Catalytic converter

 

(57) Abstract:

The invention relates to catalytic converters. The catalytic Converter comprises a coated catalyst channel having an inlet opening for passing gas flow in the longitudinal direction and at least first and second generators turbulence. The turbulence generators are designed to create a turbulent gas flow and spaced from each other and the inlet. The first turbulence generator is located closer to the inlet opening of the channel than the second turbulence generator. The longitudinal center of the first turbulence generator is displaced longitudinally from the inlet channel at a distance X1defined by the expression of 0.01<[X/(DhReSc)] > 0.015 g, where Dh- hydraulic diameter of the channel, Rethe Reynolds number, Scthe Schmidt number 1 for gas. The technical result is the optimization of the relationship between pressure drop and misoperations gases due to the introduction of turbulence in the channel of the catalytic Converter. 7 C.p. f-crystals, 7 Il.

The present invention relates to the creation of catalytic converters, in which optimalities Converter.

Usually the catalytic Converter comprises a substrate formed of a significant number of small adjacent channels through which flows a gas or mixture of gases, which must be converted by the catalyst, deposited on a substrate in the form of a coating. For designing catalytic converters can be used various materials such as ceramic materials or metal, for example stainless steel or aluminum.

The cross-section of the channels of the ceramic substrate catalytic Converter is usually rectangular or polygonal, for example hexagonal. This type of catalytic Converter is manufactured by extrusion, which allows you to get the channels having the same cross-section along their full length, the walls of the channels are smooth and even.

In the manufacture of substrates for catalytic converters of corrugated metal strip or foil alternating with flat strips or foil, and the specified design wrapped (wrapped) with respect to an axis. The cross-section of the received channel is triangular or trapezoidal. Commercially available catalytic metal is about ceramic catalytic converters, the walls of these channels are smooth and even.

The most important characteristic of the catalytic Converter is massoperedacha, which takes place between the gas (or gas mixture flowing through the channels) and channel walls of the catalytic Converter. The coefficient of mass transfer, which is a measure of the rate of mass transfer must be high to achieve high efficiency catalytic conversion.

In catalytic converters mentioned type, which are used in internal combustion engines or in industry, the channels have a relatively small cross section and the gas, the velocity of flow, which are commonly used flows in relatively regular layers in the direction of the length of the channels. Thus, the gas flow is mainly laminar. Only a short length near the inlet channel has a cross-flow directed to the channel wall. In order to characterize the gas flow, use the so-called Reynolds number, the value of which for this type of applications is in the range from 100 to 600. Until the Reynolds number remains below guiding the laminar gas flow is formed near the channel walls the boundary layer, and in this boundary layer, the velocity of gas flow is practically zero. The specified boundary layer reduces the coefficient of mass transfer, especially in the case of the so-called fully developed flow. In order to increase the rate of mass transfer, the gas must be directed to the channel surface, which leads to the reduction of the boundary layer and increases the transfer from one layer to another. This can be accomplished through the use of turbulent flows. In smooth and smooth channels laminar flow becomes turbulent in the case when the Reynolds number reaches values above approximately 2000. If you want to achieve specified values of the Reynolds number in the channels of the catalytic converters of the type described here is the speech, you want to ensure that the flow speed of the gas, substantially higher than those typically used. Therefore, in the previously mentioned catalytic converters with low Reynolds number, you want to create turbulence in an artificial way, for example through the installation of special generators of turbulence inside the channels.

We already know a large number of different turbulence generators. Raptorama turbulence in the form of transverse riffles. In the publication GB-A-2001547 described catalytic Converter having channels with made in them by the turbulence generators in the form of transverse perforated metal shutters of the structural material. Known also combinations of these two types of generators turbulence.

A common characteristic of turbulence generators of these types is their ability to significantly increase mesopredator. However, it is also critical to increase the pressure drop. In fact, the increase in the pressure drop exceeds the increase in the mass transfer. The pressure drop depends on the configuration, size and geometry of the turbulence generators. However, it is well known that the turbulence generators create too much pressure drop, which is not possible to use them in commercial applications.

The present invention is based on the understanding of the fact that the turbulence generators must have the same configuration and must be installed in the channels of the catalytic Converter in such a way as to obtain the optimum ratio of pressure drop to misoperation. In the applications considered here and the end-to-end within the perimeter of the channel. The inlet openings of the channels of the catalytic Converter, the mass transfer coefficient is high enough, because the boundary layer is very thin. The thickness of the boundary layer gradually increases in the direction of the main stream, and the mass transfer coefficient, namely, the ratio of the mass transfer to the surface area decreases.

