US2239549A - Silencing device for pulsating gases - Google Patents

Description

April 1941- A. s. CHlPLEY 2,239,549

SILENCING DEVICE FOR PULSATING GASES Filed March 4, 1940 2 Sheets-Sheet l lfiec/ f" QM MAW Api'fi 22, 1941. A. s. CHIPLEY SILENCINC- DEVICE FOR PULSATING GASES Filed March 4, 1940 2 SheetsSheet 2 Ffiwezz/arx Q j iii 541 6f @1 1 Patented Apr. 22, 1941 2,239,549 SILENCING DEVICE FOR PULSATING GASES Alfred S. Chipley, Chicago, 111., assignor to Butgess Battery Company, Chicago, 11]., a corporation of Delaware Application March 4, 1940, Serial No. 322,085

(01. ISL-57) 11 Claims.

This invention relates to devices .used for the prevention of noise caused by flowing, pulsating gases, such as the exhaust gases of internal combustion engines, or, as the terms are loosely used, to mufiiers and silencers for such pulsating gas systems.

This application is a continuation in part of Alfred S. Chipley copending application Serial No. 271,031, filed May 1',- 1939, now Patent 2,205,899, granted June 25, 1940.

Although the invention is useful 'for the prevention of noise caused by pulsating gases generally, including, for example, the intake and delivery of air compressors, the most severe conditions are met in the prevention of noise caused by the exhaust of internal combustion engines and for this reason the invention will be illustrated and described as applied to this particular problem.

A considerable variety of silencer constructions have been used and are now in use in coping with the problem of preventing or reducing to a minimum the noise attendant upon the operation of internal combustion engines. These various forms of apparatus operate on divers principles and are grounded on as many diiferent conceptions of the causes of noise. A particular silencer may, for example, be of the baiile, resonator, three-pass, two-pass, expansion chamber, or pack. type, in simple or compound form, or it may embody a combination of two or more of these well-lmown types of apparatus. The object of combining the different forms of apparatus is to take advantage of the characteristics peculiar to each and thus obtain a device having the desired silencing characteristics. The resultant product or" such a combination contains a plurality of classifiable silencing sections." This expression will be used herein to denote a unit (which may be only a part or" the complete silencer) of one of the :iorms of silencing apparatus, such as those enumerated above.

A new type of noise-preventing device, known as the snubber, has recently been developed and commercially used. This device is fully described in Ralph L. Leadbetter Letters Patent Nos. 2,189,423 and 2,189,424, both dated February 6, 194.0. As therein more fully disclosed, the snubber comprises a snubber tube into which the exhaust gases are projected at high velocity from the exhaust ports of the engine, an unconstricted shunt or by-pass passageway being provided around the snubber tube from the inlet to the outlet of the device. The snubber may be used as the silencer itself or a snubbing section may be employed in combination with other types of silencing sections in the building up or a composite device designed to accomplish a specified function with the desired degree of perfection. The snubber operates on a gas-inertia principle and, although it difiers in operation from most of the other types of mufiiers and silencers in that it operates to modify the gas slug pressure-velocity peaks and thus remove the primary cause of noise rather than to merely'suppress the noise after it has been generated or minimize secondary reverberation in the exhaust system, it may be loosely referred to as a muflier or silencer.

The snubber tube of a snubber type of silencer is generally in the form of a perforated sheet metal member. It has been found that under certain circumstances, for example, when the device is used with a Diesel engine, especially one of the low speed, low pressure type, solid materials carried by the exhaust gases stick to the inside surface of the snubber tube and cause I an accumulation of tarry deposits. This material may in time plug the perforations and deprive the silencer of its ability to efiectively snub the exhaust slugs. Accordingly, one object of the invention disclosed in the copending application above referred to was to obviate the possibility of plugging of the snubber tube oi a snr-bber type of silencer, or a snubber section thereof. A further object was to simplify this type of apparatus and to thereby reduce the cost of the device without at the same time sacrificing its high silencing eiiiciency or depriving it oi other desirable characteristics. Means for achieving these ends are fully disclosed in said application.

