Blade of a fluid-flow machine featuring a multi-profile design

Abstract

A blade of a fluid-flow machine has a cross-section, which in at least one part of the blade height in at least one flow-line profile section is formed by at least two partial profiles separated from each other, with each of the individual partial profiles having the shape of a blade profile.

Description

This application claims priority to German Patent Application DE 102007024840.9 filed May 29, 2007, the entirety of which is incorporated by reference herein.

The present invention relates to blades of fluid-flow machines, such as blowers, compressors, pumps and fans of the axial, semi-axial and radial type using gaseous or liquid working media. The fluid-flow machine may include one or several stages, each having a rotor and a stator. In individual cases, the stage can have only a rotor. The rotor includes a number of blades, which are connected to the rotating shaft of the machine and transfer energy to the working medium. The rotor may be designed with or without a shroud at the outer blade ends. The stator includes a number of stationary blades, which may either feature a fixed or a free blade end on the hub and on the casing side. Rotor drum and blading are usually enclosed by a casing; in other cases (e.g. aircraft or ship propellers) no such casing exists. The machine may also feature a stator, a so-called inlet guide vane assembly, upstream of the first rotor. Departing from the stationary fixation, at least one stator or inlet guide vane assembly may be rotatably borne, to change the angle of attack. Variation is accomplished for example via a spindle accessible from outside of the annulus. In an alternative configuration, multi-stage types of said fluid-flow machines may have two counter-rotating shafts, with the direction of rotation of the rotor blade rows alternating between stages. Here, no stators exist between subsequent rotors. Finally, the fluid-flow machine may—alternatively—feature a bypass configuration such that the single-flow annulus divides into two concentric annuli behind a certain blade row, with each of these annuli housing at least one further blade row. FIG. 2 shows examples of four possible configurations of fluid-flow machines, where a casing 1, a hub/rotor drum 2, a machine axis 3 and an annulus 9 are indicated in each view, along with the blade configurations.

The fluid flow in the blade rows of aerodynamically highly loaded fluid-flow machines is characterized by the very high degree of re-direction to be attained. The required re-direction of the fluid flow can be so extreme, either in parts of the blade height or along the entire blade height, that premature separation of the boundary layer flow on the blade profile and in the side-wall area on the hub and casing will occur with conventionally designed state-of-the-art blade profile sections. Conventional blades without additional design features for stabilising the profile and wall boundary layers, as shown in FIG. 1, are unsuitable due to the occurrence of extremely high pressure losses and the inability to attain the flow re-direction required. Moreover, the secondary flows occurring in the area of the confining side walls (on hub and casing) will be uncontrollable, resulting in further, very high total pressure losses. In consequence, the fluid-flow machine will have a generally bad performance as regards efficiency and the stability margin available.

Blade rows with a profile design according to the state of the art, see FIG. 1, have too small an operating range and too high losses to attain the operating characteristics required for modern fluid-flow machines, this being due to the high aerodynamic loading of the boundary layers, i.e. the two-dimensional boundary layers on the profile and the three-dimensional boundary layers on hub and casing walls.

In a broad aspect, the present invention provides for a blade of a fluid-flow machine which is characterized by improved efficiency.

The present invention provides for a blade for application in a fluid-flow machine which, in at least one part of the annulus width (or the blade height, respectively) in at least one flow-line section, is formed by at least two separate profiles, each of which featuring essentially the shape of a blade profile with a rounded nose (leading edge).

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

FIG. 1 is a schematic representation of a blade according to the state of the art,

FIG. 2 shows possible configurations of fluid-flow machines relevant to the present invention,

FIG. 3 shows an example of a blade according to the present invention in schematic representation,

FIG. 4 shows further examples of blades according to the present invention in meridional view,

FIG. 5 provides a definition of meridional flow lines and flow-line profile sections,

FIG. 6a shows a multi-profile design according to the present invention, as viewed in a flow-line profile section,

FIG. 6b shows further types of multi-profile design, as viewed in a flow-line profile section,

FIG. 7a shows examples of a multi-profile design in the center area of a blade, three-dimensional view,

FIG. 7b shows examples of a multi-profile design at the fixed blade end, three-dimensional view,

FIG. 7c shows examples of a multi-profile design at the free blade end, three-dimensional view,

FIG. 8 provides a definition of zones for particularly favorable positioning of the fore-profile trailing edge according to the present invention.

