EP0585441B1 - Nitrogen oxide-poor burner - Google Patents

Abstract

PCT No. PCT/EP93/00666 Sec. 371 Date Jan. 19, 1994 Sec. 102(e) Date Jan. 19, 1994 PCT Filed Mar. 19, 1993 PCT Pub. No. WO93/19325 PCT Pub. Date Sep. 30, 1993.In order to improve a burner for generating hot gas having a burner pipe, comprising a support pipe followed by a flame pipe, a nozzle arranged in the support pipe, a fuel jet exiting from the nozzle, a shield separating a precombustion chamber and a combustion chamber from one another in the burner pipe, the shield having a central passage penetrated by the fuel jet, recirculation openings arranged in the flame pipe and allowing an outer recirculation of cooled flue gas and an element for suppressing the outer recirculation during a starting phase of the burner, such that a reliable suppression of the outer recirculation during the starting phase is possible it is suggested that the element for suppressing the outer recirculation be arranged within the burner pipe and be controllable via a control means guided through an interior of the support pipe.

Description

Burners for hot gas generation with a burner tube comprising a support tube and a flame tube adjoining it, with a nozzle arranged in the support tube, from which a fuel jet emerges, with an orifice separating an antechamber arranged in the support tube and a combustion chamber arranged in the flame tube, which orifice separates from the fuel jet has penetrated central passage, with an external recirculation of cooled flue gas allowing recirculation openings and with an element arranged within the burner tube for adjusting the external recirculation.

From EP-A-0 430 011 a burner of the type described at the outset is known, which is designed to supply a large amount of exhaust gas to the combustion air of the combustion chamber, especially also in the starting phase.

Furthermore, this burner is constructed in such a way that the amount of combustion air supplied can be adjusted to adapt to different circumstances, such as different boilers.

A burner with external recirculation is known from DE-PS 39 06 854. The disadvantage of such burners is that due to the heating of the elements provided for the suppression of the external recirculation during the starting phase, their function is impaired.

Suppression of external recirculation is desirable because during the start-up process for heating the external recirculation gases, too much heat is removed from the gasification process of the fuel and the flame, so that the flame is broken off or extinguished.

The invention has for its object to improve a burner of the generic type.

This object is achieved according to the invention in a burner of the type described in the introduction in that the external recirculation from a boiler space surrounding the flame tube takes place through openings in the flame tube into an interior of the flame tube lying downstream of the nozzle and in that the element for adjusting the external recirculation is via a control means guided by an interior of the support tube can be controlled such that it suppresses the external recirculation during a start phase of the burner and that in the warm operating state after the start phase the external recirculation occurs in the interior of the flame tube located downstream of the nozzle.

The advantage of the solution according to the invention can be seen in the fact that a reliable suppression of the external recirculation is possible during the starting phase.

The advantage of the solution according to the invention can also be seen in the fact that with it the element for suppressing the external recirculation is arranged inside the burner tube and is therefore already exposed to lower temperatures, and in addition that the control means are guided through the support tube they are exposed to the cooled combustion air flowing into the combustion chamber and are therefore also shielded from high temperatures, so that overall the problems known from the prior art are avoided in the solution according to the invention.

The term suppression of the external recirculation during the starting phase is to be understood as a suppression of the external recirculation given with warm burners by more than 50%, preferably more than 70% and in special cases by more than 85%. A complete suppression of external recirculation represents an extreme case of the teaching according to the invention.

A particularly advantageous variant of the solution according to the invention provides that the element for suppressing the external recirculation is an element which shuts off a recirculation gas flow within the burner tube in a slide-like manner. With such a slide-like element, the recirculation gas flow in the burner tube can be suppressed in a structurally simple manner and thus also reliably.

A structurally particularly simple solution provides that the slide-like element is a slide having an annular jacket and movable in the axial direction. This is the structurally simplest and therefore the cheapest to implement.

It is particularly advantageous if the slide has a sealing surface that is cylindrical with respect to the axis. With this cylindrical sealing surface, the slide can be arranged in a simple manner in the burner tube.

For design reasons, it is also advantageous if the slide is guided on an inside of the flame tube, so that any additional measures for guiding the slide can be omitted.

The solution described above is one of the structurally simplest and therefore cheapest solutions. A somewhat more complex, but functionally improved solution provides that the slide-like element has an annular sealing surface with respect to the axis, which is in a substantially perpendicular to the axis Level lies. With this construction of the sealing surface, problems of different heating of the individual parts, which occur with a cylindrical sealing surface, can be avoided, since the sealing surface is perpendicular to the direction of displacement of the slide and thus all different tolerances resulting from the displacement of the slide-like element are compensated. In particular, the tightness of a sealing surface arranged in this way is considerably greater and can be achieved with extremely simple means.

It is also particularly advantageous with this solution that the displacement of the slide-like element is kept relatively small.

In addition, this solution offers the advantage that a space, for example between the flame tube and the slide-like element, can be kept sufficiently large so that there is no risk that the slide-like element and the adjusting mechanism provided for this jam due to different heating of the parts.

In addition, the sealing surface perpendicular to the axis prevents any unburned oil from dripping out of the burner tube, which could lead to pollutant emissions.

A particularly advantageous constructive solution provides that the slide-like element is part of a cladding tube running inside the support tube.

In this case, the slide-like element is preferably a collar of the cladding tube protruding beyond the diaphragm in the direction of the combustion chamber.

