Patent Application
20160108920
The present invention relates to a centrifugal compressor.
Conventionally, as a compressor used in a plant or the like, a centrifugal compressor is known. Several improvements are proposed in order to enable miniaturization of the centrifugal compressor, or operation at a small flow rate.
For example, Patent Literature 1 discloses a centrifugal compressor in which a flow path width of one part of a diffuser is narrowed by use of a variable diaphragm mechanism in order to enable operation at a small flow rate.
Additionally, Patent Literature 2 discloses a centrifugal compressor in which a flow path height of a diffuser flow path is gradually increases and a flow path width is enlarged in order to attain miniaturization and enlarge an operating range to a large flow rate side.
In the centrifugal compressor, it is generally known that, when a flow angle (angle formed by the discharge direction of fluid from the impeller and the radial direction of the impeller) increases, a loss becomes large, and rotating stall causing an uneven circumferential flow occurs, thereby resulting in generation of a malfunction such as shaft vibration. In order to prevent the malfunction such as the shaft vibration, the flow angle is reduced. That is, it is effective to bring the discharge direction of the fluid from the impeller close to the radial direction of the impeller. Then, for example, as described in Patent Citation 1 and Patent Citation 2, the flow path width of the diffuser is narrowed, so that the flow velocity of the fluid can be increased, and the flow angle can be reduced.
However, in the diffuser of the centrifugal compressor described in each of Patent Citation 1 and Patent Citation 2, while the flow path width of the one part of the flow path is narrowed, a flow path width of the diffuser section at an inflow position, in which the fluid discharged from the impeller flows, is not narrowed. Accordingly, in the diffuser described in each of Patent Citation 1 and Patent Citation 2, the flow velocity of the fluid at the inflow position of the fluid to the diffuser is not sufficiently increased, which sometimes causes rotating stall.
The present invention has been made in view of the above circumstances, and an object of the invention is to provide a centrifugal compressor in which a malfunction such as shaft vibration due to rotating stall and degradation of performance due to friction losses or the like are suppressed.
A centrifugal compressor according to the present invention includes: an impeller that is rotatable around an axis, and discharges fluid, which flows in an axial direction along the axis, in a direction inclined from the axial direction; a casing section that houses the impeller; and a diffuser section that circulates the fluid discharged from the impeller, wherein the impeller includes a hub and a shroud that are arranged along the axial direction side by side, and a plurality of blades that are arranged between the hub and the shroud, wherein a flow path width of the diffuser section at an inflow position where the fluid flows in the diffuser section is narrower than a flow path width of the impeller at a discharge position where the fluid discharges from the impeller, and wherein a flow path width enlarged section wider than the flow path width of the diffuser section at the inflow position is provided on a downstream side with respect to the inflow position of the diffuser section.
The centrifugal compressor according to the present invention includes: the impeller that discharges the fluid, which flows along the axial direction, in the direction inclined from the axial direction; the casing section that houses the impeller; and the diffuser section that circulates the fluid discharged from the impeller, wherein the impeller has the hub and the shroud that are arranged along the axial direction side by side, and the plurality of blades that are arranged between the hub and the shroud.
Then, according to the centrifugal compressor according to the present invention, the flow path width of the diffuser section at the inflow position where the fluid flows in the diffuser section is narrower than the flow path width of the impeller at the discharge position where the fluid discharges from the impeller. Thus, the flow velocity of the fluid at the inflow position where the fluid flows in the diffuser section is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
Additionally, according to the centrifugal compressor according to the present invention, the flow path width enlarged section wider than the flow path width of the diffuser section at the inflow position is provided on a downstream side with respect to the inflow position of the diffuser section. Thus, it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid circulating in the diffuser section, compared to a case where the flow path width from the inflow position of the diffuser section to the downstream side is the same.
In a centrifugal compressor of a first aspect of the present invention, the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud, the hub side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the hub side wall at the inflow position, and the shroud side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the shroud side wall at the inflow position.
Thus, the both side walls at the flow path width enlarged section of the diffuser section are disposed in the direction in which the flow path width of the diffuser section enlarges, and it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section to the downstream side is the same.
In a centrifugal compressor of a second aspect of the present invention, the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud, and the hub side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the hub side wall at the inflow position.
