JP5023560B2 - Mixed flow pump - Google Patents

Description

  The present invention relates to a mixed flow pump, and is particularly suitable for a mixed flow pump having a region where discharge-side fluid leaks on the back surface of an impeller.

  A conventional axial thrust reduction method for a mixed flow pump will be described with reference to FIG. FIG. 3 is a sectional view of a peripheral portion of an impeller of a conventional mixed flow pump. In addition, the same code | symbol as embodiment of this invention mentioned later shows the same thing or an equivalent.

  The mixed flow pump 50 includes a rotating shaft 9, an impeller 20 including a hub 4 attached to the rotating shaft 9 and blades 1 provided on the outer periphery of the hub 4, and a suction casing 30 that guides fluid to the impeller 20. And a discharge casing 40 composed of an outer peripheral discharge casing 41 and an inner peripheral discharge casing 42 for guiding the fluid discharged from the impeller 20. And it has the area | region 3 formed with the back surface of the impeller 20, the inner surface of the inner peripheral discharge casing 42, and the outer peripheral surface of the rotating shaft 9, and the back side area | region 3 of this impeller 20 and the suction side area | region of the impeller 20 Are provided with a plurality of balance holes 8 in direct communication with each other. This balance hole 8 is for reducing the pressure difference in the suction side of the impeller 20 by reducing the pressure in the rear side region of the impeller 20 and reducing the suction side thrust acting on the impeller 20. It is.

  In addition, as a patent document relevant to this prior art, Unexamined-Japanese-Patent No. 7-332281 (patent document 1) is mentioned, for example.

JP 7-332281 A

  However, in the conventional mixed flow pump 50, the suction side directional thrust acting on the impeller 20 is reduced by forming the balance hole 8 and lowering the pressure in the rear region 3 of the impeller 20, so that the suction side In order to greatly reduce the directional thrust, it is necessary to enlarge the balance hole 8. When the balance hole 8 is enlarged, there is a problem that the leakage flow rate returned to the suction side is increased and the pump efficiency is lowered.

  The objective of this invention is providing the mixed flow pump which can reduce the total thrust added to a rotating shaft, reducing the amount of fluid leaks to an impeller back surface, and suppressing the fall of pump efficiency.

In order to achieve the above-mentioned object, the present invention provides a rotating shaft, an impeller comprising a hub attached to the rotating shaft and blades provided on the outer periphery of the hub, and a suction casing for guiding fluid to the impeller. A discharge casing comprising an outer peripheral discharge casing and an inner peripheral discharge casing for guiding the fluid discharged from the impeller, and a rear surface of the impeller, an inner surface of the inner peripheral discharge casing, and an outer peripheral surface of the rotary shaft. In the mixed flow pump having the formed region, the first region into which the fluid on the discharge side of the impeller leaks and flows in the region in the axial direction, and the fluid in the first region flows in through the throttle channel second with partitions in the region, the annular member each side surface has a flat surface perpendicular to the axial direction, provided on the outer periphery of the rotary shaft, an outer peripheral surface of the rotary shaft, the suction-side end of the rotary shaft of Small diameter extending from A first step formed by a first outer peripheral surface and a first vertical surface extending outwardly from the opposite end side of the first outer peripheral surface; and an outer periphery of the first vertical surface A second outer peripheral surface having a diameter larger than that of the first outer peripheral surface extending toward the opposite end side, and a second vertical surface extending outward from the opposite end side of the second outer peripheral surface vertically. The second step portion is formed, and the annular member is fitted to the second step portion from the suction side end portion of the rotating shaft, and the second step portion is formed on the second portion from the surface facing the first region. The surface facing the region 2 is mounted so as to be small, and the impeller is mounted on the first step portion from the suction side end portion of the rotating shaft in a state where the annular member is mounted on the second step portion. It is in fitting and wearing .

A preferred specific configuration example of the present invention is as follows.
(1) The throttle channel is formed by a gap between the annular member and the inner peripheral discharge casing.
(2) The gap between the annular member and the inner peripheral discharge casing is long and narrow in the axial direction to provide a fluid bearing function .

  According to the mixed flow pump of the present invention, the total thrust applied to the rotating shaft can be reduced while reducing the amount of fluid leaking to the rear surface of the impeller and suppressing the reduction in pump efficiency.

