US 3233697 A
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Feb. 8, 1966 G. SLAYTER ETAL 3,233,697
MUFFLER INTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Original Filed June 7, 1960 2 Sheets-Sheet 1 INVENTORS GAMES Smvrm, Roam-r G Passe-u. &
BY Mann A. Moran/v Arron/vars Feb. 8, 1966 e. SLAYTER ETAL 3,233,697
MUFFLER INTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Original Filed June '7, 1960 2 Sheets-Sheet 2 INVENTORS GAMES SLAYrER, Panzer 6. Russsu &
Z WILLARD L. Manamv A 7 Rfi/E Y5 United States Patent 3,233,697 MUFFLER INTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Games Slayter, Newark, and Robert G. Russell, Granville, Ohio, and Willard L. Morgan, Spartanhurg, S.C., assignors to Owens-Corning Fiberglas Corporation, a corporation of Delaware Original application June 7, 1960, Ser. No. 34,408, now Patent No. 3,109,511, dated Nov. 5, 1963. Divided and this applicatiouMay 6, 1963, Ser. No. 278,330
2 Claims. (Cl. 181-42) This application is a division of our copending application Serial No. 34,408, filed June 7, 1960, now Patent No. 3,109,511.
This invention relates to an improved muffling system and more particularly to a vehicle muflling system in which components are lined with highly refractory fibers.
Present mufilers include casings or walls of one or more wraps of steel which enclose a plurality of internal steel battles to mutile the sound of the engine and exhaust gases. These mufflers are subjected to conditions which cause the casings to be attacked with the result that the mufilers are relatively short lived. For example, particularly in winter and on short trips, liquids of an acidic nature from the engine will deposit on and attack the interior surface of a muffler casing. On long trips the mufller casing also tends to become very hot, the gases within the casing often being over 1600 F. under normal operating conditions and may be substantially higher than this if a spark plug is not functioning with the result that a cylinder exhausts a mixture of air and raw fuel into the exhaust system where it burns partially. Oil expelled from the engine through the exhaust system, and deposited in the mufller, may also smolder and thereby further increase interior temperatures. Elevated mufiler casing temperatures increase the rate at which the casing oxidizes or rusts.
There is also reason to believe that conventional mufflersmay increase the amounts of certain deleterious contaminants in exhaust gases. Available evidence indicates that exhaust gases in contact with hot iron or steel undergo a reaction which increases the amounts of olefins in the gases. This reaction can occur in conventional muffiing systems, wherever exhaust gases contact hot steel or oxidized cast iron components of an exhaust system.
In addition, the bare metal walls of conventional muf- ,flers and mufiling systems extract heat rapidly from the exhaust gases, thus causing the gases to cool rapidly. Such cooling prevents secondary combustion in the exhaust system that might otherwise consume at least part of the carbon monoxide and olefins in the exhaust gases. In present mufiiing systems, secondary combustion is very rare and may onlyoccur at high operating speeds when raw fuel and air flow through the exhaust system.
The present invention relates to a muffling system having a lined component and to an insulating liner which overcomes the above-discussed disadvantages of existing muffling systems. The liner is preferably made of highly refractory fibers held together by a suitable binder, the
. liner being located near the inner surface of the component, between it and the exhaust gases. There is a much smaller tendency for condensation to occur with the new exhaust system because the exhaust gases are kept out I of contact with the cold walls of the system, and because the linear remains hot longer after the engine is stopped.
Any such liquid that does condense, as in winter when the engine is not operated for a long enough period to heat the liner sufficiently, will eventually evaporate in the tern components at much lower temperatures by comparison with conventional systems, the walls being approximately 300 F. or less when the exhaust gases are 1600 F. when a liner only one-half inch thick is used. The relatively cool walls thus tend to oxidize, rust, and warp to a much smaller degree than formerly and no special steels are required for the mufiler components as might otherwise be necessary. In addition, the new liner prevents contact between the exhaust gases and the steel or cast iron walls of the lined exhaust system component and thus prevents an increase in the amount of olefins which otherwise occurs. Reduction in heat loss from the manifold under the hood also reduces driver discomfort in the summer when the maniold is lined in accordance with the invention. Because the insulating liner prevents rapid extraction of heat from the exhaust gases to the mufiier walls, the exhaust gases remain at much higher temperatures and can undergo secondary combustion in the system. The liner also provides an effective surface in contact with which combustion of the gases can proceed. To aid in secondary combustion, air can be added to the exhaust gases at a point upstream of the mufiier to provide additional oxygen for combustion of the remaining fuel in the exhaust gases.
