JP6339422B2 - Fluid pump - Google Patents

Description

  The present invention relates to a fluid pump for transferring fluid.

  When the liquid is transferred through the pipe, a centrifugal pump is mainly used. There is liquefied gas in the liquid to be transferred. Some of the above liquefied gases have a boiling point of −150 ° C. or lower. For example, liquid nitrogen, liquid oxygen, liquid argon, liquefied natural gas (LNG), and the like.

In general, examples of centrifugal pumps for low-temperature liquefied gas include the following.
(1) Shaft seal pump (for example, Non-Patent Document 1 below)
(2) Submerged pump (for example, Patent Document 1 below)
(3) Magnet coupling drive sealless pump (for example, Patent Document 2 below)

The above (1) shaft seal pump, (2) submerged pump, and (3) magnet coupling drive sealless pump have the following problems.
(1) Shaft seal pump When the shaft seal is worn due to wear, low-temperature liquefied gas is likely to leak from the shaft seal portion.
(2) Submerged pump The motor and bearing are in low-temperature liquefied gas. For this reason, a bearing using a special lubricant is required. Moreover, the precooling time of the motor is long, and during that time the liquefied gas is vaporized, resulting in a large loss. Further, during operation, the liquefied gas is vaporized due to the heat generated by the motor and the bearing, resulting in a large loss.
(3) Magnet coupling drive sealless pump Magnet coupling and bearing are in low temperature liquefied gas. For this reason, a bearing using a special lubricant is required. Moreover, the pre-cooling time of the magnet coupling is long, and during that time the liquefied gas is vaporized, resulting in a large loss. Also, during operation, the liquefied gas is vaporized by the heat generated by the magnet coupling and the bearing, resulting in a large loss.

Patent Document 3 below discloses the following (4) centrifugal saddle type sealless pump.
The motor and the impeller are arranged such that the motor is on the upper side and the impeller is on the lower side.
The motor, the rotation transmission means, and the impeller exist in a sealed space where the low-temperature liquefied gas is introduced in communication with each other,
A pump for low-temperature liquefied gas, which is pumped by giving a pressure difference to the low-temperature liquefied gas when the impeller is rotationally driven by the motor.

In the (4) centrifugal saddle type sealless pump disclosed in Patent Document 3, the motor, the rotation transmitting means, and the impeller are communicated with each other and are present in a sealed space into which the low-temperature liquefied gas is introduced. Thereby, there is no leakage of the low-temperature liquefied gas like the pump of (1) mentioned above. Moreover, precooling time is shortened compared with the pump of (2) (3). Therefore, the loss of liquefied gas is reduced.

JP-A-6-288382 JP-T-2001-514360 JP 2012-92913 A

Cryostar Internet Catalog Model GBSD (http://www.cryostar.com/pdf/data-sheet/en/gbsd.pdf)

  Here, for example, in city gas and steelworks, there is a need to transfer low-temperature liquefied gas through piping over a long distance. If it cannot be transferred by piping, it will be transferred using a cylinder, and the transfer efficiency will drop at a stretch. For transfer by piping, a pump that discharges liquid at high pressure is required.

  However, in the pumps described in the above prior art documents, no means for discharging the liquid at high pressure has been proposed. In particular, there is no mention of a means for obtaining a high range while avoiding a significant design change such as increasing the thickness of the member.

The present invention has been made to solve the above problems, and has the following objects.
For example, a fluid pump that can easily obtain a high stroke while avoiding a significant design change such as increasing the thickness of a member.

The fluid pump according to claim 1 employs the following configuration in order to achieve the above object.
An impeller that increases the pressure of the fluid by rotating;
A motor for rotating the impeller;
A rotation transmission member for transmitting rotation of the motor to the impeller;
A space in which the impeller, the rotation transmission member, and the motor each exist with the fluid;
Provided in the rotation transmission member, the primary side space that is the introduction side of the impeller, and a communication path that communicates the secondary side space that is the opposite side ,
The motor is arranged on the upper side and the impeller is on the lower side,
Between the motor and the impeller, there is provided a heat adjusting unit that keeps the impeller in the liquid phase of the low-temperature liquefied gas and keeps the motor in the gas phase of the low-temperature liquefied gas,
The communication path is formed by communicating a vertical channel and a horizontal channel with each other,
As for the said horizontal flow path, the secondary side opening is opening in the heat regulation part between a motor and an impeller .

The fluid pump according to claim 2 adopts the following structure in addition to the structure described in claim 1.
The rotation transmission member is pivotally supported by a shaft seal, and the shaft seal is disposed between the opening on the secondary side of the communication path and the impeller.

The fluid pump according to claim 3 employs the following structure in addition to the structure described in claim 1 or 2.
A plurality of the impellers are arranged along the rotation transmission member.

