JPS59185896A - Centrifugal impeller - Google Patents

Abstract

PURPOSE:To reduce leaking loss, by forming a suitable number of grooves in the end face of a blade which faces a shroud section in a casing so that labyrinthes are formed. CONSTITUTION:A blade 4B is formed in its end face with a groove 7 forming a labyrinth 8. With this arrangement the flow of leak is small in comparison with a blade having no groove in its end face due to the labyrinth effect by which the kinetic energy of the flow entering into the groove 7 through a gap 6 is converted into the heat energy. In order to exhibit the labyrinth effect the width (l) of the labyrinth 8 is made substantially equal to the size epsilon of the gap 6. Further, if more than two grooves 7 are formed in the end face of the balde 4B to provide a plurality of labyrinthes 8, the labyrinth effect may be moreover enhanced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an open-type centrifugal impeller used in centrifugal compressors, mixed flow compressors, radial turbines, etc. Conventionally, centrifugal impellers used in industrial compressors are As shown in FIG. 1, a stone plate 2, a side plate 3 and a blade 4 fixed to both 2 and 3.
In other words, this centrifugal impeller 1 is housed within a casing 5.

The impeller 1 is suitable for high efficiency machines, but cannot be applied to high peripheral speed machines.

For this reason, in high peripheral speed machines, an open centrifugal impeller I consisting of a stone plate 1 and blades 4 is used, as shown in Fig. 2(a)Cb).
A is used. Although this impeller IA does not require a side plate, it is necessary to provide a shroud portion 5a in the shroud casing 5 instead.

Losses related to centrifugal compressor impellers include collision loss,
These include friction losses, leakage losses, and secondary flow losses. The leakage loss is due to leakage occurring between adjacent flow paths separated by the blades of the impeller, and this leakage does not occur in the impeller 1 with side plates shown in FIG.

On the other hand, in the open type impeller IA shown in FIG. 2(a), in the gap 6 between the planar tip of the blade 4A and the shroud part 5a of the casing, the blade 4A is Since leakage occurs from the pressure side X to the negative pressure side Y, leakage loss increases, which may lead to a decrease in efficiency.

Generally, the leakage loss is proportional to the amount of leakage, and the amount of leakage is proportional to the gap 6 between the blade 4A and the casing shroud portion 5a. For this reason, it is necessary to make the gap 6 as small as possible, but there is a limit to making the gap 6 small considering deformation of the impeller during rotation, vibration of the shaft, etc., so it is not necessary to make the gap 6 small. It is possible.

[Purpose of the invention]

In view of the above, it is an object of the present invention to reduce leakage loss and improve efficiency.

[Summary of the invention]

In order to achieve the above object, the present invention provides an open centrifugal impeller consisting of a stone plate and a plurality of blades, in which an arbitrary number of grooves are provided on the end surface of the blades facing a shroud portion provided in a casing. It is characterized by the formation of

[Embodiments of the invention]

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

In FIG. 3(a), 2 is a stone plate, 4B is a blade, and this blade 4B has a groove 7 on its end surface, as shown in FIG. 3(b).
One is provided to form a labyrinth 8. 5a is a shroud portion of the casing 5; 6 is the shroud portion 5;
a and the end face of the blade 4B, that is, the labyrinth 8.

In the impeller IB having the above configuration, the leakage flow is caused by the labyrinth effect in which kinetic energy is converted into thermal energy when it flows into the groove 7 through the gap 6, so no groove is provided on the end surface of the blade. This decreases compared to the conventional impeller IA (Fig. 2). However, when the width t of the labyrinth 8 is larger than the size ε of the gap 6, the labyrinth effect is reduced, so it is necessary to make t about the same size as 6.

The groove 7 can be formed only on an impeller whose blade thickness is at least as thick as possible, and can be easily formed using a '1=Iy, Nc processing machine. In addition, if the thickness of the blade 4B is sufficiently large, the blade 4B has two
The labyrinth effect can be further improved by providing a plurality of grooves 7 to form a large number of labyrinths 8. As roughly shown in FIG. 5, the pressure surface side of the labyrinth 8 may be formed with a sharp edge. - [Effects of the Invention] As explained above, if the present invention is applied, leakage loss can be reduced and efficiency can be improved.

[Brief explanation of drawings]

Figures 1 and 2 (a) are meridional cross-sectional views of a conventional centrifugal impeller with side plates and an open type centrifugal impeller, and Figure 2 (b) is a cross-sectional view taken along line A-A in Figure (a). 3(a) and 5(b) are a meridional plane sectional view showing an embodiment of the centrifugal impeller of the present invention, and a BB sectional view of FIG. 3(a), and FIGS. It is a partial sectional view of a modification of an impeller. 2...Stone plate, 4B...Blade, 5...Casing,
5a...Shroud part, 6...Gap, 7...Groove, 8...Labyrinth. Agent Patent Attorney Akio Takahashi Z 1 Figure 3 x 5 Figure 581-

Claims (1)

[Claims] 1. In an open centrifugal impeller consisting of a stone plate and a plurality of blades, a labyrinth is formed by providing an arbitrary number of grooves on the end surface of the blade facing a shroud portion provided in a casing. A centrifugal impeller characterized by: 2. The centrifugal impeller as set forth in claim 1, wherein the thickness of the labyrinth is determined by the clearance between the shroud portion of the casing and the shroud side end surface of the blade.