JP4311200B2 - Submersible pump device for liquefied gas tank - Google Patents

Description

  The present invention relates to a submerged pump device for a liquefied gas tank mainly used for transporting liquefied natural gas (LNG).

Conventionally, as this type of pump device, for example, the one described in Patent Document 1 is known.
JP, 6-185487, A (patent 3231453) gazette The "submersible pump device for liquefied gas tanks" indicated in the above-mentioned patent documents 1 is added to a thrust bearing in the state where a pump generated predetermined discharge pressure. Axial thrust balancer that can function to make the thrust force almost zero, and when the pump discharge flow rate becomes excessive, it closes and the pressure difference between the high pressure pump body and the outside of the pump body is small And a high-pressure holding valve that changes from a closed state to an open state.

  In the pump device described in Patent Document 1, the plurality of discharge holes for discharging the liquefied gas from the pump body to the pumping pipe are formed in a direction perpendicular to the rotation axis, and the discharge side of the final stage impeller As for the diffuser provided in, a radial diffuser whose flow passage expansion direction is perpendicular to the rotation axis c is used, and the circumferential inclination of the discharge hole for discharging the liquefied gas coincides with the flow passage direction of the radial diffuser. It has a structure that does not.

Generally, the pump efficiency of a submerged pump device installed in a liquefied gas tank and used for transporting liquefied gas is about 75%, and 25% is a loss.
The breakdown of the 25% loss is about 16% hydraulic loss from suction to the last stage impeller, about 4% hydraulic loss from the last stage impeller to the discharge hole, and about 5% leakage loss. There is about 4% hydraulic loss from the last stage impeller to the discharge hole.
Most of the hydraulic loss from the final stage impeller to the discharge hole is such that the discharge hole for discharging the liquefied gas is provided at right angles to the rotation axis as in the submerged pump device described in Patent Document 1. It is considered that this is because the circumferential inclination of the discharge hole does not coincide with the flow direction of the radial diffuser.

  The present invention has been made to improve such a conventional problem, and provides a submerged pump device for a liquefied gas tank in which pump efficiency is improved by reducing hydraulic loss from the final stage impeller to the diffuser. It is the purpose.

The submerged pump device for a liquefied gas tank according to the present invention includes a pump body suspended in a pumping pipe installed in the liquefied gas tank, a rotation driving means for rotationally driving an impeller of the pump body, and a pressure increased by the impeller. A submerged pump device for a liquefied gas tank, comprising a diffuser having a plurality of discharge holes for discharging liquefied gas to a pumping pipe, axially downstream of a radial diffuser provided on the discharge side of the final stage impeller A diffuser is provided, and a discharge member formed with a plurality of discharge holes for introducing the pressurized liquefied gas to the pumping pipe is provided further downstream of the axial diffuser, and the plurality of discharge holes are arranged in the circumferential direction of the rotating shaft. It is formed at intervals so as to incline, and is also formed to incline toward the downstream side in the axial direction .

  With the above configuration, since the liquefied gas discharged from the final stage impeller is smoothly discharged to each discharge hole, hydraulic loss from the final stage impeller to the diffuser can be reduced, thereby improving the overall pump efficiency. Can be improved.

The submerged pump device for a liquefied gas tank according to the present invention includes a pump body suspended in a pumping pipe installed in the liquefied gas tank, a rotation driving means for rotationally driving an impeller of the pump body, and a pressure increased by the impeller. A submerged pump device for a liquefied gas tank, comprising a diffuser having a plurality of discharge holes for discharging liquefied gas to a pumping pipe, axially downstream of a radial diffuser provided on the discharge side of the final stage impeller A diffuser is provided, and a discharge member having a plurality of discharge holes is formed further downstream of the axial diffuser. The plurality of discharge holes are formed at intervals so as to be inclined in the circumferential direction of the rotating shaft, and in the axial direction. together are inclined to the downstream side, the continuous to the outlet side of the discharge hole, and that a flow path substantially parallel to the axis of the rotary shaft formed in the inner peripheral portion of the liquid being pumped tube A.

  With the above configuration, since the liquefied gas discharged from the final stage impeller is smoothly discharged to each discharge hole, the hydraulic loss from about 4% from the final stage impeller to the diffuser can be reduced to about 2%. Therefore, the overall pump efficiency can be improved by about 2% compared to the conventional one.

According to the submerged pump device for a liquefied gas tank of the present invention, since the liquefied gas discharged from the final stage impeller is smoothly discharged to each discharge hole, hydraulic loss from the final stage impeller to the diffuser is reduced. This can improve overall pump efficiency.

