EP0283435B1 - Burner - Google Patents

Abstract

The burner has a motor, a fuel pump and a fan. An easily replaceable component unit (27), the drive shaft (33) of which is coupled to the burner motor, is surrounded by the flame tube (21). The component unit (27) has a drive shaft (33), supported in an adaptor sleeve (37), for driving the gasifier (17). When the burner is started up, the rotatable gasifier (17) is heated by the heater (39). Once the gasifier has reached a predetermined temperature, the supply of fuel takes place through the line segment (19') and through the nozzle (71) to the immediate vicinity of the inner wall of the gasifier (17). Because of the rapid rotation, the fuel is distributed over the entire inner wall of the gasifier (17) and evaporates. Particularly in the mixing head (29), the evaporated fuel mixes with the combustion air flowing in through the opening (77) and is directed radially to the outside by a deflector (31, 31'). Shortly after leaving the mixing head (29), the flame touches the short flame tube (21) and emerges from it. After a short travel in the flame tube, the flame can expand and decompress. As a result, a high flame temperature is avoided, and the formation of nitrogen oxides is diminished. A portion of the combustion gases is recirculated through the recirculation opening (79) and serves to heat the gasifier (17) after the shutoff of the electric heater (39).

Description

The invention relates to a burner with a rotating, hollow-body-shaped carburetor, which has an inlet for air and an outlet for gas / air mixture, drive means for rotating the carburetor and means for supplying fuel to the carburetor.

A distinction is made between atomizer burners and carburetor burners. In atomizer burners, the fuel is sprayed with a nozzle and burned in a combustion chamber with the supply of air. Since the atomizing performance of the nozzle can only be varied within narrow limits, atomizing burners have the disadvantage that their performance cannot be regulated continuously. Nor can they be built for very low power. The smallest nozzles are designed for an oil consumption of around 1.4 kg per hour. Since the output of the atomizer burner cannot be continuously regulated, atomizer burners are operated intermittently with low heat requirements. Since the operating intervals cannot be chosen to be as short as required, relatively large boilers are required as energy stores. The intermittent operation has the disadvantage that the repeated starting and switching off of the burner brings strong temperature changes to the materials as well as a high soot and pollutant load for the boiler, chimney and environment. Incomplete combustion and soot formation, which occur particularly in the start-up phase, have a significant impact on the overall efficiency of a heating system. Furthermore, the radiation losses from the large boilers further reduce the overall efficiency.

In contrast to the atomizer burners described, gasification burners generally have the advantage that they can be regulated continuously down to very low outputs in accordance with the heating requirement. Furthermore, a significant reduction in the emission of pollutants, for example unburned hydrocarbons and soot, is achieved in the combustion of gasified fuel.

Despite the many advantages that gasification burners have, they are only used to a small extent. A major reason for this is that most gasification burners need a lot of maintenance. Gasification burners usually tend to form undesirable deposits in the gasification chamber, which will soon significantly affect the effectiveness of the gasification and thus the operation of the burner.

EP-A-0 036 128 describes a gasification burner with an electrically heatable gasification chamber. The temperature of this gasification chamber is measured by a temperature sensor and kept at an optimal value by means of a control device in order to avoid coking of fuel. Another measure to avoid coking is that the gasification chamber has no air inlet openings. In addition, a rotating cleaning element in the form of a wiper is housed in the gasification chamber. This wiper is used to finely distribute the fuel on the heated carburetor walls and to prevent the formation of deposits, so that there is no harmful influence of deposits on the evaporation of the fuel. The gas formed in the gasification chamber leaves the chamber through a nozzle at a relatively high speed. The combustion air is conveyed by a fan. The burner described has the disadvantage that it requires a relatively large amount of electrical energy to evaporate the fuel. Burners of this type are also relatively expensive because they require a temperature sensor and a temperature controller. Compared to other gasification burners, where the fuel and air are mixed before combustion in the gasification chamber, the combustion of the gas emerging from a nozzle at a relatively high speed has the disadvantage that it causes relatively high noise. Furthermore, cold start problems can arise because the air is not heated or is only slightly heated before combustion. Furthermore, it is also disadvantageous that after-burning of gasified fuel can take place with a sooting flame. It is also possible for unburned hydrocarbons to emerge from the gasification chamber after they have been switched off.

