Background

The present invention is related to the field of rotor systems. More specifically, the invention is related to a free floating rotor system for conversion between kinetic energy in a fluid flow and electric energy. The invention can be used to generate electric energy from a fluid flow or as a pump pumping fluid from an electric motor.

Downhole oil wells, power is used for various equipment. Power is often transferred by hydraulic pressure or electrical current from top side. To control downhole equipment, signals may be electrical signals or acoustic signals.

Autonomous control based upon foreseen situations planned ahead is also important. In this case, power to operate downhole equipment is still needed. Power to be used in case of loss of power from top side power can be temporarily stored e.g. in batteries. In case of emergency, need for downhole power can be crucial.

The present invention provides power downhole by utilizing part of the power flowing in the pipeline to generate electricity locally.

To the rotor being designed free floating has the advantage of not having conventional and vulnerable bearings but is supported by fluid.

The combination of the rotor of the present invention integrated with a brushless alternator or with a brushless motor makes possible alternators and pumps with less tear and wear and longevity of moving parts than alternative solutions.

Description of related art

The expression free floating rotor is a term that is used for various support mechanisms. In this invention, a free floating rotor implies that the rotor is suspended by a flow of fluid passing the rotor. The rotor in operation is not supported by a conventional bearing such as a ball bearing, roller bearing or slide bearing, but part of the flow is used for the operational support. Magnetic axial centering is a means for stabilizing the centering of the rotor of the invention further when needed. Conventional turbines for converting a flow of fluid to electric energy use a rotating turbine rotor axially connected to a conventional electric generator. The axle from the rotating turbine penetrates a wall separating the fluid from the environment and is connected to a generator located separated from the fluid. Similarly, a conventional electric pump has the mechanical parts of the pump in contact with the fluid to be pumped while the motor is located separated from the fluid and with a shaft penetrating a wall of a pipeline in which fluid is to be pumped.

US 4582255A presents an invention with a free floating rotor which is supported by liquid. A flow of liquid makes the rotor lift off from its support and openings in the rotor also makes the rotor rotate and atomizes the liquid. No electricity is involved in this invention.

Using electromagnets and/ or permanent magnets is known e.g. from maglev [Magnetic Levitation] trains. In such trains, in addition to operate as propulsion of such trains, magnets are used to levitate a train in order to prevent direct contact between the train and the rail, or rails, it is moving along. This known technique is not described in detail in the present invention. It can be used both to ensure centering and in fact also as an alternate means for converting between rotational energy and electrical energy.

Commercial magnetic bearing products from companies like Resolve

Magnetic Bearings Inc. are known for years. Such bearings use a controller to make a rotating part float in order to eliminate the need for lubrication and reduce friction, particularly in high speed applications. Passive magnetic bearings, such as

Mantelfield bearings, are also known in the art. Summary of the invention

Rotor system comprising a rotor inside a stator housing, having one inlet and one outlet for a fluid stream, the rotor being adapted to be completely surrounded by a flowing fluid, the rotor being adapted to be supported free floating in the flow of fluid surrounding and flowing past the rotor; and the rotor being integrated with a rotor of a brushless alternator; or the rotor being integrated with a rotor of a brushless motor, for conversion between kinetic power and electric power. Optionally for the rotor system, the stator housing further comprising valves adapted for directing fractions of the flow of fluid in order to stabilize the rotor.

Optionally for the rotor system, between the rotor and the housing, magnetic forces are used to stabilize the rotor.

Optionally for the rotor system, maglev techniques are adapted to be used for combined longitudinal support and for conversion between kinetic power and electric power.

Optionally for the rotor system, the rotor being integrated with the brushless alternator adapted for powering a BOP.

Optionally for the rotor system, the motor being adapted for pumping said fluid.

Optionally for the rotor system, the rotor system being adapted to be used with said fluid being electrically conductive.

Optionally for the rotor system, the rotor being adapted to be opened for including additional functional devices inside the rotor.

Brief description of the drawings

The invention is to be understood with reference to the following drawings wherein like numbers in different figures refer to like components.

Fig. 1 is an illustration of a free floating rotor system for generating electrical energy in a borehole;

Fig. 2 is a schematic diagram of a pipeline utilizing a free floating rotor system integrated with a brushless power generator as a secondary power source for a BOP (Blow Out Preventer);

Fig. 3 is an illustration of a free floating rotor system for pumping a fluid in a borehole with a brushless electrical motor.

Detailed description

Fig. 1 illustrates a preferred embodiment in which the rotor is rotated as a result of a flow of fluid passing. This embodiment is an electric generator producing electric current from a flow of fluid. When in operation, impeller blades installed on the rotor make the rotor rotate to produce power and consequently results in longitudinal pressure in the opposite direction of the fluid flow. This pressure is opposed by a fluid flow 207 outside the rotor 100.

The rotor is loosely, i.e. with an opening with wide clearance of multiple millimeters, placed inside two cylinder openings of the stator with two longitudinal ends of the rotor. This is similar to a slide bearing, but a wider clearance and without direct mechanical bearing between the rotor and the stator when operational.

When the rotor system is at rest and no flow is present, the rotor 100, comprising its connected parts, rests on a lower part of the stator 200 comprising a flow inlet 101 . When the flow of fluid commences, the rotor 100 is hovered by a flow of fluid underneath the rotor. If this commencing flow of fluid starts abruptly and possibly uncontrolled, the rotor may get stuck in the outlet of the flow outlet 1 10, bringing the flow to a halt, if flow is not present at all times on the upper part of the rotor. In order to prevent this possibility, a flow is ensured by preventing the rotor from blocking the flow of fluid. This can be done by guiding a flow of fluid 107 to the upper part of the rotor so that a sufficient pressure keeps the rotor from blocking the fluid flow outlet 1 10.

