Abstract:
A lubrication system for a fan drive gear system includes a main lubrication system and an auxiliary lubrication system. The auxiliary lubrication system including a collection channel disposed about the fan drive gear system for collecting expelled lubricant and an auxiliary pump including an inlet receiving lubricant from the collection channel and an outlet in communication with an auxiliary passage. The auxiliary pump supplies lubricant through the auxiliary passages to a bearing passage for communicating lubricant to a bearing. The auxiliary passages include a reservoir after the outlet of the auxiliary pump and before the bearing passage for storing lubricant.

Description:
BACKGROUND  
       [0001]    A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines. 
         [0002]    The high pressure turbine drives the high pressure compressor through an outer shaft to form a high spool, and the low pressure turbine drives the low pressure compressor through an inner shaft to form a low spool. An epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different than the turbine section so as to increase the overall propulsive efficiency of the engine. 
         [0003]    Lubrication of the gear assembly is normally provided by a main lubrication system. An auxiliary lubrication system is further provided to maintain a supply of lubricant should the main lubrication system temporarily not provide a sufficient supply of lubricant such as in low or reduced-G operating conditions. 
         [0004]    Accordingly, it is desirable to design and develop improved auxiliary lubrication systems that operate in concert with the main lubricant system to maintain lubricant flow to the geared architecture. 
       SUMMARY  
       [0005]    A lubrication system for a gear system according to an exemplary embodiment of this disclosure, among other possible things includes an inlet passage, an auxiliary pump including an inlet receiving lubricant from the inlet passage and an outlet in communication with an auxiliary passage, a bearing passage in communication with the auxiliary passage for communicating lubricant to a bearing of the gear system, and a reservoir disposed within the auxiliary passage after the outlet of the auxiliary pump and before the bearing passage. 
         [0006]    A further embodiment of the foregoing lubrication system, including a collection channel disposed at least partially about the gear system and in communication with the inlet passage for directing lubricant to the inlet of the auxiliary pump. 
         [0007]    A further embodiment of any of the foregoing lubrication systems, including a valve for directing lubricant between the bearing passage and a main lubricant supply responsive to a condition within a main lubricant system. 
         [0008]    A further embodiment of any of the foregoing lubrication systems, wherein the reservoir includes a first reservoir disposed between the auxiliary pump and the valve and a second reservoir disposed between the valve and the bearing passage. 
         [0009]    A further embodiment of any of the foregoing lubrication systems, including a bypass in communication with the inlet passage, the bypass including a plurality of openings for draining lubricant. 
         [0010]    A further embodiment of any of the foregoing lubrication systems, wherein the reservoir comprises a volume over a fixed length greater than a volume of the auxiliary passage over a length equal to that of the reservoir. 
         [0011]    A further embodiment of any of the foregoing lubrication systems, wherein the reservoir comprises a volume determined to hold a quantity of lubricant required for operation of the fan drive gear system for a desired time. 
         [0012]    A further embodiment of any of the foregoing lubrication systems, wherein the gear system comprises a fan drive gear system. 
         [0013]    A fan drive gear system according to an exemplary embodiment of this disclosure, among other possible things includes a sun gear providing a driving input, a plurality of intermediate gears driven by the sun gear, a ring gear intermeshed with the intermediate gears, a main lubrication system, and an auxiliary lubrication system including a collection channel disposed at least partially about the fan drive gear system for collecting expelled lubricant, an auxiliary pump including an inlet receiving lubricant from the collection channel and an outlet in communication with an auxiliary passage, a bearing passage in communication with the auxiliary passage for communicating lubricant to a bearing, a reservoir disposed within the auxiliary passage after the outlet of the auxiliary pump and before the bearing passage for storing lubricant. 
         [0014]    The fan drive gear system of the foregoing embodiment including, a journal bearing supporting rotation of each of the plurality of intermediate gears, and the bearing passage is in communication with each of the journal bearings. 
         [0015]    The fan drive gear system of any of the foregoing embodiments including a valve for directing lubricant between the bearing passage and a main supply responsive to a condition within main lubrication system. 
         [0016]    The fan drive gear system of any of the foregoing embodiments wherein the reservoir includes a first reservoir disposed between the auxiliary pump and the valve and a second reservoir disposed between the valve and the journal bearings. 
         [0017]    The fan drive gear system of any of the foregoing embodiments, including a bypass in communication with the collection channel. 
         [0018]    The fan drive gear system of any of the foregoing embodiments, wherein the reservoir comprises a volume determined to hold a quantity of lubricant required for operation of the fan drive gear system for a desired time. 
