Patent Publication Number: US-9897101-B2

Title: Impeller for centrifugal rotary machine, and centrifugal rotary machine

Description:
TECHNICAL FIELD 
     The present invention relates to an impeller used for a centrifugal rotary machine such as a centrifugal compressor, a blower, and a centrifugal pump. 
     Priority is claimed on Japanese Patent Application No. 2012-244784, filed Nov. 6, 2012, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     In centrifugal rotary machines such as centrifugal compressors, there has been market demand for an increase in performance through improvement of a head, expansion of an operating range, or the like, and thus various measures have been taken, for the demand. 
     Here, in a flow path of an impeller used for the centrifugal rotary machine, a flow flowing in a direction different from a main stream, i.e., a secondary flow, may occur in some cases. Due to the secondary flow, a low energy fluid is accumulated in the flow path of the impeller and speed and energy of the fluid of the accumulated portion become considerably deficient. For this reason, such a secondary flow is one factor that degrades performance of the centrifugal rotary machine. 
     Patent Literature 1 discloses an impeller for a centrifugal compressor in which performance is improved by suppressing a secondary flow flowing from a pressure side toward a suction side of a blade in an impeller. Specifically, in the impeller, a boundary layer flow in a side wall surface of a flow path prevents the secondary flow from flowing to transect the flow path from the pressure side to the suction side of the blade with a riblet installed along a flow of a main stream from the side wall surface. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Japanese Unexamined Patent Application, First Publication No. H9-264296 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the impeller of the rotary machine, a secondary flow different from that disclosed in Patent Literature 1 occurs in some cases. The secondary flow is a flow flowing in an axial direction away from a disc on the suction side in each flow path. Thus, a low energy fluid is accumulated in a position which is located at the suction side and away from the disc (directly under a cover in the case of a closed impeller), and is a factor that degrades performance of the rotary machine. 
     The present invention provides an impeller for a centrifugal rotary machine in which performance can be further improved by suppressing a secondary flow flowing away from a disc in an opposite direction of a rotary direction serving as a suction side of a blade. 
     Solution to Problem 
     According to a first aspect of the present invention, an impeller for a centrifugal rotary machine includes: a disc formed in a discoid shape about an axis; and a plurality of blades including a leading edge into which a fluid flows and a trailing edge out of which the fluid flows and arranged at intervals in a circumferential direction on a face facing a direction of the axis, wherein the blades each include a first section rising from the disc and inclined toward an opposite direction of a rotary direction as the distance from the disc and a second section continuing from the first section and inclined toward a forward direction of the rotary direction as the distance from the disc between the leading edges and the trailing edges in the blades. 
     According to the impeller described above, as the first section of the blade is inclined toward the opposite direction of the rotary direction, the first section is disposed to swell toward the opposite direction of the rotary direction. For this reason, the secondary flow occurring at the opposite direction of the rotary direction and flowing away from the disc is pushed toward the first section swollen toward the opposite direction of the rotary direction. Thus, the secondary flow is divided into a tangential direction component at a point at which the secondary flow comes into contact with the first section and a normal direction component that is a component perpendicular to the tangential direction component and pushing the secondary flow toward the first section. Here, if the first section is not inclined toward the opposite direction of the rotary direction, the secondary flow is not in contact with the first section and a component in the normal direction becomes 0 (zero). As such, the entire secondary flow flows away from the disc. According to an aspect of the present invention, since a portion of the secondary flow flows in the normal direction and the remainder flows in the tangential direction, the entire secondary flow does not flow toward a position away from the disc. Further, as the secondary section of the blade is inclined toward the forward direction of the rotary direction, it is possible to receive a pressing force of the fluid from the forward direction of the rotary direction. For this reason, even when the first section is inclined toward the opposite direction of the rotary direction, it is possible to effectively use the pressing force from the fluid and compression efficiency is not reduced. 
