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Siemens : Patent Issued for Method for Profiling a Replacement Blade as a Replacement Part for an Old Blade for an Axial-Flow Turbomachine (USPTO 9771803)

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10/05/2017 | 07:30pm CET

By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Cornelius, Christian (Sprockhovel, DE); Matthias, Torsten (Mulheim an der Ruhr, DE), filed on August 14, 2012, was published online on September 26, 2017.

The assignee for this patent, patent number 9771803, is SIEMENS AKTIENGESELLSCHAFT (Munich, DE).

Reporters obtained the following quote from the background information supplied by the inventors: "A gas turbine, in particular a non-stationary gas turbine, usually has an operating life of about 30 years. During this period of time, technical innovations, particularly for improving the thermal efficiency of the gas turbine, have hitherto become commercially viable. It is desirable that an already installed gas turbine is equipped at least partially with these technical innovations, in order thereby to achieve a corresponding increase in efficiency in the gas turbine. To implement the technical innovations in the already installed gas turbine, it is customary to provide modified components which have the technical innovations and are exchanged with their older counterparts in the gas turbine. The aim is to exchange as small a number of components as possible in the gas turbine in order to keep the outlay in terms of upgrading and the costs of this as low as possible.

"The stationary gas turbine for power station use is conventionally designed in an axial type of construction. The compressor of the gas turbine usually has a plurality of stages arranged axially one behind the other in the throughflow direction, each stage comprising moving blades assigned to a rotor and forming a moving blade ring and guide blades forming a guide blade ring. The moving blades rotate, together with the rotor, with respect to the fixed guide blades, while, in particular, the fluidic efficiencies of the moving blades and guide blades determine the fluidic efficiency of the stage. It has been possible in recent years to achieve considerable improvements in stage efficiency, using numerical flow solvers in the profiling of the blades. Thus, it is desirable that, particularly for the compressor of the gas turbine, the existing blading is removed and is replaced with blading designed from modern standpoints. The rotor remains in the gas turbine, and therefore the mechanical interface between the blading and the rotor at the blade fastening remains unchanged.

"If, however, the profiling of the new blading leads to a change in the centers of gravity of the airfoils, the mechanical stress upon the blade fastening changes. As a rule, this leads to adverse loads upon the blade fastening, therefore the profiling of the new blading has to be coordinated with the maximum permissible load values of the blade fastening. As a rule, this results in restrictions in the profiling of the new blading, the result of this being that efficiency increases which can be achieved in principle cannot be implemented.

"Particularly where the compressor rotor blades are concerned, it became clear that, in profiling, introducing a rearward sweep in the lower half of the flow duct increases the aerodynamic performance of the compressor rotor blades. This, however, entails a corresponding displacement of the blades' centers of gravity and of the blade trailing edge in the direction of the downstream guide blade roll. Owing to this displacement of centers of gravity, the recently prevailing symmetry of the load upon the blade fastening within the blade grooves is impaired, so that the degree of rearward sweep is severely limited in the profile of the compressor rotor blades. In order nevertheless to provide the compressor rotor blades with the rearward sweep, the deviation of the stringing line of axial sections of the new blading compared with the stringing line of axial sections of the old blading was limited within a still permissible range. What was achieved thereby was that the load in the blade root and at the circumferential groove does not become inadmissibly high when the gas turbine is in operation. On account of this, however, an appreciable potential and efficiency improvement remained unused.

"This could be remedied by shortening the chord length of the blade root of the new blading. However, this measure would be disadvantageous in terms of the aerodynamic load bearing capacity and stability of the new blading and its structural integrity.

"US 2003/012645 A1 describes a method for retrofitting a guide blade, in which an existing guide blade is replaced by a new guide blade.

"WO 2009/103528 A2 discloses compressor blades having a sinusoidal sweep. The sinusoidal form of the sweep results in transition sweeps. This is intended to satisfy requirements with respect to increased efficiency and noise control"

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "An object herein is to provide a method for profiling a replacement blade as a replacement part for an old blade for an axial-flow turbomachine, a rotor blade and a stator blade for a gas turbine and also the gas turbine with the rotor blade and/or with the stator blade, the gas turbine having high thermodynamic efficiency.

"This object is achieved by means of the features of the independent claims. Preferred refinements of these are specified in the further patent claims.

"The method according to aspects of the invention for profiling a replacement blade as a replacement part for an old blade for an axial-flow turbomachine has the steps: acquisition of the hub contour geometry and casing contour geometry of the flow duct of the old blade which is tension-mounted on one side of the hub or casing and of the axial position of the center of gravity of the airfoil and/or of the maximum utilizable axial construction space of the old blade; design of the geometry of the airfoil of the replacement blade, the tension-mounting-side section of the airfoil of the replacement blade lying essentially at the same location as the tension-mounting-side section of the airfoil of the old blade, and the airfoil of the replacement blade being inclined at its leading edge upstream with respect to the tension mounting with a view to optimizing the stage efficiency, with the result that the airfoil has a rearward sweep; definition of a tension-mounting-near region of the airfoil of the replacement blade, in which region the positive influence of the rearward sweep upon the stage efficiency is classified as low; axial displacement of the airfoil portion, arranged outside the region, of the replacement blade upstream until the axial position of the center of gravity of the airfoil of the replacement blade coincides essentially with the axial position of the center of gravity of the airfoil of the old blade and/or the mechanical integrity of the replacement blade is achieved, utilizing the maximum utilizable axial construction space of the old blade, the leading edge being inclined downstream with respect to the tension mounting in the region from the tension-mounting-side section of the airfoil of the replacement blade as far as the displaced airfoil portion of the replacement blade, with the result that the airfoil has a transition sweep in this region.

