Patent Publication Number: US-10760495-B2

Title: Fluid manifold for gas turbine engine and method for delivering fuel to a combustor using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 14/135,655 filed Dec. 20, 2013, now U.S. Pat. No. 9,995,220, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The application relates generally to gas turbine engines and, more particularly, to fuel manifolds for gas turbine engines. 
     BACKGROUND OF THE ART 
     Fuel conveying passages, conduits, and manifolds employed internally within gas turbine engines and other high-temperature equipment are exposed to high temperatures, particularly those located adjacent the combustor. Internal fuel manifolds are particularly exposed to high temperatures given their proximity to the combustor. While the fuel flowing through such internal fuel manifolds provides some cooling, as the fuel is injected into the combustor, and thus the volume of fuel flowing through the manifold decreases, those portions of the manifold furthest away from the fuel inlet are more prone to overheating. If temperatures get too high, fuel tends to decompose within these fuel conveying passages causing undesirable accumulations of carbon or coke, which can lead to poor combustor fuel distribution which is detrimental to the life of the engine. 
     SUMMARY 
     In one aspect, there is provided a fuel manifold of gas turbine engine, the manifold comprising: a ring-shaped fuel conveying body; a plurality of fuel injection nozzles on the body; and at least two fuel conduits defined within the body, each of the fuel conduits being fluidly connected to a respective separate group of the fuel injection nozzles, each of the fuel conduits extending from a conduit inlet to a conduit end, each of the fuel conduits including: a first portion extending continuously between the conduit inlet and an inflexion of the conduit, the inflexion being a single exit of the first portion such that fuel flows uninterrupted between the conduit inlet and the inflexion; and a second portion downstream of the first portion and connected thereto in serial flow communication, the second portion extending between the inflexion and the conduit end, the respective separate group of fuel injection nozzles of the fuel conduit fluidly communicating exclusively with the second portion of the fuel conduit. 
     In another aspect, there is provided a method for delivering fuel to a combustor of a gas turbine engine, the method comprising: injecting fuel into a conduit of a fuel manifold; directing the fuel through a continuous first portion of the conduit; directing the fluid from the first portion into an inflexion of the conduit being a single exit of the first portion; directing the fuel from the inflexion into a second portion of the conduit in serial flow communication with the first portion; carrying the fuel in the second portion in a direction different from that of the fuel in the first portion; and as the fuel flows through the second portion of the conduit, exiting the fuel from the second portion of the conduit into a plurality of fuel injection nozzles in exclusive fluid flow communication with the second portion for ejection into a combustor of the gas turbine engine. 
     In a further aspect, there is provided a method for delivering fuel to a combustor of a gas turbine engine, the method comprising: injecting fuel into two conduits of a fuel manifold; for each of the two conduits: directing the fuel through a continuous first portion of the conduit; directing the fluid from the first portion into an inflexion of the conduit being a single exit of the first portion; directing the fuel from the inflexion into a second portion of the conduit in serial flow communication with the first portion; carrying the fuel in the second portion in a direction different from that of the fuel in the first portion; and as the fuel flows through the second portion of each of the conduits, exiting the fuel from the second portion into a plurality of respective separate group of fuel injection nozzles in exclusive fluid flow communication with the second portion for ejection into a combustor of the gas turbine engine. 
