JP2009068373A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the compressor efficiency of a centrifugal compressor 1 in a lower flow rate operating range while enlarging the operating range of the centrifugal compressor 1 to the lower flow rate side. <P>SOLUTION: The centrifugal compressor is provided with an outer ring 13 coupled to a front end of an outer edge in a plurality of impeller blades 7, an annular housing recessed part 15 for housing an outer ring 13 in a shroud wall 3f of a casing 3, an annular downstream auxiliary passage 17 partitioned between a rear side wall surface of the housing recessed part 15 and a rear side surface of the outer ring 13, an upstream auxiliary hole 19 in an upstream side of a front edge position of an impeller blade 7 in the shroud wall 3f of the casing 3, and an annular treatment cavity 21 for allowing the flow of gas from the downstream auxiliary passage 17 to the upstream auxiliary hole 19 side inside the casing 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor that is used in a turbocharger, 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. 3 is a longitudinal sectional view of a centrifugal compressor according to the prior art. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  The centrifugal compressor 101 according to the prior art includes a casing 103, and the casing 103 has a shroud wall 103f on the inner side. A hub 105 is disposed in the shroud wall 103f of the casing 103, and the hub 105 is rotatable about an axis (axis of the hub 105). Further, a plurality (only one is shown) of impeller blades 107 are provided on the outer peripheral surface of the hub 105 along the circumferential direction, and the outer edges of the impeller blades 107 are close to the shroud wall 103f of the casing 103, respectively. It is.

  An air supply port 109 for supplying air to the impeller blade 107 side is formed at the front peripheral edge of the shroud wall 103 f of the casing 103, and compressed air is provided at the rear peripheral edge of the shroud wall 103 f of the casing 103. An annular exhaust passage 111 for exhausting the air is formed. A slit-shaped downstream auxiliary hole 113 is formed downstream of the front edge position of the impeller blade 107 in the shroud wall 103f of the casing 103 (on the downstream side as viewed from the gas flow, in other words, on the rear side). A slit-like upstream auxiliary hole 115 is formed upstream of the front edge position of the impeller blade 107 in the shroud wall 103f of the casing 103 (upstream from the gas flow, in other words, the front). ing. Further, an annular treatment cavity 117 that allows air to flow from the downstream auxiliary hole 113 side to the upstream auxiliary hole 115 side is formed inside the casing 103, and the treatment cavity 117 is connected to the downstream auxiliary hole 113 and the upstream auxiliary hole 115. It communicates with the auxiliary hole 115.

  Therefore, when the centrifugal compressor 101 is operated, the hub 105 is rotated by, for example, rotation of a turbine wheel (not shown), and the plurality of impeller blades 107 are integrally rotated. Thereby, the air supplied from the air supply port 109 to the impeller blade 107 side can be compressed using the centrifugal force, and the compressed air can be exhausted from the exhaust passage 111.

Further, when the flow rate of air supplied from the air supply port 109 decreases during the operation of the centrifugal compressor 101, a part of the air supplied to the impeller blade 107 flows backward, and the treatment is performed from the downstream auxiliary hole 113. It flows into the cavity 117. The air flowing into the treatment cavity 117 flows from the downstream auxiliary hole 113 side to the upstream auxiliary hole 115 side, flows out of the upstream auxiliary hole 115, and is supplied again to the impeller blade 107 side. That is, the surging phenomenon of the centrifugal compressor 101 can be suppressed by circulating a part of the air supplied to the impeller blade 107 side between the downstream auxiliary hole 113 and the upstream auxiliary hole 115. Therefore, 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, during operation of the centrifugal compressor, a so-called clearance flow that flows relatively from the pressure surface side to the suction surface side of the impeller blade 107 occurs via the clearance between the shroud wall 103f of the casing 103 and the outer edge of the impeller blade 107. . Further, when the flow rate of the air supplied from the air supply port 109 decreases, the air inflow angle with respect to the positive pressure surface of the impeller blade 107 increases, and the clearance flow at the front end portion of the outer edge of the impeller blade 107 increases. Therefore, even if the operating range of the centrifugal compressor 101 is expanded to the low flow rate side, in the low flow rate operating range, the air flow between the adjacent impeller blades 107 is caused by the clearance flow at the front end portion of the outer edge of the impeller blade 107. A large turbulence will occur, and energy loss between adjacent impeller blades 107 will increase, leading to a reduction in compressor efficiency of the centrifugal compressor 101 in the low flow rate operating region.

  That is, it is a problem that the centrifugal compressor 101 according to the prior art is not sufficient to improve the compressor efficiency of the centrifugal compressor 101 in the low flow rate operating range while expanding the operating range of the centrifugal compressor 101 to the low flow rate side. There is.

  It is possible to eliminate the clearance flow by providing an outer sleeve connected from the front end portion to the rear end portion of the outer edge of the plurality of impeller blades 107, but a part of the air supplied to the impeller blade 107 side. Cannot be circulated, and the operating range of the centrifugal compressor 101 cannot be expanded to the low flow rate side.

