US2189425A

US2189425A - Surge filter for pulsating gases

Info

Publication number: US2189425A
Application number: US236635A
Authority: US
Inventors: Ralph L Leadbetter
Original assignee: Burgess Battery Co
Current assignee: Burgess Battery Co
Priority date: 1938-10-24
Filing date: 1938-10-24
Publication date: 1940-02-06
Anticipated expiration: 1957-02-06

Description

Feb. 6, 1940. R a., LEADBETTER' 2,189,425

SURGE FILTER FOR PULSATING GASES Filed Oct. 24, 1938 2 perforated impedance member 2, the latter being in alignment with inlet conduit 3 and, optionally, round or oval in cross section. A tail pipe '4 connects with by-pass chamber 4a. The only entrance into chamber I is via impedance member 2. The area of gap b between contiguous ends of conduit 3 and member 2, that is, the area of the surface generated by drawing lines from points on the periphery of the inner end of conduit 3 to the nearest points of the periphery of the mouth of member 2, should not be substantially less than the cross-sectional area of inlet conduit 8.- Restated, and oy Way of example, if conduit member 3 andimpedance member 2 are circular in transverse section and have the same diameters, b should not be substantially less than one-fourth a. With this relationship it will be seen that a substantially unrestricted passageway is provided through which the gases may `flow, as indicated by the arrows, without entering snubber chamber I. This 'unrestricted passageway is the shunt path referred to above.

In the operation loi the device, the gas slugs are projected through inlet conduit 3 toward snubber chamber I. The path of least resistance would be from the inlet conduit directly to outlet conduit 4 through by-pass chamber la, but

- a portion of each slug has sulcient inertia imparted by the extremely high pressure conditions within the cylinder of the exigirle at the moment the exhaustv'alve opens to cause that portion of the slug to enter snubber chamber I via perfol rated member 2. The velocity energy of the slug is transformed into static pressure within impedance member 2 as the slug is brought to a cushioned stop, the pressure being dissipated by v an expansion ci. the gases into thespace of chamifrom, chamber I., resulting, rather, in a relatively gradual introduction of gases into the chamber and a relatively gradual restoration of the gases from this chamber to the by-pass chamber 2. A snubber effect is thereby obtained which reduces the gas-velocity-peaks of the flowing gases whereas a chamber without the impedance means described would merely reflect and possibly aggravate the pulsations. Additionally, it may be noted that the time lag caused by the impedance and the cooling (and therefore contraction) of the expanding gases materiallyV aid the snubbing operation in reducing the magnitude of the velocity peaks.

No representation is made that the device above described is alone capable of preventing f or attenuating pulsating gas noises to a degree considered satisfactory to the art except in certain cases. Thisdatcibeis-emoient in the smoothing of the gas fiow and therefore in the removal of ythe cause of noise. In particular, sounds in the lower frequency ranges are prevented by virtue of the invention. However, the device is intended" to be used in conjunction with means for attenuatingl the high frequency sounds. A simple expansion chamber or a packed muii'ier constructed in'accordance with the disclosure of Schnell Patent No. 1,811,762, dated June 23, 1931,

may be used for this purpose. Such a unit may be connected either in conduit 3y or in conduit 4.

A construction in which the snubbing unit above described is combined with a simple expansion chamber is shown in Figs. 2 and 3. A cylindrical shell 5 is provided with end flanges 6 and 'l having inlet opening 3 and outlet opening 9 therein, respectively. Inlet snout Il! is mounted in end iiange B at inlet opening 8 and exhaust snout Il is mounted at opening 9 in end fiange 1. A partition I2 having an openingA I3 therein in alignment with inlet opening 8 and an opening I4 not in alignment with inlet opening 8 is arranged transversely Within shell 5 in spaced relation to inlet end flanged to form by-pass chamber i5. A shell I6, including closure member. Il. denes snubber chamber I3 into which an impedance means in the form of a perforated. closed-ended tube It projects. The latter opens into by-pass chamber I5 at opening I3. snubber chamber I8 is entirely closed so that gases vmay enter it only via opening I3 and perforations 2K6. The gases must leave this chamber by the same path. Perforated conduit 2I connects Icy-pass chamber I5 with theoutlet open- The ing 3 and may be integral with exhaust snout Il, as shown. The perforations in the walls of conduit 2i permit expansion of the gases traveling through the conduit into space 22. l

The operation of the snubbing unit of the device of Figs. 2 and 3 is as above described. The high velocity portion of a slug entering the device through inlet snout III jumps the gap c and is snubbed in the snubbing chamber I6. The remainder of the gases by-pass from opening 8 directly to conduit 2l and are exhausted to the atmosphere. The gases entering into and operated upon by the snubbing unit are gradually restored to by-pass chamber I5 whence they flow through conduit 2i to the atmosphere. Expansion chamber 22 cooperates with the snubber unit in removing or preventing substantially all of the noises which would otherwise becaused by the pulsating gases.

