Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1989-04-17
1990-09-25
Fuller, Benjamin R.
Acoustics
Sound-modifying means
Muffler, fluid conducting type
181287, 244 1N, B64F 126
Patent
active
049587005
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a protective facility for suppressing the noise of large, high-speed gas flows, especially for aircraft engines, in which there is erected behind the engines an obliquely inclined, latticed directing element, behind which is located an approximately horseshoe-shaped sound absorption wall approximately twice the height of the directing element.
A protective facility of this type is known from DE-PS 3023707. In this instance, the gas flows which emerge at high noise intensities from aircraft engines during a test operation are deflected upward by a latticed directing element with no risk of backflow into the engine, while the noise is directed, more or less unabated, through the directing element until it is absorbed by the sound absorption wall.
This noise absorption wall is horseshoe-shaped, so that sound emerging to the sides and the rear can be sufficiently absorbed.
It is not possible, however, with a sound absorption wall configuration of this type, to also reduce noise radiated from the intake region of the engine or to reduce interfering wind loads, which in some circumstances can even prevent an engine test.
The object of the invention is therefore to configure the known sound protection facility such that sound radiation in all directions can thereby be largely reduced, so that environmental impact is greatly diminished.
To achieve this object, according to the invention two pivotable door leaves covered with sound absorption material are hinged at the front edges of the free arms of the horseshoe-shaped sound absorption wall, with these leaves being capable of pivoting through approximately 60.degree. inward and being of such length that when completely swung inward, they leave a gap for the nose of an aircraft.
This addition to the sound absorption wall, which when swung inward covers the intake region of the engines as well, ensures that practically all residents in the surrounding area are only exposed to a reduced amount of noise during engine testing.
The door leaves can be movable on a plurality of rails, running concentrically around the pivot point and configured as arcs of a circle about the pivot point.
Advantageously, the door leaves have a box-shaped cross section in top view, with a triangular extension at the rear end, the triangular tip of which is mounted, in the area of the ends of the horseshoe-shaped sound absorption walls, as a rotation point, so that in the swung-in position, the sound absorption walls of the door leaves abut the other sound absorption walls without a gap.
To be moved, the door leaves can be driven by motors, associated with each rail and synchronized with one another, which act on the drive rollers guided in the rails through propeller shafts and angle gears.
The configuration and operation of an exemplary embodiments of the invention are explained in more detail with reference to a schematic drawing, the figure of which shows a top view of the overall facility with the aircraft undergoing the engine test.
As the drawing indicates, erected behind the aircraft 1, with for example four engines 2, 3, 4 and 5, is first a latticed directing element in the form of a metal mesh lattice 6, transparent to sound, sloping against the direction of the oncoming flow so that the gas flows emerging from the engines 2-5 are deflected upward, while the sound waves, more or less unhindered, strike the sound absorption wall 7 and are largely absorbed there. Located on each side of the aircraft are additional sound absorption walls 8 and 9 with inwardly angled extensions 12 and 13 at the rear end which form, with the exception of gaps 10 and 11 covered in a noise-suppressing manner, a complete horseshoe-shaped sound absorption wall surrounding the aircraft.
As a result, most of the noise radiated from the engines is suppressed. With a configuration of this type, however, noise radiated from the engine intake area can emerge freely at the front and thus lead to considerable noise impact. The invention therefore provides for additional door leaves 16 and
REFERENCES:
patent: 3096847 (1963-07-01), Hardy
patent: 3141639 (1964-07-01), Klein
patent: 3604530 (1971-09-01), Duthion et al.
patent: 3842941 (1974-10-01), Gerber
Fuller Benjamin R.
Rheinhold & Mahla GmbH
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