COMBUSTION CHAMBER FOR A GAS TURBINE, AND ENGINE

[0001]This application claims priority to German Patent Application 102024133092.9 filed Nov. 12, 2024, the entirety of which is incorporated by reference herein.

[0002]The invention relates to a combustion chamber for a gas turbine, in particular an engine of an aircraft, which is in particular of annularly encircling form, having an outer wall and an inner wall which are arranged in relation to a longitudinal axis extending between them, and having a front plate which extends on an inlet side between the outer wall and the inner wall, in particular orthogonally to the longitudinal axis, wherein the outer wall, the inner wall and the front plate delimit an in particular annularly encircling combustion space, wherein the combustion space extends over a length of the combustion chamber from an in-jector-side inlet side, with an inlet-side height, to a downstream outlet opening, with an outlet-side height. The invention furthermore relates to an engine.

[0003]A combustion chamber of said type is specified in EP 1 522 792 B1 , which discloses an RQL (rich-quench-lean) combustion chamber.

[0004]Further combustion chambers for an engine of an aircraft are specified in EP 1 775 516 A2 and EP 3 321 584 A1.

[0005]The invention is based on the object of providing a combustion chamber of the type mentioned at the outset and an engine with an optimized emission characteristic during operation.

[0006]The invention is achieved for the combustion chamber by the features of Claim 1, and for the engine by the features of Claim 9.

[0007]In the case of the combustion chamber, it is provided that, in a longitudinal section through the combustion chamber, the outer wall and/or the inner wall extend(s) so as to approach the longitudinal axis in a continuous (kink-free and/or jump-free) and strictly monotonic (consistent) manner in the (main) flow direction (or axial direction in relation to the longitudinal axis), wherein the approach is configured to be steeper on the inlet side than on the outlet side (with the outlet opening).

[0008]In mathematical terms, the approach can be interpreted as a slope or gradient in relation to the longitudinal axis. If, in the longitudinal section, the longitudinal axis were to represent an abscissa of a Cartesian coordinate system (with an ordinate positioned for example at the inlet side), the section edges of the outer wall and/or of the inner wall would correspond to strictly monotonically extending, continuous curves having a slope which continuously decreases in magnitude from the inlet side in the direction of the outlet opening, that is to say the magnitude of the gradient is greatest on the inlet side.

[0009]The longitudinal axis extends in particular centrally through the front plate, which is arranged in particular orthogonally to it. Preferably, an injector main body of at least one injector of the combustion-chamber arrangement, which is assigned to the combustion chamber, is arranged along and/or symmetrically on and/or in relation to the longitudinal axis.

[0010]The inlet-side height is measured at the axial position of the front plate (on its side facing towards the combustion space) from the outer wall to the inner wall orthogonally to the longitudinal axis. The outlet-side height is measured at the axial position of the outlet opening from the outer wall to the inner wall orthogonally to the longitudinal axis.

[0011]Here, according to definition, the outlet opening is arranged in an outlet plane oriented orthogonally to the longitudinal axis, and between the combustion-chamber walls. The outlet opening extends from the downstream end of the outer wall to the downstream end of the inner wall. If the downstream ends are arranged at different axial positions, the outlet opening extends from the downstream end of that combustion-chamber wall which ends further upstream (outer wall or inner wall) to the other combustion-chamber wall (inner wall or outer wall), that is to say one of the combustion-chamber walls may protrude axially beyond the outlet opening.

[0012]The front plate may have a heat shield on the combustion-chamber side and be of single-walled and/or double-walled form.

[0013]The outer wall and/or the inner wall may be of single-walled or double-walled form.

[0014]In the case of an annularly encircling combustion chamber, the longitudinal section is oriented in particular parallel to a central longitudinal axis around which the combustion chamber is arranged. Preferably, the combustion chamber is in this case of rotationally symmetrical form, wherein the design according to the invention of the outer wall and/or of the inner wall is provided over the entire peripheral direction. When extended peripherally, the longitudinal axis forms a longitudinal surface which extends in particular radially centrally (in relation to the central central longitudinal axis) and/or orthogonally in relation to the front plate.

[0015]The shaping according to the invention of the combustion-chamber walls (the outer wall and/or the inner wall) results in advantageous flow guidance being achieved, wherein reverse-flow regions induced by sudden changes in the routing of the combustion-chamber walls, which are associated with increased dwell time of the flow and thus nitrogen-oxide formation, are avoided. In this way, the proposed design of the combustion-chamber walls contributes to low nitrogen-oxide emissions during operation.

[0016]Particularly preferably, the profile of the outer wall and/or the inner wall is formed so as to be elliptical-arc-shaped, and/or circular-arc-shaped on a circular arc, in the longitudinal section. The arc curves (in each case, if appropriate) facing towards the combustion space. With a corresponding formation of both combustion-chamber walls, the arrangement of the combustion-chamber walls, viewed as a whole, resembles the shape of a biconcave lens in the longitudinal section.

[0017]Here, in the case of a circular-arc-shaped profile, preferably the circular arc has a circle radius of between 3.5 times and 10 times the length, in particular of between 5 times and 8 times the length. In the case of an elliptical-arc-shaped profile, preferably a first radius is between 80% and 100% and a second radius is between 100% and 120% of the (above-defined) circle radius.

[0018]In an expedient embodiment variant, it may be provided that the outer wall and the inner wall have the same circle radius and/or the same first radius and second radius, and are in particular arranged mirror-symmetrically with respect to one another in relation to the longitudinal axis. A different circle radius and/or a different first radius and second radius is also possible.

[0019]It is advantageous if a ratio of the inlet-side height to the outlet-side height is between 1.4 and 1.6 (with 1.4≤h1/h2≤1.6), preferably is 1.5.

[0020]Preferably, an angle α between the front plate and the outer wall and/or the inner wall is between 45° and 90° (with α less than 90°, that is to say 45°≤α<90°), in particular between 60° and 90° (60°≤α<90°).

[0021]Preferably, the length (of the combustion chamber) between the inlet-side height and the outlet-side height is configured according to the specification 1≤L/h1≤3, in particular 1.6≤L/h1≤2.3 (for liquid fuels) or 1≤L/h1≤2.3 (for hydrogen-containing fuels).

[0022]The combustion chamber may be designed to be mountable at an end (on the outlet side), for example by means of fastening means that are arranged closer to the outlet side than to the inlet side.

[0023]The engine has a combustion-chamber arrangement comprising at least one injector and a combustion chamber according to one of the preceding exemplary embodiments. The combustion-chamber arrangement is designed in particular for operation with a kerosene-based and/or alternative liquid fuel and/or for operation with a gaseous, in particular hydrogen-containing, fuel.

[0024]The invention will be discussed in more detail below on the basis of an exemplary embodiment with reference to the drawing. In the drawing:

[0025]FIG. 1 shows a schematic illustration of a combustion-chamber arrangement with a circular-arc-shaped inner wall and a circular-arc-shaped outer wall in a longitudinal section.

[0026]FIG. 1 shows a schematic illustration of a combustion-chamber arrangement 100 for a gas turbine, in particular an engine of an aircraft, in a longitudinal section through a combustion chamber 10 along a longitudinal axis M. The combustion-chamber arrangement 100 is surrounded by an outer casing 12 of the engine, on which it is mounted for example at one end by means of fastening means 8, 9. The combustion-chamber arrangement 100 is designed in particular for RQL (rich-quench-lean) operation with liquid fuel, for example a kerosene-based and/or alternative fuel, and/or a gaseous fuel, for example a hydrogen-containing fuel.

[0027]The combustion-chamber arrangement 100 comprises at least one injector 2 and the combustion chamber 10, into which the injector 2 opens out at an inlet side with an injector main body 20. The injector main body 20 is arranged in particular along the longitudinal axis M and/or symmetrically in relation thereto.

[0028]The combustion chamber 10 is in particular formed encirclingly around a central longitudinal axis (not shown here) annularly, wherein it is preferably of at least substantially rotationally symmetrical form. On the inlet side, on an injector-side inlet side 13 (on which the injector is arranged in the mounted state), the combustion chamber 10 has a front plate 4 which is preferably arranged orthogonally to the longitudinal axis M and/or at least substantially mirror-symmetrically in relation thereto. As shown in FIG. 1, the front plate 4 may be of double-walled form and/or have a combustion-space-side heat shield 5.

[0029]Moreover, the combustion chamber 10 has an outer wall 6 and an inner wall 7, between which the longitudinal axis M is positioned in the longitudinal section and which are in particular of annularly encircling form. The outer wall 6 and the inner wall 7 are in the present case for example of single-walled form, but may also be of double-walled form, for example for cooling purposes.

[0030]The front plate 4 is arranged between the outer wall 6 and the inner wall 7, preferably in a manner extending from the outer wall 6 to the inner wall 7, possibly interrupted by fittings such as the injector 2.

[0031]The outer wall 6, the inner wall 7 and the front plate 4 delimit on the inlet side and laterally an in particular annularly encircling combustion space 1 which extends over a length L from the injector-side inlet side 13 to an outlet side, said outlet side having a downstream outlet opening 14. Here, according to definition, the outlet opening 14 is arranged in an outlet plane oriented orthogonally to the longitudinal axis M, and between the combustion-chamber walls (outer wall 6 and inner wall 7), wherein, in FIG. 1, it extends by way of example from the downstream end of the outer wall 6 to the downstream end of the inner wall 7.

[0032]On that side of the front plate 4, in particular of the heat shield 5, which faces towards the combustion space 1, the combustion space 1 or the combustion chamber 10 has an inlet-side height h1. The inlet-side height h1 is measured from the outer wall 6 to the inner wall 7 orthogonally to the longitudinal axis M. On the outlet side, axially at the position of the outlet opening 14, the combustion space 1 has an outlet-side height h 2 from the outer wall 6 to the inner wall 7.

[0033]The shaping according to the invention of the outer wall 6 and/or the inner wall 7 results in advantageous effects on the nitrogen-oxide emissions during operation. In this case, in the longitudinal section through the combustion chamber 10 along the longitudinal axis M, the outer wall 6 and/or the inner wall 7 extend(s) so as to approach the longitudinal axis M in a continuous and strictly monotonic manner in the flow direction. The approach is steeper from the inlet side 13 than towards the outlet side 14. Were the longitudinal axis M to represent an abscissa of a Cartesian coordinate system (with an ordinate positioned for example at the inlet side 13), the section edges of the outer wall 6 and/or of the inner wall 7 would correspond to curves having a slope which continuously decreases in magnitude from the inlet side 13 in the direction of the outlet opening 14. There are no kinks and/or jumps in the wall route.

[0034]This formation of the outer wall 6 and/or of the inner wall 7 is provided preferably over the entire outer wall 6 and/or inner wall 7, preferably annularly encirclingly in the case of the design as an annular combustion chamber, in the peripheral direction.

[0035]An inlet-side angle α between the front plate 4 with the heat shield 5 (on that side of the latter facing towards the combustion space 1) and the outer wall 6 and/or the inner wall 7 is between 45° and 90°, in particular between 60° and 90°, in the present case approximately 84° by way of example. An outlet-side angle β between the plane of the outlet opening 14 (orthogonal to the longitudinal axis M) and the outer wall 6 and/or the inner wall 7 is closer to 90° and, in the present case, is between 85° and 90°, approximately 87° by way of example.

[0036]As made clear in FIG. 1 by the dashed illustration of two circular arcs K, the profile of the outer wall 6 and the inner wall 7 is in the present case of circular-arc-shaped form by way of example, wherein the two circular arcs curve inwards in the direction of the longitudinal axis M or the outer wall 6 and the inner wall 7 are convexly shaped inwards. Viewed as a whole, the arrangement of the combustion-chamber walls (outer wall 6, inner wall 7) thus resembles the shape of a biconcave lens in the longitudinal section shown. A circular and/or elliptical-arc-shaped formation with different radii (not shown here) is also possible.

[0037]In the present case, the outer wall 6 and the inner wall 7 have the same circle radius by way of example and are arranged mirror-symmetrically with respect to one another in relation to the longitudinal axis M. Different circle radii or ellipse radii (not shown here) are also possible. The circle radius preferably corresponds to between 3.5 times and 10 times, in particular between 5 times and 8 times, the length L of the combustion chamber 10. The length L is preferably dimensioned according to the specification 1≤L/h1≤3, for example 1.6≤L/h1≤2.3 (for liquid fuels) or 1≤L/h1≤2.3 (for gaseous, hydrogen-containing fuels).

[0038]A ratio of the inlet-side height h1 to the outlet-side height h2 is preferably between 1.4 and 1.6.

[0039]The described circular-arc-shaped and/or elliptical shaping of the combustion-chamber walls with curving in the direction of the longitudinal axis M advantageously leads to a continuously converging combustion space 1, wherein the height at the axial centre of the combustion space 1 is closer to the outlet-side height h2 than to the inlet-side height h1. In this way, if appropriate, mixing air added approximately in this region (not shown here) can enter the flow within the combustion space 1 relatively deeply. Moreover, the continuous shaping offers a relatively great amount of leeway in the configuration of the axial position of mixing-air openings in the combustion chamber walls that are possibly to be arranged, which can also contribute to the optimization of the emission characteristic.

[0040]In summary, in particular the combination of the aforementioned dimensioning rules leads to a combustion chamber 10 which is extremely advantageous, in particular with regard to nitrogen-oxide emissions, and which can be operated in an optimized manner not only with liquid fuels, such as kerosene and/or synthetic fuels, but in particular also with (pure or mixed) hydrogen as fuel.

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