Patent Grant
11371370
The present invention relates to a flow arrangement with surrounding-flow structures for placing in a hot gas duct of a turbomachine.
The turbomachine can be, for example, a jet engine, such as, for example, a turbofan engine. In functional terms, the turbomachine is subdivided into a compressor, a combustion chamber, and a turbine. In the case of a jet engine, for instance, sucked-in air is compressed by the compressor and combusted with admixed kerosene in the downstream combustion chamber. The resulting hot gas, which is a mixture of combustion gas and air, flows through the downstream turbine and is thereby expanded. The volume through which the hot gas flows, that is, the path from the combustion chamber via the turbine to the nozzle, is referred to as the “hot gas duct.”
The flow arrangement addressed here is provided for arrangement in the hot gas duct and has a plurality of surrounding-flow structures. At least some of the surrounding-flow structures are designed as deflecting blades; other surrounding-flow structures are preferably support struts or corresponding claddings. Like the preceding reference to a jet engine, these are intended to illustrate the present subject, but first and foremost not to limit it in terms of generality. The turbomachine can also be, for example, a stationary gas turbine or steam turbine.
The present invention is based on the technical problem of presenting an especially advantageous flow arrangement for placing in the hot gas duct of a turbomachine.
In accordance with the invention, this object is achieved by the flow arrangement of the present invention. The flow arrangement has a first surrounding-flow structure and a second surrounding-flow structure, wherein the second surrounding-flow structure is provided as a deflecting blade and has a lesser profile thickness than the first surrounding flow structure, which is arranged at the suction end of the second surrounding-flow structure. Furthermore, although the surrounding-flow structures are arranged with a partial axial overlap, the trailing edge of the second surrounding-flow structure is, at the same time, displaced downstream of the trailing edge of the first surrounding-flow structure. In figurative terms, initially different surrounding-flow structures, which, in a conventional construction, are provided in separate segments that axially follow one another, are pushed into one another to a certain extent (axial overlap), but not fully, by way of the present flow arrangement.
By displacing backward the trailing edge of the second surrounding-flow structure (referred to hereinafter also as the “thin deflecting blade”), it is possible to produce a suction at the trailing edge of the first surrounding-flow structure (referred to hereinafter also as the “thick blade”). Accordingly, the flow from the trailing edge of the aerodynamically more unfavorable thick blade can be accelerated away and the trailing flow can be refined or made uniform, which reduces detrimental secondary flows, for example, and can also have a noise-reducing effect. In figurative terms, the thin deflecting blade brings about a load relief and a smooth flow off the trailing edge of the thick blade (Kutta condition). In regard to the uniformity of the flow to the downstream rotor, this can be of advantage or also help to improve the efficiency of the turbine overall by approximately 0.25% to 0.5%, for example.
Preferred embodiments are presented in the dependent claims and in the entire description, without a distinction always being made in detail in the presentation of the features between the flow arrangement and a corresponding turbomachine or uses associated therewith. Implicitly, in any case, the disclosure is to be read as relating to all claim categories.
Each of the surrounding-flow structures has a leading edge and a trailing edge, between which two mutually opposite lateral surfaces of the respective surrounding-flow structures extend in each case. The profile thickness is constituted between the lateral surfaces. In detail, the mean line between the leading edge and the trailing edge of the respective surrounding-flow structure extends in the middle between the lateral surfaces in each case and the profile thickness then results as the largest circle diameter on the mean line (the circle touches the lateral surfaces and the center point lies on the mean line). The thin deflecting blade can have, for example, a profile thickness that is reduced by at least 50%, 60%, 70%, or 80% in comparison to the first surrounding-flow structure, with possible upper limits (independent thereof) of, for example, at most 99%, 97%, and 95% (respectively, increasingly preferred in the named sequence).
Insofar as, in general, in the scope of this disclosure, different structures are compared with one another, such as, for instance, the surrounding-flow structures are compared with one another or also with other blades of the turbine (see below), the basis is the design of the respective structure in its respective radial middle. What is regarded in each case, therefore, is the shape at half height (viewed radially) of the corresponding surrounding-flow structure or of the deflecting blade or of the blade element. The influence on the flow can be greatest at the radial middle of the gas duct. Preferably, however, the respective structures are nevertheless designed correspondingly in relation to one another over their entire height (at any rate, in a comparison at the same percent height in each case).
