JPH07305698A - Turbo-type fluid machine - Google Patents

Abstract

PURPOSE:To provide a turbo-type fluid machine in which vibration or noise to be generated in operating in the low flow rate range is prevented, and expansion of the operating range can be realized. CONSTITUTION:An inlet guide vane is constituted by forming the vane chord upstream from a rotary shaft 2 rotatably supporting the vanes longer than the vane chord downstream from it by using a blade profile wherein its maximum thickness exists near the front edge for the vanes 3, 31, 41, so that ends of mutually adjacent vanes may be overlapped on each other in the full closed state. Moreover, protrusions 15 are provided on the wall surface facing the vane end surface in order to prevent damage to be generated caused by contact of mutual vanes when the vane overspeed is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor for pumping gas,
The present invention relates to a turbo type fluid machine such as a blower.

[0002]

2. Description of the Related Art Conventionally, a method for stabilizing the flow in a suction casing of a compressor or a blower is as follows: (1) A method of providing a movable circular blade row in the suction casing (Japanese Utility Model Laid-Open No. 2-19899), 2) There is a method of providing a movable straightening vane at the impeller entrance (Japanese Patent Publication No. 3-25640).

[0003]

In a turbo compressor having a suction casing that sucks in a flow from a direction other than the rotation axis of the impeller, each of the turbo compressors is composed of a circular blade row composed of a plurality of vanes rotatably supported. Inlet guide vanes are used to control the flow rate. The suction casing is usually bilaterally symmetrical with respect to the plane including the rotation axis of the impeller, and the inflowing flow is also bilaterally symmetrical. When operating at a large flow rate, each vane is set in a substantially radial direction, so that the entire inlet guide vane is also symmetrical and the flow can be smoothly guided. On the other hand, when operating on the low flow rate side, each vane is set in a direction close to the tangent of a circle centered on the rotation axis of the impeller, and the flow passage area between the vanes is reduced. For this reason, the shape of the entire inlet guide vane is asymmetrical, and there are portions where the inflow angle is appropriate and angles where the vane angle is not appropriate. Therefore, a non-uniform and unstable flow is generated downstream of the inlet guide vanes, and the impeller sucks this flow, which causes noise and vibration. Among the conventional techniques, it is difficult to remove the non-uniformity upstream of the impeller with only (1), and in (2), the manufacturing price increases. An object of the present invention is to provide a proper shape and proper arrangement of the vanes forming the inlet guide vane,
To provide a turbo-type fluid machine capable of expanding an operating range on a low flow rate side by reducing a non-uniform and unstable flow upstream of an impeller and preventing noise and vibration generated in the impeller. It is in.

[0004]

In order to solve the above problems, an airfoil having a maximum thickness in the vicinity of the leading edge is used as a vane, and a vane chord length upstream of a rotary shaft that rotatably supports the vane. Is greater than the chord length of the downstream vane and is fully closed, the inlet guide vane is configured so that the ends of adjacent vanes overlap. Further, a protrusion is provided on the wall surface facing the end surface of the vane to prevent damage caused by mutual contact of the vanes when the over-rotation of the vane occurs.

[0005]

When operating at a flow rate lower than the design flow rate, the inlet guide vane is set to a low opening degree to reduce the flow passage area between the vanes. At this time, there are vanes in which the flow enters from the direction of the warp line of the vane tip and those which do not, but since the maximum thickness of the vane airfoil exists near the leading edge,
The flow is guided on the surface of any vane without large scale separation. Further, since the vanes have a length in which the ends of adjacent vanes overlap with each other in the fully closed state, the flow can be reliably guided in the direction along the vanes at the trailing edge of any vane. Therefore, the uniformity of the flow at the outlet of the inlet guide vane is ensured in the circumferential direction. The vanes had a length in which the ends of adjacent vanes overlap with each other in the fully closed state.However, since the projections are provided on the wall surface facing the end faces of the vanes, contact between the vanes due to over-rotation does not occur, so Damage is prevented.

In the space between the outlet of the inlet guide vane and the inlet of the impeller, the flow diverts from the radially inward direction to the impeller axial direction, and in many cases, the inner side is the impeller rotating shaft. When the flow rate is high, the flow velocity is high and the inlet guide vane outlet flow is highly uniform, so that flow instability is unlikely to occur. However, when the flow rate decreases, the uniformity of the outlet flow of the inlet guide vane deteriorates, so that a vortex flow is generated and the flow becomes unstable. If the distance between the outlet of the inlet guide vane and the inlet of the impeller is increased, the vortex will be attenuated and the flow will be stabilized, but in terms of strength, it is desirable to shorten the impeller rotating shaft. When the outlet of the inlet guide vane is close to the rotating shaft of the impeller, this instability is suppressed because there is no space for the vortex to grow into an unstable flow. In the vane chord length, if the downstream side of the rotary shaft that rotatably supports the vane is made shorter than the upstream side, the distance that the trailing edge of the vane separates from the impeller rotary shaft becomes small even when the vane has a small opening. Instability can be suppressed.

