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US 2003/0196425 A1Published application
Jet nozzle mixer
AssigneeNone recorded
InventorJack H. Anderson
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AssigneeNone recorded
InventorJack H. Anderson
Estimating the term…
A second stage external jet nozzle mixer (20) includes identically formed lobes (48), which equal in number the lobes of the first stage internal mixer (42). The external mixer works with the internal mixer, and furthers the mixing of the jet engine internal bypass flow with the internal jet engine core flow. This mixing levels the disparate flow velocities attendant with the jet engine exhaust, reduces the peak velocities from the jet engine core and increases the lower bypass velocities of the jet engine internal bypass flow. Because noise is a function of jet exhaust velocity to the 7th power, and because peak velocities from the core flow are reduced, the jet noise is thereby reduced. In addition, the lobes of the external jet nozzle mixer are designed to entrain external air into the jet engine internal flow. This additional entrainment of external air further reduces the overall jet velocity, and further decreases noise. Implementation is effected by external lobe design. As the external mixer lobes extend axially outwardly from their attachment to the engine nozzle, they expand from an essentially circular base to an undulating configuration whose apices increase in height. The lobes include complex curvatures that greatly enhance mixing of the gases and ambient cooling air, and thereby reduce noise. At the lobe terminus, the lobe area remains the same as for the jet engine for which it is designed. The interior surfaces of the lobes force the impinging hot gases in all directions towards the interior of the mixer, essentially 45° C. to 60° C., to effect a vigorous mixing of the gases. Simultaneously, additional ambient cooling air is forced from the exterior surfaces of the lobes to mix further with the internally mixed gases. These actions cause the smaller gas cores, which were formed by the first stage mixer, to break into innumerable forms which are both cooler and considerably noise attenuated. In part, the internal contours of the lobes act as flutes to produce a lifting effect which causes the primary hot and cold flows to mix before exiting the nozzle. The external contours of the lobes act as venturi chutes which accelerate the cooler secondary flow of ambient air. The lobes thereby act collectively as an injector to force the cooler ambient secondary flow into the previously mixed primary flow as it exits the nozzle. These actions further reduce the noise level. Incidental to noise reduction is a salutary increase in thrust efficiency and consequent decrease in fuel consumption, and closer spacing of the lobes to thrust reverser buckets for enabling an increased capture of the exhaust by the buckets when deployed in their thrust-reversing position.
In a nozzle for a jet engine having an existing first stage mixer which includes a number of first stage lobes, the improvement comprising a second stage mixer coupled to the first stage mixer, said second stage mixer having a plurality of identically formed lobes which equal in number those of the first stage lobes.
The improvement according to claim I wherein the existing first stage lobes mix hot gases from combustion in the jet engine with bypass air to diminish the velocity of the hot gases, and in which said second stage lobes have interior surfaces which are configured to further mix the mixed hot gas-bypass air mixture and further to level the velocities of the mixed hot gas-bypass air mixture and thereby reduce jet engine noise.
The improvement according to claim I in which said second stage identically formed lobes are configured (a) on their interior surfaces to force impinging hot gases from the jet engine towards the interior of said second stage mixer and (b) on their exterior surfaces to mix with ambient cooling air to form gas cores which are smaller than those formed by the first stage mixer and to break the smaller gas cores into innumerable forms which are both cooler and noise attenuated.
In a nozzle for a jet engine having an existing first stage mixer which includes a number of first stage lobes, a method for cooling exhaust engine exhaust gases and for attenuating engine exhaust noise comprising the steps of:
In a nozzle for a jet engine having an existing first stage mixer which includes a number of first stage lobes, a method for cooling hot exhaust engine exhaust gases and for attenuating engine exhaust noise comprising the steps of:
A method for attenuating engine exhaust noise in a jet engine, in which hot exhaust gases from the jet engine are first mixed with bypass air to provide a cooler and lower flow velocity mixture thereof, comprising the step of:
Dependencies are inferred from the claim text.
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Nozzles having means for adding air to the jet or for augmenting the mixing region between the jet and the ambient air, e.g. for silencing:…
Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto: nozzles having means for adding…
Reversing fan flow: using thrust reverser flaps or doors mounted on the fan housing
Plants including a gas turbine driving a compressor or a ducted fan: in which part of the working fluid by-passes the turbine and combustion chamber
Term end not estimated
Not Applicable
Not Applicable
1. Field of the Invention
FIGS. 1a and 1b are perspective views of an end portion of a jet engine nozzle assembly to which is attached both a thrust reverser and a second stage external jet nozzle mixer as embodied in the present invention.
FIG. 2 is schematic drawing illustrating the interior of the jet engine shown in FIG. 1 with a known first stage internal mixer in the interior of the engine and the second stage inventive external jet nozzle mixer at the terminus of the engine, including the decrease in distance between the jet nozzle mixer of the present invention and the thrust reverser buckets, as compared to its non-use.
FIG. 3a is a view of the engine and its internal mixer shown in FIG. 2 taken along line 3-3 thereof, and FIG. 3b is a perspective view of the cone and surrounding vanes of the internal mixer.
Because the present invention was devised particularly with respect to the Pratt & Whitney JT8D-217/219 Series engine, the following discussion will be directed specifically thereto; however, it is to be understood that the present invention is equally relevant for use in other jet engines and, therefore, is not to be limited to a specific jet engine.
Accordingly, FIGS. 1a and 1b illustrate a nozzle assembly 18 relating to, for example, a Pratt & Whitney JT8D-217/219 Series jet engine to which a jet nozzle mixer 20 as embraced by the present invention is attached at its exhaust terminus 19. Assembly 18 also supports a thrust reverser having a pair of thrust reverser buckets 22. The attachment of the thrust reverser buckets to assembly 20 is effected by bars 24 which are pivotally linked to a pair of diametrically opposed mechanisms housed within fairings 26, one of which is shown in FIG. 1. The fairings are secured at opposite sides of the assembly. The thrust reversers and the linking bars are of conventional design and are unmodified when coupled with the present invention. The fairings are also of conventional design, but a part of the structure covered thereby is i slightly modified as will be explained below with respect to FIGS. 12 and 13.
As shown also in FIG. 2, mixer 20, because of its added axial length, is positioned closer to thrust reverser buckets 22 when they are deployed as brakes. Such closer positioning is demonstrated by the different lengths “x” and “y” of FIG. 2. The ameliorative result of such closer positioning permits the buckets to capture a greater portion of the exhaust for braking purposes than previously obtainable. However, it is important that mixer 20 not be located too close to buckets 22 so that the flow of the redirected exhaust gases are not adversely affected and that the doors, linkages and the mixer are not deleteriously stressed.