In order to achieve a good seal in the plane perpendicular to the axis, it is provided that the collar of the cladding tube can be sealingly applied to an annular bead in the flame tube. The collar is preferably provided with an annular flange and the annular bead is also provided with a sealing element or is designed as such.

With regard to the arrangement of the diaphragm, no further details have been given in this connection. So it is particularly advantageous if the cladding tube carries the screen.

As an alternative to the provision of a collar, a further solution provides that the slide-like element is an end section of the cladding tube which is closed off by the cover.

This section can expediently be placed against an annular bead in the flame tube.

Furthermore, it is favorable with this solution if the cladding tube carries the nozzle assembly, for example via a tripod.

A particularly favorable and preferred solution provides that the cladding tube as a whole can be displaced in the axial direction in the burner tube with the nozzle assembly and the diaphragm.

Another advantageous development of the solution according to the invention provides that the slide-like element is a shielding ring dividing a recirculation space into an inner and an outer recirculation space.

In this case, the slide-like element is not only there to suppress the recirculation gas flow to the outer recirculation, but at the same time it separates the recirculation space into an inner and an outer recirculation space.

In this case, it is particularly easy to shut off the recirculation gas flow if the shielding ring can be sealingly applied to the orifice to suppress the external recirculation. This means that the shielding ring can be moved from a position at a distance from the diaphragm, in which it allows external recirculation, to a position in sealing contact with the diaphragm.

So that two advantageous functions are combined in the shielding ring, so that a considerably improved function of the burner can be achieved with a structurally simple solution.

It is advantageous if an annular sealing surface lying outside a projection of a mixing tube on the panel is formed between the diaphragm and the shielding ring, that is to say that the sealing surface lies outside the mixing tube.

In this case, it is also advantageous if the mixing tube is not carried by the screen as in the solutions described above, but if the shielding ring carries the mixing tube, so that the mixing tube is moved simultaneously with the movement of the shielding ring. In this way, the mixing ratios created by the mixing tube in the mixing space can be changed in a simple manner simultaneously with the movement of the shielding ring.

The displaceability of the shielding ring can be realized in a structurally particularly simple manner if the shielding ring can be displaced through the struts passing through the diaphragm. This solution is particularly advantageous in the context of the present invention, since it also ensures an adjustment mechanism for the shielding ring, which is outside the hot parts of the burner. The actuating mechanism is rather cooled by the cold combustion air flowing into the combustion chamber.

In order to be able to hold and guide the struts and thus the shielding ring carried by them in a simple manner in the axial direction, it is preferably provided that the struts are displaceably guided in the axial direction on the nozzle block arranged immovably in the support tube. The nozzle assembly thus simultaneously forms a guide for the alignment of the struts in the support tube.

In the context of the exemplary embodiments described above, the external recirculation was suppressed by the slide-like element, i. H. the recirculation gas flow was shut off in the manner of a slide valve.

An alternative and preferred embodiment of the solution according to the invention provides, in contrast to the exemplary embodiments described above, that the element for suppressing the external recirculation suppresses a suction of cooled flue gas through the recirculation openings by opening a fresh air supply. This means that the recirculation gas flow is not switched off in a slide-like manner, but that the intake of cooled flue gas is suppressed by supplying fresh air into the recirculation space by means provided for this purpose, so that the cooled flue gas drawn in when the burner is in the warm operating state is replaced by the supplied fresh air is and thus the suction of the cooled flue gas is suppressed as part of the external recirculation.

In an advantageous embodiment, this is achieved in that the element for suppressing the external recirculation opens a fresh air supply in the recirculation space, that is, that fresh air is supplied directly into the recirculation space, in which a negative pressure is present, so that cooled flue gas in to a lesser extent the recirculation space is sucked in.

This can be realized particularly expediently in that the element for suppressing the recirculation can be used to supply fresh air from the antechamber into the recirculation space. With this solution, the fresh air supply is realized very easily, since fresh air is already available in the antechamber adjacent to the combustion chamber.

It is preferably provided that the element for suppressing the external recirculation can be used to supply fresh air to an external recirculation space which is separate from an internal recirculation space. In this embodiment, the recirculation space is thus also advantageously separated, in particular by a shielding element, into an outer and an inner recirculation space, so that the external recirculation can be selectively and specifically suppressed by introducing fresh air into this outer recirculation space.

This can be realized in a structurally particularly simple manner if the element opening the fresh air supply into the recirculation space is arranged radially on the outside of openings for the supply of combustion air from the prechamber. This means that in addition to the openings for the supply of combustion air during all operating states of the burner, an additional possibility for producing a fresh air supply during the starting phase is provided in the diaphragm.

The fresh air supply from the prechamber can be realized particularly simply if this takes place via ventilation openings in the panel.

In order to be able to suppress this fresh air supply after the start phase, it is provided that the ventilation openings in the panel can be closed by a closure element. The closure element can be designed in a wide variety of ways, for example as a slide or the like. It is structurally favorable if the closure elements are closure plugs which can be moved in the axial direction.

In order to keep the influence of different heating as low as possible, it is further provided that the closure elements are arranged in the prechamber, since they are then exposed to the cold fresh air flow and can be cooled by it.

In order to achieve a defined guidance of the closure elements, it is preferably provided that they are displaceably guided in the axial direction on the nozzle block held stationary in the support tube, so that a defined orientation of the closure elements can be achieved in a simple manner.

