JP6109548B2 - Compressor - Google Patents

Description

  The present invention relates to a compressor.

  In the compressor, fluid is sucked by rotation of an impeller (impeller) installed inside the casing, and the sucked fluid is guided downstream. A technique is known in which a casing treatment, an air separator, an extraction port, or the like is formed in the vicinity of the impeller inlet on the inner peripheral surface of the casing, thereby suppressing the occurrence of turning stall and surging and expanding the operating range. .

  As shown in FIGS. 14 and 15, generally, when the flow rate is decreased under a constant compressor rotation speed, self-excited vibration of the flow field called swirling stall occurs. Further, the turning stall is a phenomenon in which a local stall region generated in the compressor propagates in the circumferential direction at a speed different from that of the impeller. When the rotating stall occurs, the compressor performance is significantly lowered, and intermittent vibration stress is applied to the blades, which may lead to fatigue failure.

When the flow rate is further decreased after the rotation stall, the flow pulsation (surging) with strong sound occurs and the operation limit is reached.
The operation range of the compressor is limited by the occurrence of the turning stall and surging.
Patent Document 1 discloses a technique for controlling an air flow in a compressor, and cancels a flow disturbance having a periodicity such as a rotating stall by extracting high-pressure air in a circumferentially asymmetric pattern. Yes.

JP 2008-111435 A

  The casing treatment is, for example, a groove provided at a location overlapping the position where the blade row is present in the casing, and forms a recirculation flow in the groove. As the fluid in a relatively high pressure region in the blade row passes through the groove, the fluid is ejected to the low energy flow region (region of the inlet of the blade row). Thereby, generation | occurrence | production of a stall cell is suppressed.

  In addition, the air separator is not provided with a recirculation flow in a groove provided in the casing by installing a ring-shaped member along the circumferential direction of the casing on the upstream side of the blade row. To form a recirculation flow.

  Casing treatments and air separators are effective in extending the stable operating range of the compressor. However, there may still be periodic disturbances in the flow (swing stall), leading to a reduction in compressor efficiency.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the compressor which can suppress a efficiency fall and can expand a stable operation range effectively.

  The inventor noticed that conventional casing treatments and air separators are provided all around the inner surface of the casing, and as a result, the generation of stalled cells can be suppressed to some extent by the casing treatments and air separators. The knowledge that a cell may occur was acquired.

  The compressor according to the present invention includes an impeller, a casing that houses the impeller and forms a main flow path of fluid guided by the impeller, and a bypass flow formed by branching the main flow path at an inner surface of the casing The bypass flow path is formed nonuniformly in the circumferential direction on the inner surface of the casing or asymmetrically formed in the circumferential direction.

  According to this configuration, when the flow rate flowing through the main flow path of the compressor is decreased, a fluid in a relatively high pressure area in the impeller blade row passes through the bypass flow path, thereby causing a low energy flow area ( The fluid is ejected into the blade row inlet region). Thereby, generation | occurrence | production of a stall cell is suppressed. In addition, since the bypass channel is formed nonuniformly in the circumferential direction on the inner surface or asymmetrically formed in the circumferential direction, for example, it is formed as a region where the bypass channel is formed in the circumferential direction. There are areas that are not. Furthermore, the bypass channel has, for example, a width, a height and a length, and an interval between the bypass channels that are not constant. Swirl stall is a periodic disturbance of flow, but the development and growth of swirl stall is suppressed or the generation period of turbulence is stalled by forming the bypass flow path non-uniformly or asymmetrically. Thus, it is possible to prevent the turning period from being in agreement with or close to the turning period and to prevent the growth of turning stall.

  In the above invention, a region in which a plurality of the bypass channels are provided in parallel in the circumferential direction and a region in which the bypass channel is not provided are uneven in the circumferential direction on the inner surface of the casing. It may be formed or formed asymmetrically in the circumferential direction.

