The present invention relates to sealing arrangements employed to prevent a working medium to flow between two relatively rotatable parts from a high pressure area to a low pressure area.

In particular this invention relates to sealing in rotating machines, such as turbines (gas, steam, fluid) , compressors, pumps, etc.

The control of the working medium (gas, steam, fluid) flow inside rotating machines is of paramount importance with regards to both functionality and effectiveness.

Continuously increasing requirements for turbine efficiency demand high performance seals. These seals should operate under high pressures, rotation speeds and temperatures for long period of time.

Existing seal arrangements can be divided into two groups - contact seal arrangements, for example brush seals, and non- contact, for example such as labyrinth seals, finger seals, etc. Non contact seals have higher leakage of working medium, but longer life time in contrasts to brush seals.

In the noncontact seal arrangement a radial gap between a rotor part and a stator part is fixed and must be large enough to accommodate thermal expansion of the parts and thermal changes in the surrounding structure, as well as the centrifugal expansion of the two parts in case of the relatively rotating parts, to avoid any contact between the seal arrangement and the other part. On the other hand, the performance of the rotating machine depends on the size of such radial gap and can be enhanced by decreasing the leakage of the working medium through the radial gap.

FIG 1 shows a conventionally known labyrinth seal arrangement 1 in a rotating machine. The labyrinth seal arrangement 1 is generally comprised of successive fins 2 and cavities 3 formed along the adjacent surfaces 4, 5 of the rotor part 6 and the stator part 7 respectively.

In the following description, for the purpose of explanation, the labyrinth sealing arrangement 1 is considered for the case when the fins 2 are located on the rotor part 6. However, the fins 2 can be positioned on one of the rotor part 6 and the stator part 7, or even on both parts 6, 7.

The rotor part 6 and the stator part 7 are arranged in such way that a gap 8 of the height H is formed between them. A fin tip 9 and a surface 5 of the stator part 7 form a radial gap 10 of the height h. The working medium flows along the direction 11 from a high pressure area to a low pressure area .

One of the basic concepts of any seal arrangement 1 design is to form a fluid barrier between areas of high and low pressure of working medium in order to retard the working medium flow through the labyrinth seal arrangement 1 to a desired level. Generally, the desired retardation is achieved by forcing a high-velocity working medium to pass sequentially through the radial gaps 10, which are formed between the fin tips 9 and the surface 5 of the stator part 7, with the successive entering of the flowing working medium into the cavities 3, where energy of the flowing working medium is largely dissipated into turbulence.

Several origins of the aforementioned turbulence generation within the seal arrangement 1 can be distinguished. One of them is the friction between the high-velocity working medium and the adjacent seal surfaces, i.e. the surface 4 and/or the surface 5. Another origin is the intense friction of free shear layers between a high velocity working medium jet discharging from the radial gap 10, i.e. slit-like orifice formed between the fin tips 9 and the surface 5 of the stator part 7, and a relatively slow moving working medium in the cavities 3 immediately downstream of the radial gap 10.

Such the labyrinth seal arrangement 1 is passive obstacles for the working medium flow since dynamic effects caused by relative motion of surface 4 of the rotor part 6 and the stator part 7 is not used to reduce the working medium flow.

The efficiency of the conventionally known seal arrangements could be improved by reducing the radial gap 10. However, the radial gap 10 can only be reduced to a limited extent so as to avoid contact between the rotor part 6 and the stator part 7. In particular, such requirement should be satisfied for relatively rotating parts during the operation of the rotating machine since any contact of the rotor part and the stator part can result in damage to the parts of the rotating equipment.

The contact can be caused by many factors such as the eccentricity of a rotating part, centrifugal growth, vibrations, manufacturing tolerances, misalignment during assembling, thermal expansion, etc. As a result, the radial gap 10 has to be sufficiently large to avoid accidental contact between two parts - a stator part and a rotor part, which in turn impairs the sealing efficiency of the conventionally known seal arrangement.

There are several known approaches for minimizing the working medium flow through the seal arrangement while keeping physical radial gap between the rotor part and the stator part .