In order to increase mesopelagic and, consequently, the efficiency of the catalytic conversion, generators turbulence in the channel walls should not be placed too close to the intake holes, as massoperedacha in this area is already quite high. Therefore, the installation of generators of turbulence in this area will only lead to increased pressure drop, which is undesirable.

In accordance with the present invention provides for the establishment of the catalytic Converter, which contains a channel for the transmission of gas flow in the longitudinal direction, is covered with a catalyst containing at least first and second generators turbulence, located at a distance from each other in the longitudinal direction from the inlet channel and designed to create curb the horon, the opposite flow direction, and the second edge face facing the flow direction, and the free edges of the edge faces are interconnected by a flat connecting edge, spaced from the channel base on the value that determines its height. The first boundary line is inclined at an angle from 35 to 60orelative to the base channel, the first turbulence generator is located closer to the inlet opening of the channel than the second turbulence generator, with the longitudinal center of the first turbulence generator is displaced longitudinally from the inlet channel at a distance X1defined by the expression

0,01 < [X1/(DhReSc)] > 0, 015,

where Dh- hydraulic diameter of the channel;

Re- Reynolds number;

Scthe Schmidt number 1 for gas

when you do this:

the ratio of height e to the hydraulic diameter Dhis from 0.35 to 1.0;

the ratio of the distance P between the longitudinal centers of the first and second generators of turbulence to the specified height e is from 20 to 50; and

the ratio of the length B of the connecting face to the height of e is from 1.5 to 4.0.

The channel may have a triangular or trapezoidal cross-Sich, the edge can be as well as first made inclined in the direction to the base, preferably the angle of inclination of these edges is from 35 to 50 degrees.

In Fig. 1 shows schematically a perspective view, with tear-out, channel catalytic Converter, and digging in the channel allows us to consider the turbulence generators in accordance with the present invention.

In Fig. 2 shows schematically a longitudinal cross section of the channel is shown in Fig. 1.

In Fig. 3 shows a detailed perspective view of the elements of the foil (foil elements) used for the formation of the catalytic Converter based on the principles explained with reference to Fig. 1.

In Fig. 4 shows a longitudinal section of deployed elements of the foil shown in Fig. 3.

In Fig. 5 shows a cross section along the line 5-5 of Fig. 4.

In Fig. 6 shows a cross-section similar to those shown in Fig. 5, collected together in a batch of items from the foil.

In Fig. 7 shows a cross-section similar to those shown in Fig. 6, an alternative variant of the present invention.

We now turn to a consideration of Fig. 1, which schematically illustrates the inlet 1 of channel 2 and the rest of the channel 2 Kyle in the longitudinal direction (i.e. to the right in Fig. 1) is the gas flow. The drawing shows the first turbulence generator 3, mounted closer to the intake port 1, and the second turbulence generator 4, which is offset from him in the longitudinal direction. Can also be provided and additional turbulence generators. Channel 2 has a height h. The turbulence generators are from the base 8 of the channel. The distance X1from the inlet to the longitudinal center of the first turbulence generator 3 is defined by the following expression

0,01 < [X1/(DhReSc)] > 0,015,

where Dh- hydraulic diameter of the channel, which is equal to four times the cross-sectional area of the channel divided by the said perimeter;

Rethe Reynolds number (ul/, where u is the gas velocity, 1 is the characteristic size of the channel, that is, the hydraulic diameter Dhis the mass density of the gas, and represents the velocity of the gas).

Scthe Schmidt number for the gas, and more specifically, the Schmidt number 1 (also known as the number of Prenda), which is the kinematic viscosity of the gas divided by the diffusion coefficient. The kinematic viscosity is equal to the dynamic viscosity divided by plott the gas velocity. Thus, the optimal position of the first turbulence generator 3 is dependent on the prevailing operating conditions.

As becomes clear from consideration of Fig. 2, each generator of turbulence 3, 4 has a specific geometrical configuration. For example, each generator of turbulence has turned back the first marginal edge with an oblique slope of 5, and that face is turned in the direction opposite to the direction of flow of the stream, flat connecting face 6 and a forward-facing second boundary face with an oblique slope 7, and this face facing in the same direction as the direction of flow of the stream. The connecting line 6 connects between the free edges 9, 10 of the inclined faces 7, 5.

