DE29518919U1 - Mixing device for a burner - Google Patents

Abstract

The mixing device has a burner tube, a coaxial centring hub (22) to receive the burner jet shaft (26). It has an air input tube round the jet shaft with fuel jet (30), ending downstream in a conical air jet, vortex-forming wings (40) in the air input tube, and an annular disc (20) to close the air input tube. The centring hub is fitted upstream of the annular disc, and is aligned with the central jet aperture of the disc. The air input tube is downstream of the annular disc, which has air passage apertures between the hub and the tube. The vortex forming wings are downstream of the air passage apertures, projecting into the tube.

Description

WESTPHAL- M USSC^J LHS S.

PATENT ATTORNEYS - EUROPEAN PATENT ATTORNEYS

mekO43

MEKU Metallverarbeitiings GmbH

Robert-Bosch-Strasse 4

78083 Dauchingen

Mixing device for a burner

The invention relates to a mixing device for a burner according to the preamble of claim 1.

A mixing device of this type is known, for example, from DE 3 9 3 0 569 C2 and DE 92 12 924 Ul. In these known mixing devices, the centering hub for the nozzle shaft is held coaxially in the air guide tube, with the swirl vanes serving to support and hold the centering hub. The air guide tube passes axially through the ring disk, which closes the annular space between the burner tube and the air guide tube. This known mixing device is structurally complex. Adaptation to different burner outputs is only possible by structural changes.

The invention is based on the object of creating a mixing device of the type mentioned at the beginning, which is structurally simpler and can therefore be manufactured more cost-effectively. Preferably, the mixing device should also be adjustable to suit different burner outputs.

This object is achieved according to the invention by a mixing device with the features of claim 1.

Advantageous embodiments of the invention are specified in the subclaims.

In the mixing device according to the invention, the air guide pipe is located downstream on the ring disk, while the centering hub for the nozzle shaft is arranged upstream on the ring disk. In this way, the ring disk can serve both as a carrier for the air guide pipe and as a carrier for the centering hub and thus for the nozzle shaft. This results in a simple design of the mixing device, which reduces the amount of material used and simplifies production, so that the mixing device is cost-effective. The combustion air is guided through air passage openings in the ring disk into the air guide pipe, with the swirl vanes being arranged downstream on these air passage openings so that they can also be carried by the ring disk.

Preferably, the entire mixing device is only supported by the ring disk in the burner tube. This makes it possible to mount the entire mixing device in the burner tube in a simple, axially adjustable manner. To do this, the ring disk is mounted on its outer circumference in a guide and sealing ring that can be slid in the burner tube.

In a simple design, the mixing device can be adapted to different burner outputs by changing the average cross-section of the annular gap between the conical air nozzle of the air guide tube and the fuel nozzle. This allows the air flow through the

Air nozzle in combination with a burner-side blower pressure control can be adapted to the fuel flow rate of the fuel nozzle.

The speed at which the combustion air is supplied to the flame via the air nozzle must remain within a specified range. Therefore, this type of adjustment is only possible if the power of the fan used to supply the combustion air to the burner tube and thus to the air guide tube is adjustable. By adjusting the fan power, it is ensured that the exit speed of the combustion air at the air nozzle does not increase unacceptably when the passage cross-section of the air nozzle is reduced.

If the blower output cannot be adjusted sufficiently on the burner side and/or the mixing device is to be operated with a higher blower output overall without any structural changes, the passage cross-section of the air passage openings in the ring disk should preferably be adjustable. If the burner output is reduced below a certain minimum, the passage cross-section of the air passage openings can be reduced so that a smaller amount of air enters the chamber formed by the air guide tube and the fuel nozzle. This also reduces the amount of combustion air supplied to the flame via the air nozzle without the exit speed of the combustion air at the air nozzle changing in an unacceptable way.

The adjustment of the passage cross-section of the air passage openings is preferably achieved by an adjusting ring, which covers the air passage openings more or less by rotation or axial displacement relative to the ring disk.

In the following, the invention is explained in more detail with reference to embodiments shown in the drawing.

