Patent Publication Number: US-2016245117-A1

Title: In-line deaerator device for windmill-auxiliary oil system for fan drive gear system

Description:
BACKGROUND 
     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. 
     A speed reduction device such as 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. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a reduced speed such that both the turbine section and the fan section can rotate at closer to optimal speeds. 
     The gear assembly requires lubrication to prevent premature wear of bearing surfaces. Accordingly, a lubrication system that includes a main pump and main reservoir is used during engine operation. However, when the engine is not operating, airflow through the fan may cause the gear assembly to rotate. Also, certain maneuvers with the engine operating may briefly interrupt the operation of the main system. An auxiliary system is therefore provided that utilizes lubricant drained from the gear assembly to maintain lubricant flow to the bearing surfaces when the main system is not operating. Drained lubricant may be aerated and therefore have a reduced effectiveness. 
     SUMMARY 
     In one exemplary embodiment, a lubrication system for a fan drive gear system of a turbofan engine includes an auxiliary pump for communicating lubricant to bearings of a gear system. A deaerator is disposed between a lubricant source and the auxiliary pump for separating gases is contained within the lubricant. The deaerator includes a vane section for inducing a radial flow in the lubricant for separating gas from the lubricant. 
     In a further embodiment of the above, the deaerator includes a first outlet for lubricant disposed radially outside of a second outlet for gas. 
     In a further embodiment of any of the above, the second outlet includes a vent that extends radially out of the deaerator to exhaust gas. 
     In a further embodiment of any of the above, the vane section includes a plurality of vanes extending radially outward transverse to a direction of lubricant flow for inducing a radial component to lubricant flow. 
     In a further embodiment of any of the above, the deaerator includes a conduit including a chamber between the vane section and the first outlet and the second outlet. The radial flow component is induced by the vane section drives the lubricant against the inner walls of the chamber leaving the gas spaced apart from the inner walls. 
     In a further embodiment of any of the above, the radial flow in the lubricant includes a swirl that drives heavier lubricant against inner walls of the deaerator and leaves the gas to flow about a central line of the conduit. 
     In a further embodiment of any of the above, a gutter capturing lubricant exhausted from the fan drive gear system, the gutter in communication with the auxiliary pump through the deaerator. 
     In a further embodiment of any of the above, a bearing supports at least one gear of the fan drive gear system. The bearing is in communication with an outlet of the auxiliary pump to receive lubricant. 
     In a further embodiment of any of the above, a mechanical link between a portion of the fan drive gear system and the auxiliary pump for driving the auxiliary pump. 
     In a further embodiment of any of the above, a valve assembly for directing lubricant from the auxiliary pump to at least one bearing in response to a reduction in lubricant flow from a main lubricant system below a predetermined flow rate. 
     In another exemplary embodiment, a gas turbine engine includes a fan including a plurality of fan blades rotatable about an axis. A geared architecture is driven by a turbine section for rotating the fan about the axis. A main lubricant system directs lubricant flow to at least one bearing surface of the geared architecture. An auxiliary lubricant system directs lubricant flow to the at least one bearing surface responsive to a reduction in lubricant flow from the main lubricant system below a predetermined flow rate. The auxiliary lubricant system includes a deaerator communicating lubricant to an auxiliary pump. The deaerator includes a vane section for inducing a radial flow in the lubricant for separating gas from the lubricant prior to entering the auxiliary pump. 
     In one exemplary embodiment, the deaerator includes a first outlet for lubricant disposed radially outside of a second outlet for gas. 
     In a further embodiment of the above, the second outlet includes a vent that extends radially out of the deaerator to exhaust gas. 
     In a further embodiment of the above, the deaerator includes a conduit including a chamber between the vane section and the first outlet and the second outlet. A radial flow component induced by the vane section drives the lubricant against the inner walls of the chamber leaving the gas spaced apart from the inner walls. 
     In a further embodiment of the above, a bearing supports at least one gear of the geared architecture. The bearing is in communication with an outlet of the auxiliary pump to receive lubricant. 