In one prior art design for relatively rotating parts (US Patent N'l 482 031) this is achieved by using of a "stepped" surface of the stationary part, which prevents the working medium to flow through a seal arrangement without entering the cavities between the fins and, thus, increases the losses due to the friction between a high-velocity flow and seal surfaces and minimizes the leakage flow.

In another configuration (US Patent No. 3 940 153) the seal arrangement employs specially chosen wall positioning and wall curvature to introduce sharp turns in the working medium flow path providing the additional friction in shear layers.

However the efficiency of such conventional labyrinth seal arrangement depends not only on the height h of radial gap 10, but also on the number of successive fins in a row along axial direction. The longer the labyrinth seal arrangements, in other words the more successive fins in a row in axial direction, the more efficient the labyrinth seal arrangement is .

Nevertheless there are a lot of applications inside rotating machines that require short seal arrangements because of limited space for placing conventional seal arrangements. For example, conventional labyrinth sealing arrangement of three fins is placed on a surface of a stator vane for sealing of the radial gap between a stator vane and a rotor in a turbine. In this particular case the space is limited by physical size of the stator vane. The efficiency of such short conventional labyrinth is rather low. The same situation is with sealing of the radial gap between a rotor blade and a casing.

As mentioned hereinbefore, a primary concern is to maintain the minimum flow of the working medium between the stator and the rotor of the rotating machine, while preventing any mechanical interaction between two parts .

Accordingly, the object of the present invention is to provide another variant of the seal arrangement to minimize the working medium flow from a high pressure area to a low pressure area. Therefore, the efficiency of such seal arrangement is increased.

The object of the present invention is achieved by a micro compressor seal arrangement as defined in claim 1. Advantageous embodiments of the present invention are provided in dependent claims. Features of claim 1 can be combined with features of dependent claims, and features of dependent claims can be combined together.

In an aspect of the present invention, a micro compressor seal arrangement to minimize a working medium flow from a high pressure area to a low pressure area through a gap is presented.

The micro compressor seal arrangement comprises a rotor part and a stator part, wherein the rotor part and the stator part are relatively rotating parts about a rotation axis, located opposite to each other and arranged in such way that there is a gap formed between the rotor part and the stator part .

The rotor part comprises a rotor body of a shape symmetrical about the rotation axis and at least one rotor group of rotor fins extending in the gap towards the stator part. The at least one rotor group of rotor fins is arranged in such way that

the rotor fins of the at least one rotor group extending out of the rotor body with a rotor fin height in radial direction towards the stator part and

the rotor fins of the at least one rotor group are distributed in circumference direction on the rotor part. The stator part comprises a stator body of a shape symmetrical about the rotation axis and at least one stator group of stator fins extending in the gap towards the rotor part. The at least one stator group of the stator fins is arranged in such way that

the stator fins of the at least one stator group extending out of the stator body with a stator fin height in radial direction towards the rotor part and the stator fins of the at least one stator group are distributed in circumference direction on the stator part.

According to the present invention the at least one stator group of stator fins and the at least one rotor group of rotor fins are arranged and configured to minimize the working medium flow from the high pressure area to the low pressure area by creating antistreamwise pressure.

The present invention is based on the insight that as such the rotor groups of the rotor fins and the stator groups of the stator fins represent an axial flow compressor arrangement or radial compressor arrangement.

Conventionally axial flow or radial compressor arrangements are used to increase the pressure of the working medium flow, therefore to achieve higher pressure of the working medium on the output of the conventional compressor and to pump the working medium toward the next stage of the rotating machine.

The present invention propose to arrange such compressor, but micro one, in the area where the seal arrangement is required in such way that such micro compressor arrangement creates antistreamwise pressure by retarding the working medium flow and pumping the working medium flow back to the high pressure area .

Thus, proper selection of the characteristics and configurations for the rotor fins and the stator fins, such as, for example shape, height, and proper placement the rotor groups and the stator groups relatively each other and relatively to the working medium flow might allow achieving even zero or negative leakage of the working medium through such micro compressor seal arrangement.

In other words the dynamic effects caused by relative motion of the rotor part and the stator part are used to minimize the working medium flow. Such micro compressor seal arrangement endeavours to reverse the working medium flow back to the high pressure area.

