WO1996034230A1 - Fuel-oil vaporising burner for low outputs - Google Patents

Abstract

The proposed fuel-oil vaporising burner (1) is divided into a combustion chamber (3) and a vaporising chamber (2) arranged above said combustion chamber (3). The heating oil is introduced from above into the vaporising chamber (2) where it is mixed with hot air and thus vaporised. The heating oil vapour is taken downwards from the vaporising chamber (2) into the combustion chamber (30 and is finely divided by two perforated distribution plates (12, 13) an expanded-metal grid (14) and a further grid (22). The oil vapour is burnt at the grid-like combustion chamber wall (21). When the combustion process is started, the air is electrically heated. During operation, the heating oil is vaporised by the heat radiated back from the flame.

Description

 OIL EVAPORATION BURNER FOR SMALL PERFORMANCES

The invention relates to an oil vapor burner for small outputs according to the preamble of claim 1.

Firing systems are usually used to generate heat that is used directly or indirectly. Heating oil, which is burned with the help of oil burners, is often used as fuel. The heat generated is used, for example, for space heating, hot water preparation, for cooking or for industrial processes. The oil burner has to bring the heating oil into a highly flammable condition by atomizing and distributing it. This is the only way to ensure that the heating oil burns out as completely as possible. In addition, the oil burner has the task of mixing the heating oil with the combustion air.

In conventional oil burners, the fine distribution of the heating oil is achieved with atomizing nozzles. It is not possible to dimension oil burners of this type so small that they are suitable for outputs of less than 10 kilowatts. If the heating power is low, the nozzle diameters become very small and then clog up continuously because the heating oil contains impurities and the combustion air contains parts which are larger than the nozzle diameter.

Large oil burners can be operated at low outputs by constantly switching them on and off, but this greatly increases the total pollutant emissions. The relationship between heating oil and combustion air is not correct during the switch-on process for the first 200-300 milliseconds. Clean combustion cannot take place in this phase.

One was therefore looking for designs for oil burners which guarantee complete, low-pollutant combustion of the heating oil even at low outputs. For outputs of less than 10 kilowatts, which corresponds to mass flow rates of less than one kilogram of heating oil per hour, oil burners have therefore been developed in which the fine distribution of the heating oil is achieved not by means of nozzles but by evaporation. However, the known oil evaporation burners have the disadvantage that moving parts are arranged in the room where the evaporation takes place. This makes the oil evaporation burners susceptible to faults and maintenance-intensive. The patent specification CH 626 703 (publication date November 30, 1981) describes, for example, an evaporation burner for heating oil, in which the evaporation takes place with the aid of a variable speed rotor and through a recirculation of hot combustion gases.

An annular flame holder, which is arranged in the front region of the combustion chamber, is used to generate the recirculation of hot combustion gases. The cup-shaped rotor is arranged concentrically to the flame holder at a radial distance. The fuel evaporation takes place on the inner surface of the rotor shell in the heat exchange with the recirculating combustion gases. The flame holder has the function of a ring neck ejector which sucks a mixture of recirculating combustion gases and vaporous heating oil from the cup-shaped rotor into the flame core by means of combustion air. The combustion air flows through an air duct into the combustion chamber.

In addition, the published patent application DE 31 23 078 (published on December 30, 1982) proposes an oil evaporation burner which has a rotating oil distributor which throws the heating oil in finely divided form onto the inner surface of a heated evaporation device. The resulting oil vapor then flows in the direction of the combustion chamber, where it comes into contact with the combustion air and burns. The oil distributor is fed with heating oil by a hollow drive shaft from an oil quantity regulator. An air quantity regulator is coupled with the oil quantity regulator, which precisely doses the combustion air supplied via a blower.

Finally, the patent specification CH 679 516 (publication date February 28, 1992) describes a process for the combustion of liquid fuels with the aid of film evaporation of the Fuel. The film evaporation is brought about by a recirculation swirl flow in a swirl chamber. This recirculation swirl flow of hot combustion gases is driven by a rotor. The recirculation is channeled through a rotating or stationary sleeve. The film evaporation takes place within this sleeve. The combustion of the fuel takes place in the annular space which surrounds the inner sleeve. The rotor, which ensures film evaporation, is either arranged in the sleeve or is formed by the sleeve itself. The rotor is bladed. It can be equipped with wire brushes, which partially replace the blades.

An oil evaporation burner according to the preamble of claim 1 is known from patent specification EP 0 405 481. In this burner, the evaporation chamber and combustion chamber are arranged horizontally one behind the other. The liquid, e.g. Heating oil, is broken up mechanically and only partially evaporated.

The object of the invention is to create an oil evaporation burner for small outputs, which is of simpler construction than the known oil evaporation burner and works more effectively than it.

The object is achieved with the aid of the features of claim 1 according to the invention. Advantageous further developments are the subject of the subclaims.

The proposed oil evaporation burner is divided into a combustion chamber and an evaporation chamber arranged above the combustion chamber. The heating oil is introduced into the evaporation chamber from above. There it is then mixed with hot air and thereby evaporates. The heating oil vapor falls from the evaporation chamber down into the combustion chamber. It burns down on the outside of the curved, lattice-like combustion chamber floor. The air is heated electrically when the combustion process starts. During operation, the heating oil evaporates due to the heat of the flames.

A possible embodiment of the proposed oil vaporization burner is shown in FIG. 1. It shows: 1 shows a section through the proposed oil evaporation burner.

The evaporation chamber 2 in the proposed oil evaporation burner 1 is arranged directly above the combustion chamber 3. It is divided into a cylindrical, broad, lower section 4, a central, frustoconical section 5 and a likewise cylindrical, narrow, upper section 6. A feed passage 7 opens at its upper end face. The longitudinal axis of this feed passage 7 is in relation to the axis of symmetry

8 of the evaporation chamber 2 inclined by approximately 45 °. The feed passage 7 preferably has a circular cross section. His jacket 24 then has the shape of a round tube. The inlet opening

9 for the combustion air is located on the upper end face of the feed passage 7. In an upper section of the feed passage 7 there is also an electrical heating element 10 for heating the combustion air. The oil line 11 opens into a lower section of the feed passage 7.

The middle section 5 and the lower section 4 of the evaporation chamber 2 are separated from one another by a perforated, circular distribution plate 12. Below this perforated distribution plate 12 there is an expanded metal grating 14. Distribution plate 12 and expanded metal grille 14 represent distribution devices for the oil vapor / combustion air mixture.

The expanded metal grid 14 is held by a ring 15 with a U-shaped cross section. The ring 15 is attached to the inside of the jacket 16 of the evaporation chamber 2.

The combustion chamber 3 is divided into an upper cylindrical section 17 and a lower section 18, which preferably has the shape of a hemisphere or a spherical section. The upper section 17 is covered on its upper side with a perforated, circular distribution plate 13. A perforated chrome steel bowl 20, which has the shape of a hemisphere or a ball section, is arranged below this distribution plate 13. It protrudes into the lower section 18 of the combustion chamber 3. Distribution plate 13 and chrome steel bowl 20 provide distribution bodies for the combustion according to.

Immediately above the curved jacket of the lower combustion chamber section 18 there is also a curved grid 22. It also has the shape of a hemisphere or a spherical section. Its inner surface serves for the fine distribution of the oil vapor combustion mixture. The jacket 21 of the combustion chamber 3 serves as a burning surface for the oil vapor combustion mixture.

However, there are also embodiments of the proposed oil vaporization burner 1, in which both the upper section 17 and the lower section 18 of the combustion chamber 3 are hollow-cylindrical (not shown). In this case, the perforated chrome steel bowl 20 is also cylindrical and has a circular, flat bottom. In addition, the grid 22 is also flat and circular. The burning surface for the oil vapor combustion mixture is formed by the flat bottom of the combustion chamber 3.

The jacket 21 of the combustion chamber 3, the jacket 16 of the evaporation chamber 2 and the jacket 24 of the feed passage 7 are preferably seamlessly connected to one another. However, there is also the possibility that the jacket 21 of the combustion chamber 3 and the jacket 16 of the evaporation chamber 2 are fastened to one another with the aid of a flange connection 23. In this case, an annular seal 19 ensures that the connection is airtight. This is important, since the ingress of external air causes an increase in carbon dioxide emissions.