     According to a second aspect of the present invention, the impeller for the centrifugal rotary machine may further includes a third section disposed closer to the leading edge than the first section, rising from the disc, and inclined toward the forward direction of the rotary direction as the distance from the disc; and a fourth section disposed closer to the leading edge than the second section, continuing from the third section, and inclined toward the forward direction of the rotary direction as the distance from the disc. 
     According to the second section, the third section, and the fourth section described above, since it is possible to receive reliably the pressing force of the fluid from the forward direction of the rotary direction on the leading edge side of the blade and suppress the secondary flow flowing away from the disc in the rear side of the rotary direction, performance can be further improved. 
     According to a third aspect of the present invention, the impeller for the centrifugal rotary machine may further includes: a fifth section disposed closer to the trailing edge than the first section, rising from the disc, and inclined toward the opposite direction of the rotary direction as the distance from the disc; and a sixth section disposed closer to the trailing edge than the second section, continuing from the fifth section, and inclined toward the opposite direction of the rotary direction as the distance from the disc. 
     According to a fourth aspect of the present invention, the impeller for the centrifugal rotary machine may further includes: a seventh section disposed closer to the trailing edge than the fifth section, rising from the disc, and inclined toward the forward direction of the rotary direction as the distance from the disc; and an eighth section disposed closer to the trailing edge than the sixth section, continuing from the seventh section, and inclined toward the forward direction of the rotary direction as the distance from the disc. 
     According to a fifth aspect of the present invention, a centrifugal rotary machine includes: a rotary shaft configured to rotate about an axis; the impeller for the centrifugal rotary machine externally engaged with the rotary shaft and configured to rotate together with the rotary shaft; and a casing configured to rotatably support the rotary shaft and cover the impeller from an outer circumference side of the impeller. 
     According to the centrifugal rotary machine described above, as the blade of the impeller includes the first section and second section, at a contact point between the blade and the secondary flow occurring at the opposite direction of the rotary direction, since a portion of the secondary flow flows in the normal direction of the contact point and the remainder flows in the tangential direction, the entire secondary flow does not flow toward a position away from the disc. Further, it is possible to receive the pressing three of the fluid from the forward direction of the rotary direction by the second section. 
     Advantageous Effects of Invention 
     According to the impeller and the centrifugal rotary machine described above, as the blade includes the first section and the second section, it is possible to suppress the secondary flow flowing away from the disc in the opposite direction of the rotary direction, effectively use the pressing force from the fluid, and improve performance. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall schematic diagram showing a centrifugal compressor related to an embodiment of the present invention. 
         FIG. 2  is a perspective view showing an impeller in the centrifugal compressor related to the embodiment of the present invention, a portion of which is cut out. 
         FIG. 3  is a meridional view showing a major part of the impeller in the centrifugal compressor related to the embodiment of the present invention. 
         FIG. 4A  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 1 -X 1  of  FIG. 3 . 
         FIG. 4B  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 2 -X 2  of  FIG. 3 . 
         FIG. 4C  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 3 -X 3  of  FIG. 3 . 
         FIG. 4D  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 4 -X 4  of  FIG. 3 . 
         FIG. 4E  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 5 -X 5  of  FIG. 3 . 
         FIG. 4F  is a cross-sectional view of the blade of the impeller the centrifugal compressor related to the embodiment of the present invention, showing a cross section X 6 -X 6  of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the blade of the impeller in the centrifugal compressor related to the embodiment of the present invention, showing a direction of a secondary flow of  FIG. 4C . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Hereinafter, a centrifugal compressor (centrifugal rotary machine)  100  related to an embodiment of the present invention will be described. 
     As shown in  FIG. 1 , the centrifugal compressor  100  includes a casing  102 , a rotary shaft  101  which is axially supported via a journal hearing  103  and a thrust bearing  104  inside the casing  102  and configured to be rotatable about an axis O, and an impeller  1  externally engaged with the rotary shaft  101  in parallel with an axis O direction. 