Thus, the present invention is proposed to provide a new micro compressor seal arrangement to minimize the working medium flow from the high pressure area to the low pressure area through the gap .

Further embodiments of the present invention are subject of the further sub-claims and of the following description, referring to the drawings .

In a possible embodiment of the micro compressor seal arrangement the stator fins of the at least one stator group are evenly distributed in circumference direction on the stator part. And the rotor fins of the at least one rotor group are evenly distributed in circumference direction on the rotor part . This feature allows creating antistreamwise pressure that is consistent and continuous along the circumference direction.

In other possible embodiment of the micro compressor seal arrangement the distance in circumference direction between each two neighboring rotor fins of the at least one rotor group is no more than five times of the rotor fin height.

In case the distance between each two neighboring rotor fins of the at least one rotor group are more than five times of the rotor fin height, a part of the working medium flow will pass through such micro compressor seal arrangement without being influenced the micro compressor seal arrangement.

In enhanced embodiment of the micro compressor seal arrangement the stator fin height of each stator fin of the at least one stator group is no more than the rotor fin height .

This is to prevent any contacts of the stator fins and the rotor body and therefore to provide reliability and life-span of the micro compressor seal arrangement and the rotating machine in whole .

In enhanced embodiment of the micro compressor seal arrangement the at least one rotor group and adjacent stator group are arranged in such way that the distance between the at least one rotor group and adjacent stator group in axial direction is no more than five times of the rotor fin height.

Otherwise the rotor group and adjacent stator group do not work as a harmonious system to create antistreamwise pressure, but are just separate fins along the working medium flow. In other words it will be a labyrinth seal arrangement with low efficiency.

This feature allows the rotor group and adjacent stator group work as a micro compressor arrangement.

In other possible embodiment of the micro compressor seal arrangement the at least one rotor group and the at least one stator group are assembled in such way that each rotor group is followed by the stator group in a direction of the working medium flow. Two neighboring rotor group and stator group assembled in such way form a group assembly. This feature allows increasing efficiency of the micro compressor seal assembly in whole.

Only the pair of the rotor group and the stator group is able to retard reverse the working medium flow and convert rotation motion of the working medium flow into excessive antisreamwise pressure.

Presence of only one of these groups - whether the rotor group or the stator group - allows only slowing down the working medium flow. In this case such seal arrangement will work as an ordinary obstacle for the working medium flow. However the presence of a further stator group of the stator fins increases efficiency of the micro compressor seal arrangement in case it is arranged in the direction of the working medium flow in front of the group assembly which is the first group assembly in the direction of the working medium flow.

Such further stator group arranged in front of the first group assembly guides the working medium flow to standing afterwards the group assemblies. The further stator group provides better flow angles for working medium flow into to the rotor fins of the rotor group of the group assemblies standing afterwards. And as a result there is better performance of the successive group assemblies. Therefore the efficiency of the micro compressor seal arrangement in whole increases .

In other enhanced embodiment of the micro compressor seal arrangement each rotor fin is a blade and each stator fin is a vane. Furthermore the blades of the at least one rotor group are arranged thus that they form a negative attack angle relatively to the direction of the working medium flow.

In conventional compressor arrangements the blades are placed thus that they form a positive attack angle. It allows the conventional compressor arrangements to push the working medium forward. Arranging the blades with the negative attack angle allows effectively retarding the working medium flow and creating antistreamwise pressure.

For a more complete understanding of the present invention and advantages thereof, reference is now made to the following description taken in accompanying drawings. The invention is explained in more details below using exemplary embodiments which are specified in the schematic figures of the drawings, in which:

FIG. 1 schematically illustrates the conventionally known seal arrangement (prior art) ;

FIG. 2 schematically illustrates an embodiment of the micro compressor seal arrangement in accordance with the present invention;

FIG. 3 schematically illustrates an embodiment of the micro compressor seal arrangement in accordance with the present invention;

FIG. 4 schematically illustrates a segment of a rotor part in accordance with the present invention;

FIG. 5 schematically illustrates location of the rotor fins of the rotor groups and the stator finds of the stator groups relatively each other in accordance with the present invention;

FIG. 6 schematically illustrates an embodiment of the micro compressor seal arrangement in accordance with the present invention;

Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details.

