RU2453698C2 - Downhole generator - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: proposed generator comprises protective casing, connector assembly, at least one attachment assembly, rotor with hydraulic turbine and permanent magnets, and excitation winding. Said excitation winding is fixed inside said protective casing. Disk is attached to rotor. Tight inducting baffle is arranged between permanent magnets and excitation winding. Said baffle comprises inducting parts. Note here that generator comprises, at least, one compensator of pressure and thermal expansion with compensation piston. Piston is sealed relative to protective casing. Note also that chamber under compensation piston communicates via openings with chamber accommodating rotor while chamber above compensation piston communicates via holes with ambient medium. Note that compensation piston is spring loaded toward the side opposite hydraulic turbine to create surplus pressure in chamber accommodating rotor.

EFFECT: simplified design, higher reliability and power output, smaller sizes.

5 cl, 2 dwg

Description

The invention relates to electric machines. Specifically, the invention is intended for a generator installed in a well and intended, for example, to power a downhole tool. The generator converts the energy of the flushing fluid into electrical energy, which is necessary to power the downhole navigation and geophysical instruments during drilling and the transmitter of the electromagnetic communication channel. For the telemetry system to work at great depths, an increase in the power of the transmitting device to 1 kW or more is required. To get more power with the small dimensions of the generator is very problematic.

A self-contained turbine unit (electric generator), also designed to power the telemetry system, contains a hydraulic turbine driven by a wash fluid stream, an oil-filled stator filled with an epoxy compound, and a rotor of an alternating current generator with permanent magnets located on the same shaft with a hydraulic turbine. (Molchanov A.A., Siraev A.X. Borehole autonomous systems with magnetic recording. M., Nedra, 1979, pp. 102-103).

This generator consists of a stator located inside the unit and a six-pole annular magnetic rotor made from the outside. The rotor is also a casing for the working blades of a three-stage hydraulic turbine. In front of each stage of the working blades of the hydraulic turbine, in turn, there are three stages of guide vanes assembled on the outer casing, which increases the diameter of the device. To prevent the flushing fluid from entering the generator and the bearing units, sealing devices are installed, the internal cavity of the generator is filled with transformer oil.

Due to the fact that the generator operates in the temperature range from -40 to + 130 ° C, at drilling depths of up to 3500 m or more, and the oil volume changes with temperature, a compensator for pressure and thermal expansion of the lubricating fluid (oil) is introduced. The compensator for pressure and thermal expansion of the lubricating fluid is made inside the inlet fairing of the generator. It consists of two thin profile plates, one of which is convex and the other is concave. The compensator for pressure and thermal expansion of the lubricating fluid is designed to compensate for changes in the volume of oil in the oil-filled cavity of the generator under operating conditions with increasing temperature, as well as equalizing the pressure inside and outside the generator.

The disadvantages of this generator are low reliability, small resource, large dimensions and weight of the device, the complexity of the design.

These shortcomings are due primarily to the fact that a multistage turbine with guide vanes is used as a drive. The use of a hydraulic turbine with guiding devices as a drive places high demands on the quality of cleaning the washing liquid from fractions of drill cuttings and foreign objects, the ingress of which into the gap between the working and guide vanes of the hydraulic turbine can lead to its stop (jamming). The presence of guiding devices of a hydraulic turbine increases the diametrical dimension of the electric generator, which is undesirable when drilling wells of relatively small diameter.

The second design flaw is the complexity and unreliability of the pressure compensator and thermal expansion of the lubricating fluid. Due to the elasticity of the walls of the compensator, the pressure of the lubricating fluid is always less than the pressure of the environment. This can result in flushing fluid entering the generator’s lubrication system and in the wear of bearings, seals and other parts.

Known electric generator according to the patent of the Russian Federation No. 2331149, prototype. This electric generator contains a protective housing, at least one attachment point, a rotor with a hydraulic turbine and a device for converting mechanical energy into electrical energy.