     The centrifugal compressor  100  uses a centrifugal force of the impeller  1  rotated with the rotary shaft  101  to cause a fluid F 0  supplied from a suction port  105   c  formed in the casing  102  to flow from a flow path  105   a  of an upstream side to a flow path  105   b  of a downstream side in stages. Also, while the fluid F 0  flows, the centrifugal compressor  100  rises pressure of the fluid F 0  and discharges the fluid F 0  from a discharge port  105   d.    
     Next, the impeller  1  will be described. 
     The impeller  1  is externally engaged with the rotary shaft  101  and rotates about the axis O with the rotary shaft  101  in a rotary direction R. Note that, in the embodiment, the plurality of (six) impellers  1  are provided and configures a multi-stage centrifugal compressor. 
     As shown in  FIG. 2 , each impeller  1  includes a disc  3  formed in a substantially discoid shape when viewed in the axis O direction, a plurality of blades  4  provided on the disc  3 , and a cover  5  configured to cover the blades  4  in the axis O direction. 
     The disc  3  has an end face facing a first direction of the axis O direction and configured to have a small diameter and an end face facing a second direction of the axis O direction and configured to have a large diameter. Further, as the two end faces are connected by a curved surface  3   a  gradually enlarged in diameter from the first direction to the second direction of the axis O direction, the disc  3  has a substantially discoid shape when viewed in the axis O direction and is a member having substantially an umbrella shape as a whole. 
     In addition, a through-hole  3   b  configured to penetrate through the disc  3  in the axis O direction is formed inside in a radial direction of the disc  3 . As the rotary shaft  101  is inserted and fitted into the through-hole  3   b , the impeller  1  can be fixed to the rotary shaft  101  and rotated integrally with the rotary shaft  101 . 
     The blades  4  are a plurality of members disposed at certain intervals in the circumferential direction of the axis O, i.e., the rotary direction R, so as to rise from the curved surface  3   a  in the disc  3  to the first direction in the axis O direction. 
     In addition, the plurality of blades  4  are each formed to be curved toward the opposite direction of the rotary direction R as they go from the inside toward the outside in the radial direction of the disc  3 . Also, a face facing the forward direction of the rotary direction R is a pressure side of the blade and a face facing the opposite direction of the rotary direction R is a suction side of the blade. 
     The cover  5  is a member formed integrally with the plurality of blades  4  so as to cover the blades  4  from the first direction of the axis O direction, and has substantially an umbrella shape that gradually enlarges in diameter toward the second direction of the axis O direction. In other words, in the embodiment, the impeller  1  is a closed impeller having a cover  5 . 
     Also, a space surrounded by the two neighboring blades  4 , the disc  3 , and the cover  5  is defined as an impeller flow path FC in which the fluid F 0  can flow from the inside toward the outside in the radial direction. The fluid F 0  is introduced from the first direction of the axis O direction of the impeller  1 , i.e., the leading edge  4   a  side of the blade  4 , into the impeller flow path FC, and is discharged horn the trailing edge  4   b  side of the blade  4  serving as the outside in the radial direction. 
     Next, the blades  4  will be described in greater detail. 
     As shown in  FIGS. 3 and 4A to 4F , the blades  4  each include a portion B, a portion A, a portion C, and a portion D in order from the leading edge  4   a  toward the trailing edge  4   b.    
     The portion A includes a first section  10 A formed at a position near the disc  3  so as to continue from the disc  3  on a side closest to the leading edge  4   a  in the blade  4 , and a second section  11 A extending away from the disc so as to continue from the first section  10 A. In other words, the first section  10 A and the second section  11 A are consecutively formed using an imaginary line L defined at a halfway position of a direction in which the blade  4  rises (in the embodiment, a central position of a direction in which the blade  4  rises) as a boundary. 
