The present invention, consists of an original combination of hydrodynamic and active electromagnetic bearing, named here as "hybrid journal bearing". This hybrid bearing could be used as one of the main components in the rotating machinery applications.

State of the art

Journal bearings are components which are used to carrying loads created during shaft rotation.

The invention that we describe here is related with oil lubricated hydrodynamic journal bearings and with active magnetic bearings.

In hydrodynamic journal bearings, a lubricant is used, in order to create hydrodynamic lubrication and to separate the rotating shaft from the bearing pads. The active magnetic bearings consist of electromagnets in the circumference, in radial (actinic) form round the rotating shaft, in order to retain the shaft in a desired position, using an appropriate controller unit and the shaft does not touch the journal during its movement.

Both the hydrodynamic and the active magnetic bearings present advantages and disadvantages concerning their design and operation.

Regarding the hydrodynamic journal bearings the major advantages are the below: · the design of the bearing and exterior shell is very simple,

• the radial clearance required for the operation is very small,

• the manufacturing cost is relatively small,

• the operation produces low levels of noise,

• their load carrying capacity can be of very high level,

• they can withstand impact loads, and

• they operate reliably in high, intermediate and low angular velocities. Disadvantages of the hydrodynamic journal bearings could be

• the wear of shaft and bearing materials produced by the contact between them through the lubricant,

• the high friction coefficients corresponding to extreme operation of machine. High friction results in high cost of maintenance activities and replacement parts and the use of very durable and hard materials is required for manufacturing the rotor - bearing system and the bearings. The use of high cost systems of damage diagnosis is also required, in order to avoid the danger of damage or accident caused by the possible high wear, which is coming from the high frictional forces. Usually the journal bearings are designed in order to support only radial or only axial loads. Therefore important restriction in their application exists, as they cannot be used in applications where carrying both axial and radial loads is required. Such a characteristic application is the thrust system of naval application, where the need for installing both of axial and thrust bearings exists. This requirement drives to high manufacturing and maintenance cost.

An important drawback of hydrodynamic journal bearings is also that these are not ecological, due to lubricant which is essential for their operation. Also, the lubrication system requires high attention, because there always exists the danger of (a) environmental pollution and lubricant leakage, with unfavourable repercussions for the environment and fines' imposition in the industry and (b) pollution of the lubricant with particles, causing the acceleration of the bearing metals wear.

Additional drawback could be considered the need for storage and transport system of the lubricant, which always increases the cost of installation.

On the other hand, the advantages of active magnetic journal bearings would be numbered as below:

• they have the possibility of operating in much higher revolutions per minute (above 20.000 RPM), compared to hydrodynamic journal bearings. This is because their angular velocity is limited only by the strength of material of the rotor,

• they always have stabilized operation, without any mechanic contact, resulting in long life time, with considerably lower cost of maintenance, · a lubrication system is not required, avoiding thus the lubricant storage and transport system, so the probability of pollution does not exist. The periodical replacement of the lubricant is also avoided. This is an important advantage against the conventional technologies, both from cost and pollution caused by the machinery point of view, · the electromagnetic bearings are active elements that allow the measurement and the control of the position of shaft, giving the possibility of choosing the equilibrium position accurately,

• the technology of active magnetic bearings, due to the incorporated systems, provides the possibility of follow-up and monitoring of the machine without additional systems, as well as identification of the system characteristics,

• the dynamic operational characteristics of a rotor-bearing system, the stiffness and damping coefficients can be altered during the operation, giving thus the possibility of restriction of undesirable oscillations, active and real time balancing, measurement of applied forces and determination and control of the position of v e rotor

However, active magnetic bearings also have some important drawbacks, such as:

• they require big consumption of electric power, due to the electromagnets,

• the interruption of the electric power of the electromagnets is not allowed because in such a case the rotor is being rubbed on the internal surface of the bearing, without me possibility of reducing the friction between rotor and bearing, during the rotation of the shaft. And that is resulting in the fast wear or even the destruction of electromagnetic bearing, the presence of Uninterruptible Power Supply (UPS) for the uninterrupted operation of the system requires big storage volumes and high cost of maintenance, it is also essential to note that electromagnetic bearings have a high production cost, mainly because of the sensors' and the controller's cost prices.

