JP6768428B2 - Pre-standby operation pump - Google Patents

Description

The present invention relates to a preceding standby pump.

Preliminary standby operation is a measure against localized torrential rain (so-called guerrilla rainstorm). When rainwater is once introduced into an underground river, etc., the pump operation is started in advance and the amount of water changes suddenly. It is an operation method corresponding to.

FIG. 1 is a diagram for explaining an operating state of the preceding standby operation. As shown in FIG. 1, in the preceding standby operation, first, the impeller is started to rotate in the air state before the impeller is submerged based on the rainfall information and the like regardless of the suction water level (A: air operation). As the water level rises from the low water level, the water level reaches the position of the impeller, and the operating state of the pump is that the air supplied from the intake port is taken from the operation of stirring the water with the impeller (B: air-water stirring operation). After the operation of gradually increasing the amount of water while sucking it together with water (C: air-water mixing operation), the process shifts to the normal operation (D: steady operation) in which water is discharged at the rated flow rate.

By the way, in a normal vertical shaft pump, when the water level drops from a high water level to below the bell suction port, a large amount of air enters at once from the bell suction port exposed to the atmosphere, causing violent vibration and noise. become.

On the other hand, the preceding standby operation pump is provided with an intake port for naturally aspirating air in the atmosphere into the bell in response to a decrease in static pressure in the bell due to a decrease in water level. As a result, when the water level drops from the high water level, the operation shifts from the steady operation to the operation of gradually reducing the amount of water while sucking the air supplied from the intake port together with the water (C: air-water mixing operation). When the water level further drops to reach a predetermined airlock water level, an air pool is formed below the impeller, and the water above the impeller is agitated by the impeller (E: airlock operation). In the airlock operating state, the water above the impeller is only agitated by the impeller and the pump flow rate is zero. When the water level rises again, it shifts to the air-water mixing operation.

Such a preceding standby operation pump has the following problems due to the intake structure. That is, (1) the larger the static pressure fluctuation of the intake port portion during the air-water mixing operation, the more easily the pump vibrates. Further, (2) If the amount of intake air from the intake port is small in the partial flow rate region where the rated flow rate transitions to the airlock, the airlock may not be established due to the insufficient amount of intake air. In this case, when the water level further drops and reaches below the bell suction port, large vibration and noise are generated.

Patent Document 1 discloses a structure in which a pipe is provided so as to protrude from the inner surface of the bell and an intake port is formed at the tip of the pipe. Further, Patent Document 2 discloses a structure in which an intake port is formed in a slit shape along the circumferential direction on the inner surface of the bell.

Japanese Patent Application Laid-Open No. 3-138481 Japanese Patent No. 4436484

In the intake structure disclosed in Patent Document 1, there is a concern that the pump flow rate may decrease or blockage due to the accumulation of impurities in the pipe portion in the bell mouth due to the influence of the pipe protruding inward in the radial direction. In addition, since advanced standby pumps are often used in public works projects, customers require that parts such as bell mouths be integrally manufactured by casting in order to ensure long-term reliability, but to some extent. If it is attempted to integrally cast a pipe that is thin enough for a casing having the same wall thickness, the cost will be high.

On the other hand, in the intake structure disclosed in Patent Document 2, the intake port is formed on the inner surface of the casing. In general, as the flow rate decreases as the water level decreases, the centrifugal field on the inner surface of the casing becomes stronger. Therefore, in the intake structure disclosed in Patent Document 2, the centrifugal field becomes stronger as the water level decreases and approaches the airlock water level. Due to the influence of, the amount of intake air decreases, making it difficult for the airlock to succeed. Further, in the vicinity of the inner surface of the casing, the static pressure fluctuation due to the influence of the impeller rotation is large, which causes vibration during intake.

The present invention has been made in consideration of the above points. An object of the present invention is to provide a preceding standby operation pump capable of increasing the intake amount in a partial flow rate region where the rated flow rate transitions to an airlock.

The preceding standby operation pump according to the embodiment is
It is provided with an impeller and a casing for accommodating the impeller.
A convex portion is provided on the inner surface of the casing on the upstream side in the mainstream direction from the impeller.
An intake port is formed near the apex of the convex portion.
The convex portion has a guide surface on the upstream side in the mainstream direction and the downstream side in the mainstream direction, respectively, in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to the above-mentioned preceding standby operation pump, since the guide surfaces are provided on the upstream side in the mainstream direction and the downstream side in the mainstream direction of the intake port, the fluid in the vicinity of the intake port flowing along the vicinity of the guide surface is from the guide surface. The flow velocity tends to increase as compared with the fluid flowing in the distant flow path. According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, so the static pressure decreases in the vicinity of the intake port. As a result, the amount of intake air supplied from the intake port can be increased in the partial flow rate region where the rated flow rate transitions to the airlock, and the success rate of the airlock can be increased. Further, especially at the rated flow rate, due to the influence of the impeller rotation, periodic static pressure fluctuations occur in the circumferential direction even inside the bell mouth on the upstream side in the axial direction from the impeller. The inventors of the present invention have empirically known that the static pressure fluctuation in this part is larger toward the inner wall of the bell mouth (outside in the radial direction), and confirmed by the prediction by the flow analysis. In the intake shape according to the present embodiment, since the intake port is provided near the apex of the convex portion located radially inside from the inner surface of the casing, the static pressure fluctuation in the vicinity of the intake port is reduced. As a result, it is possible to reduce the generation of vibration during intake.

