초록 ▼

Disclosed is a segmented mixing device for reducing jet engine exhaust noise wherein mixing is enhanced between adjacent exhaust flows and between exhaust flow and free-stream flow. The device does so with a very small degradation in aircraft performance. The device is a segmented, triangular or tra

Disclosed is a segmented mixing device for reducing jet engine exhaust noise wherein mixing is enhanced between adjacent exhaust flows and between exhaust flow and free-stream flow. The device does so with a very small degradation in aircraft performance. The device is a segmented, triangular or trapezoidal shaped, curved extension to a nozzle's sleeve that results in a serrated trailing edge. The nozzle extensions enhance the natural free mixing of the jet's exhaust flows and therefore reduce the acoustic energy associated with the velocity differences between the streams in which they are imbedded. The novel structure forces adjacent flows to penetrate into one another to a greater depth than that achievable with free mixing and results in a more uniform flow in a shorter stream wise distance while limiting high frequency noise through utilization of root radii in the order of 15 to 20% of the segment's width at the intersection of a parent nozzle.

대표청구항 ▼

1. A segmented mixing device for jet engines comprising a segmented, substantially triangular or trapezoidal shaped, curved extension of a nozzle sleeve wherein a plan view of said nozzle extension comprises a sinusoidal or “saw toothed” wave shape, said nozzle extension having a semi-

1. A segmented mixing device for jet engines comprising a segmented, substantially triangular or trapezoidal shaped, curved extension of a nozzle sleeve wherein a plan view of said nozzle extension comprises a sinusoidal or “saw toothed” wave shape, said nozzle extension having a semi-round valley radius and a semi-round tip radius, said semi-round root radius larger than said semi-round tip radius. 2. A segmented nozzle extension for a jet engine wherein a plan view of said nozzle extension comprises a sinusoidal or “saw toothed” wave shape, said nozzle extension having a semi-round valley root radius and a semi-round tip radius, said semi-round valley root radius larger than said semi-round tip radius, to prevent a rise in high frequency noise and a loss of thrust. 3. A segmented nozzle extension comprising sinusoidal or “saw toothed” wave shape segments with semi-round intersections with a baseline nozzle and semi-round trailing edges, said semi-round intersections with the baseline nozzle having radii in the order of 15% to 20% of a planform width of the segments at the intersection with the baseline nozzle. 4. A segmented extension for a jet engine, said nozzle extension having an outer surface curving inward, toward an engine centerline, thereby forcing an outer flow into an inner flow, and, said nozzle extension having a planform shape with differing semi-round valley root an tip radii which creates a stream wise vortex thereby enhancing rapid mixing of the outer flow and the inner flow. 5. A segmented nozzle extension for a jet engine, said nozzle extension having an outer surface curving outward, away from an engine centerline, thereby forcing an inner flow into the outer flow, and, said nozzle extension having a planform shape with differing semi-round valley root and tip radii which creates a streamwise vortex thereby enhancing rapid mixing of the outer flow and the inner flow. 6. A nozzle extension according to claims 1 , 2 , 3 , 4 or 5 utilized on an internal or external plug primary nozzle and a secondary nozzle of dual flow exhaust systems. 7. A nozzle extension according to claims 1 , 2 , 3 , 4 or 5 utilized on a nozzle of a mixed flow exhaust system and a flow splitter between a primary and secondary stream of those systems. 8. A nozzle surface separating adjacent flows, said surface having an extension according to claims 1 , 2 , 3 , 4 , or 5 for providing enhanced mixing of the adjacent flows and preventing a rise in high frequency noise above about 2000 Hz, and a drag reduction on downstream surfaces. 9. A nozzle surface separating adjacent flows, said surface having an extension according to claims 1 , 2 , 3 , 4 , or 5 for providing enhanced mixing of the adjacent flows and preventing a rise in high frequency noise above about 2000 Hz, or a drag reduction on downstream surfaces. 10. A method for reducing noise radiated from a jet engine exhaust flow comprising the steps of:adding an extension according to claims 1 , 2 , 3 , 4 , or 5 to a gas flow nozzle; and,configuring said extension to reduce noise at frequencies nominally below 2000 Hz while inhibiting an increase in noise nominally above 2000 Hz. 11. In combination:a gas flow nozzle;said gas flow nozzle having a trailing edge; a segmented extension for said gas flow nozzle; and, said extension having semi-round tips of predetermined radii and valleys having radii exceeding said predetermined radii for enhancing a reduction of low frequency noise by inhibiting an increase in high frequency noise and a loss of thrust. 12. The combination according to claim 11 wherein said extension has a triangular planform. 13. The combination according to claim 11 wherein said extension has a trapezoidal planform. 14. A method for controlling exhaust flow from a jet engine comprising the steps of: providing a segmented extension mixing device incorporating a planform shape with semi-round intersections with a baseline n ozzle and semi-round trailing edges, said intersections have a semi-round root radius and said trailing edges have a semi-round tip radius, said semi-round root radius larger than said semi-round tip radius providing rounding of the upstream intersection between extension and baseline nozzle which permits a primary flow to exit the nozzle sooner and in a more radial manner thereby increasing the strength of a streamwise vortex rounding the trailing edge to increase a spanwise average turning angle of a secondary flow resulting in greater penetration of the secondary flow into the primary flow and increased mixing of the two flows; and providing the planform shape and trailing edge radius of the mixing device with a turning angle increase of 10% to 30% over a sharp pointed triangular configuration.