they superimpose themselves appropriately, a turbulent flow comprising a mixture of fuel and air and that is ignited inside a combustion chamber downstream of the premixing burner in the direction of flow, whereby a flame of premix is formed which is as spatially stable as possible. In this case, the spatial position of the premix flame is determined by the aerodynamic behavior of the turbulent flow, the turbulence coefficient which increases with the increase of the propagation along the burner axes, consequently it reaches be unstable; and finally, as a result of a discontinuous cross-sectional transition between the burner and the combustion chamber, it is fragmented into an annular turbulent flow with the formation of a backflow zone, in the forward region of which, in the direction of the flow, the premix flame is formed. Of special importance is the aerodynamic stability of the formation of the backflow zone, which nevertheless depends in a highly sensitive manner on the design, shape and size of the turbulence generator. For example, if the front most forward in the direction of the flow formation of the backflow zone is not spatially stabilized successfully, pulsations or thermoacoustic vibrations occur to an increased degree within the combustion system, significantly altering total combustion and the release of heat. In consideration of this fact, pre-blended burner systems previously known and in use, are restricted to the total sizes in which the maximum burner diameter at the burner outlet is only 180 MI. Premixed burners of this type additionally have a relatively pointed conical angle, that is, small, less than or equal to 18 °, so that the length of the burner tends to be large relative to the diameter of the burner that is flipped current below, but still very capable of being handled for assembly and maintenance purposes. However, wherever large combustion chambers have to be ignited, so-called multi-burner arrays have been used, which provide for the use of the above premix burners. Arrangements for multiple burners of this type are described for example by DE 42 23 828 Al or DE 44 12 315 Al. For operating arrays of multiple burners of this type, which are suitable for example for the ignition of a combustion chamber of a silo, a sophisticated arrangement of a large number of premixed burners serving respectively as main burners or pilot burners, is required to achieve the final effect of allowing the combustion chamber to continue to be operated with emission values as low as possible in the full load interval. However, there is a desire to reduce the complexity and with this also the number of individual premix burners that are required to light the combustion chambers of large dimensions, without having to accept quality losses in the combustion process. Same time. In addition, for reasons related to increasingly stringent environmental standards with respect to the reduction of emission values, the objective is to replace the previously operated single diffusion burners, which are used primarily for the ignition of combustion chambers. of silos, of large dimensions, by burner systems more environmentally acceptable, more modern. In particular with regard to the prevention of acquisition costs for the first time and a high conversion, it is desirable to provide premixed burners of the largest possible dimensions, so that they are able for example to continuously maintain the operation of such silos combustion chambers., of large dimensions, with only a single premixed burner. Studies and theoretical tests have shown that simply the scaling, for example, of a known double cone burner of EP 0 321 809 Bl, does not achieve the objective, especially since, as already mentioned, the length of the burner could be increased disproportionately. To this must be added the width of the slot for the inlet air that extends tangentially on the axis of the burner and through which the incoming combustion air flows to the turbulence generator to generate the desired turbulent flow, similarly it could be increased disproportionately, so that a good mixing of the fuel and the incoming combustion air with a suitable quality can no longer be ensured. A very important and at the same time critical additional aspect of a desired increase in size or an increase in the performance of previously known pre-mixer burner systems is related to the downstream termination of conical conical shell-shaped segments the space for the turbulent flow of the turbulence generator, which in the example of the double cone burner described in EP 0 321 809 Bl, end in axially directed total locking elements. These total blocking elements contribute to the formation of vortices of undesirable separation, which, as coherent eddy structures, lead to instabilities of the combustion and, associated with these to thermoacoustic vibrations or pulsations. Arrangements of the premixed burner (for example US 5,588,826) are also known which, as a difference from the premixing burner described above, have a transition geometry interposed between the turbulence generator and the combustion chamber, for example in the form of a hollow cylindrical mixing tube. However, transition geometries of this type are extremely aerodynamically sensitive, since the flow separations in this zone can lead to flashback or spontaneous ignition. Similarly, because of their complex production, transition geometries of this type contribute decisively to production costs. Brief Description of the Invention The invention is based on the object of developing a premixed burner according to the characteristics of the pre-characterization clause of claim 1 in such a way that, despite the increase in size of the dimensions of the burner, the properties of the optimized burner in the case of pre-mix burners known previously, will be retained virtually unchanged. Thus, the objective is to increase the burner size of previously known pre-mix burner systems to reduce the number of burners in multiple burner arrangements, as described at the beginning, and also to reduce the costs of the associated system. Similarly, it is proposed that it will be possible with larger premix burner systems to replace the previously known single diffusion burners that are used, for example, for the ignition of the combustion chambers of a silo, by a burner of premixed only. The solution that achieves the object on which the invention is based is specified in claim 1. The features that advantageously develop the idea of the invention are the subject of the sub-claims and are described in the description, in particular with reference to the exemplary modalities. According to the invention, a premixing burner according to the pre-characterization clause of claim 1 is developed in such a way that, at least in the region of the downstream end of the turbulence generator, a shaped element enclosing the segments with a conical shell shape with an internal wall turned towards the conical shell segments is provided, and that the conical shell-shaped segments terminate in the inner wall in a level manner while maintaining their shape.