In accordance with the present invention the following conditions are met:

The angle that defines the slope of the first edge face 5 relative to the base 8 channel 2 catalytic Converter, must be between 35 to 60 degrees (and preferably, from 35 to 50 degrees), and the ratio of (i) height e top face 6 relative to the base 8 to (ii) the hydraulic diameter Dhchannel 2 must be from 0.35 to 1.0. Moreover, the ratio of (i) the distance between P protagnist from 20 to 50. The ratio of (i) the longitudinal length B face 6 of each generator of turbulence 3, 4 (ii) the height of e should be from 1.5 to 4.0.

The channel region opposite each of the generators of turbulence, mainly extended in position 12 to minimize the pressure drop caused by the presence of the turbulence generator. However, the gas flow in the extended area 12 is not involved in the main gas flow; rather, it slowly moves in swirls and therefore has minimal effect on the turbulence. Usually, e is approximately 50-60% of the height of the channel h, and the active area of the cross-section for gas flow in the region where the turbulence generator is about one-fourth of the active zone of the cross-section for gas flow at a location upstream of the turbulence generator. Thus, the velocity of the gas moving after the turbulence generator will be approximately 4 times higher than the gas velocity in the place, located upstream relative to the turbulence generator.

The preferred cross-sectional shape of channels in accordance with the present invention is a triangular or trautvetteri with the present invention and due to their location at a given distance from each other and from the inlet 1 into channel 2, having a cross-section of mostly triangular or trapezoidal shape, achieved increased massoperedacha and, consequently, increased catalytic conversion, but which is accompanied by only a very moderate increase in pressure drop. When the gas stream approaches the turbulence generator 3, the flow velocity is increased locally in the reduced area of the cross section. When the gas passes through the turbulence generator 3 and leaves the edge 9 formed at the junction between the face 6 and the second edge face 7, there is a strong turbulent motion by this division and by greatly expanding the area of the cross section, which now comes the gas. This process very effectively increases mesopredator.

The second turbulence generator 4 is calculated on the distance of P from the first turbulence generator 3, which allows the extent possible, the fullest use of the created in the manner described above turbulence, and allows the formation of a zone of repeated contact, denoted by 0 in Fig. 1, before the gas reaches the second turbulence generator 4. In this way predotvreschen became turbulent. In the area of re-contact 0 gas will be a significant degree of flow near a smooth surface before it reaches the second turbulence generator 4.

It is important that the edges 9, 10 of the turbulence generators 3, 4 are sharp enough to create the split point (point offset). The radius r of the edges (see Fig. 2) must be such as to ensure that the relation r to Dhin the range from 0.04 to 0.2.

By giving generators turbulence specific configuration in accordance with the present invention, they are also effective at higher velocities of gas flow, in which turbulent flow can also be created in the smooth channel. Turbulence, which occurs naturally, is enhanced due to the effect of convergence/divergence, and also due to the mechanism of separation and re-contacting gas.

The increase in the mass transfer in accordance with the present invention can be used in the following way. Mesopredator j is usually defined in accordance with the expression

j = hmA(w1s-w1w)

in which

the density of the gas,

hm- coefficient misoperate is mnoe value)

w1w- mass fraction of substance 1 at the surface.

Member of the expression (w1s- w1w) is a measure of the concentration of unconverted gas. If hmincreases, at a constant surface area A, also increases the catalytic conversion. On the other hand, if there is no need to increase j and, instead, massoperedacha is maintained constant, may be reduced the surface area of the channel. In this case also becomes possible to reduce the number of carrier material (stainless steel or aluminum in the case of catalytic converters from metal, and cover flush (washcoat)), and also very expensive noble metals used in the catalytic Converter, can be obtained substantial economic benefits.

If, instead, for a given frontal area of the catalytic Converter, it is desirable to reduce the surface area of the channel, such a reduction in area can be achieved by increasing the hydraulic diameter. This leads to a pressure drop that can be used to reduce excessive pressure drop arising from the creation of turbi (increase in hm). Therefore, a higher mass transfer coefficient is compensated by the decrease of the surface area of the channel. And in this case it is possible to reduce the number of carrier material and coating washing, and also very expensive noble metals used in the catalytic Converter, resulting in substantial economic gains.