EP-A-0 067 271 shows a continuously adjustable oil burner with an electrically heated evaporation device which has air inlet openings and which is monitored by a thermostat. This evaporation device is cup-shaped, air inlet openings being provided on the bottom of the cup. In this cup there is a rotating cylinder for oil distribution. This cylinder fills the evaporator space in the cup to a small gap. For the oil distribution, oil is supplied to the rotating cylinder via a hollow drive shaft, which is then thrown by centrifugal force from the radial bores in the rotating cylinder onto the inner walls of the evaporator chamber. However, oil burners of this type have not found commercial use. It is disadvantageous that the gasification chamber tends to become contaminated, the air inlet or the air / gas mixture outlet being disturbed. Since the pressure difference between the air inlet and the air / gas mixture outlet is very small, even slight contamination leads to a sooty flame. Another disadvantage is that the rotating cylinder absorbs a great deal of heat via the cylinder jacket surface and conducts it via the drive shaft to the drive motor, which can be damaged if costly devices are not used to protect it. The need for thermostat monitoring of the carburetor also contributes to increasing the purchase costs for the burner.

US Pat. No. 3,640,673 describes a burner for a petroleum oven in which a fan is arranged in the gasification chamber which can be heated electrically and by the flame of the burner. There is a relatively large space between the periphery of the fan and the heated wall surface of the gasification chamber. There is a spray disc for the fuel on the drive shaft for the fan. When fuel is sprayed onto the spray disc during operation, it distributes the fuel into fine droplets which are thrown outwards by centrifugal force. They are mixed by the fan with the preheated air flowing into the gasifier chamber. Since the distance between the periphery of the fan and the heated wall surface of the gasification chamber is relatively large, most fuel droplets evaporate without ever coming into contact with a wall surface. The few droplets of fuel that hit the heated wall of the gasification chamber then evaporate there. The disadvantage here is that deposits form on the walls, which adversely affect evaporation, particularly in the start-up phase, when the gasification chamber is only heated electrically. This can lead to start problems. Unburned hydrocarbons also escape during the start and shutdown phases. Another disadvantage of the burner described is that it can only be operated with petroleum, is practically an atmospheric burner and is therefore not suitable for use in a boiler.

EP-A 0 166 329 describes a gasification burner in which a rotor provided with blades, the blades of which extend into the vicinity of the heatable wall of the gasification chamber, is arranged. The carburetor chamber has an air inlet. The fuel supplied via the rotor shaft is finely distributed by the rotor and mixed with compressed air, whereby it evaporates in the hot gasification chamber. The mixture can then escape through openings in a burner plate at relatively high pressure and burn with a low-noise blue flame.

For the sake of completeness, reference is made to the oil burner described in CH-PS628724, which is an atomizing burner but also features a gasification burner. It has the inherent disadvantage of the atomizer burner that it cannot be regulated in a wide output range. Even in the lowest performance range, it still requires a relatively high throughput of 1.6 to 2.1 kg of oil per hour.

In order to gasify the sprayed oil droplets, a mixing tube and a flame tube are provided coaxially with the nozzle. In operation, the oil is injected through the nozzle into the mixing tube, into which the air necessary for combustion is also blown. A flame then forms at the end of the mixing tube. Part of the hot combustion gases is then recirculated to the beginning of the mixing tube and mixed there with the oil mist / air mixture for the purpose of heat exchange. Thanks to the recirculation of some of the combustion gases, this burner enables the oil droplets in the mixing tube to be largely gasified and thus better combustion with less soot formation. However, this advantage is paid for by the increased formation of nitrogen oxides (NO _x ). The burner requires a long flame tube. Since the flame does not relax until it emerges from the flame tube, there is a relatively large flame zone with very high temperatures, which favors the formation of nitrogen oxides. As already mentioned, the burner also has the disadvantage that it cannot be regulated over a wide output range. In the lowest performance range, it requires a relatively high oil throughput of 1.6 liters per hour. The burner described offers additional problems when starting and when switching off. This is all the more serious because the burner has to be operated intermittently. A problem at the start is the ignition of the oil droplets flowing out of the atomizer nozzle. In contrast to an ordinary atomizer burner, an optimal arrangement of the ignition electrodes is prevented by a wall with an air screen. There is therefore a great risk that no ignition will occur even with repeated attempts to start. Another problem is the fact that the mixing tube is cold at the start and therefore has no vaporizing effect. The flame is therefore sooty until the mixing tube has reached a high temperature and is able to evaporate the oil that hits it. When the burner is switched off, the oil dripping from the nozzle burns with a strongly sooting flame. Furthermore, since the mixing tube near the nozzle is still glowing bright red when it is switched off, it radiates a lot of heat towards the nozzle, which can lead to coking of fuel in the nozzle. This can clog the nozzle, especially if it is a small nozzle.

