Connection duct

The invention is a connection duct between the blower and a mixing device of a burner. The connection duct expands wedge-shaped along a first direction and diverts air from the blower to a second direction. The connection duct further comprises diverting means for diverting the air in a circular flow around the second direction corresponding to a longitudinal axis of the mixing device. The diverting means comprise a tube section with at least one inflow opening arranged in the peripheral wall of the diverting means. A truncated cone comprising a tapering section is arranged in the tube section so that the tapering section faces in the direction of the mixing device. A passage cross-section of the inflow opening can be adjusted by a tube arranged in the peripheral wall which can be rotated around the tube's longitudinal axis and bears against the internal surface of the tube section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Patent Application Serial No. 20 2009 010 689.6, filed Aug. 7, 2009, the entire contents of which is herein incorporated fully by reference.

FIGURE FOR PUBLICATION

To be determined by the U.S.P.T.O.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a connection duct between a blower of a burner and a mixing device of that burner. More specifically, the present invention relates to a connection duct between a blower and a burner and a mixing device of the burner such that a favorable influx of air into the mixing device is accomplished so that the air is swirled already before it enters the air nozzle in order to achieve an optimal airflow for attaining a stable flame.

2. Description of the Related Art

The related art involves burners with a blower and a mixing device; and, wherein the blower creates an airflow in a first direction and the air is introduced into the mixing device. For this purpose, connection ducts between the blower of a burner and a mixing device of a burner are known, by which the air created by the blower is introduced into the mixing device. It is known, that the blower is introduced into the extension of the longitudinal axis of the mixing device.

One difficulty that arises is that the blower is subjected to a high thermal load by the combustion chamber. Therefore, it is also known to arrange the blower such that the air flows out in a first direction, and to divert the air in a connection duct in a second direction, so that the blower can be offset laterally in relation to the longitudinal axis of the mixing device, where the thermal load is less for the blower.

What is not appreciated by the prior art is that the air flow is not optimized when introduced to the mixing chamber of the burner. Accordingly, there is a need for an improved connection duct between a blower and a burner and a mixing device of a burner such that a favorable influx of air into the mixing device is accomplished.

The invention teaches that this aspect is achieved through a connection duct between a blower of a burner and a mixing device of a burner, for diverting outflowing air from the blower from a first direction to a second direction, and wherein the connection duct further comprises diverting means for diverting the air in a circular flow around the second direction.

ASPECTS AND SUMMARY OF THE INVENTION

An aspect of the present invention is to provide a connection duct between a blower of a burner and a mixing device of a burner, for diverting outflowing air from the blower from a first direction to a second direction.

Another aspect of the present invention is to provide diverting means for diverting the air in a circular flow around the second direction such that a favorable influx of air into the mixing device is accomplished.

The connection duct, as taught by the invention, between the blower of a burner and the mixing device of the burner which diverts the air flowing out of the blower in a first direction into a second direction, which in particular is perpendicular in relation to the first direction, is characterized in that means are provided in the connection duct which direct the air in a circular flow around the second direction. In this manner, the air is swirled already before it enters the air nozzle in order to achieve an optimal airflow for attaining a stable flame.

A preferred embodiment is that the second direction corresponds to a longitudinal axis of a mixing device, so that the air is introduced by the connection duct into the mixing device in the desired direction.

The connection duct preferably expands wedge-shaped along the first direction in order to further aid the influx of air into the burner tube in the direction towards the air nozzle and to increase the static combustion air pressure.

Another aspect incorporates the means for directing the air in a circular flow around the second direction as a tube section with at least one inflow opening arranged in the peripheral wall and developed in a longitudinal axis, wherein the longitudinal axis runs parallel to the second direction and the air from the first direction flows into the tube section from the first direction tangentially through the inflow opening. With a tangential inflow, the desired circular flow results on the inside wall of the tube section.

A further aspect is a passage cross-section of the inflow opening that is variable, so that the air volume and the air velocity can be changed.

