Patent Publication Number: US-7712452-B2

Title: Fuel delivery system for an aircraft engine

Description:
BACKGROUND 
   Conventional reciprocating aircraft engines include multiple cylinder head assemblies used to drive a crankshaft. During operation, in order to drive the crankshaft each cylinder head assembly requires fuel, such as provided by a fuel pump. For example, as illustrated in  FIGS. 1A and 1B , a conventional aircraft engine  10  includes separate cylinder assemblies, collectively referred to as  12 , and a fuel distribution assembly  14  that provides fuel to each cylinder assembly  12  from the fuel pump (not shown). As illustrated, the fuel distribution assembly  14  includes a hub  16 , connector tubes  18 , and fuel nozzles  20  where each connector tube  18  and fuel nozzle  20  connects the hub  16  to a corresponding cylinder assembly  12 . In use, the hub  16  receives fuel from the fuel pump and distributes the fuel to each cylinder assembly  12  through each corresponding connector tube  18  and fuel nozzle  20 . 
   During operation, as a piston (not shown) reciprocates within each cylinder assembly  12 , the piston generates a force within the cylinder assembly  12  sufficient to cause relative motion of the cylinder assembly  12 . For example, as a piston within a cylinder assembly  12 - 1  fires, the loads generated by the piston on the crankshaft causes the cylinder assembly  12 - 1  to generate a load on the crankcase  22  which carries the cylinder assemblies  12 . This load causes the crankcase  22  to bend or flex such that the operational cylinder assembly  12 - 1  moves relative to the then non-operational cylinder assemblies  12 - 2 ,  12 - 3 . To prevent damage to the fuel distribution assembly  14  as caused by the relative motion of the cylinder assemblies, the connector tubes  18  of the fuel delivery assembly are formed of a generally flexible material. As a result, during operation of the aircraft engine  10 , as each cylinder assembly  12 - 1 ,  12 - 2 ,  12 - 3  moves relative to each other, the connector tubes  18  absorb the motion of the cylinder assemblies  12 - 1 ,  12 - 2 ,  12 - 3  relative to the hub  16 . Accordingly, the flexibility of the connector tubes  18  helps to prevent the development and propagation of fractures within the fuel delivery system during operation. 
   SUMMARY 
   Conventional fuel delivery systems for aircraft engines can suffer from certain deficiencies. For example, while the fuel distribution assembly  14  provides fuel to each cylinder assembly  12  from the fuel pump during operation, the fuel distribution assembly  14  cannot purge the fuel contained within the connector tubes  18  at the conclusion of operation of the engine  10 . Accordingly, once the engine  10  is turned off, a portion of the fuel contained within the connector tubes  18  drains into the cylinder assemblies  12  through corresponding nozzles  20 . In this post-operational state, the cylinder assemblies  12  absorb heat from the engine components which, in turn, vaporizes the fuel contained in the cylinder assemblies  12  and connector tubes  18 . Vaporization of the fuel within the fuel distribution assembly  14  can disrupt the operation of the fuel pump during a subsequent operation of the engine. 
   Embodiments of the present invention provide a fuel delivery system that allows fuel to be purged from an engine following engine operation and that allows for relative motion of the cylinder assemblies during operation while minimizing the application of excessive loads on the fuel delivery system. The engine includes a fuel delivery system having a fuel rail and fuel delivery devices, such as fuel injectors, that deliver fuel to corresponding cylinder assemblies. The use of the fuel rail and fuel injectors allows unused fuel to be purged from the engine at the end of the engine&#39;s operating cycle, thereby minimizing the creation of fuel vapor within the engine. The fuel delivery system also includes fuel rail coupling members that are constructed and arranged to secure each cylinder assembly to the fuel rail and to absorb at least a portion of a load generated by the corresponding cylinder assembly on the fuel rail during operation. The fuel rail coupling members allow motion of the cylinder assemblies relative to the fuel rail during operation and minimize the application of potentially damaging forces on the fuel rail. 
   In one arrangement, a fuel delivery system for an aircraft engine includes a fuel rail, a set of fuel delivery devices, and a set of fuel rail coupling members. The fuel rail includes a set of fuel delivery ports disposed between a fuel inlet and a fuel outlet of the fuel rail. Each fuel delivery device of the set of fuel delivery devices is disposed between each fuel delivery port of the set of fuel delivery ports and a corresponding cylinder assembly of the aircraft engine. Each fuel delivery device is configured to provide fuel from the fuel rail to the corresponding cylinder assembly. Each fuel rail coupling member of the set of fuel rail coupling members is constructed and arranged to secure a corresponding cylinder assembly to the fuel rail and to absorb a load generated by the corresponding cylinder assembly on the fuel rail. 