Figure 1: An axial section through the mixing device inserted into the burner tube in a first embodiment,

Figure 2: The mixing device in an axial section along the line II-II in Figure 3,

Figure 3: A view of the mixing device from the front,

Figure 4: An axial section of the mixing device in a second embodiment according to the section line IV-IV in Figure 5,

Figure 5: A view of the mixing device of Figure 4 from the front,

Figure 6: The adjusting ring of the mixing device of the second version,

Figure 7: The mixing device in a third version from behind,

Figure 8: An axial section of the third embodiment according to the section line VIII-VIII in Figure 7,

Figure 9: An axial section of the third embodiment according to the section line IX-IX in Figure 7,

Figure 10: A view of the third version from the front,

Figure 11: An axial section of the mixing device in a fourth version according to the section line XI-XI in Figure 12,

Figure 12: A view of the fourth embodiment from the front,

Figure 13: A top view of the ring disk of the fourth embodiment ,

5
Figure 14: An axial section of Figure 13,

Figure 15: A plan view of the adjustment ring of the fourth version from the front,

Figure 16: An axial section of Figure 15,

Figure 17: A top view of the ring disk in a fifth embodiment,

Figure 18: An axial section of Figure 17 and

Figure 19: A top view of the adjustment disc of the fifth embodiment.

Figures 1 to 3 show a first embodiment of the mixing device. The mixing device is inserted into a burner tube 10. A recirculation tube 12 is attached to the burner tube 10 downstream by means of a bayonet lock 14. The recirculation tube 12 engages axially in the burner tube 10 up to recirculation openings 16 in the wall of the burner tube 10. Combustion gases from the combustion chamber can be returned to the flame burning in the recirculation tube 12 through the recirculation openings 16 distributed at the same distance over the circumference of the burner tube 10.

The mixing device is inserted into the burner tube 10, whereby the mixing device is mounted in the burner tube 10 so that it can be moved axially by means of a substantially cylindrical guide and sealing ring 18. The downstream edge of the guide and sealing ring 18 slides more or less over the recirculation openings 16 depending on the axial adjustment, so that the passage cross-section of the recirculation openings 16 and thus the recirculation of the combustion gases can be adjusted by axially moving the mixing device.

The mixing device has a circular ring disk 20, which sits with its outer circumference in the guide and sealing ring 18, so that the ring disk 20 is sealed on the outer circumference against the inner wall of the burner tube 10. The ring disk 20 is pierced in the middle by a nozzle opening. On the upstream side, a centering hub 22 is attached to the ring disk 20, which adjoins the nozzle opening. To attach the centering hub 22 to the ring disk 20, the centering hub 22 passes through the nozzle opening of the ring disk 20 with a collar 24, which is flanged outwards on the downstream side of the ring disk 20 in order to fix the centering hub 22 to the ring disk 20. The centering hub 22 serves to accommodate the nozzle shaft 26 of the burner. A screw is screwed into a threaded hole 28 of the centering hub 22 to fix the nozzle shaft 26. The liquid or gaseous fuel is fed through the nozzle shaft 26 and atomized under pressure through the fuel nozzle 30 arranged at the front end of the nozzle shaft 26.

On the downstream side of the ring disk 20, a short air guide tube 32 is attached, preferably welded, which narrows at its front end to form a conical air nozzle 34. The diameter of the air guide tube 32 is larger than the diameter of the centering hub 22. In the circular ring area between the centering hub 22 and the air guide tube 32, the ring disk 20 has air passage openings 36. In the illustrated embodiment, 6 sector-shaped air passage openings 36 are provided with the same mutual angular distance and with the same angular width, as shown in Figure 3. The combustion air supplied via the burner tube 10 passes through the air passage openings 3 6 into the chamber 3 8 formed by the air guide tube 3 2 and the fuel nozzle 3 0 and exits to the flame through the annular gap formed by the fuel nozzle 30 and the air nozzle 34.