A further aspect is a tube with an opening arranged in the peripheral wall for varying the passage cross-section of the inflow opening which is arranged so that it can be rotated around its longitudinal axis and which particularly bears against one external surface at least in sections of the internal surface of the tube section. In this manner, space-saving means for varying the passage cross-section are provided.

According to a preferred embodiment of the invention, the tube has a tangentially arranged deflector, which favors splitting-up the airflow.

An embodiment of the means for directing the air into a circular flow around the second direction is that the means are developed as a tube section with two diametrically opposed inflow openings arranged in the peripheral wall and a longitudinal axis, wherein the longitudinal axis runs parallel to the second direction and the air from the first direction flows tangentially into the tube section through the inflow openings, where between the blower and the tube section an air deflector is arranged approximately parallel to the first direction such that a part of the inflowing air flows in through one of the inflow openings and a part of the inflowing air is diverted by means of the air deflector and flows into the tube section through the diametrically opposed inflow opening. Consequently, air flows tangentially through two diametrically opposed inflow openings into the tube section, which improves the homogenous swirling.

The air deflector is preferably arranged so that it can be varied within the connection duct, so that the air volume of the inflow openings can be variably distributed. An increase of the angular momentum of the air column can be achieved by a helicoidal extension of the external radial air duct.

Preferably, a truncated cone is arranged in the tube section, the tapered section of which faces into the direction of the mixing device, in order to facilitate an airflow in the direction of the mixing device that is as non-turbulent as possible.

The mixing device preferably comprises a burner tube, where the tube section at the same time forms the burner tube of the mixing device, so that the swirled air flows directly into the burner tube in this manner.

A burner as taught by the invention comprises a blower, a mixing device, and a connection duct as taught by the invention.

In a further embodiment of the present invention, the burner comprises a blower, where the blower speed is steplessly variable, in order to vary the air volume required for the combustion, the air velocity, and the air pressure, especially in combination with a fuel nozzle that can be axially shifted toward the air nozzle arranged on the nozzle connection of the mixing device.

In a further embodiment of the present invention, the mixing device comprises a nozzle connection with a nozzle by means of which the fuel is supplied, where the fuel quantity is steplessly variable, for example with the help of an appropriate fuel pump or an appropriate fuel valve. The burner can also be operated in a modulating operating mode, particularly in combination with the variable speed-controlled blower and the axially shiftable nozzle connection, in addition to a single or multistage operation of the burner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to several embodiments of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms, such as top, bottom, up, down, over, above, and below may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. The words “connect,” “couple,” and similar terms with their inflectional morphemes do not necessarily denote direct and immediate connections, but also include connections through mediate elements or devices.

FIGS. 1 to 3show different views of a mixing device10, which comprises a burner tube20, which is supplied with combustion air from a blower120. A flame-tube30connects axially to the burner tube20. In principle, it is possible that the flame-tube30attaches directly to the burner tube20and is thus shaped partially overlapping, wherein every conceivable connection between the burner tube20and the flame-tube30is possible. In the present embodiment, the burner tube20terminates on one interior side of a casing110of a burner100, wherein the flame-tube30is attached outside of the casing110of the burner100with the help of an adapter ring80. The flame-tube30has an expanded diameter compared to the burner tube20. It is also possible, however, that the diameter of the flame-tube tapers compared to the burner tube20or that the burner to20and the flame-tube30have essentially identical diameters. The mixing device10comprises a longitudinal axis1. The longitudinal axis1of the mixing device essentially corresponds to the longitudinal axis of the burner tube20and the longitudinal axis of the flame-tube30.

Between the burner tube20and the flame-tube30, a junction region is formed which in an overlapping arrangement of the burner tube20and the flame-tube30comprises the end sections of the burner tube20and/or the flame-tube30that are facing each other and can as presently include the adapter ring80, if an adapter ring80is used.

