Abstract:
A device for protecting aircraft equipment against contact by a foreign object including an interference arrangement disposed in an air inlet upstream from the aircraft equipment where the interference arrangement is configured to physically obstruct passage of the foreign object within the air inlet.

Description:
CROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
       [0001]    The present application claims priority to U.S. provisional patent application No. 61/773,235 filed on Mar. 6, 2013, the entire contents of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to systems for protecting aircraft and aircraft components against damage from foreign object impact. More particularly, the invention concerns an apparatus arrangement for protecting a precooler of a geared turbofan engine from foreign object impact damage. 
       RELATED ART 
       [0003]    It is known to bleed hot, compressed air generated by an aircraft engine and to provide that compressed air to equipment on the aircraft to perform certain onboard functions. Specifically, it is known to siphon hot, compressed air (also referred to as “bleed air”) from an aircraft engine so that the hot air may be used for aircraft functions outside of the aircraft engine. For example, the bleed air may be used in an aircraft&#39;s heating, ventilation, and air conditioning (“HVAC”) system, the aircraft&#39;s anti-icing system, and the aircraft&#39;s fuel tank inerting system. 
         [0004]    For an HVAC system installed in an aircraft with two engines, bleed air typically is siphoned from each engine and is sent to respective left and right side HVAC packs. The bleed air may be mixed with recirculated air in the cockpit and passenger cabin, where the bleed air conditions (i.e., heats) the cabin temperature and pressurizes the aircraft&#39;s interior. 
         [0005]    For the wing anti-icing system, the hot bleed air may be used to heat areas of the aircraft which are prone to ice accumulation, such as along a wing&#39;s leading edge. 
         [0006]    With respect to the aircraft&#39;s fuel tank inerting system, the bleed air may be used to reduce the oxygen content within the aircraft&#39;s fuel tank(s), thereby minimizing the possibility of fuel ignition within the fuel tank(s). 
         [0007]    Depending upon the location where the bleed air is removed from an engine, the bleed air may exit the engine at temperatures up to 450° C. or more. Specifically, bleed air taken from a location near to the low pressure turbine may be at a temperature of about 120° C. Bleed air from a location near to the high pressure turbine may be at a temperature of about 500° C. Since the temperature of the bleed air may be too hot to directly circulate within the various systems of the aircraft, the hot bleed air may have to be cooled prior to use with one or more of the aircraft&#39;s other systems. As a result, it is known to provide a cooling device, commonly referred to as a precooler, to cool the hot bleed air down to temperature between about 200° C. to 232° C. depending on the usage. For engines such as turbofan engines, which use a turbine driven fan to provide thrust, a precooler is typically housed proximate to each engine, such as within the engine&#39;s nacelle or above the engine&#39;s pylon. 
         [0008]    A precooler typically utilizes outside (or ambient) that is air drawn into by the fan to cool the hot, bleed air. Once inside the nacelle, the ambient air may be between 70° C., at low altitude on a hot day, and −60° C., at high altitude on a cold day. The precooler typically includes a cross flow air-to-air heat exchanger, which transfers heat energy from the streams of the hot, bleed air to the stream of cold, ambient air, while the two streams remain separated from one another. As should be apparent to those skilled in the art, a stream of cooled, bleed air exits from the precooler for use within the aircraft. Consequently, a stream of heated, ambient air also exits from the precooler and is discharged into or around the engine nacelle or outside the aircraft, for example, above the pylon installation. 
         [0009]    Typically, precoolers collect the outside ambient air through an air inlet that is positioned in a manner so as to not directly face the incoming ambient airflow. For example, the precooler air inlet may be disposed within the nacelle behind the fan and oriented such that its opening faces a direction perpendicular to the direction of the ambient airflow. In other arrangements, the precooler air inlet may extend through the nacelle or through the pylon and include an opening so as to expose the inlet to the ambient air outside the aircraft. This opening does not directly face the incoming ambient airflow but is instead positioned at an angle, typically perpendicular, relative to the airflow. 
         [0010]    In these conventional arrangements, it is unlikely that a foreign object would enter the precooler air inlet due to the orientation of the air inlet relative to the direction of ambient airflow. Therefore, traditionally, precooler foreign object exposure has not been a significant concern. 
