Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Radial flow devices
Reexamination Certificate
1999-12-27
2001-07-24
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Radial flow devices
C416SDIG002
Reexamination Certificate
active
06264429
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a compressor blade or vane and a compressor using such a blade or vane.
German Patent DE 31 41 948 C2, corresponding to U.S. Pat. No. 4,431,376, describes a blade or vane with a conical blade or vane section for the compressor of a gas turbine. It is stated that when gas flows at high velocity through blades or vanes of a compressor disposed in rows, shock waves can be experienced. The gas flows in a boundary layer along the surface of the blades or vanes that are affected. Separation of that boundary layer from the blade or vane surface can occur because of a shock wave. That causes aerodynamic losses. Those losses limit the efficiency of the blades or vanes. Such losses are of particular importance in a transonic flow field, i.e. in a flow field which contains adjacent regions of local subsonic velocity and local supersonic velocity. It is possible to optimize the section of the blade or vane in order to reduce those losses. That patent specifies a blade or vane with a conical blade or vane section, a profiled suction surface and a profiled pressure surface. The blade or vane has good aerodynamic performance capability and can also be manufactured in a simple manner. The objective of that device is further optimization of the efficiency of a compressor blade or vane.
An aircraft propeller with specially configured propeller blade sections is described in U.S. Pat. No. 4,773,825. The propeller blade sections are constructed in such a way that different loading conditions can be dealt with during a flight operation, for example in a climb or cruise phase.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a compressor blade or vane having particularly good properties with respect to efficiency, and a compressor using such a blade or vane, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a compressor blade or vane, comprising a blade or vane section having a blade or vane leading edge point; a blade or vane trailing edge point; a straight line section chord extending from the blade or vane leading edge point to the blade or vane trailing edge point and having a given length; and a suction surface profile with a convex curvature and a pressure surface profile opposite the suction surface profile, each of the profiles connecting the blade or vane leading edge point and the blade or vane trailing edge point, the suction surface profile having a radius of curvature at a suction surface intersection point with a reference straight line cutting the section chord at right angles at 5% of the given length, the radius of curvature being less than half of the given length.
A compressor blade or vane configured in this way offers the advantage of having particularly low aerodynamic losses especially under flow conditions with large Reynolds numbers and high degrees of turbulence. The concepts of Reynolds number and degree of turbulence should be understood herein in accordance with a definition given in a book entitled “Strömungslehre (Fluid Flow Science)” by Heinz Schade and Ewald Kunz, Verlag Walter De Gruyter, Berlin and N.Y., 1989, Pages 290 and 325.
The invention is based on the knowledge that the usual optimizations of compressor blades and vanes, in accordance with experimental measurement data gained in wind tunnels, do not adequately reflect the real conditions in a compressor. Generally speaking, the flow conditions with large Reynolds numbers and high degrees of turbulence mentioned are only achievable in the wind tunnel with a high degree of complication, if at all. However, they are of considerable importance in a compressor, particularly in a compressor of high power. The construction of the novel compressor blade or vane described above is undertaken on the basis of this knowledge.
In accordance with another feature of the invention, the blade or vane section encloses a circle with a maximum diameter, which maximum diameter defines a maximum section thickness, with a center distance vertical or straight line passing through the center of this circle intersecting the section chord at right angles and being at a center distance from the blade or vane leading edge point which is less than 32% of the length of the section chord and is, in particular, located between 15% and 30% of the length of the section chord. This geometrical feature implies a particular improvement in the properties of the compressor blade or vane with respect to the aerodynamic losses in flows with large Reynolds numbers and high degrees of turbulence.
In accordance with a further feature of the invention, the suction surface profile has a suction surface tangent at the suction surface intersection point and the pressure surface profile has a pressure surface tangent at a pressure surface intersection point with the reference vertical or straight line, the suction surface tangent and the pressure surface tangent enclosing between them a tangent angle of between 5° and 20°.
With the objects of the invention in view there is also provided a compressor blade or vane, comprising a blade or vane section having a blade or vane leading edge point; a blade or vane trailing edge point; a straight line section chord extending from the blade or vane leading edge point to the blade or vane trailing edge point and having a given length; a suction surface profile having a convex curvature and a pressure surface profile opposite the suction surface profile, each of the profiles connecting the blade or vane leading edge point and the blade or vane trailing edge point; a circle enclosed by the blade or vane section and having a center and a maximum diameter, the maximum diameter defining a maximum section thickness; and a center distance straight line passing through the center, intersecting the section chord at right angles and being spaced at a center distance from the blade or vane leading edge point, the center distance being less than 32% of the given length. The advantages of this compressor blade or vane follow in accordance with the above statements.
In accordance with another feature of the invention, the suction surface profile has a suction surface tangent at a suction surface intersection point with a reference vertical or straight line cutting the section chord at right angles at 5% of the length of the section chord and the pressure surface profile has a pressure surface tangent at a pressure surface intersection point with the reference vertical or straight line, the suction surface tangent and the pressure surface tangent enclosing between them a tangent angle of between 5° and 20°.
With the objects of the invention in view there is additionally provided a compressor blade or vane, comprising a blade or vane section having a blade or vane leading edge point; a blade or vane trailing edge point; a straight line section chord extending from the blade or vane leading edge point to the blade or vane trailing edge point and having a given length; a suction surface profile having a suction surface tangent at a suction surface intersection point with a reference straight line cutting the section chord at right angles at 5% of the given length; a pressure surface profile disposed opposite the suction surface profile and having a pressure surface tangent at a pressure surface intersection point with the reference straight line; and the suction surface tangent and the pressure surface tangent enclosing a tangent angle of between 5° and 20° between them.
The advantages of this compressor blade or vane follow correspondingly from the above statements.
In accordance with another feature of the invention, the blade or vane section encloses a circle with a maximum diameter, and the maximum diameter defines a maximum section thickness, in which case, with the designations:
D for the maximum section thickness,
L for the length of the section chord and
T for the t
Koeller Ulf
Moenig Reinhard
Greenberg Laurence A.
Lerner Herbert L.
Look Edward K.
Siemens Aktiengesellschaft
Stemer Werner H.
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