The adapter ring80comprises an end section81facing the burner tube20and an end section82facing the flame-tube30, wherein the adapter ring80with its end section81is attached to the outside of the casing110and in its end section82comprises an overlap with the flame-tube30and is connected with the flame-tube30by means of a quarter-turn fastener. Alternatively, a connection can also be made by press-fit or by welding.

In the junction region of burner tube20and flame-tube30, recirculation openings85are arranged, which, depending on the connection between the burner tube20and the flame-tube30, can be arranged in an end section of the burner tube20facing the flame-tube30, in an end section of the flame-tube30facing the burner tube and/or in the adapter ring80, wherein they are arranged in the adapter ring80in the present case. Combustion gases from the combustion chamber can be recycled through the recirculation openings85into the flame of the mixing device10.

A separation disk50is inserted into the burner tube20, the outside diameter of which essentially corresponds to the inside diameter of the burner tube20and which comprises a centric opening51, through which a nozzle connection40with a fuel nozzle42is run coaxially. An air nozzle60is arranged coaxially on the separation disk50, which is developed so that it comprises an inlet opening61that is facing the burner tube20and which tapers from the diameter of the inlet opening61up to the discharge opening63which is facing the flame tube30. The air nozzle60comprises a flange64on its opening61, which in the present example is formed by the separation disk50. The air nozzle60essentially has a conical shape, which can also comprise an arched outer casing or an outer casing like a truncated cone. It is also possible that the air nozzle60initially has a cylindrical section which connects to a tapering section.

The casing110of the burner100comprises an opening112through which the air nozzle60projects, wherein the air nozzle60seals the casing110of the burner100on the combustion air side by means of the flange62, i.e. by means of the separation disk50. For that purpose, a seal66is arranged between the flange62and the inside wall of the casing110, wherein the flange62comprises an outside diameter that is larger than that diameter of the opening112of the casing110and the air nozzle60on the end of the burner tube that has an outside diameter which essentially corresponds to the diameter of the opening112. The flange62and the seal66are pressed from the inside against the inside wall of the casing110, for example by spring loading.

The separation disk50comprises swirl openings53which puts the air that flows through the burner tube20into the air nozzle60in rotation around the longitudinal axis1of the mixing device10.

A nozzle connection40is axially inserted in the air nozzle60, by means of which the fuel, for example, is supplied both in a gaseous form as well as in a liquid form. At the front end of the nozzle connection40, the fuel is discharged atomized through the fuel nozzle42. The supplied gaseous or liquid fuels can be fossil, synthetic, or biogenic fuels.

The fuel nozzle42can be developed as a fuel nozzle for liquid fuels, or as a gas nozzle. It is also possible that the nozzle connection40is developed with an annular gas nozzle in the area of the fuel nozzle42for liquid fuels, for oil for example, so that the burner100can be operated as a dual-fuel operation with gas and liquid fuel.

The mixing device10comprises two ignition electrodes55of a transistorized ignition system with which the atomized fuel is ignited. The ignition electrodes50are angled on their free ends such that their free ends are positioned at a smaller distance than their ends that are not angled, where the free ends are essentially bent in front of the discharge openings63of the air nozzle60. The flame is ignited between both ends of the ignition electrodes55. The fuel nozzle42is arranged in this instance such that the flame in the flame-tube30extends in front of the discharge opening63of the air nozzle60. The externally attached ignition electrodes55can be replaced without having to disassemble the burner100. The ignition electrodes55can also be used as ionization electrodes if the flame is monitored with an ionization current. If no ionization monitoring is used, the flame can be monitored optically and/or by means of direct measurement of the combustion quality using a CO or O2sensor.

