CENTRIFUGAL COMPRESSOR

Abstract

A centrifugal compressor is able to cause air to efficiently flow to an impeller thereof, and enables improvement of operating efficiency. The centrifugal compressor has: a casing having an inlet flow channel and a connection flow channel formed therein, the inlet flow channel having a suction port provided at one place thereof, the connection flow channel being connected to the inlet flow channel; a main shaft inserted in the casing; an impeller fixed to the main shaft and arranged in the inlet flow channel; and an inlet guide vane unit having a plurality of inlet guide vanes arranged upstream of the impeller of the inlet flow channel. In the inlet guide vane unit, an arrangement interval between inlet guide vanes at a suction port side is narrower than an arrangement interval of inlet guide vanes at a side opposite to the suction port side.

Description

TECHNICAL FIELD

One or more embodiments of the present invention relate to a centrifugal compressor having: inlet guide vanes; and a suction port at one place thereof.

BACKGROUND

Centrifugal compressors are used in turbo freezing machines, petrochemical plants, natural gas plants, and the like. In a centrifugal compressor, pressure increase due to centrifugal force is obtained by kinetic energy being given to a fluid by rotation of an impeller and the fluid being blown outward in a radial direction. Disclosed in Patent Literature 1 is a turbo charger (supercharger), which is one type of centrifugal compressors, and includes inlet guide vanes that straighten air that flows to an upstream side of an impeller (blades for compressor) and that adjust the amount of the air flowing therein (see Patent Literature 1).

CITATION LIST

Patent Literature

• Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2010-71140 A

SUMMARY

By the angle of the inlet guide vanes with respect to the impeller, that is, the opening, being made variable, and resistance in the flow channel being made changeable; the amount of air flowing therein is able to be adjusted. Further, in some centrifugal compressors, the inlet guide vanes are fixed. Centrifugal compressors have, in the rotating direction of the main shafts, distribution in the amount of fluid that flows to the impellers, and when the difference in the flow rate is increased, operating efficiency of centrifugal compressors is reduced.

One or more embodiments of the present invention may provide a centrifugal compressor that is able to cause air to efficiently flow to an impeller thereof, and enable improvement of operating efficiency.

A centrifugal compressor according to one or more embodiments of the present invention may include a casing having an inlet flow channel and a connection flow channel formed therein, the inlet flow channel having a suction port provided at one place thereof, the connection flow channel being connected to the inlet flow channel, a main shaft inserted in the casing, an impeller fixed to the main shaft, and arranged in the inlet flow channel, and an inlet guide vane unit having plural inlet guide vanes arranged upstream of the impeller of the inlet flow channel. In the inlet guide vane unit, an arrangement interval between the inlet guide vanes at the suction port side is narrower than an arrangement interval between the inlet guide vanes at a side opposite to the suction port side.

Here, it may be that in the inlet guide vane unit, arrangement intervals among a first group of the inlet guide vanes that are at an end portion side at the suction port side and that are 25% of all of the inlet guide vanes are narrower than arrangement intervals among a second group of the inlet guide vanes that are at an end portion side opposite to the suction port and that are 25% of all of the inlet guide vanes.

Further, it may be that in the inlet guide vane unit, a relation between a maximum value dmax and a minimum value dmin of intervals between the inlet guide vanes is expressed as 0.6≦dmin/dmax<1.0.

Further, it may be that in the inlet guide vane unit, intervals between the inlet guide vanes change, with reference to a reference line of a sine function along a rotating direction of the main shaft, in a range of equal to or less than 20% of amplitude of the reference line.

Further, it may be that in the inlet guide vane unit, a position where the interval between the inlet guide vanes is the widest is at a position moved to an upstream side in the rotating direction of the main shaft from an end portion opposite to the suction port by an angle larger than 0° and equal to or less than 40°.

Advantageous Effects of Invention

According to one or more embodiments of the present invention, by arrangement intervals of inlet guide vanes being changed according to positions thereof, circumferential direction distribution of a fluid flowing to an impeller is able to be equalized, and operating efficiency is able to be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a schematic configuration of a compressor according to one or more embodiments.

FIG. 2 is a sectional view along a line A-A of FIG. 1.

FIG. 3 is a partial enlarged view of an inlet guide vane unit.

FIG. 4 is a graph illustrating an example of distribution of flow rate of a fluid flowing therein.

