Power plants – Reaction motor – Air passage bypasses combustion chamber
Reexamination Certificate
1999-06-22
2001-08-21
Thorpe, Timothy S. (Department: 3746)
Power plants
Reaction motor
Air passage bypasses combustion chamber
Reexamination Certificate
active
06276127
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field
The subject invention is in the field of equipment and apparatus for reducing the perceivable noise produced by the effluent from gas turbine engines, i.e. jet engines. More particularly, it is in the field of lobed mixers used for suppressing the noise caused by jet engine effluent. Limits on the perceived noise produced by jet engines on airplanes are continuously becoming more restrictive and more prevalent with sophisticated noise measuring systems installed at many airports to enforce the restrictions.
2. Prior Art
The U.S. Patents listed below provide a sample of the prior art in this particular field:
3,153,310
4,835,961
4,077,206
4,909,346
4,148,878
5,216,879
4,819,425
5,638,675
There is also applicable prior art in a NASA report: NASA CR114584 titled “Task V Noise Suppression Of Improved Augmentors For Jet Stol Aircraft.” This report describes a flat array of rectangular corrugations with a relatively hotter and higher velocity gas mixture flowing on one side of the corrugations and relatively cooler, lower velocity air flowing on the other side, as different from having the two flows separated by a flat plate. Tests indicated that the corrugations augmented mixing of the two flows and it is well known in the art that such mixing reduces perceivable noise produced by the effluent. It is also known in the art that the amount of suppression increases with increases in the ratio of wetted areas of the passageways involved to the cross sectional areas of the passageways and with decreasing width dimensions of the convolutions of the passageways.
In view of these facts and the need for improved suppression of the perceivable noise produced by jet engines, the primary objective of the subject invention is to provide a jet engine noise suppressing mixer having passageways having relatively high ratios of wetted areas to cross sectional areas in its passageways and having corrugations in the passageways having relatively small width dimensions relative to the radius of the mixer.
SUMMARY OF THE INVENTION
The subject invention is a noise suppressing mixer for jet engines. It is installed on an engine so that the effluent from the engine passes through it and, because of the configuration of the mixer, is mixed with ambient or bypass air flowing over the mixer. The mixer is circular at its forward end and becomes radially lobed with the radial dimensions of the lobes increasing to a point downstream, i.e. aft, of the forward end. At that point circumferential lobes in the radial walls of the radial lobes are initiated with the circumferential dimensions of these lobes increasing fairly uniformly with increasing distance aft.
In a typical embodiment of the mixer the radial width of the circumferential lobes is in a range of ½ to ⅛ the circumferential width of the radial lobes. As an example there may be 5 to 20 circumferential lobes on each side of a radial lobe. Also, the maximum radial dimension (width) of the circumferential lobes is in a range of 0.015 to 0.15 of the maximum radius of the mixer with a range of 0.025 to 0.050 preferred. There may be a plug in the mixer (a streamlined shaped body) occupying the center or core of the mixer or the lobes may extend close to the center of the mixer. In such an embodiment the circumferential lobes may be confined to the outer ⅓ to ⅔ of the radial lobes. The circumferential lobes significantly increase the ratio of wetted area of the passageways of the mixer to the cross sectional areas of the mixer.
The invention is described in more detail below with reference to the attached drawings.
REFERENCES:
patent: 4077206 (1978-03-01), Ayyagari
patent: 4149375 (1979-04-01), Wynosky et al.
patent: 4335801 (1982-06-01), Stachowiak et al.
patent: 4401269 (1983-08-01), Eiler
patent: 4543784 (1985-10-01), Kirker
patent: 5262807 (1993-11-01), Steckbeck et al.
patent: 5638675 (1997-06-01), Zysman et al.
patent: 5884472 (1999-03-01), Presz, Jr. et al.
patent: 6082635 (2000-07-01), Seiner et al.
Jenny Robert W.
Rodriguez William H
Thorpe Timothy S.
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