The mixing device10comprises recirculation means70which are arranged axially fixed inside of the mixing device10and which can be used to change the passage cross-section86of the recirculation openings85by adjustment. The recirculation means70are particularly developed as an annular element with a peripheral wall71, which in an alternative embodiment can comprise a base72to form a cup-shaped element in this way, which is open in the direction of the flame-tube30, for example. In this case, the outside diameter of the peripheral wall71of the recirculation means70essentially corresponds to the inside diameter of the adapter ring80, wherein a clearance is provided, if necessary, but where the adapter ring80generally serves as the guide tube for the recirculation means70. In the base72of the recirculation means70a centric opening73is arranged, which is positioned upstream of the discharge opening74of the air nozzle60and the nozzle connection40with the fuel nozzle42. The ignition electrodes55are run through two further openings of the base72of the recirculation means70. The centric opening73of the base72of the recirculation means70can be developed as a discharge opening74in the form of a nozzle.

Openings75are arranged in the peripheral wall71of the recirculation means70. Both the recirculation openings85as well as the openings75are developed as slots which are inclined particularly towards the longitudinal axis1of the mixing device10, wherein the recirculation openings85and the openings75preferably correspond essentially in their form and inclination. The recirculation means70are axially fixed in that they abut on the end of the burner tube20facing the flame-tube30which is inserted overlapping inside on the adapter ring80. The recirculation means70are preferably additionally axially fixed in that the centric opening73of the base72on the air nozzle60is arranged fixed to the discharge opening63of the air nozzle60, for example. For this purpose, especially a flange64is arranged on the discharge opening63of the air nozzle60which is fixed on the base72of the recirculation means70by welding or by screwing, for example. The base72of the recirculation means70can particularly serve as a dividing wall against the heat between the burner tube20and the flame-tube30. In addition, insulation can be arranged between the recirculation means70and the outside of the casing110of the burner100in order to reduce the heat load on the combustion chamber.

The recirculation means70are developed and arranged rotatably around their longitudinal axis inside of the mixing device10, which in particular corresponds with the longitudinal axis1of the mixing device10, in order to vary the passage cross-section86of the recirculation openings85during rotation around their longitudinal axis. This occurs particularly as a result that by rotating the recirculation means70around their longitudinal axis, the opening75are either arranged aligned with the recirculation openings85and therefore free the complete passage cross-section86of the recirculation openings85or during the further rotation of the peripheral wall71of the recirculation means70cover the recirculation openings85at least partially or completely and thus vary the passage cross-section86up to the complete closure of the recirculation openings85.

The rotation of the recirculation means70occurs especially by means of an actuating element inside of the mixing device10. Present here is the actuating element through the air nozzle, which is connected axially and torque-proof with the recirculation means70and is developed torque-proof on a support43arranged on the air nozzle60for the nozzle connection40. The support43holds the nozzle connection40coaxially in the burner tube20and the air nozzle60. The support43comprises especially a first element43aand a second element43b, which are connected torque-proof by means of a claw coupling44(see especiallyFIG. 6). The second element43bhere is arranged upstream of the separation disk50, which is connected with the air nozzle60, while the first element43ais arranged upstream of the second element43band is connected upstream with an actuation plate90, by means of which the support43is particularly attached in the casing110of the burner100. The actuation plate90permits especially an airtight sealing of the casing110of the burner100and is preferably arranged pivoted in the casing110.

When turning the actuation plate90, therefore, the first element43aof the support43is rotated by means of the claw coupling44and at the same time the second element43bof the support43and above the separation disk50as well as the air nozzle60arranged on it including the recirculation means70arranged on the air nozzle60, so that in this manner with the help of the actuation plate90, the recirculation means70can be adjusted from outside of the burner100, in order to be able to vary the passage cross-section86of the recirculation openings85during the operation of the burner100.

The rotational travel of the actuation plate90is preferably limited by means of a slot92arranged in the actuation plate90which is developed as a curved segment, and a peg93guided in the slot92, which is arranged torque-proof for example on the outside wall of the casing110limited, in order to adjust the positions uniquely so that they can be visible from the outside, in which the recirculation means70either completely open, or completely close, the recirculation openings85. An adjustment of the actuation plate90can either occur manually or also automatically, especially automated with the help of a controller.

