JP2010236401A - Centrifugal fluid machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To a centrifugal fluid machine having characteristics highly efficient in a wide operation flow rate range only by improving the structure extremely simply. <P>SOLUTION: The centrifugal fluid machine 20 has: a rotary shaft 6; a centrifugal impeller 4 mounted on the rotary shaft; a casing 5 for storing the rotary shaft and the centrifugal impeller; and a suction passage means provided integrally with or independently from the casing. The suction passage means has: a suction nozzle 1 having a passage formed for guiding a flow from the direction orthogonal to the rotary shaft to the impeller; an annular passage means 8 with an annular passage connected with the passage of the suction nozzle formed; a movable inlet guide vane 3 disposed on the downstream side of the annular passage means for forming a circular blade row; and a rotatable guiding blade 2 disposed in a connection part of the suction nozzle and the annular passage means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a centrifugal fluid machine, and more particularly to a centrifugal fluid machine suitable for a case where there is a suction flow channel into which a working fluid flows from a radial direction that is substantially perpendicular to a rotation axis.

  An example of a conventional so-called radial suction type centrifugal fluid machine is described in Patent Document 1. In the centrifugal compressor described in this publication, a suction casing that forms a radial suction flow path is provided on the upstream side of the impeller. Then, in order to make the gas flow to the impeller uniform, the casing guide blades that are arranged at a plurality of locations in the circumferential direction on the upstream side of the impeller and that have different shapes are rotated around the mounting portion to the casing. It is possible to move. Thereby, a turning force is given to the gas flow at the guide blade outlet, and the work of the impeller is changed to control the capacity of the compressor.

  An example of a radial suction type turbo compressor is described in Patent Document 2. In this turbo compressor, in order to prevent vibration and noise that occur during low-flow-side operation and to expand the operating range, the partition plate provided near the bottom of the suction casing and the suction casing upstream of the impeller in the circumferential direction The mounting angle of the circular blade row composed of a plurality of blades arranged at intervals is made movable.

Japanese Utility Model Publication 2-198999 JP-A-6-193596

  In a centrifugal fluid machine, an inlet guide vane (guide vane, guide vane) is arranged upstream of the impeller, and the flow may be controlled by changing the mounting angle of the inlet guide vane to give a pre-swirl to the flow. . In a centrifugal fluid machine that controls the flow rate with an inlet guide vane, when the suction direction upstream of the centrifugal impeller is so-called radial suction, that is, when suction is performed through a nozzle from a direction substantially perpendicular to the axial direction, suction is performed. Unless some means is provided in the casing, the flow flowing into the inlet guide vane becomes non-uniform in the circumferential direction. As a result, there is a risk that the loss at the inlet of the impeller increases, leading to a decrease in the efficiency of the fluid machine or the occurrence of noise vibration.

  In order to eliminate such inconvenience, in the centrifugal compressor described in Patent Document 1, inlet guide vanes having different blade angles and shapes are arranged in a circular blade row in the suction passage on the upstream side of the impeller, The inflow loss to the inlet guide vane is reduced. In the centrifugal compressor described in this publication, when the inlet guide vane is fully opened, that is, when the pre-turn is set to 0 °, the flow is smoothly guided to the inlet guide vane, so that the loss can be surely reduced.

  However, when trying to make the pre-turn at an angle other than 0 °, that is, when operating at a partial flow rate, the flow around the plurality of blades arranged in the circumferential direction of the inlet guide vane is not uniform. With the blades located above, the blade angle can be set relatively depending on the flow, but with the blades located below, a large angle of attack is produced. As a result, a large loss occurs partially and the efficiency is lowered. In addition, the outlet angle of each of the plurality of inlet guide vanes changes, the flow angle is not constant in the circumferential direction, and the swirl flow to be given upstream of the impeller is not easily uniform in the circumferential direction.

  In the turbo compressor described in Patent Document 2, a rotatable partition plate is provided in an annular flow path portion that converts a flow flowing from a suction nozzle that forms a radially inward flow path into a circumferential flow, The wraparound flow is controlled. Then, a swirl component is effectively applied to the flow by a plurality of inlet guide vanes arranged in the circumferential direction. In the compressor described in this publication, swirl can be imparted while reducing loss by the movable blades, but since the flow is controlled after flowing into the annular flow path, the amount of swirl flow imparted is limited.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to improve the efficiency of a centrifugal fluid machine with a very simple structure and to have a wide operating flow rate characteristic. . Another object of the present invention is to provide high fluid performance with a simple suction channel structure in a radial suction type centrifugal fluid machine.

