An anti-pollution device for treating the exhaust gases from internal combustion engines and burners in general, functioning also as exhaust silencer

Abstract: The device, which serves both to control harmful emissions and to lower the noise levels of exhaust gases from internal combustion engines and burners in general, comprises a duct (3) created between the coils (4, 4') of a spiral element and open at either one or both ends; the element is fashioned in a material of low thermal conductivity, and the coiled surfaces exposed to the exhaust gases can be coated with catalytic materials capable of speeding up the reduction or oxidation of pollutants.

Description: An anti-pollution device for treating the exhaust gases from internal combustion engines and burners in general, functioning also as exhaust silencer. The present invention relates to an anti-pollution device for the treatment of exhaust gases from internal combustion engines and burners generally, which also performs the function of a silencer, i.e. a device for incorporation into the pipeline through which fumes generated by the combustion of fuel are exhausted from internal combustion engines or from the combustion chambers of burners, to the end of controlling or eliminating harmful emissions (CO, HC, NOx and particulate matter), and at the same time of reducing exhaust noise levels. It is known from US-A-3,066,755 an exhaust gas treating device, for treating exhaust gases from an internal combustion engine, comprising at least one inlet pipe for receiving said gases and at least one outlet pipe for discharging said gases, a wall structure defining a single spiral duct through which the exhaust gases can flow from the at least one inlet pipe to the at least one outlet pipe, said wall structure comprising two metal walls defining the outer surfaces of the wall structure that are in direct contact with the exhaust gases, said metal walls being supported in spaced relation to each other and a filler of refractory material being disposed within the space between the walls. The scope of the refractory material is to absorb heat from the exhaust gases in order to obtain heat conditions favourable to improving the completeness of the combustion of combustible materials contained in the exhaust gases. However, there is a considerable loss of heat within the exterior of the device through said metal walls, said loss of heat reducing considerably the efficiency of the device with respect to the completeness of combustion of the combustible materials contained in the exhaust gases. In addition, the metal walls must be formed from a metal having a high resistance to the thermal and chemical deterioration caused by the contact with the exhaust gases, which increases substantially the cost of the device. It is an object of the present invention to provide an exhaust gas treating device in which the losses of heat towards the exterior of the device are minimized and a high resistance of the wall structure to thermal and chemical deteriorarion caused by the exhaust gases is obtainable at low costs. The stated object is achieved by adopting an anti-pollution device for the treatment of exhaust gases from internal combustion engines and burners in general, functioning also as a silencer, comprising at least one inlet pipe for receiving said gases and at least one outlet pipe for discharging said gases, a wall structure including a material possessing a low coefficient of thermal conductivity and defining a single spiral duct through which the exhaust gases can flow from the at least one inlet pipe to the at least one outlet pipe, characterized in that said wall structure has at least outer surfaces formed from said material. Said outer surfaces may be coated with catalytic materials such as platinum, palladium or rhodium, able to promote the oxidation or reduction of pollutants in the exhaust gases. In the case of exhaust gases containing notable quantities of so-called particulate matter, i.e. the solid combustion residue as produced typically by Diesel engines, said outer surfaces may be undulated, or embodied with projections of sawtooth profile, so as to trap and thus favour the combustion of such particulate matter. The advantages of the present invention are: the facility of utilizing a single device to control emissions in and reduce the noise level of exhaust gases; simplicity in construction; marked reduction in manufacturing costs; greater efficiency. Two embodiments of the present invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: fig 1 is a longitudinal section through a device according to the invention, in which the spiral element is fashioned in sheet metal with a suitably treated surface; fig 2 is the section through II-II, fig 1; fig 3 is a longitudinal section through a device according to the invention, in which the spiral element is fashioned in ceramic material; fig 4 is the section through IV-IV, fig 3. In the drawings, 1 denotes a pipe through which exhaust gases are directed into the device; A and B denote the longitudinal axis of the pipe and of the device, respectively; 2 denotes a cover fitted to the front end of the device, i.e. the inlet end; 3 denotes a spiral duct of which the walls 4 are created by the single coils of an element fashioned from metal coated with a material of low thermal conductivity and receding spirally from the axis AB of the device. 4' denotes the same spirally coiled walls of an element fashioned in ceramic material such as cordierite. 5 denotes a void between the front cover 2 and the spirally coiled walls 4, which may be filled with sound-absorbent or sound-reflecting material. 6 denotes the outermost coil of the spiral element, which provides the external casing of the device in the event that the walls 4 are fashioned in metal with a coating of low thermal conductivity (fig 1); 7 denotes the outer casing of a device in which the walls 4' of the spiral element are ceramic material (fig. 3). 8 denotes a ring enclosing the innermost turns of the spiral duct at the inlet end and affording a central hole 9 by which these same innermost turns are caused to communicate with the exhaust pipe 1. 10 denotes a central baffle partly enclosing the rear end of the spiral duct 3, which consists in a circular dish pressed from the rear cover 11 of the device; 12 denotes a void between the rear cover 11 and the turns of the duct 3 not enclosed by the battle 10, which may be filled with sound-absorbent or sound-reflecting material. 13 denotes a tail pipe associated with the device by insertion through the periphery of the rear cover 11 in such a way as to communicate with the outermost turns of the spiral duct 3; C denotes the axis of the pipe 13. The embodiment of fig 3 further comprises a layer of insulating material 14 sandwiched between the outermost coil 6 of the spiral element and the casing 7; also, the surface of each coil or wall 4' affords a plurality of projections 15 exhibiting a sawtooth profile, which serve to trap particulate matter. Operation of the device will now be described. Hot combustion gases generated by fuel combustion in an engine, or a burner generally, characterized by a high content of pollutant emissions and sound pressure waves of high intensity, are directed from the exhaust pipe 1 into the spiral duct 3 by way of the hole 9 in the inlet ring 8. The temperature of the walls 4 or 4', whether of metal with a coating of low thermal conductivity or of ceramic material, is raised to a level such as will promote further combustion of the pollutants present in the gases (CO, HC); further combustion in turn pushes the temperature of the walls 4 or 4' still higher, thereby enhancing the destruction process. This further combustion of carbon monoxide and hydrocarbons can be rendered more advantageous yet by coating the walls 4 or 4' with a platinium or palladium based cacalytic material. Such a material might also be formulated with rhodium, to the end of catalyzing the reduction of nitrogen oxides. The sawtooth projections 15 increase the ability of the device to trap any particulate matter on the surface of the walls 4 or 4', whereupon such matter will burn by reason of the high temperature of the coils. In addition to the emission control thus obtained, sound pressure waves carried in the gases are also damped, principally by collision with the surfaces of the spiral duct and by interference of the acustic waves in the outlet to the tail pipe 13.

