EP0166329B1 - Burner, especially a burner for burning liquid fuel in the gaseous state - Google Patents

Abstract

1. Burner, particularly burner for the combustion of liquid fuel in the gaseous state, comprising a gasification chamber (11) formed by a housing (13), and a rotor (33) located in the gasification chamber (11), said rotor (33) being provided with blades (31) and capable of bieng driven by a motor (37), said gasification chamber (11) comprising inlet means (41, 43 ; 45) for fuel and air, a wall surface (12) capable of being heated electrically and/or by the flame of the burner for evaporating the fuel, and means (29) for discharging the produced fuel/air mixture, characterized in that the blades (31) of the rotor (33) extend radially to the proximity of the heatable wall surface (12).

Description

The invention relates to a burner, in particular a burner for burning liquid fuels in the gaseous state. However, the burner is also suitable for the combustion of suspensions of solid fuels in a carrier liquid. The burner has a gasification chamber formed by a housing and a rotor arranged in the gasification chamber and provided with blades and driven by a motor, the gasification chamber having inlet means for fuel and air, a wall surface which can be heated electrically and / or by the flame of the burner for the evaporation of the Has fuel and means for outlet of the fuel / air mixture generated.

In household burners of conventional design, 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 cannot be regulated continuously down to a low output. Atomizer burners are designed for maximum performance and are operated intermittently with low heat requirements. Therefore, relatively large boilers are required as energy storage for the breaks. The repeated start-up of the burner brings a strong change in temperature of the materials as well as a high soot and pollutant load in the boiler; Chimney and exhaust. Incomplete combustion and soot formation have a significant impact on the overall efficiency of a heating system. Radiation losses due to large boilers also contribute to a reduction in efficiency.

In contrast to atomizing burners, gasification burners have the advantage that they can be regulated continuously to very low outputs in accordance with the heating requirement, the aforementioned disadvantages being avoided. Furthermore, combustion significantly reduces the emission of pollutants, for example unburned hydrocarbons and soot.

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. With many gasification burners, undesirable deposits can form in the gasification chamber, which will soon significantly impair the effectiveness of the gasification.

EP-A 0 036 128 describes a carburetor burner with a carburetor chamber which has no air inlet openings and in which a wiper which rotates quickly with a motor is accommodated in order to finely distribute the fuel on the heated carburetor walls and to prevent the formation of deposits 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. This burner has the advantage that it requires little maintenance and is reliable in operation. The disadvantage, however, is that, in contrast to other gasification burners, where fuel and air are mixed before combustion in the gasification chamber, it causes more noise. Since only the fuel is heated at the start, but not the air before the combustion, cold start problems can arise. It is also disadvantageous that after-burning takes place with a sooting flame, unless particularly expensive measures are taken to prevent the further escape of gasified fuel.

EP-A 0067271 shows an oil burner with a heated evaporation device having air inlet openings. This 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, which fills the evaporator space in the cup to a small gap. For 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 surface and transports it to the drive motor via the drive shaft, which can be damaged if costly precautions are not taken to protect it.

US-A 3640673 describes a burner for a petroleum oven, in which a fan is arranged in a 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 gasification chamber. Since the distance between the periphery of the fan and the heated wall surface of the gasification chamber is relatively large, most of the fuel evaporates droplets 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 can form on the walls, which adversely affect evaporation, particularly in the start-up phase when the gasification chamber is only electrically heated. 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.

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 described, in particular ensures quiet operation and requires little maintenance work.

According to the invention, this is achieved in that the blades extend radially into the vicinity of the heatable wall surface.

The fuel / air mixture generated in the gasification chamber leaves the gasification chamber under relatively high pressure, so that the burner is particularly suitable for use in boilers with a relatively high flue gas resistance. Since the air and fuel are mixed before the combustion, the flame is relatively silent. Tests have shown that no deposits form in the area of the heated wall surface of the gasification chamber. It is assumed that the high peripheral speed of the rotor tears the oil out into extremely small oil droplets, which evaporate immediately. Interestingly, relatively high temperatures of the carburetor chamber walls are possible without coking. It is assumed that the blades, which bring about a compression of the gas / air mixture, exert a pneumatic wiper action, which cleans the gasification chamber walls. In any case, the rotating blades ensure a considerable pressure difference between the air inlet and the fuel / air mixture outlet, so that a considerable cleaning effect is already achieved by the flow caused thereby. The burner is therefore largely maintenance-free. Since the gas emerging from the gasification chamber is a mixture of fuel and air, there are no cold start problems. It is also advantageous that the heatable wall surface of the gasification chamber is adjacent to the peripheral parts of the rotor. The fuel / air mixture has the highest compression in this area, so that the heat transfer takes place very effectively here.

