EP0048438B1 - Oil and gas burner for installation in a heating boiler and a steam generating boiler - Google Patents

Description

The invention is based on an oil-only burner of the type specified in the preamble of claim 1. Such burners, as described in DE-A-27 00 671 and 27 51 524 and in DE-U-79 19 481 , are characterized by simple structure, high operational reliability and good combustion.

The object of the invention is to develop a burner according to the preamble of claim 1 so that it can be operated with heating oil or heating gas without changing components from one to the other to simplify production and storage while largely using the existing parts with the least possible effort the other mode of operation is adjustable burner or can be produced as a pure gas burner.

From DE-A-2 834 401 a burner is known which has a gas supply pipe which is arranged as a double jacket pipe and is arranged concentrically to a central oil supply in an air supply chamber. In this burner, a mixing chamber is provided between the gas outlet openings at the downstream end of the double jacket tube and a baffle plate which has a central opening and leaves an annular gap between its outer circumference and a short burner mouthpiece. The baffle plate serves in the usual way as a flame holder. This burner therefore belongs to another - not oil-burning - type of burner, in which there is no thermal treatment of the oil prior to combustion in a mixing tube and the fumes burn essentially freely in the boiler. The use of a double-walled pipe for the gas supply results in a large space requirement. This gas supply is not suitable for retrofitting in an oil burner of the type according to the invention, in particular because of the ignition and ionization electrodes present and the reduction in the free cross section of the air supply line.

US-A-2 672 190 shows a non-generic combined oil and gas burner, the oil burner part of which is spatially and component-wise separated from an annular chamber with outlet openings for gas supply. A similar arrangement is also shown in US Pat. No. 2,051,397. Both documents are therefore unable to give any indication of an embodiment in which existing components of an oil burner are used to supply gas.

From US-A-3 367 384 also a non-generic burner is known, in which a compressed air-oil mixture passes through two chambers in a cylinder, each of which has a diaphragm downstream as an outlet opening, the diameter of which is larger than the opening cone of the Compressed air-oil mixture is in the orifice plane. The second orifice in the cylinder is followed by a space that is open to the boiler and through the outer wall of which secondary air is supplied. In each of the two chambers, negative pressure is to be generated in stages, by means of which a backflow of parts of the ignited mixture is to be brought about. Gas or powdered fuel can also be fed to the upstream chamber through radially extending feed lines. This is an oil burner that has a vacuum chamber that is necessary for the function as an oil burner, to which supply lines can be connected without any problems in order to expand it to operate with fuel gas or powdered fuel.

Ultimately, GB-A-716 841 disclose an oil burner and GB-A-819 977 measures to expand this burner to include additional gas operation. This expansion takes place in such a way that essential parts, in particular the air supply pipe and an insert body which causes air swirling, are replaced by differently designed, complicated components which also enable gas to be supplied.

The above object is achieved according to the invention by the features highlighted in the characterizing part of claims 1, 13 and 14. Preferred and expedient configurations are the subject of the dependent claims. Pure gas burners can also be produced with the components that enable optional operation with heating oil or heating gas as fuel. This greatly simplifies the production and storage of pure oil burners, combined oil-gas burners and pure gas burners.

• Fig. 1 zeit einen Längsschnitt durch die wesentlichen Teile eines Brenners gemäss der Erfindung.
• Fig. 2 zeigt einen Schnitt längs der Linie 11-11 in Fig. 1.
• Fig. 3 bis 5 zeigen jeweils in Teilschnitten weitere Ausführungsformen der Gaseinströmöffnung am inneren Umfang der ringförmigen Gaszuführkammer.
• Fig. 6 zeigt im Querschnitt durch einen Brenner eine Ausbildung der Blende mit einer Mehrloch-blendenöffnung.
• Fig. 7 zeigt im Querschnitt durch einen Brenner zwei Ausbildungen der Blende mit Blendenöffnungen mit einem gezahnten bzw. gezackten Rand.

The invention is illustrated in the drawing, for example, and described in detail below with reference to the drawing.