         [0011]    However, as aircraft requirements and demands change, the positioning of the precooler air inlet has been altered thus warranting consideration of foreign object intrusion. For example, geared turbofan (GTF) engines typically have a lower fan air pressure than non-GTF engines. To compensate for this lower pressure, a fan air inlet with a ninety-nine percent recover is required. As a result, the precooler of the GTF engine is fitted with a forward facing air inlet scoop disposed directly downstream from the fan. This scoop is vulnerable to hail and other foreign objects which are carried in the ambient airflow which passes through the fan into the nacelle. Such objects are typically travelling a high speed and could impact and damage the scoop, the precooler, or the heat exchanger contained therein. Such foreign object impact could effect the performance of these components in flight and may require costly delays on the ground for inspecting and repairing the precooler arrangement. 
         [0012]    Accordingly, there is a need for a device for protecting exposed precooler arrangements, and other exposed aircraft arrangements and components, from foreign object contact and damage. 
       BRIEF SUMMARY 
       [0013]    The disclosure concerns a device for protecting aircraft equipment against contact by a foreign object including an interference arrangement disposed in an air inlet upstream from the aircraft equipment where the interference arrangement is configured to physically obstruct passage of the foreign object within the air inlet. 
         [0014]    The disclosure further provides a precooler for a geared turbofan aircraft engine including a heat exchanger, an air inlet scoop disposed upstream from and in fluid communication with the heat exchanger, the scoop facing a direction of travel of the aircraft so as to directly receive ambient airflow entering the engine from outside of the aircraft, and an interference arrangement disposed upstream from the heat exchanger and configured to physically obstruct passage of a foreign object within the precooler. 
         [0015]    The invention also provides a geared turbofan aircraft engine assembly, including a nacelle, an engine disposed within an annular cavity of the nacelle and supported by a pylon, a precooler configured to receive and condition hot bleed air from the engine and ambient air entering the nacelle from an exterior of the aircraft, where the precooler comprises a forward facing scoop configured to receive the ambient air, and where the precooler further comprises an interference arrangement configured to physically obstruct passage of a foreign object travelling in the ambient air within the precooler. 
         [0016]    The above described and other features are exemplified by the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0017]      FIG. 1  is side view of an aircraft turbine engine having a foreign object protection arrangement according to an exemplary embodiment of the invention; 
           [0018]      FIG. 2  is a schematic cross-sectional view of the engine of  FIG. 1 ; 
           [0019]      FIG. 3  is an enlarged partial view thereof; 
           [0020]      FIG. 4  is partial front view of the engine of  FIG. 1 ; 
           [0021]      FIG. 5  is a side view of the precooler of the engine of  FIG. 1 ; 
           [0022]      FIGS. 6A and 6B  are top and side schematic cross-sectional views, respectively, of the precooler of  FIG. 5  showing a foreign object protection arrangement; 
           [0023]      FIGS. 7 and 8  are front perspective views thereof with a scoop of the precooler omitted; 
           [0024]      FIGS. 9 and 10  are similar views thereof with an alternate embodiment of the foreign object protection arrangement; 
           [0025]      FIG. 11  is a foreign object protection arrangement in another embodiment of the invention; 
           [0026]      FIG. 12  is an enlarged partial view thereof; and 
           [0027]      FIG. 13  is a cross-sectional schematic view of the foreign object protection arrangement of  FIG. 11  disposed in the precooler. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1-3  show various views of an aircraft engine system in accordance with the invention. Therein, an aircraft turbine engine  10  is depicted as housed within a nacelle  12 . The nacelle  12  has a tubular shape and is suspended from a wing  14  by a pylon  16 . The nacelle  12  forms an annular cavity  18  around the turbine engine  10  through which air can flow. In use, the turbine engine  10  drives a fan  20  positioned in front of the turbine engine  10 , which draws ambient air  25  into the cavity  18  through a front air inlet  22 . This fan air or ambient air  25  passes through the nacelle  12  and out of a rear air outlet  24 . Some of the ambient air  25  is mixed with fuel and combusted within the turbine engine  10  and some of the ambient air  25  is drawn past the turbine engine  10  to provide thrust. This arrangement is known as a turbofan. In one embodiment, the engine  10  includes a reduction gear mechanism utilized for driving the fan  20 . This type of aircraft engine arrangement is known as a geared turbofan (GTF) engine. 
         [0029]    The ambient air  25  is drawn into the nacelle  12  from outside of the aircraft and is typically lower in temperature relative to the temperature of air inside the engine. This cold ambient air  25  enters the turbine engine  10  via a turbine inlet  26  and passes through a low pressure compressor  28  followed by a high pressure compressor  30 . The ambient air  25  is then mixed with fuel and ignited in a combustion chamber  32 . The combustion gasses  39  pass through high and low pressure turbines  34  and  36 , causing rotation. The high and low pressure turbines  34 ,  36  are connected to the fan  20  and/or to the above-referenced GTF gear mechanism and, due to their rotation, drive the fan  20 . The combustion gases  39  exit from the high and low pressure turbines  34 ,  36  and exit through a nozzle  38  and a turbine outlet  40  at a rear of the engine  10 . 