The air passage openings 3 6 are punched out of the sheet metal of the ring disk 2 0 in such a way that the punched-out tab is in contact with the sheet metal of the ring disk 20 at one radial edge each.

remains connected. The tabs are bent up from the plane of the ring disk 20 so that they form swirl vanes 40 which protrude into the chamber 38. The swirl vanes 40 are each bent up in the same circumferential direction and preferably rest with their outer edge on the inner wall of the air guide tube 32. The swirl vanes 40 impart a rotational speed component around the nozzle shaft 26 to the combustion air entering the chamber 38, so that the combustion air exits the air nozzle 34 with swirl.

In the annular space between the air guide tube 32 and the burner tube 10, ignition electrodes 42 for igniting the burner flame and a sight tube 44 for observing the burner flame are inserted into the annular disk 20 which is closed in this area.

In this first embodiment, the mixing device has predetermined passage cross sections for the combustion air, which are determined by the cross section of the air passage openings 36 and the passage cross section of the annular gap formed by the air nozzle 34 and the fuel nozzle 30. In order to adapt the mixing device to different burner outputs, the passage cross section of the annular gap formed by the air nozzle 34 and the fuel nozzle 30 is adapted to the fuel throughput. To do this, the cone angle or the opening diameter of the air nozzle 34 is changed. A change in the passage cross section of the annular gap causes a change in the exit speed of the combustion air, unless the air delivery of the fan is also changed. Adapting the mixing device to the burner output by changing the air nozzle 34 should therefore be accompanied by an adjustment of the fan.

If a change or adjustment of the blower output is only possible to a limited extent, the passage cross-section of the air passage openings 36 is preferably changed to adapt to the burner output. A change in the passage cross-section of the air passage openings 36 leads to an unchanged

The delivery volume of the blower leads to a different dynamic pressure in the burner tube 10, whereby the passage cross-section of the air passage openings 36 forms a throttle point for the combustion air, so that the pressure in the chamber 38 and thus the exit speed of the combustion air through the annular gap of the air nozzle 34 do not change significantly when the amount of combustion air exiting is adjusted by adjusting the cross-section of the air passage openings 36.

The second embodiment shown in Figures 4 to 6 corresponds in structure to the first embodiment of Figures 1 to 3. Only an additional adjustment of the cross-section of the air passage openings 36 is provided. For this purpose, an adjustment ring 46 is arranged on the upstream side of the ring disk 20. The adjustment ring 46 is a sheet metal stamping shown as an individual part in Figure 6. The adjustment ring 46 has the shape of a circular ring disk and is fixed with its inner circumference between a shoulder screwed into the outer wall of the centering hub 22 and the ring disk 20. The radial width of the adjustment ring 46 is so large that the adjustment ring 46 covers the circular ring area of the air passage openings 36 of the ring disk 20. The adjusting ring 46 has air passage openings 48 which correspond in size and arrangement to the air passage openings 36 of the ring disk 20. The adjusting ring 46 can be rotated relative to the ring disk 20 by means of grip tabs 50 formed on its outer circumference between a first position in which the radial webs 52 between the air passage openings 48 of the adjusting ring 46 coincide with the radial webs 54 between the air passage openings 36 of the ring disk 20, and a second position in which these webs 52 of the adjusting ring 46 are offset by the web width relative to the webs 54 of the ring disk 20 and reduce the passage cross-section of the air passage openings 36 of the ring disk 20. In the first position, the air passage openings 3 6 of the ring disk 2 0 have their maximum free passage cross-section. When the

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When the adjusting ring 46 is moved from the first to the second position, this passage cross-section is continuously reduced until it reaches its minimum value in the second position. The rotation of the adjusting ring 46 takes place in the direction of rotation in which the webs 52 of the adjusting ring 46 slide from the side corresponding to the free end of the swirl vanes 40 over the passage openings 3 6 of the ring disk 20. The swirl-generating effect of the swirl vanes 40 is therefore not impaired when the passage cross-section of the air passage openings 3 6 is reduced, but rather increased, since the free passage area of the air passage openings 3 6 is increasingly covered.

The adjusting ring 46 is preferably slightly curved so that it is clamped between its outer edge resting on the ring disk 20 and its inner edge resting on the shoulder of the centering hub 22. The adjusting ring 46 thus rests with friction on both the ring disk 20 and the shoulder of the centering hub 22 so that it can be adjusted against this friction and is secured in its respective setting by friction.

