EP0232677B1 - Burner, particularly burner for burning liquid fuel in gaseous state - Google Patents

Abstract

The burner has a motor (11), a fuel pump (13) and a fan (15). In the flame tube (81) is a gasification chamber having a gasification chamber housing (75) coaxially located to the flame tube (81), and a housing (75) located at a distance therefrom. The rotor (17) located in the housing (75) can be axially moved with respect to the bearing (29), thereby causing a slot between the axial bearing surfaces (51, 53). Through this slot fuel is ejected into the gasification chamber by the rotation of the rotor (17). The opening of the slot between the axial bearing surfaces (51, 53) depends on the oil pressure which is determined by signals of the heating control 24. The fuel throughput may be controlled in steps or continuously according to the heat requirements. The electric heating (77) is only used during the start phase. In operation of the burner the heat requirements for the gasifying chamber (25) are covered by the recirculation of hot combustion gases through the recirculation gas inlet (73).

Description

The invention relates to a burner, in particular a burner for burning liquid fuels in the gaseous state, with a motor for driving a fan and / or a fuel pump, with a carburetor chamber formed by a housing and having at least one heatable wall, with one in the carburetor chamber arranged rotatable device, the drive shaft is coupled to the motor, and with a jacket surrounding the drive shaft, which serves as a fuel supply member in the carburetor chamber. Such a burner is described in EP-A-O 136 522.

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 regulated continuously, atomizer burners are operated intermittently with low heat requirements. Since the operating intervals cannot be chosen 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 heavy 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 during 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 rotatable device in the form of a wiper is accommodated 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. A modified form of this gasification burner is described in the aforementioned EP-A-O 136 522. The burners described in these documents have the disadvantage that they require 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 with a sooting flame can take place, unless particularly expensive measures are taken to prevent the further escape of gasified fuel from the pressurized gasification chamber.

EP-AO 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 fed 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, whereby the air inlet or the air / gas mixture outlet is 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 via the drive shaft leads to the drive motor, which can be damaged if costly devices are not taken 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 that 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. Another disadvantage of the burner described is that it is practically an atmospheric burner and is therefore not suitable for use in a boiler.

In the non-prepublished EP-A 0 166 329 a gasification burner is described 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 also made to the oil burner described in CH-PS 628 724, which is an atomizer 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, as has already been mentioned, it cannot be regulated over a wide performance range and requires a relatively high oil throughput in the lowest performance range. The burner described offers additional problems when starting and stopping. This is all the more serious because the burner has to be operated intermittently. At the start, the mixing tube is cold 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 is re-burned 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.

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. In particular, 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.

According to the invention, this is achieved in a burner of the type mentioned at the outset in that the carburetor-side end of the casing has a first axial bearing surface, that the rotatable device has a second axial bearing surface, and in that adjusting means are provided in order to move the two axial bearing surfaces apart or towards one another to let fuel into the carburettor chamber or shut off the fuel supply according to the heat demand. The burner therefore does not require a nozzle and avoids the disadvantages associated with it, such as the risk of clogging, lack of controllability, impossibility of operation in a low power range, incomplete combustion and soot formation, etc. The rotating axial bearing surface ensures a good distribution of the fuel in the carburettor chamber, which causes the ensures complete gasification of the fuel. The amount of fuel delivered per unit of time can easily be regulated by the delivery pressure. Since there is a relative movement between the axial bearing surfaces during operation, there is no risk of clogging. After-burning is avoided when the burner is switched off because the thrust bearing surfaces are close together and no longer allow fuel to flow out. An extremely simple construction is possible, which does not require high-precision parts such as atomizer nozzles. Since the axial bearing surfaces at Ab rub against each other, self-cleaning takes place.

The adjusting means are expediently formed by a hydraulic device and a spring. This enables a simple and reliable construction. The hydraulic device advantageously consists of a recess in an axial bearing surface. Fuel can thus flow into this recess during operation and generate a pressure which drives the two axial bearing surfaces apart and enables the fuel to exit. This construction is extremely simple and cheap.

The spring is advantageously a helical spring arranged in a space between the drive shaft and the casing, one end of which rests on a flange or adjusting ring of the drive shaft and the other end on a slide ring, which in turn rests on a shoulder of the casing. This results in a simple and reliable construction of the actuating means, with the lubrication of the slide ring by the fuel being possible. However, it would also be possible to arrange the coil spring and the other elements in a room where the fuel does not flow around them.

