US3779339A

US3779339A - Muffler

Info

Publication number: US3779339A
Application number: US00258988A
Authority: US
Inventors: H Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-06-02
Filing date: 1972-06-02
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18

Abstract

Gas flow induced by a pulsating pressure source such as an internal combustion engine, is conducted through a main duct having an acoustical impedance created by parallel branched, resonator chambers acting as low pass filters to gate low frequency pressure pulsations while absorbing higher frequency acoustical energy. Angled connecting passages between the main duct and the resonator chambers impart spin to the gas and create turbulent conditions for sonic wave transmission. This invention relates to noise abatement devices or mufflers of the wave filter type.

Description

[ Dec. 18, 1973 United States Patent [1 1 Johnson 3,243,01! 3/l966 Hill.............

[ MUFFLER [76] Inventor:

n 0 ms nle RM .1 Wn 0 G mF n mh .10 4 r e mm im ma a mm m PA Howard R. Johnson, 3300 Mt. Hope Rd., Grass Lake, Mich. 49240 June 2, 1972 Appl. No.: 258,988

Attorney-Harvey B. Jacobson [22] Filed:

[57] ABSTRACT Gas flow induced by a pulsating pressure source such as an internal combustion engine, is conducted through a main duct having an acoustical impedance created by parallel branched, resonator chambers acting as low pass filters to gate low frequency pressure pulsations while absorbing higher frequency acoustical energy. Angled connecting passages between the main 98 00 50 4 9 oo 9 .m 7 omm7 6 ,5R 87 mw1 8 m7 4m. o 1 8F 00 1 m h c r. 8 ue US .L Hf C d SLd UmF HUT 555 [ll [5 6] References Cited UNITED STATES PATENTS duct and the resonator chambers impart spin to the r m o w m c .w w n e 0 d S t r n S 0 e e S e g n m .I. .m b F .n a ma .0 .I m .mmw c o a n r m U Sf m m avi w aa [Wu m T m r n VS i r mmme s swmm a UTm 8868 4465 HHHH 8888 5 JJWM T Pigman .m X a M McCurdy..;...........................

m ymm m r mc u C MDM 94822 402346 999999 HHHHHH 53 26 l l MUFFLER The use of side branch acoustical wave filters for attenuating certain sound'frequencies, known to exist in the exhaust conduits of internal combustion engines, is well known as disclosed for example, in US. Pat. No. 1,910,672- to Bourne. Such wave filters include side branch resonator chambers connected to a main flow duct by communicating orifices or necks that are short I in comparison with the wave lengths of the pulsations dealt with.

As a general practice in noise abatement, flow discontinuities such as the aforementioned side branch type are used to increase acoustical impedance by wave reflection and interference in the main flow duct with which the discontinuity is associated so that only a small fraction of the acoustical energy exits with the gas. Where the side branch flow area is equal to or less than that of the main duct,the impedance is such that relatively narrow stop frequency bands are established. Further, if the side branch duct is closed, it also acts as a low pass filter while the impedance at one of the stop frequency bands approaches inifity where the closed duct included a resonator chamber to effect relatively large sound absorption in the stop band embracing the resonant frequency. Thus, a wave filter may be constructed in accordance with well known acoustical the-.

ory and supporting empirical data, to suppress only the undesirable higher frequency pulsations in a flow stream of gas without appreciably affecting the lower frequency pulsations. Harmonic analysis of flow in the intake or exhaust conduits of a pulsating pressure source, such as an internal combustion engine, show that alternating fiow at several different higher frequencies are superimposedon the lower unidirectional flow-inducing frequencies of the pressure pulsations and it is these higher frequencies that suffer attenuation by resonator types of side branch wave filters in accordance with the present invention.

The thermal efficiency of a suitable wave filter of the aforementioned type having a low pass frequency characteristic anda cut-off frequency range, was heretofore unsatisfactory for internal combustion engine muffler installations because of size limitations. In accordance with the present invention, however, the thermal efficiency is significantly improved by initially baffling flow to create turbulence and imparting a spin to the gas within the resonator chambers along an arcuate flow passage, to effect a substantial reduction in size. Despite this spin, the gas can exit the resonator chambers and reenter the main flow stream because of the fact that the internal combustion engine operates as a chemical batch process.

The spin of the gas is produced by the orientation of side branch connecting passages at an acute angle in the direction of flow relative to the main flow stream and the circular configuration of the resonator chambers disposed in tangential relation to the connecting passages. The angular orientation of each connecting passage creating a maximum coriolis effect on the flowing gas and its converging flow area, enhances the spinning action or vortical motion produced. The spinning motion imparted to the gas provides turbulent conditions for transmission of the sound waves and lowers gas temperature which is a function of the acoustical velocity. Thus, pressure pulsations from the internal engine, enhanced by the spinning effect on the gas achieves a gating action from each resonator chamber comparable to the phenomenon in a pulse jet engine wherein cyclic combustion at sonic frequencies unidirectionally gates the inflow of air through the exhaust nozzle.

These together with other objects and advantages which willbecome subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout and in which: I

FIG. 1 is a perspective view showing one embodiment of and installation for the present invention.

FIG. 2 is a top sectional view taken substantially through a plane indicated by section line 22 in FIG. 1.

FIG. 3 is a vertical sectional view taken substantially through a plane indicated by section line 33 in FIG.

FIG. 4 is a schematic illustration of the basic wave filter structure associated with the present invention.

Referring now to the drawings in detail, FIG. 1 shows a typical installation of a muffler device 10 between an exhaust conduit 12 from a pulsating pressure source such as an internal combustion engine, and a tail pipe 14 connected to a discharge pressure region or. atmosphere. In the illustrated embodiment, the muffler device includes a cylindrical housing 16 closed at one axial end by the cover 18 and at the other axial end by an end wall 20 to which the tail pipe is connected by elbow portion 22. The conduit 12 is connected to the housing in substantially tangential relation by the connector formation 24.

