JP2013002280A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress surging of a centrifugal compressor 1 in order to expand an operating range of the centrifugal compressor 1 to the low-flow-rate side while achieving compactification of the centrifugal compressor 1 and simplification of the configuration of the centrifugal compressor 1.SOLUTION: An impeller 11 is rotatably provided in a housing 3. The impeller 11 includes a wheel 13, a plurality of full blades 19, and a plurality of splitter blades 21. A plurality of through-holes 31 are formed from the back 13d of the wheel 13 to the central part of the outer peripheral surface 13h. The plurality of through-holes 31 are arranged at regular intervals on the circumference centering around the axial center 13c of the wheel 13. An opening 31a on the tip side of each through-hole 31 is located at the root of the splitter blade 21.

Description

  The present invention relates to a centrifugal compressor that is used in a supercharger, a gas turbine, an industrial air facility, and the like and compresses a gas such as air using centrifugal force.

  In recent years, various studies have been made to expand the operating range of a centrifugal compressor, and there are those shown in Patent Document 1 and Patent Document 2 as centrifugal compressors having an expanded operating range.

  Hereinafter, a centrifugal compressor according to the prior art will be described with reference to FIG.

  Here, FIG. 5 is a schematic cross-sectional side view of the main part of the centrifugal compressor according to the prior art. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 5, the centrifugal compressor 101 according to the prior art includes a housing 103, and the housing 103 has a shroud 103 s inside. An impeller 105 is rotatably provided in the shroud 103s of the housing 103. The impeller 105 is rotatable around an axis 107c (in other words, an axis of the impeller 105), and A plurality of blades 109 (only one is shown) are provided on the outer peripheral surface 107 h of the wheel 107 at intervals. Here, the outer peripheral surface 107 h of the wheel 107 extends radially outward from the axial direction of the wheel 107 (in other words, the axial direction of the impeller 105), and the tip edge (outer edge) 109 t of each blade 109 is formed in the housing 103. It extends along the shroud 103s.

  An inlet 111 for sucking air A (an example of gas) is formed on the inlet side (upstream side) of the impeller 105 in the housing 103, and on the outlet side (downstream side) of the impeller 105 inside the housing 103. An annular diffuser flow path 113 (one of the exhaust flow paths) for exhausting the compressed air A by decelerating is formed. In addition, a bleed hole 115 is formed on the downstream side of the front edge 109f (front edge position) of the blade 109 in the shroud 103s of the housing 103. An outflow hole 117 through which air A can flow out to the inlet side of the impeller 105 is formed on the upstream side of the front edge 109 f of 109. An annular treatment cavity 119 that allows the flow of air A from the extraction hole 115 side to the outflow hole 117 side is formed inside the housing 103.

  Therefore, when operating the centrifugal compressor 101, by rotating the impeller 105, the air A sucked from the suction port 111 to the impeller 105 side can be compressed by utilizing the centrifugal force. The compressed air A is exhausted from the diffuser channel 113.

  If the flow rate (actual flow rate) of the air A sucked from the suction port 111 decreases during the operation of the centrifugal compressor 101, a part of the air A sucked into the impeller 105 side flows backward and the air is extracted into the air extraction hole 115. And flows into the treatment cavity 119. The air A that has flowed into the treatment cavity 119 flows from the extraction hole 115 side to the outflow hole 117 side, and then flows out from the outflow hole 117 to the inlet side of the impeller 105. Thereby, a part of the air A sucked into the impeller 105 side is circulated between the outflow hole 117 and the bleed hole 115, so that the apparent flow rate of the air A sucked into the impeller 105 side is larger than the actual flow rate. can do. Therefore, surging of the centrifugal compressor 101 can be suppressed, and the operating range of the centrifugal compressor 101 can be expanded to the low flow rate side.

JP 2006-342682 A JP 2003-31496 A

  By the way, in the centrifugal compressor 101 according to the above-mentioned prior art, although the surging of the centrifugal compressor 101 can be suppressed and the operating range of the centrifugal compressor 101 can be expanded to the low flow rate side, the housing 103 has an annular shape. The treatment cavity 119 needs to be formed, which leads to an increase in the size of the housing 103 and a complicated configuration of the housing 103, in other words, an increase in the size of the centrifugal compressor 101 and a complicated configuration of the centrifugal compressor 101. There is.

