Patent Publication Number: US-10323528-B2

Title: Bulged nozzle for control of secondary flow and optimal diffuser performance

Description:
BACKGROUND 
     The subject matter disclosed herein relates to turbomachines, and more particularly, the last nozzle stage in the turbine of a turbomachine. 
     A turbomachine, such as a gas turbine engine, may include a compressor, a combustor, and a turbine. Gasses are compressed in the compressor, combined with fuel, and then fed into to the combustor, where the gas/fuel mixture is combusted. The high temperature and high energy exhaust fluids are then fed to the turbine, where the energy of the fluids is converted to mechanical energy. In the last stage of a turbine, low root reaction may induce secondary flows transverse to the main flow direction. Secondary flows may negatively impact the efficiency of the last stage and lead to undesirable local hub swirl, which negatively affects the performance of the diffuser. As such, it would be beneficial to increase root reaction to control secondary flow and reduce local hub swirl. 
     BRIEF DESCRIPTION 
     Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
     In a first embodiment, a turbine nozzle disposed in a turbine includes a suction side extending between a leading edge of the nozzle and a trailing edge of the turbine nozzle in an axial direction and transverse to a longitudinal axis of the turbine nozzle, and extending a height of the nozzle in a radial direction along the longitudinal axis, a pressure side disposed opposite the suction side and extending between the leading edge of the turbine nozzle and the trailing edge of the turbine nozzle in the axial direction, and extending the height of the nozzle in the radial direction, and a bulge disposed on the suction side of the nozzle protruding relative to the other portion of the suction side in a direction transverse to a both the radial and axial directions. 
     In a second embodiment, a system includes a turbine including a first annular wall, a second annular wall, and a last nozzle stage, which includes a plurality of nozzles disposed annularly about a rotational axis. Each nozzle includes a height extending between the first and second annular walls, a leading edge, a trailing edge downstream of the leading edge, a suction side extending between the leading edge and the trailing edge in an axial direction, and extending the height of the nozzle in a radial direction, a pressure side disposed opposite the suction side and extending between the leading edge of the nozzle and the trailing edge of the nozzle in the axial direction, and extending the height of the nozzle in the radial direction, and a bulge disposed on the suction side of the nozzle that protrudes in a direction transverse to a radial plane extending from the rotational axis. 
     In a third embodiment, a system includes a turbine, which includes a first annular wall, a second annular wall, and a last stage including a plurality of nozzles disposed annularly about a rotational axis. Each nozzle includes a height between the first and second annular walls, a leading edge, a trailing edge disposed downstream of the leading edge, a suction side extending between the leading edge and the trailing edge in an axial direction, and extending the height of the nozzle in a radial direction, a pressure side disposed opposite the suction side and extending between the leading edge of the nozzle and the trailing edge of the nozzle in the axial direction, and extending the height of the nozzle in the radial direction, and a bulge on the suction side of the nozzle that protrudes in a direction transverse to a radial plane extending from the rotational axis and extends in the axial direction, wherein each nozzle of the plurality of nozzles is angled relative to the radial plane toward the pressure side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention 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 diagram of one embodiment of a turbomachine in accordance with aspects of the present disclosure; 
         FIG. 2  is a perspective front view of one embodiment of a nozzle in accordance with aspects of the present disclosure; 
         FIG. 3  is a front view of one embodiment of a partial array of nozzles designed with a suction bulge in a stage of a turbine in accordance with aspects of the present disclosure; 
         FIG. 4  is a back view of one embodiment of a partial array of nozzles designed with a suction bulge in a stage of a turbine in accordance with aspects of the present disclosure; 
         FIG. 5  is a top section view of two adjacent nozzles in accordance with aspects of the present disclosure; 
         FIG. 6  is a graphical representation of a non-dimensional throat distribution defined by adjacent nozzles in a stage of a turbine in accordance with aspects of the present disclosure; 
         FIG. 7  is a graphical representation of a non-dimensional distribution of the maximum nozzle thickness divided by the maximum nozzle thickness at 50% span in accordance with aspects of the present disclosure; 
         FIG. 8  is a graphical representation of a non-dimensional distribution of the maximum nozzle thickness divided by the axial chord in accordance with aspects of the present disclosure; 
         FIG. 9  is a section view of a nozzle with a suction side bulge in accordance with aspects of the present disclosure; 
         FIG. 10  is a schematic of a nozzle angled toward the pressure side relative to a radially stacked airfoil in accordance with aspects of the present disclosure; and 
         FIG. 11  is a perspective view of a nozzle with a 3 degree pressure side tilt as compared to a radially stacked airfoil in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     Following combustion in a gas turbine engine, exhaust fluids exit the combustor and enter the turbine. Low root reaction may introduce strong secondary flows (i.e., flows transverse to the main flow direction) in the last stage of the turbine, reducing the efficiency of the last stage. Additionally, secondary flows in or around the bucket hub may introduce undesirable swirl, which may appear as a swirl spike in the bucket exit flow profile, which negatively affects the performance of the diffuser. A nozzle design having a bulge on the suction side, a slight tilt toward the pressure side implemented in the last stage, and an opening of the throat near the hub region may be used to enable root reaction, thus reducing secondary flows and undesirable swirl. 