From DE-A-3 346 431 a burner with a rotating evaporator pot has become known. This is closed on the flame side and only has an outlet for the vaporized fuel on the engine side. The evaporator pot is surrounded by an annular deflection chamber for the air supply. Gasified fuel and air then flow between the evaporator pot and the flame tube in two concentric streams of annular cross-section, meet a baffle ring, mix and then form a flame. The disadvantage here is that the evaporator chamber is not exposed to a strong flow of hot gases, so that deposits form there, which soon impair the function of the burner. In particular, there is a strong release of unburned hydrocarbons when the burner is switched off.

FR-A-2 269 029 also shows a burner which has a rotating evaporator pot which is closed on the flame side. The inside of the evaporator pot is lined with a wire mesh, which serves to prevent the fuel from escaping. This burner requires a powerful fan with a relatively high energy consumption, because both the fresh air and the air / gas mixture are deflected several times. A further disadvantage is that after the burner has been switched off, a lot of fuel still evaporates from the wire network previously coated with air and therefore remained relatively cool, so that a strong release of hydrocarbons occurs.

US-A-2 535 316 shows a burner with a spherical gasification chamber which rotates slowly. The fuel flowing through a line forms an oil bath at the bottom of the chamber, from which the lighter fractions evaporate. The remaining tar and coke residue forms a thin layer on the chamber wall and slowly moves upwards due to the slow rotation. There, an air stream flows against this layer and burns it away continuously. The disadvantage here is that when the burner is switched off, the oil bath causes a strong release of soot, tar and unburned hydrocarbons.

It is an object of the present invention to provide a burner of the type mentioned at the outset, which at least partially avoids the disadvantages of the known burners described. It should enable operation at low outputs and / or an adjustment of the output according to the heating requirement, be reliable and require little maintenance work. It should also meet high environmental protection requirements and e.g. Ensure clean combustion during operation, generate little nitrogen oxides and do not cause emissions of unburned hydrocarbons when switched on and off.

According to the invention, this is achieved by a burner, with a rotating hollow-shaped carburetor, which has an inlet for air and an outlet for the gas / air mixture, with a drive shaft for rotating the carburetor and for driving a fan in order to rotate the carburetor rapidly to distribute the fuel as a thin film evenly over the inner wall of the carburetor, and means for supplying fuel to the carburetor, a flame tube being provided at a distance from the carburetor and a recirculation inlet at the inlet of the carburetor for the recirculation of hot combustion gases, and at a distance from Outlet of the carburetor is arranged a deflecting part or a baffle plate. Since the carburetor rotates quickly, no atomizer nozzle is required to distribute the fuel over the inner wall of the carburetor. The disadvantages of the burners with atomizing nozzles can thus be avoided. Instead of atomizing the fuel, it can e.g. be directed in the form of a jet against the inner wall of the carburetor. The fuel then adheres to the inner wall. However, the centrifugal force causes it to be pressed firmly against the inner wall and therefore to spread as a thin film over the entire inner wall. This favors the gasification of the fuel. It is also possible to arrange the burner vertically as a so-called lint burner without fuel flowing out. In continuous operation, the heat necessary for gasification is supplied by the recirculation of hot combustion gases. Such hot combustion gases flow from the flame backwards past the outer wall of the carburetor and penetrate into the inlet of the carburetor. This makes it possible to switch off the electric heating after starting the burner and to draw the gasification heat from the hot gases generated during the combustion. Due to the high temperature in the carburetor and the rapid flow of air and combustion gases, continuous cleaning takes place. This makes it possible to burn even relatively poor oil qualities perfectly. It is also important that the burner output can be easily regulated in a ratio of about 1: 3. The deflecting part deflects the gas / air mixture emerging from the outlet of the carburetor and thus also the flame, which on the one hand promotes the recirculation of hot combustion gases and enables the formation of a flame with a relatively low flame temperature. This has the advantage that little nitrogen oxides are formed.

The carburetor advantageously has the shape of a cylindrical pipe section. This training makes the production of the carburetor much easier. For example, it can be made from cylindrical tube material. The cylindrical design also has the advantage that the centrifugal forces cause a good distribution of the fuel over the entire inner wall. It is therefore sufficient if the fuel supply line is guided somewhat into the pipe section. The fuel supply line can extend through the inlet of the carburetor into the interior of the carburetor. It is therefore not necessary to supply fuel through the drive shaft of the carburetor, which would require a relatively expensive construction. However, if desired, the fuel can of course also be supplied by the drive shaft.

A nozzle directed towards the wall of the carburetor is expediently provided at the end of the fuel supply line, which nozzle extends up to close to the inner wall of the carburetor or close to the surface of the surface-enlarging means. The nozzle is only a narrowing of the fuel line to approximately 1 mm cross-section, that is, it is not an atomizing nozzle as used in atomizing burners. In order to prevent fuel from leaking at the ends of the pipe section, expediently min a radially inward approach is provided at the outlet end of the pipe section.

