Abstract:
A self-pumping fuel injector includes a pump and a motor for, in-part, delivering fuel to a combustor at higher fuel pressures during start-up and ramping-up conditions. Each pump may include a stationary flow interuptor that intermittently and variably supplies fuel to a rotating spindle that, in-turn, expels the fuel into a nozzle of the injector for improve fuel spray distributions.

Description:
[0001]    This application claims priority to U.S. Patent Appin. No. 61/918,452 filed Dec. 19, 2013. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a gas turbine engine and, more particularly, to a self-pumping fuel injector and method of operation. 
         [0003]    Gas turbine engines, such as those that power modem commercial and military aircraft, include a compressor section to pressurize a supply of air, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases and generate thrust. All sections operating in unison under a wide variety of flight conditions including, but not limited to, idle, take-off, cruise, and deceleration. 
         [0004]    The combustor section generally includes a fuel system having a plurality of circumferentially distributed fuel injectors that axially project into a combustion chamber to supply fuel to be mixed with the pressurized air. This fuel supply through the injectors must be controlled by the fuel system to meet the demands of the various flight conditions while maintaining engine efficiency and minimizing emissions. To do so, fuel systems may include complicated and heavy hydromechanical devices that may include a plurality of multi-staged fuel manifolds, isolation or servo valves between individual injectors and the manifolds, low and high pressure fuel pumps delivering and bypassing fuel to the manifolds, and a wide array of electronic control features. 
         [0005]    Unfortunately, even with such complex and expensive systems, operation of individual fuel injectors is limited to fuel pressures and flows from the upstream manifolds, and fuel isolation provided by the interposed servo valves. Controlling (ramping up or down) of fuel flow through each individual injector, or individually tuning a fuel injector, to further refine operating performance is generally not available. Yet further, fuel atomization under start-up and low power conditions is limited by available fuel pressure. 
       SUMMARY 
       [0006]    A self-pumping fuel injector for a gas turbine engine according to one non-limiting embodiment of the present disclosure includes a nozzle, and an integral pump constructed and arranged to deliver fuel to the nozzle. 
         [0007]    Additionally to the foregoing embodiment, the pump is a rotating pump. 
         [0008]    In the alternative or additionally thereto, in the foregoing embodiment a drive device operably connects to the pump. 
         [0009]    In the alternative or additionally thereto, in the foregoing embodiment the drive device and the pump are rotatably coupled. 
         [0010]    In the alternative or additionally thereto, in the foregoing embodiment the drive device is an electric motor. 
         [0011]    In the alternative or additionally thereto, in the foregoing embodiment the pump has a housing and a spindle rotateably supported by the housing along a rotational axis. 
         [0012]    In the alternative or additionally thereto, in the foregoing embodiment the housing defines a fuel outlet disposed concentric to the rotational axis. 
         [0013]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes an end portion of the spindle disposed at the fuel outlet and defining at least in-part a helical passage in communication with the fuel outlet, an axially extending channel defined by the spindle, a fuel inlet defined by the housing, and wherein the central channel communicates between the fuel inlet and the helical passage. 
         [0014]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes a radial outer surface of the spindle, a radial inner surface of the spindle defining the channel, an inlet port defined by the spindle, and wherein the inlet port communicates through the outer and inner surfaces and communicates between the fuel inlet and the channel 
         [0015]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes an outlet port defined by the end portion and communicating between the helical passage and the channel, and wherein the helical passage communicates between the fuel outlet and the outlet port. 
         [0016]    In the alternative or additionally thereto, in the foregoing embodiment the helical passage is defined by the outer surface and the housing. 
         [0017]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes a fuel inlet and a fuel outlet defined by the housing, a helical passage defined at least in-part by the spindle and orientated to spiral concentrically about the axis, and wherein the helical passage is in continuous communication with the fuel outlet and is in intermittent communication with the fuel inlet as the spindle rotates. 
         [0018]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes a drive device, the spindle having and extending axially from a first end portion, a mid portion, and an opposite second end, and wherein the second end portion is engaged to the drive device, the first end portion is at least in-part in the fuel outlet, and the mid portion defines an inlet port being in intermittent communication with the fuel inlet and continuous communication with the helical passage. 