In general, in the scope of this disclosure, “axially” refers to the longitudinal axis of the turbomachine, which, for example, coincides with an axis of rotation of the rotors. “Radially” refers to the radial directions that are perpendicular to and point away from the axis of rotation, and a “rotation” or “rotationally” or the “direction of rotation” relates to the rotation around the longitudinal axis. The first surrounding-flow structure and the second surrounding-flow structure are arranged following each other—for example, on account of the axial overlap—also in the direction of rotation. In other words, “axial” overlap means, for example, that a projection of the first surrounding-flow structure radially onto the longitudinal axis has an overlap with a projection of the second surrounding-flow structure radially onto the longitudinal axis.
In the scope of this disclosure, “a” and “an” are to be read as indefinite article and hence are always to be read as “at least one.” Via a full rotation around the longitudinal axis, the flow arrangement can therefore have a plurality of first and second surrounding-flow structures in each case, such as, for example, at least 4, 5, or 6, with possible upper limits (independent thereof) of, for example, at most 30, 20, or 15. In each case, the first surrounding-flow structures and the second surrounding-flow structures are then arranged preferably with identical constructions and with rotational symmetry. As is made clear below in detail, there can also be third and, under certain circumstances, fourth or even more surrounding-flow structures, which can then likewise be designed as thin deflecting blades. Therefore, for example, at least two and preferably no more than nine, eight, seven, six, five, four, or three thin deflecting blades can be provided rotationally between two thick blades in each case.
In one preferred embodiment, the first surrounding-flow structure is provided as a bearing support strut or as a cladding, in particular as a cladding of a bearing support strut. The support strut is a bearing component of the turbomachine and, together with further support struts that are arranged rotationally, it preferably carries the bearing of the turbine shaft, in particular the high-pressure turbine shaft. The bearing is preferably arranged in the turbine center frame, that is, in the so-called mid turbine frame. The support struts can each extend radially outward away from the bearing and the bearing is thus held centered in the housing in a more or less spokelike manner.
Preferably, the first surrounding-flow structure is a cladding, in which it is also possible to convey a supply line, for example, and which is preferably a cladding of a support strut and, for aerodynamic reasons, is therefore attached to the actual bearing component. In this case also, additional supply lines, etc. can then be conveyed as well. Such a cladding is also referred to as a fairing. The bearing function or the enclosure of the support strut necessitates a certain structural size, that is, a large profile thickness. This is an aerodynamic drawback, which, however, is compensated for at least in part by the combination with the thin deflecting blade.
In general, the first surrounding-flow structure can also be provided so as to be non-deflecting; preferably, it is weakly deflecting at only 5°, but has no effect on the flow (as a consequence of the change in radius and the principle of angular momentum, no impulse is transmitted to the flow). With its bottom surface, the first surrounding-flow structure (thick blade) faces the thin deflecting blade. More deflection is necessary at the bottom side of the thick blade, because, as a consequence of the greater thickness, its bottom side extends axially into the trailing edge—for example, it is inclined by no more than 10° or 5° with respect to the axial direction. At the trailing edge of the thick blade, the thin deflecting blade produces, for one thing, an acceleration (nozzle effect). Furthermore, the trailing flow is “sucked away” from the trailing edge.
In one preferred embodiment, the thin deflecting blade has its maximum curvature at the place where it has the axial overlap with the first surrounding-flow structure. This design with a strong curvature is comparable to a support surface with extended Fowler flap, which further increases the suction produced at the trailing edge of the thick blade.
In one preferred embodiment, the trailing edge of the thin deflecting blade is displaced by at least 0.5 times, further and especially preferably at least 0.7 or 0.9 times, the axial length of the blading of a downstream directly following rotor with respect to the trailing edge of the first surrounding-flow structure (axially downstream). Preferred upper limits, which, in general, can also be independent of the lower limits of interest, lie at most at 4 times, further and especially preferred at most at 2.6 or 2.2 times, the axial length. The “axial length” is obtained as the axial fraction of the chord length of the rotating blades of the rotor (if the rotor is equipped with different blades, then a mean value formed from the chord length is taken into consideration).