As shown in FIG. 1, according to the state of the art, a conventional blade 6, has a leading edge 7, a trailing edge 8, a pressure side 5 and a suction side 4, is positioned between a casing 1 and a hub/rotor drum 2, and features no subdivision into several, successive profiles over a selected part of the blade height. Known are only so-called tandem configurations, in which re-direction is accomplished via two physically separate blade rows. FIG. 1 shows a profile section of the blade on the right of the meridional section shown on the left. In the meridional section, flow takes place from the left to the right, as indicated by the bold arrow. A machine axis 3 is also shown in the meridional section. On conventional blades, flow around the individual profile sections of the blades (see profile section P-P) takes place separately from the leading edge onward, without fluid communication between the blade sides.

FIG. 3 shows one embodiment of a blade 6 according to the present invention. Here again, the blade is shown in meridional section on the left, with flow taking place from the left (left-hand side of the illustration). Profile section P-P (taken along section line P-P from the meridional view) is shown on the right in FIG. 3. The blade 6 of the present invention also includes a leading edge 7, a trailing edge 8, a pressure side 5 and a suction side 4, and is positioned between a casing 1 and a hub/rotor drum 2. The blade 6 also has a plurality of passages 10 between the pressure side 5 and the suction side 4 that create several sub-divisions of the profile (see especially the profile section P-P on the right), each featuring different length and shape in the direction of the blade height and being arranged in a selected partial area of the blade height (annulus width). In the section P-P shown on the right, it can be seen how adding the passages 10 to the blade 6 has, in effect, created three separate airfoils on the single blade 6 at that section P-P. Deviating from the representation here selected, the present invention obviously also applies to blades featuring a larger or a smaller number of subdivisions and the passages 10 can be numbered and configured as desired to provide a desired result at various heights along a blade 6.

FIG. 4 shows further embodiments of blades according to the present invention having different quantities and configurations of passages 10 to create unique sets of subdivisions and airfoil configurations at various heights of the disclosed blades 6. Accordingly, example (a.) shows a single passage 10 creating a profile subdivision in the center area of the blade 6. Example (b.) shows two successive passages 10 creating profile subdivisions in the center area of the blade 6. Example (c.) shows a blade with a free end adjacent the casing 1 and passages 10 at the inner and outer ends of the blade 6 creating respective profile subdivisions. Example (d.) shows two obliquely oriented passages 10 creating profile subdivisions arranged in the area of the trailing-edge 8 near the hub 2 and the casing 1. Example (e.) shows a single passage 10 creating a profile subdivision near the casing 1 in the area of the trailing-edge 8. Example (f.) shows a blade 6 with a free end adjacent the hub 2 and having passages 10 at the inner and outer ends of the blade 6 to create smaller profile subdivisions at the blade ends.

FIG. 5 provides a precise definition of meridional flow lines and flow-line profile sections. The mean meridional flow line m is established by the geometrical center of the annulus 9 between the casing 1 and the hub/rotor drum 2. If a perpendicular is erected at any point of the mean flow line m, the development of annulus width W along the flow path and a number of perpendiculars is obtained by use of which, with equal relative division of the perpendiculars in the direction of the annulus width, further meridional flow lines m_n may be determined. The section of a meridional flow line m with a blade 6 provides a flow-line profile section. Further considerations on the blade 6 according to the present invention are based on flow-line profile sections.

FIG. 6a shows blade configurations according to the present invention in a selected flow-line profile section. Representation (1.) shows a subdivision into two profiles, i.e. fore-profile and first aft-profile (N=2) which, as a result of their large maximum thickness, are bulbous and drop-shaped. Representation (2.) shows a subdivision into two profiles (N=2), with the fore-profile being slender relative to the first aft-profile. Representation (3.) shows a subdivision into two profiles (N=2), with the fore-profile and the first aft-profile being approximately equally slender.

