US2512823A - Air intake and exhaust silencer for internal-combustion engines - Google Patents

Description

June 1950 A. BLUNDELL 2,512,823

AIR INTAKE AND EXHAUST SILENCER FOR INTERNAL-COMBUSTION ENGINES Filed April 22, 1946 2 Sheets-Sheet l pnweml'w Wual [Ml/71M June 27, 1950 BLUNDELL 2,512,823

AIR INTAKE AND EXHAUST SILENCER FOR INTERNAL-COMBUSTION ENGINES Filed April 22, 1946 2 Sheets-Sheet 2 6 FIQ.3. F-IQ.4.

& '4

Fig.5

Patented June 27, 1950 AIRINTAKE ANDEXHAUST SILENCER FOR INTERNAL-COMBUSTION ENGINES Alfred Blundell, Coleshill, England Application April 22, 1946, Serial .No. 663,893 In Great Britain May 2, 1945 .2 Claims- (Cl. 181-47) This invention relates to the attenuation of sound waves and more particularly to the reduction or elimination of the noises occurring in the induction and also the exhaust systems of internal combustion engines.

The sound waves producing these noises are of 'ahighly complex order and include .both high and low frequency bands the amplitude and ratio of which vary with diflerent engines and different designs of induction or exhaust systems for the same engine.

For this season it has previously been considered necessary to deal separately with the high and the low frequencies and to provide apparatus for this purpose involving an elaborate system of cylindrical chambers traversed by an open-ended tube in acoustic connection therewith and adapted for connection with, or formed as part of the induction pipe. The process of acoustical impedance being the combine function of a sound wave passage and a capacity chamber, the combination being acoustically adapted to suit individual frequency bands the sound wave passage being the inertance component and the chamber being the capacitance component, the combine function in series performing the function of acoustic impedance.

The object of the invention .is to provide a silencer which, although of extremely simple construction and whose linear dimensions are small as compared with the major wavelengths of the noise frequencies dealt with, will efiectually attenuate sound waves of both high and low frequencies, by the process of acoustical impedance and sound wave reflection, the entire function occurring within the same chamber and same fluid mass. Therefore the function of the components of inertance and capacitance in series occurring within the same fluid medium or media.

The communication to the chamber of the silencer from the engine air intake or exhaust system may be at any angle to the axis of the chamber i. e. at right angles, parallel or co-axial therewith.

Furthermore the communication to the aforesaid chamber may be via a cylindrical or spherical chamber formed at the apex of the first mentioned conical chamber and in direct communication therewith.

Particularly in the case of exhaust silencers the central conduit may be extended into the apex of said conical chamber, said conduit being perforated at that end.

Referring to the drawings,

Figures 1 and 2 are perspective, and longitudinal cross sectional views of a preferred embodiment of the present invention.

Figures 3 and 4 are sectional views of simplified versions of the present invention.

Figure 5 is a development in longitudinal section of the silencer shown in Figure 3 and,

Figure 6 is an example of the present invention applied to the exhaust system of an internal combustion engine.

Refer-ring toFigures 1 and 2, the conical-chamber I i closed at its larger end 2 in interiorly concave fashion, said end 2 carrying a conduit 3 open at both ends and co-axial with the axis of the conical chamber I.

At the apex 4 of the conical chamber l is formed a spherical chamber 5 indirect communication with the conical chamber l and also adapted to communicate with the engine induction system via the opening 6.

In Figure 3 the opening 5 to the induction system is-co-axial with the axis of the conical chamher I and conduit 3.

In Figure 4 a cylindrical connecting chamber 1 is shown between the induction connection 6 and the conical chamber I.

Figure 5 shows a development of Figure 3 in which a second conical chamber 8 is arranged coaxial with the first conical chamber l in such amanner that the larger end of the first conical chamber 1 communicates via ports 9 with the apex end of the second conical chamber 8.

With reference to Figure 7, the invention is shown applied to the exhaust system of an engine wherein the conical chamber I is connected to the rear end of an orthodox silencer. However, the central conduit 3 in this case is preferably provided with perforations ID at the inner end. Alternatively the silencer may be incorporated within the cylindrical casing of an orthodox silencer in either case the exhaust pipe I I is a continuance of the central conduit 3. If desired the silencer for the exhaust system can be of the type shown in Figure 5.

