JP5905059B2 - Centrifugal pump - Google Patents

Description

  The present invention relates to a centrifugal pump, and more particularly to a casing structure of a centrifugal pump.

  2. Description of the Related Art Conventionally, a double suction centrifugal pump, which is a kind of this kind of centrifugal pump, includes a casing 1 and an impeller 3 provided on a main shaft 2 as shown in FIG. The casing 1 has a spiral suction passage 11 located on the side of the impeller 3 in the direction of the rotational axis of the impeller 3 and a discharge passage 12 formed around the rotational axis of the impeller 3. . The impeller 3 has an impeller internal flow path 13 inside, and the impeller internal flow path 13 communicates with the suction flow path 11 of the casing 1 through a suction port portion 14 that opens toward the rotation axis, and rotates. A discharge port portion 15 that opens in a radial direction orthogonal to the shaft center communicates with the discharge flow path 12 of the casing 1.

In a state where the impeller 3 rotates around the rotation axis by driving the main shaft 2, the water flowing into the suction flow path 11 of the casing 1 swirls along the spiral shape of the suction flow path 11 and the blades of the suction flow path 11. It flows into the impeller inner flow path 13 through the suction port portion 14 of the impeller 3 from the terminal portion toward the car. The water flowing into the impeller inner flow path 13 receives a centrifugal force due to the rotation of the impeller 3 and is ejected from the discharge port portion 15 to the discharge flow path 12 of the casing 1.
As prior art documents, there are Patent Documents 1 and 2.

JP-A-3-290096 JP 61-49195 A

  In the above-described configuration, when the water flow swirling in the suction flow path 11 of the casing 1 flows into the suction port portion 14 of the impeller 3 from the terminal end toward the impeller of the suction flow path 11, it is indicated by an arrow in FIG. 10. Thus, it turns in the direction along the rotational axis of the impeller 3.

  This sudden diversion of the water flow causes flow separation and increases the head loss. An increase in head loss increases the pressure drop, leading to a reduction in suction performance due to the occurrence of cavitation. Cavitation causes harmful events such as reduced pump performance, vibration and noise, erosion, and damage.

  For this reason, in patent document 1, the suction port part which makes a water flow flow into an impeller has a shape similar to a bell mouth, a suction port part protrudes from a casing inner surface, and is cyclic | annular or arcuate between a suction port part and a casing inner surface. The water flow that flows in the direction perpendicular to the pump shaft enters the groove portion of the suction port, and the swirl component increases due to the water flow inducing action of the groove portion while reducing the flow velocity, so that the water flow swirls While moving over the suction port, the direction is changed in a direction parallel to the pump shaft.

  In Patent Document 2, in both suction centrifugal pumps, the cross-sectional shape of the entire circumferential portion of the suction port portion to the impeller is a curved surface from the upstream start point to the downstream end point of the water flow sucked into the suction port portion. And the water flow at the upstream start point is larger than the curvature radius of the curved surface on the other downstream side. The direction is changed following the curved surface.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a centrifugal pump with an improved casing shape that causes noise from the pump.

