Patent Publication Number: US-2017356304-A1

Title: Systems and methods for reducing fluid viscosity in a gas turbine engine

Description:
BACKGROUND 
     The field of the disclosure relates generally to gas turbine engines and, more particularly, to systems and method for reducing fluid viscosity in a gas turbine engine. 
     Gas turbine engines typically include squeeze film dampers that provide damping to rotating components, such as a rotor shaft, to reduce and control vibration. At least some known squeeze film dampers include a bearing support member, such as an outer race of a rolling element bearing supported shaft, fitted within an annular housing chamber that restricts radial motion of the bearing support member. An annular film space is defined between an outer surface of the outer race and an opposite inner surface of the bearing housing such that damper oil can be introduced therein. Vibratory and/or radial motion of the shaft and its bearing generate hydrodynamic forces in the damper oil within the annular film space for damping purposes. The damper oil is generally provided by an oil supply system including a pump that circulates the damper oil through the annular film space. 
     In known squeeze film damper systems, damping is generally based on a viscosity of the damper oil, wherein colder temperature oil is generally highly viscous which is stiffer and more resistant to shear and/or tensile stress. During cold weather engine start conditions, highly viscous oil may lead to rotordynamic instability within the engine. By heating the damper oil and lowering its viscosity, engine stability is increased. Some known oil viscosity systems are external systems that include an auxiliary oil line which couples to an engine oil tank. The auxiliary oil line pumps the oil out of the oil tank to heat and then returns the oil to the oil tank. However, external systems need to be connected to the oil tank and extract the oil for the oil to be heated and reduce viscosity. 
     BRIEF DESCRIPTION 
     In one aspect, a fluid viscosity system for use in a gas turbine engine is provided. The fluid viscosity system includes an induction assembly coupled to a fluid line within the gas turbine engine. The induction assembly includes an electromagnet. The induction assembly further includes an electronic oscillator electronically coupled to the electromagnet. The electronic oscillator is configured to generate an alternating current (AC) that is transmitted to the electromagnet at a predetermined frequency and magnitude such that a viscosity of a fluid channeled through the fluid line is reduced at least partially due to induction heating. 
     In another aspect, a gas turbine engine is provided. The gas turbine engine includes a damping system. A fluid line coupled in flow communication to the damping system and configured to channel an oil through the fluid line to the damping system. The gas turbine engine further includes a fluid viscosity system that includes an induction assembly coupled to the fluid line. The induction assembly includes an electromagnet. The induction assembly further includes an electronic oscillator electronically coupled to the electromagnet. The electronic oscillator is configured to generate an alternating current (AC) that is transmitted to the electromagnet at a predetermined frequency and magnitude such that a viscosity of the oil channeled through the fluid line is reduced at least partially due to induction heating. 
     In yet another aspect, a method for reducing fluid viscosity with a fluid viscosity system in a gas turbine engine is provided. The fluid viscosity system includes an induction assembly is coupled to a fluid line. The induction assembly includes an electromagnet and an electronic oscillator electronically coupled to the electromagnet. The method includes channeling a flow of fluid through the fluid line, and inducing an alternating current (AC) by the electronic oscillator. The method further includes transmitting to the electromagnet the AC at a predetermined frequency and magnitude such that a viscosity of the fluid channeled through the fluid line is reduced at least partially due to induction heating. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a schematic illustration of an exemplary gas turbine engine in accordance with an example embodiment of the present disclosure. 
         FIG. 2  is a schematic illustration of an exemplary fluid viscosity system from the turbofan engine shown in  FIG. 1 . 
         FIG. 3  is a perspective view of an exemplary metallic fluid line section that may be used with the fluid viscosity system shown in  FIG. 2 . 
         FIG. 4  is a flow diagram of an exemplary embodiment of a method for reducing fluid viscosity with a fluid viscosity system, such as the fluid viscosity system shown in  FIGS. 1 and 2 , in a gas turbine engine. 
     
    
    
     Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of this disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of this disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein. 
     DETAILED DESCRIPTION 
     In the following specification and claims, reference will be made to a number of terms, which shall be defined to have the following meanings. 
     The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
     As used herein, the terms “processor” and “computer,” and related terms, e.g., “processing device,” “computing device,” and “controller” are not limited to just those integrated circuits referred to in the art as a computer, but broadly refers to a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), and other programmable circuits, and these terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, a computer-readable medium, such as a random access memory (RAM), a computer-readable non-volatile medium, such as a flash memory. Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used that may include, for example, but not be limited to, a scanner. Furthermore, in the exemplary embodiment, additional output channels may include, but not be limited to, an operator interface monitor. 