It is possible to drive the rotating carburetor in different ways. For example, the carburetor could be rotated by the air flow flowing through it. However, the rotatable carburetor advantageously has a drive shaft which is connected to the drive unit, e.g. the burner motor. This ensures that the carburetor rotates when the burner is on. Connection means, e.g. in the form of spokes, which connect the carburetor to the drive shaft or a hub seated on the drive shaft. The spokes are conveniently arranged at the outlet. This allows a fuel line to protrude into the carburetor from the inlet. Furthermore, practically the entire carburetor wall is then available for receiving an insert made of metal mesh. In order to be able to heat the carburetor when the burner is switched on, a stationary electrical heater is expediently arranged at a distance from the rotating carburetor. The carburetor is then heated up by radiant heat. A flame tube is then also advantageously arranged coaxially and at a distance from the carburetor and from the electrical heater.

An air screen with an opening for supplying air to the inlet of the carburetor is advantageously provided. This opening for air supply is expediently arranged centrally and also serves as a passage for the drive shaft for the carburetor. This directs the relatively cold air into the center of the carburetor.

At least one mixing finger projecting into the carburetor is expediently provided. This mixing finger creates turbulence which promotes the mixing of the gasified fuel with air. A number of mixing fingers is expediently arranged concentrically around the opening of the air diaphragm. This arrangement enables particularly good mixing of air with gasified fuel.

The air orifice is expediently arranged at a distance from the carburetor, the gap between the air orifice and carburetor forming the recirculation inlet. Thanks to this arrangement, it is primarily the hot recirculated gases that run along the inner wall of the carburetor, during which the cold air flows more inside the carburetor. This ensures good evaporation of the fuel and avoids re-vaporization of the fuel after the burner has come to a standstill.

An embodiment of the invention provides that a mixing head is arranged at the outlet of the carburetor. This mixing head rotates together with the carburetor and ensures good mixing of gasified fuel and air. There are various ways of forming the mixing head. The mixing head can be formed, for example, by a fan disk with radial vanes arranged at a distance from the outlet. Such a mixing head can be produced from sheet metal with little effort.

It has proven expedient to arrange a slotted baffle plate at a distance from the outlet of the carburetor. This promotes recirculation. The slitting of the baffle plate ensures that it is sufficiently cooled.

A Volustat can be provided to control the fuel supply. A volustat is understood to mean a device which, according to an input signal, delivers a corresponding delivery volume per unit of time, which is practically not influenced by resistances in the delivery line. The delivery volume is hardly influenced by the viscosity of the fuel.

The carburetor advantageously has surface-enlarging agents, e.g. a metal mesh. This increases the effective surface area of the fuel film and accelerates gasification. When using a metal mesh or a porous sintered mass, capillary forces also become effective, which facilitate the distribution of the fuel over the entire wall of the carburetor. The surface-enlarging means are expediently formed by an insert which covers the inner wall of the hollow body. Such an insert can easily be replaced during revision work if necessary. Because the fuel immediately comes into contact with the surface-enlarging metal fabric as it exits the fuel supply line, capillary and centrifugal forces, which endeavor to distribute it over the entire surface of the carburetor interior, take effect immediately. There is therefore no danger that fuel droplets will be carried away by the strong air flow in the carburetor and carried outside.

The insert advantageously has a radially inwardly projecting flange. This causes any oil droplets to be trapped and evaporated on the hot surface of the insert.

An advantageous embodiment of the invention provides that the carburetor, the mixing head and the deflection part form a unit. This can then be easily attached to the drive shaft with a screw. This simplifies the service work for the burner. Even a person without special expertise is able to replace a unit with carburetor and mixing head in the shortest possible time. This would not be possible, for example, for the replacement of a nozzle in a known atomizer burner. The carburetor and mixing head can consist of a single piece of pipe or a piece of sheet metal formed into a piece of pipe. This significantly simplifies and reduces manufacturing costs. The wings of the Misch heads can be molded out of the wall. This can be done, for example, by punching.

The wings have a dual function in the described configuration of carburetor and mixing head. They serve on the one hand as a means of mixing gasified fuel and air and on the other hand as connecting webs between the carburetor and the drive shaft. There is therefore no need for special spokes, as is the case when the carburetor and mixing head are formed as separate parts.

It is possible to use the cooling effect of the air flowing into the carburetor to cool the bearing of the drive shaft by providing a distance between the carburetor and the bearing which corresponds approximately to the length of the carburetor.

