BRPI1015154B1 - hydraulic power unit for use in remotely operated underwater vehicle and cooling method of hydraulic power unit - Google Patents

Abstract

HYDRAULIC POWER UNIT FOR SUBMARINE USE, REMOTE OPERATED UNDERWATER VEHICLE, AND HYDRAULIC POWER UNIT COATING METHOD. The present invention relates to a hydraulic power unit for underwater use comprising a housing (16) containing a fluid, an electric motor (10) mounted in the housing, a distribution pump (17), a heat exchange unit ( 20) provided outside the housing and at least one distribution conduit (32) in fluid communication with the heat exchange unit and the housing.

Description

[0001] The present invention relates to a power unit and more specifically, a power unit for subsea use. The power unit may be a hydraulic power unit, a high pressure water pump, or a task specific tool unit suitable for use in a Remote Operated Submarine Vehicle (ROV).

[0002] ROVs are commonly used to perform many offshore subsea tasks. In order to perform a variety of tasks such as inspecting, repairing or installing new equipment, the ROV will usually have work lights and a camera to assist in controlling the ROV by an operator on the surface, and a manipulator with which to perform the task .

[0003] In an ROV, a Hydraulic Power Unit (HPU) is commonly used to drive thrusters and other hydraulically operated vehicle subsystems such as pan and tilt mechanisms for cameras, and hydraulically operated tools to allow the ROV perform the tasks of intervention in the subsea infrastructure. The thrusters are the main components of the main moving system used to maneuver the ROV in and around an underwater location as necessary to carry out its designated tasks. The HPU typically consists of an electric motor coupled to a hydraulic pump unit. The engine casing is most commonly filled with oil and it is maintained at a pressure approximately one bar above ambient sea pressure in order to provide a balance between internal and external pressure when the ROV is submerged. This avoids the need for a pressure-proof wrap and sophisticated shaft seals, as would be the case with a standard wrap filled with air at atmospheric pressure as the pressure through the wrap walls is balanced so that, consequently, the wrap it only needs to be designed to provide mechanical loads associated with engine operation and assembly. It also allows the HPU to be used if necessary for operations in the total ocean depth of many thousands of meters without any further modification. The pressure differential ensures that any leakage between the wrap and sea water moves from the wrap to sea water, ensuring that sea water does not enter the engine wrap.

[0004] The mechanism for keeping the oil in the wrapper at or above the ambient pressure of the surrounding seawater is typically illustrated in the industry as a compensator. Known compensators can typically comprise a spring loaded or diaphragm-bearing diaphragm to maintain the oil in the wrap at a required pressure.

[0005] Such engines are commonly supplied with a normal use / task classification. This classification specifies the limits between which the engine must be used in order to prevent overload and subsequent damage to the engine.

[0006] Three of the critical parameters for a competitive ROV system are the size and weight of the ROV and the diameter of the umbilical that connects the ROV to a vessel on the surface, everything that needs to be kept to a minimum in order to reduce its effect launch and recovery system and ROV maneuverability.

[0007] An ROV with a lower weight than air can use a launch and recovery system with a lower power rating and minimizes the deck space required on the launch vessel. In addition, for every pound of weight added to an ROV, approximately 2 pounds of fluctuation must be added to the ROV to maintain neutral fluctuation when submerged. A smaller ROV also has greater maneuverability when working in restricted undersea locations.

[0008] Reducing the umbilical diameter reduces dredging caused by underwater currents resulting in greater ROV maneuverability. Reducing the diameter of the umbilical also results in a smaller, lighter umbilical winch requiring less deck space and a smaller support structure.

[0009] The modalities of the present invention allow increased performance and an available power output from existing engines, such as those used in an ROV without increasing the size of the engine. Alternatively, the size and weight of a replacement engine can be reduced while maintaining the same level of power output.

[00010] In accordance with a first aspect of the present invention, a hydraulic power unit for subsea use is provided comprising a housing containing a fluid, an electric motor mounted on the housing, a distribution pump, an externally supplied heat exchange unit with respect to the housing and at least one distribution conduit in fluid communication with the heat exchange unit and the housing.

[00011] The modalities of the present invention allow an electric motor with a power rating twice that of a standard motor and four times the rating of an air-cooled motor. The weight and size of the new engines are significantly less than those of a standard engine, while allowing significant gains in performance.