A wall of the gasification chamber is expediently formed by a burner plate having outlet openings. The flame thus arises directly at the gasification chamber, so that heat from the flame is already released into the gasification chamber via the burner plate. This significantly reduces the need for electrical energy, at least after the start-up phase. The outlet openings of the gasification chamber are expediently arranged near the periphery of the burner plate. The pressure is greatest there.

An advantageous embodiment of the invention provides that the housing of the gasification chamber for heat recovery has a part which extends beyond the burner plate. This expediently tubular part is then located in the immediate area of the flame, so that the heat recovery is very good. It is possible to form the housing of the carburetor chamber and a flame tube in one piece. This lowers the manufacturing costs. The heat recirculation part may have a cavity which is filled with a metal, e.g. Sodium, is provided with a relatively low melting and / or evaporation point. During operation, the metal in the cavity melts and / or evaporates, and the circulation that arises in the melt or in the gas then ensures particularly effective heat recovery.

An advantageous exemplary embodiment provides that an axially displaceable tube piece for regulating the air supply is provided practically concentrically to the shaft of the rotor.

The rotor advantageously extends in the immediate vicinity of the burner plate. Tests have shown that this prevents the flame from kicking back into the gasification chamber.

The transition points between the part for heat recovery and the housing of the gasification chamber can be designed such that no heat transfer to the housing of the gasification chamber takes place that exceeds the optimal gasification temperature. In this case, at least a large part of the heat required for evaporation can be supplied by the flame, while the electric heater only has to deliver a fraction of the necessary evaporation energy.

The rotor can be designed both as a radial compressor and as an axial compressor. Both types of rotors make it possible, at least in the case of relatively small burners, such as those used for single-family houses and smaller multi-family houses, to do without additional fans, which leads to considerable simplification and cost reduction.

The means for supplying fuel can be formed by a fuel supply channel which leads through the drive shaft of the rotor to the periphery of the rotor. This causes the drive shaft to cool so that there are no bearing problems for the drive shaft. In addition, the design of the rotor with blades has the advantage that it absorbs less heat than a rotating cylinder. A temperature sensor for maintaining an optimal carburetor temperature can be provided on the housing of the carburetor chamber.

When operating at high temperatures he is desired, the housing of the carburetor chamber can consist of ceramic or be coated on the inside with ceramic. The ceramic can also act as a catalyst for better gasification.

• Fig. 1 eine schematische Darstellung, im Schnitt, eines Ausführungsbeispiels des erfindungsgemässen Brenners,
• Fig. 2 einen Schnitt durch eine besondere Ausführungsform des Vergasergehäuses,
• Fig.3 die Ausbildung des Rotors als Radialverdichter,
• Fig. 4 die Ausbildung des Rotors als Axialverdichter, und
• Fig. 5 eine schematische Darstellung eines weiteren Ausführungsbeispiels des erfindungsgemässen Brenners.

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

• 1 is a schematic representation, in section, of an embodiment of the burner according to the invention,
• 2 shows a section through a special embodiment of the carburetor housing,
• 3 the design of the rotor as a radial compressor,
• Fig. 4 shows the design of the rotor as an axial compressor, and
• Fig. 5 is a schematic representation of another embodiment of the burner according to the invention.

The burner has a gasification chamber 11, which is formed, for example, by a housing 13. Depending on the expected operating temperatures of the burner, this housing can be made of cast aluminum or cast iron, for example. In the embodiment shown, the gasification chamber 11 has the shape of a rotating body, e.g. of a cylinder. However, as FIGS. 3 and 4 show, other rotational body shapes are also possible. When working at high temperatures, which is particularly expedient at high burner outputs, a carburetor chamber housing 13 made of ceramic material or a coating of the carburetor chamber walls made of ceramic material is also recommended. If working at relatively low temperatures, a coating made of a heat-resistant plastic, e.g. "Teflon" can be an advantage because such material prevents fuel residues from adhering.

An electric heating element 15 in the form of a heating coil is used to heat the gasification chamber 11. The wall 12 is heated by this heating winding 15. In order to maintain an optimal gasification temperature, a temperature sensor 17 can also be provided, with which the electrical heating element 15 is controlled via a control device (not shown). The gasification chamber 11 has a part 21 which extends beyond the burner plate 19 to return heat from the flame. In the exemplary embodiment shown, the part 21 encloses a flame tube or cup 23. The transition point 22 between the flame tube 23 and / or the part 21 and the housing 13 is designed in such a way that no heat transfer that exceeds the optimum gasification temperature takes place. As FIGS. 3 and 4 show, housing 13 and flame tube 23 or flame tube 23 and burner plate 19 can also consist of one piece. Figure 2 shows a special design of part 21 for heat recovery. It has a cavity 25 which has a filling 27 made of a metal, e.g. Sodium, with a relatively low melting and / or evaporation point. When the burner is in operation, the metal 27 then melts and / or evaporates, so that circulation begins in this liquid or gaseous medium, which transfers heat to the region of the gasification chamber 11.