These drawbacks outbalance the advantages of these two types of bearings as described above. So, there exists the need of development of new type of bearings to overcome the drawbacks in question. The new hybrid bearing that we propose is a new mechanical system with the following main advantages: it can operate in a wider range of angular velocities of the rotor that exceeds the restrictions of its predecessors.

• it has high load carrying capacity, because the carriage of the total load W, can be done both by the hydrodynamic bearing (receipt of load Wi,) and by the electromagnetic bearing (receipt of load W _m ) simultaneously,

• it can operate reliably in high, intermediate and low revolutions, it can hold out in shock loads, it has long lifetime and high reliability during operation, low cost of maintenance and small friction losses in bearings,

• it offers the possibility of choosing the equilibrium point precisely, of restricting the undesirable vibrations, of performing active and real time dynamic balance and of measuring the applied forces.

Many efforts have been done for the design and development of hybrid journal bearings, with permanent magnets installed in the bearing resulting on the increment of the load carrying capacity. Permanent magnetic bearings consist of cylindrically positioned permanent magnets, are in compact size and have relatively low production cost. However, they can stend only almost half of the load carrying capacity, compared to active magnetic bearings. Permanent magnetic bearings present also very small degree of damping and they are generally unstable in the axial direction.

However, there are not reported any efforts for the design and development and for the manufacture of hybrid journal bearings that would combine the hydrodynamic and the electromagnetic fields. Such a hybrid, hydrodynamic and electromagnetic bearing has particularities, as listed below among others, which make its application difficult. The present invention describes successfully such hybrid journal bearings, which solve those problems:

- The operation of both the electromagnetic part and the hydrodynamic part in one shell.

The design and application of an inventive control operation system. The periphery of the hydrodynamic bearing must meet the appropriate provisions so that is not preventing the operation of the electromagnetic field.

- The radial clearance between the rotor and the stator must be such, that the bearing can operate efficiently continuously either as hydrodynamic or as electromagnetic.

The choice of the most appropriate materials for the construction of the magnetic bearing is important, either from a point of view of load capacity and rotation speed, or from an operating temperature point of view. The material of the hydrodynamic bearing must be of high standards in terms of anti-friction properties, namely of very low friction coefficient, and resistance to temperature. Such material could be graphite and metal alloy such as graphite/metal alloy or

Graphalloy, with an operating temperature of up to 540°C.

The hydrodynamic bearing must not operate simply as a support to the magnetic bearing when there will not be requirements of high temperatures and high speeds, but it will also operate as a load and rotor reception mechanism in case of power failure in the supply of the magnetic bearing.

- In addition, the lubricant distribution in the bearing can also operate as a cooling mechanism of the hybrid system. - An innovation of the present invention is the paramagnetic pads' existence, inside of the ring of the bearing surface. These particular pads are used in order to secure the right operation of the magnetic bearing, either if this is independently working or in its hybrid mode of operation. In journal bearings the distance e between the centers of journal O, and bearing O _b is called eccentricity, and it is appeared when an external load is applied to the bearing. By the existence of the eccentricity the bearing operation follows the hydrodynamic lubrication theory. Thus, the film of lubricant operating in the hydrodynamic region, takes values of oil thickness h between h„ (minimal thickness of lubricant) and h _max (biggest thickness of lubricant), as it is shown in Figure 1.

