EP1927723A1 - Stator stage of an axial compressor in a flow engine with transverse fins to increase the action - Google Patents

Abstract

The stage has a stator vane (1) provided with a suction side (1a) and a pressure side. Transverse segments (3, 3') extend from a wall, at which the stator vane abuts, at a distance to the suction side into a flow volume. A transverse segments-chord length (3g) of the segments reduces with distance from the suction side. The segments have sides whose surface normal form an angle of 90 degrees with a surface normal of the wall. The segments are spaced at a distance to each other. The transverse segments affect a secondary flow from the pressure side to the suction side.

Description

The invention relates to a stator stage of an axial compressor of an axial flow machine, which comprises at least one stator blade, which comprises a suction side and a pressure side.

Rotor and stator stages are used alternately in axial flow machines in an axial compressor. In an axial compressor, as used for example in a gas turbine, an attempt is made to obtain the highest possible pressure build-up in each stage. Adapted to this purpose, a profile design of stator blades is made. The profile is set so that a forming flow on the stator blades remains in a working area corresponding to a design. However, the blades are bounded laterally by walls, an outer wall forming a housing, and an inner wall forming a hub. On these walls, relatively thick boundary layers are formed, especially in the middle and high-pressure compressor area. From measurements taken by J. Hübner, "Experimental and theoretical investigations of the main influencing factors on the fracture and secondary flows in compressor grids" in a dissertation, University of the Federal Armed Forces, Munich, 1996 , and U. Stark and S. Bross, "Endwall boundary separation and loss mechanisms" in AGARD-CP 571, Paper 1, 1996 , published as well as on the basis of a semi-ampirischen theory of diffusers, of H. Fernholz, "A Boundary-Layer Theoretical Investigation of Optimal Subsonic Diffusers," Ingenieur-Archiv, 35th volume, 3rd volume, pages 192-201, 1966 , published, it is clear that with the existing pressure increases and boundary layer thicknesses in stator stages of axial compressors is no longer possible to obtain an adjacent flow on the side walls.

One way to avoid a replacement as much as possible is to provide a contraction of the side walls, as proposed by J. Hübner in the above location. However, such contraction of the sidewalls results in losing some of the desired pressure build-up.

By relieving the wall-near blade area, e.g. By a twist, a profile change and / or a curvature of the blade, a wall detachment can also be avoided or reduced. However, such a procedure also has disadvantageous consequences with respect to the pressure build-up and / or adversely affects a flow behavior outside an optimum operating point of the compressor.

at H. Scheugenpflug, "Theoretical and Experimental Investigations on the Reduction of Peripheral Zone Losses of Highly Loaded Axial Compressors by Boundary Layer Influencing", Dissertation, University of the Federal Armed Forces, Munich, 1990 , It is stated that by tangential blowing out of the sidewall boundary layer, the energy lost by friction can be restored. However, bleed air from higher stages of the compressor must be used for this purpose. Also by suction flow separation can be avoided. It should be noted in this case that an overall energy balance, which includes an efficiency gain and a loss by blowing / bleeding bleed air or by suction, as a whole is positive, ie an efficiency of the axial compressor is increased overall.

A more detailed overview of the state of the art with regard to the design of axial compressors can be found in A. Wennerstrom (Editor) et al., "Secondary Flows in Turbomachines" AGARD Conference proceedings, no. 469, 1989 , and H. Prümper, "Application of boundary layers in turbomachinery" AGAROgraph, no. 164, Paper II-3,1972 Find.

From the publication DE 937 395 Leit- and Laufradgitter for axial, diagonal or radial turbomachinery are known in which one or more baffles or thin profiles in the region of a delayed near-wall fluid layer are mounted on the channel-limiting walls between the profiles to avoid secondary flows.

From the publication DE 2 135 286 are just such Leit- and impeller grille for turbomachinery described. There it is emphasized that on the Channel-limiting walls between two blades in the vicinity of the suction side of each blade only one guide should be deflected, the depth of which corresponds to about 1.1 times the amount of a local boundary layer thickness. This means that the baffles, also referred to as cross-fins, extend about 1.1 times the amount of local boundary layer thickness from the wall into a flow channel. Providing multiple vanes between two vanes is said to be not optimal.

From the EP 0 978 632 A1 is a turbomachine with intermediate blades known as flow guide. There is provided for reducing secondary flow losses of fluid flow through a bladed flow channel of a turbomachine to arrange at least one intermediate blade between two full blades on at least one flow-limiting side wall. A depth of the intermediate blade is less than a depth of the full blades that extend from one boundary wall to an opposite boundary wall. Similarly, a profile thickness is much thinner than that of a full bucket. A suction-side profile of the intermediate blade is preferably contoured in the same way as the suction-side profile of the full blade. As a result of the arrangement of the intermediate blade, the blade channel is subdivided locally into subchannels and a leading edge (blade nose) of the intermediate blades is set back (in the flow direction) relative to the leading edges (blade lugs) of the full blades. The trailing edge of the intermediate blade is preferably offset from the rear edges of the full blades, that is, offset from a main flow direction.