  According to this structure, generation | occurrence | production of turning stall can be suppressed in the area | region where the multiple bypass flow paths are provided in parallel in the circumferential direction. In addition, the existence and non-formation of the bypass flow path in the circumferential direction suppresses the development and growth of swirling stalls, and the disturbance wave generation cycle matches the swirl cycle of the stall cell. Or it avoids becoming close and prevents the growth of turning stall.

  In the above invention, the bypass flow path may be a groove-shaped flow path formed on the inner surface of the casing.

  According to this configuration, when a fluid in a region having a relatively high pressure in the blade row passes through the groove, the fluid is ejected to a low energy flow region (region of the inlet of the blade row), and the groove-shaped flow path A recirculation flow is formed within. As a result, the generation of stalled cells can be suppressed.

  In the above invention, the bypass flow path includes a first opening formed on the upstream side of the main flow path and a second opening formed on the downstream side of the main flow path, and the first opening. Alternatively, the second opening may be formed unevenly in the circumferential direction on the inner surface of the casing, or asymmetrically formed in the circumferential direction.

  According to this configuration, the fluid in a relatively high pressure region in the blade row flows into the bypass channel from the second opening, passes through the bypass channel, and then flows from the first opening to the low energy flow region. When the fluid is ejected to the (inlet region of the blade row), a recirculation flow is formed in the bypass channel. As a result, the generation of stalled cells can be suppressed. In addition, the first opening or the second opening is formed unevenly in the circumferential direction on the inner surface of the casing or asymmetrically formed in the circumferential direction, thereby suppressing the development and growth of the rotation stall. In other words, it is possible to prevent the generation period of the disturbance wave from being in a state of being close to or close to the rotation period of the stalled cell, thereby preventing the growth of the rotation stall.

  In the above invention, the bypass flow path is a place that overlaps with a position where the impeller blade row exists in the casing and is formed inside the casing, or a ring on the upstream side of the impeller. It may be formed in a shape.

  According to this configuration, when the bypass channel is formed in the casing at a position overlapping with the position where the impeller blade row is present in the casing, the recirculation flow formed in the bypass channel is Flows inside the casing. Moreover, when the bypass flow path is formed in a ring shape on the upstream side of the impeller, the recirculation flow formed in the bypass flow path is formed in the main flow path.

  According to the present invention, in the compressor, it is possible to effectively reduce the efficiency reduction and effectively widen the stable operation range.

It is a fragmentary longitudinal cross-section which shows the impeller and casing of the centrifugal compressor which concern on 1st Embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the casing treatment provided in the casing of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is an expanded view which shows the casing inner surface of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is a general | schematic expanded view which shows the casing inner surface of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is a general | schematic expanded view which shows the casing inner surface of the centrifugal compressor which concerns on 2nd Embodiment of this invention. It is a front view which shows the impeller and casing of the centrifugal compressor which concern on 1st Embodiment of this invention. It is a front view which shows the impeller and casing of the centrifugal compressor which concern on 1st Embodiment of this invention. It is a front view which shows the impeller and casing of the centrifugal compressor which concern on 1st Embodiment of this invention. It is an expanded view which shows the casing inner surface of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the casing treatment of the centrifugal compressor which concerns on 2nd Embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the casing treatment of the centrifugal compressor which concerns on 2nd Embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the air separator of the centrifugal compressor which concerns on 3rd Embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the air separator of the centrifugal compressor which concerns on 3rd Embodiment of this invention. It is a graph which shows the relationship between the discharge pressure and flow volume of a compressor. It is a graph which shows the pressure fluctuation waveform measured on the casing surface.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
A centrifugal compressor according to a first embodiment of the present invention will be described.
As shown in FIG. 1, the centrifugal compressor includes a rotating shaft 11 that is rotationally driven by a driving device such as a motor or a turbine (not shown), an impeller 12 that is fixed to the rotating shaft 11 and rotates around the axis, a rotating shaft 11, and And a casing 20 that houses the impeller 12 and forms a main flow path for the fluid.