     In this specification, the term “inflexion” is defined as an area of a fluid conduit defined between two portions of the conduit where the flow in the portion upstream of the inflexion has a direction different relative from that of the flow in the portion downstream of the inflexion. Non-limitative examples of inflexions include a local maximum of a conduit, a local minimum of a conduit, a turn of a conduit, or an elbow of a conduit. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying figures in which: 
         FIG. 1  is a schematic cross-sectional view of a gas turbine engine; 
         FIG. 2  is a front perspective view of a fuel manifold for use in a gas turbine engine such as that depicted in  FIG. 1 ; 
         FIG. 3  is a rear perspective view of the fuel manifold of  FIG. 2  partially cut-out to reveal conduits of the fuel manifold according to a first embodiment; 
         FIG. 4 a    is a rear elevation view of the fuel manifold partially cut-out of  FIG. 3 ; 
         FIG. 4 b    is a schematic of  FIG. 4 a    showing only one internal passage; 
         FIG. 4 c    is a schematic view of a cross-section of the internal passage along line  4   c - 4   c  of  FIG. 4   b;    
         FIG. 4 d    is a schematic view of a cross-section of the internal passage along line  4   d - 4   d  of  FIG. 4   b;    
         FIG. 5  is a rear perspective view of the fuel manifold of  FIG. 2  partially cut-out to reveal conduits of the fuel manifold according to a second embodiment; 
         FIG. 6 a    is a rear elevation view of the fuel manifold partially cut-out of  FIG. 5 ; 
         FIG. 6 b    is a schematic of  FIG. 6 a    showing only one internal passage; and 
         FIG. 7  is a flow chart of a method for delivering fuel to a combustor of the gas turbine of  FIG. 1  using any embodiment the fuel manifold of  FIGS. 2 to 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a gas turbine engine  10  of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan  12  through which ambient air is propelled, a compressor section  14  for pressurizing the air, a combustor  16  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  18  for extracting energy from the combustion gases. 
     Fuel is injected into the combustor  16  of the gas turbine engine  10  by a fuel system  20  which includes a fuel source (not shown) and at least one fuel conveying member which is operable to inject fuel into the combustor  16  for mixing with the compressed air from the compressor  14  and ignition of the resultant mixture. The fan  12 , compressor  14 , combustor  16 , and turbine  18  are preferably all concentric about a common central longitudinal axis  11  of the gas turbine engine  10 . 
     Referring to  FIG. 2 , the at least one fuel conveying member of the fuel injection system  20  includes an annular internal fuel manifold  22  having an inlet  30  which is connected to the fuel source. Fuel enters the fuel manifold  22  at the fuel inlet  30  and is distributed within the manifold  22 , in the manner as will be described in further detail below, before being ejected through a plurality of ejection nozzles  26 . Although the fuel manifold  22  is shown herein to have a single inlet  30 , it is contemplated that the fuel  22  could have two or more inlets  30 . 
     The fuel manifold  22  is mounted in place adjacent to the combustor  16  via suitable mounting elements, which may in one possible embodiment include several integral attachment lugs  24 . The attachment lugs  24  receive pins (not shown) engaged to the support structure. The mounting elements may allow for thermal expansion of the fuel manifold  22  at high temperatures. It is contemplated that the fuel manifold  22  could be mounted to a support structure surrounding the combustor  16 . For example, the fuel manifold  22  could be mounted to the engine case. It is also contemplated that the fuel manifold  22  could be mounted by ways other than the attachment lugs  24 . For example, Using fasteners, welds, or the like, which engage the fuel manifold in place to one or more of the combustor, the surrounding gas generator casing, etc. 
     The fuel manifold  22  has a ring-shaped body  23 . It is contemplated that the fuel manifold  22  could have shapes other than a ring. For example, the fuel manifold  22  could be a half ring or another arcuate shape. The body  23  is covered by an outer heat shield which provides the fuel manifold  22  thermal protection from the high temperature environment of the combustor  16 . It is contemplated that the outer heat shield could be omitted. The fuel manifold  22  is symmetric with respect to an axis  29 . For purposes of orientation, the axis  29  in this specification will be defined as a vertical axis. The vertical axis  29  defines two portions of the fuel manifold  22 , namely a right side  17  and a left side  19  or orientation purposes, a bottom  21  of the manifold ring  22  is defined herein to be at a location of the inlet  30  on the fuel manifold  22 , and a top  15  is defined herein to be a location of the fuel manifold  22  opposite to the inlet  30  along the vertical axis  29 , and which corresponds to a highest point of the fuel manifold  22 . The top  15  and bottom  21  thereby define upward and downward orientations for purposes of orientation in this specification. 