FIG. 5 is a graph illustrating an example of a relation between positions and intervals of inlet guide vanes.

FIG. 6 is a schematic diagram illustrating an example of the inlet guide vanes.

FIG. 7 is a graph illustrating an example of a relation between positions and intervals of inlet guide vanes.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one or more embodiments according to the present invention will be described in detail, based on the drawings. The invention is not limited by this these embodiments. Further, components in one or more embodiments described below include any component easily substitutable by those skilled in the art or any component that is substantially the same. A compressor 1 may be used as an apparatus that supplies compressed air to a freezing machine, a petrochemical plant, a natural gas plant, or the like.

As illustrated in FIG. 1, the compressor (centrifugal compressor) 1 of one or more embodiments is a multistage compression type centrifugal compressor. In one or more embodiments, the compressor 1 will be described as a multistage compression type compressor, but the compressor 1 may be a single stage compression type compressor instead. The compressor 1 has a casing 2, a drive unit 4, a main shaft 6, and a compression unit 14.

The casing 2 is a housing, and has the drive unit 4, the main shaft 6, and the compression unit 14 accommodated therein. The casing 2 has a flow channel, through which a fluid to be compressed, which is air in one or more embodiments, flows, formed therein. The casing 2 has an opening at an upstream end of the flow channel, through which air flows, the opening serving as a suction port 12, and another opening at a downstream end of the flow channel, through which air flows, this latter opening serving as a discharge port 16. The compressor 1 of one or more embodiments has one suction port 12. In the casing 2, a flow channel for air, between the suction port 12 and the compression unit 14, serves as a suction flow channel 102. In the casing 2, a flow channel for air, between the discharge port 16 and the compression unit 14, serves as a discharge flow channel 104. In the compressor 1, the suction flow channel 102 is arranged in a direction inclined with respect to an axial direction of the main shaft 6, which is, in one or more embodiments, in a direction orthogonal to the axial direction of the main shaft 6.

The drive unit 4 has an electric motor and a power transmission unit. The drive unit 4 rotates the main shaft 6, by transmitting output of the electric motor through the power transmission unit to the main shaft 6. The main shaft 6 is inserted in the casing 2, and rotatably supported with respect to the casing 2. The main shaft 6 is rotated by the drive unit 4. A rotation unit of the compression unit 14 is fixed to the main shaft 6.

The compression unit 14 is arranged in the casing 2, compresses air flowing therein from the suction port 12, and discharges the compressed air from the discharge port 16. The compression unit 14 has compression units 18a, 18b, 18c, and 18d. The compression units 18a, 18b, 18c, and 18d are arranged between the suction flow channel 102 and the discharge flow channel 104, in this order. The compression unit 18a is connected to the suction flow channel 102. The compression unit 18d is connected to the discharge flow channel 104. Since the compression units 18a, 18b, 18c, and 18d are similarly formed except for only their arrangement positions, the compression unit 18a will be described as an example.

The compression unit 18a has a flow channel, which is formed, by the casing 2, so as to discharge a fluid after sucking in and compressing the fluid. The flow channel of the compression unit 18a has an inlet flow channel 33, and a return channel 35. An upstream side of the inlet flow channel 33 is connected to the suction flow channel 102, and a downstream side of the inlet flow channel 33 is connected to the return channel 35. A downstream side of the return channel 35 is connected to an inlet flow channel 33 of the compression unit 18b of the next stage. The compression unit 18a has an impeller 32 provided in the inlet flow channel 33, and a return vane 34 provided in the return channel 35. The impeller 32 is fixed to the main shaft 6. The impeller 32 has many blades 32a arranged on a surface thereof. The impeller 32 sends air that flows into the inlet flow channel 33 towards the return channel 35, by rotating together with the main shaft 6. With a downstream side of the impeller 32 serving as a diffuser, the inlet flow channel 33 decelerates the fluid that has been accelerated by the impeller 32, and raises pressure of the fluid. The return vane 34 is arranged in the return channel 35. The return vane 34 straightens the fluid flowing in the return channel 35. The fluid that has passed the return channel 35 flows into the compression unit 18b.