As an alternative to the fresh air supply described directly into the recirculation space, another preferred exemplary embodiment of the solution according to the invention provides that the fresh air supply takes place in the vicinity of the recirculation opening.

This can be realized in a structurally advantageous manner if the fresh air supply can be produced in an annular space following the recirculation opening.

It is preferably provided for this that the fresh air supply can be controlled by a closure element arranged in the prechamber. The supply of fresh air can be realized in a structurally advantageous manner if the closure element can be used to release or close fresh air from the antechamber leading to the intermediate space.

A solution is particularly simple in which the ventilation openings can be closed with a sealing surface that is cylindrical with respect to the axis.

In terms of function, it has proven to be particularly advantageous if the closure element is guided on the inside of the support tube, since this solution makes further guidance of the closure element unnecessary and also ensures reliable operation because the support tube is not exposed to high temperatures.

In connection with the explanation of the previous exemplary embodiments, the extent to which the suppression is maintained during the starting phase was not discussed.

In the simplest case, it would be conceivable to remove the suppression of external recirculation in one go after the start phase. However, it is even more advantageous to successively reduce the suppression of the external recirculation after the start phase or at the end thereof. In the simplest case, this can be done by a step-by-step reduction, for example after defined periods have elapsed. However, it is particularly expedient if the suppression is reduced continuously in order to ensure a continuous transition to the warm operating state without suppressing the external recirculation.

In addition, it is particularly advantageous in the present invention if the burner has an internal recirculation, since optimal combustion values can be achieved with the internal recirculation.

In addition, in particular to prevent the nozzle assembly from being heated to high temperatures by the nozzle, the solution has proven that in the warm operating state after the starting phase, the external recirculation enters the interior of the burner downstream of the nozzle through the recirculation openings, so that the external recirculation neither passes through the nozzle assembly nor the nozzle and inappropriately heats it up.

With regard to the ease of maintenance, an embodiment of the solution according to the invention has proven to be optimal, in which a stationary alignment of nozzles, orifice and mixing tube in combination with predetermined internal and external recirculations is set, so that no misalignment of the burner properties is possible and only in the starting phase the suppression of the external recirculation according to the invention and the subsequent release in the warm operating state is possible.

Fig. 1

einen Längsschnitt durch ein erstes Ausführungsbeispiel eines erfindungsgemäßen Brenners;

Fig. 2

einen Längsschnitt durch ein zweites Ausführungsbeispiel eines erfindungsgemäßen Brenners;

Fig. 3

einen Längsschnitt durch ein drittes Ausführungsbeispiel eines erfindungsgemäßen Brenners;

Fig. 4

einen Längsschnitt durch ein viertes Ausführungsbeispiel eines erfindungsgemäßen Brenners;

Fig. 5

einen Längsschnitt durch ein fünftes Ausführungsbeispiel eines erfindungsgemäßen Brenners und

Fig. 6

einen Längsschnitt durch ein sechstes Ausführungsbeispiel eines erfindungsgemäßen Brenners.

Further features and advantages are the subject of the following description and the drawing of some exemplary embodiments. The drawing shows:

Fig. 1

a longitudinal section through a first embodiment of a burner according to the invention;

Fig. 2

a longitudinal section through a second embodiment of a burner according to the invention;

Fig. 3

a longitudinal section through a third embodiment of a burner according to the invention;

Fig. 4

a longitudinal section through a fourth embodiment of a burner according to the invention;

Fig. 5

a longitudinal section through a fifth embodiment of a burner according to the invention and

Fig. 6

a longitudinal section through a sixth embodiment of a burner according to the invention.

The invention relates to a wide variety of oil or gas burners and is discussed below using the example of a so-called blue burner, ie a burner in which oil is completely burned with a blue flame. However, the invention is not restricted to such blue burners. With the constructional measures described, the effects according to the invention can also be achieved with preheating burners and yellow burners.

A first exemplary embodiment of a burner according to the invention, shown in FIG. 1, comprises a burner tube, designated as a whole by 10, which has a support tube 12 which is mounted on a burner frame, not shown in the drawing. This support tube 12 carries a flame tube 14 also encompassed by the burner tube 10, the support tube 12 and the flame tube 14 being connected to one another, for example, by a fold.

A prechamber, designated as a whole by 16, is arranged in the support tube 12, which extends up to an aperture 18, which forms a partition between the prechamber 16 and a combustion chamber 20, which is essentially arranged in the flame tube 14. The aperture 18 is held centered in the support tube 12 and arranged at the transition from the support tube 12 into the flame tube 14, the aperture 18 with an outer ring flange 22 being supported on the one hand on an inside 17 of the support tube 12 and on the other hand facing the flame tube 14 Bears against an insulating ring 24, which provides thermal insulation of the insulation against false air between the flame tube 14 and the ring flange 22.

In the antechamber 16 there is also a nozzle assembly, designated as a whole by 26, with a nozzle 28, this nozzle 28 preferably being aligned coaxially with a central axis 30 of the burner tube 10.

The nozzle 28 has an outlet 32 which is arranged in the direction of the central axis 30 at a short distance upstream of a surface 34 of the orifice 18 facing the prechamber 16.

A fuel jet 36 emerges from this outlet 32, which passes through a central passage 38 of the orifice 18 and spreads in the combustion chamber 20 within the flame tube 14 downstream of the orifice 18.

