Patent Publication Number: US-2022221367-A1

Title: Burst-duct detection system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of allowed U.S. patent application Ser. No. 16/888,122 filed May 29, 2020, which published as US2020/0378861 on Dec. 3, 2020 and issuing as U.S. Pat. No. 11,287,349 on Mar. 29, 2022. 
     U.S. patent application Ser. No. 16/888,122 claimed the benefit of and priority to U.S. Provisional Patent Application No. 62/855,576 filed May 31, 2019. 
     The entire disclosure of the above patent application is incorporated herein by reference. 
    
    
     FIELD 
     The present application relates to a system for detecting a burst duct and methods of detecting a burst duct event in an aircraft. 
     BACKGROUND 
     A burst duct will release high pressure and high temperate air and increase pressure in an aircraft nacelle causing structural damage and damage to equipment not capable of operating with these severe environments caused by the burst duct. Regulations specify that a duct rupture shall not lead to an aircraft hazardous condition. 
     To relieve the over pressure in a nacelle compartment consecutive to an air duct rupture, a pressure relief system may be installed. It usually consists in a latched door that is triggered open under a given pressure differential and discharging air outside the compartment. It allows reducing, first the pressure peak occurring few hundredth seconds after the burst and secondly the stabilized pressure seen in the nacelle. 
     It may be necessary to alleviate the over-temperatures in a compartment consecutive to a duct rupture event. In this case, a temperature detection system is implemented. Once triggered, this system either commands the closure of valves associated to the air rupture source and/or sends a cockpit warning. 
     New devices and methods of detecting burst-duct events are needed so that failure of aircraft systems can be prevented. 
     BRIEF SUMMARY 
     A burst-duct detection system is provided. The system may include a manifold; a rolling diaphragm dividing a chamber within the manifold into a top portion and a bottom portion; a high pressure chamber in fluid communication with the top portion of the manifold; an ambient pressure chamber in fluid communication with the bottom portion of the manifold; a piston disposed within the top portion of the manifold and operably connected to the rolling diaphragm; a mechanical link comprising a proximal end, a distal end, and a middle portion, the mechanical link being disposed within a core chamber of the manifold and the proximal end operably connected to the piston; and an indicator piston operably connected to the mechanical link. 
     A method of detecting a burst-duct event in an aircraft is also provided. The method may include allowing air in an internal area of the aircraft to pass into a high pressure chamber within a manifold; passing the air from the high pressure chamber into a top portion of the manifold; urging a piston to move if the high pressure chamber has an air pressure that exceeds an ambient air pressure in an ambient air chamber and a sensing spring; and actuating a mechanical link operably connected to the piston to disengage an indicator piston. 
     The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter that form the subject of the claims of this application. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the disclosure as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an embodiment of a burst-duct detection system. 
         FIG. 2  illustrates an exploded view of an embodiment of a burst-duct detection system. 
         FIG. 3  illustrates several perspective views and dimensions of an example burst-duct detection system. 
         FIG. 4A  illustrates a perspective view of an embodiment of a burst-duct detection system. 
         FIG. 4B  illustrates a perspective view of an embodiment of a burst-duct detection system. 
         FIG. 4C  illustrates a perspective view of an embodiment of a burst-duct detection system that indicates that a burst duct event has occurred. 
         FIG. 4D  illustrates a perspective view of an embodiment of a burst-duct detection system before detection of a burst-duct event. 
         FIG. 5A  shows a cross-sectional view of an example of the burst-duct detection system. 
         FIG. 5B  shows a cross-sectional view of an example of the burst-duct detection system. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments are described below with reference to the drawings in which like elements generally are referred to by like numerals. The relationship and functioning of the various elements of the embodiments may better be understood by reference to the following detailed description. The embodiments, however, are not limited to those illustrated in the drawings. It should be understood that the drawings are not necessarily to scale, and in certain instances details may have been omitted that are not necessary for an understanding of embodiments disclosed herein, such as—for example—conventional fabrication and assembly. 