  That is, there is a problem that it is difficult to expand the operating range of the centrifugal compressor 101 to the low flow rate side while reducing the size of the centrifugal compressor 101 and simplifying the configuration of the centrifugal compressor 101.

  Then, an object of this invention is to provide the centrifugal compressor of a novel structure which can solve the above-mentioned problem.

  The present invention is characterized in that, in a centrifugal compressor that compresses gas using centrifugal force, a housing having a shroud (inner wall) on the inside, a shaft that is rotatably provided in the housing, and a shaft center (axial center of a wheel) ) A wheel that is rotatable around and has an outer peripheral surface extending radially outward from the axial direction (the axial direction of the wheel), and a front end edge (outer edge) that is provided on the outer peripheral surface of the wheel with a spacing in the circumferential direction And an impeller provided with a plurality of blades extending along the shroud of the housing, and an inlet (intake) of gas to the inlet side (upstream side) of the impeller in the housing An exhaust passage for exhausting compressed gas is formed on the outlet side (downstream side) of the impeller in the interior of the housing. It is summarized as the through hole to the center portion or the front end surface is formed.

  In the specification and claims of the present application, “upstream” means upstream from the flow direction of the mainstream gas, and “downstream” means from the flow direction of the mainstream gas. It is downstream.

  According to the feature of the present invention, when the centrifugal compressor is operated, the gas sucked from the suction port to the impeller side can be compressed by using the centrifugal force by rotating the impeller. . The compressed gas is exhausted from the exhaust passage.

  When the flow rate (actual flow rate) of gas sucked from the suction port is reduced during operation of the centrifugal compressor, a part of the compressed gas is transferred from the outlet side of the impeller to the back side of the wheel (near the back side). ) Through the through hole. Then, the gas that has flowed into the through hole flows toward the tip of the through hole, and flows out from the opening on the tip side of the through hole. That is, without forming a treatment cavity inside the housing, only the through hole is formed from the rear surface of the wheel to the central portion or the tip surface of the outer peripheral surface, and a part of the compressed gas is discharged to the outlet side of the impeller. And the flow rate of the gas flowing toward the outlet side of the impeller can be made larger than the actual flow rate.

  According to the present invention, without forming a treatment cavity inside the housing, only the through hole is formed from the rear surface of the wheel to the center portion or the front end surface of the outer peripheral surface, toward the outlet side of the impeller. Since the flow rate of the flowing gas can be larger than the actual flow rate, the surging of the centrifugal compressor is suppressed while reducing the size of the centrifugal compressor and simplifying the configuration of the centrifugal compressor. The operating range of the centrifugal compressor can be expanded to the low flow rate side.

FIG. 1 is a partial side sectional view of a centrifugal compressor according to a first embodiment. FIG. 2 is a side sectional view of the centrifugal compressor according to the first embodiment. FIG. 3 is a view of the wheel in the centrifugal compressor according to the first embodiment as viewed from the front end side, and the formation positions of the full blade and the splitter blade are indicated by two-dot chain lines. FIG. 4 is a partial side sectional view of a centrifugal compressor according to the second embodiment. FIG. 5 is a schematic side sectional view of a centrifugal compressor according to the prior art.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 to 3. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG.1 and FIG.2, the centrifugal compressor 1 which concerns on 1st Embodiment is used for a supercharger, and compresses air A (an example of gas) using a centrifugal force. And the specific structure of the centrifugal compressor 1 which concerns on embodiment of this invention is as follows.

  A centrifugal compressor 1 according to an embodiment of the present invention includes a housing 3, and the housing 3 is provided on a housing main body 5 having a shroud (inner wall) 5 s on the inner side and a rear side of the housing main body 5. The seal plate (cover plate) 7 and the like. The seal plate 7 is integrally connected or integrally formed with another housing (bearing housing) 9 in the supercharger.

