JP5287329B2 - Pump impeller - Google Patents

Description

  The present invention relates to a pump impeller housed in a shroud.

  The pump gives swirling energy to the working fluid flowing from the inlet by an impeller that is fixed in the shroud and rotates about a rotation shaft, and converts the swirling energy into pressure by guide vanes installed downstream of the impeller. A moving blade (impeller blade) on the impeller is fixed to a shaft interlocked with a drive source (motor or the like) via a hub, and rotates integrally with the shaft. In general, the shape of the leading edge and the trailing edge of the impeller blade is generally linear from the hub side to the shroud side so as to follow a virtual straight line extending radially outward from the shaft center (rotating shaft). Is formed. That is, the angular direction positions around the rotation axis of the hub side end portion and the shroud side end portion at the front edge portion and the rear edge portion are substantially the same. Further, the radially outer end portion of the impeller blade is called a tip, and there is a gap between the tip portion and the shroud (see Patent Document 1, etc.).

Japanese Patent Laid-Open No. 5-272491

  By the way, an important performance required for a pump is efficiency. The efficiency of the pump is the ratio of the impeller power and the energy received by the fluid, and is preferably as high as possible. Part of the power that drives the impeller is dissipated as heat due to vortices and friction generated in the fluid, resulting in energy loss. In order to obtain a highly efficient pump, it is effective to reduce the energy loss generated in the fluid.

  One of the major causes of energy loss is the occurrence of “leakage flow”. The leakage flow is a flow generated in the gap between the tip portion and the shroud in the impeller blade described above, and all the energy of the flow is lost. Therefore, if this leakage flow is reduced as much as possible, a highly efficient pump can be obtained. As a measure for reducing the leakage flow, there is a method of narrowing a gap generated between the tip portion and the shroud, but there is a limit due to a problem of machine assembly accuracy.

  An object of the present invention is to provide a pump impeller with less leakage flow generated at a tip portion.

(1) In order to achieve the above object, the present invention includes a hub that is provided inside a shroud and that rotates around a rotation shaft, and an impeller blade that is attached to the outer periphery of the hub and rotates together with the hub. The impeller blade is bent upstream in the flow direction of the working fluid in the vicinity of the tip portion, and the tip portion is compared with the portion located on the hub side from the bent portion of the impeller blade. The blade section warpage of the impeller blade from the bent portion to the tip portion is compared with the blade section warpage of the portion on the hub side from the bent portion. And relatively small .

  (2) In the above (1), preferably, the front edge side of the tip portion of the impeller blade protrudes in the rotation direction of the rotation shaft.

( 3 ) In the above (1) or (2) , preferably, the bent portion is formed in a region of 80% or more of the tip diameter in the impeller blade.

( 4 ) In any one of the above (1) to ( 3 ), preferably, the angle at which the impeller blade is bent with respect to the bent portion is 30 degrees or more.

( 5 ) In the above (2), preferably, the front edge side of the tip portion protrudes at a position rotated by 30 degrees or more in the rotation direction of the rotary shaft with the front edge side of the bent portion as the center. And

  According to the present invention, since the leakage flow at the tip portion can be reduced, the efficiency of the pump impeller can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall view of a pump according to an embodiment of the present invention, and FIG. 2 is a diagram (rotational direction projection diagram) in which a pump according to an embodiment of the present invention is projected onto a plane including a rotating shaft 2. In FIG. 2, the rotation axis 2 is expressed as the z-axis of cylindrical coordinates, the pump rotation direction is expressed as the angular direction (θ direction), and the distance from the rotation axis 2 is expressed as the radial direction (r direction).

  The pump shown in these drawings includes a cylindrical casing 8, a shaft 4 that is housed in the casing 8 and rotates around the rotary shaft 2, and a pump impeller (hereinafter simply referred to as “pump impeller”) that applies energy to the working fluid flowing from the pump inlet. (Sometimes referred to as an “impeller”) 20, a guide blade 10 that converts the swirling energy of the fluid from the impeller 20 into pressure, and a shroud 7 that covers the impeller 20 and the guide blade 10 from the outside to form an annular flow path. I have.

