JPH01267397A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To improve the performance efficiency of a centrifugal compressor provided with an open-type impeller by making it possible to adjust clearance between the end of the impeller and the shroud part of a casing so that the clearance increases during a starting period, and decreases in a regular operating condition. CONSTITUTION:A pinion shaft 2 fitted with an open-type impeller 1 on its one side is supported by each journal bearing 11 within a casing 9, and the position of the impeller 1 in its axial direction is controlled by the thrust bearing 4 of a gear shaft 3 through each thrust collar 8 which is provided for the pinion shaft 2 and the gear thrust receiving surface of the gear shaft 3. Clearance is provided between the vane end of the impeller 1 and the shroud part 10 of a casing 9, and a thrust bearing housing 5 is shifted in its axial direction by a working mechanism including hydraulic pistons 6, 7, so that the clearance can be adjusted. Then the clearance is increased in starting the compressor concerned, so that the contact of the impeller 1 with the shroud part 10 due to its vibration can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a centrifugal compressor having an open type impeller, and in particular, to prevent contact between the blade tips of the open type impeller and the casing. The present invention relates to a centrifugal compressor in which the gap between the compressors can be adjusted between startup and steady operation.

[Conventional technology]

As a conventional example of a multi-shaft centrifugal compressor having an open impeller, there is one such as that described in Japanese Patent Application Laid-open No. 70997/1983. FIG. 4 is a cutaway plan view of a conventional example, in which a pinion shaft 2 with an open type impeller 1 attached to one end is supported by a journal bearing 11 in a casing 9, and the axial position of the open type impeller 1 is The thrust bearing 4 of the gear shaft 3 (fixed to the casing 9) is connected via the thrust collar 8 provided on the shaft 2 and the gear thrust receiving surface of the gear shaft 3.
regulated by. Fluid is sucked in from the axial direction.

The structure is such that the fluid is sucked into the next stage impeller through the flow path between the impellers, thereby compressing the fluid.

In a centrifugal compressor having such an open type impeller, the gap Z (see Fig. 5) between the blade tip (long plane direction) of the open type impeller 1 and the flow path surface of the shroud 10 of the casing is determined in terms of compressor efficiency. From the point of view, smaller is better, but
In order to avoid contact between the impeller and the shroud, the value is usually taken into account the deformation of the impeller due to centrifugal force during operation, and the difference in expansion due to the difference in thermal expansion between the impeller and the casing.

This is fine if the pinion shaft 2 is a rigid shaft that operates below the primary critical rotation speed, which is the shaft's eigenvalue, but recently, in order to meet the demand for smaller and faster compressors, the primary critical rotation speed has been It has become necessary to adopt flexible shafts that operate at higher rotational speeds. In this case, since the shaft is operated at a rotation speed that exceeds the primary critical rotation speed, which is an inherent value of the shaft, the clearance Z is determined by A value that also takes into account the vibration of the impeller due to resonance was added to the above value. There must be a large gap.

As described above, the requirements for the size of the gap Z are different from the viewpoint of compressor efficiency and from the viewpoint of preventing contact between the blade tip of the open type impeller and the shroud part in order to prevent damage to the machine. .

[Problem to be solved by the invention]

As mentioned above, the gap between the blade tip of an open impeller and the shroud part of the casing should be small to improve compressor efficiency, but it must be large enough to prevent contact. There is a problem that it must be done. In particular, in conventional technology, when a flexible shaft-type pinion shaft is used that operates at a rotation speed exceeding the primary critical rotation speed, this problem occurs when the primary critical rotation speed is passed between the time of startup and the rated rotation speed. Since the gap must be made larger in consideration of vibration due to resonance, this poses a major problem in terms of compressor efficiency.

The present invention has been made to solve the above problem, and its purpose is to intentionally reduce the gap between the blade tip of the open type impeller and the shroud portion from the time the compressor is started to the steady state of operation. It is possible to increase the compressor efficiency by increasing the above-mentioned gap to avoid contact due to resonance when passing through the primary critical rotation speed, and by reducing the above-mentioned gap when the steady state of operation is reached.
Our goal is to provide centrifugal compressors.

[Means for Solving the Problem] In order to achieve the above object, the present invention incorporates a speed increasing gear,
In a single-stage or multi-stage centrifugal compressor that has an open impeller at one end of one or more pinion shafts and is operated at a rotation speed exceeding the primary critical rotation speed, the axial position of the impeller is A hydraulic or pneumatic actuation mechanism is provided to control the thrust bearing of the gear shaft through the thrust collar of the pinion shaft and the gear thrust receiving surface of the gear shaft, and to move the thrust bearing in the axial direction, and the axial movement of the thrust bearing is provided. The axial position of the impeller is changed between startup and steady operation.
It is characterized by being able to adjust the gap between the blade tip of the open type impeller and the shroud part of the casing.

