EXHAUST GAS RECIRCULATION SYSTEM

Abstract: An exhaust gas recirculation system which comprises at least one conduit (2) for communicating at least some of the exhaust gas from an exhaust system to a combustion chamber of an internal combustion engine. The conduit (2) includes, in the order specified, a heater (14) and a filter (11) for the exhaust gas. The heater (14) is capable of heating the exhaust gas so as to obviate condensation of volatiles from the gas during passage through the filter (11).

Description: Exhaust Gas Recirculation System The present invention is concerned with an exhaust gas recirculating system. Recirculating systems which divert a part of the exhaust gas from the exhaust system back to a combustion chamber of an internal combustion engine are well known. These systems generally have a beneficial effect on the combustion process in the engine, ensuring that there are less carbon monoxide, nitrogen oxides (NOJ and other noxious gases in the exhaust. Such recirculating system frequently employ a condensing unit through which the exhaust gas passes before it passes through a filter. A problem associated with this arrangement however, is condensing of volatiles from the exhaust gas, which can result in clogging of the filtration medium employed in the recirculation system. I have now developed an exhaust gas recirculation system which helps to alleviate the above problem. According to the present invention, there is provided an exhaust gas recirculation system, which recirculation system comprises means for communicating at least some of the exhaust gas from an exhaust system to a combustion chamber of an internal combustion engine, which communicating means includes, in the order specified: (a) heating means for heating the exhaust gas; and (b) filter means for filtering the exhaust gas; the heating means being capable of heating the exhaust gas so as to substantially preclude condensation of volatiles therefrom during passage through the filter means. The system according to the invention need have no moving parts, and can be readily fitted as original equipment by the manufacturer, or as a retro-fit to a previously manufactured vehicle or other apparatus having an internal combustion engine. It is preferred that the communicating means includes at least one conduit suitable for conveying exhaust gas from an exhaust system to a combustion chamber. Such a conduit is preferably of heat-resistant non-ferrous material, such as copper or the like. According to a first aspect of the present invention, the conduit can be arranged to communicate exhaust gas from an exhaust tail pipe to the combustion chamber; alternatively the conduit can communicate exhaust gas from an exhaust pipe (such as a downpipe) to the combustion chamber. It is further preferred that the conduit includes, intermediate the exhaust system and heating means, a coarse filter, for, for example filtering out solids before the recirculated exhaust gas reaches the heating means. The heating means preferably comprises at least one vaporising chamber including at least one heating element capable of heating exhaust gas to a temperature at which condensation of volatiles therefrom is substantially precluded. The heating element, which typically becomes red hot in the exhaust gas, causes any condensable volatiles (such as unburnt hydrocarbons, and water) to remain in the vapour phase ( the water therefore being injected into the engine in the form of steam). Furthermore, clogging of the abovementioned filter means by condensate from the exhaust gas is obviated. It is preferred that the heating element is arranged to communicate heat from the exhaust manifold to the vaporising chamber. Preferably a first portion of the heating element is arranged in the exhaust manifold or in the exhaust system downpipe, in contact with the hottest portion of the gases from the engine, with a second portion of the element being arranged in the vaporising chamber. The vaporising chamber is preferably sealed from the exhaust manifold in the region of the heating element by means of a peripheral seal which surrounds the heating element. The heating element is typically of ceramic material, and may be an elongate member encased in a perforated heat-resistant tube, preferably of non- ferrous metallic material (for example of copper or the like). The vaporising chamber includes an inlet for exhaust gas and an outlet for heated exhaust gas. Preferably, the inlet and outlet are remotely spaced from one another within the vaporising chamber of the heating means, typically at or adjacent opposite ends of the vaporising chamber. This arrangement is beneficial in optimising heating of exhaust gas present in the vaporising chamber prior to exit of the gas from the outlet. The abovementioned filter means advantageously comprises a thermally resistant medium, such as a suitable metallic filter element; a preferred such filter element is of stainless steel or the like, typically in the form of steel wool. It is preferred that the filter means further comprises a carbonaceous filter medium, such as charcoal, active carbon or the like. In a preferred embodiment the carbonaceous medium is arranged as a sleeve around the metallic filter element, such that the recirculated gas first passes through the metallic filter element and then through the carbonaceous filter medium. There is further provided by the present invention an exhaust system including a recirculation system substantially as hereinbefore described; the exhaust system is typically in a vehicle having an internal combustion engine. In a preferred embodiment of the invention, the exhaust system comprises: (a) a tail pipe; (b) transfer means suitable for communicating exhaust gas produced in a combustion chamber of an internal combustion engine to said tail pipe; and (c) communicating means substantially as hereinbefore described, suitable for conveying part of the exhaust gas either from said tail pipe or from said transfer means to said combustion chamber. Advantageously the communicating means are mounted to either the tail pipe or the transfer means; the communicating means preferably include at least one conduit as hereinbefore described for communicating exhaust gas to the combustion chamber via the heating means. There is still further provided an internal combustion engine comprising: (a) at least one combustion chamber; (b) intake means for communicating a combustible fluid medium to said combustion chamber; (c) ignition means for igniting said combustible mixture; and (d) an exhaust system substantially as hereinbefore described. The present invention will now be further illustrated, with reference to the accompanying diagrams, in which like parts are denoted by like numerals, wherein: Figure 1 illustrates collection of exhaust gas emitted from a tail pipe of a system according to the invention; Figure 2 illustrates collection of exhaust gas from an exhaust pipe of a system according to the present invention; Figure 3 illustrates a vaporising chamber used in a system according to the present invention; and Figure 4 illustrates a filter used in a system according to the present invention. Referring to Figure 1, there is shown a tail pipe 1 and a collector pipe 2. Exhaust gas emitted from tail pipe 1 in the direction of arrow A is collected by pipe 2 and is recirculated to the combustion chamber (not shown) of an internal combustion engine. Collector pipe 2 is mounted on tail pipe 1 via clamp 3, the relative longitudinal positioning of pipes 1, 2 being adjustable so that the spacing of a mouth 4 from an open end 5 of tail pipe 1 can be selected. Referring to Figure 2, an alternative embodiment is illustrated wherein a collector pipe 2 is mounted on a downpipe 6. A baffle 7 is arranged internally of downpipe 6 so as to divert a portion of exhaust gas into collector pipe 2. Pipe 2 includes a filter 8 which filters the exhaust gas prior to heating thereof. Collector pipe 2 then conveys exhaust gas to a vaporising chamber 9 as illustrated in Figure 3, an outlet tube 10 being arranged to communicate exhaust gas from chamber 9 to a filter 11. The delivery portion 12, and collecting portion 13, of pipes 2, 10 respectively, are remotely arranged within chamber 9 to allow thorough heating of the exhaust gas prior to removal from chamber 9. A heater 14 is arranged to communicate heat from an exhaust manifold 6 to chamber 9. Heater 14 extends through juxtaposed walls 15, 16 of manifold 6 and chamber 9. Walls 15, 16 in the region of heater 14 are sealed, so as to preclude gas communication between manifold 6 and chamber 9. Referring to Figure 4, the heated gas exiting from chamber 9 is then passed through filter 11. Filter 11 comprises an inner stainless steel filter 17 and an outer sleeve of charcoal material 18. Although not illustrated, the filtered exhaust gas is then returned to a combustion chamber of an internal combustion engine.

