US2189424A - Surge filter for pulsating gases - Google Patents

Description

Feb. 6, 1940. R. l.. LEADBETTER 2,189,424

suacf FILTER Fon PULSATING GASES Filed Aug. 51.1938 3 sheets-sheet 1 MW ",Illllmuwllunwlll.

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R. L. LEADBETTER SURGE FILTER FOR PULSATING GASES Filed Aug. 31. 1938 3 Sheets-Shes?I 2 Feb. 6, 1940. R. L. LEADBETTER SURGE FILTER FOR PULSATING GASES Filed Aug. 31, 1938 '3 Sheets-Sheet 3 lil Patentes; ses. s, 1940 siren s'rTEs PATENT GFFICE 2,189,424 sonos rumen Foa PULsA'riNG GASES Application August 31, 1938, Serial No. 227,655

l5 Claims.

This invention relates to surge filters for iiowing, pulsating gases, such as the exhaust gases of internal combustion engines, or, as the terms are loosely used, to improvements in mulers and siiencers ier such pulsating gas systems.

application is a continuation in part of my application Serial No. 156,3i0, tiled July 29',

ist?.

iithough 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 a lied to this particular problem.

A large variety of constructions have heretofore been empioyed ior the attenuation of noise resulting trom the operation of internal combustion engines. Whether such muillers employ battles, resonating chambers, or equalizing or expension chambers, an analysis of their operation discloses that their function depends entirely upon pressure fluctuations of the gas stream and thus their` eiectiveness depends upon their proximity to points of maximum pressure change in the exhaust system. Thus, a resonating chamber tuned to attenuate a particular frequency is inoperative when located at a .(velocityl antinode of that particular sound wave which it is designed to attenuate. It will be seen from the following detailed description that the present invention constitutes a radical departure from muiilers and silencers heretofore known for the reason that it operates by virtue of the inertia imparted to the gases upon being ejected from the engine cylinder into the exhaust system. The invention operates as a velocity smoothing device and depends upon pressure only in the remote sense that the inertia of the exhaust gases depend upon a pressure in the engine cylinder at the time the exhaust valve is opened.

The fundamental distinction indicated in the preceding paragraph will become more apparent as the description oi the invention proceeds.

The object of this invention is to prevent noise caused by flowing, pulsating gases by means of a device that may be located with equal eiIectiveness at any point in the conduit carrying the gas stream and to reduce back pressure and eliminate so-called period noises.

The essential element of a muiller embodying this invention is a receptacle or snubber tube v into which the exhaust gases are projected at high velocity from the exhaust ports of .the

(Cin 181-54) Part of the exhaust gases is conducted directly to the muffler outlet via a substantially unrestricted passageway Without entering the snubber tube. Only that portion of each pulsation having sufcient inertia to cause it, to jump a gap rather 5 than deviate in its course to follow the line of least pressure resistance enters the snubber tube. The velocity of the gases entering the snubber tube is arrested and the gas pressure caused thereby dissipated through perforations in the walls of the snubber tube.

Several embodimentsof the invention are illus trated in the accompanying drawings in which:

Fig. l is a longitudinal, sectional view of one form of muiller embodying the invention;

Fig. 2 is a longitudinal, sectional view on 2--2 of Fig. 4, showing a diierent species of the invention; l

Fig. 3 is a longitudinal, sectional view on 3--3 f Fis. 4; 2o

Fig. 4 is a transverse, sectional view taken at 4--4 of Fig. 3;

Fig. 5 is a transverse, sectional view taken at 5-5 of Fig. 3; and' Fig. 6 is a longitudinal, sectional view illustrating a modiiied form of muffler embodying the invention. Y

The exhaust of an internal combustion engine consists largely of a series of rapidly traveling pulses of high pressure gas known to the art as slugsf A high velocity peak, or slug, is formed each time an exhaust valve opens. Sound waves are thought to be caused by high velocityimpact of these slugs with the atmosphere. These are `.the sharp cracks characteristic of the exhaust when not properly muiiied. A low pitched rumble is maintained between explosions. These noises may be eliminated by dissipating the velocityv peaks to smooth outthe flow of the gases through the exhaust system before exhausting to the atmosphere at a relatively uniform velocity. In addition to these noises, period noises are caused at certain tiring frequencies of the engine. These periods occur when the iiring frequency substantially coincides vwith the natural resonant frequency of the exhaust system or a harmonic thereof, the timed recurrence of the pulsations tending to set the exhaust system in vibration. Periods may also occur when the exhaust slugs reinforce every second, or every third, etc., sound 5,?) wave condensation without intervening neutralizing slugs. Resonance of the exhaust system depends largely upon reection of the atmosphere impact into the system. The munler of this invention is eiiective in preventing such impacts and thus in preventing both direct and period noises.

