JP5324491B2 - Liquid pump vortex prevention device - Google Patents

Description

  The present invention relates to a submerged vortex preventing device that prevents submerged vortices from being generated in a suction liquid of a liquid pump.

  If a swirl flow occurs due to a drift in the liquid upstream of the suction part of the liquid pump, a vortex in the liquid may be generated. When this swirl flow develops in the liquid acceleration flow toward the pump suction portion, the vorticity concentrates at the center of the acceleration flow, and a very thin and strong thread-like liquid vortex is generated. When the central pressure of the vortex in the liquid falls below the vapor pressure of the liquid due to the effect of the swirling liquid force, cavitation occurs due to vacuum boiling.

  Conventionally, a submerged vortex prevention device that suppresses the generation of submerged vortices that are the basis of cavitation, as described in Patent Literature 1 and Patent Literature 2, comprises a cross plate or a cone member on the bottom surface of the pump suction portion. A submerged vortex prevention member was provided, and a rod was installed at the center of the pump to reduce the flow velocity, thereby preventing a swirling flow that would cause submerged vortices.

  3 and 4 show an example in which a cross plate is installed on the bottom surface of the pump suction portion to prevent a swirling flow that causes vortex generation in the liquid. In FIG. 3, the liquid pump has a pump shaft center 1, a shaft 2, a casing 3, an impeller 4, a suction portion including a bell mouth 5, and a suction portion bottom surface 6. A cross board 7 is provided as a submerged vortex prevention member on the bottom surface 6 of the suction portion. Further, the suction section outer flow path wall surface 8, the suction section outer flow path 9, the suction section wall surface 10, the suction section internal liquid tank 11, and the suction section internal liquid tank surface 12 are configured.

  When the shaft 2 as a drive shaft rotates with the pump shaft center 1 as a base shaft, the pressure of the liquid is increased by the impeller 4 fixed to the shaft 2, and the liquid is sucked and discharged from the impeller 4 into the flow passage surrounded by the casing 3. . The bell mouth 5 provided at the tip of the casing 3 where the liquid flows into the impeller 4 functions as a liquid inflow guide to the impeller 4. The suction part bottom surface 6, the suction part wall surface 10, and the suction part internal liquid tank surface 12 constitute a suction part internal liquid tank 11. The liquid flows into the suction-portion internal liquid tank 11 from the suction-portion outer flow passage 9 including the suction-portion outer passage wall surface 8 and the suction-portion wall surface 10.

  The suction portion draw-in flow 13 that has flowed into the suction portion outer flow path 9 is redirected to a revolving flow 14 to the suction portion internal liquid tank 11, and then flows from the liquid tank flow 15 at the bottom of the suction portion internal liquid tank 11 into the bell mouth 5. Instead of the suction flow 16, the liquid flow in the liquid pump is formed in the direction opposite to the suction direction. Here, the cross plate 7 provided on the bottom surface 6 of the suction portion reduces the flow velocity of the swirling flow that causes the generation of vortex in the liquid in the above flow.

  5 and 6 show an example in which a cone member 17 is provided instead of the cross plate 7 as a submerged vortex preventing member. The cone member 17 is configured by a tapered curved surface continuously from the suction portion bottom surface 6 to reduce the flow velocity of the swirling flow that causes the generation of the vortex in the liquid as in the cross plate 7. To form a smoother flow. Reference numeral 18 denotes an upward flow that flows along the side wall of the cone member 17.

JP-A-3-156200 JP 7-217546 A

  According to the prior art as described above, a constant cavitation suppression effect can be expected by suppressing the swirling flow generated across the flow direction and preventing the liquid vortex. However, since the liquid velocity in the pump is accelerated at a high speed by the suction portion suction flow 13 in the above configuration, if the flow velocity in the flow direction is further increased, the generation of vortex in the liquid and the cavitation due to the pressure drop at the center of the swirl flow are completely eliminated. It cannot be suppressed.

  The present invention has been made to solve the above-described problems. The shape of the submerged vortex preventing member is devised, and the deviation of the flow velocity distribution in which the flow velocity in the flow direction increases along the side surface is averaged and decelerated. Thus, a new liquid pump suction vortex preventing device that suppresses cavitation caused by vortex in liquid is provided.

  It is another object of the present invention to provide a pump suction vortex preventing device that prevents separation of the wake that flows out along the side surface of the submerged vortex preventing member and reduces liquid mixing loss.