In the above-mentioned preceding standby operation pump
The convex portion may have a guide surface on the upstream side in the secondary flow direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

Here, the gas-liquid mixing operation is started from the rated operation, and the water flow rate gradually decreases toward the airlock, so that the pump operates in a partial flow rate range. In the partial flow rate region, as the flow rate decreases in the mainstream direction, the influence of the impeller at a constant rotation speed increases, so the secondary flow direction component in the bell mouth increases, and the secondary flow direction component near the airlock. Becomes dominant. Therefore, according to such an aspect, the flow velocity of the fluid near the intake port flowing in the secondary flow direction along the guide surface increases as compared with the fluid flowing in the secondary flow direction in the flow path away from the guide surface. It tends to be. According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, so the static pressure decreases in the vicinity of the intake port. As a result, the amount of intake air supplied from the intake port can be further increased, and the success rate of the airlock can be further increased.

In the above-mentioned preceding standby operation pump
The convex portion may have a guide surface on the downstream side in the secondary flow direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to such an aspect, the fluid in the vicinity of the intake port flowing in the secondary flow direction flows along the guide surface provided on the downstream side in the secondary flow direction due to the effect of the viscosity of the fluid. As a result, peeling from the guide surface can be suppressed, so that reduction in pump efficiency due to the influence of peeling and generation of vibration / noise can be reduced.

In the above-mentioned preceding standby operation pump
The guide surface may have a curvature with respect to each flow direction.

According to such an aspect, the fluid in the vicinity of the intake port flowing in each flow direction can be guided smoothly along the guide surface. As a result, peeling from the guide surface can be suppressed, so that reduction in pump efficiency due to the influence of peeling and generation of vibration / noise can be reduced.

In the above-mentioned preceding standby operation pump
The amount of protrusion of the guide surface on the downstream side in the mainstream direction may be reduced less than the amount of protrusion on the upstream side in the mainstream direction.

According to such an aspect, the mainstream direction flow near the intake port is easily guided along the guide surface. As a result, peeling from the downstream guide surface can be suppressed, so that the pump efficiency can be reduced due to the influence of the peeling, and the generation of vibration and noise can be reduced.

In the above-mentioned preceding standby operation pump
The center of the intake port may be located on the upstream side in the mainstream direction or on the downstream side in the mainstream direction with respect to the apex of the convex portion.

According to the verification by the present inventors, the static pressure tends to be lower on the upstream side or the downstream side in the mainstream direction than the apex depending on the shape of the inner wall of the bell mouth, the shape of the convex portion, and the pump operating condition. Sometimes. Therefore, it is possible to preferably design the intake port position according to the shape of the inner wall of the bell mouth, the shape of the convex portion, and the operating condition of the pump. According to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port, and the amount of intake air supplied from the intake port can be further increased.

In the above-mentioned preceding standby operation pump
The center of the intake port may be located on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction from the apex of the convex portion.

According to the verification by the present inventors, the static pressure tends to be lower on the upstream side or the downstream side of the secondary flow than the apex depending on the shape of the inner wall of the bell mouth, the shape of the convex portion, and the pump operating condition. May occur. Therefore, it is possible to preferably design the intake port position according to the shape of the inner wall of the bell mouth, the shape of the convex portion, and the operating condition of the pump. According to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port, and the amount of intake air supplied from the intake port can be further increased.

In the above-mentioned preceding standby operation pump
The convex portion has a cylindrical portion that protrudes from the inner surface of the casing.
The intake port and the guide surface may be arranged at the tip of the cylindrical portion.

According to such an aspect, since the intake port is provided near the tip of the tubular portion on the inner diameter side of the inner surface of the casing, the static pressure fluctuation in the vicinity of the intake port due to the influence of the impeller rotation is reduced. As a result, it is possible to reduce the generation of vibration during intake.

According to such an aspect, the stress concentration between the downstream side portion of the base end portion of the cylindrical portion in the mainstream direction and the inner surface of the casing can be relaxed to make it difficult to break.

In the above-mentioned preceding standby operation pump
The amount of protrusion of the convex portion may be less than 25% of the diameter of the casing at the same axial position as the convex portion.

