Burner

Abstract

A burner has a housing on which a combustion tube is arranged, wherein the combustion tube has an opening at the end averted from the housing, wherein a mixing element is provided in the combustion tube, and the space between the mixing element and the opening forms a combustion chamber, wherein the housing has at least two mutually separate channels which open out in the mixing element, wherein gases flow through the channels and the mixing element, and mixing of the gases takes place for the first time in a combustion chamber, wherein the mixing element is produced in an additive manufacturing process and has at least two separate intermediate channels which branch in the direction of the combustion chamber in a flow direction.

Claims

1. A burner having a housing on which a combustion tube is disposed, wherein the combustion tube has an aperture at the end turned away from the housing, wherein a mixing element is provided in the combustion tube and the space between this mixing element and the aperture forms a combustion chamber, wherein the housing has at least first, second, and third channels that are separated from one another and open into the mixing element, wherein gases flow through the first, second, and third channels and the mixing element, wherein the first channel is configured to receive a first gaseous fuel and the third channel is configured to receive a second gaseous fuel, wherein at least the first channel or the third channel has at least two intermediate channels branching toward the combustion chamber in flow direction and opening into a plurality of outlet openings, wherein exhaust gas is able to flow back from the combustion chamber in the direction of the housing through one or more of the intermediate channels, and wherein the exhaust gas flowing back from the combustion chamber gives up heat via the wall of the intermediate channels to the gases flowing inward in the direction of the combustion chamber.

2. The burner according to claim 1, wherein the mixing element is constructed in one piece.

3. The burner according to claim 1, wherein three to five intermediate channels are provided in the first and third channels.

4. The burner according to claim 1, wherein at least one of the intermediate channels has helical grooves.

5. The burner according to claim 1, wherein each intermediate channel of the first channel has an outlet cross-section reduced compared with the channel cross-section of the first channel, wherein the outlet openings are disposed in such a way that the gases achieve a homogeneous mixing in the combustion chamber due to the plurality of outlet openings having reduced outlet cross-sections compared with the channel cross-section of the first channel.

6. The burner according to claim 1, wherein a UV or IR flame sensor is provided on the outlet side of the mixing element.

7. The burner according to claim 1, wherein the first channel is disposed in the second channel and the third channel is disposed in the first channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, details and advantages of the invention will become apparent on the basis of the following description hereinafter as well as on the basis of the drawings. Items or elements corresponding to one another are denoted by the same reference symbol in all figures, wherein

(2) FIG. 1 shows a schematic diagram of a burner according to the invention,

(3) FIG. 2 shows a perspective view of a mixing element according to the invention, which is designed as a two-duct system,

(4) FIG. 3 shows an imaginary exploded diagram of the mixing element from FIG. 2,

(5) FIG. 4 shows an inlet-side view of the mixing element from FIG. 2,

(6) FIG. 5 shows an outlet-side view of the mixing element from FIG. 2,

(7) FIG. 6 shows a sectional diagram of the mixing element from FIG. 2 along the line A-A,

(8) FIG. 7 shows a perspective view of a mixing element according to the invention, which is designed as a three-duct system,

(9) FIG. 8 shows an imaginary exploded diagram of the mixing element from FIG. 7,

(10) FIG. 9 shows an inlet-side view of the mixing element from FIG. 7,

(11) FIG. 10 shows an outlet-side view of the mixing element from FIG. 7,

(12) FIG. 11 shows a perspective view of a mixing element according to the invention, which is designed as a four-duct system,

(13) FIG. 12 shows an imaginary exploded diagram of the mixing element from FIG. 11,

(14) FIG. 13 shows an inlet-side view of the mixing element from FIG. 11,

(15) FIG. 14 shows an outlet-side view of the mixing element from FIG. 11,

(16) FIG. 15 shows a perspective view of a mixing element according to the invention,

(17) FIG. 16 shows a variant of FIG. 15 with indicated gas arrows,

(18) FIG. 17 shows an inlet-side view of the mixing element having a recirculatory, and

(19) FIG. 18 shows a portion of a mixing element in which at least one of the intermediate ducts has helical grooves.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(20) In FIG. 1, a schematic diagram is shown of a burner according to the invention, which has a housing 2, on which a combustion tube 3 is disposed, wherein the combustion tube 3 has an aperture 4 at the end turned away from the housing 2. A mixing element 5 is provided in the combustion tube 3, and the space between this mixing element 5 and the aperture 4 forms a combustion chamber 6. In this exemplary embodiment, a first duct 8 extends at least partly through the housing 2 and the combustion tube 3. The spatial volume or the intermediate chamber 7 between the combustion tube 3 and the first duct 8 forms a further duct.

(21) Thus the housing 2 has, separated from one another, at least two ducts 8, which open in the mixing element 5, wherein gases propagate or flow through the ducts 8 and the mixing element 5, and a mixing of these gases first takes place in the combustion chamber 6. For reasons of clarity, the connection between the housing 2 and the duct formed by the intermediate chamber 7 is not illustrated. In the combustion chamber 6, a UV or IR flame sensor is provided on the outlet side of the mixing element 5, in order to monitor the combustion process continuously. What is not illustrated is an igniter, which ignites the gas mixture in the fuel chamber 6.

(22) The mixing element 5, which is designed as a two-duct system, is shown in FIG. 2 in a perspective view, in FIG. 3 in an imaginary exploded diagram, in FIG. 4 on the inlet side and in FIG. 5 on the outlet side, and also in FIG. 6 as a sectional diagram. The imaginary exploded diagram in FIG. 3 provides merely an overview, and separation of the various components of the mixing element 5 is actually not possible, because it would lead to a destruction of the mixing element 5, since the mixing element 5 is formed in one piece by means of an additive fabrication process. The inlet side is to be understood as that side of the mixing element 5 that in the installed condition in the burner 1 adjoins the intermediate chamber 7. The outlet side is to be understood as that side of the mixing element 5 that in the installed condition in the burner 1 adjoins the combustion chamber 6.

(23) The mixing element 5 preferably has a tubular outer wall 14, which is equipped with radially inwardly projecting flow-resistance elements 16, wherein the flow-resistance elements 16 are preferably aligned transversely relative to the longitudinal axis of symmetry or axis of rotation of the outer wall 14. The flow-resistance elements 16 may be separated in radial direction by tube portions, which have a smaller diameter and a shorter longitudinal extent than the outer wall 14. Hereby it is possible that the flow-resistance elements 16, depending on their radial position, are disposed at various angles transverse relative to the longitudinal axis of symmetry of the outer wall 14. Preferably, the flow-resistance elements 16 may be designed in the manner of paddle wheels.

(24) The inner or first duct 8, through which preferably the gaseous fuel is conveyed, is branched into a multiplicity of intermediate ducts 9, which pass through the flow-resistance elements 16 and their associated tube portions. The intermediate ducts 9 have outlet apertures 10, which open in the combustion chamber 6. For the sake of clarity, possible swirl elements, baffle elements, flow-separating edges, stagnation edges, grooves, mixing nozzles, mixing valves and/or outlet elbows at the outlet apertures 10 are not illustrated. The second duct 8 or the intermediate chamber 7 for the oxidant is formed by the space bounded by the outer wall 14 and the duct 8 as well as its intermediate ducts 9. What is advantageous in this exemplary embodiment is that the intermediate ducts 9 themselves represent additional flow-resistance elements. Thus the intermediate ducts 9 have not only the function of transporting the fuel into the combustion chamber but also that of contributing to swirling of the oxidant. In this embodiment, the duct cross section 12 of the first duct 8 is made larger than the cross section of the outlet apertures 10, in order to achieve a uniform distribution of the fuel.

(25) A further mixing element 5, which is designed as a three-duct system, is shown in FIG. 7 in a perspective view, in FIG. 8 in an imaginary exploded diagram, in FIG. 9 on the inlet side and in FIG. 10 on the outlet side. The imaginary exploded diagram in FIG. 8 provides merely an overview, and separation of the various components of the mixing element 5 is actually not possible.

(26) In contrast to the two-duct system, the three-duct system has an additional duct 8, which is disposed here, for example, in the first duct 8. This additional duct 8 in turn has is own intermediate ducts 9, which pass through the flow-resistance elements 16 and their associated tube portions. This additional duct 8 may be used, for example, to inject additional fuel into the combustion chamber 6 and thereby to optimize the combustion process.

(27) A special mixing element 5, which is designed as a four-duct system, is shown in FIG. 11 in a perspective view, in FIG. 12 in an imaginary exploded diagram, in FIG. 13 on the inlet side and in FIG. 14 on the outlet side. The imaginary exploded diagram in FIG. 12 provides merely an overview, and separation of the various components of the mixing element 5 is actually not possible.

(28) In contrast to the three-duct system, the four-duct system has a tubular intermediate wall 15, which has a smaller diameter than the outer wall 14 but a substantially identical longitudinal extent.

(29) As follows in particular from FIGS. 15 and 16, the combustion air is able to flow through the inner ducts 8 into the combustion chamber 6 and to flow out again through one of the outer ducts 8. In order to change the flow direction and to feed the inwardly flowing exhaust gas to the combustion air again, a recirculator 17 is provided (FIG. 17).

(30) A special configuration of the invention provides that at least one of the intermediate ducts has helical grooves as shown in FIG. 18. In this case, it is possible, for example, that the respective groove has a rectangular cross section or is even diamond shaped. By the introduction of helical grooves into the intermediate ducts, the inlet velocity of the respective gases into the combustion chamber can be controlled, in order to achieve mixing of the oxidant and of the fuel with a high degree of homogeneity.

(31) Naturally the invention is not limited to the illustrated exemplary embodiments. Further configurations are possible without departing from the basic ideas. It is self-evident that the feed of the oxidant and of the fuel for a burner having a mixing element designed as a three-duct system or four-duct system must be appropriately adapted. Furthermore, the number of ducts is not limited to the exemplary embodiments illustrated above by way of example. Depending on requirements and field of use of the burner, even more ducts may be practical.

LIST OF REFERENCE SYMBOLS

(32) 1 Burner 2 Housing 3 Combustion tube 4 Aperture 5 Mixing element 6 Combustion chamber 7 Intermediate chamber 8 Duct 9 Intermediate duct 10 Outlet aperture 11 Outlet cross section 12 Duct cross section 13 UV or IR flame sensor 14 Outer wall 15 Intermediate wall 16 Flow-resistance element 17 Recirculator