Abstract:
An aerofoil assembly including an aerofoil and a spray element that supplies fluid to a gas turbine engine. The aerofoil has a first part with a leading edge when located in the gas turbine engine, and a second part with a trailing edge when located in the gas turbine engine. The first part has features that slide relative to and engage with complementary features of the second part to form a releasable arrangement.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns components for gas turbine engines and particularly components that inject fluid towards the compressor section of an industrial gas turbine. 
     The hot day power of an industrial gas turbine engine may be increased by injecting fine water droplets as a spray into the engine air intake. Part of the injected water may evaporate before entering the engine to create a fog which reduces the air intake temperature. 
     Power may be further augmented by adding sufficient water such that some may be carried into the compressor as droplets. The water is evaporated in the compressor which enables at least some of the compression process to be carried out at reduced temperatures. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide improved apparatus for injecting fluid, particularly water, into a compressor. 
     According to a first aspect of the invention there is provided an aerofoil spray assembly for a gas turbine engine, the aerofoil having a first part with a profile intended to provide a leading edge when located in a gas turbine engine, a second part with a profile intended to provide a trailing edge when located in a gas turbine engine, wherein the first part has features that engage with complementary features on the second part to form a releasable arrangement, characterised in that a spray element for supplying a fluid to the gas turbine is secured between the first and second parts. 
     Preferably the features that engage on the first part may slide relative to the complementary features on the second part to form the releasable arrangement. 
     Preferably the features that engage on the first part provide at least one valley that extends parallel to the leading edge and the complementary features are provided by at least one projection that extends parallel to the trailing edge and slides within the valley. 
     The first part may have an internal bore for the passage of a fluid. A third part is preferably secured between the first and second parts. 
     The third part may be a spray element that provides a fluid conduit between the bore and a nozzle on the spray element. Preferably the spray element has a plurality of arms, each arm having a nozzle at its extremity. 
     The aerofoil assembly may be provided in a gas turbine engine. Preferably the aerofoil assembly is located upstream of the compressor. Preferably the aerofoil assembly is connected to a fluid manifold for the supply of fluid to the nozzles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example only with reference to the following drawings in which: 
         FIG. 1  depicts an industrial gas turbine incorporating a spray mechanism in accordance with the invention. 
         FIG. 2  depicts an array of water injection bars; 
         FIG. 3  depicts a spray bar; 
         FIG. 4  depicts a spray bar element; 
         FIG. 5  depicts a front fairing of a spray bar; 
         FIG. 6  shows a front fairing with a spray element attached; 
         FIG. 7  shows attachment of a rear fairing to the front fairing; 
         FIG. 8  depicts the bottom surface of the spray bar; 
         FIG. 9  depicts a top cap of the spray bar. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The industrial gas turbine depicted in  FIG. 1  has an air inlet housing  2  which feeds air to an engine core which includes a compressor section  4  that compresses the fed air. The compressed air is subsequently passed to a combustor section and then to a turbine section. Fuel is added to the air stream in the combustion section and combusted. The hot combustion gasses are expanded in the turbine section to extract work which drives the compressors. 
     An inner flare  6  and outer flare  8  are provided to direct and smooth the flow of air into the compressor. Immediately before the flow of air enters the compressor it passes a spray bar arrangement  10 , which is shown in more detail in  FIG. 2 . 
     In the embodiment disclosed in  FIG. 2 , the spray bar arrangement  10  comprises eighteen spray bars  12  which extend radially between a hub  14  and a ring-shaped support  16  in a regularly spaced array. Each bar supports a number of spray elements  24  which are each provided with several spray nozzles  30 . 
     The spray bar arrangement is a non-rotating component and each spray bar within the arrangement is profiled to provide an aerodynamic surface that does not create a significant disturbance in the air flow. The bars are connected to a fluid manifold, either manifold  18   a  or manifold  18   b . Each manifold may be supplied with water independently of other manifolds to enable spray bars to supply water to the compressor independently of the remaining spray bars. Individual spray bars may be grouped with other bars to provide units which may be supplied with water selectively in stages. The volume of water supplied to the compressor can be controlled to a greater degree with such a staging arrangement and it will be appreciated that additional manifolds may be provided to further improve the staging capabilities of the fluid addition. Both manifolds may supply the same, or different fluids. 
     A spray bar of the present embodiment is shown in greater detail in  FIG. 3 . The spray bar aerofoil has a radial length between a tip  21  and a foot  23  of 490 mm and a width between a leading edge  25  and a trailing edge  27  of 100 mm. Each bar is replaceable within the engine and is formed from a number of components which are similarly replaceable should conduits or nozzles become blocked or any other reason dictate their replacement. 
     A radially extending front fairing  22  is profiled to provide the leading edge  25 . A radially extending rear fairing is profiled to provide a trailing edge  27 . The front and rear fairings are connected together and support between them a plurality of spray elements  24  within which nozzles  30  are formed. A locating pin  26  is provided at the foot, or radially inner end  23  of the bar and a cap  28  at the radially outer end or tip  21 . The locating pin  26  engages with a bush on the hub  14 , whilst the cap  28  engages an aperture in the ring  16  when the spray bar is located within the engine. 