In addition to the structure described in any one of Claims 1-3, the following structure was employ | adopted for the fluid pump of Claim 4.
The fluid is a liquefied gas.

The fluid pump according to claim 5 adopts the following configuration in addition to the configuration described in claim 4.
The liquefied gas is a combustible gas.

In the fluid pump according to the first aspect, the rotation of the motor is transmitted to the impeller by the rotation transmitting member, and the pressure of the fluid is increased by the rotation of the impeller. The impeller, the rotation transmission member, and the motor are present in the space together with the fluid. The rotation transmission member is provided with a communication passage that communicates the space on the primary side that is the introduction side of the impeller and the space on the secondary side that is the opposite side.
In the communication path, a pressure increase in the space on the secondary side is suppressed. That is, the fluid introduced from the primary side of the impeller is increased in pressure by the rotation of the impeller and flows to the secondary side of the impeller. Most of the high pressure fluid is discharged from the discharge section. At this time, a part of the fluid having a high pressure is returned to the primary side through the communication path from the space on the secondary side. The increase in pressure in the space on the secondary side is suppressed by the return of the fluid through the communication path. By such an action, the fluid pump of the present invention can easily obtain a high range without changing the design such as increasing the thickness of the member constituting the space on the secondary side. In addition, problems and malfunctions due to abnormal increase in internal pressure are prevented, and maintainability is improved.
In the fluid pump according to claim 1, the heat adjusting unit causes the motor to exist in the gas phase of the low-temperature liquefied gas and the impeller to exist in the liquid phase of the low-temperature liquefied gas. In the communication path formed by connecting the vertical flow path and the horizontal flow path to each other, a secondary side opening of the horizontal flow path opens in a heat adjusting portion between the motor and the impeller.

In the fluid pump according to claim 2, the rotation transmission member is pivotally supported by a shaft seal. The shaft seal is disposed between the opening on the secondary side of the communication path and the impeller.
For this reason, the fluid whose pressure has been increased by the impeller is hardly blocked by the shaft seal and flows into the space on the secondary side. Therefore, in the fluid pump of the present invention, an increase in pressure in the space on the secondary side is suppressed. By such an action, the fluid pump of the present invention can easily obtain a high range without changing the design such as increasing the thickness of the member constituting the space on the secondary side.

In the fluid pump according to claim 3, a plurality of the impellers are arranged along the rotation transmission member.
For this reason, the pressure in the space on the secondary side is likely to increase due to a plurality of impellers arranged along the rotation transmitting member. However, in the fluid pump of the present invention, the pressure in the space on the secondary side is increased. It is suppressed. By such an action, the fluid pump of the present invention can easily obtain a high range without changing the design such as increasing the thickness of the member constituting the space on the secondary side.

In the fluid pump according to claim 4, the fluid is liquefied gas.
The liquefied gas is easily vaporized due to heat generated by the motor. When the liquefied gas is vaporized in the space, the pressure in the space rises, and it becomes necessary to make a pressure resistant design. In the fluid pump of the present invention, a pressure increase in the space on the secondary side is suppressed. By such an action, the fluid pump of the present invention can easily obtain a high range without changing the design such as increasing the thickness of the member constituting the space on the secondary side.

In the fluid pump according to claim 5, the liquefied gas is a combustible gas.
When the combustible gas is vaporized in the space due to heat generated by the motor or the like, the pressure in the space increases and the risk of explosion or combustion increases. In the fluid pump of the present invention, a pressure increase in the space on the secondary side is suppressed. By such an action, the fluid pump of the present invention can easily obtain a high range without changing the design such as increasing the thickness of the member constituting the space on the secondary side. At the same time, it reduces the risk of explosion and combustion.

It is a figure showing the whole fluid pump composition of a 1st embodiment of the present invention. It is a figure which shows the example of various aspects of a communicating path. The test example (hole diameter 3.0mm) which plotted the pressure fluctuation of a primary side and a secondary side is shown. The test example (hole diameter 1.5mm) which plotted the pressure fluctuation of the primary side and the secondary side is shown. It is a figure which shows the whole structure of the pump for fluids of 2nd Embodiment of this invention.

  Next, an embodiment for carrying out the present invention will be described.

[First Embodiment]
FIG. 1 is a schematic view showing a first embodiment of the fluid pump of the present invention.

〔Basic structure〕
This apparatus is a fluid pump that rotates the impellers 2A and 2B by the motor 1 to increase the fluid pressure and transfer the pump. Impellers 2A and 2B that increase the pressure of fluid by rotating, a motor 1 for rotating the impellers 2A and 2B, and a rotation transmission member 3 that transmits the rotation of the motor 1 to the impellers 2A and 2B I have.