• Fig. 1 eine Ansicht eines Brenners gemäss der Erfindung,
• Fig. 2 einen Schnitt durch ein erstes Ausführungsbeispiel des Brenners,
• Fig. 3 eine Seitenansicht des Vergasers von Figur 2 von rechts gesehen,
• Fig. 4 einen Schnitt durch ein zweites Ausführungsbeispiel des Brenners, wobei jedoch im wesentlichen nur die Teile eingezeichnet sind, die anders als in Figur 2 ausgebildet sind,
• Fig. 5 einen Schnitt entlang der Linie V-V von Figur 4,
• Fig. 6 einen Schnitt entlang der Linie VI-VI von Figur 4,
• Fig. 7 einen Schnitt durch ein bevorzugtes drittes Ausführungsbeispiel eines Brenners, bei dem Vergaser und Mischkopf aus einem Stück bestehen,
• Fig. 8 die Bildung von U-förmigen Schlitzen zwecks Ausbildung der Flügel des Mischkopfes,
• Fig. 9 eine Ansicht von links der in Fig. 7 gezeigten Baueinheit.
• Fig. 10 ein viertes Ausführungsbeispiel eines Brenners mit vertikaler Anordnung des Vergasers.

Embodiments of the invention will now be described with reference to the drawing. It shows:

• 1 is a view of a burner according to the invention,
• 2 shows a section through a first embodiment of the burner,
• 3 is a side view of the carburetor of Figure 2 seen from the right,
• 4 shows a section through a second exemplary embodiment of the burner, but essentially only those parts are shown which are designed differently than in FIG. 2,
• 5 shows a section along the line VV of FIG. 4,
• 6 shows a section along the line VI-VI of FIG. 4,
• 7 shows a section through a preferred third exemplary embodiment of a burner in which the carburetor and mixing head consist of one piece,
• 8 shows the formation of U-shaped slots in order to form the wings of the mixing head,
• Fig. 9 is a view from the left of the assembly shown in Fig. 7.
• Fig. 10 shows a fourth embodiment of a burner with a vertical arrangement of the carburetor.

The burner shown in FIG. 1 has a motor 11 which serves to drive the fuel pump 13, the fan 15 and the rotatable carburetor 17 (FIGS. 2 and 3). A fuel line 19 leads from the fuel pump 13 to the carburetor 17 (FIG. 2), which is enclosed by a flame tube 21. The flame tube 21 can be easily removed by loosening the screws 23. A Volustat, a solenoid valve or another suitable device 25 serve to control the fuel supply in accordance with the control commands of the heating control 26.

Figure 2 now shows an easily replaceable assembly 27, which consists essentially of the rotatable carburetor 17, the mixing head 29, the baffle plate 31, the drive shaft 33 for the carburetor 17, the air orifice 35, the adapter sleeve 37, the fuel line piece 19 ', the electrical Heater 39 and the ignition electrode 41 is made. The assembly 27 is enclosed by the flame tube 21 after assembly. This is relatively short and protrudes only slightly beyond the mixing head 29.

The mixing head 29 consists of a fan disk with radial blades 30. Other embodiments of the mixing head 29 are described below with reference to FIGS. 4 and 6.

The drive shaft 33 is in the adapter sleeve 37 by two bearings 43, 45, e.g. Sintered bearings, stored. The axial position of the drive shaft 33 is determined, for example, by the adjusting rings 47, 49. The air panel 35 is fastened on the adapter sleeve 37 by the support 51.

The carburetor 17 is designed as a hollow rotating body and has an inlet 53 and an outlet 55. In the exemplary embodiment shown, the carburetor has the shape of a cylindrical tube piece 56 and has connection means in the form of spokes 57 at the outlet, which spokes radially inward from the tube piece 56 to one Guide hub 59. The carburetor essentially consists of the pipe section 56, the spokes 57 and the hub 59, which is used for fastening on the drive shaft 33. The carburetor 17 is fastened together with the mixing head 29 and the baffle plate 31 by the screw 61, which is screwed into the axial threaded bore 63 of the shaft 33.

It has proven to be advantageous to provide surface-enlarging means 65 in the carburetor 17. These can consist, for example, of a metal mesh through an insert 65. Such a metal mesh creates a capillary effect through which the fuel is finely distributed. However, it would also be possible to provide a large number of fine grooves on the inner wall of the carburetor 17 as a surface-enlarging agent. These grooves should run in the axial direction or helically so that a good distribution of the fuel is ensured by centrifugal forces.

A radially inwardly directed extension 67, 69 is advantageously provided at each end of the tube section 56, that is to say at the inlet 53 and at the outlet 55. This prevents liquid fuel from escaping through the acting centrifugal forces. The approach 67 also serves as a holder for the insert 65 made of metal mesh.

