JP2009068372A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the compressor efficiency of a centrifugal compressor 1 while enlarging an operating range of the centrifugal compressor 1 to the lower flow rate side. <P>SOLUTION: The centrifugal compressor is formed with a downstream auxiliary hole 13 on a downstream side of a front edge position of an impeller blade 7 in a shroud wall 3f of a casing 3, an upstream auxiliary hole 15 on an upstream side of the front edge position of an impeller blade 7 in the shroud wall 3f of the casing 3, an annular treatment cavity 17 for allowing the flow of gas from the downstream auxiliary hole 13 side to the upstream auxiliary hole 15 side inside the casing 3, an expansion part 19 whose inner diameter is expanded in the shroud wall 3f of the casing 3 so as to be directed toward the downstream side from a front edge position of an opening of the upstream auxiliary hole 15, and a throttle part 21 whose inner diameter is gradually contracted to the downstream side of the expansion part 19 in the shroud wall 3f of 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. 4 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 (an example of gas) to the impeller blade 107 side is formed at the front peripheral edge of the shroud wall 103 f of the casing 103, and the rear peripheral edge of the shroud wall 103 f of the casing 103 is formed at the rear peripheral edge. Is formed with an annular exhaust passage 111 for exhausting compressed air. 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, when the air flowing into the treatment cavity 117 flows out of the upstream auxiliary hole 115, the flow of the main air is greatly disturbed, and as shown in FIG. A large energy loss region occurs on the rear side. Therefore, in the centrifugal compressor 101 according to the prior art, as described above, the surging phenomenon can be suppressed and the operating range of the centrifugal compressor 101 can be expanded to the low flow rate side. There is a problem that it is not easy to sufficiently improve the compressor efficiency.

  FIG. 2B is a diagram showing the distribution of energy loss of the centrifugal compressor according to the prior art in a dimensionless form, and the energy loss is obtained by CFD (Computational Fluid Dynamics) analysis. The larger the value, the greater the energy loss.

  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 on the outer peripheral surface of the hub along the circumferential direction and having outer edges respectively close to the shroud wall, and the front side of the shroud wall of the casing An air supply port for supplying gas to the impeller blade side is formed at the peripheral portion, and an annular exhaust passage for exhausting compressed gas is formed at the rear peripheral portion of the shroud wall of the casing. A downstream auxiliary hole is formed downstream of the front edge position of the impeller blade on the shroud wall (downstream side when viewed from the gas flow, in other words, rear side). An upstream auxiliary hole is formed upstream of the front edge position of the impeller blade in the shroud wall of the casing (upstream as viewed from the gas flow, in other words, in front), and the downstream auxiliary hole is formed inside the casing. An annular treatment cavity that allows gas flow from the side to the upstream auxiliary hole side is formed, the treatment cavity communicates with the upstream auxiliary hole and the downstream auxiliary hole, and has an inner diameter on the shroud wall of the casing. The gist of the present invention is that the inflated portion having a diameter increased from the front end position of the opening portion of the upstream auxiliary hole toward the downstream side.

  According to the feature of the present invention, when the centrifugal compressor is operated, the hub is rotated to integrally rotate the plurality of impeller blades. 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 the 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 It flows into the treatment cavity. Then, the gas flowing into the treatment cavity flows from the downstream auxiliary hole 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 hole and the upstream auxiliary hole to suppress the surging phenomenon of the centrifugal compressor.

  Further, since the expansion portion is formed on the shroud wall of the casing from the front end position of the opening portion of the upstream auxiliary hole toward the downstream side, the gas flowing out from the upstream auxiliary hole is coupled with the viscous action of gas. Flows along the inner wall of the expansion part (a part of the shroud wall of the casing), in other words, the flow of gas flowing out from the upstream auxiliary hole is in the same direction as the flow of the mainstream gas. Bend. Thus, the mainstream gas flow at the time of flowing out from the upstream auxiliary hole is not greatly disturbed, and it is possible to avoid a region having a large energy loss on the downstream side of the upstream auxiliary hole.

  According to the present invention, it is possible to suppress the surging phenomenon of the centrifugal compressor and to avoid the occurrence of a large energy loss region downstream of the upstream auxiliary hole. It is possible to improve the compressor efficiency of the centrifugal compressor.

  An embodiment of the present invention will be described with reference to FIG. 1, FIG. 2 (a), and FIG.

  Here, FIG. 1 is a longitudinal sectional view of a centrifugal compressor according to an embodiment of the present invention, and FIG. 2A is a non-dimensionalized energy loss distribution state of the centrifugal compressor according to the embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the gas flow rate and the compressor efficiency for the centrifugal compressor according to the embodiment of the present invention and 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. 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 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.

  A slit-like downstream auxiliary hole 13 is formed in the shroud wall 3f of the casing 3 on the downstream side of the front edge position of the impeller blade 7 (on the downstream side as viewed from the gas flow, in other words, on the rear side). A slit-like upstream auxiliary hole 15 is formed upstream of the front edge position of the impeller blade 7 in the shroud wall 3f of the casing 3 (upstream as viewed from the gas flow, in other words, in front). . The slit-shaped downstream auxiliary hole 13 and the slit-shaped upstream auxiliary hole 19 may be continuous in the circumferential direction or discontinuous in the circumferential direction.