Thus, the hub side wall of the diffuser section at the flow path width enlarged section is disposed in the direction in which the flow path width of the diffuser section enlarges, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section to the downstream side is the same. Additionally, the hub side wall is disposed in the direction in which the flow path width of the diffuser section enlarges, and therefore it is possible to form the flow path in which the fluid is stably circulated, in a case where the discharge direction in which fluid discharges from the impeller is directed to a direction of the hub side wall with respect to a direction orthogonal to the axial direction.
In a centrifugal compressor of a third aspect of the present invention, the diffuser section is defined by a hub side wall provided on a side of the hub, and a shroud side wall provided on a side of the shroud, and the shroud side wall at the flow path width enlarged section is disposed in a direction in which the flow path width of the diffuser section enlarges with respect to the shroud side wall at the inflow position.
Thus, the shroud side wall of the diffuser section at the flow path width enlarged section is disposed in the direction in which the flow path width of the diffuser section enlarges, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section to the downstream side is the same.
In the above centrifugal compressor of the first aspect of the present invention, a shape of the hub side wall may be a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section, and a shape of the shroud side wall may be a tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid at the intermediate position of the diffuser section.
Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section.
In the above centrifugal compressor of the second aspect of the present invention, a shape of the hub side wall may be a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section. Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section.
In the above centrifugal compressor of the third aspect of the present invention, a shape of the shroud side wall may be a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.
Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section.
In the above centrifugal compressor of the first aspect of the present invention, a shape of the hub side wall may be a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section, and a shape of the shroud side wall may be a stepped shape in which the flow path width enlarges along the circulating direction of the fluid stepwise at the intermediate position of the diffuser section.
Thus, the flow path connecting the inflow position and the downstream side can be formed at the intermediate position of the diffuser section by a relatively easy machining process.
In the above centrifugal compressor of the second aspect of the present invention, a shape of the hub side wall may be a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.
Thus, the flow path connecting the inflow position and the downstream side can be formed at the intermediate position of the diffuser section by a relatively easy machining process.
In the above centrifugal compressor of the third aspect of the present invention, a shape of the shroud side wall may be a stepped shape in which the flow path width enlarges along a circulating direction of the fluid stepwise at an intermediate position between the inflow position of the diffuser section and the flow path width enlarged section.
Thus, the flow path connecting the inflow position and the downstream side can be formed at the intermediate position of the diffuser section by a relatively easy machining process.
In a centrifugal compressor of a fourth aspect of the present invention, a ratio of the flow path width of the diffuser section at the inflow position to the flow path width of the impeller at the discharge position is not less than 0.5 and less than 0.8.
Thus, the flow path width of the diffuser section at the inflow position is made to be a sufficiently narrow width, and the flow velocity of the fluid at the inflow position where the fluid flows in the diffuser section is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
In a centrifugal compressor of a fifth aspect of the present invention, a ratio of a flow path width of the diffuser section at the flow path width enlarged section to the flow path width of the impeller at the discharge position is not less than 0.8 and not more than 1.0.
Thus, the flow path width of the diffuser section at the flow path width enlarged section is made to be a sufficiently wide width, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section to the downstream side is the same.
In a centrifugal compressor of a sixth aspect of the present invention, the impeller discharges the fluid, which flows along the axial direction, in a direction orthogonal to the axial direction.
Thus, in the centrifugal compressor that discharges the fluid, which flows along the axial direction, in the direction orthogonal to the axial direction, it is possible to suppress a malfunction such as shaft vibration due to rotating stall, and to suppress degradation of performance due to friction losses or the like.
In a centrifugal compressor of a seventh aspect of the present invention, a flow rate coefficient is not less than 0.01 and not more than 0.05.
Thus, in the centrifugal compressor having a relatively small flow rate coefficient, it is possible to suppress a malfunction such as shaft vibration due to rotating stall, and to suppress degradation of performance due to friction losses or the like.
According to the present invention, it is possible to provide a centrifugal compressor in which a malfunction such as shaft vibration due to rotating stall is suppressed, and degradation of performance due to friction losses or the like is suppressed.
Hereinafter, a centrifugal compressor 10 of a first embodiment will be described with reference to
The centrifugal compressor 10 illustrated in
The centrifugal compressor 10 of the first embodiment is a centrifugal compressor whose flow rate coefficient is a relatively small flow rate coefficient, namely not less than 0.01 and not more than 0.05.