     Embodiments of a fluid viscosity system as described herein provide a system and method that facilitates reducing gas turbine engine fluid viscosity within a gas turbine engine. Specifically, the fluid viscosity system includes an induction assembly coupled to a fluid line which applies an alternating current (AC) at a predetermined frequency and magnitude such that a fluid channeled through the fluid line is heated to a predetermined temperature through induction heating reducing viscosity thereof. In some embodiments, a temperature sensor is coupled in flow communication with the fluid line such that a temperature of the fluid channeled through the fluid line is measured for controlling the AC generated by the induction assembly. By heating the fluid within the fluid line and reducing viscosity, fluid viscosity system may be placed anywhere along the fluid line while also increasing control over the fluid temperature. Additionally, the fluid is directly channeled to a gas turbine engine component increasing efficiency of the fluid viscosity system and reducing energy consumption. Fluid viscosity system further decreases engine weight such that overall engine efficiency is increased. 
       FIG. 1  is a schematic cross-sectional view of a gas turbine engine in accordance with an exemplary embodiment of the present disclosure. In the exemplary embodiment, the gas turbine engine is a high-bypass turbofan jet engine  110 , referred to herein as “turbofan engine  110 .” As shown in  FIG. 1 , turbofan engine  110  defines an axial direction A (extending parallel to a longitudinal centerline  112  provided for reference) and a radial direction R (extending perpendicular to longitudinal centerline  112 ). In general, turbofan engine  110  includes a fan case assembly  114  and a gas turbine engine  116  disposed downstream from fan case assembly  114 . 
     Gas turbine engine  116  includes a substantially tubular outer casing  118  that defines an annular inlet  120 . Outer casing  118  encases, in a serial flow relationship, a compressor section including a booster or low pressure (LP) compressor  122  and a high pressure (HP) compressor  124 ; a combustion section  126 ; a turbine section including a high pressure (HP) turbine  128  and a low pressure (LP) turbine  130 ; and a jet exhaust nozzle section  132 . A high pressure (HP) shaft or spool  134  drivingly connects HP turbine  128  to HP compressor  124 . A low pressure (LP) shaft or spool  136  drivingly connects LP turbine  130  to LP compressor  122 . Each shaft  134  and  136  is supported by a plurality of bearing assemblies  138  having a damping system  140 . The compressor section, combustion section  126 , turbine section, and exhaust nozzle section  132  together define an air flow path  137 . 
     In the exemplary embodiment, fan case assembly  114  includes a fan  142  having a plurality of fan blades  144  coupled to a disk  146  in a spaced apart manner. As depicted, fan blades  144  extend outwardly from disk  146  generally along radial direction R. Fan blades  144  and disk  146  are together rotatable about longitudinal centerline  112  by LP shaft  136 . 
     Referring still to the exemplary embodiment of  FIG. 1 , disk  146  is covered by rotatable front hub  148  aerodynamically contoured to promote airflow through the plurality of fan blades  144 . Additionally, exemplary fan case assembly  114  includes an annular fan casing or outer nacelle  150  that circumferentially surrounds fan  142  and/or at least a portion of gas turbine engine  116 . It should be appreciated that nacelle  150  may be configured to be supported relative to gas turbine engine  116  by an outlet guide vane assembly  152 . Moreover, a downstream section  154  of nacelle  150  may extend over an outer portion of gas turbine engine  116  so as to define a bypass airflow passage  156  therebetween. 
     During operation of turbofan engine  110 , a volume of air  158  enters turbofan engine  110  through an associated inlet  160  of nacelle  150  and/or fan case assembly  114 . As air  158  passes across fan blades  144 , a first portion of air  158  as indicated by arrows  162  is directed or routed into bypass airflow passage  156  and a second portion of air  158  as indicated by arrows  164  is directed or routed into air flow path  137 , or more specifically into booster compressor  122 . The ratio between first portion of air  162  and second portion of air  164  is commonly known as a bypass ratio. The pressure of second portion of air  164  is then increased as it is routed through HP compressor  124  and into combustion section  126 , where it is mixed with fuel  165  supplied by a fuel system  167  and burned to provide combustion gases  166 . Fuel system  167  channels fuel  165  from a fuel tank (not shown) to combustion section  126 . 