[Effect]

The axial position of the impeller is regulated by the thrust bearing of the gear shaft via the thrust collar of the pinion shaft and the gear thrust receiving surface of the gear shaft. A hydraulically or pneumatically actuated piston is installed in the engine, and the thrust bearing is moved in the axial direction by actuating each piston at startup and during steady operation, so that the gear shaft and pinion shaft also move in the axial direction at the same time. By changing the axial position of the impeller, it is possible to adjust the gap between the blade tips of the open type impeller and the shroud portion.

Therefore, during the start-up period when the primary rotational speed is passed, the gap is increased to prevent contact, and when the steady state of operation is reached, the gap is decreased to increase the efficiency of the compressor.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 is a cutaway plan view of a multi-shaft centrifugal compressor that has an open impeller with variable axial position on the same side of the casing.
The pinion shaft 2 with the attached pinion shaft 2 is supported by a journal bearing 11 in the casing 9, and the axial position of the impeller 1 is determined by the gear thrust collar 8 provided on the pinion shaft 2 and the gear thrust receiving surface of the gear shaft 3. It is regulated by the thrust bearing 4 of the shaft 3. The structure is such that the fluid is sucked in from the axial direction, passes through the flow path between the impellers, and is sucked into the impeller of the next stage, thereby compressing the fluid.

There is a gap Z as shown in FIG. 5 between the blade tips of the open type impeller 1 and the shroud part 10 of the casing.
Impeller 1, which is a rotating body, and shroud part 10 of the casing
The structure is such that there is no contact between the two. In addition, in order to adjust the gap 2 by changing the axial position of the impeller 1 between startup and steady operation, the thrust bearing housing 5 supporting the thrust bearing 4 is moved in the axial direction by a hydraulic or pneumatic actuation mechanism. It is incorporated into the casing 9 so as to be movable. Details of the thrust bearing housing section with hydraulic or pneumatic actuation mechanism are shown in FIG.

Pistons 6 are provided on both the left and right sides of the thrust bearing housing 5.
and pistons 7 are attached, and the thrust bearing housing 5 is structured to move in the axial direction when hydraulic pressure or air pressure is introduced to the bottom side of each piston to operate the pistons.

The amount of movement may be approximately a few 1 at most. When starting the compressor, hydraulic pressure or air pressure is applied to the piston 6 side to operate the piston 6. When the piston 6 operates,
As the thrust bearing 4 supported by the thrust bearing housing 5 moves to the left, the gear shaft 3 and the pinion shaft 2 whose axial position is regulated by the gear shaft 3 via the thrust collar 8 also move in the same direction. Moving. As a result, the open type impeller 1 attached to the right end of the pinion shaft 2 is separated from the shroud portion 10 of the casing, and the gap 2 becomes larger. If operation is started in this state, as shown in FIG. do not contact, and when the rotational speed has increased to the rated speed and entered a steady operating state, apply hydraulic or air pressure to the piston 7 side and operate the piston 7 to return the axial position of the thrust bearing 4 to its original position. , gear shaft 3
The pinion shaft 2 also moves to the right, making it possible to reduce the gap Z between the blade tips of the impeller 1 and the shroud portion 10. Therefore, according to this embodiment, it is possible to operate the compressor while maintaining the minimum clearance that provides good performance efficiency.

〔Effect of the invention〕

According to the present invention, in a centrifugal compressor having an open type impeller, when a flexible shaft that operates at a rotation speed exceeding the primary critical rotation speed is adopted to make the compressor smaller and faster,
The gap between the blade tip of the open impeller and the shroud part of the casing can be increased during the startup period when the primary critical rotational speed has been passed, and can be reduced during steady operation, resulting in better performance than machines with conventional structures. This has the effect of providing this type of centrifugal compressor with high efficiency. Further, since it is sufficient to provide a gap adjustment mechanism at one thrust bearing of the gear shaft, the structure is also simple.

[Brief explanation of the drawing]

Fig. 1 is a cutaway plan view of a multi-shaft centrifugal compressor with an open impeller according to an embodiment of the present invention, Fig. 2 is an enlarged view of section A in Fig. 1, and Fig. 3 is the amplitude characteristics of a flexible shaft. figure,
FIG. 4 is a cutaway plan view of a conventional multi-shaft centrifugal compressor having an open impeller, and FIG. 5 is an enlarged view of section B in FIG. 4. 1... Open type impeller, 2... Binion shaft, 3...
... Gear shaft, 4... Thrust bearing, 5... Thrust bearing housing, 6, 7... Piston for thrust bearing movement, 8... Thrust collar, 9... Casing,
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Claims (1)

[Claims] 1. A single-stage or multi-stage centrifugal device that has a speed-increasing gear built into the casing, has an open impeller at one end of one or more pinion shafts, and is operated at a rotation speed exceeding the primary critical rotation speed. In a compressor, a hydraulic or pneumatic operating mechanism that regulates the axial position of an impeller by a thrust bearing of a gear shaft via a thrust collar of a pinion shaft and a bay thrust bearing surface of a gear shaft, and that moves the thrust bearing in the axial direction. The axial movement of the thrust bearing allows the axial position of the impeller to be changed between startup and steady operation, thereby adjusting the gap between the blade tips of the open type impeller and the shroud portion of the casing. A centrifugal compressor featuring: