Improved turbo compressor.

The present invention concerns an improved turbo compressor, in particular a radial turbo compressor which consists of a housing with a volute casing in which has been provided a rotor which can turn by means of a shaft and an inlet piece forming an axial guide for the gas which is sucked in by the rotor.

In order to restrict losses with the known turbo compressors, the play between the rotor and the inlet piece, or what is called the "shroud play", is set with great precision.

With turbo compressors which are moreover provided with a diffuser having a number of outlet guide vanes on the delivery side, plays between said outlet guide vanes and the inlet piece must be avoided in order to prevent losses.

It is known that, during the assembly of turbo compressors, use is made of spacers or shims in order to adjust the play between the inlet piece and the rotor and to adjust the diffuser height, and to moreover compensate tolerance deviations of the rotor.

However, a disadvantage of such an adjustment is that setting the play in this manner between the inlet piece and the rotor and of the diffuser height is very time-consuming because of the many measuring and control operations.

With the known turbo compressors, the axial deformation of

the outer edge of the rotor, which occurs while the turbo compressor is operational due to high peripheral velocities, is compensated somewhat by selecting the axial play between the inlet piece and the rotor such that it is optimal at the maximum speed of the rotor.

This is disadvantageous, however, in that the play is larger than necessary at low speeds, which results in additional losses and thus a lower output.

The present invention aims to remedy one or several of the above-mentioned and other disadvantages.

To this end, the present invention concerns an improved turbo compressor which is formed of a housing with a volute casing in which has been provided a rotor which can turn around an axis and an inlet piece forming an axial guide for the gas which is sucked in by the rotor, whereby a diffuser with a number of outlet guide vanes has been provided on the delivery side of the rotor and whereby the turbo compressor comprises means which constantly keep the diffuser with its outlet guide vanes against the inlet piece.

An advantage of such an improved turbo compressor according to the invention is that, thanks to the presence of the above-mentioned means, after the once-only setting of the play between the rotor and the inlet piece, no separate setting of the diffuser height is required, which simplifies and quickens the assembly of the turbo compressor as compared to that of conventional turbo

compressors.

According to a preferred characteristic of a turbo compressor according to the invention, the above-mentioned inlet piece can be axially moved in relation to the rotor and the turbo compressor comprises means to adjust the axial play between the inlet piece and the rotor.

The above-mentioned means for adjusting the axial play between the inlet piece and the rotor preferably comprise an actuator to axially move the inlet piece, whereas the turbo compressor, either or not combined with said actuator, is preferably provided with measuring means to determine the axial play between the inlet piece and the rotor, such that the above-mentioned play can be set at a desired value as a function of the above-mentioned findings of the measuring means.

These preferred characteristics are advantageous in that a precise setting of the axial play between the inlet piece and the rotor is made possible and/or in that one can immediately react on changes of speed and/or deformations of the rotor by adjusting the play between the inlet piece and the rotor in an appropriate manner.

In order to better explain the characteristics of the present invention, the following preferred embodiments of an improved turbo compressor according to the invention are represented by way of example only without being limitative in any way, with reference to the accompanying drawings, in which:

figure 1 is a section of an improved turbo compressor according to the invention; figure 2 represents the part indicated by F2 in figure 1 to a larger scale; figure 3 shows a view according to figure 2, but for another position of the inlet piece.

Figures 1 to 3 represent an improved turbo compressor 1 according to the invention, provided with a housing 2 with a volute casing 3 in which has been provided a rotor 4 or "impeller" such that it can turn by means a shaft 5, whereby the shaft 5 consists for example of a motor shaft or a driven shaft of a reduction gearbox.

The turbo compressor 1 further comprises an inlet piece 6, also called "shroud", which is axially opposite the above- mentioned rotor 4 when mounted and which forms an axial guide for the gas that is sucked in by the rotor 4.

In this embodiment, the inlet piece 6 on the radial peripheral edge is provided with a flange 7 which is fixed to the volute casing 3 by means of an end flange.

To this end, the end flange 8 and the volute casing 3 are provided with a recess, such that when the end flange 8 and the volute casing 3 are fixed to one another, a space 9 is created in which the above-mentioned flange 7 of the inlet piece 6 extends with an axial play, such that the inlet piece 6 can axially move in relation to the rotor 4.

In this embodiment, the turbo compressor 1 further comprises means to adjust the axial play between the inlet piece 6 and the rotor 4 while the turbo compressor 1 is operational, which in this case comprise an actuator 10 made for example in the shape of a pneumatic, hydraulic, electrical and/or electronic actuator provided in the above-mentioned space 9 in the present embodiment, in particular between the flange 7 of the inlet piece 6 and the end flange 8.

In the above-mentioned space 9 is in this case also provided a stop 11 for the flange 7 of the inlet piece 6, which is positioned such that, when the actuator 10 falls out, a preset axial play between the inlet piece 6 and the rotor 4 will still be guaranteed.