VGap c should be suiiiciently large to permit substantially unrestricted ilow of gases through the device via openings 8, Il and 9. While-the degree of perforation of impedance members I9 and 2 (Fig. 1) is not critical, they should be sufficiently open to permit the proper degree of expansion of the gases entering them into the surrounding space. result in the loss of the necessary impedance to the flow. of gases into the snubber chamber andv the reflection of pulsations therefrom. Empirical yfindings indicate that the impedance member should be perforated suiciently to provide atotal open area of 5 per cent of, to 4 times, the crosssectlonal area of the inlet snout or exhaust pipe leading to the muliler. The snubber chamber itself should be sufcientlylarge to permit substantial expansion of the gases into it from the impedance member.

. Without limiting the invention and by way of example it is noted that a mufller constructed substantially as shown in Figs. 2 and 3 and having the following dimensions operated satisfactorily in preventing exhaust noise from a single cylinder, four cycle internal combustion gasoline engine of 2-horse-power at 1800 revolutions per Excessive perforation would i minute having a cylinder bore of 2% inches and stroke of 2% inches: shell 19 inches long by 4 inches in diameter, gap c 11/2 inches, impedance member 16 inches long by 1 inch in diameter and perforated suiciently to provide walls 4 per cent open, diameter of snubber chamber 2%' inches.

This invention is adaptable to embodiment in various forms not specifically shown or described herein but following the principles thereof. For example, inner shell IS may be concentric with perforated conduit 2| thus providing a snubber chamber occupying the entire volume of outer shell 5 except that enclosed by the imperforate inner shell. The term perforated is intended to cover all equivalent constructions wherein the member may be apertured otherwise than by stamping out small round portions of the material. Although the impedance means is illustrated as elongated and tubular, it is clear that this member may take other suitable forms. 'Ihe invention is limited only by the scope of the appended claims.

I claim:

l. In a device of the character described, gasvelocity-peak snubbing means comprising means forming a snubber chamber having substantially impervious walls, means forming a by-pass chamber, gas-flow impedance means arranged within said snubber chamber and having an entrance exteriorly thereof opening into said` by-pass chamber, a conduit extending toward said impedance means entrance for conducting pulsating gases toward said entrance, said conduit terminating short of said impedance means entrance within said by-pass chamber, and means for egress of gases from said by-pass chamber.

2. A device in accordance with claim l in which said conduit terminates short of said impedance means entrance by such a distance'that the area of the gap between the entrance to said impedance means and the contiguous end of said conduit is not substantially less than the crosssectional area of said conduit.

3. In a device of the character described. gasvelocitypeaksnubbing means comprising a shell having an opening in a wall thereof, .a transverse partition within said shell dividing the volume thereof into a snubber chamber and a by-pass chamber, said partition having an opening therein in alignment with said shell wall opening, gas-flow impedance means within said snubber chamber having an entrance at saidl chamber from the periphery of said opening in said partition the end of said tube within said snubber chamber being substantially closed, an inlet conduit extending through said shell wall opening and terminating in said by-pass chamber short of said perforated tube entrance, and an exhaust conduit connecting said by-pass chamber with the atmosphere.

5. In a device of the character described, a cylindrical shell having end closures and a transverse partition therewithin, a concentric opening in an end closure and a concentric opening in said partition, impedance means having an entrance at said opening in said partition and extending intothe space within said shell away from said end closure having an opening therein, a conduit'connecting with a source of pulsating, flowing gases and `extending through said opening in said end closure, said conduit terminating short of said impedance means entrance, and f an exhaust conduit connecting the space between said partition and said end closure having an opening therein with the atmosphere.

6. In a device of the character described, an outer shell having inlet and outlet end closures having inlet and outlet openings therein, respectively, a transverse partition arranged within said outer shell in spaced relation with said inlet end closure to form a by-pass chamber and having an opening therein in alignment with said inlet opening, an inner shell dividing the space within said outer shell and between said partition and said outlet end closure into a snubber chamber communicating with said by-pass chamber by means of said opening in said partition and an expansion chamber, a tubular member having perforated walls within said snubber chamber opening into said by-pass chamber at said opening in said partitionv the opposite end being substantially closed, and 'a perforated conduit passing through said expan,

a opening therein away from said inlet opening,

the end of said tubular member remote from said partition being covered by a perforated closure member, an inner shell surrounding said perforated tubular member and providing a space between said tubular member and said inner shell, and a perforated conduit within said outer shell and without said inner shell connecting said by-pass chamber with said outlet opening.

RALPH L. IEADBEI'IER.