JPH0431695A - Centrifugal impeller - Google Patents

Abstract

PURPOSE:To improve pressure feed characteristics in an range of low flow rate by extending the leading edge of each vane to the surface of a hub from a starting point at the specified position of a parallel section in the shroud surface, and thereby setting the length of each vane along the shroud surface at one equal to or more than the length of each vane along the surface of the hub. CONSTITUTION:A centrifugal impeller is furnished with a plurality of vanes 4 which is formed between a hub 2 fixed onto the impeller rotating shaft and shroud 3 disposed while being faced to the hub 2. A shroud surface 3a acting as the inner surface side of the shroud 3 includes a parallel section 3b on the suction side B, and it is raised up along a gently curved line from an end section at the downstream side of the parallel section 3b up to a vane outlet port 0. In this place, a leading edge 4a which is the end periphery of each vane 4 at its suction side, is linearly extended to the surface of the hub 2 from a starting point C1 in the vicinity of an end section at the upstream side of the parallel section 3b, and the length Ls of each vane along the shroud surface 3a is set at one equal to or more than the length Lh of each vane along the surface 2a of the hub. In addition, the outlet angle beta of each vane 4 is set at the angle of 30 deg. to 40 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to improvements in impellers used in centrifugal compressors and centrifugal blowers that pump fluid through rotation.

<Prior Art> Conventionally, as shown in FIG. 11, a centrifugal impeller has a hub 92 attached to a rotating shaft 91 and a shroud (side plate) 93 provided opposite to the hub 92. There is provided one in which a plurality of two-dimensional or three-dimensional blades 94 are arranged between them.

Since the shape of each component of the impeller has an important influence on impeller efficiency, various design methods have been proposed to minimize the loss in each component. However, in the impeller mentioned above, many factors are intricately intertwined and affect the impeller efficiency, so it is difficult to obtain the performance as designed. The actual situation is whether the desired performance is being secured.

For conventionally provided impellers, for example,
As shown in Japanese Patent No. 5-134797, the blade 9
The length Ls along the shroud surface 93a of No. 4 is the length Ls along the shroud surface 93a of the hub surface 9.
It is set to be shorter than the length Lh along 2a.

Further, the blade exit angle is usually set to 45° to 60″.

<Problem to be Solved by the Invention> However, according to the conventional centrifugal impeller described above, in the low flow region, the shroud surface 9 near the leading edge 94a of the blade 94
In the region E on the 3a side, swirling stall or backflow of the fluid is likely to occur, the Matsuha number at the blade outlet becomes large, and the leading edge 94
There was a problem that the efficiency was poor because the number of relative pines 71 of the blade 94 on the shroud surface 9Ba side near a was large.

In particular, in turbo compressors that use fluorocarbons, the speed of sound is as low as 100-odd meters, and there are many areas where the Matzuha number exceeds 1, which has been a bottleneck in improving efficiency. Further, since the range of air volume at the point of use is wide, it is required to exhibit high efficiency over a wide range of air volume, but the reality is that no product has been provided that satisfies this requirement.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a centrifugal impeller that can ensure good efficiency over a wide flow range.

Means for Solving the Problems> A centrifugal impeller according to the present invention to achieve the above object has a plurality of three-dimensionally shaped blades 4 arranged between the shroud surface 3a and the hub surface 2a. In the centrifugal impeller, a parallel portion 3b parallel to the rotational axis of the impeller is formed on the suction side B of the shroud surface 3a, and
extends toward the hub surface 2a from the parallel portion 3b, and the blade length Ls along the shroud surface 3a is set to be equal to or greater than the blade length Lh along the hub surface 2a, and
The blade exit angle β is set to 30@-40''.

According to the centrifugal impeller having the above configuration, the leading edge 4a of the blade 4
starts from a predetermined position on the parallel portion 3b of the shroud surface 3a C1
Since the blade length Ls along the shroud surface 3a is set to be greater than the blade length Lh along the hub surface 2a, the blade leading edge 4a on the shroud surface 3a side extends as shown in FIG. , it will protrude greatly on the suction side B (see especially Fig. 2). As a result, in the shroud 3 side region E near the leading edge 4a of the blade 4, it is possible to suppress the swirling stall or backflow of the fluid.

In addition, the blade length Ls along the shroud surface 3a is longer than before, and the diameter D2 of the starting point 01 becomes the minimum, making it possible to reduce the relative Matsuha number at the leading edge 4a of the blade 4. , it is possible to improve the pumping characteristics in the low flow rate range.

Furthermore, in addition to adjusting the shape of the blade 4 mainly on the shroud surface 3a side, the Matsuha number at the blade exit can be reduced to 1 or less by setting the blade exit angle β to 30° to 40°. Obtained. Therefore, the efficiency of the centrifugal impeller can be effectively increased as a whole.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments.

