Turbomachine with variable guide/stator blades

Abstract

A turbomachine having at least one flow path, in which at least one stator blade 2 is arranged, which is variable around a rotational axis 1, and which comprises at its radial end areas one rotary base 3 each, wherein a portion of the rotary base 3 is non-circular, when viewed in a direction of the rotational axis 1 of the stator blade 2.

Description

This application claims priority to German Patent Application DE102006052003.3 filed Nov. 3, 2006, the entirety of which is incorporated by reference herein.

The present invention relates to variable stator blades of turbomachines, such as blowers, compressors, pumps and fans of the axial, semi-axial or radial type. The working medium (fluid) may be gaseous or liquid.

A general state of the art of such turbomachines with variable stator blades is shown in Specifications US 2004/0240990 A1 and US 2004/0115051 A1, by way of example.

More particularly, this invention relates to at least one variable stator blade of a turbomachine or to a variable inlet guide vane assembly, if applicable. The respective blading is situated within a casing, which confines the passage of fluid through at least one rotor and one stator in the outward direction. While a rotor comprises several rotor blades attached to a rotating shaft and transfers energy to the working medium, a stator comprises several stator blades mostly fixed in the casing.

The aerodynamic loadability and the efficiency of turbomachines, for example blowers, compressors, pumps and fans, is limited in particular by the growth and the separation of boundary layers in the area of the radial gaps between the blading and the casing or the hub, respectively, these gaps being necessary at the annulus rim for reasons of design. In particular on rotatable variable stators, the radial gaps, which may be generated by recesses before and after the trunnion, are pronounced and entail considerable flow losses. In order to limit these losses, rotary bases of max. possible size are usually used on the inward and outward ends of the variable stators to keep small the extension of the recesses in flow direction. Now the rotary bases are usually perfectly circular. Since the diameter of the rotary bases is restricted by the distance between two adjacent blades, rotary bases must be provided, in particular in the case of narrow blade spacings as increasingly applied to modern machines, whose diameters are clearly smaller than the profile length of the blade in the respective hub or casing area. Thus, a considerable radial gap before and/or behind the rotary base is inevitable. The state of the art does not provide any solution for avoiding such radial gaps on variable stators.

FIG. 1 shows, in the meridional plane, part of a state-of-the-art turbomachine in the area of one of its variable stator rows. Besides the variable stator row proper, components in the hub area 4 and in the casing area 5 are indicated which bear the variable stator (stator blade 2) on the inner and outer side.

Not explicitly shown here, but also part of the present invention, are variable stator arrangements which are borne in either the casing or the hub of FIG. 1, with a full radial gap being provided at the respective opposite blade end.

View A-A on the right-hand side of the Figure shows the inner flow path boundary (hub) in an aspect parallel to the rotational axis of the variable stator (stator blade 2). The state-of-the-art design here shown provides rotary bases of the individual variable blades which are separately borne in the hub. Here, the blade airfoil clearly protrudes beyond the rotary base with its leading and/or trailing edge.

While the view exemplifies the rotary bases on the hub side, a principally equal arrangement of rotary bases is, in rotational axis-parallel aspect, found on the casing-side boundary of the flow path of the turbomachine.

The present invention relates to stators (stator blade 2) which are rotatably borne at least one blade end and are variable around a rotational axis 1 by a trunnion. As in all representations shown herein, inflow to the respective blade row is from the left to the right in the direction of the bold arrow.

A broad aspect of the present invention is to provide a variable stator blade of the type specified above which, while avoiding the disadvantages of the state of the art, is characterized by extensive or even complete avoidance of radial partial gaps at the blade end by a special cutback of the otherwise circular rotary base.

The present invention provides a variable stator blade for the use in a turbomachine which features on at least one of its ends, a rotary base whose cross-section, as viewed in the direction of the rotational axis of the variable stator (stator blade 2), significantly departs from perfect circularity in that two straight or curved flanks are provided by cutting back the perfectly circular shape of the rotary base on opposite sides, with the rotary bases of adjacent variable stators being borne in overlapping circular recesses in the casing or hub component, respectively.

The present invention is more fully described in the light of the accompanying drawings, showing preferred embodiments. In the drawings,

FIG. 1 is a schematic representation of a variable stator (stator blade 2) according to the state of the art,

FIG. 2 shows a solution for a variable stator in accordance with the present invention,

FIG. 3 shows another solution for a variable stator in accordance with the present invention,

FIG. 4 shows yet another solution for a variable stator in accordance with the present invention,

FIG. 5 is a schematic representation of possible rotary positions of the variable stator in accordance with the present invention,

FIG. 6 shows a plan view of a rotary base in accordance with the present invention, curved flanks, view A-A,

FIG. 7 shows another plan view of a rotary base in accordance with the present invention, straight flanks, view A-A,

FIG. 8 gives examples for sections of rotary bases in accordance with the present invention, section B-B.