FIG. 6b shows further arrangements featuring a multi-profile design according to the present invention, again in a flow-line profile section. Representation (4.) provides a profile subdivision into three individual profiles, i.e. fore-profile, first aft-profile and second aft-profile (N=3), with all three profiles having approximately equal relative thickness of more than 5 percent, and with the fore-profile and the first aft-profile being pronouncedly bulbous. Representation (5.) provides a profile subdivision into three individual profiles (fore-profile, first aft-profile and second aft-profile) with the fore-profile being slender relative to the first and second aft-profile. Representation (6.) provides a profile subdivision into three individual profiles (fore-profile, first aft-profile and second aft-profile), with all three profiles having small, but approximately equal relative thickness (less than 5 percent).

FIGS. 7a to 7c show inventive configurations of the multi-profile design in different blade areas.

FIG. 7a shows two different blades, confined by two blade ends not further specified, with sectional subdivision into fore-profile and first aft-profile (N2) in the center area of the blade, with the subdivision zone not reaching the ends of the blade. While the blade on the left has one area in multi-profile design, the blade on the right features multi-profile design in two areas of the blade height.

FIG. 7b shows two different blades, each confined by at least one fixed end, with sectional subdivision into fore-profile and first aft-profile (N=2), with the subdivision zone reaching to the fixed blade end. While the multi-profile design on the left blade is oriented essentially in flow direction, the multi-profile design on the right blade shows orientation towards the fixed wall, characterized in that the passage 10 between the fore-profile and the aft-profile provides for a contracting flow path, as viewed in the blade height direction. This arrangement applies, in particular, to the blade ends on rotor or stator platforms, as defined by the blade roots or shrouds.

FIG. 7c shows a blade, confined by at least one free end, with sectional subdivision into fore-profile, first aft-profile and second aft-profile (N=3), with the subdivision zones reaching to the free blade end and having different extension in the direction of the blade height. While the multi-profile design in the forward subdivision zone is oriented essentially in flow direction, the multi-profile design in the rearward subdivision zone shows orientation towards the free blade end, characterized in that the passage 10 between the partial profiles provides for a contracting flow path, as viewed in the blade height direction. This arrangement applies, in particular, to the blade tips of rotors and to the tips of cantilevered stators with a radial gap at the hub.

In accordance with the present invention, it can be particularly favorable to arrange the trailing edge of the fore-profile in the trailing edge and rim-near zone (TRZ) of a blade 6, see FIG. 8. The trailing edge-near zone is defined as the portion of the blade between 40 percent and 100 percent of the meridional blade chord length Cm. The rim-near zone is defined as the blade portions between 0 percent and 40 percent as well as between 60 percent and 100 percent of the annulus width (blade height).

Further description of the present invention:

• • 1. A blade of a rotor or stator row for application in a fluid-flow machine featuring a multi-profile design, with the cross-section of the blade in at least one part of the blade height (annulus width) in at least one flow-line profile section being formed by at least two separate partial profiles, and each of the individual partial profiles also featuring the shape of a blade profile.
  • 2. A blade in accordance with item 1, with the at least two partial profiles, including a fore-profile and at least one aft-profile, being of different relative maximum thickness.
  • 3. A blade in accordance with item 1 or 2, with at least one aft-profile having a relative maximum thickness larger by at least 30 percent than the upstream fore or aft-profile, respectively.
  • 4. A blade in accordance with item 1, with the at least two partial profiles, including a fore-profile and at least one aft-profile, being of equal relative maximum thickness.
  • 5. A blade in accordance with item 1, with the at least two partial profiles, including a fore-profile and at least one aft-profile, being of equal absolute maximum thickness.
  • 6. A blade in accordance with one of the items 1 to 5, with at least one zone having a multi-profile design being arranged in a center area of the blade height and not extending to the blade ends.
  • 7. A blade in accordance with one of the items 1 to 5, with at least one zone having a multi-profile design being arranged on at least one fixed blade end, confined by a blade root/shroud.
  • 8. A blade in accordance with one of the items 1 to 5, with at least one zone having a multi-profile design being arranged on at least one free blade end with a radial gap towards a hub/casing contour.
  • 9. A blade in accordance with one of the items 1 to 8, with the multi-profile design, including the passages arising between the partial profiles, being essentially oriented in the meridional flow direction.
  • 10. A blade in accordance with one of the items 1 to 8, with the multi-profile design, including the passages arising between the partial profiles, featuring an inclination in a direction of one blade end.
  • 11. A blade in accordance with one of the items 1 to 10, with the passage between two partial profiles defining a contracting flow path, as viewed in a blade height direction.
  • 12. A blade in accordance with one of the items 1 to 11, with a trailing edge of the fore-profile being arranged in a trailing edge and rim-near zone (TRZ), with the trailing edge-near zone being defined as a portion of the blade between 40 percent and 100 percent of a meridional blade chord length Cm, and the rim-near zone being defined as blade portion between 0 percent and 40 percent as well as between 60 percent and 100 percent of the annulus width (blade height).

