JPS6027839B2 - centrifugal compressor diffuser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a diffuser shape suitable for improving the performance of a centrifugal compressor.

[Background of the Invention] A bladeless diffuser used in a conventional centrifugal compressor will be explained with reference to FIG.

A centrifugal impeller 4 consisting of blades 1, side plates 2, and a core plate 3 is rotated by a rotating shaft 5, thereby sucking gas through a suction pipe 6, applying work within the impeller 4, and creating a high-speed flow. After that, lead to diffuser 7. Diffuser 7
is generally a pair of two opposing discs (diffuser plates)
It is composed of 8 and 9. In the diffuser 7, the velocity energy of the high-speed flow flowing out from the impeller is converted into pressure energy, and the pressure is recovered and collected in the downstream scroll casing 10', and the flow is collected from the discharge port (not shown). It is discharged. In a so-called high specific speed impeller that handles a large flow rate, as shown in Figures 2 and 3, the flow angle Qz of the flow at the impeller outlet and the radial component of the absolute velocity CZm vary from the side plate side to the core plate side. It usually shows a highly non-uniform (skewed) distribution. When the flow is distorted in this way at the entrance to the diffuser, the performance of the diffuser is significantly degraded, as shown in FIG. Figure 4 quotes experimental results regarding a two-dimensional diffuser, and CP is (static pressure recovery)/
(Diffuser inlet pressure), Br represents 1-(flow foundation effective cross-sectional area)/(geometric cross-sectional area of flow path) (subscript ref
represents the reference value). It is easy to imagine that a radial diffuser used in a centrifugal compressor would also have a result similar to that shown in FIG. 4. As described above, conventional diffusers for centrifugal compressors, regardless of whether they are bladeless diffusers or bladed diffusers, have the disadvantage that the performance is significantly reduced due to the non-uniformity of the flow immediately after the impeller. was there.

[Purpose of the invention]

This invention was made based on the above-mentioned matters, and aims to uniformize the flow at the entrance of the diffuser and significantly improve the performance of the diffuser.

[Summary of the invention]

The feature of this invention is that at least one of the flow path surfaces of the diffuser plate is located inside the blade outlet width of the impeller, and the average flow rate at the design flow rate is A plurality of tapered grooves are cut at an angle equal to the flow angle, and the remaining diffuser plates between these grooves form guide vanes.This uniformizes the flow distribution at the diffuser inlet, and at the same time The boundary layer on the flow path surface is activated by acceleration and turbulent sulfurization, thereby eliminating phenomena that adversely affect diffuser performance, such as peeling of the boundary layer, thereby significantly improving performance.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. 5 and 6.

Components that are the same as those in FIGS. 1 to 4 are designated by the same reference numerals and their explanations will be omitted. Although the figure shows the state of the impeller outlet and the diffuser inlet in the case of using a diffuser without blades, the same can be applied to the case of using a diffuser with blades. In Figure 5 A,
The diffuser plate 8 on the side plate 2 side of the impeller 4 is configured to be located inside the outlet width of the blade 1, and a fifth diffuser plate 8 is provided on the flow path surface of the inlet portion of the diffuser plate 8 opposite to the width end of the outlet width of the blade 1 on the side plate 2 side. As shown in the figure, a plurality of tapered grooves 11 are cut at an angle equal to the average flow angle at the design flow rate. This groove 11
The diffuser plate 8 left by cutting the guide vane 1
form 2. The flow at the impeller outlet is accelerated by the action of this tapered groove 11, so the boundary layer becomes thinner and separation is prevented. The low flow angle (circumferentially narrow) flow can be directed radially to uniformize the flow at the diffuser inlet. As a result, it is possible to achieve high performance not only near the inlet of the diffuser but also in the latter half of the diffuser, making it possible to significantly improve the performance of the centrifugal compressor. Figure 6 shows the tapered groove 1
1 and guide vanes 12 are provided on both the core plate side and the side plate side. The purpose and effect of this embodiment are also substantially the same as those described above. [Effects of the Invention] As described above, according to the present invention, by providing the tapered grooves and guide vanes at the inlet of the diffuser, the flow at the inlet of the diffuser is made uniform and the boundary layer is activated. Since wall peeling and the like are prevented, it is possible to significantly improve the performance of the diffuser at the inlet portion and the latter half of the diffuser, making it possible to provide a high-performance centrifugal compressor.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a conventional far-D compressor, Fig. 2 is an explanatory diagram (front view) of the flow at the impeller outlet, Fig. 3 is a flow distribution diagram at the impeller outlet, and Fig. 4 is an explanatory diagram (experimental results) of the influence of non-uniformity of inlet velocity distribution on the performance of a two-dimensional diffuser, and Fig. 5 shows an embodiment of the present invention, where A is a longitudinal cross-sectional view and the mouth is a front view. , FIG. 6 is a longitudinal sectional view showing another embodiment of the present invention. 2...Side plate, 3...'0 plate, 4...Impeller, 7.
... Diffuser, 8, 9... Diffuser plate, 10... Scroll casing, 11... Taper groove, 12...
・Guide blade. Figure 1 Younger brother 2 Figure 3 Leopard 4 Figure S Figure 6

Claims (1)

[Claims] 1. In a diffuser of a centrifugal compressor in which a bladeless flow path is formed between a pair of opposing diffuser plates, at least one of the flow path surfaces of the diffuser plate is located inside the blade outlet width of the impeller, and A plurality of tapered grooves are cut at an angle equal to the average flow angle at the design flow rate on the flow path surface of the opposing diffuser plate inlet portion, and guide vanes are formed by the diffuser plate remaining between the grooves. A differential user of a centrifugal compressor.