Patent ID: 12247584

DETAILED DESCRIPTION OF THE INVENTION

InFIG.1is schematically shown a multistage centrifugal compressor1according to the invention.

It essentially comprises a shaft2with a plurality of blades3thereon, wherein the shaft2is rotatably mounted in a housing4.

In this case eight blades3are present, but it is not excluded that more than eight or even more than ten blades3are present.

As is known, the housing2is provided with an inlet opening5and an outlet opening6.

The shaft2is journaled on both sides by means of bearings7.

In this case, the bearings7are rolling bearings7, and in particular double row deep groove ball bearings.

One end8of the shaft2is the driven end8, i.e. a drive, for instance in the form of a motor, is connected thereto to enable the shaft2to rotate. The drive is not shown in the figures.

The other end9of the shaft2is the non-driven end8.

According to the invention, at least one bearing7is provided with a bearing damper element10.

In this case, but not necessary for the invention, the bearings7are provided at only one end9of the shaft2with a bearing damper element10.

In this case, this concerns the non-driven end9of the shaft2.

This has the advantage that maintenance of the bearing damper element10is much simpler.

Of course, it is not excluded that the bearings7are provided with a bearing damper element10at both ends8,9of the shaft2.

InFIG.2is shown the respective bearing7on the non-driven end9of the shaft with the bearing damper element10.

According to the invention, the bearing damper element10consists of a ring11, which is arranged between the housing4and the respective bearing7. Of course, it is not excluded that the bearing damper element10is arranged between the shaft2and the bearing7.

This ring11is shown in detail inFIG.3.

The ring11comprises a plurality of slots12through the thickness of the ring11in the axial direction X-X′ and spaced from the radially-directed inner and outer surfaces13a,13bof the ring11.

There are preferably at least three slots12, wherein at least half of the slots12has one or more damping portions14awith a maximum width of 0.5 millimetre, preferably maximum 0.2 millimetre and more preferably maximum 1.15 millimetre.

The damping portions14aare preferably concentric and non-overlapping.

These damping portions14apreferably surround more than 80% and more preferably more than 90% of the centre or midpoint15of the ring.

In addition to the damping portions14a, preferably at least one slot12also has one or more spring portions14bwith a minimum width greater than the width of preferably at least 0.5 millimetre.

The spring portions14bare preferably at least twice and more preferably at least three times wider than the width of the damping portions14a.

According to the invention, the slots12are at least partially overlapping.

As already mentioned, by ‘overlapping slots’ here is meant that a line starting from the midpoint or centre of the ring11and intersecting the ring11, will intersect the respective slots8.

By “at least partially” is meant that the slots12overlap for at least a portion of their length, but not necessarily for their entire length.

Preferably, the spring portions14bof the slots12overlap at least partially with the damping portions14a.

Also, the damping portions14aare preferably further from the centre or midpoint15of the ring11than the spring portions14b.

Another embodiment of the ring11may also comprise slots12with only damping portions14aor with only spring portions14b. The embodiment with only damping portions14awill preferably be applied with said option A, as explained below, thereby creating a “squeeze film” effect. In the case of said options B and C, such thin damping portions14aare of little use since the damping is realized parallel to the slots12. In this case, the embodiment will preferably be used in which the slots12have only spring portions14b, which will mainly have a resilient effect.

The narrower or thinner damping portions14aare preferably fabricated through a wire spark process such as ‘EDM’ or ‘electrical discharge machining’.

The wider spring portions14bcan be manufactured using a water jet or a milling process.

For the further implementation of the bearing damper element10, there are several options according to the invention, which are shown in theFIGS.4to6.

A first option A according to the invention, as shown inFIG.4, concerns an embodiment wherein said slots12are filled with a liquid. This liquid has viscous properties and is, for example, but not necessarily, oil.

The axial annular surfaces16of the ring11are closed off by means of a protective cap17.

In the example shown, the protective caps17are manufactured from an elastomer, for example from rubber.

The protective caps17are fastened to the axial annular surfaces16of the ring11by means of bolts or screws18.

Of course, other fastening methods are also possible, as long as they do not block the resilient action, and therefore also the damping.

A space19is present between the protective caps17and the axial annular surfaces16of the ring which is filled with the liquid.

Alternatively, the protective caps17may be a 3D printed structure, which has some flexibility.

This means that the protective cap17, due to its structure, is flexible or deformable.

It is known that by means of 3D printing, complex structures and shapes are possible, such that a structure with the necessary flexibility can be created.

For instance, the protective cap17can be a thin-walled protective cap17, which is provided with a harmonica-structure. Such a harmonica-structure is, as is known, flexible and deformable.

A second option B according to the invention, as shown inFIGS.5and6, concerns an embodiment in which at least one of the two axial annular surfaces16of the ring11is provided with a viscoelastic material20or hysteretic damping material20that is sandwiched between two concentric discs21or the like, which discs21are attached to the ring11.

The discs21, like the protective caps17, may be fastened with bolts or screws18or in some other way.

The discs21can be embodied in many different forms.

InFIGS.5and6, they possess a slightly profiled radial inner or outer surface22, to be able to contain the viscoelastic material20or the hysteretic damping material20.

For option B, it is not necessary for liquid to be present in the slots12.

Said viscoelastic material20may be an O-ring23, as shown inFIG.5, while said hysteretic damping material20may be a metal gauze24(or “wire metal mesh”), as shown inFIG.6.

Although inFIGS.5and6the concentric discs21with the viscoelastic material20or hysteretic damping material20are attached only on one side of the ring11, it is not excluded that both axial annular surfaces16of the ring11are provided with a viscoelastic material20or hysteretic damping material20.

A third option C, which is not shown in the figures, concerns an embodiment in which said slots are 12 filled with a viscoelastic material.

This viscoelastic material is, for example, a rubber, which is attached into the slots12through vulcanization.

The slots12have only spring portions14b.

The advantage of such an embodiment is that no protective cap17or concentric discs21have to be attached to the ring11.

The operation of the multistage centrifugal compressor1is very simple and as follows.

During the operation of the centrifugal compressor1, the drive will cause the shaft2to rotate, as a result of which the blades3will suck in air through the inlet opening5, which is compressed in successive steps, and then leave the centrifugal compressor1through the outlet opening6.

During operation, vibrations will be generated, which should be damped to ensure that no resonance problems will arise.

The bearing damper element10will damp these vibrations.

In the situation ofFIG.4, the liquid in the slots12will create thin film dampers, which will provide for the damping.

The protective caps17keep the liquid in the slots12such that no liquid can flow out and because they are made of an elastomer, they will be moving along when the ring11deforms under the action of the vibrations.

For option B, as shown inFIGS.5and6, the viscoelastic material20or the hysteretic damping material20will deform to dampen the vibrations, with the ring11, as before, providing some flexibility.

In case of option C, the thicker spring portions14bwill be vulcanized, wherein the viscoelastic material in the slots12will have the same function as the liquid in the slots12of the embodiment ofFIG.4.

Due to the damping of the vibrations by the bearing damper element10, the resonance problems will be avoided. This will allow the centrifugal compressor1to rotate faster and/or to add more stages.

The present invention is by no means limited to the embodiments described as example and shown in the drawings, but a multistage centrifugal compressor according to the invention can be realized a variety of forms and dimensions without departing from the scope of the invention.