Abstract:
A method facilitates assembling a gas turbine engine that includes an oil supply and scavenge system, wherein the oil supply and scavenge system includes at least one sump cavity that includes a first scavenge port and a second scavenge port, a first oil pump and a second oil pump such that the first oil pump is in flow communication with and receives scavenge oil from the first scavenge port and the second oil pump is in flow communication with and receives scavenge oil from the second scavenge port. In addition, an oil supply source is coupled in flow communication with the first and second oil pumps.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engines and more particularly, to the oil supply and scavenge systems used within gas turbine engines.  
         [0002]     A gas turbine engine typically includes at least one bearing assembly that rotatably supports a shaft. The bearing assembly is lubricated with oil, and heat from other engine components is absorbed and dissipated by the oil. Accordingly, bearing assemblies are housed within sumps that typically include an oil supply jet that supplies lubricating oil under pressure from an external pump to the bearing assemblies, and an external scavenge pump that removes lubricating oil from the sump. In at least some know engines, the scavenge pump channels the return oil through a heat exchanger prior to returning the oil to a tank or reservoir.  
         [0003]     Within at least some applications, such as aircraft propulsion systems, interruption of the oil supply from the usual main oil pump of the engine may cause seizure of the bearing assembly, loss of engine thrust, engine fire and/or damage to the aircraft. Known methods for supplying oil to, and scavenging oil from, the various bearing sumps and gearboxes utilize a multi-element positive displacement pump. Known pumps usually are spline driven by the engine gearbox and include a supply element and a plurality of scavenge elements coupled to single or dual shafts internal to the pump. Internal failures in the pump, or the loss of drive power to the gearbox may result in the loss of supply flow of oil lubricants to the bearing, and/or loss of scavenge flow, which over time, can result in sump flooding and possible fire.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     In one aspect, a method of assembling a gas turbine engine is provided. This method comprises providing an oil supply and scavenge system that includes at least one sump cavity that includes a first scavenge port and a second scavenge port, and providing a first oil pump and a second oil pump such that the first oil pump is in flow communication with and receives scavenge oil from the first scavenge port and the second oil pump is in flow communication with and receives scavenge oil from the second scavenge port. This method also comprises providing an oil supply that is in flow communication with the first and second oil pumps.  
         [0005]     In another aspect, an oil supply and scavenge system for a gas turbine engine is provided. The oil supply and scavenge system includes at least one sump cavity, an oil supply, a first scavenge port and a second scavenge port each coupled in flow communication with at the sump cavity. The first oil pump is coupled in flow communication with the first scavenge port for receiving scavenge oil therefrom and the first oil pump is in flow communication with the oil supply. The second oil pump is coupled in flow communication with the second scavenge port for receiving scavenge oil therefrom and the second oil pump is in flow communication with the oil supply.  
         [0006]     In a further aspect, a gas turbine engine is provided. The engine includes a gearbox coupled to the engine and an oil supply and scavenge system. The oil supply and scavenge system includes at least one sump cavity and an oil supply. The oil supply and scavenge system also includes a first scavenge port and a second scavenge port each coupled in flow communication with the sump cavity, where the first oil pump is coupled in flow communication with the first scavenge port for receiving scavenge oil therefrom and in flow communication with the oil supply, and the second oil pump is coupled in flow communication with the second scavenge port for receiving scavenge oil therefrom and in flow communication with the oil supply. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is schematic illustration of an exemplary gas turbine engine; and  
         [0008]      FIG. 2  is a schematic illustration of an oil supply and scavenge system for a gas turbine engine. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]      FIG. 1  is a schematic illustration of a gas turbine engine  10 , such as the F118 engine available from General Electric Company, Cincinnati, Ohio. Engine  10  includes a forward bearing  11 , mid-bearing  12  and aft-bearing  13 , and such bearings rotatably support the main engine shafts of engine  10 .  
         [0010]     In operation, forward bearing  11 , mid-bearing  12  and aft-bearing  13  support main engine shafts (not shown) of engine  10 . During engine operation, such main engine shafts rotate at very high speeds. Lubricating oil is supplied to forward bearing  11 , mid-bearing  12  and aft-bearing  13  to provide lubrication and to extract heat from the bearings.  
         [0011]      FIG. 2  is a schematic illustration of an oil supply and scavenge system  100  that may be used with a gas turbine engine, such as gas turbine engine  10  (shown in  FIG. 1 ). System  100  provides an oil supply to the turbine engine main bearings (not shown) and engine gearbox  203 , and also removes scavenge oil from the turbine engine main bearings and engine gearbox. A first oil pump  50  and a second oil pump  60  each coupled in flow communication to system  100 .  
         [0012]     System  100  includes a plurality of oil supply components  400  which are dedicated to supply lubricant to the turbine engine bearings (not shown) and engine gearbox  203 . More specifically, in the exemplary embodiment, oil supply components  400  include an oil supply source  120 , an oil supply circuit  45 , first oil pump  50 , second oil pump  60  and an oil filter  150 . Oil supply circuit  45  channels lubricant from oil supply  120  into either first oil pump  50  or second oil pump  60  through a respective first supply pump branch  46  and/or a second supply pump branch  47 . Supply circuit  45  is also coupled to oil filter  150  such that engine oil discharged from either first oil pump  50  or second oil pump  60  is channeled through oil filter  150 . After passing through oil filter  150 , oil is then routed into turbine engine bearing sumps  200  and engine gearbox  203 .  