         [0019]    A gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a fan including a plurality of fan blades rotatable about an axis, a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor, a geared architecture driven by the turbine section for rotating the fan about the axis, and a lubricant supply system for supplying lubricant including an auxiliary pump including an inlet receiving lubricant expelled from the geared architecture and an outlet in communication with an auxiliary passage a bearing passage in communication with the auxiliary passage for communicating lubricant to a journal bearing, and a reservoir disposed within the auxiliary passage after the outlet of the auxiliary pump and before the bearing passage. 
         [0020]    A further embodiment of the foregoing gas turbine engine, including a collection channel disposed about the geared architecture with the inlet of the auxiliary pump in communication with the collection channel. 
         [0021]    A further embodiment of any of the foregoing gas turbine engines, including a valve for directing lubricant between the bearing passage and a lubricant supply. 
         [0022]    A further embodiment of any of the foregoing gas turbine engines, wherein the reservoir includes a first reservoir disposed between the auxiliary pump and the valve and a second reservoir disposed between the valve and the journal bearings. 
         [0023]    A further embodiment of any of the foregoing gas turbine engines, wherein the reservoir comprises a volume determined to hold a quantity of lubricant required for operation of the geared architecture for a desired time. 
         [0024]    Although the different examples have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0025]    These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0026]      FIG. 1  is a schematic view of an example gas turbine engine. 
           [0027]      FIG. 2  is a cross section of an example fan drive gear system. 
           [0028]      FIG. 3  is a schematic representation of an example lubrication system. 
           [0029]      FIG. 4  is a schematic representation of an example auxiliary lubrication system. 
       
    
    
     DETAILED DESCRIPTION  
       [0030]      FIG. 1  schematically illustrates an example gas turbine engine  20  that includes a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B while the compressor section  24  draws air in along a core flow path C where air is compressed and communicated to a combustor section  26 . In the combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section  28  where energy is extracted and utilized to drive the fan section  22  and the compressor section  24 . 
         [0031]    Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox or fan drive gear system, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. 
         [0032]    The example engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0033]    The low speed spool  30  generally includes an inner shaft  40  that connects a fan  42  and a low pressure (or first) compressor section  44  to a low pressure (or first) turbine section  46 . The inner shaft  40  drives the fan  42  through a speed change device, such as a geared architecture also referred to as a fan drive gear system  48 , to drive the fan  42  at a lower speed than the low speed spool  30 . The high-speed spool  32  includes an outer shaft  50  that interconnects a high pressure (or second) compressor section  52  and a high pressure (or second) turbine section  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via the bearing systems  38  about the engine central longitudinal axis A. 
         [0034]    A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . In one example, the high pressure turbine  54  includes at least two stages to provide a double stage high pressure turbine  54 . In another example, the high pressure turbine  54  includes only a single stage. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
         [0035]    The example low pressure turbine  46  has a pressure ratio that is greater than about 5. The pressure ratio of the example low pressure turbine  46  is measured prior to an inlet of the low pressure turbine  46  as related to the pressure measured at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
         [0036]    A mid-turbine frame  58  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  58  further supports bearing systems  38  in the turbine section  28  as well as setting airflow entering the low pressure turbine  46 . 
         [0037]    The core airflow C is compressed by the low pressure compressor  44  then by the high pressure compressor  52  mixed with fuel and ignited in the combustor  56  to produce high speed exhaust gases that are then expanded through the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  58  includes vanes  60 , which are in the core airflow path and function as an inlet guide vane for the low pressure turbine  46 . Utilizing the vane  60  of the mid-turbine frame  58  as the inlet guide vane for low pressure turbine  46  decreases the length of the low pressure turbine  46  without increasing the axial length of the mid-turbine frame  58 . Reducing or eliminating the number of vanes in the low pressure turbine  46  shortens the axial length of the turbine section  28 . Thus, the compactness of the gas turbine engine  20  is increased and a higher power density may be achieved. 
         [0038]    The disclosed gas turbine engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example fan drive gear system  48  is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3. 
         [0039]    In one disclosed embodiment, the gas turbine engine  20  includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor  44 . It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines. 
         [0040]    A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft., with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point. 
         [0041]    “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45. 
         [0042]    “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R)/518.7) 0.5 ]. The “Low corrected fan tip speed”, as disclosed herein according to one non-limiting embodiment, is less than about 1150 ft/second. 
