JP2016176398A - Diffuser, and centrifugal fluid machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffuser in which the separation of a flow on the pressure surfaces of vanes is suppressed, and a centrifugal fluid machine.SOLUTION: A vane 23 is formed such that the curvature radius of a pressure surface side of a front edge part 23a is varied from a shroud side wall part 21 to a hub side wall part 22, and such that the curvature radius Rb of two end parts 23a2 at which the absolute outlet angle of an impeller 12 in the front edge part 23a is large, is larger than the curvature radius Ra of a central part 23a1 at which said absolute outlet angle is small.SELECTED DRAWING: Figure 3-1

Description

  The present invention relates to a diffuser that converts kinetic energy of fluid flowing out of an impeller into pressure energy, and a centrifugal fluid machine.

  Generally, in a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor, a diffuser is provided on the downstream side of the impeller, and is configured to convert the kinetic energy of the fluid flowing out of the impeller into pressure energy. Conventionally, a diffuser in which a plurality of vanes are disposed between two opposing wall portions (a shroud side wall portion and a hub side wall portion) is known (see, for example, Patent Document 1). The vane guides the fluid that has flowed out of the impeller, and the angle at which the vane is arranged (for example, the inlet angle of the front edge) is based on the angle at which the fluid flows out of the impeller (absolute outflow angle). Is set.

Japanese Patent Laid-Open No. 06-288398

  By the way, the fluid flowing out from the impeller may flow into this type of diffuser with a velocity distribution in the vane height direction (direction parallel to the distance between the shroud side wall and the hub side wall). In this case, at the leading edge portion of the vane, the magnitude of the absolute outflow angle of the impeller tends to be different in the height direction of the vane according to the fluid flow velocity. For this reason, for example, when the absolute outflow angle of the impeller is larger than the entrance angle of the front edge portion at a part of the front edge portion, there is a possibility that separation occurs in the flow on the pressure surface side of the vane.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a diffuser and a centrifugal fluid machine that suppress flow separation on the pressure surface of the vane.

  In order to solve the above-described problems and achieve the object, the present invention includes a plurality of vanes provided on the downstream side of the impeller and disposed between the opposing shroud side wall and the hub side wall. A diffuser for converting the kinetic energy of the fluid that has flowed out into pressure energy, wherein the vane has changed the value of the radius of curvature of at least the pressure surface of the front edge from the shroud side wall to the hub side wall. Features.

  According to this configuration, since the vane has changed the value of the curvature radius of at least the pressure surface of the front edge portion from the shroud side wall portion to the hub side wall portion, the portion where the value of the curvature radius is increased It becomes duller than other parts with small values. For this reason, fluid separation at the pressure surface of the vane in a portion having a large value of the radius of curvature can be suitably suppressed.

  In the above configuration, the value of the radius of curvature may change according to the absolute outflow angle of the impeller at the front edge. According to this configuration, by changing the value of the radius of curvature according to the absolute outflow angle of the impeller, it is possible to improve the robustness against the fluctuation of the absolute outflow angle, and more suitable for fluid separation on the pressure surface of the vane. Can be suppressed.

  Further, the value of the radius of curvature of the large angle portion where the absolute outflow angle of the impeller is large may be formed larger than the value of the radius of curvature of the small angle portion where the absolute outflow angle is small. According to this structure, since the large angle part in a front edge part can be made blunt, the fluid peeling in the pressure surface of the vane in a large angle part can be suppressed suitably.

  Further, in the above configuration, the large angle portion is an end portion on at least one side of the shroud side wall portion and the hub side wall portion in the front edge portion, and the small angle portion is a portion between the shroud side wall portion and the hub side wall portion in the front edge portion. It may be an intermediate part. According to this configuration, the end can be blunted by increasing the radius of curvature of at least one end of the shroud side wall and the hub side wall at the front edge. For this reason, fluid separation at the pressure surface of the vane at the end can be suitably suppressed.

  The large angle part is an intermediate part between the shroud side wall part and the hub side wall part at the front edge part, and the small angle part is an end part on at least one side of the shroud side wall part and the hub side wall part at the front edge part. May be. According to this configuration, the intermediate portion can be blunted by increasing the radius of curvature of the intermediate portion between the shroud side wall portion and the hub side wall portion at the front edge portion. For this reason, fluid separation at the pressure surface of the vane at the end can be suitably suppressed.

