Abstract:
An example method of controlling a flow enhancement device includes providing a flow enhancement device that is configured stabilize a flow of air near a nacelle. The flow enhancement device has a first setting and a second setting that provides more stabilization than the first setting. The method includes monitoring parameters of a turbomachine to determine the stability of the flow of air near the nacelle. The method also adjusts the flow enhancement device between the first setting and the second setting based on the monitoring.

Description:
BACKGROUND 
       [0001]    This disclosure relates generally to flow stability enhancement devices for turbomachines. More particularly, this disclosure relates to controlling operation of the flow stability enhancement devices. 
         [0002]    Air typically moves into a turbomachine through a nacelle. The air passes through a fan section of the turbomachine and is then compressed and combusted. The products of the combustion are expanded to rotatably drive a turbine section of the turbomachine. 
         [0003]    As known, the turbomachine can become damaged if air moving into the turbomachine is unstable and has a substantially uneven air pressure distribution. The fan section is particularly prone to such damage. Accordingly, the nacelles of many turbomachines have a geometry that stabilizes and smoothes uneven air pressure distributions. Such nacelles are designed to passively influence air pressure distributions. That is, the geometry of the nacelle achieves the desired distortion of air to provide the turbomachine with a more uniform flow. 
         [0004]    Some turbomachine designs, however, include nacelles having a geometry that ineffectively stabilizes and smoothes uneven air pressure distributions. A flow stability enhancement device is often added to such nacelles. In these designs, the flow stability enhancement device helps stabilize and smooth uneven air pressure distributions rather than relying exclusively on the geometry of the nacelle. 
         [0005]    Boundary layer blowing devices and boundary layer suction devices are example flow stability enhancement devices. Boundary layer blowing devices require a supply of compressed air. Boundary layer suction devices require a vacuum pump. Operating such devices affects the efficiency of the turbomachine. 
       SUMMARY 
       [0006]    A method of controlling a flow enhancement device according to an exemplary aspect of the present disclosure includes, among other things, providing a flow enhancement device that is configured stabilize a flow of air near a nacelle. The flow enhancement device has a first setting and a second setting that provides more stabilization than the first setting. The method also includes monitoring parameters of a turbomachine to determine the stability of the flow of air near the nacelle, and adjusting the flow enhancement device between the first setting and the second setting based on the monitoring 
         [0007]    In a further non-limiting embodiment of the foregoing method of controlling a flow enhancement device, the first setting may correspond to a flow enhancement device that provides no stabilization 
         [0008]    In a further non-limiting embodiment of either of the foregoing methods of controlling a flow enhancement device, the adjusting may include selectively increasing or decreasing the flow enhancement device between the first setting and the second setting. 
         [0009]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow enhancement device, the flow enhancement device may comprise a boundary layer blowing device. 
         [0010]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow enhancement device, the flow enhancement device may comprise a boundary layer suction device. 
         [0011]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow enhancement device, the turbomachine may be a gas turbine engine. 
         [0012]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow enhancement device, the method may include using the parameters to establish an inlet stability and distortion parameter that quantifies the distortion of the flow of air, and adjusting the flow enhancement device based on the inlet stability and distortion parameter. 
         [0013]    A method of controlling a flow of air entering a fan section of a turbomachine according to another exemplary aspect of the present disclosure includes, among other things, influencing a flow of air near a nacelle of a turbomachine to compensate for a distortion of the flow of air, and adjusting the influencing during operation of the turbomachine based on operating conditions of the turbomachine. 
         [0014]    In a further non-limiting embodiment of the foregoing method of controlling a flow of air entering a fan section of a turbomachine, the influencing may comprise directing air from a compressed air supply through an arrangement of apertures established in the nacelle, the air moving through the apertures radially inwardly toward an axis established by the nacelle 
         [0015]    In a further non-limiting embodiment of either of the foregoing methods of controlling a flow of air entering a fan section of a turbomachine, the influencing may comprise drawing air radially away from an axis though an arrangement of apertures established in the nacelle. 
         [0016]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow of air entering a fan section of a turbomachine, the adjusting may comprise activating or deactivating a flow enhancing device. 
         [0017]    In a further non-limiting embodiment of any of the foregoing methods of controlling a flow of air entering a fan section of a turbomachine, the operating conditions may be used to establish an inlet stability and distortion parameter that quantifies the distortion of the flow of air. The adjusting may be based on the inlet stability and distortion parameter. 