     The plurality of fuel injection nozzles  26  (fourteen in the embodiment shown in  FIG. 2 ) is provided on a front face  25  of the ring-shaped body  23 . The fuel injection nozzles  26  atomize the fuel as it is injected into the combustor  16  for ignition when mixed with the compressed air therein. In the depicted embodiment, the injection nozzles  26  are disposed at equidistance form each other along a circumference  28  of the ring-shaped body  23 . Nonetheless it is possible to provide circumferentially spaced apart groups of fuel injection nozzles, in which case the spacing between fuels nozzles may not be equal throughout the circumference  28  of the fuel manifold  22 . The fuel injection nozzles  26  as described herein may be gas turbine engine fuel injection nozzles as described, for example, in U.S. Pat. Nos. 7,530,231 and 6,082,113, the entire contents of which are incorporated herein by reference. It is contemplated that the fuel manifold  22  could have more or less than fourteen injection nozzles  26 . It is also contemplated that the injection nozzles  26  could span only a portion of the circumference  28  of fuel manifold  22 . 
     Turning now to  FIG. 3 , a rear face  27  of the fuel manifold  22  is shown cut off to reveal a first embodiment of conduits (or internal passages)  32 ,  42  of the body  23 . The conduits  32 ,  42  carry fuel from the inlet  30  to the injection nozzles  26 . 
     The body  23  includes two concentric conduits  32 ,  42 , the conduit  42  being disposed inwardly of the conduit  32 . Each of the conduits  32 ,  42  is ring-shaped and runs through almost the entire circumference  28  of the fuel manifold  22  (i.e. right side  17  and left side  19 ). It is contemplated that one or both of the conduits  32 ,  42  could run on only a portion of the circumference  28  of the fuel manifold  22 . A top  31 ,  41  of the conduits  32 ,  42  corresponds to the top  15  of the body  23 , which is also a location furthest away from the fuel inlet  30 . The tops  31 ,  41  of the conduits  32 ,  42  are inflexions  34 ,  44  of the conduits  32 ,  42 . This means that at the tops  31 ,  41  are local maximums of the conduits  32 ,  42 . 
     The conduits  32 ,  42  are fluidly independent from one another, and carry fuel from the inlet  30  each to a different group of injection nozzles  26 . The conduit  32  distributes fuel to nozzles  26   a  on the right side  17  of the body  23  exclusively, and the conduit  42  distributes fuel to nozzles  26   b  on the left side  19  of the body  23  exclusively. The conduits  32 ,  42  being similar to each other, only the conduit  32  will now be described in further detail. 
     With reference to  FIGS. 4 a  and 4 b   , the conduit  32  includes a first portion  36  (shown solid in  FIG. 4 b   ) disposed on the left side  19  of the body  23 , and a second portion  38  (shown dotted in  FIG. 4 b   ) disposed on the right side  17  of the body  23  and in fluid flow communication with the first portion. The first and second portions  36 ,  38  are connected to each other by the inflexion  34 . The first portion  36  extends arcuately (i.e. it has an arcuate shape) from an inlet end  241  proximal to the inlet  30  up to the inflexion  34 , and runs through almost the entire left side  19  of the body  23 . The inlet end  241  is a lowest point of the conduit  32  and is disposed opposite to the inflexion  34  on the vertical axis  29 . It is contemplated that the inlet end  241  and the inflexion  34  could not be opposite to each other. For example, the end  241  could be at about 15 degrees from the vertical axis  29 . It is also contemplated that the inlet end  241  or the inflexion  34  could not be disposed on or about the vertical axis  29 . A cross-section of the first portion  36  of the conduit  30  is constant along a length of the first portion  36  from the inlet end  241  to the inflexion  34 . It is however contemplated that the cross-section of the first portion  36  could vary as long as the fuel would reach the inflexion  34  so as to feed the second portion  38 . Although the first portion  36  has a circular cross-section, it is contemplated that the first portion  36  could have a square, rectangular or oval cross-section. 