  Further, the leading edge portion may increase at a constant rate from the value of the radius of curvature at the small angle portion to the value of the radius of curvature at the large angle portion. According to this configuration, it is possible to suitably suppress fluid separation on the pressure surface of the vane while forming the shape of the front edge portion of the vane relatively easily.

  In addition, the leading edge portion may increase stepwise from the value of the curvature radius at the small angle portion to the value of the curvature radius at the large angle portion. According to this configuration, since the shape of the front edge of the vane is further simplified, the manufacturing process of the vane can be simplified.

  Further, the leading edge portion may increase at an increasing rate that continuously changes from the value of the radius of curvature at the small angle portion to the value of the radius of curvature at the large angle portion. According to this configuration, the radius of curvature of the leading edge can be finely adjusted, so that fluid separation can be accurately suppressed.

  Moreover, the front edge part is good also as a shape which spaced apart the large angle part from the peripheral edge of the impeller rather than the small angle part. According to this configuration, it is possible to reduce the vibration by weakening the interference between the large angle portion and the impeller.

  Moreover, it is good also as a centrifugal fluid machine provided with the above-mentioned diffuser. According to this configuration, since fluid separation at the pressure surface of the vane at the large angle portion can be suitably suppressed, the fluid can be circulated without peeling inside the diffuser, and pressure recovery can be achieved with the diffuser. It is possible to improve the efficiency of the centrifugal fluid machine.

  According to the present invention, since the vane has changed the value of the radius of curvature at least on the pressure surface side of the front edge portion from the shroud side wall portion to the hub side wall portion, the portion where the value of the radius of curvature is increased It becomes duller than other parts with small values. For this reason, fluid separation at the pressure surface of the vane in a portion having a large value of the radius of curvature can be suitably suppressed.

FIG. 1 is a longitudinal sectional view of an impeller and a diffuser showing an outline of a centrifugal pump. FIG. 2 is a partial cross-sectional view of the diffuser showing the configuration of the vane. FIG. 3A is a diagram illustrating an example of a configuration in which the curvature radii at both ends of the front edge are changed to be larger than those at the center. FIG. 3-2 is a diagram illustrating another example of a configuration in which the curvature radii at both ends of the front edge are changed to be larger than those at the center. FIG. 3-3 is a diagram illustrating another example of a configuration in which the curvature radii at both ends of the front edge are changed to be larger than those at the center. FIG. 4 is a partial cross-sectional view of the diffuser showing a configuration in which the radius of curvature at the front edge is changed only on the pressure surface side of the vane. FIG. 5 is a partial cross-sectional view of the diffuser showing the configuration of the vane when the radius of curvature of the center portion at the front edge portion is formed larger than both end portions. FIG. 6 is a diagram illustrating an example of a configuration in which the radius of curvature of the central portion of the front edge portion is changed more greatly than that of both end portions. FIG. 7 is a partial cross-sectional view of a diffuser showing a configuration of a vane according to a modification.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, the constituent elements in the embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined, and when there are a plurality of embodiments, the embodiments can be combined.

  FIG. 1 is a longitudinal sectional view of an impeller and a diffuser showing an outline of a centrifugal pump. FIG. 2 is a partial cross-sectional view of the diffuser showing the configuration of the vane. FIG. 2 shows a cross section perpendicular to the rotation axis of the impeller. In the present embodiment, a centrifugal pump is illustrated as an example of a centrifugal fluid machine, but it can be applied to a centrifugal compressor, a centrifugal blower, or the like. As shown in FIG. 1, the centrifugal pump 10 has an impeller (centrifugal impeller) 12 that rotates in a predetermined rotation direction (arrow R direction) around a rotation shaft 11, and a fluid that flows out from a peripheral edge 12 a of the impeller 12. And a diffuser 13 that forms a flowing flow path.

  The impeller 12 includes a hub 12b formed so as to spread from the rotary shaft 11 in the circumferential direction, a shroud 12c disposed to face the hub 12b, and a circumferential space at an appropriate interval between the hub 12b and the shroud 12c. And 12d of blades formed side by side. The impeller 12 guides the fluid sucked from the suction port 12e that opens in the axial direction of the rotating shaft 11 along the blade 12d, and causes the fluid pressurized by the rotation to flow out from the peripheral edge 12a in the radial direction.

