Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C32/00—Bearings not otherwise provided for
  • F16C32/06—Bearings not otherwise provided for with moving member supported by a fluid cushion formed, at least to a large extent, otherwise than by movement of the shaft, e.g. hydrostatic air-cushion bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C17/00—Sliding-contact bearings for exclusively rotary movement
  • F16C17/04—Sliding-contact bearings for exclusively rotary movement for axial load only
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/72—Sealings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C39/00—Relieving load on bearings
  • F16C39/06—Relieving load on bearings using magnetic means
  • F16C39/063—Permanent magnets

Definitions

• the present invention relates to a bearing system for the rotor in rotating machines, as disclosed in the preamble of claim 1.
• the rotor In existing rotating machines, the rotor is supported both axially and radially. This may be done using bearings which are lubricated, magnetic, gas-dynamic etc. A common feature of all these bearings is that the length of the rotor shaft increases. Complex and costly support systems are also a necessity, except in the case of gas-dynamic bearings. Gas-dynamic bearings of the foil type do not require such support systems, but their bearing strength is for the present far less than that required for rotating machines with high output or pressure.
• hydrodynamic and hydrostatic gas bearings have been proposed and to some ex- tent tested but have not achieved significant popularity.
• Typical for hydrodynamic bearings for example a foil bearing, is that their rotation generates a lift which gives bearing strength.
• hydrostatic bearings external pressurisation is carried out using specially formed recesses in the bearings. This bearing type requires separate seals.
• the main object of the present invention is therefore to provide an improved bearing system for the rotor in rotating machines, with combined bearing and sealing of the ro- tor.
• the design may be compact, allowing the rotor to be made shorter and more rigid for enhanced rotor- dynamic performance, or alternatively shorter and thinner for weight reduction, that the sealing aspect has much less importance than before, and that the costs are cut substan- tially as a result of the reliability or even the practicability of using the rotating machine in a subsea environment.
• the actual working medium in the machine may also be used during operation of the system so as to further reduce the complexity compared with known solutions.
• a gas film can be formed with rigidity and damping according to the same principle as in a radial bearing with desired dynamic rigidity and damping.
• the axial bearing can be formed according to the hydrostatic principle, which involves a flow restriction before and after the bearing surface, so as to obtain rigidity with accompanying damping.
• the axial bearing can also be formed using a combination of the two principles.
• FIGs. IA and IB show schematically the difference between a traditional rotating machine in the form of a compressor with motor-powered rotor, and the corresponding machine formed in accordance with the invention
• Fig. 2 is a schematic sectional view of the basic structure of a component incorporating combined bearing and seal which constitutes a part of the present bearing system;
• Fig. 3 shows schematically an embodiment with several of the components from Fig. 2 and a start-up/run-down accumulator;
• Fig. 4 is a further schematic view of a second embodiment with the possibility of altering the clearance geometry of the bearing system or internal pressure differences in the rotating machine;
• Fig. 5 shows schematically the same as Fig. 2, but in this case the component is made having two sets of radial hole patterns for increased damping in the bearing system by means of gas exchange;
• Fig. 6 shows schematically an embodiment of the invention with compressor and motor located in the same housing.
• the present invention will be explained in more detail in connection with rotating machines, as for example a compressor for use in subsea environments and which has a motor-powered rotor.
• rotating machines as for example a compressor for use in subsea environments and which has a motor-powered rotor.
• this should not be understood as meaning that the invention relates solely to the illustrated compressor, as it is of course suitable other rotating machine types and environments of use.
• the figures only show details which are important for the understanding of the invention.
• the traditional compressor has a motor-powered rotor, equipped with respectively a bearing system 13 and a sealing system 14 which are placed on a rotor shaft 12 at each end outside a compressor housing 11.
• these external bearing and sealing systems in the case of the present invention are replaced by at least two components 17, of which just one is shown, and which are located inside the compressor housing 15.
• the new component 17 also functions as a combination of a bearing and seal for the rotor 16, see Fig. 2.
• the compressor can be equipped with a suitable motor, see Fig. 6, which is arranged inside the compressor housing.
• Fig. 2 The principle of the combined bearing and seal 17 from Fig. IB is illustrated in greater detail in Fig. 2.
