CN112576521B

CN112576521B - Combined type sweeping cabin impeller for improving sweeping cabin capacity of centrifugal deep well pump

Info

Publication number: CN112576521B
Application number: CN202011446640.7A
Authority: CN
Inventors: 付国涛; 陈九慧; 洪武平; 陈光亮
Original assignee: HUANGGONG MACHINE GROUP CO Ltd
Current assignee: HUANGGONG MACHINE GROUP CO Ltd
Priority date: 2020-12-09
Filing date: 2020-12-09
Publication date: 2023-01-13
Anticipated expiration: 2040-12-09
Also published as: CN112576521A

Abstract

The invention discloses a combined type stripping impeller for improving the stripping capability of a centrifugal deep well pump, which comprises a centrifugal impeller and an axial flow type preposed fluid processor; the centrifugal impeller is a closed impeller and comprises a front cover plate, centrifugal blades and a rear cover plate; the axial flow type preposed fluid processor is positioned between the inlet side of the centrifugal impeller and a suction bell mouth of the deep-well pump and is fixedly connected to the centrifugal impeller; the axial flow type preposed fluid processor is of a closed guide wheel structure and comprises a plurality of helical blades and a fixed outer ring for fixing the helical blades. The composite type cabin sweeping impeller has strong suction capacity and good cabin sweeping effect under the condition of low liquid level.

Description

Combined type sweeping cabin impeller for improving sweeping cabin capacity of centrifugal deep well pump

Technical Field

The invention relates to the field of oil storage and transportation, in particular to a composite type sweeping impeller for improving the sweeping capacity of a centrifugal deep well pump.

Background

With the increasing awareness of the global environment protection, the demand of liquid cargo ships for residual liquid in the cargo hold after unloading is higher and higher during marine transportation according to the international requirement of the ocean convention. In particular for hazardous chemical ships, minimizing the residual contents in the tanks after unloading is one of the most important goals pursued. At present, liquid cargo ships usually adopt liquid cargo pumps to unload, and liquid cargo residues can be inevitably generated because the working principle of various types of pumps is limited, and the liquid cargo in a cargo hold can not be completely pumped completely. Therefore, how to improve the tank cleaning capability of the liquid cargo pump and reduce the residual amount of the liquid cargo is an aim pursued in the field of oil storage and transportation, and one of the most important technical means is to reduce the residual amount of the liquid cargo by selecting a proper type of the liquid cargo pump or providing a novel structure of the liquid cargo pump.

The sliding vane pump is generally considered to be a liquid cargo pump type with strong sweeping capacity, and when the sliding vane pump is used as a cargo oil pump, the oil unloading process is simple, and only one sliding vane pump is adopted for oil guiding, oil unloading and sweeping operation. However, the flow of the sliding vane pump is relatively small, the abrasion loss of the sliding vane is large in the working process, the sliding vane pump needs to be replaced frequently, the fault-free operation period is short, and the maintenance cost is high. Particularly, in the occasion of dangerous chemical transportation, the sliding vane pump is often difficult to use. In comparison, the centrifugal pump has the advantages of large flow, simple structure, high operation reliability and relatively low use and maintenance cost, so the centrifugal pump is the best choice for the cargo oil pump for ships, and the centrifugal deep well pump is the best choice for the transportation of dangerous chemicals by ships.

In the process of discharging the liquid cargo in the ship cargo hold by using the deep-well pump, two processes of direct pumping and discharging through the deep-well pump and stripping and discharging of the liquid cargo in the discharging pipe of the deep-well pump are needed. During the process of discharging residual liquid cargo in the discharge pipe of the deep-well pump in a stripping mode, the pump cavity (the impeller and the volute) needs to maintain a certain discharge pressure so as to ensure that gas at the bottom of the discharge pipe of the deep-well pump does not leak from the side of the pump cavity, thereby ensuring enough air pressure to ensure that the liquid cargo can be successfully stripped. The pump chamber discharge pressure is greatly dependent on the pressure at the pump inlet and the medium conditions at a certain rotational speed, and the liquid level of the residual liquid cargo is reduced to the lowest possible level and air is easily sucked in to form a gas-liquid mixture under the application requirement that the residual liquid cargo is required to be as small as possible. Since centrifugal pumps are sensitive to inlet suction gas, their pressurization and delivery capacity drops dramatically due to rising inlet gas content, and are believed to lack gas delivery capacity, conventional centrifugal deep well pumps have difficulty maintaining sufficient pressure at the pump chamber outlet at low liquid levels, and must perform stripping operations with a high residual liquid content, and therefore their sweep capacity is significantly insufficient.