  The impeller 12 includes a hub 13 provided integrally with the rotary shaft 11 and a plurality of blades 14 provided on the outer peripheral surface of the hub 13. The hub 13 is formed with a curved surface 13c whose outer diameter gradually increases from an end portion 13a on one end side of the rotating shaft 11 toward an end portion 13b on the other end side. The plurality of blades 14 are arranged on the curved surface 13 c of the hub 13 at equal intervals in the circumferential direction.

  The casing 20 includes a main flow path 21 that is continuous from the upstream side of the impeller 12 toward the impeller 12 along the axial direction of the rotary shaft 11, a diffuser 23 that is formed in an annular shape on the outer peripheral side of the impeller 12, and A spiral volute (not shown), which is continuously formed in the circumferential direction on the outer circumferential (downstream) side of the diffuser 23 and whose cross-sectional area in a cross section orthogonal to the circumferential direction gradually expands along the circumferential direction, is provided. Yes.

Next, with reference to FIGS. 1-3, the casing treatment formed in the compressor of this embodiment is demonstrated.
The casing treatment is, for example, a plurality of grooves 24 formed on the inner surface 22 of the casing 20. The groove 24 is an example of a bypass channel. As shown in FIGS. 1 and 2, one end of the groove 24 is located at a position where the blade row is present in the casing, and the other end is located upstream of the impeller 12. When the flow rate flowing through the main flow path 21 of the compressor is decreased, a recirculation flow is formed in the groove 24 as shown in FIG. The fluid in the region of relatively high pressure in the blade row of the impeller 12 passes through the groove 24, whereby the fluid is ejected to the low energy flow region (region of the blade row inlet) upstream of the impeller 12.

  As shown in FIG. 3, a plurality of grooves 24 are provided in parallel with each other. Thereby, generation | occurrence | production of turning stall and surging can be suppressed effectively. The groove may be formed parallel to the axial direction as shown in FIG. 9A, or parallel to the circumferential direction as shown in FIG. 9B (with respect to the axial direction). (Vertically). Further, as shown in FIG. 9C, the groove may be formed in an oblique direction with respect to the axial direction (or circumferential direction). Further, as shown in FIG. 9D, a plurality of honeycomb-shaped openings may be arranged side by side instead of the grooves. The casing treatment is not necessarily formed by a plurality of grooves as shown in FIG. 3 or FIGS. 9A, 9B, and 9C, and may be formed as a single groove that is not divided.

As shown in FIG. 4, the casing treatment includes an installation area A in which a plurality of grooves 24 are provided in parallel in the circumferential direction and a non-installation area B in which no grooves 24 are provided. The inner surface 22 is not uniform in the circumferential direction or asymmetric in the circumferential direction.
Here, that the casing treatment is formed unevenly (or non-uniformly) in the circumferential direction is, for example, a non-installation region B where the groove 24 is not provided at one or more locations in the circumferential direction. That means.

Further, the case where the casing treatment is formed asymmetrically in the circumferential direction is, for example, a case where a plurality of grooves 24 are provided in parallel in the circumferential direction and provided in two or more locations in the circumferential direction of the installation area A 2, the installation intervals, the installation widths (for example, W ₁ , W ₂ , W _{3 in} FIG. 4) or the installation depths of the plurality of installation areas A are different. For example, in a plurality of installation areas A, at least one installation area A may be different from the remaining installation areas A in the installation interval, installation width, installation depth, or the like.
For example, FIG. 6 shows an example in which when a plurality of installation areas A are provided in the circumferential direction, the installation interval θ of each installation area A is different and the casing treatment is asymmetric in the circumferential direction. FIG. 7 shows an example in which when a plurality of installation areas A are provided in the circumferential direction, the installation width W of each installation area A is different and the casing treatment is asymmetric in the circumferential direction. Further, FIG. 8 shows an example in which when a plurality of installation areas A are provided in the circumferential direction, the installation depth D of each installation area A is different and the casing treatment is asymmetric in the circumferential direction.

