JP5283487B2 - Centrifugal pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal pump with an improved casing shape, which has been an impediment to pump suction performance. <P>SOLUTION: The centrifugal pump has a protrusion 62 protruding in the rotational axis direction of an impeller 53 at a portion continuous to a periphery of an opening edge of a suction port part 60 of an impeller chamber 58 in an inner wall face of a suction flow passage 54 of the casing 51. The protrusion 62 has a shape satisfying a condition in which B/A is 0.23 to 0.31, wherein a distance in a rotational axis center direction from a blade start end position to a top of the protrusion in the impeller chamber in the rotational axis center direction of the impeller 53 is B, and a distance from the blade start end position in the impeller chamber to an ultimate position in an inner wall face of the suction flow passage 54 of the casing 51 opposed to the intake port part is A. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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 volute suction channel 11 positioned on the side of the impeller 3 in the direction of the rotation axis of the impeller 3 and a discharge channel 12 formed around the rotation 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 volute 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. There exists patent document 1 as a prior art document.
JP-A-3-290096

  In the configuration described above, when the water flow swirling in the suction flow path 11 of the casing 1 flows into the suction opening 14 of the impeller 3 from the terminal end of the suction flow path 11 toward the impeller, in FIG. As indicated by the arrow, the direction is changed 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.

  This invention solves the above-mentioned subject, and it aims at providing the spiral pump which aimed at the improvement of the casing shape used as the obstruction factor of pump suction performance.

  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 has a convex portion that protrudes in the direction of the rotational axis of the impeller at a portion connected to the periphery of the opening edge of the suction port portion of the impeller flow passage on the inner wall surface of the suction flow passage. The distance in the rotational axis direction from the blade start end position in the flow path to the top of the convex portion is B and In the direction of the rotational axis of the impeller, the distance from the blade starting end position in the impeller inner flow path to the farthest position on the inner wall surface of the suction passage of the spiral casing facing the suction inlet of the impeller is A, A shape satisfying a condition that B / A is 0.23 to 0.31 is formed.

Further, the centrifugal pump of the present invention is characterized in that it has a shape that satisfies a condition that B / A is 0.25 to 0.29.
In the centrifugal pump of the present invention, the convex portion is formed integrally with the casing.

In the centrifugal pump of the present invention, the convex portion is formed of a ring-shaped member and is attached to a casing.
Moreover, the centrifugal pump of the present invention is a double-suction centrifugal pump in which the casing has the suction flow path on both sides in the rotational axis direction of the impeller.

  As described above, according to the present invention, the inner wall surface of the suction flow path of the casing has a convex portion that protrudes in the direction of the rotational axis of the impeller at a portion connected to the periphery of the opening of the suction opening of the flow path in the impeller. As a result, the sudden turning flow can be relaxed and the pump suction performance can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A and 1B, both suction centrifugal pumps include an impeller 53 that is 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.

  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 that protrudes in the direction 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 part 62 forms a terminal part of the suction channel 54 toward the impeller 53. The convex portion 62 can be efficiently provided by being integrally formed when the casing 51 is cast.

  The convex portion 62 has a shape that satisfies the following conditions. That is, as shown in FIG. 1B, the distance in the rotational axis direction of the impeller 53 from the blade start end position in the impeller flow path to the top of the convex portion 62 is B, and the rotational axis of the impeller 53 is If the distance from the blade start end position in the impeller inner flow path in the center direction to the farthest position on the inner wall surface of the suction flow path 54 of the spiral casing 51 facing the suction inlet 60 of the impeller 53 is defined as A The shape portion 62 has a shape that satisfies the condition that B / A is 0.23 to 0.31. Preferably, the shape satisfies the condition that B / A is 0.25 to 0.29, more preferably B / A is 0.27 to 0.28.

  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 54 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 swirling in the suction channel 54 of the casing 51 turns in a direction along the rotational axis of the impeller 53 when flowing from the terminal end of the suction channel 54 to the suction port 60 of the impeller 53. At this time, the end portion of the suction channel 54 is raised in the direction of the rotational axis of the impeller 53 to form a convex portion 62 within the above numerical range, as shown by an arrow in FIG. It is possible to relieve the suddenly turning flow and suppress the occurrence of cavitation to improve the pump suction performance, and to suppress the deterioration of the pump performance due to the occurrence of cavitation, the generation of vibration and noise, erosion, and damage.
Example 1
FIG. 2 shows B / A and pump suction performance when the flow rate is 54%, 75%, 100% and 118% of the maximum efficiency point discharge amount Q in a pump having a casing and an impeller with a specific speed Ns280. It is a graph which shows the relationship with the suction specific speed S3% in 3% head fall which is a value which shows.