According to such an aspect, since the amount of protrusion of the convex portion is relatively small, there is less concern about the accumulation of impurities in the bell mouth due to the influence of the convex portion. Further, since the convex portion does not have to be thin like a pipe shape and the intake port may be provided by post-processing, the production cost when the convex portion is integrally cast with the casing can be significantly reduced.

The preceding standby operation pump according to the embodiment is
It is provided with an impeller and a casing for accommodating the impeller.
A convex portion is provided on the inner surface of the casing on the upstream side in the mainstream direction from the impeller.
An intake port is formed near the apex of the convex portion.
The convex portion has a guide surface having a curvature on the upstream side in the mainstream direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to the above-mentioned preceding standby operation pump, since a guide surface having a curvature is provided on the upstream side of the intake port in the mainstream direction, the fluid in the vicinity of the intake port flowing in the mainstream direction is guided smoothly along the guide surface. can do. As a result, it is possible to prevent the occurrence of a stagnation region due to the collision of the fluid on the upstream side of the intake port, and it is possible to reduce the decrease in pump efficiency due to the increase in flow path loss. Further, the flow velocity of the fluid in the vicinity of the intake port flowing along the guide surface tends to increase as compared with the fluid flowing in the flow path away from the guide surface. According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, so the static pressure decreases in the vicinity of the intake port. As a result, the amount of intake air supplied from the intake port can be increased in the partial flow rate region where the rated flow rate transitions to the airlock, and the success rate of the airlock can be increased. Further, since the intake port is provided near the apex of the convex portion on the inner diameter side of the inner surface of the casing, the static pressure fluctuation in the vicinity of the intake port due to the influence of the impeller rotation is reduced. As a result, it is possible to reduce the generation of vibration during intake.

In the above-mentioned preceding standby operation pump
The convex portion may have a guide surface having a curvature on the downstream side in the mainstream direction so that the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to such an aspect, the fluid in the vicinity of the intake port flowing in the mainstream direction flows smoothly along the guide surface provided on the downstream side in the mainstream direction due to the effect of the viscosity of the fluid. As a result, peeling from the guide surface can be suppressed, so that reduction in pump efficiency due to the influence of peeling and generation of vibration / noise can be reduced.

In the above-mentioned preceding standby operation pump
The convex portion may have a guide surface having a curvature on the upstream side in the secondary flow direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to such an aspect, the fluid in the vicinity of the intake port flowing in the secondary flow direction can be guided smoothly along the guide surface, and peeling from the guide surface can be suppressed. Further, the fluid in the vicinity of the intake port flowing in the secondary flow direction along the guide surface tends to have an increased flow velocity as compared with the fluid flowing in the secondary flow direction in the flow path away from the guide surface. According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, so the static pressure decreases in the vicinity of the intake port. As a result, the amount of intake air supplied from the intake port can be further increased, and the success rate of the airlock can be further increased.

In the above-mentioned preceding standby operation pump
The convex portion may have a guide surface having a curvature on the downstream side in the secondary flow direction, in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases.

According to such an aspect, the fluid in the vicinity of the intake port flowing in the secondary flow direction flows smoothly along the guide surface provided on the downstream side in the secondary flow direction due to the effect of the viscosity of the fluid. As a result, peeling from the guide surface can be suppressed, so that deterioration of pump efficiency due to occurrence of peeling and generation of vibration / noise can be reduced.

In the above-mentioned preceding standby operation pump
The amount of protrusion of the guide surface on the downstream side in the mainstream direction may be reduced less than the amount of protrusion on the upstream side in the mainstream direction.

According to such an aspect, the fluid in the vicinity of the intake port flowing in the mainstream direction is likely to be guided along the guide surface provided on the downstream side in the mainstream direction. As a result, peeling from the guide surface can be suppressed, so that reduction in pump efficiency due to the influence of peeling and generation of vibration / noise can be reduced.

In the above-mentioned preceding standby operation pump
The center of the intake port may be located on the upstream side in the mainstream direction or on the downstream side in the mainstream direction with respect to the apex of the convex portion.

According to the verification by the present inventors, the static pressure tends to be lower on the upstream side or the downstream side in the mainstream direction than the apex depending on the shape of the inner wall of the bell mouth, the shape of the convex portion, and the pump operating condition. Sometimes. Therefore, according to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port, and the amount of intake air supplied from the intake port can be further increased.

In the above-mentioned preceding standby operation pump
The center of the intake port may be located on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction from the apex of the convex portion.

According to the verification by the present inventors, the static pressure tends to be lower on the upstream side in the secondary flow direction than the apex depending on the shape of the inner wall of the bell mouth, the shape of the convex portion, and the pump operating condition. is there. Therefore, according to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port, and the amount of intake air supplied from the intake port can be further increased.

In the above-mentioned preceding standby operation pump
The convex portion has a cylindrical portion that protrudes from the inner surface of the casing.
The intake port and the guide surface may be arranged at the tip of the cylindrical portion.