In order to solve the above-described problems, a centrifugal pump according to the present invention includes a casing and an impeller that rotates about a rotation axis, and the casing has a spiral shape that is located on the side of the impeller in the direction of the rotation axis of the impeller. It has a suction flow path and a discharge flow path formed around the rotation axis of the impeller. The impeller has blades disposed in the impeller internal flow path and the impeller internal flow path, and the impeller internal flow path is the impeller. Communicating with the suction passage of the casing at the suction opening that opens in the direction of the rotation axis of the casing, and communicating with the discharge passage of the casing at the discharge opening that opens in the radial direction of the impeller. The casing bulges in the inner wall surface of the suction flow passage around the opening edge of the suction inlet of the impeller internal flow passage in the direction of the rotational axis of the impeller, and the top of the water flow in the radial direction of the impeller Convex part that passes with radial flow velocity that forms a velocity component Is a straight line that passes through the apex and is orthogonal to the rotational axis of the impeller as a first base line, and the impeller at a predetermined distance h from the first base line to the impeller side along the rotational axis direction of the impeller. A plane perpendicular to the rotation axis of the second axis is defined as a reference plane, a line passing through the intersection of the reference plane and the inner peripheral surface of the convex portion and parallel to the rotation axis of the impeller and perpendicular to the first base line is defined as a second line. In the case of a base line, the distance Lx from the vertex to the intersection of the first base line and the second base line, and the radial flow velocity maximum position where the radial flow velocity of the water flow is maximum around the rotation axis of the impeller The distance Lxa is larger than the distance Lxb at the radial flow velocity minimum position where the radial flow velocity is minimum, and from the inner circumferential surface to the outer circumferential surface of the convex portion on the straight line parallel to the first baseline on the reference plane. Around the rotation axis of the impeller with the distance as the width on the reference surface of the convex part Reference surface on the width in the radial direction velocity maximum position radial velocity of the water flow is maximum is greater than the reference plane width in the radial direction velocity minimum position radial velocity is minimized, further, the impeller from the first baseline The distance H to the opening edge of the suction port along the rotation axis is constant around the rotation axis of the impeller .

  In the spiral pump of the present invention, the convex portion is characterized in that the distance Lx between a predetermined distance along the circumferential direction from the radial direction maximum flow velocity position is larger than the distance Lxb at the radial direction minimum flow velocity position.

In the spiral pump of the present invention, the convex portion has a convex curved surface whose inner peripheral surface smoothly changes into a quadratic curve toward the rotation axis side of the impeller.
In the spiral pump of the present invention, the convex portion has a curved surface whose inner peripheral surface changes smoothly along the circumferential direction.

  Further, in the spiral pump of the present invention, the convex portion has a convex curved surface whose inner surface smoothly changes in an arc shape toward the rotation axis side of the impeller, and extends from the radial maximum flow velocity position in the circumferential direction. The distance Lx up to a position of 120 ° is greater than the distance Lxb at the minimum radial flow velocity position.

  Moreover, the spiral pump of the present invention is characterized in that the convex portion is replaceable formed separately from the casing.

  According to the present invention, the distance Lxa at the maximum radial flow velocity position where the radial flow velocity of the water flow is maximum around the rotation axis of the impeller is larger than the distance Lxb at the minimum radial flow velocity position where the radial flow velocity is minimum. Thus, separation of the water flow that occurs when the water flow turns over the convex portion while turning and changes direction parallel to the rotational axis of the impeller can be suppressed, and generation of noise due to cavitation can be suppressed.

The perspective view which shows the principal part of the centrifugal pump in embodiment of this invention (A) is a cross-sectional view of part A in FIG. 1, (b) is a cross-sectional view of part B in FIG. Sectional drawing which shows the centrifugal pump in embodiment of this invention Schematic diagram showing radial flow velocity distribution in analysis Graph showing the circumferential distribution of radial flow velocity Graph showing the circumferential distribution of radial flow velocity The front view which shows the centrifugal pump in embodiment of this invention The top view which shows the coupling of the centrifugal pump in embodiment of this invention Graph showing noise improvement Sectional view showing a conventional centrifugal pump

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 3, both suction centrifugal pumps include an impeller 53 driven by a main shaft 52 inside a casing 51. The casing 51 has a spiral suction passage 54 located on the side of the impeller 53 in the direction of the rotational axis of the impeller 53, and a discharge passage 55 formed around the rotational axis of the impeller 53. doing.

  As shown in FIG. 4, when the winding angle θ indicates the rotation angle in the flow direction of the water flow 622 with the straight line connecting the rotation axis center and the tongue 511 as 0 °, the suction flow path 54 is formed in the casing 51. From the winding angle 0 ° to 360 ° with the tongue portion 511, the width in the direction of the rotation axis and the radial direction becomes narrow.