  A feature of the present invention that achieves the above object is that a rotating shaft, a centrifugal impeller attached to the rotating shaft, a casing that accommodates the rotating shaft and the centrifugal impeller, and a suction flow provided integrally or separately from the casing. In the centrifugal fluid machine having the passage means, the suction passage means is connected to the suction nozzle formed with a passage for guiding the flow to the impeller from a direction orthogonal to the rotation axis, and to the passage of the suction nozzle. An annular channel means formed with an annular channel, a movable inlet guide vane that is arranged downstream of the annular channel means and constitutes a circular blade row, and is arranged at a connection portion between the suction nozzle and the annular channel means And a rotatable guide vane.

  In this feature, it is preferable to provide a driving means for driving the guide vanes and the inlet guide vanes and a control means for controlling the driving means. The control means has a plurality of guide vanes, and the control means independently sets each guide vane angle. It is further desirable to be controllable. Further, the driving means may drive the guide vanes and the inlet guide vanes in conjunction with each other.

  According to the present invention, the movable guide means for guiding the flow in a predetermined direction is provided in the portion that flows from the radial flow channel to the annular flow channel. A fluid machine having the following characteristics can be obtained. Further, in a radial suction type centrifugal fluid machine, particularly a centrifugal compressor, high fluid performance can be obtained with a simple suction flow path structure.

The cross-sectional view ((a) figure) and longitudinal cross-sectional view ((b) figure) of the suction part of one Example of the compressor based on this invention. The cross-sectional view of the suction flow path of the conventional compressor. The cross-sectional view of the suction part of the other Example of the compression machine which concerns on this invention. The figure explaining the characteristic curve of a centrifugal fluid machine.

  Embodiments of a centrifugal fluid machine according to the present invention will be described below with reference to the drawings. In this embodiment, a centrifugal compressor is taken up as a centrifugal fluid machine. However, the centrifugal fluid machine is not limited to a centrifugal compressor, and may be a centrifugal pump or the like. However, the suction flow is preferably changed from a radially inward flow to an axial flow.

  FIG. 1 shows a suction flow path portion of a centrifugal compressor, FIG. 1 (a) is a cross-sectional view, that is, a cross-sectional view taken along the line XX of FIG. 1 (b), and FIG. It is shown by a YY arrow cross-sectional view of FIG. For comparison, FIG. 2 shows a cross-sectional view of an example of a conventional homogeneous centrifugal compressor.

  In the centrifugal compressor 20, one (single stage) or plural (multistage) centrifugal impellers 4 are attached to a rotary shaft 6 driven by a motor (not shown). The suction side end of the rotating shaft 6 is rotatably supported by a bearing 14 held in the casing 5. A vaned diffuser or a vaneless diffuser is disposed downstream of the centrifugal impeller 4 and converts the kinetic energy imparted to the fluid by the impeller 4 into pressure energy. A return channel portion is provided downstream of the diffuser portion to convert the radially outward flow into the radially inward flow and lead it to the next stage impeller. In FIG. 1, illustration of the downstream part from the return channel part is omitted. After repeating the same structure by the number of impellers, the compressed gas is sent out of the machine through the discharge nozzle.

  A suction passage is formed on the upstream side of the first stage impeller 4. The working gas sent from the outside to the centrifugal compressor 20 is first connected to the pipe 11 and led to the suction nozzle 1 protruding in the radial direction from the casing 5 of the centrifugal compressor 20. The suction nozzle 1 has a shape that narrows inward in the radial direction in the longitudinal section (FIG. 1B), and spreads in the width direction inward in the radial direction in FIG. 1A. It has a different shape.

  On the downstream side of the suction nozzle 1, an annular flow path 8 is formed which is connected to the suction nozzle 1 and is formed by cutting the casing 5 into an annular shape. An annular inlet guide vane channel 3 d that is radially inward of the annular channel 8 and shorter in the axial direction than the annular channel 8 is connected to the annular channel 8. The impeller suction passage 4d is connected to the inlet guide vane passage 3d and the passage in the impeller 4. The impeller suction flow path 4d converts a radially inward flow into an axial flow.

  In the inlet guide vane channel 3d, inlet guide vanes (hereinafter also referred to as IGVs) 3 having airfoil blades 3a are arranged at substantially equal intervals in the circumferential direction. The shape of the blade 3a of the IGV 3 is preferably an airfoil, but may be a plate shape. The IGV 3 is provided with a shaft for attachment to the casing 5 at an intermediate portion thereof. The IGV 3 can rotate around this axis, and its mounting angle can be changed according to the operating conditions.

  Here, as a feature of the present invention, one movable guide vane 2 is disposed on the upstream side of the IGV 3 and substantially at the center of the connection portion between the suction nozzle 1 and the annular flow path 8. The movable guide vane 2 is provided with a rotating shaft 2d extending in the axial direction of the centrifugal compressor 20 at an intermediate portion thereof. The rotating shaft 2 d is held by the casing 5 at the outer peripheral end of the annular flow path 8. The tip of the rotating shaft 2d is connected to a driving means (not shown).

