EP1012445A1

EP1012445A1 - Blade for a turbo-machine and steam turbine

Info

Publication number: EP1012445A1
Application number: EP98951240A
Authority: EP
Inventors: Mathias Deckers
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1997-09-08
Filing date: 1998-08-31
Publication date: 2000-06-28
Anticipated expiration: 2018-08-31
Also published as: DE59805843D1; JP2001515983A; EP1012445B1; CN1100195C; WO1999013199A1; JP4217000B2; US6354798B1; KR20010023783A; ATE225460T1; EP1012445B2; CN1269865A

Abstract

The invention relates to a blade (1) for a turbo-machine (11) which is oriented along a blade axis (2). Cross-sectional profiles (5) situated axially at a distance to each other and perpendicular to the blade axis (2) are offset parallel to each other towards the central area (10) in the top end area (4) and in the base end area (3) of the blade (1) in such a way that the blade (1) is displaced along the blade axis (2) in a convex manner. In addition, cross-sectional profiles (5a, 5b; 15a, 15b) situated at an axial distance to each other are twisted in relation to each other in the base end area (3) and/or the top end area (4). The invention further relates to a steam turbine (11).

Description

description

Bucket for a flow machine and steam turbine

The invention relates to a blade for a turbomachine, the blade being directed along a blade axis and having a foot end region, a head end region and a central region and a cross-sectional region arranged perpendicularly to the blade axis along this blade axis. The invention further relates to a steam turbine, in particular a high-pressure or medium-pressure steam turbine.

The efficiency of a flow machine, in particular a steam turbine, is reduced by the flow losses that occur. The improvement of the efficiency and thus the reduction of such flow losses deals e.g. the article "Advanced Steam Turbine Technology for Verified Operating Efficiency" by R.B. Scarlin, in "Power-Gen Europe 95", May 16-18, 1995, Amsterdam RAI the Netherlands, Book 2, Vol. 4, page 229 ff. This describes the development of three-dimensional turbine blades, taking into account various flow losses, such as gap losses, losses through the blade profile and losses in the end regions of the turbine blade (endwall losses). to

To reduce the latter losses, an inclination of the turbine blade in the circumferential direction is specified. An inclination of the turbine blade in the area of the blade tip and the hub area of the turbine blade leads to a curved blade, such a bend being applicable only to guide blades due to the mechanical properties. Furthermore, the article states in general that a rotation of the blade also has an influence on the inclination of the blade, so that with a three-dimensional design in the end regions of the blade, both the blade inclination, the blade rotation and the blade profile are at disposition. In the article "Modern Blade Design for Improvement in Steam Turbine Efficiency" by M. Jansen and W. Ulm in "VDI Reports" No. 1185, 1995, pages 277-290, an increase in the efficiency of a steam turbine, in particular, is also pointed out a high pressure or medium pressure steam turbine. The influence of different flow losses for different steam turbines is shown. A special configuration of the turbine blade reduces the flow losses. The three-dimensionally designed turbine blades have an inclination in a foot region and a head region of the turbine blade. The article compares the flow losses of these three-dimensional turbine blades with purely cylindrical blades. Such cylindrical blades have pressure and suction sides parallel to the blade axis and thus have neither a twist nor an inclination. As a further alternative to the three-dimensionally designed turbine blades, so-called twisted turbine blades are described, which have an increasing twist and a changing blade profile due to their height.

DE 31 48 995 AI describes an axial turbine, such as a steam turbine or a gas turbine, with a large number of guide vanes arranged at a distance from one another on the circumference. The guide vanes used are twisted over their height and have a changing inlet angle. From a certain height, measured from the root of the blade (root), the change in the inlet angle increases continuously in the area of the tip of the guide blade. The use also increases continuously over the height of the guide vane. The cross-sectional profile of the guide blade changes continuously from the blade root to the blade tip, the guide blade becoming ever slimmer. When designing the guide vane, further changes are made to the height of the Guide blade regarding the outlet angle, the size and shape of the guide blade are taken into account.

In the German Auslegeschrift 11 68 599 an axial compressor with blades and / or guide vanes, which have a modified cross-section in the area of the wall surfaces to compensate for the flow influence caused by these wall surfaces, is specified. Inlet guide vanes are arranged in the axial compressor along the gas flow path in front of the rotor and guide vanes. These inlet or inlet guide vanes have a curved cross section, except in the area of the walls. The middle vane part with the arched cross section merges into a smooth and continuously curved surface in each wall region in the non-arched cross-sectional profile in the wall regions. The cross-sectional profiles of the airfoil thus change continuously over the height of the outlet guide vane. The inlet angle remains constant over the entire height of the inlet guide vane.