According to such an aspect, since the intake port is provided near the tip of the tubular portion radially inside the inner surface of the casing, the static pressure fluctuation in the vicinity of the intake port due to the influence of the impeller rotation is reduced. As a result, it is possible to reduce the generation of vibration during intake.

According to such an aspect, the stress concentration between the downstream side portion of the base end portion of the cylindrical portion in the mainstream direction and the inner surface of the casing can be relaxed to make it difficult to break.

In the above-mentioned preceding standby operation pump
The amount of protrusion of the convex portion may be less than 25% of the diameter of the casing at the same axial position as the convex portion.

According to such an aspect, since the amount of protrusion of the convex portion is relatively small, there is less concern about the accumulation of impurities in the bell mouth due to the influence of the convex portion. Further, since the convex portion does not have to be thin like a pipe shape and the intake port may be provided by post-processing, the production cost when the convex portion is integrally cast with the casing can be significantly reduced.

According to the present invention, in the preceding standby operation pump, the intake amount in the partial flow rate region where the rated flow rate transitions to the airlock can be increased.

FIG. 1 is a diagram for explaining an operating state of the preceding standby operation. FIG. 2 is a schematic view showing the structure of the preceding standby operation pump according to the embodiment. FIG. 3 is an enlarged schematic view of a lower end portion of the casing of the pump shown in FIG. 2, particularly a bell mouth portion in which an intake port is located. FIG. 4 is a schematic view of the inner surface of the lower end portion of the casing shown in FIG. 3 as viewed from the downstream side in the mainstream direction. FIG. 5A is a front view of an example of the convex portion as viewed from the inside in the radial direction of the pump. FIG. 5B is a side view of the convex portion shown in FIG. 5A as viewed from the secondary flow direction. FIG. 5C is a side view of the convex portion shown in FIG. 5A as viewed from the mainstream direction. FIG. 5D is a side view of a modified example of the convex portion as viewed from the secondary flow direction. FIG. 5E is a side view of a modified example of the convex portion as viewed from the mainstream direction. FIG. 5F is a side view of a modified example of the convex portion as viewed from the secondary flow direction. FIG. 6A is a front view of a modified example of the convex portion as viewed from the inside in the radial direction of the pump. FIG. 6B is a side view of the convex portion shown in FIG. 6A as viewed from the secondary flow direction. FIG. 6C is a side view of the convex portion shown in FIG. 6A as viewed from the mainstream direction. FIG. 7 is a schematic diagram for explaining a physical mechanism in which the static pressure decreases in the vicinity of a wall surface having a curved surface such as an intake port according to the embodiment. FIG. 8 is a side view of still another deformation example of the convex portion as viewed from the secondary flow direction. FIG. 9 is a graph showing the static pressure fluctuation of the intake port position in the first embodiment and the comparative example. FIG. 10 is a graph showing the static pressure fluctuation of the intake port position in the second embodiment and the comparative example.

The preceding standby pump according to the embodiment will be described in detail below with reference to the accompanying drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed and exaggerated from those of the actual product for the convenience of easy understanding of the illustration.

FIG. 2 is a schematic view showing the structure of the preceding standby operation pump according to the embodiment. FIG. 3 is an enlarged schematic view of a lower end portion of the casing of the pump shown in FIG. 2, particularly a bell mouth portion in which an intake port is located. FIG. 4 is a schematic view of the inner surface of the lower end portion of the casing shown in FIG. 3 as viewed from the downstream side in the mainstream direction.

As shown in FIGS. 2 to 4, the preceding standby operation pump 10 includes an impeller 11 and a casing 12 for accommodating the impeller 11.

Of these, the casing 12 has a tubular shape extending in the axial direction, and a rotating shaft 18 is rotatably inserted inside the casing 12. The impeller 11 is coaxially fixed to the lower end of the rotating shaft 18. The number of blades of the impeller 11 is, for example, five.

A prime mover 19 is attached to the upper end of the rotary shaft 18, and the impeller 11 and the rotary shaft 18 are integrally rotated by the driving force output from the prime mover 19. The rotation of the impeller 11 causes the fluid in the casing 12 to flow, so that the fluid is discharged from the upper end of the casing 12 and new liquid is sucked in from the lower end of the casing 12.

In the present specification, the direction in which the casing 12 extends (that is, the axial direction) is referred to as the mainstream direction 21, and the rotational direction of the impeller 11 is referred to as the secondary flow direction 22.

In the present embodiment, as shown in FIG. 3, the casing 12 has a main body portion 12a in which the impeller 11 is housed, and a bell mouth 12b arranged below the main body portion 12a. The main body 12a and the bell mouth 12b are connected by a flange 12c at the upstream end position of the impeller 11.