  The impeller 20 includes a hub 5 and impeller blades 9. The hub 5 is fixed to the shaft 4 and rotates around the rotation shaft 2 inside the shroud 7. The hub 5 of the present embodiment rotates in the direction of an arrow 3 shown in FIG. 3 described later (that is, the counterclockwise direction in FIG. 3). The shaft 4 is interlocked with a drive source such as a motor, and the impeller 20 rotates integrally with the shaft 4. A plurality of impeller blades 9 are attached to the outer periphery of the hub 3 and guide the working fluid flowing from the pump inlet side between the blades. The radially outer end (that is, the outer peripheral edge) of the impeller blade 9 is referred to as a tip portion 6. The tip portion 6 faces the shroud 7, and a gap is formed between the tip portion 6 and the shroud 7.

  The guide blades 10 are a plurality of blades bridged between the shroud 7 and the casing 8 on the downstream side of the impeller 20. Therefore, it does not rotate like the impeller 20.

Here, the impeller 20 according to the present embodiment will be described in detail.
FIG. 3 is a top view of the impeller according to the embodiment of the present invention, and FIG. 4 is a cross-sectional view of the impeller according to the embodiment of the present invention cut along a plane including the rotating shaft 2. In addition, the same code | symbol is attached | subjected to the same part as the previous figure, and description is abbreviate | omitted (the following figure is also the same).

  In these drawings, the side surfaces of three cones (conical surfaces) parallel to the shroud 7 are considered, and the conical surface closest to the hub 5 is SA, the conical surface passing through the tip portion 6 and closest to the shroud 7 is SC, A conical surface located in the middle of SA and SC and in the vicinity of the tip portion 6 is defined as SB. That is, in FIG. 3, the conical surface SA is defined such that the difference dR_AB between the conical surfaces SA and SB and the difference dR_BC between the conical surfaces SB and SC are equal.

  Here, the blade edge of the impeller blade 9 is the blade edge on the upstream side (pump inlet side) of the flow path as the leading edge 11 and the blade edge on the downstream side of the flow path (guide blade 10 side) is the rear edge. Let it be edge 12. Furthermore, the downstream blade surface (lower blade surface in FIG. 4) on which a relatively high pressure acts is a positive pressure surface 91, and the upstream blade surface (upper side in FIG. 4) on which a relatively low pressure acts. The blade surface) is a suction surface 92.

  As shown in FIG. 4, the impeller blade 9 of the present embodiment is bent at the intersection line with the conical surface SB. Here, the intersecting line between the conical surface SB and the impeller blade 9 is a bent portion 25. The impeller blade 9 is bent upstream in the flow direction 1 of the working fluid at the bent portion 25, and the tip portion 6 is compared with the portion located on the hub 5 side from the bent portion 25 as shown in FIG. And located upstream in the flow direction 1 of the working fluid. Although details will be described later, when the impeller blade 9 is bent in this manner, the leakage flow in the tip portion 6 can be reduced.

  Here, when the radial distance from the rotating shaft 2 to the tip portion 6 is the tip diameter R, it is preferable to set the conical surface SB in an area of 80% or more of the tip diameter SP. That is, when the radial distance from the rotation shaft 2 to the conical surface SB is Rsb, the conical surface SB is preferably set so that “Rsb ≧ 0.8R” is satisfied. When the conical surface SB, that is, the bent portion 25 is set in this way, it is possible to suppress a decrease in energy conversion efficiency of the entire blade surface.

  The angle (PX (see FIG. 4)) at which the impeller blade 9 is bent upstream in the flow direction 1 of the working fluid with respect to the bent portion 25 is preferably 30 degrees or more. This will be described in more detail. A plane SP including the rotation axis 2 is defined as shown in FIG. 3, and points where the plane SP and the conical surfaces SA, SB, SC intersect on the suction surface 92 of the impeller blade 9 are respectively defined. When the points PA, PB and PC are taken, the impeller blade 9 is bent so that an angle PX (see FIG. 4) formed by a straight line connecting the point PA and the point PB and a straight line connecting the point PB and the point PC is 30 degrees or more. It is preferable. This is because if the impeller blades 9 are bent in this way, the occurrence of leakage flow can be more effectively reduced.