  The motor 1 constitutes a motor unit 20 surrounded by the pressure-resistant walls 4A and 4B. The impellers 2 </ b> A and 2 </ b> B are accommodated in the volute housing 7 to constitute a pump unit 19. In this example, the motor 1 is arranged on the upper side, and the impellers 2 </ b> A and 2 </ b> B are on the lower side, and these are connected by the rotation transmission member 3.

  The rotation of the motor 1 is transmitted to the impellers 2A and 2B by the rotation transmission member 3. As the impellers 2 </ b> A and 2 </ b> B rotate, fluid is introduced from the introduction portion 6 formed in the lower part of the volute housing 7. The introduced fluid is increased in pressure by the impellers 2 </ b> A and 2 </ b> B and is discharged from the discharge portion 8 formed on the upper side surface of the volute housing 7.

  In the present invention, the introduction side provided with the fluid introduction portion 6 is referred to as a primary side. The side opposite to the introduction side is referred to as the secondary side. In the present embodiment, the introduction side, that is, the primary side is the lower side. The opposite side, that is, the secondary side is the upper side.

〔fluid〕
As the fluid, liquids such as water, oil, and liquefied gas are mainly applied. In the following description, an example in which the fluid is a low-temperature liquefied gas will be described. The low-temperature liquefied gas may exist as a gas because a part of the liquid pumped in the illustrated system is vaporized. The present invention is intended to include such a pump. The liquefied gas includes various low-temperature liquefied gases such as liquefied nitrogen, liquefied oxygen, and liquefied carbon dioxide. The liquefied gas includes various liquefied combustible gases such as liquefied natural gas and liquefied petroleum gas.

[Motor]
The motor 1 constitutes a motor unit 20 surrounded by the pressure-resistant walls 4A and 4B.

  The motor 1 can be manufactured based on a motor having a general structure such as a DC motor or a three-phase induction motor. In addition, an energy efficient pump can be obtained by using a PM motor (permanent magnet motor).

  In this example, the motor 1 is accommodated in a space surrounded on the outside by the pressure-resistant walls 4A and 4B. The space inside the pressure walls 4A, 4B is a motor space 5 in which the motor 1 is accommodated. A motor unit 20 is formed including the pressure walls 4A and 4B and the motor 1.

[Pump part]
The impellers 2 </ b> A and 2 </ b> B are accommodated in the volute housing 7 to constitute a pump unit 19.

  The impellers 2A and 2B are arranged in the volute housing 7 and are driven to rotate. The volute housing 7 communicates with the introduction portion 6 for introducing the low-temperature liquefied gas. The impellers 2A and 2B rotate in the volute housing 7 to increase the pressure of the low-temperature liquefied gas introduced from the introduction unit 6 by centrifugal force. The low-temperature liquefied gas whose pressure has been increased is discharged from a discharge portion 8 provided on the outer peripheral portion of the volute housing 7. A space in the volute housing 7 is an impeller space 9 in which the impellers 2A and 2B are accommodated.

  A plurality of the impellers 2 </ b> A and 2 </ b> B are arranged along the rotation transmission member 3. In this example, there are two. The first-stage impeller 2A is arranged on the introduction side close to the introduction part 6, and the second-stage impeller 2B is arranged on the opposite side of the introduction part 6.

In the figure, reference numeral 10 denotes an inducer 10 that helps the flow of the low-temperature liquefied gas. The inducer 10 is attached to the end of the rotation transmission member 3 on the introduction portion 6 side. A pump portion 19 is formed including the impellers 2 </ b> A and 2 </ b> B, the volute housing 7, and the inducer 10.
(Rotation transmission member)

  The motor 1 and the impellers 2A and 2B are connected to each other by a rotation transmission member 3 that transmits rotational driving therebetween.

  In this example, the rotation transmission member 3 is a single shaft that is common to both the rotation shaft of the motor 1 and the rotation shafts of the impellers 2A and 2B. The rotation transmitting member 3 is coaxial with both the rotating shaft of the motor 1 and the rotating shafts of the impellers 2A and 2B. The rotation transmission member 3 is not limited to the one that is common to the motor 1 and the impellers 2A and 2B, but the shaft for the motor 1 and the shaft for the impellers 2A and 2B are separated and coupled by a coupling or the like. It can also be used. That is, the rotation transmission member 3 can include one or more shafts that are coaxial with respect to both the rotation shaft of the motor 1 and the rotation shafts of the impellers 2A and 2B.

〔space〕
The impellers 2A and 2B, the rotation transmission member 3, and the motor 1 are present in the space 14 together with the low-temperature liquefied gas. The space 14 is formed by connecting the motor space 5, the impeller space 9, and the shaft space 13 to each other. That is, the motor space 5, the impeller space 9, and the shaft space 13 each form part of the space 14. In other words, the pressure housing 4, the shaft cover 12, and the pressure-resistant walls 4 </ b> A and 4 </ b> B of the motor 1 form one pressure-resistant space 14 that communicates with each other.