As shown in FIGS. 2 to 4, a plurality of convex portions 13 are provided at equal intervals in the circumferential direction (secondary flow direction 22) on the inner surface of the bell mouth 12b on the upstream side of the mainstream direction 22 from the impeller 11. In the illustrated example, the number of the convex portions 13 is 4, but the number is not limited to this, and may be 1 to 3 or 5 or more.

An intake port 14 is formed near the apex of the convex portion 13. The cylindrical space (intake hole) extending from the intake port 14 is formed so as to penetrate the convex portion 13, and is communicated with an annular air chamber 17 provided outside the convex portion 13. An air pipe 16 having one end exposed to the atmosphere is connected to the air chamber 17, and air in the atmosphere is released from the air pipe 16 according to the difference pressure between the pressure near the intake port 14 and the atmospheric pressure. It is supplied to the intake port 14 through the air chamber 17.

The convex portion 13 can be manufactured by casting, for example, integrally with the casing 12. The smaller the protrusion amount of the convex portion 13, the lower the production cost when the convex portion 13 is integrally cast with the casing 12, and the less the concern about the accumulation of impurities in the bell mouth 12b due to the influence of the convex portion 13. Therefore, it is preferable. For example, the amount of protrusion of the convex portion 13 may be less than 25% of the diameter of the casing 12 at the same axial position as the convex portion 13.

FIG. 5A is a front view of an example of the convex portion 13 as viewed from the inside in the radial direction of the pump 10. FIG. 5B is a side view of the convex portion 13 shown in FIG. 5A as viewed from the secondary flow direction 22. FIG. 5C is a side view of the convex portion 13 shown in FIG. 5A as viewed from the downstream side in the mainstream direction 21.

As shown in FIGS. 5A and 5B, the convex portion 13 has a guide surface 15a on the upstream side in the mainstream direction in which the amount of protrusion from the inner surface of the casing 12 gradually decreases as the distance from the end of the intake hole 14 increases. have. Since the guide surface 15a is provided on the upstream side of the intake port 14 in the mainstream direction, the static pressure in the vicinity of the intake port 14 can be reduced.

FIG. 7 is a schematic diagram for explaining the physical mechanism by which the static pressure decreases in the vicinity of the intake port. As shown in FIG. 7, when the guide surface has a convex shape toward the flow path, the fluid flowing through the flow path A near the guide surface tends to flow along the guide surface. ..

Here, the fluid flowing along the guide surface has a longer path to pass between the cross sections S1-S2 in the flow direction than the fluid flowing in the flow path B away from the guide surface, so that the fluid in the vicinity of the guide surface is longer. Tends to increase the flow velocity.

According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, and as a result, the static pressure tends to decrease in the vicinity of the guide surface. Therefore, the static pressure is reduced in the vicinity of the intake port formed on the guide surface.

By the way, as mentioned in the column of background technology, the conventional preceding standby pump has the following problems due to the intake structure. That is, (1) the greater the static pressure fluctuation of the intake port portion during the air-water mixing operation, the more likely it is that the pump will vibrate. Further, (2) If the amount of intake air from the intake port is small in the partial flow rate region where the rated flow rate transitions to the airlock, the airlock may not be established due to the insufficient amount of intake air. In this case, large vibration and noise are generated when the water level drops below the bell suction port.

On the other hand, in the present embodiment, as described above, since the guide surface 15a is provided on the upstream side of the intake port 14 in the mainstream direction, the fluid in the vicinity of the intake port 14 flowing along the guide surface 15a is the guide surface 15a. The flow velocity tends to increase as compared to the fluid flowing in a more distant flow path. According to Bernoulli's equation, the increase in flow velocity is accompanied by a decrease in static pressure, so the static pressure decreases in the vicinity of the intake port. As a result, the amount of intake air supplied from the intake port 14 can be increased in the partial flow rate region where the rated flow rate transitions to the airlock, and the success rate of the airlock can be increased.

Further, in the present embodiment, since the intake port 14 is provided near the apex of the convex portion 13 on the inner diameter side of the inner surface of the bell mouth 12b, the static pressure fluctuation in the vicinity of the intake port 14 due to the influence of the rotation of the impeller 11 is generated. It will be reduced. As a result, it is possible to reduce the generation of vibration during intake.

As shown in FIGS. 5A and 5B, it is desirable that the guide surface 15a on the upstream side in the mainstream direction has a curvature with respect to the mainstream direction 21. In this case, the fluid in the vicinity of the intake port 14 flowing in the mainstream direction 21 can be guided smoothly along the mainstream direction upstream guide surface 15a, and peeling from the mainstream direction upstream side guide surface 15a can be suppressed.