In the compressor 1, the main shaft 6 of the compression unit 14 rotates via the power transmission unit by drive of the electric motor of the drive unit 4. The impeller 32 then rotates together with the main shaft 6. Thereby, a fluid: is sucked in from the suction port 12; flows into the suction flow channel 102; flows into the inlet flow channel 33 of the compression unit 18a via an inlet guide vane unit 100; and is accelerated by the impeller 32, and thereafter, kinetic energy is converted to internal energy by the diffuser. Further, the fluid is turned back to the inlet flow channel 33 of the compression unit 18b by the return channel 35, and is accelerated by the impeller 32, and thereafter, kinetic energy is converted to internal energy by a diffuser. In the compressor 1, after being similarly compressed in the compression units 18c and 18d, the fluid is discharged from the discharge port 16 of the discharge flow channel 104.

Next, in addition to FIG. 1, by use of FIG. 2 to FIG. 3, the inlet guide vane unit (IGV, or guiding guide vanes) 100 will be described. FIG. 2 is a sectional view along a line A-A of FIG. 1. FIG. 3 is a partial enlarged view of the inlet guide vane unit.

The inlet guide vane unit 100 is, as described above, in a flowing direction of the fluid, arranged in a flow channel upstream of the impeller 32 of the compression unit 18a, which is arranged most upstream in the flowing direction of the fluid. The inlet guide vane unit 100 has plural inlet guide vanes 101. The plural inlet guide vanes 101 are arranged over the entire circumference of the main shaft 6, at predetermined intervals in a rotating direction of the main shaft 6, as illustrated in FIG. 2. That is, an inlet guide vane 101 is arranged at a distance from an inlet guide vane 101 adjacent thereto in the rotating direction (circumferential direction) of the main shaft 6. The inlet guide vanes 101 are each a plate like member extending in a radial direction of the main shaft 6. Depending on their positions in the rotating direction, the inlet guide vanes 101 are shaped differently, and their surfaces at the suction port 12 side are curved surfaces convexed to a side opposite to the suction port 12 so as to guide the air flowing therein from the suction port 12 to the center side of the main shaft 6. The air that has flown in from the suction port 12 passes between the inlet guide vanes 101 and advances to a position, at which the impeller 32 of the inlet flow channel 33 is arranged.

In the inlet guide vane unit 100, when an interval between the inlet guide vanes 101 is d, this interval changes depending on the position in the rotating direction of the main shaft 6. The interval d is, as illustrated in FIG. 3, a diameter of the smallest circle that joins end portions of two adjacent inlet guide vanes 101, the end portions being at the center side of the main shaft 6. In the inlet guide vane unit 100, an interval between the inlet guide vanes 101 of a suction port side end portion 120 is narrower than an interval between the inlet guide vanes 101 of a terminal side end portion 122. The suction port side end portion 120 is a position nearest to the suction port 12 along a rotating direction R of the main shaft 6. The terminal side end portion 122 is a position nearest to a terminal 112 along the rotating direction R of the main shaft 6. The terminal 112 is a position opposite to the suction port 12 in the flowing direction of the air in the suction flow channel 102, and is a position rotated by 180 degrees from the suction port side end portion 120 in the rotating direction R. In one or more embodiments, the terminal side end portion 122 is 0 degrees, and the angle that increases as rotated in the rotating direction R (circumferential direction position) is 8.

FIG. 4 is a graph illustrating an example of distribution of flow rate of a fluid flowing therein. FIG. 4 is measurement results of weight flow rate of air (air that has passed the inlet guide vanes 101) that flows into the inlet flow channel 33 of the compressor 1 according to one or more embodiments, in which the interval between the inlet guide vanes 101 of the suction port side end portion 120 has been made narrower than the interval between the inlet guide vanes 101 of the terminal side end portion 122. A comparative example is measurement results of weight flow rate when intervals between inlet guide vanes 101 are made constant along the rotating direction R. By the interval between the inlet guide vanes 101 of the suction port side end portion 120 being made narrower than the interval between the inlet guide vanes 101 of the terminal side end portion 122, through adjustment of the intervals between the inlet guide vanes 101 according to their positions; even if the compressor 1 has a suction port at one place and is configured such that air flows in only from a part of the circumferential direction, as illustrated in FIG. 4, the weight flow rate of the air at positions (circumferential direction positions) along the rotating direction R is able to be equalized. Specifically, by adjustment of the intervals between the inlet guide vanes 101, the weight flow rate of air is able to be more equalized than when the intervals are made constant. The inlet guide vane unit 100 is able to supply air to the impeller 32 evenly.

