Patent Publication Number: US-2023160341-A1

Title: Integrated lubrication system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of Italian Patent Application No. 102021000029891, filed on Nov. 25, 2021, which is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an integrated lubrication system. More particularly, the present disclosure relates to an integrated lubrication system for a bearing and a seal. 
     BACKGROUND 
     In modern aircraft engines, lubrication systems are provided to cause a flow of lubrication fluid to mechanical components. The mechanical components require continuous lubrication to avoid wearing and overheating. For example, mechanical components such as propeller shaft support bearings and carbon seals require lubrication. These components require significant flow rates to withstand high loads and to provide cooling that counteracts generated friction. Lubrication systems typically include dedicated piping externally routed on the stationary engine frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of the present disclosure will be apparent from the following description of various exemplary embodiments, as illustrated in the accompanying drawings, wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. 
         FIG.  1    shows a schematic view of an engine, according to an embodiment of the present disclosure. 
         FIG.  2    shows a schematic, cross-sectional view of a gearbox assembly and a propeller shaft of the engine of  FIG.  1    having an integrated lubrication system, the cross section taken along a centerline of the engine of  FIG.  1    according to an embodiment of the present disclosure. 
         FIG.  3    shows a schematic, partial cross-sectional view of the integrated lubrication system of  FIG.  2   , according to an embodiment of the present disclosure. 
         FIG.  4    shows a schematic, partial view of the engine of  FIG.  1   , according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Features, advantages, and embodiments of the present disclosure are set forth or apparent from a consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the disclosure as claimed. 
     Various embodiments are discussed in detail below. While specific embodiments are discussed, this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure. 
     The terms “forward” and “aft” refer to relative positions within a gas turbine engine or vehicle, and refer to the normal operational attitude of the gas turbine engine or vehicle. For example, with regard to a gas turbine engine, forward refers to a position closer to an engine inlet and aft refers to a position closer to an engine nozzle or exhaust. 
     The present disclosure relates to an integrated lubrication system that provides lubrication fluid to multiple elements within an engine. In one example, the integrated lubrication system provides lubrication fluid to multiple bearings in an engine. The bearings may be propeller shaft bearings. In one example, the integrated lubrication system provides lubrication fluid to multiple bearings and a carbon seal in an engine. The integrated lubrication system of the present disclosure may allow for providing lubrication fluid to multiple elements of an engine during low power operating conditions (e.g., engine idling conditions, aircraft taxiing conditions, etc.) and high power operating conditions (e.g., aircraft take off conditions, aircraft climbing conditions, etc.). The integrated lubrication system of the present disclosure may allow for providing lubrication fluid to multiple elements of an engine without the need for a dedicated lubrication supply line to each element of the multiple elements. This may be achieved through the use of spray bars and jet outlets. 
       FIG.  1    shows an engine  10 . The engine  10  may be a turboprop engine or an unducted single fan engine. The engine  10  may include a nacelle  12 . The nacelle  12  houses a gearbox assembly  100 , a propeller shaft  30 , and a shaft  28 . A plurality of bearings  114  may be located between the propeller shaft  30  and the nacelle  12  to allow relative rotation therebetween. The plurality of bearings  114  may be propeller shaft bearings. A plurality of fan blades  14  are coupled to the propeller shaft  30 . Rotation of the shaft  28  causes rotation of the propeller shaft  30  which in turn causes rotation of the plurality of fan blades  14 . A nose  16  may be coupled at a forward end of the engine  10 . 
     With continued reference to  FIG.  1   , the shaft  28  is rotationally coupled to a low pressure compressor  18  and a low pressure turbine  26 . The engine  10  also includes a high pressure compressor  20 , a combustor  22 , and a high pressure turbine  24 . The engine  10  operates in a manner well known in the art. 
       FIGS.  2  and  3    show partial cross-sectional views of the gearbox assembly  100  and propeller shaft  30  of  FIG.  1   . The gearbox assembly  100  may include a gearbox  106  that couples the propeller shaft  30  to the shaft  28  ( FIG.  2   ). An integrated lubrication system  200  exists in the gearbox assembly  100  and the propeller shaft  30 . That is, the integrated lubrication system  200  is integrated between a forward end of the gearbox assembly  100  and an aft end of the propeller shaft  30 . The integrated lubrication system  200  may be housed within the propeller shaft  30  and a gearbox housing  102  of the gearbox assembly  100 . The integrated lubrication system  200  may provide lubrication to one or more seals  112  and one or more bearings  114 . The one or more seals  112  may be a carbon seal. The one or more bearings  114  may be tapered rolling bearings. 
     The integrated lubrication system  200  may include a plurality of lubrication supply lines  104  and one or more scavenge features  136 . The plurality of lubrication supply lines  104  may include a first gearbox supply line  122 , a second gearbox supply line  124 , a first bearing supply line  120 , and a second bearing supply line  126 . Although two of each of the gearbox supply line and bearing supply line are shown, more or fewer may be provided. Each of the plurality of lubrication supply lines  104  may include a spray bar  110 . Each spray bar  110  has one or more jet outlets  116  through which a lubrication fluid may exit the respective lubrication supply line  104 . The spray bars  110  may be leaning onto the propeller shaft hollow cavity to spill the oil from a gearbox oil manifold  108  and to target the rotating propeller shaft  30  (e.g., one or more grooves  134  therein). Although two jet outlets  116  are shown, more or fewer may be provided. The first gearbox supply line  122  and the second gearbox supply line  124  may supply a lubrication fluid to the gearbox oil manifold  108 . The one or more scavenge features  136  may allow for the lubrication fluid from the seal  112  and/or the one or more bearings  114  to drain toward the scavenge port (not visible). 
     The lubrication fluid supplied in the plurality of lubrication supply lines  104  may be oil. The lubrication fluid may be caused to flow to the plurality of lubrication supply lines  104  from a lubrication fluid supply source (not shown). The lubrication fluid may be a pressurized lubrication fluid, such as, for example, a pressurized oil. 
     In  FIG.  3   , two areas of lubrication are shown and may include a first region of lubrication A and a second region of lubrication B. The lubrication fluid may be present in the first region of lubrication A and may be supplied from the first gearbox supply line  122 . A similar first region of lubrication A may be located on a not visible bottom portion of the integrated lubrication system  200  and the lubrication fluid therein may be supplied by the second gearbox supply line  124  ( FIG.  2   ). The first region of lubrication A may include one or more grooves  134  formed in an inner wall  31  of the propeller shaft  30 . When multiple components need lubrication (e.g., multiple bearings and seals), one or more separators  130  may be present on the propeller shaft  30  to generate independent cavities within the one or more grooves  134 , such as cavities  138  for the lubrication fluid. The one or more grooves  134  and/or cavities  138  may collect the lubrication fluid from the spray bars  110  of the first gearbox supply line  122  and the second gearbox supply line  124  and supply the collected lubrication fluid to the components in need of lubrication. In the case of the system  200  shown in  FIG.  3   , this results in delivery of lubrication fluid form the cavities  138  to the seal  112  and both of the depicted one or more bearings  114 . The first region of lubrication A, and, thus, the lubrication fluid therein, may extend through pass-through holes  132  in a wall of the propeller shaft  30  to the seal  112  and the one or more bearings  114 . The lubrication fluid present in the first region of lubrication A may be subject to centrifugal forces, as will be described herein. 
     With continued reference to  FIG.  3   , the second region of lubrication B may include spaces formed between the gearbox housing  102 , the seal  112 , the one or more bearings  114 , and the plurality of lubrication supply lines  104 . The second region of lubrication B may include the lubrication fluid present in the one or more scavenge features  136 . The lubrication fluid present in the second region of lubrication B may be supplied from the seal  112  and/or the one or more bearings  114 . The lubrication fluid present in the second region of lubrication B may represent lubrication fluid draining from the integrated lubrication system  200 . The lubrication fluid present in the second region of lubrication B may be subject to gravitational forces, as will be described herein. 
     A forward end of the engine  10  is shown in  FIG.  4   . As previously described, the engine  10  may include a plurality of fan blades  14  and a nacelle  12 . The nacelle  12  may house a gearbox assembly  100  and one or more bearings  114  coupled to the propeller shaft  30 . An aft end of the gearbox assembly  100  may be coupled to the shaft  28 . During operation of the engine  10 , a thrust  300  and a moment  302  are generated. The thrust  300  and the moment  302  may result in a radial load  400  on the one or more bearings  114  and an axial load  402  on the one or more bearings  114 . 
     With reference to  FIGS.  1  to  4   , the one or more bearings  114  and the seals  112  may be subject to high load and/or high rotational speed conditions, thus, needing continuous lubrication to avoid wearing and overheating. The one or more bearings  114  require significant oil flow rates to withstand high loads given by the propeller shaft  30 . The seals  112  require a cooling oil flow to counteract the friction generated by the rubbing faces of the seals  112 . The integrated lubrication system  200  provides a plurality of lubrication supply lines  104  that have compact architectures allowing different arrangements (e.g., oil jets and under-race lubrication) to achieve optimal performances throughout operation of the engine  10 . The integrated lubrication system  200  provides an integration strategy of the lubrication system for multiple components arrangement (e.g., propeller shaft bearings and carbon seals) with the engine frame and other modules, including both jet and under-race lubrication. That is, the integrated lubrication system  200  combines the lubrication systems of the one or more bearings  114  and the seals  112 . The plurality of lubrication supply lines  104  are integrated together with other existing lubrication items, such as, for example, the gearbox oil manifold  108 . The integrated lubrication system  200  results in whole portions of supply lines being avoided, with a resulting reduction in weight, parts count, and system complexity. 