[00012] Optionally, the power unit is a Hydraulic Power Unit (HPU), suitable for use in a Remote Operated Submarine Vehicle (ROV). Improving the efficiency of an HPU has the advantage of increasing the payload of the ROV. Alternatively, since the size of the power unit required for a given ROV can be reduced, the weight of the ROV can also be reduced.

[00013] The weight savings according to an embodiment of the invention can be 300 kg. Reducing the size of the power unit and increasing efficiency helps to maximize the power density of the Hydraulic Power Unit (HPU). The power density of an HPU, according to the prior art, is typically in the range of 0.30 kW / kg to 0.25 kW / kg. The power density of an HPU according to the present invention is typically 0.45 kW / kg to 0.35 kW / kg. These numbers refer to the complete HPU comprising the engine and the pump unit.

[00014] Optionally, the electric motor comprises a rotor and a stator including stator coils that pass through the stator core and extend beyond its end faces.

[00015] Optionally, the electric motor is a standard submerged motor. Optionally, at least one distribution duct extends radially around at least one of the four stator coils. Typically, two distribution ducts are provided surrounding each end of the stator.

[00016] Typically, the at least one distribution conduit comprises a nozzle ring. The nozzle ring can be U-shaped in cross section with two straight flanges forming an annular chamber with the inner surface of the motor housing or housing, hereinafter referred to as the motor housing. The port or ports on the nozzle ring provide fluid communication between the chamber and the interior of the engine casing.

[00017] Typically, the distribution duct is arranged in an inner wall of the motor casing. Optionally, the sealing devices seal a matching surface between the straight flanges and the inner wall of the motor casing.

[00018] Advantageously, the doors are spaced circumferentially around the duct. Typically, the ports direct the fluid radially inward towards the stator coils. Typically, the doors are cylindrical. Optionally, the doors are tapered.

[00019] According to an embodiment of the invention, nozzle rings are advantageous since the homogeneous distribution of fluid achieved by spraying fluid from the ring nozzles simultaneously around the target being cooled reduces the occurrence of hot spots developed in the stator coils while the motor is in use.

[00020] Optionally, the heat exchange unit is located outside the wrap. Typically, a tube of the heat exchange unit has a serpentine shape. Typically, the pump circulates the fluid between the engine casing, the heat exchange unit and the annular chamber of the at least one distribution duct. Advantageously, the fluid is also a refrigerant or a heat transfer fluid, the fluid being able to transfer heat produced by at least one motor rotor bar and / or iron losses to the rotor core, shaft, stator and winding coils. stator, for a heat exchange unit.

[00021] Optionally, the fluid can be water, ethylene glycol, hydrochlorofluorocarbon (HCFC) or other refrigerant provided that suitable types of support are used and the winding insulation system is compatible.

[00022] Advantageously, the fluid is liquid at room temperature and can be oil. If the fluid is oil, it can be at least one of transformer oil, mineral oil, silicone oil, or synthetic oil with electrical insulating properties. Transformer oil is highly refined and contains few additives providing it with the ability to absorb a quantity of water while maintaining an acceptable dielectric strength. Hydraulic type oil is not suitable due to the additives it may contain. At higher operating temperatures some of the additives, for example, zinc, are deposited on warmer internal surfaces such as windings and this compromises the insulation properties resulting in premature insulation failure.

[00023] In specific embodiments of the present invention the fluid can have a viscosity in the range of 10cSt to 40 cSt at 20 C. This ensures adequate lubrication of the shaft supports and acceptable winding losses of the motor. Preferably, the viscosity is in the range of 10 cST to 15 cSt at 20 C.

[00024] Advantageously, the circulation pump used to circulate the fluid is mounted on the motor shaft. Advantageously, the circulation pump is located inside the casing, avoiding the need for pump shaft seals and, thereby, reducing the risk of the circulation fluid becoming contaminated with foreign fluids or solids from outside the casing.

[00025] Optionally, the delivery pump is a centrifugal pump. Optionally, the fins can be provided on the outer surface of the wrap. Increasing the effective surface area of the wrap and thereby providing additional cooling of the fluid within the wrap.

[00026] The Hydraulic Power Unit (HPU) can drive the hydraulic thrusters used to maneuver a Remote Operated Vehicle (ROV) in and around an undersea location as necessary to perform its designated tasks. Typically, the ROV has two or more vertical and / or horizontal thrusters.