It is, therefore, a principal object of the invention to provide an improved muflling system including an interior, insulating liner.
Another object of the invention is to provide an exhaust system where fewer deleterious substances are present in the exhausted gases.
Still another object of the invention is to provide a muffler having a longer life than those presently known in the art.
Yet another object of the invention is to provide a muffling system in which the exhaust gases are maintained at higher temperatures so that additional, secondary combustion can occur therein.
Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:
FIG. 1 is a somewhat schematic view, with parts broken away and parts in cross section, of an engine and a muifling system embodying the principles of the inventron;
FIG. 2 is a greatly enlarged view in cross section of a muffler of the system shown in FIG. 1;
FIG. 3 is a view in transverse cross section taken along the line 3-3 of FIG. 2;
FIG. 4 is a view in perspective of a liner segment used in the mufiiing system and the mufller of FIGS. 1-3;
FIG. 5 is a view in vertical cross section of a mold for making the segment shown in FIG. 4;
FIG. 6 is a somewhat schematic view in cross section of modified apparatus for lining mufiling systems; and
FIG. 7 is a view in cross section of further modified apparatus for lining mufiling systems.
Referring to FIG. 1, an eight cylinder engine is indicated at 10, the cylinders of Which are connected to a mufili-ng system indicated generally at 12, although the two banks of cylinders can alternately be connected to separate mufiling systems. The system 12 includes lined manifolds 14, a lined connecting pipe 15, a lined' exhaust pipe 16, a lined mufiler 18, and a tailpipe 20 which can be lined or not.
The mufiler 18 (FIGS. 2 and 3) includes a casing 22 comprising two half sections 24 and 26 which can be bolted together at flanges 28 and 30 (FIG. 3) extending longitudinally thereof. Suitable conecting pipes 32 and 34 (FIG. 2) are afiixed to end walls of the casing 22 for connection with the exhaust pipe 16 and the tailpipe 20, in a maner well known in the art. Within the casing 22 is a perforate metal tube 36, which is spaced from the casing 22 by suitable spacers 38, reinforced cement rings being suitable for this purpose. Within the perforate tube 36 is a cylindrical liner 40 made of a plurality of circular or ring segments 42 which are placed in coaxial, end-to-end relationship and preferably cemented together by a ceramic band. The outer diameter of the segments 42 is large enough to enable them to be held tightly within the tube 36 and the inner diameter of the segments 42 is sufiicient to form a passage for exhaust gases from the engine 10. The walls of the segments 42 are at least A" thick to provide reasonable strength and have been made in thicknesses up to approximately 1 /2 of either porous or non-porous ceramic of the type described below.