     Combustion gases  166  are routed through HP turbine  128  where a portion of thermal and/or kinetic energy from combustion gases  166  is extracted via sequential stages of HP turbine stator vanes  168  that are coupled to outer casing  118  and HP turbine rotor blades  170  that are coupled to HP shaft or spool  134 , thus causing HP shaft or spool  134  to rotate, thereby supporting operation of HP compressor  124 . Combustion gases  166  are then routed through LP turbine  130  where a second portion of thermal and kinetic energy is extracted from combustion gases  166  via sequential stages of LP turbine stator vanes  172  that are coupled to outer casing  118  and LP turbine rotor blades  174  that are coupled to LP shaft or spool  136 , thus causing LP shaft or spool  136  to rotate, thereby supporting operation of booster compressor  122  and/or rotation of fan  142 . Combustion gases  166  are subsequently routed through jet exhaust nozzle section  132  of gas turbine engine  116  to provide propulsive thrust. Simultaneously, the pressure of first portion of air  162  is substantially increased as first portion of air  162  is routed through bypass airflow passage  156 , including through outlet guide vane assembly  152  before it is exhausted from a fan nozzle exhaust section  176  of turbofan engine  110 , also providing propulsive thrust. HP turbine  128 , LP turbine  130 , and jet exhaust nozzle section  132  at least partially define a hot gas path  178  for routing combustion gases  166  through gas turbine engine  116 . 
     In operation, each shaft  134  and/or  136  generally rotates about longitudinal centerline  112 . However, during some operating conditions, such as, but not limited to, engine start, shaft  134  and/or  136  undergoes an eccentric or orbiting motion which induces vibration and deflection that may propagate or transfer to other turbofan engine  110  locations. In the exemplary embodiment, damping system  140  includes an oil supply system  180  that circulates oil  182  through a damper (not shown) such as a squeeze film damper. Damping system  140  is provided at the bearing positions of shafts  134  and/or  136  to transfer vibratory and/or radial motion to hydrodynamic forces in oil  182  and facilitates reducing vibration and deflection loads within turbofan engine  110 . In alternative embodiments, damping system  140  may be positioned at any location along rotating shafts  134  and/or  136 . 
     It should be appreciated, however, that exemplary turbofan engine  110  depicted in  FIG. 1  is by way of example only, and that in other exemplary embodiments, turbofan engine  110  may have any other suitable configuration. It should also be appreciated, that in still other exemplary embodiments, aspects of the present disclosure may be incorporated into any other suitable gas turbine engine. For example, in other exemplary embodiments, aspects of the present disclosure may be incorporated into, e.g., a turboprop engine, a military purpose engine, and a marine or land-based aero-derivative engine. 
       FIG. 2  is a schematic illustration of an exemplary fluid viscosity system  200  from turbofan engine  110  (shown in  FIG. 1 ). In the exemplary embodiment, oil supply system  180  includes fluid viscosity system  200  that facilitates reducing oil viscosity  182  that is channeled to the squeeze film damper of damping system  140  (shown in  FIG. 1 ). Fluid viscosity system  200  includes an induction assembly  202  coupled to a fluid line  204  which is positioned within turbofan engine  110 . Induction assembly  202  includes an electromagnet  206  defined within at least a portion  208  of fluid line  204 . Induction assembly  202  further includes an electronic oscillator  210  electronically coupled to electromagnet  206 . Specifically, electromagnet  206  includes a metallic fluid line section  212  and an inductor coil  214  that is extended around metallic fluid line section  212  a predetermined number of times and coupled to electronic oscillator  210 . 
     Fluid viscosity system  200  further includes an electromagnetic shield  216  at least partially surrounding induction assembly  202 . Additionally, a temperature/viscosity sensor  218  is coupled in flow communication with fluid line  204  and is operatively coupled to a controller  220 . Controller  220  is further operatively coupled to electronic oscillator  210 . In the exemplary embodiment, temperature sensor  218  is positioned downstream of induction assembly  202 . In alternative embodiments, temperature sensor  218  may be positioned at any other location that enables fluid viscosity system  200  to function as described herein. 