Embodiments of the present invention will be described in detail with reference to the drawings.
1 is a cross-sectional view of a submersible pump device installed in a liquefied gas tank, FIG. 2 is an enlarged cross-sectional view of the submersible pump device, FIG. 3 is a partially cutaway perspective view taken along line AA in FIG. It is sectional drawing which follows the BB line of FIG.
The pump main body 1 is provided inside a pumped liquid pipe 3 installed almost vertically in the liquefied gas tank 2 from the ceiling 2 a of the liquefied gas tank 2.
The pumping pipe 3 has a lower end reaching the vicinity of the bottom of the liquefied gas tank 2, and a tapered contact surface formed at the lower part of the pump body 1 is formed on the seat surface 3 b of the opening 3 a opened at the lower end surface. Liquid-tight contact is made from above.

The upper end side opening 3 c of the pumping pipe 3 is closed by a head plate 4, and the pump body 1 is suspended in the pumping pipe 3 by a hanging wire 5 hanging from the lower surface of the head plate 4. The liquefied gas discharged from the discharge port provided in the upper part of the pump body 1 rises in the pumping pipe 3 as indicated by the arrow in FIG. 1 and is connected to the upper part of the pumping pipe 3. 6 is discharged.
As shown in FIG. 2, the pump body 1 has a cylindrical pump casing 1a having a diameter smaller than that of the pumping pipe 3, and contacts the flange portion 7a of the suction member 7 connected to the lower end of the pump casing 1a. Surface 7b is formed.
The pump body 1 has an integral structure with a rotary drive means 8 made of an electric motor, and a motor casing 8a of the rotary drive means 8 is connected to the upper end of the pump casing 1a via a discharge member 9, and the pump casing 1a and the motor are connected to each other. A rotating shaft 10 is provided so as to penetrate the center of the casing 8a.

The rotating shaft 10 is arranged between an upper portion and an intermediate portion by an upper bearing 12 provided on an end plate 8b that closes an upper end of the motor casing 8a, a middle bearing 13 provided on the discharge member 9, and a lower bearing 14 provided on the suction member 7. The part and the lower part are rotatably supported.
The upper bearing 12 and the middle bearing 13 are formed by ball bearings, and a high-pressure discharge pressure from the final stage impeller is introduced directly below the middle bearing 13 to cancel the thrust force acting on the rotary shaft 10. Thus, there is provided axial thrust balancing means 15 that makes the thrust force of the rotary shaft 10 substantially zero.
The lower bearing 14 that supports the lower end side of the rotating shaft 10 is formed of a static pressure sliding bearing, and suppresses shaft vibration at the lower end of the rotating shaft 10.

The pump casing 1a is divided into a plurality of stages, and an impeller 1b is accommodated in each pump casing 1a.
Each impeller 1b is fixed to the rotary shaft 10, and rotates in the pump casing 1a with the rotation of the rotary shaft 10. The lower end of the rotary shaft 10 is provided at the lower end of the pump casing 1a. An inducer 17 for increasing the pressure of the liquefied gas sucked from the suction valve 16 is fixed.
The rotation driving means 8 connected to the upper part of the pump casing 1a is composed of a stator 8b provided on the inner peripheral surface of the motor casing 8a and a rotor 8c fixed to a rotating shaft 10 penetrating through the central portion of the stator 8b. The rotary shaft 10 is driven to rotate by electric power supplied from the outside via the cable 18.

The liquefied gas sucked from the suction valve 16 by the rotation of the rotating shaft 10 is boosted by the inducer 17 and then boosted by the impeller 1b of each stage of the pump body 1, and the liquefied gas of each stage impeller 1b. A radial diffuser 1c provided on the discharge side converts the dynamic pressure component from the impeller 1b into a static pressure so that the pressure is sequentially increased to reach the final stage impeller 1b.
An axial diffuser 1d is provided on the discharge side of the final stage impeller 1b , and the discharge member 9 is provided on the downstream side of the axial diffuser 1d .
The axial diffuser 1 d has a plurality of discharge ports 1 e, and these discharge ports 1 e are connected to the inlets of the discharge holes 1 g formed in the discharge member 9.
The discharge member 9 is formed with a plurality of discharge holes 1g for guiding the pressurized liquefied gas to the pumping pipe 3, and these discharge holes 1g are formed at intervals so as to incline in the circumferential direction of the rotary shaft 10. And it is formed so as to incline toward the downstream side in the axial direction .
And the exit side of each discharge hole 1g formed in the discharge member 9 is connected to the flow path 1f formed in the inner peripheral part of the liquid raising pipe 3 so that it may be substantially parallel to the axis line of the rotating shaft 10. FIG.