     Turning now to the figures,  FIG. 1  is a diagram of one embodiment of a turbomachine  10  (e.g., a gas turbine engine). The turbomachine  10  shown in  FIG. 1  includes a compressor  12 , a combustor  14 , and a turbine  16 . Air, or some other gas, is compressed in the compressor  12 , mixed with fuel, fed into the combustor  14 , and then combusted. The exhaust fluids are fed to the turbine  16  where the energy from the exhaust fluids is converted to mechanical energy. The turbine includes a plurality of stages  18 , including a last stage  20 . Each stage  18 , may include a rotor, coupled to a rotating shaft, with an annular array of axially aligned blades or buckets, which rotates about a rotational axis  26 , and a stator with an annular array of nozzles. Accordingly, the last stage  20  may include a last stage stator  22  and a last stage rotor  24 . For clarity,  FIG. 1  includes a coordinate system including an axial direction  28 , a radial direction  32 , and a circumferential direction  34 . Additionally, a radial plane  30  is shown. The radial plane  30  extends in the axial direction  28  (along the rotational axis  26 ) in one direction, and then extends outward in the radial direction. 
       FIG. 2  is a front perspective view (i.e., looking generally downstream) of an embodiment of a nozzle  36 . The nozzles  36  in a last stage  20  are configured to extend in a radial direction  32  between a first annular wall  40  and a second annular wall  42 . Each nozzle  36  may have an airfoil type shape and be configured to aerodynamically interact with the exhaust fluids from the combustor  14  as the exhaust fluids flow generally downstream through the turbine  16  in the axial direction  28 . Each nozzle  36  has a leading edge  44 , a trailing edge  46  disposed downstream, in the axial direction  28 , of the leading edge  44 , a pressure side  48 , and a suction side  50 . The pressure side  48  extends in the axial direction  28  between the leading edge  44  and the trailing edge  46 , and in the radial direction  32  between the first annular wall  40  and the second annular wall  42 . The suction side  50  extends in the axial direction  28  between the leading edge  44  and the trailing edge  46 , and in the radial direction  32  between the first annular wall  40  and the second annular wall  42 , opposite the pressure side  48 . The nozzles  36  in the last stage  20  are configured such that the pressure side  48  of one nozzle  36  faces the suction side  50  of an adjacent nozzle  36 . As the exhaust fluids flow toward and through the passage  38  between nozzles  36 , the exhaust fluids aerodynamically interact with the nozzles  36  such that the exhaust fluids flow with an angular momentum relative to the axial direction  28 . Low root reaction may introduce strong secondary flows and undesirable swirl in the last blade stage  20  of the turbine, reducing the efficiency of the last blade stage  20  and the performance of the diffuser. A last nozzle stage  24  populated with nozzles  36  having a bulge  52  protruding from the lower part of the suction side, which opens the throat near the hub region, (and in some embodiments, a slight tilt toward the pressure side  48 ) may encourage root reaction, thus reducing secondary flows and undesirable swirl. 
       FIGS. 3 and 4  show a front perspective view (i.e., facing generally downstream in the axial direction  28 ) and a back perspective view (i.e., facing generally upstream against the axial direction  28 ), respectively, of a partial array of nozzles  36 , extending in a radial direction  32  between first and second annular walls  40 ,  42 , designed with a suction side bulge  52  in a last nozzle stage  24  of a turbine  16 . Note that the width of the passages  38  between the nozzles  36  begins near the bottom of the nozzles  36  having a width W 1 . The passage  38  width W 2  is smallest when the bulge  52  is largest, around 20-40% up the height  54  of the nozzle  36  and the radial direction  32 , and then the passage  38  width W 3 , W 4  gets larger toward the top of the nozzles  36  as the bulge  52  subsides. 
