Method and apparatus for selectively varying an effective fluid flow area of a jet engine exhaust nozzle

A fluid jet reaction propulsion apparatus comprising duct means for communicating a flow of motive fluid to an exhaust portal, said duct means defining nozzle means including an exhaust nozzle throat for accelerating said flow of motive fluid to define a fluid jet, and area varying means disposed always entirely upstream of said exhaust nozzle throat for varying the area of the latter which is available for downstream flow of said motive fluid therethrough.

In a jet engine of the type comprising a source of motive fluid, and having a tail pipe defining a flow path for said flow of motive fluid and defining a converging nozzle throat, a center body in said tail pipe spaced upstream of said nozzle throat and carrying means for defining a reverse flow motive fluid wake extending downstream therefrom toward said nozzle throat, means for relatively moving said fluid wake to and through said nozzle throat.

The method of varying the flow coefficient of an exhaust nozzle of a jet engine, said exhaust nozzle defining a nozzle throat through which is discharged a flow of motive fluid, said method including the steps of:

• providing means for forming a reverse flow fluid wake in said flow of motive fluid upstream of and extending downstream toward said nozzle throat, and moving a portion of said reserve flow fluid wage to and through said nozzle throat to reduce the area thereof available for downstream flow of said motive fluid.

Jet propulsion engine apparatus comprising a source of engine motive fluid, an axially and circumferentially extending wall defining a flow path for axial flow of said engine motive fluid therein, said flow path converging in a downstream axial direction with respect to flow of said motive fluid from said engine to define a nozzle throat whereat said wall physically encompasses a minimum effective flow area for said motive fluid, said nozzle throat opening downstream to ambient, a center body disposed centrally within said flow path spaced upstream of said nozzle throat, said center body defining a downstream axially extending termination portion of substantially frusto-conical shape, said termination portion comprising means for originating upstream of said nozzle throat and within said motive fluid an aerodynamic fluid recirculation wake extending axially downstream therefrom toward said nozzle throat, said nozzle apparatus further comprising means for moving said fluid wake axially with respect to said nozzle throat between a first position of relatively lesser (or, no) partial obstruction of said nozzle throat by said fluid wake with respect to effective flow area thereof which is available for downstream flow of said motive fluid, and a second position wherein said fluid wake effects a relatively larger partial obstruction of said nozzle throat.