US2465625A - Centrifugal compressor - Google Patents

Description

Mgr-c1129, 1949.l G. Au;

CENTRIFUGAL cuPnEssoR 2 Sheets-Sheet 1 und Aug. 1o, 1944 INVENToR 65086 AOE ATTORNEYS March 29, 1949.l G, AUE

GENTRIFUGALCOMPRESSOR I 2 Sheets-Sheet 2 I Filed Aug. 10. 1944 INVEN-ro'n- GEORG HUE v.rl'omuzwrs Patented Mar.- 29, 1949 CENTRIFUGAL COMPRESSOR Georg Aue, winterthur, switzerland, assigner to Sulzer Frres, Socit Anonyme, Winterthur, 1

Switzerland Application August 10, 1944, Serial No. 548,830 In Switzerland October 18, 1943 4 Claims. (CL 230-127) The invention is characterized in that the part of the blade outlet edge which lies in the'iiow disturbed by the stationary wall of the casing has a greater radius of rotation than the part lying in the undisturbed ow, and by this means the end is attained that the disturbed flow, on account of the increased supply of energy, leaves the impeller with at least approximately the same energy as the undisturbed ilow.

If the ow passages of the impeller are arranged so as to be oblique to the impeller axis, it is advisable to give the blade outlet edge a direction which is inclined relative to the impeller axis, so that this edge has a greater radius of rotation in the neighborhood of the stationary wall of the casing than in the neighborhood of the rotating surface of the impeller body. For compressors in which only one side of a flow passage is directly bounded by the stationary casing wall, while ythe other side is bounded by the surface of the impeller body, it may be preferable to give the blade outlet edge in the neighborhood of the surface of the impeller body and in the neighborhood of the stationary casing wall a greater radius of rotation than inthe middle region of the edge in which the undisturbed flow emerges. In centrifugal compressors Whose impellers have double blades which are bounded on both sides directly by the wall of the stationary casing Without the intermediary of a covering plate, the outlet edge may to advantage have a greater radius of rotation in the parts adjacent to the stationary wall of the casing than in the middle region where the undisturbed i'low emerges.

The accompanying drawings illustrate apparatus embodying the invention, in which:

f Fig. 1 shows a longitudinal section through one example of execution. l

Fig. 2 shows the impeller in perspective.

Fig. 3 shows the development in one plane of a ow passage in the impeller of the compressor according to Fig. 1.

Fig. 4 shows a cross-section to a larger scale on the line III-III of Fig. 3.

Figs. 5 and 6 are sectional viewsof other modifications of the invention, and Fig. '7 is a fragmentary sectional view of still another modification of the invention.

The compressor (Figs. 1-4) has an impeller I,

which is formed in one piece with the blades 2 by forging and milling and is mounted overhung on the shaft 3. The ow passages 4 ofthe impeller, formed by the blades, are arranged inclined to the axis 5 of the impeller. On the outer side they have no covering plate, and lie therefore direct on the stationary wall 6 of. the casing 1, whilst on therinner side they are bounded by the surface IIJ of the impeller body. Air or another gas or a vapour is drawn out of the passage 8 and led in a compressed state through the passage 9.

The energy which is imparted to the medium to be compressed through the impeller, is not equally great for all parts of a. cylindrical section (for instance IV-IV) in spite oi the fact that all parts have the same peripheral speed.

The flow passages 4 of the impeller turn with a very high peripheral speed. The medium led through the ow passage has therefore a considerable relative speed with respect to the casing wall surface 6, a speed which is considerably greater than the relative speed with respect to the impeller surface I0.

In the neighbourhood of the casing wall 6 the flow encounters friction which impedes it. The flow particles led in the neighborhood of the casing wall 6 have, in consequence of the withdrawal of energy, less energy than the flow particles led inthe neighbourhood of the surface I0 or of'those in the interior of the ow passage l.

At the position I2 of the cylindrical section IV-IV, the medium to be compressed, in spite of having the same peripheral speed, has less energy than at the' position I3. The blade outlet edge I4 is therefore arranged inclined to the axis 5 of the impeller. At the position I5 in the neighbourhood of the casing Wall it has the greatest radius of rotation. The iiow parts which are led along near the casing wall 6 leave the ilow passage in the region of a greater blade speed.

Additional energy is supplied to the part of the medium to be compressed which is flowing along the casing wall. With a suitable Obliquity of the edge I4, so much additional energy will be imparted that also the disturbed flow particles will issue at the outlet edge I5 with essentially the same energy content as the other ow parts which are disturbed less or not at all. In this way a uniform ow in the diiusor, free from disturbance, is ensured.

In order to maintain vparticularly high compression ratios, the ow passages 4 can rotate with a peripheral speed which exceeds the vethe neighbourhood of the high peripheral speeds.

In Fig. 2 the blades 2 follow helical lines and are curved backwards relative to the direction of rotation I6 of the impeller I. In this way it is possible to have the absolute outlet speed of the compressed medium not exceeding, or at least not essentially exceeding, the velocity of sound, v

in spite of the peripheral speeds of the impeller being considerably over the speed-of sound.

The impeller la of the compressor according to Fig. 5 has radial blades -2a which lie close to the wall 6a of the stationary casing 1a without the intermediary of a covering plate. The outlet edge Ma has a greater radius of` turning in its part ISa in the neighbourhood ofthe stationary casing wall than in its part |30. in the neighbourhood of the body of the impeller.' The increase is chosen in such a way that the flow disturbed by the friction on the casing wall 6ay issues from the wheel, in consequence of the increased energy introduced by the blade projecting out to a greater outlet radius, with approximately the same quantity of energy as the undisturbed ow in the middle of the blade passage 4a.

If the flow along the surface of the impeller body la should also experience a perceptible disturbance, for instance as a result of friction on the wall, the blade outlet edge I4c may have a somewhat greater radius of rotation also in the region of the point I3c.than in the region Md of the edge, which is farther away from the impeller body la, as shown in Fig. 7. In this way the boundary layer flowing along the surface of the impeller will be accelerated in such a way that it also issues with the same amount of energy as the undisturbed flow in the middle of the flow passage.

The compressor according to Fig. 6 has an impeller Ib with double blades 2b which lie close to the wall 6b of the stationary casing 'Ib without the intermediary of a covering plate. The outlet edge Mb has therefore at both sides at the position I5b a greater radius of rotation than in the middle. In this way the fiow disturbed by the same amount of energy as the average undisturbed flow.

' material by milling. In order to reduce the Preferably the impeller is made from the full amount of milling required, the impeller may for instance be previously pressed in a die. Suitable materials to use are thosewhich have the most favourable relation between specific gravity and strength. Particularly suitable are light metals and their alloys.

I claim:

l. In a centrifugal compressor, a rotor hub, blading attached to said hub having radially directed cross-sections in planes normal to the rotor axis, said blading being attached the length of one of its edges to said hub, a casing enclosing said hub and said blading, inlet an'd outlet passages in said casing, a surface of said casing lying along, out of contact with, but in close proximit'y to the length of an edge of said blading opposite the edge of its attachment to said rotor, said surface together with .said hub and said blading defining flow passages vthrough the compressor, and inlet and outlet edges to said blading adjacent said inlet and outlet' passages respectively completing with the aforementioned two edges the bounding of said blading, said outlet edges being so shaped as to have a greater radius of rotation about said rotor axis adjacent said casing surface than intermediate said surface and said hub.

2. A compressor according to claim 1 in which the ilow passages are arranged oblique to the REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Foster et al. Dec. 28, 1897 Number FOREIGN PATENTS Country Date" Birmann May 22, 1934 l Germany Dec. 18, 18822

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