  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 casing having a shroud wall on the inside thereof, and a shaft center (axial center of a hub) are disposed in the shroud wall of the casing. ) And a plurality of impeller blades provided along the outer peripheral surface of the hub and having outer edges close to the shroud wall, respectively, on the front peripheral edge of the shroud wall of the casing An air supply port for supplying gas to the impeller blade side is formed, and an annular exhaust passage for exhausting compressed gas is formed at a rear peripheral edge portion of the shroud wall of the casing, and a plurality of the impeller blades An outer ring is provided to be connected to the front end of the outer edge, and an annular receiving recess for receiving the outer ring is formed in the shroud wall of the casing. An annular downstream auxiliary passage is formed between the rear side wall surface of the housing recess and the rear side surface of the outer ring, and is upstream of the front edge position of the impeller blade in the shroud wall of the casing. An upstream auxiliary hole is formed on the upstream side, in other words, the front side when viewed from the flow, and an annular treatment cavity is formed inside the casing to allow gas flow from the downstream auxiliary passage side to the upstream auxiliary hole side. The gist is that the treatment cavity communicates with the downstream auxiliary passage and the upstream auxiliary hole.

The front side is the upstream side when viewed from the gas flow, and the rear side is the downstream side when viewed from the gas flow. According to the characteristics of the present invention, the centrifugal compressor is operated. When doing so, the said hub is rotated and the said several impeller blade is rotated integrally. Thereby, the gas supplied to the impeller blade side from the air supply port can be compressed using centrifugal force, and the compressed gas can be exhausted from the exhaust passage.

  Further, during operation of the centrifugal compressor, when the flow rate of the gas supplied from the air supply port decreases, a part of the gas supplied to the impeller blade side flows backward, and the downstream auxiliary passage passes through the downstream auxiliary passage. It flows into the treatment cavity. Then, the gas flowing into the treatment cavity flows from the downstream auxiliary passage side to the upstream auxiliary hole side, flows out of the upstream auxiliary hole, and is supplied again to the impeller blade side. That is, part of the gas supplied to the impeller blade can be circulated between the downstream auxiliary passage and the upstream auxiliary hole to suppress the surging phenomenon of the centrifugal compressor.

  Further, the outer ring is provided so as to be connected to the front end portions of the outer edges of the plurality of impeller blades, and the annular housing recess for housing the outer ring is formed in the shroud wall of the casing. Therefore, even in a low flow rate operating region, it is possible to suppress the clearance flow at the front end portion of the outer edge of the impeller blade and stabilize the gas flow between the adjacent impeller blades.

  According to the present invention, since the surging phenomenon of the centrifugal compressor can be suppressed and the gas flow between the adjacent impeller blades can be stabilized even in a low flow rate operation region, the operation of the centrifugal compressor It is possible to improve the compressor efficiency of the centrifugal compressor in the low flow rate operation region while expanding the region to the low flow rate side.

  An embodiment of the present invention will be described with reference to FIG.

  Here, FIG. 1 is a longitudinal sectional view of a centrifugal compressor according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a centrifugal compressor according to a modification of the embodiment of the present invention. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 1, a centrifugal compressor 1 according to an embodiment of the present invention is used in a turbocharger, and compresses air (an example of gas) using centrifugal force. And the specific structure of the centrifugal compressor 1 which concerns on embodiment of this invention is as follows.

  The centrifugal compressor 1 includes a casing 3, and the casing 3 has a shroud wall 3f on the inner side. The casing 3 is integrally attached to another casing (not shown) of the turbocharger.

  A hub 5 is disposed in the shroud wall 3f of the casing 3, and the hub 5 is integrally connected to one end of a turbine shaft TS rotatably provided in another casing. It can rotate around an axis (the axis of the hub 5, in other words, the axis of the turbine shaft TS). A turbine wheel (not shown) is integrally connected to the other end of the turbine shaft TS.

  A plurality of (only one shown) impeller blades 7 are provided along the circumferential direction on the outer peripheral surface of the hub 5, and the outer edges of the impeller blades 7 are close to the shroud wall 3 f of the casing 3, respectively. .

  An air supply port 9 for supplying air to the impeller blade 7 side is formed in the front peripheral edge of the shroud wall 3 f of the casing 3, and the air velocity is provided in the rear peripheral edge of the shroud wall 3 f of the casing 3. An annular diffuser flow path (exhaust flow path) 11 that exhausts compressed air while converting energy into pressure energy is formed. A scroll channel (not shown) is formed at the peripheral edge of the diffuser channel 11, and this scroll channel is connected to an intake manifold (not shown) of the internal combustion engine.

  An outer ring 13 is provided at the front end of the outer edge of the plurality of impeller blades 7, and an annular housing recess 15 for housing the outer ring 13 is formed on the shroud wall 3 f of the casing 3. Yes. Further, an annular downstream auxiliary passage 17 is defined between the rear side wall surface of the housing recess 15 and the rear side surface of the outer ring 13, and the front edge position of the impeller blade 7 on the shroud wall 3 f of the casing 3 is defined. In addition, a slit-like upstream auxiliary hole 19 is formed on the upstream side (upstream side when viewed from the gas flow, in other words, the front side). The slit-shaped upstream auxiliary hole 19 may be continuous in the circumferential direction around the axis of the casing 3 or may be discontinuous in the circumferential direction.