         [0030]    As illustrated in  FIG. 2 , the compressors  28  and  30 , combustion chamber  32 , and turbines  34  and  36  are enclosed by an engine casing  41 , which forms the outer wall of the turbine engine  10 . The annular cavity  18  extends around the engine casing  41  and is bounded at its outer extent by an inner surface of the nacelle  12 . 
         [0031]    As can be seen in  FIGS. 2-3 , a stream of hot, compressed air  42  is bled from the turbine engine  10 . This hot bleed air  42 , which is preferably drawn from both the low and high pressure compressors  28  and  30  via conduits  44  and  46 , respectively, is sent to the hot air inlet  48  of a precooler  50 . 
         [0032]    The precooler  50  serves to cool the stream of hot bleed air  42 , producing a stream of cooled hot bleed air  52  which can be used in other aircraft systems, for example, in the aircraft&#39;s HVAC system, in an anti-icing system, or it can be fed to an engine starter valve of an opposite engine, etc. 
         [0033]    In use, a stream of cold air  54 , taken from the ambient air  25  drawn in by the fan  20 , is received at a cold air inlet  56  of the precooler  50 . See, particularly,  FIG. 3 . The streams of cold air  54  and hot bleed air  42  pass through a heat exchanger  58  disposed within the precooler unit  50 . The heat exchanger  58  allows heat energy from the stream of hot bleed air  42  to be transferred to the stream of cold air  54 , thereby cooling the former and heating the latter. In this way, the hot bleed air  42  is reduced in temperature to a safe and sufficient level before being directed on for further use within the aircraft as the cooled hot bleed air  52 . 
         [0034]    The heat exchanger  58  may be embodied in a variety of ways. For example, the hot bleed air  42  may be fed through a plurality of tubes or fins made of a conductive material. The cold ambient air  54 , as it passes through the precooler  50 , flows past the tubes or fins, thereby allowing the heat transfer to occur. In this way, the cold ambient air  54  is heated to produce heated ambient air  64 . Similarly, the hot bleed air  42  is cooled to produce the cooled, hot bleed air  52 . The heated ambient air  64  passes through the precooler  50  into the cavity  18  and is exhausted at the rear of the engine  10  through the rear outlet  24 . The stream of cooled hot bleed air  52  exits the precooler  50  from a cooled hot air outlet  60 , which is connected to the appropriate aircraft systems via a conduit  62 . The cooled hot bleed air  52  is thusly directed onward for further use within the aircraft, as discussed. 
         [0035]    A scoop  68  is provided at a cold air inlet  56  of the precooler  50  so as to increase the volume and/or pressure of the ambient air  25  captured and fed into the precooler  50 . As will be appreciated by those skilled in the art, the scoop  68  may be designed to maximize inlet pressure and minimize the pressure loss of the flow of ambient air  25  therein. A fan air valve  70  for regulating the stream of the cold ambient air  54 , and thereby the temperature of the cooled hot bleed air  52 , is also provided between the scoop  68  and the cold air inlet  56 . The size and location of the fan air valve  70  is also chosen to maximize inlet pressure and minimize the pressure drop. As shown in  FIG. 3 , the valve  70  is illustrated by way of example as a butterfly valve. 
         [0036]    As shown in  FIGS. 1-6 , the precooler  50  is disposed in the annular cavity  18  directly downstream of the fan  20 . The scoop  68  and the cold air inlet  56  of the precooler  50  face forward with respect to a direction of travel. In this way, the scoop  68  and hence the precooler  50  directly receive the cold ambient airflow  54 . This is shown particularly in  FIG. 4  which illustrates the direct exposure of the precooler scoop  68  just aft of the fan  20 . 
         [0037]    This forward facing orientation of the precooler  50  and scoop  68  is advantageous in that the precooler  50  is exposed to a maximum inlet airflow pressure. However, this orientation of the precooler  50  exposes the precooler  50  and its various components to the threat of foreign object damage. As mentioned, the ambient air  25  that enters the annular cavity  18  is drawn from outside of the aircraft and is then driven through the cavity  18  by the fan  20 . This airflow  25  is untreated and thus may include foreign objects such as hail, debris, etc. The cold ambient airflow  54  which enters the precooler  50  is composed entirely of the ambient air  25  and thus may include these hazards. Due to the forward facing nature of the precooler assembly  50 , foreign objects and the like may be delivered by the cold ambient airflow  54  at a high speed directly into the scoop  68  and could make contact with the inners walls of the scoop  68 , the inner walls of the cold air inlet  56 , the fan air valve  70 , or may enter the body of the precooler  50  itself and could strike the heat exchanger  58 . As mentioned, such a heat exchanger  58  typically includes fins or ribs through which air passes. These and other elements of the heat exchanger  58  and precooler assembly  50  can be relatively fragile and are thus susceptible to damage due to a foreign object strike. 
         [0038]    To protect the illustrated precooler system  50  from foreign object damage, an interference arrangement is provided in or on the precooler  50 . The interference arrangement is configured to prevent passage of foreign objects while at the same allow the cold ambient air  54  to enter and pass through the precooler with a minimal drop in airflow pressure so as to allow for effective functioning of the heat exchanger  58 . 
         [0039]    The interference arrangement can take any of a number of forms. A first exemplary embodiment of the interference arrangement is shown schematically in  FIGS. 6A-6B . Therein, a plurality of rods or tubes  51  are disposed in the cold air inlet  56  upstream of the precooler  50  and its heat exchanger  58 . The rods  51  are disposed vertically (i.e., parallel to the Y-axis) with respect to the engine  10  and are arranged generally perpendicular to the direction of the airflow  54  which travels generally in the Z-direction. (See reference axes in  FIGS. 1 ,  6 A, and  6 B.) The rods  51  extend substantially parallel to one another and, as shown, are arranged in two linear rows which extend along the X-axis. A first row  52  of the rods  51  is disposed upstream relative to a second row  53  of the rods  51 . The rods  51  of the first row  52  are staggered with respect to the rods  51  of the second row  53 . That is, the rods  51  of the first and second rows  52 ,  53  are dis-aligned with respect to the direction of the airflow  54 . As such, when viewed from the scoop  68  along the Z-axis, each rod from the second row is disposed downstream from and in between two rods  51  of the first row  52 . The exception to this, of course, are the two rods  51  at either end of the second row. This staggered arrangement can be seen in  FIG. 6A  and also in  FIGS. 7 and 8  which provide a perspective view of the precooler  50  with the scoop  68  removed.  FIGS. 9 and 10  show an alternate version of the interference arrangement where only a single row of the rods  51  is disposed in the cold air inlet  56  of the precooler  50 . Further alternate versions include the two rows  52 ,  53  of the rods discussed above and additional rows of rods  51 . For example, such arrangement could include a third row of rods  51 , a fourth row of rods  51 , and so on. These additional rows may be staggered and/or aligned with the rods  51  of the upstream rows. 
         [0040]    The rods  51  are shown by way of example in the Figures as being generally cylindrical and as including a circular cross-section which is consistent across their length. More generally, the rods  51  may include a curvilinear cross-section or a rectilinear cross-section or a cross-section having a combination of curvilinear and rectilinear features. Additionally, the cross-section of the rods  51  may vary from rod to rod and even may vary within a single rod  51  across its length. 
         [0041]    As shown in the drawings, the rods  51  can be of equivalent size in terms of thickness and length, or they may vary in size between the first and second rows, or within a single row. The spacing between the rods  51  may be uniform and consistent across a respective row. Alternatively, this spacing may vary. For example, the spacing between rods  51  in areas of likely foreign object impact may be reduced relative to spacing rods  51  in low impact zones. 
         [0042]    In an alternate embodiment of the invention, the rods  51  of one or more of the rows  52  and  53  are arranged horizontally with respect to the engine  10 , i.e. the rods  51  are arranged along the X-axis. In a further embodiment, the rods  51  of one or more of the first and second rows  52 ,  53  are arranged at an angle between the X and Y axes such that the rods extend angularly with respect to the engine  10 , not horizontally or vertically. In another embodiment, some or all of the rods  51  of one or more of the rows  52  and  53  may extend in a curvilinear path across the cold air inlet  56  rather than in a linear fashion. 
         [0043]    As illustrated, the rods  51  are disposed in the cold air inlet  56  of the precooler assembly  50 . In general, the rods  51  may be disposed at any location that is sufficient for occluding the passage of foreign objects within the precooler assembly  50  while still permitting sufficient cold airflow  54  through the heat exchanger  58  to efficiently and effectively cool that hot bleed air  42 . For example, the rods  51  may be disposed on or in close proximity to the heat exchanger  58 , i.e., downstream of the cold air inlet  56 . Alternatively, the rods  51  may be installed within the scoop  68  or at the forward opening of the scoop  68 . 
