JPH078597U - Centrifugal compressor - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To prevent performance deterioration due to rapid expansion of the flow path width,
Provided is a centrifugal compressor in which a step of a flow passage narrowed by a vaneless diffuser width control unit is gradually changed. In a centrifugal compressor having a part of a vaneless diffuser wall as a movable wall, the movable wall is formed by a plurality of ring-shaped members 4 and 7 having an axle as a center.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a centrifugal compressor that can be used as an industrial centrifugal compressor, a gas turbine centrifugal compressor, and the like.

[0002]

[Prior art]

 An example of a conventional centrifugal compressor is shown in FIG. (A) of a figure is a front view of an essential part, (b) is a BB arrow sectional view of (a).

In the figure, the centrifugal compressor comprises a suction casing 1, an impeller 2, vaneless diffuser members 3 and 5, a vaneless diffuser width control member 4, and a scroll 6.

Note that FIG. 5 is a schematic diagram of the flow shown in the enlarged view of FIG.

[0005]

[Problems to be solved by the device]

 The conventional centrifugal compressor has the following problems to be solved.

That is, in the centrifugal compressor having the conventional diffuser width control structure, in the low flow rate region, the vaneless diffuser width control member 4 is moved to narrow the flow passage width of the impeller outlet portion to reduce the flow passage width. The radial backflow of the flow along the wall surface is prevented to prevent noise from increasing and the operating range from decreasing. However, in the low flow rate region, the flow path narrowed by the vaneless diffuser width control member 4 and the downstream There is a drawback that the step difference between the flow path width and the flow path becomes large and sudden expansion loss occurs, resulting in performance degradation.

In order to solve the above-mentioned drawbacks, the present invention aims to provide a centrifugal compressor in which a step between a flow passage narrowed by a vaneless diffuser width control member 4 and a flow passage downstream thereof is gradually changed. And

[0008]

[Means for Solving the Problems]

 As a means for solving the above problems, the present invention is characterized in that, in a centrifugal compressor having a part of a vaneless diffuser wall as a movable wall, the movable wall is formed by a plurality of ring-shaped members centering on an axle. It intends to provide a centrifugal compressor that does.

[0009]

[Action]

 Since the present invention is constructed as described above, it has the following effects.

That is, since a part of the movable vaneless diffuser wall is formed by a plurality of ring-shaped members centering on the axle, the vaneless diffuser movable member on the upstream side is moved in the low flow rate region to narrow the width. In that case, the vortex flow generated downstream of the vaneless diffuser movable member is reduced because the degree of change is reduced by the stepwise flow path formed by the next vaneless diffuser movable member installed further downstream. Performance deterioration of the compressor in the flow rate range is prevented.

[0011]

【Example】

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram of this embodiment, (a) is a front view of a main part, (b) is a sectional view taken along the line BB of (a), and FIG. 2 is a flow path showing the flow in FIG. 1. FIG. 3 is an enlarged view of a main part, and FIG. 3 is a comparison diagram of operating performance between the present embodiment and the conventional example.

The same members as those of the conventional example are designated by the same reference numerals, and the description thereof will be omitted unless necessary.

In FIG. 1, 1 is a suction casing, 2 is an impeller, 3 a and 5 are vaneless diffuser members, 4 is an upstream diffuser width control member, and 7 is a downstream provided to form a stepwise expansion flow path. A side diffuser width control member, 6 is a scroll, and 8 is an axle. The configuration is the same as the conventional example except that a plurality of diffuser width control members are provided on the upstream side and the downstream side.

In the above configuration, when the impeller 2 rotates, the fluid is pumped by the impeller 2 in the radial direction, and the vaneless diffuser members 3a and 5 and the movable upstream diffuser width control member 4 and the downstream diffuser width control member 7 are provided. Flows into the vaneless diffuser formed in.

In the low flow rate region, the upstream side diffuser width control member 4 is moved so as to narrow the diffuser flow path to reduce noise and prevent surge in the low flow rate region. At this time, the downstream side diffuser width control member 7 The upstream side diffuser width control member 4 is formed in a shape in which the downstream side channel width is gradually increased.

In general, when the flow path is rapidly expanded, a fluid, particularly a compressible fluid, causes energy loss due to pressure drop due to rapid expansion, vortex generation, heat transfer, etc., as seen in the orifice effect and the like. However, this embodiment gradually changes the expansion of the flow path as described above, so that energy loss, that is, performance deterioration is prevented.

Incidentally, in the case of the centrifugal compressor as in this embodiment, since the fluid travels along the curved path while including the spiral element, another performance is added to its performance. They are qualitatively described with reference to FIG. 2 as follows.