The impeller 13 is connected to a driving device such as a motor and a turbine (not illustrated) through a rotary shaft (not illustrated) along the axis A, and is rotatable around the axis A. The impeller 13 has a hub 1 and a shroud 2 arranged along the axial direction of axis A, and a plurality of blades 3 arranged between the hub 1 and the shroud 2. Although only one blade 3 is illustrated in
The impeller 13 is provided with a space defined by an inner wall la of the hub 1 and an inner wall 2a of the shroud 2, and the space is partitioned into a plurality of spaces by the plurality of blades 3. Then, the impeller 13 applies radial centrifugal force to fluid flowing along the axial direction (direction illustrated by the arrow in
The diffuser section 15 is a fluid flow path defined by a hub side wall 15a provided on the hub 1 side and a shroud side wall 15b provided on the shroud 2 side. As illustrated in
The fluid, the flow velocity of which is reduced when passing through the diffuser section 15, is compressed, and flows in a volute section (volute chamber) 16 communicated with diffuser section 15. The compressed fluid that flows in the volute section 16 is discharged to a discharge pipe (not illustrated) through a discharge port (not illustrated).
Herein, operation of the centrifugal compressor 10 will be described.
In the centrifugal compressor 10, the driving device such as the motor and the turbine (not illustrated) rotates the impeller 13 around the axis A. The impeller 13 rotates, so that fluid taken from a suction port (not illustrated) is introduced into the casing section 11. To the fluid introduced into the casing section 11, centrifugal force in the direction orthogonal to the axis A (radial direction) is applied through the blades 3 by the rotation of the impeller 13. The fluid, to which the centrifugal force is applied, is discharged from the impeller 13, and flows in the diffuser section 15. The flow velocity of the fluid that flows in the diffuser section 15 reduces, and the fluid becomes compressed fluid to be discharged to the volute section 16. The compressed fluid that flows in the volute section 16 is discharged to the discharge pipe (not illustrated) through the discharge port (not illustrated).
Now, flow path widths of the impeller 13 and the diffuser section 15 will be described.
As illustrated in
Thus, the flow velocity of the fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, so that occurrence of rotating stall is suppressed. On the other hand, when the flow velocity of the fluid is increased, losses due to friction between the fluid and the hub side wall 15a and friction between the fluid and the shroud side wall 15b increase. Therefore, in the first embodiment, a flow path width enlarged section 15c in which the flow path width of the diffuser section 15 is enlarged is provided on the downstream side of the inflow position where the fluid flows in the diffuser section 15, in order to suppress the losses due to the friction.
As illustrated in
As illustrated in
The flow path width of the diffuser section 15 (distance in the axial direction between the hub side wall 15a and the shroud side wall 15b) in a range in a circulating direction of the fluid (direction orthogonal to the axial direction) from the inflow position where the fluid flows in the diffuser section 15 to L1 is constant, namely the flow path width W2. Then, at a position (intermediate position) where the distance from the inflow position is between L1 and L2, the hub side wall 15a that defines the diffuser section 15 has a tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid. Additionally, at the position (intermediate position) where the distance from the inflow position is between L1 and L2, the shroud side wall 15b that defines the diffuser section 15 also has a tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid.
The hub side wall 15a at a position where the distance from the inflow position where the fluid flows in the diffuser section 15 is between L2 and L3 is disposed in a direction in which the flow path width of the diffuser section 15 enlarges with respect to the hub side wall 15a at the inflow position where the fluid flows in the diffuser section 15. Similarly, the shroud side wall 15b is disposed in a direction in which the flow path width of the diffuser section 15 enlarges with respect to the shroud side wall 15b at the inflow position where the fluid flows in the diffuser section 15. At the position where the distance from the inflow position is between L2 and L3, the flow path width of the diffuser section 15 is constant, namely a flow path width W3.
As described above, the flow path width enlarged section 15c that is wider than the flow path width of the diffuser section 15 at the inflow position of the diffuser section 15 is provided on the downstream side in the circulating direction of the fluid with respect to the inflow position where the fluid flows in the diffuser section 15.
