Patent Publication Number: US-2021172455-A1

Title: Diffuser pipe with radially-outward exit

Description:
TECHNICAL FIELD 
     The present invention relates generally to centrifugal compressors for gas turbine engines, and more particularly to diffuser pipes for such centrifugal compressors. 
     BACKGROUND 
     Diffuser pipes are provided in certain gas turbine engines for diffusing a flow of high speed air received from an impeller of a centrifugal compressor and directing the flow to a downstream component, such as an annular chamber containing the combustor. The diffuser pipes are typically circumferentially arranged at a periphery of the impeller, and are designed to transform kinetic energy of the flow into pressure energy. Diffuser pipes seek to provide a uniform exit flow with minimal distortion, as it is preferable for flame stability, low combustor loss, reduced hot spots etc. Some diffuser pipes discharge air to impinge directly on the combustor, which may increase losses in combustor stability. 
     SUMMARY 
     There is disclosed a compressor diffuser for a compressor section of a gas turbine engine, the compressor section having a center axis, the compressor diffuser comprising: diffuser pipes in a circumferential array about the center axis, one or more of the diffuser pipes having a tubular body with a first portion extending from an inlet of said diffuser pipe, a second portion extending along a generally axial direction relative to the center axis, and a bend portion fluidly connecting the first and second portions, an exit segment of the second portion defining a pipe outlet, the exit segment curved radially outwardly relative to the center axis. 
     There is disclosed a gas turbine engine, comprising: a compressor having an impeller rotatable about a center axis, and having a radial impeller outlet; a diffuser with diffuser pipes fluidly connected to receive fluid from the radial impeller outlet, and each of the diffuser pipes having a tubular body including a generally radial portion, a bend portion and a generally axial portion, the generally axial portion having an axial segment spaced from the center axis a constant radial distance and terminating at an exit segment, the exit segment extending radially outward relative to the center axis from the axial segment to a pipe outlet; and a combustor downstream of the diffuser. 
     There is disclosed a method of supplying air from a compressor section of a gas turbine engine to a combustor of the gas turbine engine, the method comprising: conveying air from an outlet of an impeller of the compressor section toward the combustor through a diffuser pipe, the air being conveyed through the diffuser pipe along a generally radial direction, then along an axial direction generally parallel to a center axis of the compressor diffuser, and then radially outwardly from the center axis through a pipe outlet of the diffuser pipe and toward the combustor. 
    
    
     
       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 perspective view of an impeller and diffuser pipes of a centrifugal compressor of the gas turbine of  FIG. 1 ; 
         FIG. 3A  is a perspective view of one of the diffuser pipes of  FIG. 2 ; 
         FIG. 3B  is another perspective view of the diffuser pipe of  FIG. 3A ; 
         FIG. 3C  an enlarged perspective view of an end of the diffuser pipe in  FIG. 3A ; 
         FIG. 4  is graph plotting radial distance of one of the diffuser pipe of  FIG. 3A  along a length of said diffuser pipe; 
         FIG. 5  is a perspective view of another diffuser pipe of a centrifugal compressor of the gas turbine of  FIG. 1 ; 
         FIG. 6  is a perspective view of another diffuser pipe of a centrifugal compressor of the gas turbine of  FIG. 1 ; 
         FIG. 7A  is a perspective view of another diffuser pipe of a centrifugal compressor of the gas turbine of  FIG. 1 ; and 
         FIG. 7B  is another perspective view of the diffuser pipe of  FIG. 7A . 
     
    
    
     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 along an engine center axis  11  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. The compressor section  14  may include a plurality of stators  13  and rotors  15  (only one stator  13  and rotor  15  being shown in  FIG. 1 ), and it may include a centrifugal compressor  19 . 
     The centrifugal compressor  19  of the compressor section  14  includes an impeller  17  with vanes and a compressor diffuser  14 A. The compressor diffuser  14 A includes a plurality of diffuser pipes  20 , which are located downstream of the impeller  17  and circumferentially disposed about a periphery of a radial outlet  17 A of the impeller  17 . The diffuser pipes  20  convert high kinetic energy at the impeller  17  exit to static pressure by slowing down fluid flow exiting the impeller. The diffuser pipes  20  also redirect the air flow from a radial orientation to an axial orientation (i.e. aligned with the engine axis  11 ). In most cases, the Mach number of the flow entering the diffuser pipe  20  may be at or near sonic, while the Mach number exiting the diffuser pipe  20  may be less than 0.25 to enable stable air/fuel mixing, and light/re-light in the combustor  16 . 