As described above, in the casing treatment, the installation area A and the non-installation area B are formed in a uniform manner in the circumferential direction on the inner surface 22 of the casing 20 or asymmetric in the circumferential direction. Compared with the case where treatment is performed (when the groove 24 is provided on the entire circumference), it is possible to suppress a decrease in compressor efficiency.
In other words, by forming the casing treatment non-uniformly (or non-uniformly) in the circumferential direction, a turbulence pattern that counteracts the periodic flow disturbance (swirl stall) is generated, and the development and growth of swirl stall is effective. Can be suppressed.

  In addition, by forming the casing treatment asymmetrically in the circumferential direction, it effectively cancels out the periodic flow disturbance (swirl stall) compared to simply forming the casing treatment symmetrically in the circumferential direction. Can do. It can be avoided that the generation period (frequency) of the disturbance wave coincides with or close to the rotation period (frequency) of the rotation stall cell, and the growth of the rotation stall can be prevented from being promoted.

  In the example described above, the case where the casing treatment is installed on the inner surface 22 of the casing 20 of the centrifugal compressor has been described, but the present invention is not limited to this example. For example, the casing treatment may be provided on the inner surface of the casing of the axial compressor. FIG. 9 is a developed view of the casing, and shows the relationship between a plurality of grooves or openings constituting the casing treatment and the blades of the axial compressor. And as above-mentioned, the installation area | region A in which the several groove | channel or opening is provided, and the non-installation area | region B in which the groove | channel or opening is not provided are uneven in the circumferential direction on the inner surface of the casing or in the circumferential direction. By being formed asymmetrically, the same effect as that described in the centrifugal compressor can be obtained.

[Second Embodiment]
Next, a casing treatment of the centrifugal compressor according to the second embodiment of the present invention will be described. The overlapping description of the configuration of the rotary shaft 11, the impeller 12 and the casing 20 of the centrifugal compressor will be omitted.

  A concave groove 33 or a stepped portion 34 is formed on the inner surface of the casing 20 in the circumferential direction. A cylindrical inner cylinder member 30 is installed inside the casing 20 so as to be separated from the casing 20. As a result, a bypass passage 35 having a first opening 31 formed on the upstream side of the main passage 21 and a second opening 32 formed on the downstream side of the main passage 21 is formed. The casing treatment is composed of a plurality of bypass channels 35.

  As shown in FIGS. 10 and 11, the second opening 32 is located at a position where the blade row is present in the casing 20, and the first opening 31 is located upstream from the impeller 12. When the flow rate flowing through the main flow path 21 of the compressor is decreased, a recirculation flow is formed in the bypass flow path 35 as shown in FIGS. A fluid in a relatively high pressure region in the blade row of the impeller 12 flows into the bypass flow path 35 from the second opening 32, passes through the bypass flow path 35, and then flows from the first opening 31 to a low energy flow. Fluid is ejected to the region (region of the blade row inlet).

  A plurality of bypass channels 35 are provided in parallel along the circumferential direction. Thereby, generation | occurrence | production of turning stall and surging can be suppressed effectively.

  Further, in the casing treatment having the bypass channel 35, the first opening 31 and the second opening 32 are not uniform in the circumferential direction or asymmetric in the circumferential direction on the inner surface 22 of the casing 20, as shown in FIG. Is formed. The present invention is not limited to the case where the first opening 31 and the second opening 32 are both asymmetrical, and the same effect can be obtained when either the first opening 31 or the opening 32 is asymmetrical. Is obtained.

  Here, that the casing treatment is formed unevenly (or non-uniformly) in the circumferential direction is, for example, that the first opening 31 and the second opening 32 are not provided in one or more places in the circumferential direction. A non-installation area is provided.