The carburetor end of the jacket is advantageously formed by a ceramic tube. This can also be designed as a bearing for the drive shaft of the rotatable device. Such training proves to be expedient because relatively high temperatures occur in this area.

A spray edge is advantageously formed on the periphery of the second axial bearing surface. This allows the oil droplets to be torn off easily during rotation and thus promotes a fine distribution of the fuel.

If it were also possible to design the carburetor chamber as a closed chamber protected from air access, according to one embodiment of the invention, the carburetor chamber is provided with an air inlet in the region of the jacket surrounding the drive shaft. The mixing of fuel and air before combustion enables the burner to operate quietly. Furthermore, the air supply in the vicinity of the drive shaft cools it and thus protects the bearings and the motor.

A recirculation inlet is expediently additionally arranged at the air inlet, a coaxial arrangement being particularly simple and expedient. This enables recirculation of hot exhaust gases, which heats up the carburettor housing and the carburetor chamber. This has the advantage that no electrical heating is necessary after the start-up phase. The heat of vaporization is therefore supplied by the flame. The build-up of deposits is prevented by strongly heating the carburetor housing. The suffering frost effect prevents the microscopic oil droplets from touching the hot wall. Instead, the oil droplets dance on a kind of air cushion until they have completely evaporated. The desired strong heating of the carburetor chamber wall can be achieved in particular by arranging the recirculation inlet on the periphery of the air inlet. An electrical heater for the starting phase is expediently arranged on the wall of the carburetor housing at the recirculation inlet. Since hot gases recirculate immediately after the flame has formed, the electrical heating can be made relatively small and can be switched off shortly after starting.

The carburetor housing is advantageously formed by a cylindrical or conical tube. This results in a particularly simple and cheap construction of the carburetor housing. The inside of the tube is advantageous with a larger surface insert, e.g. a metal mesh. This facilitates the evaporation of the fuel.

If it were also possible for the rotatable device in the evaporator chamber to have only the described second axial bearing surface, in order to serve the distribution of the oil, it proves to be advantageous to further design the rotatable device as a rotor provided with blades, the blades of which extend up to the proximity of the inner wall of the tube is sufficient. An even better distribution of the fuel is then achieved by means of this rotor. In addition, there is intensive mixing of the fuel with air and a promotional effect for the fuel / air mixture in addition to the other advantages which are described in EP-A 0 166 329 mentioned at the outset.

A device that can be controlled by a heating controller, e.g. a pressure reducing valve provided to regulate the pressure in the fuel supply line. Depending on the heating requirement, the pressure can be regulated between approximately 0.5 and 5 bar, which corresponds to regulating the output in a ratio of 1 to 10. This regulation can thus be carried out in a simple and reliable manner using very simple means. Since operation with a throughput of approximately 0.1 kg of fuel per hour is also possible, the burner can also be used where so-called cup burners were previously used. Cup burners burn with a strongly sooting flame, produce exhaust gases that are heavily contaminated, are not very reliable and require a lot of maintenance work. Replacing cup burners with environmentally friendly and reliable burners is therefore an old but not yet achieved goal.

It is possible to arrange a further bearing at the motor-side end of the casing and to provide a connection to the pressure side of the fuel pump on the side of the casing further away from the motor and to provide a connection for the suction side of the fuel pump on the other side of the further bearing. In this way, any leakage oil flowing through the further bearing is continuously drawn off. There are therefore no sealing problems.

A particularly simple embodiment of the invention is characterized in that the casing has two bearings arranged at a distance from one another for mounting the drive shaft, between which a space is arranged, that a connection for the pressure side of the fuel pump is provided between the bearings and that a passage from the space mentioned is arranged to the recess in the axial bearing surface. This results in an extremely simple construction. This simple construction is particularly suitable in the event that work is carried out with low pressures. At low pressures, there are hardly any sealing problems, so that a construction in which a connection is provided for the suction side of the fuel pump can be dispensed with.

The device that can be controlled by the heating control is a so-called Volustat with particular advantage. This is understood to mean a device which, according to an input signal, delivers a corresponding delivery volume which is practically not influenced by resistances in the delivery line. The delivery volume is hardly influenced by the viscosity of the fuel. When using a Volustat, it is possible to keep the force required to move the two axial bearing surfaces apart or towards one another to a minimum. In other words, this means that a relatively soft spring with a flat spring characteristic can be used. This in turn means that the pressure of the liquid fuel in the jacket is always low, so that there are no sealing problems. No special precautions need to be taken, e.g. Suction, to ensure a good seal. When using a Volustat, pressures of about 0.3 to 0.8 bar are generated with a fuel throughput of 0.4 to 2.5 kg per hour.

