Expansion turbine

Abstract

An expansion turbine, exhibiting at least one turbine rotor that is mounted on an axial bearing, wherein an axial disk (2l) of the axial bearing is configured in the shape of an axial bearing spindle. The axial disk (2l) is preferably positioned substantially in the middle of the overall length of the turbine shaft (1).

Description

The invention relates to an expansion turbine that has at least one turbine rotor that is mounted on an axial bearing.

Expansion turbines have been used for a long time for cooling in the case of industrial gases, such as, for example, hydrogen, helium and nitrogen. In this case, heat is removed from the process gas to be depressurized via substantially isentropic gas depressurization and the conversion of the force of flow in a rotational movement of the turbine rotor to the process gas. Thus, the process gas to be depressurized is cooled in this process in the turbine stage.

Various designs exist for the bearing arrangement of expansion turbines. Dynamic gas-bearing expansion turbines have gas bearings that do not require an external supply of gas bearings to operate. Only for starting up and shutting down is a temporary supply with bearing gas necessary. In the case of dynamic gas-bearing expansion turbines, radial bearings and an axial bearing are used for the bearing arrangement of the turbine shaft. The central functional element of the axial bearing arrangement here is the axial disk that takes up the axial thrust on the turbine shaft in the direction of the turbine and in the opposite direction.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The generic expansion turbines or their axial bearing arrangement can be explained in more detail below based on the embodiment that is shown in FIGS. 1a and 1b. In this connection,

FIGS. 1a and 1b show schematized lateral sectional views through the embodiment.

An upper axial bearing 3 and a lower axial bearing 4 are shown. The axial bearings 3 and 4 are used to take up the axial disk 2 that is connected to the turbine shaft 1. The axial disk 2 together with the axial bearing 3 on the one hand and the axial bearing 4 on the other hand in each case forms two pairs of bearing effective surfaces. These pairs of bearing effective surfaces have the object of taking up the axial thrust in both possible directions along the axis of rotation of the turbine shaft 1.

The actual zone of the bearing arrangement is in the bearing effective surfaces near the shank of the turbine shaft 1 in the inner area of the axial disk 2. The outer area of the bearing effective surfaces primarily conveys gas from outside to inside in the bearing zone. The zone of maximum load capacity is marked with a circle 5 in FIG. 1a.

If high peripheral speeds now occur, the bearing effective surfaces of the axial disk 2 deform—as shown in FIG. 1b—by a few microns in absolute length in an elastically concave manner. This undesirable, elastically concave deformation reduces the load capacity of the axial bearing for the following reasons:

The load capacity is determined essentially by the distance between the pair of bearing effective surfaces on the rotor (axial disk 2) to the stator (axial bearing 3 or axial bearing 4). The distance between the bearing effective surfaces from the rotor to the stator is only a few microns in the state of operation. In principle, it holds true that the smaller the possible distance that is to be set between the bearing effective surfaces, the greater the load capacity of the axial bearing. The elastically concave deformation of the bearing effective surfaces on the rotor reduces the possible distance to be set between the bearing effective surfaces. The elastic deformation on the outside edge of the rotor (axial disk 2) increases the minimum possible distance to the stator (axial bearing 3 or axial bearing 4), since otherwise, if the bearing effective surfaces are too close together, the rotor and stator will collide. In this case, it holds true that: the load capacity decreases with increasing distance of the bearing effective surfaces from rotor and stator.

With increasing speed, a latent imbalance of the turbine rotor 1 results in increasing wobbling of the axial disk 2. Because of the unfavorable elastically concave deformation on the outside edge, the wobbling increases the risk of collision and reduces the bearing effective surface on the axial disk 2.

Moreover, the elastically concave deformation of the axial disk 2 counteracts the functioning of the axial bearing arrangement—namely a geometric unit that pumps from the outside inward, with a cross-sectional constriction and delayed flow, leading to pressure build-up.

Based on the indicated properties of the existing design, the potential and functionality of the bearing effective surfaces for the axial bearing cannot be exhausted at higher rpms.

The object of this invention is to provide expansion turbine, exhibiting at least one turbine rotor that is mounted on an axial bearing, which avoids the previously described drawbacks.

To achieve this object, an expansion turbine that has at least one turbine rotor that is mounted on an axial bearing is proposed, which is characterized in that the axial disk of the axial bearing is designed in the form of an axial bearing spindle.

Corresponding to another advantageous embodiment of the expansion turbine according to the invention, the axial disk is arranged essentially in the middle of the overall length of the turbine shaft or the turbine rotor.

The expansion turbine according to the invention as well as other configurations of the same can be explained in more detail below based on the embodiment that is shown in FIGS. 2a and 2b. In this connection, FIGS. 2a and 2b show schematized lateral sectional views through the embodiment.

In turn, an upper axial bearing 3 and a lower axial bearing 4 are shown. As is readily seen in FIGS. 2a and 2b or the axial disc has a concave periphery 6 formed by surfaces 7 and 8 that converge toward nadir 9. Serve to hold the axial disk 2′, which is connected to the rotor shaft 1, which axial disk is designed, according to the invention, in the form of an axial bearing spindle. The zone of maximum load capacity is also labeled with a circle 5 in FIG. 2a.

If high peripheral speeds now occur, the result is also an elastic and—because of the spindle shape—convex deformation of the bearing effective surfaces of the axial disk 2′ by a few microns in absolute length, as is shown in FIG. 2b. This elastic convex deformation now increases the load capacity of the axial bearing, however, for the following reasons:

The elastic convex deformation of the axial disk 2′ that occurs influences the distance of the bearing effective surfaces that is to be set between the rotor (axial bearing spindle) and the stator (axial bearing 3 or 4) in a positive way. The minimum possible distance of the bearing effective surfaces between the rotor and the stator is reduced, and the maximum load capacity is increased.

The axial disk 2′ is preferably arranged in the middle of the overall length of the turbine rotor. Because of the geometric shaping of the axial disk 2′ as an axial bearing spindle, the gyroscopic effect of a spinning top counteracts possible wobbling induced by a latent imbalance of the turbine shaft 1. The convexity of the elastic convex deformation of the bearing effective surfaces of the rotor is uncritical compared to a possible risk of collision on the outside edge of the axial disk 2′.

Moreover, the elastic convex deformation of the axial disk 2′ is supportive of the functioning of the bearing effective surfaces. A cross-sectional constriction occurs from the outside edge of the axial disk 2′ inward to the bearing effective surface near the shank 1 of the turbine rotor. Thus, the compression action of the bearing effective surfaces is required.

Because of the cited properties of the expansion turbine according to the invention, the potential and functionality of the bearing effective surfaces for the axial bearing can now be fully exhausted at higher rpms for the first time.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding German application No. 10 2007 029 881.3, filed Jun. 28, 2007 is incorporated by reference herein.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

1. An expansion turbine, comprising at least one turbine rotor mounted on an axial bearing, wherein the bearing has an axial disk (2′) configured in the shape of an axial bearing spindle.

2. The expansion turbine according to claim 1, wherein the axial disk (2′) is positioned in the middle of the overall length of the turbine shaft (1).

3. The expansion turbine according to claim 1 wherein the axial disk (2′) has a concave periphery.

4. The expansion turbine according to claim 2 wherein the axial disk (2′) has a concave periphery.