     Here, in connection with the blade  4 , an inclined angle formed between the blade  4  and an imaginary line L 1  rising at a right angle from the curved surface  3   a  of the disc  3  (the imaginary line L 1  rising at a right angle from a tangential line L 2  in a contact point P between the blade  4  and the curved surface  3   a ) is assumed to be a lean angle α. 
     In the blade  4 , the first section  10 A rises from the disc  3  having the lean angle α inclined toward the opposite direction of the rotary direction R and is formed to be smoothly curved as the distance from the disc  3 . 
     The second section  11 A continues from the first section  10 A toward the cover  5  and extends to be smoothly curved and inclined toward the forward direction of the rotary direction R the distance from the disc  3 . 
     Here, examples of positions in which the first section  10 A and the second section  11 A are formed are illustrated in  FIGS. 4B, 4C, and 4D . In other words, in the embodiment, the first section  10 A and the second section  11 A are, for example, formed at a position corresponding to 1.5% to 65% along a meridional plane of the impeller  1  from the leading edge  4   a.    
     In the embodiment, in the first section  10 A, the lean angle α is maximized at a position of 40% while the lean angle α gradually increases from the leading edge  4   a  side of the blade  4  and then gradually decreases toward the trailing edge  4   b  side of the blade  4 . In other words, at a position corresponding to 40% along the meridional plane, the first section  10 A of the blade  4  is most inclined toward the opposite direction of the rotary direction R. A position which is most inclined toward the opposite direction of the rotary direction R is not limited to the position corresponding to 40% along the meridional plane, and the numerical value of 40% is an example. 
     In addition in the second section  11 A, a degree of curvature is maximized at a position of 40% while the degree of curvature gradually increases from the leading edge  4   a  side of the blade  4 , and then gradually decreases toward the trailing edge  4   b  side of the blade  4 . In other words, at a position corresponding to 40% along the meridional plane, the second section  11 A of the blade  4  is most inclined toward the forward direction of the rotary direction R. A position which is most inclined toward the forward direction of the rotary direction R is not limited to the position corresponding to 40% along the meridional plane, and the numerical value of 40% is an example. 
     The portion B is a portion located closer to the leading edge  4   a  side of the blade  4  than the portion A, and includes a third section  10 B formed at a position near the disc  3  so as to continue from the disc  3  and a fourth section  11 B extending away from the disc so as to continue from the third section  10 B using the imaginary line L as a boundary. 
     As shown in  FIG. 4A , the third section  10 B is provided to have the lean angle α inclined toward the forward direction of the rotary direction R, rise from the disc  3  at a side closer to the leading edge  4   a  of the blade  4  than the first section  10 A, and extend in a linear shape as the distance from the disc  3 . 
     In addition, the fourth section  11 B extends to straightly extend the third section  10 B in a linear shape without being inclined from a connection section of the third section  10 B and the fourth section  11 B at a side closer to the leading edge  4   a  of the blade  4  than the second section  11 A. In other words, the fourth section  11 B is inclined toward the forward direction of the rotary direction R. 
     Here, an example of positions in which the third section  10 B and the fourth section  11 B are formed is illustrated in  FIG. 4A , in other words, in the embodiment, the third section  10 B and the fourth section  11 B are, for example, thrilled from a position corresponding to 0% on the meridional plane of the impeller  1  to a position of the leading edge  4   a  side of the portion A, i.e., near the leading edge  4   a.    
     The portion C is a portion located closer to the trailing edge  4   b  side of the blade  4  than the portion B, and includes a fifth section  10 C formed at a position near the disc  3  so as to continue from the disc  3  and a sixth section  11 C extending away from the disc  3  so as to continue from the fifth section  10 C using the imaginary line L as a boundary. 
     As shown in  FIG. 4E , the fifth section  10 C is provided to have the lean angle α inclined toward the opposite direction of the rotary direction R, rise from the disc  3  at a side closer to the trailing edge  4   b  of the blade  4  than the first section  10 A, and extend in a linear shape as the distance from the disc  3 . 