  According to the preferable configuration example (1), a pressure difference between the first region and the second region can be generated with a simple structure without forming a special throttle channel such as a pore. it can.

  Moreover, according to the said preferable structural example (2), the bearing reliability of a rotating shaft can be improved.

  Furthermore, according to the preferable configuration example (3), the annular member can be accurately and easily positioned with respect to the inner peripheral discharge casing.

  Hereinafter, a mixed flow pump according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a peripheral portion of an impeller 20 of a mixed flow pump 50 according to an embodiment of the present invention, and FIG. 2 is an explanatory view of thrust in each part of the mixed flow pump 50 of FIG. The mixed flow pump 50 of the present embodiment is an example of a horizontal axis pump, but the present invention is also applicable to a vertical axis pump.

  The mixed flow pump 50 includes the rotating shaft 9, the impeller 20, the suction casing 30, the discharge casing 40, and the annular member 10.

  The rotary shaft 9 extends from the suction casing 30 side to the discharge casing 40 side and is rotatably supported by a thrust bearing and a radial bearing (not shown).

  The impeller 20 is attached to the rotation shaft 9 and is rotated together with the rotation shaft 9. The impeller 20 is configured by integrally forming a hub 4 expanded in a substantially conical shape and a plurality of blades 1 provided obliquely on the outer circumferential surface of the hub 4. The hub 4 has a central boss portion 4 a fitted into the first step portion 9 a of the rotating shaft 9 from the end side of the rotating shaft 9, and the opposite step portion side of the central boss portion 4 a is brought into contact with the stopper 14. Yes.

  The suction casing 30 forms a suction flow path 15 that guides fluid (in this embodiment, water) to the impeller 20. The suction casing 30 includes two suction casings 31 and 32. Note that the suction casing 32 forms an outer peripheral side flow path of the impeller 20.

  The discharge casing 40 forms a discharge channel 16 that guides the fluid discharged from the impeller 20. The discharge channel 16 is formed between an outer peripheral discharge casing 41 and an inner peripheral discharge casing 42 that constitute the discharge casing 40. A plurality of guide vanes 2 are provided in the discharge channel 16.

  The end of the outer periphery discharge casing 41 and the end of the suction casing 32 are joined so that the outer periphery discharge casing 41 continues from the suction casing 32. The end portion of the inner peripheral discharge casing 42 and the outer peripheral end portion of the hub 4 are opposed to each other with a gap so that the inner peripheral discharge casing 42 continues from the hub 4.

The inner peripheral discharge casing 42 includes a casing part 42A that forms a discharge flow path, and a cylindrical part 42B that is in close contact with and fixed to the inside of the casing part 42A. The cylindrical portion 42 </ b> B is provided coaxially with the rotating shaft 9 and the annular member 10, and has a circular inner peripheral surface that is slightly larger than the circular outer peripheral surface of the annular member 10 . Note that the inner peripheral discharge casing 42 may be configured by integrally forming the two members 42A and 42B with the same member.

  In the mixed flow pump 50, a region 3 surrounded by the rear surface of the hub 4 of the impeller 20, the inner surface of the inner peripheral discharge casing 42, and the outer peripheral surface of the rotating shaft 9 is formed. In this region 3, the first member 3 </ b> A in which the fluid on the discharge side of the impeller 20 leaks and flows in the axial direction by the annular member 10, and the fluid in the first region 3 </ b> A flows through the throttle channel 13. It is partitioned into a second region 3B. The 2nd field 3B is connected with the suction channel 15 side via piping which is not illustrated, for example.

  The annular member 10 is fixedly provided on the outer periphery of the rotary shaft 9 and is rotated together with the rotary shaft 9. Specifically, the annular member 10 is fitted and fixed to the second step portion 9 b of the rotating shaft 9 from the end side of the rotating shaft 9. The mounting structure of the annular member 10 and the impeller 20 is formed with two step portions 9a and 9b on the outer peripheral surface of the rotating shaft 9, and the annular member 10 and the impeller 20 are sequentially mounted from the suction side end of the rotating shaft 9. Structure.

  The throttle channel 13 is configured by a gap between the annular member 10 and the cylindrical portion 42B. The throttle channel 13 is long and narrow in the axial direction and has a function as a fluid bearing.