The nozzle assembly 26 is preferably still held with a base 38 on the screen 18 and this is preferably guided in the support tube 12.

Within the combustion chamber 20, the orifice 18 is adjoined by a mixing tube, designated as a whole by 40, which, following the orifice 18, is provided with circumferential openings 42, through which recirculation of flue gas from one inside the flame tube 14 and outside of the mixing tube 40 lying recirculation space 44 into a mixing space 46 located inside the mixing tube 40, which is also penetrated by the fuel jet 36.

Combustion air is also fed to the mixing chamber 46 from the pre-chamber 16 via openings 48 in the diaphragm 18 which are arranged around the passage 38 and which are preferably chamfered on their side facing the pre-chamber 16 and thus contribute to noise reduction of the burner.

An internal recirculation 50 takes place in the recirculation space 44 while the burner according to the invention is running, which starts from an end 52 of the mixing tube facing away from the orifice 18 and flows back to the circumferential openings 42 as well as an external recirculation 54 in which cooled smoke gases in the boiler space on an outside flow around the flame tube 14 and pass through recirculation openings 56, which are preferably arranged in the periphery thereof near the end of the flame tube 14 facing the support tube.

This external recirculation 54 enables a reduction in the combustion temperature and thus a reduction in the nitrogen oxide content of the burner.

In order to suppress the external recirculation 54 through the recirculation openings 56, a slide 62 which bears against the inside 58 of the cylinder with a cylindrical outside 60 is arranged in the interior of the flame tube 14 and is designed as a cylindrical ring and can thus be displaced in the direction of the central axis 30 within the flame tube 14. that either the recirculation openings 56 are closed or exposed. The annular slide 62 is only guided through its outside 60 on the inside 58 of the flame tube and to Closing the recirculation openings is displaced in the direction of the diaphragm 18, so that its jacket 64 stands on the inside 58 of the flame tube 14 in front of the recirculation openings 56 and closes them. To open the recirculation openings 56, the slide 62 is moved away from the diaphragm 18, so that the jacket 64 releases the recirculation openings.

A linkage 66 is provided as the control means for actuating the slide 62, which is passed through an opening 68 of the diaphragm 18 and is guided inside the support tube 12 through the prechamber 16, in particular an area of the prechamber 16 cooled by the combustion air flowing to the combustion chamber 20 is and runs to an actuator 70 which is, for example, a hydraulic or pneumatic cylinder or another linear displacement unit.

During the start phase of the burner, the slide 62 with its jacket 64 can thus be moved in front of the recirculation openings 56 and thus suppresses the external recirculation 54 into the mixing space 46, so that the burner burns stably in the start phase. After completion of the starting phase, the slide 62 is displaced in the direction away from the diaphragm 18 via the actuating member 70 and the linkage 66, to the extent that the jacket 64 clears the recirculation openings 56. In this case, the burner burns again with external recirculation and thus reduced nitrogen oxide content.

A second exemplary embodiment, shown in FIG. 2, is provided with the same reference numerals insofar as it has parts identical to the first exemplary embodiment, so that reference is made in full to the statements relating to the first exemplary embodiment.

In contrast to the first exemplary embodiment, in the second exemplary embodiment shown in FIG. 2, the diaphragm 18 is held on a cladding tube 72 which runs coaxially to the supporting tube 12 within the latter. The cladding tube 72 has a front section 74 which is closed on the jacket side and which on the one hand supports the panel 18, but extends beyond it and forms a collar 76a which projects beyond the panel 18 in the direction of the combustion chamber 20 and on its front side facing away from the panel 18 At the end of an annular flange 78 is formed in order to collect dripping oil during the starting process and then to evaporate there. In the same way as in the first exemplary embodiment, the screen 18 carries the mixing tube 40, which is also designed identically to the first exemplary embodiment.

Furthermore, the recirculation openings 56 are provided in direct connection to the support tube 12 in the flame tube 14.

To suppress the external recirculation 54, the collar 76a extends from the orifice 18 into the combustion chamber 20 to such an extent that it can be positioned with its outer surface 80 inside the flame tube 14 in front of the recirculation openings 56.

To seal the recirculation openings 56, the flame tube 14 is provided with an annular bead 76b projecting on the inside 58 thereof, in which a sealing ring 84 is inserted on the side facing the panel 18, the annular bead 76b with the sealing ring 84 on a side opposite the panel the recirculation openings 56 is arranged.

The sealing ring 84 has such a radius that the ring flange 78 of the collar 76a can be placed against it and thus a sealing surface lying in a plane 86 perpendicular to the central axis 30 is created between the sealing ring 84 and the ring flange 78, which is also on the faceplate 18 opposite side of the recirculation openings 56.

The outer recirculation 54 can thus be completely suppressed by applying the ring flange 78 to the sealing ring 84. According to the invention, however, it is also sufficient to suppress the external recirculation 54 by not providing a complete seal between the collar 76a and the annular bead 76b, so that the sealing ring 84 is also not absolutely necessary.

If, on the other hand, the cladding tube 72 is moved away from the combustion chamber 20 in the direction of the central axis 30, the ring flange 78 lifts off the sealing ring 84 and is retractable to the extent that the ring flange 78 lies on the side of the recirculation openings 56 facing the orifice 18 and thus the Recirculation openings 56 again allow the external recirculation 54 into the recirculation space 44.

