EP2623793A1 - Blade row and flow machine - Google Patents

Abstract

The cascade has blades (2, 2') arranged adjacent to each other in a peripheral direction (U). Two adjacent blades include rear edges (4) with different angles. The blades are staggered and profiled differently across an entire height or a part of the height. The blades are adjustable to different degrees. An arrangement of the blades in the peripheral direction is continued periodically multiple times. A position and angles of front edges (8) of the blades change due to a restagger across the entire height. An independent claim is also included for a turbomachine.

Description

The invention relates to a blade grid for a turbomachine according to the preamble of patent claim 1 and a turbomachine.

In turbomachines or turbo machinery, especially in compressors and hydraulic pumps, but also in turbines, it comes in partial and overload operation to unstable flow conditions and greatly increased losses. The unstable flow conditions lead to strong pressure fluctuations that can damage the blade structures. On the other hand, the flow can completely collapse in compressors and hydraulic pumps in the throttled state. This limits the operating range of the turbomachine and can lead to damage to the turbomachine when exceeding the allowable limits.

Decisive for the unstable flow state is the separation of the flow of the individual blades in the lattice composite. To suppress the separation can lead to a time-varying inflow to the blades. In a known measure, the blade affected by detachment oscillates about a suspension axis. In another measure, vibrating vanes are located in the inflow of the vanes affected by detachment, creating a harmonic, oscillating inflow to the vanes. An example is a vibrating Vorleitbeschaufelung. A further measure provides, by means of injection points distributed over the circumference, to introduce fluid which has a flow angle and / or flow impulse deviating from the main flow, thereby locally changing the inflow of the blades affected by detachment. A disadvantage of these active measures, however, is that, on the one hand, it is necessary to apply energy for influencing the flow, which energy can be taken from the overall process, thereby reducing the overall efficiency. Second, complex structural and regulatory changes are necessary to implement these measures, which lead to increased development effort, increased susceptibility to interference and increased machine weight.

Furthermore, passive measures are known in which the blades of a blade grid are different profiled and / or arranged asymmetrically in the blade grid. So will in the DE 10 2008 049 358 A1 proposed to profile blades of a Verdichtereintrittsleitgitters such that in an asymmetric inflow a symmetrical outflow from the blade grid is carried out. For this purpose, the blades each have an altered front blade area. In the GB 2 046 849 B1 there is shown a vane assembly having an asymmetrical arrangement of vanes, the trailing edges of which are in a circumferentially considered line and thus in an identical axial position. The EP 1 508 669 A1 shows a measure in which blades of a Vorleitgitters are profiled differently for the consideration of an asymmetric flow of a Vorleitschaufelrings.

The object of the invention is to provide a blade grid for a turbomachine, which eliminates the aforementioned disadvantages and increases the operating range of turbomachines over the known measures. Furthermore, it is an object of the invention to provide a turbomachine with an enlarged operating range.

This object is achieved by a blade grid having the features of patent claim 1 and by a turbomachine having the features of patent claim 8.

A vane grille according to the invention for a turbomachine has a multiplicity of vanes arranged in the circumferential direction next to one another, of which at least two adjacent vanes have different trailing edge angles according to the invention.

As a result of the at least two different trailing edge angles, the blade grid is asymmetrical in the circumferential direction, whereby an asymmetrical outflow takes place due to the variation in the rear blade area and an asymmetrical inflow in the circumferential direction with respect to a flow angle and flow impulse to a downstream blade grid affected by detachment is thereby produced. When viewed in the direction of flow, the separation behavior in the blade grid, which follows the asymmetrical blade grid, is thereby suppressed. The solution according to the invention makes it possible to expand the operating range in which a turbomachine can be operated and thereby ensure safe operation even in partial and overload. Furthermore, the flow losses are reduced by the asymmetric blade grid according to the invention and thus the efficiency is increased. The Integration of the blade grid in a turbomachine can be done without additional installations and with little design measures. This allows the use of the blade grid in already designed turbomachines, without a re-interpretation of turbomachines is necessary. The asymmetric arrangement according to the invention can be used in compressors or hydraulic pumps and in turbines, both in machines through which a gaseous and a liquid medium flows. The blade grid can also be designed in an axial design, in a radial design or in a mixed diagonal design.