A large number of theoretical studies and tests carried out experimentally to increase the size of the previously known form of the premixed burners, which usually have a maximum burner diameter on the outlet side of the burner of 180 m, led to the realization that the structure of the downstream end of the conical shell-shaped segments has a significant influence on the stability of the flame formation of the premixing burner, in particular in the attempt to form the premixed burner with such a large volume as possible. Thus, it was found that in most cases of the premixed burners that are in use the end regions of the conical shell-shaped segments extend in the direction of flow towards a hollow cylindrical flow channel, which is joined either directly by the combustion chamber or by an additional mixing zone in the form of a mixing tube. In order to avoid the separation eddies that follow directly from the conical shell-shaped segments in the flow direction, it has been observed according to the invention that, immediately after leaving the turbulence generator, the turbulent flow is capable of widely dispersing without making the turbulent flow unstable if, while maintaining its shape, the individual tapered shell segments are kept in close contact with the inner wall of the flow channel attached to the turbulence generator. The concept of "maintaining its shape" means for the purposes of the invention, that the shape of the conical shell-shaped segments formed in the manner of segments of a cone, remain unchanged in the region where they come to be. in contact with the inner wall of the shaped element enclosing the conical shell-shaped segments, as if the conical shell-shaped segments could penetrate unimpeded through the shaped element in a radially outward direction. The inner wall of the shaped element also serves to form a flow channel attached to the conical shell-shaped segments downstream. Depending on the shape and size of the shaped element, it also serves as a mixing tube or as a joining element, in the direction of a piece with projections, by means of which the turbulence generator can be connected to a chamber of combustion in the direction of flow, such as for example a combustion chamber of a silo or some other structure of the channel. In order to be able to manufacture the premixing burner as compact as possible, ie with a burner length that is as small as possible, conical angles of at least 11 ° are used, but preferably in the range of 20 ° and larger , in which the angles of the conical shell-shaped segments surround the turbulent flow space in a manner of conical widening. For example, burners with a burner diameter in the outlet region of more than 500 mm having a burner length well below one meter, can be made possible. To ensure good mixing of the fuel mixture and the air inside the turbulence generator, it is also advantageous to increase the number of conical segments and, associated therewith, the number of air inlet slots, so that in this way achieve the smallest possible width of the slot per air inlet slot. BRIEF DESCRIPTION OF THE DRAWINGS Without restriction of the general idea of the invention, it is described later by way of example based on the exemplary embodiments with reference to the figures, in which: Figure 1 + Figure 2 show a representation in perspective of a premixed burner with a cylindrically shaped element, figure 3 + figure 4 show | a perspective representation of a premixed burner with a shaped element of truncated cone shapeFigure 5 shows a sectional representation through a premixed burner with a shaped element of truncated cone shape, and Figure 6 + Figure 7 show a perspective representation of a premixed burner with a shaped element that has an entrance region formed in a tunnel-like manner. Detailed Description of the Invention Shown in Figure 1 is a perspective representation of a premixed burner, with the direction of observation from the downstream side towards the turbulent flow space of a turbulence generator 2 which is enclosed by a multiplicity of segments 1 shaped like a conical shell. Figure 2 shows the same premixed burner, but from a different viewing angle, which is facing the turbulence generator 2 from the outside, the generator is enclosed by eight segments 1 in the form of a conical shell in the exemplary embodiment represented. The additional refinements of the exemplary embodiment shown in Figures 1 and 2 are the same in each case, so that there is no further distinction between Figure 1 and Figure 2. The illustrated premix burner has a central receiving unit 3. , which takes the form of a receiving sleeve and is proposed for a central fuel supply unit, for example in the form of a fuel nozzle for liquid fuels or a fuel lance for a pilot flame (not shown) that is going to be pushed in and held. The conical shell-shaped segments 1, connected at their ends upstream to the receiving unit 3, mutually enclose slots 4 for air intake and are positioned with respect to a burner axis A that extends centrally through the burner of premixed in such a way that they delimit a space for the turbulent flow that widens conically in. the flow direction at a conical angle? Each individual conical shell segment 1, however, has, depending on the type of fuel, at least one supply line 5 of the fuel by means of which the fuel can be mixed in the incoming combustion air flow that it passes through the air inlet slots 2. While retaining their shape, the individual conical shell-shaped segments 1 open outwardly with their downstream end on an inner wall 6 of an element 7 shaped with a cylindrical shape surrounding the segments 1 in the shape of a conical shell. The individual conical shell-shaped segments 1 are connected to the inner wall 