  As shown in FIG. 1, the diffuser 13 is a space that is provided on the downstream side of the impeller 12 and that is formed by the shroud side wall 21 and the hub side wall 22 that face each other. Here, a distance between the shroud side wall portion 21 and the hub side wall portion 22 forming the diffuser 13 is defined as a height h of the diffuser 13, and a direction extending from one of the shroud side wall portion 21 and the hub side wall portion 22 to the other is increased. The direction. As shown in FIG. 2, the diffuser 13 includes a plurality of vanes 23 that are arranged in the circumferential direction at appropriate intervals between the shroud side wall 21 and the hub side wall 22. These vanes 23 are each formed in a circular arc shape, and are arranged in a circular blade row on the radially outer side of the impeller 12.

  Further, the vane 23 is disposed with a predetermined angle (inlet angle β) between the center line (camber line) P at the front edge portion 23 a and the peripheral edge 12 a of the impeller 12. This inlet angle β can be set to an appropriate angle, for example, to coincide with the angle of the flow of fluid flowing out from the impeller 12 rotating at the rated rotational speed at the rated flow rate (absolute outflow angle α). Regarding the shape and number of the vanes 23, known techniques relating to the diffuser can be applied, and are appropriately set according to the performance required for the centrifugal pump 10. Further, the vanes 23 are arranged so that the distance from the adjacent vane 23 toward the radially outer side from the peripheral edge 12a of the impeller 12 increases. As a result, the flow passage area of the diffuser 13 formed by the shroud side wall portion 21, the hub side wall portion 22 and the adjacent vanes 23 and 23 increases toward the downstream side, so the flow velocity of the fluid flowing through the diffuser 13 is reduced. As a result, the kinetic energy of the fluid is converted into pressure energy. Further, the vane 23 has an arcuate outer peripheral surface side as a pressure surface 23b and an inner peripheral surface side as a negative pressure surface 23c.

  Here, as shown in FIG. 2, the fluid flowing out from the peripheral edge 12a of the rotating impeller 12 has a velocity component (radial velocity component Vr) directed radially outward from the impeller 12, and a direction along the circumferential direction. Velocity component (circumferential velocity component Vs). For this reason, the fluid has a velocity component (absolute velocity component Vf) in the direction in which the radial velocity component Vr and the circumferential velocity component Vs are added, and flows out from the peripheral edge 12a. In the present embodiment, an angle formed by the absolute velocity component Vf and the circumferential velocity component Vs is defined as an absolute outflow angle α of the impeller 12.

  By the way, the fluid flowing out of the impeller 12 tends to have a velocity distribution that varies in the height direction of the impeller 12 due to the shape of the impeller 12 and the like. This fluid flows into the diffuser 13 with a velocity distribution in the diffuser 13. Therefore, at the front edge portion 23a of the vane 23, the radial velocity component Vr varies in the height direction of the vane 23 (diffuser 13), so that the absolute outflow angle α of the fluid flowing out of the impeller 12 is the height. A different situation occurs in each direction.

  Specifically, as shown in FIG. 2, when the radial velocity component Vr is the first radial velocity component Vr1 and the circumferential velocity component Vs is the first circumferential velocity component Vs1, The absolute outflow angle α is the first absolute outflow angle α1 corresponding to the magnitude of the first absolute velocity component Vf1. On the other hand, due to the fluctuating speed distribution, the magnitude of the radial speed component Vr is larger than the first radial speed component Vr1, and the magnitude of the circumferential speed component Vs is the first circumferential speed component Vs. When the second circumferential velocity component Vs2 is smaller than the component Vs1, the absolute outflow angle α corresponds to the second absolute velocity component value Vf2, and is larger than the first absolute outflow angle α1. It becomes.

