JP4433863B2 - Submersible pump device for liquefied gas tank - Google Patents

Description

  The present invention relates to a submerged pump device for a liquefied gas tank that is installed in a liquefied gas tank that stores liquefied gas such as liquefied natural gas and that transports the liquefied gas.

Conventionally, as this kind of submerged pump device, for example, one disclosed in Patent Document 1 is known.
In the submerged pump device for a liquefied gas tank described in Patent Document 1, a pump main body is suspended in a pumping pipe installed in the liquefied tank, and a blade for boosting the liquefied gas is provided in a casing of the pump main body. A car and an electric motor for driving the impeller are provided.
The rotating shaft that links the impeller and the motor is rotatably supported by hydrostatic bearings installed in the upper and lower stages of the casing, and acts near the rotating shaft near the hydrostatic bearing provided in the middle stage. A shaft thrust balance means for supporting the thrust force is installed.
In addition, an inducer is provided at the lower end of the rotating shaft, and even when the liquid level of the liquefaction tank is lowered by the inducer, the pump is prevented from being disabled due to cavitation.
JP 7-317695 A

However, in the conventional submersible pump device described in Patent Document 1, since the swirl component is included in the flow downstream of the inducer, a so-called pre-swirling flow is generated for the impeller, so that the total lift of the impeller is reduced. .
In general, at the design point, the amount of decrease in the total lift due to the pre-turn of the inducer and the pre-turn of the impeller is substantially equal. For this reason, when an attempt is made to improve the total head with the submersible pump device described in Patent Document 1, the submerged pump device is expensive because it is necessary to enlarge the pump body.
In addition, it is necessary to increase the diameter of the pumped pipe to install the pump device, and the equipment cost increases, and the increase in mass due to the increase in the size of the pump body increases labor costs during disassembly and assembly. There is also a problem.

  The present invention was made in order to improve such a conventional problem, and an object of the present invention is to provide a submerged pump device for a liquefied gas tank in which a total lift is improved by arranging a guide vane downstream of an inducer. To do.

A submerged pump device for a liquefied gas tank according to the present invention is a submerged pump device for a liquefied gas tank that transports a liquefied gas by dropping the pump main body into a pumping pipe installed in the liquefied gas tank, and sucking the pump main body An inducer for boosting the liquefied gas sucked from the suction port , and an impeller provided on the downstream side of the inducer for further boosting the liquefied gas boosted by the inducer and discharging it into the pumping pipe The guide vane is provided between the inducer and the impeller so that the distance from the inducer is 5 to 15% of the outer diameter of the inducer, and rectifies the liquefied gas pressurized by the inducer and flows into the impeller And a hydrostatic shaft that is provided at a boss portion that forms the center portion of the guide vane and rotatably supports the lower end side of the rotation shaft to which the inducer and the impeller are attached. One in which was formed from the.

With the above configuration, the swirl component in the liquefied gas boosted by the inducer is rectified by the guide vane provided on the downstream side of the inducer and the pressure is recovered, so that the total lift of the inducer is improved, The liquefied gas, which has been pressurized by the inducer and rectified by the guide vanes and has a uniform flow without any pre-swirl, flows into the impeller and is further increased in pressure by the impeller, increasing the size of the pump body. Without increasing the total head.
In addition, since the total head can be improved without increasing the size of the pump body, a submerged pump device can be obtained at a low cost, and it is not necessary to increase the diameter of the pumping pipe for installing the pump body. Reduction can be achieved.

Furthermore , the boss outer diameter of the guide vane is supported by rotatably supporting the lower end side of the rotating shaft to which the inducer and the impeller are attached to the boss portion provided at the center portion of the guide vane via a hydrostatic bearing. Therefore, the boss diameter of the inducer can be reduced without enlarging or reducing the meridional flow path, so that the performance of the inducer due to flow path resistance is not lowered, and the flow flowing into the impeller is uniform. Therefore, the performance of the impeller is also improved.
Further, by providing the bearing bracket on the downstream side of the inducer, damage to the reverse flow cavitation of the inducer can be avoided.

