JPH0251080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential user with guide vanes used in centrifugal and mixed flow type fluid machines.

[Conventional technology]

A conventional centrifugal fluid machine equipped with this kind of differential user, for example, a centrifugal compressor, as shown in FIGS. 1 and a differential user 6 having a guide vane 9 provided on the exit side of the differential user 6. The impeller 1 is rotated by a rotating shaft 11, whereby the fluid sucked from the suction port 5 is given work within the impeller 1, becomes a high-speed flow, and is introduced into the guide vane 9 of the differential user 6.

The above-mentioned differential user 6 includes a pair of differential user plates 7 and 8 disposed opposite to each other on the outer periphery of the impeller 1, and a plurality of differential blades arranged in a circular row of blades in a flow path 13 formed between both the differential user plates 7 and 8. The velocity energy of the high-speed flow flowing out from the impeller 1 is converted into pressure energy in the differential user 6, and the pressure is continuously recovered in the downstream scroll casing 10 while the discharge port (Fig. (not shown).

[Problem to be solved by the invention]

The leading edge of the guide vane 9 is formed linearly in the width direction of the differential user flow path 13, and the characteristics of a centrifugal compressor equipped with a differential user 6 having such a guide vane 9 are as shown in FIG. . In other words, the stage characteristic A of the differential user with guide vanes has a greater pressure recovery than the stage characteristic B of the differential user without guide vanes, so that a higher head can be obtained. On the other hand, the point S ₁ shown in Fig. 3,
_S2 is the surge point of differential user A with vanes and differential user B without vanes, that is, the flow rate limit point at which stable operation is possible, and the former's surge point _S1 is on the large flow side compared to the latter's surge point _S2 , so it is not possible to operate. The disadvantage is that the range is narrower.

On the other hand, on the small flow rate side with respect to the design flow rate, as shown in Fig. 4, the flow at the inlet of the guide vane 9 has an incidence of Δi with respect to the vane angle, and this value increases and exceeds the limit value. Then, near the inlet of the guide vane 9, the flow separates as shown at C in FIG. 4, causing a stall phenomenon. As a result, the flow within the differential user 6 becomes unstable, which adversely affects the flow within the impeller 1 on the upstream side, making steady operation impossible.

Therefore, in order to expand the stable operating range of a diff user with guide vanes, it is necessary to prevent separation by suppressing the development of the boundary layer (area of low pressure) on the suction surface of the vane against flows with even greater incidence. It is necessary to delay the onset.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved diff user with guide vanes that can suppress separation of the boundary layer in a flow with a large incidence.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, all of the guide vanes are provided with at least one triangular shaped portion on the leading edge thereof, and this triangular is arranged in the flow path with the apex of the diffuser facing the entrance of the diffuser flow path and located near the center in the width direction of the diffuser flow path.

[Operation] In the differential user having the guide vanes configured in this way, when the flow flows into the guide vanes,
The apex of the triangle forming the leading edge generates a vortex line,
These vortex trains advance along each of the leading edges and impart kinetic energy to the boundary layer on the suction surface of the guide vane, activating the boundary layer and suppressing its separation, thus reducing the occurrence of large incidences. With respect to the flow, the development of a boundary layer on the negative pressure surface of the guide vane can be suppressed, and the occurrence of separation can be delayed.
When the flow collides with the guide vane part, the velocity perpendicular to the leading edge of the flow becomes smaller than the velocity flowing into the part, which reduces the impact of shock waves when the flow is high velocity. Can be done.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 5a and 5b, 1 is an impeller, and 6 is a differential user installed opposite the outlet of the impeller 1. 8, and a plurality of guide vanes 14 arranged in a circular row at the entrance of the diffuser flow path 13 formed between the diffuser plates 7 and 8.
The guide vane 14 has a front edge 14a formed in a triangular shape, and an apex 15 of the triangle is located near the center of the width of the diffuser flow path 13, and both bottom points 16 of the triangle are located near the center of the width of the diffuser flow path 13.
a and 16b are fixed to the diffuser plates 7 and 8, respectively.

The guide vanes 14 are usually formed by two-dimensionally curving a flat plate to match the flow. It is also possible to twist the triangular tip 15 of. In the differential user having the guide vanes configured in this manner, when the flow 19 has a high velocity as shown in FIG. be able to.

In a differential user with guide vanes, if the leading edge is formed in a straight line like the conventional guide vanes,
When the velocity of the flow relative to the guide vane exceeds Ma=1, for example, when the velocity of the flow is supersonic, a shock wave is generated at the leading edge of the guide vane. However, with the guide vane according to the present invention, as shown in FIG. When the receding angle of 14b is α, it becomes Ucos α, and the speed is
Since Ucosα is smaller than the inflow velocity U, shock waves are less likely to be generated.

