EP0683883A1

EP0683883A1 - Blue-flame burner with optimized combustion characteristics

Info

Publication number: EP0683883A1
Application number: EP95905077A
Authority: EP
Inventors: Bernhard Knapp; Manfred Bader; Lutz Mardorf
Original assignee: Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR
Current assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Priority date: 1993-12-18
Filing date: 1994-12-17
Publication date: 1995-11-29
Anticipated expiration: 2014-12-17
Also published as: ATE199451T1; EP0683883B1; ES2154722T3; GR3035908T3; PT683883E; ATE283449T1; DK0683883T3; WO1995016882A1

Abstract

The invention concerns a liquid-fuel burner comprising a housing (10), a precombustion chamber (48) containing a nozzle assembly (24) with a nozzle (28) which produces a jet of fuel (80), a combustion chamber (92) in which the fuel jet broadens out, a partition (90) between the precombustion and combustion chambers, and a fan (16) designed to force a stream of combustion air into the combustion chamber, the fuel burning essentially stoichiometrically with a blue flame. In order to improve the burner to minimize the amounts of pollutants in the combustion gases, the invention proposes that, in addition to a stream of combustion air (102) entering the combustion chamber near the fuel jet, a second, recirculation-stabilizing stream of air (106) enters opposite the first stream, at a defined radial distance further out from the first stream. Inside the combustion chamber, an inner recirculation stream (112) is formed which is stabilized by the second stream of combustion air.

Description

Combustion-optimized blue burner

The invention relates to a burner for liquid media comprising a burner housing which has a support tube and an adjoining flame tube, a nozzle assembly arranged in the support tube in a prechamber with a nozzle generating a fuel jet, and an essentially mixing tube-free burner chamber arranged in the flame tube in which the fuel jet spreads, a separating element between the prechamber and the combustion chamber with a central opening through which the fuel jet passes, a blower for generating a combustion air flow entering the combustion chamber, which comprises a partial flow close to the fuel jet, the fuel having a blue-burning one in the combustion chamber Flame burns essentially stoichiometric or near stoichiometric.

DE-OS 40 09 222 discloses a burner for the stoichiometric combustion of liquid or gaseous fuels from an atomizer nozzle. With this burner, air is passed through a screen into the atomizer nozzle

Combustion chamber in which the fuel emerging from the nozzle also enters. In addition, slit-shaped openings running parallel to the flow direction are provided in the wall of the combustion chamber, via which recirculation of cold combustion gases from outside the burner tube takes place, which are mixed with the fuel and the air entering around the atomizing nozzle in order to achieve stoichiometric combustion in the combustion chamber to obtain.

EP-A-0 430 011 also discloses a blue-burning burner in which a mixture of fresh air and recirculating combustion gases are supplied and mixed around an atomizer nozzle before they again lead to stoichiometric combustion with the fuel coming from the atomizer nozzle.

In all of the exemplary embodiments, the combustion air and recirculating combustion gas are mixed in front of the plane in which an orifice of the nozzle is located, and after this in a mixing chamber the combustion air and the recirculating combustion gases are mixed with the fuel, which then enter the actual combustion chamber. In special embodiments, the feed is

Fresh air divided, on the one hand into a first part, which mixes directly with the recirculating combustion gases, and, on the other hand, into a second part, which is the

Flows around the atomizer nozzle and serves to cool the atomizer nozzle, so that the cooling of the atomizer nozzle, in particular the oil nozzle, is adjustable. This fresh air is then also in a mixing chamber with the remaining fresh air and the recirculating combustion gas and the fuel

mixed. A controllable burner is known from DE-OS 27 12 564, in which a baffle plate is present and a vacuum region is created downstream of the baffle plate by generating a rotating hollow air column, so that combustion gases are sucked back into this vacuum region. The rotating hollow air column is generated by radial slots running in the radial direction and covered with scoops.

In addition, external air inlets for fresh air are provided for higher outputs.

In addition, the atomizer nozzle with the ignition electrodes is arranged in a closed space, to which only as much fresh air is supplied as is necessary to move the ignition spark.

DE-PS 29 08 427 discloses a burner in which, with the addition of flue gases, substoichiometric combustion takes place in a primary combustion zone with direct supply of a jacket air stream enveloping the fuel flow and then in a superstoichiometric secondary combustion zone, in the residual air over the peripheral area of the primary Combustion zone is fed, another combustion takes place.

The residual air is fed coaxially around the respective burner in at least two partial flows, which reach the flame from the burner mouth after a certain free flow path. From DE-OS 31 09 988 a so-called blue burner is known, in which internal recirculation is forced through a mixing tube, the fuel jet emerging from an atomizer nozzle being supplied on the one hand with this directly surrounding combustion air and on the other hand, further air passage bores are provided radially on the outside, but these are lie radially inside the mixing tube.

A burner with a recirculation is known from EP-A-0 538 761, in which the external recirculation is generated by a longitudinal direction of the slots, these slots extending with their longitudinal direction in the circumferential direction.

In addition, fresh air flowing around the nozzle is blown into the combustion chamber through an orifice.

Similar burners are for example from DE-PS

27 00 671 or DE-PS 38 01 681 known.

With these burners, a so-called mixing tube is required to form a stable recirculation flow, which defines a single recirculation flow of hot gas and thus enables the flame to burn blue.

A blue burning of the flame is understood to mean that this flame burns a completely gasified fuel, which makes it necessary, in particular when oil is used as fuel, that flows from the nozzle into the Small oil droplets initially emerging from the fuel jet are essentially completely evaporated until they are burned by the flame.

The problem with these known burners is that the overall design of the burner requires that all parts be coordinated for a single burner output, so that a burner for other burner outputs requires a completely new design.

Starting from DE-OS 40 09 222, the invention has for its object to improve a burner of the generic type in such a way that a low-pollutant and stable stoichiometric or near-stoichiometric combustion allows.

This object is achieved according to the invention in a burner of the type described at the outset in that, in addition to the partial flow near the fuel jet, a recirculation-stabilizing partial flow of combustion air occurs at a defined distance from the latter in a defined distance, that in the combustion chamber one of the blue-burning flame to the non-burning part of the Forms back internal recirculation flow of fuel jet and that the recirculation-stabilizing partial flow of the combustion air stabilizes the internal recirculation flow. The advantage of the solution according to the invention can be seen in the fact that the additional recirculation-stabilizing partial flow of the combustion air enables the internal recirculation flow in the combustion chamber to be stabilized.

This creates a burner in which the locally defined supply of the combustion air flow makes it possible to ensure stable recirculation flows and thus a blue burning of the flame essentially without mechanical flow-guiding elements in the combustion chamber.

Alternatively or in addition to this, the above-mentioned object is achieved according to the invention in a burner of the type described in the introduction in that in the burner housing

Openings are provided through which an external recirculation flow leading to cold combustion gases into the

Combustion chamber occurs that the external recirculation flow enters the combustion chamber near the separating element and is so large that a flame root of the blue-burning flame is at least 1 cm away from the nozzle and that there is a non-burning part between the nozzle and the flame root of the fuel jet spreads conically with the addition of combustion air.

The advantage of this solution according to the invention can be seen in particular in the fact that the external recirculation flow, which was only used according to the prior art, in particular the content of harmful combustion gases To reduce nitrogen oxides, is now used according to the invention to position the flame root at a sufficiently large distance from the nozzle, namely in that additional, essentially non-oxidizing or only slightly oxidizing gas is introduced into the combustion chamber to a sufficient extent via the external recirculation flow is thus increased the mass flow through the combustion chamber and thus brings about the necessary distance between the flame root and the nozzle which is required to obtain a sufficiently long non-burning part of the fuel jet which is required to achieve a complete evaporation of the droplets.