       FIG. 2  shows the impeller  17  and the plurality of diffuser pipes  20 , also referred to as “fishtail diffuser pipes”, of the centrifugal compressor  19 . Each of the diffuser pipes  20  includes a diverging (in a downstream direction) tubular body  22 , formed, in one embodiment, of sheet metal. The enclosed tubular body  22  defines a flow passage  29  (see  FIG. 3A ) extending the length of the diffuser pipe  20  through which the compressed fluid flow is conveyed. The tubular body  22  includes a first portion  24  extending tangentially and radially from the center axis  11  (i.e. in a direction that has both tangential and radial components) along a radial axis R extending from the engine axis  11 , and is sometimes referred to herein as a generally radial portion  24 . An open end is provided at an upstream end of the tubular body  22  and forms an inlet  23  (see  FIG. 3A ) of the diffuser pipe  20 . In some embodiments, such as the one shown in  FIG. 2 , the first portion  24  also extends generally tangentially from the periphery and radial outlet  17 A of the impeller  17  to remove swirl from the flow exiting the impeller  17 . The radially and tangentially-extending first portion  24  in  FIG. 2  is inclined at an angle θ1 relative to the radial axis R. The angle θ1 may be selected to correspond to a direction of fluid flow at the exit of the blades of the impeller  17 , such as to facilitate transition of the flow from the impeller  17  to the diffuser pipes  20 . 
     The tubular body  22  of the diffuser pipes  20  also includes a second portion  26 , which is disposed generally axially and is sometimes referred to herein as a generally axial portion  26 . The generally axial portion  26  is connected to the first portion  24  by an out-of-plane curved or bend portion  28 , sometimes referred to as the “elbow” of the diffuser pipe  20 . An open end at the downstream end of the second portion  26  forms a pipe outlet  25  (see  FIG. 3A ) of the diffuser pipe  20 . Preferably, but not necessarily, the first portion  24  and the second portion  26  of the diffuser pipes  20  are integrally formed together and extend substantially uninterrupted between each other, via the curved, bend portion  28 . 
     The large radial velocity component of the flow exiting the impeller  17 , and therefore entering the first portion  24  of each of the diffuser pipes  20 , may be removed by shaping the diffuser pipe  20  with the bend portion  28 , such that the flow is redirected axially through the second portion  26  before exiting via the pipe outlet  25  to the combustor  16 . In  FIG. 1 , the combustor  16  is a reverse-flow combustor  16  positioned to receive fluid flow from the pipe outlet  25 . It will thus be appreciated that the flow exiting the impeller  17  enters the inlet  23  and the upstream first portion  24  and flows along a generally radial first direction. At the outlet of the first portion  24 , the flow enters the bend portion  28  which functions to turn the flow from a substantially radial direction to a substantially axial direction. The bend portion  28  may form a 90 degree bend. At the outlet of the bend portion  28 , the flow enters the downstream second portion  26  and flows along a substantially axial second direction different from the generally radial first direction. By “generally radial”, it is understood that the flow may have axial, radial, and/or circumferential velocity components, but that the axial and circumferential velocity components are much smaller in magnitude than the radial velocity component. Similarly, by “generally axial”, it is understood that the flow may have axial, radial, and/or circumferential velocity components, but that the radial and circumferential velocity components are much smaller in magnitude than the axial velocity component. 
     Referring to  FIGS. 3A and 3B , the tubular body  22  of each diffuser pipe  20  has a radially inner wall  22 A and a radially outer wall  22 B. The tubular body  22  also has a first side wall  22 C spaced circumferentially apart across the flow passage  29  from a second side wall  22 D. The radially inner and outer walls  22 A,  22 B and the first and second side walls  22 C,  22 D meet and are connected to form the enclosed flow passage  29  extending through a length L of the tubular body  22 , where the length L is defined from the inlet  23  to the pipe outlet  25 . The radially inner wall  22 A corresponds to the wall of the tubular body  22  that has the smallest turning radius at the bend portion  28 , and the radially outer wall  22 B corresponds to the wall of the tubular body  22  that has the largest turning radius at the bend portion  28 . 
