Abstract:
An aeroengine is provided with a splitter apparatus disposed in a section of ain inlet duct. The splitter apparatus can be actuated from a stowed position to a deployed position to allow splitter(s) to selectively move from out of the inlet flow to a position extending into the inlet duct to divide the inlet flow into multiple passages.

Description:
TECHNICAL FIELD  
       [0001]    The described subject matter relates generally to gas turbine engines, and more particularly to controlling noise in aircraft. 
       BACKGROUND OF THE ART  
       [0002]    Future turboprop aircraft will be larger, heavier and with more powerful engines. Traditionally the aircraft engine industry has pointed to the propellers as the dominant noise source, but with modern electronic propeller control strategies, propeller contribution to the total noise of the engine is reduced and compressor noise propagating from the engine intake can become the dominant source of noise. This is particularly true during the approach phase of flight just before landing. At approach conditions the performance of the engine inlet is less important than in other flight phases since the engine operates at lower power and the conditions are not maintained for long enough to be significant for block fuel burn. Consequently, the industry has made a great effort to improve inlet noise attenuation capabilities, particularly under flight approach conditions. 
         [0003]    Accordingly, there is a need to provide an improved engine inlet system for aircraft gas turbine engines. 
       SUMMARY  
       [0004]    In one aspect, there is provided an aeroengine having a compressor inlet system, comprising an inlet duct for directing an air flow to a compressor, and an inlet splitter moveable between a stowed position in which the splitter is disposed substantially out the air flow so that the inlet duct provides substantially only one passage to the compressor, and a deployed position in which the splitter is disposed in the inlet duct to divide the inlet duct into at least two passages to the compressor, and wherein at least one surface of the splitter exposed to the air flow includes an acoustic treatment configured to reduce aeroengine noise. 
         [0005]    In another aspect, there is provided an aeroengine having an inlet system, the inlet system comprising an inlet duct for directing an air flow from an inlet opening to a compressor rotor, and an inlet splitter apparatus disposed within a section of the inlet duct and having at least one splitter plate pivotally mounted to a wall of the inlet duct about an axis substantially parallel to a direction of the air flow, the at least one splitter plate being pivotally moveable between a deployed position in which the at least one splitter plate extends from the wall of the inlet duct into the inlet duct to expose both sides of the plate to the air flow, and a stowed position in which one side of the at least one plate is positioned against the wall of the inlet duct and the other side of the at least one plate is substantially exposed to the air flow. 
         [0006]    In a further aspect, there is provided an aeroengine having an inlet system, the inlet system comprising an inlet duct for directing an air flow from an inlet opening to a compressor rotor, the inlet duct having a section including opposed and substantially flat first and second peripheral walls, an inlet splitter apparatus disposed within said section of the inlet duct and including first and third splitter plates pivotally mounted to the first peripheral wall about respective first and third axes substantially parallel to a direction of the air flow, and second and fourth splitter plates pivotally mounted to the second peripheral wall about respective second and fourth axes substantially parallel to the direction of the air flow, the splitter apparatus being operative between a stowed position in which the first and third splitter plates are pivoted to a position parallel to and adjacent the first peripheral wall and the second and fourth splitter plates are pivoted to a position parallel to and adjacent the second peripheral wall, and a deployed position in which the first and second splitter plates are pivoted to extend from the respective first and second peripheral walls into the inlet duct to in combination form a first partition wall extending through said section and the third and fourth splitter plates are pivoted to extend from the respective first and second peripheral walls into the inlet duct to in combination form a second partition wall extending through said section of the inlet duct. 
         [0007]    Further details and other aspects of the described subject matter will be apparent from the detailed description and drawings included below. 
     
    
     
       DESCRIPTION OF THE DRAWINGS  
         [0008]    Reference is now made to the accompanying figures in which: 
           [0009]      FIG. 1  is a schematic cross-sectional view of a turboprop aeroengine as an example illustrating application of the described subject matter; 
           [0010]      FIG. 2  is a schematic partial perspective view of the turboprop aeroengine of  FIG. 1 , illustrating an inlet system having splitter plates in a stowed position in an inlet duct; 
           [0011]      FIG. 3  is a schematic partial perspective view of the turboprop aeroengine of  FIG. 1 , illustrating the inlet system having splitter plates in a deployed position in an inlet duct; 
           [0012]      FIG. 4  is a schematic front elevational view of the inlet duct of  FIG. 3  showing the splitter plates in the deployed position forming two partition walls which divide a single air passage defined within a section of the inlet duct, into three air passages extending through the section of the inlet duct; 
           [0013]      FIG. 5  is a schematic front elevational view of the inlet duct of  FIG. 2  according to another embodiment; and 
           [0014]      FIG. 6  is a schematic top plan view of a splitter plate having perforations or noise absorption material to form an acoustic treatment area thereon. 
       
    
    
       [0015]    It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
       DETAILED DESCRIPTION  
       [0016]      FIG. 1  illustrates a turboprop aeroengine as an example of the application of the described subject matter, which generally includes in serial flow communication (indicated by arrows) a compressor section  12  for pressurizing air, a combustor  14  in which the pressurized air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  16  for extracting energy from the combustion gases to drive the compressor rotors in the compressor section  12  and further drive a propeller  18  through a reduction gear box  20 . 
         [0017]    It should be noted that the terms downstream and upstream are defined with respect to the direction of the air flow entering into and passing through the engine, indicated by arrows. 
         [0018]    In this example, the turboprop aeroengine may provide an inlet system  22  having an inlet duct  24  for directing the airflow indicated by the arrows, from an inlet opening  26  to a first compressor rotor (not numbered) of the compressor section  12 . The inlet duct  24  according to one embodiment, may have an upstream portion  28  (intake portion) and a downstream portion  30  (engine inlet portion) which is annular around the power shaft (not numbered) of the engine to direct the air flow in an annular stream toward the first compressor rotor of the compressor section  12 . 
         [0019]    Referring to  FIGS. 1-6  and according to one embodiment, the upstream portion  28  of the inlet duct  24  may be defined with a peripheral wall (not numbered), having opposed and substantially parallel top and bottom walls  32 ,  34  with curved or rounded side walls  38 ,  40  (see  FIGS. 4 and 5 ). Alternatively, side walls  38 ,  40  may be flat and the upstream portion  28  may define a rectangular cross-section. An inlet splitter apparatus (not numbered) may be provided in the inlet system  22  and may be disposed within a section  44  (see  FIG. 1 ) of the upstream portion  28  of the inlet duct  24 . The section  44  in  FIG. 1  is disposed adjacent the inlet opening  26 , but may be disposed in other locations within the upstream portion  28  of the inlet duct  24 . 
         [0020]    One or more acoustic treatment areas  42  may be provided on an inner surface of the inlet duct  24  which is in the section  44  as shown in  FIG. 1 , but may be located in other locations within the upstream portion  28  of the inlet duct  24 . 
         [0021]    The inlet splitter apparatus according to one embodiment may include four splitter plates (or may include at least one plate, as indicated in  FIG. 5 )  46 ,  48 ,  50  and  52  operatively mounted within the section  44  of the inlet duct  24 . For example, the splitter plates  46  and  50  may be pivotally mounted to the top wall  32  about respective pivotal axes  46   a  and  50   a  which are substantially parallel to a direction of the air flow as indicated by the arrow, and the splitter plates  48  and  52  may be pivotally mounted to the bottom wall  34  about respective pivotal axes  48   a  and  52   a  which are substantially parallel to the direction of the airflow as indicated by the arrow. The splitter apparatus may be operative between a stowed position as shown in  FIG. 2  and a deployed position as shown in  FIG. 3 . In the stowed position, the splitter plates  46  and  50  may be pivoted to a position parallel to and adjacent the top wall  32  and the splitter plates  48  and  52  may be pivoted to a position parallel to and adjacent the bottom wall  34 . In the deployed position, the splitter plates  46  and  48  may be pivoted to extend from the respective top and bottom walls  32 ,  34  into the section  44  of the inlet duct  24  to in combination form a first partition wall (not numbered) extending through the section  44  of the inlet duct  24  and the splitter plates  50  and  52  may be pivoted to extend from the respective top and bottom walls  32 ,  34  into the section  44  of the inlet duct  24  to in combination form a second partition wall (not numbered) extending through the section  44  of the inlet duct  24 . 
         [0022]    As illustrated in  FIG. 2 , when the splitter plates are positioned parallel to and adjacent the respective top and bottom walls  32 ,  34  of the inlet duct  24  in the stowed position, section  44  of the inlet duct  24  is configured as substantially a single passage extending through the section  44  of the inlet duct  24  as shown in  FIG. 3 . When the splitter plates extend transversely into the inlet duct  24  in the deployed position, the single passage defined by section  44  of the inlet duct  24  is divided into three separate passages by the two partition walls extending through the section  44  of the inlet duct  24 , as shown in  FIG. 4 . 
         [0023]    It is understood that when the inlet splitter apparatus changes from the stowed position to the deployed position, the length/diameter ratio of the section  44  of the inlet duct  24  increases to thereby improve attenuation of the noise propagation from the compressor section  12  forwards to the inlet opening  26 . 