An object of the present invention is to provide a silencing section of the snubber type in which the inlet and outlet of the section are concentric with respect to the outer shell of the device.

in the accompanying drawings Fig. l is a longitudinal, sectional view of a simple embodiment of the invention;

Fig, 2 is a transverse, sectional view taken at the line 2-2 of Fig. 1;

Figs. 3, 4, 5, and 6 are longitudinal, sectional views of further embodiments of the invention; and

Fig. 7 is a transverse, sectional view taken at the line l of Fig. 6.

Referring specifically to Fig. 1, this unit is enclosed within a shell including side walls I, preferably of circular cross section, and end closures 2 and 3. An inlet opening 4 is provided in inlet-end closure 2 and an inlet snout 5 may be mounted in the closure member at inlet opening 4 for convenience in mounting the silencer in the exhaust system of the engine. Opening 4 and snout 5 are disposed substantially concentrically in inlet-end closure 2 with respect to the shell walls I. An outlet opening 6 is provided concentrically in outlet-end closure 3.

A transverse baflie I is disposed in alignment with the gaseous stream which enters the unit through inlet opening 4 as indicated by the arrow. This baflle is preferably generally conical in shape, a shown in the drawing, and is arranged with its apex pointing upstream. Plane, semispherical, or baflles having other shapes may be used. The ballies I does not span the entire cross section of the shell interior, an annular opening 8 being left between the baflie and shell walls i for the flow of gases. Three or four legs 8 may be formed in the manufacture of heme l as a convenient means for mounting it within shell E.

An outlet tube In extends through outlet open= ing 6 toward battle. 1. This tube terminates short of the baffle to provide a free passageway for gases passing through the annulus 8 into bypass zone 62 and directly into the open end it] of tube Ill. The latter is slotted, as indicated at I3, or otherwise apertured to a limited extent. A plurality of short slots, perforations or openings of any other nature may be used in place of the slot shown. A partition I4 extends radially from outlet tube III at its open end II. This partition is substantially coextensive with baiile '1, leaving an annular opening I5 between it and shell I in alignment with opening 8. It may be flat but is preferably somewhat dished and lipped at its edges, as shown, to prevent ringing of this member and to prevent edge noise .-due to the rush of gases past the partition through opening I5 into chamber I6. If support of partition I4 and outlet tube I0, other than" that furnished by outlet-end closure 3, is desired, legs I! may be formed integrally with partition I4 or separate mounting members may be used for this purpose.

In the operation of this device, the'exhaust gases comprising pulsations or slugs traveling at high velocity followed by the slower moving tailings are projected toward baffle 1 within the unit. The stream is spread radially by the baflle and caused to flow through annular opening 3 toward openings I5. The slugs or portion of the gases having sufiicient inertia to carry them over the distance between bafli'e l and partition I4 pass through openingIS and into chamber I6. The energy of these rapidly traveling gases is transformed into static form by the building up of a pressure in chamber I6. This pressure" condition is dissipated by leakage of the gases from chamber I6 into outlet tube I through slot I3. These gases are then exhausted from the unit through outlet opening 6.

The tailings passing through opening 8, lacking sufllcient-inertia to jump the gap between bafiie I and partition I4, by-pass directly to outlet tube I0, entering this tube through open end I I. This path is the one of least resistance since it is not constricted as is the alternative passageway through chamber I6 in which the apertured walls of outlet tube III offer an impedance to the free flow of gases from chamber I6 into the tube. It is for this reason that the gases by-pass chamber I unless driven into this chamber by virtue of their own inertia. The recombined gases pass from the unit through outlet opening 6 and are exhausted to the atmosphere in a relatively smoothly flowing stream.

A device embodying a slightly modified form of the invention is shown in Fig. 3. This device is housed-within a shell 2| having inletand outlet- end headers 22 and 23. Shell 2| is preferably cylindrical and inlet and outlet openings 24 and 25, respectively, are provided concentrically in headers 22 and 23, respectively. A baflle 2i, outlet tube 21 having a slot or other aperture 28, and partition 29 are arranged within the shell in the manner described above. In addition, an aperture'd intermediate shell 30 extends between partition 29 and outlet-end header 23, being nested within the outer shell 2| in spaced relation to the latter. Perforations 3I or a plurality of slots may be employed in achieving a limited opening in intermediate shell 30.

