Patent Application
20210285640
This application claims priority to German Patent Application DE102020106842.5 filed Mar. 12, 2020, the entirety of which is incorporated by reference herein.
The invention relates to a nozzle for a combustion chamber of an engine for the purposes of providing a fuel-air mixture at a nozzle exit opening of the nozzle.
An (injection) nozzle for a combustion chamber of an engine, in particular for an annular combustion chamber of a gas turbine engine, comprises a nozzle main body which has the nozzle exit opening and which, aside from a fuel-guiding duct for conveying fuel to the nozzle exit opening, has multiple (at least two) air-guiding ducts for conveying air, which is to be mixed with the fuel, to the nozzle exit opening. A nozzle commonly also serves for swirling the supplied air, which is then, having been mixed with the supplied fuel, conveyed at the nozzle exit opening of the nozzle into the combustion chamber. Multiple nozzles are for example combined in one nozzle assembly, which comprises multiple nozzles arranged adjacent to one another, commonly along a circular line, for the purposes of introducing fuel into the combustion chamber.
Nozzles known from the prior art, for example from U.S. Pat. No. 9,423,137 B2 or U.S. Pat. No. 5,737,921 A, with multiple air-guiding ducts and with at least one fuel-guiding duct provide that a first air-guiding duct extends along a nozzle longitudinal axis of the nozzle main body and a fuel-guiding duct is situated radially further to the outside than the first air-guiding duct with respect to the nozzle longitudinal axis. At least one further air-guiding duct is then additionally provided radially further to the outside than the fuel-guiding duct with respect to the nozzle longitudinal axis. An end of the fuel-guiding duct, at which fuel flows out of the fuel-guiding duct in the direction of the air from the first air-guiding duct, is in this case typically situated, with respect to the nozzle longitudinal axis and in the direction of the nozzle exit opening, before the end of the second air-guiding duct, from which air then flows out in the direction of a mixture of air from the first air-guiding duct and fuel from the fuel-guiding duct. It is also known from the prior art, and for example also provided in U.S. Pat. Nos. 9,423,137 B2 or 5,737,921, for such a nozzle to be equipped with a third air-guiding duct, the possibly radially outwardly offset end of which follows the end of the second air-guiding duct in the axial direction.
It is also known from the prior art to provide, at an end, situated in the region of the nozzle exit opening, of an air-guiding duct situated radially at the outside, an air-guiding element for guiding air that flows out of the at least one further air-guiding duct. By means of an air-guiding element of said type, the commonly swirled air flowing out of the further air-guiding duct is diverted radially inward in order to achieve mixing with the fuel from the fuel-guiding duct and the additional air in particular from the 1st, inner air-guiding duct. In this way, it is sought to generate a spray cloud with fuel-air mixture, in which the fuel is present in finely distributed droplets.
In the case of nozzles known from practice, it has been found here that, under some circumstances, too much fuel evaporates already in the region of the end of the fuel-guiding duct and, consequently, zones which are strongly enriched with fuel are generated, which in turn lead to undesired soot emissions. In this context, it is proposed for example in EP 3 462 091 A1 to design the nozzle, in the region of the nozzle exit opening, such that an air flow from the air-guiding duct or the air-guiding ducts are configured, and coordinated with one another, such that a maximum flow-off angle, with respect to the nozzle longitudinal axis, at which air is conducted out of the air-guiding duct in the direction of the combustion chamber lies below 50°. In this way, improved scattering and distribution in particular of the liquid fuel in a radially outward direction with respect to the nozzle longitudinal axis and a center of the nozzle exit opening can be achieved.
Against this background, it is the object of the proposed solution to further improve a nozzle known from the prior art.
Said object is achieved by means of a nozzle according to claim 1.
According to said claim, a nozzle for a combustion chamber of an engine is proposed, in the case of which the nozzle comprises, on the nozzle main body, at least one additional jet generator duct for generating at least one fuel jet which is directed radially inward and/or in the direction of the center of a nozzle exit opening.