The centrifugal cargo oil pumps such as the centrifugal deep-well pump have high-flow and long-period reliable operation capacity and are particularly suitable for conveying dangerous chemicals, so that the cargo oil pump of the liquid cargo ship has strong tank sweeping capacity on the premise of ensuring the advantages of the centrifugal pump. Generally, in order to improve the cavitation performance or the suction performance of the centrifugal pump, people easily think of a mode of additionally arranging an inducer structure in front of a centrifugal impeller, but no matter the inducer is a split inducer or the inducer with an impeller integrated structure, the basic principle is to avoid cavitation or cavitation in the pressurizing process by slowly pressurizing from an inlet to an outlet of the inducer, and avoid cavitation or cavitation in the centrifugal impeller due to pressurizing of the inducer.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the composite type stripping impeller for improving the stripping capability of the centrifugal deep-well pump, and the impeller has strong stripping capability on the premise of ensuring the centrifugal deep-well pump to ensure large flow and long-period reliable operation.

The purpose of the invention is realized by the following technical scheme:

a compound-type stripping impeller for improving the stripping capability of a centrifugal deep well pump comprises a centrifugal impeller and an axial-flow type preposed fluid processor;

the centrifugal impeller is a closed impeller and comprises a front cover plate, centrifugal blades and a rear cover plate;

the axial flow type preposed fluid processor is positioned between the inlet side of the centrifugal impeller and the suction bell mouth of the deep-well pump and is fixedly connected to the centrifugal impeller; the axial flow type preposed fluid processor is of a closed guide wheel structure and comprises a plurality of helical blades and a fixed outer ring for fixing the helical blades.

Further, the bending direction of the blades of the axial flow type preposed fluid processor is opposite to the bending direction of the blades of the centrifugal impeller, and the projections of the blades of the axial flow type preposed fluid processor and the blades of the centrifugal impeller are in an X shape.

Furthermore, a front cover plate of the centrifugal impeller extends out of a fixed inner ring with internal threads along the opposite direction of fluid suction, external threads are arranged outside the fixed outer ring of the axial flow type preposed fluid processor, and the axial flow type preposed fluid processor is fixedly connected to the centrifugal impeller through meshing of the external threads and the internal threads.

A kind of stripping pump of the cabin, this stripping pump of the cabin includes the above-mentioned impeller, liquid discharge pipe, gas stripping pipe that connects to pump outlet, and liquid discharge pipe valve and gas control valve set in liquid discharge pipe, gas stripping pipe separately, and the said gas stripping pipe is communicated with bottom of the said liquid discharge pipe; when the device is in a low liquid cargo residue condition, the impeller continuously rotates to convey a gas-liquid two-phase medium, and a certain pressure is maintained; and introducing air through the gas sweeping cabin pipe, and discharging residual liquid in the liquid discharge pipe.

The invention has the following beneficial effects:

the axial flow type preposed fluid processor with strong gas-liquid mixing and pressurizing capacity is added at the inlet section of the centrifugal impeller, gas-liquid two-phase media are sent to the inlet of the centrifugal impeller under the condition of low inlet pressure and high gas content through the multi-spiral structure in the fluid processor, and the gas-liquid two-phase media are uniformly mixed before entering the centrifugal impeller, so that the pressurizing capacity of the centrifugal impeller under the condition of low-liquid-level gas-containing conveying is ensured, and the cabin cleaning capacity of the centrifugal deep-well pump is greatly enhanced. The practical test and application result of the sweeping cabin pump adopting the impeller show that the combined type sweeping cabin pump impeller can greatly improve the pressurization capacity of the centrifugal pump under the low-liquid-level gas-containing conveying condition, and the use of the combined type sweeping cabin impeller can reduce the liquid cargo residual amount to 60% of the convention requirement.

