Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1997-01-31
1998-02-17
Dang, Khanh
Acoustics
Sound-modifying means
Muffler, fluid conducting type
440 89, B63H 2132, F01N 712
Patent
active
057193584
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an arrangement for muffling the exhaust sound of boat motors. The invention is concerned primarily with boats that are fitted with two-stroke diesel motors or engines. Pronounced and abrupt variations in pressure are generated in the exhaust conduits of such motors, resulting in highly disturbing noise, particularly in the case of large motors or engines. By large is meant here a motor or engine power of from about 300 hp to 2,000 hp or more.
It is known to dampen exhaust sound with conventional mufflers constructed, for instance, of chambers which have perforated internal partition walls or are filled with flow-attenuating material. In the case of large two-stroke diesel motors, however, these mufflers are extremely bulky and take up a large amount of space in the stern of the boat. They are also expensive, among other things because the exhaust gases are mixed with cooling water and hence require the application of special technical solutions and materials.
In the case of outboard motors for instance, exhaust sound can be dampened by leading the exhaust gases out into the water. However, with regard to a large diesel motor, and especially a two-stroke diesel motor, quite different conditions apply. It is essential in motors of this kind that the counterpressure in the exhaust conduit is low and does not exceed a given highest value, so as not to impair the running properties of the motor. The increased counter-pressure that occurs when the exhaust conduit is extended down so as to discharge beneath the surface of the water creates a serious drawback. Another problem is that under certain conditions subpressures are liable to occur in the exhaust conduit, for instance when the motor is stopped abruptly. If the exhaust conduit discharges beneath the surface of the water, water may be drawn into the conduit by suction and, in the worst case, reach the motor and cause damage thereto.
Because of these problems, present-day conventional large two-stroke diesel motor installations, and also other motor installations, include an exhaust pipe which discharges into the ambient air, often in the transom of the vessel, without including a muffler. Such installations result in highly disturbing noise.
An attempt to reduce noise is reported in U.S. Pat. No. 4,002,136. This publication describes a boat in whose stern there has been built on each side of the boat a box or chamber 20 which lies partially beneath the waterline of the boat. An exhaust pipe 16 extending from the boat motor 12 discharges into the chamber 20 above the waterline. The bottom of the chamber is formed by the bottom of the hull of the boat and has an open slot 52 through which exhaust gases can flow out into the water. The transom 31 of the boat contains a plurality of through-penetrating openings 40 which connect that part of the chamber located above the water with the surroundings. When the motor is idling or running at low speeds, the openings 40 prevent a counterpressure build-up in the chamber of such magnitude as to impair running of the motor. The open slot or gap 52 is adapted so that as the boat makes speed in a forward direction, the water flow will facilitate the outflow of exhaust gases.
DE 422,846 describes a motor boat whose bottom includes a downwardly open exhaust chamber b into which an exhaust pipe d discharges. There is pivotally mounted in the chamber b a flap c which is caused by the water flowing past the flap to take a position in which exhaust gases can be drawn from the chamber by suction both when the boat moves forwards and when the boat moves backwards.
U.S. Pat. No. 5,007,870 teaches a water scooter which includes a water-jet drive. In the embodiments illustrated in FIGS. 7 and 8, an exhaust pipe 22 extends out through the transom of the vessel and discharges into a muffler box 38 mounted externally of the transom. The bottom of the box 38 includes an opening 39 through which exhaust gases can flow out into the water.
SUMMARY OF THE INVENTION
The object
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Dang Khanh
Ingenjorsfirma Jan Lindholm AB
LandOfFree
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