Since the spokes 57 are located at the outlet, the fuel line piece 19 ′ can extend into the interior of the carburetor 17 through the inlet 53. At the end of the fuel line piece 19 'there is a nozzle 71 which is directed towards the wall of the carburetor and which extends close to the insert 65, so that fuel which flows out immediately makes contact with the metal mesh.

On the flame tube 21 there is an extension ring 73 which presses against a sealing ring 75 at the air screen 35. This ensures that the air required for combustion can only flow through the central opening 77 in the air panel 35. At the opening is 77 a recirculation inlet 79 is provided for the carburetor 17. This recirculation inlet 79 is formed in that the air screen 35 is arranged at a distance from the carburetor 17. This creates a gap 79 between the air orifice 35 and the carburetor 17, which forms the recirculation inlet.

The burner works as follows: When starting, the heating control 26 first switches on the electric heater 39 for about two minutes. During this time, the radiation from the heating coils causes the gasifier 17 and the insert 65 to be heated to approximately 550 ° C. After this preheating time, the burner motor 11 is started, which drives the pump 13, the fan 15 for the combustion air supply, so that the carburetor 17 is rotated. The oil delivered by the pump 13 flows through the fuel line 19, 19 'to the nozzle 71 and wets the insert 65 made of metal mesh. Thanks to the capillary action of the metal mesh and the centrifugal force, the fuel is distributed over the entire insert 65 and evaporates thanks to the high temperature. The vaporized fuel is mixed with the air flowing in through the opening 77 and ignited at the outlet 55 by the ignition electrode 41. A blue flame forms at the annular gap between the outlet 55 of the carburetor and the baffle plate 31, which extends far beyond the end of the flame tube 23. A part of the hot combustion gases generated by the flame flows from the outlet 55 between the carburetor 17 and the flame tube 23 backwards to the recirculation inlet 79 and thereby heats the carburetor 17. The electric heater 39 can then be switched off. The returned hot gases then flow from the inlet 53 to the outlet 55 again and mix on the one hand with gasified fuel and on the other hand with incoming fresh air. Because the fresh air flows into the center of the inlet, it does not cool the carburetor excessively, which could affect the gasification. The mixing head 29 arranged at the outlet 55 effects a good mixing of air, recirculated gases and evaporated fuel, so that an optimal combustion takes place. When the burner is switched off, the fuel supply through the nozzle 71 stops immediately. However, the carburetor 17 continues to rotate for some time, air being conveyed through the fan 15 even further. Until the carburetor 17 comes to a standstill, the fuel in the metal mesh 65 evaporates and still burns completely. Since the cold parts in the carburetor, i.e. the shaft 33, the spokes 57 and the hub 59 are not wetted by fuel, no unburned hydrocarbons emerge from the carburetor after the burner has been switched off. The same applies to the start phase.

It should be noted that the mixing head 29 and the baffle plate 31 deflect the gas / air mixtures emerging from the outlet 55 and thus the flame in the direction of the inner wall of the flame tube 21. The flame thus touches the flame tube 21 shortly after its formation. This has the advantage that the flame tube can be dimensioned briefly. This in turn allows the burner to be used with a large number of different boilers. It is of particular importance that the flame leaves the flame tube shortly after its formation and can expand. This reduces the flame temperature. A lower flame temperature has the important advantage from the point of view of environmental protection that little nitrogen oxides are formed. Despite the short flame tube 21, however, sufficient recirculation for heating the evaporator is ensured because the flame bears against the flame tube and thus causes sufficient pressure in the rear part of the flame tube.

The exemplary embodiment according to FIGS. 4 to 6 basically differs from the exemplary embodiment according to FIG. 2 only in that the mixing head 29 is designed differently and that 35 mixing fingers 81 are provided on the air panel. Otherwise, the burner according to FIG. 4 is of the same design as that of FIGS. 1 and 2, so that reference can be made to the relevant description.

5 shows, the mixing fingers 81 are arranged concentrically around the opening 77 of the air screen 35. These mixing fingers cause turbulence in the carburetor chamber and thus cause a good mixing of gasified fuel and air.

The mixing head 29 advantageously consists of one piece. It has a deflection part 31 ', from the periphery of which wings 30 extend toward the carburetor 17. These blades 30 are approximately the same distance from the axis of rotation 83 as the periphery of the carburetor 17. As FIG. 6 shows, the blades 30 are arranged in the direction of rotation 85 of the mixing head in such a way that they tend to convey air from the outside inwards . However, this is not the case in the operation of the burner because the air flowing through the carburetor counteracts this tendency. A particularly intensive mixing of fuel and air is achieved by the vanes 30, so that a calm flame is produced on the periphery of the mixing head 29.

