JPH0311197A - Fluid machine - Google Patents

Abstract

PURPOSE:To reduce the disc friction loss of fluid machines by installing a blowout construction in a low pressure part as against a suction construction, and a suction construction in a high pressure part as against a blowout construction, and installing ducts leading fluid from blowout to suction constructions. CONSTITUTION:Chambers 6a, 6b are formed inside casings 2a, 2b, and communicated with gaps 9a, 9b between an impeller 1 and the casings 2a, 2b through small holes and grooves 8a, 8b opened in surface materials 7a, 7b on inner walls of the casings 2a, 2b. Furthermore, ducts 10a, 10b are communicated from the chambers 6a, 6b to blowout ports 11a upstream of the inlet of the impeller 1. Since the blowout ports 11a have pressure lower than the gaps 9a, 9b, the fluid in the gaps 9a, 9b blows into the chambers 6a, 6b through small holes and grooves 8a, 8b opened in the surface materials 7a, 7b, and blows out to the blowout ports 11a through the ducts 10a, 10b. Suction and blowout are made using a small pressure difference existing in the channel to reduce disc friction of fluid machines.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluid machine in which an impeller is rotatably housed in a casing.

[Conventional technology]

Conventionally, when reducing disk friction using suction, the Proceedings of the 20th Turbulence Symposium (1988)
As discussed on pages 130 to 137, the structure was such that suction was carried out from the surface of the rotating disk.

[This is because the above-mentioned conventional technology has a structure in which suction is performed from the surface of the rotating disk and discharged to the outside from the rotating shaft.

Centrifugal force acts on the fluid sucked into the disk, and a large pressure difference is required between the suction section on the disk surface and the discharge section of the rotating shaft6. Since the centrifugal force is large on the outer circumferential side, depending on the suction structure, the sucked fluid may be blown out to the outer circumferential side, and even in the above-mentioned conventional technology, turbulence caused by one blowout from the outer circumferential side has been a problem. Furthermore, when the sucked fluid is discharged from the rotating shaft to the stationary side, a shaft seal is required, resulting in losses such as sliding friction.

An object of the present invention is to provide a fluid machine that reduces disk friction loss without providing a suction and discharge structure on a rotating body.

[Means to solve the problem]

The above purpose is to create a hole in the inner wall of the casing that houses the impeller.
A suction and blowout structure such as a groove is provided, and the blowout structure is provided in a low pressure section for the suction structure.

In contrast to the blowout structure, a suction structure is provided in the high pressure section.

This is accomplished by providing a duct inside the casing for conducting fluid from the suction structure to the discharge structure, respectively.

[Effect]

Generally, if the gap between the side surface of the impeller and the inner wall of the casing is large, the flow in that gap will be

A rotating boundary layer near the side of the impeller with a high-speed rotational velocity component and a radially outward velocity component; a stationary boundary layer near the inner wall of the casing with a low-speed rotational velocity component and a radial inward velocity component;
and a core layer which rotates without any radial velocity component between the image boundary layers. In the core layer, centrifugal force and pressure balance, so there is no radial flow, but in the boundary layer on the 5th rotation side, the rotating speed increases due to being dragged by the rotating disk, and as the centrifugal force exceeds the pressure, the flow flows outward in the radial direction. On the other hand, in the stationary boundary layer, the swirling speed is small and the flow is inward. The velocity distribution of this radial flow has an inflection point and is unstable compared to a flow along a flat plate. Furthermore, the flow in the stationary boundary layer is decelerated and unstable, and transitions to turbulence faster than the accelerated flow in the rotating boundary layer.

Therefore, suction structures such as holes and grooves are provided on the inner wall of the casing to suck in the unstable decelerated flow of the stationary side boundary layer, and to allow the high-speed swirling flow of the core layer to flow close to the stationary wall, thereby stabilizing the flow of the stationary side boundary layer. This prevents the transition to turbulence.

〔Example〕

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

In FIG. 1, the impeller 1 has a casing 2a.

It is housed so as to be rotatable around a rotating shaft 3 within the blade 2b, and is composed of several blades 4 and side plates 5a and 5b on both sides thereof. Casing 2, ].

Chambers 6a and 6b are provided inside the casings 2b, and the surface material of the inner walls of the casings 2a and 2b is provided with chambers 6a and 6b. It communicates with gaps 9a and 9b between one impeller and the casing through small holes and grooves 8a and 8b made in holes a and 7b. Furthermore, chambers 6a, 6
From b is the duct 10a.

10b communicates with the air outlet 11a upstream of the impeller inlet.

Since the air outlet 11a has a lower pressure than the gaps 9a and 9b,
The fluid in the gaps 9a and 9b is the surface material 7a.

The duct 10a is sucked into the chambers 6a, 6b through small holes and grooves 8a, 8b made in the duct 7b.

The air is blown out through the air outlet 11a through the air outlet 10b.

The flow in the gaps 9a and 9b when there is no suction has the velocity distribution shown in Fig. 9. In other words, the flow as a whole is dragged by the impeller and turns, and especially in the center, the centrifugal force and pressure are balanced. Therefore, there is a core layer that rotates like a rigid body without a radial velocity component. On the other hand, because a boundary layer is formed near the wall, pressure is applied in the core layer.