German Auslegeschrift 28 41 616 describes a guide vane ring for an axial turbine with guide vanes, the guide vanes being arranged between an inner and an outer ring and the profile thickness of the airfoil changing in proportion to the blade pitch. The change in the blade profile takes place via the

Height of the guide vane in that there is no change in the shape of the leading edge (pressure side), but the protrusion on the trailing edge gradually increases in size over the height with a simultaneous increase in the thickness of the guide vane. The profile change is carried out in such a way that the thickness of the guide blade increases while its chord length remains the same. Such a guide vane ring can be used in steam turbines, gas turbines and compressors.

DE 42 28 879 AI specifies an axially flow-through turbine with at least one row of curved guide vanes. Due to the blade curvature, both the entry and edge and the trailing edge of the guide vanes are not in the same axial plane. The curvature of the blades is perpendicular to the chord, which is achieved by shifting the profile cuts both in the circumferential direction and in the axial direction. From a turbine housing wall

(Cylinder) towards a turbine hub, the guide vanes taper, so that their cross section changes accordingly, the blade profile remaining essentially unchanged over the blade height. In addition to the curvature and the taper, a twisting of the blade is also carried out over the length of the blade of the guide blade in order to take into account the change in the peripheral speed of the blades following the guide blade above the channel height. The blade is therefore adjusted by deflecting the center of gravity of the profile cuts perpendicular to the

Profile chord (curvature or bend), ie an axial and circumferential deflection at the same time, combined with a chord length variation.

Inclined turbine blades for a steam turbine are also described in the article "Development of three-dimensional stage viscous time marching method for optimization of short height stages" by G. Singh, P.J. Walker, B.R. Haller, in: "VDI Reports No. 1185, 1995, pp. 157-179.

The object of the invention is to provide a blade with low flow losses for a flow machine. Another object of the invention is to provide a steam turbine with low flow losses.

According to the invention, the object directed to a blade for a flow machine is achieved by such a blade which is directed along a blade axis and has a foot end region, a foot axis, along this blade axis

Head end region and in between a central region and a cross-sectional profile perpendicular to the blade axis, where cross-sectional profiles axially spaced apart in the direction of the blade axis are offset from one another in the same direction from the foot end region to the central region and from the head end region to the central region, and wherein cross-sectional profiles axially spaced apart from one another are rotated by a difference angle in the foot end region and / or in the head end region.

When the blade is installed in a turbine with a turbine shaft, axially in the direction of the blade axis is synonymous with radial with respect to the turbine shaft. With the displacement of axially spaced cross-sectional profiles in the head end area and in the foot end area and an additional twist in the foot end area and / or in the head end area, there is a reduction in the flow losses in the edge zones (head end area, foot end area), which affect the hub of a turbine shaft and the inner circumference of a turbine housing are assigned. The rectified shift to the central region hm causes the turbine blade to incline in a belly shape perpendicular to the blade axis

(bent) is. With an additional twisting of the axially spaced cross-sectional profiles, an additional increase in efficiency, i.e. a reduction in flow losses.

The axially spaced cross-sectional areas in the foot end area and in the head end area are preferably rotated in the same direction towards the central area. As a result, the rotation is reduced again over the entire height of the blade from the head end region to the foot end region.

The blade is preferably designed to be arranged in a blade ring which has a circumferential direction, the cross-sectional direction coinciding locally with the circumferential direction. This results in a bending in the peripheral zones of the blade in the circumferential direction with a simultaneous rotation (angle adjustment) in the end regions of the blade, whereby a reduction in flow losses and thus an increase in the efficiency of a flow machine can be achieved. In steam turbines in particular, this results on the one hand in an increase in the mechanical exit energy with the same thermal energy input, and on the other hand in a reduction in the thermal energy use and thus the environmental impact due to pollutant emissions with the same exit energy compared to purely cylindrical or purely inclined or purely curved blades.

The cross-sectional profiles are preferably rotated with respect to their center of gravity or with respect to the blade axis (if different, e.g. due to inhomogeneous mass distribution). The angle of rotation that occurs is referred to below as the stagger angle and performing the rotation as the stagger angle change.

In a cross section perpendicular to the blade axis, the cross sectional profile along the blade axis is preferably the same everywhere. The cross-sectional profile therefore does not change over the height of the blade. Here, the cross-sectional area of the cross-sectional profiles is preferably also constant. The blade preferably has a combination of a circumferential deflection of the center of gravity of the cross-sectional profiles (bending in the circumferential direction) and a staggering of the cross-sectional profiles (without changing the profile) in the top and bottom end area (hub and housing area).

Depending on the expansion of the blade in the direction of the blade axis (blade length, blade height) for expansion of the blade in a direction perpendicular to the blade axis (blade width) and the flow conditions when the blade is used in a flow machine, the blade in the middle region is preferably cylindrical. The sides (pressure side, suction side) of the blade therefore run parallel to the blade axis. The blade is preferably designed as a guide blade or rotor blade of a steam turbine, in particular a high-pressure or medium-pressure steam turbine. The blade preferably has a small length to width ratio, as is the case in particular for blades for a high-pressure steam turbine.

