SILENCER FOR A COMBUSTION APPARATUS

Abstract: A silencer is used in combination with a combustion apparatus or a combustion engine, said silencer being in the form of a casing (19) filled with granulate such as sand (36), pellets or the like, the induction air or exhaust gases being taken into and out from the granulate through an inlet conduit and an outlet conduit, respectively, said conduits having their openings situated inside the granulate and being covered by said granulate.

Description: Silencer for a combustion apparatus The present invention relates to a silencer in combination with a combustion apparatus or combustion engine, A silencer in this connection must have such properties that it does not disturb the course of combus¬ tion. In the first place it is thus a condition that the flow resistance in the silencer is kept sufficiently low, which has up to now resulted in that in known combustion apparatus with a silencer on the exhaust and/or induction side, the silencer has been formed as far as possible with ' free through-flow. In certain cases the air or gases have passed through steel wool or fibre material with relatively large flow area between the fibres. On the other hand it is known to use sand, pellets or similar granulates as filter material for purifying air, for example, to air raid shelters. In this case there is generally a suction fan on the outlet side of the filter, which sucks gas or air through the filter. No operational stoppage is risked, should resistance in the sand filter be too great. However, it has been found that the flow resistance in a filter consisting of sand is considerably less than one could expect with regard to the fact that seen superficially, sand- forms a rather compact mass. Against the background of the above, the invention has the object of.providing a silencer combined with a combustion apparatus which gives comparatively very good sound damping, while at the same time the silencer will be easy to clean. This problem is solved in accordance with the invention by combining a combustion apparatus with a silencer, formed to guide the induction air or exhaust gases to or from the combustion apparatus through a granulate such as sand, gravel, pellets or similar grainy material. As distinguished from traditional filters or silencers containing a sound-damping mass, where the gas or air is let into an inlet chamber in which one side of the. mass is situated, and departs to an outlet chamber where the other side of the gas is situated, the gas or air at the silencer will be led out via a place inside the granulate mass and thereafter taken out from it again at a place also inside the mass. More effective sound damping or silencing is thus obtained, since the sound waves are not released into any inlet or outlet chamber outside the mass. In practical trials with a combustion apparatus of the kind illustrated in the U.S. patent 3 853 453 in combination with a silencer having sand as . sound damping material, it has been found that silencing will be better than in the types of previously known silencers tried out in combination with said combustion apparatus. The known apparatus operates with so-called pulsating combustion and is sensitive, inter alia, as far as working with correct pressure conditions on the induction side as well as the exhaust side. It must therefore be regarded as an extremely surprising result that such- an apparatus can function together with a silencer where the gas or air is guided through a granulate as sound-damping material. The granulate grain size can be in the range of 1-3 mm. The silencer in accordance, with the . invention combined with a combustion apparatus has the characterizing features apparent from the following patent claims. In the case where sand is used as sound damping material, the silencer can be manufactured at a relatively low price. Cleaning the silencer can be performed in an extremely simple way by quite simply letting the sand run out through an emptying opening in the silencer casing, new and clean sand being subsequently supplied via a filling opening in the casing. This cleaning by exchanging cheap sound-damping material can be carried out in a short time and without special craftsmanship by practically anybody at all. The dirty sand can be subsequently washed in a special plant and can be used again. The silencer will also function as a filter which thus signifies cleaning of the air and the exhaust gases, T! OMPI which in the greatest degree is desirable in certain cases. These and other distinguishing features and advantages of the invention will now be explained in more detail in the following description of a few combinations of a combustion apparatus and a silencer in accordance with the invention, depicted on the appended drawings. Fig. 1 is a schematic depiction of an apparatus for pulsating combustion in combination with a silencer in accordance with the invention, placed on the exhaust side and the induction side, respectively, Fig. 2 is a view of the wide side of the silencer, Fig. 3 is a view of the narrow side of the silencer, Fig. 4 is a section along the line 4-4 in Fig. 3, Fig. 5 is a section along the line 5-5 in Fig c 2, Fig. 6 illustrates an alternative embodiment, Fig. 7 illustrates a further alternative embodiment. As is apparent from the figures, the silencer A is formed with a casing 10 in the form of a simple box with two pair of sides 12,12 and 14,14, respectively, and end walls 16,18. In the example illustrated, the casing is intended for use upstanding on the end wall 16, but if so desired it can be also used lying on one side. Two parallel, mutually spaced tubular channel members 20,22 are disposed in the casing which members are identic¬ ally alike, for which reason only the member 20 is described in the following. The member 20 comprises an internal sleeve 24 consist¬ ing of metal wire netting rolled up into a sleeve. About this sleeve there is wound a layer of cellular plastics 26 with open cells. The ends of the two elements 20,22 rest against the bottom end wall 16 of the casing. A pipe stub 28,30 is attached to each member and extends out through the upper end wall of the casing. The pipe stub 28 is intended for connection to the induction side of the combustion apparatus 29 in Fig Q 1 in the way illustrated. In the upper end wall 18 of the casing there is a filling opening 32 with a cover, and at the bottom end of the casing there is an emptying opening 34 with a cover 0 The casing has been filled with sand through the opening 32 up to the level 38. The granular size of the sand is substantially in the range of about 1 mm when the silencer is connected to the induction side of the apparatus, and suitably in the range of about 3 ram when the silencer is connected to the exhaust side of the apparatus. The foamed plastics sheaths 26 on the two tubular elements 20,22 are so constituted that they do not let through grains of sand but allow the through-passage of air or exhaust gases. The netting sleeves 24 only form an inner support for the foamed plastics sheaths. When the silencer is in use, air or exhaust gases flows into the stub 30 to the tubular member 22 and through it out into the sand 36 and over to the other tubular member 20, into it and out through the stub 28. When the sand 36 is quite new and clean, the greater part of the gas or air will take the shortest path over the members 20,22, which signifies that to begin with the major portion of the flow-over takes place in the upper area of the silencer in the figure. According as how this area is polluted with particles of dirt, the area where the major portion of the flow-over takes place will be moved further downwards in the casing. Since the air or the gas flow thus substantially follows the paths denoted by the arrows 40, only a part of the whole granulate quantity will form filter material, while the sound waves are dampened with the aid of the whole granulate quantity in the casing. When the silencer is to be cleaned out, this is done by tipping out the sand through the emptying opening 34 and filling new sand via the filling opening 32 0 The silencer illustrated in Fig. 4 has its inlet and outlet, respectively, situated at the same end of the casing 10, and for this reason it is suitable for connectin as a silencer to the induction side of the apparatus, as is indicated schematically in Fig. 1. In this figure there is also illustrated a silencer B connected to the exhaust side and which is depicted separately in Fig. 6 as an alternative embodiment. The silencer in Fig. 6 also has a casing 10 and a tubular member 42 comprising a netting and a foamed plastics sleeve round it, the member being connected to an inlet pipe 44. The casing is filled with sand 36 in this case as well. On the outlet side of the silencer there is a tubular member 46 suitably having a larger diameter than the tubular member 42 and of which the upper end portion is closed off by a sealing tube ' 46a, so that the exhaust-gases can only come into the tubular member after having passed a certain amount of sand. An inner pipe 48 is inserted in the tubular member 46 to form the outlet pipe, and has its- bottom end 46b situated outside the bottom end of the casing, while its upper end 46c is in the vicinity of the upper end of the tubular member 46. By means of this arrangement, the exhaust gases will pass through the sand in substantially the same way as the flow in the silencer in Fig. 4, i.e D so that the main flow first takes place at the upper area of the silencer, while the overflow area moves downwards gradually in the casing according as the sand becomes polluted and is given a greater flow resistance. In Fig. 7 there is finally illustrated an embodiment which is advantageous with regard to manufacture, fitting, adjustment to the grain size used in the granulate, dis¬ mantling and cleaning, and which also withstands high temperatures. In this case the tubular members 20,22 in Fig. 4 have their correspondence in two cylindrical helical springs 50,52, the diameters of which are approximately the same as the diameters of the members 20,22. The springs can have a wire diameter of 2 mm, for example, but this diameter can be selected greater or smaller according to require- . mentSo The springs are wound with their turns lying closely adjacent each other, and the gap between the turns can be between 1 and 3 mm according as the diameter of the grains used in the granulate. However, it is also possible to hj c-.-rr a spring with the turns in contact with each other and then extend the spring to a greater or less degree during fittin to obtain the desired flow gaps,, The springs can thus be adjusted to the granulate in question in a simple way. The silencer in accordance with the invention has bee described in conjunction with a combustion apparatus for pulsating combustion, but the silencer in accordance with the invention can naturally be used for other combustion apparatus as well, e.g. diesel engines. O PI

