DE102008026638A1 - Exhaust manifold for internal combustion engines - Google Patents

Abstract

The subject of this invention is an exhaust manifold for internal combustion engines, the u. a. consists of a cylinder flange (1), at least one manifold pipe (2) and a close-coupled exhaust catalytic converter. The exhaust gas catalytic converter comprises a tubular housing (10), at least one exhaust gas discharge pipe (11) and a tubular, catalytically coated functional element (12) in the housing (10). The at least one elbow pipe (2) is introduced into the jacket of the housing (10), the at least one, axially oriented exhaust gas exhaust pipe (11) extends from the center of the functional element (12) and a heat exchanger pipe (13) around the functional element (12). led around.

Description

The The invention relates to exhaust manifold for internal combustion engines, comprising a cylinder flange, at least one manifold tube and a close-coupled exhaust gas catalytic converter according to the preamble of claim 1.

Catalytic converters require a certain minimum temperature, so that the catalytic reaction, with which the pollutants contained in the exhaust gas of internal combustion engines such as NO _x or CO can be converted to nitrogen and carbon dioxide, takes place. The highest pollutant concentration in the exhaust gas occurs after starting the engine. Unfortunately, at this point the catalytic converter is cold and can not develop its cleaning action. To shorten the time to reach the operating temperature, there are two principal measures: Firstly, the mass to be heated of the components touched by the exhaust gas is made as small as possible, on the other hand, the catalyst is positioned as close as possible to the engine. The combination of these two principles has led to the formation of so-called startup catalysts.

conventional Starting catalysts have as a carrier of the catalytically active Noble metal layers either a ceramic monolith or a so-called metallites. In both cases they are bodies that are crossed by a plurality of parallel honeycomb channels. While flowing through this channels becomes the exhaust gas flow laminarized with the result that the sitting in the center of the flow filaments pollutant molecules the at the channel surface sitting precious metal layer barely reach. Suffer from the conversion rate. As a result, the channels must be relatively long be interpreted what a correspondingly increased amount of precious metal to Episode has with the known financial consequences.

Of Another is observed that in the known catalytic converters the exhaust gas tends to concentrate in the center of the honeycomb body. The consequence of this is a further reduction of the exhaust gas purification capacity. This is unsatisfactory.

Of the present invention has for its object to provide an exhaust manifold specify close to the engine installed catalytic converter, in which the described Disadvantages of the conventional Catalysts are eliminated.

These Task is solved through an exhaust manifold with the features of claim 1.

The The present invention is based on the principle that exhaust gases are no longer as in the prior art axially but radially through which the catalytically active Precious metal layer carrying functional body to flow. Surprisingly It has been found that a radial flow compared to the axial flow considerable Has advantages, especially if the exhaust gas flow as here radially from outside to flows inside. In particular, the flow distribution over the Surface of the catalyst support and the flow velocity significantly homogenized by the volume of the catalyst support. By the radial structure is achieved a large cross-sectional area, which in turn leads to low flow velocities in the catalyst carrier leads, so that the pollutant molecules enough Have time to react to the precious metal surface. in view of the low flow rate and the small channel length is omitted in the conventional Catalytic converters inevitable and harmful laminarization of Exhaust gas flow. The catalyst carrier body can be made with a low mass, making it fast heating up. Furthermore The exhaust gases in the catalyst carrier body suffer only a small amount Pressure loss, which benefits the engine performance.

One Another advantage is the built-in heat exchanger element. This can while the starting phase are used to heat the catalyst carrier body. By appropriate control of the heat exchange medium, the Heat exchanger element be used at high engine power, the exhaust gas temperature lower to overheat of the catalyst carrier and prevent the noble metal layers, which is built-in close to the engine Starting catalysts often is a problem. Furthermore, leads a Equalization of the temperature to an increased Lifespan.

According to one Design for this purpose, serving as a heating element heat exchanger element as Induction coil can be realized. With the help of such an induction coil can the catalyst carrier body or, if it should not be made of metal, the precious metal layer be brought to operating temperature very quickly. Thanks to the large surface and the shallow depth becomes a high percentage of the noble metal layer heated.

advantageously, is the heat exchanger element a pipe coil. Alternatively, the heat exchanger element as Plate heat exchanger formed be.

Preferably is the flow through the heat exchanger element controllable by valve.

The catalytic functional element itself can be realized in different ways. Preferred is a wound metal foam or a silicon carbide filter cartridge.

Based the drawing is intended to illustrate the invention in the form of an embodiment explained become.

The figure shows purely schematically an exhaust manifold for internal combustion engines, comprising a cylinder flange 1 , three manifold pipes 2 and a close-coupled exhaust catalyst. This comprises a tubular housing 10 , at least one exhaust gas discharge pipe 11 and a tubular, catalytically coated functional element 12 in the case 10 ,

The manifold pipes 2 are radially in the jacket of the housing 10 introduced. As a result, the exhaust gases flow radially and through the catalytically active functional element 12 , After getting the functional element 12 flow through, they leave the case 10 through that in the center of the functional element 12 seated exhaust gas discharge pipe 11 ,

To the catalytic functional element 12 is a serving as a heat exchanger element tube coil 13 wrapped. In the piping is a valve 14 used, which the flow through the heat exchanger element 13 makes controllable. Depending on the operating state, the heat exchanger medium can be used as cooling or as heating.

Claims (8)

Exhaust manifold for internal combustion engines, comprising a cylinder flange ( 1 ), at least one manifold pipe ( 2 ) and a close-coupled exhaust gas catalyst, this comprising - a tubular housing ( 10 ), - at least one exhaust gas discharge pipe ( 11 ) - and a tubular, catalytically coated functional element ( 12 ) in the housing ( 10 ) characterized by the features - the at least one manifold tube ( 2 ) is in the casing of the housing ( 10 ), - the at least one exhaust gas discharge pipe ( 11 ) is axially oriented and extends from the center of the functional element ( 12 ), - around the functional element ( 12 ) is a heat exchanger element ( 13 ) led around. Exhaust manifold according to claim 1, characterized by the feature - the heat exchanger element ( 13 ) is a pipe coil. Exhaust manifold according to claim 1, characterized by the feature - the heat exchanger element ( 13 ) is a plate heat exchanger. Exhaust manifold according to one of claims 1 to 3, characterized by the feature - the flow through the heat exchanger element ( 13 ) is by means of valve ( 14 ) controllable. Exhaust manifold according to at least one of claims 1 to 4, characterized by the feature - the heat exchanger element ( 13 ) also includes a heating element. exhaust manifold according to claim 5, characterized by the feature - the heating element is realized as an induction coil. Exhaust manifold according to one of claims 1 to 6, characterized by the feature - the catalytic functional element ( 12 ) is realized by a wound metal foam. Exhaust manifold according to one of claims 1 to 6, characterized by the feature - the catalytic functional element ( 12 ) is realized as a silicon carbide filter cartridge.