In particular, in this exemplary embodiment the sufficient length of the non-burning part of the fuel jet creates the possibility of mixing the hot gases from the internal recirculation flow into the non-burning part of the fuel jet and thus in turn the possibility of reliably evaporating the oil droplets in the fuel jet down to the flame root that ultimately a stable blue-burning flame is created, which is highly insensitive to small changes in the setting parameters.

As an alternative or in addition to the solutions described above, the above-mentioned object is achieved with a

Burner of the type mentioned in the invention solved in that openings are provided in the burner housing, through which an external, cold combustion gas carrying recirculation flow enters the combustion chamber, the external recirculation flow near the separating element enters the combustion chamber and this shields an internal recirculation flow against the separating element, which as in the combustion chamber from the blue-burning flame to the non-burning part of the Forms backward flow of fuel jet.

In this solution according to the invention, the outer recirculation flow which is usually used to reduce the pollutants, in particular the nitrogen oxides, is used according to the invention to shield the hot combustion gases of the inner recirculation flow from the cold separating element and thus to prevent excessive cooling of these hot combustion gases by the cold separating element. Rather, these hot combustion gases are supplied to the fuel jet essentially with little or no cooling in order to ensure that the oil droplets evaporate as optimally as possible through the heat input.

The solution according to the invention also has the great advantage in connection with the use of an external recirculation flow that due to the lack of mechanical

Flow control elements in the combustion chamber, in particular due to the lack of a mixing tube, no problems with regard to pollutant emissions occur when the burner is started, which lead to the external recirculation varying must be set. Rather, the solution according to the invention has the great advantage that already at the start of the

An optimal low-pollutant combustion takes place so that the complex regulation of the external recirculation, as described, for example, in DE-PS 39 06 854, can still be carried out, but not because of the available good pollutant values without this regulation

is required.

No details have so far been given regarding the course of the internal recirculation flow in the combustion chamber. An advantageous exemplary embodiment provides that the inner recirculation flow flows from the flame on an inside of the flame tube in the direction of the separating element. In this position, the internal recirculation flow can be stabilized particularly simply and sustainably by the recirculation-stabilizing partial flow of the combustion air.

In a particularly expedient embodiment with an inner recirculation flow, the inner recirculation flow is yellow-burning.

A particularly advantageous effect of the inner recirculation flow, in particular with regard to the heat transfer to the fuel jet for the evaporation of the oil droplets, can be achieved if the inner recirculation flow through the partial flow which stabilizes the recirculation

passes through. With regard to the direction in which the recirculation-stabilizing partial flow enters the combustion chamber, no further details have been given in connection with the previous explanation of the exemplary embodiments. For example, the recirculation-stabilizing partial flow could be directed parallel to the cone jacket of the fuel jet. However, it is particularly advantageous if the recirculation-stabilizing partial flow enters the combustion chamber essentially parallel to the direction of flow of the fuel jet.

It is particularly advantageous if the partial flows enter the combustion chamber at the same location, regardless of the amount of air set.

By locally determining the entry of the partial flows into the combustion chamber, the stabilization of the recirculation flow can be achieved particularly advantageously with the simplest means with each setting of the fuel quantity and air quantity.

In connection with the previous explanation of individual exemplary embodiments, no mention was made of the partial flows via which the air volume is set.

From the combustion calculation, it would be theoretically possible to make the amount of air adjustable via the partial flow close to the fuel jet or via the partial flow which stabilizes the recirculation or via both. For reasons of simplicity and a streamlined solution, however, it is advantageous if only one of the partial flows to adjust to the air volume to adjust

The amount of fuel is adjustable.

To stabilize the recirculation flows with each setting of the air quantity and fuel quantity, it has proven to be particularly expedient if the recirculation-stabilizing partial flow can be adjusted with regard to the air quantity. The adjustability of the recirculation-stabilizing partial flow can be used in particular to achieve an advantageous stabilization of the recirculation flow at any burner output, since this partial flow acts directly on the formation of the recirculation flows and thus an adjustment of the same can be carried out in such a way that the recirculation flow due to the local entry of this partial flow into the Combustion chamber can be stabilized.

The recirculation-stabilizing partial flow preferably enters the combustion chamber in the form of a ring flow interrupted in the circumferential direction around its fuel jet, as a result of which the stabilization of the recirculation flow is further improved, since "flow" through the ring flow in the radial direction is possible in a simple manner at the points of the interruption while stabilizing vortices are created between breaks. Since a maximum gas velocity occurs in the flame at maximum fuel quantity, it is also particularly advantageous if the air quantity in the recirculation-stabilizing partial flow is maximal at maximum fuel quantity and minimal with minimum fuel quantity, so that the air quantity of the recirculation-stabilizing partial flow is at maximum fuel quantity and thus largest Gas velocity of the flame also maintains sufficient recirculation flow for the flame to burn blue in the combustion chamber.

With regard to the adjustability of the recirculation flow, it has also proven to be advantageous if the amount of air in the sub-stream close to the fuel jet is constant at all settings of the amount of fuel, so that the sub-stream close to the fuel jet always ensures a basic supply of the fuel jet with air. In an extreme case, the amount of air in the partial stream near the fuel jet is dimensioned such that the maximum amount of fuel in the partial flow of the recirculation-stabilizing stream is maximum and with a minimum amount of fuel, the combustion air flow is formed only by the partial stream near the fuel jet.

In an advantageous embodiment of the burner according to the invention it is provided that the amount of air in the sub-stream near the fuel jet is between about 0.6 times and about 0.2 times the amount of air of the maximum recirculation-stabilizing sub-stream, this being provided in particular for a burner whose

Burner output can be varied by a factor of five. With regard to the type of design of the fuel jet, no further details were given in the explanation of the previous exemplary embodiments. For example, a particularly simple and effective working embodiment provides that the fuel jet forms a pointed cone starting from a simply connected nozzle opening, in particular essentially a full cone, in which the most homogeneous possible droplets of the oil are distributed.

With regard to the orientation of the partial stream close to the fuel jet when entering the combustion chamber, no further details have also been given. An advantageous exemplary embodiment provides that the fuel-near partial flow is essentially parallel to the flow direction of the

Fuel jet enters the combustion chamber.

Preferably, the partial stream near the fuel jet enters the fuel chamber flowing around the fuel jet in order to enable this part of the combustion air to be mixed well with the fuel jet in the combustion chamber.

This can be achieved particularly advantageously if the partial flow near the fuel jet and the fuel jet enter the combustion chamber through the same central inflow opening in the separating element. No details have so far been given regarding the location of the feed of the partial stream close to the fuel jet into the combustion chamber. An advantageous exemplary embodiment provides that the partial flow near the fuel jet flows into the combustion chamber in the region of a circumference of the nozzle head of the nozzle.

However, it is even more advantageous, particularly due to the spatial conditions in the area of the nozzle, if the partial stream near the fuel jet flows along a defined outer profile of the nozzle head and thus enters the combustion chamber in the immediate vicinity of the fuel jet.

In the simplest case, the cross section required for the partial flow near the fuel jet can be made available by the partial flow near the fuel jet flowing into the combustion chamber through a passage between the nozzle head and an edge of an inflow opening provided for the partial flow near the fuel jet, so that the size of the passage has the flow cross section for the partial stream close to the fuel jet.

A particularly advantageous mixing of the partial flow close to the fuel jet and the fuel in the combustion chamber results when the inflow opening for the

is designed to generate turbulence near the fuel jet. In the simplest case, it is provided that the inflow opening is provided with a swirl edge or a swirl cutting edge.

With regard to the construction of the burner housing, no detailed information has been given in connection with the previous exemplary embodiments. An advantageous exemplary embodiment provides that the burner housing comprises a prechamber in which the nozzle is arranged and which is separated from the combustion chamber by the separating element. Such a construction of the burner housing has the advantage of great simplicity and high structural flexibility.

