Fluid resistance reduction device

Abstract

To provide a fluid resistance reduction device which enables reduction of fluid resistance (hydrodynamic energy loss) caused by secondary flow and a spiral vortex row.SOLUTION: A fluid resistance reduction device 1 includes: casings 2, 3; and a rotating body 4 housed in the casings 2, 3. The rotating body 4 is configured to rotate to cause a liquid to flow into the rotating body 4 along an axial direction of the rotating body 4 and out therefrom along a radial outward direction of the rotating body 4. A gap space 11, into which a part of the fluid flowing out from the rotating body 4 flows, is formed between the casings 2, 3 and the rotating body 4. In the gap space 11, a structure 12 is formed concentrically relative to a rotation axis of the rotating body 4 on a surface of the rotating body 4 which faces the casings 2, 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluid resistance reduction device that has the function of reducing fluid resistance (hydrodynamic energy loss) caused by secondary flows and spiral vortex streets. [Background technology]

[0002] Conventionally, techniques have been proposed to reduce energy loss and improve pump efficiency, such as a technique to reduce the occurrence of secondary flows in the inter-blade flow passages and improve pump efficiency (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-214897 Summary of the Invention [Problem to be solved by the invention]

[0004] However, secondary flows that cause a decrease in pump efficiency are not limited to occurring in the inter-blade flow passages. For example, in a pump device 100 such as a centrifugal pump, secondary flows (flows that flow radially outward along the surface of the rotor in the clearance space) and spiral vortex streets occur in a clearance space 103 (leakage passage) formed between a casing 101 and an impeller 102 (rotor), causing fluid energy loss (a decrease in pump efficiency) (see FIG. 7). Therefore, further development of technology to reduce such fluid resistance (fluid energy loss) has been desired.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a fluid resistance reduction device that can reduce fluid resistance (hydrodynamic energy loss) caused by secondary flows and spiral vortex streets in gap spaces. [Means for solving the problem]

[0006] The fluid resistance reduction device of the present invention is a fluid resistance reduction device comprising a casing and a rotating body housed inside the casing, wherein the rotating body is configured so that, as the rotating body rotates, liquid flows in along the axial direction of the rotating body and flows out along the radial outward direction of the rotating body, and a gap space is formed between the casing and the rotating body into which some of the outflowing liquid flows, and in the gap space, a structure is formed concentrically with respect to the rotation axis of the rotating body on the surface of the rotating body facing the casing.

[0007] According to this configuration, in the clearance space formed between the casing and the rotor, the structure is formed concentrically with respect to the rotation axis of the rotor on the surface of the rotor facing the casing, which makes it possible to suppress the generation of a secondary flow (a flow in the radially outward direction along the surface of the rotor in the clearance space) of the liquid that has flowed into the clearance space and to suppress the generation of a spiral vortex street in the clearance space, thereby reducing the fluid resistance (fluid energy loss) caused by the secondary flow and the spiral vortex street in the clearance space.

[0008] In the fluid resistance reduction device of the present invention, the structure may be a circular recess formed concentrically with the rotation axis of the rotating body.

[0009] According to this configuration, the circular recess formed concentrically with the rotation axis of the rotor can suppress the generation of a secondary flow of the liquid that has flowed into the gap space.

[0010] In the fluid resistance reduction device of the present invention, the circular protrusions may be formed in a plurality of concentric circles with respect to the rotation axis of the rotor.

[0011] According to this configuration, the occurrence of secondary flows of the liquid that has flowed into the gap space can be suppressed by the plurality of circular protrusions formed concentrically with respect to the rotation axis of the rotor.

[0012] In the fluid resistance reduction device of the present invention, the height of the circular convex portion may be set to a value equal to or smaller than the size of a vortex generated in the vicinity of the rotating body.

[0013] With this configuration, the height of the circular convex portion is set to a value equal to or less than the size of the vortex generated near the rotor, thereby improving the effect of the circular convex portion in suppressing the generation of secondary flows of the liquid that has flowed into the gap space. Note that "a value equal to or less than" means "the same value or a value smaller than that."

[0014] In the fluid resistance reduction device of the present invention, the circular recessed portion may be formed in a plurality of concentric circles with respect to the rotation axis of the rotor.

