WO2008155243A1

WO2008155243A1 - Row of guide vanes

Info

Publication number: WO2008155243A1
Application number: PCT/EP2008/057103
Authority: WO
Inventors: Thomas Mokulys; Ralf Greim; Said Havakechian; Ivan William Mcbean
Original assignee: Alstom Technology Ltd
Priority date: 2007-06-20
Filing date: 2008-06-06
Publication date: 2008-12-24

Abstract

The invention relates to guide vanes (1, 2) of an adjustable row of guide vanes (3) of a turbomachine comprising, in each case, a first immobile part (4, 5) which is fastened to the housing, and a second, mobile part (6, 7) which is disposed downstream from the first part, wherein the second part (6, 7) is fastened on an adjustable ring (9). According to the invention, the first and second parts (4 - 7) of each guide vane (1, 2) each are configured aerodynamically smooth in such a way that minimal flow losses occur in all adjustment positions. The first and second parts comprise a profile line which corresponds to a parallel shift of the profile line of the suction side of the guide vanes (1, 2). The adjustable row of guide vanes (3) enables the mass flow (10, 13) to be controlled and throttled and the deflection (a1, a2) of the flow to be controlled.

Description

vane row

Technical area

The invention relates to a guide vane row for an axial turbomachine, in particular an adaptable vane row for controlling the mass flow of a turbine.

State of the art

In turbomachinery, variable vane rows are often used to control mass flow and control controlled mass flow rates within the bladed flow path. This measure is used in most cases to regulate the flow through the machine in adaptation to different operating conditions. Adjustable guide blade rows therefore allow an enlargement of the operating range of a turbomachine. They are used, for example, in stationary gas and steam turbines for power generation, as well as in compressors and aircraft engines.

For gas and steam turbines, the setting of the guide vane row is the

Control of the mass flow and the inlet angle of the flow. As such, the vane row functions as a baffle or throttle as disclosed, for example, in WO 2005/054633. In aircraft engines, however, a setting of the first blade row is known, which serves to control the thrust while maintaining the passage cross-section and the air mass flow, as shown for example in US 2003/0059291.

Known adjustable vane rows are distinguished according to the manner of geometric adjustment. In a first type of adjustable rows of vanes, for example in WO 2005/054633, the individual vanes of an axial flow-through stage are radially along each one with respect to the axially positioned machine shaft rotated axis to effect a change in the staggering angle. The adjustment of the vanes requires a mechanical device for each vane and a sufficiently wide radial gap on the housing and shaft to allow a non-contact rotation of the vane.

In a second type of adjustable vane rows, as disclosed for example in EP 808992, the blades of an axial turbine stage are each divided into two axially separated parts. To control the mass flow, a portion of each vane is displaced in the circumferential direction, this being realized for all the vanes by a single mechanical movement in the circumferential direction and by a single rotatable ring device. This second type is mainly used in steam turbines. In the second type, the radial gap on the housing and shaft is smaller than in the first type. As a result, the aerodynamic losses at the radial gap are correspondingly smaller. However, these losses increase due to the step-shaped blade profile caused by the movement of the blade parts on the ring device.

Presentation of the invention

The object of the present invention is to provide a guide blade row for an axial-type turbomachine, which provides control of the

Mass flow through the machine and a minimum varying exit angle of the flow from the provided with the device guide vane row over a wide operating range is used. The vane row as such should assume the function of a baffle or throttle. In particular, aerodynamic losses on the row of vanes should be as low as possible, and this can be achieved in as many positions as possible. Finally, the mechanical realization of the setting should be as simple and inexpensive.

This object is achieved according to the invention by a guide blade row for a turbomachine with the features according to claim 1.

An airfoil row for an axial-type turbomachine has a number of vanes each having a leading and a trailing edge, each one of which first, arranged upstream and a second, the first part arranged downstream part. Both parts extend over the entire, radial longitudinal extent of the blade, wherein the longitudinal direction of the blade corresponds essentially to the radial direction perpendicular to the shaft axis of the turbomachine. The first part includes the leading edge of the blade and a portion of the pressure and suction sides of the blade. In this case, it extends, measured along the axial chord of the blade, over a larger area along the pressure side than along the suction side. The first part is attached to the stationary inner casing of the turbomachine and therefore immovable. The second part comprises the trailing edge of the blade and also a part of the pressure and suction side. He extends, according to the first part, over a smaller area along the pressure side than along the suction side. The second part is attached to a ring on the inner housing, which is movable in the circumferential direction of the turbomachine.