     During operation of turbofan engine  110 , for example during engine start conditions, oil  182  may be at a lower temperature such that oil  182  is highly viscous and more resistant to shear and/or tensile stress within damping system  140 . Fluid viscosity system  200  facilitates increasing the temperature of oil  182  and reducing viscosity of oil  182 , such that when oil  182  is channeled through damping system  140  vibration and radial motion of rotor shaft  134  and/or  136  is reduced. Specifically, fluid viscosity system  200  heats oil  182  through induction heating to a predetermined temperature and viscosity. Electronic oscillator  210  generates and transmits a high-frequency alternating current (AC)  222  at a predetermined frequency and magnitude through electromagnet  206 . The rapidly alternating magnetic field penetrates metallic fluid line section  212  generating eddy currents  224  therein. Eddy currents  224  flowing through electrical resistance of metallic fluid line section  212  heats metallic fluid line section  212  by Joule/resistance heating which causes oil  182  within to increase in temperature and reduce viscosity. In alternative embodiments, induction heat may be generated by magnetic hysteresis losses. In yet other embodiments, induction heat may be generated by series-resonance electromagnetism. Alternatively or additionally, fluid viscosity system  200  may include any other heating system that enables fluid within a fluid line to be heated and reduces viscosity. For example, fluid viscosity system  200  may include an electrical conduction assembly. 
     In some embodiments, temperature sensor  218  measures the temperature of oil  182  which is received by controller  220 . Controller  220  controls electronic oscillator  210 , for example, by setting the frequency and magnitude of AC  222  of electronic oscillator  210  based on temperature and flow rate of oil  182 . In alternative embodiments, controller  220  may control electronic oscillator  210  by use of one or more of ambient temperature measurements, engine operation time, engine shutoff time, and others. Furthermore, controller  220  turns fluid viscosity system  200  on/off such that fluid viscosity system  200  is operable only when fluid heating and viscosity reduction is needed. In alternative embodiments, controller  220  may be included within a full authority digital engine (or electronics) control (FADEC). 
     In the exemplary embodiment, oil  182  is inductively heated to a minimum temperature of 50° Fahrenheit (10° Celsius) to reduce viscosity thereof. In alternative embodiments, oil  182  is heated to any other temperature that reduces viscosity and enables damping system  140  to function as described herein. Additionally or alternatively, temperature sensor  218  may be a viscosity sensor or a process sensor that measures/calculates the viscosity of oil  182  such that fluid viscosity system  200  receives viscosity measurements to control the viscosity of oil  182  through the system. In other embodiments, electromagnetic shield  216  at least partially surrounds induction assembly  202  such that electronic interference with other electrical turbofan engine  110  components is reduced. 
     In the exemplary embodiment, a portion of fluid line  204  includes metallic fluid line section  212  such that electromagnet  206  can be formed therein. Metallic fluid line section  212  is any material that has good electrical and thermal conductivity, for example, and not by way of limitation, iron, nickel, and copper. Furthermore, in the exemplary embodiment, fluid line  204 , including metallic fluid line section  212 , has a generally circular shaped cross-sectional profile with a perimeter length  226  wrapped with inductor coil  214 . In some embodiments, metallic fluid line section  212  is sized to further facilitate induction heating as discussed below in reference to  FIG. 3 . In other embodiments, metallic fluid line section  212  is S-shaped within inductor coil  214  such that oil  182  flowing therein makes multiple passes through inductor coil  214 . By heating oil  182  within metallic fluid line section  212 , fluid viscosity system  200  may be positioned anywhere along fluid line  204 . Furthermore, energy consumption is reduced because the heated oil  182  is channeled directly to damper assembly  140 . 
       FIG. 3  is a perspective view of an exemplary metallic fluid line section  300  that may be used with fluid viscosity system  200  (shown in  FIG. 2 ). In this alternative embodiment, metallic fluid line section  300  has a generally cross shaped cross-sectional profile with a perimeter length  302  that is wrapped with inductor coil  214  (shown in  FIG. 2 ). As compared with metallic fluid line section  212  with perimeter length  226  (shown in  FIG. 2 ), perimeter length  302  is greater than perimeter length  226 . The increased length of perimeter length  302  further facilitates induction heating efficiency because the flow of oil  182  therethrough has greater surface contact with metallic fluid line section  300  increasing induction heating thereof. In alternative embodiments, metallic fluid line section  300  may have any other shape that increases fluid contact with induction assembly  202 . 
     In reference to  FIGS. 2 and 3 , fluid viscosity system  200  has been discussed with respect to oil supply system  180  for damping system  140 . It should be appreciated, however, that fluid viscosity system  200  may facilitate induction heating of any other fluid within turbofan engine  110  (shown in  FIG. 1 ). For example, in an alternative embodiment, fluid viscosity system  200  may be coupled to fuel supply system  167  (shown in  FIG. 1 ) to facilitate induction heating of fuel  165  (also shown in  FIG. 1 ). During cold ambient temperatures, ice particles may form within fuel  165 , as such, fluid viscosity system  200  inductively heats fuel  165  reducing ice particles therein. 