In the flow path width enlarged section 15c, the shape of the hub side wall 15a and the shape of the shroud side wall 15b are desirably horizontally symmetrical with respect to the center axis of the flow path.
In the first embodiment, a ratio of the flow path width W2 of the diffuser section 15 at the inflow position to the flow path width W1 of the impeller 13 at the discharge position is not less than 0.5 and less than 0.8. Additionally, a ratio of the flow path width W3 of the diffuser section 15 at the flow path width enlarged section 15c to the flow path width W1 of the impeller 13 at the discharge position is not less than 0.8 and not more than 1.0. However, as described above, the respective ratios are selected such that the flow path width W3 of the diffuser section 15 at the flow path width enlarged section 15c is wider than the flow path width W2 of the diffuser section 15 at the inflow position.
As described above, the centrifugal compressor 10 of the first embodiment includes the impeller 13 that discharges fluid, which flows along the axial direction, in the inclined direction from the axial direction (radial direction orthogonal to the axial direction), the casing section 11 that houses the impeller 13, and the diffuser section 15 that circulates the fluid discharged from the impeller 13, wherein the impeller 13 has the hub 1 and the shroud 2 arranged along the axial direction side by side, and the plurality of blades 3 arranged between the hub 1 and the shroud 2.
According to the centrifugal compressor 10 of the first embodiment, the flow path width W2 of the diffuser section 15 at the inflow position where the fluid flows in the diffuser section 15 is narrower than the flow path width W1 of the impeller 13 at the discharge position where the fluid is discharged from the impeller 13. Thus, the flow velocity of the fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
According to the centrifugal compressor 10 of the first embodiment, the flow path width enlarged section 15c having the flow path width W3 wider than the flow path width of the diffuser section 15 at the inflow position of the diffuser section 15 is provided downstream with respect to the inflow position of the diffuser section 15. Thus, it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid circulating in the diffuser section 15, compared to a case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
In the first embodiment, the diffuser section 15 is defined by the hub side wall 15a provided on the hub 1 side, and the shroud side wall 15b provided on the shroud 2 side. Then, the hub side wall 15a at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges with respect to the hub side wall 15a at the inflow position. Additionally, the shroud side wall 15b at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges with respect to the shroud side wall 15b at the inflow position.
Thus, the both side walls at the flow path width enlarged section 15c of the diffuser section 15 are disposed in the direction in which the flow path width of the diffuser section 15 enlarges, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to the case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
In the first embodiment, the shape of the hub side wall 15a is the tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid at the intermediate position between the inflow position of the diffuser section 15 and the flow path width enlarged section 15c, and the shape of the shroud side wall 15b is the tapered shape in which the flow path width gradually enlarges along the circulating direction of the fluid at the intermediate position of the diffuser section 15. Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section 15.
In the first embodiment, the ratio of the flow path width W2 of the diffuser section 15 at the inflow position to the flow path width W1 of the impeller 13 at the discharge position is not less than 0.5 and less than 0.8. Thus, the flow path width W2 relative to the flow path width W1 is made to be a sufficiently narrow width, and the flow velocity of the fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
In the first embodiment, the ratio of the flow path width W3 of the diffuser section 15 at the flow path width enlarged section 15c to the flow path width W1 of the impeller 13 at the discharge position is not less than 0.8 and not more than 1.0. Thus, the flow path width W3 relative to the flow path width W1 is made to be a sufficiently wide width, and it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to the case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
Now, a centrifugal compressor 10 of a second embodiment will be described with reference to
In the first embodiment, the both side walls (the hub side wall 15a and the shroud side wall 15b) of the diffuser section 15 at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges. On the contrary, in the second embodiment, one side wall (hub side wall 15a) of a diffuser section 15 at a flow path width enlarged section 15c is disposed in a direction in which a flow path width of the diffuser section 15 enlarges.
The second embodiment is a modification of the first embodiment. Configurations other than the shape of the hub side wall 15a which defines the diffuser section 15 are similar to those of the first embodiment, and therefore the description of the configurations will be omitted.