     Fuel travels upwardly in the first portion  36  (indicated by arrow  56 ) until it reaches the inflexion  34  and the second portion  38 . The first portion  36  is not directly connected to any of the injection nozzles  26   a  of the right side  17  to which the conduit  32  delivers fuel. Instead, all the fuel entering the first portion  36  exits the first portion  36 . Fuel flowing in the first portion  36  of the conduit  32  cools the body  23  before it reaches the downstream second portion  38  and the injection nozzles  26   a . By circulating the fuel through the manifold  22  by prior to injecting any of the fuel provides improved cooling of the manifold  22 , which, in turn, avoids high wetted wall and fuel temperatures. 
     The second portion  38  extends between the inflexion  34  and a conduit end  45  of the conduit  32 , and runs through the entire right side  17  of the body  23 . The fuel traveling in the second portion  38  travels downwardly (as indicated by arrow  60 ). The inflexion  34  provides a change of direction of the flow, and flow in the second portion  38  is in a direction opposite from the flow in the first portion  36 . The second portion  38  is exclusively connected to the injection nozzles  26   a  that are disposed on the right side  17  of the body  23 . In the embodiment shown herein, the second portion  38  is connected to seven injection nozzles  26 . Enough fluid has to be provided to the second portion  38  of the conduit  32  so that every injection nozzle  26   a  on the right side  17  is fed with an adequate amount of fuel. The injection nozzles  26   a  expel the fuel to the combustor  16  (arrows  62 , only one being referred to avoid cluttering the drawings). The fuel injected in the conduit  32  can&#39;t access the injection nozzles  26   a  of the right side  17  until the fuel has flown through the first portion  36  and changed direction from upward to downward at the inflexion  34 . The fuel injected in the conduit  32  does not access any of the injection nozzles  26   b  of the left side  19 , as those are fed by the conduit  42  exclusively. 
     In order to ensure that the fuel reaches each of the fuel injection nozzles  36  at a desired velocity, a cross-section flow area of the second portion  38  of the conduit  32  may decrease along a length of the second portion  38  from the inflexion  34  to the conduit end  45 , as can be seen in  FIGS. 4 b , 4 c  and 4 d   . This decrease in cross-section flow area of the second portion  38 , which may be continuous and gradual, is designed to maintain the velocity of the fuel substantially constant through the second portion  38 . In the embodiment shown in  FIG. 4 a   , the cross-section flow area at location  70  of the second portion  38  is larger than the cross-section flow area at location  72  of the second portion  38 . In the embodiment shown, the location  70  is upstream of the location  72  along the length of the second portion  38  from the inflexion  34  to the conduit end  45 . It is however contemplated that the cross-section of the second portion  38  of the conduit  32  could vary in a manner different from described above or could not vary at all, as long as the fuel reaches the conduit end  45 . Although the second portion  38  has a circular cross-section, it is contemplated that the second portion  38  should be square, rectangular or oval in cross-section. The first and second portions  36 ,  38  could have different cross-sections (shapes and dimensions). 
     Fluid in the conduit  32  travels counter-clockwise when the fuel manifold  22  is seen from the rear face  27  as shown in  FIG. 4 a   . Fluid in the conduit  42  travels in opposite direction from the fluid in the conduit  32 , i.e. counter-clockwise when the fuel manifold  22  is seen from the rear face  27  as shown in  FIG. 4   a.    
     Turning now to  FIG. 5 , the rear face  27  of the fuel manifold  22  is shown cut out to reveal a second embodiment of conduits (or internal passages)  132 ,  142  of the body  23 . The conduits  132 ,  142  are symmetric with respect to each other relative to the vertical axis  29 . The left side  19  receives the conduit  132  only, and the right side  17  receives the conduit  142  only. In this embodiment, the conduits  132 ,  142  are restricted to one portion of the circumference  28 . 