     In addition, the sixth section  11 C extends to straightly extend the fifth section  10 C in a linear shape without being inclined from a connection section of the fifth section  10 C and the sixth section  11 C at a side closer to the trailing edge  4   b  of the blade  4  than the second section  11 A. In other words, the sixth section  11 C is inclined toward the opposite direction of the rotary direction R. 
     Here, an example of positions in which the fifth section  10 C and the sixth section  11 C are formed is illustrated in  FIG. 4E . In other words, in the embodiment, the fifth section  10 C and the sixth section  11 C are, for example, formed from the trailing edge  4   b  side of the portion A to a position corresponding to 85% along the meridional plane of the impeller  1 . 
     The portion D is a portion located closer to the trailing edge  4   b  of the blade  4  than the portion C, and includes a seventh section  10 D formed at a position near the disc  3  so as to continue from the disc  3  and an eighth section  11 D extending away from the disc so as to continue from the seventh section  10 D using the imaginary line L as a boundary. 
     As shown in  FIG. 4E , the seventh section  10 D is provided to have the lean angle α inclined toward the forward direction of the rotary direction R and extend in a linear shape away from the disc  3  at a side closer to the trailing edge  4   b  of the blade  4  than the fifth section  10 C, as with the leading edge  4   a  of the blade  4 . 
     In addition, the eighth section  11 D extends to straightly extend the seventh section  10 D in a linear shape without being inclined from a connection section of the seventh section  10 D and the eighth section  11 D at a side closer to the trailing edge  4   b  of the blade  4  than the sixth section  11 D. In other words, the eighth section  11 D is inclined toward the forward direction of the rotary direction R as with the leading edge  4   a.    
     Here, an example of positions in which the seventh section  10 D and the eighth section  11 D are formed is illustrated in  FIG. 4F . In other words, in the embodiment, the seventh section  10 D and the eighth section  11 D are, for example, formed from the trailing edge  4   b  side of the portion C to a position corresponding to 100% along the meridional plane of the impeller  1 , i.e., near the trailing edge  4   b.    
     As described above, at at least one place between the leading edge  4   a  and the trailing edge  4   b  of the blade  4 , there is a place inclined toward the opposite direction of the rotary direction R on a side closer to the disc  3  than the imaginary line L. 
     Such a centrifugal compressor includes the first section  10 A in which the blade  4  is inclined toward the opposite direction of the rotary direction R. The first section  10 A is disposed to swell toward the opposite direction of the rotary direction R. Thus, when the secondary flow F flowing along the suction side of the blade  4  away from the disc  3  as shown in  FIG. 5  occurs in the opposite direction of the rotary direction R of the blade  4  along with the rotation of the impeller  1 , the secondary flow F may contact and push the first section  10 A. 
     In other words, the secondary flow F is divided into a tangential direction component F 1  at a point A on the suction side of the blade  4  in contact with the first section  10 A and a normal direction component F 2  perpendicular to the tangential direction component F 1 . Also, the normal direction component F 2  is a component pushing the secondary flow F toward the first section  10 . 
     Here, if the first section  10 A is not inclined toward the opposite direction of the rotary direction R, the secondary flow is not in contact with the first section  10 A and the normal direction component F 2  becomes 0 (zero). As such, the entire secondary flow F flows away from the disc  3 . On the other hand, in the embodiment, since a portion of the secondary flow F flows in a normal direction F 2  and the remainder flows in a tangential direction F 1 , the entire secondary flow F does not flow toward a position away from the disc  3 . 
     In addition, as the blade  4  includes the second section  11 A inclined toward the forward direction of the rotary direction R, it is possible for the blade  4  to receive the pressing force of the fluid F 0  on the pressure side of the blade  4 . For this reason, even when the first section  10 A is inclined toward the opposite direction of the rotary direction R, compression efficiency is not reduced. 