[0015] According to this configuration, the occurrence of secondary flows of the liquid that has flowed into the gap space can be suppressed by the plurality of circular recesses that are formed concentrically with respect to the rotation axis of the rotor.

[0016] In the fluid resistance reduction device of the present invention, the depth of the circular recess may be set to a value equal to or smaller than the size of a vortex generated in the vicinity of the rotating body.

[0017] According to this configuration, by setting the depth of the circular recess to a value less than the size of the vortex generated near the rotating body, the effect of the circular recess in suppressing the generation of secondary flows of liquid that flows into the gap space is improved.

[0018] In the fluid resistance reduction device of the present invention, the structure may be a circular protrusion formed concentrically with respect to the rotation axis of the rotating body.

[0019] According to this configuration, the circular convex portion formed concentrically with the rotation axis of the rotor can suppress the generation of a secondary flow of the liquid that has flowed into the gap space. [Effects of the Invention]

[0020] According to the present invention, it is possible to reduce fluid resistance (hydrodynamic energy loss) caused by secondary flows and spiral vortex streets. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing a main part of a fluid resistance reduction device (pump device) according to an embodiment of the present invention. [Figure 2] FIG. 1 is a perspective view of a rotor (impeller) according to an embodiment of the present invention. [Figure 3] 2A to 2C are diagrams showing examples of structures (recesses) according to an embodiment of the present invention. [Figure 4] 3A to 3C are diagrams showing examples of structures (protrusions) according to an embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing the effect of reducing fluid resistance (torque average value) in the embodiment of the present invention. [Figure 6] FIG. 10 is a diagram showing another example of a structure (a combination of a recess and a protrusion). [Figure 7] FIG. 10 is an explanatory diagram of a secondary flow occurring in a clearance space of the pump device. [Figure 8] FIG. 10 is an explanatory diagram of how to determine the size of a vortex generated near an impeller. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid resistance reduction device according to an embodiment of the present invention will now be described with reference to the drawings. In the present embodiment, a fluid resistance reduction device used as a pump device such as a centrifugal pump will be described as an example.

[0023] The configuration of a fluid resistance reduction device (pump device) according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a main part of the pump device according to this embodiment. Fig. 2 is a perspective view of a rotor (impeller) according to this embodiment. As shown in Fig. 1, in the pump device 1 according to this embodiment, an impeller 4 is housed inside casings 2 and 3.

[0024] As shown in FIG. 2, the impeller 4 is formed with a hole 5 through which a shaft (not shown) passes, and an inlet 6 through which a liquid (such as water) flows in is formed around the hole 5. In addition, an outlet 7 through which the liquid flows out is formed on the side surface of the impeller 4. The impeller 4 is a closed-type impeller 4 including a main plate 8 and a side plate 9, and a plurality of blades 10 (closed blades) are provided between the main plate 8 and the side plate 9. In this way, the impeller 4 is configured such that, as the impeller 4 rotates, liquid flows in from the inlet 6 along the axial direction of the impeller 4 (to the right in FIG. 1), and flows out from the outlet 7 radially outward of the impeller 4 (upward in FIG. 1).

[0025] 1, in the pump device 1 of this embodiment, a clearance space 11 into which a portion of the liquid flowing out from the outlet 7 flows is formed between the casings 2, 3 and the impeller 4. Then, as shown in FIGS. 1 and 2, a structure 12 is formed concentrically with respect to the rotation axis of the impeller 4 on the surface of the impeller 4 facing the casings 2, 3.

[0026] FIG. 3 is a diagram showing an example of the structure 12 (protrusion) of this embodiment. In the example of FIG. 3, a convex portion 12 (circular protrusion) concentric with the rotation axis of the impeller 4 is formed on the surfaces of the main plate 8 and the side plate 9 of the impeller 4 (surfaces facing the casings 2 and 3). In this case, the height of the circular protrusion 12 is preferably set to a value equal to or less than the size of the vortex generated near the impeller 4. In other words, the height of the circular protrusion 12 is preferably set to a value equal to or less than the size of the vortex generated near the impeller 4. Note that in the example of FIG. 3, one circular protrusion 12 is formed on the surfaces of the main plate 8 and the side plate 9 of the impeller 4, but the scope of the present invention is not limited thereto. One circular recess 12 may be formed on the surfaces of the main plate 8 and the side plate 9 of the impeller 4. In this case, the depth of the circular recess 12 is preferably set to a value equal to or less than the size of the vortex generated near the impeller 4.