     Each of the conduits  132 ,  142  has an arcuate shape, with a respective inflexion  134 ,  144  disposed at the top  15  of the body  23 . The inflexions  34 ,  44  are elbows (or U-turns), redirecting the flow of fuel at 180 degrees. The inflexions  34 ,  44  are disposed at a highest point of each of the conduits  132 ,  142 , which is also a point furthest away from the fuel inlet  30 . It is contemplated that the inflexions  134 ,  144  could be disposed away from the vertical axis  29  and/or that the inflexions  134 ,  144  could be located at a location in the fuel manifold  22  between the top  15  and the bottom  21  of the body  23 . For example they could be at a mid-height of the fuel manifold  22 . 
     The conduits  132 ,  142  are fluidly independent from one another, and carry fuel from the inlet  30  to the injection nozzles  26   b  on the left  19 , and the injection nozzles  26   a  on the right  17  side of the body  23 , respectively. The conduits  132 ,  142  being similar, only the conduit  132  will now be described in further detail. 
     With reference to  FIGS. 6 a  and 6 b   , the conduit  132  includes a first portion  136  (shown solid in  FIG. 6 b   ) and a second portion  138  (shown dotted in  FIG. 6 b   ). The first and second portions  136 ,  138  are fluidly connected to each other at the inflexion  134 . The first portion  136  is disposed radially outwardly relative to the second position  138 , and both lie in a common plane that is perpendicular to the central longitudinal axis  11  of the engine  10 . It is contemplated, however, that the first portion  136  could be disposed inwardly relative to the second position  138 . It is also contemplated that the first portion  136  and second portions  138  could cross (without fluidly connecting) each other. The first portion  136  could for example have a substantially zigzag shape, thus extending on each side of the second portion  138 . The first and second portions  136 ,  138  could also be in a same plane perpendicular to the front  25  and rear faces  27  of the fuel manifold  22 . 
     The first portion  136  extends from an inlet end  141  proximal to the inlet  30  up to the inflexion  134 . As such, the first portion  136  runs through the entire left side  19  of the body  23 . The end  141  is a lowest point of the conduit  132  and is disposed about opposite to the inflexion  134  on the vertical axis  29 . It is contemplated that the inlet end  141  could not be opposite to the inflexion  134 . For example, the inlet end  141  could be at about 15 degrees from the vertical  29 . Fuel travels upwardly in the first portion  136  (indicated by arrow  156 ) until it reaches the inflexion  134 . Fuel exits the first portion  136  of the conduit  132  only at the inflexion  134 . The first portion  136  is not directly connected to any of the injection nozzles  26   b  of the left side  19 . All the fuel entering the first portion  136  exits the first portion  136 . As such, the first portion  136  is continuous and has only a single exit, namely the inflexion  134 . Fuel flowing in the first portion  136  of the conduit  132  cools the body  23  of the fuel manifold  22  before reaching the downstream second portion  138  and the injection nozzles  26   b . Cooling of the fuel manifold  22 , avoids high wetted wall and fuel temperatures. The cross-section of the first portion  136  of the conduit  132  is constant along the length of the first portion  136  from the inlet end  141  to the inflexion  134 . It is however contemplated that the cross-section of the first portion  136  could vary as long as the fuel reaches the inflexion  134  and feeds the second portion  138 . 
     The second portion  138  extends between the inflexion  134  and a conduit end  145  of the conduit  132 . The fuel traveling in the second portion  138  travels downwardly (as indicated by arrow  160 ). Because of the 180 degree elbow shape of the inflexion  134 , flow in the second portion  138  is in opposite direction from the flow in the first portion  136 . The second portion  138  is connected the injection nozzles  26   b  of the left side  19  of the body  23  exclusively. In the embodiment shown herein, the second portion  138  is connected to seven injection nozzles  26   b . Enough fluid has to be provided to the second portion  138  of the conduit  132  so that every injection nozzle  26   b  on the left side  19  is feed with an adequate amount of fuel. The injection nozzles  26   b  expel the fuel to the combustor  16  (arrows  162 , only one being referred to avoid cluttering the drawings). The fuel injected in the conduit  132  can&#39;t access the injection nozzles  26   b  of the left side  19  until the fuel has flown through the first portion  136  and turned at the inflexion  134 . The fuel injected in the conduit  132  whether the first portion  135  or the second portion  138  does not access any of the injection nozzles  26   a  of the right side  17 , as this is achieved by the conduit  142  exclusively. 