In one embodiment, the blades are staggered circumferentially with respect to their leading blade over their entire height, so that the blades also have different leading edge angles. The leading edge angle is changed by the same amount as the trailing edge angle. This embodiment allows the use of uniform or identical blades.

In an alternative embodiment, the blades are circumferentially differently staggered with respect to their leading blade over part of their height. In this embodiment, the blades each have at least two profile regions, which are located one behind the other in the transverse direction of the blade, and which are twisted relative to one another. The blades thus have at least two different blade angle components each. A blade angle portion of the non-staggered region is the same for all blades. A vane angle portion of the redistributed region varies between the vanes and may increase or decrease, whereby the vanes in this region each have a modified trailing edge angle and a leading edge angle varied by the same amount.

In a further embodiment, the blades are profiled differently in the circumferential direction with respect to their leading blade over their entire height. In this embodiment, the blades are equally staggered with respect to their leading edges and thus have the same leading edge angle. However, the trailing edge angles of the blades vary. For example, the blades have different curved trailing edge regions from a certain same chord length.

In another embodiment, the blades are profiled differently in the circumferential direction with respect to their leading blade only over part of their height. This can be, for example, a local deformation of an outer region, viewed in the transverse direction of the blade, of the trailing edge, the orientation of which is changed in the circumferential direction over several blades of, for example, an orientation in the direction of rotation in an opposite direction.

In addition to the preceding embodiments, the blade grid can cooperate with an adjusting device, so that the blades are adjustable in different degrees in the circumferential direction.

Particularly good effects can be achieved if the exemplary aforementioned arrangements of the blades are repeated in the circumferential direction several times periodically.

A preferred turbomachine has a symmetrical blade grid and an upstream asymmetric blade grid moving circumferentially relative to the symmetrical blade grid in accordance with the invention.

Such a turbomachine has an increased operating range and a higher efficiency than conventional turbomachines. The turbomachine may be a compressor, a hydraulic pump and a turbine. The turbomachine can also be flowed through with any liquid or gaseous medium.

The turbomachine may have an adjusting device for staggering the blades of different degrees, which enables both the formation of a symmetrical blade grid and the formation of an asymmetrical blade grid. Ideally, the adjustment allows the control of each blade individually, whereby a maximum of flexibility in staggering is achieved. Alternatively, however, predetermined symmetries and asymmetries can be set, which considerably simplifies the setting of the respective blade grid.

The asymmetric blade grid can be designed both as a stator grid and as a rotor grid. When forming the blade grid according to the invention as a stator grid can have fixed blades or cooperate with an adjusting device for adjusting the blades.

Other advantageous embodiments of the invention are the subject of further subclaims.

Figur 1

einen Ausschnitt eines ersten Ausführungsbeispiels eines erfindungsgemäßen Schaufelgitters,

Figur 2

eine Schnittdarstellung einer Schaufel und beispielhafte Umstaffelungen,

Figur 3

einen Ausschnitt eines zweiten Ausführungsbeispiels eines erfindungsgemäßen Schaufelgitters,

Figur 4

eine Schnittdarstellung eines dritten Ausführungsbeispiels einer Schaufel eines erfindungsgemäßen Schaufelgitters und beispielhafte Profiländerungen im Hinterkantenbereich,

Figur 5

eine konforme Abbildung eines beispielhaften Flutbahnabschnitts des erfindungsgemäßen Schaufelgitters,

Figur 6

Beispiele asymmetrischer und periodischer Anordnungen der Schaufeln des erfindungsgemäßen Schaufelgitters,

Figur 7

einen Ausschnitt eines beispielhaften Verdichterstators in Diagonalbauweise, und

Figur 8

einen Ausschnitt eines beispielhaften Verdichterstators in Radialbauweise.

In the following preferred embodiments of the invention will be explained in more detail with reference to schematic representations. Show it:

FIG. 1

a detail of a first embodiment of a blade grid according to the invention,

FIG. 2

a sectional view of a blade and exemplary Umstaffelungen,

FIG. 3

a detail of a second embodiment of a blade grid according to the invention,

FIG. 4

a sectional view of a third embodiment of a blade of a blade grid according to the invention and exemplary profile changes in the trailing edge region,

FIG. 5

a conformal illustration of an exemplary flood track section of the blade grid according to the invention,

FIG. 6

Examples of asymmetrical and periodic arrangements of the blades of the blade lattice according to the invention,

FIG. 7

a section of an exemplary compressor stator in diagonal construction, and

FIG. 8

a section of an exemplary compressor stator in radial construction.