     In addition, the blade  4  includes the third section  10 B and the fourth section  11 B which are inclined toward the forward direction of the rotary direction R at the position corresponding to 0% along the meridional plane. As such, when the fluid F 0  is introduced into the flow path FC, it is possible for the blade  4  to reliably receive the pressing force of the fluid F 0  on the pressure side at the leading edge  4   a  side of the blade  4 . Therefore, the fluid F 0  can be compressed with higher efficiency. 
     According to the centrifugal rotary machine of the embodiment, the first section  10 A of the blade  4  is inclined toward the opposite direction of the rotary direction R and the second section  11 A of the blade  4  is inclined toward the forward direction of the rotary direction R between the leading edge  4   a  and the trailing edge  4   b . For this reason, the secondary flow F flowing away from the disc  3  in the opposite direction of the rotary direction R can be suppressed, and accumulation of the low energy fluid at a position in the opposite direction of the rotary direction R of the blade  4 , which is a position away from the disc  3 , i.e., close to the cover  5 , can be suppressed. 
     In addition, the pressure side of the blade  4  can receive the pressing force from the fluid F 0  to effectively use the force, maintain compression efficiency while suppressing the secondary flow F, and improve performance. 
     The embodiments of the present invention have been described above in detail, but some design changes can be made without departing from the spirit of the technical scope of the present invention. 
     For example, the blade  4  may have the first section  10 A inclined toward the opposite direction of the rotary direction R and the second section  11 A inclined toward the forward direction of the rotary direction R so as to continue from the first section  10 A provided on at least one place between the leading edge  4   a  and the trailing edge  4   b  of the blade  4 . Therefore, an inclination direction and a shape with respect to the third section  10 B, the fourth section  11 B, the fifth section  10 C, the sixth section  11 C, the seventh section  10 D, and the eighth section  11 D are not limited to the above-described embodiments. Further, the third section  10 B, the fourth section  11 B, the fifth section  10 C, the sixth section  11 C, the seventh section  10 D, and the eighth section  11 D may be provided to be arranged on the imaginary line L 1  without being inclined in the rotary direction R. 
     In addition, the first section  10 A and the second section  11 A are provided to be curved in the above-described embodiments, but may be provided in a linear shape. 
     In addition, the description has been made on the assumption that the impeller is the closed impeller in the above-described embodiments, but an open impeller having no cover  5  may be used. 
     In addition, the centrifugal compressor  100  is not limited to the multi-stage compressor, and the above-described blade  4  of the impeller  1  can also be applied to a single-stage compressor. 
     Also, the centrifugal compressor is not necessarily used as the centrifugal rotary machine in the present invention, and a blower and a centrifugal pump may be used. 
     INDUSTRIAL APPLICABILITY 
     According to the impeller and the centrifugal rotary machine described above, as the blade includes the first section and the second section, it is possible to suppress the secondary flow flowing away from the disc in the opposite direction of the rotary direction, effectively use the pressing force from the fluid, and improve performance. 
     REFERENCE SIGNS LIST 
       1  Impeller 
       3  Disc 
       3   a  Curved surface 
       3   b  Through-hole 
       4  Blade 
       4   a  Leading edge 
       4   b  Trailing edge 
       5  Cover 
       10 A First section 
       11 A Second section 
       10 B Third section 
       11 B Fourth section 
       10 C Fifth section 
       11 C Sixth section 
       10 D Seventh section 
       11 D Eighth section 
     O Axis 
     F 0  Fluid 
     F Secondary flow 
     P Contact point 
     F 1  Tangential direction component 
     F 2  Normal direction component 
     FC Impeller flow path 
     L, L 1  Imaginary line 
     L 2  Tangential line 
     R Rotary direction 
       100  Centrifugal compressor (centrifugal rotary machine) 
       101  Rotary shaft 
       102  Casing 
       103  Journal bearing 
       104  Thrust bearing 
       105   a  Flow path 
       105   b  Flow path 
       105   c  Suction port 
       105   d  Discharge port