         [0044]    In one embodiment of the invention, the rods  51  are heated by any known conventional means. The heating of the rods  51  prevents accumulation of ice on the rods  51 . As such, if hail or other frozen debris is intercepted by the rods  51 , it will melt due to the heated rods and then eventually pass through the precooler as moisture or vapor. 
         [0045]    As mentioned, the interference arrangement of the invention can assume any form that is configured to prevent or at least inhibit the passage of foreign objects while at the same allow the cold ambient air  54  to enter and pass through the precooler with a minimal drop in airflow pressure so as to allow for effective functioning of the heat exchanger  58 . 
         [0046]      FIGS. 11-13  show another alternate embodiment of the interference arrangement. Here, the interference arrangement comprises a thick screen  200  including first screen elements  202  and second screen elements  204 . In the illustrative embodiment, the first and second elements  202 ,  204  are disposed perpendicular to one another and each element  202 ,  204  includes ends  206  fixed to a frame  208 . The screen  200  is disposed in the cold air inlet  56  of the precooler assembly  50 , as particularly shown in the schematic illustration of  FIG. 15 . The screen  200  extends across the area of the inlet  56  and is disposed substantially perpendicular to the direction of the cold airflow  54 . The various first elements  202  are arranged parallel to one another and orthogonally with respect to the second elements  204 . Similarly, the various second elements  204  are arranged parallel to one another, but yet are orthogonal to the first elements  202 . The first and second elements  202 ,  204  are essentially rods or bars which intersect where they cross each other or are fixedly woven at these locations so as to essentially bypass one another. The first and second elements  202 ,  204  essentially form a grid which in the current embodiment delimits a plurality of square-shaped spaces  210 . 
         [0047]    As shown in  FIG. 13 , the screen  200  is disposed within the cold air inlet  56  just upstream from the precooler  50  and the heat exchanger  58 . The screen  200  extends across an interior area of the cold air inlet  56  so as to be disposed substantially perpendicular to a direction of the cold airflow  54 . 
         [0048]    The screen  200  prevents foreign objects from directly striking the fins  59  of the heat exchanger  58 . That is, the first and second screen elements  202 ,  204  are shaped, sized, and disposed to intercept hail, debris, and other foreign objects which may be contained within the cold air  54 . Furthermore, the spaces  210  delimited by the elements  202 ,  204  are sized to minimize the pressure drop of the cold airflow  54  as it moves through the precooler  50  to thus allow effective operation of the heat exchanger  58 . 
         [0049]    As with the rods  51 , the descriptions of the screen arrangement  200  are merely exemplary. The shape, size, orientation, and disposition of the first screen elements  202  and the second screen elements  204 , may vary and be altered within the broad scope of this disclosure. For example: the elements  202  and  204  may extend angularly, horizontally, or vertically with respect to the engine; the cross-section of the elements  202 ,  204  may be curvilinear, rectilinear, or both; the cross-section of the elements  202 ,  204  may be consistent across their respective length and consistent in like elements or the cross-section may vary in one or both respects; etc. The elements  202 ,  204  may be disposed uniformly across the respective arrangement  200  or non-uniformly. Additionally, the screen arrangement  200  may be disposed at any suitable position within the precooler assembly  50 . That is, the arrangement  200  may be disposed at any location that is sufficient for occluding the passage of foreign objects within the precooler assembly  50  while still permitting sufficient cold airflow  54  through the heat exchanger  58  to efficiently and effectively cool that hot bleed air  42 . For example, the arrangement  200  may be disposed on or in close proximity to the heat exchanger  58 , i.e., downstream of the cold air inlet. Alternatively, the arrangement  200  may be installed within the cold air inlet  56 , within the scoop  68 , or at the forward opening of the scoop  68 . 
         [0050]    Again similar to the rods  51 , the screen arrangement  200  may be heated by any known conventional means in order to prevent accumulation of ice on the various elements  202 ,  204 . 
         [0051]    While the above discussed embodiments of the foreign object interference arrangement have been described with respect to a precooler unit of a GTF engine, the application of the invention is of course not limited to this configuration. The discussed interference arrangements, and/or additional alternate embodiments thereof, may be utilized in a precooler unit of a non-GTF engine or in any other suitable engine assembly or aircraft component that requires protection from contact by a foreign object in a received airflow stream. 
         [0052]    As used herein the terms “comprising” (also “comprises,” etc.), “having,” and “including” is inclusive (open-ended) and does not exclude additional, unrecited elements or method steps. The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. The term “or” means “and/or.” Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. 
         [0053]    While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.