The values of the radial clearance c = R _b -R _y can be estimated by the below inequality,

500 < R _b /c < 1000 (1) Where c, ho and h _max are combined with the relation:

For the active magnetic bearings the equilibrium point is usually the center of the bearing, or in other words the eccentric operation is not usual. In the hybrid bearing described in the present the equilibrium point is considered to be eccentric, giving thus the possibility to the hydrodynamic lubrication to be developed. According to the literature, the gap (g ₀ ) between the magnets and the rotating shaft should lie inside the region: g\ ≤ g ₀ ≤ g2 (3) where g\ = 300 mm and g ₂ = 500 mm. Due to the existing eccentricity, g ₀ and g _max should satisfy the following inequalities: gi≤ g _o και g _max < g ₂ (4)

In order, for the bearing to operate in both of the two regions, the magnets are not placed in distance equals to radius of the bearing (R _f ,) but in a bigger radius R _m , defined as:

R _m = R _b + g (5)

Thus the magnets are placed in a distance g from the internal surface of the inner ring. If the minimum oil film thickness h _Q is added, then, in that position, the total distance of the magnets from rotor can be calculated, as shown in Figure 1 : g _* = g + K (6)

And the equation (4) becomes: g, ^≤ g„ => g,≤g + => g, ^~ h≤g

g Or ^ g_ (7) c

£ _m» ≤ g, => + g≤g _I => 2c - h + g≤g ₂

The dimensionless minimum oil film thickness h ₀ /c can be found using the

Raymondi and Boyd diagram as a function of Sommerfeld number, as shown in Figure 2.

From equations (7) and (8) the magnets should lie in distance g/c satisfying the inequalities. In Figure 2, the ratio g/c is given as a function of Sommerfeld number. Thus if the radial clearance is c = 100 μηι, and S = 0.1 then from Figure 2 the following inequality can be obtained:

2.5 < g /c≤ 3.5 (9) or

250 μm < g≤ 350 μη (10)

After the selection of the radial clearance c, and for each Sommerfeld number the corresponding distance g can be calculated. High values of g / c correspond in small Sommerfeld numbers, while smaller values g / c in relatively higher Sommerfeld numbers. Concluding, the new hybrid journal bearing design, as it is described in the present can be realized. This is due to the effective design of hydrodynamic and magnetic characteristics of the bearing as described in the present. The present invention refers to a hybrid journal bearing, that combines the hydrodynamic and electromagnetic field, aiming at the exploitation of advantages of these two types of bearings eliminating at the same time their drawbacks, as described above.

Summary of invention

The present invention describes a hybrid journal bearing, that comprises both an electromagnetic part and a hydrodynamic part, wherein both parts are in a common nutshell, are regulated by the same control system and are operating in the same control volume, in which hybrid journal bearing - the equilibrium point is eccentric,

- the electromagnets are placed internally, perimetrically at a specific distance from the internal surface of the inner ring,

- the material of the bearings may be graphite, metal alloy, graphite/metal alloy or Graphalloy and may have operating temperatures of up to 540°C, - the hydrodynamic bearing operates as support to the magnetic bearing when there will not be requirements of high temperatures and high speeds and will also operate as a load and rotor reception mechanism in case of power failure in the supply of the magnetic bearing,

- the lubricant distribution in the bearing can also operate as a cooling mechanism of the hybrid system, - the hybrid journal bearing is effective independently on the number of coils of the electromagnet, the material of the coils is clean copper (Cu) of magnetic permeability μ = 1 , and the diameter of the wire of copper depends on the operational specifications of the bearing, - the material of the stator and the rotor is ferromagnetic, the electromagnetic field of the hybrid journal bearing may be used while the hydrodynamic field operates, aiming at (a) the increase of load carrying capacity, (b) the control of the response of the rotating shaft during instabilities (oil whirl and oil whip) and (c) the imposition of external parametric excitation for diagnosis of damage of the rotating system.

Advantageously, in the hybrid journal bearing of the present invention, the internal part of the hydrodynamic bearing is from metal alloy of graphite (Graphalloy) with low friction coefficient and resistance in high temperatures up to the 540°C. An additional advantage of the hybrid journal bearing of the present invention is that the magnets are placed circumferentially in bigger diameter than that of the internal ring of the bearing, and can be activated in every eccentricity and attitude angle, where the hydrodynamic bearing operates, wherein for the proper operation of the hybrid journal bearing the ratio of the magnetic gap g of the bearing which distinguishes the minimum distance between the external surface of the rotor and the stator, over the radial clearance c of the hydrodynamic journal bearing, should lie between specific values, that depend on the Sommerfeld number and the radial clearance of the bearing. Preferably, the hybrid journal bearing according to the present invention further comprises a number of sectors from paramagnetic material corresponding to the number of electromagnets, which sectors from paramagnetic material are placed inside the ring of the bearing surface in front of the magnetic poles, so that they supplement the gap up to the internal diameter of graphalloy material, for the unhindered operation of both the hydrodynamic and the electromagnetic fields of the hybrid journal bearing.