[0027] FIG. 4 is a diagram showing an example of the structure 12 (protrusion) of this embodiment. In the example of FIG. 4, three convex portions 12 (circular convex portions) are formed concentrically with respect to the rotation axis of the impeller 4 on the surfaces of the main plate 8 and the side plate 9 of the impeller 4 (surfaces facing the casings 2 and 3). Note that in the example of FIG. 4, three circular convex portions 12 are formed on the surfaces of the main plate 8 and the side plate 9 of the impeller 4, but the scope of the present invention is not limited thereto. Two or four or more circular convex portions 12 may be formed concentrically on the surfaces of the main plate 8 and the side plate 9 of the impeller 4. In this case, it is preferable that the height of the circular convex portions 12 be set to a value equal to or less than the size of a vortex generated near the impeller 4. Furthermore, multiple circular recesses 12 may be formed concentrically on the surfaces of the main plate 8 and the side plate 9 of the impeller 4. In this case, it is preferable that the depth of the circular recesses 12 be set to a value equal to or less than the size of a vortex generated near the impeller 4.

[0028] The scale of the structure 12 (the height of the convex portion and the depth of the concave portion) can be calculated as follows. For example, as shown in FIG. 8, the distance R to the middle position of the gap space (leakage flow path) and the circumferential velocity there can be calculated by multiplying the radius R of the impeller 4 by the distance R. d and the aspect ratio h / R of the height h of the gap space (leakage path) d The corrected values ​​are used as the characteristic length L and the characteristic velocity U, respectively, to predict the size of the vortex s. Here, the dimensionless constant s + is set to be 300 to 500. Then, the predicted value (size of the vortex) is used as a reference value, and the scale of the structure 12 (height of the convex portion and depth of the concave portion) is set to be a value equal to or less than that value.

[0029] FIG. 5 is a diagram showing the effect of reducing fluid resistance (torque average value) of the pump device 1 of this embodiment. In FIG. 5, Example 1-1 corresponds to the example of the structure 12 of FIG. 3. That is, the structure 12 is a protrusion, the number of structures 12 is one, and the structure 12 is arranged at the center position in the radial direction. The torque average value of Example 1-1 is 9.04×10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0030] Example 1-2 corresponds to an example in which the structure 12 of Example 1-1 is provided on the radially outer side. That is, the structure 12 is a protrusion, the number of structures 12 is one, and the structure 12 is arranged on the radially outer side. The average torque of Example 1-2 is 9.04×10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0031] Example 1-3 corresponds to an example in which the structure 12 of Example 1-1 is provided on the radially inner side. That is, the structure 12 is a protrusion, the number of structures 12 is one, and the structure 12 is arranged on the radially inner side. The average torque of Example 1-3 is 9.07×10 -3 Nm, and compared to the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0032] Example 1-4 corresponds to the example of the structures 12 in Fig. 4. That is, the structures 12 are protrusions, the number of structures 12 is three, and the structures 12 are arranged on the inside, the central position, and the outside in the radial direction. The average torque of Example 1-4 is 9.03 x 10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0033] Example 1-5 corresponds to an example in which one of the radially outer convex portions is removed from the structure 12 of Example 1-4. That is, the structure 12 is a convex portion, the number of structures 12 is two, and the structures 12 are arranged at the radially inner and central positions. The average torque of Example 1-5 is 9.04×10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0034] Example 2-1 corresponds to an example in which the structure 12 of Example 1-1 is configured as a recess. That is, the structure 12 is a recess, the number of structures 12 is one, and the structure 12 is arranged at the center position in the radial direction. The average torque value of Example 2-1 is 9.04×10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0035] Example 2-2 corresponds to an example in which one recess is added to the radially outer side of the structure 12 of Example 2-1. That is, the structure 12 is a recess, the number of structures 12 is two, and the structures 12 are arranged at the center position and the outer position in the radial direction. The average torque of Example 2-2 is 9.09 × 10 -3 Nm, and compared with the comparative example in which the structure 12 is not formed, the -3 A reduction in fluid resistance (torque average value) of Nm was achieved.