Between the first element43aand the second element43bof the support43, a spring45, in particular a coil spring45, is arranged (see particularlyFIG. 6), which is tensioned between appropriate peripheral projections on the first element43aand the second element43band therefore causes the second element43bincluding the separation disk50arranged on it to be pressed against the inside wall of the casing110, so that with the help of the separation disk50and the seal66arranged on the inside wall of the casing110, the opening112is sealed through which the air nozzle60of the mixing device10is run, occurs.

FIGS. 4 and 5provide perspective, partial sectional views of the mixing device10according toFIGS. 1 to 3, where the air nozzle60on the side of the burner tube is not terminated by the separation disk50. The sealing between the interior space of the burner tube20and the interior space of the flame-tube30preferably occurs through the base72of the recirculation means70. The separation disk50can especially be dispensed with if the already swirled air is supplied into the burner tube20.

FIGS. 7 to 10show different views of the burner100with a mixing device10according toFIGS. 1 to 3, from which it can be seen that in one embodiment, the nozzle connection40including the fuel nozzle42is arranged axially shiftable in the mixing device10. In this context especially,FIGS. 7,9, and10show the nozzle connection40in a first position, in which the fuel nozzle42is positioned in the discharge opening63of the air nozzle60, whileFIG. 8shows the position of the nozzle connection40, in which the fuel nozzle42is positioned axially offset upstream of the discharge opening63of the air nozzle60.

In order to be able to adjust the nozzle connection40axially, a spindle47is arranged on the upstream end of the nozzle connection40, which is guided by an adjusting nut48. When turning the adjusting nut48, therefore, the spindle47and the nozzle connection40that follows, including the fuel nozzle42, is either turned into or out of the mixing device10, depending on the direction of rotation. Because the spindle47projects out of the upstream end of the burner tube from the housing110of the burner100, it is especially possible that an axial movement of the nozzle connection40can also occur during the operation of the burner100. The axial position of the nozzle connection40is steplessly adjustable by means of the adjusting nut48.

Locking means can be provided, so that when the adjusting nut48is in the desired position, the adjusting nut48can be locked in order to prevent unintentional movement of the adjusting nut48.

Furthermore, an interlocking device49can be provided so that an interlock is possible to lock the adjusting nut48in the axial direction to prevent that the spindle47is axially pulled out completely. When the interlocking device49is loosened, the spindle47including the nozzle connection40and the fuel nozzle42attached thereon can be pulled out axially from the mixing device10, so that the fuel nozzle42can be easily replaced in this manner. In this context, the interlocking device49is particularly developed as a shiftable plate49aarranged transverse to the longitudinal axis1of the mixing device10, with a keyhole type opening49b(see especiallyFIGS. 4,6, and11), so that during the engagement of the smaller part of the keyhole type opening49b, the axial locking of the adjustment nut48and, when the adjusting nut48is engaged in the widened part of the keyhole type opening49b, the adjusting nut48including the threads (not shown) and the nozzle connection40can be pulled out.

The nozzle connection40can in particular be axially shifted manually or automatically, especially if the automatic shift can be shifted by a controller.

FIGS. 11 to 15show different components of the burner100with the mixing device10, the blower120, and a fuel pump140.

The blower120generates airflow along a first direction x (see especiallyFIGS. 11 and 16), which is supplied into the burner tube20of the mixing device10by means of a connection duct130. The embodiment of the connection duct130is explained in greater detail by means ofFIGS. 16 to 18, which in principle is independent of the actual embodiment of the mixing device10. The blower120generates an airflow in the first direction x, in which the air flows into the connection duct130, wherein the connection duct130diverts the air into a second direction y, which especially runs perpendicular to the first direction x. The second direction y in particular corresponds to the longitudinal axis1of the mixing device10, so that the connection duct130ensures that the air flows into the mixing device10in the direction of the longitudinal axis1, but the blower120does not have to be arranged in the extension of the longitudinal axis1, where the thermal load is high, but can be arranged offset to longitudinal axis1, where the thermal load is less.

In the first direction x, the connection duct130expands wedge-shaped in order to already provide a velocity component in the second direction y.