It will be seen that an additional impedance is provided to the how of gases following the restricted passageway through the unit. Gases projected through annular opening 32 into space 33 must pass through apertured shell 30 as well as the slotted walls of tube 21 in order to pass into the latter. An intermediate expansion of the gases is permitted in space 34. This device, al-

though somewhat more costly to build than that of Fig. 1, is useful especially for heavy duty service.

A simplified form of the invention is illustrated in Fig. 4. It is intended particularly for very small size units, miniature silencers of which a plurality 'may be connected in series in the exhaust system. It comprises cylindrical shell 40 having end headers H and 42, the latter being provided with concentric inlet and outlet openings 43 and 44, respectively. Gases entering the unit through inlet snout 46 and inlet opening 43, as indicated by the arrow, impinge against batile 46 and are spread to an annular stream passing through opening 47 between the periphery of the baflle and the lateral walls of shell 4|. The high and low velocity constituents of the gases then separate, in the manner described above, into two streams. The stream of high velocity slugs project forwardly into space 48 and thence into outlet tube 49.via perforations 50 in the walls of the tube. Apertured partition 5| serves to sup: port tube 49 and also to somewhat cushion tlie impact of the rapidly moving slugs. The more slowly moving gases enter outlet tube 48 at what may be considered to be an open end of the tube designated by the numeral 52. The straps 53 are employed to support baflle 46 and may be either separate elements fastened to the baflie and outlet tube 49 or may be unitary extensions of the outlet tube. In either case they are not of sumcient area to interfere with the free flow of gases into tube 49 at its open end 52 directly from openmg The device of Fig. 5 is a compound unit composed of two sections. The first section is a snubbing section of the type more fully described in the Chipley copending application above referred to. The second section is similar to that shown in Fig. 1. In the illustrated unit, an inner shell 60 having distributed perforations 6| is nested within outer shell 62 and between baille 63 and partition 64. An inlet snout 65 passes through inlet opening 66 provided concentrically in inlet-end closure 61. An opening 68 is provided in bailie 63 in alignment with inlet opening 66. The inlet snout 55 terminates, in effect, short of batlle 63, extension strips 69 being used only for the purpose of supporting baflle 63.

The second section oi the unit contains an ap- .ertured outlet tube extending through outlet 55 through by-pass chamber 11. The gases en- \lo tering the snubber chamber pass therefrom through apertures CI to join the by-passed gases in annular channel 16. These recombined gases then pass on into the second muilling section and divided to follow alternative paths through chamber 18 or by-pass chamber I4 in the manner fully described above.

Another compound unit is illustrated in Figs. 6 and '7. This device is essentially a combination of two sections similar to that of Fig. 1. arranged in series within a housing 80. The baflie ll of the first section, however, is provided with a relatively small opening 82 in alignment with inlet opening 83 The purpose of this opening is to permit a portion of the gases entering the sectionlthrough inlet opening 83 to pass directly to apertured tube 84 and thence to the second muming section of the series. The balance of the gases entering the first section-are spread by baille 8| and pass either into chamber 88 or by.. pass chamber 8 between partition 81 and baflle II. The gases following all three of the alternative paths are conducted to the second section of the unit through conduit 84 where they are again spread by baiile 88 and eventually are exhausted from the unit through apertured outlet conduit 88.

The energy or impact 0! the incoming, ex-

' haust gases against baille II is somewhat modified by means of the opening i2 and the direct passage through the first section of the unit thereby provided. Noises due to this impact are considerably reduce'd in this way.

It is not feasible to illustrate the large number oi possible modified forms that the invention: may take. The principal alternative constructions have been shown and describedK'It will be understood that the various elements showrpf in connection with a particular embodiment of the invention may be used ipr a corresponding Pu pose in one of the other illustrated units.

The dimensions and relative proportions of the several units herein described are generally as indicated in the drawings. These dimensions, on the whole, are not critical, although the space between the end oi /the apertured outlet conduit and the contiguous baifle should, in each case, be sufilcient to provide a passageway of area equal to or greater than the area oi the outlet conduit. The walls oi the outlet conduits, shell 50 II in Fig. 3, andfshell 88 in Fig. 5 should be sufficiently apertured to provide an open area approximately equal to from 30 to 100 per cent of the area of the outlet conduit of the unit.