From the US 3,039,736 For example, a turbomachine with a turnaround passage formed between two adjacent blades and boundary surfaces is known. For reducing a secondary flow of a boundary layer fluid at least one projecting from the boundary surface of the flow channel fence is provided. A depth with which the fence projects into the passage resembles, for example, a thickness of the local boundary layer. The projecting depth of the fence increases with a distance along the chord at a rate sufficient to limit the steady increase in boundary layer fluid along the fence.

Overall, it should be noted that in axial compressors about 60% of the losses caused by flow separation on the walls of the housing and hub. The strong increase in pressure in a compressor stage and the boundary layer thicknesses on these side walls customary there inevitably lead to flow separation at these points.

The invention is therefore based on the technical object to provide a compressor stage for an axial compressor of a turbomachine, in which the losses, in particular due to flow separation on the walls, are reduced, that is, an increase in efficiency is achieved.

The object is achieved by a stator stage of an axial compressor of a turbomachine with the features of claim 1. Advantageous embodiments of the invention will become apparent from the dependent claims.

To achieve an increase in efficiency, it is provided that at a stator stage of an axial compressor of a turbomachine comprising at least one stator blade, which in turn comprises a suction side and a pressure side, spaced from at least one wall, to which the stator blade adjacent to the suction side the stator vane extend a plurality of cross blades in a flow volume, wherein Quedamellen chord lengths of the plurality of cross blades with a distance from the suction side of the stator blade decrease. This means that the transverse lamella closest to the suction side of the stator blade has a largest transverse lamella chord length and the farthest lamella farthest from the suction side of the stator blade has the shortest transverse lamella chord length. The flow volume is that volume of the stator stage through which a fluid flows during operation. Such transverse blades, which are arranged on a wall spaced from the suction side of a stator blade between two adjacent stator blades, are capable of influencing a secondary flow forming therefrom from a pressure side of a stator blade arranged adjacent to the suction side of the at least one stator blade Extent of detachment is reduced and thereby a Resistance or loss due to the secondary flow along the at least one wall is reduced. Furthermore, it is achieved by the plurality of transverse lamellae that a secondary flow promoted corner separation at the at least one wall adjacent, in the main flow direction rear corner of the stator blade suction side is reduced, which also leads to a reduction in the efficiency losses.

By providing the transverse lamellae 3, 3 ', substantially higher pressure increases along the wall can be "endured" without any disadvantageous separation of the flow occurring. This means that for a given pressure build-up a much shorter distance is sufficient for this, without major losses occur. This makes it possible to create more compact stator compressor stages. With the cross blades on the wall thus the detachment on the side walls and also on the suction side of the blades of the compressor grating, in particular thus a corner separation, reduced.

In a preferred embodiment of the invention, it is provided that the transverse lamellae comprise a first side and an opposite second side whose surface normal to a surface normal of the at least one wall is an angle between 70 ° and 110 °, more preferably between 85 ° and 95 ° and most preferably of 90 °. This means that the transverse lamellae each extend preferably in the radial direction into the flow volume from the wall. This ensures that the secondary flow which forms parallel to the wall surface is best prevented from propagating.

A particularly small additional flow resistance due to the transverse lamellae is obtained when the first side of the transverse lamellae has a surface curvature which corresponds to the surface curvature of the suction side of the at least one stator blade.

It is also advantageous to provide that the second side of the transverse lamellae has the same surface curvature as the first side. This means that the cross blades in this embodiment, a parallel aligned first and second side, each having a surface curvature corresponding to that of the stator blade, which has the stator blade in the corresponding area adjacent to the at least one wall. The transverse blades are preferably oriented so that the surface of the suction side of the at least one stator blade can be brought into registry with the first side of the transverse blades by rotations about a central axis of the compressor stage. The transverse lamella or the first side of each transverse lamella can thus be regarded as a surface section of the stator blade, which is arranged so as to be twisted along the wall about an azimuthal angle about the central axis of the axial compressor.

In a preferred embodiment of the invention, the transverse lamellae have a front edge facing the main flow and an opposite rear edge, an outer edge adjoining the at least one wall and an inner edge projecting into the flow volume and lying opposite the outer edge, wherein a maximum transverse lamella chord length , measured from the leading edge to the trailing edge, is greater than a maximum cross-blade depth measured from the outer edge to the inner edge. This embodiment offers the advantage that the transverse lamellae are approximately adapted to an extent of the secondary flow area. As a result, an effective influencing of the secondary flow can be carried out.