The third exemplary embodiment according to FIGS. 7 to 9 represents a significant simplification compared to the second exemplary embodiment. Otherwise, the burner is of the same design as that of FIGS. 1 and 2, so that reference can be made to the relevant description for details. The assembly 27 consists essentially of the rapidly rotating carburetor 17 with the mixing head 29 and the deflection part 31 ', the drive shaft 33 for the carburetor 17, the air shield 35, the adapter sleeve 37, the fuel line piece 19', the electric heater 39 and the ignition electrode 41. The assembly 27 is enclosed by the flame tube 21 after assembly. Reference number 28 denotes a flange for fastening the assembly 27 to the fan 15 (FIG. 1). The fasteners supply takes place by tightening the screw 34. The drive shaft 33 is mounted in the adapter sleeve 37 by two bearings 43, 45. The bearing 45 is located at a relatively large distance from the carburetor 17, so that it is well protected against the effects of heat. In order to achieve this, an axially adjustable support 51, which can be fixed with a screw 50, is provided on the adapter sleeve 37, which has arms or spacer elements 52 in order to carry the air screen 35. In operation, the spacing of the air screen 35 from the bearing 45 ensures that the drive shaft 33 is cooled between the bearing 45 and the carburetor 17 by the fresh air. The spacer elements 52 can be connected to the support 51 or the air panel 35, for example, by means of screws 46, 48.

The coupling between motor 11 and drive shaft 33 takes place via a coupling piece 36, which has a thread 38, a body 40 made of elastomeric material and a thread 42. The thread 38 can be screwed into an axial thread in the shaft of the motor 11 (FIG. 1) by turning the mixing head 29. The carburetor 17, the mixing head 29 and the deflection part 31 'form a unit 18 which is fastened to the drive shaft 33 with a screw 61. This unit can be cheaply made from a piece of pipe. It is also possible to manufacture from a piece of sheet metal, which is then rolled into a piece of pipe and welded at the abutting ends or otherwise connected. The deflecting part 31 'is then inserted in the part of the pipe section forming the mixing head 29 and welded or otherwise connected to the pipe section. The mixing head 29 is formed by the front part of the pipe section. The mixing head 29 is separated from the carburetor 17 by a constriction 69 '. This constriction corresponds to approach 69 of FIG. 2 and forms an inwardly protruding barrier which prevents the liquid fuel from flowing into the mixing head without vaporization.

The mixing head 29 has blades 30. These wings 3 can be formed from the wall by previously forming U-shaped slots 32 (FIG. 8) in the sheet metal piece or in the wall and bending the tabs 30 °. The blades 30 project inwards and are advantageously arranged in the direction of rotation of the mixing head 29 in such a way that they have the tendency to convey air from the outside inwards. In operation, however, the air flowing through the carburetor counteracts this tendency. It is thereby achieved that the vanes 30 bring about an intensive mixing of gasified fuel and air, so that a calm flame arises at the periphery of the mixing head 29.

An advantage of the construction described is that no additional connecting means, e.g. Spokes, as are necessary in the embodiment of FIGS. 2 and 3, to connect the carburetor 17 to the drive shaft 33.

Tests have shown that in many cases an insert (Fig. 2:65) made of metal mesh can be dispensed with. This is particularly true when the carburetor 17 is made relatively long. In the case of a short carburetor 17, it is advantageous to provide an insert 65 made of metal mesh with a bent edge. This edge represents a flange 66 which still protrudes radially into the carburetor chamber and is used to trap any fuel droplets so that they evaporate.

On the flame tube 21 there is an extension ring 73 which presses against a sealing ring 75 at the air screen 35. This ensures that the air required for combustion can only flow through the central opening 77. Thanks to the spacing of the carburetor 17 from the air screen 35, a recirculation inlet 79 is created.

A fire-resistant steel is preferably suitable as the material for the unit 18 and the flame tube 21.

The burner according to the fourth exemplary embodiment according to FIG. 10 is configured practically the same as that of FIGS. 7 to 9, so that reference can be made to the preceding description for details. The burner of Fig. 10 is a so-called fall burner, i.e. a burner that is arranged vertically instead of horizontally. The carburetor 17 has a slightly conical section 17 '. This has the effect that, when the carburetor 17 rotates, the centrifugal force compensates for the force of gravity which acts on the fuel which threatens to flow down the inner wall of the carburetor 17 after it has left the fuel line 19 '. Despite the vertical arrangement of the carburetor 17, the fuel is therefore distributed fairly uniformly over the inner wall, and it evaporates. The burner can be arranged vertically with the mixing head facing upwards.