During the adjustment of the vane row, the first part of each vane remains fixed, while the second part of each vane is movable by means of the ring in the circumferential direction between an initial position and an end position defined by contact with the adjacent vane. Similarly, the reverse case, namely that the first part is movable and the second part is fixed, is the subject of this invention. For the aerodynamic mode of action, the assignment of the fixed and movable part has no relevance.

In the initial position of the ring, the first and second parts are in contact, the two parts complement each other to a complete blade. The entire mass flow passes through the channel between the blades. In an intermediate position, the ring with the second parts of the blades is circumferentially displaced relative to the initial position, so that a gap has opened between the two parts through which flows a part of the mass flow. The mass flow then passes through this gap between the first part and the second part of each blade as well as through the original channel between the second part of each blade and the first part of the blade adjacent in the blade row. The rotatable ring allows varying the width of this gap, the channel width of the original channel and thus also the distribution of the mass flow through the two channels. In an end position of the ring, that is at maximum displacement of the ring, the second part of each blade is in contact with the first Part of the blade in the vane row adjacent. The gap between the first and second part is now open to the maximum and has expanded to the actual flow channel, since the original channel is now closed. The entire mass flow now flows through this gap, and no mass flow passes through the original flow path between the second part of the blade and the first part of the adjacent blade.

The flow channel width represented by the narrowest cross-section of adjacent blades in the end position is smaller than the original channel width in the initial position. The adjustment of the guide vane row thus makes it possible to regulate the flow cross-section of the mass flow in the manner of a baffle or a throttle valve.

In addition to regulating the mass flow, the exit angle also varies from the guide row, but only slightly and in an aerodynamically advantageous manner, which is a significant advantage of the invention. The mass flow flowing through the original channel between the second part of each blade and the first part of an adjacent blade at the initial position of the ring undergoes a deflection corresponding to the stagger angle of the blades. By contrast, the mass flow flowing between the first part and the second part of each blade upon displacement of the ring experiences a deflection which is larger in comparison, resulting in a slightly larger exit angle of the flow.

The first and second parts of each blade are inventively designed to aerodynamically form the equivalent of a single blade having a single overall aerodynamic smooth profile (i.e., a profile perpendicular to the longitudinal axis of the blade) in the initial and final positions of the ring. Both parts are also designed to each have an aerodynamic smooth axial profile (i.e., a profile parallel to the shaft axis of the machine) when the ring is displaced as a single piece in the mass flow. As a result, the gap formed between the first and second part of each blade also has an aerodynamic smooth profile. This makes it possible for the flow through the gap between the first and second part to experience no or at least minimal losses due to flow separation, since there are no abrupt profile changes or step-shaped profiles.

The avoidance of flow separation also has the advantage that the Rotor downstream of the guide vane row according to the invention may be made less robust compared to existing rotors, since this must withstand a less turbulent flow. This allows a cost saving in the turbomachine.

The tangential movement of the second parts of the blades by means of a ring (in the circumferential direction) allows the adjustment of the guide blade row as a whole and thus a mechanically simple and cost-effective adjustment of the guide blade row, as Einzelverstellmechanismen be avoided for each blade.

According to the invention, the first parts and the second parts of the vane are aerodynamically designed in that their axial profiles are aerodynamically smooth and their end regions, i. their with respect to the mass flow through the blade row front and rear edges are provided with curves. The final shape of the curves and radii is created using standard aerodynamic design criteria. In particular, detachment tendencies are taken into account, which e.g. be displayed by a high so-called "Boundary Layer Shape Factor".