  The present invention includes a suction part that sucks liquid in a shaft axial direction by a shaft having an impeller that is housed in a casing and rotates, and is connected to the suction part and supplies liquid from a direction opposite to the suction part suction direction. In the liquid pump having the suction portion outer passage, the suction portion bottom surface connecting the suction portion and the suction portion outer passage, and the suction portion inner liquid tank provided between the suction portion and the suction portion outer passage, the suction portion outer passage An in-liquid vortex preventing member is provided on the bottom surface of the suction part that is reversed and sucked by the suction part, and the in-liquid vortex prevention member is fixed to the upper disk and the bottom surface of the suction part. And a connection part that connects the upper disk and the lower disk, and a side surface of the connection part has a curved surface that continues from the bottom surface of the suction part.

  The submerged vortex preventing member forms a curved flow from a part of the liquid sucked from the suction portion outer passage by the connecting portion having the curved surface, and decelerates the flow velocity of the sucked liquid in the liquid. It is characterized by preventing the generation of vortices.

  In addition, the upper disk of the submerged vortex preventing member is provided with a separation preventing part including a convex portion that suppresses separation of the fluid guided to the upper part of the submerged vortex preventing member by a connecting portion having a curved surface. .

  In addition, the separation preventing portion formed of a convex portion in the upper disk of the submerged vortex preventing member has a substantially wing-shaped cross section symmetrical to the pump shaft center.

  The liquid pump suction liquid vortex prevention device according to the present invention has an upper disc and a lower disc and a small-diameter connecting portion for connecting them, fixing the lower surface of the lower disc to the bottom surface of the pump suction portion, By providing an in-liquid vortex prevention member with a curved side surface of the connecting part, a curved flow that draws and reverses the flow of liquid into the curved surface part of the side of the connecting part is formed, and the flow velocity of the liquid toward the suction part is increased. It is possible to decelerate and suppress cavitation associated with the liquid pressure drop.

  In addition, the upper surface of the upper part upper disk has a curved surface with a swelled central part, and its cross section is a substantially airfoil shape symmetric about the pump shaft center, so that the liquid flows out of the curved flow along the side of the connecting part. Can be prevented and liquid mixing loss can be reduced.

It is a schematic diagram which shows the vortex prevention apparatus in the suction liquid of the liquid pump of this invention. It is CC line arrow line view of FIG. It is a schematic diagram which shows the vortex prevention apparatus in the suction liquid of the conventional liquid pump. It is an AA arrow directional view of FIG. It is a schematic diagram which shows the vortex prevention apparatus in the suction liquid of the other conventional liquid pump. It is a BB line arrow directional view of FIG.

  The configuration of the submerged vortex prevention device of the liquid pump of the present invention is shown in FIGS. The submerged vortex prevention device includes a pump shaft center 1, a shaft 2 provided with an impeller 4 at its tip, a casing 3 formed with a bell mouth 5 at its end, a suction portion bottom surface 6, and a suction portion outer channel wall surface 8. The suction portion outer flow path 9, the suction portion wall surface 10, the suction portion internal liquid tank 11, the suction portion internal liquid tank surface 12, and the submerged vortex prevention device 19.

  The submerged vortex prevention member 19 of the present invention includes an upper disk 21, a lower disk 22, and a connection portion 23 for connecting them. The side surface of the connecting portion 23 is a curved surface. On the upper surface of the upper disk 21, a separation preventing portion 24 composed of a convex portion bulging upward is formed to prevent separation, and the cross section has a substantially airfoil cross-sectional shape symmetric with respect to the pump shaft center. Here, the same components as those in the conventional example will be described using the same reference numerals.

  The flow is entangled in the concave portion forming the curved surface of the side surface of the connecting portion 23 of the submerged vortex preventing member 19 to form a curved flow 20 that is reversed. Thereby, the deviation of the flow velocity distribution in which the liquid flow velocity is partially increased is averaged along the side surface of the connecting portion 23, and the flow velocity in the flow direction along the side surface of the connecting portion 23 is reduced. At the same time, the friction loss is reduced by using a taper shape in which the slope gradually increases from the lower disk 22 to the lower portion of the connection portion 23, thereby suppressing cavitation due to the vortex in the liquid.