In the hybrid journal bearing described herein, the ratio of the length of the bearing over the diameter of the shaft (L / D) can be any ratio from 0.25 until ∞ where a hydrodynamic bearing can operate.

Preferably, the hybrid journal bearing according to the present invention may operate from zero rotational speed of the shaft, until the maximum rotational speed where the electromagnetic journal bearing can operate (50.000rpm).

Advantageously, the hybrid journal bearing according to the present invention further comprises a pipe of diameter d _a , via which the lubricant is imported in the interior of the hybrid journal bearing, in order to realize the hydrodynamic lubrication.

Preferably, the hybrid journal bearing according to the present invention further comprises two lids, one in each side of the hybrid journal bearing, aiming at the protection of the interior of the hybrid journal bearing (inductors, stator, graphalloy material, sectors of paramagnetic material), from exterior factors that can influence the operation of the hybrid journal bearing.

Optionally, the hybrid journal bearing according to the present invention comprises electromagnets which are created by coils of inductors, connected in pairs, aiming at the better regulation of the stability of the rotating shaft and at the increase of load carrying capacity.

Unlike on a classic journal bearing where the electromagnets are placed externally, it is a particular characteristic of the hybrid journal bearing of the invention that here the elctromagnets are placed internally. The material of the coils is clean copper (Cu), and the diameter of the wire of copper depends on the operational specifications of the bearing. The material of the stator and the rotor is ferromagnetic, and this invention is effective independently on the number of coils of the electromagnet.

A particular characteristic of the invention is also the use of a controller (i.e. of a Fuzzy Logic Controller), which activates the hydrodynamic or the electromagnetic or even both the two field of the bearing simultaneously, exploiting the advantages of each one, operating individually as hydrodynamic or as electromagnetic, or as hydrodynamic and electromagnetic simultaneously, optimising thus their general behaviour and their capacity. The controller can operate by checking the radial (actinic) speed component of the shaft, or by checking the position of the shaft, or operates aiming at the dynamic damping and it is connected with the electromagnets via the signal amplifier and sensors.

Description of the invention The present invention describes a hybrid journal bearing that can exploit the advantages of both hydrodynamic and electromagnetic bearing components.

The present invention describes a hybrid journal bearing, which has the possibility of operating, simultaneously or selectively, as hydrodynamic or as electromagnetic or as both. The hydrodynamic and electromagnetic field of the hybrid journal bearing of the present invention operate within a common nutshell. With the suitable controller, the new type of hybrid bearing, described in the present invention, exploits the advantages of the hydrodynamic and the electromagnetic bearing and it operates occasionally as hydrodynamic, or as electromagnetic, or as hybrid (i.e. electromagnetic and hydrodynamic simultaneously). By this way, the hybrid journal bearing that is described by the present invention, obtains the optimum dynamic behaviour. It can, that is to say, operate as hydrodynamic bearing, as hydrodynamic bearing with control of response via the operation of the electromagnets of the bearing in cases of instability (oil whirl and oil whip), as hydrodynamic bearing using the electromagnets as external parametric exciter used for the recognition of the system and localisation of possible damage, as hydrodynamic and electromagnetic simultaneously in order to increase the load carrying capacity when this is necessary or as electromagnetic bearing only, without the participation of hydrodynamic operation.

A hybrid journal bearing that is at the same time hydrodynamic and electromagnetic according to the present invention, presents a lot of advantages. It develops the advantages of the hydrodynamic oil field as well as of the electromagnetic one. The hybrid journal bearing offer the possibility of wider range of rotational speeds of the axis (higher than these of hydrodynamic or the magnetic journal bearing).

