JP5294729B2 - Expansion turbine - Google Patents

Description

  The present invention relates to an expansion turbine having at least one turbine rotor supported by a thrust bearing.

Expansion turbines have been used for a long time to generate cryogenic temperatures in gas process technologies such as hydrogen, helium and nitrogen, as disclosed in, for example, US Pat. In this case, the process gas loses due to gas expansion in the turbine, and the fluid power of the gas is converted into the rotational motion of the turbine rotor, thereby depriving the process gas of heat output. Therefore, in this process, the process gas is cooled in the turbine stage.
JP 2000-120402 A

  There are various structural types of expansion turbine bearing mechanisms. The gas bearing installed in the dynamic pressure gas bearing type expansion turbine does not require the supply of bearing gas from the outside while the turbine is operating, but it is necessary to supply the bearing gas temporarily when starting and stopping. In a dynamic pressure gas bearing type expansion turbine, a radial bearing and a thrust bearing are incorporated in a turbine shaft bearing mechanism. In this case, the main functional element of the thrust bearing mechanism is a thrust disk that absorbs the thrust force acting on the turbine shaft both in the turbine flow direction and in the reverse direction.

  A structural example of a main part of a thrust bearing mechanism used in a conventional expansion turbine will be described in detail with reference to FIG.

  In FIG. 2, the turbine shaft 1 is arranged vertically, and the turbine flow flows from top to bottom. A thrust disc 2 coupled to the turbine shaft 1 is disposed between the upper thrust bearing 3 and the lower thrust bearing 4. The thrust disc 2 forms a bearing working surface with the thrust bearing 3 on the upper surface side, and forms a bearing working surface with the thrust bearing 4 on the lower surface side. The pair of bearing action surfaces are action surfaces for absorbing the thrust force acting on the turbine shaft 1 in both directions along the rotation axis of the turbine shaft 1.

  The main region that performs the original function as the bearing working surface is an inner region that is biased to the vicinity of the turbine shaft 1 in the bearing working surface of the thrust disc 2. The outer region of the bearing working surface first serves to carry the bearing gas from the outside to the main region on the bearing working surface from the outside to the inside. A portion 5 surrounded by a circle in FIG. 2A shows a main region where the load load is the highest as a thrust bearing.

  When the turbine rotates at a high speed and a high peripheral speed is generated in the thrust disk 2, the bearing working surface of the thrust disk 2 becomes concave by a few micrometers in absolute length as shown exaggeratedly in FIG. Elastically deforms. This concave elastic deformation is undesirable because it reduces the bearing load capacity of the thrust bearing mechanism for the reasons described below.

  The bearing load capacity force of the thrust bearing mechanism substantially depends on the size of the facing gap between the bearing acting surface on the turbine rotor side (thrust disk 2) and the bearing acting surface on the stator side (thrust bearing 3 or thrust bearing 4). Determined. The facing gap between the bearing working surface on the turbine rotor side and the bearing working surface on the stator side is only a few micrometers in the operating state. As a basic principle, the bearing load capacity of the thrust bearing mechanism increases as the opposing gap on the bearing acting surface becomes narrower. When the bearing working surface on the turbine rotor side is elastically deformed into a concave shape by high speed rotation, the facing gap of the bearing working surface is inevitably narrowed. The elastic deformation of the bearing working surface on the turbine rotor side due to such high-speed rotation appears particularly near the outer edge of the thrust disc 2, and thereby the minimum allowable clearance with respect to the bearing working surface (thrust bearing 3 or thrust bearing 4) on the stator side. As a result, the value of must be increased. The reason for this is that if the facing gap between the bearing working surfaces becomes too narrow during high-speed rotation, the bearing working surfaces on the turbine rotor side and the stator side may mechanically interfere with each other, causing damage. In this case, as a matter of course, the bearing load capacity of the thrust bearing mechanism decreases as the facing gap between the bearing working surfaces on the turbine rotor side and the stator side increases.

  Further, when the rotational speed of the turbine is increased, the oscillation of the thrust disk 2 is increased due to the potential non-equilibrium (core runout or the like) of the turbine shaft 1. When this oscillation increases, the risk of mechanical interference between the bearing working surfaces increases due to the concave elastic deformation that appears particularly conspicuously at the outer peripheral edge of the thrust disc, and in some cases, the bearing working surface of the thrust disc 2 Will be damaged.

  Further, when the thrust disc 2 is elastically deformed into a concave shape, an important function of the thrust bearings on both sides thereof, that is, the flow of the bearing gas decelerated by the pressure increase due to the narrow cross-sectional area between the thrust discs. This results in an impediment to the ability of the geometric unit to pump the bearing gas from outside to inside.

  Therefore, in the conventional expansion turbine, due to the characteristics of the thrust bearing mechanism as described above, the bearing load capacity and the function that the bearing working surface of the thrust bearing mechanism should exhibit should be fully utilized when the turbine has a relatively high rotational speed. There is a problem that can not be.

  The main object of the present invention is to solve the above-mentioned problems in an expansion turbine having at least one turbine rotor supported by a thrust bearing, and to realize the original bearing load capacity and function of the thrust bearing mechanism even during high-speed rotation. It is providing the expansion turbine which can exhibit stably.

  In order to solve this problem, in the expansion turbine according to the present invention, the thrust disk constituting the thrust bearing mechanism for supporting the turbine rotor is spindle-shaped, that is, two conical cones having the same shape are concentrically between the top surfaces of the heads. It is formed in the form of an overlapped spindle.