I claim:

1. In a device of the character described including a cylindrical shell, a silencing section having an inlet and an outlet both disposed ap-' proximately at the axis of said shell, a transverse baiile member spaced downstream from said inlet and incompletely spanning the cross section of said shell to provide a substantially annular opening between said baille member and said shell, and an open ended apertured tube extending from said outlet toward said baiile member and terminating short thereof, the area of said annular opening being not substantially less than the cross-sectional area of said tube, the construction and arrangement being such that all gases entering said silencing section at said inlet may travel therethrough in a generally forwardly direction without reversal. I

2. A device in accordance with claim 1 in which the end of the apertured tube contiguous the baffle member is spaced therefrom a distance sufficient to provide a passageway for gases into the end of said tube having a minimum crosssectional area not substantially less than the cross-sectional area of said tube.

3. A device in accordance with claim 1 an having a, partition substantially coextensive with said baflie member and extending radially from said apertured tube at the end thereof.

4. A device in accordance with claim 1 and including an apertured partition extending transversely from the apertured tube to the shell at a point intermediate the length of said tube.

5. In a device of the character described including a cylindrical shell, a silencing section having an inlet and an outlet both disposed approximately at the axis of said shelL/an imperiorate transverse bailie spaced fro (said inlet and disposed in the gas stream fro said inlet, at least portions of the periphery said baille being spaced from said shell to per it free passage oi gases between said battle a 6 said shell, a transverse partition spaced do, stream from said battle, at least portions oI the periphery oi! said partition being spaced from said shell to permit free passage of gases between said partltion and said shell, and .an apertured conduit connecting the space between said baflle and said partition with said outlet of said muflling section, the construction arrangement being such that all gases entering said silencing section at said inlet may travel therethrough in a generally forwardly direction without reversal.

6. The device of claim 5 in which the bailie is general ly conical shaped and is arranged with its apex in upstream position.

jlfIn a device of the character described in- ,cluding an outer cylindrical shell, a silencing sec? tion having an inlet and an outlet both disposed approximately at the axis of'said shell, an imperforate transverse baflle spaced from said inlet and disposed in the gas stream from said inlet, at least portions of the periphery of said baflie being spaced from said shell to permit free passage of gases between said baflle and said shell,

' a transverse partition spaced downstream from tween said intermediate shell and said apertured conduit.

8. A device of the character described comprising a cylindrical housing, end closures for said housing having an inlet and an outlet opening respectively, a, substantially imperforate transverse bafile spaced from said inlet, the periphery of said baille being spaced from said housing, an apertured outlet tube extending from said outlet toward said bailie and terminating short thereof,

and means extending between said outlet tube and said baflie to support the latter, the construction and arrangement being such that all gases entering said device at said inlet opening may pass by said baflle and into said outlet tube without reversal of their generally forwardly movement.

9. A device of the character described comprising an elongated cylindrical housing having an inlet opening disposed concentrically in the inlet end and an outlet opening disposed concentrically in the outlet end thereof, first and second transverse partitions spaced apart and spaced from the inlet end of said housing, said first partition having an opening therein in alignment with said inlet opening, an apertured shell nested within said housing in spaced relation thereto and extending between said partitions, an apertured outlet conduit extending from said outlet opening toward but terminating short of said second partition, and a third partition extending radially from the end of said outlet conduit, the peripheries of all three of said partitions being spaced from said housing to permit free flow or gases between said partitions and said housing.

10. A device of the character described comprising a cylindrical housing having an inlet opening and an outlet opening concentrically of the respective ends thereof, a first transverse partition having an opening at its center and di vlding said housing into two silencing sections, said first section comprising: a transverse bafile spaced from said inlet opening, at least a portion of the periphery of said bailie being spaced from thereof; said second section comprising: a secand transverse baflle spaced from said first partition, at least a portion of the periphery of said second baille being spaced from said housing to permit the free flow of gases between said second baflle and said housing, a second apertured tube extending from said outlet opening of said housing toward but terminating short of said second baflle, and a third partition substantially coextensive with said second bailie and extending radially from said apertured tube at the end thereof, the construction and arrangement being such that all gases entering said device at said inlet opening may travel therethrough in a generally forwardly direction Without reversal.

ii. The device oi claim 10 in which said first mentioned transverse bailie is provided with an opening of small size as compared with said in let opening in alignment with said inlet opening.

ED S. CHELEY.

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