According to the invention, blades are to be mounted in a blade grid of a turbomachine in such a way that that in the circumferential direction an asymmetrical outflow from the blade grid with respect to flow angle and flow velocity and thus takes place in the relative system of a subsequent blade grid an asymmetric inflow. In a preferred embodiment, the following blade grid is symmetrical. The asymmetrical outflow is generated by two or more adjacent blades have different trailing edge angles in the circumferential direction. The vane grille according to the invention can be used in compressors or in hydraulic pumps and in turbines, both in machines through which gaseous and also liquid medium flows.

The trailing edge angle is understood to be an angle between a tangent of the skeleton line in the region of the trailing edge and an axis in the circumferential direction (see FIG. FIG. 4 , Angle α). The trailing edge angle α depends on the one hand on the blade profile in the rear blade area. On the other hand, the trailing edge angle α depends on the staggering of the respective blade in the blade grid and thus on the blade angle. The blade angle or stagger angle is understood to mean an angle between the chord and the axis in the circumferential direction (see FIG. FIG. 2 , Angle β). The transverse direction of the blade is understood to mean an orientation of the blade between a rotor-side blade root and a blade tip. In axial compressors, the blade direction is equal to the radial direction. An extension of the blade in the transverse direction of the blade is understood across all construction types - axial, radial or diagonal construction - as a blade height.

The asymmetry can be realized by a plurality of measures, which are explained in more detail below with reference to the figures. Preferred measures are a staggering over the entire blade height ( Figures 1 and 2 ), a staggering over a part of the blade height (also FIG. 2 ), a modified profiling over part of the blade height ( FIGS. 3 and 4 ) and a modified profiling over the entire blade height (also FIG. 4 ).

Figures 1 and 2 show a staggering over the entire blade height in a compressor stator in axial construction. There FIG. 2 is a sectional view, the sectional view can also show a staggering over a portion of the blade height. However, the following is based on the Figures 1 and 2 a graduation over the entire blade height exemplified. For clarity, is in FIG. 2 only the blade angle β outlined. An asymmetric blade grid 1 according to the invention has a multiplicity of blades 2 which are arranged next to one another in the circumferential direction. The blade grid 1 is, for example, a part of a compressor stator in an axial construction. The blades 2 have a uniform profile and are staggered differently in the circumferential direction with respect to their leading blade 2 'over their entire height. As a result, the blade angle β varies starting from a blade angle β _{0 which} , compared to the leading blade 2 ', is increased Δβ + or reduced Δβ -. By changing the blade angle β, the position of its trailing edges 4 changes in the circumferential direction, so that the same profiled adjacent blades 2 show a different outflow behavior. In addition, the blades are 2 viewed by the pivoting with their trailing edges 4 in the circumferential direction no longer on a line, but are at different axial positions, whereby the discharge behavior is additionally changed. The position of their leading edges 8 and their leading edge angle changes due to the staggering over the entire height analogous to the trailing edge angle α. The leading edge angle is understood to mean an angle between a tangent of the skeleton line in the region of the front edge 8 and the axis in the circumferential direction (not sketched).

FIG. 3 shows an altered profiling over a part of the blade height in a compressor stator in axial construction. The illustrated blade grid 1, for example, forms part of a compressor stator in Axialbauweise. In the exemplary embodiment shown, the blades 2, viewed in the transverse direction of the blade, are profiled differently in the outer region 6 of their trailing edges 4. In this case, the region 6 turns from an orientation in the direction of rotation in an orientation in the opposite direction, whereby the trailing edge angle α of the blades 2, starting from a trailing edge angle α ₀ relative to the respective leading blade 2 'to the circumferential direction increases Δα + or smaller Δα - is. The trailing edge angle α is removed in the blades 2 at a uniform position in the transverse direction of the blade, wherein it is preferably removed in the region of the maximum profile change. Likewise, the blade angle β is preferably removed in the region of the maximum profile change. Each blade 2 has a constant blade angle component β _const and a varying blade angle component β _{var as} a result of the local profiling relative to a flood track segment. Also, each blade 2 has a constant trailing edge angle component α _const and a varying trailing edge angle component α _var relative to a floodpath section. The angle components α _const , β _const are the same and constant in the unchanged profile range in all blades 2. in the Range of profile change, however, vary the angular components α _var , β _var from a blade 2 to a leading blade 2 '. For reasons of clarity, the angle components α _const , β _const , α _var , β _var in FIG. 3 Not shown.