       FIG. 5  is a top view of two adjacent nozzles  36 . Note how the suction side  50  of the bottom nozzle  36  faces the pressure side  48  of the top nozzle. The axial chord  56  is the dimension of the nozzle  36  in the axial direction. The passage  38  between two adjacent nozzles  36  of a stage  18  defines a throat D o , measured at the narrowest region of the passage  38  between adjacent nozzles  36 . Fluid flows through the passage  38  in the axial direction  28 . This distribution of D o  along the height of the nozzle  36  will be discussed in more detail in regard to  FIG. 6 . The maximum thickness of each nozzle  36  at a given height is shown as T max . The T max  distribution across the height of the nozzle  36  will be discussed in more detail in regard to  FIGS. 7 and 8 . 
       FIG. 6  is a plot  58  of throat D o  distribution defined by adjacent nozzles  36  in the last stage  20  is shown as curve  60 . The vertical axis  62 , x, represents the percent span between the first annular wall  40  and the second annular wall in the radial direction  32 , or the percent span along the height  54  of the nozzle  36  in the radial direction  32 . That is, 0% span represents the first annular wall  40  and 100% span represents the second annular wall  42 , and any point between 0% and 100% corresponds to a percent distance between the annular walls  40 ,  42 , in the radial direction  32  along the height of the nozzle. The horizontal axis  64 , y, represents D o , the shortest distance between two adjacent nozzles  36  at a given percent span, divided by the D o,AVG , the average D o  across the entire height of the nozzle  36 . Dividing D o  by the D o,AVG  makes the plot  58  non-dimensional, so the curve  60  remains the same as the nozzle stage  22  is scaled up or down for different applications. One could make a similar plot for a single size of turbine in which the horizontal axis is just D o . 
     As can be seen in  FIG. 6 , as one moves in the radial direction  32  from the first annular wall  40 , or point  66 , the bulge  52  maintains D o  at about 80% of the average D o . At point  68 , about the middle of the bulge  52 , (e.g., approximately 30% up the height  54  of the nozzle), the bulge  52  begins to recede and D o  grows to approximately 1.3 times the average D o  at the second annular wall  42 , or point  70 . This throat D o  distribution encourages root reaction in the last blade stage  20 , which improves the efficiency of the last blade stage and performance of the diffuser, which may result in a substantial increase in power output for the turbine. In some embodiments, the may increase power output by more than 1.7 MW. 
       FIG. 7  is a plot  72  of the distribution of T max /T max  at 50% span as curve  74 , as compared to a nozzle of conventional design  76 . The vertical axis  78 , x, represents the percent span between the first annular wall  40  and the second annular wall in the radial direction  32 , or the percent span along the height  54  of the nozzle  36  in the radial direction  32 . The horizontal axis  80 , y, represents T max , the maximum thickness of the nozzle  36  at a given percent span, divided by the T max  at 50% span. Dividing T max  by T max  at 50% span makes the plot  72  non-dimensional, so the curve  74  remains the same as the nozzle stage  22  is scaled up or down for different applications. One could make a similar plot for a single size of turbine in which the horizontal axis is just T max . 
     As can be seen in  FIG. 7 , as one moves in the radial direction  32  from the first annular wall  40 , or point  82 , T max  starts out at approximately 83% of T max  at 50% span and then quickly approaches T max  at 50% span. From 35% span to about 60% span, T max  is substantially the same as T max  at 50% span. At point  84 , or approximately 60% span, T max  diverges from T max  at 50% span, and remains larger than T max  at 50% span until the nozzle  22  reaches the second annular wall  42 , or point  86 . 
       FIG. 8  is a plot  86  of the distribution of T max /axial chord as curve  88 , as compared to a nozzle of conventional design  90 . The vertical axis  92 , x, represents the percent span between the first annular wall  40  and the second annular wall  42  in the radial direction  32 , or the percent span along the height  54  of the nozzle  36  in the radial direction  32 . The horizontal axis  94 , y, represents T max , the maximum thickness of the nozzle  36  at a given percent span, divided by the axial chord  56 , the dimension of the nozzle  36  in the axial direction  28 . Dividing T max  by the axial chord  56  makes the plot  86  non-dimensional, so the curve  88  remains the same as the nozzle stage  22  is scaled up or down for different applications. 