• an approximately cylindrical stator 18, i.e., the stationary part surrounding the rotor 16 is formed with a bore 19, whereby an annular clearance is formed between stator and rotor.
• the stator 18 thus constitutes a "bearing point" for the rotor 16.
• the pressure difference is used, i.e., the pressure drop across the clearance, to obtain the function as combined rotor bearing and seal.
• this is symbolised by means of P2 and Pl, that is to say the outlet pressure and the inlet pressure of the compressor, respectively.
• the annular clearance has a geometric configuration that gives sufficient rigidity and damping in the relevant fre- quency ranges, as symbolised by K and C in Fig. 2.
• the rigidity can be provided by allowing the annular clearance to converge towards the lower pressure, so that the inlet clearance is greater than the outlet clearance. Positive direct rigidity is thus obtained in the bearing.
• Positive direct damping may be provided by means of the characteristics of the surface 20 of the stator facing the rotor, e.g., by means of a honeycomb structure or other type of roughness in the surface.
• the stator 18 is, for example, mounted in a T- shaped groove (not shown) with loose fit in the compressor housing.
• Positive direct rigidity is a known concept in the field of rotor dynamics and entails the countering of radial motion of the rotor by the bearing, so that the same holds the rotor centred in the clearance for correct positioning in relation to the stator.
• Direct positive damping means that the rotor is "braked" or damped by the bearing.
• FIG. 3 an embodiment is illustrated which is an example of the use of the present invention where the bearings/seals 3, 4, 5 are of the type referred to above in connection with Fig. 2.
• internal seals 1, 2 are also arranged between each impeller.
• the last-mentioned can be configured as a converging clearance or other suit- able geometry so as to improve the rotordynamic properties if found expedient.
• the internal seals may alternatively only have a function as seals having conventional design.
• the bearings/seals require a pressure difference in order to cause the required rigidity and damping. This is a fact that must be taken into account during start-up and shut-down.
• the difference in pressure can be obtained by means of an accumulator 6 which is put in communication with the respective bearings/seals 3, 4, 5 in any suitable way.
• the accumulator is filled with gas pressurised to the outlet pressure P2 for injection into the bearings/seals 3, 4, 5.
• An alterna- tive is the mounting of special start-up and run-down bearings 7 which also additionally are shown in Fig. 3, for example, bearings of the same type as used in magnetic bearings, and which withstand contact for a brief period during start-up or run-down.
• the concept according to the invention can be implemented in a hermetic compressor, where the motor is placed in a pressurised gas atmosphere, or in a conventional, externally powered rotating machine.
• a designated shaft or axle seal 8 must then be used to seal against the atmosphere.
• Such a seal may however be made substantially smaller than normal, as the shaft diameter will only be dimensioned for transfer of necessary torque.
• the advantage of the reduced shaft diameter is that the area of use of high-pressure compressors is extended as a consequence of the fact that smaller seals withstand greater pressure.
• technical limitations on allowed seal pressure depend on seal diameter. Since when using the present invention there is no need for a separate support bearing outside the seal, the diameter can be made substantially smaller than in a conventional rotating machine.
• a control means for example, a control valve 17 which alters the pressure in a cavity between the stator and the compressor housing, or in the stator, in such manner that the pressure forces change the geometry of the bearing and seal clearance.
• the damping can be further increased with the aid of the alternative configuration of the surface of the stator 18 facing the rotor 16.
• the bore 19 in the stator 18 has a surface structure 21 consisting of an external radial hole pattern and a corresponding internal hole pattern, but so positioned relative to each other that a gas exchange can take place in the direction of the greater pressure P2.
• the motor 22 and the compressor 23 can, as shown schematically in Fig. 6, also be lo- cated in the same housing 24. This means that external sealing is advantageously not required.
• a passive permanent magnetic bearing see Fig. 2
• a passive permanent magnetic bearing can be used to support the rotor. This will reduce the load on the fluid film and increase the overall rigidity of the bearing, which is essential at start-up or shut-down.
• the passive permanent magnetic bearing is arranged integrated in the bearing and seal combination or separately next to the combination.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39033261

Family Applications (1)

Country Status (2)

Cited By (3)

Citations (1)

• 2006
  • 2006-08-08 NO NO20063588A patent/NO20063588L/no not_active Application Discontinuation
• 2007
  • 2007-08-06 WO PCT/NO2007/000279 patent/WO2008018800A1/en active Application Filing

Patent Citations (1)

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