FIG 2 illustrates a micro compressor seal arrangement 12 to minimize a working medium (gas, steam, fluid) flow from a high pressure area 13 to a low pressure area 14 in accordance with the present invention.

The micro compressor seal arrangement 12 comprises a rotor part 6 and a stator part 7. The rotor part 6 and the stator part 7 are arranged in such way that there is a gap 8 of the height H between them.

The rotor part 6 comprises a rotor body 15 of a shape symmetrical about a rotation axis 17. The stator part 5 comprises a stator body 16 of a shape symmetrical about a rotation axis 17.

The rotor part 6 and the stator part 7 are located opposite to each other, so the surface 4 of the rotor part 6 is opposite to the surface 5 of the stator part 7.

Both parts 6, 7 are of a shape symmetrical about a rotation axis 17. At least one of the rotor part 6 and the stator part 7 is convex. Another part 6, 7 is concave. The rotor part 6 and the stator part 7 are configured to be relatively rotating parts within the rotating machines, such as turbines (gas, steam, etc.), compressors, pumps, etc.

In other words, the rotor part 6 may be convex, whereas the stator part 7 may be concave. In this case the rotor part 6 rotates inside the stator part 7. And vise versa, the rotor part 6 may be concave, whereas the stator part 7 is convex. In this case the stator part 7 is located inside the rotor part 6. And the rotor part 6 rotates around the stator part 7 while the rotor part 6 and the stator part 7 have the same rotation axis 17.

The rotor part 6 comprises at least one rotor group of rotor fins 18 extending in the gap 8 towards the stator part 7, arranged in such way that the rotor fins 18 of the at least one rotor group extending out of the rotor body 15 with a rotor fin height h _rf in radial direction towards the stator part 7. Hereinafter the rotor fin height h _rf refers to the distance from the surface 4 of the rotor body 15 to a rotor tip 19 of the rotor fin 18. Still there is a radial gap 10 between the rotor tip 19 and the surface 5 of the stator part 7.

Hereinafter the radial direction refers to the direction along a radius that is a line from the center of the rotor part 6 and the stator part 7 to the outer surface perpendicular to the rotation axis 17. The rotor fins 18 of the at least one rotor group are distributed in circumference direction on the rotor part 6 as it is shown on FIG 2. The location of the rotor fins 18 in the rotor group relatively each other in circumference direction on should be defined by experts. However in the preferable case the rotor fins 18 of the at least one rotor group are evenly distributed in circumference direction on the rotor part 6.

The stator part 7 comprises at least one stator group of stator fins 20 extending in the gap 8 towards the rotor part 6, arranged in such way that the stator fins 20 of the at least one stator group extending out of the stator body 16 with a stator fin height h _sf in radial direction towards the rotor part 6. Hereinafter the stator fin height h _Sf refers to the distance from the surface 5 of the stator body 16 to the stator tip 21of the stator fin 20. Still there is the radial gap 10 between the stator tip 21 and the surface 4 of the rotor part 6.

The stator fins 20 of the at least one rotor group are distributed in circumference direction on the stator part 7 as it is shown on FIG 2. The location of the stator fins 20 in the stator group relatively each other in circumference direction should be defined by experts. However in the preferable case the stator fins 20 of the at least one stator group are evenly distributed in circumference direction on the stator part 7

Number of the rotor fins 18 in the rotor group and number of the stator fins 20 in the stator group should be defined by experts. However in preferable case the number of the rotor fins 18 should be chosen so that the distance L _rf (shown on FIG 4) in circumference direction between each two neighboring rotor fins 18 of the at least one rotor group is no more than five times of the rotor fin height h _rf .

Since the rotor fins 18 of the at least one rotor group can be of different shape. Hereinafter the distance L _rf (shown on FIG 4) in circumference direction between each two neighboring rotor fins 18 refers to the distance in circumference direction between each two neighboring rotor fins 18 that is measured on the one half of the rotor fin height h _rf .

The stator fin height h _sf of the at least one stator group should be defined by experts. However in the preferable case the stator fin height h _sf of each stator fin 20 of the at least one stator group should be no more than the rotor fin height h _rf .