In addition to the fluid making the rotor rotate, fluid is utilized to balance the rotor comprising connected parts. Fluid can be used to balance the rotor both longitudinally and radially.

When the flow 202, 203 of fluid in a pipe is running and the rotor is

operational, flow is introduced through the flow inlet 101 . A primary part of the flow in this flow is controlled via a stream valve 410 to a blade wheel 105 for making the rotor 100 rotate. In Fig. 1 , this blade wheel is shown on an inside of the rotor 100. The blade wheel can alternatively, or in addition, be placed on an outside of the rotor.

A stream of fluid to the back of the rotor is controlled via a back stream valve

402. This valve can be important for balancing the pressure from the rotor when the rotor is used to convert kinetic power to electrical power, i.e. to function as an alternator or generator.

A stream of fluid to the front of the rotor is controlled via a front stream valve

403. This valve can be important for balancing the pressure from the rotor when the rotor is used to convert electrical power to electrical power, i.e. to function as a pump.

A controller (not presented in the drawings) controls these three valves, or more for improving control, in order to balance the pressure of the rotor in the flow of fluid opposing the pressure from the power produced by the rotor. This balancing prevents the rotor from scrubbing against the stator in a longitudinal direction.

In order to obtain axial centering of the rotating rotor, the rotor is balanced for rotational stability. The path of fluid flow is designed symmetrical for assisting self- centering of the rotor. To further stabilize the rotation, additional valves may be added (not presented in the drawings) to adjust fluid pressure at different radial positions around the rotor. A controller may be arranged to actively stabilize the rotation with these valves. Optionally, the rotor can be stabilized by comprising self- centering magnetic bearing support (not presented in the drawings). In addition to radial stabilization, magnetic levitation, also called maglev, can be used for longitudinal balancing. A controller may be arranged to actively stabilize magnetic bearing support, both radially and longitudinally.

In this embodiment, the generator is brushless in order to allow the flow of fluid to completely surround the rotor. Because a brushless generator , also called a brushless alternator, is known in the art, its operation will not be described in detail in this application. In principle, a brushless alternator comprises two sections on one shaft; the exciter and the main alternator. The exciter supplies rectified DC current to the rotating field coils of the main alternator. The rotor of the invention is arranged on this same shaft.

The power originating from a brushless generator 300, also called brushless alternator, is alternating current. This power will generally be transformed and/or rectified and adapted as required. Such transformation will not be further covered in the present document.

Fig. 2 presents an offshore oil installation utilizing the invention in a preferred embodiment. Reference 600 represents a so called BOP or Blow Out Preventer valve. This valve is used as part of a security system to prevent a blowout in an emergency situation in an oil well and can be electrically operated. If the primary electrical power source for operating downhole installations is disturbed in such an emergency situation, secondary electrical power is available from a free floating rotor integrated with a brushless generator 300 according to the present invention. A parallel pipeline segment 520 as indicated in the drawing is used for diverting a fraction of the fluid in the main pipeline 510 and kinetic power from this fraction is utilized to generate electric power that may be used for operating the BOP valve. The operation of the BOP valve is initiated either by autonomous downhole detection of an emergency situation; by acoustic signals from topside; by wireline or otherwise known in the art. The power conductor from the brushless generator 300 to the BOP 600 is indicated with 610.

In order to further increase the reliability of the support of electrical power to the BOP 600, more than one brushless generator 300 can be arranged as backup or to be controlled in parallel in order to supply power for the BOP 600. Known in public art is how to arrange and select alternative supplies of power for increasing reliability and will not be further described here.

Another preferred embodiment of the present invention will now be presented.

A rotor of the invention is arranged on a shaft. This rotor will act as a pump in a pipeline for fluid. A rotor of a brushless motor is arranged on this same shaft and the fluid will flow completely over the free floating rotor of the invention and the rotor of the brushless motor when operating. Brushless motors are widely used in high quality equipment because of longevity, little tear and wear and low maintenance requirements for such motors.

Yet another preferred embodiment of the present invention is revealed by designing the rotor 100 to be easily opened in order to replace the blade wheel or for adding devices for different additional functions. Such devices may depend upon complementing devices outside the rotor. Such functions include:

heating of the fluid flow by designed electromagnetic loss in the rotor;

heating of the fluid flow by designed mechanical losses in the rotor;

analyzing the fluid flow by comprising instruments for analyzing inside the rotor and collect its required electrical power by converting kinetic power to electrical power.

Communication with the rotor system for operating such services can be performed e.g. by modulated signals in the electromagnetic circuits present, by acoustics or otherwise. Infornnation can also be stored locally in the rotor for later inspection.

One of the advantages of the present invention is that it comprises no part in need for regular service or change due to wear and tear. It also comprises no moving parts penetrating the shell of a pipeline.

The present invention can advantageously be used for a wide range of alternators, generators and pumps involving a conversion between kinetic power and electrical power and also to operate devices inside the pipeline.

In the present document the term alternator is to signify the same as generator.

The following references are used in the present document:

100 Rotor

101 Flow inlet

105 Blade wheel

1 10 Flow outlet

200 Stator

202 Back stream

203 Front stream

300 Brushless generator

301 Rotor of brushless generator

302 Stator of brushless generator

350 Brushless motor

351 Rotor of brushless motor

352 Stator of brushless motor

402 Back stream valve

403 Front stream valve

410 Flow valve

510 Pipe

520 Pipe branch

600 BOP (Blow Out Preventer)

610 Power conductor