Drawings

FIG. 1 is a schematic structural view of a centrifugal deep well pump equipped with a composite type stripping impeller;

FIG. 2 is a schematic view of a structure of a threaded connection type composite sweeping impeller;

FIG. 3 is a schematic view of a nested welded composite sweeping impeller;

FIG. 4 is a schematic view of the internal structure of the composite type sweeping blade wheel;

the device comprises a motor 1, a composite impeller 2, a suction bell mouth 3, a pump body outlet 4, liquid cargo 5, a suction well 6, a liquid discharge pipe 7, a gas scavenging pipe 8, a gas control valve 9, a liquid discharge pipe valve 10, a centrifugal impeller 21, axial flow type preposed

fluid processors

22 and 211, centrifugal blades 212, a rear cover plate 213, a fixed inner ring 214, spiral blades 221 and a fixed outer ring 222.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will be more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

As shown in fig. 1, the centrifugal deep well pump with the composite type stripping impeller comprises a motor 1, a composite type impeller 2, a suction bell mouth 3, a pump body outlet 4, a liquid discharge pipe 7, a gas stripping pipe 8, a gas control valve 9 and a liquid discharge pipe valve 10.

The composite impeller 2 is fixed on the rotating shaft of the motor 1 and is driven by the motor 1 to rotate.

As shown in fig. 2 to 4, the composite impeller 2 includes a centrifugal impeller 21 and an axial flow type pre-fluid processor 22. The centrifugal impeller 21 is a closed impeller, and includes a front cover plate 211, centrifugal blades 212, and a rear cover plate 213.

An axial flow pre-fluid processor 22 is located between the inlet side of the centrifugal impeller 21 and the suction bell 3 of the deep well pump and is fixedly connected to the centrifugal impeller 21. The axial flow type pre-fluid processor 2 is a closed guide wheel structure, and includes a plurality of helical blades 221, and a fixed outer ring 222 for fixing the helical blades.

As shown in fig. 2, as one embodiment, the connection mode of the centrifugal impeller 21 and the axial flow type pre-fluid processor 22 is a threaded connection, that is, a front cover plate 211 of the centrifugal impeller 21 extends out of a fixed inner ring 214 with an internal thread in the opposite direction of fluid suction, an external thread is arranged outside a fixed outer ring 222 of the axial flow type pre-fluid processor 22, and the axial flow type pre-fluid processor 22 is fixedly connected to the centrifugal impeller 21 through the engagement of the external thread and the internal thread.

As another embodiment, as shown in fig. 3, the centrifugal impeller 21 and the axial flow type pre-fluid processor 22 are connected by a nested welding method, that is, a fixed outer ring 222 of the axial flow type pre-fluid processor 22 and a fixed inner ring 214 of the centrifugal impeller 21 are concentrically nested, and a part exposed from the fixed outer ring 222 is welded to the centrifugal impeller 21. The processing difficulty is greatly reduced by the two connection modes. And when connecting, need to guarantee the concentricity in order to avoid producing the unbalanced force, adopt clearance fit, connect after confirming the axial position of the leading fluid processor 22 of axial-flow type, guarantee joint strength.

The centrifugal deep well pump of the invention firstly ensures that the sweeping capacity of the centrifugal cargo oil pump is improved by adding the axial flow type preposed fluid processor 22 with strong gas-liquid mixing and conveying capacity and strong supercharging capacity near a close dead point at the inlet section on the premise that the centrifugal impeller 21 is as close to the cabin bottom as possible, and the axial length of the axial flow type preposed fluid processor 22 is shorter, thereby ensuring that the whole impeller has compact structure and the center of the centrifugal impeller cannot be raised. The axial flow type preposed fluid processor adopts a plurality of helical blades inside to realize that gas-liquid two-phase media are uniformly mixed and sent to the inlet of the centrifugal impeller 21 under the state of high gas content and realize strong pressurization capacity close to a dead point, so that the centrifugal deep well pump can have two-phase conveying capacity and maintain enough outlet pressure under the condition of extremely low liquid cargo residual liquid level, the residual liquid cargo at the outlet pipe of the deep well pump can be discharged smoothly by adopting a steam stripping mode, and the cabin sweeping capacity of the centrifugal cargo oil pump is greatly enhanced. And an additional auxiliary device is not needed, so that the cabin sweeping system is greatly simplified, and the installation space can be effectively saved.

