DE19539923C1 - Static mixer for e.g. fuel and ammonia-air mixt. - Google Patents

Abstract

The static mixer is located in a channel, with a prim. fluid passing its swirl-promoting surfaces (3,4), which have a leading edge facing into the flow. The leading edge (2) is transverse to the direction of prim. flow (S). Lines (7,8) connecting leading and trailing (5, 6) edges of the surfaces, extend perpendicular to the leading edge, and subtend angles ( alpha , beta ) with the plane (E) which includes the leading edge itself.

Description

The invention relates to a device in a fluid leading channel according to the preamble of claim 1.

In a known device of this type are based on a common, transverse to the flow direction Front edge of flat, swirling surfaces alternating opposite to each other with respect to the direction of flow arranged (DE-AS 11 88 563). Here stand out from the individual vortices are not generated against each other, so that noticeable pressure drops occur.

There is a secondary in many areas of process engineering to mix fluid into a primary fluid. The primary fluid can e.g. B. Be flue gas from a combustion process, the purpose denitrification in a catalyst ammonia or ammonia / air mixture should be added as a secondary fluid. To one complete implementation of the ammonia with the stick Reaching material oxide places high demands on homo distribution of ammonia as Se  secondary gas in the primary gas containing nitrogen oxide. Wuh the required homogeneity of the ammonia concentration tion distribution of z. B. ± 5% with mixer elements, the egg cause high pressure loss, without problems chen, arises in particular in power plant technology often the task of keeping the goal set as low as possible to achieve according to pressure loss. Often it is for the Ver mix available flow path briefly in relation to the hy draulic diameter of the channel carrying the primary gas. Furthermore, in many cases there is demand, in particular also for a catalyst that the inflow immediately before the first catalytic converter position only one in amount and direction has a small range of variation. Accordingly, the Ver mixing process at a sufficient distance before the most catalyst layer are brought to completion.

In addition to mixing a secondary gas into a primary gas is often just a homogenization of the state size like the temperature and the speed, or the Ingredient concentrations in a flow from one fluid required.

For homogenizing a flow from a gas, such as cooling or heating air, or for mixing two air flows under different condition are in DE 29 11 873 C2 and in DE-GM 82 19 260.5 devices have been proposed that flow freely around one or more mixing blades, Front edges directed at an acute angle against the flow have, the course of both in the direction of flow the primary gas flow as well as a transverse to it Has component. Due to the acute angle employment such a mixing wing against the main direction of the gas flow form a pressure and a on the mixing wing Suction side similar to that of an aircraft wing. In as a result of the pressure difference, equalizing flows occur  "curl up" into vertebrae. The vertebrae point in the neighborhood of their place of origin a high energy density and a small diameter. Take with you These vortices expand the flow path by their Rotational energy via flow friction to neighboring Transfer flow zones.

In DE 29 11 873 C2, the secondary gas is due to a appropriate placement of the mixing blade at the source of the Vortex with the vortex expansion into the primary gas flow mixed in. Such interference must inevitably fig an increased pressure loss or own energy requirement of the Plant to be accepted.

In the DE magazine "VGB-Kraftwerkstechnik" vol. 73 (1993), Issue 5, pp. 450-455 describes a mixer with which one high mixing quality achieved with low pressure loss shall be. The construction effort is much higher forth than with the mixing blade concepts described above.

The invention is based on the technical problem Device for homogenizing a fluid flow and Interference of a secondary fluid flow in a primary fluid to create flow, the following following requirements it is enough:

• - high homogenization and / or mixing quality already after a short flow path,
• - low pressure drop,
• - short installation length,
• - low manufacturing costs,
• - not susceptible to interference, e.g. B. by deposit formation,
• - low separation of coarse and fine dust.

According to the invention, this problem is solved by claim 1.  

In a device according to the invention, at least two vortex-generating surfaces, their parallel leading edges directed orthogonal to the direction of the primary fluid flow are arranged in the channel such that an opposing Ver swirl and thus good homogenization or mixing fluid flow is forced.

According to a first embodiment of the invention, each area is che by one on the upstream side in the flow direction of the primary fluid aligned thin-walled body, such as a Sheet metal or a plastic sheet that materialized before is partially bent out from the front edge.

In an advantageous development of the invention the areas arranged in pairs in opposite directions by a Gusset plate to be connected. The gusset plate serves both for aerodynamic and mechanical stabilization tion.

The front edge can be formed by a tube with nozzles, through which secondary fluid is blown into the primary fluid becomes. The secondary fluid becomes uniform thanks to the invention mixed with the primary fluid.

In contrast to the circumstances with mixed wing concepts According to DE 29 11 873 C2, the generated vortex according to the Invention from the beginning on a low energy density; of the As a result, vortex can also have a low pressure drop to be generated.  

