EP0007424B1 - Burner device for combustion of liquid fuel - Google Patents

Description

The invention relates to a burner arrangement for the combustion of liquid fuels, with a cylindrical swirl chamber which is closed on one side by a rear wall and opens on the other side in a combustion chamber, with an opening or openings for supplying the combustion air in the jacket of the swirl chamber , wherein the combustion air is introduced through the openings and generates a vortex sinking flow, and with a cylindrical jacket tube downstream of the vortex chamber, which surrounds the chamber concentrically and is open to the furnace side.

A vortex sinking flow is to be understood as an air movement which is circular, with a slight air compression towards the edge of the vortex chamber due to the centrifugal forces. This air flow creates a negative pressure inside the vortex that can be used to suck in the fuel. The burner arrangement therefore does not require a fuel pump. All that is required to convey the fuel is that it is introduced in the region of the axis of the swirl sinking flow, since experience has shown that the negative pressure reaches its maximum value here.

The introduced fuel, which is fed in a compact jet, is immediately torn apart by the turbulence within the air movement and divided into the finest particles and burned soot-free at the appropriate temperature conditions. The beam diameter is between 0.5-2.0 mm, for example. The negative pressure of the introduction that can be generated in the swirl chamber is between - 0.03 and - 0.15 bar. DE-B 1 157 333 discloses a burner arrangement of the type mentioned at the outset for the combustion of liquid fuels. A fuel atomizer nozzle is located near the mouth of the swirl chamber. The vortex flow is first generated in the vortex chamber; the fuel is only absorbed when it exits the swirl chamber. This arrangement is primarily aimed at combustion with an excess of oxygen, since the vortex flow is to form a stable vortex. The fuel-air mixture flows essentially tangentially. The flow is limited by the annular design of the combustion chamber. In the known arrangement, it is disadvantageous that a hollow rod, which carries the fuel line and ends in a fuel nozzle, forms a foreign body which produces air resistance, which in turn requires an increased air supply energy.

In contrast, there is the task of creating an airway that is as resistant as possible, the negative pressure of the vortex sinking flow being largely used to suck in the fuel. At the same time, it should be possible in principle to use the device in the area of stoichiometric combustion, i.e. to operate with relatively small amounts of air. As a result, the kinetic energy of the air is used as economically as possible. Furthermore, the required air pressure should be so low that it can be generated with relatively simple fans.

This object is achieved by a device according to the invention, in which, in a burner arrangement of the type mentioned at the outset, the inlet opening for the fuel is arranged centrally on the rear wall of the swirl chamber, the fuel leaving the inlet opening as a compact jet, and in which a concentrically located guide sleeve is installed, which is provided on its side in the region of the swirl chamber with peripherally distributed suction openings.

The burner arrangement according to the invention has the advantage that disruptive elements within the swirl chamber can be eliminated. As a result, the air pressure and thus the required power of the fan for the combustion air can be significantly reduced. Another advantage is that part of the fuel that flows out of the opening looks for a creepage path along the walls of the swirl chamber. These not inconsiderable portions of the fuel are torn apart by the air flow at the edge of the swirl chamber, with further energy utilization taking place.

The built-in guide sleeve causes forced recirculation of part of the burning mixture. A large part of the energy to be used in the fans is obviously not used at all to maintain the circulation and breakdown of the oil droplets, but rather to counteract the build-up in the casing. This wastes considerable energy uselessly. It has been shown that when a concentric cylindrical guide sleeve is installed, which is provided with peripherally distributed suction openings on its side in the region of the swirl chamber, the air pressure to be used can be considerably reduced. In addition to the reduced energy consumption, the reduced fan power also reduces the noise pollution caused by the airflow noise.

Another effect that is achieved is that larger oil droplets, which are due to the centrifugal force more in the outer region of the swirling current movement, are returned again and thus travel a longer distance so that they can evaporate more completely.

On the other hand, a device is known from DE-B 2517756, in which In the area of the inlet opening for the fuel, a strong swirl and thus a vortex sinking flow is generated, with the aid of which the fuel can be sucked in. This arrangement, however, lacks a closed vortex chamber, which is simultaneously a mixing and atomizing chamber, but in which no combustion takes place. However, the principle of the mixing and atomizing chamber only makes it possible to combine the suction process with a mixing and atomizing process, whereby at the same time the ratio between fuel and combustion air, which is also the atomizing medium, can be set in the range of the stoichiometric ratio.

In order to be able to adapt the guide sleeve to different burner conditions, heat demand numbers and the like, it is arranged adjustably across the end wall of the combustion chamber, with the adjustment also being able to change the clear width of the suction openings. This can be done structurally simply by the guide sleeve being slidably attached to several supports.

An increase in the circulation effect can furthermore be brought about by the fact that the casing tube of the burner projects beyond the guide sleeve and has a constriction in the protruding area.

For good stability, it is advantageous to press the guide sleeve out of temperature-resistant ceramic fiber material.

During combustion, the entire combustion air is preferably also used as an atomizing medium in order to use its energy content as completely as possible. This also means that only a relatively low air pressure has to be maintained for the incoming combustion air. The fuel particles are mixed with the air completely homogeneously and thus achieve a very short burnout time. Combustion can be carried out stoichiometrically over wide load ranges. The power can be controlled simply by changing the amount of combustion air supplied by controlling the drive power of the associated fan. A very simple controller can thus be assigned to the combustion device.

Usually the air flow for generating a vortex sinking flow is made possible by the fact that the feed openings to the vortex chamber are cut obliquely, so that a supply air flow occurs tangentially to an imaginary circle within the vortex chamber and rotates the contents of the vortex chamber. However, it is also possible to use appropriately designed air baffles or impact bodies which produce the same effect. The inlet opening for the fuel is arranged "centrally"; this choice of words also means that it is possible to deviate from the exact center position or that several openings have to be provided. It is essential that the fuel is supplied in the region of the strongest negative pressure in order to be as precise as possible to be able to maintain high flow rates.

The burner arrangement described is primarily suitable for being used for household burners which have only low fuel oil consumption. For example, so-called micro burners are required for single-family houses, which have an oil consumption in the range of 1-3 kg of oil per hour.

• Figur 1 die erfinderische Brenneranordnung und
• Figur2 ein Detail dieser Brenneranordnung.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawing. The figures in the drawing show:

• Figure 1 shows the inventive burner arrangement and
• Figure 2 shows a detail of this burner arrangement.

1 shows an embodiment of a burner arrangement. The fuel, usually heating oil, is fed from a storage container 31 to the actual burner via a line 32. A float regulator 33 is installed between the storage container and the burner, which ensures that the pressure between the burner fuel inlet and the level of the float regulator 33 is always the same. This ensures the proportionality between the negative pressure and the amount of fuel in the unit of time. The line 32 ends in a bore 34 which ends in an armature housing 54.

A soft iron anchor 55 is movably mounted in the armature housing and can be pulled into the armature housing 54 against the force of a spring 57 by the coil 56. The armature 55 has a collar 58 which limits the movement of the armature into the armature housing 54. The armature runs on the side facing away from the coil 56 into a valve needle 60 which opens and closes a further bore, the inlet opening 30. The armature-coil arrangement is contained in a housing bush 61, which is screwed to a cylindrical housing 35, which has two different-sized cylindrical bores from the two base sides of the cylinder, which are connected to one another via the inlet opening 30. The soft iron anchor 55 moves in one of these bores in the interior of the armature housing 54; the other is the swirl chamber 43. The housing 35 is embedded in an end wall 51 which is part of the burner housing. In order to achieve a flow of the fuel that is as uniform as possible by equalizing the viscosity, a tank heater 50 is installed in the reservoir 31.

Air is brought in via an air line 41 via an annular air duct 36 with connecting piece 37 machined into the end wall 51. The air line 41 also has a weight-loaded valve 38, with the help of which air is prevented from entering the combustion chamber through the swirl chamber 43 and cooling it down when the burner arrangement is switched off. The air line 41 has a control valve 39, via which the air drawn in by an air compressor 40 is pressed into the air duct 36 at a pressure of approximately between 0.03 and 0.3 bar.

The air channel 36 ends in the openings 44, 44 ', which are incorporated into the jacket of this chamber for supplying the combustion air to the swirl chamber 43. They allow an air supply in which a vortex sinking flow (cyclone) is formed within the vortex chamber 43. The inlet opening 30 for the fuel is arranged centrally on the front side of the chamber 43 in relation to this swirling iron flow forming in the chamber.

The jacket of the swirl chamber 43 has a cylindrical inner wall, a total of twelve rotationally symmetrically distributed openings (bores) 44 (or 44 ') being present. The average distance between the opening openings is approximately 5 mm from the inlet opening 30, measured from a projection of the center of the openings 44 onto the axis of the swirl chamber 43.

It is essential that the openings 44, 44 'lie such that the air is guided into the swirl chamber 43 at an angle of 10-60 ° in deviation from the normal direction. The air is accordingly blown tangentially to the periphery of a circle imagined within the swirl chamber 43. It is also possible to set the biasing direction of the openings 44, 44 'obliquely to the axis of the swirl chamber 43, so that the direction of the jet is directed somewhat towards or away from the inlet opening 30. The vortex chamber 43 is preferably designed such that it is of the same cross-section from the inlet opening 30 to the mouth.

Furthermore, it is possible to provide only one nozzle ring instead of several nozzle rings which lie one behind the other in the axial direction.

The end wall 51 forms the end of a conventional boiler, which is equipped with the usual exchanger tubes (not shown) and side walls 52. Due to the good atomization, mixing and gasification and subsequent combustion with a short flame, there is no need to install a brick lining in the Hetzkessei; the Kesseiwandflächen can be cooled. However, it is often useful to provide a cooling jacket in which the boiler water to be heated is preheated.

On the inside of the end wall 51, a jacket tube 63 is arranged, which has a much larger diameter than the diameter of the swirl chamber 43 and concentrically surrounds its opening. The casing tube 63 can, for example, have a cylindrical shape or be designed to open or taper in the manner of a truncated cone. Other shapes are also possible.

The strong swirling iron flow, which is caused within the swirl chamber 43 by the blowing in of the combustion and atomizing air, therefore continues in the direction of the casing tube 63 and ensures the establishment of a stable, concentrated flame.

The fuel jet does not exit droplet 30, i.e. sprays out, but in a compact jet with e.g. 1 mm diameter. The oil consumption is in such an arrangement, which is operated under 75% full load, about 3-4 kg of oil per hour. Due to the turbulence and centrifugal forces that act within the vortex sinking flow, the jet inside and outside the vortex chamber 43 is fully captured and divided into fine droplets and then burned in the area of the casing tube 63. It should be noted that the droplet size is reduced to such an extent that a soot-free, essentially blue-flame combustion takes place.

To ignite and trigger the combustion, an ignition coil 70 is provided in the burner arrangement according to FIGS. 1 and 2, which consists of an approximately 1 mm thick wire made of a heat-resistant, low-scaling chromium-nickel alloy. The filament of the ignition coil 70 is disposed such that it is penetrated by the jet of uncombusted effluent Gem ^i- ULTRASONIC when flowing out of the swirl chamber 43, and this ignited at a natural temperature of about 700-900 ° C. The ignition coil 70 is supplied with the energy for the annealing process via electrical leads.

Furthermore, a flame detector 46 is provided for monitoring the flame, via which a switch-off can take place if the flame is absent.

Since the inlet opening 30, through which the oil flows in, has a diameter of 1-2 mm (depending on the embodiment, these values may also be exceeded and undershot), slight contaminations usually contained in the fuel do not lead to a blockage of the inlet opening, so that the Susceptibility to operation is low. Test runs have shown that with a diameter of the inlet opening 30 between 1 and 2 mm and a pressure of the combustion air of 0.03 and 0.15 bar before the entry into the air channels within the swirl chamber 43, a vacuum can be generated which is sufficient for Suck fuel without additional pumps within line 32 and produce a compact jet of sufficient throughput (ie 2-3 kg of oil per hour).

Another control option is provided by the burner arrangement in that the float regulator 33 can be set differently so that the fuel supply can be regulated.

It turns out that the diameter of the openings 44 and 44 'and the diameter of the inlet opening 30 must be coordinated. For example, it has been found that twelve air channels 44 each with a 3 mm diameter Knives with an air pressure of between 0.03 and 0.3 bar are compatible with a diameter of the inlet opening 30 of 1 mm, whereby 2-3 kg of oil per hour (depending on the negative pressure) flow in at medium power. It is also important that the pressure difference caused by the level difference of the float regulator inlet opening corresponds to a fuel column between 0 and 30 mm.

It was observed that, for example, when the inlet opening 30 is reduced to 0.5 mm under the conditions mentioned, a stable flame can no longer be produced.

However, since the conditions for all occurring operating conditions must be determined individually experimentally, which is within the professional discretion, be it with these brief instructions.

The burner output can be regulated by adjusting the air supply through the air compressor 40, as a result of which the negative pressure in the swirl chamber 43 is variably set and the fuel supply through line 32 and inlet opening 30 is thus controlled. Numerous levels are possible between the full load and zero levels. In addition, the openings 44 and 44 'can also be opened and closed in a controllable manner by means of slides, screens and the like.

The burner is simply switched off by closing the inlet opening 30 by the needle 60. Accordingly, no complicated extinguishing and leakage regulations, as with atomizing nozzles, are required.

FIGS. 1 and 2 show embodiments in which a cylindrical guide sleeve 76 is provided within the jacket tube and concentric to the jacket tube 63 and is fastened to the end wall 51 via supports 77. The fuel-air mixture emerging in vortices is partially drawn behind the guide sleeve into the intermediate space 78 between the sleeve and the casing tube 63 and drawn back into the mixture flow near the axis via peripherally distributed suction openings 79. The direction of flow is indicated by the arrows. The guide sleeve 76 is made of heat-resistant material. It can also have elongated holes for adjusting the sleeve in the axial direction, so that the sleeve can be fixed in different positions with respect to corresponding carriers, thereby specifying different clear widths of the suction openings 79.

When using a guide sleeve 76, the diameter of which is approximately 50-80% of that of the casing tube 63, the operating air pressure of the air compressor 40 can be significantly reduced. Measurements have shown that the air pressure requirement can be reduced to 50% of the air pressure with the same flame quality, which is possible without a guide sleeve. The material of the guide sleeve 76 is preferably a ceramic, high-temperature-resistant, sintered or pressed fiber material made of Si-Al or Zr-carbides, as are known for example under the names REFRAX (manufacturer Carborundum) or FIBERFAX.

To stabilize the flame, the jacket tube 63 of the burner extends beyond the guide sleeve 76 and has a constriction 83 in the protruding area 80. This constriction, in the form of a truncated cone, can, for example, reduce 5-20% of the largest diameter. so that only 95-80% of the original diameter - in certain cases even less - are available.

Claims (4)

1. A burner device for combustion of liquid fuels, with a cylindrical vortex chamber (43), said chamber being closed at one side by a rear wall, said chamber opening at the other side into a combustion chamber with an aperture or apertures (44, 44') in the shell of the vortex chamber (43) for the supply of combustion air, the combustion air being introduced into the apertures (44, 44') and producing a vortex depression stream (cyclone), and with a cylindrical shell tube (63) positioned after the vortex chamber (43) and being open towards the furnace side, characterized by that the input aperture (30) for the fuel is positioned centrically in the rear wall of the vortex chamber (43), the fuel leaving the input aperture (30) as a compact jet, and that a baffle sleeve (76) is concentrically built into the shell tube (63), said baffle sleeve (76) comprising peripherically distributed suction ports (79), said suction ports being positioned within the range of the vortex chamber.

2. A burner device according to claim 1, characterized by that the baffle sleeve (76) is adjustable in axial direction relative to the shell tube (63) whereby the inner width of the suction ports (79) is being adjusted at the same time.

3. A burner device according to claim 1, characterized by that the shell tube (63) projects beyond said baffle sleeve (76) and includes a constriction (83) in the range of the projecting portion (80).

4. A burner device according to claim 1, characterized by that the baffle sleeve (76) is formed by pressing from a temperature resistant ceramic fibre material.

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