SYSTEM FOR THE CIRCULATION OF GAS IN AIRS GAPS OF ROTATING MACHINES

Abstract

A system for the recirculation of gas in air gaps of rotating machines via an ejector, a motor and a pump, including circulating a gas extracted from a gas-extraction unit which is located in the pump. This gas circulates in the gap between the rotors and the stator of the motor. The rotor of the motor is coupled to the shaft of the pump, and in one or more embodiments the gas from the gas-extraction unit flows from the pump to the ejector in order to be injected into the air gap between the rotor and the stator, thereafter returning to a process line. In one or more embodiments, the gas from the gas-extraction unit flows from the pump, and is injected directly into the air gap, and thereafter passes via the ejector in order to recirculate the gas to the process line.

Claims

1. A system for the circulation of gas in annular spaces of rotating machines, comprising: a pump, provided with a gas-extraction unit and coupled to a rotor of a motor through a shaft, said rotor surrounded by a stator forming an annular space between said rotor and said stator; an ejector comprising a converging nozzle, which is provided with a motivating inlet and a narrowing at its outlet, said converging nozzle being connected to a discharge line of the pump through a first pipe, said ejector being further provided with a perpendicular suction inlet, said suction inlet being connected to the gas-extraction unit through a second pipe, said converging nozzle and suction inlet both being interconnected to a throat where a mixture of motivation fluid and gas coming from the gas-extraction unit occurs, said throat being coupled to a diffuser where the mixture of motivation fluid and gas is pressurized, wherein the gas-extraction unit of pump separates the process fluid gas from a process line, and wherein the annular space is connected to a discharge of the ejector through a third pipe; and the annular space is connected to the process line upstream of the pump through a fourth pipe.

2. The system according to claim 1, wherein a discharge fluid of the ejector includes a high fraction of gas-gas volume fraction (GVF) and low viscosity.

3. A system for the circulation of gas in annular spaces of rotating machines, comprising: a pump, provided with a gas-extraction unit and coupled to a rotor of a motor through a shaft, said rotor surrounded by a stator forming an annular space between the rotor and the stator; an ejector comprising a converging nozzle, which is provided with a motivating inlet and a narrowing in its outlet, said converging nozzle being connected to a discharge line of the pump through a first pipe, said ejector being further provided with a perpendicular suction inlet, said suction inlet being connected to the annular space through a second pipe, said converging nozzle and suction inlet both being interconnected to a throat where a mixture of motivation fluid and gas coming from the annular space occurs, said throat being coupled to a diffuser where the mixture of motivation fluid and gas is pressurized, wherein the gas-extraction unit of the pump is connected to the annular space through a third pipe; wherein a discharge of the ejector is connected to a process line upstream of the pump through a fourth pipe, and wherein the ejector sucks gas from the annular space through the suction inlet.

4. The system according to claim 3, wherein gas circulating through the annular space is of low viscosity.

5. The system according to claim 1, wherein it the system is used by subsea equipment, subsea pumping, subsea engines, subsea compressors or rotating machines.

6. The system according to claim 3, wherein the system is used by subsea equipment, subsea pumping, subsea engines, subsea compressors or rotating machines.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present application may be well understood from the accompanying illustrative figures, which in a schematic and non-limiting scope manner represent:

[0019] FIG. 1Ejector and its components;

[0020] FIG. 2Schematic of the high GVF fluid circulation of the discharge of the ejector through air gap (air gap); and

[0021] FIG. 3Schematic of the air gap (air gap) circulation of gas suctioned by the ejector.

DETAILED DESCRIPTION

[0022] The present application describes systems for injecting gas into the air gaps of rotating machines (air gap) (20), such systems comprise the use of a pump (32), a motor (18) and an ejector (10). The present application, by way of illustration, will describe two or more embodiments.

[0023] The present application uses an ejector (10) which is an equipment for suctioning or pressurizing fluids, as can be seen in FIG. 1, the ejector (10) comprising a converging nozzle (02) (nozzle) having a motivating inlet (22) and a narrowing (16) in its outlet, further provided with a perpendicular suction inlet (54), said converging nozzle (02) and suction inlet (54) both being interconnected to a throat (04) where the mixture of suction gas (08) and motivation fluid (48) occur, and said throat (04) being continued by or coupled to a diffuser (06), which is responsible for the pressurization of mixture of gas (08) and motivation fluid (48) and therefore conditioning the discharge fluid (12) to the required pressure. The pressurized fluid (48), at certain P.sub.m e Q.sub.m (motivation pressure and flow), is received in motivating inlet (22) of ejector (10), and when it passes through converging nozzle (02), its potential energy is converted in kinetic energy, due to narrowing (16) of area imposed by the nozzle (02), so that immediately after the nozzle (02) a low pressure zone (56) is generated. The low pressure generated causes a pressure differential between the suction inlet (54) and the throat (04), receiving fluid at certain P.sub.s e Q.sub.s (suction pressure and flow) by means suction inlet (54).

