Abstract:
A gas turbine engine has a nacelle, a plurality of pipes and a drains assembly, the drains assembly including a drains mast that extends through the nacelle and provides an outlet for the pipes. The engine is characterised in that drains assembly has a connection block defining internal passages and is arranged to connect between the pipes and the drains mast. The connection block also has lateral connections to the pipes enabling the nacelle to have a lower profile; thereby reducing aerodynamic drag.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is entitled to the benefit of British Patent Application No. GB 0701683.5 filed on Jan. 30, 2007. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a drain assembly for discharging fluids from pipes and conduits of a gas turbine engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    A gas turbine engine requires a drain assembly to collect excess or spilled fluids from various service pipes and to discharge the fluids safely overboard. The drain assembly comprises a drains mast that extends through a nacelle surrounding the engine. Identification markings are placed on the mast to indicate particular fluid spill and therefore assist engine fault diagnosis. 
         [0004]    Drain assemblies must be positioned at or near to the bottom dead centre of the engine to allow the spilled fluids to exit the drains mast via gravity. Conventional engine drain assemblies, as shown in  FIG. 3 , comprise a mounting bracket off which the mast extends, the pipes are routed through the hollow mast. Although a working design, this conventional arrangement means that the distance between the engine and the external surface of the nacelle is particularly large and the powerplant is therefore disadvantaged by aerodynamic losses and weight. 
       SUMMARY OF THE INVENTION 
       [0005]    Therefore, it is an object of the present invention to provide a more compact drains assembly and therefore a more aerodynamic and lighter nacelle. 
         [0006]    In accordance with the present invention, a gas turbine engine comprises a nacelle, a plurality of pipes and a drains assembly, the drains assembly includes a drains mast that extends through the nacelle and provides an outlet for the pipes characterised in that drains assembly comprises a connection block defining internal passages and is arranged to connect between the pipes and the drains mast. 
         [0007]    Preferably, the connection block includes an elastomeric material. 
         [0008]    Preferably, a mounting bracket is arranged to mount the connection block to the engine. 
         [0009]    Preferably, the connection block includes lateral connections to the pipes. 
         [0010]    Preferably, a portion of the pipes at the connection is at an angle that is greater than the mounting angle of the engine. 
         [0011]    Preferably, the angle is up to 5 degrees greater than the mounting angle of the engine. 
         [0012]    Preferably, the connection block includes a lateral surface that is at an angled greater than the mounting angle of the engine. 
         [0013]    Alternatively, the connection block includes a lateral surface that has two or more regions that are angled greater than the mounting angle of the engine. 
         [0014]    Conveniently, the drains mast includes internal tubes defining outlets, the internal tubes are connected to the passages of the connection block. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic section of part of a ducted fan gas turbine engine; 
           [0016]      FIG. 2  is a front view of an aircraft showing a wing mounted engine; 
           [0017]      FIG. 3  is a view of a prior art drain assembly; 
           [0018]      FIG. 4  is a view on a drain assembly in accordance with the present invention; 
           [0019]      FIG. 5  is a cross-section A-A shown in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to  FIG. 1 , a ducted fan gas turbine engine generally indicated at  10  has a principal and rotational axis  11 . The engine  10  comprises, in axial flow series, an air intake  9 , a propulsive fan  12 , an intermediate pressure compressor  13 , a high-pressure compressor  14 , combustion equipment  15 , a high-pressure turbine  16 , and intermediate pressure turbine  17 , a low-pressure turbine  18  and a core exhaust nozzle  19 . A nacelle  21  generally surrounds the engine  10  and defines the intake  9 , a bypass duct  22  and an exhaust nozzle  23 . 
         [0021]    The gas turbine engine  10  works in the conventional manner so that air entering the intake  9  is accelerated by the fan  12  to produce two air flows: a first airflow into the intermediate pressure compressor  13  and a second airflow which passes through a bypass duct  22  to provide propulsive thrust. The intermediate pressure compressor  13  compresses the airflow directed into it before delivering that air to the high pressure compressor  14  where further compression takes place. 
         [0022]    The compressed air exhausted from the high-pressure compressor  14  is directed into the combustion equipment  15  where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines  16 ,  17 ,  18  before being exhausted through the nozzle  19  to provide additional propulsive thrust. The high, intermediate and low-pressure turbines  16 ,  17 ,  18  respectively drive the high and intermediate pressure compressors  14 ,  13  and the fan  12  by suitable interconnecting shafts  27 . 
         [0023]    The fan  12  is circumferentially surrounded by a structural member in the form of a fan casing  24 , which is supported by an annular array of outlet guide vanes  25 . 