• Fig. eine Ansicht des Brenners,
• Fig. 2 einen Schnitt durch den Brenner von Figur I,
• Fig. 3 eine bevorzugte, vereinfachte Ausführungsform der leicht auswechselbaren Einheit 12 von Figur 2.

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

• 1 is a view of the burner,
• 2 shows a section through the burner of FIG. I,
• 3 shows a preferred, simplified embodiment of the easily exchangeable unit 12 from FIG. 2.

The burner shown in the drawing has a motor II which serves to drive the fuel pump 13, the fan 15 and the rotatable device 17. The rotating device 17 is part of an easily replaceable unit 12. The rotating device 17 is connected via the drive shaft 19 and the coupling 21 to the motor shaft, which is not visible in the drawing. A jacket 23 enclosing the drive shaft 19 serves as a fuel supply element in a carburetor chamber 25. In the exemplary embodiment shown, the jacket 23 is formed by the adapter sleeve 27 and a ceramic tube 29 inserted at the end of the adapter tube on the carburetor side. The ceramic tube is firmly connected to the adapter sleeve by the screw 31 and also serves as a bearing for the drive shaft 19. Instead of the parts 27 and 29, the jacket 23 could also consist of a piece of metal. However, a ceramic bearing 29 has the advantage that it is very heat-resistant and can therefore withstand the high temperatures in the carburetor chamber 25.

Another bearing 33 for the drive shaft 19 is arranged in the vicinity of the motor-side end of the adapter sleeve 27. A mechanical seal 35 is located in front of this bearing. A lip seal 37 is arranged at a distance behind the bearing 33.

From the pressure side of the fuel pump 13, the line 39 leads to a connection 41, which leads to the space 43 between the two bearings 29 and 33. Another connection 45 is used to extract any leakage oil from the space 47 between the bearing 33 and the seal 37. The line 49 leads from the connection 45 to the suction side of the fuel pump 13.

It is of particular importance that axial bearing surfaces 51 and 53 are provided both on the ceramic tube 29 and on the rotatable device 17, and that adjusting means are provided in order to move these axial bearing surfaces 51, 53 apart or towards one another in order to produce fuel in accordance with the heat requirement let the jacket 23 in the carburetor chamber 25. A recess 55 on an axial bearing surface 53 and a helical spring 57 in the space 43 between the drive shaft 19 and the adapter sleeve 27 serve as adjusting means. One end of the helical spring 57 rests on the adjusting ring 59, which is fastened to the drive shaft 19 with a screw 61. The other end of the coil spring 57 bears against a slide ring 63 which bears against an end face of the bearing 29. The coil spring 65 serves to press the mechanical seal 35 against the bearing 33.

The coil spring 57 acts on the adjusting ring 59 and is therefore endeavored to press the axial bearing surface 53 against the axial bearing surface 51. As long as this pressure is high enough, no fuel can flow into the carburetor chamber 25. However, if the oil pressure in the chamber formed by the recess 55 is large enough, it moves the device 17 against the force of the spring 57 in the axial direction to the right, so that the two axial bearing surfaces 51 and 53 move apart and release a gap through the fuel can flow into the carburetor chamber 25. The higher the pressure in the line 39, the more the gap opens and the more fuel flows into the carburetor chamber 25. To enable this flow, a groove 67 extends in the axial direction from the chamber 43 to the recess 55 in the device 17. Since the device 17 rotates during operation, the fuel droplets are thrown in the radial direction in the gasifier chamber 25 at high speed by the centrifugal force. The spraying of the fuel is further facilitated by the fact that a spraying edge 69 is provided on the periphery of the axial bearing surface 51.

The carburetor chamber 25 has an annular air inlet 71 in the area of the bearing 29. Coaxial with this air inlet 71 is an annular recirculation inlet 73 through which hot fuel gases came into the gasifier from the flame can flow back. At the recirculation inlet 73, an electrical heater 77 is arranged on the wall of the carburetor housing 75. The carburetor housing 75 is formed by an approximately cylindrical or conical tube. The inside of this tube 75 is provided with a surface-increasing insert 79, for example a metal mesh. This facilitates the evaporation of the fuel. A flame tube 81 is provided coaxially and at a distance from the carburetor chamber. The flame tube 81 is divided by a ring 83 into a front part 85 and a rear part 87. In the front part 85, which forms the actual flame tube, there is a tubular insert 89 made of heat-insulating ceramic fibers.

