US3032259A - Turbocompressor having a radial diffuser - Google Patents

Abstract

881,882. Centrifugal pumps and compressors. SULZER FRERES S.A. Dec. 8, 1958 [Dec. 23, 1957], No. 39514/58. Class 110 (1). A centrifugal pump or compressor comprises a first ring 4 concentric with the rotor shaft and forming a part of one of the walls of the diffuser of the pump or compressor, the flow cross-section of the diffuser being adjustable by varying the distance S between the diffuser walls by axial movement of the first ring 4, a second ring 13 concentric with but axially spaced from the ring 4 and restrained from axial movement, and at least three motiontransmitting members 12 extending between the two rings and arranged at the same angle of akew α in relation to the rotorshaft, the rings 4, 13 being relatively rotatable and the members 12 being arranged to convert relative rotation of the rings into axial movement of the first ring 4. As shown, the ring 4 is held against push members 11 and the members 12 by a spring 10 and the excess of the pressure between the diffuser walls over that behind the ring 4. Each motion-transmitting member 12 has two spherical ends, one located in a guide passage 14, and the other in a recess 16 in the ring 13. A space 19 containing the motion-transmitting members 12 is sealed off from the diffuser by metal bellows or other sealing members 20 and the first ring 4 has a sealing ring 7. The second ring 13 is rotated by a worm 17 engaging a toothed segment 18 and rotation of the ring will displace the members 12 as in the upper diagram of Fig. 2, which shows the mechanism with the skew angle α at a maximum. The arrangement described compensates for the increasing percentage reduction in flow cross-section for a given movement of the ring 4 as the distance between the walls decreases. An adjusting screw 22 may be provided for adjusting the effective length of the member 12.

Description

y 1962 K. JASSNIKER 3,032,259

TURBOCOMPRESSOR HAVING A RADIAL DIFFUSER Filed Nov. 26, 1958 INV EN TOR.

ate

U ite States The present invention relates to a turbocompressor having a diffuser whose flow area can be changed by changing the distance between opposite walls of the diffuser, an axially movable annular member forming part of one of the opposed walls of the diffuser and placed coaxially of the rotation axis of the compressor being provided for this purpose.

In a conventional turbocompressor the flow area of the diffuser can be changed by means of an annular insert in one of the diffuser walls which insert is part of a tubular hydraulic piston arranged in a suitable cavity of the pump housing and actuated by means of a pressure liquid.

This conventional arrangement is simple and satisfactory as long as the actuating liquid of the hydraulic piston can be mixed with the medium which is pumped by the compressor. If the two media cannot be mixed and must be definitely separated, the conventional arrangement is unsatisfactory because it is extremely difficult to completely seal the tubular piston in the cylindrical cavity which has an annular cross section. A control problem may be added to the aforesaid difficulty. Suppose the diffuser has an axial clearance x and a flow area Q, a reduction of the axial clearance by the length a may effect a reduction of the flow area of the diffuser by If the initial clearance of the diffuser is a reduction of the clearance by the same length a effects a reduction of the initial flow area by approximately The same control stroke of the piston produces an increasing reduction of the flow area at decreasing flow area Q. If the pump is used as a drainage pump which may be controlled in a relatively rough manner this control characteristic is unimportant. However, it becomes very important and may be the cause of control instabilities which are difficult to compensate, if the compressor forms 'part of a sensitive system, for example, of a refrigeration cycle.

It is an object of the present invention to provide a compressor having a diffuser whose flow area can be changed by mechanical means which are completely sealed against the inside of the diffuser so that no medium pumped by the compressor can escape or mix with another medium. In the compressor according to the invention an annular member which forms part of a wall of the diffuser of the compressor is axially movable but not rotatable and is propped against a ring element, which is coaxial of the rotation axis of the compressor and rotatable, by means of at least three props which are placed substantially in an imaginary cylindrical surface which is coaxial of the rotation axis of the compressor. The inclination of the props relatively to the rotation axis of the compressor is changed upon rotation of the ring element whereby the annular wall member is axially displaced.

The annular member is preferably urged against the props and the latter against the ring element by suitable spring means.

In a preferred embodiment of the invention connecting ice means are interposed between the annular member and the props, the connecting means being guided in the pump housing to move parallel to the rotation axis of the compressor. These connecting means prevent rotation of the annular wall member and assure a definite guidance in the axial direction.

It is advisable to seal the portion of a cavity in the compressor housing containing the link means operatively connecting the annular wall member and the ring element against the operating medium passing through the diffuser by means of expansible elements.

A sealing packing may be provided between the circumferential surface of the annular member and the respective surface of an annular opening in the compressor housing in which opening the annular member is axially movable. In this way the pressure on the side of the annular member which is remote from the diffuser channel is equal to the static pressure in the inlet of the diffuser, due to the leakage of medium from the diffuser at the inner diameter of the annular member. This static pressure is smaller than the pressure exerted on the annular member by the medium flowing through the diffuser so that the annular member is urged to move outwardy and against its props.

A preferred arrangement for the link or propping means between the annular member and the ring element includes props or pin elements having spherical ends whereby one spherical end of the pin elements extends into a suitable recess in the ring element and the other spherical end of the pin element abuts against the aforesaid connecting means and is received in the respective guide in the compressor housing.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in connection with the accompanying drawing, in which:

FIG. 1 is an axial sectional view of a compressor according to the invention.

FIG. 2 shows the axially displaceable wall member and its actuating mechanism, forming part of the compressor shown in FIG. 1, in two different operating positions, the actuating mechanism including adjusting means.