In the present embodiment, as shown in FIGS. 5A and 5B, the amount of protrusion of the convex portion 13 from the inner surface of the bell mouth 12b gradually decreases toward the downstream side of the mainstream direction 21 as the distance from the end of the intake port 14 increases. It has a guide surface 15b on the downstream side in the mainstream direction. Since the guide surface 15b is also provided on the downstream side of the intake port 14 in the mainstream direction, the fluid in the vicinity of the intake port 14 flowing in the mainstream direction 21 flows smoothly along the guide surface 15b on the downstream side in the mainstream direction. Become. As a result, peeling from the guide surfaces 15a and 15b can be suppressed, so that it is possible to reduce the decrease in pump efficiency due to the influence of the peeling, the generation of vibration / noise, and the decrease in the intake amount due to the increase in static pressure.

As shown in FIGS. 5A and 5B, it is desirable that the guide surface 15b on the downstream side in the mainstream direction has a curvature with respect to the mainstream direction 21. In this case, the fluid in the vicinity of the intake port 14 flowing in the mainstream direction 21 can be guided smoothly along the downstream side guide surface 15b in the mainstream direction, and the separation from the mainstream direction downstream side guide surface 15b is more effective. Can be suppressed.

In the present embodiment, as shown in FIGS. 5A and 5C, the convex portion 13 gradually reduces the amount of protrusion from the inner surface of the casing 12 on the upstream side of the secondary flow direction 22 as the distance from the end of the intake port 14 increases. It has a guide surface 15c on the upstream side in the secondary flow direction. Since the guide surface 15c is provided on the upstream side of the intake port 14 in the secondary flow direction, the static pressure in the vicinity of the intake port 14 can be further reduced by the physical mechanism described with reference to FIG. 7.

As shown in FIGS. 5A and 5C, it is desirable that the guide surface 15c on the upstream side in the secondary flow direction has a curvature with respect to the secondary flow direction 22. In this case, the fluid in the vicinity of the intake port 14 flowing in the secondary flow direction 22 can be guided smoothly along the upstream side guide surface 15c in the secondary flow direction, and is guided from the upstream side guide surface 15c in the secondary flow direction. Peeling can be suppressed more effectively.

Further, as shown in FIGS. 5A and 5C, the convex portion 13 has a secondary flow in which the amount of protrusion from the inner surface of the casing 12 gradually decreases toward the downstream side of the secondary flow direction 22 as the distance from the end of the intake port 14 increases. It has a guide surface 15d on the downstream side in the direction. Since the guide surface 15d is also provided on the downstream side of the intake port 14 in the secondary flow direction, the fluid in the vicinity of the intake port 14 flowing in the secondary flow direction 22 smoothly flows to the guide surface 15d on the downstream side in the secondary flow direction. It will flow along. As a result, peeling from the guide surfaces 15c and 15d can be suppressed, and a decrease in the intake amount due to an increase in static pressure can be suppressed.

As shown in FIGS. 5A and 5C, it is desirable that the guide surface 15d on the downstream side in the secondary flow direction has a curvature with respect to the secondary flow direction 22. In this case, the fluid in the vicinity of the intake port 14 flowing in the secondary flow direction 22 can be guided smoothly along the downstream side guide surface 15d in the secondary flow direction, and is guided from the downstream side guide surface 15d in the secondary flow direction. Peeling can be suppressed more effectively.

In the present embodiment, as shown in FIGS. 5A to 5C, the center of the intake port 14 is positioned so as to coincide with the apex of the convex portion 13, but the present embodiment is not limited to this.

For example, as shown in FIG. 5D, the center of the intake port 14 may be located on the upstream side in the mainstream direction or on the downstream side in the mainstream direction from the apex of the convex portion 13. According to the verification by the inventors of the present invention, depending on the shape of the flow path (that is, the shape of the inner wall of the bell mouth, the shape of the convex portion 13) or the pump operating condition, the upstream side in the mainstream direction or the downstream side in the mainstream direction from the apex of the convex portion 13 It was confirmed that the static pressure on the side may tend to be lower. Therefore, according to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port 14, and the amount of intake air supplied from the intake port 14 can be further increased.

Further, for example, as shown in FIG. 5E, the center of the intake port 14 may be located on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction from the apex of the convex portion 13. According to the verification by the present inventors, the static pressure tends to be lower on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction than the apex of the convex portion 13 depending on the flow path shape or the pump operating condition. I was able to confirm that there may be. Therefore, according to such an aspect, the static pressure of the fluid can be further reduced in the vicinity of the intake port 14, and the amount of intake air supplied from the intake port 14 can be further increased.

Further, in the present embodiment, as shown in FIGS. 5A and 5B, the guide surfaces 15a and 15b have the same reduction in the amount of protrusion on the downstream side in the mainstream direction as the reduction in the amount of protrusion on the upstream side in the mainstream direction. It was, but it is not limited to this.