Next, the operation of the submerged pump device for a liquefied gas tank constructed as described above will be described.
When the rotary shaft 10 is rotationally driven by the rotary drive means 8 to transport the liquefied gas stored in the liquefied gas tank 2, the inducer 17 provided on the rotary shaft 10 and a plurality of impellers 1b in the pump cage 1a. Are simultaneously rotated, and the liquefied gas in the liquefied gas tank 2 is sucked from the suction port 1h through the suction valve 16.
The liquefied gas sucked from the suction port 1h is boosted by the inducer 17 and then boosted by the impeller 1b at each stage to reach the final impeller 1b.
The liquefied gas further pressurized by the impeller 1b at the final stage flows into the axial diffuser 1d from the radial diffuser 1c provided on the discharge side, and the discharge hole of the discharge member 9 from the discharge port 1e provided in the axial diffuser 1d. 1 g is discharged.

Since each discharge port 1e of the axial diffuser 1d is inclined in the circumferential direction in advance as shown in FIG. 4, it is discharged from the discharge port 1e of the axial diffuser 1d from the final stage impeller 1b via the radial diffuser 1c. The liquefied gas smoothly flows into the inlets of the plurality of discharge holes 1g formed in the discharge member 9.
Then, the discharge hole 1g inclined in the circumferential direction and the axial direction reaches the outlet side of the discharge hole 1g while changing the flow so as to be substantially parallel to the axis of the rotary shaft 10, and is pumped so as to be substantially parallel to the axis of the rotary shaft 10. It is discharged into a flow path 1f formed in the inner periphery of the tube 3 .
This is a conventional submersible pump apparatus, since the pressure losses from the final stage impeller was about 4% between the diffuser can be reduced to about 2%, 2% compared to the overall pumping efficiency to the conventional Can be improved.
Further, the liquefied gas discharged into the pumping pipe 3 rises through the pumping pipe 3 and is discharged into the transport pipe 6 connected to the upper part of the pumped liquid pipe 3, and transported to the destination by the transport pipe 6. Is done.

In the above-described embodiment, the case where the axial diffuser 1d is provided on the discharge side of the final stage impeller 1b has been described. However, it is possible to reduce the hydraulic loss only by inclining the discharge hole of the radial diffuser 1c in the circumferential direction. Can do.
The inclination angle of the discharge hole 1e in the circumferential direction can be set to an appropriate value according to conditions such as the diameter and rotation speed of the impeller 1b.

  The submerged pump device for a liquefied gas tank according to the present invention can be applied to pumps used for special purposes such as a pump for liquid fuel supply of a rocket in addition to an industrial pump for transporting a fluid such as LNG.

It is sectional drawing of the state which installed the immersive pump apparatus for liquefied gas tanks which becomes embodiment of this invention in the liquefied gas tank. 1 is an enlarged cross-sectional view of a submersible pump device for a liquefied gas tank according to an embodiment of the present invention. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which follows the BB line of FIG.

Explanation of symbols

1 Pump body 1b Impeller 1c Radial diffuser 1d Axial diffuser 1e Discharge port 1f flow path
1 g Discharge hole 2 Liquefied gas tank 3 Pumped liquid 8 Rotation drive means

Claims (2)

A pump body suspended in a pumping pipe installed in a liquefied gas tank, rotation driving means for rotating and driving an impeller of the pump body, and liquefied gas pressurized by the impeller is discharged to the pumping pipe A submerged pump device for a liquefied gas tank comprising a diffuser having a plurality of discharge holes , wherein an axial diffuser is provided downstream of a radial diffuser provided on the discharge side of the final impeller, and the axial diffuser is further provided. Provided on the downstream side is a discharge member having a plurality of discharge holes for guiding the pressurized liquefied gas to the pumping pipe, and the plurality of discharge holes are spaced so as to incline in the circumferential direction of the rotating shaft. A submerged pump device for a liquefied gas tank, wherein the submerged pump device is formed so as to be inclined toward the downstream side in the axial direction . A pump body suspended in a pumping pipe installed in a liquefied gas tank, rotation driving means for rotating and driving an impeller of the pump body, and liquefied gas pressurized by the impeller is discharged to the pumping pipe A submerged pump device for a liquefied gas tank comprising a diffuser having a plurality of discharge holes , wherein an axial diffuser is provided downstream of a radial diffuser provided on the discharge side of the final impeller, and the axial diffuser is further provided. A discharge member having a plurality of discharge holes is provided on the downstream side, and the plurality of discharge holes are formed at intervals so as to incline in the circumferential direction of the rotating shaft, and also incline toward the downstream side in the axial direction. together are formed as, continuous to the outlet side of the discharge hole, and to characterized in that the flow path substantially parallel to the axis of said rotary shaft formed in the inner peripheral portion of the liquid being pumped tube Liquefied gas tank for a submersible pump device.

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