  As a case where the absolute outflow angle α changes in the height direction of the vane 23 (diffuser 13), for example, (1) the flow velocity (for example, the radial velocity component Vr) at both ends of the front edge portion 23a is larger than the flow velocity at the central portion. (2) It is assumed that the flow velocity at the central portion (for example, the radial velocity component Vr) at the front edge portion 23a is larger than the flow velocity at both ends. In both cases (1) and (2) described above, the absolute outflow angle α (second absolute outflow angle α2) of the portion where the flow velocity is large is larger than the entrance angle β of the front edge portion 23a of the vane 23. In that case, fluid separation is likely to occur on the pressure surface 23b of the vane 23, and the efficiency of the centrifugal pump 10 may be reduced due to the separation.

  In order to solve this problem, in the present embodiment, the front edge 23a of the vane 23 is formed with a curved surface, and the curvature radius of the front edge 23a is changed in the height direction. First, as an example in which the absolute outflow angle α changes, a case where the flow velocity (for example, the radial velocity component Vr) at both ends of the front edge portion 23a is larger than the flow velocity at the central portion will be described. FIG. 3A is a diagram illustrating an example of a configuration in which the curvature radii at both ends of the front edge are changed to be larger than those at the center. In FIG. 3A, the dotted line Q indicates the curvature circle of the front edge portion 23a, and the alternate long and short dash line S indicates the center position of the curvature circle of the front edge portion 23a.

  The flow velocity of both end portions (large angle portions) 23a2 on the shroud side wall portion 21 side and the hub side wall portion 22 side in the front edge portion 23a is the center portion 23a1 (intermediate portion, small angle portion) between the shroud side wall portion 21 and the hub side wall portion 22. 3), the vane 23 is formed such that the radius of curvature Rb of both ends 23a2 of the front edge 23a is larger than the radius of curvature Ra of the central portion 23a1, as shown in FIG. 3-1. According to this configuration, the absolute outflow angle α (first absolute outflow angle α1) at the central portion 23a1 is equal to or smaller than the entrance angle β of the front edge portion 23a (the absolute outflow angle α is small), and the both ends 23a2 Even when the absolute outflow angle α (second absolute outflow angle α2) is larger than the entrance angle β of the front edge portion 23a, by increasing the curvature radius Rb of the both end portions 23a2, the both end portions 23a2 are formed. It can be blunt. For this reason, fluid separation at the pressure surface 23b of the vane 23 at both ends 23a2 (large angle portion) can be suitably suppressed, and robustness against fluctuations in the absolute outflow angle α can be enhanced. Therefore, since the fluid can be circulated without peeling off the diffuser 13, the pressure recovery is achieved by the diffuser 13, and the efficiency of the centrifugal pump 10 can be improved.

  Further, in FIG. 3A, the front edge portion 23a is formed such that the curvature radius Rb of both end portions 23a2 is larger than the curvature radius Ra of the central portion 23a1, and both end portions 23a2 are determined from the value of the curvature radius Ra of the central portion 23a1. Is increased at a constant rate up to the value of the radius of curvature Rb. According to this configuration, it is possible to suitably suppress fluid separation at the pressure surface 23b of the vane 23 while relatively easily forming the shape of the front edge portion 23a of the vane 23.

  In the configuration of FIG. 3A, the front edge portion 23a is increased at a constant rate from the value of the curvature radius Ra of the central portion 23a1 to the value of the curvature radius Rb of both end portions 23a2, but the curvature radius Rb and the curvature radius are increased. If Ra satisfies the condition of Rb> Ra, another configuration can be adopted. FIGS. 3-2 and 3-3 are diagrams showing other examples of configurations in which the radii of curvature of both end portions at the front edge portion are changed larger than those at the center portion. As shown in FIG. 3-2, the front edge portion 23a may be increased stepwise from the value of the curvature radius Ra of the central portion 23a1 to the value of the curvature radius Rb of both end portions 23a2. In this configuration, since the shape of the front edge portion 23a of the vane 23 is further simplified, the manufacturing process of the vane 23 can be simplified. Further, as shown in FIG. 3C, the front edge portion 23a may be increased at an increasing rate that continuously changes from the value of the curvature radius Ra of the central portion 23a1 to the value of the curvature radius Rb of both end portions 23a2. . In this configuration, since the radius of curvature of the front edge portion 23a can be finely adjusted, fluid separation can be accurately suppressed.

