JPH0676697U - Centrifugal compressor - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to widen the flow rate range for stable operation. [Configuration] A first slit provided concentrically with the impeller on the diffuser wall at the diffuser inlet and a second slit provided concentrically with the first slit on the diffuser wall in the middle of the diffuser are formed by the bypass flow passage. Configure to communicate.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a centrifugal compressor applied to gas compression, air blowing, and the like. The centrifugal compressor in this specification includes a centrifugal blower.

[0002]

[Prior art]

FIG. 3 is an explanatory diagram of a conventional centrifugal compressor used for compressing gas and blowing air. In the figure, the present centrifugal compressor has a vaned diffuser, and the vaned diffuser has a plurality of blades 201 installed between the radius R ₁ and the radius R ₂ in a rotationally symmetrical manner with respect to the rotary shaft 202 of the impeller. Further, two annular discs 203 and 204 are installed so as to sandwich the blade 201. The vaned diffuser is composed of these two discs 203 and 204 and the blade 201. In the center of the figure, there is shown a velocity triangle of the flow at the radius R ₁ of the inlet of the blade 201 flowing out from the impeller and flowing into the vaned diffuser. This flow flows in the direction of C ₁ design indicated by the solid line at the design point, and the incident angle i to the blade 201 at this time is indicated by i design.

[0003]

[Problems to be solved by the device]

In the conventional centrifugal compressor as described above, when the flow rate is reduced, the flow velocity at the inlet of the blade 201 flowing out from the impeller and flowing into the vaned diffuser becomes smaller in the radial direction of the triangle, and the flow becomes a dotted line. It changes to the direction of C ₁ surge shown by. Therefore, the incident angle i at the entrance of the blade 201 increases from idesign to isurge, the blade 201 stalls, and surging occurs. As described above, in the conventional centrifugal compressor, as the flow rate is decreased, the surging of the vanes 201 in the vaned diffuser causes surging, so that the flow rate range in which stable operation is possible is narrowed.

[0004]

[Means for Solving the Problems]

 The centrifugal compressor according to the present invention is intended to solve the above-mentioned problems, and includes a first slit provided concentrically with the impeller on the diffuser wall of the diffuser inlet, and the above-mentioned diffuser wall in the middle of the diffuser. The present invention is characterized by a second slit provided concentrically with the first slit, and a bypass passage connecting the first slit and the second slit to each other.

[0005]

[Action]

 That is, in the centrifugal compressor according to the present invention, the first slit provided concentrically with the impeller on the diffuser wall at the diffuser inlet and the first slit concentrically provided with the first slit on the diffuser wall in the middle of the diffuser. The second slit is communicated with the bypass passage, and the pressure in the middle of the diffuser is higher than the pressure at the diffuser inlet, so that a circulating flow is generated in the bypass passage. When the flow rate in the centrifugal compressor decreases, the flow rate of the circulating flow in the bypass flow path increases and the flow rate at the diffuser inlet is compensated, so the velocity triangle at the diffuser inlet does not change. As a result, even if the flow rate in the centrifugal compressor decreases, the incident angle at the diffuser inlet does not increase and the flow rate at which surging occurs decreases.

[0006]

【Example】

 1 and 2 are explanatory views of a centrifugal compressor according to an embodiment of the present invention. In the figure, the centrifugal compressor according to the present embodiment is used for gas compression, air blowing, etc., and has a vaned diffuser, and the vaned diffuser has a radius R₁And radius R ₂ A plurality of blades 101 are installed symmetrically with respect to the rotary shaft 102 of the impeller, and two annular disks 103 and 104 are installed so as to sandwich the blade 101. The vaned diffuser is composed of these two discs 103 and 104 and the blade 101. In this centrifugal compressor, the radius R of the blade 101 inlet is set to this one disk 103.₁There is a circular slit 110 in the vicinity, and a radius R intermediate between the blade 101 inlet and the blade 101 outlet._BAlso, circular slits 111 are provided respectively. Furthermore, a bypass channel 112 that connects these two slits 110 and 111 is provided. In this centrifugal compressor, in order to fix the disc 103 separated by both slits 110 and 111, a nozzle blade 113 that guides the flow in the bypass flow passage 112 is provided, but instead of this nozzle blade 113 The disk 103 may be fixed with a bolt or the like.