  An annular treatment cavity 17 that allows air to flow from the downstream auxiliary hole 13 side to the upstream auxiliary hole 15 side is formed inside the casing 3. The treatment cavity 17 includes the downstream auxiliary hole 13 and the upstream auxiliary hole. 15 is communicated.

  In the shroud wall 3 f of the casing 3, an expanding portion 19 having an enlarged inner diameter is formed from the front end position of the opening portion of the upstream auxiliary hole 15 toward the downstream side. In other words, the inner diameter D1 of the shroud wall 3f of the casing 3 at the rear end position of the opening portion of the upstream auxiliary hole 15 is larger than the inner diameter D2 of the shroud wall of the casing 3 at the front end position of the opening portion of the upstream auxiliary hole 15. ing. The inner diameter D1 of the shroud wall 3f of the casing 3 at the rear end position of the opening of the upstream auxiliary hole 15 is smaller than the inner diameter Dcav of the treatment cavity 17.

  On the downstream side of the expansion portion 19 in the shroud wall 3 f of the casing 3, a throttle portion 21 whose inner diameter is gradually reduced is formed, and this throttle portion 21 is upstream of the front edge position of the impeller blade 7. positioned.

  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.

  In addition, when the flow rate of 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 is performed from the downstream auxiliary hole 13. It flows into the cavity 17. The air flowing into the treatment cavity 17 flows from the downstream auxiliary hole 13 side to the upstream auxiliary hole 15 side, flows out of the upstream auxiliary hole 15, and is supplied again to the impeller blade 7 side. That is, a part of the air supplied to the impeller blade 7 side is circulated between the downstream auxiliary hole 13 and the upstream auxiliary hole 15, and the surging phenomenon of the centrifugal compressor 1 can be suppressed.

  Further, since the expansion portion 19 is formed on the shroud wall 3f of the casing 3 from the front end position of the opening portion of the upstream auxiliary hole 15 toward the downstream side, the air flowing out from the upstream auxiliary hole 15 together with the viscous action of air. Flows along the inner wall of the expansion part 19 (a part of the shroud wall 3f of the casing 3), in other words, the flow of the air flowing out from the upstream auxiliary hole 15 is in the same direction as the flow of the mainstream air. Bend. As a result, the main flow of air flowing out of the upstream auxiliary hole 15 is not greatly disturbed, and as shown in FIG. 3A, a region with a large energy loss is generated on the downstream side of the upstream auxiliary hole 15. Can be avoided. In addition, the energy loss in Fig.3 (a) is calculated | required by CFD analysis, and it has shown that energy loss is so large that a numerical value is large.

  Further, since the throttle portion 21 is formed on the shroud wall 3f of the casing 3 on the downstream side of the expansion portion 19, the flow velocity of the air is once reduced in the expansion portion 19 and the flow velocity of the air is rapidly accelerated in the expansion portion 21. be able to. Thereby, the distortion level (air flow deviation) generated on the downstream side of the upstream auxiliary hole 15 can be reduced on the inlet side (near the upstream side) of the impeller blade 7.

  As described above, according to the embodiment of the present invention, while suppressing the surging phenomenon of the centrifugal compressor 1, it is possible to avoid the occurrence of a region with a large energy loss on the downstream side of the upstream auxiliary hole 15, and the upstream auxiliary hole. The distortion level generated on the downstream side of the impeller blade 7 can be relaxed on the inlet side of the impeller blade 7, so that the operating range of the centrifugal compressor 1 is expanded to the low flow rate side, and as shown in FIG. 1 compressor efficiency can be improved. 3 is obtained by CFD analysis of the compressor efficiency of the centrifugal compressor 1 according to the embodiment of the present invention, and the comparative example in FIG. 3 is related to the prior art. The compressor efficiency of the centrifugal compressor 101 (see FIG. 4) is obtained by CFD analysis.

  The present invention is not limited to the description of the above-described embodiment, and can be implemented in various other aspects. 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. FIG. 2 (a) is a diagram showing the distribution of energy loss of the centrifugal compressor according to the embodiment of the present invention in a dimensionless form, and FIG. 2 (b) is the energy loss of the centrifugal compressor according to the prior art. It is a figure which shows in a form which made the distribution state of non-dimensional. It is a figure which shows the relationship between the flow volume of gas and compressor efficiency about the centrifugal compressor which concerns on embodiment of this invention, and the centrifugal compressor which concerns on a prior art. 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 Downstream auxiliary hole 15 Upstream auxiliary hole 17 Treatment cavity 19 Expansion part 21 Restriction part

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 the circumferential direction on the 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,
A downstream auxiliary hole is formed downstream of the front edge position of the impeller blade in the shroud wall of the casing, and an upstream auxiliary hole is formed upstream of the front edge position of the impeller blade in the shroud wall of the casing. An annular treatment cavity that allows gas flow from the downstream auxiliary hole side to the upstream auxiliary hole side is formed in the casing, and the treatment cavity communicates with the upstream auxiliary hole and the downstream auxiliary hole. There,
The centrifugal compressor, wherein an expansion portion having an inner diameter increased on the shroud wall of the casing is formed toward a downstream side from a front end position of the opening portion of the upstream auxiliary hole.   A throttle part having an inner diameter gradually reduced is formed on the downstream side of the expansion part in the shroud wall of the casing, and the throttle part is located upstream of the front edge position of the impeller blade. The centrifugal compressor according to claim 1.

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