     The tubular body  22  diverges in the direction of fluid flow F therethrough, in that the internal flow passage  29  defined within the tubular body  22  increases in cross-sectional area along its length L which extends between the inlet  23  of the diffuser pipe  20  and the pipe outlet  25 . This increase in cross-sectional area of the flow passage  29  through each diffuser pipe  20  may be continuous along the complete length L of the tubular body  22 , or the cross-sectional area of the flow passage  29  may increase in gradual increments along the length L of the tubular body  22 . In the illustrated embodiment, the cross-sectional area of the flow passage  29  defined within the tubular body  22  increases gradually and continuously along its length L, from the inlet  23  to the pipe outlet  25 . The pipe outlet  25  is circumscribed by a peripheral edge of the diffuser pipe  20  at its exit, where the peripheral edge is defined by the inner, outer, and side walls  22 A,  22 B,  22 C,  22 D. The direction of fluid flow F is generally along a pipe center axis  21  of the tubular body  22 . The pipe center axis  21  extends through each of the first, second, and bend portions  24 ,  26 ,  28  and has the same orientation as these portions. The pipe center axis  21  is thus curved. In the illustrated embodiment, the pipe center axis  21  is equidistantly spaced from the radially inner and outer walls  22 A,  22 B of the tubular body  22 , and from the first and second side walls  22 C,  22 D, along the length L of the tubular body  22 . 
     In an embodiment, the second portion  26  of the tubular body  22  has a section that is at a constant distance from the center axis  14 . Referring to  FIGS. 3B and 3C , the axial, second portion  26  of the tubular body  22  has an axial segment  26 A. The axial segment  26 A is a portion of the second portion  26  that occupies some or all of the length of the second portion  26 . In an embodiment, the axial segment  26 A has a length of up to approximately 50% of the length L of the tubular body  22 . In  FIG. 3C , the axial segment  26 A has a length between approximately 20% and 40% of the length L of the tubular body  22 . In  FIG. 3C , the axial segment  26 A has a length between approximately 20% and 25% of the length L of the tubular body  22 . In the illustrated embodiment, the axial segment  26 A occupies less than all of the length of the second portion  26 . The axial segment  26 A extends parallel to the center axis  11  of the engine  10 , such that the fluid flow F has an orientation being parallel to the center axis  11  through the axial segment  26 A. The axial segment  26 A is the same radial distance from the center axis  11  over the length of the axial segment  26 A. The axial segment  26 A is a constant radial distance from the center axis  11  over the length of the axial segment  26 A. The pipe center axis  21  along the axial segment  26 A is the same radial distance from the center axis  11 . A distance RD measured from the pipe center axis  21  to the center axis  11  has a constant value over the length of the axial segment  26 A. Other features of the tubular body  22  may also, or alternatively, be the same radial distance from the center axis  11  along the axial segment  26 A. For example, the radially inner wall  22 A along the axial segment  26 A may be the same radial distance from the center axis  11 . For example, the radially outer wall  22 B along the axial segment  26 A may be the same radial distance from the center axis  11 . The axial segment  26 A is thus able to convey the fluid flow F axially, such that any radial or circumferential velocity components of the fluid flow F are much smaller in magnitude than the axial velocity component over the length of the axial segment  26 A. 
     The tubular body  22  of each diffuser pipe  20  has an exit segment  27 . The exit segment  27  is a downstream portion of the tubular body  22  through which the flow is conveyed. In the illustrated embodiment, the exit segment  27  extends axially from the axial segment  26 A, such that the axial segment  26 A has a downstream end at the exit segment  27 . In the illustrated embodiment, the exit segment  27  extends over a portion of the length L of the tubular body  22 , and is positioned downstream of the bend portion  28  and of the axial segment  26 A. The exit segment  27  begins at a downstream end of the axial segment  26 A and terminates at the pipe outlet  25 . The exit segment  27  includes and defines the pipe outlet  25 . The exit segment  27  is disposed entirely within the second portion  26  of the tubular body  22  in the illustrated embodiment and is a part thereof. The exit segment  27  is the last portion of the tubular body  22  through which the flow is conveyed. The exit segment  27  in an embodiment has a length that is a maximum of, or does not exceed, approximately 10% of the length L of the tubular body  22 . The exit segment  27  in the illustrated embodiment is within the last 25% of the length L of the diffuser pipe  20 . The exit segment  27  may be the last 10% of the length L of the diffuser pipe  20 . 