The present invention provides for a significantly higher aerodynamic loadability of rotors and stators in fluid-flow machines, with efficiency being maintained or even improved. A reduction of the number of parts and the weight of the components of more than 20 percent seems to be achievable. Application of the concept to the high-pressure compressor of an aircraft engine with approx. 25,000 lbs thrust leads to a reduction of the specific fuel consumption of up to 0.5 percent.

LIST OF REFERENCE NUMERALS

1 Casing

2 Hub/rotor drum

3 Machine axis

4 Suction side

5 Pressure side

6 Blade

7 Leading edge

8 Trailing edge

9 Annulus

10 Passage/passage opening

Claims

1. A blade of a fluid-flow machine, the blade having a cross-section, which in at least one part of a blade height in at least one flow-line profile section is formed by at least two partial profiles separated from each other, with each of the individual partial profiles having a shape of a blade profile.

2. The blade of claim 1, with the at least two partial profiles including a fore-profile and at least one aft-profile of different relative maximum thickness.

3. The blade of claim 2, with one aft-profile having a relative maximum thickness larger by at least 30 percent than the fore-profile.

4. The blade of claim 1, with the at least two partial profiles including a fore-profile and at least one aft-profile of equal relative maximum thickness.

5. The blade of claim 1, with the at least two partial profiles including a fore-profile and at least one aft-profile of equal absolute maximum thickness.

6. The blade of claim 1, with at least one zone of the blade having a multi-profile design being positioned in a center area of the blade height.

7. The blade of claim 1, with at least one zone of the blade having a multi-profile design being positioned on at least one fixed blade end, confined by a blade root/shroud.

8. The blade of claim 7, with at least one zone of the blade having a multi-profile design being positioned on at least one free blade end with a radial gap towards a hub/casing contour.

9. The blade of claim 1, with the multi-profile design being arranged essentially in a meridional flow direction.

10. The blade of claim 1, with the multi-profile design having an inclination in a direction of one blade end.

11. The blade of claim 1, with a gap between two partial profiles defining a contracting flow path, as viewed in a blade height direction.

12. The blade of claim 1, with a trailing edge of a fore profile being arranged in a trailing edge and rim-near zone (TRZ), with the trailing edge-near zone being defined as a portion of the blade between 40 percent and 100 percent of a meridional blade chord length (Cm), and the rim-near zone being defined as blade portions between 0 percent and 40 percent as well as between 60 percent and 100 percent of a blade height/annulus width.

13. The blade of claim 2, with at least one zone of the blade having a multi-profile design being positioned in a center area of the blade height.

14. The blade of claim 2, with at least one zone of the blade having a multi-profile design being positioned on at least one fixed blade end, confined by a blade root/shroud.

15. The blade of claim 2, with at least one zone of the blade having a multi-profile design being positioned on at least one free blade end with a radial gap towards a hub/casing contour.

16. The blade of claim 2, with the multi-profile design being arranged essentially in a meridional flow direction.

17. The blade of claim 2, with the multi-profile design having an inclination in a direction of one blade end.

18. The blade of claim 2, with a gap between two partial profiles defining a contracting flow path, as viewed in a blade height direction.

19. The blade of claim 2, with a trailing edge of a fore profile being arranged in a trailing edge and rim-near zone (TRZ), with the trailing edge-near zone being defined as a portion of the blade between 40 percent and 100 percent of a meridional blade chord length (Cm), and the rim-near zone being defined as blade portions between 0 percent and 40 percent as well as between 60 percent and 100 percent of a blade height/annulus width.