JPH09324797A - Revolving stall restraining device of fluid machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid generation of revolving stall in a small flow territory by radially forming a plurality of grooves on at least one side wall of opposed walls through the flow passage of a diffuser with no vane in which the discharge flow from an impeller flows. SOLUTION: A diffuser with no vane 1 is constituted of walls 1a, 1b opposite to each other through a flow passage 3 opening a discharge port 3a on the outer circumference, and a plurality of grooves 2a, 2b are radially formed on the inner faces of the respective walls 1a, 1b. At operation, an impeller 5 is rotated in the arrow mark direction, liquid flowing in a suction port 4 is discharged from the discharge port 3a through the flow passage 3 by the impeller 5 as shown in the arrow mark. At this time, inward flow is caused by pressure gradient in the radial direction within the grooves 2a, 2b so as to increase the flow of a main flow by the portion, angular motion loss of the main flow is caused when the flow toward the interior of the groove flows in the groove, because the inward flow has no revolution, and at outflow from the groove to the main flow, angular momentum of the main flow falls remarkably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swirl stall suppressing device for a fluid machine such as a centrifugal compressor, a blower, a pump having a vaneless diffuser or a vaned diffuser.

[0002]

Fluid machines such as centrifugal compressors, blowers, and pumps having a vaneless or vaned diffuser are
It is known that turning stall is generated in the bottom flow rate region and the drivable region is narrowed. Then, when the operation is continued under the state where such a rotating stall occurs, the wall static pressure of the diffuser immediately after the impeller exit changes with time, and thus the pressure pulsation in the diffuser causes the impeller rotating shaft to move. The runout becomes large, causing bearing damage, and it becomes impossible to continue stable operation as a fluid machine.

[0003]

In order to avoid the inconvenience caused by the occurrence of the rotating stall as described above, the fluid machine is operated at a flow rate higher than a predetermined flow rate, or a part of the flow rate is bypassed. The method of doing is conventionally adopted. However, even with this method, there is a dislike that energy is wasted and it does not match the sense of the age of energy saving.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a turning stall suppressing device capable of avoiding the occurrence of turning stall in a low flow rate region.

[0005]

According to the invention of the present application (the invention according to claim 1), the inner surface of at least one of the walls facing each other through the passage of the vaneless diffuser into which the discharge flow from the impeller flows is provided. The object is achieved by forming a plurality of grooves radially. Further, the invention of the present application (the invention according to claim 2) is characterized in that between each of the blades on the inner surface of at least one of the walls facing each other through the flow path of the diffuser with blades into which the discharge flow from the impeller flows. The above object is achieved by forming grooves radially.

[0006]

The inward flow is induced in the groove formed in the diffuser of the invention according to claim 1 by the radial pressure gradient, and the flow rate of the main flow increases by that amount, and the inward flow in the groove is increased. Since the flow does not have swirl, it induces the angular motion loss of the main flow when the flow into the groove enters from the main flow to the groove, and it significantly reduces the angular momentum of the main flow when it flows out from the groove. . Therefore, the mainstream loses the swirling speed correspondingly, the mainstream peripheral speed decreases, and as a result, the flow angle increases and a flow similar to that at the time of high flow rate is realized. Damage is also prevented. The groove formed between the blades of the diffuser with blades according to the second aspect of the invention also functions to suppress the rotation stall by the same action as the groove of the first aspect of the invention.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a radial diffuser without blades, and FIG. 1 (A) is a schematic view of its internal structure.
FIG. 1B shows a sectional view taken along line XX of FIG. The vaneless diffuser 1 is composed of walls 1a and 1b facing each other through a flow path 3 that opens a discharge port 3a on the outer circumference, and a plurality of grooves 2a and 2 are radially formed on the inner surfaces of the walls 1a and 1b.
b is formed. 4 is a suction port, 5 is an impeller, and 5a is a rotating shaft of the impeller 5 and is connected to a drive motor (not shown). During operation, the impeller 5 rotates in the direction of the arrow, and the liquid flowing from the suction port 4 is As shown by the arrow, the impeller 5 passes through the flow path 3 and is discharged from the discharge port 3a. In addition, the groove 2
Although a and 2b are provided on the walls 1a and 1b, respectively, the present invention is not limited to this and may be provided on either one of the walls.