Since the secondary flow along the at least one wall does not form over the entire profile length of the stator vane profile, it is provided in a preferred embodiment that the transverse lamella chord length of the suction side closest to the plurality of transverse lamellae is between 30% to 70%, more preferably between 40% and 60%, and most preferably 50%, of a stator chord. As a rule, it suffices if the cross lamella with the maximum quedamella chord length has a transverse lamella chord length of 50% of a stator chord length in order to optimally influence the secondary flow and adds no "unnecessary" flow resistance beyond the positive effect to the compressor stage ,

A contour of the transverse lamellae is in each case preferably designed such that a front and inner contour of the transverse lamella approximates and / or corresponds to a streamline course of the main flow, spaced from the wall. This ensures that the cross-blade is flowed around by the main flow as low as possible and provides no additional flow resistance or the lowest possible additional flow resistance. The front contour faces the main flow direction. The inner contour protrudes into the flow volume, i. into a passage between the stator wings, into it.

A good approximation is obtained with a transverse lamella in which a chamfered edge is formed between the front edge and the inner edge.

An embodiment which has proven to be particularly advantageous is one in which one of the plurality of transverse lamellae has an equidistant spacing from the suction side of the stator blade and the several transverse lamellae are mutually spaced apart. This means that the transverse lamellae are equidistant from each other and from the stator blade in the azimuthal direction. The area along the wall is thus subdivided into several zones, thereby eliminating pressure equalization along the wall between the various zones. As advantageous, a cross-plate number between 2 and 10 has been found.

Other embodiments may provide a non-equidistant arrangement of the transverse blades.

As optimum equidistant spacing, a distance between 3% and 7%, more preferably between 4% and 6% and most preferably 5% of a profile length of the suction side of the stator blade has been found.

In one embodiment of the invention, it is provided that the transverse lamella depth of the plurality of transverse lamellae has the same maximum transverse lamella depth.

In another preferred embodiment of the invention it is provided that the transverse lamella depth of the plurality of transverse lamellae decreases with a distance from the suction side of the stator blade.

The configuration of the stator stage is particularly advantageous when extending from one of the at least one wall opposite wall to which the at least one stator blade also adjacent, one or preferably also a plurality of additional transverse lamellae. This means that the at least one wall can represent both an outer wall and a hub. Optimally, however, transverse lamellae are arranged on both the hub-forming wall and the outer wall.

The arrangement of the transverse lamellae preferably takes place such that in each case the rear edge of the plurality of transverse lamellae and / or the additional transverse lamellae terminate with a corresponding rear edge of the stator blade in the axial direction of the turbomachine. The secondary flow is formed between the stator blades. This means that in the axial direction behind the stator blades no cross blades arranged transversely to the propagation direction of the secondary flow have to be provided. If, on the other hand, the transverse lamellae are arranged such that their rear edge does not terminate with the edge of the profile of the stator blade but "end" in the main flow direction in front of the stator blade trailing edge, then at least a part of the secondary flow can form such that corner removal is undesirably assisted.

Particularly preferably, the plurality of transverse fins are arranged within a volume in which a secondary flow caused by wall detachment from the pressure side of an adjacently arranged further stator blade to the suction side of the at least one stator blade forms into the main flow in an operation corresponding to a design of the turbomachine the at least one transverse lamella and / or the further transverse lamellae are aligned transversely to the secondary flow. The orientation of the Slats transverse to this Sekundarströmun.9. Is the cause of the designation of the slats as cross blades. This is transverse not only in the sense of 90 ° to understand.

Fig. 1

eine Ansicht experimentell sichtbar gemachter Strömungslinien entlang einer Seitenwand einer Stator-Stufe eines Axialverdichters nach dem Stand der Technik,

Fig. 2

eine Darstellung einer Druckverteilung, die mit der in Fig. 1 dargestellten Stator-Stufe korrespondiert nach dem Stand der Technik,

Fig. 3

eine schematische Darstellung eines Ausschnitts einer Stator-Stufe nach dem Stand der Technik,

Fig. 4

eine schematische Darstellung einer AusfOhrungsform einer Stator-Stufe mit Querlamellen, die die gleiche Querlamellen-Sehnenlänge aufweisen,

Fig. 5

eine schematische Darstellung eines Ausschnitts einer Stator-Stufe eines Axialverdichters mit Querlamellen, die eine unterschiedliche Querlamellen-Sehnenlänge und eine unterschiedliche Querlamellentiefe aufweisen,

Fig. 6

einen schematischen Ausschnitt eines Schnitts durch eine mit der Ausführungsform nach Fig. 4 korrespondierenden Stator-Stufe,

Fig. 7

einen Ausschnitt einer Schnittzeichnung durch eine schematische Stator-Stufe einer Ausführungsform nach Fig. 5,

Fig. 8, Fig. 9

schematische Darstellungen einer druckgetriebenen Ablösung an einer ebenen Wand ohne Querlamellen und mit Querlamellen,

Fig. 10

eine grafische Darstellung des Totaldruckverlustbeiwerts, aufgetragen gegen eine relative Schaufelhöhe für eine axiale Statorverdichterstufe mit und ohne Querlamellen.