The object directed to a steam turbine is achieved for a steam turbine which is directed along a turbine axis and has an inflow region, an outflow region and a blading region arranged in terms of flow technology between the fact that in the blading region a blade directed along a blade axis is arranged, which over the Blade axis has an inclination and a twist, which each increase from a foot end region to a central region and decrease from the central region to a head end region.

With such a configuration of the steam turbine comprising the blade with increasing and decreasing inclination and twisting, a reduction in the flow losses in the area of a turbine shaft directed along the turbine axis and a turbine housing surrounding the turbine shaft is achieved.

The blade with increasing and decreasing inclination and rotation is preferably assigned to the inflow area. It is therefore preferably arranged in the first stage and / or the subsequent stages. This applies both to steps comprising a blade ring made of moving blades or guide blades. Since the proportion of so-called secondary losses (edge losses) in the hub and housing area is particularly high in the first stages of a high-pressure or medium-pressure steam turbine (for example up to 30% of the total losses) and is reduced by the specified blade shape, this can result in a noticeable The increase in efficiency can be achieved. A twisted blade, ie a blade with twisting and changing the cross-sectional profile and / or the cross-sectional area increasing over its length, is preferably arranged in the outflow region. A purely cylindrical blade, that is to say with side walls parallel to the blade axis, is provided axially between the steps, comprising the twisted blade and the blade with increasing and decreasing inclination as well as change in the angle of the blade. Such an arrangement of blades of different geometries provides a steam turbine with low flow losses and high efficiency.

The blade for a flow machine and the steam turbine are explained in more detail using the exemplary embodiments shown in the drawing. They show a partially schematic and not to scale representation

1 shows a longitudinal section through a high-pressure steam turbine,

2 shows a cross section of a detail through a blade ring,

3 shows a spatial representation of the blade area of a blade,

4 shows a cross section through the blade area of the blade according to FIG. 3 and

5 shows a further cross section through the blade according to FIG. 3 axially spaced from the cross section according to FIG. 4 in the direction of the blade axis.

The same reference numerals have the same meaning in all the figures. 1 shows a flow machine, a high-pressure steam turbine 11, in a longitudinal section, which is directed along a turbine axis 17. The steam turbine 11 has a turbine shaft 20 which is directed along the turbine axis 17 and is surrounded by a turbine housing 18. Along the turbine axis 17, the steam turbine 11 has an inflow region 12 for action fluid, superheated steam, and an outflow region 13 for the superheated steam. A blading area 14 is provided axially between the inflow area 12 and the outflow area 13. In the blading area 14, in the axial direction alternately one after the other, in a corresponding blade ring 21, guide vanes 9 and rotor blades 8 follow each other Arranged in between in the direction of the blade axis 2 is a central region 10. With the foot end area 3, a moving blade 8 borders on the turbine shaft 20 and a guide blade 9 on the turbine housing. The reverse applies to head end area 4. The rotor blades 8 and / or guide blades 9 closest to the inflow region 12 are each designed as a blade 1 which is inclined and rotated in the foot end region 3 and in the head end region 4. Rotary vanes 8 and guide vanes 9 located downstream of the outflow region 13 are each designed as twisted vanes 19 with twisting increasing over the blade axis 2 and changing cross-sectional profile. Purely cylindrical blades 16 are arranged in the blading area 14 axially between the inclined and twisted blades 1 and the twisted blades 19, the suction and pressure sides of which are each parallel to the blade axis 2.

FIG. 2 shows a section of a blade ring 21 in which blades 1 are arranged next to one another in the circumferential direction 6a. For the sake of clarity, the blade ring 21 is unwound along the circumferential direction 6a and is shown with only two blades 1. The circumferential direction 6a corresponds to the circumference of the turbine shaft 20 in a section perpendicular to the turbine axis 17. The main flow direction 22 of the steam flowing in the steam turbine 11 is perpendicular to the circumferential direction 6a of the blade ring 21.

FIG. 3 shows a spatial representation of the blade area 23 of a blade 1 directed along a blade axis 2. The airfoil area 23 has a foot end area 3, a head end area 4 and in between a central area 10. For the sake of clarity, a fastening region adjoining the foot end region 3 and with which the turbine blade 1 is fastened in the turbine shaft 20 or the turbine housing 18 is not shown. Furthermore, a shroud possibly adjoining the head end area 4 is also not shown. In the head end region 4 and the foot end region 3, the turbine blade 1 is inclined in a cross-sectional direction 6, which preferably corresponds to the circumferential direction 6a of the blade ring 21, and is rotated in the axial direction by a difference angle Δβ (see FIGS. 4 and 5). The increasing in the foot end region 3 towards the central region 10 and increasing circumferential bend corresponds to the same rotation and circumferential bend as in the head end region 4. Starting from the foot end region 3, this means that a cross-sectional profile 5 is rotated along the blade axis 2 and shifted in the direction of the Middle region 10 and from the middle region 10 to the head end region 4, the rotation and displacement is withdrawn. The degree of displacement and twisting remains constant over the height of the central region 10. The size of the turning back and shifting back over the head end area 4 is preferably the same as the shifting and twisting in the foot end area 3.

