US2469125A

US2469125A - Centrifugal compressor for high stage pressures

Info

Publication number: US2469125A
Application number: US555790A
Authority: US
Inventors: Meisser Christian
Original assignee: Sulzer AG
Current assignee: Sulzer AG
Priority date: 1943-12-11
Filing date: 1944-09-26
Publication date: 1949-05-03
Anticipated expiration: 1966-05-03
Also published as: NL115026B

Description

May 3, 1949. c. MEISSER 2,469,125

CENTRIFUGAL COMPRESSOR FOR HIGH STAGE-PRE$SURES Filed Sept. 26, 194.4 2 Sheets-Sheet 1 INVENTOR CHRIST/AN ME/SSE/E BY I Q:....;.., Q...-. ..:22,, J

ATTORNEYS 3,1949. c. MEISSEIRI I 2,469,125

CENTRIFUGAL COMPRESSOR FOR HIGH STAGE-PRESSURES Filed se mze, 1944 v 2 Sheets-Sheet 2 N INVENTOR Q mu, QM.

ATTO RNEYS Patented May 3, 1949 CENTRIFUGAL COMPRESSOR FOR HIGH STAGE PRESSURES Christian Meisser, Davos-Dorf, Switzerland, assignor to Sulzer Frres, Socit Anonyme, Winterthur, Switzerland Application September 26, 1944, Serial No. 555,790 In Switzerland December 11, 1948 The invention relates to a centrifugal compressor for high stage-pressures and consists in that the blades of the rotor extend diagonally to the rotor axis and have at least two zones, whereby in the inlet'zone the angle of inclination of the backwardly bent blade-surface with respect to the peripheral direction increases from the value required for freedom from shock at the inlet at normal load to a maximum value, whilst in the outlet zone the blade-surfaces have a decreasing angle of inclination, whose cosine at the point of outlet is greater than the ratio of the relative velocity to twice the peripheral velocity, so that the angle of inclination is again reduced from the maximum value to a value at which the absolute outlet velocity does not exceed the velocity of sound to such an extent that Mach sound waves can be formed.

Advantages with regard to the flow through the compressor, its construction and its working, are obtainablewith a compressor according to the invention. The increase in the angle of inclination of the blades with respect to the peripheral direction, from the inlet onwards in the direction of flow, causes a retardation of the relative flow, accompanied by a rise in pressure. In consequence of the direction of flow in this zone of the rotor being mainly axial, the centrifugal and Coriolis accelerations have no essential influence. The medium flowing in this man- ;8 Claims. (Cl. 230-134) ner thoughthe second zone of therotor has, in

consequence of its precompression, a higher specific gravity, so that an increase in the stagepressure is made possible by guiding the flow from a smaller to a greater diameter under the action of greater centrifugal and Coriolis accelerations.

In the second rotor-zone with backwardly bent blades, i. e. the zone at the outlet end,'the angle of inclination with respect to the peripheral direction decreases up to the blade-outlet, whereby, in addition. to the desired reduction of v the absolute outlet velocity, a relative accelera tion of the flow occurs, which prevents any excessive loading of the blades or any deviation may be obtained at the part of the rotor where the diameter increases, for instance by a contion and service conditions by making the two parts of the rotor separately and of different materials. In consequence of the inlet part of the rotor being of smaller diameter, it is subjected to lower mechanical stresses than the outlet part. The material used to make it can have less strength and at the same time require a less careful method of construction to be adopted than for the outlet part, which is very highly stressed in consequence of the high peripheral speeds and is therefore preferably shaped, at least approximately, as a disc of uniform strength and without any central bore. I Thus the inlet part with its hub might be made of a casting, for instance of steel, light metal, or such like. It would also be possible to ilnish the blades of the inlet part together with the hub as one pressed part, for instance from some kind I of plastic material, such as Bakelite, Pressspahn, etc. Further the blades and. the hub of the inlet part could each be made separately as pressed parts and then fitted together, for instance by welding or by means of suitable grooves in the hub. The blades of the inlet part could be made together with the hub from one piece of metal by adopting some suitable method of machining, for instance, by milling from the solid or from pre-shaped material.