In the second embodiment, as illustrated in
Although the centrifugal compressor 10 illustrated in
In the modification of the second embodiment, the hub side wall 15a is disposed in the direction in which the flow path width of the diffuser section 15 enlarges, and therefore it is possible to form the flow path in which the fluid is stably circulated, and a friction loss caused by the hub side wall 15a is suppressed, in a case where a discharge direction in which fluid discharged from the impeller 13 is directed (inclined) to the direction of the hub side wall 15a with respect to the direction orthogonal to the axial direction.
Like the modification of the second embodiment, a compressor of a type of discharge in a direction inclined to the hub side wall 15a with respect to the direction orthogonal to the axial direction of the impeller 13 is called a mixed flow compressor. In the second embodiment, the compressor is not called the mixed flow compressor, but called a centrifugal compressor which means a compressor that converts fluid flowing in the axial direction into fluid including a velocity component in a direction orthogonal to an axis A (centrifugal direction).
As described above, according to the centrifugal compressor 10 of the second embodiment, a flow path width W2 of the diffuser section 15 at the inflow position where the fluid flows in the diffuser section 15 is narrower than a flow path width W1 of the impeller 13 at a discharge position where the fluid is discharged from the impeller 13. Thus, a flow velocity of fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
In the second embodiment, the hub side wall 15a at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges with respect to the hub side wall 15a at the inflow position. Thus, the hub side wall 15a of the diffuser section 15 at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
In the second embodiment, the shape of the hub side wall 15a is a tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at an intermediate position between the inflow position of the diffuser section 15 and the flow path width enlarged section 15c. Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section 15.
Now, a centrifugal compressor 10 of the third embodiment will be described with reference to
In the first embodiment, the both side walls (the hub side wall 15a and the shroud side wall 15b) of the diffuser section 15 at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges. On the contrary, in the third embodiment, one side wall (shroud side wall 15b) of a diffuser section 15 at a flow path width enlarged section 15c is disposed in a direction in which a flow path width of the diffuser section 15 enlarges.
The third embodiment is a modification of the first embodiment. Configurations other than the shape of the shroud side wall 15b which defines the diffuser section 15 are similar to those of the first embodiment, and therefore the description of the configurations will be omitted.
In the third embodiment, as illustrated in
As described above, according to the centrifugal compressor 10 of the third embodiment, a flow path width W2 of the diffuser section 15 at the inflow position where the fluid flows in the diffuser section 15 is narrower than a flow path width W1 of the impeller 13 at a discharge position where the fluid is discharged from the impeller 13. Thus, a flow velocity of fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
In the third embodiment, the shroud side wall 15b at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges with respect to the shroud side wall 15b at the inflow position. Thus, the shroud side wall 15b of the diffuser section 15 at the flow path width enlarged section 15c is disposed in the direction in which the flow path width of the diffuser section 15 enlarges, so that it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of the fluid, compared to a case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
In the third embodiment, the shape of the shroud side wall 15b is the tapered shape in which the flow path width gradually enlarges along a circulating direction of the fluid at the intermediate position of the diffuser section 15. Thus, it is possible to form the flow path that allows the fluid to stably circulate in the flow path at the intermediate position of the diffuser section 15.
Now, a centrifugal compressor 10 of the fourth embodiment will be described with reference to
In the first embodiment, between the flow path having the flow path width W2, provided at the inflow position of the diffuser section 15, and the flow path width enlarged section 15c having the flow path width W3, provided downstream of the diffuser section 15 (at the intermediate position), both the hub side wall 15a and the shroud side wall 15b have tapered shapes in which the flow path width gradually enlarges along the circulating direction of fluid.
On the contrary, in the fourth embodiment, in place of the tapered shape, a stepped shape in which the flow path width enlarges along the circulating direction of the fluid stepwise.
A flow path width of a diffuser section 15 (distance in the axial direction between a hub side wall 15a and a shroud side wall 15b) in a range in the circulating direction of the fluid (direction orthogonal to the axial direction) from an inflow position where the fluid flows in the diffuser section 15 to L4 is constant, namely a flow path width W2. Then, at a position where the distance from the inflow position is between L4 and L3, the flow path width of the diffuser section 15 is constant, namely a flow path width W3.
In the fourth embodiment illustrated in
In the fourth embodiment illustrated in
As described above, according to the centrifugal compressor 10 of the fourth embodiment, a flow path width W2 of the diffuser section 15 at the inflow position where the fluid flows in the diffuser section 15 is narrower than a flow path width W1 of an impeller 13 at a discharge position where the fluid is discharged from the impeller 13. Thus, a flow velocity of fluid at the inflow position where the fluid flows in the diffuser section 15 is sufficiently increased, and occurrence of rotating stall is suppressed, so that it is possible to suppress a malfunction such as shaft vibration due to rotating stall.
According to the centrifugal compressor 10 of the fourth embodiment, the flow path width enlarged section 15c having the flow path width W3, which is wider than the flow path width W2 of the diffuser section 15 at the inflow position of the diffuser section 15, is provided on the downstream side with respect to the inflow position of the diffuser section 15. Thus, it is possible to suppress degradation of performance due to, for example, friction losses caused by increase in the flow velocity of fluid circulating in the diffuser section 15, compared to a case where the flow path width from the inflow position of the diffuser section 15 to the downstream side is the same flow path width, namely the flow path width W2.
In the fourth embodiment, the shape of the hub side wall 15a is the stepped shape in which the flow path width enlarges along the circulating direction of the fluid stepwise at the intermediate position between the inflow position of the diffuser section 15 and the flow path width enlarged section 15c, and the shape of the shroud side wall 15b is the stepped shape in which the flow path width gradually enlarges along the circulating direction of the fluid at the intermediate position of the diffuser section 15. Thus, the flow path connecting the inflow position and the downstream side can be formed at the intermediate position of the diffuser section 15 by a relatively easy machining process.
Now, a centrifugal compressor 10 of the fifth embodiment will be described with reference to
In the first embodiment to the fourth embodiment, a single-stage centrifugal compressor provided with the volute section 16 downstream of the diffuser section 15 is described. However, the centrifugal compressor 10 of the fifth embodiment is a multistage centrifugal compressor in which fluid compressed by an impeller 13 and a diffuser section 15 at the first stage flows in an impeller 13 and a diffuser section 15 at a next stage.
The fifth embodiment is a modification of the first embodiment. Configurations are similar to those of the first embodiment except that a return bend 17 and a return vane 18 are provided in place of the volute section 16, and therefore the description of the configurations will be omitted.
In the first embodiment, compressed fluid that flows in the flow path width enlarged section 15c of the diffuser section 15 flows in the volute section 16 provided downstream of the flow path width enlarged section 15c. On the contrary, in the fifth embodiment, compressed fluid that flows in a flow path width enlarged section 15c of the diffuser section 15 flows in the return bend 17 provided downstream of the flow path width enlarged section 15c. The compressed fluid that flows in the return bend 17 is guided to the impeller 13 at the next stage (second stage) via the return vane 18.
In a case where a two-stage centrifugal compressor is employed as the centrifugal compressor 10 of the fifth embodiment, the fluid guided to the impeller 13 at the second stage is discharged to the diffuser section 15 at the second stage. The fluid further compressed in the diffuser section 15 at the second stage is guided to a volute section 16 similar to the volute section illustrated in
In a case where a three-stage centrifugal compressor is employed as the centrifugal compressor 10 of the fifth embodiment, fluid guided to an impeller 13 at a second stage is discharged to a diffuser section 15 at a second stage. The fluid further compressed in the diffuser section 15 at the second stage flows in a return bend 17 at the second stage. The compressed fluid that flows in the return bend 17 at the second stage is guided to an impeller 13 at a next state (third stage) via the return vane 18. The fluid guided to the impeller 13 at the third stage is discharged to a diffuser section 15 at the third stage. The fluid further compressed in the diffuser section 15 at the third stage is guided to a volute section 16 similar to the volute section illustrated in
As described above, the two-stage or the three-stage centrifugal compressor 10 is employed as the centrifugal compressor 10, so that it is possible to further increase a compression ratio of fluid. Additionally, an effect similar to the effect of the first embodiment can be exerted by the shapes of the impeller 13 and the diffuser section 15 at each stage.
As the shape of the diffuser section 15 at each stage, not only the shape described in the first embodiment, but also any shape described in the second embodiment to the fourth embodiment can be employed.
Additionally, in the fifth embodiment, the two-stage and the three-stage centrifugal compressor 10 are described. However, a modification of a four or more stage centrifugal compressor 10 may be employed.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/066989 | 6/20/2013 | WO | 00 |