A third embodiment is shown in Figures 7 to 10. Unless otherwise described below, this third embodiment corresponds to the preceding second embodiment. While in the second embodiment the adjusting ring 46 is rotatably mounted in order to adjust the passage cross-section of the air passage openings 36, the adjusting ring 46 in the third embodiment is axially adjustable.

As can be seen from Figure 7, the adjusting ring 46 is arranged in its angular position so that its webs 52 coincide with the area of the air passage openings 36 of the ring disk 20, in which the respective swirl vane 40 is bent upwards, so that a straight axially parallel air passage through the air passage openings 36 is not possible. In order to

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passes through the air passage openings 3 6, the adjusting ring 46 is axially adjustable. In one end position of its axial displacement, the adjusting ring 46 rests against the ring disk 20, so that the webs 52 of the adjusting ring 46 partially cover the air passage openings 36. If the adjusting ring 4 6 is increasingly lifted axially from the ring disk 2 0, the webs 52 of the adjusting ring 4 6 hinder the passage of air through the air passage openings 36 less and less.

A mechanism shown in Figure 9 is used for the axial adjustment of the adjusting ring 46. A Z-shaped support tab 56 is attached to the ring disk 20. A screw bolt 58 with an outer collar is supported on the free leg of the support tab 56 that is parallel to the ring disk 20. The end of the screw bolt 58 that passes through the support tab 56 is screwed into a threaded bushing 60 that is attached to a web 52 of the adjusting ring 46. A helical compression spring 62 that coaxially encloses the screw bolt 58 and the threaded bushing 60 is supported at one end on the support tab 56 and at the other end on the adjusting ring 46. By turning the screw bolt 58, the adjusting ring 46 can be lifted more or less far away from the ring disk 20 against the force of the helical compression spring 62. Since the screw bolt 58 runs parallel to the nozzle shaft 26, adjustment, e.g. by means of a pin wrench or via an extension rod that protrudes outwards on the rear of the burner, is possible even when the mixing device is installed and even during operation.

Figures 11 to 16 show a fourth embodiment.

In this fourth embodiment, the ring disk 20, as shown in the individual illustration in Figures 13 and 14, has completely punched out air passage openings 36 and no swirl vanes 40. The adjusting ring 46 is arranged on the downstream side of the ring disk 20. The swirl vanes 40 are

punching the air passage openings 48 of the adjusting ring 46 and bent up from the adjusting ring 46, as shown in the individual illustration in Figures 15 and 16. The air guide tube 32 with the conical air nozzle 34 is welded to the downstream side of the adjusting ring 46.

The adjusting ring 46 has tabs 64 projecting beyond its outer circumference with elongated holes 66 running in the circumferential direction. Screws 68 engage through these elongated holes 66 and are screwed into threaded holes 70 in the ring disk 2 0. When the screws 68 are loosened, the adjusting ring 46 can be turned against the ring disk 2 0 in order to adjust the passage cross-section of the air passage openings 3 6. In the desired setting, the screws 68 are tightened in order to fix the adjusting ring 46.

In this fourth design, an adjustment to the burner output is possible, on the one hand, by adjusting the adjusting ring 46. On the other hand, by loosening the screws 68, the adjusting ring 46 can be easily exchanged with the air nozzle 34, so that an air nozzle 34 with a different outlet cross-section can be used. Since in this design the swirl vanes 40 are not molded onto the ring disk 20, the ring disk 20 can also be inserted rotated by 180°, so that a mirror-symmetrical installation to Figure 13 is achieved. The same ring disk 20 can therefore be used with burners in which the ignition electrodes 42 are arranged to the right or left in relation to the sight tube 44.

In the embodiments described above, the swirl vanes are formed on the ring disk 20 or the adjusting ring 46, depending on which of these parts is arranged downstream. However, it is also possible to form the swirl vanes 40 on the respective upstream part (ring disk 20 or adjusting ring 46), whereby the swirl vanes 40 then reach through the air passage openings (36 or 48) of the other downstream part.

