U.S. patent number 3,905,445 [Application Number 05/381,000] was granted by the patent office on 1975-09-16 for vortex turbulence noise generation suppressor.
This patent grant is currently assigned to Bolt Beranek and Newman Inc.. Invention is credited to Terry D. Scharton.
United States Patent |
3,905,445 |
Scharton |
September 16, 1975 |
Vortex turbulence noise generation suppressor
Abstract
This disclosure deals with structures for suppressing a
substantial percentage of noise that normally is attendant upon
vortex generation from jet engines, blown flaps, turbine outlets
and the like, involving successive tubular sections of successively
reduced width disposed longitudinally, preferably along a common
axis.
Inventors: |
Scharton; Terry D. (Santa
Monica, CA) |
Assignee: |
Bolt Beranek and Newman Inc.
(Cambridge, MA)
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Family
ID: |
26911875 |
Appl.
No.: |
05/381,000 |
Filed: |
July 20, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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217369 |
Jan 12, 1972 |
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Current U.S.
Class: |
181/213 |
Current CPC
Class: |
F01N
13/082 (20130101); F02K 1/40 (20130101) |
Current International
Class: |
F01N
7/08 (20060101); F02K 1/40 (20060101); F02K
1/00 (20060101); F01N 001/00 () |
Field of
Search: |
;181/46,56,60,33H,33HA,33HB,33HC,33HD |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hartary; Joseph W.
Assistant Examiner: Weldon; U.
Attorney, Agent or Firm: Rines Rines Shapiro and Shapiro
Parent Case Text
This is a continuation application of Ser. No. 217,369, filed Jan.
12, 1972, now abandoned.
Claims
What is claimed is:
1. A noise generation suppressor for breaking up the exhaust of a
jet outlet into a plurality of streams while minimizing
flow-dividing drag, having, in combination, means including a
plurality of successive longitudinally extending passages of
successively smaller cross-dimension for dividing said exhaust into
a plurality of streams and for breaking up the vortex pattern of
said exhaust, each of said passages having an inlet at one end and
an outlet at the opposite end, each inlet being located adjacent
the outlet of the preceding passage and remote from the inlet of
the preceding passage, and each passage being substantially freely
open and devoid of transverse sub-division along said
cross-dimension throughout most of its length.
2. A noise generation suppressor as claimed in claim 1 and in which
said passages are of about equal length.
3. A noise generation suppressor as claimed in claim 1 and in which
each of said passages overlaps only a portion of the preceding
passage.
4. A noise generation suppressor as claimed in claim 1 and in which
said passages have substantially cylindrical cross-section.
5. A noise generation suppressor as claimed in claim 1 and in which
said passages have substantially rectangular cross-section.
6. A noise generation suppressor as claimed in claim 1 and in which
said passages comprise plate members.
7. A noise generation suppressor as claimed in claim 1 and in which
said passage outlets are rectangular slits.
8. A noise generation suppressor as claimed in claim 1 and in which
said jet outlet has associated therewith a converging potential
core and in which said passages are located within the converging
potential core.
Description
The present invention relates to the suppression of the generation
of noise in exhaust outlets such as jet engines, blownflap
structures for producing additional lift in aircraft, turbines and
similar systems, all having vortex-type exhausts, generically
referred to herein as jet outlets.
Numerous types of passive and dynamic noise suppressors have been
proposed through the years for reducing the generation of noise in
fluid flow systems, such as, for example, those associated with
vehicular engines and the like as described, for example, in U.S.
Letters Pat. No. 2,893,508, issued July 7, 1959 to Clayton H. Allen
and Jordan J. Baruch and assigned to Bolt Beranek and Newman Inc.,
the assignee of the present invention. Particular problems,
however, exist in connection with the noise generated in the
production of vortices associated with jet outlets of the
before-mentioned types, as discussed, as an illustration, in an
article by G. S. Beavers et al. entitled "Vortex Growth in Jets,"
appearing in the Journal of Fluid Mechanics, Vol. 44, Part I, 1970.
Attempts have been made to overcome this problem by multi-tube
devices that, for example, break up the jet into small uncorrelated
jet outlets, as described by G. S. Schairer et al. in AIAA Paper
No. 68-1023, "Perspective of SST Aircraft Noise Problem," October,
1968, particularly FIG. 30. Such devices, however, are complex and
involve breaking the jet circumferentially, which has been found
actually not to be necessary to the purposes of the present
invention. In accordance with a discovery underlying the present
invention, to the contrary, it has been found that the base
pressure drag inherent in such multi-element suppressors may be
eliminated with a much simpler design that only breaks up the jet
radially.