     The actuation of the burst-duct detection system (BDDS) may occur when a burst duct event occurs on the aircraft engine. When this occurs, a large amount of air may enter the nacelle and cause the nacelle pressure to increase relative to the surrounding ambient pressure (outside air pressure). This increase in nacelle pressure may flow to the BDDS sensing mechanism, thus increasing the pressure on one side of the rolling diaphragm. The larger force caused by the increased pressure may overcome the sensing mechanism spring force, and the opposing ambient pressure. When this occurs the piston will move thereby moving the integrally connected mechanical link that may unlock the indicator piston. Once the indicator piston is no longer locked, the actuating spring may push the indicator piston into the airstream providing an external visual indication that alerts an aircraft mechanic that a burst duct event has occurred prompting the repair of the burst duct inside the nacelle. 
     Once the aircraft is on the ground, the aircraft engine will be shut down and no air will be exiting from the engine burst duct. At that point, the nacelle air pressure and the ambient pressure may equalize. With equal pressure on the rolling diaphragm, the sensing spring will move the sensing mechanism to an initial position, and the mechanical link will latch onto the second locking slot on the indicator piston, locking the indicator piston in the actuated position and preventing an aircraft mechanic from resetting the indicator piston by simply pushing the indicator piston into the nacelle. 
     To reset the indicator piston, the aircraft mechanic will need to gain access to the indicator reset cavity covered by the reset indicator cover. Once the mechanic removes the reset indicator cover, the mechanical link can be pulled to the position, unlocking the indicator piston, the aircraft mechanic can then push the indicator piston, compressing the actuating spring, and then by simply releasing the mechanical link to lock the indicator piston in place. 
       FIG. 1  shows a perspective view of a burst-duct detection system (BEDS)  100 . The system  100  may be a device that includes a manifold  101  containing the sensing components (not pictured) and air filters  103 . The top plate  102  may be for covering the internal components. 
     The manifold  101  houses the differential pressure indicator components. The manifold  101  along with a thermal barrier or heat shield (not pictured) may also provide a controlled thermal barrier that may provide a fire barrier during a fire event, to limit damage to temperature-sensitive indicator components. The fire barrier may allow enough thermal energy to prevent exposure of indicator components to the nacelle external environment and/or to limit malfunction due to freezing water. 
     The construction of the manifold may be any suitable material that meets the design and performance standards required to operate in the environments encountered in aircraft devices. For example, the manifold may be made of aluminum with an anodize coating. The manifold may be designed to meet the pressure, vibration and temperature requirements of the desired environment and specific application. 
     The manifold design may have a contact area with the air in the nacelle external air stream. The manifold outer surface may provide a heat sink and along with insulation on the internal area, which may be exposed to high temperatures from the engine compartment, may control the internal indicator component temperatures. 
       FIG. 2  shows an exploded view of an example of the BDDS  100 . The BDDS  100  may include a manifold  101  that defines a high pressure chamber  200  and an ambient pressure chamber  201  within the manifold  101 . A piston  202  may be disposed within a chamber within the manifold  101  and operably connected to a mechanical link  204 . The mechanical link  204  may be disposed within indicator reset cavity  205 . An indicator piston  206  is disposed within a core chamber  207  of the manifold  101 . 
     The first filter element  220  may be disposed within the high pressure chamber  200  of the manifold  101 . A second filter element  221  may be disposed within the ambient pressure chamber  201  of the manifold  101 . The first filter element  220  may be a high pressure filter, and the second filter element  221  may be an ambient pressure filter. A retainer plug  211  provides guidance to the piston  202  and the diaphragm guide  212  provides guidance to rolling diaphragm. A sensing spring  213  counteracts differential pressure. An O-ring  214  provides a seal between the manifold  101  and the top plate  102 . The O-ring  215  provides a seal between the manifold  101  and the filter elements  220  and  221 . The O-ring  216  provides a seal between the manifold  101  and the indicator reset cover  218 . The actuating spring  217  is operably connected to the indicator piston  206 . Screws  219  secure the indicator reset cover  218  to the manifold  101 . 
       FIG. 3  shows several views and example dimensions of an embodiment of the BDDS  100 . The dimensions provided in  FIG. 3  are one of many examples and should not be construed as limiting. 