  By the way, the front edge 11 side of the tip portion 6 of the impeller blade 9 of the present embodiment protrudes in the rotation direction (θ direction) 3 of the rotating shaft 2 as shown in FIG. That is, the front edge 11 of the impeller blade 9 is provided with a protruding portion 26 in which the tip portion 6 protrudes in the rotation direction 3 of the rotating shaft 2. Although details will be described later, when the impeller blades 9 are protruded in this manner, the leakage flow in the tip portion 6 can be reduced.

  Here, the front edge 11 side (HC) of the tip portion 6 is provided at a position rotated about 30 degrees toward the rotation direction 3 of the rotary shaft 2 around the front edge 11 side (HB) of the bent portion 25. It is preferable. This will be described in more detail. As shown in FIG. 3, when the points where the conical surfaces SA, SB and SC intersect with the leading edge 11 are points HA, HB and HC, respectively, straight lines connecting the points HA and HB. It is preferable to form the protruding portion 26 so that an angle HX formed by the straight line connecting the point HB and the point HC is 30 degrees or more. If the impeller blades 9 are bent in this way, the occurrence of leakage flow can be more effectively reduced.

  Further, it is preferable that the warpage of the blade cross section from the bent portion 25 to the tip portion 6 in the impeller blade 9 is relatively smaller than the warpage of the blade cross section of the portion on the hub 5 side from the bent portion 25. That is, in the impeller blade 9 of the present embodiment, a blade section having a weak warpage is used in the region radially outward (on the shroud 7 side) from the conical surface SB close to the tip portion 6, and radially inward (hub) from the conical surface SB. In the region on the 5th side, a blade section with strong warpage is used. If the blade cross section is configured in this way, the leakage flow at the tip portion 6 can be reduced while maintaining high energy conversion efficiency in the region inside the conical surface SB occupying most of the impeller blade 9. This point will be described below.

  FIG. 5 is a view showing a cross-sectional shape of the impeller blade 9 in the circumferential direction, that is, a cross-sectional view of the impeller blade 9 cut along a conical surface parallel to the shroud 7. FIG. 5A is a blade cross-sectional view of the impeller blade 9 at the conical surface SB, and FIG. 5B is a blade cross-sectional view of the impeller blade 9 at the conical surface SC. FIG. 6 is a pressure distribution diagram on the blade cross section shown in FIG. In FIG. 6, the vertical axis represents pressure and the horizontal axis represents the position from the leading edge 11 on the blade surface. In FIG. 6, the pressure distribution indicated by the solid line is that of the blade cross section shown in FIG. 5A, and the pressure distribution indicated by the broken line is that of the blade cross section shown in FIG.

  In general, when a working fluid flows around a moving blade (impeller blade), a pressure difference due to lift is generated on the blade surface, and the working fluid receives energy by the pressure difference. The pressure difference between the pressure surface and the suction surface becomes the blade load, and the blade load represents the strength of energy given to the fluid.

  When the blade warp 21 is large as shown in FIG. 5A, the lift force generated increases and the blade load 32 (see FIG. 6) also increases. On the other hand, when the warp 23 is small as shown in FIG. 5B, the generated lift is also reduced, and the blade load 35 (see FIG. 6) is also reduced. In the tip portion 6 of the impeller blade 9, due to the pressure difference (blade surface pressure difference) generated between the blade surfaces, leakage flows from the high pressure surface 91 side to the low pressure surface 92 side. Therefore, from the viewpoint of reducing the leakage flow, it is better that the blade surface pressure difference is small.

  By the way, from the viewpoint of blade design, since the impeller peripheral speed increases toward the tip portion 6 side farther from the rotating shaft 2, increasing the blade surface pressure difference on the tip portion 6 side increases energy conversion efficiency. Therefore, from the viewpoint of improving the energy conversion efficiency and improving the pump efficiency, it is desirable to increase the blade surface pressure difference closer to the tip portion 6. However, when the blade surface pressure difference in the tip portion 6 is increased, the leakage flow increases as described above, which may cause a reduction in efficiency.