As shown in FIG. 2A, the pressure inside the vaned diffuser increases as the radius increases. The solid line in the figure shows the pressure distribution at the design point. Since the pressure in the slit 111 having the radius R _B of the disk 103 is higher than that in the slit 110 having the radius R _1, an arrow is drawn in the bypass passage 112 that connects the two slits 110 and 111. A circulating flow occurs in the direction indicated by. When the flow rate in the centrifugal compressor decreases, the pressure distribution changes as shown by the dotted line, and the pressure difference between the two slits 110 and 111 increases, so that the circulation flow in the bypass flow passage 112 increases and the blade 101 at the inlet of the blade 101 increases. Make up for the flow rate. (B) of the figure shows the flow velocity triangle at the inlet of the blade 101. The velocity triangle at the design point shown by the solid line in the figure is the velocity shown by the dotted line as the flow rate decreases in the absence of this bypass flow passage 112. Although it has a triangular shape, it changes like a velocity triangular shape shown by a one-dot chain line due to an increase in the circulation flow due to the bypass flow passage 112. As a result, as shown in FIG. 6C, the rate of increase of the incident angle with the decrease of the flow rate in the centrifugal compressor is smaller than that in the case of the conventional centrifugal compressor, and the flow rate at which surging occurs is decreased. The bypass passage 112 may be provided in the other disc 104 or both discs 103 and 104. Further, the same action and effect can be obtained by providing the vaneless diffuser without the blade 101.

In a conventional centrifugal compressor, when the flow rate is reduced, the velocity of the flow at the blade inlet that flows out of the impeller and flows into the vaned diffuser becomes smaller, so that the flow velocity in the radial direction of the triangle becomes smaller. The angle increases and the wing stalls, causing surging. As described above, in the conventional centrifugal compressor, as the flow rate is decreased, surging occurs due to blade stall in the vaned diffuser, so the flow rate range for stable operation is narrowed. In the compressor, one or both of the disks 103 and 104 that form the vaned diffuser have a half-diameter R at the inlet of the blade 101.₁Radius R near the blade and at the entrance of wing 101₁And wing 101 exit radius R₂Intermediate R with _B Concentric circular slits 110 and 111 are provided at the positions, and these two slits 110 and 111 are connected by a bypass flow passage 112. Even if the flow rate in the centrifugal compressor is reduced below the design point, the blade 101 inlet The flow rate in the blade is supplemented by the circulation flow in the bypass flow passage 112 and the change in the velocity triangle at the inlet of the blade 101 is suppressed, so that the rate of increase in the incident angle at the inlet of the blade 101 is reduced and the flow rate at which surging occurs is reduced. To do.

[0009]

[Effect of device]

 The centrifugal compressor according to the present invention is configured as described above, and even if the flow rate in the centrifugal compressor is reduced, the incident angle at the diffuser inlet does not increase and the flow rate at which surging occurs is reduced. The possible flow range is widened.

[Brief description of drawings]

FIG. 1 (a) is a sectional view of a centrifugal compressor according to an embodiment of the present invention, and FIG. 1 (b) is a sectional view taken along line bb in FIG. 1 (a).

FIG. 2 is an explanatory diagram of its operation.

FIG. 3 is a sectional view of a conventional centrifugal compressor.

[Explanation of symbols]

 101 blade 102 rotating shaft 103 disk 104 disk 110 slit 111 slit 112 bypass flow path 113 nozzle blade

Claims (1)

[Scope of utility model registration request] 1. A first slit provided concentrically with the impeller on a diffuser wall at the diffuser inlet, and a second slit provided concentrically with the first slit on the diffuser wall in the middle of the diffuser. And a bypass flow path that connects the first slit and the second slit to each other.