In connection with the previous exemplary embodiments, it was not discussed in detail how the combustion air flow is led into the combustion chamber.

It is particularly advantageous if the entire combustion air flow is passed through the prechamber, since this ensures that the burner has a particularly simple construction.

For reasons of structural simplicity, it is also preferably provided that the combustion air flow enters the combustion chamber through the separating element.

With regard to the routing of the combustion air through the separating element, it is expediently provided that the separating element has an inflow opening facing the nozzle for the partial flow close to the fuel jet. In addition, it is expediently provided, in particular in order to allow the recirculation-stabilizing partial flow to enter the combustion chamber at the desired location, that the separating element has at least one radially external opening for the recirculation-stabilizing component relative to the inflow opening for the partial flow near the fuel jet

Has partial flow.

With regard to the design of the combustion chamber, no further details have likewise been given in connection with the previous exemplary embodiments. An advantageous exemplary embodiment provides that the combustion chamber is enclosed by a flame tube of the burner, so that this flame tube of the burner permits a defined geometrical environment of the combustion chamber and thus in particular a defined configuration of the recirculation flows.

To reduce the nitrogen oxide emission, this flame tube is preferably provided with openings for forming the external recirculation flow.

With regard to the design of the combustion chamber itself, no further details have been given in connection with the previous description of the individual exemplary embodiments. One advantageous exemplary embodiment provides that the combustion chamber extends from a plane which is close to the nozzle opening. Such training the Combustion chamber allows the individual recirculation flows, in particular the inner and the outer recirculation flow, to be optimally guided to the non-burning part of the fuel jet.

A particularly simple and efficient design of the combustion chamber provides that it has an essentially constant cross section between the separating element and the area of the flame root. This has the advantage that there is sufficient space for guiding and forming the recirculation flows, in particular the inner recirculation flow.

No specific information was given regarding the separating element. For example, the separating element could be designed according to EP 0 430 011. However, it is structurally particularly simple if the separating element is an aperture.

The aperture in turn could also be curved, as follows. As known for example from DE-OS 40 09 222. However, it is particularly advantageous if the orifice extends in one plane, since such a shape of the orifice also allows optimal guidance of the recirculation flows to the non-burning part of the fuel jet in the area of the orifice. It is particularly favorable if the combustion chamber has a non-burning part of the fuel jet and a recirculation space extending around it, which offers optimal possibilities for supplying the individual recirculation flows to the non-burning part of the fuel jet.

The recirculation space is expediently designed such that it extends at least to the flame root in order to create sufficient space for the internal recirculation flow.

In order to be able to stabilize the recirculation flows particularly optimally, it is provided that the recirculation-stabilizing partial flow enters the recirculation space.

The recirculation-stabilizing partial flow is preferably designed such that it enters the combustion chamber symmetrically to an axis of the combustion chamber and thus to an axis of the recirculation space.

The recirculation-stabilizing partial flow is preferably designed such that it enters the combustion chamber in the form of a current pattern lying on a cylinder. This form of the recirculation-stabilizing partial flow enables a particularly optimal stabilization of the internal recirculation flow. In particular, the cylinder is designed as a circular cylinder which is defined by a partial circle lying in the center thereof.

With regard to the current pattern, no further details have been given. For example, it would be possible to use the current pattern as a uniform closed ring flow in the form of the

Cylinder. However, it is particularly advantageous if the flow pattern is composed of parallel individual part streams, since these individual part streams make it possible to let the recirculation flows pass through the recirculation-stabilizing partial stream in the region of the non-burning part of the fuel jet in a particularly advantageous manner.

This is particularly advantageously possible if the component streams are arranged at a constant angular distance from one another in order to create defined spaces between the individual component streams through which the recirculation flows can pass.

With regard to the dimensioning of the component streams in relation to the angular spacing between them, it has proven to be particularly advantageous if the ratio of the angular spacing between two component streams to the angular width of the inlet cross section of each component stream is between approximately 10 and approximately 0.1. It is more advantageous if this ratio is between approximately 3 and approximately 0.1, better between approximately 2 and approximately, 0.1, still better between approximately 1 and approximately 0.1, and it has proven particularly optimal if this ratio is in the range of about 1.5 to about 0.3.

Furthermore, no further details on the

Dimensioning of the recirculation space made. It is preferably provided that the circular ring region has a pitch circle diameter which lies in a range from approximately 0.2 to approximately 0.7 an outer diameter of the combustion chamber or the recirculation space

A particularly optimal effect of the recirculation-stabilizing partial flow can be achieved if the recirculation space has an outer diameter, for example corresponding to the inner diameter of the flame tube, which is approximately 1.5 to 3 times larger than the diameter of the partial circle of the circular cylinder.

It is even more advantageous if the recirculation space has an outer diameter which is approximately 1.8 to approximately 2.6 times, more preferably approximately 2 to approximately 2.5 times, larger than the diameter of the pitch circle of the circular cylinder. Particularly optimal results have been obtained if the outer diameter of the recirculation space is approximately 2.4 ± 10% as large, more optimally approximately 2.5 times as large as the pitch circle diameter. In order in particular to optimally stabilize the flame and to prevent the flame from flickering spatially, it has proven to be particularly expedient if a flame space is connected to the recirculation space.

This flame chamber can have the same inner diameter as the recirculation chamber for large outputs, but it has proven advantageous in terms of spatial stabilization, in particular for small outputs, if the flame chamber has a diameter which is at most the same size or smaller than the recirculation chamber.

Particularly preferred values result when the diameter of the flame space is in the range of approximately 0.6 to 0.9 times the diameter of the recirculation space. It is particularly advantageous if the inner diameter of the flame space is in the range of approximately 0.8 times the inner diameter of the recirculation space.

With regard to the expansion of the combustion chamber, no defined information was given either. Also in order to keep the flame as stable as possible, it has proven to be advantageous if the flame has a flame root located in the combustion chamber.

No detailed information has so far been given regarding the introduction of the external recirculation flow into the combustion chamber. For example the external recirculation flow is introduced into the combustion chamber in accordance with EP 0 430 011. However, it is particularly advantageous if the external recirculation flow enters the combustion chamber separately from the combustion air flow.

This exemplary embodiment has the great advantage that the outer recirculation flow can be guided in a defined manner on the one hand and also defined in terms of the mass flow on the other hand, which is important for the aspects according to the invention, in particular the guidance of the outer recirculation flow to shield the inner recirculation flow from the separating element and the dimensioning of the

Mass flow is important for reaching a sufficiently long non-burning part of the fuel jet. This also defines the volume for the internal recirculation flow.

This can be achieved constructively with particularly simple means if the outer recirculation flow enters the combustion chamber directly through recirculation openings in the flame tube.

With regard to the dimensioning of the external recirculation flow, no quantitative information has yet been given. An advantageous exemplary embodiment provides that a maximum area of the openings provided for the entry of the combustion air flow into the combustion chamber corresponds approximately to the area of the recirculation openings provided in the flame tube for the external recirculation flow. With this dimensioning, a sufficiently large mass flow is guaranteed in the recirculation flow in order to obtain a sufficiently elongated part of the non-burning fuel jet in the combustion chamber.

Furthermore, it is possible to arrange a flow stabilization element in the flame tube, which element extends from the diaphragm in the direction of a foot region of the flame to a maximum of approximately a quarter of the distance between the diaphragm and the flame. This flow stabilization element has nothing to do with the mixing tube known from the prior art, since the known mixing tube only permits the formation of a single recirculation flow, while the flow stabilization element according to the invention is also designed such that it permits the formation of several recirculation flows that can be defined by the recirculation-stabilizing partial flow, in particular the formation of the recirculation flows required for the respective fuel quantities and air quantities.

For this reason, it is particularly advantageous if the flow stabilizing element extends at most over approximately one sixth of the distance between the diaphragm and the foot region of the flame. However, the flow stabilization elements explained above are not absolutely necessary for the sufficient stabilization of recirculation flows and always create the risk of soot deposits in the burner.

