JP2010048160A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the service life of an impeller 5 and to reduce power required to rotate the impeller 5, while sufficiently enhancing compressor efficiency of a centrifugal compressor 1. <P>SOLUTION: A downstream auxiliary hole 15 is formed downstream side of a front edge position of a blade 9 in a shroud wall 3f of a casing 3, an upstream auxiliary hole 17 is formed upstream of the front edge position of the blade 9 in the shroud wall 3f of the casing 3, an annular treatment cavity 19 for allowing an air flow from a downstream auxiliary hole 15 side to an upstream auxiliary hole 17 side is formed in the casing 3 and a spray mechanism 21 for spraying micro droplet D in the treatment cavity 19 is arranged at radially outside of the should wall 3f in the casing 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor that compresses a gas such as air using centrifugal force.

  In recent years, various developments have been made on centrifugal compressors used in vehicle superchargers, marine superchargers, gas turbines, and the like. Hereinafter, general centrifugal compressors will be described with reference to FIG. Here, FIG. 3 is a sectional side view of a general centrifugal compressor. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  The general centrifugal compressor 101 includes a casing 103, and the casing 103 has a shroud wall 103f on the inner side. An impeller 105 is rotatably provided in the shroud wall 103f of the casing 103, and the impeller 105 rotates around an axis (the axis of the hub 107, in other words, the axis of the impeller 105). A possible hub 107 and a plurality of blades 109 (only one is shown) are provided on the outer peripheral surface of the hub 107 at intervals. Here, the outer edge of each blade 109 extends along the shroud wall 103 f of the casing 103.

  An air supply port (intake port) 111 for supplying air (an example of gas) to the impeller 105 side is formed in the upstream peripheral portion (front peripheral portion) of the shroud wall 103f of the casing 103. An annular diffuser flow path (exhaust flow path) 113 is formed on the downstream peripheral edge (rear peripheral edge) of the shroud wall 103f of the casing 103 to decelerate and exhaust the compressed air.

  Therefore, for example, the plurality of blades 109 are rotated integrally with the hub 107 by driving a motor or the like (in other words, the impeller 105 is rotated). Thereby, the air supplied to the impeller 105 side from the air supply port 111 can be compressed using centrifugal force, and the compressed air can be decelerated from the diffuser flow path 113 and exhausted.

  By the way, in recent years, the need for a higher pressure ratio of the centrifugal compressor 101 has increased, and accordingly, the mainstream air temperature, particularly the air temperature on the outlet side of the impeller 105, has increased, and the creep life of the impeller 105 has been increased. It tends to decrease. As a countermeasure, a centrifugal compressor that suppresses an increase in the mainstream air temperature by a cooling action by heat of vaporization of fine water droplets has been developed (see Patent Document 1).

That is, in the centrifugal compressor according to the prior art, fine water droplets are appropriately sprayed from the spray mechanism (spray nozzle) disposed in front of the impeller in the shroud wall of the casing toward the impeller during operation. . As a result, fine water droplets can be vaporized in the mainstream air, and the mainstream air temperature can be lowered by the cooling action of this heat of vaporization. As a result, the temperature difference between the air temperature between the outlet side and the inlet side of the impeller is reduced. Can be small. Therefore, the creep life of the impeller can be extended, and the compression process in the centrifugal compressor can be brought close to the isothermal compression process, thereby reducing the power required for the rotation of the impeller.
Japanese Patent Application Laid-Open No. 11-148489

  However, in the centrifugal compressor according to the prior art, since the spray mechanism is disposed in front of the impeller in the shroud wall of the casing, the main flow is likely to be disturbed on the inlet side of the impeller, and the centrifugal compressor There is a risk of hindering improvement in compressor efficiency.

  Therefore, the present invention provides a centrifugal compressor having a novel configuration capable of extending the life of the impeller and reducing the power required for the rotation of the impeller while sufficiently improving the compressor efficiency of the centrifugal compressor. The purpose is to do.