       FIG. 4A  shows a perspective view of an example of a BDDS  100 . The BDDS  100  may have an indicator piston opening  400  in which the indicator piston (not pictured in  FIG. 4A ) is disposed. The system may have an ambient pressure opening  402  that is in fluid communication with the ambient pressure chamber  201 . The ambient pressure chamber  201  is in fluid communication with ambient air. The high pressure chamber  200  may be in fluid communication with an internal area of an aircraft. In some aspects, the high pressure chamber  200  is not in fluid communication with the ambient pressure chamber  201 . 
       FIG. 4B  shows a perspective view of a BDDS  100 . The BDDS  100  may have a sensing mechanism cavity  403 . The BDDS  100  may comprise a projection  407  that defines an indicator spring access cavity  404 . The indicator spring access cavity  404  provides access to the core chamber (not pictured) of the manifold  101 . 
       FIG. 4C  shows the BDDS  100  with the indicator piston  405  protruding from the manifold  101 , indicating that a burst duct event has been detected.  FIG. 4D  shows the indicator piston  405  in the indicator opening  400  before a burst duct event is detected. 
       FIGS. 5A and 5B  show an example of a differential pressure sensing mechanism, which includes the piston  202 , rolling diaphragm  500 , and sensing spring  501 . The sensing spring  501  is disposed within the bottom portion  505  of the manifold  101  opposite the piston  202  and operably connected to the mechanical link  204 . The mechanical link  204  may be a linear actuator, comprising a proximal end  514 , a distal end  516 , and a middle portion  515 . The middle portion  515  may be a loop through which the indicator piston  206  passes and with which the indicator piston  206  engages. 
     The mechanism provides the function of sensing the differential pressure between the compartment in fluid communication with the high pressure chamber  200  and external airflow (ambient pressure). The differential pressure sensing mechanism ports air pressures from the external air stream and from inside the nacelle so that it acts as a differential pressure-sensing device. The piston  202  may be attached to a rolling diaphragm  500  that provides for low sliding friction and allows the use of static seals. The rolling diaphragm  500  may be disposed between the mechanical link  204  and the piston  202 . 
     The piston  202  will move once the differential force exceeds the prescribed differential pressure. The spring force for the BDDS will have a relative low force versus displacement profile allowing for a relatively large displacement for a given differential pressure permitting the actuation of the indicator piston via the mechanical link that will provide an indication of a burst duct event yet prevent actuation due to vibration. 
       FIG. 5A  shows a cross-sectional view of an example of a BDDS  100 . The rolling diaphragm  500  divides a chamber in the manifold  101  into a top portion  504  and a bottom portion  505 . The piston  202  is disposed within the top portion  504  and is operably connected to the rolling diaphragm  500 . Ambient pressure conduit  502  connects the ambient pressure chamber  201  with the top portion  504 . The high pressure conduit  503  connects the high pressure chamber  200 . Arrows  506  depict the flow of high pressure air through a high pressure filter  220 , into the high pressure chamber  200 , into the high pressure conduit  503 , and into the top portion  504 . Once the pressure in the top portion  504  exceeds the pressure in the ambient pressure conduit  502  and the force of the sensing spring  501 , the piston  202  actuates the mechanical link  204 . The mechanical link  204  is operably connected to the indicator piston  206  in the core chamber  507  of the manifold  101 .  FIG. 5A  shows the mechanical link  204  half-way through actuation. The mechanical link  204  disengages with the indicator piston  206 , thereby allowing the indicator piston  206  to exit the manifold  101  at least partially. 
       FIG. 5B  shows a cross-sectional view of an example of a BDDS  100  half-way through actuation. Once the mechanical link  204  disengages the indicator piston  206 , an actuating spring  508  that is operably connected to a distal end  512  of the indicator piston  206  moves the indicator piston  206  such that a proximal end  513  of the indicator piston  206  protrudes from the manifold  101 . The indicator piston  206  may have a first locking slot  509  that engages the mechanical link  204 . The indicator piston  206  may have a second locking slot  510  that can engage the mechanical link  204  after the first locking slot  509  disengages the mechanical link  204  and the high pressure chamber  200  and the ambient pressure chamber  201  have about equal pressure. 