Referring more particularly to the drawing, numeral 1 designates a diffuser having two parallel walls 2 and 3. A portion of the wall 3 is formed by an annular member 4 which is coaxial of the rotation axis of the compressor and axially movable so that the diffuser clearance S can be changed. The member 4 is received in an annular cavity 5 in the compressor housing 6. The annular member 4 has ashoulder 9 resting on a spring 10 and is pressed by the latter through connectingmeans 11 and props orpins 12 against aring element 13. The latter is coaxial of and rotatable on the rotation axis A-B of the compressor.

A packing 7 is interposed between the circumferential surface of the annular member 4 and the opposed cylindrical wall of the cavity 5. There is no packing in the clearance between the inner circumference of the annular plate 4 and the casing 6. Since the cavity 5 communicates relatively freely with the inlet of the diffuser, the pressure in the cavity 5 cannot noticeably rise above the static pressure at the inlet of the diffuser whereas the pressure acting on the relatively large surface of the member 4 which forms a side wall portion of the diffuser is higher due to the increase of the static pressure in the diffuser. This higher pressure assists the action of the spring 10.

Theconnecting means 11 do not serve only for transmitting pressure but also for axially guiding the movement of the annular member 4 and preventing rotation of theannular member. The elements Ill are axially guided in suitable guides 14 in the casing 6. These guides 14 also individually receive spherical ends 15 of the props orpin elements 12, the other ends of theelements 12 being individually provided with spherical heads 15 which individually rest insuitable recesses 16 in thering element 13.

A great number of conventional means may be used for rotating thering elements 13. The drawing shows a worm 17 cooperating withteeth 18 onthe circumference of thering 13. In order to prevent leakage of the operating medium of thecompressor into a chamber or cavity 19 of the compressor casing which accommodates the actuating mechanism for effecting the axial displacement of the annular member 4 elastic wall members or elements, for example, tubular bellows 2t, are provided which individually surround the connecting means it and which are connected with the annular member 4 and with the stationary compressor housing 6. Theconnecting means 11 are preferably in the form of pins which are inserted in suitablecylindrical recesses 21 in the annular member 4.

Fig. 2 illustrates the principle of the displacing mechanism according to the invention. The upper part of FIG. 2 shows the mechanism in a position in which thering 13 is in one of its extreme positions whereby theprop 12 is at an angle or with respect to the rotation axis AB of the compressor. The lower part of FIG. 2 shows the other extreme position of thering 13 in which theprops 12 are parallel to the axis A-B. The mechanism is so designated that the range of axial displacement of the annular member 4 is equal to the length x. In the upper part of FIG. 2 the space between the wall 2 and the member 4 amounts to S whereas in the lower part of FIG. 2 it amounts to S". For moving the mechanism from one end position to the other extreme end position thering 13 must travel through a path W. If the angle a=V :L the length L is changed at first relatively more at a certain reduction of the path N whereas the subsequent change of the length L at the subsequent reduction of the path W to zero becomes infinitely small. Due to this geometric characteristic of the propping mechanism according to the invention the progressive reduction of the flow area at a linear displacement is avoided which is of advantage when controlling the output of a compressor by means of adjusting the width-of the diffuser clearance.

In the modification of the mechanism shown in FIG. 2 the initial stroke of the control mechanism can be adjusted by manipulation of an adjusting screw 22. The invention is not limited to the mechanism shown and described by way of example. The configuration of the individual elements of the propping or connecting mechanism may, of course, be changed without departing from the purview of the present invention. The compressor may have a plurality of stages.

I claim:

1. A turbocompressor comprising a casing, a rotor, a diffuser arranged around said rotor and being, in part, formed by said casing, said diffuser having opposite walls, an axially movable annular member placed coaxial of said rotor and having a surface portion forming part of one of said walls, said casing having an inside surface portionextending radially'of the rotation axis of said-rotor, a rotatable ring element placed coaxial of said rotor and resting against said surface portion, said casing having a portion interposed between and spaced from said annular member and said surface portion and having apertures, plural link means connected to said annular member and to said ring element and extending through said apertures and constructed and arranged so as to axially displace said annular member for changing the flow area of said diffuser upon a rotary motion of said ring element, and axially yieldable Wall members fluid tightly connected to and interposed between said annular member and said casing portion and forming a space around each of said link means completely separated from the inside of the compressor containing the fluid to be compressed.

2. A turbocompressor as defined in claim 1 including spring means interposed between said annular member and said casing for pressing said annular member against said link means and the latter against said ring element and the said ring element against said surface portion.

3. A turbocompressor as defined in claim 1 in which said link means include connecting means connected to said annular member and slidably guided in said apertures to move in a direction parallel to the rotation axis of said rotor for preventing rotation of said annular member upon a rotary motion of said ring element.

4. A compressor accordingto'claim 3 wherein said casing has a cavity accommodating said annular membet and at least a portion of said connecting means, said wall members being tubular and placed in said cavity and individually surrounding said portion of said connecting means in said cavity.

5. Acompressor according to claim 3 wherein said link means includes pin elements having spherical ends interposed between and abuttingly engaging said connecting means and said ring element, said pin elements being placed in a substantiallycylindrical imaginary surface which is coaxial of the rotation axis of said rotor, said pin elements being slanted to a greater or lesser degree with respect to said rotation axis upon a rotary motion of said ring element in one or in the opposite direction for changingthe axial position of said connecting means and of said annular member in said casing.

6. A turbocompressor according to claim 1 wherein said casing has a cavity having an annular opening accommodating said annular member, said opening and said annular member having corresponding opposite cylindrical outside surfaces, packing means being placed between said cylindrical surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,322,810 Moody Nov. 25, 1919 2,285,976 Huitson June 9, 1942 2,875,696 Zborowski Mar. 3, 1959 2,933,237 Darrow et a1. Apr. 19, 1960 FOREIGN PATENTS 78,038 Germany Nov. 13, 1894 305,214 Great Britain Jan. 29, 1929 (Application date)

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