         [0019]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes the housing defining a fuel chamber in communication with the fuel inlet, a flow interuptor of the pump engaged rigidly to the housing and radially disposed adjacent to the mid portion in the fuel chamber, a port defined by and communicating radially through the flow interuptor, and wherein the port is in continuous communication with the fuel inlet and in intermittent communication with the helical passage as the spindle rotates. 
         [0020]    In the alternative or additionally thereto, in the foregoing embodiment a bearing of the pump is radially disposed between the housing and the spindle and in the fuel chamber. 
         [0021]    In the alternative or additionally thereto, in the foregoing embodiment the injector further includes a retainer of the pump engaged to the housing, and wherein the bearing and the flow interuptor are disposed radially between the retainer and the spindle. 
         [0022]    In the alternative or additionally thereto, in the foregoing embodiment an annular sub-chamber of the chamber is defined radially between the retainer and the housing and is constructed and arranged to retain fuel to cool the pump. 
         [0023]    In the alternative or additionally thereto, in the foregoing embodiment the pump has an impeller concentrically connected to the spindle. 
         [0024]    In another non-limiting embodiment of the present disclosure a method of operating a self-pumping fuel injector for a gas turbine engine includes the steps of powering a drive device of the self-pumping fuel injector, operating a pump of the self-pumping fuel injector through the drive device, and flowing fuel from the pump and through a fuel nozzle of the fuel injector. 
         [0025]    In addition to the foregoing embodiment, the method has the further step of increasing drive device speed to increase flow through the fuel nozzle. 
         [0026]    In the alternative or addition thereto, in the foregoing embodiment the method includes the additional step of increasing drive device speed to increase fuel pressure in the fuel nozzle. 
         [0027]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description are briefly described as follows: 
           [0029]      FIG. 1  is a schematic cross-section of a gas turbine engine; 
           [0030]      FIG. 2  is a partial longitudinal schematic cross-section of a combustor section according to one non-limiting embodiment that may be used with the gas turbine engine shown in  FIG. 1   
           [0031]      FIG. 3  is a cross section of a fuel pump and motor of a fuel injector; 
           [0032]      FIG. 4  is an exploded perspective view of the fuel pump with a housing removed to show internal detail; and, 
           [0033]      FIG. 5  is a schematic view of a second, non-limiting, embodiment of a self-pumping fuel injector. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbo fan 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 flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section  26  then expansion through the turbine section  28 . 
         [0035]    The engine  20  generally includes a low spool  30  and a high spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  or engine case via several bearing structures  38 . The low spool  30  generally includes an inner shaft  40  that interconnects a fan  42  of the fan section  22 , a Low Pressure 
         [0036]    Compressor  44  (“LPC”) of the compressor section  24  and a Low Pressure Turbine  46  (“LPT”) of the turbine section  28 . The inner shaft  40  drives the fan  42  directly or through a geared architecture  48  to drive the fan  42  at a lower speed than the low spool  30 . An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. 
         [0037]    The high spool  32  includes an outer shaft  50  that interconnects a High Pressure Compressor  52  (“HPC”) of the compressor section  24  and a High Pressure Turbine  54  (“HPT”) of the turbine section  28 . A combustor  56  of the combustor section  26  is arranged between the HPC  52  and the HPT  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate about the engine central longitudinal axis A that is collinear with their longitudinal axes. 
         [0038]    Core airflow is compressed by the LPC  44  then the HPC  52 , mixed with the fuel and burned in the combustor  56 , then expanded over the HPT  54  and the LPT  46 . The LPT  46  and HPT  54  rotationally drive the respective low spool  30  and high spool  32  in response to the expansion. Although depicted as a turbofan in the disclosed non-limiting embodiment, 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 such as a turbojets, turboshafts, and three-spool (plus fan) turbofans wherein an intermediate spool includes an Intermediate Pressure Compressor (“IPC”) between a LPC and a HPC, and an Intermediate Pressure Turbine (“IPT”) between a HPT and a LPT. 