     In another exemplary embodiment, a method of designing a lubrication system for a fan drive gear system of a turbofan engine includes configuring a main lubricant system for providing lubricant to at least one bearing system during a first engine operating condition. An auxiliary lubricant system is configured for communicating lubricant to the at least one bearing surface during a second engine operating condition. During the second engine operating condition the main lubricant system provides a lubricant flow below a desired lubricant flow rate threshold. A deaerator is defined within the auxiliary lubricant system between a source of captured lubricant and an auxiliary pump for separating gases from the captured lubricant. The deaerator includes a vane section for inducing a radial flow in the lubricant for separating gases from the lubricant. 
     In one exemplary embodiment, a deaerator is defined to include a first outlet for lubricant disposed radially outside of a second outlet for gas. The second outlet is configured to include a vent that extends radially out of the deaerator to exhaust gas. 
     In a further embodiment of any of the above, the deaerator is configured to define a conduit including a chamber between the vane section and the first outlet and the second outlet. A radial flow component induced by the vane section drives the lubricant against the inner walls of the chamber leaving the gas spaced apart from the inner walls. 
     Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure 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. 
     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 
         FIG. 1  is a schematic view of an example gas turbine engine. 
         FIG. 2  is a schematic view of an example lubrication system for a fan drive gear system. 
         FIG. 3  is a schematic view of an example de-aerator embodiment for removing air from lubricant. 
         FIG. 4  is a schematic view of a vane section of the example de-aerator of  FIG. 3 . 
         FIG. 5  is a schematic view of an outlet section of the example de-aerator of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor 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  drives air along a core flow path C. Air passing through the core flow path C is compressed and communicated to the combustor section  26  where the compressed air is mixed with fuel and ignited to produce a high energy flow that expands through the turbine section  28 . 
     Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
     The exemplary 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 and the location of bearing systems  38  may be varied as appropriate to the application. 
     The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a first (or low) pressure compressor  44  and a first (or low) pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a speed change mechanism, which in exemplary gas turbine engine  20  is illustrated as a geared architecture  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 second (or high) pressure compressor  52  and a second (or high) pressure turbine  54 . A combustor  56  is arranged in exemplary gas turbine  20  between the high pressure compressor  52  and the high pressure turbine  54 . 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 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
     The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  58  includes airfoils  60  which are in the core airflow path C. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. It will be appreciated that each of the positions of the fan section  22 , compressor section  24 , combustor section  26 , turbine section  28 , and fan drive gear system  48  may be varied. For example, gear system  48  may be located aft of combustor section  26  or even aft of turbine section  28 , and fan section  22  may be positioned forward or aft of the location of gear system  48 . 
     The engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the engine  20  bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture  48  is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine  46  has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine  20  bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  has a pressure ratio that is greater than about five 5:1. Low pressure turbine  46  pressure ratio is pressure measured prior to inlet of low pressure turbine  46  as related to the pressure at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
     The geared architecture  48  may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans. 
     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 (10.67 km). The flight condition of 0.8 Mach and 35,000 ft (10.67 km), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption CTSFCT—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “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 1.45. “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° R)]0.5. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second (350 m/second). 
     The example gas turbine engine includes the fan  42  that comprises in one non-limiting embodiment less than about twenty-six (26) fan blades. In another non-limiting embodiment, the fan section  22  includes less than about twenty (20) fan blades. Moreover, in one disclosed embodiment the low pressure turbine  46  includes no more than about six (6) turbine rotors schematically indicated at  34 . In another non-limiting example embodiment the low pressure turbine  46  includes about three (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. 
     A lubrication system  62  is provided in the gas turbine engine  20  to provide lubrication to at least one bearing surface. The lubrication system  62  provides lubricant to the geared architecture  48  and includes a main lubrication system  65  and an auxiliary lubrication system  67 . The main lubrication system  65  includes a main lubricant pump  66  that draws lubricant from a main reservoir  64  to provide lubricant flow to the geared architecture  48  during engine operation. The main lubricant system  65  provides lubricant flow to the engine  20  when it is operating normally. In some instances, the engine  20  may not be operating or may be operating at a condition where lubricant flow through the main lubrication system  65  is not providing lubricant flow above a desired threshold value. Accordingly, the auxiliary lubrication system  67  is provided to supplement lubricant flow to the bearing surfaces during engine operating conditions where the main lubricant system  65  is not providing sufficient flow. 