In addition, the distance between the inducer and the guide vane is 5 to 15% of the outside diameter of the inducer, so that the efficiency of the inducer and the suction performance of the impeller are not lowered, and the state of liquid supercavitation Even when the pump body is operated, the cavitation does not reach the guide vane, so there is no fear of the guide vane being damaged by the cavitation, and it is not necessary to lengthen the rotating shaft, so that the pump body can be downsized.

  In the submerged pump device for a liquefied gas tank of the present invention, the distance between the guide vane and the impeller is 5 to 15% of the outer diameter of the inducer.

  With the above configuration, in a low flow rate region where a part of the liquefied gas pressurized by the impeller causes a back flow, the guide vane collides with a flow having a swirling component that flows back from the impeller and suppresses the swirling. In addition to the improvement, the effect of eliminating the unstable characteristics of the lift curve can be obtained.

In the submerged pump device for a liquefied gas tank of the present invention, since the boss ratio of the guide vane (boss outer diameter Dgh / blade outer diameter Dit) is 0.3 to 0.5, the outer diameter of the guide vane is set to the first stage impeller. in which the set to ± 10% of the range of the inner diameter of the sliding surface of the mouth ring provided on the upstream side (Dm).

  With the above configuration, there is no large step between the outer diameter of the guide vane and the sliding surface of the mouth ring, so the liquefied gas rectified by the guide vane flows smoothly into the impeller, so that the pump efficiency is improved. There is no decline.

According to the submerged pump device for a liquefied gas tank of the present invention, the swirl component in the liquefied gas boosted by the inducer is rectified by the guide vane provided on the downstream side of the inducer, and the pressure is recovered. As the total lift of the inducer is improved, the liquefied gas, which is rectified by the guide vanes and has a uniform flow without pre-turning, flows into the impeller and is further increased in pressure by the impeller. The total head can be improved without increasing the size.
Further, since the pressure of the liquefied gas is further increased by the impeller, the total head can be improved without increasing the size of the pump body.
Furthermore, since the distance between the inducer and the guide vane is 5 to 15% of the outer diameter of the inducer, the efficiency of the inducer and the suction performance of the impeller are not lowered, and the state of super cavitation Even when the pump body is operated, the cavitation does not reach the guide vane, so there is no fear of the guide vane being damaged by the cavitation, and it is not necessary to lengthen the rotating shaft, so that the pump body can be downsized.

Embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view of a submersible pump device for a liquefied gas tank, FIG. 2 is an enlarged view of the vicinity of the inducer, and FIG. 3 is a detailed view of the vicinity of the inducer.
A pump main body 1 of the submerged pump device shown in FIG. 1 is disposed from above in a pumping pipe 2 installed almost vertically in a liquefied gas tank (not shown) for storing liquefied gas such as liquefied natural gas (LNG). It is suspended by a suspension means 3 made of a wire rope.
The lower end of the pumping pipe 2 is opened near the bottom of the liquefaction tank, the suction valve 4 is attached to the opening 2a, and the tapered receiving seat 2b formed on the inner peripheral surface of the opening 2a A tapered seating surface 1b formed on the outer peripheral surface of the casing 1a of the pump body 1 is in liquid-tight contact from above.

The casing 1a of the pump body 1 is composed of a cylindrical pump casing 1c having a smaller diameter than the inner diameter of the pumping pipe 2 and a motor casing 1d. A suction port 1e having a smaller diameter than the inner diameter of the pump casing 1c is provided at the lower end of the pump casing 1c. It is open.
The central axis of the pump casing 1c and the motor casing 1d has the rotary shaft 4 penetrating in the axial direction, and the inducer 5 provided in the suction port 1e is fixed to the lower end of the rotary shaft 4; A plurality of impellers 6 provided in the pump casing 1c are fixed above the inducer 5, and a rotational drive comprising an electric motor housed in the motor casing 1d is provided on the upper side of the rotating shaft 4. The rotor 8a of the means 8 is fixed. A plurality of guide vanes 7 are provided between the inducer 5 provided in the suction port 1e of the pump casing 1c and the first stage impeller 6.