A proposed nozzle is thus formed, on the one hand, at the nozzle exit opening, with at least one guiding element for guiding a resulting fuel-air mixture radially outward with respect to the nozzle longitudinal axis and the center of the nozzle exit opening, wherein said fuel-air mixture is generated in particular by means of at least one first, inner air-guiding duct which extends along the nozzle longitudinal axis, by means of at least one fuel-guiding duct which is situated radially further to the outside than the first air-guiding duct, and by means of at least one further (second) air-guiding duct which is situated radially to the outside of the fuel-guiding duct. On the other hand, an additional jet generator duct is additionally provided for the purposes of enriching a zone close to the center at the nozzle exit opening with fuel. By means of the at least one fuel jet that can be generated by means of the at least one additional jet generator duct, it is thus possible for an inner recirculation zone in the region of the center of the nozzle exit opening to be enriched with fuel in a targeted manner. This can increase the stability of a flame formed as a result of ignition of the fuel-air mixture. Thus, whilst fuel injected via the fuel-guiding duct is predominantly (owing to the design of the nozzle and in particular of its at least one guiding element) mixed with air, and directed radially outward, at the nozzle exit opening, a fuel jet directed radially inwardly and/or in the direction of the center of the nozzle exit opening is provided by means of the at least one additional jet generator duct for the purposes of enriching an inner recirculation zone in the region of the center of the nozzle exit opening. A discrete fuel jet which is directed radially inward and/or in the direction of the center of the nozzle exit opening can thus be generated by means of the at least one additional jet generator duct.
A control device may be provided at the nozzle in order to actively control the generation of the at least one fuel jet, that is to say in particular to control this in a manner dependent on an engine state on the basis of various process parameters (for example with regard to the jet pressure) and possibly also initiate said generation only when required.
In one design variant, by means of the at least one jet generator duct, at least one fuel jet in a radially inward direction and/or in the direction of the center of the nozzle exit opening can be generated at the end of the inner air-guiding duct. The fuel jet that can be generated by means of the at least one jet generator duct can thus be generated in targeted fashion in the region of a rear end, which adjoins the nozzle exit opening, of the inner air-guiding duct. In this way, it can be ensured that the fuel injected via the jet generator duct is predominantly present only in the inner recirculation zone close to the center, without the guidance of the further fuel-air mixture radially outward, adhering to a maximum flow-off angle, being undesirably impaired as a result.
For example, the nozzle may have a further, third air-guiding duct which is situated radially further to the outside than the one further (second) air-guiding duct, such that a nozzle of said type has at least three air-guiding ducts via which air is provided at the nozzle exit opening. In one design variant, an edge of an exit opening of the jet generator duct is offset, along the nozzle longitudinal axis, with respect to an edge of an exit opening of the one further (second) air duct by at most a first spacing which corresponds to at most three times a second spacing by which the edge of the exit opening of the one further (second) air-guiding duct is offset, along the nozzle longitudinal axis, with respect to an edge of an exit opening of the third air-guiding duct. Thus, in this design variant, the exit openings of the air-guiding ducts and of the jet generator duct are present in close spatial proximity to one another in the region of the nozzle exit opening. In this way, the fuel-air mixture that is formed, and the flow thereof, can be influenced in targeted fashion and kept stable.
Alternatively or in addition, an exit opening of the fuel-guiding duct may extend on the nozzle main body in a circular arc shape or circular ring shape about the nozzle longitudinal axis. An exit opening, provided in the region of the nozzle exit opening, of the fuel-guiding duct thus has a circular-arc-shaped or circular-ring-shaped course. By contrast to this, an exit opening of the jet generator duct may be formed as a discrete circular opening on an inner lateral surface of the nozzle main body, which opening borders the first, inner air-guiding duct in order to generate a defined fuel jet which is directed radially inward and/or in the direction of the center of the nozzle exit opening and which is thinner than the air flows originating from the air-guiding ducts.
In one design variant, the jet generator duct and the fuel-guiding duct are connected to one another by means of a branching point within the nozzle main body. The jet generator duct and the fuel-guiding duct are thus fed by means of a common fuel supply within the nozzle main body, such that one proportion of the fuel conveyed via said fuel supply passes into the fuel-guiding duct, whereas another proportion passes into the jet generator duct. In particular, in this context, it may be provided that the jet generator duct and the fuel-guiding duct are fed with fuel from the same fuel system.
For the provision of a sufficient quantity of fuel via the jet generator duct in the recirculation zone close to the center at the end of the nozzle, one design variant may provide that an exit opening of the fuel-guiding duct has a cross-sectional area which corresponds to at least 8 times, in particular at least 10 times, a cross-sectional area of an exit opening of the jet generator duct. One or more exit openings, distributed over the circumference, of a fuel-guiding duct are thus larger than an exit opening of the jet generator duct by a factor of at least 8 or 10. In particular, a cross-sectional area, and thus an area through which flow passes, of an exit opening of the fuel-guiding duct may lie in a range from 8 times to 25 times the cross-sectional area of the jet generator duct. The following may thus apply for a cross-sectional area As of the jet generator duct in relation to a cross-sectional area AK of a fuel-guiding duct: for example 8AS≤AK≤25AS, in particular 10AS≤AK≤20AS. An exit opening of the jet generator duct is thus several times smaller than an exit opening of the fuel-guiding duct.