The hybrid journal bearing of the invention has the possibility of receiving higher external load W, because part of the load can be received from hydrodynamic journal bearing (receipt of load W _/ ,) while the rest from electromagnetic journal bearing (receipt of load W _m ). Also, it can reliably operate in high, intermediate and low revolutions, it can withstand in shock situations, avoiding high frictions in extreme situations of machine operation. The use of lubricant is not essential for every case of operation, big consumption of electric power is not essential, no problems are created in the shaft and in bearing, in case where electric power is interrupted, or in case of instability, where rub situation of the shaft on the internal part of the bearing is possible, because of the type of the material used for the construction of the internal part of the bearing. Furthermore, the hybrid journal bearing described by the present invention, has a long lifetime, high operational reliability, low maintenance cost and small friction losses. It is possible to determine precisely the choice of the shaft equilibrium point in the hybrid journal bearing of this invention. There is also the possibility to restrict undesirable oscillations as well as to proceed with the active and real time balancing of the rotor and the measurement of the applied loads.

Also, starting its operation, it can start to operate as active magnetic bearing, raising the supported shaft upwards. Then it can continue the operation as hybrid, with parallel oil lubricant inflow as the speed is increased, and finally it can be operated at the nominal rotational speed as hydrodynamic bearing. Furthermore it can operate as hybrid when the following phenomena are present: (a) instability of oil whirl or oil whip, (b) increment of applied load and (c) need of control (identification) of the operation of the bearings.

Concluding, the proposed hybrid journal bearing could be considered as a multifunctional new journal bearing.

Short description of Figures

The invention is described below referring to the attached Figures.

Figure 1 shows the distances among the rotor, the inner ring of the bearing and the electromagnets. Figure 2 presents the values of the ratio of the magnetic gap over the radial clearance ig/c), as a function of the Sommerfeld number. This diagram is used in order to indicate the operational restrictions of the proposed hybrid journal bearing.

Figure 3 shows the hybrid journal bearing, in its final form, where inside of the bearing the rotor (5) is rotating. Also, the pipe of the lubricant insertion (1) and the position monitoring sensors (6) of the rotor are shown.

Figure 4, shows the hybrid journal bearing, in its final form, without the rotor, so that the interior of the bearing appears.

Figure 5, shows the hybrid journal bearing, without the rotor and the one from the two lids, so that the components constituting the hybrid journal bearing are depicted. Figure 6, shows a section of the hybrid journal bearing, in which its geometrical characteristics are presented.

Figure 7, shows the stator of the hybrid journal bearing, which is constituted by numerous leaves of metal, in the case that alternate current is used for the inductors.

Figure 8, shows the hybrid journal bearing, in front and in sectional view. Its characteristic geometry dimensions appear. Figure 9, shows a design of the hybrid journal bearing, in which the connections of the controller (12) with the various parts are appeared.

Detailed description of Figures

The hybrid journal bearing described herein comprises the stator, the lids, the internal ring, the paramagnetic parts of the internal ring, the inductors and the pipe of lubricant, as these appear in the Figures 4 and 5. Stator is distinguished with number 3, the lids with number 2, the internal ring with number 7, the paramagnetic parts of the internal ring with number 13, the inductors with number 4 and the pipe of lubricant with number 1. Inside the hybrid journal bearing the rotor is rotating, indicated by the number 5 (Figure 3). There are sensors of the position of the shaft, which are also indicated with number 6, shown in Figure 3. The sensors (6) are used to monitor the position of the rotor (5) each time moment, in order to control the pressure of the lubricant and the current of the inductors (4), using the controller (12), as shown in Figure 9. Hybrid journal bearing is also constituted by eight poles (8), as shown in Figure 6), which are combined in pairs, so that higher force of magnetization is achieved. In higher diameters, it would be possible to use more than eight poles. After the combination of the eight poles (8) as shown in Figure 6, four pairs of opposite poles (9) as shown in Figure 9, are finally resulted, two in the X-axis and two in the Y-axis (Figure 9). The way that the inductors of the eight poles (8) shown in Figure 6) are connected in pairs (15, as shown in Figure 9), is such where the direction of the current can produce magnetic flow (14, as shown in Figure 9) between these poles.