The outer surface 80 preferably lies neither on the inside 58 of the flame tube 14 nor on an inside of the support tube 12, but runs at a distance from them. Sealing against an inner side 17 of the support tube 12 takes place by means of an annular seal 90 lying between this and the outer surface 80, which is preferably fastened on the closed section 74 of the cladding tube 72.

To suppress the external recirculation, a seal is thus made once in the plane 86 between the ring flange 78 and the sealing ring 84 and once between the outer surface 80 and the inside 88 of the support tube 12 by means of the ring seal 90.

The cladding tube 72 also extends further into the pre-chamber 16, but is perforated in this area through a large number of openings 92, so that the combustion air flowing into the combustion chamber 20 can pass through the cladding tube.

In the cladding tube 62 and displaceable therewith, the nozzle assembly 26 is arranged, which is supported on the cladding tube 72 via holding arms 94 forming a tripod.

To move the cladding tube 72, the actuator 70 is arranged on a side opposite the orifice 18 on the burner frame 94, which is, for example, a hydraulic cylinder which can be actuated by the pressure of the oil supplied to the nozzle 28, this pressure by means of a valve 98 for the hydraulic cylinder 70 can be switched on or off.

In this exemplary embodiment, a piston rod 100a of the hydraulic cylinder 70 engages the nozzle assembly 26 via a holder 100b and displaces it with the cladding tube 72 in the direction of the central axis 30 either in the direction of the combustion chamber 20 or in the opposite direction, a spring 104 preferably being provided, which acts on the nozzle assembly 26 in the direction of the combustion chamber 20, so that, without the action of the actuating member 70, the cladding tube 72 is also displaced in the direction of the combustion chamber and rests with its ring flange 78 on the sealing ring 84 within the flame tube.

By switching the valve 98 and thus actuating the hydraulic cylinder 70, the nozzle assembly is pulled back in the direction away from the combustion chamber 20 and thus also the already described release of the recirculation openings 56 after the starting phase.

The advantage of the second exemplary embodiment can be seen in the fact that firstly there is a seal within the flame tube 14 and secondly by a movement in the direction of the central axis 30, so that the plane 86 in which the seal takes place is perpendicular to the central axis 30.

In particular, all problems that can arise due to different thermal expansion in the flame tube 14 and in the cladding tube 72 are thus avoided. In addition, a sufficiently large distance can be maintained between the flame tube 14 and the cladding tube 72 in order to avoid problems due to excessive heating for the seal to suppress the external recirculation 54.

Furthermore, it is particularly advantageous that the recirculation openings 56 can be dimensioned such that their slot width is smaller, on the other hand their circumferential extent is larger, so that the cooled flue gases are distributed more evenly from the external recirculation 54 and, in addition, only a small adjustment path for the displacement of the cladding tube 72 is required to suppress the external recirculation 54.

In addition, according to the invention, all the elements for suppressing the recirculation, i.e. the collar 76a with the ring flange 78 and the ring bead 76b with the sealing ring 84, as well as the ring seal 90 are located within the combustion chamber 20 and in the same way the control means 100a, 100b for the actuation of the elements 76 for suppressing the external recirculation 54 within the burner tube 10 and specifically arranged in the support tube 12, in particular in an area which is flowed through by cold combustion air for the combustion chamber 20.

A third exemplary embodiment shown in FIG. 3 is constructed similarly to the second exemplary embodiment. The third exemplary embodiment differs from the second exemplary embodiment, however, in that the cladding tube 72 is not provided with a collar 76a, but extends to the level of an end face of the diaphragm 18, but not beyond it.

An end section 76a 'of the cladding tube 72 takes over the function of the collar 76a and, together with the cladding tube 72, is so far in the direction of the combustion chamber displaceable so that it can be positioned with its end face 80 'within the flame tube 14 in front of the recirculation openings 56 in order to suppress the external recirculation 54.

To seal the recirculation openings 56, the flame tube is provided in the same way as in the second exemplary embodiment with the annular bead 76b protruding on the inside 58, which, however, does not have a sealing ring 84 but only an end-side contact surface 83 which faces the end face 19 of the diaphragm and which is downstream of the recirculation openings 56 is arranged.

The contact surface 83 has such a radial extent that the end section 76a 'of the cladding tube 72 can be placed against it, in particular with the end face 19 of the diaphragm 18, so that an essentially tight seal with a between the end contact surface 83 and the end face 19 in the plane 86 perpendicular to the central axis 30 sealing surface can be reached, the plane 86 being downstream of the recirculation openings 56 and additionally the ring seal 90 also ensuring a seal between the cladding tube 72 and the support tube 12.

Suppression of the external recirculation 54 is sufficient in the third exemplary embodiment for the starting phase of the burner when the recirculation is suppressed substantially, that is to say more than 50% or in particular more than 70%, so that it is sufficient if the end section 76a 'with the end face 19 in is a small distance from the end face 83, which can be of the order of one millimeter. The remaining gap still allows a small amount of recirculation, but does not lead to the disturbances in the starting phase mentioned at the beginning.

In addition, it is advantageously provided in the third exemplary embodiment that the hydraulic cylinder 70 first displaces the cladding tube 72 with the end section 76a ′ in the direction of the annular bead 76b in the starting phase in such a way that the external recirculation is suppressed, but then after the burner has started The end section 76a 'is moved successively in several steps away from the annular bead 76b after defined periods of time, thus increasingly reducing the suppression of the external recirculation 54 until full recirculation 54 through the recirculation openings 56 is permitted after the start phase has ended.