  The impeller 53 has an impeller flow path 58 between the hub 56 and the shroud 57, and a plurality of blades 59 are formed at predetermined positions of the hub 56 and the shroud 57. The impeller inner flow path 58 communicates with the suction flow path 54 of the casing 51 at a suction port portion 60 that opens toward the rotation axis direction of the impeller 53, and is directed in a radial direction orthogonal to the rotation axis center of the impeller 53. A discharge port portion 61 that opens to communicate with the discharge flow path 55 of the casing 51. The blades 59 are joined to the hub 56 and the shroud 57 and extend from the start end position in the suction port portion 60 to the end position in the discharge port portion 61.

  The casing 51 has a convex portion 62 along the periphery of the rotational axis of the impeller 53 at a portion connected to the periphery of the opening edge of the suction port portion 60 of the impeller inner passage 58 on the inner wall surface of the suction passage 54. The convex portion 62 may be integrally formed when the casing 51 is cast, or may be formed separately from the casing 51 to be exchangeable.

  The convex portion 62 has a shape that satisfies the following conditions. That is, as shown in FIG. 1 and FIG. 2, the convex portion 62 rises in the direction of the rotational axis of the impeller 53, and the radial flow velocity at which the water flow 622 forms a velocity component in the radial direction of the impeller 53. The inner peripheral surface 624 that faces the suction port portion 60 and reaches the opening edge 601 is a quadratic curve (circle, ellipse, parabola, It forms a convex curved surface that changes smoothly into a part of a hyperbola.

  And the convex part 62 makes the line extended in the direction orthogonal to the rotational axis X of the impeller 53 from the vertex 623 the 1st base line L1, and is predetermined distance to the rotational axis direction of the impeller 53 from the 1st base line L1. A plane perpendicular to the rotational axis X of the impeller 53 at a position h is defined as a reference plane α, and the inner peripheral surface of the convex portion 62 on a straight line parallel to the first base line L1 on the plane of the reference plane α. The distance from 624 to the outer peripheral surface 626 is defined as the reference surface width Lw of the convex portion 62, and the reference surface width Lw at the maximum radial flow velocity position where the radial flow velocity of the water flow is maximum around the rotation axis of the impeller is A shape that is larger than the reference surface width Lw at the radial flow velocity minimum position where the radial flow velocity is minimum is formed.

  Further, the convex portion 62 has a vertex 623 as a second base line L2 which is a line passing through the intersection line 625 between the reference surface α and the inner peripheral surface 624 of the convex portion 62 and parallel to the rotational axis X of the impeller 53. When the distance from the first base line L1 to the intersection of the first base line L2 and the second base line L2 is Lx, the radial flow velocity at which the radial flow velocity of the water flow 622 is maximum around the rotation axis of the impeller 53 A curved surface in which the inner peripheral surface of the convex portion 62 smoothly changes along the circumferential direction so that the distance Lxa at the maximum flow velocity position A is larger than the distance Lxb at the minimum radial flow velocity position B where the radial flow velocity is minimum. Make. The distance Lx corresponds to the width on the inner peripheral surface side of the reference surface upper width Lw.

  In the convex portion 62, the distance H from the first base line L <b> 1 to the opening edge 601 of the suction port 60 along the rotational axis direction of the impeller 53 is constant around the rotational axis of the impeller 53. In the present embodiment, the distance Lx at a predetermined distance La along the circumferential direction from the maximum radial flow velocity position A is greater than the distance Lxb at the minimum radial flow velocity position B, but the length of the predetermined distance La is arbitrarily set. This will be described later.

  In the above-described configuration, the water flowing into the suction flow path 54 of the casing 51 is sucked while swirling along the spiral shape of the suction flow path 54 in a state where the impeller 53 rotates around the rotation axis by driving the main shaft 52. It flows into the impeller inner flow path 58 from the end portion of the flow path 54 through the suction port portion 60 of the impeller 53. The water that has flowed into the impeller inner flow path 58 receives a centrifugal force due to the rotation of the impeller 53 and is ejected from the discharge port portion 61 to the discharge flow path 55 of the casing 51.

  The water flow 622 swirling in the suction flow path 54 of the casing 51 turns in a direction along the rotational axis X of the impeller 53 when flowing from the suction flow path 54 to the suction port 60 of the impeller 53. At this time, the water flow 622 accompanied by the radial flow velocity passes through the convex portion 62 formed around the rotation axis of the impeller 53, thereby rapidly turning in the rotation axis direction, particularly the flow along the casing 51. By suppressing the flow and separating the flow from the casing 51, the generation of cavitation can be suppressed and the generation of noise can be suppressed. Furthermore, it is possible to suppress the pump suction performance deterioration, pump performance deterioration, vibration generation, erosion, and damage due to the occurrence of cavitation.

  This will be described in detail below. FIG. 4 is a schematic diagram showing the flow of the water flow 622 in the centrifugal pump of the present invention, and FIG. 5 is a graph showing the relationship between the winding angle of the suction flow path 54, the distance Lx, and the radial flow velocity V, and the distance Lx Is a dimensionless value, which is a standard value of the distance Lx when the distance Lx is constant over the entire length of the convex portion 62, and is a value of the distance Lx at each winding angle around the rotation axis of the impeller 53. The radial flow velocity V is a dimensionless value, and is an average flow velocity obtained by dividing the pump suction amount by the area of the suction port 60 at each winding angle around the rotation axis of the impeller 53. It is a value obtained by dividing the value of the radial flow velocity V.

  In FIG. 5, a locus K1 shows a case of a reference example in which the distance Lx is constant over the entire length of the convex portion 62. Under this condition, the radial flow velocity V at each winding angle around the rotation axis of the impeller 53 is shown. This is indicated by a locus K2.

  The trajectory K3 is according to the present embodiment, and the distance Lx is the minimum radial flow velocity position within the predetermined distance La along the circumferential direction from the radial flow velocity maximum position A and the winding angle from 0 ° to 90 °. B shows a case where the distance Lx is gradually decreased according to the radial flow velocity V at each winding angle, which is larger than the distance Lxb at B, and the distance Lx in the range from the winding angle 0 ° to 120 ° as shown by the locus K4. May be larger than the distance Lxb at the radial direction flow velocity minimum position B, and the distance Lx may be gradually decreased according to the radial direction flow velocity V at each winding angle. The radial flow velocity V at each winding angle around the rotation axis of the impeller 53 under the condition of the locus K3 is indicated by a locus K5. In the locus K4, the radial flow velocity V is substantially the same as the locus K5.

  As is clear from FIG. 5, in the present embodiment, the radial flow velocity maximum position A is in the range of the winding angle from 0 ° to 30 °, and a predetermined distance La along the circumferential direction from the radial flow velocity maximum position A, Since the distance Lx is larger than the distance Lxb at the radial direction flow velocity minimum position B in the range (region) where the winding angle is 0 ° to 90 °, or in the range (region) from the winding angle 0 ° to 120 °, the water flow in the present embodiment. The radial flow velocity V (K5) of 622 is smaller than the radial flow velocity V (K2) in the case of the reference example. As shown in Table 1, the negative pressure state representing the state of separation and cavitation is Compared to the reference example, the number is reduced in the present embodiment.

この結果、水流６２２が旋回しながら凸状部６２を乗り越えて羽根車５３の回転軸心Ｘと平行な方向に方向転換する際に、不均一な流れ込みで流速が速くなる領域において生じる水流６２２の剥離が抑制でき、キャビテーションの発生を抑制して騒音の発生を抑制することができる。さらに、剥離が抑制できることにより、吸込性能の低下、ポンプ性能の低下、振動の発生、壊食、損傷を抑制することができる。

As a result, when the water flow 622 turns over the convex portion 62 while turning and changes direction parallel to the rotational axis X of the impeller 53, the water flow 622 generated in a region where the flow velocity becomes high due to uneven flow. Separation can be suppressed, generation of cavitation can be suppressed, and generation of noise can be suppressed. Furthermore, by suppressing peeling, it is possible to suppress the suction performance, pump performance, vibration, erosion, and damage.