  In such a configuration, the fluid flowing in the suction casing 30 from the suction side is boosted by the impeller 20 and then discharged to the discharge flow path 16 formed by the discharge casing 40 and passes through the guide blade 2 to the discharge side. To be leaked.

  Here, since there is a gap between the fixed inner peripheral discharge casing 42 and the hub 4 of the rotating impeller 20, a part of the fluid discharged from the impeller 20 is transferred to the hub 4 of the impeller 20. It flows into the 1st field 3A formed in the back.

  Then, the fluid that has flowed into the first region 3A is decompressed through the throttle channel 13 and flows into the second region 3B. Here, since the throttle channel 13 is formed to have a long sealing function in the axial direction with a narrow gap between the annular member 10 and the cylindrical member 42B, the amount of fluid flowing into the second region 3B is reduced. The pressure in the second region 3B is made extremely low (in other words, close to the pressure in the suction flow path 15), and the pressure difference between the first region 3A and the second region 3B is increased while being extremely small. Can do. The fluid that has flowed into the second region 3B is returned to the suction flow path 15.

  The thrust acting on the rotating shaft 9 of the mixed flow pump 50 will be described. The thrust acting on the rotating shaft 9 includes a thrust acting on the impeller 20 and a thrust acting on the annular member 10.

As shown in FIGS. 1 and 2, the thrust acting on the impeller 20 includes a discharge side thrust 21 acting on the front surface of the hub 4, a suction side thrust 22 acting on the blade 1, and a suction side acting on the back surface of the hub 4. It consists of a directional thrust 23. The total thrust bets acting on the impeller 20, as shown in FIG. 2, has a thrust acting on the suction side direction. Therefore, the mixed flow pump 50, it is important to reduce the total thrust bets impeller 20 acting on the suction side direction. In FIG. 2, the discharge side thrust is indicated by minus and the suction side thrust is indicated by plus.

Further, as shown in FIGS. 1 and 2, the thrust acting on the annular member 10 includes a discharge-side thrust 24 acting on the surface (front surface of the annular member 10) 11 of the annular member 10 forming the first region, It consists of a suction side thrust 25 acting on the surface of the annular member 10 forming the region 2 (the back surface of the annular member 10) 12. The total thrust bets acting on the annular member 10, as shown in FIG. 2, has a thrust acting on the discharge side direction. Thus, the total thrust bets acting on the rotary shaft 9, as shown in FIG. 2, it is possible to reduce the total thrust Ri greatly by preparative acting on impeller 20.

  Note that the leakage flow rate can be reduced as the length of the annular member 10 in the axial direction becomes longer. However, if the length is increased too much, the friction loss of the seal sliding portion increases, and conversely, the pump efficiency is lowered. Therefore, it is desirable to set the axial length of the annular member 10 so that improvement in pump efficiency and reduction in thrust applied to the rotating shaft 9 can be achieved simultaneously.

Further, as the radial dimension of the annular member 10 increases, the difference between the discharge-side thrust 24 acting on the front surface 11 of the annular member 10 and the suction-side thrust 25 acting on the rear surface 12 of the annular member 10 increases. the total thrust bets acting in the suction side direction 10 is increased, it is possible to reduce the overall thrust bets rotary shaft 9. However, the friction loss acting on the annular member 10 whose radial dimension increases is increased, and the pump efficiency is lowered. Therefore, it is desirable to set the radial dimension so that improvement in pump efficiency and reduction in thrust applied to the rotary shaft 9 can be achieved simultaneously.

  According to the present embodiment, the rotating shaft 9, the impeller 20 including the hub 4 mounted on the rotating shaft 9 and the blades 1 provided on the outer periphery of the hub 4, and the suction casing for guiding fluid to the impeller 20. 30, and a discharge casing 40 including an outer peripheral discharge casing 41 and an inner peripheral discharge casing 42 for guiding the fluid discharged from the impeller 20, and the rear surface of the impeller 20, the inner surface of the inner peripheral discharge casing 42, and the rotating shaft 9. In the mixed flow pump 50 having the region 3 formed by the outer peripheral surface, the first region 3A and the first region 3A in which the fluid on the discharge side of the impeller 20 leaks and flows in the region 3 in the axial direction. Is provided on the outer periphery of the rotary shaft 9 to reduce the amount of fluid leaking to the rear surface of the impeller 20 and to improve the pump efficiency. Suppress the decline While, it is possible to reduce the total thrust applied to the rotary shaft 8. That is, thrust in the reverse direction can be generated on the rear surface of the impeller 20 and the annular member 10, and by increasing the throttle resistance of the throttle channel 13 through which fluid flows from the first region 3A to the second region 3B. The function of reducing the amount of inflow from the first region 3A to the second region 3B and the function of increasing the difference between the pressure of the first region 3A and the pressure of the second region 3B can be achieved. it can. This greatly reduces the amount of fluid leakage from the discharge side of the impeller 20 to the first region 3 </ b> A, while generating a large discharge-side thrust in the annular member 10 to reduce the suction-side thrust by the impeller 20. Can be offset.