According to the present invention the at least one stator group of stator fins 20 and the at least one rotor group of rotor fins 18 are arranged and configured to minimize the working medium flow from the high pressure area 13 to the low pressure area 14 by creating antistreamwise pressure.

Hereinafter a direction 11 of the working medium, i.e. streamwise direction, means the direction of the working medium flow that is driven by a pressure-gradient from the high pressure area 13 to the low pressure area 14. Therefore the antisteamwise direction means the direction from the low pressure area 14 to the high pressure area 13. The antistreamwise direction is opposite to the direction 11 of the working medium flow, in other word opposite to the streamwise direction.

The rotor part 6 and the stator part 7 of the micro compressor seal arrangement 1 can comprise plurality of the rotor groups and the stator groups. The number of such groups and their relative location on the rotor part 6 and the stator part 7 respectively should be defined by experts depending on the requirements and characteristics of the rotating machine.

However in the preferable case each rotor group of the rotor fins 18 is followed by the stator group of the stator fins 20 in the direction 11 of the working medium flow. Such two neighboring rotor group and stator group assembled in such way form a group assembly.

The micro compressor seal arrangement 12 can comprise plurality of the group assemblies. The number of such group assemblies should be defined by experts. However in the preferable case the micro compressor seal arrangement 12 comprises no more than 3 group assemblies. Otherwise the length of the micro compressor seal arrangement 12 in axial direction is too high. And the micro compressor seal arrangement 12 can be replaced by conventional labyrinth seal arrangement 1.

Also the distance L _rsg between the at least one rotor group and adjacent stator group in axial direction should be chosen by experts. However in preferable case it should be no more than five times of the rotor fin height h _rf .

Hereinafter the distance L _rsg between the rotor group and adjacent stator group in axial direction are measured as the distance between two neighboring planes 22 that are perpendicular to the rotation axis 17, and created through the utmost dots of the rotor fins 18 of the rotor group and the stator fins 20 of the stator group (as it shown on FIG 5) .

The distance between every two neighboring group assemblies in axial direction also should be no more than five times of the rotor fin height h _rf . In this case such plurality of group assemblies works as a harmonious system, in other words as a one micro compressor seal arrangement 12.

And vice versa, in case the distance between every two neighboring group assemblies in axial direction is more than five times of the rotor fin height h _rf , such two neighboring group assemblies will work as two separate micro compressor seal arrangements 12.

In enhanced embodiment of the micro compressor seal arrangement 12 a further stator group 23 of the stator fins 20 arranged in the direction of the working medium flow 11 in front of the group assembly 24 which is the first group assembly in the direction 11 of the working medium flow.

Such further stator group 23 of the stator fins 20 arranged in front of the first group assembly 24 guides the working medium flow to standing afterwards the group assemblies. The further stator group 23 provides better flow angles for working medium flow into to the rotor fins 18 of the rotor group of the first group assembly 24 standing afterwards. And as a result there is better performance of the successive group assemblies. Therefore the efficiency of the micro compressor seal arrangement in whole increases.

In enhanced embodiment of the micro compressor seal arrangement 12 each rotor fin 18 is a blade and each stator fin 20 is a vane. Therefore each rotor fin 18 of the at least one rotor group is configured to be a blade. It means, including, but not limited to that each rotor fin 18 is shaped and structured as a rotor blade . Accordingly each stator fin 20 of the at least one stator group is configured to be a vane. It means, including, but not limited to that each stator fin 20 is shaped and structured as a stator vane.

Additionally the blades 18 of the at least one rotor group are arranged such that they form a negative attack angle a relatively to the direction 11 of the working medium flow. In particularly the blades 18 of the at least one rotor group are arranged such that a chord line of each blade 18 form a negative attack angle a relatively to the direction 11 of the oncoming flow of the working medium. The angle of attack, well known in fluid dynamics, is the angle between a reference line on a body (often the chord line of an airfoil) and the oncoming flow. In conventional compressor arrangements the blades are arranged such that they form positive angle of attack relatively to the oncoming working medium flow. As a result of it such conventional compressor arrangement is able to achieve higher pressure of the working medium on the output of the conventional compressor and to pump the working medium toward the next stage of the rotating machine.