As shown in FIGS. 2 and 3, the muffler device includes a rigid core structure generally denoted by reference numeral 26 that is fixed internally within the housing by the assembly bolts 28 that also hold the cover 18 assembled with the housing 16 to seal the interior thereof. A main flow duct or channel is formed within the housing by the core structure including a peripherally outer circular portion 32 connected in series with an inner circular portion 34 as more clearly seen in FIG. 2. The inlet end 36 of the fiow duct communicates with the conduit 12 while the outlet end 38 opens into an axial outlet chamber 40 centrally located within the housing in communication with the outlet elbow 22 through the bottom wall 20.

The main duct 30 constitutes a flow passage for gas conducted in one direction as indicated by the main flow stream arrows 42. Baffle means including a baffle chamber 44 is formed within the core structure adjacent to the inlet end 36 of the duct, into which a portion of the flow stream is diverted to impart some spinning motion thereto and thereby initially establish some turbulence in the main gas flow stream. The main flow passage in duct 30, following the baffle chamber, is provided with a plurality of wave filter types of discontinuities 46 at spaced locations along both

portions

32 and 34 of the duct in order to create the desired acous- 1 tical impedance for noise abatement purposes.

As more clearly seen in FIG. 4, each of the discontinuities or wave filter formations 46 includes a resonator chamber or cavity 48 of circular configuration that is volumetrically enlarged relative to an associated side branch duct or connecting passage 50 tangentially connected to ,the resonatorchamber. The side branch duct the convergence of its flow passage in the direction of 5 flow and its tangential relationship to the resonator chamber 48, imparts a spinning motion to the gas entering and exiting from the resonator chamber.

In accordance with acoustical wave filter theory and practice as aforementioned, the branch duct 50 is made shorter in length than the wavelengths of the lowest pressure pulsations dealt with. Further, the maximum flow area (b) of the branch duct is equal to or less than the flow area (a) of the main duct 30. The acoustical wave filter 46 is thereby designed to suppress the objectionable noise producing, alternating pulsations at the higher frequencies while gating or permitting the low frequency, unidirectional flow pulsations to pass. Since the wave filters are associated with the flow of hot gas from an internal combustion engine, the spinning motion imparted to the gas by the unique configuration and arrangement of the wave filters 46 accounts for a thermal efficiency for this type of muffler device that makes it practical for the size limitations of installations including two cycle engine as well as diesel engine power plants.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modificationsand equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In combination with a source of pressure pulsating at relatively lower frequencies and a conduit connected to said source through which a flow of gas is induced by said pulsating pressure, wave filter means for reducing noise produced by sonic pulsations at relatively higher frequencies, comprising elongated passage means connected to the conduit for establishing a flow path for said gas between said source and a discharge pressure region, resonator chamber means connected to the passage means for establishing substantially infinite acoustical impedance at said higher frequencies, gas spin means responsive to flow of the gas between the passage means and the resonator chamber means for imparting vortical motion thereto, and means for initially imparting turbulence to the gas entering the passage 'means from the conduit.

2. The combination of claim 1 wherein said passage means includes a housing to which the conduit is connected and a core fixed internally within the housing forming an elongated main duct, the resonator means and the gas spin means being formed within the core.

3. The combination of claim 2 wherein said gas spin means includes a branch duct extending from the passage means at an acute angle in the direction of flow and connected tangentially to the resonator chamber means.

4. The combination of claim 3 wherein said resonator chamber means includes at least one closed cavity enclosing a volume larger than the branch duct, the branch duct having a cross-sectional flow area that is less than that of the passage means.

5. The combination of claim 4 wherein said main duct includes peripherally outer and inner arcuate portions connected in series, the outer portion having an inlet end connected to the conduit and the inner portion having an outlet end.

6. The combination of claim 1 wherein said passage means-includes a radially outer inlet end, a radially inner outlet end, and an arcuate duct interconnecting the inlet and outlet ends.

7. In combination with a source of pressure pulsating at relatively lower frequencies and a conduit connected to said source through which a flow of gas is induced by said pulsating pressure, wave filter means for reducing noise produced by sonic pulsations at relatively higher frequencies comprising elongated passage means connected to the conduit for establishing a flow path for said gas between said source and a discharge pressure region, resonator chamber means connected to the passage means for establishing substantially infinite acoustical impedance at said higher frequencies, gas spin means responsive to flow of the gas between the passage means and the resonator chamber means for imparting vortical motion thereto, said passage means including a housing to which the conduit is connected and a core fixed internally within the housing forming an elongated main duct, the resonator means and the gas spin means being formed within the core.

8. The combination of claim 7 wherein said resonator means comprises a plurality of closed cavities connected in parallel to said main duct by the gas spin means.

9. The combination of claim 7 wherein said resonator chamber means includes at least one closed cavity connected to the passage means by the gas spin means.

Claims

1. In combination with a source of pressure pulsating at relatively lower frequencies and a conduit connected to said source through which a flow of gas is induced by said pulsating pressure, wave filter means for reducing noise produced by sonic pulsations at relatively higher frequencies, comprising elongated passage means connected to the conduit for establishing a flow path for said gas between said source and a discharge pressure region, resonator chamber means connected to the passage means for establishing substantially infinite acoustical impedance at said higher frequencies, gas spin means responsive to flow of the gas between the passage means and the resonator chamber means for imparting vortical motion thereto, and means for initially imparting turbulence to the gas entering the passage means from the conduit.

6. The combination of claim 1 wherein said passage means includes a radially outer inlet end, a radially inner outlet end, and an arcuate duct interconnecting the inlet and outlet ends.