[0024] Motivation and suction flows are summed in throat (04) of ejector (10), conditioning the increase of mixture fluid speed. Downstream of throat (04), a diffuser (06) is responsible for converting speed again into pressure, and thus the pressure in discharge (58) of ejector (10) may be sized intermediate the motivation pressure and suction pressure.

[0025] The system described below encompasses two or more embodiments using an ejector (10), in order to provide separate gas recirculating through air gap (20) (air gap).

[0026] One or more embodiments of the system for injecting gas into the air gaps of rotating machines (30), represented by the schematic in FIG. 2, comprises an ejector (10) which uses as motivation fluid (48) the discharge fluid line (36) of pump (32), said ejector (10) being connected to discharge line (36) through pipe (44). In one or more embodiments, system (30) also comprises a pump (32) having in its constitution a gas-extraction unit (24) responsible for extracting from the fluid of the process line (34), the gas (08) to be used by the ejector (10). One or more embodiments of the system (30) also has a motor (18) comprising a stator (26) and a rotor (28), wherein this rotor (28) is coupled to shaft of pump (32), and wherein rotor (28) surrounded by stator (26) forms an air gap (20) (air gap).

[0027] Gas (08) which come from gas-extraction unit (24) of pump (32), is sucked by ejector (10), via suction inlet (54), the ejector (10) and gas-extraction unit (24) are connected through pipe (46). The mixture of gas (08) and motivation fluid (48) occurs in throat (04) of ejector (10) and then is pressurized by diffuser (06) and injected in air gap (20) between rotor (28) and stator (26) by means of a pipe (38).

[0028] The fluid from discharge (12) of ejector (10) contains very high GVF (gas volume fraction) content, such characteristic conditions the gas, along with some remaining fluid, to be mostly circulated by air gap (air gap) (20) through a pipe (38), and therefore, a very low viscosity fluid in air gap (air gap) (20) is obtained, which implies in minimal drag losses, to which the rotating and static surfaces may be subjected to.

[0029] Following the discharge fluid circulates through air gap (20), it is injected in process line (34) through a pipe (42) upstream of pump (32). Such configuration may be used in systems requiring a fluid be circulated with high pressure by air gap (air gap) (20), and accordingly certain liquid amount may be received and drained from air gap (air gap) (20).

[0030] One or more embodiments of the system for injecting gas into the air gaps of rotating machines (40), represented by the schematic in FIG. 3, comprises an ejector (10) which uses, as motivation fluid (48), the discharge fluid line (36) from pump (32), said ejector (10) being connected to the discharge line (36) through pipe (44). One or more embodiments of system (40) also comprises a pump (32) having in its constitution a gas-extraction unit (24) responsible for extracting fluid from process line (34), the gas (08). One or more embodiments of system (40) also has a motor (18) comprising a stator (26) and a rotor (28), wherein such rotor (28) is connected to the shaft of pump (32), and wherein rotor (28) surrounded by stator (26) forms an air gap (20) (air gap).

[0031] Said gas (08), from gas-extraction unit (24), is sucked by ejector (10), via suction inlet (54), in order to circulate in air gap (20) before being pressurized by ejector (10). The gas-extraction unit (24) is connected to the air gap (20) of motor (18) through pipe (50), and air gap (20) of motor (18) is connected to suction inlet (54) of ejector (10) through pipe (52). Ejector (10) is responsible for mixing the gas (08) coming from air gap (20) with motivation fluid (48), said mixing occurs in throat (04) of ejector (10) and afterwards it is pressurized by diffuser (06) and injected in process line (34) through pipe (38) connecting the discharge (58) of ejector (10) to said process line (34) upstream of pump (32).

[0032] In one or more embodiments of system (40), the gas (08) does not circulate with very high GVF, however when air gap (20) sucks gas (08) from gas-extraction unit (24), a very low viscosity fluid circulates in air gap. Therefore, this configuration may be used in systems where the operating pressure in air gap (air gap) (20) is approximately equal to suction pressure of pump (32).

[0033] Effects and benefits related to embodiments may include: [0034] Increase in efficiency of motor (18); [0035] Reduction of losses due to drag; [0036] The fact of dispensing a barrier fluid system, typically used to ensure the integrity and functioning of motor-hydraulic system; [0037] To decrease the operating cost of the subsea pumping/compressor system; [0038] To simplify the interface between motor (18) and surface unit by reducing barrier fluid lines; [0039] To decrease the space required on the platform to adopt subsea pumping systems; [0040] To use compact equipment without moving parts capable of mobilizing low viscosity fluid at low pressure and conditioning it for recirculation; [0041] To use a separate process fluid pressurized by a subsea equipment or device to promote recirculation of this gas through the air gap (20) between the stator (26) and rotor (28); and [0042] To use a separator gas for circulating in air gap (air gap) (20) from a separator upstream of rotating equipment or integrated with rotating equipment.