• Fig. 1 time a longitudinal section through the essential parts of a burner according to the invention.
• FIG. 2 shows a section along the line 11-11 in FIG. 1.
• 3 to 5 each show in partial sections further embodiments of the gas inflow opening on the inner circumference of the annular gas supply chamber.
• Fig. 6 shows in cross section through a burner an embodiment of the diaphragm with a multi-hole diaphragm opening.
• Fig. 7 shows in cross section through a burner two configurations of the diaphragm with diaphragm openings with a toothed or serrated edge.

The oil burner, as shown in Fig. 1 and 2, corresponds in its basic structure to known oil burners, as shown and described in DE-A-27 00 671 and 27 51 524 and in DE-U-79 19 481.

The burner shown has a housing, designated overall by 2, which encloses an air supply chamber 4, into which air is conveyed by a fan which is arranged in a fan chamber 6 arranged above. The housing 2 comprises a support tube 8, in which a flame tube 10 is inserted, the ge with an outer flange 12 via a seal 14 against an inner flange 16 of the support tube 8. At the end of the flame tube 10, an oil retaining flange 18 is fixedly connected to the flange 12 and retains any oil that drips off in the flame tube 10. An oil feed tube 20 is arranged coaxially in the support tube 8 and carries a tube 22 at its rear end, around which a compression spring 24 is arranged, which is supported against the end of the oil feed tube 20 on the one hand and a pressure disk 26 in a housing opening 28. The pressure atomizing nozzle 30 is screwed into the front of the oil supply pipe 20. The tube 22 can be the oil feed line. When an oil preheater is arranged, the power supply for the preheating element can be passed through this tube. The oil is then supplied through a separate line 32, which is led laterally to the oil supply pipe 20 and can be seen in FIG. 1 and is guided through a further bore in the rear housing wall 34.

The oil supply pipe 20 is carried by a ring 36 which is fastened via support legs 38 to a plate-shaped diaphragm 40 which is essentially flat and is offset at its edge against the plane of the central region. This shoulder 42 on the circumference of the circular disk serves to center a seal 44, by means of which the diaphragm 40 is sealed on its circumference in such a way that no air can pass through here.

A diaphragm opening 46 is provided centrally in the diaphragm 40 and is therefore also concentric to the axis of the pressure atomizing nozzle 30. The aperture 46 is the only passage for the combustion air. The diameter of the aperture 46 depends on the respective nominal throughput of the burner. The proportion of the combustion air is determined by them. For ignition, a pair of ignition electrodes 52 is provided, which is passed through the aperture 40. An ionization electrode 54 is also provided, which is also passed through the aperture.

The ignition electrodes 52 lie with their tips in front of a mixing tube 48. This construction corresponds to that according to DE-U-79 19 481. However, the ignition electrodes can also be arranged in the area of the aperture 46, as shown in DE-A-27 00 671 and described.

The burner described is further provided in the usual way with a drive motor for the impeller, which generally simultaneously drives the oil pressure pump. A conventional automatic burner control is also provided, as well as an ignition transformer. A solenoid valve is preferably also provided between the oil pump and the atomizing nozzle.

The blower can also be designed in a known manner with the axis of rotation lying transversely to the axis of the nozzle instead of as described with the axis of rotation parallel to the nozzle axis.

As shown, the mixing tube 48 can have a full-walled design. However, in order to prevent pulsations, for example in the front area, it can be perforated or otherwise provided with openings that reduce or suppress pulsations, but do not hinder the recirculation of the hot gases.

The flame tube 10 is of such a length that it is ensured that the fuel gas flow lies downstream of the mixing tube 48 against the inner wall of the flame tube. This ensures that stable recirculation can occur in the area of the mixing tube.

In order to be able to operate a burner of the known type described above, which is operated with heating oil, and optionally also with heating gas, a second orifice 56 is provided downstream of the orifice 40 at a distance therefrom, which is provided with an orifice opening 58 in its center coaxially with the axis of the nozzle 30 is. The diameter D _{2 of} the aperture 58 is equal to or greater than the diameter 0 of the aperture 46. Even with the same diameter, however, an ejector effect still occurs because the air jet can constrict behind the aperture 46. The orifice opening 58 preferably has a diameter D ₂ which is larger than the diameter D _{i of} the orifice opening 46. Downstream of the orifice 56, the mixing tube 48 is provided coaxially with the orifice opening 58 and has an inlet cross section 50 at its end facing the orifice. can recirculate hot combustion gases from the back of the flame front forming in the flame tube 10.