  An annular treatment cavity 21 that allows air to flow from the downstream auxiliary passage 17 side to the upstream auxiliary hole 19 side is formed continuously inside the casing 3 in the housing recess 15. The auxiliary passage 17 and the upstream auxiliary hole 19 communicate with each other. Instead of the treatment cavity 21 being continuously formed in the housing recess 15 in the casing 3, the treatment cavity 21 is formed in the casing 3 so as to be partitioned from the housing recess 15 as shown in FIG. It doesn't matter.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  When the centrifugal compressor 1 is operated, the hub 5 is rotated by the rotation of the turbine wheel, and the plurality of impeller blades 7 are integrally rotated. Thereby, the air supplied to the impeller blade 7 side from the air supply port 9 can be compressed using centrifugal force, and the compressed air can be exhausted from the diffuser flow path 11. Note that the air exhausted from the diffuser passage 11 is sent to the intake manifold of the internal combustion engine via the scroll passage.

  Further, when the flow rate of the air supplied from the air supply port 9 decreases during the operation of the centrifugal compressor 1, a part of the air supplied to the impeller blade 7 flows backward and treatment from the downstream auxiliary passage 17. It flows into the cavity 21. The air that has flowed into the treatment cavity 21 flows from the downstream auxiliary passage 17 side to the upstream auxiliary hole 19 side, flows out of the upstream auxiliary hole 19, and is supplied again to the impeller blade 7 side. That is, part of the air supplied to the impeller blade 7 side is circulated between the downstream auxiliary passage 17 and the upstream auxiliary hole 19, and the surging phenomenon of the centrifugal compressor 1 can be suppressed.

  Further, an outer ring 13 is provided so as to be connected to the front end portions of the outer edges of the plurality of impeller blades 7, and an annular housing recess 15 for housing the outer ring 13 is formed in the shroud wall 3 f of the casing 3. Therefore, even in a low flow rate operating region, the clearance flow at the front end portion of the outer edge of the impeller blade 7 can be suppressed, and the air flow between the adjacent impeller blades 7 can be stabilized.

  Further, since the front end portions of the outer edges of the plurality of impeller blades 7 are connected by the outer ring 13, the natural frequency of the plurality of impeller blades 7 can be increased and the vibration damping performance of the plurality of impeller blades 7 can be increased. .

  As described above, according to the embodiment of the present invention, the surging phenomenon of the centrifugal compressor 1 can be suppressed, and the air flow between the adjacent impeller blades 7 can be stabilized even in the low flow rate operation region. The compressor efficiency of the centrifugal compressor 1 in the low flow rate operating region can be improved while the operating range of the centrifugal compressor 1 is expanded to the low flow rate side.

  Further, since the natural frequency of the plurality of impeller blades 7 can be increased and the vibration damping performance of the plurality of impeller blades 7 can be increased, the stress concentration of the impeller blades 7 during operation of the centrifugal compressor 1 can be reduced, The fatigue life of the impeller blade 7 can be extended.

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

It is a longitudinal section of a centrifugal compressor concerning an embodiment of the present invention. It is sectional drawing of the centrifugal compressor which concerns on the modification of embodiment of this invention. It is a longitudinal cross-sectional view of the centrifugal compressor which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Casing 3f Shroud wall 5 Hub 7 Impeller blade 9 Air supply port 11 Diffuser flow path 13 Outer ring 15 Containing recessed part 17 Downstream auxiliary passage 19 Upstream auxiliary hole 21 Treatment cavity

Claims (2)

In a centrifugal compressor that compresses gas using centrifugal force,
A casing having a shroud wall on the inside;
A hub disposed within the shroud wall of the casing and rotatable about an axis;
A plurality of impeller blades provided along an outer peripheral surface of the hub and having outer edges respectively close to the shroud wall;
An air supply port for supplying gas to the impeller blade side at the front peripheral edge of the shroud wall of the casing, and an annular exhaust flow for discharging compressed gas to the rear peripheral edge of the shroud wall of the casing A road is formed,
An outer ring is provided to be connected to the front end of the outer edge of the plurality of impeller blades, and an annular housing recess for housing the outer ring is formed in the shroud wall of the casing,
An annular downstream auxiliary passage is formed between the rear side wall surface of the receiving recess and the rear side surface of the outer ring, and the upstream auxiliary passage is located closer to the gas flow than the front edge position of the impeller blade in the shroud wall of the casing. A hole is formed, and an annular treatment cavity that allows gas flow from the downstream auxiliary passage side to the upstream auxiliary hole side is formed in the casing, and the treatment cavity is formed in the downstream auxiliary passage and the upstream auxiliary hole. A centrifugal compressor characterized by being in communication.   The centrifugal compressor according to claim 1, wherein the treatment cavity is continuously formed in the housing recess.

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