In particular, when soot deposits in the combustion chamber are to be prevented as much as possible, it is advantageously provided that the combustion chamber is designed free of flow stabilization elements for recirculation arranged within it.

In particular, the combustion chamber - as already mentioned at the beginning - is designed without a mixing tube.

No details have so far been given on the question of the setting of the air volume of the combustion air flow. An advantageous exemplary embodiment provides that an adjusting device is provided for adjusting the air quantity of the combustion air flow.

The adjusting device is preferably designed such that when the amount of air is set, the location of the entry of the combustion air flow into the combustion chamber in the radial direction is essentially invariant to the fuel jet. This has the great advantage that by determining the location of the

Entry of the combustion air flow an optimal stabilization of the recirculation is possible with all settings of fuel quantity and combustion air quantity. It has proven to be particularly advantageous if the adjusting device has locally fixed openings for the combustion air flow, which can be adjusted to different cross sections.

This is expediently solved structurally in such a way that the adjusting device comprises an adjusting element which is rotatably mounted on the diaphragm and with which the cross section of an opening provided in the diaphragm can be adjusted.

In the simplest case, the adjusting element is designed as an adjusting disk rotatably mounted on the diaphragm, which can be brought into different rotational positions relative to the diaphragm and to the openings provided in the diaphragm.

On the one hand, this setting element can be designed in such a way that it can be set in different discrete setting positions.

Alternatively, it is advantageous if the setting element is continuously adjustable, so that the cross sections between a maximum value and a continuously

The minimum value can be varied.

The adjusting device can be designed such that it can be adjusted manually, for example with an appropriate tool. In the case of a variable control of the air quantity, it is particularly advantageous if the setting device can be set via a controllable actuator.

With regard to the adjustability of the nozzle, no further details have yet been given either. An advantageous exemplary embodiment provides that the nozzle is a return nozzle.

Such a return nozzle can be adjusted particularly simply by assigning an adjustable return valve to it, which enables the return of the return nozzle to be variably adjusted and thus also the amount of fuel emitted by the nozzle.

In the simplest case, the return valve is designed in such a way that different amounts of fuel in the fuel jet can be set with it. However, it is even more advantageous if the return valve is continuously adjustable, so that the fuel quantity can be continuously adjusted and adjusted.

In particular when the fuel quantity is to be controlled, provision is advantageously made for the return valve to be adjustable by means of an actuator. A particularly advantageous embodiment of the solution according to the invention provides that the burner has a control with which the fuel quantity and the air quantity of the combustion air flow can be adjusted. With such a control, an optimal setting of both the amount of fuel and the amount of combustion air can be achieved, in particular in a simple manner

stoichiometric or near stoichiometric combustion.

It is preferably provided that the controller controls the actuator of the return valve.

As an alternative or in addition to this, it is advantageous if the controller controls the actuator of the adjusting device.

In the case of activation of only one of the two actuators, it is conceivable to predefine the setting of the fuel quantity or the air quantity, or vice versa, and via the

Adjust the actuator for the other size. However, it is particularly advantageous if the controller controls both the actuator of the return valve and the actuator of the adjusting device.

It is also advantageous, in particular to ensure complete combustion of the fuel, if the control is assigned a probe that detects complete combustion. Thus there is also the possibility that the control adjusts the air volume and the fuel volume according to a stoichiometric or near-stoichiometric combustion.

With regard to the specification of the burner output, several options are also conceivable when providing a control according to the invention. An advantageous exemplary embodiment provides that the control burner outputs can be predetermined. Alternatively, it is conceivable that the

Control burner outputs can be variably specified.

A particularly advantageous exemplary embodiment provides that the control regulates the amount of fuel and the amount of air in accordance with a predetermined output on the one hand in accordance with this output and on the other hand with regard to stoichiometric or near-stoichiometric combustion.

In connection with the exemplary embodiments according to the invention, it has hitherto been assumed that the adjustability of the fuel quantity via the nozzle is possible through one and the same nozzle.

As an alternative to this, an advantageous exemplary embodiment provides that the amount of fuel can be adjusted in that the burner is designed as a kit with different nozzles that can be inserted into the same burner housing. The amount of fuel is adjusted by inserting the appropriate nozzle into the burner. It is preferably provided that the nozzles all have essentially the same spray pattern and in particular a substantially identical outer contour on the air flow side and only deliver different amounts of fuel.

Furthermore, an advantageous embodiment regarding the adjustment of the air quantity provides that the air quantity is adjustable in such a way that the burner is designed as a kit with setting parts for the air quantity of the combustion air flow that can be interchangeably inserted into the same burner housing. By providing the different adjustment parts, an adjustment of the combustion air flow is possible.

It is particularly advantageous if the local entry of the combustion air flow into the combustion chamber can also be adjusted with the setting parts.

It is preferably provided that at least one partial flow of the combustion air flow can be set for all setting parts.

It is particularly expedient if the inflow location of the partial flows is the same for all setting parts.

A particularly advantageous exemplary embodiment provides that the partial flow near the fuel jet is constant in the setting parts, while the recirculation stabilizing one

Partial flow with different setting parts

different values can be set. With regard to the constructive solution, it is provided in a particularly advantageous embodiment that the kit comprises an identical burner housing for all burner outputs.

In particular, it is provided that the kit for everyone

Burner performance includes an identical fan.

It is also advantageous if the kit comprises an identical combustion chamber.

Finally, it is advantageous if the kit comprises an identical nozzle assembly for all burner outputs.

Further features and advantages of the solution according to the invention are the subject of the following description and the drawing of some exemplary embodiments.

The drawing shows:

1 shows a longitudinal section through a first embodiment of a burner according to the invention.

2 shows a partial longitudinal section through a nozzle of the burner according to the invention;

Fig. 3 is an enlarged view of a front area of the

Nozzle according to FIG. 2; FIG. 4 shows a section along line IV-IV in FIG. 3;

5 shows a section along line V-V in FIG. 1 with the recirculation-stabilizing partial stream maximally or reduced to zero, with the adjusting disk partially broken away;

FIG. 6 shows a section as in FIG. 5 with a reduced recirculation-stabilizing partial flow with the adjusting disk partially broken away;

Fig. 7 shows a section as in Fig. 5 with minimal recirculation stabilizing. Partial flow;

8 shows a perspective illustration of the conditions in the combustion chamber with the flame tube partially broken away;

Fig. 9 is an enlarged fragmentary representation of the in

Fig. 1 shown section in the area of the aperture, with maximum recirculation stabilizing. Partial flow in the upper and reduced to zero minimal recirculation-stabilizing partial flow in the lower half;

10 shows a section similar to FIG. 1 of a second exemplary embodiment of the burner according to the invention; 11 shows a section similar to FIG. 1 of a third exemplary embodiment of the burner according to the invention;

12 shows a section similar to FIG. 1 of a fourth exemplary embodiment;

13 shows a section similar to FIG. 1 of a fifth exemplary embodiment;

14 shows a section similar to FIG. 1 of a sixth exemplary embodiment of the burner according to the invention;

15 shows a section along line XII-XII in FIG. 14 with maximum recirculation stabilizing! Partial flow and the aperture provided for setting the same;

16 shows a section as in FIG. 15 with the orifice used for a reduced recirculation-stabilizing partial flow; and

FIG. 17 shows a section as in FIG. 15 with the orifice used for the minimal, recirculation-stabilizing partial flow reduced to zero.

A first embodiment of an inventive

The burner, shown in FIG. 1, comprises a burner housing, designated as a whole by 10, with a support tube 12 and a flame tube 14 adjoining this. Arranged in the support tube 12 in an end region opposite the flame tube is a blower, designated as a whole, which comprises a blower drive 18 and a blower wheel 20. This fan 16 produces a

Air tube 22 passing through the support tube 12 and flowing in the direction of the flame tube 14.

