Abstract:
An air turbine starter device comprises a rotor arranged in a cavity of a housing, a first manifold having a cavity with a port operative to direct compressed air to the rotor, a second manifold having a cavity with a port operative to direct compressed air to the rotor, wherein the first manifold is larger than the second manifold.

Description:
BACKGROUND 
       [0001]    Gas turbine engines often use an air turbine starter to start the gas turbine. The air turbine starter is usually mechanically connected to the gas turbine engine, and receives compressed air from an air source such as an auxiliary power unit or another compressed air such as an air compressor. 
         [0002]    The compressed air enters a manifold and is distributed to a number of nozzles or other apertures that direct the compressed air to the turbine starter turbine that rotates when the compressed air exits the nozzles and impinges on the turbine starter turbine. The turbine starter turbine is mechanically connected through shafts and gearing to the gas turbine engine, which is driven to rotate to a starting speed by the air turbine starter. When the gas turbine engine is rotating at a starting speed, the gas turbine engine may be started and the air turbine starter may be mechanically disengaged from the gas turbine engine. 
         [0003]    Typically the compressed air that enters the manifold of the air turbine starter is controlled by a valve that controls the flow of compressed air to the air turbine starter. Thus, when the valve is open the compressed air flows to the air turbine starter, and the gas turbine engine core rotates. 
       BRIEF DESCRIPTION 
       [0004]    An air turbine starter device comprises a rotor arranged in a cavity of a housing, a first manifold having a cavity with a port operative to direct compressed air to the rotor, a second manifold having a cavity with a port operative to direct compressed air to the rotor, wherein the first manifold is larger than the second manifold. 
         [0005]    An air turbine starter system comprises air turbine starter device comprises a rotor arranged in a cavity of a housing, a first manifold having a cavity with a port operative to direct compressed air to the rotor, and a second manifold having a cavity with a port operative to direct compressed air to the rotor, wherein the first manifold is larger than the second manifold, a first control valve operative to control a flow of compressed air to the first manifold and a second control valve operative to control a flow of compressed air to the second manifold. 
         [0006]    A method for controlling an air turbine starter system comprises closing a first valve that is operative to control a flow of compressed air to a first manifold of an air turbine starter device, opening a second valve that is operative to control a flow of compressed air to a second manifold of an air turbine starter device, such that the flow of compressed air to the second manifold is operative to drive a rotor of the air turbine starter system to a first speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The subject matter which is regarded as the present disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  illustrates block diagram of a prior art example of an air turbine start system. 
           [0009]      FIG. 2  illustrates a block diagram of an air turbine start system. 
           [0010]      FIG. 3  illustrates a cross-sectional view of an example of the primary manifold and the secondary manifold. 
           [0011]      FIG. 4A  illustrates a view of a portion of the primary manifold and the secondary manifold in operation. 
           [0012]      FIG. 4B  illustrates another view of a portion of the primary manifold and the secondary manifold in operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates block diagram of a prior art example of an air turbine start system  100 . The system  100  includes an air source  102  that outputs compressed air. A control valve  104  is arranged between the air source  102  and the air turbine starter  106 . When the control valve  104  is in an open position, air flows from the air source  102  to the air turbine starter  106 . The air turbine starter  106  is mechanically linked to the engine core  108  such that when the control valve  104  is open and air flows to the air turbine starter  106 , the rotation of the air turbine starter  106  drives the engine core  108  to rotate. 
         [0014]    In operation gas turbine engines, particularly engines used in commercial aircraft are started and stopped frequently. When a gas turbine engine is stopped, it starts to cool down. However, the internal components, for example, the rotor tend to cool at different rates such that portions of the rotor may warp or bow due to uneven temperatures in different parts of the rotor. Typically, the portions of the rotor that are located higher in the engine cool more slowly than the portions of the rotor that are located lower in the engine due to the thermal dynamic properties of the hot air in the engine. 
         [0015]    If the engine is started while the rotor is warped, the rotor is effectively out of balance, which may cause undesirable wear to the engine. 
         [0016]    To mitigate the warpage of the rotor, and instigate more even cooling in the engine core, operators have used the air turbine starter to rotate the engine core at a relatively low speed (below engine start speed) to circulate the air in the engine, and rotate portions of the engine from the cooler lower areas of the engine to the warmer upper areas of the engine. The rotation of the engine mitigates the warpage of the rotor due to the rotor being exposed to air having different temperatures in the upper portions of the engine and the lower portions of the engine, and the circulation of the air in the engine. 
         [0017]    Referring to  FIG. 1 , the control valve  104  and the air turbine starter were designed to drive the gas turbine engine to a start speed, which is faster than the speed desired to effectively reduce the warpage of the rotor. Thus, to rotate the engine at a lower speed, the operator would repeatedly open and close the control valve  104  for short intervals. This repetitive type of operation tends to wear the control valve  104  prematurely, and does not use the air from the air source efficiently. 
         [0018]    The methods and systems described herein provide for an air turbine starter system that has a secondary control valve and a secondary air manifold that allows the air turbine starter to be operated at a speed that is relatively lower than the engine start speed. The system reduces the wear on the control valves, reduces operator interaction with the system, rotates the engine core at a desired speed for uniform cooling, and uses the air from the air source more efficiently. 