[0036] As described above, according to the pump device 1 of this embodiment, in the gap space 11 formed between the casings 2, 3 and the impeller 4, the structure 12 is formed concentrically with respect to the rotation axis of the impeller 4 on the surface of the impeller 4 facing the casings 2, 3, so that it is possible to suppress the generation of a secondary flow (a flow in the radially outward direction along the surface of the impeller 4 in the gap space 11) of the liquid that has flowed into the gap space 11, and to suppress the generation of a spiral vortex street in the gap space 11. This makes it possible to reduce the fluid resistance (fluid energy loss) caused by the secondary flow and the spiral vortex street in the gap space 11, and improve the pump efficiency.

[0037] In this embodiment, the circular recess 12 formed concentrically with the rotation axis of the impeller 4 can suppress the generation of a secondary flow of the liquid that has flowed into the gap space 11. In this case, if the depth of the circular recess 12 is set to be equal to or less than the size of the vortex that is generated near the impeller 4, the effect of the circular recess 12 in suppressing the generation of a secondary flow of the liquid that has flowed into the gap space 11 is improved.

[0038] Furthermore, the circular protrusions 12 formed concentrically with respect to the rotation axis of the impeller 4 can suppress the generation of secondary flows of the liquid that has flowed into the clearance space 11. In this case, if the height of the circular protrusions 12 is set to be equal to or less than the size of the vortex that is generated near the impeller 4, the effect of the circular protrusions 12 in suppressing the generation of secondary flows of the liquid that has flowed into the clearance space 11 is improved.

[0039] Although the embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to these, and can be modified and changed according to the purpose within the scope of the claims.

[0040] For example, in the above description, the impeller 4 is a closed-type impeller 4 including the main plate 8 and the side plate 9, but the impeller 4 may be an open-type impeller 4 including only the main plate 8 (without the side plate 9). In this case, the concentric structures 12 (concave and convex portions) can be formed on the surface of the main plate 8 (the surface facing the casings 2 and 3).

[0041] In the above description, the concentric structure 12 is either a recess or a protrusion. However, as shown in FIG. 6, the concentric structure 12 may be a combination of a recess and a protrusion. [Industrial Applicability]

[0042] As described above, the fluid resistance reduction device according to the present invention has the effect of being able to reduce fluid resistance (hydrodynamic energy loss) caused by secondary flows and spiral vortex streets, and is useful when used as a pump device such as a centrifugal pump. [Explanation of symbols]

[0043] 1. Fluid resistance reduction device (pump device) 2 Casing 3 Casing 4 Rotating body (impeller) 5 holes 6 Inlet 7 Outlet 8 Main plate 9 Side Panel 10 Feathers 11. Interstitial Space 12 Structure (concave, convex)

Claims

1. A fluid resistance reduction device including a casing and a rotating body housed inside the casing, the rotating body is configured such that, as the rotating body rotates, liquid flows in along an axial direction of the rotating body and the liquid flows out along an outward radial direction of the rotating body, a clearance space into which a portion of the outflowing liquid flows is formed between the casing and the rotating body, In the gap space, a structure is formed concentrically with respect to a rotation axis of the rotor on a surface of the rotor facing the casing, The height or depth of the structure is set to a value equal to or less than the size of a vortex generated in the vicinity of the rotating body, A fluid resistance reduction device characterized in that the size of the vortex is predicted by the following formula. [Equation 1] however, s: vortex size, s + : a dimensionless constant between 300 and 500, ν: kinematic viscosity coefficient, U: Representative speed (A(Ω×R)), Re: Reynolds number (UL / ν), R: distance from the axial center of the rotating body to the middle position of the rotating body, A: aspect ratio (h / Rd), h: the height of the gap space at the intermediate position of the rotating body, Rd: radius of the rotating body, Ω: a predetermined angular velocity when the rotor rotates, L: Representative length (A x R), ν: kinematic viscosity coefficient.

2. The fluid resistance reduction device according to claim 1 , wherein the structure is a circular convex portion formed concentrically with respect to the rotation axis of the rotor.

3. The fluid resistance reduction device according to claim 2 , wherein the circular protrusions are formed in a plurality of concentric circles around the rotation axis of the rotor.

4. The fluid resistance reduction device according to claim 1 , wherein the structure is a circular recess formed concentrically with the rotation axis of the rotor.

5. The fluid resistance reduction device according to claim 4 , wherein a plurality of the circular recesses are formed concentrically with respect to the rotation axis of the rotor.

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