Also arranged in the support tube 12 is a nozzle assembly, designated as a whole by 24, which has a nozzle carrier 26 with a nozzle 28 screwed into it. The nozzle 28 is designed as a return nozzle described in detail below and is supplied with liquid fuel, in particular oil, via a nozzle feed line 30, while part of the fuel fed into the nozzle feed line 30 flows back again via a nozzle return line 32, throttling the return line via an adjustable return valve 34 arranged in the nozzle return line 32.

The fuel is fed into the nozzle feed line 30 via a fuel feed pump 36, which is preferably also driven by the drive 18 of the blower 16, in particular on the same shaft as the blower wheel 20. This fuel feed pump 36 is fed with fuel via a pump feed line 38 and is also connected to a return line 40, in which excess fuel flows back from the fuel feed pump 36. The nozzle return line 32 after the return valve 34 also opens into this return line 40. 2, 3 and 4, the nozzle 28 comprises a nozzle head 50, which in turn is screwed onto a nozzle body 52 and receives a swirl body 54.

The nozzle head 50 is in turn also screwed into the nozzle carrier 26 so that the nozzle body 52 lies in a recess 56 of the nozzle carrier 26, the recess 56 forming a fuel supply area 58 which is connected to the nozzle feed line 30 and a return area 60 which is connected to the nozzle return line 32 is connected.

The fuel entering the fuel supply area 58 preferably flows through a filter 62 and then flows through two opposite inlet channels 64 of the nozzle body 52 into further inlet channels 66 in the swirl body 54 and from these, as shown in FIG. 3, into an annular inlet space 68 of the swirl body 54 , which is closed by a support plate 70 which closes the swirl body 54 on the end face. From the annular inlet space 68, the fuel enters into a swirl space 74 located radially inside the annular inlet space 68, in which a swirl flow is formed which corresponds to the orientation of the swirl channels 72, and from this swirl space 72 the fuel passes through an annular circumferential gap 76 into a spray bore 78, from which a conical fuel jet 80 emerges. Opposed to the spray-out bore 78 is a return channel 82 in the swirl body 54, which passes through the swirl body 54 and merges into a return channel 84 arranged in the nozzle body 52, which then finally opens into the return area 60 of the recess 56, which in turn then in turn communicates with the nozzle return line 32 communicates.

Further details of the nozzle 28 used in accordance with the invention result from the German patent 42 15 122, to which full reference is made in this connection.

The nozzle assembly 24 together with the nozzle 28 is within the

Support tube 12 arranged in a prechamber 48, which is also traversed by the air flow 22.

The prechamber 48 is closed off by a diaphragm designated as a whole by 90 and inserted into the support tube 12, to which a combustion chamber 92 adjoins, which is located downstream of the nozzle 28 and is enclosed by the flame tube 14. The flame tube 14 is also preferably held on the support tube 12.

The orifice 90 is arranged in such a way that the spray bore 78 with a nozzle opening is close to or in the plane 89 of the orifice 90 and the fuel jet 80 emerging at the nozzle 28 essentially spreads completely in the combustion chamber 92. For this purpose, the screen 90 is provided with an inflow opening 94 arranged coaxially to the longitudinal axis 86 of the nozzle 28. The inflow opening 94 is also selected to be large enough that between an edge 96 of the inflow opening 94 and an outer side 98 of the nozzle head 50 facing this edge 96 there remains an annular passage 100 through which a partial stream 102 close to the fuel jet, one overall from the antechamber 48, into the combustion chamber 92 incoming combustion air flow passes.

In order to reduce the flow velocity in the partial flow 102, the edge 96 of the inflow opening 94 is also provided with a vortex edge 104, which leads to the formation of eddies in the partial flow 102 and is formed, for example, by a step-like cross-sectional constriction of the inflow opening 94.

Another partial flow 106 of the combustion air flow entering the combustion chamber 92 from the pre-chamber 48 passes through openings 110 arranged radially outside the inflow opening 94 in a circular ring area 108, which are preferably on the partial circle 109 at equal angular intervals and with spaces 111 around the center of the circular ring area 108 are arranged.

The openings 110 preferably have an extension in the azimuthal direction with respect to the pitch circle 109 which corresponds to an angle which is approximately one to two times the angle corresponding to the extension of the spaces 111. However, the openings 110 can extend in the azimuthal direction over an angle which corresponds to approximately 0.1 to approximately 8 times the angle of the extension of the spaces 111.

The openings 110 are arranged in such a way that the partial flow 106 of the combustion air flow enters the combustion chamber 92 through the spaces 111 between the openings 110 in the form of a flow pattern corresponding to a circumferentially interrupted ring flow and thus the formation of an inner recirculation flow 112 and also an outer flow Recirculation flow 119 in the combustion chamber 92 is stabilized so that a flame root 114 of a flame 116 formed in the combustion chamber 92 is at substantially the same distance from the orifice 90, irrespective of a quantity of fuel carried by the fuel jet 80 and a corresponding amount by the partial flows 102 and 106 corresponding amount of combustion air entering the combustion chamber 92.

The flows according to the invention in the combustion chamber 92, shown in FIG. 8, thus include the partial flow 102 close to the fuel cone, which is cylindrically surrounding the fully conical fuel jet 80, which enters the combustion chamber 92 with a flow direction 103, which runs parallel to a flow direction 79 of the fuel jet 80. Furthermore, the recirculation-stabilizing partial flow 106 which has a flow direction 79 parallel flow direction 107 in the form of individual flows 105 enters the combustion chamber 92, the individual flows 105 lying on a circular cylinder which has the shape of the circular ring region 108 in cross section on the orifice 90 and is defined by the partial circle 109 lying in the middle of the jacket.

The flame root 114 in turn adjoins a non-burning part 81 of the fuel jet 80, which has a length of approximately 1 to approximately 4 cm, preferably approximately 1 to approximately 3 cm, and from this the flame 116 spreads out, which spreads out creates an inner wall region 15 of the flame tube 14 before it leaves it.

The area of the combustion chamber 92 from the orifice 90 to the inner wall area 15 on which the flame 116 contacts forms a so-called recirculation space 91. In this, hot gas flows in the form of an internal recirculation 112 between the flame tube 14 and the partial flow 106 back in the direction to the aperture 90 and in front of the aperture 90 inwards between the individual streams 105 in the direction of the non-burning part 81 of the fuel jet 80 in order to heat the non-burning fuel on the way to the flame root 115 and also the combustion air.

In addition, cold combustion gas exits the respective boiler in the form of the outer one via outer recirculation openings 118 arranged in the flame tube 14 after the orifice 90 Recirculation flow 119 into the recirculation space 91 close to the orifice and substantially prevents contact between the hot gases of the inner recirculation flow 112 and the cold orifice 90.

The outer recirculation flow 118 also passes close to the blinding between the individual flows 105 and then mixes with the combustion air flow 102, 106 by the through the

Increase flame tube 14 mass flow passing through so far that the flame root 114 remains at a constant distance of at least 2 cm from the orifice 90 and thus also from the nozzle 28 that the non-burning part 81 of the fuel jet 90 is long enough to hold the oil droplets to evaporate almost completely in the same.

Preferably, the sum of the areas of the openings provided for the entry of the combustion air flow into the combustion chamber, in particular the sum of the areas of openings 110 and the inflow opening 94, is such that it is at most approximately the sum of the areas of the recirculation openings for the external recirculation, in particular the Sum of the areas of the outer recirculation openings 118 formed as elongated slots in the circumferential direction.