   In one arrangement, a fuel delivery system for an aircraft engine includes a crankcase assembly, a set of cylinder assemblies, and a fuel delivery system. The crankcase assembly includes a crankcase housing and a crankshaft disposed within the crankcase housing. Each cylinder assembly of the a set of cylinder assemblies having a cylinder housing, a piston, and a connecting rod, the piston and connecting rod being disposed within the cylinder housing, the piston coupled to the connecting rod and the connecting rod coupled to the crankshaft. The fuel delivery system includes a fuel rail, a set of fuel delivery devices, and a set of fuel rail coupling members. The fuel rail includes a set of fuel delivery ports disposed between a fuel inlet and a fuel outlet of the fuel rail. Each fuel delivery device of the set of fuel delivery devices is disposed between each fuel delivery port of the set of fuel delivery ports and a corresponding cylinder assembly of the set of cylinder assemblies. Each fuel delivery device is configured to provide fuel from the fuel rail to the corresponding cylinder assembly. Each fuel rail coupling member of the set of fuel rail coupling members is constructed and arranged to secure a corresponding cylinder assembly to the fuel rail and to absorb a load generated by the corresponding cylinder assembly on the fuel rail as the piston and connecting rod reciprocate within the cylinder housing. 
   In one arrangement, a method for assembling a fuel delivery system of an aircraft engine includes disposing a fuel rail within the aircraft engine, the fuel rail having a set of fuel delivery ports disposed between a fuel inlet and a fuel outlet of the fuel rail. The method includes securing the fuel rail to a set of cylinder assemblies using a set of fuel rail coupling members, each fuel rail coupling member of the set of fuel rail coupling members securing a corresponding cylinder assembly to the fuel rail, each fuel rail coupling member constructed and arranged to absorb a load generated by the corresponding cylinder assembly on the fuel rail. The method includes disposing a set of fuel delivery devices between each fuel delivery port of the set of fuel delivery ports and the corresponding cylinder assembly of the aircraft engine, each fuel delivery device configured to provide fuel from the fuel rail to the corresponding cylinder assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. 
       FIG. 1A  illustrates a top view of a prior art engine. 
       FIG. 1B  illustrates a side view of the prior art engine of  FIG. 1A . 
       FIG. 2  illustrates a top view of an engine having a fuel delivery system, according to one embodiment of the invention. 
       FIG. 3  illustrates a top perspective view of the engine of  FIG. 2 . 
       FIG. 4  illustrates a perspective exploded view of the fuel delivery system of  FIG. 2 . 
       FIG. 5  illustrates a fuel rail coupling member of the fuel delivery system of  FIG. 2 , which secures a fuel rail to a corresponding cylinder assembly of the engine. 
       FIG. 6  illustrates a schematic overhead view of the fuel delivery system of  FIG. 2 . 
   

   DETAILED DESCRIPTION 
   Embodiments of the present invention provide a fuel delivery system for an engine that allows fuel to be purged from the engine following engine operation and that minimizes the ability for the engine to place excessive loads on the fuel delivery system. The engine includes a fuel delivery system having a fuel rail and fuel delivery devices, such as fuel injectors, that deliver fuel to corresponding cylinder assemblies. The use of the fuel rail and fuel injectors allows unused fuel to be purged from the engine at the end of the engine&#39;s operating cycle, thereby minimizing the creation of fuel vapor within the engine. The fuel delivery system also includes fuel rail coupling members that are constructed and arranged to secure each cylinder assembly to the fuel rail and to absorb load generated by the corresponding cylinder assembly on the fuel rail during operation. The fuel rail coupling members allow motion of the cylinder assemblies relative to the fuel rail during operation and minimize the application of potentially damaging forces on the fuel rail. 
     FIGS. 2-6  illustrate an arrangement of an engine  50 , such as an aircraft engine, having a crankcase assembly  52 , a set of cylinder assemblies  54 , and a fuel delivery system  56 . The crankcase assembly  52  includes a crankcase housing  58  and a crankshaft (not shown) disposed within the crankcase housing  58 . Each cylinder assembly  60  of the set of cylinder assemblies  54  includes a cylinder housing  62  secured to the crankcase housing  58  of the engine  50 . For example, as indicated in  FIG. 3 , each cylinder assembly  60  couples to the crankcase housing  58  by fasteners that are inserted through a series of openings  64  defined by the cylinder assembly  60  and secured to the crankcase housing  58 . 