  Therefore, in the present embodiment, as described above, a blade section having a weak warp is used in a region radially outward from the conical surface SB close to the tip portion 6, and a warp is strong in a region radially inward from the conical surface SB. The wing cross section is used. If the blade cross section is formed in this way, the blade surface pressure difference can be increased in the region from the hub 5 to the vicinity of the tip portion 6 to increase the energy conversion efficiency, and the blade surface pressure difference can be reduced in the vicinity of the tip portion 6. As a result, the leakage flow can be suppressed, and the high efficiency of the entire pump can be realized.

  Here, the operation and effect of the impeller of the present embodiment configured as described above will be described in comparison with the prior art.

FIG. 7 is a cross-sectional view of an impeller according to the prior art cut along a plane including a rotation axis.
In this figure, points PA, PB, PC are intersections of the conical surfaces SA, SB, SC and the blade suction surface. The impeller blade shown in this figure uses a weakly warped blade cross section in a region radially outward from the conical surface SB and uses a highly warped blade cross section in a region radially inward from the conical surface SB. However, unlike the present embodiment, the conical surface SB is not bent.

  In the conventional technology configured as described above, even if the warpage of the blade section near the tip portion is weakened, it is difficult to reduce the leakage flow without reducing the blade surface pressure difference. This is because the region where the warp is weak is relatively smaller than the region where the warp is strong, and the effect of pressure on the working fluid is also reduced. That is, in FIG. 7, since the warpage of the blade cross section is relatively strong on the radially inner side from the conical surface SB, the pressure at the point PB becomes low as shown in FIG. However, this is because the pressure at the point PB exceeds the pressure difference reducing effect exhibited by weakening the warpage in the vicinity of the tip portion 6, and the pressure at the point PC is also lowered.

  On the other hand, the impeller blade 9 according to the present embodiment is bent upstream in the flow direction 1 of the working fluid in the vicinity of the tip portion 6, and the tip portion 6 is bent from the bent portion 25 to the hub 5. Compared with the portion located on the side, the fluid is located on the upstream side in the flow direction 1 of the working fluid. When the impeller blades 9 are formed in this way, the point PC on the tip portion 6 side is more susceptible to pressure from a point PBU closer to the distance than the point PB located on the negative pressure surface 92.

  In general, the pressure of the working fluid increases as the distance from the suction surface 92 increases. Therefore, the pressure at the point PBU located upstream of the point PB on the conical surface SB is higher than the pressure at the point PB. Thereby, since the pressure of the point PC in this Embodiment becomes higher than the pressure of the point PC of a prior art, the blade surface pressure difference in the tip part 6 is reduced, and a leak flow can be reduced. Therefore, according to the present embodiment, the leakage flow at the tip portion 6 can be reduced, so that the efficiency of the pump impeller can be improved.

  By the way, the impeller blade 9 according to the present embodiment includes a protruding portion 26 in addition to the above configuration. Next, this effect will be described below in comparison with the prior art.

FIG. 8 is a top view of an impeller according to the prior art.
In this figure, points HA, HB, and HC are the intersections of the conical surfaces SA, SB, and SC and the leading edge 11, and points HB2 and HC2 are points on the conical surfaces SB and SC that are points of the points HB and HC. It is a point located downstream. Although it is desirable that the pressure at the point HC2 that affects the leakage flow is high, it is also affected by the low pressure at the point HB2, and the pressure at the point HC2 drops to near the pressure at the point HB2, thus reducing the leakage flow. Difficult to do. The same applies to the points HB and HC at the leading edge 11.

  On the other hand, the front edge 11 side of the tip portion 6 in the impeller blade 9 according to the present embodiment protrudes in the rotation direction of the rotating shaft 2. When the impeller blade 9 is formed in this way, the pressure at the point HC2 on the tip portion 6 side is not easily influenced by the pressure from the point HB closer than the downstream point HB2 as in the prior art. . In general, as described with reference to FIG. 7, the pressure on the negative pressure surface 92 increases as it approaches the front edge 11, so that the pressure at the point HB is higher than the pressure at the point HB <b> 2. Thereby, since the pressure of the point HC in this Embodiment becomes higher than a prior art, the blade surface pressure difference in the tip part 6 is reduced, and a leak flow can be reduced. Therefore, if the protruding portion 26 is provided in addition to the bent portion 25 as in the present embodiment, the leakage flow can be further reduced, so that the efficiency of the pump impeller can be further improved.