On the other side of the flange 7, a spring 12 is in this case provided in the above-mentioned space 9, exerting a pressure on the flange 7, away from the direction of the rotor 4. This is advantageous in that, if the actuator 10 falls out, for example in case of a defect, the inlet piece 6 will not be pressed against the rotor 4.

The turbo compressor 1 according to the invention preferably also comprises measuring means to determine the axial play between the inlet piece 6 and the rotor 4.

In the given example, the above-mentioned measuring means are made in the form of one or several distance sensors 13 which are either mounted on the inlet piece 6 or on the volute casing 3 respectively, and which make it possible to

determine the axial play between the inlet piece 6 and the rotor 4.

In this case, a diffuser 14 is provided on the delivery side of the rotor 4, between the inlet piece 6 and the volute casing 3, which is made in the form of a diffuser plate 15 on which are provided a number of outlet guide vanes 16.

In this embodiment, the above-mentioned diffuser plate 15 is at least partially provided in a recess 17 provided to that end in the volute casing 3, such that this diffuser plate 15 can shift according to the axial direction of the rotor 4.

Preferably, the turbo compressor 1 comprises means 18 which constantly keep the diffuser 14 with its outlet guide vanes 16 against the inlet piece 6, which means 18 are in this case made in the form of elastic means, for example a spring 19 provided in the above-mentioned recess 17, between the diffuser plate 15 and the volute casing 3, and which pushes the diffuser 14 against the inlet piece 6.

According to a preferred characteristic which is not represented in the drawings, an improved turbo compressor 1 according to the invention is finally also provided with a controller which is connected to the above-mentioned measuring means to determine the axial play between the inlet piece 6 and the rotor 4 on the one hand, and to the above-mentioned actuator 10 in order to axially move the inlet piece 6 on the other hand.

The working of an improved turbo compressor 1 according to the invention is very simple and as follows.

While the rotor 4 is being driven, the turbo compressor 1 sucks in a gas via the inlet piece 6 which is flung away by the rotor 4 as a result of the centrifugal forces and which subsequently flows through the outlet guide vanes 16 towards the volute casing 3, such that the kinetic energy is converted into pressure.

The above-mentioned spring 12 hereby constantly pushes against the flange 7, such that, when there is no control signal from the actuator 10, the inlet piece 6 will be constantly pressed against the stop 11 so as to guarantee a preset axial play between the inlet piece 6 and the rotor 4.

Should there be an axial movement of the rotor 4 and/or an axial deformation of the rotor 4 at high rotational speeds, this will be detected by means of the above-mentioned measuring means.

Should it turn out that the above-mentioned determined play between the inlet piece 6 and the rotor 4 may not be optimal, an appropriate signal will be sent to the actuator 10 in order to obtain an axial movement of the inlet piece 6.

The above-mentioned control signal for the actuator 10 may for example originate from the above-mentioned controller

which compares the measured axial play between the inlet piece 6 and the rotor 4 to a preset desired value and, if both values differ, it will command the actuator 10 to adjust said play.

The above-mentioned desired value may hereby be a constant value, but it may also be a variable value as a function of for example the rotational speed of the rotor, the outlet pressure of the turbo compressor 1 and/or the like.

Naturally, the above-mentioned measuring means can be made in other ways to this end than in the form of distance sensors, such as in the form of a rotational speed sensor or a pressure sensor or a combination of different types of sensors and/or meters.

Since the diffuser 14 is constantly pressed with its outlet guide vanes 16 against the inlet piece 6, a constant diffuser height D will be maintained, whereas the play between the inlet piece 6 and the rotor 4 is constantly adjusted, depending on the immediate conditions while the turbo compressor 1 is operational.

The above-mentioned means 18 which constantly keep the diffuser 14 with its outlet guide vanes 16 against the inlet piece 6 can also be realised in other ways according to the invention than in the shape of the above-mentioned spring, such as in the shape of screws which, according to a special characteristic of the invention, are screwed through the above-mentioned outlet guide vanes 16.

Such a variant of a turbo compressor 1 whereby screws are screwed through the outlet guide vanes 16 may be interesting for example in applications having broad outlet guide vanes 16.

According to another special characteristic of the invention, the diffuser 14 can be fixed in an almost inseparable manner to the inlet piece 6, for example by means of gluing, welding or the like.

In the above-described embodiment of an improved turbo compressor 1 according to the invention, the inlet piece 6 can be axially moved, but it is also possible according to the invention to provide the turbo compressor 1 with a fixed inlet piece 6, whereby the play between the rotor 4 and the inlet piece 6 is set only once, but whereby, thanks to the presence of the above-mentioned means 18 which constantly keep the diffuser against the inlet piece 6, the diffuser height no longer has to be set as separate.

Consequently, such an improved turbo compressor 1 according to the invention is advantageous in that it can be assembled in a faster and simpler way than conventional turbo compressors.

Naturally, an improved turbo compressor 1 can be used to compress any sort of gas or mixture of gases such as air or the like.

The present invention is by no means restricted to the embodiments described as an example and represented in the

accompanying drawings; on the contrary, such an improved turbo compressor according to the invention can be made in various shapes and dimensions while still remaining within the scope of the invention.