The connection duct130is especially designed so that it comprises means which divert the air that inflows in the first direction x in a circular flow around the second direction y. In this manner, an intrinsic angular momentum of the airflow is already achieved in connection duct130, which benefits the working method of the mixing device10to the extent that improved turbulence between the inflowing air and the injected fuel occurs, so that a more stable flame can be achieved in this manner.

The connection duct130comprises a tube section132, the longitudinal axis of which runs parallel to second direction y and therefore parallel to longitudinal axis1of the mixing device10and which particularly, at least in sections, corresponds with the burner tube20. The tube section132comprises at least one, presently two diametrically opposed inflow openings134. The airflow along the first direction x can inflow tangentially into the tube section132through one of the two inflow openings134. Air can likewise flow tangentially into the tube section132through the diametrically opposed inflow opening134, but after being diverted by 180° from the first direction x. In this manner, with the help of the connection duct130, air is directly supplied tangentially into the burner tube20, wherein a circular flow is generated around the longitudinal axis1of the mixing device10and therefore already swirled air is supplied to the air nozzles60through the burner tube20, so that the separation disk50with swirl openings53can be dispensed with, if necessary, or alternatively is further swirled through the swirl openings53of the separation disk50in the direction around the longitudinal axis1of the mixing device10. The direction of the swirl openings53in this context corresponds in particular to the direction of the circular flow around the longitudinal axis1of the mixing device10, in order to disturb the airflow as little as possible. Also the inclination of the recirculation opening85and the openings75of the recirculation means70correspond in particular to the directional swirl of the inflowing air, in order to disturb the airflow as little as possible.

The diversion of the air flowing out of blower120into the inflow opening134particularly occurs by means of an air deflector138, with partitions the connection duct130into two air ducts, one of which diverts air to the first inflow opening134and the other diverts air by 180° into the second inflow opening134, in order to be able to supply air in this manner through both inflow openings134into the tube section132tangentially. The position of the air deflector138inside the connection duct130can be adjusted by means of a bolt139, for example, in order to be able to vary the air volume which flows through both inflow openings134.

Furthermore, means are provided by means of which a passage cross-section135of the inflow openings134can be variably adjusted. The means are developed as tube136which with its outside wall bears against the inside wall of tube section132and/or the inside wall of the air deflector138. The tube136comprises two diametrically arranged openings137, which are particularly developed as slots in direction of the longitudinal axis1of the mixing device10, where the tube136is arranged pivoted around the longitudinal axis1, so that depending on the rotation and the position of the tube136and the openings137relative to the inflow openings134, the inflow openings134can be opened more or less, thereby varying the passage cross-section135of the inflow openings134. The rotation of the tube136occurs especially by means of an actuator150(see particularlyFIG. 2), which can preferably be actuated from the outside of the burner casing, so that a variation of the passage cross-section of the inflow openings134can be done during the operation of burner100. The actuator150comprises a slot152which guides a peg153, which limits the rotational travel of the actuator150, so that also without having to open the burner casing it can be seen whether the inflow openings134presently have a maximum or minimum passage cross-section or one which is in-between the two extreme positions.

The airflow in direction of the longitudinal axis one of the mixing device10benefits further from the fact that in tube section132, particularly in the burner tube20, a truncated cone is arranged, the tapered section of which faces in the direction of the mixing device10or the flame-tube30, wherein presently the second element43band a support43of the nozzle connection40is developed as a truncated cone element.

An alternative embodiment of the connection duct130inFIGS. 17 and 18is shown inFIGS. 19 and 20. It is possible, as illustrated inFIGS. 19 and 20, that the air deflector138arranged in connection duct130can be omitted, so that the air flowing out of the blower120flows partially into the first inflow opening134and partially merely on the outside of the burner tube20, diverted into the diametrically opposed inflow opening134. In place of the air deflector138, a deflector131can be tangentially arranged on the tube136, particularly on one of the openings137, which particularly extends through the first inflow opening134into the connection duct130and favors a partitioning of the airflow. For this purpose, the deflector131is also turned when tube136turns, so that a variation of the passage cross-section of the inflow opening134can also occur in this manner.