FIG. 2 is a comparison vector diagram of the main flow velocity, circumferential velocity, and radial velocity of the fluid in the diffuser discharged from the impeller at the time of operation, in the case without the conventional groove and in the case of forming the groove in the present invention. As described in the above operation, the circumferential speed V′Θ in the case of forming a groove is lower than the circumferential speed VΘ in the case of no groove, and the radial speed Vr in the case of no groove is Because of the internal backflow, ΔVr
To V′r, and the main flow direction velocity V ′ becomes larger than the flow velocity α ′ of α in the main flow direction velocity V in the case where there is no groove, indicating that a high flow rate is realized. .

FIG. 3 shows a cross-sectional view of the internal structure of a radial diffuser with vanes. The vaned diffuser 6 has a plurality of vanes on the inner surface of walls 6a, 6b (6a not shown) facing each other through a flow path. 7a and 7b (7a is not shown), and grooves 8a and 8b are radially formed between the blades 7a and 7b.
(8a is not shown) is formed. In addition, 5 is an impeller and 5 a is a rotating shaft of the impeller 5. The fact that the grooves 8a and 8b of the diffuser 6 with blades have the function of suppressing the rotation stall is that the groove 2 of the diffuser 1 without blades.
The description is omitted because it is the same as a and 2b.

Although the radial diffuser has been described in the above embodiments, in the axial diffuser with blades shown in FIG. 4, the groove 11 is formed on the inner surface of the wall of the vane diffuser 10 into which the discharge flow from the impeller 9 flows. By forming the radial diffuser, the rotating stall can be suppressed similarly to the groove formed in the radial diffuser. And
In either form, the depth, width and length of the groove are individually determined by the size and characteristics of the fluid machine.

[0011]

[Example] In a radial diffuser without blades, diffuser diameter = 600 mm, impeller diameter = 251 mm, rotation speed = 3000 rpm, groove width = 10 mm, groove depth = 1 m
m (formed on the inner surface of both walls) or 3 mm (formed only on the inner surface of one wall) and the number of grooves = 32, the flow coefficient Φ =
Fig. 5 shows the circumferential velocity distribution characteristics during low flow rate operation of 0.067.
("Upper 3mm" has a depth of 3mm only on the upper wall.
When the groove is formed, “Botth 1 mm” is the case where the groove having a depth of 1 mm is formed on both walls. ). As can be seen from FIG. 5, the circumferential velocity is significantly lower in the case of forming the groove than in the case of not forming the groove, and it is understood that the effect of suppressing the turning stall is remarkable.

[0012]

According to the first and second aspects of the present invention, the occurrence of a rotating stall can be suppressed by a simple machining of forming a groove on the diffuser, bypass operation is not required, and the fluid machine becomes stable. Energy saving operation is possible. Further, it is possible to prevent the bearing from being damaged due to the rotating stall, and it is possible to extend the life of the machine operation.

[Brief description of drawings]

1 shows a radial diffuser without vanes, FIG.
1A is a schematic view of the internal structure, and FIG. 1B is a sectional view taken along line XX of FIG. 1A.

FIG. 2 is an explanatory diagram of a turning stall suppression effect.

FIG. 3 is an internal sectional view of a radial diffuser with vanes.

FIG. 4 is a sectional view of an axial diffuser with blades.

FIG. 5 is a circumferential velocity distribution characteristic diagram of a radial diffuser without blades during low flow rate operation.

[Explanation of symbols]

 1 Diffuser without blades (radial) 1a, 1b Opposing walls 2a, 2b Groove 3 Flow path 3a Discharge port 4 Suction port 5 Impeller 5a Rotating shaft 6 Diffuser with blades (radial) 6a, 6b Opposing wall 7a, 7b Blade 8a, 8b Groove 9 Impeller 10 Diffuser with blade (axial) 11 Groove

Claims (2)

[Claims] 1. A plurality of grooves are radially formed on an inner surface of at least one of walls opposed to each other through a flow path of a vaneless diffuser into which a discharge flow from an impeller flows. Turning stall suppression device. 2. A groove is radially formed between each of the blades on the inner surface of at least one of the walls facing each other through the flow path of the vaned diffuser into which the discharge flow from the impeller flows. Rotational stall suppression device for fluid machinery.