         [0024]    An actuation system  54  according to one embodiment may be provided to actuate the respective splitter plates  46 ,  48 ,  50 ,  52  in their pivotal motion between the stowed and deployed positions as shown in  FIG. 4 . The actuation system  54  may be electric, hydraulic or pneumatic using auxiliary power extracted from the engine or any other aircraft power source. A hydraulic cylinder  56  as an actuator is shown in  FIG. 5 . Like the reduced requirement for inlet performance during aircraft landing approach flight, such extraction of auxiliary power from the engine is not limiting power or is not sustained for a long enough duration to be a block fuel driver. The actuation system  54  moves the respective splitter plates  46 ,  48 ,  50 ,  52  in unison to effectively create two partition walls in the inlet duct when deployed. 
         [0025]    In icing conditions the system may be periodically and partially cycled by the actuators to crack the ice. 
         [0026]    Depending on inlet geometry, other configurations can be conceived with different numbers of splitters as required to optimize the balance between cost, weight and noise attenuation capabilities. For example, two splitter plates may be pivotally mounted to the respective top and bottom walls of the inlet duct to operatively form one partition wall in the deployed position. 
         [0027]    The number of the splitter plates may also be reduced to one in another embodiment as shown in  FIG. 5 . The only one splitter plate  36  may be pivotally mounted to the peripheral wall of the inlet duct, such as to either one of the top and bottom walls  32 ,  34  (an arrow in broken lines indicates the pivotal motion). When only one splitter plate  36  is provided, the splitter plate may be substantially rectangular as shown in  FIG. 6  and may have a width (from the edge which is pivotally connected to one of the top and bottom walls to an opposite free edge) substantially equal to a distance measured from the top wall  32  to the bottom wall  34 , thereby forming a partition wall to separate section  44  of the inlet duct  24 , into two separate passages extending through the section  44 . 
         [0028]    As illustrated in  FIGS. 2-3 , it is understood that the pivotal axes  46   a  and  50   a  are spaced apart by a distance to allow free pivotal motion of the respective splitter plates  46  and  50  and the pivotal axes  48   a  and  52   a  are spaced apart by, for example the same distance to allow free pivotal motion of the respective splitter plates  48  and  52 . The splitter plates according to one embodiment may have identical shapes such as rectangular. A length dimension of the splitter plates may be determined by the length of the section  44  of the inlet duct  24  to be equipped with the inlet splitter apparatus. The width dimension of the splitter plates may be determined by the cross-sectional dimension of the section  44  of the inlet duct  24  such that the partition walls formed by the splitter plates in the deployed position, can be formed without significant gaps between adjacent splitter plates. 
         [0029]    The acoustic treatment area  42  defined on the inner surface of the inlet duct  24  may absorb acoustic energy when exposed to noise propagation through the inlet duct  24 . In order to improve the absorption of acoustic energy, the total area of acoustic treatment surfaces within the inlet duct  24  may increase when the splitter apparatus is deployed in the inlet duct  24 . For example, the splitter plates  46 ,  48 ,  50  and  52  may define an acoustic treatment area at one or both sides thereof by having acoustic treatment material applied thereto or by having perforations extending through one side to the other side thereof, as shown in  FIG. 6 . In the deployed position, the additional acoustic treatment areas defined on the one or both sides of the respective splitter plates are exposed to noise propagation through the inlet duct  24 , thereby improving noise attenuation. Furthermore, additional acoustic treatment may also be provided by the treatment area  42  in the inlet duct  24  which is covered by splitter plates in the stowed position but is exposed when the splitter plates are in the deployed position. 
         [0030]    The additional acoustic treatment areas defined on one or both sides of the splitter plates in the deployed position, may be tuned to attenuate a first dominant noise frequency which is different from a second dominant noise frequency. The acoustic treatment area  42  affixed on the inner surface of the peripheral wall of the inlet duct  24  may be tuned to substantially attenuate the second dominant noise frequency. 
         [0031]    The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the described subject matter. For example, the described subject matter may be applicable to any suitable engine, such as aeroengines configured differently from the turboprop aeroengine as illustrated in the drawings. For example, it may be suitable to provide in a turboshaft (helicopter), turbofan, or other gas turbine or other type of aeroengine. Still other modifications which fall within the scope of the described subject matter will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.