[00027] Optionally, the ROV has one or more manipulation or cutting arms, an element for carrying out water samples, light and temperature sensors.

[00028] Optionally, the power unit can comprise at least two pumps. In a preferred option, the power unit comprises two pumps mounted in the housing.

[00029] Conveniently, each pump can be adapted to pump fluid along an associated circuit between the housing and the heat exchange unit.

[00030] Independent heat exchange units and / or distribution ducts can be associated with each pump.

[00031] In accordance with a second aspect of the present invention, a method of cooling an electric power unit for use in a Remote Operated Submarine Vehicle is provided, the method comprising the steps of: a) circulating fluid within a housing; b) transfer heat from one or more of the motor rotors, stators and one or more stator coils from an engine mounted in the housing to the fluid; c) circulating the fluid through a heat exchange unit provided externally with respect to the housing to cool the fluid by loss of heat to the surrounding water; d) pass the cooled fluid through a distribution duct inside the housing.

[00032] In some embodiments of the present invention, the distribution duct has at least one distribution port.

[00033] The engine can be part of a Hydraulic Power Unit (HPU) of a Remotely Operated Vehicle (ROV). Typically, the cooled fluid is directed from at least one distribution port to the engine parts within the engine casing.

[00034] Currently, the classification of an engine used in an ROV is based on underwater use where cooling is provided only by the surrounding water. The heat produced by the engine is dissipated through the engine casing into the water where the ROV is operating. The movement of the oil inside the engine casing is based on convection currents. Oil circulation is therefore limited and hot spots can be developed.

[00035] In some embodiments of the present invention, method steps (a), (c) and (d) can be achieved with the use of a pump. Optionally, the pump is a centrifugal pump.

[00036] In an embodiment of the present invention the step of method (c) can include fluid circulation through a heat exchange unit located outside the motor casing.

[00037] In some embodiments of the present invention the distribution conduit of method step (d) can be a nozzle ring.

[00038] The modalities of the present invention will now be described by way of example only and with reference to and as illustrated in the attached drawings, in which:

[00039] Figure 1 is a sectional view of a hydraulic power unit in accordance with an aspect of the present invention;

[00040] Figure 2 is a cross-sectional view of one end of the stator of the hydraulic power unit of Figure 1; and

[00041] Figure 3 is a sectional view of an alternative hydraulic power unit according to another aspect of the present invention.

[00042] Figure 1 illustrates an illustrative embodiment of a hydraulic power unit for subsea use comprising an electric motor 10 and a pump 17 used to move oil 15 around the inside of an engine casing 16. When in use, the motor 10 generates heat which is transferred to oil 15 in contact with motor 10 inside the casing 16. Oil 15 is cooled by passing it through a heat exchange unit 20.

[00043] The particular embodiment described here comprises an electric rotor 10 within a peripheral motor casing 16, within which a cylindrical shaped rotor 11 is mounted. The annular stator 12 surrounds the rotor 11 within the motor casing 16. The annular stator 12 has ends 14 that extend beyond the ends of the rotor 11, in the direction of the casing 16.

[00044] Wrap 16 is filled with oil 15, although it is noted that other fluids can be used, for example, transformer oil, mineral oil, silicone oil or synthetic oils with electrical insulating properties.

[00045] In the illustrated embodiment, the rotor 11 is mounted centrally within the casing 16. An axis 25 extends from the center of the rotor 11 into a hydraulic pump 13 which is mounted at the end of or adjacent to the motor casing 16 The other end of the shaft 25 is mounted on an annular support 33 on a wall of the casing 16. Leaning on the support 33 on the inner wall of the motor casing 16 is a propeller 17 of a centrifugal pump 27. The axis 25 passes through the center of the propellant 17. Those skilled in the art will realize that the centrifugal pump 27, according to this embodiment of the present invention, can be another type of rotodynamic pump, positive displacement pump or any other device for moving fluids. The shaft 25 is supported at one end of the casing by a central protrusion 26 within the end plate 34 and brackets 33 on the wall of the casing 16. The end plate 34 forms a pump chamber 28 where the impeller 17 is mounted. Positioned radially outside the central projection 26 are ports 36 allowing oil 15 to move from the engine chamber 37 to the pump chamber 28. The two outlet ports 18 positioned above and below the chamber 28 allow fluid communication between the chamber 28 and two ducts 29 outside the casing 16. The two ducts 29 that extend from the outlet ports 18, converge into a tube 19. The tube 19 is in fluid communication with an exchange unit of heat 20.