   Each cylinder assembly  60 , as indicated in a cut-away view of a cylinder assembly in  FIG. 6 , includes a piston  66  and a connecting rod  68  disposed within the cylinder housing  62 . The connecting rod  68  connects to both the piston  66  and the crankshaft (not shown) carried by the crankcase assembly  52 . The piston  66  and connecting rod  68  are configured to reciprocate within the cylinder housing  62  to drive or rotate the crankshaft. While the engine  50  can have any number of cylinder assemblies, in one arrangement, as indicated in  FIGS. 2-6 , the engine includes six cylinder assemblies  60 , with three cylinder assemblies  60  being mounted to either side of the crankcase housing  58 . 
   The fuel delivery system  56  is configured to provide fuel from a fuel source to each of the cylinder assemblies  60 . In one arrangement, the fuel delivery system  56  includes a fuel rail  80 , a set of fuel delivery devices  59 , and a set of fuel rail coupling members  84 . The fuel rail  80  is configured as a generally tubular structure having a set of fuel delivery ports  86  disposed between a fuel inlet  88  and a fuel outlet  90 . In one arrangement, as particularly illustrated in  FIG. 6 , the fuel inlet  88  is fluid communication with a fuel source or tank  92  by way of a fuel pump  94 . The fuel pump  94  is configured to withdraw fuel from the fuel source  92  and deliver the fuel under pressure to the fuel inlet  88  of the fuel rail  80 . Also in the arrangement shown, the fuel outlet  90  is in fluid communication with the fuel source  92  by way of a fuel pressure regulator  96 . The fuel pressure regulator  96  is configured to receive, from the fuel outlet  90 , unused fuel carried by the fuel rail  80  and deliver the unused fuel to the fuel source  92 . The combination of the fuel rail  80  with the fuel pump  94 , fuel pressure regulator  96  and the fuel source  92  forms a fluid circuit. 
   As indicated in  FIG. 2 , the engine includes two separate fuel rails  80 ,  80 ′, one fuel rail  80  configured to carry fuel to cylinder assemblies  60  disposed on a first side of the crankcase housing  58  and a second fuel rail  80 ′ configured to carry fuel to cylinder assemblies disposed on a second, opposing side of the crankcase housing  58 . For convenience, the following description will focus on a single fuel rail  80  associated with the engine  50 . 
   In one arrangement, with particular reference to  FIGS. 2 and 3 , the fuel rail  80  is disposed along a length of the engine  50  as defined by serially-located cylinder assemblies  60 . For example, as illustrated, the fuel rail  80  extends along the head portions of the first, second, and third cylinder assemblies  60 - 1  through  60 - 3 . The fuel rail  80  is positioned relative to the engine  50  in this manner to minimize interference with the engine&#39;s operation (e.g., operation of the cylinder assemblies or cooling of the engine  50 ). 
   The fuel rail  80  provides fuel to the cylinder assemblies via fuel delivery devices  59 . Each fuel delivery device of the set of fuel delivery devices  59  is configured to divert a portion of the fuel flowing through the fuel rail  80  into a corresponding cylinder assembly  60 . For example, as indicated in  FIG. 4 , each of the cylinder assemblies  60 - 1  through  60 - 3  includes its own corresponding fuel delivery device  59 - 1  through  59 - 3 . During operation, as a volume of fuel flows from the inlet port  88  toward the exit port  90 , the first fuel delivery device  59 - 1  provides a portion of the fuel volume to the first cylinder assembly  60 - 1 , the second fuel delivery device  59 - 1  provides a portion of the fuel volume to the second cylinder assembly  60 - 2 , and the third fuel delivery device  59 - 3  provides a portion of the fuel volume to the third cylinder assembly  60 - 3 . While each fuel delivery device  59  can be configured in a variety of ways, in one arrangement, the fuel delivery device  59  is configured as a fuel injector that atomizes the received fuel and provides the atomized fuel to the corresponding cylinder assembly  60 . 
   The set of fuel rail coupling members  84  are configured to secure the fuel rail  80  to the set of cylinder assemblies  54 . The set of fuel rail coupling members  84  are also constructed and arranged to absorb loads generated by the corresponding cylinder assembly  60  relative to the fuel rail  80  during operation. For example, to fuel rail coupling members  84  allow the cylinder assemblies  60  in the set of cylinder assemblies  54  to move relative to each other while minimizing the load that each cylinder assembly  60  places on the fuel rail  80  during operation. Accordingly, the fuel rail coupling members  84  secure the fuel rail  80  to the engine  50  while minimizing potential damage to the fuel rail  80  as caused by operation of the engine  50 . 
   As illustrated in the embodiment shown  FIGS. 2-6 , the number of fuel rail coupling members  84  corresponds to the number of cylinder assemblies  60  disposed on either the first or second side of the crankcase housing  58 . For example, with particular reference to  FIG. 4 , the engine  50  includes, on one side of the crankcase housing  58 , three cylinder assemblies  60 - 1  through  60 - 3 . To secure the fuel rail  80  to the engine  50 , three fuel rail coupling members  84  are used: a first fuel rail coupling member  84 - 1  that secures the fuel rail  80  to the first cylinder assembly  60 - 1 , a second fuel rail coupling member  84 - 2  that secures the fuel rail  80  to the second cylinder assembly  60 - 2 , and a third fuel rail coupling member  84 - 1  that secures the fuel rail  80  to the third cylinder assembly  60 - 1 . 
   While the fuel rail coupling members  84  can be configured in a variety of ways, in one arrangement and with particular reference to the fuel rail coupling member  84 - 1  of  FIGS. 4 and 5 , the fuel rail coupling member  84 - 1  includes a compliant support  100  and a bracket  102 . The bracket  102  is configured to secure the compliant support  100  to the fuel rail  80  and to secure the fuel rail  80  to the cylinder assembly  60 - 1 . The compliant support  100 , in one arrangement, is configured to yield elastically upon application of a force thereto to absorb at least a portion of a load generated by the cylinder assembly  60 - 1  on the fuel rail  80  during operation. For example, while the compliant support can be formed from a variety of materials, in one arrangement, the compliant support  100  formed of a rubber material that compresses in response to application of a compressive loading. Accordingly, the compressive properties of the compliant support  100  allow for dissipation of at least a portion of the load generated by the cylinder assembly  60 - 1  on the fuel rail  80 . 
   In use, and with particular attention to  FIG. 6 , each cylinder assembly  60  receives fuel from the corresponding fuel delivery device  59 . The fuel explodes within each cylinder assembly housing  62  and causes the piston  66  and a connecting rod  68  to reciprocate within the cylinder assembly housing  62 . Forces generated by cylinder assemblies  60  on the crankshaft (not shown) disposed within the crankcase housing  58  causes the crankcase housing  58  to flex or bend, such as at the location of cylinder assemblies  60 . Accordingly, such flexure causes each cylinder assembly  60  and attached bracket  102  to move relative to the fuel rail  80 . 
   With particular reference to cylinder assembly  60 - 1 , as the cylinder assembly  60 - 1  moves along a substantially vertical direction  104 , along a substantially horizontal direction  106 , or along some combination of the two directions  104 ,  106 , the cylinder assembly  60 - 1  moves the bracket  102  relative to the fuel rail  80 . Accordingly, because the compliant support  100  is disposed between the fuel rail  80  and the bracket  102 , the compliant support  100  becomes compressed in response to such loading. This compression helps to absorb a least a portion of the load generated by the cylinder assembly  60 - 1  on the fuel rail  80 , thereby minimizing excessive loading on and potential damage to the fuel rail  80 . 
   At the conclusion of the engine&#39;s operation, because the engine  50  is configured with the fuel delivery system  56  as described above, a user can drain fuel from the engine to minimize vaporization of the fuel within the engine  50 . For example, while the engine  80  is hot after operation, the fuel pressure regulator  96  receives unused fuel from the cylinder assemblies  60  and from the fuel rail  80  via fuel outlet  90  and delivers the unused fuel to the fuel source  92 . Accordingly, because the fuel delivery system  56  allows fuel to be purged from the engine  50  after engine operation, the fuel delivery system  56  minimizes the ability for portions of the engine  50  to become disrupted by fuel vaporization. 
   While various embodiments of the invention have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
   For example, as indicated above, each bracket  102  of the fuel rail coupling members  84  is configured to secure a corresponding compliant support  100  to the fuel rail  80  and to secure the fuel rail  80  to a corresponding cylinder assembly. In one arrangement, each bracket  102  is moveably coupled a corresponding cylinder assembly  60 . In one arrangement, with particular reference to  FIGS. 4 and 5 , each bracket  102  includes a bracket portion  110  that defines an aperture  112 . The aperture  112  is sized and shaped to receive a protrusion  114 , such as a post, extending from a corresponding cylinder assembly, such as shown with respect to cylinder assembly  60 - 1 . The diameter of the aperture  112  is larger than an outer diameter of the protrusion  114 . In this configuration, when the protrusion  114  extends into the aperture  112 , the bracket  102  secures the fuel rail  80  to the cylinder assembly  60 - 1  while allowing both vertical  104  and longitudinal  108  motion of the fuel rail  80  relative to the cylinder assembly  60 - 1 . Such motion can be caused, for example, when operation of other cylinder assemblies  60 - 2 ,  60 - 3  within the set of cylinder assemblies causes the fuel rail  80  to move within the engine  50 . 
   For example, assume that during operation, the second cylinder assembly  60 - 2  fires and generates a horizontal and vertical load on the fuel rail  80 . The compliant support  102  of the coupling member  84 - 2  absorbs at least some of the vertical and longitudinal forces generated by the cylinder assembly  60 - 2  on the fuel rail  80 . However, generally longitudinal motion of the cylinder assembly  60 - 2  can cause the fuel rail  80  to translate along the longitudinal direction  106  relative to adjacent cylinder assemblies  60 - 1 ,  60 - 3 . Because the diameter of the aperture  112  for each coupling member  84 - 1 ,  84 - 3  is larger than an outer diameter of the protrusion  114  for each adjacent cylinder assembly  60 - 1 ,  60 - 3 , substantially longitudinal translation of the fuel rail  80  causes the brackets  102  to translate relative to the protrusions  114  of each cylinder assembly  60 - 1 ,  60 - 3 . Accordingly, the configuration of the brackets minimizes loading of the fuel rail  80  at any of the locations of the coupling member  84 - 1 ,  84 - 3  as caused by longitudinal translation of the fuel rail  80  within the engine  50 . 
   As indicated above, the fuel rail coupling members  84  include compliant supports configured to absorb at least a portion of the lateral and vertical loads applied to the fuel rail  80  by a corresponding cylinder assembly  60 . In one arrangement, the fuel delivery devices  59  also operate to absorb these lateral and vertical loads. For example, with particular attention to  FIG. 4 , each fuel delivery device  59 , such as a fuel injector, includes compliant members  120 ,  122  disposed at opposing ends. As illustrated, the fuel injectors include a first compliant member  120 , such as one or more O-rings, disposed at a cylinder assembly coupling end of the fuel injector  54  and a second compliant member  122 , such as one or more O-rings disposed at a fuel rail coupling end of the fuel injector  54 . The first and second compliant members  120 ,  122  act to seal a fluid pathway between the fuel rail  80  and the corresponding cylinder assembly  60 . For example, the cylinder assembly coupling end of the fuel injector  54  is disposed within a corresponding port of the cylinder assembly  60  such that interaction between the cylinder assembly port and the cylinder assembly coupling end of the fuel injector  54  compresses the first compliant member  120  to seal the fuel injector  54  relative to the cylinder assembly  60 . Also, the fuel rail coupling end of the fuel injector  54  is disposed within a corresponding fuel delivery port  86  such that interaction between the fuel delivery port  86  and the fuel rail coupling end of the fuel injector  54  compresses the second compliant member  122  to seal the fuel injector  54  relative to the fuel rail  80 . The first and second compliant members  120 ,  122  also absorb at least a portion of a load generated by the cylinder assembly  60 - 1  on the fuel rail  80  during operation. 
   As indicated above, the fuel rail  80  is configured as a generally tubular structure having a set of fuel delivery ports  86  disposed between a fuel inlet  88  and a fuel outlet  90 . In one arrangement, the fuel rail  80  also includes one or more fuel sensor ports  130  each of which configured to carry a corresponding fuel sensor  132 , such as a temperature sensor or a pressure sensor. The fuel sensors  132  allow various aspects (i.e., pressure, temperature) of the fuel to be electronically monitored such as by a central controller (not shown). As a result of such monitoring, the controller can adjust various parameters of the engine  50  to minimize fuel consumption and/or maximize operating efficiency of the engine  50 .