Such actuation of the hydraulic cylinder 70 is preferably carried out by applying pressure to the hydraulic cylinder with the pressure of the fuel supplied to the nozzle 28 by means of the valve 98.

In a fourth exemplary embodiment or solution according to the invention, shown in FIG. 4, those parts which are identical to those of the first and second exemplary embodiments are also provided with the same reference numerals, so that in this regard reference is made to the explanations regarding the above exemplary embodiments, in particular the first exemplary embodiment , can be referenced.

In the fourth exemplary embodiment, the burner tube 10 is likewise formed from the support tube 12 and the flame tube 14 and, in addition, the diaphragm 18 is held centered in the support tube 12, the annular flange 22 of which extends to the inside 17 of the support tube 12. The aperture 18 rests with the annular flange 22 on the insulating ring 24 and is thus thermally insulated against false air from the flame tube 14 and the support tube 12 by this insulating ring 24.

In the same way as in the first exemplary embodiment, the recirculation openings 56 are arranged in the flame tube 14.

Furthermore, in the same way as in the first exemplary embodiment, the nozzle assembly 26 is connected to the cover 18 via the base 38.

In contrast to the first exemplary embodiment, however, the screen 18 does not support the mixing tube 40, but the mixing tube 40 is in turn held by a shielding ring 110 which, starting from an end face 112 of the mixing tube 40 facing the screen 18, extends radially outwards to the inside 58 extends of the flame tube, and forms an annular space 114 between itself and the inside 58, in which the recirculation openings 56 open regardless of the position of the shielding ring 110. Furthermore, the shielding ring 110 forms a surface 116 facing the orifice 18, which runs parallel to a surface 118 of the orifice 18 facing the combustion chamber 20. Preferably, surface 118 and surface 116 are perpendicular to plane 86 ' to the central axis 30. The shielding ring 110 also closes with its outer edge 120 essentially tightly with the inside 58 and thus always separates the recirculation space 44, specifically into a recirculation space 44a, into which the inner recirculation 50 leads, and a recirculation space 44b, in which the outer recirculation 54 passes through the recirculation openings 56. The outer recirculation space 54 thus feeds cooled flue gas to the mixing tube 40 via its end face 112 facing the orifice 18, while the inner recirculation space feeds hot flue gas to the mixing tube 40 via the circumferential openings 42.

The shielding ring 110 can now be moved in the solution according to the invention in such a way that its surface 116 abuts the surface 118 of the diaphragm 18 and thus separates the outer recirculation space 44b from the mixing space 46, so that the outer recirculation 54 is suppressed. On the other hand, the shielding ring 110 can be displaced in the direction of the combustion chamber 20 so that a channel leading from the annular space 114 into the mixing space 46 is formed between the surface 118 and the surface 116 of the shielding ring 110, so that the external recirculation 54 can take place.

To move the shielding ring 110 with its surface 116 essentially parallel to the surface 118, a linkage 122 is provided, each having struts 122a penetrating openings 120 in the diaphragm, which extend from a guide ring 122b guided on the nozzle assembly 26. This guide ring is in turn connected to the actuator 70 via a linkage 122c.

The guide ring 122b, which is slidably supported on a cylindrical surface 128 of the nozzle assembly 26, guides the surface 116 parallel to the surface 118.

The advantage of this solution can be seen in the fact that the internal recirculation 50 and the external recirculation 54 can be set according to optimal operating conditions by the separation of the recirculation spaces 44a and 44b.

In a fifth exemplary embodiment, shown in FIG. 5, those parts which are identical to those described above, in particular the first and the third exemplary embodiment, are provided with the same reference numerals, so that reference is made to the explanations in this regard.

In the same way as in the fourth exemplary embodiment, a shielding ring 110 is arranged in the fifth exemplary embodiment, but is fixed with the surface 116 at a constant distance from the surface 118 of the screen 18. The shielding ring 110 thus separates the outer recirculation 54 from the inner recirculation 50 through the recirculation openings 56. The shielding ring 110 thus acts as a separation between the outer recirculation 54 and the inner recirculation 50, but is not displaceable in order to prevent the outer recirculation 54.

In order to suppress the external recirculation, ventilation openings 130a are provided lying radially on the outside, which are located radially outside of a projection of the mixing tube 40 onto the orifice 18 with respect to the axis 30. These ventilation openings 130a can be closed with closure elements 130b, the closure elements 130b in the simplest case being closure plugs which can be inserted into the ventilation openings 130a parallel to the direction of the axis 30 in order to close them. These sealing plugs sit on pins 132a, which in turn are guided on a cylinder surface 134 with a guide ring 132b on the nozzle assembly 26 in the direction of the axis 30. The guide ring 132b is in turn displaceable by a linkage 132c which is connected to the actuator 70.

If the sealing plugs 130b are moved away from the diaphragm 18 in the direction of the axis 30 and thus the ventilation openings 130a are opened, these lead in the outer recirculation space 44b to a reduction in the negative pressure required for drawing in the cooled flue gases through the recirculation openings 56 and thus prevent the external recirculation . At the same time, fresh air is fed through the ventilation openings 130a into the outer recirculation space 44b, which passes from this outer recirculation space 44b into the mixing tube 40 and thus contributes to a further oxygen supply for the fuel jet 36. The ventilation opening 130a and the sealing plugs 130b are thus largely already protected from the high temperatures by the shielding ring 110 of the combustion chamber 20, so that no problems due to uneven heating occur in the area thereof, in particular when the ventilation openings 130a are closed by means of the sealing plugs 130b.