  Next, before describing the operation of the centrifugal compressor 20 of the present embodiment configured as described above, the operation of the conventional centrifugal compressor 20b will be described for comparison. FIG. 2 shows a suction section of a conventional centrifugal compressor 20b in a cross-sectional view. In the conventional centrifugal compressor shown here, the guide vane 2a arranged at the connection portion between the suction nozzle 1 and the annular flow path 8 is a fixed guide vane whose direction cannot be changed. FIG. 2A shows an example in which the direction of the blade 3 a of the IGV 3 is directed in the radial direction, and a flow without a pre-turn is guided to the suction side of the impeller 4. FIG. 2B shows a case where the blade 3a of the IGV 3 is rotated by the same centrifugal compressor as that shown in FIG. 2A, and a flow having a pre-turn is guided to the suction side of the impeller 4.

  In FIG. 4, the performance curve when operating the centrifugal compressor 20b having this conventional suction shape is indicated by a broken line. FIG. 2A corresponds to the case where the vehicle is operated at the point A in FIG. 4 because the IGV 3 does not give a pre-turn, that is, the vehicle is operated at the maximum flow rate. The blade 3a of the IGV 3 is directed in the radial direction.

  In FIG. 2A, the main flow 7 flowing in from the suction nozzle 1 is divided into two equal parts by the fixed guide vanes 2a, and flows into the left and right annular flow paths 8. When the flow 7 flows down the annular flow path 8, a part of the flow 7 becomes a flow 7a passing through the flow path formed between the blades 3a of the IGV 3. The flow that has passed between the blades 3a finally flows into the impeller 4 as an axial flow without a pre-turn.

  At this time, the flow 7a flowing between the blades 3a from the side opposite to the suction nozzle, that is, the lower side in FIG. 2A, flows into the impeller 4 into the flow 7a flowing between the blades 3a from the upper side. It is hard to flow compared with. However, if the cross-sectional area of the annular flow path 8 is set to a certain size, there is no significant loss. Further, the uniformity of the flow distribution in the circumferential direction is not significantly impaired.

  On the other hand, in order to move the centrifugal compressor 20b at the small flow rate operation point represented by the point C in FIG. 4, when a strong pre-turn is given using the IGV3, as shown in FIG. The blade 3a is inclined from the radial line. In this case, the flow 7a between the blades 3a is guided to the impeller 4 relatively smoothly on the left half side in FIG. On the other hand, on the right half side of the figure, when the flow 7 flows between the blades 3a of the IGV 3, the flow 7a has a large angle of attack.

  This flow in the right half is accompanied by a large separation when flowing into the blade 3a and has a large loss. Moreover, the velocity distribution of the flow flowing into the impeller 4 becomes a very non-uniform flow in the circumferential direction, and the performance of the impeller 4 is lowered, and consequently the performance of the compressor 20b is lowered. Further, in the annular flow path 8, separation occurs in the IGV 3 disposed downstream, so that the flow becomes unstable at a place where the left and right wraparound flows collide. As a result, the characteristics of the compressor 20b may be destabilized. When the characteristics of the compressor 20b become unstable, noise and vibration are generated due to the unstable characteristics.

  On the other hand, in the compressor 20 of the embodiment shown in FIG. 1, when the IGV 3 is used to give a strong swirl, the movable guide vane 2 is provided at the connection portion between the suction nozzle 1 and the annular flow path 8, so that this movable The guide blade 2 can be rotated to change the distribution ratio of the main flow 7 to the left and right. As a result, the main flow 7 flowing out from the suction nozzle 1 flows into the annular flow path 8 at an angle close to the tangential direction of the annular flow path 8 and turns in one direction in the annular flow path 8. For this unidirectional flow, each vane 3a of the IGV 3 can be set within an appropriate angle of attack, so that the flow 7a smoothly flows into the flow path formed between the vanes 3a.

  As described above, the movable guide vane 2 is provided at the connection portion between the suction nozzle 1 and the annular flow path 8, and the movable guide vane 2 is inclined from the neutral position when giving a strong turn to the impeller 4, so that the flow loss is reduced. it can. Moreover, since the uniformity of the flow distribution in the circumferential direction is maintained, the performance of the compressor 20 does not deteriorate. Furthermore, since the working fluid flows in one direction in the annular flow path 8, it is possible to avoid collision of the left and right flows in the annular flow path 8, and the flow does not become unstable in the annular flow path 8.

  In FIG. 4, the characteristic of the compressor in a present Example is shown as a continuous line. As described above, the characteristics of a typical example of a conventional compressor are shown together with a broken line. The horizontal axis is the flow rate Q, and the vertical axis is the head H and the efficiency η. When the angle of IGV3 is 0 degree, what draws the same performance curve as the compressor of a present Example is selected as a conventional compressor. When the angle of the IGV 3 is increased, the compressor of the present embodiment has a characteristic that the curve of the head H and the efficiency η shifts to the small flow rate side as compared with the conventional one, and the operation on the small flow rate side becomes possible.