As a result of the low pressure drop, they decrease forces acting on the vortex generating surfaces, so that a suspension device for the surface (s) or partial surfaces can be carried out with less material.

For mixing processes it is advantageous to use the vortex arranging surfaces so that smaller, swirling areas rotating in the same direction, in which a small-rough moderate premixing takes place, to larger vortex areas superimpose in which the large-scale homogenization causes becomes.

In a particularly interesting embodiment of the invention the vortex-generating surfaces are arranged such that the addition of the partial vertebrae in one channel section NEN clockwise and one in the other channel section left-turning vortex results. Such a symmetrical Configuration of two partial vertebrae is appropriate Duct dimensions fluidically stable and causes a very good homogenization or mixing in the respective channel sections.

This configuration is particularly advantageous when on a bend follows the mixing section. From the stream mungslehre is known that a flow through a manifold oppositely rotating pair of vertebrae induced.

According to a further embodiment of the invention two opposing vortices before reaching the manifold generated whose directions of rotation with that of the natural vertebrae arising in manifolds matches, pas the flow of said bend without flow separation or with greatly reduced dimensions of the flow separation areas. As a result, elaborate manifold baffles are over liquid. This significantly reduces the costs  taking into account that the cost of the crumb merleitbleche are usually higher than the cost for which we generating and homogenizing or mixing be acting internals themselves.

A slight tendency of the opposing vertebrae to go out deletion by overlay is advantageous in that a subsequent duct bend also without baffles is flowed free of transfer. However, it is a more extensive one Homogenization of the concentration fields by mixing the opposite vortices are desired with each other, according to a further embodiment of the invention in the flow field of opposing vortexes two cross without contact built-in baffles that are configured in the configuration of a Roller coaster are arranged. By means of this baffleord the two opposite vortices are superimposed so that there is a partial mixing without the vortex wipe each other out.

The invention is based on the schematic drawing Solutions to exemplary embodiments with further details explained in more detail. Show it:

Figure 1 is a perspective view of an elementary construction group of a device according to the invention, which is installed in a channel leading a primary fluid.

Figure 2a is a plan view of an assembly according to Fig. 1.

Figure 2b is a plan view of a modification of the elementary module of Fig. 1.

Figure 3 is a view in the direction of the arrow III in Figure 1 from the front of a further modified assembly..;

Fig. 4 shows another elementary assembly of a device according to the invention in a perspective Dar position as Fig. 1;

Fig. 5 is a perspective view of a channel in which a device according to the invention with several ren assemblies according to Figures 1 and 2a is installed and above this device has a 90 ° elbow mer.

FIG. 6a, 6b and 6c are sectional views of planes A, B and C in FIG. 5;

Fig. 7 is a plan view of a modified apparatus according to the invention are used in the designed according to the principle of Figure 4 modules.

8a is a side view from above of a device according to the invention built-in baffles. and

Fig. 8b is a plan view of the baffle arrangement according to Fig. 8a.

In Figs. 1 to 3 for simplicity, the same reference numbers are Be for the same or equivalent parts.

The assembly shown in Fig. 1 and Fig. 2a is installed in a channel in which a primary fluid flows in the direction of arrow s. The assembly has a transverse to the main flow direction s extending tube 1 , on the downstream side of the front edges 2 of two in the longitudinal direction of the tube 1 adjoining, oppositely curved thin-walled plates 3 , 4 connect. The plates 3 , 4 can be formed from metal sheets or thin-walled plastic plates. The rear edges 5 , 6 of the thin-walled plates run in opposite directions as shown. The tangents t on the front edges 2 of the plates 3 , 4 ver run parallel to the flow direction s and span a plane E, which forms a plane of symmetry between the two plates 3 , 4 and contains the front edges 2 . Connection lines 7 , 8 standing vertically on the leading edges 2 between the leading edges 2 and the trailing edges 5 , 6 are inclined at different angles α, β with respect to the plane E.

The pipe 1 contains perforated or slotted nozzles (not shown) arranged along the front edges 2 , via which a primary fluid is blown out in the directions of the arrows u, v, on the curved undersides of the plates 3 , 4 .

Instead of curved, the plates could also be flat, in which case the connecting lines 7 , 8 would include an equally large angle of attack. However, the curved version shown in the figures is preferred, because this enables better turbulence and thus homogenization of the primary fluid and better mixing of the secondary fluid blown via the tube 1 .

The plates 3 , 4 are connected for mechanical stabilization and to form a pair of plates by means of a gusset plate 9 which extends in the plane according to FIGS. 1 and 2a in a plane perpendicular to the plane E.

In the variant according to FIG. 2b, the plates 3 , 4 are curved in two directions.

