Patent Publication Number: US-2007102583-A1

Title: Systems and methods for reducing surge loads in hose assemblies, including aircraft refueling hose assemblies

Description:
TECHNICAL FIELD  
      The present invention is directed generally toward reducing surge loads in hose assemblies, including reducing surge loads in hose assemblies used in systems for in-flight refueling of aircraft.  
     BACKGROUND  
      In-flight refueling (or air-to-air refueling) is an important method for extending the range of aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, the aircraft to be refueled (e.g., the receiver aircraft) must be precisely positioned relative to the tanker aircraft in order to provide safe engagement while the fuel is dispensed to the receiver aircraft. The requirement for precise relative spatial positioning of the two rapidly moving aircraft makes in-flight refueling a challenging operation.  
      There are currently two primary systems for in-flight refueling. One is a hose and drogue system, which includes a refueling hose having a drogue disposed at one end. The hose and drogue are trailed behind the tanker aircraft once the tanker aircraft is on station. The pilot of the receiver aircraft then flies the receiver aircraft to intercept and couple with the drogue for refueling. Another existing system is a boom refueling system. The boom refueling system typically includes a rigid boom extending from the tanker aircraft with a probe and nozzle at the distal end. The boom also includes airfoils controlled by a boom operator stationed on the refueling aircraft. The airfoils allow the boom operator to actively maneuver the boom with respect to the receiver aircraft, which flies in a fixed refueling position below and aft of the tanker aircraft.  
      One challenge associated with in-flight refueling systems includes surge loads generated during the refueling process. For example, high surge pressures can be generated in the refueling hose by any sudden or rapid changes in the flow rate of fuel passing through the refueling hose (e.g., starting or stopping the fuel flow, increasing or decreasing the fuel flow, etc.) The sudden changes in flow rate can in turn cause surge loads or surge pulses in the system, which can travel up the refueling hose and back into the tanker aircraft fuel system. In some instances, the surge loads can damage the various components of the fuel system (e.g., pumps, tanks, plumbing, etc.) and/or other aircraft systems or components. One approach for damping or otherwise suppressing such surge loads is to use surge suppressors positioned within the aircraft at various locations along the fuel system to intercept the surge loads. Conventional surge suppressors can include, for example, one or more canisters having bladders or other types of suppression areas positioned to absorb at least a portion of the surge loads before the loads can potentially damage the various systems of the aircraft.  
      One drawback with conventional surge suppressors, however, is that they are typically not designed for the large surge loads generated during in-flight refueling operations. Most surge suppressors are only configured to handle the relatively small surge loads generated during ground refueling operations, rather than the large surge loads that can be generated during in-flight refueling operations. Another drawback with conventional surge suppressors is that the bladders need to be filled or “charged” with nitrogen or another suitable gas both before and during use. The charging process can be time-consuming and inefficient, and can create a requirement for additional hardware on the aircraft (e.g., pumps, tanks, plumbing, etc.) Still another drawback with conventional surge suppressors is that the performance of the suppressors can change significantly based on the operating conditions of the aircraft. For example, the gas in the bladder can be affected by changes in temperature and/or pressure as the aircraft is in flight. Such changes can negatively affect the performance of the surge suppressor, particularly during in-flight refueling operations when the generated surge loads can be relatively large. Accordingly, there is a need to improve the systems and methods for suppressing or otherwise reducing surge loads in hose assemblies.  
     SUMMARY  
      The following summary is provided for the benefit of the reader only, and does not limit the invention. Aspects of the invention are directed generally to aerial refueling systems. An airborne refueling system in accordance with one aspect of the invention includes a fuel delivery device having a flexible fuel line configured to be deployed overboard an aircraft during aerial refueling and a drogue coupled to the fuel line. The system can further include a surge damping portion positioned along the fuel line away from the aircraft to suppress surge loads traveling along the fuel line.  