     The auxiliary lubricant system  67  includes an auxiliary pump  68  that draws lubricant from a gutter  70 . The gutter  70  captures oil that is exhausted from other bearing assemblies or the geared architecture  48  as is shown schematically in  FIG. 1 . 
     Referring to  FIG. 2  with continued reference to  FIG. 1 , the example lubrication system  62  provides lubricant to the geared architecture  48 . It should be understood that although lubrication of the geared architecture  48  is disclosed by way of example, other systems requiring lubricant are within the contemplation of this disclosure. 
     In this example, the geared architecture  48  comprises a sun gear  72  that drives a plurality of intermediate gears  74  that in turn drives a ring gear  78 . Each of the intermediate gears  74  are supported for rotation by a bearing  76 . In this example, the bearing  76  is a journal bearing that defines a bearing surface between the rotating gear and a fixed shaft. As appreciated, rotation of the intermediate gears  74  upon the bearing surfaces  76  in the absence of sufficient lubricant flow may have a detrimental effect to operation and result in premature wear. Accordingly, the auxiliary lubricant system  67  is provided to maintain a desired predetermined level of lubricant flow during all engine operating conditions regardless of the amount of lubricant that can be provided by the main lubrication system  65 . 
     The auxiliary lubrication system  67  includes the auxiliary pump  68  that draws lubricant from a gutter  70 . The gutter  70  captures lubricant that is exhausted from the geared architecture  48 . A valve system  112  directs lubricant between the main lubrication system  65  and the auxiliary lubrication system  67  in response to the level of flow provided by the main lubrication system  65  and also may switch between systems responsive to detecting a specific engine operating condition. 
     The lubricant system  62  further includes a scavenge pump  82  that draws lubricant from a sump  80  and directs that lubricant back to the main reservoir  64 . 
     The auxiliary system  67  is operational during instances where the main system flow is interrupted or where the engine may not be operating to drive the main pump  66  of the main lubrication system  65 . During conditions where the main lubrication system flow is interrupted the engine may still be operating and driving the geared architecture, and during certain conditions where the engine is not operating, the fan section  22  ( FIG. 1 ) may be driven by air flow and thereby drive the geared architecture  48 . Any rotation of the gears  74  within the geared architecture  48  in the absence of lubricant may have detrimental effects to the bearing  76 . Accordingly, the auxiliary lubrication system  67  provides lubricant flow during times where the engine may be windmilling. 
     In this embodiment, the auxiliary pump  68  is driven through a mechanical link  110  with the geared architecture  48 . Accordingly, in response to windmilling of the fan section  22  that drives the geared architecture  48 , the auxiliary pump  68  will be driven such that lubricant flow can be maintained to the bearings  76 . Other mechanisms to drive the auxiliary pump  68  in the absence of engine power may also be utilized and are within the contemplation of this disclosure. 
     Lubricant captured in the gutter  70  is directed through a deaerator  84  disposed before an inlet  92  of the auxiliary pump  68 . Lubricant captured in the gutter  70  can include gases and air that can reduce the effectiveness of the lubricant supplied to the bearings  76 . Accordingly, the deaerator  84  is provided between the gutter  70  and the inlet  92  of the auxiliary pump  68  for removing a substantial portion of gases and air from the lubricant. The deaerator  84  separates lubricant from any gases or air trapped therein. 
     In the disclosed example, lubricant and air mixture  86  is communicated to the deaerator  84 . Lubricant  90  is then communicated to the inlet  92  of the auxiliary pump  68 . Trapped gases such as air  88  are vented through an outlet  104  and away from the auxiliary pump  68 . Air and gases trapped in the lubricant can also have a detrimental effect and reduce the effectiveness of the auxiliary pump  68 . Accordingly, it is desirable to remove as much air and gases trapped in the liquid lubricant as is possible prior to the lubricant being communicated to the inlet  92 . Accordingly, lubricant significantly void of any gases and air is exhausted through the pump outlet  94  to the valve assembly  112  and thereby to the bearing  76  of the geared architecture  48 . 
     Referring to  FIG. 3  with continued reference to  FIG. 2 , the example deaerator  84  includes an initial inlet  96  that receives lubricant and air mixture  86 . The lubricant and air mixture  86  is initially flowed through a vane assembly  98  before entering a chamber  100 . 
     Referring to  FIG. 4  with continued reference to  FIG. 3 , the example vane assembly  98  includes a plurality of vanes  102  that extend radially outward within the deaerator  84 . Each of the vanes  102  induces a swirl and/or radial flow component to the lubricant and air mixture  86 . Accordingly, the lubricant and air mixture  86  is swirled by the vane assembly  98  and flows within the chamber  100  defined within the deaerator  84 . The swirling flow generates centrifugal forces that drive the heavier liquid lubricant outward towards inner walls  114  of the chamber  100 . The lighter air and gas component remains within a central portion of the chamber  100  disposed along a center line  116 . The swirling and radial components of the liquid and gas mixture  86  provides for separation of the liquid lubricant from the air in other gases that may be trapped within the lubricant. The heavier lubricant is flung radially outward against the inner walls  114  of the chamber  100 . The lubricant flow moves through the chamber  100  towards the outlet assembly  104 . The outlet assembly  104  includes a first outlet  108  that is disposed radially outward of a central or second outlet  106 . 
     Referring to  FIG. 5  with continued reference to  FIG. 3 , the example outlet  104  includes the first outlet  108  for lubricant that is circumferentially and radially outward of the second outlet  106  for gases and air. The first outlet  108  receives the liquid lubricant that is traveling along the inner walls  114  of the chamber  100 . The second outlet  106  is disposed substantially centrally within the chamber  100  such that air and other gases schematically indicated at  88  can be vented from the deaerator  84 . As appreciated, vented gases  88  may include some lubricant but for the most part, the majority of liquid lubricant will be flung outward and proceed through the first outlet  108  that is disposed radially outward along the inner walls  114  of the chamber  100 . 
     Accordingly, lubricant in the substantially liquid form without gas and air is communicated through a conduit  90  to the inlet  92  of auxiliary pump  68 . Therefore, lubricant that is exhausted through the outlet  94  is substantially void of air in other gases and thereby provides the desired lubrication properties for lubricating and maintaining the bearing  76  in the geared architecture  48 . 
     Referring to  FIGS. 1, 2 and 3 , the example disclosure includes a method of designing a lubrication system  62  for a fan drive gear system  48  that includes a first step of configuring a main lubricant system  65  for providing lubricant to at least one bearing surface  76  during a first engine operating condition. In this example, the first engine operating condition includes a condition where the main lubrication system  65  is being driven by active operation of the gas turbine engine. 
     The method further includes designing and configuring an auxiliary lubrication system  67  that communicates lubricant to at least one bearing surface  76  during a second engine operating condition. In this example, the second engine operating condition is a condition wherein the main lubricant system  65  is not providing lubricant at a flow rate above a desired threshold value to maintain lubrication of the example bearings  76 . In this example, the second engine operating condition may also include an instance where the engine  20  is not operating but the fan  22  is rotating responsive to air flow through the bypass passage B. This condition is commonly understood and known as windmilling and will drive the geared architecture  48  such that lubrication of the bearings  76  is required. 
     The method further includes defining a deaerator  84  within the auxiliary lubricant system  67  between a source of captured lubricant such as the example gutter  70  and an auxiliary pump  68 . The deaerator  84  provides for separating of lubricant from gases that may be trapped in the lubricant due to the capturing of the exhaust of lubricant from the geared architecture  48 . 
     The method further includes defining the deaerator  84  to include a first outlet  108  for lubricant and a second outlet  106  for venting gases to provide for the separation of lubricant and air. 
     The method further includes defining the deaerator  84  to include a chamber  100  between a vane section  98  that induces swirl into the lubricant and gas mixture to drive the lubricant towards the outer walls  114  of the chamber  100 , leaving the gas within an inner or central part of the chamber  100  for exhausting through the second outlet  106  that is radially inward of the first outlet  108  for lubricant. 
     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.