The disadvantages of the generator are the unreliability and complexity of the design, due to the low reliability of the field windings, and low reliability, due to adverse operating conditions of the field coil.

The tasks of its creation are to simplify the design, increase power while reducing the diametrical dimensions and weight of the generator.

The solution to this problem was achieved in a downhole generator containing a protective housing, an electrical connector, at least one attachment point, a rotor with a hydraulic turbine and permanent magnets and an excitation winding, motionlessly installed in the inner cavity of the protective housing, so that according to the invention between the permanent magnets and the field winding is sealed magnetically permeable partition. A disc is attached to the rotor. Permanent magnets can be mounted on the end of the disk, and the magnetically permeable partition is made radial. Permanent magnets can be mounted on the cylindrical surface of the disk, and the magnesium-permeable partition is made cylindrical. The magnetically permeable partition may comprise magnetically permeable parts. At the upper end of the rotor, a hole can be made for filling the lubricant into the rotor cavity. The generator may contain at least one compensator for pressure and thermal expansion, communicating with the cavity of the leading coupling half. The field winding and the electrical connector can be connected by wires passing through holes made in a protective housing and filled with a compound.

The invention is illustrated in FIG. 1 and 2, where Fig. 1 shows a first embodiment of a generator, Fig. 2 shows a second embodiment of a generator,

The downhole generator (FIGS. 1 and 2) is installed in the drill pipe string or in the casing (not shown in FIGS. 1 and 2) and contains a protective housing 1 and at least one fastening device 2. In the fastening device 2, the electric generators are made holes 3 for the passage of drilling fluid.

The generator contains a rotor 4 with a turbine 5. The turbine 5 has obliquely mounted flat blades mounted at an angle of 20 ... 60 ° to the axis.

The protective housing 1 has an electrical connector 6 at the bottom, to which high-voltage wires 7 are connected, connecting the electrical connector 6 to the field winding (s) 8. Field coil 8 is fixedly mounted in the internal sealed cavity 9 of the protective housing 1. The generator contains permanent magnets 10, in a certain way connected with the rotor 4, and a sealed magnetically permeable partition 11 between the field winding 8 and the permanent magnets 10. The magnetically permeable partition 11 may have magnetically permeable hours and 12 and generally made of solid steel. The rotor 4 is mounted on bearings 13 and 14. The bearing 13 on the side of the hydraulic turbine is protected by a seal 15 to prevent leakage of the lubricating fluid from the cavity 16 in which the rotor 4 is located and which cannot be made absolutely airtight. The installation of the bearing 14 in the downhole generator is not necessary with good balancing of the rotor 4 and the hydraulic turbine 5.

To fill the cavity 16 with lubricating fluid, an axial hole 17 is provided, made in the rotor 4, in its upper part, and plugged with a screw 18.

To compensate for the flow of lubricating fluid, thermal expansions and variable pressure in the well, at least one compensator for pressure and thermal expansion 19 (FIGS. 2 and 3) must be provided in front of the protective housing 1 of the generator (FIG. 2). It is most advisable to make 2 ... 8 pressure compensators and thermal expansion 19 of small dimensions and place them inside the protective housing 1 from the side of the turbine 5, since only the cavity 16 needs compensation, and the internal cavity 9 is sealed and can be filled with an inert gas or non-conductive compensatory fluid, or compound, and does not need compensation, provided that the walls of the protective housing 1 are of sufficient thickness to counter hydrostatic pressure in the well 600 ... 100 0 atm.

Each compensator for pressure and thermal expansion 19 contains a compensation piston 20 mounted and sealed relative to the protective housing 1. The cavity 21 under the compensation piston 20 has a hole (s) 22 connected to the cavity 16, and the cavity 23 above the compensation piston 20 is connected with a hole (s) 24 s environment to compensate for pressure changes and thermal expansion of the lubricant. The compensation piston 20 is spring-loaded by a spring 25 in the direction opposite to the hydraulic turbine 5 to create excess pressure in the cavity 16. This will prevent the drilling fluid containing abrasive particles from entering the cavity 16.

