Catalyst arrangement with flow guide body

Details Catalyst arrangement with flow guide body Catalyst arrangement with flow guide body

1990-03-28

1992-04-14

Hart, Douglas

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

422176, 422171, F01N 328

Patent

active

051036410

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a catalyst arrangement, particularly for internal combustion engines, having a diffusor widening in the flow direction preceding a honeycomb-like catalyst body and a confusor, narrowing in the flow direction, following the catalyst body, and at least one flow guide body in the diffusor and/or confusor, and to a method for producing it.
A catalyst arrangement of this kind is known for instance from German Patent Document A 34 30 399 or A 34 30 400. The most common catalyst arrangements contain a honeycomb-like catalyst body with a plurality of parallel channels, which may comprise either a ceramic basic material or textured metal sheets. Since typical exhaust lines have a much smaller cross section than a catalyst body, a conically widening diffusor portion is typically disposed upstream of each catalyst body and a confusor portion is typically disposed downstream of the catalyst body as a transition to the normal exhaust lines. One known problem in catalyst arrangements is that the catalyst body is not exposed uniformly over its entire cross-sectional face, so that to make for uniform utilization, flow guide bodies are for instance used.
From German Patent Document A 35 36 315, it is also known to use flow guide bodies that generate a spin in the flow upstream of the catalyst body.
From German Patent Document C 34 17 506, two divided catalyst bodies of different cross sections are also known, which enable adaptation to various installation conditions.
German Patent Document A 30 12 182 also discloses two-stage catalyst bodies for achieving conditions that are optimally adapted to the various combustion exhaust gases.
Finally, German Published, Unexamined Patent Application DE-OS 23 13 040 also discloses a catalyst body that for manufacturing reasons is made slightly conical, by being pressed into a slightly conical housing.
In catalyst arrangements, however, the problem of uniform oncoming flow to the upstream side of a catalyst body has not been satisfactorily solved. All the known devices act like throttles in the flow of exhaust gas and thus undesirably increase the counterpressure of the exhaust gas, which impairs engine efficiency. Even so, the known flow guide bodies still do not achieve uniform oncoming flow to the catalyst body. A further factor is that optimal utilization of the space needed for the diffusor and confusor is not attainable.
The object of the present invention is therefore to create a catalyst arrangement that effects an optimal oncoming flow to the catalyst body. Besides this, either the utilization of the volume required for the diffusor and confusor should be improved, or this volume should be reduced. Finally, better cold starting behavior of the catalyst is to be attained.
To attain these objects, the catalyst arrangement is proposed wherein the flow guide body comprises a plurality of channels disposed beside and/or in one another and through which a fluid can flow, all or at least some of which channels have an increasing cross section in the flow, direction in the diffusor and a decreasing cross section in the flow direction in the confusor; and wherein the open cross-sectional area of the flow guide body is substantially larger on one side than on the other, for instance more than twice as large and preferably approximately 4 to 6 times as large.
According to the invention, flow guide bodies can be used equally well in both the diffusor and confusor. In the diffusor, the open cross-sectional area of the flow guide bodies must increase, while in the confusor it must decrease, so that the same flow guide body can be used in each, simply facing in opposite directions. Consequently, the ensuing description will merely consider that flow guide body in the diffusor, although all the information provided, unless expressly otherwise stated, applies equally to the reversed arrangement in the confusor.
A flow guide body that comprises a plurality of channels, some of which widen conically, can guide the flow much more uniformly over the entire face en

REFERENCES:
patent: 3929420 (1975-12-01), Wood
patent: 3953176 (1976-04-01), Sautala et al.
patent: 3964875 (1976-06-01), Chang
patent: 4039294 (1977-08-01), Mayer et al.
patent: 4209495 (1980-06-01), Kobayashi
patent: 4521947 (1985-06-01), Nonnenmann
patent: 4634459 (1987-01-01), Pischinger

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