In the variant according to FIG. 3, the plates are "arched" in the area adjoining the front edge 2 , ie they have a negative tangent angle. Although they could be curved in the same direction as in Fig. 1 (ge dashed contour 3 '' left outside in Fig. 3), they can also be arched back after a turning point W (solid contour in Fig. 3), so that altogether similar inclination angles α, β result as in the embodiment according to FIG. 1.

In this case, the plates 3 , 4 can be connected by an intermediate plate 9 . This gusset plate 9 is used in the embodiments described so far by the cross-shaped connection of the plates 3 , 4 to prevent vibrations conditions of the plates 3 , 4 acted upon by the vortices of the primary fluid and possibly the secondary fluid. In addition, the gusset plate helps to ensure that the swirl of the flow generated by the oppositely curved plates 3 , 4 is strengthened ver. However, it can also be advantageous to bend the ends of the gusset plate 9 in such a way that a secondary vortex field that is opposite to the primary vortex field is generated in the core of the flow field. In this way it can be achieved that the vortices in the far field cancel each other out by superimposition, so that a swirl-free outflow from the mixing section can be achieved. This can be important for the inflow to subsequent components, such as a honeycomb catalyst.

If the device according to the invention is to be used exclusively for the homogenization of a primary fluid, that is to say no secondary fluid is added, a tube 2 is left over . Instead, a rod can then be provided along the front edges 2 , or the front edges 2 themselves can limit the plates 3 , 4 on their sides facing the primary flow.

Fig. 4 shows an embodiment of the device according to the invention, in which vortex-generating surfaces 3 ', 4 ' aerodynamically generated by blowing out of the tube 1 in different directions, if necessary, with different intensities. These "virtual" surfaces can even be curved due to the flow of the primary fluid. The curvature decreases with increasing intensity of the secondary fluid injection (pressure, amount).

Fig. 5 shows an overall designated by the reference numeral 20 vertical flow channel having a 90 ° elbow 21 at its head end. This channel is subdivided into a total of four parallel sections by bulkheads 22 , 23 , 24 un, an assembly according to FIGS. 1 and 2a being arranged in each channel section. The outer side edges 10 of the plates 3 , 4 abut the lateral channel walls (not designated).

A, B, C and D designate four cross-sectional planes of the channel 20 , the plane C lying approximately in the middle of the elbow 21 . The levels A, B, C are shown together with a vortex configuration brought about by the invention in FIGS . 6a, 6b and 6c. In Fig. 6a is shown in the top view of the plane A, that arranged in the left channel half assemblies, and in the right channel half oppositely disposed components, such as with reference to FIGS. 1 and 2a are described in detail in opposite circular Create vortex pairs, the vortex pairs being clockwise in the left half of the channel and counterclockwise in the right half of the channel. The circular vertebrae complement each other above the bulkheads 22 and 24 in the respective two channel halves to form elliptical, counter-rotating vortices according to FIG. 6b, which are separated because of the higher than the bulkhead walls 22 , 24 bulkhead 23 .

In the plane C shown in Fig. 6c, the elliptical vertebrae are then no longer separated and overlay the "natural" vertebrae in the manifold 21st

It is a phenomenon known from fluid mechanics that a flow through a manifold with a homogeneous flow produces a pair of vortices rotating in opposite directions, as is shown in plane E D in FIG. 5. According to the invention, in the plane X built-in device according to FIG. 5, counter-rotating vortices are already generated in the plane B, which have the same directions of rotation as the "natural" vortices generated in the manifold 21 . This ensures that the flow in the channel passes the manifold 21 without flow separation, but at least with greatly reduced dimensions of flow separation areas. This eliminates the need for elbow baffles, which are normally provided in manifolds. The cost of such baffles is higher than the cost of the device according to the invention.

The length of the bulkheads 22 , 23 , 24 can be 0.5 to 2.5 times the hydraulic diameter of each channel section. For the fluidic reasons given above, a configuration is preferred in which the middle bulkhead 23 is longer than the bulkheads 22 , 24 . The trailing edges of the bulkheads can have opposite bends 25 , 26 in directions which correspond to the directions of rotation of the vortices generated by each assembly. For the sake of simplicity, this is only shown for the bulkhead wall 22 in FIG. 5.

Fig. 7 shows an alternative to the device as shown in Fig. 5 and Fig. 6a. In this embodiment, tubes 1 'with nozzles without plates, that is, with purely aerodynamically generated swirl surfaces 3 ', 4 'are used, as they are shown in principle in Fig. 4, but pressure and / or outgoing flow towards the center of the tube decreases. Such pipes 1 'are each arranged diagonally crosswise in the individual channel sections in the cross section X ( Fig. 5). Of course, the arrangement according to FIG. 7 can also be implemented with "materialized" surfaces, such as plates according to FIGS. 1 to 3.

In the configurations shown in FIGS. 5 to 7, the flow through the surfaces 3 , 4 ; 3 ', 4 ' generated vortex spirally upwards. Due to the opposing arrangement of the surfaces in the right half of the channel with respect to the left half of the channel, opposing vortices are generated above the device, which enable a free flow through the elbow 21 without the use of baffles.

However, it may also be desirable to further homogenize the vortex concentration fields by mixing the opposite vortices together. In this case, the configuration according to FIG. 8 is provided. There are guide plates 30 , 31 arranged in the roller coaster-like configuration shown in FIG. 8 in the channel section downstream of the device according to the invention. These baffles 30 , 31 are adapted to the spiral geometry of the oppositely rising vertebrae and cross without contact in the manner shown in FIG. 8b in particular.

In a further embodiment of the invention, two arrangements of the type shown in the various examples ( FIGS. 5, 6a, 7) are arranged one behind the other in the flow direction in the channel.

In the first arrangement, fuel gas is injected into the primary fluid, like flue gas, injected and ignited to the primary flow to heat up. In the second arrangement, the actual Secondary fluid, such as ammonia, for catalytic denitrification of the primary fluid.

Claims (14)

1.Device in a fluid-conducting channel with an alternating inclination to the flow direction, produce the surfaces which have front edges facing the fluid flow, the front edges being oriented transversely to the flow direction of the fluid flow, characterized in that at least two vortex-generating surfaces ( 3 , 4 ; 3 ', 4 ') starting from parallel len leading edges ( 2 ) are arranged in a common flow cross-section of the channel so that they generate a pair of counter-rotating vortices in a region of the channel downstream of the device. 2. Device according to claim 1, characterized in that the vortex-generating surfaces ( 3 , 4 ) on the front edges ( 2 ) in the flow direction (s) have duri fende tangents (t) and are arched away from the front edge ( 2 ). 3. Apparatus according to claim 2, characterized in that connecting lines ( 7 , 8 ) between the front edges ( 2 ) and rear edges ( 5 , 6 ) of the surfaces ( 3 , 4 ), which are perpendicular to the front edge, at different angles of attack ( α, β) to an upstream direction (s), the front edge ( 2 ) containing plane (E) are inclined. 4. Device according to one of claims 1 to 3, characterized in that the vortex-generating surfaces have at least two partial surfaces ( 3 , 4 ) which from the common front edge ( 2 ) in the direction of the leading edge successively in opposite directions outwards from the plane ( E) are bent away. 5. Device according to one of claims 1 to 4, characterized in that the front edge ( 2 ) on a tube ( 1 ) is formed with nozzles through which a secondary fluid is blown into the primary fluid. 6. Apparatus according to claim 4 or 5, characterized in that the two partial surfaces ( 3 , 4 ) of thin-walled bodies, in particular made of sheet metal or plastic, and preferably together in pairs by means of a transverse to the front edge ( 2 ) and in the flow direction (S) arranged gusset plate ( 9 ) are the verbun. 7. The device according to claim 6, characterized in that the vortex-generating surfaces ( 3 , 4 ) are provided with openings which connect the suction side with the pressure side. 8. Device according to one of claims 1 to 7, characterized in that two pairs of vortex-generating surfaces are arranged so that the generated ge opposing vortexes have directions of rotation as they would be generated by the flow through a subsequent elbow ( 21 ) by itself. 9. Device according to one of claims 1 to 8, characterized in that the channel is divided into by bulkheads ( 22 , 23 , 24 ), towards the ends of open channel sections, in each of which at least a pair of the vortex-generating surfaces ( 3 , 4 ) is arranged on, with the bulkheads in the levels (E). 10. The device according to claim 9, characterized in that the length of the bulkheads ( 10 , 11 , 12 ) is 0.5 to 2.5 times the hydraulic diameter of each channel section. 11. The device according to claim 9 or 10, characterized in that the rear edges of the bulkhead walls ( 22 ) opposing bends ( 25 , 26 ) gene in direction, which correspond to the directions of rotation of the generated vertebrae. 12. The device according to one of claims 1 to 11, characterized in that the front edges ( 2 ') of the vortex-generating surfaces are arranged crosswise on diagonals in a common flow cross section of the primary fluid-carrying channel. 13. The device according to one of claims 1 to 12, characterized in that in the flow field of the counter-rotating vortices two non-contact crossing guide plates ( 30 , 31 ) are arranged in the configuration of an Ach tram. 14. Device according to one of claims 5 to 13, characterized characterized that you a second Vorrich device of the same type seen in the direction of flow is switched, via which a fuel gas in the primary fluid is blown in.