All of the muiiiers are illustrated in their preferred forms, that is, contained within a single enveloping shell.

cross-section, the ends being closed by anges II and I2 having inlet opening I3 and outlet opening I4, respectively. Inlet snout I5 is 'mounted in inlet opening I3 and outlet snout I6 is mounted in outlet opening I4. These snouts are provided for convenience in mounting the mufer in the exhaust line. Two snubber units are arranged in series within the muler. v-The primary snubber unit consists of a perforated snubber tube I'I mounted between partitions I8 and I9. Partition I8 is spaced from end flange II to form primary by-pass chamber and' is provided with openings 2| and 22, the former opening being concentric with opening I3 in flange II and the latter opening being in nonalignment with opening I3. The. mouth of the snubber tube I1 is mounted on partition I8 at opening ZI, the remote end of the snubber tube being closed by partition I9. The ends of inlet snout I5 and/or snubber tube I1 may extend into by-pass chamber 20, but a gap a between contiguous ends of these two members not substantially less than one-fourth of the diameter of vsnout I5 must be provided. In other words, the cylindrical area forming the gap between the snout I5 and snubber tube I1 should not be substantially less than the cross-sectional area of the exhaust pipe of the engine. Substantially unrestricted' flow of gases through snout I5 and by-pass Ichamber 20 to opening 22 is thus provided with the result that back pressure due to restriction within the muilier is'practically nil.

Perforated conduit 23 is mounted in openings 22 and 24 to carry the gases from primary bypass chamber to the secondary snubber unit. Conduit 23.is perforated so that gases dissipated from snubber tuber I1 through `the perforations therein may enter conduit 23. Space 25 operates as an expansion chamber to attenuate the high frequency vsound waves and pulsations in conduit 23. l

The secondary snubber unit is constructed the same as the primary unit except that the snubber tube may be somewhat shorter. Partitions 26 and 21 support snubber tube 28 and conduit 29. A gap b is provided subject to the limitation above set forth -whereby the gases from conduit 23 may enter secondary by-passchamber 30 and pass through conduit 29 to the muiiier outlet. 'I'he snubber tube 28 and conduit 29 are perforated as abovegdescribed. Perforations 3I may be provided in partition 21, if desired, to

j permit direct escape of gases from space 32 to chamber 33 at the outlet end of the mui'lier. Chamber 33, as well`asspace 32, operate as expansion chambers to further attenuate the sound waves and gas pulsations, but this chamber 33 may be dispensed with and snubber tube 28 and conduit 29 mounted directly in end ange I2. In this case outlet snout I8 may be integral with conduit 28.

The engine exhaust gases enter the muiiier through snout I5 and opening I3. 'I'he inertia of the`s1ug causes a portion of the gases forming the slug to jump the gap "a and project into primary snubber tube I1 wherein the velocity energy is transformed into static pressure which is dissipated through the perforations of the snubber tube. The snubber tube must be of suf- The muiiler of Fig. 1 employs a shell II) which may be circular or elliptical iny rit 4% open, gap a being 11@ inches.

is one inch and the secondary snubber tube is 7.

ficient volume and sufficiently perforated to accommodate the velocity peak portion of the slug but must not be so extensively perforated that the slug will be permitted to project through the walls of the snubber tube Without undergoing the transformation described. The portion of the gases of the pulsation which do. not have suicient inertia to jump the gap and enter the snubber tube follow the path of less resistance and flow through by-pass chamber 20 into conduit 23. A primary smoothing has been accomplished by the operation of the primary snubbing unit functioning'as a surge filter and the gases are delivered to the secondary snubbing unit by conduit 23 and are there operated upon in a manner similar to that above described. The gases finally emerge from thevmufller in a relatively smoothly flowing stream. 'I'he velocity peaks of the slugs entering the primary snubber tube are of relatively large magnitude, the peaks of the slugs. entering the secondary snubber tube are greatly modified and the peaks are inconsequential as the gases leave the device. Although the velocity of the gases leaving the muflier may still gradually rise and fall, there is no sound produced because there is no impact of the moving gases with the atmosphere.