The casing treatment being formed asymmetrically in the circumferential direction means that, for example, when a plurality of bypass channels 35 are provided in the circumferential direction, the installation intervals of the plurality of first openings 31 or the second openings 32 or This means that the installation widths (for example, W ₁ , W ₂ , W _{3 in} FIG. 5) are made different.

  As described above, the casing treatment is formed unevenly in the circumferential direction or asymmetrically in the circumferential direction on the inner surface 22 of the casing 20, so that the casing treatment is simply applied to the entire circumference (bypassing the bypass channel around the entire circumference). As compared with the case of the above), it is possible to suppress a decrease in the compressor efficiency and reduce the processing cost.

  For example, by forming the casing treatment non-uniformly (or non-uniformly) in the circumferential direction, a turbulence pattern that counteracts periodic flow disturbance (swirl stall) is generated, and the development and growth of swirl stall is effective. Can be suppressed.

  In addition, by forming the casing treatment asymmetrically in the circumferential direction, it effectively cancels out the periodic flow disturbance (swirl stall) compared to simply forming the casing treatment symmetrically in the circumferential direction. Can do. It can be avoided that the generation period (frequency) of the disturbance wave coincides with or close to the rotation period (frequency) of the rotation stall cell, and the growth of the rotation stall can be prevented from being promoted.

  Further, the recirculation flow in which the fluid in the high pressure region passes through the bypass flow path 35 and is ejected to the low pressure portion (the stall region) can suppress the generation of the stall cell, and the operating range of the compressor is widened.

[Third Embodiment]
Next, an air separator for a centrifugal compressor according to a third embodiment of the present invention will be described. The overlapping description of the configuration of the rotary shaft 11, the impeller 12 and the casing 20 of the centrifugal compressor will be omitted.

  The inner surface of the casing 20 is not formed with a groove or a stepped portion in the circumferential direction, but is separated from the casing 20 and a cylindrical inner cylinder member 40 is installed inside the casing 20. As a result, a bypass passage 45 having a first opening 41 formed on the upstream side of the main passage 21 and a second opening 42 formed on the downstream side of the main passage 21 is formed. The air separator is composed of a plurality of bypass channels 45.

  As shown in FIGS. 12 and 13, the first opening 41 and the second opening 42 are located upstream of the impeller 12 and in the main flow path 21 formed by the housing 20. When the flow rate flowing through the main flow path 21 of the compressor is decreased, a recirculation flow is formed in the bypass flow path 45 as shown in FIGS. A fluid in a relatively high pressure region at the end of the blade row of the impeller 12 flows into the bypass channel 45 from the second opening 42, passes through the bypass channel 45, and then flows from the first opening 41 to the low level. Fluid flows in the energy flow region (region of the blade row inlet). Thereby, the flow of the fluid can be separated into the forward flow portion and the recirculation portion on the upstream side of the impeller 12.

  A plurality of bypass channels 45 are provided in parallel along the circumferential direction. Thereby, generation | occurrence | production of turning stall and surging can be suppressed effectively.

  Further, in the air separator having the bypass channel 45, the first opening 41 and the second opening 42 are formed unevenly or asymmetrically in the circumferential direction on the inner surface 22 of the casing 20.

  Here, the air separator is formed unevenly (or non-uniformly) in the circumferential direction, for example, the first opening 31 and the second opening 32 are not provided in one or more places in the circumferential direction. A non-installation area is provided.

  Further, the air separator is formed asymmetrically in the circumferential direction, for example, in the case of providing a plurality of bypass channels 45 in the circumferential direction, the installation interval of the plurality of first openings 41 or the second openings 42, This means that the installation width or installation height differs.

  As described above, when the air separator is simply formed in the circumferential direction on the inner surface 22 of the casing 20 in an uneven manner or asymmetrical in the circumferential direction, the air separator is simply applied to the entire circumference (the bypass channel is arranged around the entire circumference). As compared with the case of the above), it is possible to suppress a decrease in the compressor efficiency and reduce the processing cost.