Instead of a single-hole diaphragm opening, as shown in the drawing, a multi-hole diaphragm opening can also be provided. In the case of the multi-hole aperture, one aperture is arranged coaxially with the nozzle axis, while the other apertures are arranged symmetrically around the central aperture. Such multi-hole orifices can have an advantageous effect with regard to the mixing of air and gas and the flame stability. They can also lead to noise reduction, especially when operating with heating oil. Such multi-hole screens are described in DE-A-29 18 416.

An embodiment of such a multi-hole diaphragm is shown in FIG. 6. The aperture passage here has a central opening 146 through which the nozzle conveys the oil. A plurality of further air passage openings 148 are arranged around the central opening 146, in such a way that they lie within an area circumscribed by the projection of the clear cross section of the mixing tube 48 with the circumscribing circle 150. In FIG. 6, the flame tube 10 and the support tube 8 indicated. The outer air passage openings 148 have a cross section stretched in the radial direction. This cross section can have the shape of a compact drop, for example, as shown in the drawing. However, it is also possible to provide an approximate trapezoidal shape.

Another way to improve the mixing of air and gas and the flames To improve stability when operating with a combustible gas is shown in Fig. 7.

The aperture 46 is provided with radial projections on its edge. As shown in FIG. 7 above, these projections can be designed as radially projecting teeth 152. In Fig. 7 below an embodiment in the form of prongs 154 is shown. The teeth or serrations are provided here symmetrically around the circumference of the aperture 46, i.e. with the same radial extension and with the same angular distance. It is of course also possible to serrate or serrate the edge of the diaphragm opening in a different way.

The diaphragm 56 can in turn consist of a circular plate and be essentially identical to the diaphragm 40. The edges 60 and 62 of the two diaphragms 40 and 56 are aligned in the illustrated embodiment and sealed against one another by seals 44. The edge 62 of the panel 56 bears against the flange 12 of the flame tube 10 via a seal 64. The seal or the seals 44 between the edges 60 and 62 of the orifices 40 and 56 determine the distance a between the two orifices 40 and 56 and thus the height of the annular outlet 66 of the annular chamber 72 formed between the two orifices.

As shown in FIG. 2, the orifice 40 is provided with two bores 68 in a plane which is guided essentially horizontally through the orifice, into which the ends of gas supply pipes 70 are inserted. The pipe ends can be attached by rolling. The tubes 70 extend through the housing substantially parallel to the axis of the pressure atomizing nozzle 30. They can either be brought together in the housing and then be guided through the housing rear wall 34 with a single outlet or, as shown in the drawing, both can be guided independently through the housing wall 34 and provided on the outside with angles or bends 92 and via a T- Pieces are connected, which is provided with a hose connection. This is connected in the usual way to a gas connection, preferably via a solenoid valve.

When the oil supply and the gas supply are switched off, a negative pressure is generated behind the aperture 46 by the air flow passing through it, through which gas 72 is sucked in from the annular chamber. The mixture formed in this way is ignited by means of the electrodes 52 and then burns within the flame tube 10. The operation is monitored via the ionization electrode 54 as in the case of oil operation.

To switch from one operating mode to the other, it is only necessary to make a switch, for example to change two plugs provided for the respective operating mode, so that a solenoid valve for the gas supply is actuated via the burner control unit instead of a solenoid valve in the oil supply line and vice versa . It is therefore not necessary to replace any components in order to change from one operating mode to the other. The special design of the burner with the pressure atomizing nozzle 30 located behind the orifice 46 ensures that the air flow keeps it cool even when the gas is operated, so that oil does not become stained within the nozzle even when the gas is operated for a long time. It is therefore possible to switch directly from gas operation to oil operation. As with the pure gasification oil burner, the pressure in the seals 44 and 64 is determined by the spring 24. Since these seals are not exposed to any appreciable internal pressure, a relatively low contact pressure is sufficient, so that a defined distance can be maintained between the plate edges 60 and 62 even when the seals are not too hard. If necessary, rigid spacing devices can also be provided, for example spacer knobs pressed out of one of the plates, against which the other plate rests.