Fig. 11a, 11b

schematische Schnittansichten jeweils durch eine schematische Passage einer Verdichter-Statorstufe quer zur Hauptströmungsrichtung einer Hinterkante einer Statorschaufel, betrachtet entgegen der Hauptströmungsrichtung, wobei eine Anzahl der Querlamellen unterschiedlich ist,

Fig. 12a, 12b

schematische Schnittansichten jeweils durch eine schematische Passage einer Verdichter-Statorstufe quer zur Hauptströmungsrichtung auf Höhe einer Hinterkante einer Statorschaufel mit einer optimal angepassten Querlamellenanzahl, die eine nicht abgestufte Querlamellentiefe (a) und eine mit einem Abstand vor der Saugseite der Statorschaufel abnehmenden Querlamellentiefe (b) aufweisen, und

Fig. 13a, 13b

schematische Schnittansichten entlang einer Hauptströmungsrichtung von Ausschnitten schematischer Verdichter-Statorstufen.

The invention will be explained in more detail below with reference to preferred embodiments with reference to a drawing. Hereby show:

Fig. 1

a view of experimentally visualized flow lines along a side wall of a stator stage of an axial compressor according to the prior art,

Fig. 2

a representation of a pressure distribution with the in Fig. 1 Stator stage shown corresponds to the prior art,

Fig. 3

1 is a schematic representation of a section of a stator stage according to the prior art,

Fig. 4

1 is a schematic representation of an embodiment of a stator stage with transverse blades, which have the same cross-blade chord length,

Fig. 5

1 is a schematic representation of a section of a stator stage of an axial compressor with transverse blades, which have a different cross-blade chord length and a different cross-blade depth,

Fig. 6

a schematic section of a section through one with the embodiment according to Fig. 4 corresponding stator stage,

Fig. 7

a section of a sectional drawing through a schematic stator stage of an embodiment according to Fig. 5 .

Fig. 8, Fig. 9

schematic representations of a pressure-driven detachment on a flat wall without cross blades and with cross blades,

Fig. 10

a plot of the total pressure loss coefficient, plotted against a relative blade height for an axial Statorverdichterstufe with and without cross blades.

Fig. 11a, 11b

schematic sectional views in each case by a schematic passage of a compressor stator stage transversely to the main flow direction of a trailing edge of a stator blade, viewed in the direction opposite to the main flow direction, wherein a number of transverse blades are different,

Fig. 12a, 12b

schematic sectional views in each case by a schematic passage of a compressor stator stage transversely to the main flow direction at the level of a trailing edge of a stator blade with an optimally adapted Querlamellenanzahl having a non-stepped cross-plate depth (a) and with a distance in front of the suction side of the stator blade decreasing cross-plate depth (b) , and

Fig. 13a, 13b

schematic sectional views along a main flow direction of cut-outs of schematic compressor stator stages.

In Fig. 3 schematically a section of a stator stage of an axial compressor according to the prior art is shown. The stator stage comprises at least one stator blade 1. Adjacent to the at least one stator blade 1, a further stator blade 1 'is arranged. The at least one stator blade 1 and the adjacent stator blade 1 'each adjoin a wall 2 forming an outer wall. A flow direction of a main flow 4 is indicated by double arrows. In this state-of-the-art stator stage, a thickness of a wall boundary layer 4c grows in the region of the stator blade 1 or adjacent stator blade 1 '. This is due to the fact that the main flow 4 is delayed by a profiling of the stator blade 1 or adjacent stator blade 1 '. In addition, between the adjacent stator blade 1 'and the stator blade 1, there is a secondary flow 4b extending along the wall 2 from a pressure side 1b of the adjacent stator blade 1' to a suction side 1a of FIG At least one stator blade 1 is formed. By means of this secondary flow 4b, a further secondary flow 4d or a corner detachment of the flow caused thereby in a corner 5 is promoted and reinforced. The corner separation takes place on the suction side 1a of the stator blade 1 in a direction away from the main flow 4 facing away from the wall 2 corner 5 instead. This flow behavior of a prior art stator stage which forms along the wall 2 is experimental in FIG Fig. 1 shown.

A main axis of the turbomachine is oriented parallel to the display plane. Profiles of three stator blades 1, 1 ', 1 "can be seen: The main direction of flow is from bottom left to top right This flow direction, which deviates from an axial direction of the turbomachine, is caused by a rotor stage located upstream of the stator stage visualized flow lines 4a is in Fig. 1 to recognize that it comes in a passage 6 between the stator blades 1 to a flow separation.

In Fig. 2 is one with Fig. 1 corresponding schematic representation of a wall pressure distribution of a stator stage according to the prior art shown. In this illustration, only two stator blades 1, 1 'are shown. Lines of constant static pressure cp less than 0 are entered by means of dashed lines and the line constants of positive pressure by solid thin lines. The line shown in bold and denoted by SL represents a detachment line. The inflow direction of the main flow 4 is indicated by an arrow. It can be seen that the detachment line SL runs obliquely to the main flow direction. Contrary to a two-dimensional flow separation with dead water and backflow otherwise known in fluid dynamics, there is rather a strong wall near flow 4b in the separation area behind the SL separation line (see Fig. 1 ). This wall-near flow transports fluid in the separation region from a pressure side 1b 'of the adjacent blade 1' to the suction side 1a of the blade 1. Approximately at the point where the SL detachment line hits the suction side 1a of the stator blade 1, the corner separation forms in connection with Fig. 3 already discussed. The flow separations on the wall and at the corner of the stator blade 1 provide a major contribution to so-called "Fringe losses". Experiments in the prior art to avoid the corner separation on the suction side of the stator blade 1 by so-called boundary layer fences, were previously unsuccessful in axial compressors. Although a flow separation on the suction side of the stator blade could be reduced, in return, the separation on the side wall was intensified.