The ratio of the area of the recirculation openings 118 to the area of the central inflow opening 94 is between approximately 0.3 to approximately 19.2, preferably between approximately 0.9 and 5.1. The flame chamber 117 then adjoins the recirculation chamber 91. In the first exemplary embodiment shown in FIGS. 1 to 9, the partial flow 102 near the fuel jet is preferably designed such that it stabilizes the corresponding recirculation flow without the recirculation-stabilizing partial flow 106 at the lowest burner output (FIG. 9 lower half) and then the recirculation-stabilizing partial flow in the case of large burner outputs 106 takes over the stabilization (FIG. 9 upper half) which the partial stream 102 near the fuel jet can no longer perform.

If the burner is dimensioned differently, it is also possible to provide both the partial flow 102 close to the fuel jet and a minimum partial flow 106 which stabilizes recirculation at the lowest power.

Such stabilization of the recirculation flows 112 and 119 can be achieved in particular if an outer diameter of the recirculation space 91 of the combustion chamber 92, for example corresponding to the inner diameter of the flame tube, is approximately 1.5 to approximately 3.9 times, better still approximately two to three times of the diameter of a partial circle 109 of the annular region 108, it is even more advantageous if the inner diameter of the recirculation space 91 of the combustion chamber 92 is approximately 2.2 to approximately 2.6 times, more preferably approximately 2.2 to approximately 2, 5 times the diameter of the pitch circle 109. The ratio of the diameter of the pitch circle 109 to

The diameter of the central inflow opening 94 is between approximately 1.0 and approximately 4.2, preferably approximately 2.6 to approximately 4.0, more preferably approximately 2.8 to approximately 3.5 and preferably between approximately 1.82 and approximately 2.0 .

In addition, it is advantageous if the central inflow opening 94 is dimensioned such that an outer diameter of the recirculation space 91 of the combustion chamber 92 is approximately 3.4 to approximately 8.5 times, more preferably approximately 4 to approximately 6 times, even better is about 4.4 to about 5.9 times the diameter of the central inflow opening 94.

The diameter ratios at which the adjustable blue burner according to the invention still works in all power ranges are summarized in Table I, the inner diameter of the flame tube corresponding to the outer diameter of the recirculation space 91 being "flame tube (14)", the diameter of the pitch circle having "pitch circle (109)". "and the diameter of the inflow opening are designated" inflow opening (94) ".

Preferred ranges of the diameter ratios, staggered according to individual burner outputs, are shown in Table II, the burner working with these diameter ratios with low emissions. Optimal emission values are approximately available with the diameter ratios given in Tables III and IV. In order to adapt the combustion air quantity of the combustion air flow to different burner capacities, an adjusting device, designated as a whole by 120, is provided, which, as shown in FIGS. 5 to 7, comprises an annular adjusting disc 122 which has openings 124 identical to the openings 110, which also in FIG the same angular distances as the openings 110 and at the same radial distance from a center of the annular region 108. For its part, the annular adjusting disk 122 lies, as shown enlarged in FIG. 9, in a cylindrical disk-shaped depression 126 provided in the diaphragm 90, which is open to the antechamber 48. The rotatable guidance of the shim takes place via the

Storage of the same with its outer edge 128 on one

cylindrical edge 130 of depression 126.

The shim 122 is adjustable so that, as shown in FIGS. 5 to 7, either the openings 124

are congruent with the openings 110 so that the maximum cross section is available for the partial flow 106 replacing the individual openings 110, or rotatable so that the openings 124 are no longer congruent with the openings 110 and only the overlapping regions of the openings 110 and 124 let the partial flow 106 pass so that the air volume of the partial flow 106 is reduced, as shown in FIG. 6. As shown in FIG. 7, the partial flow 106 can be completely interrupted, namely when the openings 124 are at a gap between the openings 110. To twist the adjusting disk 122, it is provided in a partial area of its outer edge with a toothing 132, in which a toothing 134 of an adjusting pinion of the adjusting device 120, designated as a whole by 136, engages. This adjusting pinion is in turn rotatably mounted on the diaphragm 90, and in the simplest case in a further cylindrical bearing recess 138 in the diaphragm 90, the rotatable bearing being in contact with the toothing 134 on cylindrical wall surfaces 140

Storage deepening 138 takes place. The bearing recess 138 opens towards the antechamber 48.

Both the adjusting disk 122 and the adjusting pinion 136 are held in their respective recesses 126 and 138 by fixing elements (not shown in FIG. 9), so that they each abut the recesses on the bottom side.

In the case of the first exemplary embodiment, the setting pinion 136 is, for example, self-lockingly mounted in the bearing recess 138 and is provided, for example, with a slot 142, which makes it possible to turn the setting pinion 136 using a conventional screwdriver, so that setting the setting disks 122 is also possible, the respective settings of the shims 122 are maintained by the self-locking adjustment pinion 136. The first embodiment now works such that when the partial flow 106 is interrupted, only the combustion air flowing from the partial flow 102 through the passage 100 into the combustion chamber 92 is available as combustion air quantity. The amount of fuel emitted from the nozzle 28 into the fuel jet 80 is adjusted in accordance with this amount of air, the amount of fuel being adjusted so that the flame 116 burns blue and stoichiometric or near-stoichiometric combustion occurs. This adjustment of the fuel quantity takes place via the adjustment of the return valve 34 and thus via the fuel flow returning from the nozzle 28 via the nozzle return line 32 into the return line 40.

In the case of larger outputs, by adjusting the adjusting disk 122, the sub-stream 106 can also contribute to the sub-stream 102 of the combustion air stream close to the fuel jet, this sub-stream 106 having the higher burner outputs

Recirculation flow 112 additionally stabilized. With the maximum amount of combustion air in the partial flow 106, approximately 5 times the cross-sectional area is available for the entry of the combustion air flow from the pre-chamber 48 into the combustion chamber 92 than with a completely prevented partial flow 106.

The amount of fuel discharged from the nozzle 28 into the fuel jet 80 is adjusted by the aforementioned setting of the return valve 34 with a corresponding throttling of the fuel returning from the nozzle 28. With all power settings of the invention

The distance between the flame root 114 of the flame 116 and the diaphragm 90 is essentially constant and it is a blue burning of the flame 116 with essentially stoichiometric or at all power settings of the burner

Near stoichiometric combustion adjustable.

In a second exemplary embodiment of the burner according to the invention, shown in FIG. 10, those parts which are identical to the first exemplary embodiment are provided with the same reference symbols. With regard to the description of these parts, reference can therefore be made in full to the statements relating to the first exemplary embodiment.

In contrast to the first exemplary embodiment, which has no additional flow guide elements in the combustion chamber 92, a flow guide ring 150 is provided in the second exemplary embodiment, which is arranged at a distance from the orifice 90, and with its front edge 152 up to a maximum of up to a quarter a distance between the aperture 90 and the foot portion 114 of the flame 116 extends. Furthermore, the flow guide ring 150 is arranged with a rear edge 154 facing the orifice 90 at a distance from the orifice 90, so that the recirculation flow 112 between the in the edge 154 and a front side 156 of the orifice 90 from rarely the orifice 90 in the flow guide ring 150 can occur. The Flow ring 150 also serves to additionally stabilize the recirculation flow 112, a significant distance between the front edge 152 and the foot region 114 of the flame 116 being necessary in order to ensure the formation of a strong recirculation flow 112 when the burner according to the invention has different power ratings and to support the effect of the recirculation-stabilizing partial flow 106.

The flow guide ring 150 is preferably held on the orifice 90 with webs 158.

In a third exemplary embodiment of a burner according to the invention, shown in FIG. 11, those parts which are identical to the first exemplary embodiment are provided with the same reference numerals, so that with regard to the description of these parts, full reference can also be made to the embodiment of the first exemplary embodiment . In contrast to the first exemplary embodiment, an actuator 160 is provided for the setting of the return valve 34 and an actuator 162 for the setting of the setting pinion 136, both of which can be controlled via a common controller 164.

This control 164 is preconfigured via an input 166 power settings of the burner according to the invention, the control 164 for each power setting at the input 166 the corresponding setting of Return valve 34 and the actuator 162 of the adjusting device 120 performs. For example, this can be carried out by positions of the actuators 160 and 162 which can be predetermined in a memory of the controller 164.

To additionally ensure that flame 116, as a blue-burning flame, stoichiometrically or

burns close to stoichiometric is an additional one

Lambda probe 168 arranged in the exhaust gas flow of the flame 116, which is also connected to the controller 164, so that the controller 164, after rough adjustment of the power via the actuators 160 and 162, is additionally able to carry out a fine adjustment of either the amount of combustion air or the amount of fuel, to maintain stoichiometric or near stoichiometric combustion conditions.

In the simplest case, the control 164 is constructed in such a way that the desired outputs of the burner according to the invention can be set by means of a setting transmitter, for example manually.

In an improved embodiment of the third exemplary embodiment, the control 164 is designed in such a way that, via an overall control of a system, for example a heating system, in which the burner according to the invention is integrated, a specification is made for the required output of the burner according to the invention, so that the control 164 then, depending on the requested output of the burner according to the invention, the actuators 160 and 162 are adjusted accordingly and a fine adjustment on the basis of the measured values of the

Lambda probe 168 carries out.

In a fourth embodiment, shown in Fig.

12, those parts which are identical to the above exemplary embodiments are provided with the same reference numerals, so that reference is made in full to the description of these exemplary embodiments.

In contrast to the previous exemplary embodiments, the flame tube 14 is narrowed radially over its length in the region of the flame chamber 117 following the recirculation chamber 91 up to the front end 170, so that the inner wall region 15 against which the flame 116 rests is already radially offset inwards.

This flame tube makes it possible, particularly with small burner outputs, preferably less than 20 kW, to obtain a flame 116 which is stable in the flame tube 14. Furthermore, this geometry prevents undesired drawing in of smoke gases from the front end of the flame tube 14.

In a fifth embodiment, shown in Fig.

13, in the same way as in the fourth exemplary embodiment, reference is made to the above explanations with regard to the parts provided with the same reference symbols. In contrast to the previous exemplary embodiments, the openings 110 are closed by means of conical plugs 172 which are held on rods 174 and are movably guided in the axial direction of the support tube 12 via a guide 176 on the nozzle assembly 24 in the support tube 12. Depending on how far the conical plugs 172 protrude into the openings 110, a reduction in the cross-sectional area of each opening 110 is possible.

In a sixth embodiment of a burner according to the invention, shown in FIG. 14, those are

Parts which are identical to those of the first exemplary embodiment are provided with the same reference numerals, so that reference can also be made in full to the statements relating to the first exemplary embodiment with regard to these parts.

In contrast to the first exemplary embodiment, a power setting is also possible in the sixth exemplary embodiment, shown in FIGS. 14 to 17, but in this exemplary embodiment the burner according to the invention is constructed in the form of a kit. Instead of a nozzle 28 designed as a return nozzle with a nozzle return line 32 and a return valve 34 provided therein for adjusting the fuel flow, a set of several nozzles 228 are provided, each of which has the same spray pattern and the same air flow side Deliver outer contour and thus the same shape of the fuel jet 80, but with different amounts of fuel. With these nozzles 228, the fuel is supplied via the fuel feed pump 36 and the nozzle feed line 30, but a nozzle return line 32 is unnecessary.

The different nozzles 228 correspond to different outputs of the burner according to the invention.

In order to adapt the combustion air flow to the different fuel quantities of the different nozzles 228, several orifices 290a to 290c are provided, the orifice 290a being assigned to the nozzle 228 which emits the largest amount of fuel, the orifice 290c to the nozzle which emits the smallest amount of fuel and the orifice 290b to a nozzle 228 is assigned, the amount of fuel between the maximum and minimum amount of fuel.

The orifices 290a to c differ in the cross section of the openings 210 provided for the partial flow 106, but not with regard to their position, the openings 210a being identical to the openings 110 with regard to the total cross section of the openings, while the openings 210b show a total cross section which corresponds to an intermediate setting, for example shown in FIG. 6, and thus also an intermediate output of the corresponding nozzle 228. The openings 210 are completely absent from the orifice 290c, so that this corresponds to the position of the adjusting device 120 shown in FIG. 7, in which the partial flow 106 is completely prevented and the combustion air flow is formed only by the partial flow 102.

Depending on the nozzle 228 mounted in the nozzle assembly 24, one of the orifices 290a to 290c is to be installed in the support tube 12, the orifices 190 being removably held in the support tube in the fourth exemplary embodiment. For this purpose, a holding ring 292 is used, for example, on the nozzle assembly 24

Tripod 294 held, which acts on the respective panel 290 on its side facing the pre-chamber 48 296 and presses it against a sealing ring 298 in the direction of the flame tube 14. The nozzle assembly 26 as a whole is displaceable in the direction of a longitudinal axis 300 of the support tube 12 and is acted upon by a spring (not shown in FIG. 14) in the direction of the flame tube 12. It is thus possible to remove the diaphragm 290 in the direction of the prechamber 48, while the diaphragm 290 is fixed in the direction of the flame tube 14 by the abutment, for example designed as a sealing ring 298.

Furthermore, in the same way as is preferably shown in connection with the first exemplary embodiment, the combustion chamber 92 is designed free of mechanical flow guiding elements, so that when the nozzle 228 corresponding to the respective power and the respective orifice 290 are installed, a stable design is likewise formed the appropriate recirculation flow 112 is ensured and it is also ensured that the flame 116 as a blue-burning flame delivers a stoichiometric or near-stoichiometric combustion. Furthermore, a function corresponding to the first exemplary embodiment is ensured by the cross sections of the openings 210 correspondingly provided for the partial flow 106.

Claims

PATENT CLAIMS

1. Burner for liquid media comprising a burner housing (10) which has a support tube (12) and an adjoining flame tube (14), a nozzle block (24) arranged in the support tube (12) in a prechamber (48) a fuel jet (80) generating nozzle (28), a substantially mixing tube-free combustion chamber (92) arranged in the flame tube (14), in which the fuel jet (80) spreads, a separating element (90) between the prechamber (48) and the combustion chamber (92) with a central opening (94) through which the fuel jet (80) passes, a fan (16) for generating a combustion air flow entering the combustion chamber (92), which comprises a partial flow (102) close to the fuel jet, in which Combustion chamber (92) which burns fuel with a blue-burning flame (116) essentially stoichiometrically or near-stoichiometrically,

characterized in that in the combustion chamber (92) in addition to the fuel stream near the partial stream (102) opposite this recirculation-stabilizing partial flow (106) of combustion air, which is located at a radially outer distance, occurs in the combustion chamber (92) and forms an internal recirculation flow (112) which runs back from the blue-burning flame (116) to the non-burning part (81) of the fuel jet (80) that the recirculation-stabilizing partial flow (106) of the combustion air stabilizes the internal recirculation flow (112).

2. Burner according to the preamble of claim 1 or according to claim 1, characterized in that openings (118) are provided in the burner housing through which a cold combustion gas leading external recirculation flow (119) enters the combustion chamber (92) that the outer recirculation flow (119) enters the combustion chamber (92) near the separating element (90) and is so large that a flame root (114) of the blue-burning flame (116) is at least 1 cm from the nozzle (28) and that Between the nozzle (28) and the flame root (114) a non-burning part (81) of the fuel jet (80) spreads conically with the addition of combustion air (102, 106).

3. Burner according to the preamble of claim 1 or according to claim 1 or claim 2, characterized in that in the burner housing (10) openings (118) are provided through which an external cold combustion gases leading recirculation flow (119) enters the combustion chamber (92), that the outer recirculation flow (119) near the separating element (90) into the

Combustion chamber (92) occurs and that this shields an internal recirculation flow (112) from the separating element (90), which returns as in the combustion chamber (92) from the blue-burning flame (116) to the non-burning part (81) of the fuel jet (80) developing current.