  In the above description, the impeller blade 9 including both the bent portion 25 and the protruding portion 26 has been described. However, if any one of them is provided, the leakage flow in the tip portion 6 is reduced, so that the efficiency of the pump impeller is reduced. Can be improved.

1 is an overall view of a pump according to an embodiment of the present invention. The figure which projected the pump which concerns on embodiment of this invention on the plane containing a rotating shaft. The top view of the impeller which concerns on embodiment of this invention. Sectional drawing which cut | disconnected the impeller which concerns on embodiment of this invention by the plane containing a rotating shaft. The figure which shows the cross-sectional shape in the circumferential direction of the impeller blade in embodiment of this invention. FIG. 6 is a pressure distribution diagram on a blade cross section shown in FIG. 5. Sectional drawing which cut | disconnected the impeller which concerns on a prior art by the plane containing a rotating shaft. The top view of the impeller which concerns on a prior art.

1 Direction of flow flowing in from pump inlet 2 Pump rotation shaft (rotation shaft)
3 Pump rotation direction 4 Shaft 5 Hub 6 Tip 7 Shroud 8 Casing 9 Impeller 10 Guide vane 11 Blade leading edge (front edge)
12 Wing trailing edge
20 Impeller blade cross-sectional shape with strong warp 21 Warp amount of impeller blade with strong warp 22 Impeller blade cross-sectional shape with weak warp 23 Warp amount of impeller blade with weak warp 25 Bending portion 26 Protruding portion 30 On the pressure surface of an impeller blade with strong warp Pressure distribution 31 Pressure distribution on the suction surface of the impeller blade with strong warpage 32 Pressure difference between the pressure surface and suction surface of the impeller blade with strong warpage 33 Pressure distribution on the pressure surface of the impeller blade with weak warpage 34 Pressure surface of the impeller blade with weak warpage Upper pressure distribution 35 Pressure difference between pressure surface and suction surface of impeller blade with weak warpage 91 Pressure surface 92 Pressure surface SA, SB, SC Conical surface SP parallel to shroud surface Plane PA including pump rotation axis Blade surface, SA surface , SP plane intersection PB Blade negative pressure surface, SB plane, SP plane intersection PC Blade negative pressure surface, SC plane, SP plane intersection PX Connect a line connecting point PA and point PB with point PB and point PC The point HA on the upstream side of the point PB on the angle PBU SB plane formed by the straight line HA The intersection of the blade leading edge and the SA plane HB The intersection of the blade leading edge and the SB plane HC The intersection HX of the blade leading edge and the SC plane Angle HB2 between the straight line connecting HA and point HB and the straight line connecting point HB and point HC Point HC2 Point HC2 on the downstream side of the blade leading edge on the intersection line of the blade suction surface and the SC surface Point on the line downstream of the blade leading edge R Tip diameter Rsb Radial distance from the pump rotation axis to the SB surface

Claims (5)

A hub that is provided inside the shroud and rotates about a rotation axis;
A plurality of impeller blades attached to the outer periphery of the hub and rotating together with the hub;
The impeller blade is bent upstream in the flow direction of the working fluid in the vicinity of the tip portion,
The tip portion is located on the upstream side in the flow direction of the working fluid, compared to the portion located on the hub side from the bent portion of the impeller blade ,
A pump impeller characterized in that a warp of a blade section from the bent portion to the tip portion in the impeller blade is relatively small as compared to a warp of a blade section of a portion on the hub side from the bent portion . The pump impeller according to claim 1,
A pump impeller characterized in that a front edge side of a tip portion of the impeller blade protrudes in a rotating direction of the rotating shaft. The pump impeller according to claim 1 or 2 ,
The pump impeller characterized in that the bent portion is formed in an area of 80% or more of the tip diameter in the impeller blade. The pump impeller according to any one of claims 1 to 3 ,
The pump impeller characterized in that an angle at which the impeller blade is bent with respect to the bent portion is 30 degrees or more. The pump impeller according to claim 2,
The pump impeller characterized in that the front edge side of the tip part protrudes at a position rotated about 30 degrees or more in the rotation direction of the rotary shaft with the front edge side of the bent part as the center.

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