     As can be seen in  FIG. 8 , as one moves in the radial direction  32  from the first annular wall  40 , or point  96 , T max  starts out smaller than the conventional design, but grows larger than the conventional design as the bulge reaches its maximum divergence from the conventional design at point  98 . From point  98  to the second annular wall  42  (point  100 ), the T max  approaches the T max  of the conventional design. This maximum thickness T max  distribution encourages root reaction in the last blade stage  20 , which improves the efficiency of the last blade stage and performance of the diffuser, which may result in a substantial increase in power output for the turbine. In some embodiments, the may increase power output by more than 1.7 MW. 
       FIG. 9  is a side section view of a nozzle  36  with a suction side  50  bulge  52 . The dotted lines  102  in  FIG. 9  represent the suction side wall  102  of a radially stacked nozzle (i.e., a similar nozzle design without a bulge  52 ). The bulge  52  protrudes from the suction side  50  in a direction transverse to the radial plane  30  extending from the rotational axis  26  out in the radial direction  32  in one direction, and in the axial direction  28  in a second direction. Distance  104  represents the distance the bulge protrudes from the hypothetical suction side  102  of a radially stacked nozzle without a bulge  52  at the point along the height  54  of the nozzle  36  at which the bulge  52  is at its maximum protrusion. As may be seen in  FIG. 9 , the bulge  52  may begin to protrude at a position between approximately 0-20% of the height of the nozzle  36  (i.e., 0-20% of the span from the first annular wall  40  to the second annular wall  42 ). That is, the profile of a nozzle  36  with a bulge  52  may begin to diverge from the hypothetical suction side wall  102  of a radially stacked nozzle at any point from the bottom of the nozzle  36  (i.e., where the nozzle  36  meets the first annular wall  40 ) to approximately 20% of the height  54  of the nozzle  36 . For example, the bulge  52  may begin to protrude at approximately 0%, 2%, 5%, 15%, or 20% of the height  54  of the nozzle  36 , or anywhere in between. In other embodiments, the bulge may begin to protrude between 1% and 15% of the height  54  of the nozzle  36 , or between 5% and 10% of the height  54  of the nozzle  36 . The bulge  52  may have a maximum protrusion  104  (i.e., the maximum deviation from the suction side wall  102  of a radially stacked nozzle) between approximately 0.5% and 10% of the height  54  of the nozzle  36 . Alternatively, the maximum bulge protrusion  104  may be between approximately 0.5% and 5.0%, or between 1.0% and 4.0% of the height  54  of the nozzle  36 . The bulge  52  may reach its maximum protrusion  104  between approximately 20% and 30% of the height  54  of the nozzle  36  (i.e., between approximately 20% and 30% of the span from the first annular wall  40  to the second annular wall  42 ). For example, the maximum bulge protrusion may occur at approximately 20%, 22%, 24%, 26%, 28%, or 30% of the height  54  of the nozzle  36 , or anywhere in between. In some embodiments, the bulge  52  may reach its maximum protrusion  104  between approximately 20% and 30%, between 22% and 28%, or between 23% and 27% of the height  54  of the nozzle  36 . Upon reaching the maximum bulge protrusion  104 , the profile of a nozzle  36  with a suction side bulge  52  begins to converge with the suction side wall  102  of a radially stacked nozzle. The bulge  52  may end (i.e., the profile of the nozzle  36  with a suction side bulge  52  converges with the suction side wall  102  of a radially stacked nozzle) at a point between approximately 50% and 60% of the height  54  of the nozzle  36  (i.e., between approximately 50% and 60% of the span from the first annular wall  40  to the second annular wall  42 ). In other embodiments, the bulge  52  may end at a point between approximately 52% and 58%, 53% and 57%, or 54% and 56% of the height  54  of the nozzle  36 . That is, the bulge  52  may end at a point approximately 50%, 52%, 54%, 56%, 58%, or 60% of the height  54  of the nozzle  36 , or anywhere in between. In some embodiments, the bulge  52  may extend along the entire length of the suction side  50  in the axial direction  28 , from the leading edge  44  to the trailing edge  46 . In other embodiments, the bulge  52  may extend only along a portion of the suction side  50 , between the leading edge  44  and the trailing edge  46 . A last stage stator  22  populated with nozzles  36  having bulges  52  on the suction side  50  encourages root reaction, which helps to reduce secondary flows and undesirable swirling. Implementation of the disclosed techniques may increase the performance of both the last stage and the diffuser, resulting in a substantial benefit in the output of the turbomachine. In some embodiments, the disclosed techniques may improve the performance of the last blade stage by approximately 200 KW or more, and may improve diffuser performance by approximately 1500 KW or more, for a total benefit of approximately 1700 KW or more. It should be understood, however, that benefits resulting from implementation of the disclosed techniques may vary from turbomachine to turbomachine. 