     The spray elements are shown in greater detail in  FIG. 4 . Each spray element  24  has a plurality of arms that are provided with nozzles  30  at their end. The nozzles are directed towards the compressor to deliver a spray of water in a downstream direction. Water is supplied to the spray element via a fluid inlet  32  that engages with an aperture  48  provided in the front fairing of the spray bar. Grooves are provided within the outer surface of the inlet into which o-rings are mounted to minimise water leakage from a manifold in the front fairing in this embodiment but could be replaced by other sealing arrangements such as face seals or gaskets. The water inlet feeds a cavity within the spray element that divides the flow of water equally between the four nozzles  30 . For the eighteen bar spray arrangement of the embodiment shown, with each bar having six spray elements with four nozzles each, four hundred and thirty two nozzles are provided in total which supply water to the compressor as a fine mist. 
     A front fairing is shown in  FIG. 5 . The fairing is initially formed as a profiled extrusion having an internal hollow bore  50  and lock surfaces  46 ,  44  towards the rear surface  42  of the component. The extruded fairing is machined to provide a series of flat mounting surfaces  47  at the rear of the component which are interleaved by locking portions  45  that contain the lock surfaces  44 ,  46 . 
     Further machining is performed on the component to provide each mounting surface  47  with an aperture  48  that extends to the hollow bore  50  and a series of bolt holes  52  that are used to secure the spray elements in place. 
     The lock surfaces  44 ,  46  each has a radially extending valley of a generally “V” shaped cross-section. 
     The spray element is attached to the front fairing as shown in  FIG. 6 . The fluid inlet of the spray element is inserted into the aperture  48  and “O” rings provide a fluid tight seal preventing leakage. The nozzles  30  of the spray element are in fluid communication with the bore in the front fairing  20 . 
     Bolts  54  are inserted through the spray element into the bolt holes  40  in the front fairing and are tightened to secure the spray element to the front fairing. It will be appreciated that once all the spray elements are attached it will be possible to supply water to the front fairing to an equivalent pressure to that used in operation and test operation of each spray element and nozzle. If any operate incorrectly it is a simple matter to remove and replace a defective spray element. 
     The heads of the bolts  54  do not extend beyond the plane of the rear surface  42  of the front fairing. However, it is desirable that the length the screw thread of the bolt extends into the front fairing is significantly greater than the distance between the outer face of the bolt head and the plane of the rear surface  42  of the front fairing. As depicted in  FIG. 7  a rear fairing  22  is attached to the front fairing using the lock faces  44 ,  46  and complementary faces on the rear fairing. The bolt is therefore further secured against release by the rear fairing and is secured such that it cannot come loose to such an extent that it detaches from the front fairing. 
     It will be appreciated that a gas turbine engine comprises a number of parts that rotate at significant velocity. Ingress of foreign objects can cause great damage to the engine requiring high cost to repair. By ensuring the bolts and spray elements cannot work loose the risk of damage to the engine is mitigated. 
     The rear fairing is an extruded component having complementary radially extending engaging features which engage the lock faces  44 ,  46  of the front fairing. The rear fairing and the front fairing slide relative to each other and are secured in the desired relative location by a support plate  64  that is provided within a cavity  62  formed in the base between the front and rear fairings. 
     The support plate  64  has an integral locating pin  26  that is adapted to be inserted into a bush in the hub  14 . The plate is secured to the front and rear fairings by bolts  66 . A plug  68  is placed in the end of the hollow bore  50  to prevent leakage of water. 
     At the opposite end of the spray bar a cap  70  is provided that engages with apertures in the ring element  16 . Initially, the cap is slid over the end of the fairings and a pin is inserted through the cap and the front fairing through aperture  72  thereby securing the cap in location. A rubber boot is slid over the end of the spray-bar to provide a seal between the front fairing and the cap and to prevent the pin from falling out. A clip  76  is secured to the cap  70  by bolts  78  to hold the boot and pin in position. 
     A manifold plate is secured to the front fairing to allow water to enter the hollow bore  50  through aperture  80 . The top of the hollow bore  50  is closed by a weld or screw in blank  90 . 
     The spray bar may be tested at this point by subjecting it to a pressure test. Any deficiencies or problems may be rectified by removal and replacement of a defective part before the bar is inserted into the engine. 
     To assemble the spray bar assembly  10  a jig is used to centre the hub  14  and ring  16  before the spray bars are attached. The spray bars are inserted from the outside of the ring towards the hub. The locating pin engages with a bush in the hub and the cap is bolted to the ring. Once complete the spray bar assembly is bolted to the compressor section of the gas turbine engine and the water supply manifolds  18   a ,  18   b  are attached. 
     Various modifications may be made without departing from the scope of the invention. For example, the aerofoil may provide turn to the flow of fluid into the compressor—acting as a guide-vane. Additionally, the aerofoil may be located elsewhere in the gas-turbine e.g. within the diffuser or pre-diffuser upstream of the compressor. Additionally, the spray bars may have applications in other industries where it is desirable to eject droplets of a fluid into a flow of a further fluid.