The guide vanes 7 project radially from the inner peripheral surface of the suction port 1 e, and a cylindrical boss portion 7 a through which the distal end side of the rotating shaft 4 passes is provided at the center of each guide vane 7. .
The boss portion 7a of the guide vane 7 has a tapered shape in which the outer diameter and one end side of the boss portion 7a provided at the center of the inducer 5 are substantially the same diameter and the other end side is slightly larger in diameter. The liquefied gas sucked into the suction port 1e by the reducer 5 flows smoothly into the impeller 6, and the liquefied gas sucked into the suction port 1e and boosted by the inducer 5 has a plurality of pressures. The swirl component is rectified by the guide vanes 7 and flows into the impeller 6.
In other words, the guide vane 7 functions as a rectifying plate that rectifies the flow of the liquefied gas converted into the flow in the rotation direction by the inducer 5 in the linear direction. This rectification function and the performance of the inducer 5 are maximized. In order to obtain a high head even with a small pump body 1 by exerting it to the limit, the parameters of each part shown in FIG. 3 are set as follows.

If the distance L1 between the inducer 5 and the guide vane 7 is too long, the efficiency of the inducer 5 is lowered and the rotating shaft 4 must be lengthened.
Further, since the distance between the inducer 5 and the impeller 6 is increased, in the case of a vertical pump such as a submerged pump device, the distance of the liquefied gas pushed up to the impeller 6 by the inducer 5 is increased. There arises a problem that the suction performance is lowered.
On the other hand, if the distance L1 is too short, when the pump body 1 is operated in a super cavitation state in which the total head is lowered when the liquefied gas in the liquefied gas tank is at an extremely low liquid level, the cavitation is generated in the guide vane 7. This leads to a problem that the guide vane 7 is damaged.
Therefore, in the embodiment of the present invention, the distance L1 from the inducer 5 to the guide vane 7 is set to 5 to 15% of the outer diameter Dit of the blade of the inducer 5.

It has been confirmed by experiment that the cavitation does not reach the guide vane 7 even in the super cavitation state, or the influence is small even if it reaches.
If the distance L2 from the guide vane 7 to the first stage impeller 6 is long, the rectification effect by the guide vane 7 is increased. However, if the distance L2 is too long, the rotating shaft 4 must be lengthened, and thus the pump body 1 is prevented from being downsized. .
Similarly to the distance L1 from the inducer 5 to the guide vane 7, if the length is too long, the distance of the liquefied gas pushed up to the impeller 6 by the inducer 5 increases, so that the suction performance of the impeller 6 is deteriorated.
On the contrary, if the length is short, an unstable flow caused by the flow separated by the guide vanes 7 near the exit of the guide vane 7 flows into the impeller 6, so that the performance of the impeller 6 is deteriorated.

Therefore, the distance L2 from the guide vane 7 to the impeller 6 is set to 5 to 15% of the outer diameter Dit of the blade of the inducer 5.
In this way, in the low flow rate region where a part of the liquefied gas pressurized by the impeller 6 causes a back flow, the guide vane 7 collides with a flow having a swirling component that flows back from the impeller 6 to suppress the pre-turn, so that the total lift In addition, the effect of eliminating the unstable characteristics of the head curve can be obtained.
The inner diameter (same as the outer diameter of the boss portion 7a) Dgh of the guide vane 7 that rectifies the liquefied gas pressurized by the inducer 5 depends on the boss ratio (the outer diameter of the boss Dgh / the outer diameter of the blade Dit). It has a big impact.
For this reason, reducing the outer diameter Dgh of the boss portion 7a is important in improving the suction performance of the inducer 5.
Therefore, in the embodiment of the present invention, the boss ratio of the guide vane 7 is set to 0.3 to 0.5 .