         [0043]    The example gas turbine engine includes the fan  42  that comprises in one non-limiting embodiment less than about 26 fan blades. In another non-limiting embodiment, the fan section  22  includes less than about 20 fan blades. Moreover, in one disclosed embodiment the low pressure turbine  46  includes no more than about 6 turbine rotors schematically indicated at  34 . In another non-limiting example embodiment the low pressure turbine  46  includes about 3 turbine rotors. A ratio between the number of fan blades  42  and the number of low pressure turbine rotors is between about 3.3 and about 8.6. The example low pressure turbine  46  provides the driving power to rotate the fan section  22  and therefore the relationship between the number of turbine rotors  34  in the low pressure turbine  46  and the number of blades  42  in the fan section  22  disclose an example gas turbine engine  20  with increased power transfer efficiency. 
         [0044]    Referring to  FIG. 2  with continued reference to  FIG. 1 , the example fan drive gear system  48  comprises an epicyclical gear box that includes a sun gear  66  that is attached to a connector shaft  62 . The sun gear  66  is engaged to drive intermediate gears  68  that are in turn intermeshed with a ring gear  70 . The intermediate gears  68  are supported for rotation on journal bearings  72 . The journal bearings  72  are in turn supported by a carrier  74 . 
         [0045]    In this example, the fan drive gear system  48  comprises a star gear system where the carrier  74  remains fixed such that the intermediate gears  68  are driven by the sun gear  66  but remain in a specific location as is fixed by the carrier  74 . The ring gear  70  is driven for rotation about the intermediate gears  68  to drive a fan shaft  64 . The fan shaft  64  extends forward of the fan drive gear system  48  to drive the fan section  22 . 
         [0046]    As appreciated, although a star gear system is disclosed; other gear systems such as a planetary gear system are within the contemplation of this disclosure. In a planetary gear system, the carrier is mounted for rotation such that the intermediate gears  68  rotate about the sun gear  66  and the ring gear  70  is fixed. 
         [0047]    A lubrication system  82  ( FIG. 3 ) provides lubricant to the geared fan drive gear system  48 . In this example, a lubricant manifold  76  ( FIG. 2 ) is mounted to the fan drive gear system  48  to provide lubricant to the journal bearings  72 . Lubricant expelled from the fan drive gear system  48  during operation is captured by a gutter  78 . The gutter  78  is circumscribed about an outer periphery of the ring gear  70 . 
         [0048]    In this specification, the term oil and lubricant are utilized to describe a fluid that supplied to the journal bearings and gears to provide both desired lubricity along with heat removal. Any oil or lubricant could be utilized with the example system and are within the contemplation of this disclosure. 
         [0049]    Referring to  FIGS. 3 and 4  with continued reference to  FIG. 2 , the example fan drive gear system  48  is supplied with lubricant by the lubrication system  82 . The example lubrication system  82  comprises a main system  84  and an auxiliary system  86 . The main system  84  includes a main tank  90  and a main pump  92  that pumps lubricant through a main passage  114  to the gears  66 ,  68 ,  70  and journal bearings  72 . During normal operation, the main system  84  supplies lubricant of sufficient volume to the gears  66 ,  68 ,  70  and journal pin  72  to remove heat from the fan drive gear system  48  and to provide sufficient lubricant to maintain a desired operability of the gears and journal bearings. 
         [0050]    The example auxiliary system  86  provides lubricant to the gears  66 ,  68 ,  70  and journal bearings  72  during interruption in lubricant supplied by the main system  84 . The auxiliary system  86  collects oil that is accumulated in the gutters  78  and supplies that oil to an inlet  104  of auxiliary pump  102 . The auxiliary pump  102  pumps lubricant through auxiliary passage  108  that is in communication with bearing passage  80  that supplies lubricant to the journal bearing  72 . The auxiliary pump  102  utilizes lubricant obtained from the gutter  78  to supply a sufficient amount of lubricant to the inlet  104  of the auxiliary pump  102  such that it remains sufficiently primed. 
         [0051]    An inlet passage  98  is in communication with the gutter  78  through a port  120 . Lubricant that is flung radially outward from the fan drive gear system  48  is captured within the gutter  78  and communicated through the port  120  to the inlet passage  98  then on to the auxiliary pump  102 . The amount of lubricant captured during normal operation of the fan drive gear system  48  exceeds the capacity of the inlet passage  98  and therefore a bypass  100  is provided in communication with the inlet  98 . Lubricant overflows from the inlet passage  108  into the bypass  100  where it is directed through openings  122  to a sump  88  or a bearing compartment. A sump pump  94  may be included to pump lubricant to the main tank  90 . 