      In several embodiments, the surge damping portion can include a compressible material disposed annularly about at least a portion of the fuel line. The compressible material can include, for example, solid rubber, foam rubber, silicone rubber, a foam material such as closed-cell foam or other suitable types of foam, or other suitable materials having a desired damping characteristic. In other embodiments, the surge damping portion and corresponding compressible material can include a bladder disposed annularly about at least a portion of the fuel line at least partially filled with a gas (e.g., air or another suitable gas). In still further embodiments, the system can include a plurality of surge damping portions positioned along the fuel line away from the aircraft.  
      A system for reducing surge loads in hose assemblies in accordance with another aspect of the invention can include a hose having a first segment and a second segment. The hose can include any type of flexible fluid conduit configured to carry a fluid. The system can further include a surge damping portion positioned annularly about at least a portion of the second segment of the hose. The surge damping portion is positioned to dampen radially expanding surge loads traveling along a longitudinal axis of the hose. In several embodiments, the surge damping portion can include a compressible material disposed annularly about at least a portion of the second segment of the hose.  
      A method for refueling an aircraft in accordance with another aspect of the invention can include aerially deploying from a tanker aircraft a portion of a refueling system that includes a flexible fuel line and a drogue. The method can further include suppressing surge loads traveling along the fuel line using a surge damping portion positioned along at least a portion of the fuel line away from the tanker aircraft. In several embodiments, for example, suppressing surge loads traveling along the fuel line includes transferring energy from radially expanding surge loads into a compressible material disposed annularly about at least a portion of the fuel line. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partially schematic, isometric illustration of a tanker aircraft having an aerial refueling device including a surge damping portion configured in accordance with several embodiments of the invention.  
       FIG. 2A  is an enlarged, partially schematic side cross-sectional view of a portion of a hose assembly of the aerial refueling device and the surge damping portion shown in  FIG. 1 .  
       FIG. 2B  is a cross-sectional view of the hose assembly and the surge damping portion taken along line  2 B- 2 B of  FIG. 2A .  
       FIGS. 3A-3C  are enlarged, partially schematic side cross-sectional views of the surge damping portion illustrating stages of a method for damping or otherwise suppressing a surge load using the surge damping portion of  FIGS. 1-2B .  
       FIG. 4  is an enlarged, partially schematic side cross-sectional view of a portion of a hose assembly and a surge damping portion configured in accordance with another embodiment of the invention.  
       FIG. 5  is an enlarged, partially schematic side cross-sectional view of a portion of a hose assembly and a surge damping portion configured in accordance with still another embodiment of the invention.  
       FIG. 6  is an enlarged, partially schematic side cross-sectional view of a portion of a hose assembly and a surge damping portion configured in accordance with yet another embodiment of the invention.  
    
    
     DETAILED DESCRIPTION  
      The present disclosure describes systems and methods for reducing surge loads in hose assemblies, including surge loads in hose assemblies used in aircraft refueling systems. Certain specific details are set forth in the following description and in  FIGS. 1-6  to provide a thorough understanding of various embodiments of the invention. Well-known structures, systems and methods often associated with such systems have not been shown or described in detail to avoid unnecessarily obscuring the description of the various embodiments of the invention. In addition, those of ordinary skill in the relevant art will understand that additional embodiments of the invention may be practiced without several of the details described below.  
       FIG. 1  illustrates a system  100  that includes a tanker aircraft  102  positioned to couple with and refuel a receiver aircraft  110  using an aerial refueling device  120  configured in accordance with an embodiment of the invention. The tanker aircraft  102  has a fuselage  103 , wings  104 , and one or more engines  105  (two are shown in  FIG. 1  as being carried by the wings  104 ). In other embodiments, the aircraft  102  can have other configurations. In a particular aspect of the embodiment shown in  FIG. 1 , the aerial refueling device  120  can include an on-board portion  122  (e.g., a hose reel activator and associated valving) and a deployable portion  124 . The deployable portion  124  can include a flexible fuel line or hose  126  and a drogue  128 . The position of the drogue  128  can be controlled to couple with a probe  112  of the receiver aircraft  110 . The hose  126  can include one or more surge damping portions  150  (only one is shown in  FIG. 1 ) configured to damp or otherwise suppress surge loads traveling through the hose  126  from the drogue  128  toward the on-board portion  122  of the refueling device  120 . Further details of the surge damping portion  150  and associated systems and methods for damping and/or suppressing surge loads are described below with reference to  FIGS. 2A-6 .  