The axial profiles of the first and second part of each blade as well as the profile of the gap between the first and second part are characterized by the features of a parting surface by each blade. The profile of this separation surface according to the invention extends substantially along a curvature which is the same or similar to the curvature of the suction side of the blade. Both boundary surfaces of the gap between the first and second run according to the separation surface parallel to each other. The gap flow between the first and second part undergoes an exit angle according to these parallel boundary surfaces when leaving the gap. This exit angle is slightly greater than the exit angle of the flow through the original channel between the second part of a blade and the first part of the adjacent blade, since the exit angle of the original channel flow is determined by the curvature of the suction side and the pressure side of the adjacent blade. This generates the slightly stronger deflection of the mass flow through the gap between the first and second part of the blades and thereby the regulation of the inlet angle of the flow to the rotor of the machine.

In one embodiment of the invention, the profile of the parting surface for creating the first and second blade part can be seen in two parts. The first and longer part starts at the pressure side of the blade and extends in the direction of the suction side. It runs along a line that corresponds to the axially displaced profile line of the suction side of the entire bucket. An axial displacement means a displacement parallel to the shaft axis of the machine. The profile of the second and shorter part of the parting surface, which extends from the first part to the suction side, has a spline, so that a smooth connection to the suction side is created.

In an extended embodiment, the location of the interface, i. the extent of the axial displacement of the profile line of the suction side, determined by the end edge of the separation surface on the pressure side of the blade. According to the invention, this end edge lies in a range from 80 to 90% of the axial chord of the blade starting from the front edge of the blade. The end edge of the second part of the separation surface on the suction side, starting from the leading edge of the blade, is in a range of 40-60% of the axial chord.

In order to minimize flow separations on the first and second part of a blade, in particular in the region of the end edge of the parting surface, the first and second part are rounded in the region of the end edges of the parting surface.

Rounding the first and upstream portions of the blade at the edge where the interface meets the suction side of the blade has a radius of curvature of a minimum size such that flow along the first and second portions does not separate from the profile surfaces. The radius of curvature also has a maximum size, so that the overall profile of the blade with the first and second part in contact with each other, yet aerodynamically smooth.

A rounding at the second and downstream part at the edge where the parting surface meets the suction side of the blade forms the leading edge of the second part. This rounding may have a radius of curvature that is equal to or less than the radius of curvature of the leading edge of the first part. Finally, the second part at the edge where the interface meets the pressure side of the blade is also rounded. Brief description of the drawings

FIGS. 1 to 6 each show a detail of an adjustable guide vane row of a turbomachine according to the invention, the vane row being transposed into a plane. The figures represent a sequence of different positions of the first and second parts of the blades. FIG. 7 shows an embodiment of a single blade in the guide blade row according to the invention with details of the axial profile of the separating surface between the first and second parts of the blade. The profile shown is exemplary of a so-called cylindrical blade. This is constant over the height, also known under prismatic. In addition, the invention is also applicable to blades with a profile of variable height, as well as blades formed e.g. have a lean or sweep or have a variable stagger angle above the height.

Embodiment of the invention

FIG. 1 shows by way of example two blades 1, 2 of a row of guide blades 3 of an axial turbomachine, each having a first upstream part 4, 5 and a second part 6, 7 arranged downstream of the first part 4, 5. The first parts 4, 5 are fixed to a part 8 of the stationary housing of the turbomachine. The second parts 6, 7 are fastened to a ring 9 which can be moved in the circumferential direction of the machine. In the initial position of the blade parts 4-7 shown in FIG. 1, the first part 4 of the blade 1 is in contact with the second part 6 thereof. Likewise, in the blade 2 adjacent in the blade row 3, the first upstream part 6 is in contact with the blade second part 7. The characterized by an arrow 10 mass flow through the turbomachine flows through a according to the initial position original flow channel 1 1 with a passage cross-section D _first The mass flow 10 is deflected by the guide vane row 3 in this initial position in a direction which is characterized by the angle Ch.

Figure 2 shows a first adjustment position of the vane row 3. By displacement of the ring 9 with the second parts of the vanes in the tangential or circumferential direction T, the second parts 6 and 7 of the first parts 4 and 5 moved away. The passage cross-section or channel width of the flow channel 11 is reduced to D ₂ , and it has an additional flow channel 12 formed between the first and second parts through which flows a partial mass flow with the flow direction 13. Due to the curvature of the flow channel 12 of the partial mass flow 13 is directed in a direction with the angle α ₂ . The resulting angle of the total mass flow remains almost unchanged.