  In the configurations of FIGS. 3-1 to 3-3, the curvature radii Rb of both ends 23a2 are set to the same value. However, the curvature of each end 23a2 depends on the actual velocity distribution of the fluid flowing out from the impeller 12. The radius Rb may be changed as appropriate. In the above configuration, the radius of curvature of both the end portions 23a2 of the front edge portion 23a is increased. However, the radius of curvature of at least one end portion 23a2 is set in accordance with the actual velocity distribution of the fluid flowing out from the impeller 12. Just make it bigger. Moreover, in the said structure, although the curvature circle of the front edge part 23a was made into the perfect circle, if the curvature radius of the front edge part 23a changes, it is good also as an ellipse shape.

  Further, in the above configuration, as shown in FIG. 2, the radius of curvature of both end portions 23a2 is increased on both the pressure surface 23b and the negative pressure surface 23c. On the other hand, when the absolute outflow angle α is larger than the inlet angle β of the leading edge 23a of the vane 23, fluid separation is more likely to occur at the pressure surface 23b than at the negative pressure surface 23c. For this reason, as shown in FIG. 4, only the pressure surface 23b side of the vane 23 is good also as a structure which enlarges a curvature radius. According to this configuration, fluid separation at the pressure surface 23b of the vane 23 can be more effectively suppressed.

  Subsequently, as an example in which the absolute outflow angle α changes, a case where the flow velocity (for example, the radial velocity component Vr) of the central portion 23a1 in the leading edge portion 23a is larger than the flow velocity of the both end portions 23a2 will be described. FIG. 5 is a partial cross-sectional view of the diffuser showing the configuration of the vane in the case where the radius of curvature of the central portion at the front edge portion is formed larger than both ends, and FIG. 6 shows the radius of curvature of the central portion at the front edge portion. It is a figure which shows an example of the structure changed more largely than both ends. In FIG. 6, similarly to FIGS. 3-1 to 3-3, the dotted line Q indicates the curvature circle of the front edge portion 23a, and the alternate long and short dash line S indicates the center position of the curvature circle of the front edge portion 23a. Yes.

  The flow velocity of the central portion 23a1 (intermediate portion, large angle portion) between the shroud side wall portion 21 and the hub side wall portion 22 at the front edge portion 23a is the both end portions (small angle portion) on the shroud side wall portion 21 side and the hub side wall portion 22 side. When the flow velocity is higher than 23a2, the vane 23 is formed such that the radius of curvature Ra of the central portion 23a1 is larger than the radius of curvature Rb of both end portions 23a2, as shown in FIGS. According to this configuration, the absolute outflow angle α (first absolute outflow angle α1) at both ends 23a2 is equal to or smaller than the entrance angle β of the front edge portion 23a (the absolute outflow angle α is small), and the central portion (large angle). Portion) Even when the absolute outflow angle α (second absolute outflow angle α2) at 23a1 is larger than the entrance angle β of the front edge portion 23a, by increasing the radius of curvature Ra of the central portion 23a1, The central portion 23a1 can be blunt. For this reason, fluid separation at the pressure surface 23b of the vane 23 in the central portion (large angle portion) 23a1 can be suitably suppressed, and robustness against fluctuations in the absolute outflow angle α can be improved. Therefore, since the fluid can be circulated without peeling the inside of the diffuser 13, the pressure recovery by the diffuser 13 can improve the efficiency of the centrifugal pump 10.

  In the configuration of FIG. 6, the radius of curvature Rb of both ends 23a2 is increased at a constant rate from the value of the radius of curvature Ra of the central portion 23a1, but as described above, the radius of curvature Rb and the radius of curvature Ra. If the condition of Ra> Rb is satisfied, as described with reference to FIGS. 3-2 and 3-3, steps are performed from the value of the curvature radius Rb of the both end portions 23a2 to the value of the curvature radius Ra of the central portion 23a1. Alternatively, it may be increased at a rate of increase that continuously changes from the value of the radius of curvature Rb of both ends 23a2 to the value of the radius of curvature Ra of the central portion 23a1.