Stator (3, shown in Figure 5) is constituted by numerous metal slices (10, as in Figure 7) linked between them, avoiding eddy currents, in the case that alternating current (AC) is used for the power supply of the inductors (4, as in Figure 5). If the current, which is used for the power supply of the inductors (4, as in Figure 5) is direct (DC), stator (3, Figure 5) can then be constituted by compact material. Its external diameter is 2 · R _m , as it appears in Figure 6. Each pole also has width b and it has an angle a (a = 22.5°, in the case of eight poles) from the Y direction, as it appears in Figure 6. The width of external ring of the stator (3) is also b, as it appears in Figure 6. The length of stator (3) is Lb, as it appears in Figure 8. The material of the stator (3) is diamagnetic, in order to achieve high magnetization force.

In each one of the eight poles (4, as in Figure 5) of the stator (3, as in Figure 5), copper coils are placed to form the inductor (4). The number of coils of each pole (8, as in Figure 6) is N _w and the diameter of wire of inductor (4, as in Figure 5) is d _w . The poles (8, Figure 6) are linked into pairs, via the inductors (4, Figure 5), in order to become four poles (9, Figure 9), two in the Y direction (axe) and two in the X direction (axe), as it is shown in Figure 9. Each pole (9, Figure 9), is connected with signal amplifier (1 1 , Figure 9) and with the controller (12, Figure 9). The controller (12, Figure 9) regulates the current in each pole (9, Figure 9), aiming to hold the rotor (5, Figure 3) at the desirable position. The height of the apparent surface of inductors (4, Figure 6) of each pole (8, Figure 6) is h _c , the width is w _c and the surface^ x w _c , as it appears in Figure 6.

The internal ring (7, Figure 6) is used so that the suitable distances of rotor (5, Figure 6) from the electromagnets (9, Figure 9) (electromagnetic journal bearing) and from the internal surface of the hybrid journal bearing (hydrodynamic journal bearing, for which usually: 500≤ R _h / c≤ 1000 ) are maintained. These distances are distinguished as g and c in Figure 6. The maximum width of the internal ring (7, Figure 6) is r and the minimum one is equal to the gap of electromagnetic field (g) minus the radial clearance of hydrodynamic field (c). The parts of the internal ring ( 13, Figure 6) that have the smaller width are manufactured from not magnetic material, e.g. aluminium or stainless steel serial 400, so that they do not influence the operation of magnetic field. The internal ring (7, Figure 6) and the parts of the internal ring (13, Figure 8) has length Lb, as it appears in Figure 8, can be hold out in high temperatures and have very low friction coefficient, for the case where the rotor (5, Figure 6), while it is rotating, rubs on the internal ring (7, Figure 6). The material of the internal ring (7, Figure 6) can be graphite and metal alloy (graphice/metal alloy or Graphalloy), with operational temperature up to roughly 540°C. Also this material can be any material holding out in high temperatures and have very low coefficient of friction, for the case that the rotor (5, Figure 6), while rotating, rubs on the internal ring (7, Figure 6), or in the case of total loss of power where the loaded rotor (5, Figure 6) comes into contact with the ring (7, Figure 6). This allows the decreased wear of both the bearing and the shaft in unanticipated or extreme operational conditions.

The pipe of the oil lubricant (1 , Figure 5) is at preference, plastic with thermal insulation and is used for importing the lubricant in the interior of the hybrid journal bearing. The pipe of lubricant ( 1 , Figure 5) can be also from other materials, like aluminium or copper with thermal insulation. The lubricant enters between the rotor (5, Figure 3) and the internal side of the inner ring, of the hybrid journal bearing. The pipe of lubricant (1) has the essential length, so that it penetrates the stator (3) and the internal ring (7) or the paramagnetic parts of the internal ring (13), as it appears in Figure 6. The diameter of pipe of lubricant (1) is d„ , as it appears in Figure 8. The lubricant comes out from the hybrid journal bearing from the sides, between the internal ring (7) and the paramagnetic parts of the internal ring (13) and the lids (2) of the hybrid journal bearing. In the case where all the lubricant comes out from the hybrid journal bearing, the space between the rotor (5) and the internal ring (7) remains empty. The lubricant is also used for the refrigeration of the hybrid journal bearing.