FIGS. 3 to 6 show further positions of the adjustable guide blade row 3, in each case with increasing displacement of the ring 9 in the tangential direction T. The passage cross-section of the flow channel 11 decreases proportionally, the passage cross-section of the flow channel 12 of the partial mass flow 13 correspondingly increasing. In the end position in FIG. 6, the second part 6 of the blade 1 contacts the first part 5 of the blade 2 adjacent in the guide blade row. The partial mass flow 13 now flows in maximum size through the channel 12, the flow channel 11 being closed and the original mass flow 10 has dropped to zero. The passage cross-section D _{3 of} the flow channel 12 is in the end position, however, smaller than the passage cross-section D _{1 of} the original flow channel 11 in the initial position according to FIG 1. With increasing adjustment of the guide vane row is due to the constant reduction of the total passage cross-section of the two flow channels 11 and 12, a restriction of the total mass flow. With increasing adjustment of the guide vane row also increases the proportion of the partial mass flow 13 of the total flow and thus also the proportion of the mass flow with

Deflection in the direction marked with angle α ₂ direction. With the adjustment of the guide vane row so the extent of the deflection is regulated.

In the initial position, each intermediate position and the end position, due to the aerodynamic design of the first and second parts of the blades, a low-loss flow of the original mass flow 10 and of the partial mass flow 13 is always guaranteed. This can be achieved by the inventive shape of the parts 4-7, as shown for example in Figure 7.

Figure 7 shows the axial profile of a single vane 1 or 2 of the adjustable vane row. It is characterized by a front edge 20, a trailing edge 21, as well as a pressure side 22 and a suction side 23. A parting line with profile line 24 divides the blade profile into a first part 25 and a second part 26, corresponding to parts 4, 5, 6 and 7 in FIGS. 1-6. The dividing line extends from the pressure side 22 of the blade to the suction side 23 of the blade and from the blade root in the radial longitudinal direction of the blade to the blade tip. The dividing line 24 has according to the invention a first section 27 and a second end section 28. The two sections together form a continuous line without sharp creases or corner points and in particular flow gently into the profile lines of the suction side and pressure side. The first portion 27 corresponds to a parallel displacement of a part of the profile line of the suction side 23 in the axial direction A. The end portion 28 has a spline to form a connection from the first portion 27 to the suction side 23 continuously and without sharp corners.

In order to realize the throttling function of the adjustable guide _{blade row} , the point at which the profile line 24 reaches the pressure side 22, for example in a range of 80-90% of the axial chord C _axιa ι, measured from the front edge 20 of the blade, and the point where the dividing line reaches the suction side 23, for example, in a range of 40-60% of the axial chord C _axιa ι, also measured from the front edge 20 of the blade.

In order to ensure a low-loss flow, in particular to avoid flow separation, the regions E and F of the first part and the points G and H of the second part are designed with curves with specifically selected radii of curvature. In particular, the rounding at point E must be chosen to be sufficiently gentle. At point E, for example, the radius of curvature Ri is approximately equal to the radius of curvature of the leading edge R _{LE of} the first part 25. In one embodiment, the radius of curvature Ri at the point E and the radius of curvature of the leading edge R _LE are dependent on the selected basic profile shape and the blade load dependent thereon 0.5 <RjR _LE ≤ 2.0 is selected.

At point H, the radius of curvature R _{2 is} arbitrary, but smaller than the radius of curvature R _{LE of} the leading edge of the first part 25. The radius of curvature at the point G can be chosen arbitrarily large. The rounding at point F can be carried out arbitrarily, as it only minimally influences the flow behavior. LIST OF REFERENCE NUMBERS

