Patent ID: 6520286
Filing Date: 2003-02-18
Classification: F01N,F02D,F02P,Y02A,Y02T

Abstract:
A device for silencing a gas flow directed therethrough and being adapted for installation in a flow system, said device comprising:a casing, at least one acoustic chamber and contained in the casing, said chamber being through-flowed by gas, at least one inlet pipe for leading gas into one of said at least one acoustic chamber, at least one passage of a length L and of a representative cross-sectional area a for leading gas from each one of the at least one acoustic chamber to another of the at least one acoustic chamber or to an exterior environment or an exterior chamber, optionally one or more monolithic bodies comprised in each of one or more of said at least one acoustic chamber, said device showing at least two through-flowed transitions of cross-sectional area for the flow of the gas between a relatively lower cross-sectional area ai and a relatively higher cross-sectional area Ai, the device fulfilling the following criteria: (i) the average sound attenuation {overscore (&Dgr;dB)} conferred by each transition of cross-sectional area, approximated by the following expression: Î”&it;â€ƒ&it;dB_=1n&it;k&it;&Sum;i=1n&it;log10&it;Aiai,n being the total number of transitions of cross-sectional area of the device, Ai being the relatively higher cross-sectional area at the iâ€²th transition of cross-sectional area of the gas flow, ai being the relatively lower cross-sectional area at the iâ€²th change of cross-sectional area of the gas flow, k being a constant of the value 6.25 dB, is at least 8.0 dB when the device comprises no more than two acoustic chambers, 6.0 dB when the device comprises three acoustic chambers, 5.0 dB when the device comprises 4 or more acoustic chambers, (ii) the pressure loss across each acoustic chamber expressed as the dimensionless parameter &zgr;jâ€², defined as the ratio between the static pressure loss over the chamber and the dynamic pressure at a location in said passage: Î¶jâ€²=Î”&it;â€ƒ&it;pj12&it;Ï &it;â€ƒ&it;u2,&Dgr;pj being the static pressure loss over the jâ€²th chamber, exclusive of the static pressure loss over a monolith optionally comprised in the jâ€²th chamber, &rgr; being the density of the gas at said location, u being a velocity of the gas at said location, preferably the mean gas velocity, is at the most 1.0.