In Fig. 4 schematically a section of a stator stage of an axial compressor is shown, in which spaced from the suction side 1a of the stator blade 1, a transverse blade 3 and further transverse blades 3 'are arranged, which extend from the wall 2 in a flow volume 7. The transverse blade 3 and the further transverse blades 3 'are spaced apart along an azimuthal direction 8 from a suction side 1a of the stator blade 1 and from each other equidistantly. The stator blade 1 has a profile length 1j and a chord length 1g. The cross-blade 3 preferably has a clearance from the suction side 1a which is preferably between 3% and 7%, more preferably between 4% and 6% and most preferably 5% of the profile length 1j of the suction side 1a of the stator blade 1. The same distance, the cross blades 3, 3 'of each other.

The transverse blade 3 and the further transverse blades 3 'each have a first side 3a or 3a' and an opposite side 3b and 3b ', respectively. These each have a curvature which corresponds to the surface curvature of the suction side 1a of the stator blade 1. In a first approximation, therefore, the first side 3a and the second side 3b are parallel to one another, if it is assumed that a lamella thickness is small compared to a radial diameter or a stator blade height of the axial compressor stage. Advantageously, at least for the first side 3a, a surface of the suction side 1a of the stator blade 1 can be brought to cover the first side 1a by a virtual rotation along the azimuth direction 8 about the central axis of the turbomachine. The fins 3 and further fins 3 'further have a main flow 4 facing front edge 3c, 3c' and an opposite edge 3d, 3d 'on. Between the front edge 3c, 3c 'and the rear edge 3d, 3d', a maximum transverse lamella chord length 3g or 3g 'can be determined. The transverse lamella 3 and the further transverse lamellae 3 'furthermore have one of the outer wall facing Outer edge 3e or 3e 'and a projecting into the flow volume 7 inner edge 3f and 3f. Between the outer edge 3e and the inner edge 3f, a transverse lamella depth 3h or 3h 'can be determined in each case. The lamellae are designed such that a maximum transverse chord length 3g is greater than a maximum cross lobe depth 3h. Furthermore, in the embodiment according to Fig. 5 the transverse lamella 3 and the further transverse lamellae 3 'are formed such that they each have the same transverse lamella chord length 3g and the same transverse lamella depth 3h. Further, the cross blades 3, 3 'are formed so that the front edge 3c and the inner edge 3f are interconnected by a tapered edge 3i. This means that a "front inner corner" of the transverse blades 3, 3 'is bevelled. This causes an adaptation to a flow line course of the main flow 4 adjacent to the transverse blades 3, 3 '.

In Fig. 6 is a section of a schematic cross-sectional drawing through a stator stage shown with the embodiment according to Fig. 4 corresponds. Between a outer wall 2a and an opposite wall 2b, which forms the hub, a stator 1 is arranged. Both on the outer wall forming wall 2a and on the opposite wall 2b transverse blades 3, 3 'are arranged, each having a same cross-plate depth 3h, 3h'. The illustrated embodiment is intended to indicate a real stator stage only schematically. In particular, the transverse louver depth 3h, 3h 'is shown greatly enlarged in relation to a distance of the wall 2a from the opposite wall 2b. Furthermore, in reality, surface normals 9 and 10 of the first sides 3a and the opposite side 3b of the transverse blades 3, 3 'are preferably oriented perpendicular to a respective surface normal 11 of the wall 2 and the opposite wall 2b, respectively.

In Fig. 5 a preferred embodiment of a stator stage is shown schematically. The related to Fig. 4 described features and advantages apply essentially also for the embodiment according to Fig. 5 , In this embodiment, however, decreases both a Queriamellen chord length 3g, 3g 'and a transverse lamella depth 3h, 3h' with a distance from the suction side 1a of the stator blade of the individual transverse blades 3, 3 'from. This leads to an optimal Reduction of unwanted losses. Both in the embodiment according to Fig. 4 as well as the embodiment according to Fig. 5 closes the rear edge 3d, 3d 'of the cross blades in each case with a rear edge 1d of the stator blade in the axial direction.

While the in Fig. 5 illustrated embodiment of the stator stage represents a preferred embodiment, it will be apparent to those skilled in the art that embodiments are also conceivable in which the louver depths 3h, 3h 'of the plurality of transverse blades 3, 3' are identical.