       FIG. 5B  also shows that the first locking slot  509  comprises a dimension  511  that is selected (predetermined) such that the mechanical link  204  does not disengage the indicator piston  206  in the absence of a burst-duct event. In some aspects, the first locking slot has a depth of about 2.4 mm to about 3.18 mm. 
     Once the aircraft returns to ground and the engine is shut off, the pressure equalizes between the core chamber  507  and external air, thereby actuating the mechanical link to revert back to its normal position and lock the indicator piston in place by engaging with the second locking slot. 
     To reset the BDDS, to get access to the mechanical link  204 , the cover  102  may be removed and access is then available to the mechanical link  204 , which can then be reset using basic hand tools. The system design prevents manually resetting the indicator piston by simply pushing the indicator piston back into the manifold  101 . The BDDS allows for the resetting of the indicator with no special tooling by accessing the indicator piston through the indicator reset cavity. 
     Filters  220  and  221  limit the contaminants seen by the sensing components of the BDDS. The filters  220  and  221  provide a barrier for contaminants from fouling the differential pressure sensing mechanism and the indicator piston mechanism. Contamination of different sizes can have an order of magnitude increase in the friction forces of sliding surfaces contained in the system, thereby negatively impacting the sensitivity of the indicator actuation. 
     In some aspects, the filters  220  and  221  may include a stainless steel screen. 
     In some aspects, the ambient pressure chamber  201  may be in fluid communication with the core chamber  507  inside the manifold  101 . In some aspects, the core chamber  507  has two openings to the external air stream. The first opening houses the indicator piston  206 . The indicator opening  400  has a metal to metal poppet seal creating a barrier and blocking contaminants from entering the indicator housing. The second opening passes external air through the ambient pressure filter (second filter element  221 ) to the core chamber  507 . The core chamber  507  may be pressure balanced by having pressure in the airstream and inside the BDDS housing. Having a pressure balance eliminates the impact of ambient air pressure variation at different altitudes causing variable loads on the indicator piston  206 . 
     In some aspects, the system comprises a metal to metal seal between the manifold  101  and the indicator piston  206  where the indicator piston  206  extends into the airstream. Advantageously, a metal to metal seal is not as affected by temperature and contaminants as an elastomeric seal. Also, there will be a fixed resistance force between the indicator piston  206  and manifold  101 . 
     In some aspects, the distal end of the indicator piston  206  may comprise a protrusion that extends perpendicular to a longitudinal direction of the indicator piston  206 . This protrusion may prevent the indicator piston from ejecting from the manifold  101  when the mechanical link disengages the first locking slot as a burst-duct event is detected. 
     A burst-duct event in an aircraft may be detected using the system and methods disclosed herein. A method of detecting a burst-duct event may include allowing air in an internal area of the aircraft to pass into a high pressure chamber within a manifold. The air entering the high pressure chamber may be passed through a filter and into a top portion of the manifold. As the pressure differential increases a piston moves, thereby actuating a mechanical link operably connected to the piston to disengage an indicator piston. 
     The method may include moving the indicator piston to a position where a portion of the indicator piston protrudes from the manifold once the mechanical link disengages a first locking slot on the indicator piston. In some aspects, the method may include engaging the mechanical link with a second slot on the indicator piston when the high pressure chamber and the ambient pressure chamber have about equal pressure. 
     In some aspects, the operating pressure of the system may be from about 17.2 kPa (2.5 psig) to about 137.9 kPa (20 psig). In some aspects, a burst pressure may be about 34.5 kPa (5 psig). In some aspects, the BDDS actuation pressure may be about 20.7 kPa (3 psig). 
     The materials of the system may be selected so that the system may operate at temperatures of about −54° C. to 400° C. 
     All of the systems and methods disclosed herein can be made and executed without undue experimentation in light of the present disclosure. While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. In addition, unless expressly stated to the contrary, use of the term “a” is intended to include “at least one” or “one or more.” For example, “a device” is intended to include “at least one device” or “one or more devices.” 
     Any ranges given either in absolute terms or in approximate terms are intended to encompass both, and any definitions used herein are intended to be clarifying and not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges (including all fractional and whole values) subsumed therein. 
     Furthermore, the invention encompasses any and all possible combinations of some or all of the various embodiments described herein. It should also be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.