Making the rotor of the compressor in two parts has further the advantage that one and the same outlet part of the rotor can be adopted for different working conditions by fitting it with interchangeable inlet parts, since only the latter have to be suited within wide limits to changing working conditions. .The number of blades'of the inlet part or of the-several inlet parts may be the same as the number in the main rotor, or the number may be lessor greater. When the number of blades on the inlet part and on the outlet part of the rotor is the same,

they may be arranged directly in line with eachv on the one or more inlet parts are displaced with respect to each other, the angles of both to the peripheral direction at theregion of displacement may be the same or different. Theform of the blades may be aerofoil. The centrifugal compressor may be constructed in such a way that it is possible quickly to change the inlet part, or the several inlet parts, for parts with' a dlflerent inlet-characteristic.

Fixed or adjustable guide blades may be ar ranged in front of the inlet parts. If these guide blades are flxed, it would be possible to constructthem as supporting ribs connected to the inlet casing, for taking a rotor bearing.

In order that the medium handled may be guided to the inlet part in a manner suitable to changeable working conditions, and in order to ensure high emciencies over a Very large service range, the guide blades may be constructed so that they can be adjusted while the compressor is at rest or while it is running. They may be movable about the rotor axis or have an axis of rotation cutting or crossing the rotor axis. In addition to the guide blades, the blades on one or several inlet parts of the rotor might also be arranged adjustable in the manner mentioned. In. the case of blades automatically adjustable duringservice, this could be effected by adopting electrical, hydraulic, pneumatic or mechanical means and dependent on one or several servicefactors, for instance the pressure of the medium handled.

In so far as the blades of the inlet part of the rotor and of the guide apparatus are ar- 4 the peripheral direction decreases to the outlet angle 48:. The cosine or the angle p; is greater than the ratio of the relative velocity to twice the-peripheral velocity. With theworkin'g con ditions occurring in practice the angle will amountto about 45. The separation between the zonesE and- F in Figs. 2 and 3 occurs approximately along the line 3-3, at a point of inflection in the bending of the blades. Whilst the blades of the inlet part have an increasin pitch and an increasing cross-section of flow and extend for the most part axially, the outlet part can have blades of a constant pitch and extend in a pronounced radial direction and less pronounced axial direction, thus'causing the angle of inclination of the blade with respect to the peripheral direction to be reduced, as desired, from the maximum value p: to the outlet angle B3. I

The centrifugal compressor according to Fi 4 has a rotor part 9 at the outlet end which is machined, along with the blades ll'L'out or the.

solid. The material used is preferably a lightmetal alloy of great tensile strength, for instance, Duralumin, Elektron, and such like, in order to be able towithstand the centrifugal stresses occurring at peripheral velocities of 400 m./sec.

ranged to be adjustable, their adjusting mechanisms could be coupled together in accordance; with some law of motion which ensures a high overall efficiency. the combined adjustment being eifected either automatically or by hand.

Examples of executions in accordance with the I subject matter of the invention are represented on the accompanying drawings, where Fig. I shows in longitudinal section a centrifugal compressor whose rotor is in one piece, and

- of centrifugal compressors consisting of an inlet part and an outlet part, developed along the line 11-11 of Fig. 4.

Fig. 7 shows in longitudinal section a centrifugal compressor whose rotor is formed of four parts, and

Fig. 8 a blade arrangement for. that compressor developed along the line I1IIII in Fig. 7.

The centrifugal compressor according to Figs. 1 and 2 has a rotor l, which is provided with backwardly bent blades 2 extending diagonally to the rotor axis and arranged in the form of a screw. The rotor I, which has no central bore, is flanged to the shaft 3 and carried overhung in one or more bearings 4. At the inlet end the covering hood 5 is connected to the rotor I. The rotor I is surrounded by the casing 6 which leads through a diffusor 1 into the outlet spiral 8.

The blades 2, arranged diagonally extended on the rotor body I and in the form of a screw (Figs. 1, 2 and 3), have two zones E and F (Figs. 2 and 3). At the beginning of the inlet zone E the blades 2 are inclined at the angle #1 to the peripheral direction u, as is obtained from the inlet triangle of velocities for given working con- "ditions'at normal loading for inlet free from shock, and amounts for instance to 30. In the direction of flow indicated by the arrow A the angle increases up to a maximum value 52, and amounts for instance to 60. In the outlet zone the angle which the blade surface makes with and higher. In order to prevent any bending stresses in the cross-section of the blades [0 nor-' mal to the rotor axis, they extend radially to that :axis. By screwing backwards lnthe axial direction they make an angle with respect to the peripheral direction whose cosine is greater than the ratio of the relative velocity to twice the peripheral velocity. In this way, in spite of the peripheral velocity of the rotor being higher than the velocity of sound in the medium handled, the,