Whereas it is basically possible for an exit opening of the jet generator duct to be provided on an inner lateral surface that borders the first, inner air-guiding duct, it is the case in one design variant that the at least one exit opening of the jet generator duct is alternatively provided on a central body which is situated within the inner air-guiding duct. In this way, it is for example possible for a fuel jet which is directed into the center to be generated already close to the center in the air-guiding duct by means of the jet generator duct (which runs within the central body).
In particular, by means of the axial spacing (measured along the nozzle longitudinal axis) of the central body or of the exit opening, provided thereon, of the jet generator duct to the nozzle exit opening, the size of a jet cone in which the fuel injected via the jet generator duct is present at the nozzle exit opening before said fuel impinges on the air flow that originates from the at least one further (second) air-guiding duct can be varied.
For example, the nozzle may extend with its nozzle main body with an overall length along the nozzle longitudinal axis, in the final third of which overall length exit openings of the air-guiding ducts of the nozzle are situated, whereas the at least one exit opening, provided on the central body, of the jet generator duct is present in a first or second third of the overall length. Consequently, in such a design variant, the central body within the first, inner air-guiding duct is, with the at least one exit opening of the at least one jet generator duct, offset relatively far axially forward (upstream) and thus spaced apart from the nozzle exit opening to a relatively great extent. In this way, it can for example be achieved that, at the end of the first, inner air-guiding duct, fuel injected via the jet generator duct centrally into the first, inner air-guiding duct is present so as to be distributed over the entire cross-sectional area, through which flow passes, of the inner air-guiding duct, and a relatively broad spray cone for the additionally injected fuel is thus present at the end of the first, inner air-guiding duct.
In an alternative design variant, the central body may however also be arranged with the exit opening of the jet generator duct in a final third of the nozzle main body in order, at the nozzle exit opening, to have a narrower jet cone for the fuel additionally injected in jet form.
Basically, the jet generator duct within the nozzle main body (that is to say in particular in a shell section for the first, inner air-guiding duct or in a central body in the first, inner air-guiding duct) may be fed with fuel from the same fuel supply as the fuel-guiding duct. Alternatively, different fuel supplies and thus different fuel systems are provided for the fuel-guiding duct under the jet generator duct within the nozzle main body.
The proposed solution is basically in particular combinable with a nozzle design as proposed in EP 3 462 091 A1. Accordingly, in one design variant, it is for example the case that an end of the fuel-guiding duct at the nozzle exit opening is bordered by a flow-off edge situated radially to the outside. The air-guiding element protrudes for example relative to said flow-off edge—with a defined length—in an axial direction in relation to the nozzle longitudinal axis such that
The flow-off edge of the fuel-guiding duct and the axially protruding air-guiding element of the air-guiding duct situated radially to the outside are in this case thus, in order to influence an air flow from the air-guiding duct, designed and coordinated with one another such that, by means of an axial protruding length of the air-guiding element, the one or more reference angles corresponding to the geometrical specifications given above are adhered to. Here, the reference angle according to the above-stated variant (a) and the reference angle according to the above-stated variant (b) may be identical. It is thus possible for one corresponding straight boundary line to satisfy, for example, both of the conditions stated above under (a) and (b), and to thus run both tangentially with respect to the axially protruding air-guiding element and in this case simultaneously through a point at the flow-off edge and a point of the air-guiding element which protrudes to a maximum extent in an axial direction beyond the flow-off edge.
By means of the proposed design of the flow-off edge and of the air-guiding element at the end of the nozzle, it can be achieved that, when the nozzle has been installed on the combustion chamber in the intended manner, a maximum flow-off angle with respect to the nozzle longitudinal axis at which air is conducted from the air-guiding duct in the direction of the combustion chamber is less than 50°. In particular, it can be achieved that said air is unconditionally conducted to the fuel-air mixture or the spray composed of fuel from the fuel-guiding duct and air from the first, inner air-guiding duct (and possibly from a further air-guiding duct that is situated between the inner air-guiding duct and the radially outermost air duct which has the air-guiding element at its end). By means of the proposed nozzle design, a maximum flow-off angle with respect to the nozzle longitudinal axis at which air is conducted from the air-guiding duct situated radially to the outside in the direction of the combustion chamber is less than 50°. In this way, the fuel consequently more effectively follows the flow path of the air which, in the case of multiple (at least two) air-guiding ducts situated radially to the outside, flows out of the radially outermost air-guiding duct of the nozzle. Thus, in one design variant, a fuel-air mixture which is generated in the central region at the end of the nozzle and in which the fuel is already present in a distributed manner in droplet form readily follows a flow path of the air flowing out of the air-guiding duct situated radially to the outside, such that the fuel in droplet form is directed radially outward to a greater degree and is more intensely mixed with air, leading to a more uniform distribution of the fuel and thus to a reduction of soot emissions.