In a particular commercial muffler of the type illustrated in Fig. 1 designed for a single cylinder four cycle gasoline -engine of 2 horse power and having a 1 inch diameter exhaust pipe, the primary snubber tube is 8 inches long, sumciently perforated with 32 inch holes to render Gap bn inches long and perforated as specified for the primary snubber tube. In this particular muffler the primary snubber tube is 11/2 inches in diam- 'eter and the secondary snubber tube is one inch in diameter.

The muffler illustrated in Figs. 2 to 5 is similar to that above described in that two snubbing units are enclosed within the shell 34. End flanges 35 and 36 are provided with openings-31l and 38, respectively in which inlet snout 39 and outlet snout 40 are mounted. Primary snubber tube 4I abuts outlet end flange 36 at 42 and passes through openings in partitions 43 and 44, opening into primary by-pass chamber 45 leav ing a gap c" between the end of inlet snout 39 and the open mouth of snubber tube, 4I. A secondary snubber tube 46 is arranged between end ange 35 which it abuts at 41, and partition.

43, the snubber tube opening into secondary bypass chamber 48. The primary snubber tube is in substantially axial alignment with inlet snout 39 and the secondary snubber tube is in substantially axial alignment with a nozzle or gas directing member 49 associated with an openingin partition 44. A gap "d is provided as shown. Gases are conducted from the muffler by means of perforated conduit 50 illustrated as integral with outlet snout 49.

1n the operation with this form of the muIIier the exhaust slugs are filtered successively by the primary and secondary snubber tubes as above described. However, the pressure generated. in

primary snubber tube 4I dissipates by flow of operated upon by the primary snubber unit are Y collected for projection into the'secondary'unit.

Each form ci mumer has advantages for particular installations.

vIn a particular commercial mufiler of this type designed for a six cylinder engine having a cylinder bore of 3%, inches, stroke 4% inches (displacement 217.8 cubic inches) and 87 brake horse power at 3600 revolutions per minute, the shell is 24 inches long between end, anges and is 61/2 inches in diameter. The primary snubber tube is 19 inches long by 2 inches in diameter and the secondary snubber tube is 15 inches long by 2 inches in diameter. Both by-pass chambers are 4 inches deep. Spacing c may be 3A inch and d 1/2 inch. The outlet conduit 38 is of the same diameter as the tail pipe of the exhaust system, about 1% inches.

Perforated partition 52 is not an indispensable element of the muiiler but is useful for supporting inlet snout 39 and provides expansion chamber 53 for the better attenuation of high frequency waves.

The modified embodiment shown in Fig. 6 is of a simpler construction than the forms above described. A number of modifications shown are adaptable to the muillers above described. Intake snout 54 and exhaust snout 55 are provided in openings in end anges 56 and 51, respectively, and tube 58, which may be an extension of the concentrically located intake and exhaust snouts, extends through the muiiler shell 59. Partitions 60 and 6| are provided in the tube to form primary snubber tube 62 and secondary snubber tube 63. A partition 64 divides the interior of the muilier shell into two compartments, 64 and 65. Openings 66 and 61 are ,provided in the Walls of tube 58 near the inlet and outlet endssl of the muffler, respectively. Openings 68 and 69 extend a short distance on either side of partition 64, but do not extend beyond partition 60.

Openings 66 and 69 are equivalent to the gaps provided in the other forms of the muiiler disclosed. These openings must be sufficiently open to allow substantially unrestricted now of gases through them into the spaces surrounding the snubber tubes. v

The exhaust gas pulsations are lteredor attenuated by the muiller shown in Fig. 6 by the compound snubber action described above. A slug projects successively into primary snubber tube 62 and secondary snubber tube 63, the gases passing from the exhaust line through openings 66 into chamber 64 again re-entering the tube through opening 68, passing into chamber 65 and leaving the muiiler through openings 6l and the muiller tail pipe attached to exhaust snout 55. A large portion of the gases of 'each slug is dissipated from the snubber tubes through the perforations therein.

If desired, shell 59 may be lined with soundabsorbing material 10 of substantial thickness, a perforated wall 1I being provided to maintain the sound-absorbing material in place; or perforated membrane 'll may be used without the sound-absorbing material to provide an expansion chamber. Attenuation, especially of the high frequency sounds, is improved when either of these devices is used.