       FIG. 2A  is an enlarged, partially schematic side cross-sectional view of a portion of the hose  126  and the surge damping portion  150  shown in  FIG. 1 . The hose  126  includes a fluid conduit having an inner portion or layer  130  surrounded by an outer portion or layer  132 . The inner and outer layers  130  and  132  of the hose  126  extend along a longitudinal or flow axis F of the hose  126 . The inner layer  130  of the hose  126  can be configured to carry fuel or other types of liquids. In several embodiments, for example, the inner layer  130  can include a soft rubber material that acts as a fluid seal. As described in greater detail below, the inner layer  130  can also be configured to transmit surge loads into the surge damping portion  150 .  
      The outer layer  132  of the hose  126  is an outer body that can provide a protective shroud or layer around the inner layer  130  in case of a liquid and/or vapor leak in the inner layer  130 . Accordingly, the outer layer  132  is generally isolated from fluid communication with the fuel or other liquid in the hose  126 . The outer layer  132  can include a rubber material or other suitable material that meets the desired operational requirements for the hose  126  (e.g., flexibility, strength, rigidity, etc.) In other embodiments, the inner layer  130  and/or the outer layer  132  of the hose  126  can be formed from other suitable materials or have other arrangements.  
       FIG. 2B  is a cross-sectional view of the hose  126  and the surge damping portion  150  taken along line  2 B- 2 B of  FIG. 2A . Referring to  FIGS. 2A and 2B  together, the surge damping portion  150  can include a compressible material  152  disposed annularly about the hose  126  such that the compressible material  152  is an integral part of the hose  126  between the inner layer  130  and the outer layer  132  of the hose  126 . As described in greater detail below with respect to  FIGS. 3A-3C , the compressible material  152  is positioned to absorb energy from a surge load traveling through the hose  126 . The compressible material  152  can include solid rubber, foam rubber, silicone rubber, a foam material such as closed-cell foam or other suitable types of foam, or a variety of other suitable materials having the desired damping characteristics. Furthermore, in other embodiments described below with  FIG. 4  the compressible material can include a suitable gas.  
      The compressible material  152  of the surge damping portion  150  can have a durometer value of approximately 10 to 90. The durometer value of the compressible material  152  can vary in accordance with the desired damping characteristics and/or operational requirements for the hose  126  and corresponding surge damping portion  150 . Although compressible material  152  having a lower durometer value can improve the damping rate of the surge damping portion  150 , the durometer value of the compressible material  152  should not be so low that the material overheats during operation. Furthermore, the durometer value of the compressible material  152  should be sufficient to provide the necessary stiffness to the hose  126  to meet the necessary operational requirements (e.g., flight loads during refueling operations). On the other hand, the durometer value should not be so high that the hose  126  and corresponding surge damping portion  150  are too stiff and/or do not have a desired damping functionality.  
      In the illustrated embodiment, the surge damping portion  150  has a length L (as shown in  FIG. 2A ) along the hose  126  and a thickness T (shown in both  FIGS. 2A and 2B ) between the inner layer  130  and the outer layer  132  of the hose  126 . The length L and thickness T of the surge damping portion  150  can be adjusted based on the desired damping characteristics for a particular application. In applications where large surge loads are expected, for example, the length L and/or thickness T can be increased to accommodate the larger loads. On the other hand, in applications where the surge loads are anticipated to be relatively small, the length L and/or thickness T of the surge damping portion  150  can be decreased.  