By providing the transverse lamellae 3, 3 ', substantially higher pressure increases along the wall can be "endured" without any disadvantageous separation of the flow occurring. This means that for a given pressure build-up a much shorter distance is sufficient for this, without major losses occur. This makes it possible to create more compact stator compressor stages. With the cross blades on the wall thus the detachment on the side walls and also on the suction side of the blades of the compressor grating, in particular thus a corner separation, reduced.

16 sich dem Druck der Ablösung aufprägt. In dem Ablösegebiet entsteht eine Sekundärströmung 14b, die der Strömung 14 entgegengerichtet ist. In Fig. 10 sind in dem Ablösegebiet Querlamellen 13 eingebracht, die das Druckgebiet der Sekundärströmung in mehrere Gebiete gleichen Drucks aufteilen. Eine Ausdehnung des Sekundärströmungsgebiets an der Wand 12 wird so verkleinert und die Randverluste hierdurch minimiert. Zwischen den Querlamellen 13 kommt es zu einer Ausbildung einer veränderten Sekundärströmung 14e, die einer Wirkung der Querlamellen förderlich ist.An explanation of how the cross blades act, is based on the 8 and 9 be explained. In Fig. 9 a separation along a separation line 15 is shown, which arises in a flow 14 with a strong pressure gradient. It is believed that the pressure of the outside flow $\frac{\mathrm{dp}}{\mathrm{dx}}$$\frac{}{}$

16 imposes itself on the pressure of detachment. In the separation region, a secondary flow 14b is created, which is opposite to the flow 14. In Fig. 10 are introduced in the Ablösegebiet transverse fins 13, which divide the pressure area of the secondary flow into several areas of equal pressure. An expansion of the secondary flow area on the wall 12 is thus reduced and the edge losses are thereby minimized. Between the cross blades 13 there is a formation of an altered secondary flow 14e, which is conducive to an effect of the transverse blades.

mit

• p _r1 : gemittelten Totaldruck der Zuströmung des Verdichtergitters,
• p_r2 (u,z): lokaler Totaldruck im Nachlauf des Verdichters,
• q ₁ : mittleren dynamischen Druck der Zuströmung des Verdichtergitters.

In experiments in a two-dimensional compressor test, an integral total pressure loss coefficient ζ has been reduced by up to 10%. The total pressure loss coefficient ζ is defined as follows: $$\mathit{\zeta }\left(uz\right)=\frac{{\stackrel{\mathit{~}}{\mathit{p}}}_{\mathit{r}\mathit{1}}\mathit{-}{\mathit{p}}_{\mathit{r}\mathit{2}}\left(uz\right)}{{\stackrel{\mathit{~}}{\mathit{q}}}_{\mathit{1}}}$$

With

• p _r1 : averaged total pressure of the inflow of the compressor grille,
• p _r2 ( u , z ): local total pressure in the wake of the compressor,
• q ₁ : average dynamic pressure of the inflow of the compressor grille.

The integrate loss coefficient results from the integration of the local loss coefficient over the blade pitch and the blade height of the compressor grid. The blade pitch indicates the distance of the stator blades. The stator height indicates a radial span of the stator blade, i. a distance from the hub to the outer wall. It is thus integrated azimuthally and radially.

A local total pressure loss coefficient results from a difference of the average total pressure of the inflow (indicated by a bar above the variable) and the local total pressure in the wake of the compressor grating, which is normalized with the mean dynamic pressure of the inflow.

In Fig. 10 shows a change in the integrated over the division of the total pressure coefficient In a Verdlchter stator passage (dashed data curve) compared with a reference configuration (solid line of the data curve). Through the cross blades on the walls, there is a reduction in the losses on the walls and on the blade. Shown is a total pressure loss coefficient against a relative blade height. A solid line 21 corresponds to values for a compressor stage without cross blades. A dashed line 22 shows the total pressure loss coefficient for a Statorverdichterstufe with transverse fins. It can be clearly seen that the total pressure loss coefficient near the walls is reduced.

In Figures 11a and 11b are schematic sectional views each represented by a schematic passage of a compressor stator stage transversely to the main propagation direction at the level of a trailing edge of a stator blade, viewed in the direction opposite to the main flow direction, wherein a number of cross blades is different. Shown are schematic compressor stator stage configurations. Shown is a passage of a compressed stator grid, similar to those of 6 and 7 , The illustration is simplified in that the boundary wall 2a and the opposite boundary wall 2b are assumed to be straight. The section through the stator stage is shown at the trailing edge transverse to the axial direction, ie, the main flow direction of the stator stage, with an upper edge 24 and a lower edge 25 indicating half a passage height above the stator blade and below the stator blade, respectively, and not actually existing To represent components of the stator. The viewing direction is opposite to the main flow direction. The trailing edge 1d of the stator blade is located in a center of the considered passage. Above the suction side are located at equidistant intervals a plurality of cross blades 3, 3 '.