A support 93 is fastened on the adapter sleeve 27 with the screws 91 and carries the ignition electrode 95 and the air screen 96. The air inlet 71 is located in the air panel 96. Between the air panel 96 and the ring 83 connected to the flame tube 81 there is an annular heat-resistant seal 91 '. In the exemplary embodiment shown, the rotatable device 17 is designed as a rotor provided with blades 98. The blades 98 extend into the vicinity of the inner wall of the carburetor housing 75. They bring about a good mixing of fuel, air and recirculated gas, the mixture compressed by the blades 98 being able to flow out through an annular opening 99 between the carburetor housing 75 and the rotor 17.

The rotor 17 is fastened with a screw 18 at the end of the drive shaft 19. The end of the rotor 17 is covered by a plate 20.

From the drawing it can be seen that the flame tube 81 can be easily removed from the fan housing 14 by loosening screws 16. For service work, the unit 12 can also be removed after loosening the fuel line connections 41, 45 and the screw 24. This unit 12 essentially comprises the casing 23 with all the mechanics, the carburetor 25 and the ignition electrode 95.

A device 22 that can be controlled by the heating controller 26 is provided in order to regulate the fuel supply. The commercially available fuel pumps usually have means, e.g. a pressure reducing valve, with which the desired pump pressure can be set manually. Instead of the manual setting, an actuator is provided in the burner according to the present exemplary embodiment. In this exemplary embodiment, the controllable device 22 consists of an actuator and the means mentioned for setting the pump pressure. The device 22 can be actuated by the heating control 26. In the simplest case, the actuator is a solenoid, with which the pump pressure is changed, for example, from 2 bar to 4 bar according to the heat requirement. The burner then works as a two-stage burner. When using two solenoids, four different levels are also possible. However, if a servomotor is used, it is possible to continuously regulate the pump pressure from, for example, 0.5 to 5 bar.

At the start, the heater control 26 first turns on the electric heater 77 for about two minutes. During this time, the heater 77 and the adjacent insert 79 are heated to approximately 550 _° . After this preheating time has elapsed, the actual starting phase takes place in the usual way as with an atomizer burner. The pressure of the fuel in the recess 55 causes a force which tends to move the rotor 17 to the right in the axial direction against the force of the coil spring 57, so that a gap is opened between the axial bearing surfaces 51 and 53 by the fuel in the carburetor chamber 25 is thrown. When the oil droplets strike the hot surface of the insert 79, an oil vapor is formed which is mixed with the combustion air by the rotor 17. When the mixture emerges from the gap 99, it is ignited by the electrode 95, and a blue flame immediately arises. Some of the hot gases that are now produced are sucked in by the injector effect of the air entering through the air inlet 71 and flows through the space between the carburetor housing 75 and the insert 89 to the recirculation inlet 73 and through this into the carburetor chamber. From now on, these hot combustion gases ensure the heat supply necessary for the evaporation, so that after the start-up phase the electric heater 77 can be switched off completely. Since both the rotor 17 and the bearing 29 heat up during operation, the oil is heated before spraying. An additional oil preheater is therefore not necessary. Due to the recirculated combustion gases, all parts of the carburettor are heated up so that, thanks to the presence of oxygen, continuous self-cleaning takes place.

As has already been explained in more detail earlier, the oil throughput can be changed in individual stages or continuously depending on the heating requirement. In the shutdown phase, when the oil pressure in the line 39 drops, the helical spring 57 causes the rotor 17 to move axially to the left, so that the axial bearing surface 51 rests on the axial bearing surface 53 and no more fuel can escape. This reliably prevents afterburning.

It should also be noted that any leakage oil is constantly sucked out of the space 47 via the line 49. Should the lip seal 37 become defective, the pump 13 draws in air via the leak that has occurred, so that the burner goes into a fault.

It has already been mentioned in the description of FIG. 2 that the flame tube 81 can be easily removed from the fan housing 14 by loosening screws 16. The unit 12 can also be easily removed. Figure 3 now shows a preferred embodiment of the unit 12. It is structurally much simpler than the unit 12 shown in Figure 2 and therefore also significantly cheaper to manufacture.

