• a converging-diverging nozzle circular in cross section disposed at an intermediate section of said channel for flowing recirculated exhaust gas therethrough, said nozzle having a throat and having a converging section and a diverging section shaped such that the velocity of the recirculated exhaust gas is sonic at the throat of said nozzle when a pressure difference between the entrance and exit pressures of said nozzle exceeds a predetermined magnitude;
• a conical valve member in said nozzle coaxially therewith to extend through said throat;
• the surface of said valve element and inner surfaces of the diverging section defining therebetween an angle from about 7 to 10 degrees in longitudinal section;
• and
• means for supporting and moving said valve member axially thereby to vary the cross-sectional area of said channel at said throat.