In the inlet guide vane unit 100, arrangement intervals among a first group 130 of inlet guide vanes 101 at the suction port side end portion 120 side, the first group 130 being 25% of all the inlet guide vanes 101, are possibly narrower than arrangement intervals among a second group 132 of inlet guide vanes 101 at the terminal side end portion 122 side, the second group 132 being 25% of all the inlet guide vanes 101. If the number of inlet guide vanes 101 that are 25% of all of the inlet guide vanes 101 includes a decimal point, the numerical value is rounded up. In the inlet guide vane unit 100, by the arrangement intervals of the first group 130 being made narrower than the arrangement intervals of the second group 132, the weight flow rate of air is able to be equalized. The inlet guide vane unit 100 is able to supply air to the impeller 32 evenly.

Further, in the above description, the intervals of the inlet guide vanes 101 that are 25% of the total number of inlet guide vanes 101 arranged at each of the suction port side end portion 120 side and the terminal side end portion 122 side are compared with each other, but limitation is not made thereto. In the inlet guide vane unit 100, intervals between inlet guide vanes included in a range of 45 degrees before and after a base point, which is the suction port side end portion 120, that is, in a range of 90°, may be made narrower than intervals of inlet guide vanes 101 included in a range of 45° before and after a base point, which is the terminal side end portion 122, that is, in a range of 90°. By the intervals between the inlet guide vanes 101 included in the ranges that are set based on the angles satisfying the above relation as described above, air is able to be supplied evenly.

Further, it may be that the intervals between the inlet guide vanes 101 are changed gradually in the rotating direction, but inlet guide vanes 101 arranged at equal intervals may be included.

In the inlet guide vane unit 100, a maximum value dmax, and a minimum value dmin, of the intervals between the inlet guide vanes 101 possibly satisfy a relation, “0.6≦dmin/dmax<1.0”. By the difference between the arrangement intervals being kept in the above range, the weight flow rate of air is able to be equalized more infallibly.

In the inlet guide vane unit 100, it is possible that the intervals between the inlet guide vanes 101 are changed gradually in the rotating direction R. Specifically, of one round in the rotating direction R, possibly: a half round (corresponding to an angle range of 180°) is an increasing region; and a half round (corresponding to an angle range of 180°) is a decreasing region.

FIG. 5 is a graph illustrating an example of a relation between positions and intervals of inlet guide vanes. In the inlet guide vane unit 100 illustrated in FIG. 5: 360 degrees of one round is one cycle; and based on a sine function, in which the interval becomes maximum when θ is 0° at the terminal side end portion and the interval becomes minimum when θ is −180° and 180° at the suction port side end portion 120, the intervals between the inlet guide vanes 101 are increased and decreased. As illustrated in FIG. 5, by the intervals between the inlet guide vanes 101 being increased and decreased based on the sine function, the flow rate is able to be made more even. Further, when the intervals are changed with the sine function, the difference between the maximum value and the minimum value may be in the above described range.

The intervals between the inlet guide vanes may be changed based on points on the sine function, based on the sine function, but limitation is not made thereto. In the inlet guide vane unit, the intervals between the inlet guide vanes may be changed, with reference to a reference line of the sine function along the rotating direction of the main shaft, in a range of 20% or less of the amplitude of the reference line. That is, the intervals between the inlet guide vanes may be deviated in a certain range from points on the sine function. For example, the intervals may be changed stepwisely, by intervals between plural inlet guide vanes being made the same. Accordingly, by the intervals between the inlet guide vanes being changed, with reference to the reference line of the sine function, in the range of 20% or less of the amplitude of the reference line; the weight flow rate of air is also able to be equalized in the rotating direction. Further, in the inlet guide vane unit, with a reference line of a sine function along the rotating direction of the main shaft being a reference, intervals between inlet guide vanes may be changed in a range of 5% or less of the amplitude of the reference line, and the intervals between the inlet guide vanes may be changed in a range of 5% or less of the amplitude of the reference line.

FIG. 6 is a schematic diagram illustrating an example of the inlet guide vanes. Further, as illustrated in FIG. 6, an angle θa formed between: a line extended from an end portion of a pressure surface 140, which is a surface of the inlet guide vane 101, the surface being at the suction flow channel 102 side, the end portion being at a center 142 side of the main shaft 6; and a line joining the end portion and the center 142, may be equal to or larger than 0° and equal to or less than 10°. Accordingly, the formed angle θa becomes positive in a direction opposite to the rotating direction, with a center side end portion of the inlet guide vane 101 being the center. By the pressure surface 140 of the inlet guide vane 101 having the shape satisfying the above described range, the straightening effect is able to be improved more.