         [0039]    In one non-limiting example, the gas turbine engine  20  is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  bypass ratio is greater than about six (6:1). The geared architecture  48  can include an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3:1, and in another example is greater than about 2.5:1. The geared turbofan enables operation of the low spool  30  at higher speeds that can increase the operational efficiency of the LPC  44  and LPT  46  and render increased pressure in a fewer number of stages. 
         [0040]    A pressure ratio associated with the LPT  46  is pressure measured prior to the inlet of the LPT  46  as related to the pressure at the outlet of the LPT  46  prior to an exhaust nozzle of the gas turbine engine  20 . In one non-limiting embodiment, the bypass ratio of the gas turbine engine  20  is greater than about ten (10:1), the fan diameter is significantly larger than that of the LPC  44 , and the LPT  46  has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans. 
         [0041]    In one embodiment, a significant amount of thrust is provided by the bypass flow path B due to the high bypass ratio. The fan section  22  of the gas turbine engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the gas turbine engine  20  at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust. 
         [0042]    Fan Pressure Ratio is the pressure ratio across a blade of the fan section  22  without the use of a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non-limiting embodiment of the example gas turbine engine  20  is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of (“T”/518.7 0.5 ) in which “T” represents the ambient temperature in degrees Rankine The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example gas turbine engine  20  is less than about 1150 fps (351 m/s). 
         [0043]    With reference to  FIG. 2 , the combustor  56  may be annular in shape, concentrically disposed to axis A, and may generally include a bulkhead assembly  60 , an outer wall  62 , an inner wall  64 , and a diffuser case module  66 . The outer and inner walls  62 ,  64  project axially in a downstream direction from the bulkhead assembly  60 , and radially define an annular combustion chamber  68  therebetween. An annular cooling plenum  70  is generally defined radially between the outer diffuser case module  66  and a diffuser inner case  72 . The bulkhead assembly  60  and walls  62 ,  64  are located in the cooling plenum  70  immediately downstream from the compressor section  24 . 
         [0044]    The annular bulkhead assembly  60  extends radially between, and in this disclosed non-limiting embodiment, is secured to the forward most ends of the walls  62 ,  64 . Assembly  60  generally includes an annular hood  74 , a wall or heat shield  76  that defines the axial upstream end of the combustion chamber  68 , and a plurality of swirlers  78  (one shown) spaced circumferentially about engine axis A and generally projecting or communicating through the wall  76 . A plurality of circumferentially distributed hood ports  80  accommodate a respective plurality of self-pumping fuel injectors  82  as well as direct compressed air C into the forward end of the combustion chamber  68  through the associated swirler  78 . 
         [0045]    The bulkhead assembly  60  introduces core combustion air into the upstream end of the combustion chamber  68  while dilution and cooling air is introduced into the combustion chamber  68  through the walls  62 ,  64  and from the plenum  70 . The plurality of fuel injectors  82  and respective swirlers  78  facilitate the generation of a blended fuel-air mixture that supports combustion in the combustion chamber  68 . 
         [0046]    Each fuel injector  82  is self-pumping and may include a drive device  84 , a pump  86  and a fuel nozzle  88  all substantially orientated along a rotational axis  90 . The pump  86  is generally mounted between an external surface of the diffuser case module  66  and the drive device  84  along the axis  90 . The elongated fuel nozzle  88  may substantially extend longitudinally along the axis  90  from the pump  86 , through the diffuse case module  66  and into the cooling plenum  70 . A distal end portion  92  of the nozzle  88  projects radially outward with respect to axis  90  and through one of the hood ports  80  and into the respective swirler  78  for generally distributing and atomizing fuel therein. 
         [0047]    Referring to  FIGS. 3 and 4 , the pump  86  of the self-pumping fuel injector  82  generally includes a housing  94  that defines a fuel chamber  96 , a fuel inlet  98  and a fuel outlet  100 . In the chamber  96 , the pump  86  further has a spindle  102 , fore and aft bearings  104 ,  106 , a flow interuptor  108 , a bearing retainer  110  and an axial retaining nut or fastener  112 . The spindle  102  has a first end portion  114 , a mid-portion  116  and an opposite second end portion  118 . The spindle  102  generally carries radial inner and outer surfaces  120 ,  122 , wherein the inner surface  120  defines a fuel channel  124  substantially orientated concentric to axis  90 . 