The working principle of the centrifugal deep well pump is as follows:

under normal liquid level, the motor 1 drives the centrifugal impeller 21 and the axial flow type preposed fluid processor 22 to rotate through the long shaft, liquid cargos 5 in the oil suction well 6 are sucked through the inlet bell mouth 3, then are guided and boosted through the axial flow type preposed fluid processor 22, are boosted through the centrifugal impeller 21 and are output through the liquid discharge pipe 7.

Under the condition of low liquid cargo residue, the centrifugal impeller 21 and the axial flow type preposed fluid processor 22 continue to rotate, liquid cargo and part of gas are firstly uniformly mixed by the axial flow type preposed fluid processor 22 to form a gas-liquid two-phase medium, and then the gas-liquid two-phase medium enters the centrifugal impeller 21. The continuous rotation of the centrifugal impeller 21 and the axial flow type preposed fluid processor 22 ensures that the composite impeller 2 keeps certain pressure, and realizes strong supercharging capacity close to a close dead point. Meanwhile, one end of the gas sweeping cabin pipe 8 is connected with the bottom of the liquid discharging pipe 7, air is introduced through the gas sweeping cabin pipe 8, and residual liquid in the liquid discharging pipe 7 is discharged. A gas control valve 9 and a liquid drain pipe valve 10 are respectively located on the gas scavenge trunk pipe 8 and the liquid drain pipe 7 for regulating the flow of gas and liquid, respectively.

In order to improve the gas-liquid mixing and conveying capacity and the small-flow supercharging capacity, the bending direction of the blades of the axial flow type preposed fluid processor 22 is opposite to the bending direction of the blades of the centrifugal impeller 21, and the projections of the blades and the blades are in an X shape.

Experimental results show that when the centrifugal deep-well pump is used for sweeping the cabin, the residual quantity of liquid cargos in the cabin is far less than the requirement of the international convention, the residual quantity is 60 percent of the requirement of the international convention, and the effect of super-sweeping is achieved.

The composite type cabin-sweeping pump impeller structure can be widely applied to various centrifugal cargo oil pumps including centrifugal deep-well pumps.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.

Claims

1. A combined type stripping impeller for improving the stripping capability of a centrifugal deep well pump is characterized in that the combined type stripping impeller is used for discharging residual liquid and simultaneously conveying gas-liquid two-phase media under the condition of low-liquid-level gas-containing conveying, and comprises a centrifugal impeller and an axial-flow type preposed fluid processor;

the centrifugal impeller is a closed impeller comprising a front cover plate, centrifugal blades and a rear cover plate;

the axial flow type preposed fluid processor is positioned between the inlet side of the centrifugal impeller and a suction bell mouth of the deep-well pump and is fixedly connected to the centrifugal impeller; the axial flow type prepositive fluid processor is of a closed guide wheel structure and comprises a plurality of helical blades and a fixed outer ring for fixing the helical blades;

the bending direction of the blades of the axial flow type preposed fluid processor is opposite to the bending direction of the blades of the centrifugal impeller, and the projections of the blades and the centrifugal impeller are in an X shape;

the front cover plate of the centrifugal impeller extends out of a fixed inner ring with internal threads along the opposite direction of fluid suction, external threads are arranged outside the fixed outer ring of the axial flow type preposed fluid processor, and the axial flow type preposed fluid processor is fixedly connected to the centrifugal impeller through the external threads and the internal threads in a meshed mode.

2. A sweep cabin pump, characterized in that, the sweep cabin pump includes the compound type sweep cabin impeller of claim 1, the liquid discharge pipe connected to the outlet of the pump, the gas sweep cabin pipe, and the liquid discharge pipe valve and the gas control valve respectively arranged on the liquid discharge pipe and the gas sweep cabin pipe, and the gas sweep cabin pipe is communicated with the bottom end of the liquid discharge pipe; when the device is in a low liquid cargo residue condition, the impeller continuously rotates to convey a gas-liquid two-phase medium, and a certain pressure is maintained; and introducing air through the gas sweeping cabin pipe, and discharging residual liquid in the liquid discharge pipe.