  As shown in FIG. 6, the range in which the distance Lx is larger than the distance Lxb at the radial flow velocity minimum position B can be arbitrarily set, and the distance Lx is gradually reduced in the range of the winding angle from 0 ° to 90 °. In the case (trajectory K6), when the distance Lx is maintained constant in the range from the winding angle 0 ° to 90 ° and then gradually decreased in the range from the winding angle 90 ° to 210 ° (trajectory K7), the winding angle 0 ° to 90 °. When the distance Lx is kept constant in the range up to ° and then gradually decreased in the range from 90 ° to 300 ° (trajectory K8), the distance Lx is gradually reduced in the range from 0 ° to 300 ° ( Trajectory K9), a configuration in which the distance Lx is gradually reduced in a quadratic curve (trajectory K10) in the range of the winding angle from 0 ° to 300 ° is possible.

  Note that the radial flux V at 0 ° in FIG. 5 decreases due to a decrease in the radial component due to the shape of the tongue 511 and an increase in the frictional resistance of the casing. Furthermore, the winding angle is only described up to 300 ° in FIGS. 5 and 6 because the top 621 of the convex portion contacts the casing 51 and is absorbed when it exceeds 300 ° in the present embodiment. It is to become.

  As shown in FIGS. 7 and 8, the change in the noise measured at four locations D1 to D4 around the centrifugal pump 800 under the condition that the centrifugal pump 800 is connected to the motor 802 with the coupling 801 is used. Shown in

  FIG. 9 shows the noise in the case of the reference example in which the distance Lx is constant over the entire length of the convex portion 62, and a predetermined distance La along the circumferential direction including the radial direction flow velocity maximum position A, as in this embodiment. Differences from noise when the distance Lx is greater than the distance Lxb at the radial flow velocity minimum position B in the range of the winding angle from 0 ° to 90 ° are shown at four measurement positions D1 to D4. As shown in FIG. 9, even if the discharge amount of the pump is changed, the noise in the present invention at the four measurement positions D1 to D4 is in a range lower than the noise in the reference example.

In the present embodiment, by making the distance H constant, the shape of the convex portion becomes simple, and the manufacture becomes easy and the cost can be reduced.
Furthermore, by forming the convex portion so that the distance Lx in the predetermined distance range along the circumferential direction including the radial flow velocity maximum position is larger than the distance Lxb in the radial flow velocity minimum position, the radial flow velocity is high. Separation can be suppressed in a predetermined distance range where separation is likely to occur, and generation of noise can be more effectively suppressed.

  Particularly, in the range of the winding angle from 0 ° to 120 °, the radial flow velocity is faster than the average flow velocity, and it is desirable that this range be a predetermined distance range. More desirably, the predetermined distance range is 0 ° to 90 ° at which the radial flow velocity is 1.4 times or more of the average flow velocity.

  Moreover, although the predetermined distance range can be set over a winding angle of 0 ° to 360 °, in the present embodiment, when the winding angle is 0 ° to 90 °, the casing weight is increased by 1%. On the other hand, when the winding angle is 0 ° to 360 °, the casing weight is increased by 4%, and the weight is increased four times as compared with the case where the winding angle is 0 ° to 90 °. Considering the cost, it is more effective to carry out in a range of a winding angle of 0 ° to 90 ° which is highly effective.

Furthermore, in this Embodiment, by making the inner peripheral surface of a convex-shaped part into a smooth curved surface, a flow becomes difficult to produce a sudden change in an inner peripheral surface, and it can suppress peeling more.
In the present embodiment, the convex portion 62 is integrally formed when the casing 51 is cast, but the portion where the distance Lx is larger than the distance Lxb at the radial direction flow velocity minimum position B is formed separately from the casing 51. It is also possible to make it replaceable. By making it replaceable, the pump can be easily restored by replacing the convex portion 62 without replacing the casing 51 when the convex portion 62 is damaged, and the noise, vibration, and suction performance are in the operating state. Improvement can also be achieved by exchanging the convex part 62 when it deteriorates due to the change.

