DE2828319A1 - Liquid fuel burner - utilises air cyclone in mixing and atomising chamber for drawing in fuel - Google Patents

Abstract

Liquid fuel and combustion aire are brought into contact in a mixing and atomising chamber. Combustion takes place in a relatively small space with a blue flame. The air in the mixing and atomising chamber forms a cyclone, the fuel being introduced in the region of the rotating axis of this cyclone. The regulation of the combustion rate is controlled exclusively by the metering of the air introduced into the mixing and atomising chamber. The fuel is introduced as a compact jet with a specified diameter which can be a maximum of 2 mm.

Description

Method for operating a burner without a fuel pump

The invention relates to a method for operating a burner in the area of stoichiometric combustion, in which liquid fuel and combustion air in a substantially constant ratio in a mixing and atomizing chamber are brought together, with a negative pressure there due to the air guidance and metering can be produced, with the aid of which fuel is sucked into said chamber. The invention also relates to a burner assembly for performing the Procedure.

A burner construction is known (niepenberg, industrial oil firing, Verlag Gustav Kopf 8 Co, Stuttgart, 2nd edition 1973), in which a two-stage air supply is applied to the bl. The oil arrives using an injector design at a point with negative pressure in the central air flow, that is, through the air sucked in. With the amount of air supplied over time, the amount of air that is sucked in can simultaneously amount of oil can be varied. According to the cited literature, it can also be said about keep the ratio of oil to air constant within a certain burner control range.

In the case of the known burner, the air duct is based on the Venturi system a negative pressure is generated in which Area of sucked fuel is admitted.

As far as can be seen from the literature, the fuel must have a Injector construction are introduced. Due to the high air speed that takes place in the area of the nozzle mouth, the combustion is distributed over one relatively long distance, while in many cases the combustion on a relatively small space should take place.

It is therefore the task of a burner of the type described above Kind to the effect that no atomizing nozzle in terms of construction is required for the fuel, although a substantially stoichiometric Burning is possible. The combustion should take place in a relatively small room. Nebulization and gasification must therefore largely break up the fuel particles take place in a limited volume, so that a blue flame is possible trains. The energy required for this should be as low as possible.

In addition, there should be control options for the operation of the burner be given.

These tasks are performed when applying a procedure to the Operation of a burner solved in which the air is guided so that it is within the mixing and atomizing chamber forms a cyclone and in which the fuel is initiated in the area of the axis of the cyclone.

"Cyclone" is to be understood here as an air movement which is circular, with a slight air compression due to centrifugal forces takes place towards the edge of the mixing chamber. Surprisingly, this air flow results a negative pressure inside the cyclone, which can be used to feed the fuel suck in. The burner therefore does not need a fuel pump. This is just it is necessary that the fuel is introduced in the area of the axis of the cyclone, therefore experience has shown that the negative pressure reaches its maximum value.

The imported fuel, preferably in a compact jet, However, it can also be supplied in a slightly atomized form, due to the turbulence within the movement of air immediately torn and divided into the finest particles and burned soot-free under appropriate temperature conditions. Is beneficial when the fuel is essentially as a compact jet with a jet diameter from 0.5 to 2.0 mm is fed. Here is the one in the mixing and atomizing chamber Negative pressure that can be generated in the area of the nozzle inlet between - 0.03 and - 0.15 bar located.

It has also proven to be advantageous if the speed component perpendicular to the fuel jet axis of the relative speed of the air flow Entry into the mixing chamber between about 40 and 250 m / sec. amounts to. It will however, this speed is not measured directly, but based on measurements of the quantities QXA determined from the following equation: Q v = speed Q = amount of air in the unit of time; A = cross-sectional area under a "stoichiometric" Combustion within the meaning of the invention is understood to be one in which neither Soot (measured according to BACHARACH; soot number 0), still a significant proportion of oxygen the combustion gases occur (oxygen content in the order of 0.1 to 0.1 %). Depending on the requirements, the combustion process can also be under or over stoichiometric can be carried out without the formation of soot.

"Liquid fuels" are understood to mean, in particular, heating oils. These can be EL, L or S heating oils. The corresponding viscosity values are specified in accordance with DIN. In the case of oils, the viscosity drops sharply with heating, so that, under certain circumstances, a heavy fuel oil can be turned into one with the viscosity properties of a medium-heavy fuel oil through heating. However, other substances such as alcohols, low-boiling aliphatics or aromatics are also suitable for combustion. to use constantly. This makes it possible to achieve that only a relatively low air pressure has to be maintained for the incoming combustion air. Another important advantage is that the fuel particles are mixed completely homogeneously with the air and thus a very short burnout time is achieved.

The method according to the invention further enables that over a wide area Stoichiometric load ranges a combustion can be carried out. The control The performance can be carried out simply by adjusting the amount of combustion air supplied over time is changed by controlling the drive power of the associated fan. This means that the method can be based on a very simple control option.

The burner arrangement for carrying out the method has an inlet opening, which is followed by a mixing and atomizing chamber enclosed by a jacket, into which the fuel jet arrives. It also has a Y-ine opening through which the combustion air can be fed to the mixing and atomizing chamber. These features can also be found in the prior art mentioned at the beginning.

The burner arrangement according to the invention differs from the prior art technology to the effect that the opening or openings for supplying the combustion air in the jacket of the mixing and atomizing chamber are incorporated and an air duct allow a cyclone to be formed within the mixing and atomizing chamber is, and that the inlet opening for the fuel centrally on the end face the chamber is arranged.

Usually the air flow to generate a cyclone is thereby used enables the supply openings to be inclined, eo that a supply air flow takes place tangential to an imaginary circle within the mixing chamber and the mixing chamber contents put in a rotation. However, it is also possible to use appropriately designed air baffles or to use impact bodies that produce the same effect. The entrance opening Hzentri8chN is arranged for the fuel; this choice of words also implies that it is possible to deviate from the exact center position or that several openings are also possible are to be provided. It is essential that the fuel is in the area of the greatest negative pressure is supplied in order to maintain a high flow rate that is as exact as possible can.

The jacket preferably has the mixing and atomizing chamber a cylindrical inner wall in which Distributed over the circumference and length individual bores or slots are provided as openings, with over the circumference of the jacket distributed in a rotationally symmetrical arrangement three to twenty, preferably twelve holes or slots are distributed.

The mixing and atomizing chamber either opens directly into the warming room of a boiler or in one surrounded by a burner jacket Space. In both cases it has proven to be advantageous if the clear width the mixing and atomizing chamber from the fuel nozzles or from the fuel nozzle is of the same cross-section until the transition into the combustion chamber. Because the fuel not atomized, but preferably supplied in a compact jet, he is not under too much pressure. It can be switched on and off in a simple manner are electrically operated by means of an electrically operated one that closes and opens the inlet opening Valve needle.

The following is based on an embodiment shown in the drawing the invention explained in more detail. The figures in the drawing show: figure 1 shows a burner arrangement according to the invention; Figure 2 shows a section along the line II ... II; Figure 3 shows the actual mixing chamber with the enlarged view Closure.

In the figure, an embodiment of a burner arrangement is shown. The, fuel, usually Heating oil EL with a viscosity of 5 cSt at 20 ° C. is fed from a storage container 31 via a line 32 to the actual burner. 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 constant. This ensures the proportionality between the negative pressure and the amount of fuel in the time unit. The line 32 ends in a bore 34 which ends in an armature housing £ 4.

A soft iron armature 55 is movably mounted in the armature housing, which is drawn into the armature housing 54 by the coil 56 against the force of a spring 57 can be. The armature 55 has a collar 58, the movement of the armature in the housing 54 bounded into it. The armature runs on the one facing away from the coil 56 page into a valve needle 60, which opens and closes another bore 30. The armature-coil arrangement is contained in a housing bushing 61, which is equipped with a cylindrical housing 35 is screwed, from the two base sides of the cylinder has two cylindrical bores of different sizes, düe over the bore 30 are in communication with each other. In one of these holes inside the Armature housing 54 moves the soft iron wrench 55; the other is the mixed and Atomization chamber 43.

The housing 35 is embedded in an end wall 51, which is part of the Burner housing is.

In order to achieve the most uniform possible flow of the fuel through equalization To achieve the viscosity, a tank heater 50 is built into the reservoir 31. This can either be via a separate circuit or via a heat exchange can be heated with the central heating boiler exchanger. Of course you can such additional heating when the appropriate operating conditions are present also omitted.

Via an annular air duct worked into the end wall 52 36 with connecting piece 37 is over an air line supplied air. The channel also has a weighted valve 38 that prevents it is that when the burner assembly is switched off through the air duct air into the Combustion chamber enters and this cools down. The air supply line also has a control valve 39, through which the air sucked in by an air compressor 40 at a pressure of is pressed approximately between 0.03 to 0.3 bar into the air duct 36.

The air duct 36 ends in the air ducts 44, which are used to supply the Combustion air to the mixing and atomizing chamber 43 in the jacket of this chamber are incorporated. They allow an air supply, with a vortex-shaped Air movement (cyclone) is formed within the chamber 43 to this in the chamber The cyclone that forms is the inlet opening for the fuel, i. H. the Bore 30, arranged centrally on the face of the chamber.

The jacket of the chamber 43 has a cylindrical inner wall, wherein a total of 12 rotationally symmetrically distributed bores 44 are present. These holes are about a = 5 mm from the outlet opening of the bore 30, measured from a projection of the center of the boreholes 44 on the axis of the Chamber 43.

It is essential that the bores 44 are located so that the air enters into the mixing chamber at an angle of 10 to 600 in deviation from the normal direction is led. The air is accordingly tangential to the periphery of an inside the mixing chamber 43 is blown in an imaginary circle, as can be seen from FIG. It is also possible, the blowing direction of the holes 44 obliquely to the axis of the Chamber 43 to put so that the direction of the jet something on the nozzle mouth is directed towards or away from this.

It is also possible, instead of one nozzle ring, to have several in the axial direction one behind the other to provide nozzle rings (indicated by dashed lines with reference number 49).

The end wall 51 forms the conclusion of a conventional boiler, the equipped with the usual exchanger tubes (not shown) and side walls 52 is. Due to the good atomization, mixing and gasification and subsequent Burning with a short flame can be dispensed with, one in the boiler To attach brickwork. The burner arrangement is insensitive to cooled surfaces. It may be, however useful to provide a cooling jacket, in which the boiler water to be heated is preheated. Preferably will continue provided that a burner jacket 63 is arranged on the inside of the end wall is, which compared to the diameter of the mixing and atomizing chamber one essential has a larger diameter and concentrically surrounds the opening. The burner jacket 63 can, for example, be cylindrically shaped or open in the manner of a truncated cone or be tapered. Other shapes are also possible. Preferably the mixing chamber 43 is designed so that it has the same cross-section from the nozzle to to the mouth is.

The strong vortex movement (cyclone) that occurs inside the mixing chamber caused by the injection of the combustion and atomization air, sets accordingly continues in the direction of the burner jacket 63 and ensures the establishment of a stable, concentrated flame.

The fuel jet 45 (see FIG. 3) emerges from the outlet opening 30 not in droplet form, i.e. H. sprayed out, but initially in a compact Beam with z. B. 1 mm diameter. The oil consumption is with such an arrangement, which is operated under 75% full load, around 3 - 4 kg of oil per hour. Because of the turbulence and centrifugal forces inside the cyclone act, the beam is fully captured inside and outside the mixing chamber, in fine droplets are broken up and then burned in the area of the burner jacket.

It should be noted that the droplet size is reduced so much is that a soot-free, essentially with a blue flame combustion takes place.

An ignition device known per se is used to initiate the combustion 47 is provided, which generates a high-voltage ignition spark between two electrodes. The electrode necks are through a corresponding hole within the end wall 52 carried out. Furthermore, a flame detector 46 is provided for monitoring the flame, which can be used to switch off if there is no flame.

In that the bore 30 through which the oil flows in has a diameter of 1 - 2 mm, (depending on the embodiment, this can also be exceeded or fallen below Values) result in minor contamination, which is usually contained in the fuel does not lead to clogging of the inlet opening, so that the susceptibility to operation is significant is reduced. Have trial runs shown that at diameters of the inlet opening 30 between 1 and 2 mm and an atomizing air pressure of 0.03 and 0.15 bar before entering the air duct inside the mixing chamber 43 a negative pressure can be generated that is sufficient to feed the fuel - heating oil EL -without additional pumps to suck in within the line 32 and a compact one To generate a jet of sufficient capacity (i.e. 2-3 kg of oil per hour).

The burner arrangement is given a further control option by that the float regulator 33 is adjustable so that the fuel supply can be regulated.