  Of the space 14, the shaft space 13 and the motor space 5 that exist on the secondary side above the pump unit 19 are pressure-resistant sealed spaces that do not have a low-temperature liquefied gas outlet. Specifically, a sealing material such as a gasket and an O-ring is used for each joint portion of the pressure-resistant walls 4A and 4B, the volute housing 7 and the shaft cover 12 of the motor unit 20, and a flange or the like is tightened with a bolt. Alternatively, a sealed structure is formed by tightening as a screw structure.

  A certain amount of clearance is secured between the motor 1 and the impellers 2 </ b> A and 2 </ b> B, and a portion of the rotation transmission member 3 that passes through the clearance is covered with a shaft cover 12. The inside of the shaft cover 12 is a shaft space 13 in which a part of the rotation transmission member 3 is accommodated.

  And between the said motor 1 and impeller 2A, 2B functions as a heat regulation part. The heat adjusting unit keeps the impellers 2A and 2B in the liquid phase of the low-temperature liquefied gas and keeps the motor 1 in the gas phase of the low-temperature liquefied gas. The portion that functions as the heat adjusting portion is a portion that includes the shaft space 13, a part of the rotation transmission member 3 existing inside the shaft space 13, and the shaft cover 12.

  Due to the presence of the heat adjusting part, the lower pump part 19 is set to a low temperature part, the intermediate heat adjusting part is set to a low temperature or a normal temperature, and the upper motor part 20 is set to a normal temperature. That is, the temperature range is divided according to the property that cold air falls and warm air rises. Therefore, the part filled with the liquid phase is from the introduction part 6 to the pump part 19 on the primary side. The secondary motor space 5 is filled with a gas phase.

The rotation transmission member 3 is pivotally supported by a bearing 16 that exists in the gas phase in the space 14. Thus, in this embodiment, the pump shaft and the motor shaft are shared by the single rotation transmission member 3. The bearing 16 shares the bearing of the motor 1 with the pump bearing. Since the bearing 16 exists in the gas phase, a lubricant such as grease can be used regardless of the solid lubricant.

[Pump function]
With such a structure, the low-temperature liquefied gas is drawn into the pump unit 19 from the introduction unit 6 by the inducer 10. The drawn low-temperature liquefied gas is increased in pressure by the impellers 2 </ b> A and 2 </ b> B to be powered and discharged from the discharge unit 8.

  At this time, the low-temperature liquefied gas that has entered the inside of the pump unit 19 basically has an outlet only at the discharge unit 8, and most of it is discharged from the discharge unit 8. A part of the low-temperature liquefied gas tries to enter the space 13 for the shaft and the space 5 for the motor, which is a sealed space, but since the space 5 for the motor is dead, the motor 1 enters the space. I won't go. However, when a part of the low-temperature liquefied gas that has become high pressure by the impellers 2A and 2B tries to enter the shaft space 13 and the motor space 5, the pressure in the shaft space 13 and the motor space 5 is changed. Try to rise.

  In particular, in a pump that discharges at a high pressure due to an increase in the length, the pressure increase in the shaft space 13 and the motor space 5 described above becomes significant.

[Higher process]
In general, when high-pressure discharge is performed in a centrifugal pump, the following methods (a), (b), and (c) can be considered.
(A) Increase in impeller diameter By increasing the impeller diameter, the centrifugal force can be increased and the pump head can be raised. The advantage is that the structure is not complicated.
(B) Increase in rotation speed By increasing the rotation speed of the impeller, the centrifugal force can be increased and the pump head can be raised.
(C) Multistage impeller By performing multistage impeller, the pump head can be increased. There is a merit that high pressure can be realized with low rotation by a small impeller. Moreover, since it is structurally the state which connected the 1 stage pump in series, if the number of stages is piled up, it can raise to arbitrary heads. Furthermore, the impeller per stage can be designed freely according to the flow rate.

  FIG. 1 shows an example in which (c) multi-stage impeller is adopted among the three methods for increasing the height of the pump described above.

  However, in a pump in which a sealed space is present on the secondary side of the impeller, if an attempt is made to increase the stroke, a high-pressure fluid flows into the sealed space and the sealed space becomes an abnormally high pressure.