"Preferably, the axial-flow turbomachine is a compressor and/or a turbine of a gas turbine. The rotor blade according to aspects of the invention for the gas turbine is the replacement blade which is designed by means of the method according to the invention. Furthermore, the stator blade according to aspects of the invention is the replacement blade which is designed by means of the method according to the invention. The gas turbine according to aspects of the invention has the rotor blade and/or the stator blade.

"The compressor blade according to aspects of the invention has an airfoil which has a leading edge, the airfoil being inclined at the leading edge upstream with respect to the tension mounting of the airfoil with a view to optimizing the stage efficiency, with the result that the airfoil has a rearward sweep, a tension-mounting-near region of the airfoil being defined, in which the positive influence of the rearward sweep upon stage efficiency is classified as low, the leading edge being inclined downstream with respect to the tension mounting in the region of the airfoil, with the result that the airfoil has a transition sweep in this region.

"The tension-mounting-near region of the airfoil of the replacement blade in which the positive influence of the rearward sweep upon the stage efficiency is classified as low corresponds preferably to the radial extent of the hub boundary layer or the tension-mounting-side secondary flow. The region is preferably 5% to 15% of the blade height of the replacement blade.

"The chord length of the blade root of the replacement blade preferably corresponds essentially to the chord length of the blade root of the old blade. Furthermore, the method preferably has the step: design of the geometry of the airfoil of the replacement blade, the airfoil being inclined at its leading edge upstream with respect to the side facing radially away from the tension mounting with a view to optimizing the stage efficiency, with the result that the airfoil has a forward sweep outside the rearward sweep. Moreover, it is preferable that the rearward sweep of the leading edge of the replacement blade extends only in the radial tension-mounting-side half of the flow duct.

"The transition sweep is designed according to aspects of the invention as a forward sweep. As a result of this, the center of gravity of the airfoil of the replacement blade is displaced forward in the flow direction, with the result that the center of gravity of the airfoil of the replacement blade assumes the position of the center of gravity of the airfoil of the old blade and/or the mechanical integrity of the replacement blade is achieved, utilizing the maximum utilizable axial construction space of the old blade. In the gas turbine, the old blade is replaced by the replacement blade.

"In this case, the old blade is demounted, for example, from a rotor of the gas turbine and the replacement blade is mounted in place of the old blade. The old blade or replacement blade is usually tension-mounted with a form fit on the rotor of the gas turbine. Since the center of gravity of the replacement blade lies essentially in the same axial position as the center of gravity of the old blade and/or the mechanical integrity of the replacement blade is achieved, utilizing the maximum utilizable axial construction space of the old blade, the stress upon the form-fit fastening of the replacement blade is essentially equal to the load upon the form-fit fastening of the old blade. This is advantageous particularly because, by the rearward sweep being provided in the profiling of the replacement blade, to achieve high stage efficiency the mechanical load upon the blade fastening when the gas turbine is in operation with the replacement blade is essentially equal to that arising when the gas turbine is in operation with the old blade.

"The transition sweep is restricted locally to the region which is near the tension mounting and which impairs the positive influence of the rearward sweep upon stage efficiency to only a slight extent. As a result, the aerodynamic influence of the transition sweep is low, whereas structural disadvantages of a blade provided as standard with a rearward sweep are reduced. The transition sweep is preferably limited to a region of 5% to 15% of the blade height of the replacement blade. The benefit of the rearward sweep can thus be utilized in the range of higher flow velocities outside 5% to 15% of the blade height of the replacement blade. Moreover, in the rotor blade according to aspects of the invention, the distance from a downstream conventional stator blade is greater than if a rotor blade were provided in the customary way with the rearward sweep and without the transition sweep. Consequently, excitation caused by aerodynamic forces brought about by the rotation of the rotor blade according to aspects of the invention is slight."

For more information, see this patent: Cornelius, Christian; Matthias, Torsten. Method for Profiling a Replacement Blade as a Replacement Part for an Old Blade for an Axial-Flow Turbomachine. U.S. Patent Number 9771803, filed August 14, 2012, and published online on September 26, 2017. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9771803.PN.&OS=PN/9771803RS=PN/9771803

Keywords for this news article include: SIEMENS AKTIENGESELLSCHAFT.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2017, NewsRx LLC

(c) 2017 NewsRx LLC, source Science Newsletters

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