     Referring to  FIGS. 3B and 3C , the exit segment  27  extends radially outward relative to the center axis  11  over its length from the axial segment  26 A to the pipe outlet  25 . The diffuser pipe  20  is thus “angled up” at its exit to direct the fluid flow F discharged from the diffuser pipe  20  in a radially outward direction. The diffuser pipe  20  in  FIGS. 3B to 3C  thus has a section with a constant radius (i.e. the axial segment  26 A) which precedes another section of the diffuser pipe  20  where the radial position of the diffuser pipe  20  is rapidly increased over a short distance leading to the exit of the diffuser pipe  20  (i.e. the exit segment  27 ). The diffuser pipe  20  has a localized bend or curve at the exit or end of the diffuser pipe  20  to direct the gas path at the exit of the diffuser pipe  20 . Thus the fluid flow F is directed radially outwardly from the pipe outlet  25  after having flowed through the diffuser pipe  20  in a direction substantially parallel to the center axis  11 . 
     The exit segment  27  thus forms a “vectored exit profile” of the diffuser pipe  20 , thereby helping to provide air to the combustor  16  at specific flow directions and distributions. The diffuser pipe  20  is thus able to deflect or to direct the fluid flow F away from a liner of the combustor  16 , which may allow the fluid flow F to avoid impinging directly on the liner of the combustor  16  when discharged from the diffuser pipes  20 . By allowing the fluid flow F to avoid impinging directly on the downstream combustor  16 , the diffuser pipes  20  and their exit segments  27  may help to reduce losses in the combustor and may help to improve combustor stability and durability. In an embodiment, the cross-sectional area distribution and the length L of the diffuser pipe  20  are the same as that of a diffuser pipe without the exit segment  27 . In such an embodiment, the radially-outwardly oriented exit segment  27  allows for a more compact arrangement of the diffuser pipe  20  and the combustor  16 , because the diffuser pipe  20  may be placed closer to the combustor  16  since direct impingement of the fluid flow F on the liner of the combustor  16  is reduced or eliminated entirely. 
     Referring to  FIGS. 3B and 3C , one or more portions of the exit segment  27  curve radially outwardly toward the pipe outlet  25 . The exit segment  27  thus has one or more portions which function to turn the fluid flow F to discharge the fluid flow F from the pipe outlet  25  in a radially-outward direction. Such a portion of the exit segment  27  begins at the exit of the axial segment  26 A and curves or turns radially-outward therefrom toward the pipe outlet  25 . The radial position of the pipe center axis  21  relative to the center axis  11  at the pipe outlet  25  is thus radially further outward of the radial position of the pipe center axis  21  at the inlet of the exit segment  27 . A distance R 1  measured from the pipe center axis  21  to the center axis  11  at the inlet of the exit segment  27  is less than the radial distance R 2  from the pipe center axis  21  to the center axis  11  at the pipe outlet  25 . This allows the fluid flow F to exit the diffuser pipe  20  in an radially outward direction. In an alternate embodiment, the exit segment  27  is curved radially outwardly and the diffuser pipe  20  is oriented in such a manner that the fluid flow F is still able to exit the diffuser pipe  20  in an axial direction or a radially inward direction. 
     In  FIGS. 3B and 3C , both the radially inner and outer walls  22 A,  22 B along the exit segment  27  are curved radially outwardly, from the inlet of the exit segment  27  to the pipe outlet  25 . In  FIGS. 3B and 3C , both the radially inner and outer walls  22 A,  2 B are turned radially outwardly. In other embodiments, one example of which is described below, only one of the radially inner wall  22 A and the radially outer wall  22 B along the exit segment  27  is curved radially outward from the axial segment  26 A to the pipe outlet  25 . In an alternate embodiment, one or both of the radially inner and outer walls  22 A,  22 B are straight along the exit segment  27 , and have a curvature of zero. In such an embodiment, one or both of the radially inner and outer walls  22 A,  22 B extend radially outwardly from the axial segment  26 A to the pipe outlet  25  as linear segments. 
     Referring to  FIG. 3C , planes P intersect the tubular body  22  (only one being shown in  FIG. 3C  for clarity). Each plane P is defined by the pipe center axis  21 , and is normal thereto. The orientation of the planes P with respect to a coordinate system of the engine  10  thus varies over the length L of the tubular body  22 . It will be appreciated that there may be a large number of planes P for a given tubular body  22 . One of these planes P is an exit plane EP, which intersects and extends through the pipe outlet  25 . The exit plane EP extends between the radially inner and outer walls  22 A,  22 B, and is tangential to both. The exit plane EP is oblique to the center axis  11 . The exit plane EP intersects the center axis  11  and forms an angle with the center axis  11  that is neither parallel nor a right angle. Thus, the plane in which the pipe outlet  25  lies is oblique to the center axis  11 . The planes P along the axial segment  26 A intersect the center axis  11  at a right angle. 