Claims: CLAIMS: 1. An exhaust gas recirculation system, which recirculation system comprises means for communicating at least some of the exhaust gas from an exhaust system to a combustion chamber of an internal combustion engine, which communicating means includes, in the order specified: (a) heating means for heating said exhaust gas; and (b) filter means for filtering said exhaust gas; said heating means being capable of heating said exhaust gas so as to substantially preclude condensation of volatiles therefrom during passage through said filter means. 2. A recirculation system according to claim 1, wherein said communicating means includes at least one conduit suitable for conveying exhaust gas from an exhaust system to a combustion chamber. 3. A recirculation system according to claim 2, wherein said conduit is arranged to communicate exhaust gas from an exhaust tail pipe to said combustion chamber. 4. A recirculation system according to claim 2, wherein said conduit is arranged to communicate exhaust gas from an exhaust manifold to said combustion chamber. 5. A recirculation system according to any of claims 2 to 4, wherein said conduit includes, intermediate between the exhaust system and the heating means, a second filter means. 6. A recirculation system according to any of claims 1 to 5, wherein said heating means comprises at least one vaporising chamber including at least one element capable of heating exhaust gas to a temperature at which condensation of volatiles therefrom is substantially precluded. 7. A recirculation system according to claim 6, wherein said heating element is arranged to communicate heat from the exhaust manifold to the vaporising chamber. 8. A recirculation system according to claim 7, wherein a first portion of the heating element is arranged in the exhaust manifold, and a second portion of the element is arranged in the vaporising chamber, the vaporising chamber being sealed from the exhaust manifold in the region of the heating element. 9. A recirculation system according to any of claims 6 to 8, wherein said vaporising chamber includes exhaust gas inlet and outlet longitudinally spaced from one another. 10. A recirculation system according to claim 9, wherein the inlet and the outlet are adjacent spaced ends of said vaporising chamber. 11. A recirculation system according to any of claims 1 to 10, wherein said filter means comprises a stainless steel filter element. 12. A recirculation system according to any of claims 1 to 11, wherein said filter means comprises a carbonaceous filter medium. 13. An exhaust system comprising: (a) a tail pipe; (b) transfer means suitable for communicating exhaust gas produced in a combustion chamber of an internal combustion engine to said tail pipe; and (c) a recirculation system according to any of claims 1 to 12, wherein said communicating means are suitable for conveying at least some of said exhaust gas from either said tail pipe or said transfer means to said combustion chamber. 14. An exhaust system according to claim 13, wherein the communicating means are mounted to either the tail pipe or the transfer means. 15. An internal combustion engine comprising: (a) at least one combustion chamber; (b) intake means for communicating a combustible fluid medium to said combustion chamber; (c) ignition means for igniting said combustible mixture; and (d) an exhaust system according to claim 13 or 14.

Inventors: HURLEY DEREK MELVIN, HURLEY, DEREK, MELVIN
Applicants: HURLEY DEREK MELVIN, HURLEY, DEREK, MELVIN
Application year: 1993
Main classification: F02M25
IPC codes: F01N5, F01N7, F02M25