The shellsof the muffiers described may be double-wrapped or they may be Wrapped with asbestos to prevent"shell noise.

As above stated, 'an internal combustion engine emits a series of timed pulsations into the exhaust system. At certain engine speeds the frequency of these pulsations may coincide with the fundamental or a harmonic of the natural resonant frequency of the exhaust system. At this time a standing wave pattern forms in the pipe. A column of gas, although traveling at high velocity, breaks into violent longitudinal oscillation causing period noises, and, when the exhaust system is connected with the body of a vehicle, as an automobile for example, the body of the vehicle responds to these vibrations. In an exhaust system in which one of the above described muiliers is inserted, each slug impinges against the closed ends of the successive snubber tubes in quick succession before it is exhausted from the muiiler. The first impact of the succeeding slug follows after a time interval. the snubber tubes are properly disposed relatively to each other, the succession of impacts occur at irregular intervals. While regularly recurring impacts might be undesirable at certain frequencies since such blows would aggravate longitudinal vibration of the exhaust system, the snubber tube muiiler having a plurality of snubber units would have no such undesirable effect, the tendency being rather to interfere with such vibration and reduce the amplitude thereof.

The muillers described herein, which have come to be known as snubbers, maybe inserted at any point of the pulsating gas system. It may be used in appropriate sizes for the muling of exhausts of .all types of engines, including large size Diesel engines. Since back pressures increase withl the velocity of the gases traveling through a conduit, and since the snubber tube muiller substantially reduces peak velocities, the back pressures are accordingly greatly reduced by the device.

While several specific' embodiments of the invention are shown, it is obvious that many modifications may be made without departing from the spirit thereof. 'I'he snubber tubes may be arranged other than in parallel relation to each other and need not be confined within a unitaryl muilier shell; More than two snubber units may be used in series, if desired. The lower limit of the gap adjacent the mouths of the snubber Atubes has been described above, but there is no critical upper limit. The expression snubber tube is used for convenience but forms other than tubular may be employed. l

I claim:

1. In a device of the character described including a shell, gas-velocity-peak snubbing means comprising a plurality of snubbing units arranged in series within said shell, each of said units comprising: means forming a chamber having an in'- let opening and an outlet opening, conduit means arranged in said inlet opening terminating within said chamber, and adapted to conduct gases directly thereinto, a4 receptacle having apertured walls and a mouth, said mouth of said receptacle being in direct communication with said chamber and in alignment with said conduit'means whereby gases conducted into said chamber may project into said receptacle; and means for ingress of gases into and means for egress of gases from said shell, said units being so arranged that the outlet opening of the chamber of one unit is iti communication with the inlet opening of the chamber of the next succeeding unit and the out'- let opening of the chamber of the last unit of the series is in communication with said shell egress means.

2. A device in accordance with claim 1 characterized in that the passageway from said in- It is apparent that when.

gress means to said egress means through said series of snubbing units is substantially unrestricted to the flow of gases therethrough.

3. In a device of the character described including a shell having meansfor ingress of gases thereinto and means for egress of gases therefrom, gas-velocity-peak snubbing means comprising a plurality of snubbing units arranged in series within said shell, each of said units comprising: means forming a by-pass chamber having an inlet opening and an outlet opening, a conduit for conducting gases into said by-pass chamber arranged in said inlet opening and terminating within said chamber, an apertured snubber tube having a- .'mouth opening into said by-pass chamber in alignment with said conduit, the end of said conduit within said chamber being spaced from said snubber tube mouth to provide a gap through which gases from said conduit may flow directly to said outlet opening;' said units being so arranged that the outlet opening of the chamber of one unit is in communication with the inlet opening of the chamber of the next succeeding unit and the outlet opening of the chamber of the last unit of the series is in communication with said shell egress means.

4. A'device in accordance with claim 3 in which the area of the gap between the conduit and the ber, a primary apertured snubber tube opening' into said primary by-pass chamber and a secondary apertured snubber tube opening into said secondary by-pass chamber, a perforated conduit connecting said by-pass chambers, a second perforated conduit connecting said secondary by.- pass chamber with said outlet opening, the mouth of said primary snubber tube being in substantial alignment With said inlet opening and the mouth of said secondary snubber tube being in substantial alignment with said perforated conduit connectingsaid by-pass chambers.