Claims: An anti-pollution device for the treatment of exhaust gases from internal combustion engines and burners in general, functioning also as a silencer, comprising at least one inlet pipe (1) for receiving said gases and at least one outlet pipe (13) for discharging said gases, a wall structure (4, 4') including a material possessing a low coefficient of thermal conductivity and defining a single spiral duct (3) through which the exhaust gases can flow from the at least one inlet pipe (1) to the at least one outlet pipe (13), characterized in that said wall structure (4, 4') has at least outer surfaces formed from said material. A device as in claim 1, wherein said wall structure (4, 4') is formed from metal interposed between said outer surfaces. A device as in claim 1, wherein between said outer surfaces, said wall structure is formed from the same material forming said at least outer surfaces. A device, as in claim 1, or 2, or 3, wherein said at least one inlet pipe (1) is connected to said spiral duct (3) at a location nearer to a central area thereof than the location at which said at least one outlet pipe (13) is connected to the spiral duct (3). A device as in one of claims 1 to 4, wherein at least one of said outer surfaces is coated with a catalytic material incorporating noble metals such as platinum, palladium and rhodium. A device as in one of the preceding claims, wherein at least one of said outer surfaces exhibits projections (15) having a sawtooth profile. A device as in one of claims 1 to 5, wherein at least one of said outer surfaces is undulated. A device as in claim 1, wherein the material possessing a low coefficient of thermal conductivity is a ceramic material.

Inventors: NIERI GIUSEPPE, NIERI, GIUSEPPE
Applicants: NIERI GIUSEPPE, NIERI, GIUSEPPE
Application year: 1991
Main classification: F01N3
IPC codes: F01N3, F01N1