Claims: CLAIMS 1. A silencer for a combustion apparatus or a combustion engine generating pressure pulses and sound waves during the combustion, comprising a silencer housing provided with an inlet for air or exhaust gases, an outlet from the casing and means inside the casing for dampening sound waves in the induction air or in the exhaust gases, characterized in that the casing is at least partially filled with a sound-damping agent in the form of a granulate (36) such as sand, gravel, pellets or the like, and that the outlet opening (22,42,50) of the inlet (30,44) in the casing as well as the inlet opening (20,46,52) of the outlet (28,46a,46b) in the casing are so situated that they are surrounded by granulate. 2 0 A silencer as claimed in claim 1, characterized in that two substantially parallel and mutually spaced tubular members (20,22,42,46) are disposed inside the casing and are * surrounded by the granulate, and form the outlet and inlet opening, respectively, of the silencer, and that the walls of at least one tubular member are permeable to air and gas but prevent passage of the granulate. 3. A silencer as claimed in claim 2, characterized in that the tubular members consist of a tubular portion of a netting (24) or the like surrounded by a sleeve of foamed plastics (26) or a similar porous ', gas or air ,permeable material. 4. A silencer as claimed in claim 1, characterized in that two channel-forming, substantially tubular members are arranged inside the casing and are surrounded by granulate to form -said outlet and inlet openings, respectively, of said silencer, and that at least one tubular member consists of a helical spring (50,52) with closely adjoining turns of winding, the spacing of said turns being such that the desired flow gaps are obtained between said turns of winding S A OMPI to prevent granulate from passing between the turns but allowing flow of air or gas. 5. A silencer as claimed in any one of the preceding claims, characterized in that the inlet and outlet of the silencer are situated at the same end of the silencer casing (Fig. 4) β 6. A silencer as claimed in any one of claims 1-4, characterized in that one of the filter members contains a pipe (48) extending out at the opposite end of the silencer casing, so that the inlet and the outlet are situated at either end of the casing (Fig. 6). 0-.-. - ,„ Vv ' IP

Inventors: OLSSON K
Applicants: MARECK BV, OLSSON K
Application year: 1980
Main classification: F01N1
IPC codes: F01N1