  Furthermore, since the throttle channel 13 is formed by the gap between the annular member 10 and the inner peripheral discharge casing 42, the first structure can be achieved with a simple structure without forming a special throttle channel such as a pore. The pressure difference between the region 3A and the second region 3B can be generated.

  Furthermore, since the gap between the annular member 10 and the inner peripheral discharge casing 42 is long and narrow in the axial direction to provide a fluid bearing function, the bearing reliability of the rotary shaft can be improved.

  Furthermore, since the two step portions 9a and 9b are formed on the outer peripheral surface of the rotating shaft 9, and the annular member 10 and the impeller 20 are sequentially mounted from the suction side end portion of the rotating shaft 9, the annular member 10 is Positioning with respect to the inner peripheral discharge casing 42 can be performed accurately and easily.

It is sectional drawing of the peripheral part of the impeller of the mixed flow pump of one Embodiment of this invention. It is explanatory drawing of the thrust in each part of the mixed flow pump of FIG. It is sectional drawing of the peripheral part of the impeller of the conventional mixed flow pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Blade | wing 2 ... Guide blade | wing, 3 ... Area | region, 3A ... 1st area | region, 3B ... 2nd area | region, 4 ... Hub, 5 ... Impeller back surface, 8 ... Balance hall, 9 ... Rotating shaft, 9a ... 1st 1 step part, 9b ... 2nd step part, 10 ... annular member, 11 ... annular member front surface, 12 ... annular member back surface, 13 ... throttle channel, 15 ... suction channel, 16 ... discharge channel, 20 ... Impeller, 30 ... suction casing, 40 ... discharge casing, 41 ... outer periphery discharge casing, 42 ... inner periphery discharge casing, 42A ... casing part, 42B ... cylindrical part, 50 ... mixed flow pump.

Claims (3)

A rotation axis;
An impeller comprising a hub attached to the rotating shaft and blades provided on the outer periphery of the hub;
A suction casing for directing fluid to the impeller;
A discharge casing comprising an outer peripheral discharge casing and an inner peripheral discharge casing for guiding the fluid discharged from the impeller;
In the mixed flow pump having a region formed by the back surface of the impeller, the inner surface of the inner peripheral discharge casing, and the outer peripheral surface of the rotating shaft,
The region is divided in the axial direction into a first region in which fluid on the discharge side of the impeller leaks and flows in and a second region in which fluid in the first region flows through the throttle channel , the annular member end surface has a flat surface perpendicular to the axial direction, provided on the outer periphery of said rotary shaft,
On the outer peripheral surface of the rotary shaft, a first outer surface having a small diameter extending from the suction side end of the rotary shaft, and a first vertical surface extending perpendicularly outward from the opposite end side of the first outer peripheral surface Of the first step portion formed by the second vertical surface, the second outer peripheral surface having a larger diameter than the first outer peripheral surface extending from the outer periphery of the first vertical surface to the opposite end side, and the second outer peripheral surface. Forming a second step portion formed by a second vertical surface extending vertically outward from the opposite end side;
The annular member is fitted to the second step portion from the suction side end of the rotating shaft so that the surface of the annular member facing the second region is smaller than the surface facing the first region of the annular member. Wearing,
The mixed flow pump , wherein the impeller is fitted and attached to the first step portion from the suction side end portion of the rotating shaft in a state where the annular member is attached to the second step portion. .   2. The mixed flow pump according to claim 1, wherein the throttle channel is formed by a gap between the annular member and the inner peripheral discharge casing.   3. The mixed flow pump according to claim 2, wherein a gap between the annular member and the inner peripheral discharge casing is long and narrow in an axial direction to provide a fluid bearing function.

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