For increased silencing efiiciency any of the above referred to silencers may be coupled in series in any suitable Way.

With reference to the drawings generally the operation of the silencer according to the present invention is as follows:

Due to the stream of air or gas or fluid mass generally from the central conduit 3 to the engine via the opening 6 in the case of the induction system and from the opening 6 to the conduit 3 in the case of the exhaust system due to inertia of the fluid stream, and in conjunction with the shape of the chamber, the fluid in the apex end of the chamber is in a turbulent and high state of motion, as compared with the fluid condition in the wide end of the chamber, the pulsation and circulation motion being relatively small. Thus Without any physical means of separation between the system and the chamber, there exists in the conical chamber l two fluid media or medium one in a high state of turbulence and inertia and one in a quiescence state. The chambers shape performin the agent of conductivity, always being automatic, for any position selected by the central conduit, for any combination of the media of response and attenuation.

The relative proportions of these two media can be varied quite readily and to a considerable degree by adjusting the length of the central conduit 3 within the chamber I and/or altering its diameter before resorting to alteration of the dimensions of the conical chamber.

In all cases sound waves of a highly complex order emanate from the engine via the opening 6 into the silencer.

The effect of the turbulent fluid mass is that of inertance and the effect of the quiescence fluid mass that of capacitance, the result giving rise to acoustic impedance, in which the high and low frequencies are attenuated, resulting in a mean frequency which is also attenuated by interference due to reflection between the cone apex and sides and the end plate diaphragm 2.

The apex volume of the chamber as well as performing the function of inertance also acts as a mean response for the combine noise frequencies and therefore the adjustment of the central conduits internal and within the chamber selects the most suitable response characteristic most adaptable for the attenuating characteristics of the apparatus.

The conical sides of the chamber are instrumental in the conductivity of the sound waves for the process of attenuation and act as conductors in series for any combination of the two media, thus eliminating any physical agent of conductivity from the source of sound other than that of the chamber sides.

By the provision of a spherical chamber 5 Figures 1 and 2 or a cylindrical chamber 1, Figure 4 the function of a resonator is provided to assist in the attenuation of the sound waves and, moreover, the required length of the conical chamber l is reduced.

If the length of the silencer requires a further reduction in length to adapt it for working conditions the construction may be that shown in Figure 5 where the effect is that of two conical chambers l and 8 in series in direct communication with one another via the ports 9.

With reference to Figure 3, A, B and C represent the positions of the end of the central conduit 3 for high medium and low frequencies respectively, either position being obtained by axial adjustment of the conduit.

I claim:

1. A silencer for the induction or exhaust systems of internal combustion engines comprising in combination a truncated conical chamber; an outwardly convex end wall to the larger end of said chamber; a single open ended conduit mounted in and passing through said end wall and extending into and partially through said chamber, and a further aperture provided in said chamber adapted to be connected to the engine, all so arranged that a direct flow of gas is permitted between said conduit and the said further aperture.

2. A silencer for the induction or exhaust systems of internal combustion engines comprising in combination a truncated conical chamber; a second truncated conical chamber surrounding said first chamber the smaller end of said second chamber communicating with said first chamber at the larger end thereof via ports at said larger end; an outwardly convex end wall to the larger end of said first chamber; a single open ended conduit mounted in and passing through said end wall and extending partially through said flrst chamber, and a, further aperture provided in said first chamber adapted to be connected to the engine, all so arranged that a direct flow of gas is permitted between said conduit and the said further aperture.

ALFRED BLUNDELL.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,489,422 Brabant Apr. 8, 1924 1,874,326 Mason Aug. 20, 1930 2,088,576 Compo Aug. 3, 1937 2,101,850 Green Dec. 14, 1937 2,252,256 Harris Aug. 12, 1941 FOREIGN PATENTS Number Country Date 382,418 Great Britain Oct. 27, 1932 817,517 France Apr. 9, 1937 833,214 France July 18, 1938 363,199 Italy Sept. 21, 1938

Images