         [0018]    A turbomachine control arrangement according to another exemplary aspect of the present disclosure includes, among other things, a nacelle of a turbomachine, a flow enhancement device configured to selectively influence a flow of air near the nacelle, and a controller configured to adjust an amount of influence provided by the flow enhancement device. 
         [0019]    In a further non-limiting embodiment of the foregoing turbomachine control arrangement, the flow enhancement device may comprise an arrangement of apertures established in the nacelle. The apertures may be configured to communicate air radially inwardly toward an axis established by the nacelle to influence the flow of air through the nacelle. 
         [0020]    In a further non-limiting embodiment of the foregoing turbomachine control arrangement, the compressed air supply may provide the air that is communicated through the apertures. 
         [0021]    In a further non-limiting embodiment of the foregoing turbomachine control arrangement, the flow enhancement device may comprise an arrangement of apertures established in the nacelle, the apertures configured to communicate air radially away from an axis established in the nacelle to influence the flow of air through the nacelle. 
         [0022]    In a further non-limiting embodiment of the foregoing turbomachine control arrangement, the controller may adjust the flow enhancement device to provide more influence over the flow of air when the air entering the nacelle is less stable than when the air entering the nacelle is more stable. 
         [0023]    In a further non-limiting embodiment of the foregoing turbomachine control arrangement, the turbomachine may be a gas turbine engine. 
         [0024]    These and other features of the disclosed examples can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0025]      FIG. 1  shows a partially exploded perspective view of an example turbomachine that has a flow enhancement device. 
           [0026]      FIG. 2  shows a schematic view of the  FIG. 1  turbomachine. 
           [0027]      FIG. 3  shows a flow of an example method used to control the flow enhancement device in the  FIG. 1  turbomachine. 
           [0028]      FIG. 4  graphically shows the performance of the  FIG. 1  turbomachine. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Referring to  FIGS. 1 and 2 , an example turbomachine  10  is an engine used to propel an aircraft (not shown). In this example, the turbomachine  10  is a gas turbine engine that includes a nacelle  14  mounted adjacent a fan section  18 . Both the nacelle  14  and the fan section  18  are circumferentially disposed about an engine axis X. 
         [0030]    During operation, air is pulled into the turbomachine  10  by the fan section  18 . The air is then pressurized, mixed with fuel, and burned in a combustor. Turbines of the turbomachine  10  extract energy from the hot combustion gases flowing from a combustor of the turbomachine. The compressed air is stored in a compressed air supply  20 , which may include bleed air from the fan section  18 . Some of the compressed air is then distributed throughout the aircraft as is known. 
         [0031]    In this example, some of the compressed air in the compressed air supply  20  is communicated to a flow enhancement device  24  at least partially established within the nacelle  14 . The example flow enhancement device  24  is configured to influence a flow of air  28  moving through the nacelle  14  into the fan section  18  of the turbomachine  10 . Influencing the flow of air  28  includes, for example, stabilizing and smoothing uneven air pressure distributions in the flow of air  28 . A person having skill in this art and the benefit of this disclosure would understand the benefits associated with influencing the flow of air  28  through the nacelle  14  using the flow enhancement device  24 . 
         [0032]    The example flow enhancement device  24  is a boundary layer blowing device that communicates a small amount of air from the compressed air supply  20  through an arrangement of apertures established in the nacelle  14 . The air moves through the apertures toward the axis X. In another example, the flow enhancement device  24  is a boundary layer suction device that pulls air radially away from the axis X. A vacuum pump (not shown) could be used to power such a boundary layer suction device. Still other examples include other types of flow enhancement devices. 
         [0033]    In this example, controller  32  controls a flow of compressed air  36  from the compressed air supply  20  to the flow enhancement device  24 . The controller  32  adjusts a valve  34  to control the flow of compressed air  36  in this example. The example controller  32  includes a memory portion  40  and a processor  44 . The processer  44  is configured to execute a program stored in the memory portion  40 . 
         [0034]    Referring to  FIG. 3  with continuing reference to  FIGS. 1 and 2 , a flow enhancement device control program  52  utilizes data collected from the aircraft. Data utilized by the program  52  may be collected by various means. A plurality of sensors  48 , for example, may be used to provide data to the controller  32 . 