The segments 42 are integral, porous bodies containing highly refractory, titania fibers, and are self-sustaining within the tube 36, requiring no internal wall or support within the bodies. The liner 40 prevents attack of the muffler casing -by keeping any corrosive liquids in the exhaust gases out of contact therewith. The titania ceramic is also resistant to acids, to high temperature steam, and to the various corrosive contaminants within the exhaust gases. The liner 40 also acts as an extremely good insulator with the result that the temperature of the casing 22 seldom exceeds 300 F., even when the exhaust gases are at 1600 F. or higher. In addition, the exhaust gases are kept out of contact with the casing 22 to prevent an increase in the amount of olefins which might otherwise result. Finally, the exhaust gases are kept at a higher temperature within the exhaust system due to the insulating effect of the liner 40 that additional combustion of these gases can take place in order to reduce the amount of deleterious contaminants therein. For this purpose, additional air can be added to the exhaust system through an air pipe 44 (FIG. 1), which is conected to the exhaust pipe 16. The air can be supplied by a small blower 46 or, duringmovemerit of the vehicle, by an air scoop. I
The segments 42, a single one of which is shown in perspective in FIG. 4, have been made from a mixture of 87 grams crystalline titania fibers from /4" to /2" long, 20 grams of wood sawdust, 25 grams of Montmorillonite and 13 grams of powdered soda-lime glass. This mixture was combined with sufficient water to make a mortar or paste of fibrous pellets which were then pressed into a mold the size and shape of the segment 42 and fired at 2500" F. to cause the soda-lime glass and Montmorillonite to form a binder for the titania fibers and to cause the sawdust to burn out and leave a porous body. The resulting body consisted essentially to 70% titania, 20% Montmorill-onite, and sodalime glass. By volume, the body contained approximately 70% air, titania fibers, and 10% binder (Montniorillonite and soda-lime glass), with an apparent density of approximately 70 pounds per cubic foot. Segments 1" thick show only slight resistance when air is blown through them. I
While the segments 42 have been made in a metal mold having an annular, tapered cavity, it has been found that the material is difficult to remove therefrom preparatory to firing. For this reason, the segments 42 are preferably made in a mold 44 shown in FIG. 5. The mold 44 includes an outer cylindrical wall 46 and an end wall 48 of paper, cardboard, or other organic material which will burn away at a temperature below the firing temperature of the segment material. A metal rod 50 which is concentric of the mold 44 extends through the end wall 48 to form an annular cavity with the end wall 48 and the cylindrical wall 46, the cavity having a shape and size similar to those of the segment 42. After the liner material is placed in the cavity and tamped therein, the metal rod 50 is removed to leave the green liner and the walk 46 and 48 which are fired as a unit, the Walls 46 and 48 burning away, with only the fired, hardened segment 42 then remaining. With this arrangement, the liner material need not be removed from the mold prior to firing.
The porous liner 49 not only provides the advantages outlined above, but also constitutes an effective acoustic material to absorb sound and muffle the noise of the exhaust gases and engine. The perforate tube 36 further enhances the acoustical absorption properties of the muffler 18, particularly for sound of lower frequency. However, the liner 40 can be made with a larger diameter and placed immediately adjacent the casing 22, with the porous tube 36 eliminated, to provide substantially as good sound absorption. It is desirable that the muffler have a volume about ten times the volumetric displacement of the engine cylinders from an acoustical standpoint.
In accordance with the principles of the invention, it also has been discovered that the liner material can 'be employed in the manifold 14 and the exhaust pipe 16 to maintain the temperature of the exhaust gases several hundred degrees higher than otherwise and also to keep th eexhaust gases separate from the steel or iron of which the manifold 14 and the exhaust pipe 16 are made to pre vent reaction on the surface thereof. The manifold 14 and the exhaust pipe 16 are also maintained at cooler temperatures by being insulated from the exhaust gases, and temperatures under the hood are decreased. Because the temperatures of the lined exhaust system components are much lower than in conventional exhaust systems, the manifold 14 can be made of welded or fabricated sheet steel, the manifold 14 in this case comprising a cylindrical metal tube 52 and shorter connecting tubes 54 of welded sheet steel. Previously, it was necessary in most instances to cast the manifold 14 which, because of its high temperature, had considerable tendency to warp, making the use of fabricated steel impractical.
The manifold 14 and the exhaust pipe 16 have been lined with segments similar to the segments 42, but of smaller diameter. However, where the manifold 14 or the exhaust pipe 16 is of relatively complicated shape, the liner can be applied to these components in the form of a thick coating on the interior walls thereof. Because sound absorption is not a consideration in the manifold 14 and the exhaust pipe 16, the liner in this casen'eed not be porous, and the sawdust or other material forming voids in the final product need not be employed or can be employed to a lesser degree. The refractory f bers in the liner material preferably are shorter than those used in the liner 40 to enable the liner material to be more easily applied to the interior of the com onent After the liner material is applied it can be fired in the mufiling system components by passing highly heated gases therethrough to provide the proper firing temperatures therein without excessively heating the outer walls of the components.