  According to a preferred embodiment of the expansion turbine according to the invention, the thrust disc is arranged at approximately the center position of the turbine shaft and thus the entire length of the turbine rotor.

  According to the expansion turbine of the present invention, the original bearing load capacity and function of the thrust bearing mechanism can be stably exhibited, particularly during high-speed rotation.

  The features and advantages of the expansion turbine according to the present invention will be described in detail with reference to the embodiment shown in FIG.

  As shown in FIG. 1A, in the expansion turbine according to the present embodiment, the turbine shaft 1 is arranged in the vertical direction, and the turbine flow flows from top to bottom. A thrust disc 2 ′ coupled to the turbine shaft 1 is disposed between the upper thrust bearing 3 and the lower thrust bearing 4, and the thrust disc 2 forms a bearing working surface with the thrust bearing 3 on the upper surface side. Further, a bearing working surface with the thrust bearing 4 is formed on the lower surface side. The pair of bearing action surfaces are action surfaces for absorbing the thrust force acting on the turbine shaft 1 in both directions along the rotation axis of the turbine shaft 1. The thrust disk 2 'is formed in a spindle shape according to the present invention, that is, in the shape of a spindle (conical shape) in which two truncated cones having the same shape are concentrically overlapped with each other at the top surfaces of the truncated surfaces. Here, a portion 5 surrounded by a circle in FIG. 1A indicates a main region where the load load becomes the highest as a thrust bearing.

  When the turbine rotates at a high speed and a high peripheral speed is generated in the thrust disk 2 ′, the bearing working surface of the spindle-shaped thrust disk 2 ′ is several micrometers in absolute length as shown in an exaggerated manner in FIG. The bearing acting surface is elastically deformed so as to be convex toward the center of the thickness of the thrust disk as the outer surface is farther from the turbine shaft 1 in a convex shape by a meter. However, this convex elastic deformation now acts to increase the bearing load capacity of the thrust bearing mechanism for the reasons described below.

  When a convex elastic deformation appears in the spindle-shaped thrust disc 2 ′, the elastic deformation is caused by the bearing acting surface on the turbine rotor side (spindle-shaped thrust disc 2 ′) and the bearing acting surface on the stator side (thrust bearing). 3 or the thrust bearing 4) is positively affected. That is, when the bearing working surface on the turbine rotor side is elastically deformed into a convex shape so that the outer edge side farther from the turbine shaft 1 is bent toward the center of the thickness of the thrust disk by high-speed rotation, the opposing gap of the bearing working surface is particularly thrust. It expands in the region near the outer edge of the disk 2 ′. As a result, the value of the minimum allowable clearance with respect to the bearing working surface (thrust bearing 3 or thrust bearing 4) on the stator side can be set small, the bearing load capacity of the thrust bearing mechanism can be increased, and high-speed rotation can be achieved. Occurrence of mechanical interference between the bearing surfaces on the turbine rotor side and the stator side due to the narrowing of the gap between the bearing surfaces at the time can also be avoided.

  The spindle-shaped thrust disc 2 'is preferably arranged at approximately the center of the turbine shaft 1 and thus the entire length of the turbine rotor. As a result, the gyro effect caused by the high-speed rotation of the thrust disk 2 ′ geometrically formed in the spindle shape is the fluctuation of the core runout induced by the non-equilibrium potentially existing in the turbine shaft 1. This effectively acts as a counter-moment to suppress the movement, and at the same time, the bearing acting surface on the turbine rotor side is elastically deformed into a convex shape, so that the outer edge portion of the thrust disc 2 ′ and the bearing on the stator side The possibility of causing mechanical interference with the working surface is further reduced.

  Furthermore, it is also beneficial from the functional aspect of the bearing working surface for the bearing gas that the spindle-shaped thrust disc 2 'is elastically deformed into a convex shape during high-speed rotation. That is, at the time of high speed rotation, the flow path cross-sectional area of the bearing gas formed by the facing gap between the bearing working surfaces decreases as it approaches the turbine shaft 1 from the outer edge of the thrust disk 2 ′ toward the inside. The function of pumping the bearing gas from the outside to the inside is promoted by generating a flow of the bearing gas that is effectively decelerated by the pressure increase due to the cross-sectional area of the channel that becomes narrower toward the inside.

It is a model side view which shows the principal part structural example of the thrust bearing mechanism in the expansion turbine by one Embodiment to this invention, (a) is a basic arrangement state, (b) shows the time of high speed rotation. It is a model side view which shows the principal part structural example of the thrust bearing mechanism in the conventional expansion turbine, (a) is a basic arrangement state, (b) shows the time of high speed rotation.

Explanation of symbols

  1: turbine shaft, 2: thrust disk, 2 ': spindle-shaped thrust disk, 3: thrust bearing, 4: thrust bearing, 5: main area of thrust bearing

Claims (1)

In an expansion turbine having at least one turbine rotor supported by a thrust bearing, a thrust disk (2 ') constituting a thrust bearing mechanism is formed by concentrically stacking two truncated cones having the same shape between the top surfaces of the truncated surfaces. the thickness of which is formed in the combined form, said turbine rotor side thrust disc constituting the bearing working surface (2 ') a thrust disc distant outer edge from the axis of the turbine rotor by the rotation (2') Elastically deformed to bend toward the center ,
An expansion turbine characterized in that the thrust disk (2 ') is arranged at a substantially central position along the entire length of the turbine shaft (1).

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