FIG. 1 is a sectional view of a main part of an embodiment of a centrifugal impeller according to the present invention. In the figure, the impeller has a rotation axis l
A plurality of blades 4 are formed between a hub 2 fixed to the hub 2 and a shroud 3 placed opposite to the hub 2, and the rotating shaft 1 is connected to a speed increasing mechanism (not shown). Rotationally driven through.

The shroud surface 3a, which is the inner surface of the shroud 3, is
It has a parallel part 3b parallel to the rotation axis of the impeller on the suction side B (upstream side), and is raised with a gentle curve from the downstream end of this parallel part 3b to the blade outlet O. There is.

Referring also to FIG. 2, the blade 4 has a three-dimensional shape whose shape changes in the blade width direction, and the leading edge 4a, which is the edge on the suction side, is the upstream end of the parallel portion 3b. The vane length Ls along the shroud surface 3a and the vane length Lh along the hub surface 2a are L s / L h ≧ 1, more preferably, it is formed so as to satisfy the relationship Ls/Lh-1.05 to 1.1. That is, the blade 4 is set to be equal to or longer than the blade length Ls along the shroud surface 3a or the blade length Lh along the hub surface 2a. As a result, the blade 4 is
The inclination angle α of the line J connecting the starting point C1 and the intersection A1 of the leading edge 4a and the hub surface 2a with respect to the rotating shaft 1 becomes gentle to about 25 to 30'', for example, and the leading edge of the blade 4 The shroud surface 3a side of the blade 4a largely protrudes toward the suction side B.The exit angle β (see FIG. 3) of the blade 4 is set to 30@ to 40''. In addition, at least several tens of squares near the blade exit are set to the same angle as the exit angle β, so that when the outer diameter is reduced or expanded according to the increase or decrease of the required head, the characteristics of the impeller can be made similar. This is preferable because it can be changed to Further, the outlet width W of the blade 4 is adjusted as appropriate depending on the designed air volume.

With the above configuration, the inclination angle α of the leading edge 4a of the blade 4 is quite gentle, and since the shroud surface 3a side of the blade 4 largely protrudes toward the suction side B, the leading edge 4a of the blade 4 is In the nearby shroud 3 side region E, it is possible to suppress the occurrence of swirling stall or backflow of the fluid. Further, the blade length Ls along the shroud surface 3a is longer than before, and the diameter D of the starting point 01 is
2 becomes the minimum, and the relative Matsuha number at the leading edge 4a of the blade 4 can be reduced, so that the flow in the direction of the impeller in the low flow rate region can be improved. Furthermore, in addition to adjusting the shape of the blade 4 mainly on the shroud surface 3a side, by setting the blade exit angle β to 306 to 40°, the relative and absolute Matsuha numbers of the blade exit O can be made 1 or less. , further, the relative Matsuha number on the wing surface at the hub surface 2 a % central flow surface and shroud surface 3 a is calculated by the leading edge 4 a
It can be set to 1 or less with some exceptions, as shown below. Therefore, the efficiency of the impeller can be effectively increased as a whole.

[Test ■] The impeller according to the present invention (Test Example 1) and the conventional impeller (Comparative Example 1) were installed in the same turbo compressor, and a comparative test of adiabatic efficiency in each air volume range was conducted. . However, Freon 11 was used as the working fluid. Further, the blade shapes in the meridian plane of Test Example 1 and Comparative Example 1 are shown in FIG. In the figure, the blade inlet diameter D2 of Test Example 1 and Comparative Example 1 is 216 mm, and the blade outlet diameter D1 is 410 mm.
mm, and further, the blade exit angle β is 30 mm in Test Example 1.
°, and Comparative Example 1 is 45''.

The results of this comparative test are shown in FIG. As is clear from the figure, Test Example 1 has better heat insulation efficiency than Comparative Example 1 in each air volume range. In addition, in the figure, the maximum insulation efficiency of Test Example 1 is set as 100% for the insulation efficiency (the same applies hereinafter).

[Test ■] In Test Example 1, the intersection point between the blade leading edge 4a and the shroud surface 3a was set closer to the blade outlet O than the parallel part 3b of the shroud surface 3a, that is, the point of intersection between the blade leading edge 4a and the shroud surface 3a was set closer to the blade outlet O than the parallel part 3b of the shroud surface 3a, that is, the point of intersection between the blade leading edge 4a and the shroud surface 3a was set closer to the blade outlet O than the parallel portion 3b of the shroud surface 3a, that is, the point of intersection of the blade leading edge 4a and the shroud surface 3a was set closer to the blade outlet O than the parallel part 3b of the shroud surface 3a. A test was conducted to compare the insulation efficiency of Comparative Example 2) with Test Example 1 to create a shape that does not protrude to the suction side B.
Each test was conducted under the same test conditions.

The results of this comparative test are shown in FIG. As is clear from the figure, the efficiency of the compressor in Comparative Example 2 is lower than that in Test Example 1 in each air volume range.

[Test ■] Test example 2 in which the blade exit angle β of test example 1 was set to 40°,
Comparative Example 3 was prepared with an angle of 45°, and a test was conducted to compare the insulation efficiency in each air volume range with Test Example 1 under the same test conditions.

Furthermore, the relative Matsuha numbers Mw from the blade leading edge 4a to the blade outlet O on the suction surface and pressure surface of the blade 4 were investigated.

Figure 7 shows the insulation efficiency in each air volume range. Further, the relative Matsuha number Mw of Test Example 1 is shown in FIG. 8, the relative Matsuha number Mw of Test Example 2 is shown in FIG. 9, and the relative Matsuha number Mw of Comparative Example 3 is shown in FIG.

However, in each figure, (a) shows the relative Matsuha number Mw on the shroud surface 3a side of the blade 4, and (b) shows the relative Matsuha number Mw at the intermediate part between the shroud surface 3a and the hub surface 2a, The figure (c) shows the relative Matsuha number Mw on the hub surface 2a side.

Further, in the figure, the horizontal axis indicates a relative position to the overall length of the blade, with the left side being the blade leading edge 4a side and the right side being the blade exit side.

As is clear from FIG. 7, in Test Example 1 and Test Example 2,
The insulation efficiency is improved compared to Comparative Example 3 in each air volume range. Furthermore, as is clear from FIGS. 8 and 9, in Test Examples 1 and 2, the relative Matsuha number Mw is 1 or less in any part of the blade 4, whereas
In Comparative Example 3, there is a portion where the relative Matsuha number Mw exceeds 1 on the shroud surface 3a side. Moreover, on the shroud surface 3a side, there is a portion where the relative Matsush number Mw between the negative pressure surface and the pressure surface is reversed. Therefore, in order to increase efficiency, the blade exit angle β should be set in the range of 30 to 40'', and the blade shape should be determined so that the relative Matsuha number Mw between the suction surface and the pressure surface does not reverse at any position. It is necessary.

The leading edge 4a of the blade 4 may have a linear shape as shown in the figure, or may have a curved shape in which the center portion is recessed toward the downstream side. In addition, the leading edge 4a and the shroud surface 3
The intersection point with a (starting point CI) may be set more roughly toward the suction side B than what is illustrated.

<Effects of the Invention> As described above, according to the centrifugal impeller of the present invention, the leading edge of the blade protrudes toward the parallel portion of the shroud surface, and the blade exit angle is 30° to 40″. As a result, the shroud length can be made larger than the hub length, which reduces the loss that occurs in the low flow range. Mitigates rotational stall backflow on the shroud surface,
Low flow characteristics can be improved. Furthermore, since the vane leading edge radius is minimum, the relative Matsuha number at the vane inlet can be reduced, and these act synergistically to provide the unique effect of increasing efficiency over a wide air volume range.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of the centrifugal impeller of the present invention, and FIG. 2 is a schematic diagram showing the meridian shape of the blade. Fig. 3 is a front view of the blade, Fig. 4 is a schematic diagram showing a planar circular blade row of the blade according to Test Example 1 and the blade according to Comparative Example 1, and Fig. 5 is the heat insulation of Test Example 1 and Comparative Example 1. A graph diagram showing efficiency. FIG. 6 is a graph showing the insulation efficiency of Test Example 1 and Comparative Example 2. Figure 7 is a graph showing the insulation efficiency of Test Example 1, Test Example 2, and Comparative Example 3. Figures 8, 9, and 10 are each of Test Example 1.
, Test Example 2, and Comparative Example 3; FIG. FIG. 11 is a graph showing the relative Matsuha number at the intermediate part between the surface and the hub surface, FIG. 11 is a graph showing the relative Matsuha number at the hub surface side, and FIG. DESCRIPTION OF SYMBOLS 1... Rotating shaft, 2a... Hub surface, 3a... Shroud surface, 4... Vane, 4a... Leading edge, β... Vane exit angle, C1... Starting point, B...・・・
Suction side, Ls... blade length along the shroud surface, Lh...
Blade length along the hub surface.

Claims (1)

[Claims] 1. Between the shroud surface (3a) and the hub surface (2a),
In a centrifugal impeller in which a plurality of three-dimensional shaped blades (4) are arranged, a parallel portion (3b) parallel to the rotation axis of the impeller is formed on the suction side (B) of the shroud surface (3a). The front edge (4a) of the blade (4) is aligned with the parallel part (3).
The vane length (Ls) along the shroud surface (3a) is set to be greater than or equal to the vane length (Lh) along the hub surface (2a). is,
A centrifugal impeller characterized in that the blade exit angle (β) is set to 30° to 40°.