     In order to ensure that the fuel reaches each of the fuel injection nozzles  26   b  at a desired velocity, the cross-section of the second portion  138  of the conduit  132  may decrease along the length of the second portion  138  from the inflexion  134  to the conduit end  145 . This decrease in cross-section of the second portion  138 , which may be continuous and gradual, is designed to maintain the velocity of the fuel substantially constant through the second portion  138 . It is however contemplated that the cross-section of the second portion  138  of the conduit of the fuel manifold  22  could vary in a manner different from described above or could not vary at all, as long as the fuel reaches the conduit end  145 . 
     With reference to  FIG. 7 , a method  60  for delivering fuel to the combustor  16  using the manifold  22  will now be described. The method  60  will be shown applied to the conduit  32  as one example of configuration where it could be applied. Flows though the conduits  42 ,  132 ,  142  are similar to the one through the conduit  32 , and could be used with the method  60 . 
     The method  60  starts at step  62  with injecting fuel to the conduit  32  of the fuel manifold  22 . Fuel is introduced via the inlet  30 , as indicated by arrow  52  and is diverted into the inlet end  241  of the first portion  36  (arrow  54 ). At step  64 , fuel is directed through the first portion  36  of the conduit  32 , thereby at least partially cooling the fuel manifold  22 . Fuel travels upwardly through the first portion  36  as indicated by arrow  56 , until it reaches the inflexion  34 . At step  66 , fuel is directed through the inflexion  34  where it undergoes a change of direction from upwards to downwards. Because the first portion  36  of the conduit  32  is continuous and has a single exit at the inflexion  34 , all of a given volume of fuel that is introduced into the first portion  36  exits the first portion  36  (i.e. flow through the first portion  36  is uninterrupted and none is diverted off for feeding fuel injectors or otherwise). Accordingly, fuel is permitted to flow through a portion of the fuel manifold  22 , in this case approximately half of the diameter of the manifold ring  22 , before being fed to some of the nozzles  26 , in this case the nozzles  26   a  for injection. At the inflexion  34  the fuel changes direction (in the case of the conduits shown herein it reverses direction) and enters the second portion  38 . At step  68 , the fuel is directed through the second portion  38  of the conduit  32 . In the second portion  38 , the fuel now travels downwardly (arrow  60 ) with the help of gravity. At step  69 , the fuel exits at those ejecting nozzles  26   a  on the right side  17  while traveling in the second portion  38  of the conduit  32 . Fuel feeds the injection nozzles  26   a  as it encounters them during its travel toward the conduit end  45 . 
     With the configuration described above, no additional coolant is necessary (although coolant may be added to the fuel manifold  22 ). The fuel itself is cooled down before being circulated back into the fuel manifold  22  to feed the injection nozzles  26 . This may ensure more consistent cooling of the fuel and of the manifold  22 . 
     It should be understood that for a given embodiment, the conduits  32 ,  42  (resp.  132 ,  142 ) may be operated simultaneously or in a sequential manner, depending on the needs of the engine  10 . 
     The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the fuel manifold may have only one conduit to feed all the injection nozzles. The conduit may be ring shaped and the inflexion may be the lowest point of the conduit and may be located adjacent to the fuel inlet. In another example, there may be more than two conduits, for example three, thereby feeding each one of three groups of injection nozzles. Although the present is described for an internal fluid manifold, it is contemplated that the conduits described herein could be applied to an external manifold. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.