During the starting phase, the ventilation openings 130a are opened so that the external recirculation 54 is suppressed. Thereafter, the ventilation openings 130a are closed by means of the sealing plugs 130b by displacing the linkage 132c with the guide ring 132b and the pins 132a in the direction of the diaphragm 18, so that the usual negative pressure builds up in the outer recirculation space 44b, which is used to insert the external recirculation 54 through the recirculation openings 56 is required.

In a sixth exemplary embodiment, shown in FIG. 6, those parts which are identical to those of the preceding exemplary embodiments are provided with the same reference symbols. With regard to the description thereof, reference is made to the explanations regarding the above exemplary embodiments, in particular the first exemplary embodiment.

In the sixth embodiment, inflow openings 148 are provided in the flame tube 14, but these are not the actual recirculation openings. The inflow openings 148 are overlapped on the outside of the flame tube 14 by a sleeve 140 of the burner tube 10 which, with respect to the axis 30, is at a radial distance from an outer wall 142 of the flame tube and one Outer wall 144 of the support tube runs. The sleeve 140 extends over the inflow openings 148 in the direction of a downstream end of the flame tube 14 and ends with the recirculation opening 56 for the cooled flue gas used for external recirculation 54 from the boiler room, so that this flue gas during the warm operating state and outside the start phase first flows through the recirculation opening 56 into a space 150 between the sleeve 140 and the outside 142 of the flame tube 14 and from this space 150 through the inflow openings 148 into the recirculation space 44.

As already mentioned, the sleeve 140 also extends over a front section 152 of the support tube 12 and overlaps ventilation openings 154a which connect the intermediate space 150 to the antechamber 16. The sleeve 140 is adjacent to the ventilation openings 154a on the outside 144 of the support tube 12 with a flange 156 and is preferably held by this flange 156 of the support tube 12, so that the space 150 is only accessible from the boiler space via the recirculation opening 56.

The ventilation openings 154a can be closed by a slide 154b which is arranged in the interior of the support tube 12 and is guided with an outer surface 158 on the inside 17 of the support tube 12. This slide 154b comprises an annular casing 160 which supports the outer surface 158 and in which two grooves 162 are machined at a distance from one another in the direction of the axis 30 are in which the sealing rings 164 are located. The sealing rings are at such a distance that when the outside 158 of the slide 154b stands in front of the ventilation openings 154a and closes them, on both sides of the ventilation openings 154a provide a seal between the slide 154b and the inside 17 of the support tube 12.

If the slide 154b is in its position closing the ventilation openings 154a, a normal external recirculation 54 takes place, the cooled flue gases flowing into the recirculation space 44 via the inflow opening 148 and the recirculation openings 56 in the flame tube.

If, on the other hand, the slide 154b is moved in the direction away from the orifice 18, so that it opens the ventilation openings 154a, fresh air can flow in through the ventilation openings 154a from the antechamber 16 into the intermediate space 150 and therefore suppresses the inflow of cold smoke gases via the recirculation opening 56 , so that no more cold flue gases flow into the recirculation space 44 through the inflow openings 148, but essentially fresh air. The outer recirculation 54 is thus suppressed during the start-up phase of the burner and the mixing chamber 46 is additionally supplied with oxygen-rich fresh air via the peripheral openings 42.

To actuate the slide 154b, in the same way as, for example, in the first exemplary embodiment, a linkage 166 is guided through the antechamber 16 and is connected to the actuating member 70.

Claims (38)