[00046] The heat exchange unit 20 is a continuous coil length of pipe. The particular embodiment described here relates to a tubular heat exchange unit 20. Those skilled in the art will realize that the heat exchange unit 20 can be a plate, wrap, adiabatic, phase change or other type of device for the transfer efficient heat from one medium or fluid to another.

[00047] The other end of the heat exchange unit 20 is in fluid communication with the tube 27 which is also in fluid communication with the fluid bypass element 35, from which two ducts 30 extend. The inlet ports 31 are provided in wrapper 16, for correction for ducts 30.

[00048] Within the motor casing 16, two distribution channels 32 are located, each distribution channel 32 encompassing the ends 14 of the stator 12. The distribution channels 32 are U-shaped in cross section. Two straight flanges 32 extend from each distribution duct 32 and join the seals 38 to the inner surface of the casing 16, forming annular chambers 21. Each chamber 21 is in fluid communication with a duct 30, through an inlet port 31. Each distribution duct 32 forms a chamber 21 and has three circumferential rows of radial openings 22, between the two flanges 23. Those skilled in the art will realize that any number of openings can be used. The openings 22 provide fluid communication between the chamber 21 and the interior of the casing 16, near the ends 14 of the stator 12. The distribution ducts 32 illustrated in figure 1 are nozzle rings with openings or distribution ports 22, cylindrical in shape. . In an alternative embodiment, the openings 22 are conical in shape. Any number of openings or doors 22 is suitable. The outer surface of the wrapper 16 is covered with fins 24 which increase the surface area of the wrapper 16 and thereby provide improved cooling.

[00049] In use, the circular movement of shaft 25 is used to energize the centrifugal pump 27. The oil 15 is moved around the motor casing 16 by the centrifugal pump 17, during which time it is heated through contact with the rotor 11 and the stator 12 of the motor 10.

[00050] The oil 15 comes into contact with the pump propellant 17 adjacent to the axis 25 and is accelerated by the rotary propeller 17 into the pump chamber 28. The oil 15 is then forced through outlet ports 18 in the casing 16 and into two ducts 29. The oil 15 is then pumped along the pipe 19 and through the coils of a heat exchange unit 20. As oil 15 passes along the pipes of the heat exchange unit 20 at temperature of the oil 15 is reduced by the heat transfer of the oil 15, through the walls of the heat exchanger 20 and into the surrounding relatively cold water (not shown). The oil 15 cools as it passes along the tortuous path of the tube in the heat exchange unit 20.

[00051] Once the oil 15 exits the end of the coils of the heat exchange unit 20, it moves along a tube 27 before being divided between two ducts 30. The cooled oil 15 then passes through the inlet ports 31 into the chambers 21 of the nozzle rings 32. The oil 15 in the chambers 21 is then pumped through the openings 22 and sprayed into the casing.

[00052] The oil 15 coming out of the openings 22 is distributed evenly through both ends 14 of the stator 12. After contact with the ends 14, the oil 15 is able to circulate within the casing 16, and in particular to flow along the length of the stator coils 14, before being thrown back into the pump chamber 28 for recirculation and cooling.

[00053] In use, oil 15 helps to cool engine 10 components, allowing engine 10 to continue to run without damage with loads much larger than those determined by its normal rating.

[00054] Figure 2 shows a cross-sectional view of an end 14 of stator 12. The partitions of stator 41 in stator 12, receive the coils of stator 40.

[00055] Figure 3 illustrates an illustrative embodiment of a hydraulic power unit 10 comprising all the characteristics illustrated in figure 1 with the following differences. Ports 18 provide fluid communication between pump chamber 28 and circulation chamber 43. An outlet port 44 provides fluid communication between circulation chamber 43 and duct 19 outside the casing 16. Tube 19 is in fluid communication with the heat exchange unit 20.

[00056] In use, oil 16 enters pump chamber 28 and is then forced through outlet ports 18 into casing 16 and into circulation chamber 43. Oil 15 then exits circulation chamber 43 through port 44 into the tube 19 and through the coils of the heat exchange unit 20.

