专利汇可以提供Asymmetric compressor air extraction method专利检索,专利查询,专利分析的服务。并且A method to mistune rotating stall aerodynamics by preventing the formation of coherent unsteady loads. Compressor air is extracted in an asymmetric circumferential pattern. The asymmetric bleed pattern disrupts the rotating stall cell rotational pattern, preventing the formation of a coherent aerodynamic excitation.,下面是Asymmetric compressor air extraction method专利的具体信息内容。
What is claimed is:
Power generation industrial axial flow gas turbines are designed to optimally operate at a fixed rotational speed and output. In addition, traditional axial flow industrial gas turbine compressors have limited variable stage geometry and air extractions. These three factors, fixed speed operation, limited variable stage geometry and limited extractions lead to significant off-design aerodynamic conditions during start-up and shutdown operations. Rotating stall occurs in axial flow compressors during these off-design operations.
Rotating stall manifests itself as local stall cells that rotate at about half the wheel speed. These cells provide coherent unsteady aerodynamic loads on both the rotor and stator blades. As the rotor changes speed, the stall cell count changes thereby setting up different nodal diameters. The vibratory response on the rotor and stator blades from the rotating stall aerodynamic loads may lead to increased sensitivity of normal blade damage and premature failures.
The invention improves axial flow compressor rotor and stator blade durability by eliminating or reducing the coherent aerodynamic forces created by rotating stall. More specifically, the invention provides a method to mistune the rotating stall aerodynamics thereby preventing the formation of coherent unsteady loads.
The invention may be embodied in a method of controlling air flow in a compressor comprising: flow disturbances created by part speed or off-design operation; extracting flow at a series of circumferentially asymmetric spaced positions at chosen axial portions of the compressor, thereby creating an extraction pattern to act against flow disturbances.
The invention may also be embodied in a method of controlling air flow in a compressor comprising: actuating extraction of compressor air, asymmetrically about a circumference of said compressor casing to act against a disturbance such as rotating stall.
Power generation industrial axial flow gas turbines are designed to optimally operate at a fixed rotational speed and output. In addition, traditional axial flow industrial gas turbine compressors have limited variable stage geometry and air extractions. These three factors lead to significant off-design aerodynamic conditions during start-up and shutdown operations. Rotating stall can occur in axial flow compressors during these off-design operations.
Rotating stall, schematically presented in
Improved axial flow compressor blade durability results from eliminating or reducing the coherent aerodynamic forces created by rotating stall. Reduction in these aerodynamic vibratory loads increases blade damage tolerance to normal operation damage such as tip rubs, corrosion and leading edge foreign object damage.
This invention improves axial flow compressor rotor and stator blade durability by eliminating or reducing the aerodynamic excitation on axial flow compressor rotor and stator blades from rotating stall. More specifically, the invention provides a method to mistune the rotating stall aerodynamics by preventing the formation of coherent unsteady loads.
Thus and more specifically, a novel manner of eliminating or reducing disturbances such as rotating stall in compressors is proposed, e.g., at a series of circumferentially spaced positions at one or more a chosen axial positions (stage) compressor air is selectively bled asymmetrically, in a circumferentially selective manner dependent upon the origin of the variations, to act against the rotating stall flow disturbances. In such a case, the air extraction process would be initiated, that is to say a rotating stall condition or potential stall condition would be countered by asymmetric extraction of air. No sensors are required as this is an operationally identified phenomenon—part speed and/or part load.
In an example embodiment of the invention, as schematically illustrated in
As mentioned above, to prevent the formation of coherent unsteady loads and thereby mistune the rotating stall aerodynamics, the invention provides an assembly wherein compressor air is extracted through a series of generally shaped holes or slots 16 on the outer diameter flow path wall 18 in an asymmetric circumferential pattern as the illustrated by way of example in
As is understood from the foregoing, the asymmetric bleed features include, at each specified axial location 20 on the compressor case 18, asymmetrically spaced extractions 16, within a specified arc length θarc at specified circumferential locations with defined extraction shapes, to provide the required total extraction flow. In an example embodiment, the arc length θarc is about 90 degrees.
For a split case application, the extractions 16 are placed on the top half case, thereby providing for easier field retrofit as well as improved accessibility for extraction manifolds and piping (not illustrated). As understood from the foregoing, the multi-stage extractions would require an extraction manifold to route the flow away from the unit.
Thus, the invention can provide the following benefits: 1) reduce/eliminate coherent unsteady aerodynamic excitation on blades; 2) retrofitable to existing engines with split case designs; 3) enabler for advanced aerodynamic blades; 4) improves compressor blade durability by increasing damage tolerance to tip rubs, corrosion pits and leading edge damage.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
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