       FIG. 4  is a flow diagram of an exemplary embodiment of a method  400  for heating fluid with a fluid viscosity system, such as fluid viscosity system  200  (shown in  FIG. 2 ), in a gas turbine engine, such as turbofan engine  110  (shown in  FIG. 1 ). With reference also to  FIGS. 1-3 , the fluid viscosity system includes an induction assembly, such as induction assembly  202 , coupled to a fluid line, such as fluid line  204 . The induction assembly includes an electromagnet, such as electromagnet  206 , and an electronic oscillator, such as electronic oscillator  210 , electronically coupled to the electromagnet. Exemplary method  400  includes channeling  402  a flow, such as oil flow  182 , through the fluid line. Inducing  404  an alternating current, such as AC  222 , by the electronic oscillator. Method  400  further includes transmitting  406  to the electromagnet the AC at a predetermined frequency and magnitude such that a viscosity of the fluid channeled through the fluid line is reduced at least partially due to induction heating. 
     In some embodiments, inducing  404  the alternating current further includes inducing  408  the alternating current through an inductor coil, such as inductor coil  214 , wherein the electromagnet includes a metallic fluid line section, such as metallic fluid line section  212 , including at least a portion of the fluid line and an inductor coil coupled to the electronic oscillator and extended around the metallic fluid line section. In other embodiments, method  400  further includes shielding  410  the gas turbine engine from electrical currents generated by the induction assembly by an electromagnetic shield, such as electromagnetic shield  216  that at least partially surround the induction assembly. 
     In certain embodiments, method  400  further includes measuring  412  a temperature of the fluid channeled through the fluid line by a temperature sensor, such as temperature sensor  218 , coupled in flow communication with the fluid line, and controlling  414  the alternating current based on the temperature measurement. In some embodiments, method  400  further includes receiving  416  a temperature measurement of the fluid channeled through the fluid line, and controlling  418  the alternating current based on the temperature measurement. 
     In other embodiments, channeling  402  the flow of fluid through the fluid line further includes channeling  420  a flow of oil through an oil line. Additionally, method  400  further includes heating  422  the oil to a predetermined temperature, such as 50° Fahrenheit. In some embodiments, channeling  402  the flow of fluid through the fluid line further includes channeling  424  a flow of fuel through a fuel line. 
     The above-described embodiments of a fluid viscosity system provide a system and method that facilitates heating gas turbine engine fluids within a gas turbine engine. Specifically, the fluid viscosity system includes an induction assembly coupled to a fluid line which applies an AC at a predetermined frequency and magnitude such that a fluid channeled through the fluid line is heated to a predetermined temperature through induction heating reducing viscosity thereof. In some embodiments, a temperature sensor is coupled in flow communication with the fluid line such that a temperature of the fluid channeled through the fluid line is measured for controlling the AC generated by the induction assembly. By heating the within the fluid line and reducing viscosity, the fluid viscosity system may be placed anywhere along the fluid line while also increasing control over the fluid temperature. Additionally, only the fluid that is directly channeled to a gas turbine engine component, such as a damper, is heated, thereby increasing efficiency of the fluid viscosity system and reducing energy consumption. The fluid viscosity system further decreases engine weight such that overall engine efficiency is increased. 
     An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) reducing oil viscosity channeled towards a damping system, increasing damping during cold engine starts and decreasing rotordynamic instability; (b) heating fuel channeled towards a combustion assembly, decreasing ice particles therein in cold ambient conditions; (c) decreasing energy requirements of a fluid viscosity system in a gas turbine engine; and (d) decreasing weight of fluid viscosity system and increasing engine efficiency. 
     Exemplary embodiments of methods, systems, and apparatus for the fluid viscosity system are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods may also be used in combination with other systems requiring reduced fluid viscosity, and the associated methods, and are not limited to practice with only the systems and methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other applications, equipment, and systems that may benefit from fluid heating. 
     Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     Some embodiments involve the use of one or more electronic or computing devices. Such devices typically include a processor or controller, such as a general purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a reduced instruction set computer (RISC) processor, an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), and/or any other circuit or processor capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer readable medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the term processor. 
     This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.