It can be seen that the diameter of the openings 44 and 49 for the Air and the diameter of the bore 30 are matched relatively precisely to one another have to. For example, it has been shown that twelve holes with a diameter of 3 mm each, in front of which there is an air pressure between 0.03 and 0.3 bar, are compatible with a The diameter of the bore 30 is 1 mm in diameter, with 2 - 3 kg of oil per hour (each after negative pressure) at medium power. It is also important that caused by the level difference between the float regulator and the fuel inlet Pressure difference corresponds to a fuel column between 0 and 30 mm.

It has been observed that, for example, when the oil inlet bore is reduced in size under the conditions mentioned, a stable flame can no longer be produced within 0.5 mm.

As the conditions for the many operating conditions that occur however, individually must be determined experimentally, what is in the professional judgment be left with these brief notes.

The burner output can be regulated by adjusting the air supply done by the compressor 40, whereby the negative pressure in the mixing chamber is variable is set and thus the fuel supply through line 32 is controlled is. Numerous levels are possible between the levels of full load and zero.

In addition, the holes 44 and 49 can also be through slides, orifices and the like can be opened and closed in a controllable manner. It was on the constructions referred to in accordance with the applicant's patent application P 27 29 321.6 (not prepublished).

The issuing of the burner is simply effected by that the bore 30 is closed by the needle 60. So they are not complicated Extinguishing and discharge controls, as with atomizing nozzles, are required in the figure 3 the individual parts of the magnetic control are shown in a somewhat enlarged form. For example, the following dimensions are selected: Diameter of the chamber 43: 15 mm, diameter of the feed channels 44: 3 mm, diameter of the fuel inlet 30: 1 mm, length of the chamber: 11 mm.

The length to diameter ratio of the chamber 43 should be approximately 0.5: 1 to 1: 0.5. However, these dimensional examples are without restriction consider.

They only serve to substantiate the economic use the invention.

L e r s e i t e

Claims (11)

Claims: Ci method for operating a burner in the area stoichiometric combustion, in which liquid fuel and combustion air in a substantially constant ratio in a mixing and atomizing chamber are brought together, with a negative pressure there due to the air flow and metering can be produced, with the help of which fuel is sucked into said chamber, characterized in that the air in the mixing and atomizing chamber is a cyclone forms and that the fuel is introduced in the area of the axis of the cyclone. 2. The method according to claim 1, characterized in that the regulation the burner output exclusively through the dosing of the into the mixing and atomizing chamber introduced air takes place. 3. The method according to claim 1 and 2, characterized in that the Underpressure that can be generated in the mixing and atomizing chamber in the area of the inlet of the fuel is between - 0.03 and - 0.15 bar. 4. The method according to claim 1, characterized in that the fuel essentially supplied as a compact beam with a diameter of 0.5 ... 2.0 mm will. 5. The method according to claim 1, characterized in that the perpendicular The speed component of the relative speed lying to the fuel axis of the air flow on entry into the mixing chamber between approximately 40 and 250 m / sec. lies. 6. Burner arrangement for performing the method according to claim 1, with an inlet opening, which is a mixing and enclosed by a jacket Downstream of the atomization chamber, into which the fuel jet arrives, and with at least one opening through which the combustion air of the mixing and atomizing chamber can be fed in, characterized in that the opening or openings (10; 11) for feeding the combustion air into the jacket of the mixing and atomizing chamber (43) are incorporated and allow an air flow in which a cyclone within the mixing and atomizing chamber is formed, and that the inlet opening (30) an essential one for the fuel centrically on the front side the chamber 43 is arranged 7. Burner arrangement according to claim 6, characterized in that that the jacket of the mixing and atomizing chamber has a cylindrical inner wall, and that distributed over the circumference and length of the jacket individual bores (44; 49) or Slits are provided as openings, being distributed over the circumference of the jacket three to twenty, preferably twelve holes in a rotationally symmetrical arrangement or slots are distributed. 8. Burner arrangement according to claim 7, characterized in that the air entering the mixing chamber at an angle in front of 10 - 600 in deviation is guided by the normal direction. 9. Burner arrangement according to claim 6, characterized by a die Electrically operated valve needle that closes and opens the inlet opening (60) 10. Burner arrangement according to claim 6, characterized by one of the mixing and Jacket tube (63) arranged downstream of the atomization chamber, concentric to the chamber includes and is open to the oven side. 11. Burner arrangement according to claim 6, characterized in that a float control valve (33) is installed in the fuel line (32).