Another possibility to exactly record the distance between the two screens 40 and 56 is to arrange or form flanges 74 on the holders of the ignition electrodes 52 and the ionization electrode 54, which determine the distance a and with which the electrodes are simultaneously clamped between the both panels can be held.

In the embodiment shown, the mixing tube 48 is fastened to the diaphragm 56 via its holders 76.

The distance a between the two orifices 40 and 56 delimiting the annular gas supply chamber 72 need only be a few millimeters and can be, for example, between 2 and 4 mm. Together with the thickness of the screen 56, which can be approximately 1.5 mm, the geometric conditions for the gasification oil burner change only insignificantly. The experiment has shown that even when an annular gas supply chamber is arranged, the operating values for heating oil operation can be maintained without difficulty.

For the burner described, the same performance can be achieved for both operating modes.

The burner described can be operated in gas operation with gases of different types, for example natural gas or town gas, but also with liquid gas, such as butane or propane.

Different heating values can be taken into account by designing the gas inflow opening and thus controlling the amount of gas. It is only necessary to provide an appropriately adapted orifice 56 or an appropriately designed mixing unit with the two orifices, the mixing tube 48 and the holder 36, with which the mixing unit is attached to the nozzle assembly.

3 to 5, which show embodiments which, apart from the design of the gas outlet openings of the above-described embodiment according to FIG. 1, are shown and 2 correspond.

In the embodiment according to FIG. 3, the edge of the diaphragm opening 58 is flanged upstream in the diaphragm 56, the free end face 80 of the flanged edge 82 determining the height b of the annular inlet cross section. In this embodiment, relatively precise inlet cross sections can be achieved for cross-flow operation, as are required, for example, for operation with gas under pressure. The edge 80 of the flanging ring 82 can also bear directly against the orifice 40, in which case cutouts can then be provided in the edge which, together with the adjoining surface of the orifice 40, limit the outlet cross sections.

In the embodiment according to FIG. 4, a ring 84 is clamped between the two screens, the inside diameter of which? is the diameter of the aperture 46 in the aperture 40. Radial gas outlet bores 86 are provided in this ring 84, as are illustrated in FIG. 4 above the center line. This version is in turn suitable for cross-flow operation with 6as under pressure. The bores can also, as shown in FIG. 4 in the lower half, run at an angle a to the axis of the nozzle, so that mixed cross-current-direct current operation is then achieved. The outlets of these bores can lie on the inner circumference of the ring 84. However, they can be arranged on a larger radius on the downstream end face of the ring.

In the embodiment according to FIG. 5, the edge of the aperture opening 46 of the aperture 40 is flanged downstream, to the extent that the flanged edge 88 engages at least partially in the aperture opening 58 of the aperture 56. This forms a coaxial annular gap 90 from which the gas flows in cocurrent with the combustion air.

The embodiments described above have the advantage that the two panels 40 and 56 can be produced from identical pressed blanks.

A burner designed exclusively for operation with heating gases, i.e. a pure gas burner, can be designed with the same components as the oil burners and combined oil-gas burners described above. In the pure gas burner, the components for oil operation, in particular the pressure atomizing nozzle 30 and the oil supply, are superfluous. Since in the oil burner and combined oil-gas burner the pressure atomizing nozzle has a favorable influence on the air flow in and downstream of the orifice opening, it is expedient in the case of a pure gas burner to provide an appropriately arranged and designed air guide body. Like the commercially available pressure atomizing nozzles, this can be designed with a dome-shaped or semi-dome-shaped end adjacent to the orifice opening. The end can also be conical or frustoconical, the cone tip also being rounded. With this configuration there is also the advantage that the. Combustion of the gas takes place in the flame tube belonging to the burner. The combustion chamber of the boiler has no influence on the combustion. In the furnace there is only a heat exchange between the hot combustion gases escaping on the tube and the walls of the furnace.

Since essentially the same components are used for the pure oil burner, the burner with optional oil and gas operation and the pure gas burner, an embodiment of a pure gas burner according to the present invention can be significantly simplified when manufacturing oil and gas burners manufacturing and warehousing.

