Abstract A sound suppression apparatus for a jet engine mounted within the tail portion of an aircraft fuselage wherein a pair of aerodynamic surfaces extend outwardly and upwardly on each side of the fuselage and are mounted for movement about a lateral axis for varying their angle of incidence. The aerodynamic surfaces or panel members from a rear perspective view, form a ''''V'''' or ''''U'''' shaped configuration, with their point of intersection with the fuselage below the main stream of engine exhaUst flow when a variable exhaust nozzle is in its takeoff and landing position or sound suppression mode. By varying the angle of incidence of the aerodynamic surfaces, the function to direct the streamwise airflow, adjacent to the external surface of the fuselage, sideways into the exhaust nozzle flow as to to come in underneath it, as an intermediate fluid stream. This intermediate airflow, causes a mixed boundary layer region beneath the engine exhaust flow which suppresses the downward radiation of the engine exhust noise. Normally, the noise in the exhaust flow would follow the surface contour of the exhaust duct or any extension thereof and spill over the end resulting in a substantial downward angle or come of noise radiation. However, through the introduction of the intermediate flow, a mixed boundary layer flow region is formed throughout the length of the exhaust duct and any undersurface extension thereof, which boundary layer detaches the noise flow from following the surface and provides for greater effectivity of noise deflecting surfaces or shields positioned about the exhaust flow.
Inventors
👤 M Manca
👤 R Drinnon
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-02 21:41
CPC Classifications
F; F02; F02K; F02K1/00; F02K1/44
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
217 words
Apparatus for shielding the sound of the exhaust nozzle flow from a jet engine mounted in an aircraft wherein the nozzle flow discharges over an aft extending variable ramp surface having a raised cruise flight position, and a lowered takeoff and landing position, comprising a pair of shield members adjustably mounted on opposite sides of the exhaust nozzle on an axis transverse to the longitudinal axis of the aircraft so as to extend laterally outwardly and upwardly therefrom and form rearwardly converging surfaces; said shield members having a chord length adjacent the exhaust nozzle of not less than approximately three diameters of the exhaust nozzle and being positioned vertically on each side of the exhaust nozzle so as to intersect the exhaust nozzle exit plane below the raised cruise flight position of the vertical ramp; means for varying the angular position of the shield members about their axes for scooping up atmospheric airflow adjacent to the exhaust nozzle and directing it into the increased nozzle exit area produced by the lowering of the variable ramp surface for the sound shielding mode so as to form an intermediate mixed boundary layer flow between the engine exhaust flow and the ramp surface for shielding the downward radiation of the engine exhaust noise during takeoff and landing of the aircraft.
Claim 2
Dependent Claim
217 words
Apparatus for shielding the sound of the exhaust nozzle flow from a jet engine mounted in an aircraft wherein the nozzle flow discharges over an aft extending variable ramp surface having a raised cruise flight position, and a lowered takeoff and landing position, comprising a pair of shield members adjustably mounted on opposite sides of the exhaust nozzle on an axis transverse to the longitudinal axis of the aircraft so as to extend laterally outwardly and upwardly therefrom and form rearwardly converging surfaces; said shield members having a chord length adjacent the exhaust nozzle of not less than approximately three diameters of the exhaust nozzle and being positioned vertically on each side of the exhaust nozzle so as to intersect the exhaust nozzle exit plane below the raised cruise flight position of the vertical ramp; means for varying the angular position of the shield members about their axes for scooping up atmospheric airflow adjacent to the exhaust nozzle and directing it into the increased nozzle exit area produced by the lowering of the variable ramp surface for the sound shielding mode so as to form an intermediate mixed boundary layer flow between the engine exhaust flow and the ramp surface for shielding the downward radiation of the engine exhaust noise during takeoff and landing of the aircraft.
Claim 3
Dependent Claim
50 words
The combination according to claim 1 comprising means for moving the variable ramp between the raised cruise flight position and the lowered takeoff and landing position, said lowered takeoff and landing position being located below said raised cruise flight position a distance approximately equal to one-fourth of the nozzle diameter.