     With reference to  FIGS.  2  and  3   , the integrated lubrication system  200  of the present disclosure allows for improved lubrication of multiple elemental arrangements, which are difficult to reach with dedicated lubrication supply lines, for example, the one or more bearings  114  (which may be two rows of propeller shaft bearings) and the seal  112  (which may be a carbon seal). The dual lubrication of the integrated lubrication system  200  allows for jet lubrication (e.g., via jet outlets  116 ) and allows for under-race lubrication (e.g., under the bearing race of the one or more bearings  114 ). 
     A jet lubrication flow may be supplied with a dedicated pressurized line (e.g., the one or more lubrication supply lines  104  may be dedicated pressurized supply lines) that provides a lubrication (e.g., oil) to an innermost diameter of the one or more bearings  114 . This is shown in  FIG.  3    via the first bearing supply line  120  having two jet outlets  116 , each being directed to one of the two bearings of the one or more bearings  114 . The lubrication is axially pumped toward the outer sides of the roller elements of the one or more bearings  114  due to the rotating motion of the roller element. The lubrication jets are, therefore, independent of shaft angular speed (e.g., angular speed of the propeller shaft  30 ). This may provide improved performance in low speed engine conditions, such as, for example, but not limited to, ground idle and taxi conditions of an aircraft. 
     The under-race lubrication flow is spilled from another oil manifold, such as, for example, the gearbox oil manifold  108 , by means of one or more spray bars  110 . The lubrication flow is sprayed and then collected within the one or more grooves  134 . The one or more grooves  134  may be rotating grooves (as they are located along the inner wall of the rotating propeller shaft  30 ). Therefore, lubrication is pumped (via a centrifugal pumping effect) through several radial holes (e.g., pass-through holes  132 ) to supply the lubrication fluid to the bearing inner races (also referred to as under races) of the one or more bearings  114  by the centrifugal forces generated in the system. This is shown in  FIG.  3    by the first gearbox supply line  122  having a spray bar  110  that delivers lubrication to the one or more grooves  134 , the pass-through holes  132 , and, thus, under both of the two bearings shown of the one or more bearings  114  and to the seal  112 . The under race lubrication flow arrangement described herein may avoid the need to have a dedicated lubrication line to each of the one or more bearings  114  and the seal  112 . Lubrication is then provided to critical locations, where high loads and metal-to-metal sliding occur. For example, on the tapered roller bearings of the one or more bearings  114 , this may be the interface between the shoulder and the roller element. The full effectiveness of the under race lubrication takes place during high speed and high load engine conditions, such as, for example, but not limited to, take off and climb conditions of an aircraft. 
     In the integrated lubrication system of the present disclosure, additional elements may require lubrication as well (e.g., additional bearings and/or seals). For example, the seal  112  may be provided with lubrication fluid and may share the same channels with the one or more bearings  114 . One or more separators  130  may be dedicated circumferential separators in the inner propeller shaft walls of the propeller shaft  30  to generate cavities  138  for supplying lubrication fluid to the one or more additional elements. The separators  130  may assist in separating the lubrication flows for the carbon seal and the propeller-shaft bearings. Furthermore, jet lubrication is performed by means of dedicated spray bars targeting the inner-most diameter of the rolling elements. 
     The integrated lubrication system  200  of the present disclosure may be implemented in any engine or turboprop engine to improve the lubrication of elements that are difficult to reach or to access. The integrated lubrication system  200  of the present disclosure reduces weight, part count, and system complexity, while taking advantage of already existing lubrication devices (e.g., reduction gearbox oil manifold). The integrated lubrication system  200  of the present disclosure may be extended to lubricate arrangements of multiple components (e.g., the propeller shaft bearings and the carbon seals). The integrated lubrication system  200  of the present disclosure combines jets (e.g., jet outlet  116 ) and under race lubrication (e.g., as shown via first bearing supply line  120  in  FIG.  2   ), which improves the lubrication quality and offers maximum performance throughout operation of the engine  10  ( FIG.  1   ). 
     The plurality of lubrication supply lines  104  may include one or more lubrication supply lines (e.g.,  120  and  126  of  FIG.  2   ), that extend radially inward toward a central axis of the engine  10  ( FIG.  1   ). The plurality of lubrication supply lines  104  may include one or more lubrication supply lines (e.g.,  122  and  124  of  FIG.  2   ), that extend parallel along the central axis of the engine  10  ( FIG.  1   ). 