[0007]

1 is a view showing a first embodiment of the present invention and is a sectional view perpendicular to the axis of a suction casing of a turbo type fluid machine. The impeller 1 is fixed to the rotating shaft 2 and rotates. The vanes 3 forming the circular blade row of the inlet guide vane are supported by the movable shaft 4, and the set angle can be changed. The flow is from the suction pipe 5 to the suction casing flow path 6
Flow into and flow into 8 and 9. Partition board 7
Prevents the unstable phenomenon caused by the collision of the streams 8 and 9.

During operation on the low flow rate side, the opening of the vane 3 is set to a low opening as shown in FIG. 1 to pre-swirl the flow upstream of the impeller, and a pressure drop is generated to reduce the flow rate. The flows 8 and 9 in the suction casing flow path 6 flow symmetrically and then flow into the vane 3. Since the circular blades formed by the vanes 3 are asymmetrical to each other, the directions of the vanes 31 to 36 coincide with the flow, but in the vanes 37 to 41, the flow must go around the vanes. FIG. 2 shows an enlarged view of 37-39 of the vanes that the flow must wrap around.
The vane position indicated by the broken line indicates a large flow rate operation. Since the maximum thickness of the vane is near the leading edge 10, even if the vane does not have the same direction as the inflow direction, the flow will be arrow 1
As in No. 1, the leading edge is smoothly wrapped around and no large-scale peeling occurs. Generally, in order to reliably guide the flow in the direction of the vanes, when the vanes are fully closed, the ends of adjacent vanes have overlapping chord lengths. When the vanes of FIG. 2 are in a fully closed state, the flow paths 12 are surrounded by vanes on both sides because the ends of adjacent vanes have overlapping chord lengths. Since the flow is surely guided in the direction of the vane in the flow path 12, even if the vane does not match the direction of the inflow flow,
A guide effect similar to matching vanes can be obtained. Therefore, during operation on the low flow rate side, even if the opening degree of the vane 3 is set to a low opening degree as shown in FIG. 1, there is no significant circumferential nonuniformity in the flow at the outlet of the inlet guide vane.

FIG. 3 shows a vane of a shape conventionally used for comparison. The flow of the vane shown by the broken line when the vane is fully opened is the same as that of the vane of the present invention shown in FIG.
When operating on the low flow rate side, a significant difference occurs when the opening of the vane is set to a low opening. Since the leading edge 10 'is thin, in a vane in which the direction of the vane and the direction of the inflow flow do not match, the flow does not wrap around the leading edge 10' as shown by the arrow 11 'and is separated from the surface, and a separated flow region 13 is generated. Further, in the fully closed state, the ends of the adjacent vanes have lengths that do not overlap each other, and since the flow path surrounded by the vanes on both sides is not configured, the flow cannot be reliably guided in the direction of the vanes. For this reason, the flow condition differs between the vane in which the direction of the vane and the direction of the inflow flow match, and the vane in which the direction of the inflow does not match, and the flow at the outlet of the inlet guide vane is significantly non-uniform in the circumferential direction. Because of inhalation of non-uniform flow, vibration,
Noise is generated and the operating range on the low flow rate side is limited. Despite these problems, in the fully closed state, the length that the ends of adjacent vanes do not overlap is often used.
This is because there is an advantage that damages due to mutual contact of the vanes do not occur when the over-rotation of the vanes occurs. In the present invention, the protrusion 15 provided on the wall surface 14 facing the end face of the vane prevents the vane from being damaged due to excessive rotation. If there are protrusions in the flow path 12, the flow cannot avoid the protrusions and the loss increases.
The protrusion 15 contacts the vane in the middle between the front edge 10 of the vane and the rotary shaft 4 rotatably supporting the vane, and the vane in the middle between the trailing edge 16 of the vane and the rotary shaft 4 rotatably supporting the vane. The protrusion 15 is located outside the flow path 12, and the flow can avoid the protrusion, so that the loss can be reduced.

FIG. 4 is a sectional view including the rotary shaft of the impeller of the first embodiment of the present invention. FIG. 1 is a cross section taken along the line AA 'in the figure. The projection 1 is formed on the wall surface 14 facing the end face of the vane.
5 are provided. The space between the trailing edge 16 of the vane 3 and the rotary shaft 2 of the impeller is set to reduce the size of the device, prevent the damping of the swirling flow generated in the vane 3, and suppress the instability of the flow.
The flow is minimized to turn from radially inward to axial.