  For example, by forming the air separator non-uniformly (or non-uniformly) in the circumferential direction, a turbulence pattern that counteracts the periodic flow disturbance (swirl stall) is generated, and the development and growth of swirl stall is effective. Can be suppressed.

  In addition, by forming the air separator asymmetrically in the circumferential direction, the flow disturbance (swirl stall) with periodicity can be effectively canceled out compared to simply forming the air separator symmetrically in the circumferential direction. Can do. It can be avoided that the generation period (frequency) of the disturbance wave coincides with or close to the rotation period (frequency) of the rotation stall cell, and the growth of the rotation stall can be prevented from being promoted.

  Further, by separating the fluid flow into the forward flow portion and the recirculation portion on the upstream side of the impeller 12, the recirculation flow is prevented from expanding and growing in the span direction, and a stall cell is generated. It can be suppressed and the operating range of the compressor is widened.

FIG. 15 shows the pressure fluctuation waveform measured on the casing surface, the thin line shows the waveform of the measured pressure fluctuation waveform data itself, and the thick line shows the blade passing frequency component from the data measured through the low-pass filter. The filtering waveform which excluded is shown.
After stall initiation, the turning stall cell gradually grows while increasing in number in the circumferential direction, and finally stabilizes as a plurality of stall cells in the circumferential direction having periodicity. The present invention inhibits the stalled cell from growing in a stable state having periodicity as shown in FIG. As a result, the stall cell is suppressed in the initial state without periodicity, and a significant performance decrease accompanying the rotation stall growth is suppressed, and the operation range is expanded.

  Note that the turning period (frequency) of the stable turning stall cell is unique to each compressor. That is, the asymmetry of the recirculation flow path including the casing treatment and the air separator shown in the present invention is such that the fluctuation period of the forced vibration flow field caused by the asymmetry is an integral multiple (harmonic) of the swirl period of the stable swirl stall cell. It is necessary to determine that it will not promote turning stall.

11 Rotating shaft 12 Impeller 20 Casing 21 Main flow path 24 Groove (Bypass flow path)
35, 45 Bypass channel

Claims (5)

Impeller,
A casing that houses the impeller and forms a main flow path of fluid guided by the impeller;
A bypass channel formed by branching the main channel at the inner surface of the casing;
With
The bypass flow path is formed unevenly in the circumferential direction on the inner surface of the casing, or formed asymmetrically in the circumferential direction,
A region in which a plurality of the bypass channels are provided in parallel in the circumferential direction and a region in which the bypass channels are not provided are formed unevenly in the circumferential direction on the inner surface of the casing. Or a compressor formed asymmetrically in the circumferential direction . The compressor according to claim 1 , wherein the bypass channel is a groove-shaped channel formed on an inner surface of the casing. Impeller,
A casing that houses the impeller and forms a main flow path of fluid guided by the impeller;
A groove-shaped flow paths made form Te on the inner surface of the casing,
With
Before SL channel, the circumferentially at the inner surface of the casing is formed nonuniformly, or circumferentially formed asymmetrically,
A region where a plurality of the flow paths are provided in parallel in the circumferential direction and a region where the flow paths are not provided are formed unevenly in the circumferential direction on the inner surface of the casing, or A compressor formed asymmetrically in the circumferential direction . Impeller,
A casing that houses the impeller and forms a main flow path of fluid guided by the impeller;
On the upstream side of the impeller, apart from the casing, a cylindrical inner cylinder member installed on the inner side of the casing;
A plurality of bypass passages formed unevenly in the circumferential direction between the inner surface of the casing and the inner cylinder member , or formed asymmetrically in the circumferential direction ;
Compressor Ru equipped with. The bypass channel has a first opening formed on the upstream side of the main channel and a second opening formed on the downstream side of the main channel,
The compressor according to claim 4 , wherein the first opening or the second opening is formed nonuniformly in the circumferential direction on the inner surface of the casing or asymmetrically formed in the circumferential direction.

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