This is shown in Figures 17 to 19 in a fifth embodiment, which otherwise corresponds to the second embodiment of Figures 4 to 6. The ring disk 20, which is shown in Figures 17 and 18, only has air passage openings 3 6.

The adjusting ring 46 arranged upstream on the ring disk 20 has swirl vanes 40 which reach through the air passage openings 36 of the ring disk 20.

Claims (12)

WESTPHAL- MUSSGNÜG3& S=JAFfT ^n rm ,&tgr;- -" t»—»·· PATENT ATTORNEYS · EUROPEAN PATENT ATTORNEYS mekO43 Protection claims 1. Mixing device for a burner, with a burner tube, with a centering hub arranged coaxially in the burner tube for receiving the nozzle shaft of the burner, with an air guide tube which coaxially encloses the nozzle shaft with the fuel nozzle and ends downstream in a conical air nozzle, with swirl vanes arranged in the air guide tube and with an annular disk closing the annular space between the burner tube and the air guide tube, characterized in that the centering hub (22) is arranged upstream on the annular disk (20) and is aligned with a central nozzle opening of the annular disk (20), that the air guide tube (32) is arranged downstream on the annular disk (20), that the annular disk (20) has air passage openings (36) in the circular ring area between the centering hub (22) and the air guide tube (32) and that the swirl vanes (40) are arranged downstream of the air passage openings (36) and protrude into the air guide tube (32). 2. Mixing device according to claim 1, characterized in that the passage cross section of the air passage openings (36) of the annular disc (20) is adjustable. 3. Mixing device according to claim 2, characterized in that an adjusting ring (46) rests on the annular disc (20), which adjustably covers the air passage openings (36) of the annular disc (20). 4. Mixing device according to claim 3, characterized in that the air passage openings (36) of the ring disk (20) are sector-shaped openings separated from one another by radial webs (54), that the adjusting ring (46) has air passage openings (48) which essentially correspond to the air passage openings (36) of the ring disk (20) and that the adjusting ring (46) is arranged opposite the ring disk (20) is rotatable between a position in which the webs (52) of the adjusting ring (46) essentially coincide with the webs (54) of the ring disk (20), and a position in which the webs (52) of the adjusting ring (46) partially cover the air passage openings (36) of the ring disk (20). 5. Mixing device according to claim 3, characterized in that the adjusting ring (46) is axially movable relative to the annular disk (20) between a position in which the adjusting ring (46) rests against the annular disk (20) and partially covers its air passage openings (36), and a position lifted away from the annular disk (20) in which the adjusting ring (46) exposes the air passage openings (36) of the annular disk (20). 6. Mixing device according to one of claims 1 to 5, characterized in that the swirl vanes (40) are punched out and bent up tabs during the production of the air passage openings (36 or 48) of the annular disk (20) or the adjusting ring (46). 7. Mixing device according to claim 6, characterized in that the swirl vanes (40) are formed on the annular disc (20) or on the adjusting ring (46), depending on which of these parts is arranged downstream. 8. Mixing device according to claim 7, characterized in that the swirl vanes (40) are arranged on the ring disk (20) or the adjusting ring (46), depending on which of these parts is arranged upstream, and that the swirl vanes (40) of the respective upstream part (20 or 46) reach through the air passage openings (48 or 36) of the respective other part (46 or 20). 9. Mixing device according to one of claims 1 to 8, characterized in that the centering hub (22) is firmly connected to the annular disk (20). 10. Mixing device according to claim 9, characterized in that the annular disc (20) sits on a collar (24) of the centering hub (22) and this collar (24) is flanged outwards for fastening the annular disc (20) or that the annular disc (20) is welded to the centering hub (22). 11. Mixing device according to one of claims 1 to 10, characterized in that the air guide pipe (32) is attached to the downstream side of the annular disk (20), preferably welded. 12. Mixing device according to one of claims 1 to 10, characterized in that the adjusting ring (46) is arranged downstream on the annular disk (20) and that the air guide tube (32) is attached to the adjusting ring (46), preferably welded.