51 Casing 52 Main shaft 53 Impeller 54 Suction channel 55 Discharge channel 56 Hub 57 Shroud 58 Impeller channel 59 Blade 60 Suction port 61 Discharge port 62 Projection 511 Tongue 601 Open edge 621 Top 622 Water flow 623 Apex 624 Inner peripheral surface 625 Intersecting line 626 Outer peripheral surface 800 Centrifugal pump 801 Coupling 802 Motor X Rotational axis L1 First baseline L2 Second baseline h Predetermined distance α Reference plane Lxa Radial flow velocity maximum at which radial flow velocity of water flow becomes maximum Distance Lx (Lxa, Lxb) Distance from the vertex 623 to the intersection of the first base line L1 and the second base line L2 along the first base line L1 Lw Width on the reference plane A Radial flow velocity maximum position B Radial flow velocity minimum position La For a predetermined distance along the circumferential direction from the maximum radial flow velocity position A V Radial flow velocity D1 to D Measurement position

Claims (6)

A casing and an impeller that rotates around the rotation axis are provided, and the casing is formed around a spiral suction passage located on the side of the impeller in the direction of the rotation axis of the impeller and around the rotation axis of the impeller. The impeller has a discharge passage, and the impeller has a flow passage in the impeller and a blade disposed in the flow passage in the impeller, and the casing in the suction port portion where the flow passage in the impeller opens toward the rotation axis of the impeller. Communicating with the suction flow path of the casing and communicating with the discharge flow path of the casing at the discharge port portion that opens toward the radial direction of the impeller,
The casing rises in the direction of the rotation axis of the impeller at a portion of the inner wall surface of the suction flow passage that is connected to the periphery of the opening of the suction opening of the impeller flow passage, and the water flow at the apex of the impeller has a radial velocity Having a convex portion that passes with a radial flow velocity forming the component;
The convex portion has a straight line passing through the apex thereof and orthogonal to the rotational axis of the impeller as a first base line, and a position separated from the first base line by a predetermined distance h along the rotational axis direction of the impeller toward the impeller side. A plane perpendicular to the rotational axis of the impeller in the reference plane, a line passing through the intersection of the reference plane and the inner peripheral surface of the convex portion, parallel to the rotational axis of the impeller and perpendicular to the first base line Is the distance Lx from the vertex to the intersection of the first baseline and the second baseline, and the radial flow velocity maximum at which the radial flow velocity of the water flow is maximum around the rotation axis of the impeller The distance Lxa at the position is larger than the distance Lxb at the radial flow velocity minimum position where the radial flow velocity is minimum,
The radius of the water flow around the rotation axis of the impeller is defined as the distance from the inner peripheral surface to the outer peripheral surface of the convex portion on the straight line parallel to the first base line on the reference surface as the reference surface width of the convex portion. The reference surface width at the radial flow velocity maximum position where the directional flow velocity is maximum is larger than the reference surface width at the radial flow velocity minimum position where the radial flow velocity is minimum,
Further, the centrifugal pump characterized in that the distance H from the first base line to the opening edge of the suction port along the rotational axis direction of the impeller is constant around the rotational axis of the impeller .   2. The centrifugal pump according to claim 1, wherein the convex portion has the distance Lxa in a predetermined distance range along the circumferential direction including the radial flow velocity maximum position larger than the distance Lxb in the radial flow velocity minimum position.   The spiral pump according to claim 1 or 2, wherein the convex portion has a convex curved surface whose inner peripheral surface changes smoothly toward the rotational axis side of the impeller.   The spiral pump according to any one of claims 1 to 3, wherein the convex portion has a curved surface whose inner circumferential surface changes smoothly along the circumferential direction.   The convex portion has a convex curved surface whose inner surface smoothly changes in an arc shape toward the rotational axis of the impeller, and the distance Lx is from the maximum radial flow velocity position to a position of 120 ° in the circumferential direction. The centrifugal pump according to any one of claims 1 to 4, wherein the centrifugal pump is larger than the distance Lxb at the minimum radial flow velocity position.   The spiral pump according to any one of claims 1 to 5, wherein the convex portion is a replaceable member formed separately from the casing.

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