  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 that is rotatably provided in the shroud wall of the casing. A hub rotatable around an axis (in other words, an axis of the impeller), and a circumferentially spaced outer periphery of the hub, and an outer edge extending along the shroud wall of the casing. An impeller having a plurality of blades, and an air supply port for supplying gas to the impeller side is formed at an upstream peripheral portion of the shroud wall of the casing, and the shroud wall of the casing An annular exhaust passage for exhausting the compressed gas is formed at the downstream peripheral edge, and downstream of the front edge position of the blade on the shroud wall of the casing. An auxiliary hole is formed, and an upstream auxiliary hole is formed on the upstream side of the front edge position of the blade in the shroud wall of the casing, and gas is introduced into the casing from the downstream auxiliary hole side to the upstream auxiliary hole side. An annular treatment cavity that allows flow is formed, and is disposed radially outside the shroud wall in the casing to spray fine water droplets in the treatment cavity, the upstream auxiliary hole, or the downstream auxiliary hole. And a spray mechanism.

  In the claims and the description, the “upstream side” means the upstream side when viewed from the mainstream flow direction, and the “downstream side” means the downstream side when viewed from the mainstream flow direction. That is.

  According to the characteristics of the present invention, when the centrifugal compressor is operated, the plurality of blades are rotated integrally with the hub (in other words, the impeller is rotated). Thereby, the gas supplied to the impeller side from the air supply port can be compressed using centrifugal force, and the compressed gas can be exhausted from the exhaust passage.

  Here, when the gas flow rate on the inlet side of the impeller decreases during the operation of the centrifugal compressor, a part of the gas supplied to the impeller side flows backward and enters the treatment cavity from the downstream auxiliary hole. Inflow. The gas that has flowed 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 to the impeller side again. In other words, a circulating flow can be generated between the downstream auxiliary hole and the upstream auxiliary hole so as to suppress the surging phenomenon of the centrifugal compressor.

  Further, when the gas flow rate on the inlet side of the impeller is small, fine water droplets are sprayed from the spray mechanism into the treatment cavity, the upstream auxiliary hole, or the downstream auxiliary hole. As a result, fine water droplets can be placed in the circulation flow and transferred from the upstream auxiliary hole to the main flow, and vaporized in the main flow gas, and the mainstream gas temperature can be lowered by the cooling action by the heat of vaporization. Furthermore, the temperature difference between the gas temperature on the outlet side and the inlet side of the impeller can be reduced. Here, since the spray mechanism is disposed on the outer side in the radial direction of the shroud wall in the casing, the main flow is not disturbed by the spray of fine water droplets by the spray mechanism.

  According to the present invention, the fine water droplets are vaporized in the mainstream gas without causing turbulence in the mainstream on the inlet side of the impeller, and the mainstream gas temperature is lowered by the cooling action by the heat of vaporization. Since the temperature difference between the gas temperature at the outlet side and the inlet side of the compressor can be reduced, the compressor efficiency of the centrifugal compressor can be sufficiently improved, while extending the life of the impeller, and the compression in the centrifugal compressor By bringing the process closer to the isothermal compression process, the power required for the rotation of the impeller can be reduced.

  An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  Here, FIG. 1 is a sectional side view of the centrifugal compressor according to the embodiment of the present invention, and FIG. 2 is an explanatory view of the operation of the centrifugal compressor according to 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 for a vehicle supercharger, a marine supercharger, a gas turbine, and the like, and uses centrifugal force for air (an example of gas). And compress it. 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. Moreover, the casing 3 is integrally attached to another casing (not shown) in a vehicle supercharger or the like.

  An impeller 5 is rotatably provided in the shroud wall 3f of the casing 3. Specifically, a hub 7 is provided in the shroud wall 3 f of the casing 3, and the outer peripheral surface of the hub 7 is in the axial direction (the axial direction of the hub 7, in other words, the shaft of the impeller 5. It gradually extends from the center direction toward the outside in the radial direction (the radial direction of the hub 7, in other words, the radial direction of the impeller 5). The hub 7 is integrally connected to one end portion (front end portion) of a rotor shaft S rotatably provided in another casing, and has a shaft center (the shaft center of the hub 7, in other words, an impeller. 5). Further, a plurality of blades 9 (only one is shown) are provided on the outer peripheral surface of the hub 7 at intervals in the circumferential direction, and the outer edge of each blade 9 extends along the shroud wall 3 f of the casing 3. Each extends.