6. The device of claim 5 in which the mouth of said primary snubber tube is spaced from the periphery of said inlet opening a distance not substantially less than one-fourth the diameter of said inlet opening and the mouth of said secondary snubber tube is spaced from the adjacent end of said conduit connecting said by-pass chambers a distance not substantially less than one-fourth the diameter of said conduit. l

7. The device of claim 5 in which a transverse partition is arranged Within said shell in spaced relation to the outlet end thereof to form an expansion chamber, said expansion chamber being in communication withsaid conduit connecting said secondary by-pass chamber and said outlet opening. 8. In a device of the character described comprising a shell having an inlet. opening and an outlet opening in the ends thereof, a partition left between said snubber tube and said partition at said inlet opening, said partition having a vent therein, a second partition within said shell spaced intermediate said first partition and the outlet end of said shell to form a'secondary bypass chamber between said two partitions, a secondary closed-ended perforated snubber tube extending in substantially axial alignment with said vent in said first partition and opening into vsaid secondary by-pass chamber, a gap being left between said secondary snubber tube and said second partition at said vent, and a conduit establishing communication between said secondary by-pass chamber and said outlet opening.

9. 'I'he construction of claim 8 and including gas-flow directing means comprising a snout -member arranged in said inlet opening in said shell in substantially axial alignment -with said snubber tube and a tubular member arranged in said vent in substantially axial alignment with said secondary snubber tube.

l0. The construction of claim 8 in which the walls of said conduit are perforated.

ll. An exhaust mulfler comprising a shell having an inlet opening and an outlet opening in the ends thereof, a perforated partition within said shell spaced from the inlet end thereof, a second partition Within said shell spaced interiorly from said first partition to form a by-pass chamber, an inlet snout arranged in said inlet opening and opening into said by-pass chamber at said perforated partition, a closed-ended perforated snubber tube extending in substantially axial alignment with said inlet snout and opening into said by-pass chamber, a vent in said second partition, tubular air-flow directing means arranged in said vent,"a third partition within saidshell spaced intermediate said Vsecond partition in the outlet end of saidshell to form a secondary by-pass chamber between said second and third partitions, a secondary perforated closed-ended snubber tube rextending in substantially axial alignment with said tubular gas-flow directing means in said second partition and opening -into said secondary bypass chamber, and a conduit having perforated walls establishing communication between said secondary by-pass chamber andl said outlet opening.

12. In a surge filter for pulsating gasesy cylind'rical shell including end closures, a transversel partition within said shell in'the middle portion thereof dividing the space therein into a primary enclosure and a secondary enclosure, a second transverse partition within said shell dividing said primary enclosure into a primary by-pass cham without said shell and terminating within said primary by-pass chamber, a perforated snubber tube Within said primary expansion chamber opening intoV said primary by-pass chamber and in substantial alignment with said inlet conduit, a third transverse partition within said shell dividing said secondary enclosure into a secondary by-pass chamber and a secondary expansion chamber the latter being at an end of said shell, a perforated tube passing through said primary expansion chamber and connecting said secondq ary by-pass chamber with said primary by-pass chamber, a secondary perforated snubber tube within said secondary expansion chamber opening into said secondary by-pass chamber and in l substantial alignment with said perforated tube, an outlet conduit connecting with said secondary expansion chamber fm' conducting cases from said shell, and a secondary perforated tube within said secondary expansion chamber connecting said secondary by-pass chamber with said outlet conduit.

13. `in an exhaust muiiier comprising a cylindrical shell having an inlet opening and an outlet opening located concentrically in the ends thereof, an inlet snout arranged in said inlet opening,

4an exhaust snout arranged in said outlet opening in substantially axial relation to said inlet snout, a tube comprising substantially an extension of said snout members passing through said shell, a transverse partition within said shell intermediate the ends thereof said partition having an opening therein through which said tube passes. said tube having openings in the walls thereof in the portions near the inlet and outlet ends of said shell and in an intermediate portion extendsaid shell, and sound-absorbing material in said annular chamber.

15. The construction of claim 13 in which a perforated membrane is arranged concentrically' within said shell and spaced therefrom to form an annular expansion chamber between said :membrane and said shell.

RALPH L. LEADBE'ITER.

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