Patent Publication Number: US-2012023967-A1

Title: Auxiliary power unit with hot section fire enclosure arrangement

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Contract No. N00019-06-C-0081 awarded by the United States Navy. The Government has certain rights in this invention. 
    
    
     BACKGROUND 
     The present disclosure relates to an auxiliary power unit (APU), and more particularly to a hot section fire enclosure arrangement therefore. 
     Many aircraft are equipped with an APU to provide electrical and pneumatic power for such tasks as environmental control, lighting, powering electronics, main engine starting, etc. 
     For aircraft APU installations, a dedicated fire zone is typically defined within the aircraft. Alternatively, some APUs include a Hot Section Fire Enclosure (HSFE) within which is a fire zone. Although effective, the HSFE may complicate access to line replaceable units (LRUs). 
     SUMMARY 
     A HSFE for a gas turbine engine according to an exemplary aspect of the present disclosure includes a multiple of supports mounted between a HSFE support ring and a shroud, at least one of the supports includes a hollow support pin which spaces the HSFE support ring relative the shroud. 
     A gas turbine engine according to an exemplary aspect of the present disclosure includes a HSFE access cover mountable to the HSFE. A first and second fireproof split ring section. A split ring retainer mountable to the HSFE access cover to retain the first and second fireproof split ring sections to sandwich a LRU component therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a partial phantom view of a rotary-wing aircraft illustrating a power plant system; 
         FIG. 2  is a general perspective view of an APU hot section; 
         FIG. 3  is a general perspective view of a gas turbine engine APU installed within an airframe of the exemplary rotary wing aircraft embodiment; 
         FIG. 4  is a longitudinal sectional view of an APU hot section; 
         FIG. 5  is a lateral sectional view of an APU hot section; 
         FIG. 6  is a lateral sectional view of a support for a HSFE for the APU hot section; 
         FIG. 7  is an exploded lateral sectional view of the support; 
         FIG. 8  is a perspective view of a support for a HSFE with a HSFE access cover for access to a LRU; and 
         FIG. 9  is a sectional view of the HSFE access cover. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a rotary-wing aircraft  10  having a main rotor system  12 . The aircraft  10  includes an airframe  14  having an extending tail  16  which mounts an anti-torque system  18 . The main rotor system  12  is driven about an axis of rotation A through a main rotor gearbox (MGB)  20  by a multi-engine powerplant system  22 —here having three engine packages ENG 1 , ENG 2 , ENG 3  as well as an Auxiliary Power Unit (APU)  24 . The engine packages ENG 1 , ENG 2 , ENG 3  and APU  24  are examples of gas turbine engines. The multi-engine powerplant system  22  generates the power available for flight operations and couples such power to the main rotor system  12  through the MGB  20 . Although a particular helicopter configuration is utilized to disclose the APU  24 , it should be further understood that various vehicles and systems such as ground carts, commercial airplanes and helicopters, military airplanes, LCAC landing craft, tanks etc., will also benefit herefrom. 
     Referring to  FIG. 2 , the APU  24  includes a Hot Section Fire Enclosure (HSFE)  30  with a HSFE aft support ring  32  to support a downstream exhaust system  34  ( FIG. 3 ) through a flange  36 . The HSFE  30  may be defined by a multiple of components disposed around the APU  24 . Gaskets (not illustrated) may be used between the constituent components of any respective joint (not illustrated); alternatively, the pitch of the bolt pattern which attach the constituent components can be designed to form a fireproof joint. 
     With reference to  FIG. 4 , the HSFE  30  defines a fire zone to at least partially enclose a combustor section  40  and an exhaust shroud  42  which are generally downstream of a turbine wheel  41 . It should be understood that various HSFE arrangements may alternatively or additionally be utilized. 
     The aft support ring  32  defines an annular eductor flow around an exhaust flow from the exhaust shroud  42 . The HSFE aft support ring  32  is spaced relative the exhaust shroud  42  through a multiple of supports  44  (also illustrated in  FIG. 5 ). It should be understood that any number of supports  44  may be utilized. 
     With reference to  FIG. 6 , each support  44  generally includes a mounting boss  46  brazed to the HSFE aft support ring  32 , a sleeve  48  brazed to the exhaust shroud  42 , a hollow support pin  50  and at least one fastener F. The hollow support pin  50  may include a hollow pin member  52  with a transverse flange  52 F to form a “T” shape ( FIG. 7 ). The flange  52 F receives the fasteners F to bolt the hollow support pin  50  to the HSFE aft support ring  32 . The hollow pin member  52  fits within and abuts a contact surface  48 S within the sleeve  48 . That is, the hollow support pin  50  supports the exhaust shroud  42  in a radial manner. 
     The hollow pin member  52  permits entry of a thermocouple  54  or others such line replaceable unit (LRU) to be mounted external to the HFSE aft support ring  32  thereby facilitating maintenance without the necessity of HFSE  30  disassembly. It should be understood that the hollow support pin  50  may be utilized for other purposes such as for a vent. One fastener Fa may be utilized to assemble the support  44  while the other fastener Fb may be utilized to assemble the support  44  and retain the thermocouple  54  ( FIG. 7 ). 
     With reference to  FIG. 8 , the HSFE  30  may additionally include a HSFE access cover  60  which mounts to the HSFE  30  in a fireproof relationship. The HSFE access cover  60  is sized to mount a LRU such as an ignitor L or other component which has a conduit or access lead L 1  connected thereto ( FIG. 9 ). The HSFE access cover  60  facilitates removal and replacement of the LRU yet maintains a fire seal. 
     With reference to  FIG. 9 , the access cover  60  is fastened to the HSFE  30  with a multiple of fasteners  62 . The lead L 1  from the ignitor L is sandwiched between two fireproof split rings  64 A,  64 B. It should be understood that various other LRUs may alternatively benefit herefrom. The split rings  64 A,  64 B are sized so that any gaps provide a large enough length to gap ratio to prevent fire penetration. A split ring retainer  66  mounts the fireproof split rings  64 A,  64 B to the access cover  60  to retain the split rings  64 A,  64 B and sandwich the lead L 1  therein. The access cover  60  and the split ring retainer  66  are sized to receive the ignitor L or other LRU to facilitate replacement without disassembly of the HSFE  30  from the APU  24 . 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.