In case of blades 18 form negative angle of attack to the oncoming working medium flow such compressor creates antistreamwize pressure.

The micro compressor seal arrangement 12 works as follows. The working medium flows in the direction 11 from the high pressure area 13 to the low pressure area 15 between the rotor part 6 and the stator part 7. Such working medium flow is nearly blocked by the rotor fins 18 and the stator fins 20 extending in the gap 8 towards the stator part 7 and the rotor part 6 respectively. Therefore the working medium flow passes through slit-like orifices formed between the rotor tips 19 and the surface 5 of the stator part 7 and the stator tip 21 and the surface 4 of the rotor part 6.

In addition to that due to the relative rotation of two parts 6, 7, the rotor fins 18 of the at least one rotor group and the stator fins 20 of the at least one stator group together transfer kinetic energy of the relatively rotating parts 6, 7 to antistreamwise pressure.

In fact as soon as the rotor part 6 starts rotating relatively the stator part 7, the micro compressor seal arrangement 12 starts working as a compressor arrangement, but in reverse direction, by endeavoring to pump the working medium back to the high pressure area 13. Such behavior of the working medium flow is connected with the negative attack angle of rotor fins 18.

The stator fins 20 of the further stator group 23 redirect the working medium flow, preparing it for the first group assembly 24.

The rotating rotor fins 18 of the rotor group of the first group assembly 24, that work as blades, makes the working medium flow rotate together with the rotor part 6 and retard the working medium flow. While the stator fins 20 of the stator group of the first group assembly 24, working as vanes, convert the increased rotational kinetic energy of the working medium flow into the excessive backflow pressure, i.e. create antistreamwise pressure. Therefore an effective pressure drop between the high pressure area 13 and the low pressure area 14 decreases. As a result of it the leakage of the working medium through the gap 8 also decreases .

Hereinafter the effective pressure drop is the difference between the pressure in the high pressure area 13 and the sum of the pressure of the low pressure area 14 and the antistreamwise pressure created by the micro compressor seal arrangement 12.

The next in axial direction group assembly that comprises the rotor fins 18 of the rotor group and the stator fins 20 of the stator group, works as described above.

It is possible to achieve significant decreasing of the effective pressure drop by having the micro compressor seal arrangement

In ideal case it is possible to create such excessive backflow pressure that the effective pressure drop is zero or close to zero. Therefore the leakage of working medium through the gap 8 between the rotor part 6 and the stator part 7 is minimized. Thus, proper selection of the characteristics and configurations for the rotor fins 18 and the stator fins 20, such as, for example shape, height, and proper placement the rotor groups and the stator groups relatively each other and relatively to the working medium flow might allow achieving even zero or negative leakage of the working medium through such micro compressor seal arrangement 12.

In fact the working medium flow from the high pressure area 13 to the low pressure area 14 through the micro compressor seal arrangement 12 depends on rotation frequency of the rotor part 6.

Such micro compressor seal arrangement 12 is especially actual for rotating machines with gaseous working medium. It is connected with the fact that gaseous working medium typically has low density and low viscosity in comparison with other types of working mediums. Also gaseous working mediums do not have surface tension. Therefore conventional seal arrangements typically used for fluid working mediums are not so effective for such gaseous working mediums or not effective at all.

For simplicity reasons, abovementioned figures are used to demonstrate the micro compressor seal arrangement 12 in which the rotor part 6 is convex, whereas the stator part 7 is concave. It should be noted that in this case the rotor part 6 is concave, whereas the stator part 7 is convex, the micro compressor seal arrangement 12 work as well in accordance with the abovementioned description.

While the present invention has been described in detail with the reference to certain embodiments, it should be appreciated that the present invention is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Reference numerals

1 - labyrinth seal arrangement

2 - fin

3 - cavity

4 - surface of the rotor part

5 - surface of the stator part

6 - rotor part

7 - stator part

8 - gap

9 - fin tip

10 - radial gap

11 - direction

12 - micro seal arrangement

13 - high pressure area

14 - low pressure area

15 - rotor body

16 - stator body

17 - rotation axis

18 - rotor fin

19 - rotor tip

20 - stator fin

21 - stator tip

22 - plane

23 - further stator group of stator fins

24 - first group assembly