  Furthermore, the curvature radius Rb of the both end portions 23a2 does not need to be the same value, and the curvature radius Rb may be appropriately changed according to the actual velocity distribution of the fluid flowing out from the impeller 12. Although the curvature circle of the front edge portion 23a is a perfect circle, it may be elliptical if the curvature radius of the front edge portion 23a changes. Furthermore, as described with reference to FIG. 4 described above, the radius of curvature of the central portion 23a1 of the front edge portion 23a may be increased only on the pressure surface 23b side of the vane 23.

  As described above, according to the present embodiment, a plurality of vanes 23 that are provided on the downstream side of the impeller 12 and are disposed between the opposed shroud side wall 21 and the hub side wall 22 are provided. The diffuser 13 converts kinetic energy into pressure energy, and the vane 23 changes the radius of curvature of at least the pressure surface 23b side of the front edge portion 23a between the shroud side wall portion 21 and the hub side wall portion 22, Since the radius of curvature Rb of both ends 23a2 of the impeller 12 having a large absolute outflow angle α in the portion 23a is larger than the radius of curvature Ra of the central portion 23a1 having a small absolute outflow angle α, both ends 23a2 are blunted. Can do. For this reason, fluid separation at the pressure surface 23b of the vane 23 at both end portions 23a2 can be suitably suppressed, and the pressure recovery by the diffuser 13 can improve the efficiency of the centrifugal pump 10.

  Further, according to the present embodiment, the vane 23 changes the radius of curvature of at least the pressure surface 23b side of the front edge portion 23a between the shroud side wall portion 21 and the hub side wall portion 22, and the impeller 12 at the front edge portion 23a. Since the curvature radius Ra of the central portion 23a1 having a large absolute outflow angle α is larger than the curvature radius Rb of both end portions 23a2 having a small absolute outflow angle α, the central portion 23a1 can be blunted. For this reason, fluid separation at the pressure surface 23b of the vane 23 in the central portion 23a1 can be suitably suppressed, and the pressure recovery by the diffuser 13 can improve the efficiency of the centrifugal pump 10.

  In addition, according to the present embodiment, the front edge portion 23a is changed from the value of the curvature radius Ra (Rb) at the center portion 23a1 (or end portion 23a2) as a small angle portion to the end portion 23a2 (or as a large angle portion). Since it increases at a constant rate up to the value of the radius of curvature Rb (Ra) at the central portion 23a1), the fluid at the pressure surface 23b of the vane 23 can be formed relatively easily while the shape of the front edge portion 23a of the vane 23 is formed relatively easily. Peeling can be suitably suppressed.

  In addition, according to the present embodiment, the front edge portion 23a is changed from the value of the curvature radius Ra (Rb) at the center portion 23a1 (or end portion 23a2) as a small angle portion to the end portion 23a2 (or as a large angle portion). Since the radius of curvature Rb (Ra) at the central portion 23a1) increases stepwise, the shape of the front edge portion 23a of the vane 23 is further simplified, thereby simplifying the manufacturing process of the vane 23. it can.

  In addition, according to the present embodiment, the front edge portion 23a is changed from the value of the curvature radius Ra (Rb) at the center portion 23a1 (or end portion 23a2) as a small angle portion to the end portion 23a2 (or as a large angle portion). Since it increases at an increasing rate that continuously changes to the value of the radius of curvature Rb (Ra) at the central portion 23a1), the radius of curvature of the leading edge portion 23a can be finely adjusted, and fluid separation can be suppressed with high precision. Can do.

  As mentioned above, although the front edge part 23a of the vane 23 demonstrated the form formed so that it might become equidistant from the peripheral edge 12a of the impeller 12 in above-described embodiment, it does not restrict to this. FIG. 7 is a partial cross-sectional view of a diffuser showing a configuration of a vane according to a modification. As shown in FIG. 7, the diffuser 113 includes a vane 123 disposed between the shroud side wall portion 21 and the hub side wall portion 22, and the vane 123 has a curvature radius Rb of both end portions 123a2 of the front edge portion 123a. It is formed larger than the radius of curvature Ra of the central portion 123a1.

  Further, the front edge portion 123a of the vane 123 has both end portions 123a2 having a large diameter separated from the peripheral edge 12a of the impeller 12 rather than the central portion 123a1. Specifically, a distance Lb between both end portions 123a2 and the peripheral edge 12a of the impeller 12 is larger than a distance La between the central portion 123a1 and the peripheral edge 12a of the impeller 12. In this configuration, both end portions (large angle portion) 123a2 having a large diameter are separated from the peripheral edge 12a of the impeller 12 rather than the central portion (small angle portion) 123a1 having a small diameter, whereby interference between the both end portions 123a2 and the impeller 12 occurs. The vibration can be reduced.