Therefore, when the absolute flow velocity at the impeller outlet is close to the sonic velocity, such as in a centrifugal compressor, performance can be improved by reducing additional loss due to the generation of shock waves.

According to the present embodiment described above, when the centrifugal compressor is operated at a flow rate other than the design flow rate, the flow 19 flowing into the guide vane 14 is directed against the warp line of the vane 14, as shown in FIG. In the leading edge portion having an incidence Δi, which is formed in a triangular shape with respect to the flow 19, vortex rows 17a and 17b are generated along the leading edges on both sides from the apex 15 of the triangle. These vortex rows 17a and 17b give kinetic energy to the boundary layer on the negative pressure surface of the guide vane 14, activating the boundary layer and suppressing separation, thereby enabling stable operation over a wider range. It is.

FIG. 8 shows another configuration of the differential user with guide vanes of the present invention. This differential user with guide vanes differs only in the leading edge of the guide vanes.
The guide vane is designated again with the reference numeral 18 and has a leading edge consisting of a section 18a and sections 18b, 18c. The portion 18a is formed into a substantially equilateral triangle and is disposed in the diffuser flow path 13 with the apex of the triangle facing the entrance of the diffuser flow path 13 and located near the widthwise center of the diffuser flow path. The portions 18b and 18c are formed into approximately right-angled triangles and are arranged between the portion 18a and the diffuser plates 7 and 8, with the apexes facing the entrance of the diffuser flow path 13.

In a differential user having such a guide vane 18, similarly to the differential user shown in FIG.
The velocity perpendicular to the oblique side of the portions 18a to 18c of the flow impinging on the leading edge of the guide vane 18 is Ucosα, where U is the velocity of the flow and α is the receding angle of the portions 18a to 18c. Since the velocity is smaller than the inflow velocity U, the generation of shock waves can be delayed.

In both of the above-mentioned embodiments, a case has been described in which the circular blade rows of guide vanes are arranged in one row, but two or more circular blade rows may be arranged in the radial direction. In addition, in FIGS. 5 and 8, the guide vanes 14, 1
The radial position of the leading edge of No. 8 is from a position that does not contact the outer circumference of the impeller 1 to a downstream position that is 1.1 times or more in terms of impeller diameter ratio than the leading edge position of the guide vane in a conventional general diff user with guide vanes. It may be set to

〔Effect of the invention〕

As explained above, according to the present invention, the apex of the triangle formed at the front edge of the guide vane provided in the diffuser flow path is located at the center of the width of the flow path, and the front edge of the triangle is By generating a vortex row, kinetic energy is applied to the boundary layer on the negative pressure surface of the guide vane to activate it, suppressing separation of the main flow and enabling a wider range of operation.

In addition, due to the influence of the receding angle of the triangular leading edge, the generation of shock waves is delayed in response to high subsonic or supersonic flows, thereby preventing an increase in loss.
The performance of the differential user with guide vanes can be improved.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a conventional centrifugal compressor with a differential user with guide vanes, and Figure 2 is
-X arrow view, Fig. 3 is an explanatory diagram of the characteristic curve of the differential user, Fig. 4 is an explanatory diagram of the flow at the guide vane inlet at a small flow rate, and Figs. 5 a and b are one of the differential users with guide vanes of the present invention. A cross-sectional view showing the embodiment and an explanatory diagram of the leading edge shape of the guide vane, FIGS. 6 and 7 are explanatory diagrams of the operation of the same embodiment, and FIGS. 8a and b are cross-sections of another embodiment according to the present invention. FIG. 4 is an explanatory diagram of the leading edge shape of the guide vane. 6...Diff user, 7,8...Diff user board,
13... Diffuser flow path, 14, 18... Guide vane, 14, 18... Guide vane, 14a, 18a... Leading edge portion, 15... Leading edge apex, 17a, 17b... Vortex row.

Claims (1)

[Scope of Claims] 1. In a diff user with guide vanes in which a plurality of guide vanes are arranged in a circular row in a diff user flow path formed by a pair of opposing diff user plates, all of the guide vanes are is provided with at least one triangular shaped portion on its front edge, and the apex of this triangle is directed toward the entrance of the flow path and is located near the widthwise center of the flow path. A differential user with guide vanes, characterized in that the differential user is disposed within a flow path. 2. A diff user with guide vanes according to claim 1, wherein a plurality of circular rows of guide vanes are arranged in a plurality of rows in the radial direction within the diff user flow path.