         [0052]    The example auxiliary lubricant system  86  includes reservoirs  110  and  112  that maintain a sufficient amount of lubricant within the auxiliary passage  108  to sustain operation of the fan drive gear system  48  for a brief period during intermittent interruptions in operation of the main lubricant system  84 . The example first and second reservoirs  110  and  112  are disposed after the auxiliary pump  102  and are continually charged or filled with lubricant. The example first reservoir  110  is disposed between the outlet  106  of the auxiliary pump  102  and the pressure responsive valve  96 . The second reservoir  112  is disposed between the pressure responsive valve  96  and the bearing passage  80 . 
         [0053]    Because lubricant is stored within the reservoirs  110 ,  112 , the auxiliary system  86  includes a sufficient amount of lubricant to compensate for intermittent interruptions of oil flow from the main lubricant system  84 . 
         [0054]    A volume  116 ,  118  of each of the reservoirs  110 ,  112 , provides for the storage of lubricant in a quantity determined to continue lubricant flow to the journal bearings  72  for a desired time. The volumes  116 ,  118  are greater than a comparable volume within the auxiliary passages  108 . In other words, the reservoir  110 ,  112  include a volume over a fixed length greater than a volume of the auxiliary passage  108  over a length equal to that of the reservoir  110 ,  112 . As appreciated, although the disclosed example includes two reservoirs  110 ,  112  located in different points along the auxiliary passage  108 , any number of reservoirs could be located within the auxiliary passage  108  to store and provide lubricant when required. 
         [0055]    A pressure responsive valve  96  is provided in the auxiliary passage  108  that directs lubricant flow responsive to a condition in the main lubricant system  84 . In the disclosed example, the valve  96  is responsive to a pressure within the main lubricant passage  114 . When pressure is at a desired level indicative of normal operation, the valve  96  directs lubricant flow from the auxiliary passage  108  back to the main tank  90 , or some other lubricant supply location. However, in response to a drop in pressure within the main lubricant system  84  and passage  114 , the valve  96  will direct lubricant flow to the bearing passage  80  and to the journal bearings  72 . 
         [0056]    The example auxiliary system  86  supplies lubricant to the journal bearings  72  only, as the journal bearings  72  have limited capacity for operation without lubricant. However, it is within the contemplation of this disclosure that the auxiliary system  86  could direct lubricant to any structure or assembly determined to require lubricant during periods of interruption of main lubricant flow. 
         [0057]    During normal operation, the main lubricant system will provide lubricant to journal bearings  72  and to the gears  66 ,  68 ,  70 . The auxiliary lubricant system  86  operates by gathering lubricant expelled radially outward with the gutter  78 . From the gutter  78 , lubricant is communicated through the port  120  to the inlet passage  98 . The inlet passage  98  fills with lubricant to maintain a pressure and supply of lubricant at the pump inlet  104 . Excess lubricant is directed into the bypass  100  and out through openings  122  to the sump  88  or bearing compartment. The pump  102  pumps lubricant through the outlet  106  into the auxiliary passage  108 . Reservoirs  110  and  112  are filled with lubricant and maintained by a continual flow from the pump  102 . The valve  96  directs lubricant flow back to the main tank  90  for use by the main lubricant system  84 . 
         [0058]    During interim periods of interruption caused by aircraft maneuvers or conditions such as low, zero or negative G maneuvers, lubricant may not flow as desired from the main lubricant system  84 . Accordingly, a pressure within the main passage  114  drops causing actuation of the valve  96  to direct oil from the auxiliary passage  108  to the bearing passage  80  and finally to the journal bearings  72 . 
         [0059]    The gutter  78  does not recover all of the lubricant communicated to the journal bearings  72  and gears  66 ,  68 ,  70 , and therefore some lubricant is lost in each pass through the auxiliary system  86 . Accordingly, the reservoirs  110  and  112  store additional lubricant to extend the duration that the auxiliary lubrication system  86  can maintain a desired supply to the journal bearings  72 . 
         [0060]    The example auxiliary lubricant system includes reservoirs that are downstream of the auxiliary pump to provide and push the lubricant in a volume sufficient to maintain operation of the fan drive gear system for an extended amount of time. Moreover, the example auxiliary lubrication system includes a gutter fed auxiliary pump that is charged with lubricant from lubricant normally expelled from the fan drive gear system. 
         [0061]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure.