Power plants – Internal combustion engine with treatment or handling of... – Divider – collector – valve means – or boundary layer device...
Patent
1995-01-27
1997-08-12
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Divider, collector, valve means, or boundary layer device...
731181, 181226, 181252, 181277, F01N 700
Patent
active
056553676
DESCRIPTION:
BRIEF SUMMARY
This application has been filed under 35 USC 371 for the invention described and claimed in international application number PCT/FR93/00703, filed Jul. 7, 1993.
The present invention relates to an inlet or exhaust line for a reciprocating machine.
According to the invention, by reciprocating machine is meant any device creating flow pulsations either in an induced manner or in a spontaneous manner, such as, for example, a combustion engine, a compressor or a heat pump.
It is known that gas inlet or exhaust pulsations of a reciprocating machine are a major source of noise, especially low-frequency noise. The same is true for the outputs of all reciprocating machines (compressors, vacuum pumps, heat pumps etc) and for the inlets of these machines.
These pulsations have very high energies at precise frequencies related to the cycle of the machine, but are very weak for different intermediate frequencies.
In fact, acoustic analysis of this noise reveals a spectrum having discrete lines of very high energy.
In order to decrease the level of noise generated by the pulsations of a combustion engine for example, exhaust lines fitted with silencers are used.
However, although these silencers enable the low-frequency pulsations of the exhaust gases to be attenuated moderately, they simultaneously introduce into the exhaust line singularities which are manifested by fluctuations and turbulence in the flow, and therefore by noise possessing medium and high frequencies.
In addition, when an exhaust line is installed on a motor vehicle, its geometrical singularities are all the more important as it has to be fitted into the space available beneath the vehicle. Thus it is frequently observed in exhaust lines that the internal cross-section of the pipe varies several times from one end of the exhaust line to the other, the exhaust line moreover including many baffles and other obstacles likely to generate noise.
As a result, the usual exhaust lines, which are constituted by tubular pipes connecting silencers, are relatively bulky and are the source of additional blowing noise; furthermore, they lead to quite appreciable pressure drops.
Devices are also known for reducing the noise of an exhaust line which generate, in the direction of the exhaust line, an acoustic wave which is as strictly as possible equal to that emitted by the latter.
However, such devices are very bulky, require very sensitive electronic and acoustic equipment and, consequently, are not very reliable under the particularly demanding use conditions of a motor-vehicle exhaust line.
Furthermore, from an energy standpoint, such devices are not very satisfactory insofar as they in no way seek to decrease the energy dedicated to the generation of the noise but, on the contrary, expend at least an equivalent amount of additional energy.
Finally, these devices employ techniques for which the design of an exhaust line, fitted to such an engine and intended to be installed on such equipment, requires complex simulations of the behaviour of the fluid within the exhaust line, bearing in mind the elements of which it will be composed, it being furthermore possible for these to be mutually interfering.
It has also already been tried to damp the flow pulsations of a fluid in a pipe with the aid of variable-geometry devices which tend to modify the resonant frequencies in the pipe by adapting the action of a restriction means to an overall measure of the flow rate of the fluid in the pipe and not to the specific pulsations of the fluid.
The present invention aims to provide a novel inlet or exhaust line which does not have the drawbacks encountered in the known technique and which enables, in a substantial way, especially the sound level of a combustion engine to be attenuated, while at the same time being simple and economical to produce.
In addition, the subject of the present invention turns out, due to its structure, to be remarkably suited to the various reciprocating machines and to the various geometrical shapes that can be imposed on it.
The subject of the pr
REFERENCES:
patent: 3166895 (1965-01-01), Slayter
patent: 3234924 (1966-02-01), May
patent: 3523418 (1970-08-01), Marsee
patent: 5372109 (1994-12-01), Thompson
Patent Abstracts of Japan, vol. 9, No. 330 (M-442)(2053) Dec. 25, 1985.
Patent Abstracts of Japan, vol. 13, No. 469 (M-883), Oct. 24, 1989.
Laumonier Janick
Peube Jean-Laurent
Tartarin Jacky
Centre National de la Recherche Scientifique "CNRS"
Hart Douglas
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