In one preferred embodiment, the leading edge of the thin deflecting blade is displaced axially downstream with respect to that of the thick blade. Preferred is a displacement by at least 0.4, 0.5, or 0.6 times the axial length of the first surrounding-flow structure (thick blade), that is, of the axial fraction of the chord length. Advantageous upper limits lie (also independent thereof) at preferably at most 1.2 times, especially preferred at most 0.9 times, the axial length.
In one preferred embodiment, the thin deflecting blade has a chord length that constitutes at least 1 times, preferably at least 1.5 times, a chord length of the blading of the rotor arranged directly following downstream. If the rotor is equipped with different blades, then, once again, a mean value is taken into consideration. Advantageous upper limits of the chord length of the thin deflecting blade lie at most at 8, 7, 6, 5, 4, or 3 times the chord length of the following rotor, in increasing preference in the order given. Especially preferred, therefore, is a chord length of about 2 to 3 times the axial length.
In one preferred embodiment, the flow arrangement has a third surrounding-flow structure, which is provided as a thin deflecting blade in analogy to the second surrounding-flow structure, but is not identical in construction to the second surrounding-flow structure. The third surrounding-flow structure is arranged on the top side of the thick blade (the thick blade lies on the suction side of the third surrounding-flow structure). At least two different thin deflecting blades are then provided rotationally between two thick blades in each case. The trailing edge of the third surrounding-flow structure is displaced preferably axially downstream with respect to that of the thick blade and is preferably free of axial displacement (not displaced) with respect to that of the second surrounding-flow structure, this preferably also applying to a fourth and, in general, further surrounding-flow structures.
In one preferred embodiment, the third surrounding-flow structure has a shorter chord length than the second surrounding-flow structure. As stated above, more deflection may be required on the bottom side of the first surrounding-flow structure, this being achieved with the longer chord length of the second surrounding-flow structure. If, between two first surrounding-flow structures, more than two different thin deflecting blades are provided rotationally, then they preferably have a decreasing chord length overall from the bottom side of the one thick blade to the top side of the other thick blade. With the varying chord length, it is possible to adjust the free flow cross section in such a way that a uniform flow to the following rotor is achieved.
In one preferred embodiment, the third surrounding-flow structure has a lesser curvature than the second surrounding-flow structure. Therefore, more deflection is achieved with a more strongly curved second surrounding-flow structure on the bottom side of the thick blade (see above). If, between two first surrounding-flow structures, more than two different thin deflecting blades are provided rotationally, then they preferably have a decreasing curvature overall from the bottom side of one thick blade to the top side of the other thick blade.
In one preferred embodiment, another thin deflecting blade is provided (fourth surrounding-flow structure), wherein the second, third, and fourth surrounding-flow structures are not identical in construction to one another. The fourth surrounding-flow structure is arranged on the suction side of the third surrounding-flow structure. Provided that exactly three different thin deflecting blades are arranged rotationally between two thick blades, a fourth surrounding-flow structure is arranged also on the pressure side of the second surrounding-flow structure.
In one preferred embodiment, the fourth surrounding-flow structure has a longer chord length than the third surrounding-flow structure or is more strongly curved, preferably both. Preferably, the chord length and/or the curvature increase or increases from the third surrounding-flow structure via the fourth surrounding-flow structure to the second surrounding-flow structure.
In one preferred embodiment, between two first surrounding-flow structures that are nearest neighbors to each other in the direction of rotation, at least four surrounding-flow structures, each of which are constructed as a deflecting blade, are arranged. Upper limits, which are independent of the lower limits, can be at most twelve, eleven, ten, or nine deflecting blades, increasingly preferred in the named sequence. Especially preferred, there can be exactly four deflecting blades. Between the first surrounding-flow structures that are nearest neighbors to each other, the second, third, fourth, and a fifth surrounding-flow structure can then preferably be arranged; compare also the additionally presented details with the preceding description.
Since, in general, a plurality of deflecting blades are provided between two first surrounding-flow structures, the latter structures can also be displaced by their trailing edges relative to each other; that is, they can be arranged stacked. In relation to the direction of rotation, an equidistant arrangement of the trailing edges of the deflecting blades is also possible in general, but, preferably, the arrangement can be non-equidistant.