In the unit 12 shown in FIG. 3, the rotatable device 17 is in turn driven by the motor II (FIG. I) of the burner via the drive shaft 19 and the clutch 21. A the drive shaft 19th enclosing jacket 23 serves as a fuel supply member in the carburetor chamber 25. The jacket 23 is formed by the adapter sleeve 27 and the bearings 29 and 33. The bearings 29 and 33 advantageously consist of a suitable bearing material, for example a sintered material. It would also be possible to form the jacket 23 from a single piece of metal. At the end of the sleeve 23, a lip seal 37 is fastened by means of a spring ring 36.

As indicated schematically, a connection 41 is provided, to which the line 39 can be connected, which is used to supply fuel.

It is again of particular importance that axial bearing surfaces 51 and 53 are provided, and that adjusting means are provided in order to move these axial bearing surfaces 51, 53 apart or towards one another in order to admit fuel from the jacket 23 into the carburetor chamber 25. On the one hand, a recess 55 in an axial bearing surface 51 and, on the other hand, a helical spring 57 serve as adjusting means. One end of the helical spring 57 rests on the adjusting ring 59, which is fastened with a screw 61 on the drive shaft 19. The other end of the coil spring 57 bears against a slide ring 63 which bears against an end face of the bearing 33.

The helical spring 57 acts on the adjusting ring 59 connected to the drive shaft 19 and therefore endeavors to press the axial bearing surface 51 against the axial bearing surface 53. As long as this pressure is high enough, no fuel can flow into the carburetor chamber 25. However, if the oil pressure in the chamber formed by the recess 55 is large enough, it moves the device 17 against the force of the spring 57 in the axial direction to the right, so that the two axial bearing surfaces 51 and 53 move apart and release a gap through the fuel can flow into the carburetor chamber 25. The higher the pressure of the line 39, the more the gap opens and the more fuel flows into the carburetor chamber 25. In order to enable this flow, a groove 67 extends in the axial direction from the chamber 43 to the recess 55. Since the device 17 rotates during operation, the fuel droplets are thrown at high speed in the radial direction into the carburetor chamber 25 by the centrifugal force. The spraying of the fuel is further facilitated in that a spraying edge 69 is provided on the rotating part 70. The rotating part 70 is firmly connected to the drive shaft 19 with the screw 18 together with the device 17.

The carburetor chamber 25 has an annular air inlet 71 in the area of the bearing 29. This air inlet is formed by the conical part 72 of the air screen 96.

This conical configuration results in an advantageous air flow into the gasification chamber, which favors the recirculation of the hot fuel gases. Coaxial with the air inlet 71 is namely an annular recirculation inlet 73 through which the hot fuel gases can flow back into the gasification chamber 25 from the flame. At the recirculation inlet 73, an electrical heater 77 is arranged on the wall of the carburetor housing 75. The carburetor housing 75 is formed by an approximately cylindrical tube. The inside of this tube 75 is provided with a surface-increasing insert 79, e.g. a metal mesh. The flame tube 81 surrounding the unit 12 is indicated by dash-dotted lines in FIG. With regard to the flame tube 81, reference is made to the description of FIG. 2.

On the adapter sleeve 27, a support 93 is fastened with screws 91, which supports the ignition electrode 95 (FIG. 2) (not shown in FIG. 3) and the air panel 96.

In the exemplary embodiment in FIG. 3, the rotatable device 17 is also designed as a rotor provided with blades 98.

For the exemplary embodiment with the easily replaceable unit 12 from FIG. 3, a Volustat is advantageously used as the controllable device 22. It is a device that delivers a delivery volume corresponding to an applied control signal. When using a Volustat, the spring 57 only has to perform a closing function when the burner is switched off. The spring 57 can thus have a flat spring characteristic and be relatively soft. As a result, there are only slight pressures in the jacket 23. With a small burner, they range from about 0.2 to about 0.6 bar, corresponding to a fuel throughput of 0.4 to 2.5 kg per hour. At these pressures, the seal 37 is generally sufficient, so that further sealing measures, such as are provided in the exemplary embodiment in FIG. 2, can generally be dispensed with. However, it is apparent to the person skilled in the art that a Volustat 22 could also be used in combination with a unit 12 according to FIG. 2.

Tests have shown that about 50 percent less nitrogen oxides are generated in the burner according to the invention than in a normal atomizer burner. It is believed that this is due to the fact that the combustion is not limited to a relatively small space as in an atomizing burner, but extends over a relatively large space, so that a relatively low flame temperature arises.