  An impeller 11 is rotatably provided in the shroud 5s of the housing body 5. Specifically, a wheel 13 is provided in the shroud 5 s of the housing body 5, and the outer peripheral surface 13 h of the wheel 13 is radially outward from the axial direction of the wheel 13 (in other words, the shaft of the impeller 11. The rear surface 13 d of the wheel 13 faces the seal plate 7. The wheel 13 is integrally connected to one end portion (front end portion) of a rotor shaft (turbine shaft) 15 rotatably provided in another housing 9 via a fixing nut 17. It can rotate around the axis 13c (in other words, the axis of the impeller 11 or the axis of the rotor shaft 15). Furthermore, two types of full blades 19 and splitter blades 21 having different axial lengths are alternately provided on the outer peripheral surface 13h of the wheel 13 at intervals in the circumferential direction. One full blade 19 and a splitter blade 21 disposed between the adjacent full blades 19. Here, the front edge 19f of the full blade 19 is located on the upstream side (front side) of the front edge 21f of the splitter blade 21, and the front edge (outer edge) 19t of each full blade 19 and the splitter blade 21 The tip edge 21t extends along the shroud 5s of the housing body 5. Instead of using two types of blades 19 and 21 having different axial lengths, blades having the same axial length may be used.

  A suction port (supply port) 23 for sucking (supplying) air A to the impeller 11 is formed in the front side portion of the housing body 5, and this suction port 23 is an air cleaner (illustrated) for purifying the air A. (Omitted) can be connected. An annular diffuser flow path 25 (an example of an exhaust flow path) that decelerates and exhausts the compressed air A is formed on the outlet side (downstream side) of the impeller 11 in the housing main body 5. A spiral scroll channel 27 (an example of an exhaust channel) is formed on the outer peripheral side of the diffuser channel 25 in the interior. Further, a discharge port 29 for discharging air A is formed at an appropriate position of the housing body 5, and this discharge port 29 communicates with the diffuser flow path 25 via the scroll flow path 27, and is used as an internal combustion engine. It can be connected to an intake manifold (not shown) of the engine.

  Then, the characteristic part of 1st Embodiment is demonstrated.

  As shown in FIGS. 1 and 3, a plurality of through holes 31 are formed from the back surface 13 d of the wheel 13 to the central portion of the outer peripheral surface 13 h, and the plurality of through holes 31 are centered on the axis 13 c of the wheel 13. Are arranged at equal intervals on the circumference. Further, each through hole 31 extends in parallel to the axial direction of the wheel 13, and the front end side opening 31 a of each through hole 31 is located at the root of the splitter blade 21. Furthermore, the base end side opening part 31b of each through-hole 31 can flow in a part of the compressed air A from the back surface 13d side of the wheel 13 (between the back surface 13d of the wheel 13 and the seal plate 7), The front end side opening 31a of each through hole 31 can flow a part of the compressed air A to the upstream side (inlet side of the impeller 11). If a part of the tip surface 13t of the wheel 13 protrudes from the fixing nut 17, a plurality of through holes 31 may be formed from the back surface 13d of the wheel 13 to the tip surface 13t. A part or all of the hole 31 may be inclined with respect to the axial direction of the wheel 13.

  Then, the effect | action and effect of 1st Embodiment are demonstrated.

  By rotating the rotor shaft 15 by the rotation of a turbine wheel (not shown) and rotating the impeller 11 integrally, the air A sucked into the impeller 11 side from the suction port 23 is compressed by utilizing centrifugal force. be able to. The compressed air A is exhausted from the diffuser flow path 25 and discharged from the discharge port 29 via the scroll flow path 27.

  If the flow rate (actual flow rate) of the air A sucked from the suction port 23 decreases during the operation of the centrifugal compressor 1, a part of the compressed air A is transferred to the hub surface (the wheel 13 of the wheel 13) on the outlet side of the impeller 11. It flows into the plurality of through holes 31 from the vicinity of the surface along the outer peripheral surface 13h via the back surface 13d side (near the back surface 13d) of the wheel 13. Then, a part of the air A that has flowed into the plurality of through holes 31 flows toward the distal end of the through holes 31 and flows out from the distal end side openings 31 a of the plurality of through holes 31. That is, a plurality of through holes 31 are formed from the back surface 13d of the wheel 13 to the central portion of the outer peripheral surface 13h without forming a treatment cavity (see the description of [Background Art]) inside the housing 3 (housing body 5). By simply circulating a part of the compressed air A between the outlet side of the impeller 11 and the tip of the through hole 31, the apparent flow rate of the air A flowing toward the outlet side of the impeller 11 is actually reduced. More than the flow rate.