  Moreover, in the compressor of a present Example, if rotation control of the movable guide blade 2 is carried out, efficiency will become high compared with the past. When the load side has the resistance curve shown in FIG. 4, the compressor of this embodiment can be used to operate in the flow rate range from point A to point B. On the other hand, when the flow rate is controlled using IGV3 when the load side has the same resistance curve using the conventional fixed guide vanes, the operation range is from point A to point C, and the controllable flow range is It is narrower than this example. That is, according to the present embodiment, the efficiency of the compressor can be improved and the flow rate range can be expanded as compared with the conventional case.

Another embodiment of the suction channel according to the present invention is shown in FIG. This embodiment differs from the embodiment shown in FIG. 1 in that the number of movable guide vanes provided at the connection portion between the suction nozzle 1 and the annular flow path 8 is plural, in this embodiment three. . FIG. 3A shows a case where no pre-swivel is given by the IGV ₃ , and the central guide vane 2b ₂ is arranged substantially vertically in the movable guide vanes 2b _{1 to} 2b ₃ arranged upstream of the IGV ₃ , and the left guide vane. 2b ₁ is tilted to the right, and the right guide vane 2b ₃ is tilted to the left. Thereby, the main flow 7 is branched into four large flows and led to the annular flow path 8, and the main flow 7 is promoted to circulate in the circumferential direction in the annular flow path 8. As a result, the circumferential uniformity of the flow flowing into the impeller 4 is further improved.

FIG. 3B shows a case where the pre-turn is given by IGV3. All the three movable guide vanes 2b _{1 to} 2b ₃ are tilted in the same direction, that is, in the right direction in the figure. Mainstream 7 branches to almost three of flow on the right side than the movable guide vanes 2b ₃ rightmost mainstream 7 hardly flow into. Thereby, a one-way swirl flow is formed in the annular flow path 8.

The flow in the annular flow path 8 in this embodiment is almost the same as that in the embodiment shown in FIG. However, since the three sheets _2b 1 ～2B ₃ arranged movable guide vanes, the flow direction length of the movable guide vane _2b 1 ～2B ₃ can be made shorter than the movable guide vanes 2 of the embodiment shown in FIG. Thereby, the stress which acts on the flat plate 2c or the drive shaft 2d can be reduced. In particular, in the compressor 20 that handles high-pressure gas, if a plurality of movable guide vanes 2b are provided as in the present embodiment, problems of insufficient strength or excessive stress of the movable guide vanes 2b can be avoided.

In any of the above embodiments, the movable guide vanes 2, 2b _{1 to} 2b ₃ and the vane 3a of the inlet guide vane 3 are driven by the same driving means (not shown). Alternatively, when driving by different driving means, it is preferable that each driving means is connected to the same control means (not shown), and this control means drives each driving means synchronously. Furthermore, when a plurality of movable guide vanes 2b1 to 2b3 are provided, it is desirable that the angle of each movable guide vane can be changed independently.

1 ... suction nozzle, 2 ... movable guide vanes, 2a ... stationary guide vanes, _2b 1 ～2B 3 _... movable guide vanes, 3 ... inlet guide vane (IGV), 3a ... vane of the inlet guide vane, 4 ... impeller 5 ... casing, 6 ... rotating shaft, 7 ... direction of flow (main flow), 7a ... direction of flow passing through IGV, 8 ... annular flow path (means), 20 ... centrifugal compressor.

Claims (4)

In a centrifugal fluid machine having a rotating shaft, a centrifugal impeller attached to the rotating shaft, a casing for housing the rotating shaft and the centrifugal impeller, and a suction flow path means provided integrally or separately from the casing,
The suction flow path means includes a suction nozzle in which a flow path that guides the flow to the impeller from a direction orthogonal to the rotation axis is formed, and an annular shape in which an annular flow path that is connected to the flow path of the suction nozzle is formed A flow path means, a movable inlet guide vane disposed downstream of the annular flow path means and constituting a circular blade row, and a rotatable guide disposed at a connection portion between the suction nozzle and the annular flow path means A centrifugal fluid machine having a blade.   2. The centrifugal fluid machine according to claim 1, further comprising drive means for driving the guide vanes and the inlet guide vane and control means for controlling the drive means.   3. The centrifugal fluid machine according to claim 2, wherein a plurality of the guide blades are provided, and the control means can control each guide blade angle independently.   The centrifugal fluid machine according to claim 2 or 3, wherein the driving means drives the guide vanes and the inlet guide vanes in conjunction with each other.

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