Claims (26)

1. A burner having: a rotating hollow evaporator (17) having an air inlet (53) and a gas/ air mixture outlet (55); a drive shaft (11) for rotating the evaporator (17) and drivng a fan (15) in order to distribute the fuel uniformly as a thin film over the evaporator inside wall by rapid rotation of the evaporator (17); and means (13, 25, 19) for supplying fuel to the evaporator (17), a flame tube (21) being disposed at a distance from the evaporator (17) and a recirculating inlet (79) being disposed near the air inlet (53) in order to recirculate hot combustion gases, a deflector (31') or a backup disc (31) being disposed at a distance from the evaporator outlet (55).

2. A burner according to claim 1, characterised in that the evaporator is in the shape of a cylindrical tubular member (56).

3. A burner according to claim 2, characterised in that an annular end member (67, 69) which extends radially inwards is provided at least at the outlet end of the tubular member (56).

4. A burner according to any of claims 1 to 3, characterised in that the fuel feed line (19') extends through the evaporator air inlet (53) into the evaporator interior.

5. A burner according to claim 4, characterised in that a nozzle (71) directed towards the evaporator wall is provided at the end of the fuel feed line (19') and extends to near the evaporator inner wall or to near the surface of the surface-increasing means (65).

6. A burner according to any of claims 1 to 5, characterised in that the drive shaft (35) is mounted in an adapter sleeve in at least one bearing (43, 45) and coupled with the drive shaft (11), for example, by means of a coupling member.

7. A burner according to any of claims 1 to 6, characterised in that connecting means (57), for example, in the form of spokes, are provided and connect the evaporator (17) to the drive shaft (33) or to a hub (59) thereon.

8. A burner according to any of claims 1 to 7, characterised in that a stationary electric heating facility (39) is disposed at a distance from the rotatable evaporator (17).

9. A burner according to claim 8, characterised in that the flame tube (21) is disposed coaxially of the evaporator (17) and electric heating facility (39).

10. A burner according to any of claims 1 to 9, characterised in that an air diaphragm (35) formed with an aperture (77) for supplying air to the evaporator air inlet (53) is provided.

11. A burner according to any of claims 1 to 10, characterised in that at least one mixing finger (81) which extends into the evaporator (17) is provided.

12. A burner according to claim 11, characterised in that a number of mixing fingers (81) are arranged concentrically around the air diaphragm aperture (77).

13. A burner according to any of claims 10to 12, characterised in that the air diaphragm (35) is disposed at a distance from the evaporator (17), the gap between the same and the diaphragm (35) being effective as the recirculation inlet (79).

14. A burner according to any of claims 1 to 13, characterised in that a mixing head (29) is disposed at the evaporator outlet (55).

15. A burner according to claim 14, characterised in that the mixing head (29) is embodied by a fan disc which is disposed at a distance from the evaporator outlet (55) and which has radial vanes (30).

16. A burner according to any of claims 1 to 15, characterised in that the backup disc (31) is slotted.

17. A burner according to claims 1 to 16, characterised in that a volustat (25) is provided to control the supply of fuel.

18. A burner according to any of claims 14 to 17, characterised in that the rotatable evaporator (17), mixing head (29) and/or backup disc (31) at the evaporator outlet (55), the drive shaft (33), the adapter sleeve (37), the air diaphragm (37), the electric heating facility (39) and the igniting electrode (41) form an interchangeable unit (27) for the burner.

19. A burner according to any of claims 1 to 18, characterised in that the evaporator (17) has surface-increasing means (65), for example, a woven metal cloth.

20. A burner according to claim 19, characterised in that the surface-increasing means are embodied by an insert (65) which covers the evaporator inner wall at least to some extent.

21. A burner according to claim 20, characterised in that the insert (65) has a radially inwardly extending flange (66).

22. A burner according to claim 14, characterised in that the evaporator (17), mixing head (29) and the deflector are a single unit (18).

23. A burner according to claim 22, characterised in that the evaporator (17) and mixing head (29) are embodied by a single tubular member.

24. A burner according to claim 23, characterised in that the radial vanes (30) are contrived by punching U-shaped slots (32) in the wall of the tubular member and bending the resulting pieces.

25. A burner according to claims 6 to 24, characterised in that a distance corresponding approximately to the length of the evaporator (17) is present between the same and a bearing (45) of the drive shaft (35).

26. A burner according to any of claims 1 to 25, characterised in that at least one part (17') of the evaporator (17) is slightly conical.

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