An object of the invention, accordingly, is to provide a new and
improved noise-generation suppressor for a jet outlet that is not
subject to such pressure drag problems and that obviates the
disadvantages of complex circumferential dividing structures,
effecting vortex noise-generation suppression, rather, with a far
more simple and effective construction.
A further object is to provide a novel noise suppressor of more
general applicability, as well.
Other and further objects will be described hereinafter and are
more particularly pointed out in the appended claims. In summary,
however, from one of its aspects, the invention contemplates a
noise generation suppressor for a jet outlet and the like having,
in combination, a plurality of hollow tubular members mounted upon
the outlet and extending therefrom along a common longitudinal
axis, the successive tubular members being of successively reduced
transverse cross dimension or width at successive longitudinally
spaced positions from the outlet along the axis.
The invention will now be described with reference to the
accompanying drawing, FIG. 1 of which is an isometric schematic
view of a preferred form of the invention as applied to cylindrical
jet outlets;
FIG. 2 is a longitudinal section illustrating vortex
generation;
FIG. 3 is a graph of experimentally obtained results; and
FIG. 4 is an end view of a rectangular geometry modification.
Referring to the drawings, a jet outlet 1, as from a jet engine or
the like, is shown having mounted thereon by means of ribs or other
brackets 2, successive cylindrical hollow vanes or tubular members
3, 3', 3", 3'", etc., each of successively reduced transverse
cross-dimension, width or diameter, and each disposed at successive
longitudinally spaced positions rearward of the outlet 1 along the
common longitudinal axis A. The successive longitudinal disposition
of the coaxial members 3, 3', 3", 3'" and their tapered
cross-dimensioning is selected to fall within the inner converging
tapered conical potential core C of FIG. 2, containing successive
regions +, -, +, -, etc. surrounding which successive oppositely
rotating vortices are generated from such jet outlets, with the
members 3, 3', 3", 3'" radially breaking-up the vortex patterns.
The successively reduced transverse width or diameter of the
successive coaxially mounted members, thus shaped to conform to the
rate of convergence of the potential core C of the vortices,
prevents large-scale vortices from being formed and produces,
rather, a set of small, annular uncorrelated jets. This has been
found to suppress much of the noise generated by the large-scale
vortex generation.
In certain applications, including that later-described in
connection with the performance illustrated in FIG. 3, the length
of the successive members 3, 3', 3", 3'" is made substantially
equal, with each member overlapping a part of the preceding member;
and the supporting brackets 2 may be disposed at different
circumferential locations or spacings for the successive members,
as shown.
Other parallel sheet configurations than successively
reduced-dimension circular cylindrical tubular members may also be
employed, where appropriate, including parallel rectangular plate
members, schematically shown at 30, 30', 30", etc. in connection
with a rectangular outlet in FIG. 4. In all cases, however, the
invention is concerned with preventing or suppressing noise
generation in the first instance, as distinguished from absorbing
already generated sound.
Comparing the radiated sound power with frequency for an
experimental jet nozzle of five-eighths inch inside diameter, as
used in a turbine nozzle, with tubular members 3, 3', 3", 3'" of
the type shown in FIG. 1, down to one-sixteenth inch for the
smallest diameter and over a longitudinal distance of about 2
inches, noise reduction of the order of 10 decibels was obtained
("Suppressed" curve in FIG. 3) over a broad frequency band
extending from 250 to 10,000 Hz. From experience with scaling
techniques in this field, it has been determined that similar
substantial improvement can be obtained with much larger
structures, as well as smaller structures. These tests show,
moreover, that these novel results can be accomplished with
relatively small thrust lost; namely, that due primarily to
friction drag.
Where the jet outlet takes a different geometrical configuration,
such as other geometrically configured outlets, as in the
before-mentioned blown flap structures for adding wing lift in some
aircraft, the tubular or plate members may assume corresponding
geometrical configurations; but with the same constructional
features and relative positioning and dimensioning
before-discussed.
Further modifications will also occur to those skilled in this art
and all such are considered to fall within the spirit and scope of
the invention as defined in the appended claims.
* * * * *