     In some embodiments, the nozzle  36  may be tilted or angled to the pressure side  48 , as compared to a radially stacked airfoil  106 .  FIG. 10  shows a schematic of nozzle  36  angled toward the pressure side  48  as compared to a radially stacked airfoil  106 . That is, the nozzle  36  may have an angle of tilt  108  toward the pressure side  48  (i.e., in the circumferential direction  34 ) from the radial plane  30 . Note that  FIG. 10  is not to scale, and for the sake of clarity, may show more or less tilt  108  than may be found in some embodiments. Note that the radially stacked airfoil  106  has a longitudinal axis that extends in the radial direction  32 , along the radial plane  30 , and may intersect with the rotational axis  26  of the turbine  16 . In contrast, the longitudinal axis  112  of the nozzle  36  may be angled toward the pressure side  48  of the nozzle  36  from the radial plane  30  by an angle  108 . The longitudinal axis  112  of the nozzle may intersect with the radial plane  30  at a point  114  at or near the first annular wall  40 , and may not intersect the rotational axis  26  of the turbine  16 . 
       FIG. 11  shows a perspective view of nozzle  36  with approximately 3 degrees of pressure side  48  tilt  108  as compared to a radially stacked airfoil  106 . That is, the nozzle  36  may tilt 3 degrees toward the pressure side  48  (i.e., in the circumferential direction  34 ) from the radial plane  30 . The tilt  108  may be anywhere between 0-5 degrees. In the embodiment shown in  FIG. 11 , the pressure side  48  tilt  108  is 3 degrees. However, it should be understood that the tilt  108  may be any degree of tilt toward the pressure side  48  between 0 and 5 degrees. A nozzle  36  with pressure side  48  tilt  108  exerts body forces on the fluid passing through the stage  24 , pushing the fluid in the radial direction toward the hub. Pushing the fluid toward the hub increases root reaction. Thus, a nozzle  36  with a suction side  50  bulge  52  and a pressure side  48  tilt  108  increases root reaction in the last blade stage  20 , which reduces secondary flows and swirling, increasing the efficiency of the last blade stage  20 , and increasing the performance of the diffuser. 
     Technical effects of the disclosed embodiments include a turbine nozzle disposed in a turbine includes a suction side extending between a leading edge of the nozzle and a trailing edge of the turbine nozzle in an axial direction and transverse to a longitudinal axis of the turbine nozzle, and extending a height of the nozzle in a radial direction along the longitudinal axis, a pressure side disposed opposite the suction side and extending between the leading edge of the turbine nozzle and the trailing edge of the turbine nozzle in the axial direction, and extending the height of the nozzle in the radial direction, and a bulge disposed on the suction side of the nozzle protruding relative to the other portion of the suction side in a direction transverse to a both the radial and axial directions. The bulge may begin at point between approximately 0% and 20% of the nozzle high, reach its maximum width at a point between approximately 20% and 40% of the nozzle height, and end at a point between approximately 50% and 60% of the nozzle height. The bulge may have a maximum width between approximately 0.5% and 10.0% of the nozzle height. Additionally, the nozzle may tilt toward the pressure side when compared to a radially stacked nozzle. A last nozzle stage populated with nozzles having bulges on the suction side encourages root reaction, which helps to reduce secondary flows and undesirable swirling In some embodiments, the disclosed techniques may improve the performance of the last blade stage by approximately 200 KW or more, and may improve diffuser performance by approximately 1500 KW or more, for a total benefit of approximately 1700 KW or more. It should be understood, however, that benefits resulting from implementation of the disclosed techniques may vary from turbomachine to turbomachine. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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.