In one preferred embodiment, at least the deflecting blades arranged between the two first surrounding-flow structures as nearest neighbors in the direction of rotation are constructed as multiple segments. It is also possible to provide the first surrounding-flow structure as part of the multiple segment. On the other hand, a subdivision may also be advantageous, however, to the extent that only the deflecting blades are combined in multiple segments or else they are formed in a ring, wherein the first surrounding-flow structures are then accordingly combined. Therefore, the first surrounding-flow structure or structures are then cast by themselves; in order to realize the axial overlap, a recess can be introduced—for example, milled—into the trailing edges of the first surrounding-flow structures in each case and the segment or the ring with the deflecting blades is then inserted into the recesses. The surrounding-flow structures of the multiple segment or ring are formed in one piece with one another; that is, they cannot be separated from one another without destruction. Preferably, they are monolithic in construction and, in particular, are formed from one casting.
The invention also relates to a turbomachine having a presently disclosed flow arrangement, which can be placed, in particular, in the mid turbine frame.
The invention also relates to the use of a presently disclosed flow arrangement in a turbomachine, in particular an aircraft engine.
The invention will be explained in detail below on the basis of an exemplary embodiment, wherein the individual features in the scope of the independent claims may also be essential to the invention in other combinations, and also no distinction is made in detail between the different claim categories.
Shown in detail are:
The surrounding-flow structures 6, 21, 22 each have a leading edge 6a, 21a, 22a and, downstream thereof, a respective trailing edge 6b, 21b, 22b. Although the thin deflecting blades are provided axially with an overlap with respect to the first surrounding-flow structures 6, they are also displaced further to a certain extent. The trailing edges 21b, 22b of the second and third surrounding-flow structures 21, 22 are displaced axially downstream with respect to the trailing edges 6b of the first surrounding-flow structures 6. In addition, the second surrounding-flow structure 21 has its greatest curvature in the region of the axial overlap with the first surrounding-flow structure 6. As a result, a stronger suction is accordingly produced and the flow from the trailing edge 6b of the aerodynamically rather unfavorable surrounding-flow structure 6 is accelerated away. The trailing flow is finer and more uniform; compare also what has been presented in the introduction of the description.
On the bottom side of the first surrounding-flow structure 6 (on the bottom in the figure), the flow has to be deflected more strongly than on the top side, because the bottom lateral surface extends essentially axially into the trailing edge 6b as a consequence of the larger wedge angle or the greater thickness. For this reason, the second surrounding-flow structure 21 is more strongly curved than the third surrounding-flow structure 22 and it has a longer chord length. The first surrounding-flow structure 6 is arranged on the pressure side of the third surrounding-flow structure 22; the flow at the trailing edge 6b is thereby forced further downward to a certain extent and thus the load on the trailing edge 6b is relieved.
In this example, the flow arrangement 20 is overall (over the entire rotation) composed of 9 first, second, and third surrounding-flow structures 6, 21, 22 in each case and therefore has 18 thin deflecting blades. In addition, it is also possible to provide a fourth surrounding-flow structure, which is likewise designed as a thin deflecting blade, so that, therefore, between two first surrounding-flow structures 6, three different thin deflecting blades would be arranged in each case (in this case, a total of 27 thin deflecting blades would be provided); compare also the description in the introduction. Regardless thereof in detail, a groupwise combination of the surrounding-flow structures 6, 21, 22 in multiple segments is preferred. In this regard, the axial displacement can be advantageous in terms of production engineering or, conversely, it would consequently be substantially more complicated to achieve the same flow guidance at the trailing edge 6b of the first surrounding-flow structure 6 by way of a first surrounding-flow structure 6 elongated to the rear.
The axial displacement between the trailing edges 21b, 22b of the second and third surrounding-flow structures 21, 22 with respect to the trailing edges 6b of the first surrounding-flow structures 6 corresponds to about 1.5 axial lengths of a following rotor 30, specifically the blading 31 thereof. The described refinement of the flow and making it more uniform is also of advantageous for the operation of the rotor 30.
Although the present invention has been described in detail on the basis of the exemplary embodiments, it is obvious to the person skilled in the art that the invention is not limited to these exemplary embodiments, but rather that modifications are possible in such a way that individual features are omitted or other types of combinations of features can be realized, without leaving the scope of protection of the appended claims. In particular, the present disclosure encompasses all combinations of the individual features shown in the different examples of embodiment, so that individual features that are described only in conjunction with one exemplary embodiment can also be used in other exemplary embodiments, or combinations of individual features that are not explicitly shown can also be employed.
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