For example, as shown in FIG. 5F, the guide surfaces 15a and 15b may have a decrease in the amount of protrusion on the downstream side in the mainstream direction less than a decrease in the amount of protrusion on the upstream side in the mainstream direction (that is, downstream in the mainstream direction). The side guide surface 15b may have a gentler inclination than the upstream side guide surface 15a in the mainstream direction). In this case, the fluid in the vicinity of the intake port 14 flowing in the mainstream direction 21 is likely to be guided along the guide surface 15b provided on the downstream side in the mainstream direction. As a result, peeling from the guide surface 15b can be suppressed, and a decrease in the intake amount due to an increase in static pressure can be suppressed.

FIG. 6A is a front view of a modified example of the convex portion 13 as viewed from the radial direction of the pump 10. FIG. 6B is a side view of the convex portion 13 shown in FIG. 6A as viewed from the secondary flow direction 22. FIG. 6C is a side view of the convex portion 13 shown in FIG. 5A as viewed from the mainstream direction 21.

In the example shown in FIGS. 6A to 6C, the convex portion 13 is a guide surface whose protrusion amount from the inner surface of the casing 12 gradually decreases as the distance from the end of the intake port 14 increases on the upstream side in the mainstream direction and the downstream side in the mainstream direction, respectively. Although it has 15a and 15b, it does not have such a guide surface on the upstream side in the secondary flow direction and the downstream side in the secondary flow direction. In this case as well, with respect to the fluid flowing in the mainstream direction, the static pressure in the vicinity of the intake port 14 can be reduced by the physical mechanism described with reference to FIG. 7, as in the embodiment shown in FIGS. 5A to 5C. .. As a result, the amount of intake air supplied from the intake port can be increased in the partial flow rate region where the rated flow rate transitions to the airlock, and the success rate of the airlock can be increased.

FIG. 8 is a side view of still another modified example of the convex portion 13 as viewed from the secondary flow direction 22. In the example shown in FIG. 8, the convex portion 13 has a cylindrical portion 31 protruding from the inner surface of the casing 12, and the intake port 14 and the guide surfaces 15a and 15b are arranged at the tip of the cylindrical portion 31.

According to such an embodiment, since the intake port 14 is positioned closer to the inner diameter side as compared with the embodiment shown in FIG. 5B, the static pressure fluctuation in the vicinity of the intake port 14 due to the influence of the rotation of the impeller 11 is more effective. Is reduced. As a result, it is possible to more effectively reduce the generation of vibration during intake.

Further, in the example shown in FIG. 8, fillets 32 are provided on the entire circumference of the base end portion of the cylindrical portion 31. In this case, the angle between the base end of the cylindrical portion 31 and the inner surface of the casing 12 is close to 180 °. As a result, the stress concentration between the base end portion of the cylindrical portion 31 and the inner surface of the casing 12 can be relaxed to make it difficult to break.

Hereinafter, the above-described embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to the following examples.

As a first embodiment, as shown in FIGS. 1 to 3, a pump 10 having four convex portions 13 provided on the inner surface of the bell mouth 12b was designed. In the first embodiment, the protrusion amount (convex height) of each convex portion 13 is set to 16% (= 15 mm) of the bell mouth diameter at the axial position where the intake port 14 is located.

Further, as the second embodiment, the pump 10 provided with the four convex portions 13 on the inner surface of the bell mouth 12b was designed as in the first embodiment. In the second embodiment, the protrusion amount (convex height) of each convex portion 13 is set to 32% (= 30 mm) of the bell mouth diameter at the axial position where the intake port 14 is located.

Further, as a first comparative example, with reference to Japanese Patent Application Laid-Open No. 3-138488, a structure is provided in which a pipe is provided so as to protrude from the inner surface of the bell mouth having the same dimensions as those in the above embodiment, and an intake port is formed at the tip of the pipe. Designed to have a pump. The protruding amount of the pipe was set to twice the protruding amount of the convex portion 13 in the second embodiment.

Further, as a second comparative example, referring to Japanese Patent No. 4436484, a pump having a structure in which an intake port is formed in a slit shape along the circumferential direction on the inner surface of a bell mouth having the same dimensions as those of the first to third embodiments. Designed.

Next, for the pumps of the first and second examples and the first and second comparative examples, the static pressure fluctuation at the intake port position during impeller rotation is numerically analyzed under the respective conditions of the rated flow rate and the 30% flow rate. (Fluid simulation of unsteady single-phase flow analysis).

FIG. 9 is a graph showing the static pressure fluctuation of the intake port position in the first embodiment and the first and second comparative examples. FIG. 10 is a graph showing the static pressure fluctuation of the intake port position in the second embodiment and the first and second comparative examples.

As shown in FIGS. 9 and 10, when the results of the first and second embodiments (convex method) are compared with the results of the first comparative example (pipe method) and the second comparative example (slit method), It was found that in the convex part method, the static pressure at the intake port position was the lowest at the rated flow rate, and the static pressure fluctuation was also small. Therefore, if the pump of the above embodiment is used, it can be predicted that the intake amount will increase and the pulsation will also decrease.