A wall of the gasification chamber 11 is formed by the burner plate 19, which has a plurality of outlet openings 29 for the hot fuel / air mixture on the periphery. In the exemplary embodiment in FIG. 1, the outlet openings 29 are arranged close to the periphery of the burner plate 19. The greatest pressure in the chamber prevails when using a radial fan. However, as FIG. 4 shows, a distribution of the outlet openings 29 over the burner plate 19 is possible in particular when using an axial fan.

It is of great importance that in the gasification chamber 11 there is not only a wiper for cleaning the heatable wall surfaces of the gasification chamber 11, but a rotor 33 provided with blades 31, the blades extending radially into the vicinity of the heatable wall surface. This rotor has the function of a wiper, which keeps the carburetor chamber 11 free of deposits. At the same time, however, the rotor 33 also functions as a fan which draws in combustion air and, mixed with evaporated fuel, presses it through the openings 29 in the burner plate 19. A significant advantage of the gasification burner described is therefore that, at least for relatively low outputs, for example up to 1.2 kg of oil per hour, it does not need an additional fan 35.

The rotor 33 is driven by the motor 37 via the shaft 39. The additional fan 35, which may be necessary for greater burner outputs, is located on the same shaft 39. The fuel is supplied through a fuel supply channel 41 via the drive shaft 39. This fuel supply channel leads via one or more branch lines 43 to the periphery of the rotor 31.

The air is fed into the gasification chamber 11 through the air inlet opening 45. A pipe section 46 is arranged displaceably in this air inlet opening. The air supply can be regulated in a simple manner by an axial displacement of this pipe section 46.

Tests have shown that it is expedient for the rotor 33 to extend in the immediate vicinity of the burner plate 19. This prevents the flame from striking back into the gasification chamber 11.

While a conventional fan wheel from a commercial oil burner is used as the rotor 33 in FIG. 1, FIGS. 3 and 4 provide for the use of a radial or axial compressor, as used, for example, for turbochargers Find motor vehicles use. Rotors 33 constructed in this way enable higher compression, so that an additional fan wheel can usually be dispensed with even at relatively high powers.

When the burner is started up, the housing 13 with the electric heater 15 is initially brought to a temperature at which the supplied fuel evaporates. The vaporized fuel then escapes through the openings 29 and is ignited by the electrode 49. The resulting flame then causes heat to be returned via part 21 of the gasification chamber 11, so that the heater 15 can be switched off. However, if precise regulation of the gasifier temperature is desired, the heater 15 can be used to supply the additional heat required. The temperature sensor 17 is used to control the heater 15.

However, previous tests have shown that the gasification burner according to the invention can operate reliably in a wide temperature range of the gasification chamber 11. While the gasification burner according to EP-A 0 036128 no longer works at a gasification chamber temperature below 340 ° C, because at this temperature the pressure builds up too slowly and the gasification chamber is thus overfilled with fuel, the burner according to the invention also works at temperatures below 340 ° C. In tests with temperatures around 500 ° C., oil throughputs of 2 kg per hour could be achieved with the burner according to the invention. It has also been shown that there are no corking problems at high temperatures. It is assumed that at high temperatures the heating oil does not come into contact with the carburetor walls due to the suffering frost effect.

In addition to the advantages already mentioned, the burner described also offers a large number of further advantages. For example, there are no temperature problems on the engine side because the combustion air cools it. It is therefore not necessary to take any special measures to protect the drive shaft bearings. The flame cup is exposed to less high temperatures because heat is continuously dissipated. There are also no cold start problems because the combustion air is preheated. The burner is very simple and compact in construction and is therefore particularly suitable as a burner for floor heating. The burner is switched off without re-steaming. The burner can easily be used for heating from above (lint burner) or heating from below. Of particular importance, however, is the low-noise combustion thanks to the optimal mixture of air and fuel and the stable blue flame, which creates no soot problems. The gasification burner according to the exemplary embodiment of FIG. 5 is constructed similarly to that of FIG. 1. The same reference numerals can therefore largely be used. In the burner of FIG. 5, the rotor divides the gasification chamber 11 into a first space 51 and a second space 53 arranged concentrically to it. The first space 51 is used to gasify the fuel. The second space, which is divided by approximately radially arranged partition walls 55, which act like the blades of a compressor, serves as an air compressor. If a fan is already present in any case, further air compression may be dispensed with, so that it would suffice if the second space 53 merely served as an air passage. Since a burner plate 19 is provided in the exemplary embodiment shown, a third space 54 is formed between the rotor 33 and the burner plate 19, which serves for the mixing of gas and air.