As for the so-called region of fully developed flow in a straight channel of a given size, the pressure drop (for a given gas velocity) is inversely proportional to the hydraulic diameter. In case of increase of the hydraulic diameter, for example, 2 times, a corresponding pressure drop. In the case of fully developed flow and the presence of areas of mass fractions, surface mass transfer is also inversely proportional to the hydraulic diameter. Thus, with increasing hydraulic diameter massoperedacha decreases. If a relatively wide channel to provide turbulence generators in accordance with the present invention, the pressure drop and massoperedacha will increase. At the same time without reducing the mass transfer pressure drop can be increased to values applicable is intesti. When the mass transfer coefficient reaches a value that exceeds 2 times the value applicable for a channel of a smaller size, then it may be provided with the same type of catalytic conversion, but using half the amount of materials (supporting material, coating, washing and precious metals).

Trials were conducted variant implementation of the present invention with a triangular channel with a height of 2.6 mm and a length of the base channel b, equal to 3.7 mm, were obtained the following parameters: X1= 15 mm; = 45o; e = 1.4 mm; Dh= 1,86 mm; P = 25 mm B = 2 mm

The technique of formation of channels in accordance with the present invention shown in Fig. 3 to 6. Series corrugated and flat foil elements 20, 22 (e.g., stainless steel or aluminum), are stacked alternately in batches. Each corrugated foil element has a trapezoidal recess 24 (Fig. 3 shows only one notch) coming through in the direction perpendicular to the riffles, and in front of each recess are extensions 12. Flat foil elements 22 in fact not completely flat, as they contain trapezoidal protrusions 26 for education generators turbule is 4 (see Fig. 6), with flat foil element 22 forms the base 8 of each triangular channel 2, and the projections 26 each flat foil element form the turbulence generators 3, 4. It should also be borne in mind that between adjacent triangular channels 2 provides another channel 30, for which a flat foil elements 22 also form the turbulence generators 32.

In Fig. 7 shows a design similar to Fig. 6, however, the channels 2 are not triangular, and trapezoidal.

After Assembly in a pack of corrugated and flat foil elements, this package is known by way of wrap (wrap) with respect to an axis parallel to the riffles. Foil elements cover a catalyst either prior to Assembly in the bag and wind up on or after the implementation of these operations.

Despite the fact that have been described preferred embodiments of the invention, it is clear that they are specialists in this field may be amended and supplemented, and can be carried out replacement of components and their destruction, which do not extend, however, beyond the scope of the following claims and correspond to its essence.

1. The catalytic Converter is in the longitudinal direction and at least first and second generators turbulence, designed to create a turbulent gas flow and spaced from each other and from the inlet, each of the turbulence generator includes a first edge face facing in the direction opposite to the direction of flow of the stream, and the second edge face facing in the direction coinciding with the direction of flow of the stream, the free edges of the edge faces are interconnected by a flat connecting face which is spaced from the base on the value that specifies the height, wherein the first boundary line is inclined to the base of the channel at an angle of 35 - 60o, and the first turbulence generator is located closer to the inlet opening of the channel than the second turbulence generator, with the longitudinal center of the first turbulence generator is displaced longitudinally from the inlet channel at a distance X1defined by the expression

0,01<[X/(DhReSc)]>0,015,

where Dh- hydraulic diameter of the channel;

Re- Reynolds number;

Scthe Schmidt number 1 for gas

the ratio of the height of the coupling faces relative to the base channel to the hydraulic diameter of the channel is 0 is Anna height - from 20 to 50 and the ratio of the length of the connecting face to its height ranges from 1.5 to 4.0.

2. The catalytic Converter according to p. 1, wherein the channel has a triangular cross-section.

3. The catalytic Converter according to p. 1, wherein the channel has a trapezoidal cross-section.

4. The catalytic Converter according to p. 1, characterized in that each channel has an extension located opposite each generator of turbulence.

5. The catalytic Converter according to p. 1, characterized in that the second boundary face tilted towards the ground.

6. The catalytic Converter according to p. 5, characterized in that the second edge face formed with a base angle of 30 to 60o.

7. The catalytic Converter according to p. 6, wherein the angle is from 35 to 50o.

8. The catalytic Converter according to p. 1, characterized in that the angle of the first boundary edge is from 35 to 50o.

 

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