         [0019]      FIG. 2  illustrates a block diagram of an air turbine start system  200 . The system  200  includes an air source  202 , which may include any suitable compressed air source including, for example, bleed air, an air compressor, a compressed air tank, or an auxiliary power unit. The air source  202  is communicatively connected to the air turbine starter  208 . The air turbine starter  208  includes a primary manifold  210  and a secondary manifold  212 . The air turbine starter is operative to receive compressed air that drives a turbine in the air turbine starter  208 . The air turbine starter  208  is mechanically connected through, for example, a gear assembly to the engine core  214  such that the rotation of the turbine in the air turbine starter  208  rotates the engine core  214 . 
         [0020]    In operation, the air from the air source  202  is routed to the primary manifold  210  and the secondary manifold  212 . A primary control valve  204  controls the air to the primary manifold  210  and a secondary control valve  206  controls the air to the secondary manifold  212 . The primary control valve  204  and the secondary control valve  206  as well as other components in the system  200  may be controlled by the controller  201  that may include, for example, a processor and memory operative to receive inputs and perform logical control functions. 
         [0021]    Though the illustrated exemplary embodiment, shows a primary control valve  204  and a secondary control valve  206 , alternate exemplary embodiments may include any suitable valve arrangement that is operative to control the flow of air from the air source  202  to the primary manifold  210  and the secondary manifold  212 . 
         [0022]      FIG. 3  illustrates a cross-sectional view of an example of the primary manifold  210  and the secondary manifold  212 . The primary manifold  210  and the secondary manifold  212  may partially define a housing  300  around the rotor  304 . The primary manifold  210  receives air from the air source  202  and distributes the air to the nozzles  302  that port the air to the turbine  304  of the air turbine starter  208 . The secondary manifold  212  also received air from the air source  202  and distributes the air to the nozzles  301 . The secondary manifold  212  is smaller in volume than the primary manifold  210 , and has fewer nozzles connected to the secondary manifold  212  than the primary manifold  210 . 
         [0023]    In operation, when the engine is cooling, an operator may open the secondary control valve  206  while the primary control valve  204  is closed, which allows compressed air from the air source  202  to enter only the secondary manifold  212  and flow through the nozzles  301  such that the air impinges on the turbine  304  and rotates the turbine in the air turbine starter  208 . The rotation of the turbine  304  in the air turbine starter  208  drives the rotation of the engine core  214  at a speed that encourages an even cooling of the rotor and other engine core  214  components. This speed may vary by the type of engine; however it is lower than the start speed of the engine. 
         [0024]    During a start operation, the primary control valve  204  and the secondary control valve  206  may both be opened (in some embodiments, the secondary control valve  206  may remain closed while the primary control valve  204  is open). When the primary control valve  204  and the secondary control valve  206  are both open, compressed air flows to the primary manifold  210  and the secondary manifold  212  such that all of the nozzles  302  and  301  emit air that impinges on the turbine  304 . The flow of compressed air through all of the nozzles  301  and  302  results in the turbine  304  rotating at an engine start speed such that the engine core  214  accelerates to the engine start speed and may be started. 
         [0025]    Since the secondary manifold is smaller and has less nozzles  301  than the primary manifold  210 , the torque of the air turbine starter (and the mechanically linked turbine engine) is lower when only the secondary manifold  212  and associated nozzles  301  receive compressed air. The torque and speed of the air turbine starter  208  is higher and may reach starting speeds when at least the primary manifold  210  and the associated nozzles  302  receive compressed air. 
         [0026]      FIG. 4A  illustrates another view of a portion of the primary manifold  210  and the secondary manifold  212  in operation. When the primary control valve  204  is closed and the secondary control valve  206  is open, compressed air  402  flows from the secondary manifold  212  through the nozzles  301  to impinge on the turbine  304 . 
         [0027]      FIG. 4B  illustrates another view of a portion of the primary manifold  210  and the secondary manifold  212  in operation. When both the primary control valve  204  and the secondary control valve  206  are open, compressed air  402  flows from the secondary manifold  212  through the nozzles  301  to impinge on the turbine  304 , and compressed air  502  flows from the primary manifold  210  through the nozzles  302  to impinge on the turbine  304 . 
         [0028]    Though the illustrated embodiment shows nozzles  301  and  302 , alternate exemplary embodiments may include any type of suitable arrangement or components that are operative to port or deliver air to impinge on the rotor  304  including for example, ports, orifices, or any other arrangement that defines a flow path from the air source  202  (of  FIG. 2 ) to the rotor  304  (of  FIG. 3 ). 
         [0029]    The methods and systems described herein provide for a turbine air start system that is operative to receive compressed air and drive the turbine air start system at a first speed and a second speed where the first speed is a cool down speed, and the second speed is an engine start speed. The system uses at least two manifolds to direct the flow of air to the turbine air start system. The first speed may be used to even the thermal distribution in the rotor of the gas turbine engine to reduce or substantially eliminate warpage of the rotor due to uneven heat distribution in the rotor. In a startup operation, the rotor may be rotated at the first, relatively slow, speed. Followed by increasing the airflow to the air turbine starter to accelerate the rotor to starting speed. 
         [0030]    The use of a turbine air start system with dual manifolds allows the turbine air start system to operate at two different speeds without repetitive cycling of the primary control valve, which causes wear to the primary control valve, and uses the compressed air inefficiently. 
         [0031]    While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.