         [0024]    A gear box  26  and drive  28  connect the high-pressure shaft  27  to a starter / generator  29 . The gear box  26  and other accessories are mounted on the fan casing  24 . Overflow or spillage pipes  32  connect between the engine accessories, and to other engine components such as bearings, to a drain assembly  34 . The drain assembly  34  is mounted to the gearbox, but could be mounted elsewhere, and extends through the nacelle  21  and provides an outlet for the pipes  32  where the spilled fluids are discharged. 
         [0025]    Referring to  FIG. 2 , the engine  10  is mounted to a wing  8  of an aircraft  7  via a pylon  9 . The wing  8  is arranged at a dihedral angle β to the horizontal. The dihedral angle β is usually between 4-8 degrees and is typically 6 degrees. The pylon  9  is usually normal to the wing&#39;s under-surface and the engine  10  is therefore mounted at an angle α, which is usually the same value as the dihedral angle. However, it should be appreciated that angle α may not necessarily be the same as the dihedral angle β. 
         [0026]      FIG. 3  shows a prior art drain assembly  34  comprising a bracket  36 , attached to the gearbox  26 , and a drains mast  38 . The drains mast  38  is an aerodynamically shaped hollow body having a flat end  40  defining outlets  42  for the pipes  32 . In all cases the pipes  32  enter the drain assembly  34  and the mast  38  from vertically above. However, this arrangement is disadvantaged because the pipes  32  require complex bends and a large gap is required between the outer surface  31  of the nacelle  21  and the engine  10  to accommodate the drain assembly  34 . Thus the prior art drains assembly  34  compromises the aerodynamic profile of the nacelle  21 . 
         [0027]      FIGS. 4 and 5  show a drains assembly  50  in accordance with the present invention. The drains assembly comprises a mounting bracket  52  and a connection block  56  for connecting between the plurality of pipes  32  and a drain mast  54 . The drain mast  54  has the same aerodynamic profile as the prior art mast  38  and similarly extends through the nacelle  21 . The drains mast  54  comprises a plurality of internal tubes  64  extending from an outlet  66  of the mast to the connection block  56 . 
         [0028]    The connection block  56  is a solid body defining internal passages  58  therethrough (only one of which is shown) and is arranged to connect between the pipes  32  and the drains mast  54 . The pipes  32  connect to the lateral sides  60  of the block  56  via interference fit between the end of the pipe  32  and the passageway  58 . The pipes  32  are further secured in place via a collar  62  that is bolted to the mounting bracket  52 . Similarly, the plurality of internal tubes  64  are connected to the connection block  56  via interference fits, with the tubes  64  extending into the connection block  56 . 
         [0029]    In a preferred embodiment, the connection block  56  comprises an elastomeric material such as rubber, but other materials that are resilient may be used. 
         [0030]    Preferably, and as seen in  FIG. 4 , the pipes  32  connect to the block  56  perpendicularly to the lateral surface  60 . So that the pipes  32  are always slightly sloping downward towards the block  56 , the angle α of the pipes  32  is required to be greater than the mounting angle α of the engine  10 . Note here that normally there are pipes  32  attached to each side of the connection block  56  and that engines on opposite wings will be angled β at ±6 degrees. Thus the lateral surfaces  60  of the connection block  56  are angled μ at 7 degrees. 
         [0031]    It should be appreciated that the angle θ of the pipes  32  may be less than or greater than stated above and is dependant on the engine&#39;s mounting angle α and/or the dihedral angle β of the wing  8 . Pipe angles θ up to 5 degrees greater than the mounting or dihedral angle α, β of the engine  10  are preferable. Pipe angles θ significantly greater than 5 degrees are still beneficial, but the benefit of a more compact and aerodynamic nacelle  21  profile is reduced because the connection block  56  will need to be positioned lower on the gearbox  26 . 
         [0032]    Note that only a portion of the pipes  32  near the connection block  56  are required to be at an angle θ that is greater than the mounting angle or dihedral angle α, β of the engine  10 . 
         [0033]    In the preferable embodiment where the pipes  32  connect to the block  56  perpendicular to the lateral surface  60 , the lateral surface  60  is therefore arranged at a corresponding angles μ i.e. μ equals θ. It is possible for the lateral sides  60  to be parallel i.e. μ does not equals θ, for example, however, this will lead to uneven immersion of the pipe into the connection block and the possibility of the pipe forming a sump on one of the engines due to the dihedral. 
         [0034]    In another embodiment, the connection block  56  comprises a lateral surface  60  having two or more regions that are angled μ differently to one another to accommodate different pipe angles θ. In this case it may be that the various pipes  32  are routed around different engine architecture therefore having different clearances.