In Fig. 11a There are eight cross blades in a passage, three of which have a smaller distance from the pressure side 1b than from the suction side 1a of the stator blade. In Fig. 11b a view of a stator step passage is shown, which comprises only six transverse blades 3. This embodiment is opposite to the Fig. 11a in that the number of transverse lamellae and the wall areas over which the transverse lamellae 3 extend along the wall 2a or the opposite wall 2b approximately coincide with the areas in which a secondary flow running transversely to the main flow direction along the walls 2a, 2b in FIG Operation of the stator can be formed. An extension of these areas, in which the disturbing secondary flow is formed, is indicated schematically by a contour 23.

In addition to the number of transverse blades 3 used in a passage, a transverse lamella depth 3h, which indicates how far the individual transverse lamellae project from the side wall 2a or opposite side wall 2b into the flow volume 7, is also important.

In Fig. 12a and 12b are schematic sectional views again each by a schematic passage of a compressor stator stage transverse to the main flow direction at the level of a trailing edge 1d of a Stator5schaufel similar to those after Fig. 11a and 11b shown. While in both views 12a and 12b a number of the plurality of transverse blades 3, 3 'is optimally selected, the transverse blades protrude in the Fig. 12a all equally far into the flow volume 7 inside. In Fig. 12b On the other hand, the transverse louver depths 3h, 3h ', 3h "of the individual transverse louvers 3, 3', 3" are different. A transverse lamella depth 3h, 3h ', 3h "decreases with a distance of the transverse lamella 3, 3', 3" from the suction side 1a of the stator blade 1ab. This means that the transverse lamella 3, 3 ', 3 ", which is farthest from the suction side 1a of the stator blade 1, projects the least far into the flow volume 7. Such a gradation of the transverse lamella depths 3h, 3h', 3h" forms on best a depth of the secondary flow region 23 measured against the side wall 2a and the opposite side wall 2b from. The transverse blades 3, 3 ', which are arranged on the side wall 2a and have an identical distance as a corresponding transverse blade 3 ", which is arranged on the opposite side wall 2b, from the suction side 1a of the stator blade, can have a different transverse blade depth 3h, 3h'. 3h "of the corresponding transverse lamella 3." Likewise, an optimal number of transverse lamellae on the side wall may deviate from that on the opposite side wall.

In Fig. 13a and 13b In each case, a schematic sectional view along a main flow direction or an axial direction of the turbomachine of sections of a schematic compressor stator stage is shown. While at the stator stage, which in Fig. 13a is shown, the individual transverse blades 3, 3 'all have an identical Querlamellensehnenlänge 3g, takes in Fig. 13b , which represents a preferred embodiment, a Querlamellensehnenlänge 3g with a distance of the transverse blades 3, 3 'from the suction side 1a of the stator blade 1ab. The Querlamellensahnanlängen 3g are thus optimally adapted to the influenced secondary flow area 23 along the side wall 2. While in the embodiment according to Fig. 13a the number and extent along the Sidewall transverse to the suction side 1a of the stator is too large, that is, a number of cross blades 3 is too high or a distance between the cross blades 3, 3 'is too large, is also an extension in the chordwise direction of at least the cross blades 3', the Jam side 1b of the next stator blade 1 'are facing, too long. As a result, parts or entire cross blades protrude into the "healthy" flow and thus cause unintentional losses. In the embodiment according to Fig. 13b this is not the case. A transverse lamellar depth is preferably chosen in this optimal embodiment, as in Fig. 12b is shown. This means that a transverse lamellar depth decreases with a distance from the suction side 1a of the stator blade 1.

The trailing edges 3d of the transverse blades and the trailing edges 1d of the stator blades 1, 1 'are all in one plane. As a result, as already mentioned above, undesired corner separation is reliably prevented by forming a transverse flow.

In the embodiments described in detail here, the transverse lamellae and further transverse lamellae have a simple geometric contour. The contour is preferably conformed to a streamline shape that forms in the mainstream spaced from the wall. This means that the contour of the cross blades is chosen so that they fill the area where the secondary flow forms along the wall as well as possible. As a result, an optimal suppression of the secondary flow is achieved and at the same time an additional resistance, which is inevitably linked to the cross blades, kept as low as possible. The leading edges and the inner edges, including the bevelled edges, may form a common continuous contour.

A (maximum) cross-blade chord length in such a case is a maximum dimension measured along the axial direction of the compressor stage. A (maximum) cross-plate depth is correspondingly a maximum distance, measured perpendicular to the adjacent side wall.

The proposed embodiments of the transverse blades and their arrangement are given only by way of example. In particular, they may have a curvature other than the curvature of the suction side of the stator vanes and be oriented differently along the wall, as long as they are oriented transversely to the secondary flow forming on the wall in the passage between the stator vanes.