A gap 59 is provided between the rotor end 57 and the carburetor housing 13 for the passage of the gasified fuel from the first space 51. This gap 59 is ring-shaped and is adjacent to the likewise ring-shaped outlet 58 for the air from the space 53. Thus, when the air flows out of space 53 of the rotor at high speed, it helps to convey gasified fuel out of space 51 through the Venturi effect. This is mixed with air in the space 54 and leaves the burner through the openings 29 to form a blue flame.

The first space 51 has at least one air inlet 61 in order to carry out a premixing of gas and air in this space 51. In contrast to the exemplary embodiment described first, however, a large part of the air required for combustion flows through space 53. However, it would also be possible to carry out the gasification in space 51 without air supply. The air supply to the space 51 can be controlled by axially displacing the pipe section 46.

Claims (22)

1. Burner, particularly burner for the combustion of liquid fuel in the gaseous state, comprising a gasification chamber (11) formed by a housing (13), and a rotor (33) located in the gasification chamber (11), said rotor (33) being provided with blades (31) and capable of being driven by a motor (37), said gasification chamber (11) comprising inlet means (41, 43; 45) for fuel and air, a wall surface (12) capable of being heated electrically and/or by the flame of the burner for evaporating the fuel, and means (29) for discharging the produced fuel/air mixture, characterised in that the blades (31) of the rotor (33) extend radially to the proximity of the heatable wall surface (12).

2. Burner according to claim 1, characterised in that the rotor (33) divides the gasification chamber (11) into a first and a second section (51, 53) of which the first one (51) serves for gasification and the second one (53) for transportation of air with or without compression.

3. Burner according to claim 1, characterised in that the rotor (33) divides the gasification chamber (11) into three sections of which the first one (51) serves for gasification, the second one (53) for transportation of air with or without compression, and the third one for mixing gas and air.

4. Burner according to one of the claims 1 to 3, characterised in that between the end (57) of the rotor and the housing (13) of the gasification chamber a gap (59) is provided as passage for gasified fuel.

5. Burner according to claim 4, characterised in that the gap (59) for passage of gasified fuel is located close to the second section (53).

6. Burner according to one of the claims 2 to 5, characterised in that the first section (51) comprises at least one air inlet (61) in order to provide in this section a premix of gas and air.

7. Burner according to one of the claims 1 to 6, characterised in that a wall of the gasification chamber (11) is formed by a burner plate (19) provided with outlet openings.

8. Burner according to claim 7, characterised in that the outlet openings (29) are located close to the periphery of the burner plate (19).

9. Burner according to one of the claims 1 to 8, characterised in that the housing (13) of the gasification chamber (11) comprises a part (21) extending beyond the burner plate (19) to provide a heat reflux.

10. Burner according to claim 9, characterised in that said part (21) for heat reflux encloses a flame tube (23).

11. Burner according to claim 10, characterised in that the housing of the gasification chamber (11) and the flame tube (23) are an integral part.

12. Burner according to one of the claims 10 or 11, characterised in that the part (21) for heat reflux comprises a cavity (25) provided with a filling (27) of a metal, e.g. sodium, having a relatively low melting and/or gasification point.

13. Burner according to one of the claims 9 to 12, characterised in that the transition zone between the flame tube (23) and/or the part (21) for heat reflux and the housing (13) of the gasification chamber (11) is constructed in such a way that it does not produce a heat reflux to the housing (13) in excess to optimum gasification temperature.

14. Burner according to one of the claims 1 to 12, characterised in that for control of the air supply an axially movable tubular member (46) is provided practically concentrically to the shaft (39).

15. Burner according to one of the claims 1 to 13, characterised in that the rotor (33) extends to the immediate proximity of the burner plate (29).

16. Burner according to one of the claims 1 to 15, characterised in that the rotor (33) is a radial compressor.

17. Burner according to one of the claims 1 to 15, characterised that the rotor (33) is an axial compressor.

18. Burner according to one of the claims 1 to 17, characterised in that the means for fuel supply are formed by a fuel supply duct (41, 43) which extends through the drive shaft (39) of the rotor (33) to the periphery of the rotor (33).

19. Burner according to one of the claims 1 to 18, characterised in that a temperature sensor (17) for maintaining an optimum gasification temperature is provided at the housing (13) of the gasification chamber (11).

20. Burner according to one of the claims 1 to 19, characterised in that the housing (13) of the gasification chamber (11) consists of ceramic material.

21. Burner according to one of the claims 1 to 19, characterised in that the gasification chamber (11) is on the inside covered with ceramic material.

22. Burner according to one of the claims 1 to 19, characterised in that the gasification chamber (11) is on the inside covered with «Teflon».

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