  Further, by forming a separation preventing portion 24 on the upper surface of the upper disk 21 and making the upper surface portion a substantially wing-shaped cross section, separation of the wake of the curved flow 20 separated from the submerged vortex prevention member 19 is prevented, and the liquid Reduce mixing loss.

  The submerged vortex preventing device according to the present embodiment is used for a liquid pump. In the conventional submerged vortex preventing device as shown in FIGS. 3 and 5, the cross plate 7 and the cone member are provided on the bottom surface 6 of the suction portion. In contrast, 17 is installed, but in the present invention, a submerged vortex prevention member 19 as shown in FIG. 1 is installed.

  In the case where there is the suction portion suction flow 13 in the direction opposite to the suction flow 16 of the bell mouth 5, if the revolving flow 14 to the suction portion internal liquid tank 11 flows so as to be orthogonal to the suction portion suction flow 13, the inside of the suction portion of FIG. The liquid tank flow 15 in the liquid tank and the upward flow 18 along the side surface of the cone member 17 in FIG. Therefore, when the submerged vortex prevention device 19 shown in FIG. 1 is installed, a flow can be entrained in the concave portion of the curved surface on the side of the connecting portion 23, and the curved flow 20 along the side surface can be created.

  Therefore, in the cross section orthogonal to the pump shaft center 1 in the concave portion of the curved surface on the side surface of the connecting portion 23, the flow area is enlarged with respect to the flow direction, and the curved flow 20 along the side surface is formed. And the upward flow 18 decelerates. Therefore, it is possible to suppress the conventional increase in the flow velocity in the direction of the upward flow 18 and to suppress cavitation accompanying the pressure drop.

Furthermore, from the lower disk 22 to the lower part of the connecting portion 23, it follows the shape of a conventional cone-shaped cone member, and can suppress cavitation caused by submerged vortices while also reducing friction loss. In the wake of the upward flow 18 along the side surface of the cone member from the prevention member 19, the separation of the flow is prevented by the separation prevention portion 24 having a substantially wing-shaped cross section symmetrical to the center of the pump axis, instead of the upper surface portion being a flat surface. The mixing loss can be reduced.

1: pump shaft center, 2: shaft, 3: casing, 4: impeller, 5: bell mouth, 6: suction portion bottom surface, 8: suction portion outer flow path wall surface, 9: suction portion outer flow path, 10: suction portion Wall surface, 11: Liquid tank in suction part, 12: Liquid tank surface in suction part, 13: Suction part suction flow, 14: Turning flow, 15: Liquid tank flow, 16: Suction flow, 18: Upflow, 19: Vortex in liquid Prevention member, 20: curved flow, 24: peeling prevention part

Claims (3)

A suction part that sucks liquid in the axial direction of the shaft by a shaft having an impeller that is housed in a casing and rotates, and a suction part outer passage that is connected to the suction part and supplies liquid from a direction opposite to the suction part suction direction In the liquid pump having a suction portion bottom surface connecting the suction portion and the suction portion outer passage, and a suction portion internal liquid tank provided between the suction portion and the suction portion outer passage,
An in-liquid vortex prevention member is provided on the bottom surface of the suction portion where the liquid from the outer passage of the suction portion is reversed and sucked into the suction portion, and the in-liquid vortex prevention member is fixed to the upper disk and the bottom surface of the suction portion. is a connecting portion for connecting the the lower circular upper disc and a lower disc is, the connecting portion side have a curved surface of the concave outer peripheral side which is continuous from the suction unit bottom, having該湾curved A liquid of a liquid pump, characterized in that a curved flow is formed from a part of the liquid sucked from the suction portion outer passage by the connecting portion, and the flow velocity of the sucked liquid is reduced to prevent generation of a vortex in the liquid. Medium vortex prevention device. The upper disk of the submerged vortex preventing member according to claim 1 , wherein the upper disk of the submerged vortex preventing member is provided with a separation preventing part including a convex portion that suppresses separation of the fluid guided to the upper part of the submerged vortex preventing member by the connecting portion having the curved surface. A device for preventing vortexing in a suction liquid of a liquid pump. 3. A liquid pump suction liquid vortex prevention according to claim 2 , wherein the peeling prevention portion made of a convex portion of the upper disk of the submerged vortex preventing member has a substantially wing-shaped cross section symmetrical about the pump shaft center. apparatus.

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