FIG. 2 shows, in the meridional plane, part of a turbomachine in the area of one of its variable stator rows (stator blade 2). Besides the variable stator row proper, components in the hub area 4 and in the casing area 5 are indicated which hold the variable stator (stator blade 2) on the inner and outer side.

Not explicitly shown here, but also object of the present invention, are variable stator arrangements which are borne in either the casing or the hub, with full radial gap at the respective opposite blade end.

View A-A on the right-hand side of the Figure shows the inner flow path boundary (hub) in an aspect parallel to the rotational axis of the variable stator (stator blade 2).

The inventive solution here shown provides for a special shape of the rotary bases 3 disposed at the blade ends. The blade airfoil 8 here lies fully on the rotary base 3 in the area of the leading edge and protrudes beyond the rotary base 3 with its trailing edge only. By cutting back two opposite rim zones of the—originally perfectly circular—rotary base 3, the latter is provided with two flanks S, D which are straight in the example here shown. Between the flank S situated in the vicinity of the convex suction side of an airfoil and the flank D situated in the vicinity of the concave pressure side of the adjacent airfoil, a gap exists which enables the variable stator (stator blade 2) to rotate through a certain angular range. The present invention allows a distance between respective axes of rotation for adjacent blades/vanes to be smaller than a diameter of a base circle of the rotary bases 3, by providing relieved portions on the adjacent rotary bases that provide additional clearance between the outer edges of the adjacent rotary bases and/or which allow the adjacent rotary bases to overlap one another (see below).

A solution according to the present invention may also provide for any other relative rotational position between airfoil and the cut-back rotary base 3 other than that selected in the representation in FIG. 2.

FIG. 3 shows, quite similar to FIG. 2, a variable stator row in the meridional plane. View A-A on the right-hand side of the Figure shows the inner flow path boundary (hub) in an aspect parallel to the rotational axis of the variable stator (stator blade 2). The inventive solution here shown provides for a positioning of the airfoil on the rotary base 3 which, in part of the range of variation of the stator, results in an overlap of the blade trailing edge and the rotary base 3 of an adjacent stator blade 2.

Not shown here, but also in accordance with the present invention is a positioning of the airfoil, which, in part of the range of variation of the stator, results in an overlap of the blade leading edge and the rotary base 3 of an adjacent stator blade 2.

Quite similar to FIG. 2, FIG. 4 shows a variable stator row in the meridional plane. View A-A on the right-hand side of the Figure shows the inner flow path boundary (hub) in an aspect parallel to the rotational axis 1 of the variable stator. The inventive solution here shown provides for a complete positioning of the airfoil on the rotary base 3. The originally perfectly circular rotary base 3 is cut back to provide two very long flanks which in the example here shown are again straight, but which also may be curved.

FIG. 5 shows three different rotary positions of the variable stator according to the present invention for:

• a) Variation towards large stagger angles of the stator blade 2 (low part-load range of the turbomachine)
• b) Intermediate rotary position and correspondingly maximum gap between the flanks (intermediate part-load range of the turbomachine)
• c) Variation towards small stagger angles of the stator blade 2 (design range and overload range of the turbomachine).

As becomes apparent from the illustration, the gap between the flanks of two adjacent rotary bases 3 is minimal or even equal to zero at the respective margins of the range of variation of the stator (i.e. at extremely large and small stagger angles of the variable stator blades).

For clarification of the concept according to the present invention, the above Figures show the opposing cutbacks of the rotary base 3 as being symmetric to the blade rotational axis and having straight flanks. Besides this representation, the scope of solution of the present invention also includes flanks which are neither straight nor of equal length.

FIG. 6 shows a rotary base 3 in rotational axis-parallel view. For clarity, the blade is omitted in the illustration. Starting out from the perfectly circular shape of the rotary base 3, two highly different cutbacks may be provided according to the present invention whose contours, with the rotary position of the variable stator being properly selected, match with each other over parts of the flank. The penetration depths S1 and S2 into the circle of the diameter D may here differ freely from each other.

A solution according to the present invention may also provide for any contour of the flanks S and D other than those selected in FIG. 6. The flow-facing (wetted) surface of the rotary base 3 may, according to the present invention, be straight, or—to provide for a particularly favorable transition between rotary bases 3 of adjacent stator blades 2—be inclined, beveled, wavy or otherwise contoured.

Similar to FIG. 6, FIG. 7 shows a rotary base 3 in rotational axis-parallel view. For clarity, the stator blade 2 is also omitted in the illustration.

Starting out from the perfectly circular shape of the rotary base 3, two straight flanks with different penetration depths S1 and S2 were selected. In this representation, as well as in the previous ones, solutions according to the present invention are shown in which the edges produced at the flanks are rectangular to the surface of the rotary base. Departing from this concept, it can be particularly favorable according to the present invention to provide the surface of the flank inclined, i.e. not parallel, in relation to the blade rotational axis 1 and/or with a special contour.

For clarity, FIG. 8 shows the section B-B through the rotary base 3 defined in FIG. 7 and a small part of the airfoil 8. While the upper part of the illustration shows the solution according to the present invention with rectangular edges of the flanks (rotary base without inclination of the flanks S and D (orientation approx. parallel to the rotational axis)), the lower part of the illustration exemplifies two matching inclinations/contours of the flanks S and D (rotary base with inclination and contouring of the flanks S and D). Here as well, the flow-facing (wetted) surface of the rotary base 3 may, according to the present invention, be straight or—to provide for a particularly favorable transition between rotary bases 3 of adjacent stator blades 2—be inclined, beveled, wavy or otherwise contoured.

LIST OF REFERENCE NUMERALS

• 1 Rotational axis
• 2 Stator blade (variable stator)
• 3 Rotary base
• 4 Hub component
• 5 Casing component
• 6 Piercing point of blade rotational axis 1
• 7 Flow-facing (wetted) surface
• 8 Blade airfoil

Claims

1. A turbomachine comprising:

at least one flow duct,

at least one of a guide blade and a stator blade arranged in the flow duct which is rotatable around a rotational axis, and which comprises at its radial end areas one rotary base each, wherein the rotary base includes a section that is non-circular, when viewed in a direction of the rotational axis.

2. The turbomachine of claim 1, wherein the non-circular section of the rotary base includes two flanks of at least one of a straight and a curved configuration, the flanks being relieved portions on opposite sides of a base circle of the rotary base.

3. The turbomachine of claim 2, wherein a least one of a casing component and a hub component of the turbomachine includes overlapping circular recesses in which rotary bases of adjacent blades are positioned.

4. The turbomachine of claim 3, wherein the two flanks are straight and parallel to one another.

5. The turbomachine of claim 3, wherein the two flanks have curved portions.

6. The turbomachine of claim 4, wherein each of the flanks is the same length.

7. The turbomachine of claim 4, wherein each of the flanks is the same distance from the rotational axis.

8. The turbomachine of claim 4, wherein each of the flanks is a different distance from the rotational axis.

9. The turbomachine of claim 1, wherein each of the flanks is parallel to the rotational axis.

10. The turbomachine of claim 1, wherein each of the flanks includes at least one of an inclined portion and a contoured portion in relation to the rotational axis.

11. The turbomachine of claim 1, wherein a least one of a casing component and a hub component of the turbomachine includes overlapping circular recesses in which rotary bases of adjacent blades are positioned.

12. The turbomachine of claim 2, wherein the two flanks are straight and parallel to one another.

13. The turbomachine of claim 2, wherein the two flanks have curved portions.

14. The turbomachine of claim 2, wherein each of the flanks is the same length.

15. The turbomachine of claim 2, wherein each of the flanks is a different distance from the rotational axis.

16. The turbomachine of claim 1, wherein each of the flanks includes at least one of an inclined portion and a contoured portion in relation to the rotational axis so that adjacent rotary bases can overlap one another.

17. A turbomachine comprising:

at least one flow duct,

at least one row of guide/stator blades positioned in the flow duct, each of which is rotatable around a rotational axis and which comprises at its radial end areas one rotary base each, wherein the rotary bases from at least one blade in adjacent blade pairs include portions recessed from a base rotary circle to provide clearance between the adjacent rotary bases such that a distance between the respective rotational axes of the adjacent blade pair is smaller than a diameter of a base circle of the rotary bases.

18. The turbomachine of claim 17, wherein the recessed portions provide clearance between outer edges of the adjacent rotary bases.

19. The turbomachine of claim 17, wherein the recessed portions allow outer edges of the adjacent rotary bases to overlap one another.

20. The turbomachine of claim 17, wherein the rotary bases from both blades in adjacent blade pairs have recessed portions.