FIG. 4 shows a modified profiling over the entire blade height. There FIG. 4 is a sectional view, the sectional view can also show a modified profiling over a portion of the blade height. However, the following is based on FIG. 4 a modified profiling over the entire blade height exemplified. In the exemplary embodiment shown, the blades 2 have differently curved trailing edge regions 6 from a certain same chord length, whereby the trailing edge angle α of the blades 2 is increased Δα + or reduced Δα, starting from a trailing edge angle α ₀ relative to the respective leading blade 2 '. By the trailing edge side different curvature, the adjacent blades 2 each have different profiles. However, the area of their leading edges 8 is identically contoured, so that the blades 2 thus have the same leading edge angle.

In order to vary the asymmetric blade arrangements, the blade grids 1 according to the preceding embodiments can interact with an adjustment device, not shown, which enables a different degree of staggering of individual blades 2.

As in the conformal illustration of a flood track section FIG. 5 is shown, the asymmetrical arrangement of the blades 2 in the circumferential direction is preferably repeated several times periodically. The flood track section shown here was placed in the transverse direction of the blade on the outer region of the blades 2. Is shown in FIG. 5 an asymmetric blade arrangement according to the invention in the embodiment of the staggering over the entire blade height (s. FIGS. 1 and 2 ). The blade grid arrangement is chosen in particular such that a harmonic and periodic angular distribution is present. Within a period, any arrangement or profile design of the blades 2 can take place. The minimum number of blades 2 per period is two. The relevant size for the arrangement or profile design of a blade 2 is its outflow angle from the blade 2. The outflow angle is essentially dependent on the trailing edge angle α and thus on the blade angle β and the profile geometry, which is why, as in FIG. 6 shown, the trailing edge angle α as a size is used to describe the asymmetric blade grid assembly.

In FIG. 6 seven examples of an asymmetrical arrangement of the blades 2 are shown with respect to the trailing edge angle α, wherein the embodiments 1, 2, 3 and 4 are preferred.

The number of blades 2 to be mounted within a period is determined by the following mutually equivalent formulations.

Formulation 1: $$\mathrm{A\; \text{'}}=\frac{{\mathrm{N}}_{\mathrm{S}1}\cdot \mathrm{n}\cdot {\mathrm{l}}_{\mathrm{S}2}\cdot \sin {\beta }_{\mathrm{S}2}}{\mathrm{\sigma \text{'}}\mathrm{\cdot }{\mathrm{c}}_{\mathrm{ax}\mathrm{-}\mathrm{S}\mathrm{2}}\mathrm{\cdot }\mathrm{60}\sec }$$

Formulation 2: $$\mathrm{A"}=\frac{{\mathrm{N}}_{\mathrm{S}1}\cdot {\mathrm{l}}_{\mathrm{S}2}}{\mathrm{\sigma "}\mathrm{\cdot }{\mathrm{r}}_{\mathrm{S}\mathrm{2}}}$$

A':

Anzahl der Schaufeln pro Periode nach Formulierung 1

A":

Anzahl der Schaufeln pro Periode nach Formulierung 2

n [1/min]:

Drehzahl der Maschine

N_s1:

Anzahl der Schaufeln des Schaufelgitters 1

r_s2 [m]:

Charakteristischer Radius der Schaufeln im Schaufelgitter 2. Dies ist der Radius, bei dem im Schaufelgitter 2 eine Ablösung auftritt, welche durch das erfindungsgemäße Schaufelgitter 1 unterdrückt wird. Bevorzugterweise entspricht r_s2 in etwa dem Außenradius der Schaufeln im Schaufelgitter 2.

l_S2 [m]:

Schaufellänge bei r_S2 im Schaufelgitter 2

β_S2 [°]:

Schaufelwinkel bzgl. Umfangsrichtung bei r_s2 im Schaufelgitter 2

C_ax-S2 [m/s]:

Axialgeschwindigkeit der Strömung bei r_S2 vor dem Schaufelgitter 2

σ':

Schaufelkoeffizient für die Formulierung 1

σ":

Schaufelkoeffizient für die Formulierung 2

The following definitions apply, wherein the blade grid 1 is the asymmetrical blade grid and the blade grid 2 is the blade grid, which follows the asymmetrical blade grid in the flow direction.

A ':

Number of blades per period after formulation 1

A ":

Number of blades per period after formulation 2

n [1 / min]:

Speed of the machine

N _s1:

Number of blades of the blade grid 1

r _s2 [m]:

Characteristic radius of the blades in the blade lattice 2. This is the radius at which a detachment occurs in the blade lattice 2, which is suppressed by the blade lattice 1 according to the invention. Preferably, r _s2 corresponds approximately to the outer radius of the blades in the blade grid 2.

l _S2 [m]:

Blade length at r _S2 in the blade grille 2

β _S2 [°]:

Vane angle with respect to the circumferential direction at r _s2 in the vane grille 2

C _ax-S2 [m / s]:

Axial velocity of the flow at r _{S2 in} front of the blade lattice 2

σ ':

Vane coefficient for Formulation 1

σ ":

Vane coefficient for formulation 2

$$\mathrm{\sigma ʺ}=\left[0,55\dots 7,25\right]$$

The asymmetric blade grid 1 according to the invention can in principle be used for the following value range: $$\mathrm{\sigma \text{'}}=\left[0.25...1.15\right]$$

$$\mathrm{\sigma "}=\left[0.55...7.25\right]$$

$$\mathrm{\sigma ʺ}=\left[1,4\dots 4,7\right]$$

Preferably, the asymmetrical blade grid 1 is used for the following range of values: $$\mathrm{\sigma \text{'}}=\left[0.65...0.75\right]$$

$$\mathrm{\sigma "}=\left[1.4...4.7\right]$$

Within a period, the maximum value difference for the arrangement or profile design of the blades 2 is a maximum of 20 °. For optimum implementation, the angle difference is a maximum of 10 °.

To clarify that the Umstaffelung invention or profile change also applies to compressors in Diagonalbauweise and in radial design, is on the FIGS. 7 and 8 directed. FIG. 7 shows a section of a compressor stator in diagonal construction and FIG. 8 shows a section of a compressor stator in radial construction. By way of example, the blades 2 are numbered. Of course, the invention can also be realized on the turbine side.

Disclosed are a blade grid for a turbomachine with a plurality of circumferentially juxtaposed blades, wherein at least two blades in the rear region have a variation for generating an asymmetric outflow, and a turbomachine, with an asymmetric blade grid, which is connected upstream of a further blade grid.

LIST OF REFERENCE NUMBERS

1

blade cascade

2

shovel

2 '

adjacent blade

4

trailing edge

6

Area

8th

leading edge

U

circumferentially

α

Trailing edge angle

β

blade angle

Δα

Change trailing edge angle

Δβ

Change bucket angle

Claims (11)

Blade grille (1) for a turbomachine, with a plurality of circumferentially juxtaposed blades (2), characterized in that at least two adjacent blades (2, 2 ') have different trailing edge angles (α). A blade grid according to claim 1, wherein the blades (2, 2 ') are staggered differently over their entire height. A blade lattice according to claim 1, wherein the blades (2, 2 ') are staggered differently over part of their height. A blade grid according to claim 1, wherein the blades (2, 2 ') are profiled differently over their entire height. A blade lattice according to claim 1, wherein the blades (2, 2 ') are profiled differently over part of their height. Blade grate according to one of the preceding claims, wherein the blades (2, 2 ') are adjustable to different degrees. Blade grate according to one of the preceding claims, wherein an arrangement of the blades (2, 2 ') in the circumferential direction is repeated several times periodically. Turbomachine with a symmetrical blade grid, characterized by an upstream asymmetric blade grid (1) moving in the circumferential direction relative to the symmetrical blade grid according to one of the preceding claims. Turbomachine according to claim 8, wherein an adjusting device for different degrees staggering of the blades (2, 2 ') is provided. Turbomachine according to claim 8 or 9, wherein the asymmetric blade grid (1) a Stator grid is. Turbomachine according to claim 8 or 9, wherein the asymmetric blade grid (1) is a rotor grid.

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