The proposed oil evaporation burner 1 works in the following way:

The combustion air is blown through the inlet opening 9 into the feed passage 7 with the aid of a fan (not shown). The air flow passes in the feed passage 7 and is heated by the electrical heating element 10. The heating element 10 is regulated to a constant evaporation temperature of the heating oil. The heating oil is fed through the oil line 11 into the feed passage 7 at a constant rate. A mass throughput of 0.5 liters of heating oil per hour is necessary for an output of 5 kW. The heating oil is preferably wheel pump promoted (not shown). In order to be able to achieve a regular combustion process, it is important that it flows continuously. The heated combustion air strikes the heating oil in the lowest end section of the feed passage 7 and brings it to evaporation in the evaporation chamber 2. The oil vapor then falls down in the evaporation chamber 2. It traverses the upper distribution plate 12, the expanded metal grid 14 and the lower distribution plate 13 and is thereby distributed regularly over the cross-sectional area of the combustion chamber 3. After passing through the perforated chrome steel bowl 20, the oil vapor is ignited with an ignition spark. The combustion of the oil vapor takes place on the outer surface of the grid-like combustion chamber antelε 21. After the operating temperature has been reached, the heating oil is evaporated by the upward radiant heat of the combustion flames.

Extensive tests have shown that a stable combustion process takes place in the proposed oil evaporation burner 1 and that no self-ignition of the heating oil vapor takes place.

Since the heating oil vapor falls from top to bottom in the proposed oil evaporation burner 1, it can also be referred to as a fall burner.

The proposed oil evaporation burner 1 has significant advantages compared to known oil evaporation burners: a simple construction is particularly advantageous. There are no moving parts susceptible to faults either in the evaporation chamber 2 or in the combustion chamber 3.

Since the proposed oil evaporation burner 1 is designed as a fall burner, no residues arise in the evaporation chamber 2 and the combustion chamber 3. The proposed oil evaporation burner 1 is consequently very easy to maintain.

Claims

claims 1. Oil evaporation burner for small outputs, with a combustion chamber (3) for burning off heating oil vapor and with an evaporation chamber (2) connected upstream and connected to the combustion chamber (3) for mixing hot combustion air and heating oil and for generating the heating oil vapor, characterized in that that the Verdampfungskaπuner (2) is arranged directly above the combustion chamber (3) and is connected at its upper end to a feed passage (7), in the upper section of the combustion air via an inlet opening (9) and in the lower section the heating oil by means of an oil line (11) can be initiated. 2. Oil evaporation burner according to claim 1, characterized gekenn¬ characterized in that in the upper portion of the feed passage (7) between the inlet opening (9) for the combustion air and the oil line (11), a heating element (10) for heating the combustion air to the Evaporation temperature of the heating oil is arranged. 3. Oil evaporation burner according to claim 1 or 2, characterized in that the longitudinal axis of the feed passage (7) is inclined by approximately 45 ° with respect to the axis of symmetry (8) of the evaporation chamber (2). 4. Oil evaporation burner according to one of the preceding claims, characterized in that in the evaporation chamber (2) a plurality of distribution devices arranged one above the other, preferably a perforated, circular distribution plate (12) and an expanded metal grid (14) are provided. 5. Oil evaporation burner according to one of the preceding claims, characterized in that the combustion chamber (3) has an upper cylindrical section (17) and a lower section (18), which is preferably formed in the form of a hemisphere or a spherical section. 6. Oil vaporization burner according to claim 5, characterized in that the combustion chamber (3) has a plurality of distribution bodies arranged one above the other, assigned to the upper or the lower section (17, 18), preferably a perforated, circular distribution plate (13) and a perforated one Chromstahlεchüssel (20) in the form of a hemisphere or a spherical section. 7. Oil evaporation burner according to claim 5 or 6, characterized in that an arched grille (22) is preferably provided in the form of a hemisphere of a spherical section immediately above the casing (21) of the lower combustion chamber section (18). 8. Oil evaporation burner according to one of the preceding claims, characterized in that the jacket (21) of the combustion chamber (3), the jacket (16) of the evaporation chamber (2) and the jacket (24) of the feed passage (7) seamlessly or with the aid of a a flange connection (23) having an annular seal (19) are connected to one another. 9. Oil evaporation burner according to one of the preceding claims, characterized in that it is designed as a Sturz¬ burner with in the evaporation chamber (2) down into the combustion chamber (3) falling heating oil vapor.