(1) Effect of narrowing the diffuser width In the vaneless diffuser, the flow angle α of the vaneless diffuser is α = tan ⁻¹ ( _cm / _cu ) where _cm : meridional velocity = Q / ( _{2π · r · b) c u} : turning speed _{≒ r 2 · c u2 / r} Q: volumetric flow rate r: diffuser radius b: diffuser width r _2: the impeller outlet radius c _u2: impeller exit turning speed flow angle α is a constant value It has been known that if the temperature becomes lower than the following value, a rotating stall will occur and cause pressure fluctuations and noise in the compressor. When the diffuser width b is narrowed in the low flow rate range, the value of the flow angle α can be made larger than that in the case where the diffuser width is not narrowed, so that the occurrence of turning stall is suppressed and the performance is stabilized and the noise is prevented. It is known that the reduction of the diffuser width near the diffuser inlet is effective in suppressing the turning stall.

(2) Performance when the diffuser width is narrowed Among the losses generated in the diffuser, the sudden expansion loss at the diffuser outlet is proportional to the dynamic pressure P _de at the diffuser outlet. Dynamic pressure P _de is ^{_{P de = γ · c me 2}} / (2g) = γ · (Q / (2π · r e · b e)) 2 / (2g) Here gamma: specific weight r _e: diffuser outlet radius b _e : Diffuser outlet width Therefore, when the diffuser width is narrowed, the compressor performance has a larger sudden expansion loss than that in the case where the diffuser width is not narrowed, resulting in a decrease in pressure and efficiency.

From the facts of (1) and (2) above, the present embodiment is configured to achieve both suppression of turning stall occurrence and reduction of sudden expansion loss, and as shown in FIG. in the following relationship deep impeller outlet radius r _e to perform suppression of rotating stall narrowing the diffuser flow path width b _e, the radius to the middle portion of the rapid expansion flow path from b _e to b _e "r _e ', width The dynamic pressure at the outlet of the diffuser parallel wall part is (r _e · b _e / (r _e ′ · b _e) compared to the case where only the diffuser member constituting r _e · b _e is inserted by inserting the member b _e ′. ')) is intended to prevent reduced performance degradation of the compressor is performed to reduce the rapid expansion loss in the diffuser ^2. the conditions for the rapid expansion loss minimum _{b e / b e' = (} (b e / b _e ") +1) because represented by / 2 and the downstream diffuser width control member 7 solid Loss by controlling so as to satisfy the relationship of the above equation can be minimized according to the width b _e formed with a width b _e 'formed by the wall on the upstream side diffuser width control member 4 and the fixed wall.

FIG. 3 shows the driving performance of this embodiment in comparison with the conventional example. It can be seen that the performance of this example is excellent.

As described above, according to the present embodiment, the flow passage of the centrifugal compressor is gradually changed by the upstream diffuser width control member 4 and the downstream diffuser width control member 7, so that there is no rapid expansion of the flow passage, Since there is no backflow along the wall surface of the exit of the vehicle 2 and the conventional rapid expansion loss is prevented, there is an advantage that high performance is maintained.

Further, since the generation of vortices and the like is suppressed, there is an advantage that noise is reduced.

[0025]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects.

That is, according to the present invention, the flow width of the diffuser is sequentially narrowed by using a plurality of ring-shaped members, which are movable walls, in the low flow rate region, thereby preventing noise and surging from occurring. At the same time, the rapid expansion loss in the downstream is reduced and the compressor performance is improved.

[Brief description of drawings]

FIG. 1 is a diagram of a centrifugal compressor according to an embodiment of the present invention,
(A) is a front view of a main part, (b) is a sectional view taken along the line BB of (a),

FIG. 2 is an enlarged view of a main part of a flow path showing a fluid flow in FIG.

FIG. 3 is a comparison diagram of operating performance between the present embodiment and a conventional example,

FIG. 4 is a view of a conventional centrifugal compressor, (a) is a front view of a main part, (b) is a sectional view taken along the line BB of (a),

FIG. 5 is a schematic view of an enlarged flow of a main part flow path of FIG. 4 of a conventional example.

[Explanation of symbols]

 1 Suction casing 2 Impeller 3a Vaneless diffuser member 4 Upstream side diffuser width control member 5 Vaneless diffuser member 6 Scroll 7 Downstream side diffuser width control member 8 Axle

Claims (1)

[Scope of utility model registration request] 1. A centrifugal compressor in which a part of the vaneless diffuser wall is a movable wall, wherein the movable wall is formed of a plurality of ring-shaped members centering on an axle.