Dual-mode plug nozzle

Abstract

A variable geometry convergent-divergent nozzle for a gas turbine engine includes a centerbody extending rearward along a longitudinal axis of the engine which has a maximum diameter section. An inner shroud surrounds the centerbody and cooperates with the centerbody to define the throat of the nozzle. An outer shroud surrounds the inner shroud and cooperates with the centerbody to define the exit area of the nozzle. Both shrouds are independently translatable to provide independent control of the nozzle throat area and the nozzle expansion ratio. Additional actuation of the inner shroud results in the throat being disposed upon a fully forward portion of the centerbody, said fully forward shroud disposition being more forward than over the maximum diameter section. The nozzle may further comprise independent translation of the centerbody with respect to the shrouds.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a national stage application under35 U.S.C. §371(c) of prior filed, co-pending PCT application serial number PCT / US2014 / 39914, filed on May 29, 2014 which claims priority to U.S. Patent Application Ser. No. 61 / 829,495, titled “Dual-Mode Plug Nozzle” and having filing date May 31, 2013, all of which is incorporated by reference herein.[0002]The US Government may have certain rights in this invention pursuant to Contract No. MDA972-01-3-0002 (DARPA) awarded by the US Department of Defense.BACKGROUND[0003]Embodiments of the present invention relates generally to nozzles for gas turbine engines and more particularly to a variable geometry nozzle which functions as a convergent nozzle, a divergent nozzle or a convergent-divergent nozzle.[0004]Variable geometry is required where exhaust systems for gas turbine engines operate over a wide range of pressure ratios (i.e. nozzle throat pressure / ambient pressure or P8 / Pamb) where...

AI Technical Summary

Benefits of technology

[0012]All of the above outlined features are to be understood as exemplary only and many more features and objectives of the embodiments may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification and drawings included herewith.

[0013]The above-mentioned need is met by the present embodiments, one aspect of which provides a nozzle for a gas turbine engine having a longitudinal axis, including a centerbody extending rearward along the longitudinal axis, the centerbody including a throat section of increased diameter relative to the remainder of the centerbody; an inner shroud surrounding the centerbody, the inner shroud having an outer surface and an inner surface, the inner surface including at least a middle section of decreased diameter relative to the remainder of the inner surface, the inner shroud being selectively moveable along the longitudinal axis in forward and aft directions relative to the centerbody; and an outer shroud surrounding the inner shroud, the outer shroud having a forward edge, an aft edge, and an inner surface extending from the forward edge to the aft edge, the outer shroud being movable in forward and aft directions relative to the centerbody. Means are provided for independently selectively moving the inner and outer shrouds in forward and aft directions relative to the centerbody. Alternatives provide for selectively independent translation of the centerbody. Embodiments provide that the relative position of the centerbody, the inner surface of the inner shroud, and the inner surface of the outer shroud, each relative to the others, collectively and together define a fluid flow path through the nozzle.

[0014]According to another embodiment, a gas turbine engine having a longitudinal axis includes a centerbody; an annular inner shroud having an outer surface and an inner surface, the inner surface including a middle section of decreased diameter relative to the remainder of the inner surface, the inner shroud selectively moveable along the longitudinal axis between forward and aft positions relative to the centerbody; an annul

Problems solved by technology

Historically, the wide range of values for A8 has resulted in degraded performance at some flight conditions.

Fixed nozzles do not kinematically change their geometry and thus do not operate efficiently over a wide range of nozzle pressure ratios (P8/Pamb).

Because of the overlapping flap and seal structure, leakage paths may be created which reduce operating efficiency.

Furthermore, for a number of engine cycles, the scheduled A9/A8 area ratio versus A8 relationship will not provide an optimum match to the engine cycle demands.

As a result, such engines will not deliver peak nozzle performance at certain key operating points.

Despite attempts in the

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