The lids (2) of the hybrid journal bearing are used for the withholding of lubricant in the space between the internal ring (7) and the paramagnetic parts of the internal ring (13) and the rotor (5), and for the protection of the electromagnets (9, Figure 9) from external factors, such as dust etc, that can cause wear. They have internal diameter, equal to the diameter of rotor (5), that is to say R,- plus the air gap g, as it appears in Figure 6. The width of lids (2) is a little larger than the width w _c of inductors (4), so that they cover the total of elements of the hybrid journal bearing, as it is shown in Figure 8, with the dimension L _p . The lids (2) can be manufactured from plastic with insulation, or from a material that can't be magnetised, as aluminium, chromium or stainless steel of class 400. The total width of the hybrid journal bearing is L _h as it is shown in Figure 8.

The sensors (6) are placed in the X ar.d Y directions, as it appears in Figure 3. The sensors (6) are distance sensors, which are connected with the controller (12), which collect the signals, as it appears in Figure 9. The controller (12) regulates the intensity of current of inductors of the electromagnets (9) and the insertion of lubricant, aiming to keep the rotor (5) in the desired equilibrium point. The controller (12) regulates the insertion of the lubricant, by controlling the current of the lubricant pump (16, Figure 9). The rotor (5) has diameter 2 ^■ Rj , as it appears in Figure 6 and its material has the ability to be magnetized, as for example iron and its alloys, steel and its alloys or stainless class 300.

The present invention can be applied in laboratorial level but also in industrial applications, as in vacuum turbomachinery and in production of energy, in natural gas compressors, in electric power plants or in aeronautics applications, where the requirement for long lifetime operation of machines in high rotational velocities (> 20.000RPM) is necessary, as well as in low revolutions when it is in waiting situation, and in axial systems of naval applications.

With the hybrid journal bearing of the present invention we completely reclaim the journal-bearing system from energy point of view, in order to eliminate the friction forces or emissions, or wear in very high revolutions and temperatures, as well as the complete control of rotor vibrations, while in low revolutions or in waiting situation, with the operation of hydrodynair.ic journal bearing we achieve the minimization of electric power consumption. The hybrid bearing of the present invention can operate also in very high temperatures (> 500°C), where the operation of classical hydrodynamic bearings isn't possible (lubricants do not work properly in such high temperatures). This alternation of operational situations adds reliability and higher lifetime to the bearing and generally to the machine.

Another example of application is .he case of planes landing, where abrupt change of load is observed. In the case cf landing, as well as in the case of plane manoeuvres in high g's (g = acceleration of gravity), in the case of blade loss from the engine of the airplane, always the question for the good operation and adaptation to the conditions of conventional bearings arises. Thus for example in the case of sudden blade loss or blades loss from the engine, the hybrid operation of the proposed bearing is more suitable for the control of increased oscillations that will be caused, as well as the re- stabilisation with beneficial effects to the safety of both passengers and plane. The possibility of the hybrid bearing to operate in high revolutions and in high temperatures in both electromagnetic and hydrcdynamic operation, without frictions or with very small frictions, with or without lubricant, with very small energy consumption, with very low level of oscillations and with control of the shaft movement, with reliability and incorporated diagnostic possibilities, renders the hybrid bearing environmentally compatible, with important impact in the National and at extension in the European and World economy.

We believe that the application of this particular invention with the use of the proposed hybrid journal bearings in the industry (in electric power plants), in the shipping (as bearings in naval engines), :n the aeronautics (as bearings of the air turbines in airplanes), contributes in the modern environmental objectives of wider modern society and in this light contributes also in the needs of modern industry, in Europe and in all over the world.