         [0013]     System  100  also includes a plurality of scavenge oil components  300  which are dedicated to withdrawing scavenge oil from the turbine engine bearings and engine gearbox  203 . More specifically, in the exemplary embodiment, scavenge oil components  300  include a plurality of first scavenge oil circuits  30 , a plurality of second scavenge oil circuits  31 , first oil pump  50 , second oil pump  60  and a heat exchanger  110 . In the exemplary embodiment, sumps  200  and gearbox  203  are each coupled in flow communication with first scavenge oil circuit  30  and second scavenge oil circuit  31 . More specifically, in the exemplary embodiment, scavenge oil is pumped through scavenge oil circuit  30  by first oil pump  50 , and scavenge oil is pumped through scavenge oil circuit  31  by second oil pump  60 . Scavenge oil discharged from oil pumps  50  and  60  is channeled through heat exchanger  110  prior to being returned to oil supply  120 .  
         [0014]     System  100  also includes a plurality of flow activated check valves  70 ,  75 ,  80 ,  85 . More specifically, in the exemplary embodiment, oil supply components  400  include check valve  75  and check valve  85 , and scavenge system components  300  include check valve  70  and check valve  80 . More specifically, check valve  75  is located in supply circuit branch  46  adjacent to and downstream of first oil pump  50 , check valve  85  is located in supply circuit branch  47  adjacent to and downstream of second oil pump  60 , check valve  70  is located in scavenge circuit branch  30  adjacent to and downstream of first oil pump  50 , and check valve  80  is located in scavenge circuit branch  31  adjacent to and downstream of second pump  60 . In the exemplary embodiment, a pressure measuring instrument (not shown) is located in supply circuit  45  downstream of oil filter  150  and is configured to provide an alert if there is a failure of first oil pump  50  and/or second oil pump  60 .  
         [0015]     During normal engine operation, oil is supplied from oil supply source  120  via pumps  50  and  60  to engine bearings  200  and to engine gearbox  203 . More specifically, in the exemplary embodiment, engine oil discharged from pumps  50  and  60  is channeled through oil filter  150  and into engine bearing sumps  200  and engine gearbox  203 . Oil filter  150  facilitates removing impurities from the supply oil prior to supplying the supply oil to the engine bearings. Scavenge oil is collected from bearing sumps  200  and engine gearbox  203  through a first scavenge port  35  and second scavenge port  36  that are each coupled in flow communication within sumps  200  and gearbox  203 . First oil pump  50  and second oil pump  60  withdraw scavenge oil and channel the scavenge oil through heat exchanger  110 . Heat exchanger  110  facilitates removing heat from scavenge oil prior to returning the oil to oil supply  120 .  
         [0016]     In the exemplary embodiment, first oil pump  50 , second oil pump  60  and related oil supply circuits  45 ,  46  and  47  and scavenge circuits  30  and  31  are each sized such that first oil pump  50  and second oil pump  60  are each individually capable of pumping and circulating one half of the total design engine oil supply required by system  100  for operation. First oil pump  50  and second oil pump  60  are each coupled to the engine gearbox  203  and drive system (not shown) in separate locations (not shown) such that drive power to each pump  50  and pump  60  is derived from a separate location on the engine gearbox  203 . Accordingly, providing drive power to first pumps  50  and  60  from separate locations on the engine gearbox  203  facilitates reducing the risk that a loss of drive power in a single area of gearbox  203  will result in loss of drive power to both first oil pump  50  and second oil pump  60 . Moreover, by utilizing two oil pumps, namely, first oil pump  50  and second oil pump  60 , system  100  also facilitates reducing the risk that failure of either pump  50  or pump  60  will result in an engine failure due to failure of system  100  to supply and scavenge sufficient volumes of oil to the engine.  
         [0017]     Also in the exemplary embodiment, the primary purpose of scavenge circuit check valves  70  and  80  is to prevent scavenge oil from reversing flow direction in the event of a failure of first oil pump  50  or second oil pump  60 . Similarly, the primary purpose of supply check valves  75  and  85  is to prevent supply oil from reversing flow direction in the event of a failure of first oil pump  50  or second oil pump  60 .  
         [0018]     The above described oil supply and scavenge system is cost-effective and highly reliable. The oil supply and scavenge system includes two oil pumps of equal capacity with each of the pumps in flow communication with oil supply circuits and oil scavenge circuits. Each sump included in the oil supply and scavenge system includes two scavenge ports, each of which are in flow communication with one of the two oil pumps. The oil supply and scavenge system can provide sufficient oil supply to, and scavenge oil from, the aircraft engine to support flight sustaining power levels in the event one of the two oil pumps fails.  
         [0019]     Exemplary embodiments of an oil supply and scavenge system are described above in detail. The systems are not limited to the specific embodiments described herein, but rather, components of the system may be utilized independently and separately from other components described herein.  
         [0020]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.