The circumferential bend here means a displacement of the cross-sectional profile 5, 5a in the direction of a cross-sectional direction 6, which preferably corresponds to the circumferential direction 6a of a blade ring 21. A rotation of the blade 1 takes place by changing the stagger angle, ie changing the angle β according to FIG. 4 and FIG. 5 by rotating the cross-sectional profile 5 about the blade axis 2, which preferably coincides with the gravity axis of the blade 1. In the case of a blade 1 with a homogeneous mass distribution over a cross section, this also corresponds to a rotation about the center of gravity 7 (center of gravity 7) of the cross-section profile 5, 5a. The cross-sectional profile 5, 5a, 5b is the same for each cross-section over the entire height of the airfoil region 23, ie in particular that the cross-sectional shape and cross-section are constant. The cross-sectional profile 5b shown in FIG. 5 is rotated relative to the cross-sectional profile 5a shown in FIG. 4 by the difference angle Δβ and shifted by the displacement value ΔU. This corresponds to a change in the stagger angle ß to the value of the stagger angle ß '(FIG. 5).

Since in a steam turbine, in particular a high-pressure steam turbine, the edge losses, i.e. The flow mechanical losses in the vicinity of the turbine shaft and the turbine housing, which can be up to about 30% of the total losses, a reduction of these edge losses due to the twisting and circumferential bending of the blade in a steam turbine leads to an increase in efficiency. The degree of twisting and circumferential bending can be adapted to the flow conditions in a steam turbine, whereby the twisting and circumferential bending can also extend over the entire central region. It is also possible that the central area is purely cylindrical, i.e. the suction side and the pressure side of the blade are directed parallel to the blade axis.

Claims

claims

1. A blade (1) for a flow machine (11), which is directed along a blade axis (2), with a foot end region (3) and a head end region (4) arranged opposite this along the blade axis (2) and an intermediate one Middle area (10) and with a cross-sectional profile (5; 5a, 5b; 15a, 15b) perpendicular to the blade axis (2), wherein in the head end area (4) to the central area (10) hm axially spaced cross-sectional profiles (in the direction of the blade axis (2) 5a, 5b) are offset from one another in a cross-sectional direction (6), and cross-sectional profiles (15a, 15b) which are axially spaced apart from one another in the foot end region (3) to the central region (10) in the same cross-sectional direction (6) and in the foot end region (3) and / or in the head end region (4) axially spaced cross-sectional profiles (15a, 15b; 5a, 5b) are rotated relative to one another by a difference angle (Δβ).

2. Blade (1) according to claim 1, wherein the axially spaced cross-sectional profiles (5a, 5b; 15a, 15b) in the foot end region (3) and in the head end region (4) to the central region (10) are each rotated in the same direction.

3. Blade (1) according to one of the preceding claims for arrangement in a blade ring with a circumferential direction (6a), the cross-sectional direction (6) coinciding locally with the circumferential direction (6a).

4. Blade (1) according to one of the preceding claims, in which the cross-sectional profiles (5a, 5b; 15a, 15b) are each rotated with respect to their center of gravity (7).

5. Blade (1) according to one of the preceding claims, in which the cross-sectional profile (5a, 5b; 15a, 15b) is the same everywhere along the blade axis (2).

6. Blade (1) according to one of the preceding claims, which is cylindrical in the central region (10).

7. Blade (1) according to one of the preceding claims, which as a guide blade (9) or blade (8) of a steam turbine

(11).

8. Steam turbine (11), in particular high-pressure or medium-pressure steam turbine, which is directed along a turbine axis (17), with an inflow region (12), an outflow region (13) and a blading region (14) arranged between them in terms of flow technology, in which Blading area (14) is arranged a blade (1) directed along a blade axis (2), which blade (1) has an inclination and a twist over the blade axis (2), each of which extends from a foot end area (3) to a central area (10 ) increase and decrease from the central area (10) to a head end area (4).

9. Steam turbine (11) according to claim 8, in which the blade (1) is assigned to the inflow region (12) with increasing and decreasing inclination and rotation.

10. Steam turbine (11) according to claim 9, in which a twisted blade (19) is assigned to the outflow region (13).

11. Steam turbine (11) according to claim 10, in which a purely cylindrical blade (16) is arranged in the direction of the turbine axis (17) between the blade (1) and the twisted blade (19).