In all illustrated embodiments, the speed of the blower120can preferably be steplessly controlled in a smooth manner (without steps). Furthermore, the quantity of the fuel which is supplied via the fuel nozzle42to the mixing device10, can also be steplessly controlled in a smooth manner (without steps).

The burner100for the mixing device10, the blower110and the connection duct130that is arranged therebetween, permits low-pollution, efficient combustion of liquid or gaseous fuels. Because of the described geometry of the connection duct130, the pressure loss of the inflowing combustion air is minimized and the blower pressure is primarily used for mixing of combustion air and fuel and to overcome the resistance on the exhaust gas side in the heat generator and in the exhaust system. Because of the geometry in the connection duct130, an increase of the static pressure of the expansion of the cross-section in the air ducts in the junction to the burner to20is produced, which stabilizes the flame even during pressure fluctuations in the exhaust gas system. Because of the swirling of the air already in the burner tube20, this creates a high angular momentum other combustion air which permits the homogenous swirling of the fuel/air mixture ahead of and after the air nozzle60with or without separation disc50and a stable low pressure zone in the recirculation area. The homogenous swirling and the optimally inflowing exhaust gases permit optimum mixing of the combustion air, the controlling hot exhaust gases, and the injected, cone-shaped, gaseous suspension fuel spray, which is optimally vaporized ahead of the root of the flame. Stable combustion occurs with a particularly low noise level in the presence of a blue flame with low NOx, CO, and CxHy emissions. This also prevents undesirable, spontaneous backfiring in the area of the root of the flame and along the recirculation zone. In this way, particularly the formation of soot on the mixing head and on the ignition electrodes55is prevented. The good mixing of combustion air, exhaust gases, and fuel permits a reduction in the injection pressure to less than 4 bar, particularly for heating oil. This permits a reduction of the burner output to below 7 kW, if normal commercial fuel nozzles42are used. By reducing the pressure losses in burner100, the system is also suitable for use in high output ranges of more than 150 kW, where previously the exponentially increasing blower output limited the use of blue flame systems with a swirl-stabilized flame. The optimally stabilized flame makes this system particularly suitable for the use of calorific value heat exchangers and boilers with high resistance on the exhaust gas side. The sealing of the air nozzle60to the flame-tube30and the combustion chamber prevents undesirable, non-defined, incorrect airflow. The resulting conditional soot formation and undesirable pressure loss are prevented.

The present burner100therefore particularly comprises a casing geometry, which by the appropriate manipulation of the combustion air can already place it into rotation through this tangential inflow into the combustion tube20already ahead of the air nozzle60. The recirculating exhaust gases are moreover supplied by means of the inclined recirculation openings85arranged in the direction of the swirl into the combustion zone. The fuel nozzle42can be axially shifted to the stationary air nozzle60, as a result of which the developing air outlet flow cross-section is variable. The velocity of the outflowing air, the air volume, and the air pressure, can therefore be varied. In connection with a speed-controlled blower120, the required air volume for combustion, the air velocity, and the air pressure can be adapted pursuant to a characteristic curve. If the fuel quantity is also varied, by means of a modulating fuel pump140or a modulating fuel valve, for example, a modulating combustion method is possible in addition to single or multistage operation.

In the claims, means or step-plus-function clauses are intended to cover the structures described or suggested herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, for example, although a nail, a screw, and a bolt may not be structural equivalents in that a nail relies on friction between a wooden part and a cylindrical surface, a screw's helical surface positively engages the wooden part, and a bolt's head and nut compress opposite sides of a wooden part, in the environment of fastening wooden parts, a nail, a screw, and a bolt may be readily understood by those skilled in the art as equivalent structures.

Having described at least one of the preferred embodiments of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes, modifications, and adaptations may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.