The present invention relates to catalytic converters for diesel engines having overhead exhaust manifold systems.
Two-stroke and four stroke medium speed diesel engines such as those manufactured by Electromotive Diesels (EMD) of LaGrange, Ill. (formerly a division of General Motors) are used in locomotives, in power generating systems, and in marine propulsion applications. An example of one common type of diesel engine, depicted in
As is also known in the art, another common type of diesel engine is a turbocharged engine which is similar to the roots-blown engine 2 depicted in
Turbocharged and roots-blown diesel engines typically have either 8, 12 or 16 cylinders arranged in a V configuration. Consequently, the manifold legs 6 of the exhaust system extend upwardly from the cylinder ports to the overhead exhaust manifold 4 in a series of four, six or eight opposing pairs. The overhead exhaust manifold 4 is typically formed of a series of manifold sections 10 such that two opposing pairs of the manifold legs 6 are connected to each manifold section 10. Each manifold section 10 also typically includes a flange 12 on one or both of the longitudinal ends thereof for bolting to flanged expansion joints positioned between the other manifold sections 10.
A need presently exists for an effective catalytic converter system for treating the exhaust gas from diesel engines. The application of catalytic converter devices to the exhaust systems of two-stroke and four-stroke diesel engines has been difficult for several reasons. In many cases, particularly in locomotive applications, there is not sufficient space around the engine for installation of a catalytic converter system. In addition, the temperature of the exhaust from two-stoke and four-stroke engines is relatively low in terms of the temperature necessary to “light-off” the catalyst to initiate and maintain the conversion reaction. Further, these engines have a relatively high lube oil consumption rate. In addition, it is difficult in locomotive and other applications to remove the exhaust manifolds from the engines due to a lack of sufficient overhead space for the lifting equipment. Also, the back pressure limits of the turbocharged diesel engines are typically very low.
The present invention satisfies the needs and alleviates the problems mentioned above. In one aspect, there is provided an improved exhaust system for a diesel engine wherein the exhaust system includes a series of pairs of upwardly extending exhaust port legs having upper outlet ends for delivering exhaust into an overhead exhaust manifold extending substantially horizontally over the diesel engine. The improvement comprises a plurality of catalytic converter elements removably positionable in the overhead exhaust manifold over the upper outlet ends of the exhaust port legs.
In another aspect, the improvement to the exhaust system preferably comprises a separate one of the catalytic converter elements being removably positionable in the overhead exhaust manifold over each of the upper outlet ends of the exhaust port legs. Further, the improvement preferably comprises the catalytic converter elements being removably positionable in the overhead exhaust manifold in opposing pairs, each of the opposing pairs of the catalytic converter elements forming a lateral V arrangement.
In another aspect, there is provided an improved overhead exhaust manifold segment for a diesel engine wherein the exhaust manifold segment has a longitudinal interior passage, a longitudinal wall surrounding the longitudinal interior passage, and a plurality of openings in a lower portion of the longitudinal wall for receiving an engine exhaust. The improvement comprises one or more catalytic converter elements removably insertable in the overhead exhaust manifold segment in a manner effective such that the engine exhaust will flow through the one or more catalytic converter elements into an upper longitudinal portion of the interior passage.
In another aspect, the improvement to the overhead exhaust manifold segment preferably further comprises four of the catalytic converter elements being insertable in the overhead exhaust manifold segment in two opposing pairs. In addition, the improvement preferably comprises the four catalytic converter elements being insertable in the overhead exhaust manifold segment in a manner such that each of the opposing pairs forms a lateral V arrangement.
Further aspects, features, and advantages of the present invention will be apparent to those in the art upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments.
An embodiment 20 of an improved overhead exhaust manifold segment for a diesel engine exhaust system is depicted in
The inventive manifold segment 20 comprises: a longitudinal interior passage 22; a longitudinal outer cylindrical wall 24 which surrounds the internal passage 22; a plurality of (preferably at least two and most preferably four) openings 26 in the bottom of the cylindrical wall 24 which are in fluid communication with the upper outlet ends of the manifold legs 6 extending from the engine cylinder exhaust ports; and one or more (preferably a plurality of) catalytic converter elements 28 which are removably insertable in the longitudinal passage 22 such that substantially all of the engine exhaust gas received in the overhead exhaust manifold via the vertical manifold legs 6 will flow through the catalytic converter element(s) 28 into an upper longitudinal portion 30 of the longitudinal interior passage 22.
The catalytic converter element(s) 28 will preferably comprise a diesel oxidation catalyst on a metal foil substrate. The substrate will preferably be constructed of layers of corrugated foil with angled channels which are spot welded together. Catalysts and catalyst substrates of this type are known in the art and are available, for example, from EcoCat Oy. Such catalysts and catalyst substrates are also described, for example, in Heikki Tuomola, et al., “A New Metallic Catalyst”, SAE Technical Paper Series, 2002.
The inventive manifold segment 20 preferably further comprises one or more track slots 34 or other types of slots which extend into the longitudinal interior passage 22 for removably receiving and holding the catalytic converter elements 28. The elements 28 can be any desired shape but are preferably rectangular and the slots 34 preferably have a corresponding U-shape. Flanged openings 36 are provided through the manifold segment wall 24 at the outer ends of the slots 34 for receiving and removing the catalytic converter elements 28. Covers 38 are removably attachable to the flanged openings 36 using bolts or other suitable attachments for closing the flanged openings 36. A sealing gasket 40 is preferably attached around the perimeter of each of the catalytic converter elements 28 for sealing against the bottom and side walls 42 and 44 of the U-shaped slots 34 and for sealing against the inner surfaces of the covers 38.
The inventive manifold segment 20 can use a single catalytic element 28, a series of at least two catalytic elements 28, or one or more pairs of opposing catalytic elements 28. If a single element 28 or a series of single elements 28 is/are used, each element will preferably be inserted laterally in a substantially horizontal orientation. If one of more pairs of opposing elements 28 are used, each pair will preferably be inserted in an upright V arrangement as illustrated in
Although generally any number of catalytic converter elements 28 could be used in the inventive manifold segment 20, the inventive manifold segment 20 most preferably includes two pairs of opposing slots 34 which hold a total of four catalytic converter elements 28. The inventive manifold segment 20 thus most preferably provides separate catalytic converter elements 28 positioned over each of the exhaust gas openings 26 in the bottom of the manifold segment 20. Additionally, each opposing pair of slots 34 and the corresponding pair of catalytic converter elements 28 positioned therein preferably form an upright V arrangement as illustrated in
Although cut away to some extent in
As will thus be apparent, the inventive system provides convenient access to the catalytic elements 28 for removal, inspection, cleaning, and/or replacement without requiring that the overhead manifold or the overhead manifold segments 20 be removed. The preferred V arrangement of the catalytic elements 28 further provides a large catalyst flow area which minimizes pressure drop through the inventive system. Further, the catalytic converter elements 28 are located in close proximity to the exhaust ports of the engine so that the temperature of the exhaust as it passes through the catalytic converter elements 28 is maximized in order to improve the operation and efficiency of the converter catalyst.
Thus, the present invention is well adapted to carry out the objectives and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.
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