Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Plural distributing means immediately upstream of runner
Reexamination Certificate
2000-03-08
2002-03-12
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Plural distributing means immediately upstream of runner
C416S22300B
Reexamination Certificate
active
06354798
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a blade for a fluid-flow or turbo machine being directed along a blade axis and having a root end region, a tip end region and a center region disposed therebetween along the blade axis, and a cross-sectional region at right angles to the blade axis. The invention also relates to a steam turbine, in particular a high-pressure or intermediate-pressure steam turbine.
The efficiency of a fluid-flow machine, in particular of a steam turbine, is reduced by flow losses which occur. An improvement in the efficiency and thus also a reduction of such flow losses is dealt with, for example, in an article entitled “Advanced Steam Turbine Technology for Improved 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. The development of three-dimensional turbine blades with regard to various flow losses, such as gap losses, losses due to the blade profile, and losses in the end regions of the turbine blade (end wall losses), is described in that article. An inclination of the turbine blade in the circumferential direction is specified in order to reduce the last-mentioned losses. An inclination of the turbine blade in the region of the blade tip as well as in a hub region of the turbine blade leads to a bent blade, in which case such a bend, due to the mechanical properties, can only be used in guide blades. Furthermore, it is stated globally in the article that twisting of the blade also has an effect on the inclination of the blade, so that the blade inclination, the blade twist as well as the blade profile are available in a three-dimensional structure in the end regions of the blade.
European Patent Application EP 0 704 602 A2, corresponding to U.S. Pat. No. 5,779,443, concerns the structure of a turbine guide blade in an intermediate stator of a steam turbine directed along a turbine axis. The blade in that case extends along a radially directed blade axis and has a pressure side and a suction side as well as an inlet edge and an outlet edge. In that case the blade is shaped along the radial direction in such a way that the pressure side has a convex curvature from a blade root region to a blade tip region lying opposite the blade root region along the blade axis.
In a particularly preferred structure, the curvature is achieved by a setting angle (bitangential angle) on radially successive, cross-sectional profiles at a distance from one another being varied parabolically with respect to the turbine axis by an appropriate rotation of the cross-sectional profiles about a fixed common outlet edge. In this way, the channel width for the steam can be reduced in the blade tip region and in the blade root region and can be increased in a blade center region lying therebetween. That leads to a shifting of part of the steam mass flow, away from the two loss-affected marginal regions of the turbine guide blade.
An increase in the efficiency of a steam turbine, in particular of a high-pressure or intermediate-pressure steam turbine, is likewise dealt with in an article entitled “Modern Blade Design for Improving Steam Turbine Efficiency” by M. Jansen and W. Ulm in “VDI Berichte” No. 1185, 1995, pages 277-290. The effect of various flow losses for various steam turbines is explained therein. A reduction in the flow losses is achieved by a special configuration of the turbine blade. In that case, the three-dimensionally constructed turbine blades have an inclination in a root region and a tip region of the turbine blade. In the article, a comparison is made between the flow losses of those three-dimensionally constructed turbine blades and entirely cylindrical blades.
Such cylindrical blades have pressure and suction sides parallel to the blade axis and therefore have neither a twist nor an inclination. So-called twisted turbine blades, which have an increasing twist and a changing blade profile over their height, are described as a further alternative to the three-dimensionally constructed turbine blades.
German Published, Non-Prosecuted Patent Application DE 31 48 995 A1 describes an axial-flow turbine, such as a steam turbine or a gas turbine, with a multiplicity of guide blades disposed at a distance from one another along the circumference. The guide blades being used are twisted over their height and have a changing inlet angle. The changing of the inlet angle increases continuously in an overlinear manner in the region of the tip of the guide blade, as from a certain height measured from the blade root. The twisting likewise increases continuously over the height of the guide blade. The cross-sectional profile of the guide blade changes continuously from the blade root to the blade tip, with the guide blade becoming increasingly slender. Further changes concerning the outlet angle, the size and the shape of the guide blade are taken into account over the height of the guide blade in the shaping of the guide blade.
German Published, Prosecuted Patent Application 1 168 599 specifies an axial-flow compressor with moving blades and/or guide blades, which have a cross-section that is changed in the region of wall surfaces to compensate for an influence on the flow brought about by those wall surfaces. In the axial-flow compressor, inlet guide blades are disposed along the gas flow path upstream of the moving blades and guide blades. Those inlet guide blades have a convex cross-section, other than in the region of the walls. A middle part of the blade, with the convex cross-section, changes over in each wall region into the un-convex cross-sectional profile in the wall regions in a smooth and constantly curved surface. The cross-sectional profiles of the blade aerofoil consequently change continuously over the height of the inlet guide blade. The inlet angle remains constant over the entire height of the inlet guide blade.
German Published, Prosecuted Patent Application 28 41 616 contains a description of a guide blade rim for an axial-flow turbine with guide blades. The guide blades are disposed between an inner ring and an outer ring and the profile thickness of the blade aerofoil changes proportionally to the blade pitch. In that case the changing of the blade profile over the height of the guide blade does not take place by a change occurring in the shape of the leading edge (pressure side), but instead the projection on the trailing edge gradually increases in size over the height, with a simultaneous increase in the thickness of the guide blade.
The changing of the profile is carried out in that case by an increase in the thickness of the guide blade, while its chord length remains the same. A guide blade rim of that kind can be used in the case of steam turbines, gas turbines and compressors.
German Published, Non-Prosecuted Patent Application DE 42 28 879 A1 specifies an axial-flow turbine having at least one row of curved guide blades. The blade curvature has the effect that both the inlet edge and the outlet edge of the guide blades do not lie in one and the same axial plane. The curvature of the blades in that case runs at right angles to the chord, which is achieved by a displacement of the profile sections both in the circumferential direction and in the axial direction. The guide blades taper from a turbine casing wall (cylinder) to a turbine hub, so that their cross-section changes correspondingly, with the blade profile remaining essentially unchanged over the height of the blade. Apart from the curvature and the tapering, a twisting of the blade aerofoil is also carried out over the blade length of the guide blade, in order to allow for the changing of the circumferential speed of the moving blades following the guide blade over the channel height. Consequently, an adaptation of the blade aerofoil takes place by a deflection of the center of gravity of the profile sections at right angles to the profile chord (curvature or bending), that is to say a simultaneous axial deflection and circumferential deflection, combin
Greenberg Laurence A.
Lerner Herbert L.
Ryznic John E.
Stemer Werner H.
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