Claims (22)

1. A burner comprising a motor (11) to drive a fan (15) and/or a fuel pump (13); a gasification chamber (25) formed by a housing (75), said gasification chamber (25) being provided with at least one heatable wall; rotatable means (17) located in the gasification chamber (25), said rotatable means (17) having a drive shaft (19) coupled to the motor (11); and a sleeve (23) enclosing the drive shaft (19) and serving as fuel supply means into the gasification chamber (25); characterized in that a first axial bearing surface (51) is provided by the end of the sleeve (23) located proximate to the gasification chamber (25), that the rotatable means (17) provide a second axial bearing surface (53), and that actuating means (55, 57) are provided to move the two axial bearing surfaces (51, 53) apart from each other or toward each other to supply fuel into the gasification chamber (25) according to the heating requirements, or to stop fuel supply.

2. The burner according to claim 1, characterized in that the actuating means comprise hydraulic means (55) and a spring (75).

3. The burner according to claim 2, characterized in that the hydraulic means are formed by a recess (55) adjacent to the axial bearing surface (53).

4. The burner according to claim 2 or 3, characterized in that the spring (57) is a helical spring located in a space (43) between the drive shaft (19) and the sleeve (23), said helical spring resting with one end at a flange or setting ring (59) of the drive shaft (19) and with the other end at a slip ring (63) which itself rests on a shoulder of the sleeve (23).

5. The burner according to one of the claims 1 to 4, characterized in that at the periphery of an axial bearing surface (51; 53) a spray rim (69) is located.

6. The burner according to one of the claims 1 to 5, characterized in that the end of the sleeve located proximate to the gasification chamber (25) is formed by a ceramic tube (29).

7. The burner according to claim 6, characterized in that the ceramic tube (29) is also a bearing for the drive shaft (19) of the rotatable means (17).

8. The burner according to one of the claims 1 to 7, characterized in that in the region of the sleeve (23) enclosing in the drive shaft (19) the gasification chamber (25) comprises an air inlet (71).

9. The burner according to claim 8, characterized in that the gasification chamber (25) comprises a recirculation gas inlet (73).

10. The burner according to claim 9, characterized in that the air inlet (71) and the recirculation gas inlet (73) are arranged coaxially.

11. The burner according to claim 10, characterized in that the recirculation gas inlet (73) is located at the periphery of the air inlet (71).

12. The burner according to one of the claims 1 to 11, characterized in that, proximate to the recirculation gas inlet (73) an electric heater (77) is located on the wall of the housing of the gasification chamber (25).

13. The burner according to one of the claims 1 to 12, characterized in that the housing (75) is formed by a substantially cylindrical or conical tube.

14. The burner according to claim 13, characterized in that the inner surface of the tube (75) is provided with a surface increasing insert, e.g. a metal gauze (79).

15. The burner according to one of the claims 1 to 14, characterized in that the rotatable means (17) are provided by a rotor having blades extending close to the inner surface of the tube (75).

16. The burner according to claim 15, characterized in that between the end of the rotor and the housing (75) a slot (99) is provided as an outlet for the gas/air mixture.

17. The burner according to one of the claims 1 to 16, characterized in that a flame tube (81) is located coaxially to and at a distance to the gasification chamber (25).

18. The burner according to one of the claims 1 to 17, characterized in that a control device (22) controllable by the heating control (24) to control the supply of fuel is provided.

19. The burner according to one of the claims 7 to 18, characterized in that near the end of the sleeve (23) located near the motor, a further bearing (33) is located, and that on the side of the further bearing (33) distant from the motor a connector for the pressure side of the fuel pump (13) is located on the sleeve (23) and that on the other side of said further bearing (33) a connector (45) is provided for the suction side of the fuel pump (13).

20. The burner according to one of the claims 1 to 5, characterized in that the sleeve (23) comprises two bearings (29, 33) spaced from each other for support the drive shaft (19), a space (43') being provided between the bearings (29, 33), said space (43') serving as fuel duct; in that a connector (41) for the fuel supply is provided, and in that a duct (67) from said space (43') to the recess (55) in the axial bearing surface (53) is provided.

21. The burner according to one of the claims 8 to 20, characterized in that the air inlet has a conical section (72).

22. The burner according to one of the claims 18 to 21, characterized in that control device (22) controlled by the heating control (26) is a volustat.

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