Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1997-04-09
1998-12-01
Dang, Khanh
Acoustics
Sound-modifying means
Muffler, fluid conducting type
181270, 181280, 181256, 181230, F01N 108
Patent
active
058441786
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
The invention relates to a resonance muffler for two cycle internal combustion engines with a rotationally symmetric resonator housing having an input pipe socket leading into it and being itself connected to an exhaust pipe including a muffler. Within the resonator housing, there are sequentially arranged, in the direction of flow, a diverging diffusor section, an optional intermediate section, as well as a converging reflector section.
2. The Prior Art
In conventional resonance mufflers, the input pipe socket leads axially into the diffusor section of the resonator housing, resulting in axial flow therethrough, and the exhaust pipe including its muffler is axially connected to the reflector section as a separate component. Because of the diverging and converging sections positioned at opposite ends within the resonator housing, a reverse negative pressure wave is formed for each injected exhaust gas pressure wave, augmenting the clearing or emptying of an internal combustion engine cylinder and resulting, over all, in improved combustion, reduced gas emission, and output efficiency. The terminal muffler is required since the resonator provides no silencing effect.
The structural length of the resonator housing and of the muffler connected thereto is inversely proportional to the number of rotations of an internal combustion engine. For reasons of noise protection, resort is had to lower and lower operative rotations, particularly in connection with small displacement two cycle engines for model airplanes, motor scythes or chain saws. At an operational engine speed of 6,000 rpm a resonance muffler of conventional structure would have an overall length of 1 m, which is unacceptable for the mentioned applications. In those cases, it has hitherto not been possible to make use of the advantages of resonance mufflers, and compact mufflers had to be used which, because they lack any resonance effect, operate uneconomically and pollute the environment. On the one hand, relatively large quantities of combusted gases remain in the cylinder during the exhaust process resulting in inferior combustion, and, on the other hand, relatively large quantities of unburned fuel mixture enter into the exhaust gas. The two effects result in an efficiency reduction of about 35% compared to a resonance muffler.
OBJECT OF THE INVENTION
It is a task of the invention to provide a resonance muffler of highly compact dimensions, so that the advantages of the resonance principle may be applied to small two cycle internal combustion engines, such as motors for airplane models, lawn mowers, chain saws, motor scythes, etc.
SUMMARY OF THE INVENTION
This task is accomplished by a resonance muffler of the kind mentioned in the introduction, which in accordance with the invention is characterized by an exhaust pipe extending coaxially through a resonator housing and an input pipe socket leading tangentially into the diffusor section.
A two-fold saving in space is achieved in this manner. On the one hand, the muffler which is arranged within the output pipe is entirely positioned within the interior of the resonator housing, extending through the resonator housing quasi as a core. On the other hand, the structural length of the resonator is drastically shortened, because owing to their tangential flow approach the exhaust gasses will flow through the resonator housing in a helical flow pattern around the core, so that their effective flow path within the resonator housing is a multiple of the structural length of the resonator housing. The initial enlargement of the cross-section of the flow and the ensuing reduction of the cross-section of the flow required by the described resonator principle, occurs naturally, because the progressive increase in pitch of the helical flow as a result of the initial deflection from the tangential input to the helical flow-through pattern corresponds to a diverging section, and the impinging of the helical flow against the other end of the resonator
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patent: 4129196 (1978-12-01), Everett
patent: 4679597 (1987-07-01), Stein
patent: 4792014 (1988-12-01), Shin-Seng
patent: 5109950 (1992-05-01), Lescher
Dang Khanh
Hormann Karl
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