  As shown in FIG. 1, for example, when the impellers 2A and 2B are arranged in two stages, the liquefied gas drawn from the primary-side inducer unit 10 is powered by the first-stage impeller 2A, and the second-stage impeller 2B. With more power. Most of the fluid that has become high pressure by the two-stage impellers 2A and 2B is discharged from the discharge section 8. A part of the fluid that has become high pressure by the two-stage impellers 2A and 2B tends to flow into the shaft space 13 and the motor space 5 on the upper side of the discharge portion 8, that is, on the secondary side. As a result, the space 13 for the shaft and the space 5 for the motor which are the sealed space on the secondary side become high pressure.

  Thus, in the structure in which the space 13 for the shaft and the space 5 for the motor, which are the sealed space on the secondary side, become high pressure, as a countermeasure, the pressure resistance strength of the components constituting the space 13 for the shaft and the space 5 for the motor must be increased. I must. That is, measures are taken such as thickening the shaft cover 12 and the pressure-resistant walls 4A and 4B. When the member is thickened in this way, an increase in cost cannot be avoided, and the weight of the motor unit 20 itself increases.

  As a measure for preventing the secondary shaft space 13 and the motor space 5 from becoming high pressure in the above-described multistage impeller structure, the following method is conceivable. For example, if a hole is made in the impeller, the pressure difference between the introduction-side and secondary-side shaft space 13 and the motor space 5 can be reduced. However, in the structure in which the second stage impeller 2B is perforated by the pumps of the second stage impellers 2A and 2B, the pressure on the introduction side of the second stage impeller 2B is the pressure in the upper space 13 for the shaft and the space 5 for the motor. It becomes. This is the pressure on the discharge side of the first-stage impeller 2A, and the pressure in the shaft space 13 and the motor space 5 on the secondary side is still higher than that in the single-stage pump. On the other hand, when a hole is made in the first stage impeller 2A, the pressure in the secondary shaft space 13 and the motor space 5 cannot be lowered or a sufficient length cannot be obtained depending on the design. After all, the method of making holes in the impellers 2A and 2B cannot solve the problem.

[Secondary side high pressure prevention structure]
Thus, in the present embodiment, the communication path 11 that allows the rotation transmitting member 3 to communicate with the primary space 14 on the introduction side of the impellers 2A and 2B and the secondary space 14 on the opposite side. Was provided.

  The rotation transmission member 3 is pivotally supported by a shaft seal 15. The shaft seal 15 is disposed between the secondary side opening 17B on the secondary side of the communication passage 11 and the impellers 2A and 2B.

  Specifically, the communication path 11 communicates the primary-side impeller space 9 with the secondary-side shaft space 13 and the motor space 5. In this example, the communication path 11 is formed by connecting a vertical flow path 11A and a horizontal flow path 11B to each other. The longitudinal channel 11A is formed along the longitudinal direction in the vicinity of the axis of the shaft-like rotation transmission member 3. The longitudinal flow path 11 </ b> A forms a primary side opening 17 </ b> A at the primary side end of the rotation transmitting member 3. The transverse flow path 11B is formed in the radial direction of the rotation transmitting member 3. The transverse flow path 11 </ b> B forms two secondary openings 17 </ b> B on the outer peripheral surface of the rotation transmission member 3.

  With such a structure, the low-temperature liquefied gas introduced from the primary side of the impellers 2A and 2B increases in pressure due to the rotation of the impellers 2A and 2B, and flows to the secondary side of the impellers 2A and 2B. Most of the low-temperature liquefied gas that has become high pressure is discharged from the discharge section 8. At this time, a part of the high-temperature low-temperature liquefied gas is recirculated to the primary side through the communication path 11 from the secondary shaft space 13 and the motor space 5. The recirculation of the low-temperature liquefied gas through the communication path 11 suppresses the pressure increase in the secondary-side shaft space 13 and the motor space 5.

  The shaft seal 15 seals between the rotating member and the fixed member. The shaft seal 15 is provided between the impeller space 9 and the shaft space 13 and seals the outer peripheral portion of the rotation transmission member 3. That is, the flow of the low-temperature liquefied gas between the impeller space 9 and the shaft space 13 is prevented in the outer peripheral portion of the rotation transmission member 3. In this example, the shaft seal 15 is provided in the opening on the primary side of the shaft space 13 in the shaft cover 12.

  The lateral passage 11 </ b> B of the communication passage 11 is provided so as to form a secondary side opening 17 </ b> B on the secondary side of the shaft seal 15. Therefore, the primary side opening 17 </ b> A of the communication path 11 is formed on the primary side of the shaft seal 15, and the secondary side opening 17 </ b> B of the communication path 11 is formed on the secondary side of the shaft seal 15.

  With such a structure, the low-temperature liquefied gas whose pressure has been increased by the impellers 2 </ b> A and 2 </ b> B is blocked by the shaft seal 15 and hardly flows into the secondary shaft space 13 and the motor space 5. Therefore, pressure increase in the secondary shaft space 13 and the motor space 5 is suppressed.

  That is, the shaft seal 15 minimizes the leakage between the rotating member and the fixed member that occurs during the operation of the pump. The space 13 for the shaft and the space 5 for the motor, which are the sealed space on the secondary side, become high pressure due to the low-temperature liquefied gas that leaks through the slight gap of the shaft seal 15. The low-temperature liquefied gas that has leaked through the shaft seal 15 is recirculated to the temporary side through the communication passage 11. Thereby, the pressure in the space 13 for shafts on the secondary side and the space 5 for motors can be equalized with the introduction pressure on the primary side having the lowest pressure in the pump.

[Example of communication passage mode]
FIG. 2 shows various examples of the communication path 11.
(A) is the same aspect as FIG. (D) is the figure which looked at the horizontal flow path 11B to the axial direction. The longitudinal channel 11A is formed in the vicinity of the axis of the shaft-like rotation transmission member 3 along the longitudinal direction. The longitudinal flow path 11 </ b> A forms a primary side opening 17 </ b> A at the primary side end of the rotation transmitting member 3. The transverse flow path 11B is formed in the radial direction of the rotation transmitting member 3. The transverse flow path 11 </ b> B forms two secondary openings 17 </ b> B on the outer peripheral surface of the rotation transmission member 3.

(B) is an example in which the horizontal channel 11B is formed in a stepped shape in the axial direction.
(C) is an example in which the vertical flow path 11A and the horizontal flow path 11B are formed in a Y shape.

(D) is formed such that the transverse flow path 11B penetrates in the radial direction of the rotation transmitting member 3. Two secondary openings 17 </ b> B are formed on the outer peripheral surface of the rotation transmitting member 3.
In (E), the transverse flow path 11 </ b> B is radially formed in the radial direction of the rotation transmission member 3. Three secondary side openings 17 </ b> B are formed on the outer peripheral surface of the rotation transmitting member 3.
In (F), the transverse flow path 11 </ b> B is radially formed in the radial direction of the rotation transmission member 3. Four secondary side openings 17 </ b> B are formed on the outer peripheral surface of the rotation transmitting member 3.

  In these examples, the hole diameter of the vertical flow path 11A is set to be large, and the hole diameter of the horizontal flow path 11B is set to be smaller than that of the vertical flow path 11A. A plurality of horizontal channels 11B are provided for one vertical channel 11A.

[Communication hole diameter]
The hole diameter of the communication passage 11 is determined according to the amount of low-temperature liquefied gas that leaks through the shaft seal 15 from the primary-side impeller space 9 to the secondary-side shaft space 13 and the motor space 5. To do.
The low-temperature liquefied gas that leaks through the shaft seal 15 and escapes to the primary side without remaining in the space on the secondary side. The pressure in the secondary space is returned to the pressure in the primary space. By determining the hole diameter of the communication path 11, the pressure in the motor unit 20 is set to a value substantially equal to the introduction pressure of the pump unit 19. The difference between the pressure on the secondary side of the motor unit 20 and the introduction pressure on the primary side of the pump unit 19 is equivalent to the frictional resistance at which the low-temperature liquefied gas or the gas evaporated from it passes through the communication path 11.

As described above, in the example described above, the hole diameter of the longitudinal flow path 11A is made larger than the hole diameter of the horizontal flow path 11B. A plurality of horizontal channels 11B are provided for one vertical channel 11A.
Even when the low-temperature liquefied gas or the gas vaporized from the low-temperature liquefied gas passes through the communication passage 11 and is clogged with ice or impurities, clogging is caused by the plurality of lateral channels 11B having a small hole diameter. The vertical flow channel 11A having a large hole diameter is not clogged, and the flow can be ensured in the other horizontal flow channel 11B that is not clogged. This prevents the secondary pressure from rising immediately.

  Impurities, ice, and the like contained in the liquid can be prevented from entering the pump by providing a strainer having a mesh sufficiently smaller than the lateral flow path 11B in the suction pipe portion of the pump. Even if the communication path 11 is clogged for some reason, it is possible to detect and deal with problems by recording the pressure fluctuation on the secondary side.

[Test example]
The difference between the pressure on the primary side and the pressure on the secondary side was measured by a fluid pump to which the T-shaped communication passage 11 shown in FIGS. 2A and 2D was applied.

  Two types were prepared: one with a hole diameter of the longitudinal flow path 11A of φ1.5 mm and one with φ3.0 mm. These hole diameters were derived from the conditions where the differential pressure was 0.01 MPa or less when the low-temperature liquefied gas was liquid nitrogen and the leakage from the shaft seal 15 was 5 L / min.

The pump shown in FIG. 1 was operated, and the secondary side pressure and the primary side introduction pressure from the start to the stop of the operation were measured. The measurement conditions are as follows.
Fluid: Liquid nitrogen (-196 ° C)
Shaft seal: Gas seal (Eagle Burgman Japan Ltd.)
Pressure gauge: Pressure transmitter GC61 (Nagano Keiki Co., Ltd.)
Record: Portable Multi Logger ZR-RX40 (OMRON Corporation)

FIG. 3 shows a measurement result in which a part of the hole diameter of the longitudinal channel 11A is φ3.0 mm.
FIG. 4 shows a measurement result in which a part of the hole diameter of the longitudinal channel 11A is φ1.5 mm.

When a part of the hole diameter of the longitudinal flow path 11A is φ3.0 (mm), the motor internal pressure, which is the secondary pressure, and the introduction pressure on the primary side are substantially equal in the vicinity of 0.06 MPa.
When a part of the hole diameter of the longitudinal flow path 11A is φ1.5 (mm), the introduction pressure on the primary side is almost constant, whereas the internal pressure of the motor, which is the secondary pressure, increases and decreases. . The introduction pressure on the primary side is substantially constant around 0.06 MPa. The internal pressure of the motor, which is the secondary pressure, was around 0.06 MPa at the start of operation, and then increased to 0.16 MPa after 10 minutes. In addition, even after 50 minutes, the motor internal pressure remains slightly higher than the introduction pressure. This is because the sealing performance of the shaft seal is not stable for about 20 minutes from the start of operation, and the leakage amount of the low-temperature liquefied gas is changed. That is, it has been clarified that the secondary pressure increases due to a change in the leakage amount during operation.

  From the above results, it can be seen that by selecting an appropriate value as the hole diameter of the communication path 11, the pressure increase on the secondary side can be prevented and the pressure difference between the primary side and the secondary side can be made uniform. Therefore, a pump that forms a sealed space on the secondary side of the impeller can be operated without applying high pressure to the sealed space.

[Second Embodiment]
FIG. 5 shows a second embodiment of the present invention.
In this example, the motor unit 20 does not have the pressure-resistant walls 4A and 4B. That is, the motor 1 is configured by the motor unit 20 being covered with outer walls 21A and 21B that are not pressure-resistant structures, and the outside of the motor unit 20 is covered with another pressure-resistant wall 22.
Other than that is the same as that of the said 1st Embodiment, and attaches | subjects the same code | symbol to the same part. Also in this example, the same operational effects as those of the first embodiment are obtained.

[Effect of each embodiment]
Each of the above embodiments has the following effects.

  In the communication passage 11, a pressure increase in the secondary shaft space 13 and the motor space 5 is suppressed. That is, the low-temperature liquefied gas introduced from the primary side of the impellers 2A and 2B increases in pressure due to the rotation of the impellers 2A and 2B, and flows to the secondary side of the impellers 2A and 2B. Most of the low-temperature liquefied gas that has become high pressure is discharged from the discharge unit 8. At this time, a part of the high-temperature low-temperature liquefied gas is recirculated to the primary side through the communication path 11 from the secondary shaft space 13 and the motor space 5. The recirculation of the low-temperature liquefied gas through the communication path 11 suppresses the pressure increase in the secondary shaft space 13 and the motor space 5. By such an action, the fluid pump according to the present embodiment has a high process without changing the design such as increasing the thickness of the members constituting the secondary shaft space 13 and the motor space 5. It will be easier to get. In addition, problems and malfunctions due to abnormal increase in internal pressure are prevented, and maintainability is improved.

  The low-temperature liquefied gas whose pressure has been increased by the impellers 2A and 2B is blocked by the shaft seal 15 and hardly flows into the secondary shaft space 13 and the motor space 5. Therefore, in the fluid pump of the present embodiment, the pressure increase in the secondary shaft space 13 and the motor space 5 is suppressed. By such an action, the fluid pump according to the present embodiment has a high process without changing the design such as increasing the thickness of the members constituting the secondary shaft space 13 and the motor space 5. It will be easier to get.

  A plurality of impellers 2A and 2B arranged along the rotation transmission member 3 tend to increase the pressure in the secondary shaft space 13 and the motor space 5. The pressure increase in the shaft space 13 and the motor space 5 on the next side is suppressed. By such an action, the fluid pump according to the present embodiment has a high process without changing the design such as increasing the thickness of the members constituting the secondary shaft space 13 and the motor space 5. It will be easier to get.

  The liquefied gas is easily vaporized due to heat generated by the motor. When the liquefied gas is vaporized in the space 14, the pressure in the secondary shaft space 13 and the motor space 5 rises, and it is necessary to make a pressure resistant design. In the fluid pump of the present embodiment, the pressure increase in the secondary shaft space 13 and the motor space 5 is suppressed. By such an action, the fluid pump according to the present embodiment has a high process without changing the design such as increasing the thickness of the members constituting the secondary shaft space 13 and the motor space 5. It will be easier to get.

  When the combustible gas is vaporized in the space 14 due to heat generation of the motor, the pressure in the secondary shaft space 13 and the motor space 5 increases, and the risk of explosion and combustion increases. In the fluid pump of the present embodiment, the pressure increase in the secondary shaft space 13 and the motor space 5 is suppressed. By such an action, the fluid pump according to the present embodiment has a high process without changing the design such as increasing the thickness of the members constituting the secondary shaft space 13 and the motor space 5. It will be easier to get. At the same time, it reduces the risk of explosion and combustion.

〔Scope of application〕
Each of the above embodiments has been described with a focus on the case where the pump has a hermetically sealed space on the secondary side of the impeller and is multistage and increases the stroke. This is because the fluid that has become high pressure by the multi-stage impeller flows into the sealed space on the secondary side, and the sealed space becomes abnormally high pressure.

In addition, when a high stroke is obtained with a centrifugal pump, among the three high stroke methods, there are many cases where (c) multi-stage impellers are often employed. This is because (a) the method of increasing the impeller diameter and (b) the method of increasing the number of rotations are limited in the cases that can be dealt with.
That is, (a) an increase in impeller diameter has a demerit that the housing of the pump becomes large. Also, depending on the head and flow rate aimed at, impeller design may become unreasonable. That is, depending on the conditions, the impeller has a lower specific speed, which may cause problems such as cavitation. Further, (b) increase in the number of rotations requires use of an inverter motor or a speed increaser in order to increase the number of rotations. In other words, there are limitations on the assembly of the rotating device. Further, when the rotational speed increases, a problem is likely to occur in the shaft strength, and the structural design needs to be changed. Further, as the rotational speed is increased, cavitation is more likely to occur and there is a structural danger, so there is a limit in increasing the rotational speed.
As described above, these are because the impeller design is limited and cavitation is likely to occur as described above.

  However, the present invention is not limited to (c) not only multi-stage impellers, but also (a) increase in impeller diameter, and (b) application to a pump that obtains a high range by increasing the number of revolutions.

[Other variations]
In each of the above-described embodiments, the example in which one or two shafts are used as the rotation transmission means has been described. However, the present invention is not limited to this, and the rotation of the motor 1 can be transmitted to the impellers 2A and 2B. Other means can be used if present. For example, the rotation may be transmitted by connecting the shaft for the motor 1 and the shaft for the impellers 2A and 2B using a gear, a chain, a belt, or the like.

Further, the particularly preferred embodiments of the present invention have been described above. However, the present invention is not intended to be limited to the illustrated embodiments, and can be implemented by being modified in various aspects. The present invention is variously modified. Is intended to include.

DESCRIPTION OF SYMBOLS 1: Motor 2A: Impeller 2B: Impeller 3: Rotation transmission member 4A: Pressure wall 4B: Pressure wall 5: Motor space 6: Introduction part 7: Volute housing 8: Discharge part 9: Impeller space 10: Inducer 11: Communication path 11A: Vertical flow path 11B: Horizontal flow path 11C: Through flow path 11D: Wall flow path 12: Shaft cover 13: Shaft space 14: Space 15: Shaft seal 16: Bearing 17A: Primary side opening 17B: Secondary side Opening 19: Pump part 20: Motor part 21A: Outer wall 21B: Outer wall 22: Pressure wall

Claims (5)

An impeller that increases the pressure of the fluid by rotating;
A motor for rotating the impeller;
A rotation transmission member for transmitting rotation of the motor to the impeller;
A space in which the impeller, the rotation transmission member, and the motor each exist with the fluid;
Provided in the rotation transmission member, the primary side space that is the introduction side of the impeller, and a communication path that communicates the secondary side space that is the opposite side ,
The motor is arranged on the upper side and the impeller is on the lower side,
Between the motor and the impeller, there is provided a heat adjusting unit that keeps the impeller in the liquid phase of the low-temperature liquefied gas and keeps the motor in the gas phase of the low-temperature liquefied gas,
The communication path is formed by communicating a vertical channel and a horizontal channel with each other,
The fluid flow pump, wherein the transverse flow path has a secondary side opening in a heat adjusting portion between the motor and the impeller . The fluid pump according to claim 1, wherein the rotation transmission member is pivotally supported by a shaft seal, and the shaft seal is disposed between the opening on the secondary side of the communication path and the impeller. The fluid pump according to claim 1, wherein a plurality of the impellers are arranged along the rotation transmission member. The fluid pump according to any one of claims 1 to 3, wherein the fluid is a liquefied gas. The fluid pump according to claim 4, wherein the liquefied gas is a combustible gas.

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