6 of the shaped element 7 along an intersection line 8, which is obtained by a virtual penetration of each segment 1 in the shape of a conical shell, individual , with the internal wall 6 of the element 7 formed cylindrically. In this way, the turbulent flow formed within the turbulence generator 2 does not suffer any alteration after flowing on the individual conical shell-shaped segments 1. Provided upstream of the shaped element 7, for purposes of an improved inlet air flow through the slots 4 for the air intake of the turbulence generator 2, there is a second shaped element 9, which is formed in a similar manner to a hollow cylinder and has a larger internal diameter than the first shaped element 7. The transition between the internal diameters of the shaped elements 7 and 9 is carried out by means of a discontinuous step 10, which is also joined by the fuel supply lines 5 of each segment 1 with conical shell shape, individual. The downstream contour of the conical element 7 is formed in a cylindrical manner and offers the possibility of a connection of simple construction, for example to a combustion chamber (not shown) placed downstream in the flow direction of the illustrated premix burner. Shown in a perspective representation in Figures 3 and 4 is an additional exemplary embodiment of a premixing burner formed in accordance with the invention., in which, as a difference of the exemplary embodiment that is represented in Figures 1 and 2, the region of the shaped element 7 is formed as a truncated cone-shaped portion terminating at a conical tip in the direction of flow. To avoid repetition, the reference numbers that have already been presented are not described. The exemplary embodiment shown in FIGS. 3 and 4 has in the region of the shaped element 7 an internal wall 6 which is shaded in the perspective representations and is joined at the downstream ends of the segments 1 in the shape of a conical shell, while that its form is maintained. Attached to the inner wall 6 of the shaped element 7 downstream is a shaped element 11 which is formed as a hollow cylinder and serves as a coupling piece or piece with projections for a next combustion chamber. . The internal wall 6 placed with respect to the segments 1 in the shape of a conical shell has the effect that the intersection lines 8 of the conical shell-shaped segments 1 with which they meet in the inner wall 6, are more small or shorter in the direction of flow than the case of the exemplary embodiment mentioned above, in which the conical shell-shaped segments are joined along a cylindrically formed internal wall, coaxially directed relative to the axis of the burner.
A representation of the graphic cross-section of the embodiment shown in FIGS. 3 and 4 can be observed in FIG. 5. The holding urion of the shape "of each segment 1 with" individual conical shell shape, with the internal wall 6 of the shaped element 7 which1 extends conically in the direction of flow in the shape of a cone, such element travels upwards in the direction of flow towards a straight cylindrical region 11. Shown in figures 6 and 7 is an embodiment further example of a premixed burner, provided with a shaped element 7 having an upstream region, the so-called flow inlet region 12, having an internal wall 6 extending conically in the shape of a tunnel in the direction of the flow. The curvature of the inner wall 6 in this region of entrance of the flow corresponds approximately to the contour of the fourth part of an ellipse. The flow inlet region 12 is joined in the direction of flow as part of the shaped element 7 by a flow region 12 'with a widely constant flow cross section, to which finally an inlet projection of a combustion chamber can be fixed (not represented). Also as in the variants described above, while retaining its shape of the conical shell-shaped segment, the conical shell-shaped segments 1 of the turbulence generator 2 end on the adjoining inner wall 6 of the shaped element 7 in a level manner, as if the conical shell-shaped segments could penetrate unimpeded through the inner wall 6, but the conical shell-shaped segments 1 end respectively by means of the intersecting lines 8 in the inner wall 6. In the case of the Inlet region of the flow, formed as the fourth part of an ellipse, the regions of the downstream end of the segments 1 in the shape of a conical shell closely follow the elliptical curvature of the inner wall 6 in this region 12. For the meaning of the reference numbers which have already been presented and are additionally provided in figures 6 and 7, reference is made to the figures mentioned above. iormente. The connection according to the invention of each individual conical shell segment by its region of the downstream end to an inner wall of a shaped element surrounding the conical shell-shaped segments, while maintaining its shape, leads to a minimal alteration of the turbulent flow that passes through the segments with conical shell shape. As a difference from previously known pre-mix burners, there are no effects of total blockage in the axial direction through the burner axis, associated with the shape according to the invention in which the conical shell-shaped segments end in the corresponding internal wall while maintaining its shape. List of reference numbers 1 segments shaped like conical shell 2 turbulence generator 3 receiving unit 4 slots for air inlet 5 fuel supply line. 6 inner wall 7 shaped element 8 intersecting plane 9 shaped element 10 stage 11 element configured in the shape of a hollow cylinder 12 flow inlet region It is noted that in relation to this date, the best method known by the applicant to carry the practice said invention is that which is clear from the present description of the invention.