  Further, as described above, a part of the compressed air A flows from the vicinity of the hub surface on the outlet side of the impeller 11 into the plurality of through holes 31 via the back surface 13d side of the wheel 13, so that the impeller 11 The backflow region (peeling region) in the vicinity of the hub surface on the outlet side can be reduced.

  Therefore, according to the first embodiment, without forming the treatment cavity inside the housing 3, it is only necessary to form the plurality of through holes 31 from the back surface 13 d of the wheel 13 to the center portion of the outer peripheral surface 13 h. Since the apparent flow rate of the air A flowing toward the outlet side can be larger than the actual flow rate, the centrifugal compressor 1 can be surging while reducing the size of the centrifugal compressor 1 and simplifying the configuration of the centrifugal compressor 1. It can suppress and can expand the operation area of the centrifugal compressor 1 to the low flow rate side. In particular, since the backflow region in the vicinity of the hub surface on the outlet side of the impeller 11 can be reduced, surging of the centrifugal compressor 1 can be sufficiently suppressed, and the operating range of the centrifugal compressor 1 can be further expanded to the low flow rate side. .

(Second Embodiment)
A second embodiment will be described with reference to FIG. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 4, the centrifugal compressor 33 according to the second embodiment has the same configuration as the centrifugal compressor 1 (see FIG. 1) according to the first embodiment, and the configuration of the centrifugal compressor 33. Among these, only the parts different from the configuration of the centrifugal compressor 1 will be described. In addition, about the component corresponding to the component in the centrifugal compressor 1 among several components in the centrifugal compressor 33, the same number is attached | subjected in drawing.

  That is, in the centrifugal compressor 33 according to the second embodiment, the opening center 31ac of the distal end side opening 31a of each through hole 31 is directed to the shroud 5s side of the housing body 5 and the inlet side of the impeller 11. It is like that. Thereby, the apparent flow rate of the air A flowing in the shroud 5s side of the housing body 5 out of the air A flowing toward the outlet side of the impeller 11 can be made larger than the actual flow rate.

  Therefore, according to the second embodiment, in addition to the effects of the first embodiment, surging of the centrifugal compressor 33 is more sufficiently suppressed, and the operating range of the centrifugal compressor 1 is further expanded on the low flow rate side. be able to.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, It can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Housing 5 Housing main body 5s Shroud 7 Seal plate 11 Impeller 13 Wheel 13c Wheel shaft center 13d Wheel back surface 13h Wheel outer peripheral surface 13t Wheel front end surface 15 Rotor shaft 19 Full blade 19f Full blade front edge 19t Full blade front edge 21 Splitter blade 21f Splitter blade front edge 21t Splitter blade front edge 23 Suction port 25 Diffuser flow path (example of exhaust flow path)
27 Scroll channel (example of exhaust channel)
29 Discharge port 31 Through hole 31a Opening side opening 31ac of through hole Opening center 31b of opening side of opening side of through hole Proximal side opening part 33 of through hole

Claims (4)

In a centrifugal compressor that compresses gas using centrifugal force,
A housing having a shroud inside;
A wheel rotatably provided in the housing, rotatable around an axial center and having an outer peripheral surface extending radially outward from an axial direction; and an outer peripheral surface of the wheel provided at a circumferential interval; and An impeller having a plurality of blades extending so that a leading edge extends along the shroud of the housing;
An inlet for sucking gas is formed on the inlet side of the impeller in the housing, and an exhaust passage for exhausting compressed gas is formed on the outlet side of the impeller in the housing,
A centrifugal compressor characterized in that a through hole is formed from the rear surface of the wheel to the central portion or the front end surface of the outer peripheral surface. The plurality of blades are composed of a plurality of full blades and a splitter blade disposed between adjacent full blades and having a leading edge located downstream of the front edge of the full blade,
2. The centrifugal compressor according to claim 1, wherein a front end side opening of the through hole is located at a root portion of a front edge of the splitter blade.   3. The centrifugal compressor according to claim 1, wherein an opening center of a front end side opening portion of the through hole is directed to the shroud side of the housing.   The number of the through holes is a plurality, and the plurality of through holes are arranged at equal intervals on a circumference centered on the axis of the wheel. A centrifugal compressor according to any one of the claims.

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