  An air supply port (intake port) 11 for supplying air to the impeller 5 side (intake port) 11 is formed in the front peripheral portion of the shroud wall 3 f of the casing 3, and the rear peripheral portion of the shroud wall 3 f of the casing 3 Is formed with an annular diffuser flow path (exhaust flow path) 13 for decelerating and exhausting compressed air. A scroll flow path (not shown) is formed inside the casing 3 so as to surround the diffuser flow path 13, and this scroll flow path can be connected to an intake manifold (not shown) such as an internal combustion engine, for example. It is.

  On the downstream side of the front edge position of the blade 9 in the shroud wall 3f of the casing 3, one or a plurality of slit-like auxiliary holes 15 (only one is shown) are formed along the circumferential direction. On the upstream side of the front edge position of the blade 9 in the three shroud walls 3f, one or a plurality of (only one shown) upstream auxiliary holes 17 are formed along the circumferential direction. Here, an annular treatment cavity 19 that allows air to flow from the downstream auxiliary hole 15 side to the upstream auxiliary hole 17 side is formed inside the casing 3, and this treatment cavity 19 is connected to the downstream auxiliary hole 15. It communicates with the upstream auxiliary hole 17.

  Instead of the slit-shaped one or more downstream auxiliary holes 15 and / or upstream auxiliary holes 17 being formed along the circumferential direction, a plurality of round or square downstream auxiliary holes and / or upstreams are formed. The auxiliary holes may be formed at intervals in the circumferential direction.

  A plurality of (only one shown) spray mechanisms (spray nozzles) 21 for spraying the fine water droplets D into the treatment cavity 19 are provided on the radially outer side of the shroud wall 3 f in the casing 3 via the support pipe 23. The plurality of spray mechanisms 21 are arranged at intervals in the circumferential direction. The plurality of spray mechanisms 21 are connected to a water droplet generator 25 that generates water droplets via a connection circuit 27, and a flow rate control valve 29 such as an electromagnetic proportional control valve is disposed in the connection circuit 27. Has been. Here, the water droplet diameter of the fine water droplets D sprayed from the spray mechanism 21 is 10 μm or less, and preferably 3.0 μm or less.

  Instead of the spray mechanism 21 that sprays the fine water droplets D into the treatment cavity 19, a spray mechanism that sprays the fine water droplets D into the upstream auxiliary hole 17 or the downstream auxiliary hole 15 may be used.

  A controller 31 is disposed in the vicinity of the casing 3, and in addition to the flow control valve 29 described above, a temperature sensor 33 that detects the air temperature on the outlet side of the impeller 5 is electrically connected to the controller 31. It is connected. And the controller 31 adjusts the opening degree of the flow control valve 29 based on the detected value (air temperature on the outlet side of the impeller 5) detected by the temperature sensor 33, and the spray flow rate of the fine water droplets D of the spray mechanism 21. It has a function as a spray flow rate control part which controls. Specifically, when the detected value detected by the temperature sensor 33 is higher than the target temperature, the controller 31 increases the opening degree of the flow rate control valve 29 to increase the spray flow rate of the fine water droplets D of the spray mechanism 21. When the detected value detected by the temperature sensor 33 is lower than the target temperature, the degree of opening of the flow rate control valve 29 is reduced to reduce the spray flow rate of the fine water droplets D of the spray mechanism 21. . Here, the target temperature is a temperature set in advance higher than the saturation temperature of water vapor.

  Instead of controlling the spray flow rate of the fine water droplets D of the spray mechanism 21 based on the air temperature on the outlet side of the impeller 5, it correlates with the air temperature on the outlet side of the impeller 5, for example, the air flow rate on the outlet side of the impeller 5. You may control the spray flow volume of the fine water droplet D of the spray mechanism 21 based on the parameter which has a relationship.

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

  When the centrifugal compressor 1 is operated, the rotor shaft S is rotated by driving a motor (not shown) or rotating a turbine wheel (not shown), for example, so that a plurality of blades 9 are integrated with the hub 7. Rotate (in other words, the impeller 5 is rotated). Thereby, the air supplied to the impeller 5 side from the air supply port 11 can be compressed using centrifugal force, and the compressed air can be exhausted from the diffuser flow path 13.