[00057] Modifications and improvements can be made to the above without departing from the scope of the invention as defined by the claims. In the above embodiments, the hydraulic power unit is described as comprising an electric motor 10, and a pump 17. It is envisaged that in one embodiment of the present invention a second pump can be provided within the hydraulic power unit. Each pump can be controlled independently and can also be adapted to pump the fluid into the heat exchange unit, through the same distribution duct and back to the housing. Alternatively, each pump can be adapted to pump fluid around an independent circuit from the housing to the same or other independent heat exchange units through the same distribution ducts or other independent and back to the housing.

[00058] By increasing the fluid flow within the hydraulic power unit, the power output can be increased without increasing the operating pressure. Available components are inexpensive to operate at pressures up to about 300 bar. Above this rating, the components tend to be more specialized and therefore more expensive. Therefore, by incorporating a second pump and increasing the effective flow rate through the hydraulic power unit, while operating at a pressure rating in line with available components such as around 250 bar, this allows more tools operated simultaneously and also results in a reduced utilization factor for individual components which extends their reliability and service life.

[00059] Such an additional pump can be mounted adjacent to the first, with a consequent increase in the length of the rotor shaft to accommodate the pump or, alternatively, the hydraulic power unit housing can be extended on the opposite side from the first pump to provide a seat for a second pump inside the housing.

Claims (11)

1. Hydraulic power unit for use in a remotely operated underwater vehicle characterized by the fact that it comprises: a housing (16) containing a fluid in a cooling circuit independent of a hydraulic power circuit; a pressure compensator; an electric motor (10) mounted in the housing (16), wherein the electric motor (10) comprises a rotor (11) and a stator (12), the stator (12) including one or more stator coils; a distribution pump (17) driven by the electric motor (10); a heat exchange unit (20) provided outside the housing (16) adapted to lose heat in the surrounding sea water; and at least one distribution duct (32) in fluid communication with the heat exchange unit (20) and the housing (16), in which the hydraulic power unit is adapted for the distribution pump (17) for circulating the fluid around the cooling circuit comprising the housing (16), the heat exchange unit (20) and at least one distribution duct (32); and wherein the distribution circuit is arranged to direct cooling fluid from the distribution circuit over one or more of the rotor (11), the stator (12) and the stator coils. 2. Hydraulic power unit according to claim 1, characterized in that the at least one distribution channel (32) comprises a nozzle ring. 3. Hydraulic power unit, according to claim 1 or 2, characterized by the fact that the distribution duct (32) extends radially around one or more of the motor rotor (11), the stator (12 ) and one or more stator coils. Hydraulic power unit according to any one of claims 1 to 3, characterized by the fact that the distribution duct (32) is arranged on a linear wall of the housing (16). 5. Hydraulic power unit according to any one of claims 1 to 4, characterized by the fact that the power unit is a hydraulic power unit with an energy density between 0.45kW / kg and 0.35 kW / kg. Hydraulic power unit according to any one of claims 1 to 5, characterized by the fact that the fluid is any one or more of a refrigerant and a heat transfer fluid. Hydraulic power unit according to any one of claims 1 to 6, characterized in that it comprises at least two pumps. 8. Hydraulic power unit according to claim 7, characterized by the fact that each pump is adapted to pump fluid along an associated circuit between the housing (16) and the heat exchange unit (20). 9. Method of cooling a hydraulic power unit as defined in any of claims 1 to 8, for use in a pressure-compensated remotely operated underwater vehicle, characterized by the fact that it comprises the steps of: circulating fluid in a circuit cooling system independent of a hydraulic power circuit, where the cooling circuit is provided to transfer heat from one or more of a motor rotor (11), a stator (12) and one or more stator coils from one motor mounted in a housing (16), the method further comprising circulating the fluid through the following steps: (a) passing the fluid through a heat exchange unit (20) provided externally from the housing (16) to cool the fluid through the loss of heat to the surrounding water; (b) passing the cooled fluid through a distribution duct (32) inside the housing (16), where the cooled fluid is directed from the distribution duct (32) over one or more of the rotor (11) of the motor, stator (12), and stator coils; and (c) transferring heat from one or more of a motor rotor (11), a stator (12) and one or more stator coils from a motor mounted in the housing (16) to the fluid. 10. Method according to claim 9, characterized by the fact that steps (a) and (b) are achieved using a pump. 11. Method according to claim 9 or 10, characterized by the fact that the cooled fluid is sprayed on one or more of the motor rotor (11), the stator (12) and the stator coils

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