absolute outlet velocity of the medium can be brought below the velocity of sound in it and prevent the occurrence of Mach waves. In .order that the rotor part 9 may be able to withstand the high centrifugal stresses, it is constructed, at least approximately, as a disc of uniform strength. In order to prevent any dangerous edge stresses this rotor part 9 is made without a central bore and flanged to the shaft 3, and it is also provided at the inlet end with a centered annular groove ll into which is inserted the central continuation of the hub i2 of the inlet part provided with the inlet blades l3 and secured to the rotor part 9 to prevent one of them turning with respect to the other. By means of the axial bolt ll fixed in the hub'of the rotor part 9 and of the covering hood 15 arranged on this bolt, the inlet part l2, i3 is secured against being axially displaced with respect to the rotor part 9.

The inlet blades l3, Fig. 4, are preferably made of aerofoil section and arranged according to the blade drawings in Figs. 5 and 6. The two rotor parts 9 and I2, supported overhung at the inlet end, are surrounded by the casing 6 which leads. into the diifusor 1 and the outlet spiral 8. The shape and arrangement of the blades correspond essentially to those shown in Figs. 1, 2 and 3.

The centrifugal compressor shown in Fig. 7 has a rotor part9 at the outlet end which is essentially shaped similarly to-the outlet part shown in Fig. 4. In the centered annular groove ll one inlet part I5 is inserted. This has also a centered annular groove IS, in which the middle inlet part I! is held. In' the same manner the first inlet part III is fixed on the middle inlet part. In the rotor part 9 at the outlet side the axial bolt I9 is fixed, whose free end has a plate 29' on which a bearing pin 2| is fitted. Through the bolt l9 the plate 20 keeps the inlet parts l5, l1 and I8 from being displaced axially. The bearing pin M is supported within a covering hood 22, held by a 9 in uniform progression over all three inlet parts.

If the blades of the inlet part and of the guide apparatus are arranged to be adjustable instead of being fixed, the two adjusting mechanisms can be coupled to each other according to a law of motion ensuring a high overall efficiency, and this combined adjustment may be effected automatically in accordance with one or more service factors or by hand. In this manner a high overall efliciency can be obtained over a wide range of working.

- I claim:

1. A centrifugal compressor suitable for high peripheral speeds, comprising a rotor, to be driven at a peripheral speed not less than 300 meters per second, with a plurality of blades extending from the inlet part on a small diameter to the outlet part on a greater diameter, the latter part being spaced axially from the former, the blades being bent backwards throughout their length and having at least two zones, one, an inlet zone in which the angle of inclination of the backwardly bent blade surfaces with respect to the peripheral direction increases from the relatively small angle required for freedom from shock at the inlet at normal load to the maximum value attained from inlet to outlet, and the other, an outlet zone in which the angle of inclination of the backwardly bent blade surfaces with respect to the peripheral direction decreases from the maximum value attained from inlet to outlet to an angle at the outlet whose cosine is greater than the ratio of the relative velocity to twice the peripheral velocity.

2. A centrifugal compressor according to claim 1 in which the inlet and outlet parts of the rotor are separable members each carrying its own blading detachably assembled into a unitary rotor structure.

3. A centrifugal compressor according to claim 2 in which the separable rotor members are constructed of different materials.

4. A centrifugal compressor according to claim 3 in which the outlet rotor member is formed at least approximately as a disc of uniform tensile strength and without any central bore.

5. A centrifugal compressor according to claim 4 in whichthe inlet rotor member consists of a relatively light blade carrying annulus assembled to the outlet member by clamping through its central bore.

6. A centrifugal compressor according to claim 1 in which the inlet'and outlet parts of the rotor are separable members each carrying its own blading detachably assembled into a unitary rotor structure and in which the blades in the inlet zone are offset. on the blades of the outlet zone.

7. A compressor according to claim 6 in which the offset of the blades in the inlet zone from the blades of the outlet zone can be adjusted by relative rotation of their respective rotor members about the rotor axis.

8. A compressor according to claim 1 in which the blades in the inlet zone have an airfoil form.

CHRISTIAN MEESSER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,042,506 DeVallat Oct. 29, 1912 1,075,300 Moss Oct. 7, 1913 1,341,882 Criqui June 1, 1920 1,771,939 Rees July 29, 1930 2,369,051 Huber Feb. 6, 1945