FIG. 3 is a graph showing the relationship between B / A and the maximum efficiency ηmax of the pump in a pump including a casing and an impeller having a specific speed Ns280.
In FIG. 2, B / A = 0.17 is experimental data of the conventional pump shown in FIG. 4, and B / A is based on the S3 value at the highest efficiency point (ηmax, 100% Q) of this pump. The value S3 and the S3 value when the flow rate is changed are plotted as S3 / S3ηmax. It can be seen that, regardless of the flow rate, the S3 value is superior to that of the conventional pump when B / A is in the range of 0.23 to 0.31. Further, the S3 value is even better when the B / A value is in the range of 0.25 to 0.29, more preferably in the range of 0.27 to 0.28.

  The reason why B / A has such an appropriate range is that when B / A is small, the suction performance is lowered by changing the flow direction toward the impeller at a steep angle, and B / A is large. This is because the suction flow path width is reduced, the flow passage cross-sectional area of the suction vortex chamber is reduced, and the flow velocity flowing into the impeller is increased, thereby reducing the suction performance.

  On the other hand, it can be seen from FIG. 3 that the efficiency decreases with an increase in B / A, but it can be seen that the reduction in efficiency can be minimized and the suction performance can be improved within the above numerical range. It has also been confirmed that the same range is suitable for Ns140 and Ns400 pumps.

In addition, it can be seen from FIG. 2 that the effect is particularly great in a region where the flow rate is lower than 100% Q (54% Q, 75% Q, 86% Q).
In the present embodiment, the convex portion 62 is integrally formed when the casing 51 is cast. However, the convex portion 62 may be formed as a ring-shaped member that is separate from the casing 51 and attached to the casing 51 with a bolt or the like. In this case, the suction performance S3 and the maximum pump efficiency ηmax can be adjusted to appropriate values by replacing the ring-shaped member.

  Further, in the present embodiment, the description has been made by showing both suction centrifugal pumps. The present invention can be applied to a pump, for example, a multi-stage single suction centrifugal pump.

Sectional drawing which shows the centrifugal pump in embodiment of this invention The graph which shows the relationship between B / A of the centrifugal pump in the same embodiment, and suction specific speed S3% in 3% head fall which shows suction performance The graph which shows the relationship between B / A and the highest efficiency (eta) max of the centrifugal pump in the same embodiment Sectional view showing a conventional centrifugal pump

Explanation of symbols

51 Casing 52 Main shaft 53 Impeller 54 Suction flow path 55 Discharge flow path 56 Hub 57 Shroud 58 Impeller wheel flow path 59 Blade 60 Suction port 61 Discharge port section 62 Convex part B Convex from the blade start end position in the impeller flow path The distance in the rotational axis direction of the impeller to the top of the blade-shaped portion A A suction flow of a spiral casing facing the inlet port of the impeller from the blade start end position in the flow path in the impeller in the rotational axis direction of the impeller Distance to the farthest position on the inner wall of the road

Claims (5)

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 has a convex portion protruding in the direction of the rotation axis of the impeller at a portion connected to the periphery of the opening edge of the suction port portion of the impeller flow passage on the inner wall surface of the suction flow passage. The distance in the direction of the rotation axis from the blade start end position in the path to the top of the convex portion is B, and in the direction of the axis of rotation of the impeller, the distance from the blade start end position in the impeller channel to the impeller inlet port A spiral pump having a shape satisfying a condition that B / A is 0.23 to 0.31 where A is the distance to the farthest position on the inner wall surface of the suction flow path of the spiral casing.   The centrifugal pump according to claim 1, wherein the pump has a shape satisfying a condition that B / A is 0.25 to 0.29.   The centrifugal pump according to claim 1, wherein the convex portion is integrally formed with the casing.   The centrifugal pump according to claim 1 or 2, wherein the convex portion is formed of a ring-shaped member and is attached to a casing.   The centrifugal pump according to any one of claims 1 to 4, wherein the centrifugal pump is a double-suction centrifugal pump in which the suction flow path is provided on both sides of the impeller in the rotational axis direction.

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