Further, in the graph shown in FIG. 9, focusing on the 30% flow rate (near the airlock), which is the partial flow rate, in the convex part method, the static pressure does not increase as in the partial flow rate of the slit method, and the slit method is used. It was found that it is possible to maintain the same static pressure distribution at the rated flow rate and at the partial flow rate of the pipe method.

10 Pre-standby operation pump 11 Impeller 12 Casing 13 Convex part 14 Intake port 15a (upstream side in mainstream direction) Guide surface 15b (downstream side in mainstream direction) Guide surface 15c (upstream side in secondary flow direction) Guide surface 15d (secondary flow direction) Downstream side) Guide surface 16 Air pipe 17 Air chamber 18 Rotating shaft 19 Motor 21 Mainstream direction 22 Secondary flow direction 31 Cylinder 32 Fillet

Claims (18)

It is provided with an impeller and a casing for accommodating the impeller.
A convex portion is provided on the inner surface of the casing on the upstream side in the mainstream direction from the impeller, and a convex portion that protrudes from the inner surface of the casing at the same axial position as the convex portion is provided.
An intake port is formed near the apex of the convex portion.
The convex portion is a guide surface including the intake port end portion on the upstream side in the mainstream direction and the downstream side in the mainstream direction, respectively, and the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the apex of the convex portion increases. A leading standby pump characterized by having a surface. The first aspect of the present invention is characterized in that the convex portion has a guide surface on the upstream side in the secondary flow direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases. The preceding standby pump described. The second aspect of the present invention is characterized in that the convex portion has a guide surface on the downstream side in the secondary flow direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases. The preceding standby pump described. The preceding standby operation pump according to any one of claims 1 to 3, wherein the guide surface has a curvature with respect to each flow direction. The preceding standby operation pump according to claim 1, wherein the guide surface has a reduction in the amount of protrusion on the downstream side in the mainstream direction less than a reduction in the amount of protrusion on the upstream side in the mainstream direction. The preceding standby operation pump according to any one of claims 1 to 5, wherein the center of the intake port is located on the upstream side in the mainstream direction or the downstream side in the mainstream direction with respect to the apex of the convex portion. The preceding standby operation according to any one of claims 2 to 6, wherein the center of the intake port is located on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction with respect to the apex of the convex portion. pump. The convex portion has a cylindrical portion that protrudes from the inner surface of the casing.
The preceding standby operation pump according to any one of claims 1 to 7, wherein the intake port and the guide surface are arranged at the tip of the cylindrical portion. The preceding standby operation pump according to any one of claims 1 to 8, wherein the protruding amount of the convex portion is less than 25% of the casing diameter at the same axial position as the convex portion. It is provided with an impeller and a casing for accommodating the impeller.
A convex portion is provided on the inner surface of the casing on the upstream side in the mainstream direction from the impeller, and a convex portion that protrudes from the inner surface of the casing at the same axial position as the convex portion is provided.
An intake port is formed near the apex of the convex portion.
The convex portion has a guide surface including the intake port end portion on the upstream side in the mainstream direction, and has a curvature such that the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the apex of the convex portion increases. Pre-standby operation pump characterized by being 10. The convex portion has a guide surface having a curvature on the downstream side in the mainstream direction in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the apex of the convex portion increases. The preceding standby operation pump described in. The claim is characterized in that the convex portion has a guide surface having a curvature on the upstream side in the secondary flow direction so that the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases. Item 10. The preceding standby operation pump according to Item 10. The claim is characterized in that the convex portion has a guide surface having a curvature on the downstream side in the secondary flow direction, in which the amount of protrusion from the inner surface of the casing gradually decreases as the distance from the intake port end portion increases. Item 12. The preceding standby operation pump according to item 12. The preceding standby operation pump according to claim 11, wherein the guide surface has a reduction in the amount of protrusion on the downstream side in the mainstream direction less than a reduction in the amount of protrusion on the upstream side in the mainstream direction. The preceding standby operation pump according to any one of claims 10 to 14, wherein the center of the intake port is located on the upstream side in the mainstream direction or the downstream side in the mainstream direction with respect to the apex of the convex portion. The preceding standby operation pump according to claim 12 or 13, wherein the center of the intake port is located on the upstream side in the secondary flow direction or the downstream side in the secondary flow direction with respect to the apex of the convex portion. The convex portion has a cylindrical portion that protrudes from the inner surface of the casing.
The preceding standby operation pump according to any one of claims 10 to 16, wherein the intake port and the guide surface are arranged at the tip of the cylindrical portion. The preceding standby operation pump according to any one of claims 10 to 17, wherein the protrusion amount of the convex portion is less than 25% of the casing diameter at the same axial position as the convex portion.