     Further aspects of the present disclosure are provided by the subject matter of the following clauses. 
     An integrated lubrication system for an engine includes a first lubrication supply line extending radially inward toward a central axis of the engine and having a first plurality of jet outlets and configured to deliver a lubrication fluid to a first location on one or more engine components, a second lubrication supply line extending parallel to the central axis and having a second plurality of jet outlets and configured to deliver the lubrication fluid to a second location on the one or more engine components, and one or more spray bars coupled with the first lubrication supply line, the second lubrication supply line, or both the first lubrication supply line and the second lubrication supply line, the one or more spray bars configured to direct the lubrication fluid towards the one or more engine components. The first lubrication supply line is configured to lubricate the one or more engine components in a first engine power condition and the second lubrication supply line is configured to lubricate the one or more engine components in a second engine power condition, the second engine power condition having a greater power output than the first engine power condition. 
     The integrated lubrication system of the preceding clause, further including a manifold, wherein the second lubrication supply line is configured to spill the lubrication fluid from the manifold to the one or more engine components. 
     The integrated lubrication system of any preceding clause, wherein the first lubrication supply line and the second lubrication supply line are each pressurized such that the lubrication fluid is a pressurized lubrication fluid. 
     The integrated lubrication system of any preceding clause, wherein the first lubrication supply line and the second lubrication supply line each comprises more than one lubrication supply line. 
     The integrated lubrication system of any preceding clause, wherein the lubrication fluid from the second lubrication supply line is pumped via a centrifugal pumping action toward the one or more engine components. 
     The integrated lubrication system of any preceding clause, further including one or more scavenge features configured to drain the lubrication fluid. 
     The integrated lubrication system of any preceding clause, further including a groove and one or more pass-through holes, the groove configured to receive the lubrication fluid from the second lubrication supply line and to deliver the lubrication fluid through the one or more pass-through holes to the one or more engine components. 
     The integrated lubrication system of any preceding clause, further including one or more separators, the one or more separators configured to divide the groove into a plurality of cavities. 
     The integrated lubrication system of any preceding clause, wherein the one or more engine components includes one or more bearings. 
     The integrated lubrication system of any preceding clause, wherein the one or more engine components further includes a seal. 
     The integrated lubrication system of any preceding clause, wherein the first lubrication supply line is configured to deliver the lubrication fluid to an innermost diameter of the one or more bearings and the second lubrication supply line is configured to deliver the lubrication fluid to an inner race of the one or more bearings. 
     An engine includes a gearbox assembly includes a gearbox housing, a propeller shaft, one or more bearings located between the propeller shaft and the gearbox housing and configured to allow relative rotation of the propeller shaft with respect to the gearbox housing, and an integrated lubrication system. The integrated lubrication system includes a first lubrication supply line configured to supply a lubrication fluid to an innermost diameter of each bearing of the one or more bearings, and a second lubrication supply line configured to supply the lubrication fluid to an inner race of each bearing of the one or more bearings. 
     The engine of the preceding clause, further includes a gearbox oil manifold, wherein the second lubrication supply line is configured to spill the lubrication fluid from the gearbox oil manifold to the one or more bearings. 
     The engine of any preceding clause, wherein the second lubrication supply line includes a spray bar configured to provide the lubrication fluid to a groove in the propeller shaft, which in turn provides the lubrication fluid to the inner race of the one or more bearings. 
     The engine of any preceding clause, wherein the first lubrication supply line and the second lubrication supply line each comprises more than one lubrication supply line. 
     The engine of any preceding clause, wherein the lubrication fluid from the second lubrication supply line is pumped via a centrifugal pumping action toward the one or more bearings. 
     The engine of any preceding clause, further including a seal that receives the lubrication fluid from the second lubrication supply line. 
     The engine of any preceding clause, further including one or more scavenge features configured to drain the lubrication fluid. 
     The engine of any preceding clause, further including a groove in an inner surface of the propeller shaft and one or more pass-through holes extending through the propeller shaft, the groove configured to receive the lubrication fluid from the second lubrication supply line and to deliver the lubrication fluid through the one or more pass-through holes to the inner race of the one or more bearings. 
     The engine any preceding clause, further including one or more separators, each being configured to divide the groove into a plurality of cavities. 
     Although the foregoing description is directed to the preferred embodiments, it is noted that other variations and modifications will be apparent to those skilled in the art, and may be made without departing from the spirit or scope of the disclosure Moreover, features described in connection with one embodiment may be used in conjunction with other embodiments, even if not explicitly stated above.