       FIGS. 3A-3C  are enlarged, partially schematic side cross-sectional views of the surge damping portion  150  shown in  FIGS. 1-2B  illustrating stages of a method for damping or otherwise suppressing a surge load in accordance with an embodiment of the invention.  FIG. 3A , for example, illustrates a preliminary stage of the method in which a surge pulse or surge load  300  initially reaches the surge damping portion  150  of the hose  126 . Surge pulses generated by fuel or other fluids passing through the hose  126 , such as the surge pulse  300  in the illustrated embodiment, generally include a radially expanding wave traveling along the hose from the drogue  128  ( FIG. 1 ) toward the on-board portion of the refueling device  120  ( FIG. 1 ). In the illustrated embodiment, for example, the surge pulse  300  is a wave traveling in a direction generally parallel to the flow axis F of the hose  126  (as shown by the arrows P). In one particular aspect of this embodiment, the inner layer  130  of the hose  126  includes a relatively soft rubber material configured to transmit the surge pulse  300  into the compressible material  152 . Accordingly, when the surge pulse  300  reaches the surge damping portion  150  of the hose  126 , the surge pulse  300  begins to expand into the compressible material  152  as shown in  FIG. 3A .  
      Referring next to  FIG. 3B , the surge pulse  300  continues to travel in the direction P along the hose  126 . As the surge pulse  300  passes through the compressible material  152  of the surge damping portion  150 , however, the energy from the surge pulse  300  is transferred to the compressible material  152  as the surge pulse displaces portions of the compressible material. In this way, the energy from the surge pulse  300  is converted to heat and, accordingly, the surge pulse  300  itself begins to shrink or otherwise dissipate. Referring to  FIG. 3C , for example, the surge pulse  300  has passed through approximately half the length of the surge damping portion  150 , and the surge pulse  300  is generally dissipated. As discussed previously, the energy (i.e., heat, pressure, etc.) from the surge pulse  300  can be transferred to the compressible material  152 , the hose  126 , and/or the fluid (not shown) passing through the hose  126 .  
      One feature of at least some of the embodiments of the surge damping portion  150  described above is that the surge damping portion  150  is relatively light and inexpensive compared with conventional surge suppression systems that can include a series of pumps and tanks to charge the nitrogen-filled canisters, as described previously. An advantage of this feature is that the surge damping portions  150  can significantly decrease the operating weight of the aerial refueling device  120  ( FIG. 1 ), which can increase efficiency and reduce the cost of operating the refueling system. Another advantage of this feature is that the complexity of the aerial refueling system is significantly reduced because the surge damping portion  150  does not require any additional tanks, pumps, or controllers for operation.  
      Another feature of at least some of the embodiments of the surge damping portion  150  described above is that the damping characteristics of the surge damping portion  150  are customizable based on anticipated loading conditions and/or operational conditions. For example, the length L and the thickness T of the compressible material  152  can be adjusted to accommodate a number of different loading conditions. The damping characteristics can be further adjusted by selecting a certain type of material having a desired durometer value for the compressible material  152 . An advantage of these features is that a hose for an aerial refueling system (such as the aerial refueling device  120  of  FIG. 1 ) can be designed to satisfy a number of different operational conditions. Furthermore, additional hoses with different suppression characteristics can be designed for the system and can be quickly and easily exchanged with the existing hose to accommodate varying operational requirements.  
      Still another feature of at least some of the embodiments of the surge damping portion  150  described above is that the surge damping portion of the hose  126  is positioned relatively close to the source of the surge loads (e.g., at or proximate to the drogue  128  ( FIG. 1 ) at a distal end of the hose  126 ). An advantage of this feature is that it can be significantly more effective to dampen or otherwise suppress surge loads or surge pulses close to the source of the surge load when the surge load is at or near its peak because it is generally easier to transfer large amounts of energy from large surge loads as opposed to transferring energy from smaller surge loads. For example, a large surge load will generally displace a larger volume of compressible material  152  and, accordingly, transfer more energy from the surge load to the compressible material  152 . The surge damping portion  150  proximate to the distal end of the hose  126  is accordingly expected to significantly improve the ability of the system to dampen or otherwise suppress large surge loads as compared with conventional surge suppressors that are positioned within the aircraft a large distance away from the source of the surge loads.  
       FIG. 4  is an enlarged, partially schematic side cross-sectional view of a portion of a hose assembly  426  and a surge damping portion  450  configured in accordance with another embodiment of the invention. The hose assembly  426  and surge damping portion  450  can be used with the aerial refueling device  120  of  FIG. 1 , or other suitable aerial refueling systems. The hose  426  illustrated in  FIG. 4  can be generally similar to the hose  126  described above with respect to  FIGS. 2A and 2B . For example, the hose  426  includes an inner layer or layer  430  surrounded by an outer layer or layer  432 . The inner and outer layers  430  and  432  can be formed from materials generally similar to the inner and outer layers  130  and  132  of the hose  126  described above with respect to  FIGS. 2A and 2B .  
      The surge damping portion  450  can be positioned along a portion of the hose  426  to damp or otherwise suppress surge loads traveling along the hose  450 . The surge damping portion  450  differs from the surge damping portion  150  described above with respect to  FIGS. 2A-2B  in that the surge damping portion  450  does not include a compressible material positioned between the inner and outer layers  430  and  432  of the hose  426 . Instead, the surge damping portion  450  includes one or more bladders  452  (only one is shown in  FIG. 4 ) positioned between the inner and outer layers  430  and  432  of the hose  426 . The bladder  452  is configured to be filled with a gas (e.g., air, nitrogen, or other suitable gases) using a gas supply  454  (shown schematically) operably coupled to the bladder  452 .  
      The bladder  452  can function in much the same way as the compressible material  152  of the surge damping portion  150  described above with respect to  FIGS. 2A-3C . For example, the bladder  452  can receive and dissipate surge loads in much the same way as the compressible material  152  described above. One particular aspect of this embodiment, however, is that the pressure within the bladder  452  can be adjusted during operation to dynamically adjust the damping or suppressing characteristics of the surge damping portion  450  based on the anticipated surge loads and/or operational conditions. For example, in situations where the surge loads are anticipated to be relatively high, the pressure in the bladder  452  can be increased to withstand the large loads. In other operational situations (either during the same refueling operation or during another refueling operation) when the surge loads are anticipated to be smaller, the pressure in the bladder  452  can be decreased. An advantage of this feature is that the hose  426  including the surge damping portion  450  can be used in a variety of operational situations, rather than requiring a user to change out the entire hose  426  or provide other types of additional surge suppression mechanisms to account for varying surge loads.  
      From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the invention. For example, a hose assembly can include any number of surge suppression portions along the hose to reduce surge loads in the hose. Furthermore, in several embodiments the hose assembly and/or surge suppression portions may have other configurations. Referring to  FIG. 5 , for example, a hose  526  in accordance with another embodiment of the invention includes an outer layer  532  and a surge damping portion  550  including compressible material  552  disposed annularly about the hose  526  and at least partially within the outer layer  532 . In one particular aspect of this embodiment, the hose  526  may not include an inner layer if the compressible material  552  of the surge damping portion  550  includes a material suitable for contact with fuel or other types of liquids. Referring to  FIG. 6 , a hose  626  in accordance with still another embodiment of the invention can include a surge damping portion  650  projecting inwardly from an outer layer  632  of the hose  626 , rather than being in and/or between one or more layers of the hose  626 . Aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, the surge damping features and methods described in the context of specific aircraft refueling systems can be implemented in a number of other aircraft or non-aircraft systems that include hose assemblies or fluid conduits where surge loads are an issue (e.g., petroleum industry applications, automotive applications, industrial or residential plumbing systems, etc.). Certain aspects of the invention are accordingly not limited to aircraft refueling systems. Further, while advantages associated with certain embodiments of the invention have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.