     Referring to  FIG. 3C , the pipe center axis  21  along the exit segment  27  is oriented at an exit angle α relative to the center axis  11 . The exit angle α is greater than zero degree and less than ninety degrees (i.e. purely radial to the center axis  11 ). In  FIG. 3C , the exit angle α is maximum of, or does not exceed, 60 degrees. In  FIG. 3C , the oblique angle β of the exit plane EP relative to the center axis  11  is maximum of, or does not exceed, 60 degrees. In  FIG. 3C , the oblique angle β of the exit plane EP relative to the center axis  11  is about 30 degrees. The effect of the exit segment  27  is to change the orientation of the pipe center axis  21  at the pipe outlet  25 , compared to its orientation through the axial segment  26 A. 
       FIG. 4  shows a planar profile of the tubular body  22  in a plane that intersects the pipe center axis  21 , and in which lie the center axis  11  of the engine  10  and radial line extending from the center axis  11 .  FIG. 4  shows a two-dimensional projection of the curved and/or twisting pipe center axis  21  onto the intersecting plane. It will be appreciated that other features of the tubular body  22  (e.g. one of the walls  22 A,  22 B,  22 C,  22 D) may also be projected onto the intersecting plane. The planar profile in  FIG. 4  is a two-dimensional representation of the pipe center axis  21  in the intersecting plane over the length L of the tubular body  22 . 
       FIG. 4  plots the normalized radial distance of the pipe center axis  21  (the y-axis) measured from the center axis  11  of the engine  10  at different points along the length L of the tubular body  22  (the x-axis). The y-axis in  FIG. 4  corresponds to a radial orientation relative to the center axis  11 , and the x-axis corresponds to an axial orientation. The distance RD of the axial segment  26 A from the center axis  11  remains constant over the length of the axial segment  26 A. The axial segment  26 A is a constant radial distance from the center axis  11 . The axial segment  26 A is the same radial distance RD from the center axis  11  along the entire length of the axial segment  26 A.  FIG. 4  shows the radially-outward displacement of the pipe center axis  21  over the length of the exit segment  27 . The distance R 1  of the inlet of the exit segment  27  from the center axis  11  is less than the radial distance R 2  of the pipe outlet  25  from the center axis  11 . 
     Referring to  FIG. 4 , a slope of the planar profile is shown. In  FIG. 4 , the slope is the change in the radial distance of the pipe center axis  21  from the center axis  11  over a length along the center axis  11 . A negative slope indicates that the radial distance of the pipe center axis  21  is decreasing over the length in question, while a positive slope indicates that the radial distance of the pipe center axis  21  is increasing over the length in question. A slope of the exit segment  27  in the plane shown in  FIG. 4  is positive. The radial distance of the exit segment  27  from the center axis  11  increases over its length. The radial distance of the exit segment  27  is highest at the pipe outlet  25 , and lowest at an upstream end of the exit segment  27 . The slope of the axial segment  26 A in the plane shown in  FIG. 4  is zero, indicating that the radial distance of the axial segment  26 A from the center axis  11  does not vary substantially over its length. The axial segment  26 A is therefore flat in the plane shown in  FIG. 4 . In an alternate embodiment, the axial segment  26 A is not flat. 