         [0048]    The first end portion  114  has a plurality of outlet ports  126  that radially extend through the inner and outer surfaces  120 ,  122  and communicate between the channel  124  and a respective helical passage  128  (two shown). The helical passages  128  may be grooves carried by the outer surface  122 , and thereby defined between the housing  94  and the outer surface  122  of the spindle  102 . The passages  128  are evenly spaced from one-another and each extend in a spiraling direction from the respective outlet port  126 , about the outer surface  122 , and generally through a distal end face  130  of the end portion  114 . It is understood and contemplated that each helical passage  128  may be internal to the end portion  114 ; however, constructed as grooves contributes toward ease of manufacturing and adds or creates a fuel cooling film  174  between the housing  94  and the end portion  114  that promotes rotation of the spindle  102 . 
         [0049]    The mid-portion  116  of the spindle  102  carries a plurality of inlet ports  132  that are equally spaced circumferentially from one-another, extend radially through the surfaces  120 ,  122 , and communicate with the channel  124 . The flow interuptor  108  is generally ring shaped and extends circumferentially around, and generally extends along the axial length of the mid-portion  116 . The interuptor  108  has radial inner and outer surfaces  134 ,  136  and at least one port  138  that communicates radially through the inner and outer surfaces  134 ,  136 . The mid-portion  116  fits slideably into a through bore  139  of the flow interuptor  108  defined by the inner surface  134 . The flow interuptor  108  may be stationary with respect to the housing  94  so that as the spindle  102  rotates the plurality of inlet ports  132  of the spindle  102  are in intermittent communication with the port  138  of the flow interuptor  108 . 
         [0050]    The bearing retainer or cup  110  is generally shaped like a cylindrical cup, and substantially surrounds and retains the bearings  104 ,  106  and the flow interuptor  108 . The retainer  110  has a cylindrical wall  140 , a annular rim  142  that projects radially inward from one end of the wall  140 , a flange  144  that projects radially outward from an opposite end of the wall  140 , a hole  146  defined by the rim  142  and through which the spindle  102  projects, and a plurality of circumferentially spaced ports  148  in the wall  140 . When the pump  86  is assembled, the rim  142  axially abuts the housing  94  in a downstream direction and the bearing  104  axially abuts an opposite upstream side of the rim  142 . The flow interuptor  108  spans axially between and abuts to the bearings  104 ,  106 . The nut  112  is located immediately aft or upstream of the bearing  106  and may have external threads for threadable engagement to the retainer  110  for holding the internal components in place. It is further understood and contemplated that the nut may be any form of fastener that engages to the retainer  110  for the purpose of holding the internal components to the retainer in the appropriate axial position. The flange  144  of the housing  94  axially abuts a rib  150  of the housing  94  that projects radially inward. Generally, the retainer  110  is in contact with the housing to maintain proper radial and axial alignment of the internal components. 
         [0051]    A portion of the outer surface  136  of the flow interuptor  108  may be fitted snugly to an inner cylindrical face of the retainer  140 . Another portion of the surface  136  defines a recess  152  located at about an axial mid-point of the flow interuptor  108 . The recess  152  creates an annular space between the retainer  140  and the flow interuptor  108  that is circumferentially continuous and provides communication between the ports  138  of the flow interuptor  108  and the ports  148  of the retainer  110 . It is further understood and contemplated that if the ports  138  and ports  148  were axially and circumferentially aligned to one-another, the recess  152  may be omitted from the flow interuptor  108 . 
         [0052]    To provide cooling for both the pump  86  and the motor  84 , an annular sub-chamber  154  of the chamber  96  is defined radially between the housing  94  and the retainer  110 . The sub-chamber  154  communicates directly with the fuel inlet  98  and acts as a manifold for supplying fuel to each one of the plurality of ports  148  of the retainer  110 . The pump  86  and motor  84  may be further cooled through the use of fuel by a shell  156  that substantially encapsulates the pump and motor thus creating a cooling reservoir  158  of fuel. The shell  156  has a fuel inlet  160  strategically located so that fuel flows or circulates about the pump and motor before entering the fuel inlet  98  of the housing  94 . Moreover, the fuel flow through the channel  124  that axially extends along a substantial length of the spindle  102  will help to minimize any heat conduction through the spindle and to the motor  84 . 