A disk 26 is attached to the rotor 4, at the end of which permanent magnets 10 are radially mounted. The magnetically permeable partition 11 is made radial (Fig. 1).

A generator embodiment is possible (FIG. 2), in which a cylindrical part 26 is mounted on the disk 16, on which permanent magnets 10 are mounted. The magnetically permeable partition 11 is cylindrical and connected to the inner end 27 of the protective housing 1 and the inner partition 28 to form an inner sealed cavity 9. On the side surface of the protective housing 1, a drainage hole 29 is made, closed by a plug 30, designed to release air when filling the cavity 16 with a lubricating fluid. For the conclusion of the wires 7, holes 31 are designed, filled with a compound after mounting the wires 7, this also contributes to the complete sealing of the internal sealed cavity 9, in which the excitation winding (s) 8 is located.

During the operation of the generator (Figs. 1 and 2), the drilling fluid passes through a hydraulic turbine 5, which begins to rotate with the rotor 4 and the disk 26. The magnetic flux passes through the magnetically permeable baffle 11 (or its magnetically permeable parts 12) and excites an electric current in the field coil 8. The resulting voltage through wires 7 is transmitted to the electrical connector 6.

When the volume of the lubricating fluid in the cavity 16 is changed for any reason, the compensation piston 20 is moved accordingly. As a result, the pressure within the cavity 16 is always maintained at 2 ... 5 atm more than the ambient pressure. This prevents the penetration of abrasive particles contained in the drilling fluid inside the cavity 16. If several pressure compensators and thermal expansion 19 are used, then one of the holes 22 (or several holes 22, if 4 ... 8 pressure compensators and thermal expansion 19 is used) are used pressure compensators and thermal expansion 19 will perform their function, even when only one of them. This significantly increases the reliability of the generator and its resource.

The application of the invention allowed:

1. Simplify the design of the generator and increase its reliability through the use of fixed field windings and their placement in a completely sealed cavity.

2. Significantly increase the service life of bearings by reducing the diameter of the rotor to the minimum possible.

3. To reduce the imbalance of the rotor of the generator by reducing its diameter and length. Only a turbine and a disk are fixed to the rotor.

4. Simplify the design of the generator.

5. To reduce the axial dimensions of the generator, especially with a radial arrangement of permanent magnets at the end of the disk (figure 1).

6. Improve maintainability of the generator by performing excitation windings non-separable and filling the cavity in which they are installed with an inert gas or non-conductive liquid, or compound.

Claims (5)

1. A downhole generator comprising a protective housing, an electrical connector, at least one attachment point, a rotor with a hydraulic turbine and permanent magnets, and an excitation winding fixedly installed in the inner cavity of the protective housing, characterized in that a tight seal is made between the permanent magnets and the excitation winding magnetically permeable baffle, a disk is attached to the rotor, and the magnetically permeable baffle contains magnetically permeable parts, while the generator contains at least one pressure compensator I and thermal expansion, having a compensation piston mounted and sealed relative to the protective housing, the cavity under the compensation piston openings connected to the cavity in which the rotor is located, and the cavity above the compensation piston connected openings to the environment, while the compensation piston is spring-loaded sideways opposite from the turbine to create excess pressure in the cavity in which the rotor is placed. 2. The generator according to claim 1, characterized in that the permanent magnets are mounted on the end of the disk, and the magnetically permeable partition is made radial. 3. The generator according to claim 1, characterized in that the permanent magnets are mounted on the cylindrical surface of the disk, and the magnesium-permeable partition is cylindrical. 4. The generator according to claim 1 or 2, characterized in that at the upper end of the rotor a hole is made for filling the lubricating fluid into the rotor cavity. 5. The generator according to claim 1 or 2, characterized in that the field winding and the electrical connector are connected by wires passing through openings made in a protective housing and filled with a compound.

Images