  Here, when the air flow rate at the inlet side of the impeller 5 decreases during the operation of the centrifugal compressor 1, a part of the air supplied to the impeller 5 side flows backward as shown in FIG. 15 flows into the treatment cavity 19. The air flowing into the treatment cavity 19 flows from the downstream auxiliary hole 15 side to the upstream auxiliary hole 17 side, flows out of the upstream auxiliary hole 17, and is supplied again to the impeller 5 side. In other words, a circulating flow can be generated between the downstream auxiliary hole 15 and the upstream auxiliary hole 17 so as to suppress the surging phenomenon of the centrifugal compressor 1.

  When the air flow rate on the inlet side of the impeller 5 is small, the controller 31 controls the spray flow rate of the fine water droplets D on the spray mechanism 21 based on the air temperature on the outlet side of the impeller 5, and the treatment cavity from the spray mechanism 21. 19 is sprayed with fine water droplets D. As a result, the fine water droplets D can be placed in the circulating flow and transferred from the upstream auxiliary hole 17 to the main flow, and vaporized in the main flow air, and the cooling temperature by the heat of vaporization can lower the main flow air temperature. In particular, the temperature difference between the air temperature at the outlet side and the inlet side of the impeller 5 can be reduced. Here, since the spray mechanism 21 is disposed on the radially outer side of the shroud wall 3 f in the casing 3, the main flow is not disturbed by the spray of the fine water droplets D by the spray mechanism 21.

  Therefore, according to the embodiment of the present invention, fine water droplets D are vaporized in the mainstream air without causing turbulence in the mainstream on the inlet side of the impeller 5, and the mainstream air temperature is cooled by the cooling effect of the heat of vaporization. And the temperature difference between the air temperature at the outlet side and the inlet side of the impeller 5 can be reduced, so that the compressor efficiency of the centrifugal compressor 1 is sufficiently improved and the life of the impeller 5 is extended. The power required for the rotation of the impeller 5 can be reduced by bringing the compression process in the centrifugal compressor 1 closer to the isothermal compression process.

  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 sectional side view of the centrifugal compressor concerning the embodiment of the present invention. It is explanatory drawing of an effect | action of the centrifugal compressor which concerns on embodiment of this invention. It is a sectional side view of a common centrifugal compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Casing 3f Shroud wall 5 Impeller 7 Hub 9 Blade 11 Supply port 13 Diffuser flow path 15 Downstream auxiliary hole 17 Upstream auxiliary hole 19 Treatment cavity 21 Spray mechanism 23 Support pipe 25 Droplet generator 27 Connection circuit 29 Flow control Valve 31 Controller 33 Temperature sensor D Fine water droplet

Claims (2)

In a centrifugal compressor that compresses gas using centrifugal force,
A casing having a shroud wall on the inside;
A hub rotatably provided in the shroud wall of the casing and rotatable about an axis, and a circumferentially spaced outer peripheral surface of the hub and having an outer edge along the shroud wall of the casing An impeller having a plurality of blades each extending in the manner as described above,
An air supply port for supplying gas to the impeller side at the upstream peripheral portion of the shroud wall of the casing is formed, and an annular exhaust flow exhausting compressed gas to the downstream peripheral portion of the shroud wall of the casing A road is formed,
A downstream auxiliary hole is formed downstream of the blade front edge position in the shroud wall of the casing, and an upstream auxiliary hole is formed upstream of the blade front edge position of the casing shroud wall; An annular treatment cavity that allows a gas flow from the downstream auxiliary hole side to the upstream auxiliary hole side is formed in the casing,
And a spray mechanism that is disposed on a radially outer side of the shroud wall in the casing and sprays fine water droplets in the treatment cavity, the upstream auxiliary hole, or the downstream auxiliary hole. Centrifugal compressor.   2. A spray flow rate control means for controlling a spray flow rate of fine water droplets of the spray mechanism based on a gas temperature on the outlet side of the impeller or a parameter correlated with the gas temperature. The centrifugal compressor described in 1.

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