1. Burner for generating hot gas having a burner pipe (10), comprising a support pipe (12) followed by a flame pipe (14), a nozzle (28) arranged in the support pipe, a fuel jet (36) exiting from said nozzle, a shield (18) separating a precombustion chamber (16) arranged in the support pipe (12) and a combustion chamber (20) arranged in the flame pipe (14) from one another, said shield having a central passage (38) penetrated by the fuel jet (36), recirculation openings (56) allowing an outer recirculation (54) of cooled flue gas and an element (62, 76, 110, 130, 154) arranged in the burner pipe (10) for adjusting the outer recirculation (54), characterized in that the outer recirculation (54) takes place from a boiler room surrounding the flame pipe (14) through openings (56, 148) in the flame pipe (14) into an interior chamber (20) of the flame pipe (14) located downstream of the nozzle (28), and in that the element (62, 76, 110, 130, 154) for adjusting the outer recirculation (54) is controllable via a control means (66, 100, 122, 132, 166) guided through an interior of the support pipe (12) such that it suppresses the outer recirculation (54) during a starting phase of the burner, and in that in the warm operating state following the starting phase the outer recirculation (54) enters the interior chamber (20) of the flame pipe (14) located downstream of the nozzle (28).
2. Burner as defined in claim 1, characterized in that the element for suppressing the outer recirculation (54) is an element (62, 76, 110) cutting off a flow of recirculation gas within the burner pipe (10) in the form of a slide.
3. Burner as defined in claim 2, characterized in that the slide-like element is a slide (62) having an annular casing and movable in the axial direction.
4. Burner as defined in claim 3, characterized in that the slide (62) has a sealing surface (60) which is cylindrical relative to the axis (30).
5. Burner as defined in claim 3 or 4, characterized in that the slide (62) is guided on an inner side (58) of the flame pipe (14).
6. Burner as defined in one of claims 2 to 3, characterized in that the slide-like element (76, 110) has a sealing surface (78, 116) which is annular relative to the axis (30) and is located in a plane (86) extending essentially at right angles to the axis (30).
7. Burner as defined in any of the preceding claims 2 to 6, characterized in that the slide-like element (76) is part of a sheath pipe (72) extending within the support pipe (12).
8. Burner as defined in claim 7, characterized in that the slide-like element is a collar (76a) of the sheath pipe (72) protruding beyond the shield (18) in the direction of the combustion chamber (20).
9. Burner as defined in claim 8, characterized in that the collar (76a) of the sheath pipe (72) is adapted to abut on an annular bead (76b) in the flame pipe (14).
10. Burner as defined in any of claims 7 to 9, characterized in that the sheath pipe (72) bears the shield (18).
11. Burner as defined in claim 9, characterized in that the slide-like element is a section (76a') at the end face of the sheath pipe (72) closed by the shield (18).
12. Burner as defined in claim 11, characterized in that the sheath pipe (72) is adapted to abut with the end section (76a') on an annular bead (76b) in the flame pipe (14).
13. Burner as defined in any of claims 7 to 12, characterized in that the sheath pipe (72) bears the nozzle assembly (26).
14. Burner as defined in any of claims 10 to 13, characterized in that the sheath pipe (72) is displaceable in the axial direction (30) as a unit with the nozzle assembly (26) and the shield (18).
15. Burner as defined in any of claims 2 to 6, characterized in that the slide-like element is a screening ring (110) dividing a recirculation chamber into an inner (44a) and an outer (44b) recirculation chamber.
16. Burner as defined in claim 15, characterized in that the screening ring (110) is adapted to abut sealingly on the shield (18) for suppressing the outer recirculation (54).
17. Burner as defined in claim 15 or 16, characterized in that an annular sealing surface (118) located outside a projection of a mixing tube (40) onto the shield (18) is formed between the shield (18) and the screening ring (110).
18. Burner as defined in any of claims 15 to 17, characterized in that the screening ring (110) bears the mixing tube (40).
19. Burner as defined in any of claims 15 to 18, characterized in that the screening ring (110) is displaceable by rods (122a) penetrating the shield (18).
20. Burner as defined in claim 19, characterized in that the rods (122a) are guided for displacement in the axial direction (30) on the nozzle assembly (26) non-displaceably arranged in the support pipe (12).
21. Burner as defined in claim 1, characterized in that a drawing in of cooled flue gas via the recirculation openings (56) is suppressible with the element (130, 154) for suppressing the outer recirculation (54) by opening a supply of fresh air.
22. Burner as defined in claim 21, characterized in that a supply of fresh air to the recirculation chamber (44b) is generatable with the element (130) for suppressing the outer recirculation (54).
23. Burner as defined in claim 22, characterized in that a supply of fresh air from the precombustion chamber (16) to the recirculation chamber (44b) is generatable with the element (130) for suppressing the recirculation.
24. Burner as defined in any of claims 21 to 23, characterized in that a supply of fresh air to an outer recirculation chamber (44b) separated from an inner recirculation chamber (44a) is generatable with the element (130) for suppressing the outer recirculation (54).
25. Burner as defined in any of claims 21 to 24, characterized in that the element (130) opening the supply of fresh air to the recirculation chamber (44b) is arranged radially outwards from openings (48) for the supply of combustion air from the precombustion chamber (16).
26. Burner as defined in any of claims 21 to 25, characterized in that the fresh air is supplied via ventilation openings (130a) in the shield (18).
27. Burner as defined in claim 26, characterized in that the ventilation openings (130a) in the shield (18) are closable by closure elements (130b).
28. Burner as defined in claim 27, characterized in that the closure elements are closure plugs (130b) movable in the axial direction.
29. Burner as defined in claim 27 or 28, characterized in that the closure elements (130b) are arranged in the precombustion chamber (16).
30. Burner as defined in any of claims 27 to 29, characterized in that the closure elements (130b) are guided for displacement in the axial direction (30) on the nozzle assembly (26) held stationarily in the support pipe (12).
31. Burner as defined in any of claims 21 to 23, characterized in that the fresh air is supplied in the vicinity of the recirculation opening (56).
32. Burner as defined in claim 31, characterized in that the supply of fresh air is generatable to an annular intermediate space (150) following the recirculation opening (56).
33. Burner as defined in claim 31 or 32, characterized in that the supply of fresh air is controllable by a closure element (154b) arranged in the precombustion chamber (16).
34. Burner as defined in claim 33, characterized in that a ventilation opening (154a) supplying fresh air from the precombustion chamber (16) to the intermediate space (150) is releasable or closable with the closure element (154b).
35. Burner as defined in claim 34, characterized in that the ventilation openings (154a) are closable with the closure element (154b) with a sealing surface (158) which is cylindrical in relation to the axis (30).
36. Burner as defined in claim 34 or 35, characterized in that the closure element (154b) is guided on an inner side (17) of the support pipe (12).
37. Burner as defined in any of the preceding claims, characterized in that an actuating device (70) acting on the control means (66, 100, 122, 132, 166) is provided for successively reducing the suppression of the outer recirculation (54) following the starting phase.
38. Burner as defined in any of the preceding claims, characterized in that the burner has an inner recirculation (50).

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