The proposed arrangement and design of the axially protruding air-guiding element with regard to the flow-off edge is in this case initially basically independent of a geometry of the air-guiding element by means of which the air flowing out at the end of the air-guiding duct is guided radially inward. Accordingly, by means of the air-guiding element, it is furthermore possible for a minimum inner diameter of the nozzle exit opening to be defined, such that, by means of the (circumferentially encircling) air-guiding element situated radially to the outside, a narrowing of the nozzle exit opening (possibly combined with a widening, which follows downstream, of the nozzle exit opening toward the combustion chamber) is realized.
In one design variant, the straight boundary line runs tangentially with respect to the flow-off edge and tangentially with respect to the axially protruding air-guiding element. Here, the flow-off edge and air-guiding element of the nozzle are consequently designed and coordinated with one another such that the reference angle between the nozzle longitudinal axis and a straight boundary line which runs tangentially with respect to the flow-off edge and tangentially with respect to the air-guiding element is less than or equal to 50°.
In a refinement which is based on this and in which the air-guiding element has a radially inwardly pointing protuberance, the straight boundary line may furthermore run through a point on the air-guiding element which, in an axial direction, is situated behind the radially inwardly pointing protuberance of the air-guiding element. By means of the radially inwardly pointing, typically convex protuberance of the air-guiding element, the possibly swirled air which flows out of the air-guiding duct situated radially to the outside is conducted radially inward, such that an air flow from the air-guiding duct has a radially inwardly pointing directional component. The flow-off edge of the fuel-guiding duct and the air-guiding element are then designed geometrically to one another and/or arranged relative to one another such that the reference angle between nozzle longitudinal axis and the straight boundary line is less than or equal to 50°, wherein, then, the straight boundary line running tangentially with respect to the flow-off edge and tangentially with respect to the air-guiding element runs through a (reference) point on the air-guiding element which is situated behind or downstream of the inwardly pointing protuberance of the guiding element.
In the context of the proposed solution, it has for example proven particularly advantageous if the flow-off edge of the fuel-guiding duct and the air-guiding element lie on an outer lateral surface of a virtual, straight circular cone, the cone tip of which lies on the—centrally running—nozzle longitudinal axis and the opening angle of which corresponds to two times the reference angle. The flow-off edge and the air-guiding element of the air-guiding duct situated radially to the outside are in this case thus designed and coordinated with one another such that an axial end of the flow-off edge and the air-guiding element which protrudes axially beyond the end of the flow-off edge make (punctiform) contact with an outer lateral surface of such a virtual straight circular cone. Here, the flow-off edge and air-guiding element are consequently designed and arranged relative to one another such that, at the nozzle exit opening, the length with which an end of the air-guiding element protrudes relative to the flow-off edge of the fuel-guiding duct in an axial direction (pointing toward the combustion chamber in the installed state) is specified by means of a straight circular cone with an opening angle which corresponds to two times the specified reference angle and the cone tip of which lies on the (centrally running) nozzle longitudinal axis.
As part of the proposed solution, an engine having at least one proposed nozzle is also provided.
The appended figures illustrate, by way of example, possible design variants of the proposed solution.
In the figures:
The air conveyed into the primary flow duct by means of the compressor V passes into a combustion chamber portion BKA of the core engine, in which the drive energy for driving the turbine TT is generated. For this purpose, the turbine TT has a high-pressure turbine 13, a medium-pressure turbine 14 and a low-pressure turbine 15. Here, the energy released during the combustion is used by the turbine TT to drive the rotor shaft S and thus the fan F in order to generate the required thrust by means of the air conveyed into the bypass duct B. Both the air from the bypass duct B and the exhaust gases from the primary flow duct of the core engine flow out via an outlet A at the end of the engine T. Here, the outlet A commonly has a thrust nozzle with a centrally arranged exit cone C.