       FIGS. 5 and 6  show embodiments of the diffuser pipe  20  in which only one of the radially inner wall  22 A and the radially outer wall  22 B along the exit segment  27  are curved or extend radially outward from the axial segment  26 A to the pipe outlet  25 . The diffuser pipes  20  shown in  FIGS. 5 and 6  are similar to the diffuser pipe  20  shown in  FIGS. 3A to 3C , and therefore the description and reference numbers of the diffuser pipe  20  in  FIGS. 3A to 3C  apply mutatis mutandis to the diffuser pipes  20  shown in  FIGS. 5 and 6 . In  FIGS. 5 and 6 , only the radially-inner wall  22 A along the exit segment  27  extends radially outward relative to the center axis  11  from the axial segment  26 A to the pipe outlet  25 . In  FIGS. 5 and 6 , the radially-outer wall  22 B is not present in the exit segment  27 . In  FIGS. 5 and 6 , the exit segment  27  is free of the radially outer wall  22 B. In  FIGS. 5 and 6 , the length of the radially outer wall  22 B is equal to the length L of the diffuser pipe  20  minus the length of the exit segment  27 . Thus  FIGS. 5 and 6  show an exit segment  27  for a diffuser pipe  20  with first and second side walls  22 C,  22 D and only the radially inner wall  22 A being turned radially outwardly. In  FIG. 5 , the tubular body  22  along the exit segment  27  is open radially-outwardly from the radially-inner wall  22 A and between the first and second side walls  22 C,  22 D. The side walls  22 C,  22 D and the radially inner wall  22 A delimit the open area. In  FIG. 6 , the tubular body  22  along the exit segment  27  is open radially-outwardly from the radially-inner wall  22 A and between the first and second side walls  22 C,  22 D. The first and second side walls  22 C,  22 D in  FIG. 6  along the exit segment  27  are smaller than the first and second side walls  22 C,  22 D along a remainder of the tubular body  22 . The first and second side walls  22 C,  22 D along the exit segment  27  extend less radially outwardly than the first and second side walls  22 C,  22 D along the remainder of the tubular body  22 . In  FIGS. 5 and 6 , only the “bottom” (i.e. the radially inner wall  22 A) of the diffuser pipe  20  in the exit segment  27  is used to direct the fluid flow F in a radially outward direction and away from the combustor  16 . 
       FIGS. 7A and 7B  show embodiments of the diffuser pipe  20  in which the exit segment  27  is curved or extends radially outward from the axial segment  26 A to the pipe outlet  25  and also has a circumferential twist. The diffuser pipe  20  shown in  FIGS. 7A and 7B  is similar to the diffuser pipe  20  shown in  FIGS. 3A to 3C , and therefore the description and reference numbers of the diffuser pipe  20  in  FIGS. 3A to 3C  apply mutatis mutandis to the diffuser pipe  20  shown in  FIGS. 7A and 7B . Referring to  FIGS. 7A and 7B , in addition to extending radially outward, the exit segment  27  also has a circumferential twist when compared to a portion of the tubular body  22  immediately upstream of the exit segment  27 , such as the axial segment  26 A. The flow path through the diffuser pipe  20  is twisted and changed to remove swirl in flow. As shown in  FIG. 7A , the exit segment  27  turns circumferentially toward the engine center axis  11 , when compared to more upstream segments of the second portion  26  of the tubular body  22 , to convey flow from the outlet  25 , and to help remove swirl from the flow. The exit segment  27  may turn circumferentially away the engine center axis  11  to change the swirl angle in fluid flow F exiting the diffuser pipe  20 . 
     Referring to  FIGS. 3A to 3C , there is disclosed a method of supplying air from the compressor section  14  to the combustor  16 . The method includes conveying air from the outlet  17 A of an impeller  17  toward the combustor  16  through a diffuser pipe  20 . The air is conveyed through the diffuser pipe  20  along a generally radial direction, then along an axial direction generally parallel to the center axis  11 , and then radially outwardly from the center axis through the pipe outlet  25  toward the combustor  16 . In an embodiment, the method includes discharging air from the pipe outlet  25  to avoid directly impinging on the combustor  16 . In an embodiment, the method includes discharging air from the pipe outlet  25  toward a position being radially outward of the combustor  16 . This may be done by deflecting the fluid flow F away from liner of the combustor  16  to avoid directly impinging against the liner. 
     The tubular body  22  may be made with advanced manufacturing or conventional methods. Using advanced manufacturing such as additive manufacturing or MIM (metal injection molding), the vector controlled exit segment  27  can be printed or injected as part of the diffuser pipe  20 . Using conventional methods such as stamping, the exit segment  27  shape may be incorporated into the tooling for the diffuser pipe  20 . 
     The diffuser pipe  20  and its exit segment  27  may be incorporated into existing engines  10  without affecting the surrounding hardware. An example of this would de-swirl cascades that are brazed to the gas generator case (GGC). The diffuser pipe  20  and its exit segment  27  may be designed such that all clearances with existing hardware (GGC, GGC tubes, and the combustor  16 ) may be maintained. The diffuser pipe  20  and its exit segment  27  may allow for a lower FSC delta associated with incorporating a vector controlled shape as part of the diffuser pipe  20 . The estimated FSC delta related to incorporating an exit vector controlled pipe may be roughly 10%, which may be a cheaper alternative to conventional cascade vanes. The diffuser pipe  20  may also be incorporated into existing engine or derivative engines for the purpose of cost reduction, and/or aero performance improvements. 
     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. 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.