4. Burner according to one of the preceding claims, characterized in that the inner recirculation flow (112) flows from the flame (116) on an inside of the flame tube (14) in the direction of the separating element (90).

5. Burner according to one of the preceding claims,

characterized in that the inner recirculation flow (112) is yellow-burning.

6. Burner according to one of the preceding claims,

characterized in that the inner recirculation flow (112) passes through the recirculation-stabilizing partial flow (106).

7. Burner according to one of the preceding claims, characterized in that the recirculation-stabilizing partial flow (106) substantially parallel to the flow direction (79) of the fuel jet (80) enters the combustion chamber (92).

8. Burner according to one of the preceding claims, characterized in that the partial flows (102, 106) enter the combustion chamber (92) independently of the set amount of air at the same location in each case.

9. Burner according to claim 8, characterized in that at least one of the partial flows (102, 106) is adjustable to adjust the amount of fuel to adjust the amount of air.

10. Burner according to claim 9, characterized in that the recirculation-stabilizing partial flow (106) is adjustable in terms of the amount of air.

11. Burner according to claim 10, characterized in that the amount of air in the recirculation-stabilizing partial flow (106) is maximum at maximum amount of fuel and minimal with minimum amount of fuel.

12. Burner according to one of the preceding claims, characterized in that the amount of air in the near-fuel jet stream (102) is constant at all settings of the amount of fuel.

13. Burner according to one of the preceding claims, characterized in that the fuel jet (80) forms a coherent nozzle opening emanating cone.

14. Burner according to one of the preceding claims, characterized in that the fuel stream near the partial stream (102) substantially parallel to the flow direction (79) of the fuel jet (80) enters the combustion chamber (92).

15. Burner according to one of the preceding claims, characterized in that the near-fuel jet partial stream (102) flows around the fuel jet (80) into the combustion chamber (92).

16. Burner according to claim 15, characterized in that the fuel stream near the partial stream (102) in the region of a circumference of a nozzle head (50) of the nozzle (28, 228) flows into the combustion chamber (92).

17. Burner according to claim 16, characterized in that the fuel stream near the partial stream (102) flows along a defined outer contour (98) of the nozzle head (50).

18. Burner according to claim 15, characterized in that the near fuel jet stream (102) and the fuel jet (80) through the same central inflow opening (94) enter the combustion chamber (92).

19. Burner according to claim 18, characterized in that the fuel jet near partial stream (102) through a passage (100) between the nozzle head (28, 228) and an edge of an inflow opening (94) provided for the fuel jet near partial stream (102) into the combustion chamber (92) flows.

20. Burner according to claim 18 or 19, characterized in that the inflow opening (94) for the fuel jet-near partial stream (102) is designed to generate turbulence.

21. Burner according to claim 20, characterized in that the inflow opening (94) is provided with a swirl edge (104).

22. Burner according to one of the preceding claims, characterized in that the entire combustion air flow (102, 106) is passed through a prechamber (48).

23. Burner according to claim 22, characterized in that the combustion air flow (102, 106) through a separating element (90) into the combustion chamber (92).

24. Burner according to claim 23, characterized in that the separating element (90, 290) has an inlet opening (94) facing the nozzle (28, 228) for the partial stream (102) close to the fuel jet.

25. Burner according to one of claims 22 to 24, characterized in that the separating element (90, 290) relative to the inflow opening. (94) for the partial stream (102) close to the fuel jet has at least one radially outer opening (110, 210) for the partial stream (106) which stabilizes the recirculation.

26. Burner according to one of the preceding claims, characterized in that the combustion chamber (92) extends from a plane (89) which is close to the plane of the nozzle opening.

27. Burner according to one of the preceding claims, characterized in that the combustion chamber (92) between the separating element (90) and the region of the flame root (114) has a substantially constant cross section.

28. Burner according to one of the preceding claims, characterized in that the separating element (90) is an aperture.

29. Burner according to one of the preceding claims, characterized in that the diaphragm (90) extends in one plane (89).

30. Burner according to one of the preceding claims, characterized in that the combustion chamber (92) one of the non-burning part (81) of the fuel jet

(80) and has a recirculation space (91) extending around it.

31. Burner according to claim 30, characterized in that the recirculation space (91) extends at least to the flame root (114).

32. Burner according to one of claims 30 or 31, characterized in that the recirculation-stabilizing partial flow (106) enters the recirculation space (91).

33. Burner according to one of the preceding claims, characterized in that the recirculation-stabilizing partial flow (106) is formed symmetrically to an axis of symmetry of the combustion chamber (92).

34. Burner according to one of the preceding claims, characterized in that the recirculation-stabilizing partial flow (106) in the form of a current image lying on a cylinder (105) enters the combustion chamber (92).

35. Burner according to claim 34, characterized in that the current pattern is composed of parallel component streams (105).

36. Burner according to claim 35, characterized in that the individual flows (105) are arranged at a constant angular distance (111) from one another.

37. Burner according to claim 36, characterized in that the ratio of the angular distance (111) between two individual component streams (105) to the angular width of the inlet cross section (110) of each individual component stream (105) is between approximately 10 and approximately 0.1.

38. Burner according to claim 37, characterized in that the ratio of the angular distance (111) between two component streams (105) to the angular width of the inlet cross-section (110) of each component stream (105) is between approximately 1.5 and 0.1.

39. Burner according to claim 38, characterized in that the ratio of the angular distance (111) between two component streams (105) to the angular width of the inlet cross-section (110) of each component stream (105) is in the range of approximately 0.7 and 0.25.

40. Burner according to one of claims 33 to 39, characterized in that the cylinder is a circular cylinder, which is fixed by a central circle lying in the same (109).

41. Burner according to claim 40, characterized in that the recirculation space (91) has an outer diameter which is approximately 1.5 to approximately 3 times larger than the diameter of the pitch circle (109) of the circular cylinder.

42. Burner according to claim 41, characterized in that the recirculation space (91) has an inner diameter which is approximately 2 to approximately 2.5 times larger than the diameter of the pitch circle (109) of the circular cylinder.

43. Burner according to claim 42, characterized in that the recirculation space (91) has an inner diameter which is approximately 2.4 times as large as the diameter of the pitch circle (109) of the circular cylinder.

44. Burner according to one of claims 30 to 43, characterized in that the flame chamber (117) adjoins the recirculation chamber (91).

45. Burner according to claim 44, characterized in that the flame space (117) has an inner diameter which is smaller than that of the recirculation space (91).

46. Burner according to claim 45, characterized in that the inner diameter of the flame space (117) is in the range of about 0.6 to about 0.9 times the inner diameter of the recirculation space (91).

47. Burner according to claim 46, characterized in that the inner diameter of the flame chamber (117) in the range of approximately 0.8 times the inner diameter of the

Recirculation space (91).

48. Burner according to one of the preceding claims, characterized in that the flame (116) has a flame root (114) lying in the combustion chamber (92).

49. Burner according to claim 48, characterized in that the combustion chamber (92) extends beyond the flame root (114).

50. Burner according to one of the preceding claims, characterized in that the outer recirculation flow (119) separately from the combustion air flow (102, 106) enters the combustion chamber (92).

51. Burner according to claim 50, characterized in that the outer recirculation flow (119) through recirculation openings (118) in the flame tube (14) enters directly into the combustion chamber (92).

52. Burner according to one of the preceding claims, characterized in that a surface of the openings (94, 110) provided for the entry of the combustion air flow (102, 106) into the combustion chamber (92) maximally approximately the surface provided in the flame tube (14) Recirculation openings (118) for the outer recirculation flow (119) corresponds.