Further, the lower bearing 12 for supporting the lower end side of the rotary shaft 4 is provided on the boss 7a of the guide vane 7. However, when a ball bearing is adopted for the lower bearing 12, the outer diameter Dgh of the boss 7a becomes too large. Since the boss ratio 0.3 to 0.5 described above cannot be obtained, in the embodiment of the present invention, by adopting a static pressure bearing for the lower stage bearing 12 and reducing the outer diameter Dgh of the boss portion 7a, A boss ratio of 0.3 to 0.5 is obtained.
Further, the difference in diameter between the outer diameter Dgh of the boss portion 7a and the suction port 1i of the impeller 6 has a great influence when the liquefied gas rectified by the guide vane 7 flows into the pump casing 1c.
Therefore, the outer diameter Dgh of the guide vane 7 is set within a range of ± 10% of the inner diameter Dm of the sliding contact surface of the mouth ring 1h provided in the suction port 1i of the pump casing 1c.
The limit of the boss ratio when a static pressure bearing is adopted for the lower stage bearing 12 can be about 0.3 if the outer diameter Dit of the inducer 5b is substantially the same as the diameter of the suction port 1i of the impeller 6. is there.

On the other hand, the upper end portion of the rotary shaft 4 provided so as to pass through the central portions of the pump casing 1c and the motor casing 1d is composed of an upper bearing 10 provided on an end plate 1k that closes the upper end portion of the motor casing 1d, and the pump casing. It is rotatably supported at three locations: a middle stage bearing 11 provided on the partition plate 1g interposed between 1c and the motor casing 1d, and a lower stage bearing 12 provided in the boss portion 7a of the guide vane 7.
The upper bearing 10 and the middle bearing 11 are ball bearings that support radial loads, and the lower bearing 10 is configured so that the outer diameter of the boss portion 7a is substantially the same as the outer diameter of the boss portion 7a of the guide vane 7. As described above, a static pressure bearing is employed.
As shown in FIG. 2, the hydrostatic bearing of the lower stage bearing 12 is provided on the inner liner 12 a that is in sliding contact with the outer peripheral surface of the rotating shaft 4, and the outer peripheral surface of the inner liner 12 a, and is fixed to the boss 7 a side by the fixing tool 13. A part of the liquefied gas pressurized by the first stage impeller 6 is introduced into the pressure receiving chamber 12c formed on the inner peripheral surface of the inner liner 12a through the passage 1f, and thereby the inner liner 12b. A hydrostatic bearing for supporting the rotating shaft 4 is formed between the outer peripheral surface of the rotating shaft 4 and 12a.

A shaft thrust balancing means 14 is provided below the middle stage bearing 11.
The axial thrust balancing means 14 is formed by a hydrostatic bearing, and supports thrust force acting on the rotating shaft 4, and is provided on a partition plate 1g interposed between the pump casing 1c and the motor casing 1d. A plurality of outlets 1j for discharging the liquefied gas pressurized by the plural stages of impellers 6 into the pumping pipe 2 are opened in an oblique direction.
In FIG. 1, reference numeral 15 denotes a power supply cable for supplying electric power to the rotary drive means 12 made of an electric motor.

Next, the operation of the submerged pump device for a liquefied gas tank constructed as described above will be described.
When electric power is supplied to the rotary drive means 12 provided on the upper part of the pump body 1 to transport the liquefied gas stored in the liquefaction tank, and the rotary shaft 4 is rotated by the rotary drive means 8, The fixed inducer 5 and impeller 6 rotate, and the liquefied gas in the liquefaction tank is sucked into the suction port 1e from the suction valve 3 provided at the lower end of the casing 1a.
The liquefied gas sucked into the suction port 1e is boosted by the inducer 5 and then flows into the pump casing 1c through the guide vane 7, and is sequentially boosted by the plurality of impellers 6 in the pump casing 1c to be discharged. 1j is discharged into the pumping pipe 2 and transported upward in the pumping pipe 2, but the liquefied gas pressurized by the inducer 5 in the suction port 1e is swirled by the rotation of the inducer 5. Contains ingredients.
This swirling component is rectified by a guide vane 7 provided on the downstream side of the inducer 5 so that the pressure is restored, so that the total lift of the inducer is improved, the pressure is increased by the inducer, and is rectified by the guide vane. Since the liquefied gas is further increased in pressure by the impeller, the total head can be improved without increasing the size of the pump body.

Also, in the case of a submerged pump device without a guide vane between a conventional inducer and an impeller, a liquefied gas containing a swirling component pressurized by the inducer becomes a so-called pre-swirling flow that directly flows into the impeller. Although the total head has been lowered, the provision of the guide vane 7 between the inducer 5 and the impeller 6 makes it possible to improve the total head even with the small pump body 1.
This is because the guide vane 7 is provided between the inducer 5 and the impeller 6 so that the swirl component generated by the inducer 5 is rectified by the guide vane 7 and the flow that matches the blade inlet angle of the impeller 6 is the first stage. Therefore, the total lift of the impeller 6 is improved.

  On the other hand, when the transport flow rate is limited and the low flow rate region is reached, the inducer 5 is operated while causing cavitation, so a part of the liquefied gas pressurized by the impeller 6 flows back to the inducer 5 side, and the lift An unstable region occurs in the curve, but in a low flow rate region where a part of the liquefied gas pressurized by the impeller causes a reverse flow, the guide vane collides with a flow having a swirling component that flows backward from the impeller, thereby suppressing the rotation. Therefore, the unstable characteristics of the head curve can be improved.

  The apparatus of the present invention improves the performance of the inducer because the swirl component in the liquefied gas pressurized by the inducer is rectified by a guide vane provided downstream of the inducer and the pressure is recovered. Since the total head can be improved without increasing the size of the pump body, it is optimal for a submerged pump device for a liquefied gas tank that transports liquefied gas.

It is sectional drawing of the immersive pump apparatus for liquefied gas tanks which becomes embodiment of this invention. It is an expanded sectional view near the diffuser of the submerged pump device for a liquefied gas tank according to the embodiment of the present invention. It is detail drawing of the diffuser vicinity of the submerged pump apparatus for liquefied gas tanks which becomes embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump main body 1e Suction port 1h Mouth ring 2 Pumping pipe 4 Rotating shaft 5 Inducer 5a Boss part 6 Impeller 7 Guide vane

Claims (3)

A submerged pump device for a liquefied gas tank that transports liquefied gas by dropping the pump body into a pumping pipe installed in the liquefied gas tank, and is provided at a suction port of the pump body, and sucked from the suction port. The distance between the inducer , which is provided on the downstream side of the inducer for boosting the liquefied gas, and the impeller that further pressurizes the liquefied gas boosted by the inducer and discharges the liquefied gas into the pumped liquid pipe. A guide vane that is provided between the inducer and the impeller so as to be 5 to 15% of the outer diameter of the inducer, rectifies the liquefied gas pressurized by the inducer, and flows into the impeller ; Provided on the boss that forms the center of the guide vane, and rotatably supports the lower end side of the rotating shaft to which the inducer and the impeller are attached. Liquefied gas tank for submersible pump apparatus characterized by comprising a hydrostatic bearing that. Distance liquefied gas tank for submersible pump device according to claim 1 which is formed by 5 to 15% of the outside diameter of the inducer between the guide vane and the impeller. In order to set the boss ratio (boss outer diameter Dgh / blade outer diameter Dit) of the guide vane to 0.3 to 0.5, the outer diameter of the guide vane is set to the mouth ring provided on the upstream side of the first stage impeller. The submerged pump device for a liquefied gas tank according to claim 1 or 2, wherein the submerged pump device is in a range of ± 10% of an inner diameter (Dm) of the sliding surface .

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