         [0053]    The motor  84  mounts to the aft end of housing  94  with a gasket or seal plate  164  disposed therebetween. The motor  84  has a rotor  166  centered to the axis  90  and releasably engaged (e.g. keyed or splined connection) to the upstream end portion  118  of the spindle  102 . The housing  94  mounts the diffuser case module  66  with a gasket  168  therebetween that acts as a thermal barrier. The shell  156  may have a conduit  162  for routing electrical power to the motor  84 . 
         [0054]    In operation, a controller  170  delivers a signal  172  (see  FIG. 2 ) that controls electric power to, and thus speed of the motor  84 . Increasing speed generally increase fuel flow through the fuel outlet  100  and at a substantially constant pressure. Fuel may enter the pump  86  from the fuel cooling reservoir  158 , through the housing fuel inlet  98  and into the fuel cooling sub-chamber  154 . From the sub-chamber  154 , fuel enters the recess  152  of the flow interuptor  108  through the plurality of ports  148  in the retainer  110 . As the spindle  102  rotates at a speed dictated by the motor  84  the ports  132  rotatably pass by the ports  138  in the stationary flow interuptor  108 . This ‘passing by’ creates the intermittent communication and thus controlled fuel flow into the channel  124 , then through the ports  126  and the helical passages  128  of the spindle  102 . The relationship between the spindle  102 , the flow interrupter  108  and the speed or revolutions per minute (“RPM”) determines the fuel delivery rate. The flow is generally driven by the orientation of the helical passages  128  combined with the spindles rotational movement that creates a centrifugal force which pushes the fuel out through the housing outlet  100 . At the downstream end portion  122  of the spindle  102 , the passages  128  (i.e. grooves) are open to an interior wall of the housing  94 , consequently fuel through the passages also enable the formation of the fuel cooling film  174  between the end portion  122  and the housing  94  that minimizes friction and promotes rotation. 
         [0055]    Because the spindles  102  of each fuel injector  82  are individually spun by respective electric motors  84  fuel spray distributions are improved over more traditional fuel injectors, thus improving engine start-up. That is, fuel distribution becomes less dependent on the number of orifices in a nozzle, thus the number of orifices may be reduced because the fuel pressure can be increased. Operating at higher pressure during start-up greatly improves spray atomization and distribution. Because the motors are variable speed and due to the relationship between the flow interuptor  108  and the spindle  102  as previously described, power consumption is kept to a minimum. 
         [0056]    Referring to  5 , a second embodiment of a self-pumping fuel injector is illustrated wherein like elements to the first embodiment have like identifying numerals except with the addition of a prime symbol. The fuel injector  82 ′ has an impeller pump  86 ′ having a spindle  102 ′ having an end portion  118 ′ connected to a rotor  166 ′ of a drive device or motor  84 ′ along a rotational axis  90 ′. The motor  84 ′ and pump  86 ′ may be encase by a shell  156 ′ containing supply fuel for cooling. An impeller  200  is concentrically attached to the spindle  102 ′ for flowing fuel in the direction of arrows  202  from a fuel inlet  98 ′ of a pump housing  94 ′ to an outlet  100 ′, thereby feeding fuel to a fuel nozzle  88 ′. 
         [0057]    A flow interuptor  108 ′ operates to shut off fuel when the pump device  84 ′ is not operating. The interuptor  108 ′ may have a spring  204  that exerts a biasing force axially against the spindle  102 ′ and toward the drive device  84 ′. A coupling  206  of the interuptor  108 ′, located between the rotor  166 ′ and the end portion  118 ′ of the spindle  102 ′, may be a helical spline that generates axial movement of the spindle  102 ′. During operation, the centrifugal force of the spinning spindle overcomes the axial biasing force of the spring  204  and thereby acts to open communications between the fuel inlet  98 ′ and the fuel outlet  100 ′. 
         [0058]    It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude and should not be considered otherwise limiting. 
         [0059]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
         [0060]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0061]    The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.