Furthermore, at least one fuel-guiding duct 26 is also formed on the nozzle main body 20. Said fuel-guiding duct 25 is situated between the first, inner air-guiding duct 26 and the second, outer air-guiding duct 27a. That end of the fuel-guiding duct 25 via which fuel flows out of the first inner air-guiding duct 26 in the direction of the air during the operation of the nozzle 2 is, with respect to the nozzle longitudinal axis DM and in the direction of the nozzle exit opening, situated before an end of the second air-guiding duct 27a from which air from the second, outer air-guiding duct 27a flows out in the direction of a mixture of air from the first, inner air-guiding duct 26 and fuel from the fuel-guiding duct 25.
Swirling elements 270a, 270b are provided in the outer air-guiding ducts 27a and 27b for the purposes of swirling the air supplied via these. Furthermore, at the end of the third, outer air-guiding duct 27b, the nozzle main body 20 also comprises an outer, radially inwardly pointing air-guiding element 271b. In the case of the nozzle 2, which is for example a pressure-assisted injection nozzle, it is the case, correspondingly to
To seal off the nozzle 2 with respect to the combustion space 30, a seal element 28 is also provided on the circumference of the nozzle main body 20. Said seal element 28 forms a counterpart with respect to a combustor seal 4. Said combustor seal 4 is mounted in floating fashion between the heat shield 300 and the head plate 310 in order, in different operating states, to compensate radial and axial movements between the nozzle 2 and the combustion chamber 3 and ensure a reliable seal.
The combustor seal 4 commonly has a flow-guiding element 40 to the combustion space 30. Said flow-guiding element 40 serves, in conjunction with the third, outer air-guiding duct 27b on the nozzle 2, for desired flow guidance of the fuel-air mixture that forms from the nozzle 2, more specifically the swirled air from the air-guiding ducts 26, 27a and 27b, and the fuel-guiding duct 25.
A combustion chamber assembly known from the prior art, corresponding to
Against this background, it is already known that, in order to influence an air flow LS from the third air-guiding duct 271b, a flow-off edge 250, which borders the end of the fuel-guiding duct 25 at the nozzle exit opening radially to the outside, and the air-guiding element 271b, which protrudes in an axial direction x along the nozzle longitudinal axis DM in relation to said flow-off edge 250, are designed and coordinated with one another such that a reference angle a between the nozzle longitudinal axis DM and a reference straight line 6 is less than or equal to 50°. Said straight boundary line 6 runs through a (first) point at the flow-off edge 250 (for example through a point at a flow-off margin of the flow-off edge 250) and tangentially with respect to the axially protruding air-guiding element 271b, in particular tangentially with respect to the flow-off edge 250 and tangentially with respect to the air-guiding element 271b, which guides the air flow LS initially radially inward. Alternatively or in addition, the straight boundary line 6 runs through a point at the flow-off edge 250 and a (reference) point, which protrudes to a maximum extent in an axial direction x beyond the flow-off edge 250, of a combustion-space-side end of the air-guiding element 271b.
In the case of the nozzle 2 illustrated in
By means of the thus selected design of the nozzle 2, the air flow LS is forced to follow a flow path with an outflow angle of less than 50°, such that the air from the third air-guiding duct 27b is unconditionally conducted to the radially outwardly flowing spray formed from the fuel from the fuel-guiding duct 25 and the swirled air from the first, inner air-guiding duct 26 and the second air-guiding duct 27a.
The resulting spray cone 5 is, in the case of the nozzle 2 of
Against this background, the design variant of
It is basically also possible for multiple exit openings of one jet generator duct 7 or exit openings of multiple jet generator ducts 7 for the purposes of generating fuel jets J to be provided over a circumference of the lateral surface of the first, inner air-guiding duct 26 about the nozzle longitudinal axis DM.
In particular, an exit opening of a jet generator duct 7 can be of relatively small and circular form on the inner lateral surface of the nozzle main body 20 which borders the first, inner air-guiding duct 26. By contrast, an exit opening of the fuel-guiding duct 25 may for example be formed so as to run in a circular arc shape or circular ring shape about the nozzle longitudinal axis DM. An exit opening of the fuel-guiding duct 25 may thus for example be formed as a slot which runs in a circular arc shape or circular ring shape on the inner lateral surface of the first, inner air-guiding duct 26, whereas relatively small discrete, circular holes are formed on the inner lateral surface for the jet generator duct 7.
As illustrated in particular on the basis of the flow courses of
In the design variants of
In the design variant of
In the design variant of
In the design variant of
In the design variants of
The design variants of
Here, the size of a spray cone for the fuel attributable to the fuel jet J differs in a manner dependent on the position of the central body 260 and of an exit opening, formed thereon, of the jet generator duct 7. Accordingly, the central body 260 of
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020106842.5 | Mar 2020 | DE | national |