A thick layer of the coating material can be applied to the inner surfaces of the manifold 14 and the exhaust pipe 16 with the apparatus shown in FIG. 6. In this instance, the binder materials and the titania fibers can be supplied separately, and titania powder can be added to increase the strength of the liner. The apparatus, indicated generally at 56, moves from left to right in FIG. 6 through the exhaust pipe 16, for example, which preferably is concommitantly rotated. Titania powder can first be supplied to the interior of the pipe 16 through a supply line 58 and the binder material then supplied through a second supply line 60, with the titania fibers then being supplied to the surface of the binder material through a third supply tube 62. The binder and titania also can be supplied through a single supply line 'as a premixed aqueous paste by means of air pressure. The liner material which is now deposited on the interior of the tube 16 is subsequently spread evenly by means of a spreader 64 which is in the form of a flexible cone or a plurality of flexible arms. In either case the spreader 64 is spaced from the inner surface of the pipe 16 by means of spacers 66 which determine the thickness of the liner.
A modified liner applicator 68 is shown in FIG. 7 and includes an outer passage 70 through which the binder or coating material is sprayed through an annular nozzle 72 which also can be a plurality of individual nozzles. The titania fibers are subsequently sprayed onto the wet coating material by means of an inner passage 74 through which the titania fibers are blown, being deflected to the wall of the pipe 16 by a deflector 76. Again, the titania fibers and the binder material can be supplied through a single spray passage.
Other binders and other highly refractory fibers, such as zircon and zirconia fibers, have been found to be suitable for use in a lined mufiiing system according to the invention. The fibers employed must be of a highly refractory nature, capable of withstanding temperatures of 1800 F. and preferably 2600 F. because the internal temperature of the exhaust system may be as high as 2600 F., or possibly higher, if a spark plug is inoperative and a mixture of air and raw gas is expelled into the exhaust system. However, the titania fibers, whether oxidized or oxygen deficient, have properties which render them particularly suitable for a mufiiing system, these fibers apparently having a catalytic effect on the exhaust gases. Titania, zirconia, and zircon fibers over an inch in length and in single crystalline form have been produced in quantities according to a process set forth in a copending application of Russell, Morgan, and Schefiier, Serial No. 31,964, filed on or about May 26, 1960, now Patent No. 3,065,091.
1. A mufiiing system component comprising a casing forming an elongate chamberhaving an inlet opening and an outlet opening, and an integral coating within said chamber forming a passage for exhaust gases between said inlet opening and said outlet opening, said coating being interposed between said passage and said casing with the inner surface of said coating being substantially unobstructed for contact with exhaust gases flowing through said component, said coating comprising highly refractory, inorganic, crystalline fibers selected from the group consisting of titania, zirconia, and zircon, and an inorganic binder.
2. A mufiling system component comprising a casing forming an elongate chamber having an inlet opening and an outlet opening, and an integral, porous coating within said chamber forming a passage for exhaust gases between said inlet opening and said outlet opening, said porous coating being interposed between said passage and said casing with the inner surface of said coating being substantially unobstructed for contact with exhaust gases flowing through said component, said porous coating comprising highly refractory, inorganic, titania fibers, and an inorganic binder holding said fibers together and forming a multiplicity of voids in said coatmg.
References Cited by the Examiner UNITED STATES PATENTS 2,065,343 12/1936 Moore et al. 181-50 2,072,961 3/1937 Nelson. 2,523,260 9/1950 Campbell 181-50 2,654,136 10/1953 Harford et al 252-62 X 2,811,457 10/1957 Speil et a1. 2,833,620 5/1958 Gier et al. 252-62 X 2,837,169 6/1958 Sawyer 181-36 2,848,349 8/1958 Rechter et al. 106-57 X 2,884,380 4/1959 Cook et al. 252-62 2,938,937 5/ 1960 Shenk. 2,981,057 4/ 1961 Buttler 181-62 X 2,991,200 7/1961 Sheridan et al. 106-57 X 3,043,094 7/1962 Nichols. 3,061,416 10/ 1962 Kazokas 181-36 3,065,091 11/1962 Russell et al. 106-57 X 3,110,545 11/1963 Beasley et a1 252-62 X FOREIGN PATENTS 654,685 12/ 1937 Germany.
679,940 9/ 1952 Great Britain.
961,667 11/ 1949 France.
LEO SMILOW, Primary Examiner.