         [0035]    In this example, the program  52  executed by the processor  44  receives engine parameters  56  as inputs. Example engine parameters  56  includes a corrected rotational speed (N1C) and an engine pressure ratios (EPR). These parameters are typically referred to as the thrust command. Other parameters could be included as well. 
         [0036]    The program  52  also receives aircraft parameters  60  as inputs. Example aircraft parameters  60  include an angle of attack α, a side-to-side command or yaw β, and a Mach number M n . The aircraft parameters  60  are typically parameters that are used to control the dynamics of flight. The aircraft parameters  60  could include other information as is known. 
         [0037]    Providing the engine parameters  56  and the aircraft parameters  60  enables the processer  44  to establish an inlet stability and distortion parameter at a step  64 . The program  52  determines whether the flow enhancement device  24  should be activated or deactivated at a decision step  64 . 
         [0038]    In one example, the program  52  the turns the flow enhancement device  24  on or off at a step  68 . The inlet stability and distortion parameter effectively quantifies the needed amount of flow enhancement. 
         [0039]    In some examples, the effect of the flow enhancement device  24  is varied based on the inlet stability and distortion parameter from the step  64 . That is, the flow enhancement device  24  may be adjusted to alter the flow a relatively small amount or a relatively large amount depending on the inlet stability and distortion parameter. 
         [0040]    In one example, the flow enhancement device  24  is not needed when the turbomachine  10  (and the aircraft) are at a cruising altitude. 
         [0041]    Many computing devices can be used to implement various functions described herein. For example, the controller  32 , which includes the processor  44  and the memory portion  40 , may comprise a portion of a dual architecture micro server card. 
         [0042]    In terms of hardware architecture, the controller  32  can additionally include one or more input and/or output (I/O) device interface(s) that are communicatively coupled via a local interface. The local interface can include, for example but not limited to, one or more buses and/or other wired or wireless connections. The local interface may have additional elements, which are omitted for simplicity, such as additional controllers, buffers (caches), drivers, repeaters, and receivers to enable communications. Further, the local interface may include address, control, and/or data connections to enable appropriate communications among the aforementioned components. 
         [0043]    The example processor  44  used in the controller  32  executes software code, particularly software code stored in the memory portion  40 . The processor  44  can be a custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the computing device, a semiconductor based microprocessor (in the form of a microchip or chip set) or generally any device for executing software instructions. 
         [0044]    The memory portion  40  can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). Moreover, the memory may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory can also have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor. 
         [0045]    The software in the memory portion  40  may include one or more additional or separate programs, each of which includes an ordered listing of executable instructions for implementing logical functions. A system component embodied as software may also be construed as a source program, executable program (object code), script, or any other entity comprising a set of instructions to be performed. When constructed as a source program, the program is translated via a compiler, assembler, interpreter, or the like, which may or may not be included within the memory. 
         [0046]    The Input/Output devices that may be coupled to system I/O Interface(s) may include input devices, for example but not limited to, a keyboard, mouse, scanner, microphone, camera, proximity device, etc. Further, the Input/Output devices may also include output devices, for example but not limited to, a printer, display, etc. Finally, the Input/Output devices may further include devices that communicate both as inputs and outputs, for instance but not limited to, a modulator/demodulator (modem; for accessing another device, system, or network), a radio frequency (RF) or other transceiver, a telephonic interface, a bridge, a router, etc. 
         [0047]    Referring to  FIG. 4  with continuing reference to  FIGS. 2 and 3 , information from a performance chart  76  may be used by the inlet stability and distortion parameter at the step  64  to determine when to activate (or deactivate) the flow enhancement device  24 . 
         [0048]    The performance chart  76  shows a performance curve  80  of the turbomachine  10  at a given angle of attack α, crosswind velocity β, and mach number M n . The flow enhancement device  24  is activated when the curve  80  exceeds a threshold value  84 . That is, the flow enhancement device  24  is activated when the inlet distortion is above the threshold value  84 . When the inlet distortion is below the threshold value  84 , the flow enhancement device  24  is deactivated. 
         [0049]    Features of the disclosed examples include avoiding parasitic losses associated with flow enhancement devices by shutting these devices off when not required. 
         [0050]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.