The present invention generally involves a system and method for operating a compressor. In particular embodiments of the present invention, the system and method may independently vary the position of stator vanes in different stages.
Gas turbines are widely used in industrial and commercial operations. A typical gas turbine includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. The compressor generally includes alternating stages of circumferentially mounted stator vanes and rotating blades. The stator vanes typically attach to a casing surrounding the compressor, and the rotating blades typically attach to a rotor inside the compressor. Ambient air enters the compressor, and each stage of stator vanes directs the airflow onto the following stage of rotating blades to progressively impart kinetic energy to the working fluid (air) to bring it to a highly energized state. The working fluid exits the compressor and flows to the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases exit the combustors and flow to the turbine where they expand to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
During various operating conditions, it may be desirable to adjust the angle of the stator vanes with respect to an axial centerline of the compressor. For example, the stator vanes may be aligned further from the axial centerline of the compressor to suppress the onset of compressor stall at lower rotational speeds associated with start up or shutdown of the compressor. Conversely, the stator vanes may be aligned closer to the axial centerline of the compressor to allow more working fluid to flow through the compressor and increase the power output of the gas turbine during heavy or sudden increases in electrical demand on the generator.
U.S. Pat. Nos. 5,281,087; 6,551,057; and 6,794,766, assigned to the same assignee as the present application, disclose an electromechanical or hydraulic system for varying the position of stator vanes. In each patent, a single actuator connects to multiple stages of stator vanes to vary the position of the stator vanes with respect to the axial centerline of the compressor. However, the length and width of the stator vanes generally decreases along the axial length of the compressor. As a result, the length of travel for both the actuator and the stator vanes varies by stage. In addition, the cumulative manufacturing tolerances associated with both the actuator and the stator vanes increases proportionally as the size of the stator vanes increases. Therefore, the ability to precisely position stator vanes in different stages using a single actuator is difficult, and a system and method for independently varying the position of stator vanes in different stages would be useful.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a compressor that includes a first plurality of stator vanes having a first position and a second plurality of stator vanes, downstream from the first plurality of stator vanes, having a second position. The compressor further includes first means for adjusting the first position of the first plurality of stator vanes separately from the second position of the second plurality of stator vanes and second means for adjusting the second position of the second plurality of stator vanes separately from the first position of the first plurality of stator vanes.
Another embodiment of the present invention is a compressor that includes a first stage of stator vanes having a first position and a second stage of stator vanes downstream from the first stage of stator vanes having a second position. A first actuator is engaged with the first stage of stator vanes, and a second actuator is engaged with the second stage of stator vanes.
The present invention may also include a method for operating a compressor. The method includes adjusting a first position of a first plurality of stator vanes and adjusting a second position of a second plurality of stator vanes separately from the first position of the first plurality of stator vanes.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.
Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Embodiments within the scope of the present invention provide a system and method for varying the position of stator vanes in a compressor. In particular embodiments, the system may adjust the position of stator vanes in one stage separately and/or independently from the position of stator vanes in another stage. As a result, embodiments of the present invention provide one or more aerodynamic, mechanical, and/or control benefits over existing variables stator vanes systems.
The compressor 10 may further include first means 24 and second means 26 for separately and/or independently adjusting the position of the stator vanes 12 in various stages. For example, as shown in
In the particular embodiment shown in
In the particular embodiment shown in
As shown in
At block 86, the control system 80 generates position commands 88, 90 that reflect pre-programmed positions for the downstream stator vanes 12 and first stage stator vanes 12, respectively, based on the speed signal 82 and the operating mode signal 84. At block 92, the control system 80 compares the position command 88 for the downstream stator vanes 12 with a feedback signal 94 for those stator vanes 12 to produce an error signal 95 that reflects the amount of adjustment needed to move the downstream stator vanes 12 to the pre-programmed position. At block 96, a control gain may be applied to the error signal 95 to adjust the error signal 95 according to the particular stage of stator vanes 12 being controlled, and the resulting combination may be provided as a control signal 98 to the second means 26 to re-position the downstream stator vanes 12. The actual position of the downstream stator vanes 12 may be measured by a linear position sensor 100, such as an LVDT position sensor to provide the feedback signal 94.
Substantially simultaneously, at block 102, the control system 80 combines the position command 90 for the first stage stator vanes 12, a feedback signal 104 for those stator vanes 12, and the control signal 98 provided to the second means 26 to determine what, if any, adjustment is needed for the position of the first stage stator vanes 12. The comparison results in an error signal 106 that reflects the amount of adjustment needed to move the first stage stator vanes 12 to the pre-programmed position, and the error signal 106 may be provided to the first means 24 to re-position the first stage stator vanes 12. The actual position of the first stage stator vanes 12 may be measured by a linear position sensor 108, such as, for example an LVDT position sensor, to provide the feedback signal 104.
The embodiments previously described with respect to
The system and methods disclosed herein are believed to provide several aerodynamic and control enhancements to existing compressor operating schemes that will improve compressor stability over a wide range of operating conditions, including startup/shutdown transients, off-line water wash, power turn down, and hot day output operations. For example, an anticipated benefit of various embodiments of the present invention may be the ability to clear compressor rotating stall at lower rotational speeds during the startups and to suppress the onset of compressor rotating stall to lower rotational speeds during the shutdowns. Minimizing the amount of time that the compressor experiences rotating stall during startup and shutdown operations reduces the vibratory stresses on the stator vanes 12 and rotating blades 14, thus enhancing the life and durability of the compressor.
Another anticipated benefit may be improved water ingestion during off-line water wash operations. Specifically, opening the first stage stator vanes 12 separately and/or independently from downstream stator vanes 12 may improve the ingestion of injected water wash solutions while avoiding compressor stalls. Conversely, during power turn down operations, closing the first stage stator vanes 12 separately and/or independently from the downstream stator vanes 12 may enhance the power turn down range by minimizing the compressor efficiency fall-off. Another anticipated benefit of embodiments within the scope of the present invention may be the ability to open the first stage stator vanes 12 separately and/or independently from the downstream stator vanes 12 to increase the airflow through the compressor during high ambient temperature days to compensate for the reduced density of the airflow associated with higher ambient temperatures.
Embodiments within the scope of the present invention may provide several mechanical benefits as well. For example, actuators that separately and/or independently position different-sized stator vanes 12 may have fewer joints and connections, reducing the cumulative manufacturing tolerances and wear associated with the actuators. The reduced cumulative manufacturing tolerances result in smaller vane angle errors. Alternately, the reduced cumulative manufacturing tolerances may allow larger individual tolerances without increasing the vane angle errors. In addition, the first and largest stage of stator vanes typically moves the farthest between extreme positions, and having one actuator control different sized stator vanes in different stages potentially creates a non-linear relationship with the smaller stator vanes in other stages that may result in larger vane angle errors. Dedicating an actuator to separately and/or independently adjust the position of the largest stage of stator vanes effectively isolates any non-linear relationship from the smaller stator vanes in other stages.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
The present application is a continuation of co-pending U.S. patent application Ser. No. 12/956,461, filed Nov. 30, 2010, the entire disclosure of which is hereby incorporated by reference herein.
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English translation of Request for Invalidation of Chinese Patent No. 201210138743.6 (equivalent of U.S. Pat. No. 9,068,470), which was filed with the Patent Reexamination Board of the Patent Office of the the State Intellectual Property Office of the People's Republic of China dated Mar. 13, 2018. |
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Number | Date | Country | |
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Parent | 12956461 | Nov 2010 | US |
Child | 15195081 | US |