Claims (14)

1. Burner for installation into heating and steam generating boilers, having an oil atomising device (20,30), having a plate-like screen (40) arranged in front of this, which has a single- or multi-aperture screen opening (46, 146, 148) coaxial with the oil atomising device (20, 30) as a through-way for the atomised oil, the screen opening (46, 146, 148) being at the same time the only through-way for the combustion air, having a mixing pipe (48) in spaced arrangement from the screen (40) and arranged coaxially downstream for forming an inlet crossection for the re-circulating combustion gas, which pipe (48) has a diameter greater than the diameter of the screen opening (46), or respec- . tively of the circle (150) surrounding it, and having a flame tube (10) coaxially surrounding the mixing pipe (48) of a length such that the flow of combustion gas meets the inner wall of the flame tube (10) downstream from the mixing pipe (48), characterised in that there is provided downstream from the first plate-like screen (40) and in spaced arrangement therefrom a second plate-like screen (56), with a screen opening (58) arranged coaxially with the screen opening (46, 146, 148) of the first screen, in that the two screens form an annular chamber (72) for the supply of a heating gas, which chamber (72) is provided in the area of the screen openings with at least one gas outlet aperture (66, 80, 86, 90), via which the gas escapes over the periphery of the screen opening, and the mixing pipe (48) is arranged downstream of and in spaced arrangement to the second screen (56) to form the inlet cross-section.

2. Burner according to claim 1, characterised in that the gas outlet apertures (66, 80, 86, 90) are located on a diameter which is greater than the diameter of the screen opening (46), respectively of the circle (150) describing the screen opening.

3. Burner according to claim 1 or 2, characterised in that the two plate-like screens (40, 56) are provided on their periphery with edges (60, 62) which are offset relative to a substantially plane central area, and are sealed off from one another with these edges.

4. Burner according to claim 3, characterised in that seals (44) defining a spacing are arranged between the edges (60, 62).

_. 5. Burner according to claim 1, characterised in that the mixing pipe (48) is secured to the second plate-like screen (56) lying downstream.

6. Burner according to claim 1, characterised in that the gas supply has at least one supply pipe (70) guided through the air supply chamber, the end of which pipe is secured in or to a bore (68) in the plate-like screen (56) lying upstream.

7. Burner according to claim 1, characterised in that the screen opening (58) in the downstream plate-like screen (56) is greater than the screen opening (46) in the upstream plate-like screen (40).

8. Burner according to claim 1, characterised in that the edge of the screen opening of one of the two plate-like screens (40, 56) is flanged, and the flange edge (82, 88) forms an annular gas outlet cross-section (80, 90) with the other plate-like screen.

9. Burner according to claim 1, characterised in that an annulus (84) provided with gas outlet apertures (48, 86) is arranged between the plate-like screens (40, 56).

10. Burner according to claim 9, characterised in that the inner diameter of the annulus (84) is flush with the screen opening (46) of the first plate-like screen (40).

11. Burner according to claim 1, characterised in that the screen aperture has a central middle aperture (46), and a plurality of further air through- passage apertures (148) around this inside a surface described by the projection of the clear opening of the mixing pipe (48).

12. Burner according to claim 1, characterised in that the edge of the screen opening (46) is serrated or toothed.

13. Burner according to claim 1 for exclusive operation with heating gas, characterised in that the oil atomisation device is replaced by an air- conducting body of roughly the same external shape which has no function regarding fuel supply.

14. Burner for installation in heating and steam generating boilers having an air supply chamber (4) and a gas supply line (70) with gas outlet apertures, through which the heating gas flows out into the combustion air flow, and a plate-like screen (40) closing off the air supply chamber (4) in an downstream direction, which screen (40) has a coaxial single- or multi-aperture screen opening (46) as a through-way for the combustion air, characterised in that there is provided downstream from the first plate-like screen (40) and in spaced arrangement therefrom, a second plate-like screen (56) lying parallel thereto, having a screen opening (58) arranged coaxially with the screen opening (46) of the first screen, in that the two screens form an annular chamber (72) for the supply of heating gas, which is provided in the area of the screen openings with at least one gas outlet aperture (66, 80, 86, 90), via which the gas flows out over the periphery of the screen opening, and having a flame tube (10) meeting the downstream side of the second plate-like screen (56), and of such a length that the flow of combustion gas meets the inner wall of the flame tube.

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