The swirling speed is high in the rotating boundary layer near the impeller, so the centrifugal force exceeds the pressure, resulting in a radially outward flow. Conversely, in the stationary boundary layer near the casing, the swirling speed is low, resulting in a radially inward flow.

Therefore, near the casing, it flows inward in a spiral manner. Figure 2 shows the change in the swirling velocity component of the stationary boundary layer when suction is performed, and Figure 3 shows the change in the radial velocity component.The swirling velocity distribution becomes closer to the inner diameter as it moves downstream, so The circumferential speed of the impeller is small, and therefore the flow velocity is also small. Therefore, as shown in Figure 2, the velocity distribution has a small change in the direction perpendicular to the wall near the wall, making it unstable against disturbances.

If suction is performed here, the low-speed flow near the 5th wall will be sucked in, and the high-speed flow in the core layer will descend near the wall, resulting in a stable swirling speed distribution. The radial velocity component has an inflection point because the flow velocity is zero in the wall and core layer, resulting in an unstable distribution.

Although the inflection point does not disappear even if suction is performed here, the flow velocity can be reduced, and the influence of instability on the combined velocity of the swirling component and the radial component can be reduced.

Because a stable velocity distribution is obtained by the suction of the stationary boundary layer, the flow remains laminar.As shown in Figure 4, the friction of the rotating disk is greater in turbulent flow than in laminar flow, and Reynolds The number increases by more than three times around 10'. Therefore, boundary layer suction significantly reduces friction losses.

In the example shown in Fig. 1, suction is performed using the pressure difference between the impeller and the low pressure section upstream of the impeller, but this multistage fluid machine effectively blows out the flow sucked in from the stationary boundary layer at the low pressure section. An example is shown in FIG. The fluid sucked in from the stationary boundary layer passes through the duct 10c and is blown out from the outlet flb.

The blowout port 11b is provided near the separation point of the front-stage diff user or the like and on the upstream side of the separation point, and the blown flow suppresses separation. Separation occurs when the flow velocity near the wall does not change in the direction perpendicular to the wall and its magnitude is zero, as shown in A of FIG. The blow is directed downstream to increase the velocity of the slow flow near the wall.

Peeling is prevented by forming a stable velocity distribution shown in FIG. 6B.

When the stationary boundary layer is sucked in and the flow is kept laminar.

A large amount of suction is required to bring the high-speed flow of the core layer down close to the wall. Therefore, FIG. 7 shows an embodiment in which both blowing and suction are used in the stationary boundary layer. The suction port 8c is provided in the high pressure section on the upstream side, and the sucked fluid passes through the duct lod inside the casing and is blown out from the blowout port 1.1c to the stationary boundary layer. Further, the suction port 8d is provided downstream of the blowout port 11c along the stationary side boundary layer flow.

The fluid sucked in from the suction port 11c passes through the duct 10s in the casing and is blown out to the low pressure section on the downstream side. The blowout port lie and the suction port 8d face the downstream and upstream sides of the stationary boundary layer flow, respectively, as shown in FIG.
Most of the fluid sucked in by the suction port 8d is transferred to the blowout port 11c.
This is the fluid blown out from. In other words, by using blowing and suction together, a layer of moving fluid caused by external fluid is formed on the wall surface, reducing the relative velocity of the flow generated by the rotating impeller, and stabilizing the flow. Measure.

〔Effect of the invention〕

According to the present invention, since the suction and blowout structure is provided inside the casing, suction and blowout can be performed using a small pressure difference within the flow path, and this has the effect of facilitating reduction of disc friction in a fluid machine.

[Brief explanation of the drawing]

FIGS. 1, 5, and 7 are longitudinal cross-sectional views of a fluid machine equipped with an embodiment of the present invention, and FIGS. 2 and 3 are swirling velocity distribution and radial velocity when suction is applied. Distribution diagram, Figure 4 is an explanatory diagram of disk friction torque, Figure 6 is a velocity distribution diagram when blowing is applied, Figure 8 is a velocity distribution diagram when suction and blowing are applied simultaneously, Figure 9 is FIG. 2 is a velocity distribution diagram between an impeller and a casing of a conventional fluid machine. 1. Impeller, 2a. Casing, 6a. Chamber. 7a...Surface material, 8a...Suction 0.10a...Duct, Figure 1...Full t:a+・-乍-shin2～-raL...'r? 71\... 7L-Surface material ♂E゛"咀Δ)K. 10Good'-?"ヮ11&-, Qll, @ L 0 609- Vine Z Diagram ■ Diagram and Inolus number pattern e ■ Diagram'￥;6 Figure

Claims (1)

[Claims] 1. In a fluid machine in which an impeller is rotatably housed in a casing, a suction means is provided on a stationary wall surface facing each side plate of the impeller, and a means for blowing out the fluid sucked from the suction means is provided in a low pressure part. A fluid machine characterized by being provided with a duct for guiding fluid from suction means to blowout means.