1 first shovel

2 second shovel

3 vane row

4 first part of the first blade

5 first part of the second blade

6 second part of the first blade

7 second part of the second blade

8 housing part

9 movable, adjustable ring

10 original mass flow

11 Flow path of the original mass flow

12 flow path of the partial mass flow

13 partial mass flow

Di, 2.3 passage cross-sections α-ι, 2 exit angle

20 leading edge

21 trailing edge

22 print side

23 suction side

24 dividing line

25 first part of the blade

26 second part of the blade

27 middle section of the profile line of the interface

28 End section of the profile line of the separating surface

A axial direction

T tangential direction

E ₁ F, G, H Endpoints on the first and second part of the blade

Caxial axial tendon

Claims

claims

An adjustable vane row (3) for a turbomachine having a number of vanes (1, 2), each having a leading edge and trailing edge (20, 21) and a suction and pressure side (23, 24), each vane (1 2) of the guide vane row (3) each have a first immovable part (4, 5) and a second part (6, 7) arranged downstream of the first part (4, 5), the second part (6, 7) is fastened in each case on a ring (9) which can be moved in the circumferential direction (T) of the turbomachine, characterized in that the first part (4, 5) comprises the front edge (20) and a part of the pressure and suction sides (22, 23) and the second part (6, 7) comprises the trailing edge (21) and a part of the pressure and suction sides (22, 23), the extension of the first part (4, 5) being measured along the pressure side (22) along the axial Tendon (C _a χ, ai) is greater than the extension of the second part (6,7) along the pressure side (22) measured along the axial vision ne (C _axιa ι), and the extension of the first part (4,5) along the suction side (22) measured along the axial chord (C _axιa ι) is smaller than the extension of the second part (6,7) along the suction side (23) measured along the axial chord (C _axιa ι), and the first part (4, 5) and the second part (6, 7) of the blade aerodynamically designed by their axial profiles aerodynamically smooth and their end portions (E , F, G, H) are provided with curves.

2. An adjustable guide blade row (3) for a turbomachine with a number of guide vanes (1, 2), each having a leading edge and a trailing edge (20, 21) and a suction and pressure side (23, 24), each guide vane (1, 2) of the guide vane row (3) each have a first, movable part (4, 5) and a second, immovable, with respect to the first part (4, 5) arranged downstream part (6, 7), wherein the first part (6 , 7) each on a in the circumferential direction (T) of the turbomachine movable ring (9) is fastened, characterized in that in each case the first part (4, 5), the front edge (20) and a part of the pressure and suction side (22, 23 ) and the second part (6, 7) comprises the trailing edge (21) and part of the pressure and suction sides (22, 23), the extension of the first part (4, 5) being measured along the pressure side (22) the axial chord (C _axιa ι), is greater than the extension of the second part (6,7) along the Pressure side (22) measured along the axial chord (C _axιa ι), and the extension of the first part (4,5) along the suction side (22) measured along the axial chord (C _axιa ι) is smaller than the extension of the second part (6,7) along the suction side (23) measured along the axial chord (C _axιa ι), and the first part (4, 5) and the second part (6, 7) of the blade aerodynamically designed by their axial profiles aerodynamically smooth and their end portions (E, F, G, H) are provided with curves.

3. Adjustable vane row (3) according to claim 1 or 2, characterized in that an axial profile line (24) of a separating surface of the guide vanes (1, 2), which the guide vanes (1, 2) in each of the first and second part (4 7, 25, 26), a first part (27) which extends from the pressure side (23) in the suction side (23) of the blade (1, 2) and a parallel displacement of the axial profile line of the suction side (23) Shovel (1, 2) in the axial direction (A) corresponds.

4. An adjustable guide blade row (3) according to claim 3, characterized in that the profile line (24) comprises a second part (28) extending from the first part (27) of the profile line (24) to the suction side (23) of the blade (1, 2) and includes a spline.

5. Adjustable guide vane row (3) according to one of the preceding claims, characterized in that the extension of the first part (4,5) of each vane (1, 2) along the pressure side (22), measured along the axial chord (C _axιa ι) , 80-90% of the axial chord (C _axιa ι), and the extension of the first part (4,5) of each vane (1, 2) along the suction side (22), measured along the axial chord (C _axιa ι) , 40-60% of the axial chord (C _axιa ι) corresponds.

6. Adjustable guide vane row (3) according to one of the preceding claims, characterized in that the radius of curvature (R-i) in the end region (E) on the suction side of the first part

(4,5) of each vane (1, 2) is in a range of 50-200% of the radius of curvature (R _LE ) of the leading edge (20) of the vane (1, 2).

7. Adjustable vane row (3) according to one of the preceding

Claims characterized in that the radius of curvature (R ₂ ) in the end region (F) on the suction side of the second part

(6,7) smaller than the radius of curvature (R _LE ) of the leading edge (20) of the blade (1,

2).