LIST OF REFERENCE NUMBERS

1, 1 "

stator

1'

adjacent stator blade

1a

suction

1b

pressure side

1d

rear edge

1g

Stator blade chord length

1j

Section length

2

wall

2a

wall

2 B

opposite wall

3

transverse blade

3 '

further cross blades

3 '

additional cross blades

3a

first page

3b

opposite side

3c

front edge

3d

rear edge

3e

inner edge

3f

outer edge

3g

Cross slat chord length

3h

Cross sipe depth

3i

bevelled edge

4

mainstream

4a

streamlines

4b

Secondary flow along the wall

4c

increasing thickness of the wall boundary layer

4d

further secondary flow

5

Area of a corner separation

6

passage

7

flow volume

8th

azimuthal

9

Surface normal of the first side 3a of the cross blades

10

Surface normal of the opposite side 3b of the cross blades

11

Surface normal of the wall

12

wall

13

cross blades

14

flow

14b

secondary flow

14d

Secondary flow in Sekundärströmungsgebiete generated by transverse fins 13

14e

changed secondary flow

15

separation line

16

pressure gradient

21

solid line

22

dashed line

23

Contour of the secondary flow area

24

upper edge

25

lower edge

SL

separation line

Claims (16)

Stator stage of an axial compressor of a turbomachine comprising at least one stator blade (1), which comprises a suction side (1a) and a pressure side (1b), and a plurality of transverse blades (3, 3 ') extending from at least one wall (2; 2b) to which the stator blade (1) adjoins, spaced from the suction side (1a) of the stator blade (1) into a flow volume, characterized in that transverse lamella chord lengths (3g ') of the plurality of transverse lamellae (3, 3') Remove a distance from the suction side (1a) of the stator blade (1). Stator stage according to claim 1, characterized in that transverse lamellae depths (3h ') of the plurality of transverse lamellae (3') decrease with a distance from the suction side (1a) of the stator blade (1). Stator stage according to one of the preceding claims, characterized in that one of the plurality of transverse blades (3) from the suction side (1a) of the stamina blade, (1) and the plurality of transverse blades (3 ') each have an equidistant spacing from one another. Stator stage according to one of the preceding claims, characterized in that the equidistant spacing between 3% and 7% is more preferably between 4% and 6% and most preferably 5% of a profile length (1j) of the suction side (1a) of the stator blade (1) , Stator stage according to one of the preceding claims, characterized in that in each case a rear edge (3d) of the plurality of transverse blades (3) and / or the additional transverse blades (3 ") with a corresponding rear edge (1d) of the stator blade (1) in complete axial direction of the turbomachine. Stator stage according to one of the preceding claims, characterized in that the cross-plate (3) has a first side (3a) and a opposite second side (3b), the surface normal (9, 10) to a surface normal (11) of the at least one wall form an angle between 70 ° and 110 °, more preferably between 85 ° and 95 ° and most preferably of 90 °. Stator stage according to one of the preceding claims, characterized in that the at least one wall (2) is an outer wall (2a) or / a hub (2b). Stator stage according to one of the preceding claims, characterized in that the first side (3a) of the cross-blade (3) has a Oberflächenkrommung corresponding to the surface curvature of the suction side (1a) of the at least one stator blade (1). Stator stage according to one of the preceding claims, characterized in that the second side (3b) of the transverse lamella (3) has the same surface curvature as the first side (3a). Stator stage according to one of the preceding claims, characterized in that the at least one transverse lamella (3) faces a flow of a main flow (4) facing the front edge (3c) and an opposite rear edge (3d), one to the at least one wall ( 2; 2a, 2b), and an inner edge (3f) projecting into the flow volume and lying opposite the outer edge (3e), wherein a maximum transverse-chamfer chord length (3g), measured from the front edge (3c) to the Rear edge (3d), greater than a maximum Querlamellenbefe (3h), measured from the outer edge (3e) to the inner edge (3f) is. Stator stage according to one of the preceding claims, characterized in that the transverse lamella chord length (3g) of the at least one transverse lamella, (3) is between 30% to 70%, more preferably between 40% and 60%, and most preferably 50%, of a stator profile chord length (1g). Stator stage according to one of the preceding claims, characterized in that a bevelled edge (3h) is formed between the front edge (3c) and the inner edge (3f). Stator stage according to one of the preceding claims, characterized in that the further transverse blades (3 ') have a same transverse blade depth (3h') as the at least one transverse blade (3). Stator stage according to one of the preceding claims, characterized in that in addition from one of the at least one wall (2a) opposite wall (2b), to which the at least one stator blade (1) also adjacent, one or more additional cross blades (3 " ). Stator stage according to one of the preceding claims, characterized in that a front and inner contour of the transverse lamellae (3) correspond to a streamline course of the main flow (4), spaced from the wall (2; 2a, 2b). Stator stage according to one of the preceding claims, characterized in that the plurality of transverse blades (3) are arranged within a volume in which one of the pressure side (1b ') of an adjacently arranged further stator blade (1') to the suction side (1a ) of the at least one stator blade (1) directed by wall detachment caused secondary flow (4b) to the main flow (4) in a corresponding design of the turbomachine operation, wherein the plurality of transverse blades (3) transversely to the secondary flow (4b) are aligned.

Images