US2404609A - Centrifugal compressor - Google Patents

Description

. July23, 1946.,

F. WHITTLE I GENTRIFUQAL COMPRESSOR Filed Nbv. 24. 1942 .2? rep far,

Patented July 23, 1946 CENTRIFUGAL COIVI PRES SOR Frank Whittle, Rugby, England, assignor to Power Jets (Research and Development) Limited,

London, England Application November 24, 1942, Serial No. 466,806 In Great Britain March 2,1940

- Claims. (Cl. 230-128) 1 In British specifications Nos. 456,976, 456,980

. and 461,887, there were described or discussed centrifugal compressors having substantially annular air intakes on each side of the plane of the impeller wheel, and it is to such or similar compressors that the present invention relates (whether they have intakes on one or both sides of the plane of the compressors), more especially when they are combined with gas turbines; or to centrifugal compressors in which there may be difliculty in supporting thecasing relatively to a bearing without obstructing an intake. The present invention seeks to provide constructional improvement affording the necessary steadiness and stiffness of mounting of compressor casings and diffusers having regard to the constructional problems which arise because of the double intake, or because of the locationand arrangement of an intake; and also to the desirability of offering the minimum of resistance to the inflowing air. Where the compressor is directly connected to a gas turbine which drives it, as in the previously proposed reaction propulsion system, it may be required to support the turbine and im-. peller by bearings on each side of the impeller and the compressor casing needs to be very rigid relatively to the bearing housings, whilst at the same time it may be desirable to avoid the use of structural partsclosely adjacent to the impeller eye. A further and important object of the invention is to afford adequate support of a wall or walls of a compressor casing against internal pressure, especially where the wall is of large area and is exposed to a substantial pressure difference. Lightness and ease and economy of construction are also obviously desirable. The invention seeks to afford these attributes.

According to the invention, a centrifugal compressor has its casing supported through the medium of a lattice or skeleton arrangement of webs or struts extending from the casing to a structural part axially spaced from the casing one side thereof, and surrounding th impeller shafting (or to such parts on each side of the casing), the said struts lying at greater radius from the axis of the shafting than air intakes formed between the casing and such structural part or parts. Preferably the struts are comprised in a triangulated structure and thus form lattice-like frames. which enclose and support bearings for the impeller shafting. In a preferred construction the struts comprised in a triangulated lattice work are embodied The said structural parts may be those in framework comprising the struts, arcuate flanges adapted to be attached to 2 the compressor casing, and arcuate flanges adapt,- ed to be attached to the structural parts; and the framework may be constructed insubstantially semi-circular halves. The struts may be inclined in relation to the axis of the impeller so that the structure which they constitute or in which they are comprised, conforms substantial- 1y to the form of a frustu'm of a cone, their ends at'greater radius being adjacent to the compressor casing and at lesser radius being adjacent to the structural part to which they attach the casing. Conveniently the frameworkcom prising'the struts and flanges may be made by castings, and further detail in relation to the construction will be made clear by the following description of an example.

Further, according to the invention, and in order to strengthen and stiffen the walls of the compressor casing against internal pressure, these walls carry externally, projecting parts preferably cylindrical webs, which extend substantial Iy axially from the walls, and supporting webs extend from other parts ofthe walls to these webs or equivalent, the rim of which forms-as it were- -a reinforcing hoop to which stress is transmitted from the wall, which hoop consequently acts in tension and prevents deformation of the wall under internal pressure. *Againthe following more detailed description of an example'will further elucidate this feature of the invention.

The accompanying drawing illustrates the 'in-.

compressor with an impeller I supported by shafting represented by a tail-shaft 2 and a quillshaft 3. The impeller runs in a casing which has walls 4, which at a lesser radius are outwardly convergent (as at 4A) and at a greater radius (as at 4B) are parallel, forming a primary dif- The inner boundaries of the walls fusing space. are curved until they are axially directed, as shown at 4C, and bolted to a flange around the edge of these parts of the walls are extensions 5 I which form walls of intake eyes. Integrally formed with the walls 4 are short cylindrical axial projections 6, carrying rims 6A.

Surrounding the tail shaft 2, is astructural part I, flanged at 1A, which encloses a bearing for that the compressor casing is required to be rigidly attached. The manner of attachment, constituting the basis of the invention, is as follows:

Four lattice-like castings are provided, each substantially as illustrated in Figure 2, and each constituted by a semi-circular flange 9, a semicircular flange I of smaller radius, and a triangulated system of struts I I. streamline section to conform with the airflow which passes over them on its way into the eyes of the impeller. Each strut is also preferably ttwisted throughout. its length, further to con.- form with the airflow, the direction .of which may be expected to vary slightly. at different axially and radially spaced stations. The, fourv frame structures :so constituted are assembled by bolts or studs attaching the flanges 9 to the flanges 6A, and the flanges 1.0 to the flanges 1A and-8A-, and the pair of structures on each side. of the compressor thusform Virtually-continuous lattice-like supports between the parts pressor casing.

Each end of each frame structure, 1. e. the parts which butt together to form. a diametral joint, is formed as shown in Figure 2, with a strut 1 IA ,whichis axially directed instead of being in- I clined; these straight struts are faced at 1 1B,- and the complementary struts llAof the two mating structures. maybe inter-attached. by bolts, and are shaped so as to be streamlined in section when mated together. In Figure'2 a strut .H is shown with portions cut away to .show their sectional shape and also to illustrate thetwist previously referred to. r

Extending radially between the projections 6 and rims 6A=-andthe walls of the casing, are integral stiffening webs l2, which help the casing walls to resist deformation, especially against the pressure within the casing. Inthis residesan important feature of the invention; outward The'struts H are of l, 8 and the com -v loads on the walls of the casing, for example on the parts 4A thereof, aretransmitted through the webs [2 to the rims 6A, which being virtually peripherally continuous are consequentlyresistant in tension, forming hoop like elements in which the stress tends to increase the radius. The structure comprised by the projecting parts 6, and their rims 6A, and the webs l2, can therefore be regarded as a form of trussing supporting the walls of the compressor.

The parts I, 8 or the flanges I 0 as may be convenient) may partially support a system of intake guide elements represented generally at l3.

What I claim is: l. A centrifugal compressor having its casing supported through the medium of an arrangement of struts extending from the casing to a structural part axially spaced from the casing and surrounding the impeller shafting and comprised in a triangulated structure forming lattice-like frames, the said struts lying at greater radius than .air intakes formed between the casing and said structural part.

2. Compressor according to claim 1,.i-n which the struts, comprised in triangulated lattice-work, are embodied in framework comprising the struts, arcuate flanges adapted to be attached to the compressor casing, and arcuate flanges adapted to be attached to th structural part. a

3. A compressor according to claim 1, inwhich the arrangement of struts is attached to the compressor casing through the medium of a short cylindrical rimmed web extending axially from the compressor casing walls, and radial webs connecting said cylindrical web with said walls to stifien and support the walls. I

4. Compressor according to claim '1 in which the struts, comprised in triangulated lattice-work; are embodied in framework comprising th struts, arcuate flanges adapted to be attached to the compressor casing, and arcuate flanges adapted to be attached to the structuralpart, said framework comprising .a casting. 5. A compressor according to claim 1, the struts being of streamline cross section and further be-. ing shaped with twist so as to conformwith'th direction of the air passing over them.

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