  In the configuration of FIG. 7 described above, the front edge portion 123a is increased at an increasing rate that continuously changes from the value of the curvature radius Ra of the central portion 123a1 to the value of the curvature radius Rb of both end portions 123a2. -1 and FIG. 3-2, it may be increased at a constant rate from the value of the curvature radius Ra of the central portion 123a1 to the value of the curvature radius Rb of both end portions 123a2, or the curvature radius Ra of the central portion 123a1. The value may be increased step by step from the value of 2 to the value of the radius of curvature Rb of both ends 123a2. Further, in the configuration of FIG. 7 described above, both end portions 123a2 are separated from the peripheral edge 12a of the impeller 12 rather than the central portion 123a1, but if the portion having a larger radius of curvature is the central portion, this central portion is more than the both end portions. Alternatively, the impeller 12 may be separated from the peripheral edge 12a.

  In the above-described embodiment, as an example of changing the curvature radius of the front edge portion 23a between the shroud side wall portion 21 and the hub side wall portion 22, the curvature radius of the portion where the absolute outflow angle α of the impeller 12 is large is the absolute radius. The configuration in which the radius of curvature of the portion where the outflow angle α is small is larger than the curvature radius of the portion where the outflow angle α is small has been described, but the present invention is not limited to this, and the radius of curvature of the portion where the absolute outflow angle α is small It is good also as a structure made small.

10 Centrifugal pump (centrifugal fluid machine)
DESCRIPTION OF SYMBOLS 11 Rotating shaft 12 Impeller 12a Periphery 12b Hub 12c Shroud 12d Blade 12e Suction port 13, 113 Diffuser 21 Shroud side wall part 22 Hub side wall part 23, 123 Vane 23a, 123a Front edge part 23b Pressure surface 23c Negative pressure surface 23a1 Central part (intermediate part) , Small angle part, large angle part)
23a2 end (large angle part, small angle part)
Ra, Rb Curvature radius α Absolute outflow angle

Claims (10)

A diffuser that is provided on the downstream side of the impeller and includes a plurality of vanes disposed between the shroud side wall and the hub side wall facing each other, and converts the kinetic energy of the fluid flowing out of the impeller into pressure energy,
The diffuser according to claim 1, wherein the vane has a value of a radius of curvature at least on a pressure surface side of a front edge portion changed between the shroud side wall portion and the hub side wall portion.   The diffuser according to claim 1, wherein the value of the radius of curvature changes according to an absolute outflow angle of the impeller at the front edge.   The value of the curvature radius of the large angle portion of the impeller having a large absolute outflow angle is formed to be larger than the value of the curvature radius of the small angle portion of the small absolute outflow angle. Diffuser as described in   The large angle portion is an end portion on at least one side of the shroud side wall portion and the hub side wall portion in the front edge portion, and the small angle portion is the shroud side wall portion and the hub side wall portion in the front edge portion. The diffuser according to claim 3, wherein the diffuser is an intermediate portion.   The large angle part is an intermediate part between the shroud side wall part and the hub side wall part at the front edge part, and the small angle part is at least one of the shroud side wall part and the hub side wall part at the front edge part. The diffuser according to claim 3, wherein the diffuser is a side end.   6. The front edge portion increases at a constant rate from the value of the radius of curvature at the small angle portion to the value of the radius of curvature at the large angle portion. The diffuser according to the item.   The said front edge part increases in steps from the value of the said radius of curvature in the said small angle part to the value of the said radius of curvature in the said large angle part. Diffuser as described in   6. The front edge portion increases at an increasing rate that continuously changes from the value of the radius of curvature at the small angle portion to the value of the radius of curvature at the large angle portion. The diffuser of any one of these.   The diffuser according to any one of claims 3 to 8, wherein the front edge portion has a shape in which the large angle portion is separated from the periphery of the impeller rather than the small angle portion.   A centrifugal fluid machine comprising the diffuser according to any one of claims 1 to 9.

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