US2392200A - Centrifugal compressor - Google Patents

Description

Jan. 1, 1946. w. s. THOMPSON CENTRIFUGAL COMPRESSOR Filed Nov. 27, 1944 lfivefitorz VencleLL S.Thomps01"n,- by '4 I Hi Attorney.

. halves i, 2.

Patented Jan. 1, 1946 UNITED STATES PATENT OFFICE CENTRIFUGAL COMPRESSOR New York Application November 27, 1944, Serial No. 565,201

Claims.

The present invention relates to centrifugal compressors with variable diffusers for operation within a wide range of load or capacity as is required in connection with the supercharging of aircraft engines and cabins.

The Object of my invention is to provide animproved construction of centrifugal superchargers,

more particularly of the diffusers thereof whereby they may be operated within a'wide range at high efficiency.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims'appended v halves l and 2 flanged together and forming an impeller chamber 3 with aninlet 4 formed by the casing half l and a discharge scroll 5. An impeller 6 is disposed within the impeller chamber 3 and secured to a shaft rotatably supported on a bearing 3. During operation, medium such as air to be compressed passes through the inlet :3 and is forced radially outward by the impeller 6 into the scroll 5,'whence it is discharged through a flanged outlet conduit 9 formed by the casing Diffuser means are provided to convert part of the velocity energyof the compressed medium discharged from the impeller into pressure sperm. This diffuser means surrounds concentrically the impeller B and in the present example is located substantially in the discharge scroll 5. More specifically, the diffuser comprises two axially spaced side walls or rings 'IB and II. The wall Ill is seated on shoulders formed by the casing half 5 and secured thereto by circumferentially spaced screws It. The wall or ring H is seated on a shoulder formed by the casing hall 2 and secured thereto by circumferentially spaced bolts or screws l3. A set of circumferentially spaced, curved difiuser vanes M is located between the side walls or rings Ill and H. In the present example the set of vanes 14 is integrally formed with the wall i l. Adjacent vanes It form diffuser passages between them, which passages increase gradually in cross-sectional area from the radiallyv inner ends ,or inlets toward the radially outer ends or outlets.

The difiuser so far described is typical of diffuser arrangements used in present day centrifuinto a comparatively gal compressors; These diffusers operate well within a small load range only. through the compressor drops below a certain value this type of diffuser causes pulsations and renders the compressor unstable. In order to reduce such pulsations and to permit a wider load range I provide in accordance with my invention additional difiuser vanes adjustably arranged be tween the aforementioned set of stationary vanes. In the present instance the embodiment in the drawing includes a second set of difiuser vanes, wedges or control members It. Each of these vanes is centrallylocated between a pair of vanes Hi and subdivides the passage formed therebetween. More specifically, each vane is in the form of a wedge-shaped member having a comparatively thin inner portion-tapering gradually thick outer portion.

Each Wedge or wedge-shaped member 55 forms a tongue and groove connection with the walls it, ii. To this end each wedge 65 is provided on opposite edges with tongues it slidably projecting into curved openings ll and grooves it formed in the side walls Hi, i i, respectively. Each wedge forms with adjacent, stationary vanes iii a pair of diffuser passages i9, 20, Fig. 2. The width of the dififuser passages i9, 28, more particularly the throat area thereof, is a minimum when the wedges or adjustable vanes 55 are moved into their inner end position, and the throat area be come maximum as the wedges iii are moved into their radially outer end positions. The end positions are determined by engagement between the ends of the tongues it with the corresponding ends of the openings ii and grooves it.

The arrangement according to my invention includes means for adjusting or positioning the adjustable diffuser vanes or wedges along the center liens or how lines between the stationary vanes M. This adjusting or positioning means comprises a ring 2! with a plurality of circumierentially spaced radial openings or slots 22 each for receiving a pin 23 projecting axially- Iroma tongue 58 of each wedge If). The ring 2! has a toothed portion with a pinion 25. The latter is secured to a shaft 25 rotatably supported on the casing half l. During operation, rotation of the shaft 28 causes turning movement of the pinion 25' which in turn effects angular displacement or movement of the ring 2!. The latter through its slot and pin connections with the wedges or adjustable vanes i5 causes the latter to move along their center lines, that is, along the grooves 11, I8. Upon rotation of the pinion 25 in one direction or rack 24 meshin 2 asoaaoo the wedges II are moved inward to reduce the minimum flow area or throat or the adjacent difluser passages and upon rotation of the pinion 2! in the opposite direction the wedges are moved outward to increasethe throat area of the adjacent difluser passages. The curved wedge shape of the adjustable vanes or wedges and the positioning thereof along the center lines between adjacent stationary vanes it smooth diffuser passages and accordingly efiective andefllcient diil'us'ion within a wide range of load. Thus, with my invention I have accomplished an improved difluser arrangement which broadly comprises a pair of axially spaced walls I or rings with a set of circumferentially spaced stationary vanes between them and another set tionary vanes.

3. Difluser arrangement for centrifugal compressors comprising a ring with a plurality of circumferentially spaced stationary vanes, a

1 plurality of adjustable vanes located between the assures of wedge-shaped vanes alternating with the impeller disposed in the impeller chamber, and

a variable diffuser for conducting compressed medium discharged from the impeller into the scroll, said difiuser comprising axially spaced side walls supported on the casing, a set of circumferentially spaced stationary vanes held on the side walls and a set of circumferentially spaced adjustable wedge-shaped vanes each centrally located between a pair of stationary vanes, and means for moving the adjustable vanes alongv the center lines'.between the stationary vanes.

2. Difluser arrangement for centrifugal compressors comprising a pair oi axially spaced rings, a set of circumferentially spaced curved stationary vanes located between the rings and secured to one of them, and a set of adjustable vanes located between the stationary vanes and dividing the passages between the stationary stationary vanes and forming tongue and groove connections with the ring, and means for moving the adjustable vanes along the center lines I between adjacent stationary vanes to vary the flow area of the passages formedbetween the vanes; a

4. Difluser arrangement for centrifugal compressors comprising a pair of axially spaced rin s. a set of stationary circumferentially spaced curved vanes secured to the rings and forming diffuser passages therewith and a set of adjustable circumierentially spaced curved wedge-shaped vanes interspersed between the stationary vanes and subdividing the diifus'er passages formed thereby, each stationary vane having curved tongues on opposite edge portions located in grooves in the rings between stationary vanes, and means for moving the ad-' justable vanes along the grooves to vary the diffuser passagesformed between them and the stationary vanes, said means comprising axially extending pins secured to the. tongues, a ring having circumierentially spaced substantially radial slots for receiving the respective pins and gear means for angularly positioning said last named ring.

5. Difluser arrangement for centrifugal compressors comprising a pair of axially spaced annular'walls, a pair of stationary circumferentially spaced vanes supported between said walls and cooperating therewith to form a diilusing passage, a tapered control member located within the diffusing passage, and means for adjustin the member substantially along the center line of the passage to vary the eflective area thereof.

Y WENDELL S. THOMPSON.

vanes, and means for positioning the adjustable vanes along the center lines between the sta-

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