FIG. 7 is a graph illustrating an example of a relation between positions and intervals of inlet guide vanes. In the example illustrated in FIG. 5, when θ is 0°, the interval between the inlet guide vanes becomes maximum, and when θ is 180°, the interval becomes minimum, but limitation is not made thereto. As illustrated with a second pattern in FIG. 7, a position in the inlet guide vane unit 100, the position being where the interval between the inlet guide vanes 101 is the widest, may be at a position moved from the terminal side end portion 122 to the upstream side in the rotating direction of the main shaft by an angle larger than 0° and equal to or less than 40°. That is, an amount of deviation 160 illustrated in FIG. 7, from a first pattern in FIG. 5, may be made larger than 0° and equal to or less than 40 degrees to the upstream side in the rotating direction. Accordingly, by the position where the interval between the inlet guide vanes 101 is the widest being deviated to the upstream side in the rotating direction, the weight flow rate is able to be adjusted in consideration of influence of the impeller, and the weight flow rate of air is able to be equalized along the rotating direction. As to the intervals between the inlet guide vanes, similarly to the position where the interval between the inlet guide vanes 101 is the widest, the position where the interval between the inlet guide vanes 101 is the narrowest may be deviated to the upstream side in the rotating direction, and may be at a position moved from the suction port side end portion 120 to the upstream side in the rotating direction of the main shaft by an angle larger than 0° and equal to or less than 40°.

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.

REFERENCE SIGNS LIST

• • 1 COMPRESSOR
  • 2 CASING
  • 4 DRIVE UNIT
  • 6 MAIN SHAFT
  • 12 SUCTION PORT
  • 14 COMPRESSION UNIT
  • 16 DISCHARGE PORT
  • 18a, 18b, 18c, 18d COMPRESSION UNIT
  • 32 IMPELLER
  • 32a BLADE
  • 33 INLET FLOW CHANNEL
  • 34 RETURN VANE
  • 35 RETURN CHANNEL
  • 100 INLET GUIDE VANE UNIT
  • 101 INLET GUIDE VANE
  • 102 SUCTION FLOW CHANNEL
  • 104 DISCHARGE FLOW CHANNEL
  • 120 SUCTION PORT SIDE END PORTION
  • 122 TERMINAL SIDE END PORTION
  • 130 FIRST GROUP
  • 132 SECOND GROUP
  • 160 AMOUNT OF DEVIATION

Claims

1. A centrifugal compressor, comprising:

a casing having an inlet flow channel and a connection flow channel formed therein, the inlet flow channel having a suction port provided at one place thereof, the connection flow channel being connected to the inlet flow channel,

a main shaft inserted in the casing;

an impeller fixed to the main shaft, and arranged in the inlet flow channel; and

an inlet guide vane unit having a plurality of inlet guide vanes arranged upstream of the impeller of the inlet flow channel,

wherein in the inlet guide vane unit, an arrangement interval between the inlet guide vanes at the suction port side is narrower than an arrangement interval between the inlet guide vanes at a side opposite to the suction port side.

2. The centrifugal compressor according to claim 1, wherein in the inlet guide vane unit, arrangement intervals among a first group of the inlet guide vanes that are at an end portion side at the suction port side and that are 25% of all of the inlet guide vanes are narrower than arrangement intervals among a second group of the inlet guide vanes that are at an end portion side opposite to the suction port and that are 25% of all of the inlet guide vanes.

3. The centrifugal compressor according to claim 1, wherein in the inlet guide vane unit, a relation between a maximum value dmax and a minimum value dmin of intervals between the inlet guide vanes is expressed as 0.6≦dmin/dmax<1.0.

4. The centrifugal compressor according to claim 1, wherein in the inlet guide vane unit, intervals between the inlet guide vanes change, with reference to a reference line of a sine function along a rotating direction of the main shaft, in a range of equal to or less than 20% of amplitude of the reference line.

5. The centrifugal compressor according to claim 4, wherein in the inlet guide vane unit, a position where the interval between the inlet guide vanes is the widest is at a position moved to an upstream side in the rotating direction of the main shaft from an end portion opposite to the suction port by an angle larger than 0° and equal to or less than 40°.