The reason for shortening the distance between the trailing edge 16 of the vane 3 and the rotary shaft 2 of the impeller is as follows. In the space between the outlet of the inlet guide vane and the inlet of the impeller, the flow is diverted from the radially inward direction to the impeller axial direction, and in many cases, the inner side is the impeller rotating shaft. When the flow rate is high, the flow velocity is high and the inlet guide vane outlet flow is highly uniform, so that flow instability is unlikely to occur. However, when the flow rate decreases, the uniformity of the outlet flow of the inlet guide vane deteriorates, so that a vortex flow is generated and the flow becomes unstable.
If the distance between the outlet of the inlet guide vane and the inlet of the impeller is increased, the vortex will be attenuated and the flow will be stabilized, but in terms of strength, it is desirable to shorten the impeller rotating shaft. When the outlet of the inlet guide vane is close to the rotating shaft of the impeller, this instability is suppressed because there is no space for the vortex to grow into an unstable flow.

During the low flow rate operation, the vane 3 is rotated and the movable shaft 4 is rotated.
When the opening is rotated by to reduce the opening, the trailing edge 16 of the vane 3 is separated from the rotating shaft 2 of the impeller. This distance is the trailing edge 1
The larger the distance between 6 and the rotary movable shaft 4, the larger the distance. In the vane 3 of the turbo fluid machine to which the present invention is applied, since the vane chord length on the downstream side of the rotary movable shaft 4 is shorter than the vane chord length on the upstream side, rotation of the trailing edge 16 and the impeller at a low vane opening degree. The increase in the distance between the shafts 2 is small. Therefore, the instability of the flow generated in the space between the outlet of the inlet guide vane and the inlet of the impeller is effectively suppressed.

Since the turbo type fluid machine to which the present invention is applied is constructed in this way, even if the opening of the inlet guide vane is set to a low opening during operation on the low flow rate side, there is a problem immediately before the impeller 1. Since the generation of a uniform flow is suppressed, noise and vibration do not occur in the impeller, which enables operation at a low flow rate.

FIG. 5 is a diagram showing a second embodiment of the present invention.
It is a cross section of the suction casing part containing the rotating shaft of an impeller. In this embodiment, the rotary movable shaft 4 of the vane 3 which constitutes the inlet guide vane is inclined with respect to the rotary shaft 2 of the impeller 1. The feature of this embodiment is that the trailing edge 16 of the vane 3 is inclined with respect to the rotating shaft 2, so that the flow starts to turn axially from the radially inward direction inside the inlet guide vane, so that the downstream of the inlet guide vane. The diversion of the flow is reduced, and the distance between the trailing edge of the vane 3 and the inlet of the impeller 1 can be reduced as compared with the first embodiment, and the flow instability control is compared with the first embodiment. This is a more effective way.

[0015]

According to the present invention, the operating range is expanded and the performance is improved.

[Brief description of drawings]

FIG. 1 is a sectional view perpendicular to an axis showing a first embodiment of a turbo fluid machine of the present invention.

FIG. 2 is an explanatory view showing a vane that constitutes an inlet guide vane of the turbo type fluid machine of the present invention.

FIG. 3 is an explanatory view showing a vane that constitutes an inlet guide vane of a conventional turbo type fluid machine.

FIG. 4 is a cross-sectional view including the rotating shaft of the impeller of the first embodiment of the turbo fluid machine of the present invention.

FIG. 5 is a cross-sectional view including a rotary shaft of an impeller of a second embodiment of the turbo fluid machine of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Rotation axis, 4 ... Vane rotation movable axis, 5 ...
Suction pipe, 6 ... Suction casing flow path, 7 ... Partition plate, 8,
9 ... Flow in the suction casing, 3, 31-41 ... Vane.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenichi Kuwahara, 603 Kandachi-cho, Tsuchiura-shi, Ibaraki prefecture

Claims (1)

[Claims] Claim: What is claimed is: 1. A flow is sucked in from a direction other than the rotational axis of the impeller, the flow is changed to an axial flow by a suction casing, and the flow rate is controlled by an inlet guide vane formed of a circular blade row provided in the suction casing. In the turbo compressor to be performed, an airfoil having a maximum thickness near the leading edge is used for the vane, and the vane chord length upstream of the rotary shaft that rotatably supports the vane is greater than the vane chord length of the downstream side. A turbo type fluid machine, wherein the inlet guide vanes are configured such that the ends of adjacent vanes overlap each other in a fully closed state.